​THE BASICS
Water is (almost) everything
Dehydration on a hot day can result in debilitating heat exhaustion or life-threatening heat stroke. If you don’t have a cast-iron gut like me (I frequently drink untreated mountain stream water), either bring plenty of water with you and/or bring a means of purifying wild water. Unfortunately, “plenty” is relative to your individual physiology and physical conditioning, the environmental conditions you’re hiking in (shade/full sun, temperature, wind, humidity), your level of activity, what you consumed prior to and during hiking, and the distance and elevation gain you are hiking.

It’s not just water, it’s electrolytes:
When you exert yourself, especially on humid days, you sweat out important nutrients (especially sodium and potassium) that balance the chemistry of your body. If that chemistry is out of balance, you can “bonk”, i.e. lose energy rapidly, become nauseous, experience painful muscle cramps, or collapse. Electrolyte imbalance can exacerbate conditions that lead to heat exhaustion and heat stroke. To compensate for electrolyte loss, practice nutritional eating habits (especially in advance of your hike) and bring balanced food with you and/or bring electrolyte supplements. Natural foods that are good for electrolyte balancing include dairy products (including cheese, yogurt, and powdered milk), coconut water, pomegranate juice, watermelon, avocado, spinach, and bananas. ​

Manufactured electrolyte supplements come in a variety of forms including pre-mixed drinks (like Gatorade), tablets to mix with water, “goo” or gel form supplements, and certain brands of energy bars. In the summer I always carry emergency electrolyte tablets in my 1st aide kit and I usually eat a couple bananas as part of my pre-hike breakfast. Some people pre-treat their to-go water with electrolytes. You can even freeze a liter of juice and or electrolyte water mixes the night before and enjoy a cool drink along the trail. If you are carrying a sleeping bag with you, you can wrap a pint or quart of ice cream in the bag, which will insulate it from melting for hours even on really hot days, and enjoy a cold and electrolyte-rich ice cream lunch.  ​

Hats with broad brims offer the best head protection but even a baseball cap will offer some sun protection.

​During your hike you can cool yourself by dipping your hat, bandana, shirt, or small pack towel in a creek and letting the water run over you, or plunge right in and take a dip—your clothing will likely dry off quickly on a hot day, but you could also take along a spare pair of shorts and a small pack towel. ​

When resting, take your boots and socks off and let your feet cool (this will help reduce friction blistering, which is exacerbated by hot boots). For this reason, trail runners are often a better option than thick hiking boots on hot days.

Lastly, remember sunglasses because. . . 

​The devil is in the sun. If your route involves moderate to significant sun exposure (i.e. not just hiking heavily forested trails), bring sunscreen with a high SPF level (50+). If you do get sunburn, you’ll want to protect your skin from further damage; in such cases it’s wise to have brought a lightweight long sleeve shirt with you or an ultralight windbreaker. This can be helpful when your burnt skin—now less able to thermoregulate your body temperature—results in you getting a chill rapidly when temperatures drop later in the day (it’s even possible to become hypothermic by way of sunburn). Be aware that sunburn can contribute to heat exhaustion and heat stroke (as well as increasing your risk of developing skin cancer) by direct heating and by reducing your skin’s ability to thermoregulate. 

Understand the symptoms of dehydration and act to remedy it immediately. Quench your thirst when you feel thirsty. Eat when you feel hungry. Stop and rest (preferably in the shade or in a breezy area) when you feel tired. Don’t wait until you’re exhausted. Examine your urine when you pee: dark yellow urine is a sign of dehydration; whitish urine is a sign of good hydration. Intentionally slowing your pace and resting more frequently can help reduce overheating and dehydration, too. 

Understand the symptoms of heat exhaustion and heat stroke (follow the link for the full run-down). In a nutshell, heat exhaustion begins to develop when you’re moderately dehydrated, with or without an electrolyte imbalance. It is characterized by moist skin (often described as clammy or cool, but not always so if someone has been exerting themselves), exhaustion, and can include dizziness, muscle cramping ("heat cramps") and nausea. Heat exhaustion is treatable by getting yourself in the shade and/or cooling yourself in a brook, drinking and eating to replenish lost water and nutrients, and resting. If left untreated, heat exhaustion can lead to heat stroke—a life threatening and harder to treat condition. Heat stroke is characterized by extreme exhaustion or collapse, hot, dry skin with elevated body temperature, and impaired mental status—those suffering from heat stroke may not be aware of their danger. Unless treated it leads to loss of consciousness, organ failure, and death. People with heat exhaustion will usually need help—get them out of the heat, cool them off with water or wetted clothing, and if they are conscious and can tolerate it, feed them fluids and food—then help them find the shortest way out of the woods. This may require rescue services. Recovery times can be long and permanent organ damage is possible.  

​If you are doing all of the things you need to do to remain cool(er) and hydrated but you still feel unusually fatigued, consider shortening your hike or turning back.​

​PREPARATION MATTERS

• Check weather forecasts before you go and adjust your itinerary accordingly. On really hot days, think about downscaling your ambitions.
• Plan your water: bring it AND be prepared to find it. In doing the latter, know where water is along your route (consult maps and guide books to make sure there is reliable water at reasonable intervals). Avoid routes that are very dry in the summer. Expect headwaters streams and springs to run dry during droughty conditions or later in summer when water levels typically run low. 

DESTINATION AND TIMING
In addition to preparing with appropriate gear and self-care, you can also make your hot weather hike more enjoyable by tweaking your itinerary and the timing of your hike.

​Time of day, season, and weather:
Hot spring days can often be harder to bear than hot summer days because of the lack of leaves on deciduous trees and the fact that your skin and body aren't yet accustomed to full-on heat after all that winter hiking—don’t underestimate the difficulty of hot spring weather hiking.

​On hot days either in spring or summer, it makes sense to start hiking earlier in order to get some miles under your belt before the sun heats up the air. Alternately, you can start hiking later in the morning and enjoy the early evening cool-off along your descent—but keep in mind that (if weather conditions are otherwise constant) early morning temperatures are typically going to be cooler than early evening temperatures. Take advantage of rain forecasts: predictions of light rain on really hot days can be excellent conditions to hike in as long as you don’t mind getting a little wet, but keep in mind that warm rain at low elevations can turn into cold, hypothermia-inducing rain at higher elevations. During the hot summer days of my 1994 Appalachian Trail through-hike I often hiked in the rain in a T-shirt without a rain jacket; this practice not only cooled me off fast it also kept my rain jacket dry for use later in the day and helped wash some of the sweaty crud out of my shirt. 

Even lower elevation mountains can offer cooling breezes: on summer days rising hot air in valleys can cause strong updrafts of cooling wind on exposed areas of higher ground, especially around cliff faces. In the northeast, the prevailing natural wind is often from the west or southwest on sunny days, so hiking the western side of the mountain may be windier and more cooling than hiking the eastern side. Keep the sun in mind, though: exposure above treeline may increase the risk of sunburn. ​

Deep, wooded stream valleys are often cooler on average than ridges or flats, and can offer the added pleasure of a dunk in a creek. As a rule, the northerly slopes of mountains are going to be cooler because they have less sun exposure, ridge tops are going to be warmer (but windier if they’re exposed), and oak or pine dominant woods are going to be warmer than maple, birch, or boreal spruce-fir forests. The relative warmth of these forest types also mirrors how soon brooks will dry out in summer. Open fields and meadows are among the hottest landscapes in the summer while areas with significant boulder fields will trap cool air and may even hold ice into the summer; these places can provide drafts of natural air conditioning (some famous examples include places like New Hampshire’s Ice Gulch, Devil’s Hopyard, and Subway in King Ravine, Vermont’s White Rocks Ice Beds and Smuggler’s Notch, and Maine’s Mahoosic Notch, among others). Planning hikes that place a good swimming hole near the end of the hike can be both pleasurable and advantageous; on really hot days plan hikes with swimming holes at several points along the route.
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By choosing appropriate destinations and routes, and timing your hike with daily heating/ cooling cycles,  you can often craft a hike that maximizes comfort on a hot day. For instance, starting early up a wooded ridgeline or warm side of the mountain in the morning (which would be hot in the afternoon), then traversing an open windy ridge mid-day, and finally descending along a cool mountain stream in a forested ravine in the afternoon is an excellent itinerary to beat the heat. 

If you own a tent, you’ve probably noticed that the holes in the bug mesh screening are quite fine—typically over 1,000 holes per square inch, much finer than your average window screen in a house. The holes have to be this fine in order to keep out “No Seeums" (Ceratopogonidae), the tiniest of biting flies, so tiny that you have to squint in order to see them. In fact, if it’s dark out, you won’t see them at all, unless you happen to shine your headlamp closely on one as it feasts on you. No Seeums, also known as “punkies” and “moose flies” are a family of biting midges 1-3 millimeters in length and translucent grey in color. They have a striped wing pattern that is barely visible to the naked eye in larger specimens. Their tiny size (about half to one quarter the size of a Black Fly) and translucent color makes them nearly invisible. If you find yourself suddenly feeling itchy in the dawn or dusk, or after dark, but can’t identify the cause, you may be the victim of a No Seeum attack. Despite their tiny size, their bite packs a punch, and like Black Flies, they slice holes in the skin then lick out the blood. 

Season & Habitat
Here in the northeast, No Seeums are most active in the twilight hours, on moderate to warm nights in the spring and early summer, near wetlands and still bodies of water. They prefer damp conditions; drought will substantially reduce their numbers. Unlike other biting flies, their larvae are not aquatic. No Seeums are not known to be vectors of pathogens in the northeast, but some people are allergic to their bites (the allergy can cause painful, long lasting itchiness). 

Ecology and Behavior
Like other species of biting fly, adult No Seeums feed on plant nectars; females will procure blood for nutrients used in egg production. Like mosquitos and black flies, No Seeums tend to attack in mobs. Overall, No Seeums are more localized and less omnipresent than mosquitos and black flies and they tend to travel less far in search of blood; sometimes it is possible to escape them by moving away from their home turf a relatively short distance, and it’s quite easy to out-walk them. I’ve never had a problem with them while hiking—only when I stop and settle down for the evening. They are too tiny to bite through clothing but can easily slip under cuffs and down collars. They will bite any area of exposed skin. They will sometimes pass through house window screens to bite people inside.

Thwarting No-Seeums
Cold weather or a strong breeze will drive No Seeums away, as will campfire smoke, natural insect repellants (such as lemon-Eucalyptus concoctions) and man-made chemical repellents (DEET, Picaridin) insect repellants. While most tents come equipped with mesh netting fine enough to keep out No-Seeums, you can easily carry them into your tent on your clothing or skin—shine a headlamp near the apex of your tent after you get inside, and squash any that came in with you (or else they will find you later). If you’re sleeping in a lean-to in No-Seeum habitat, they will come inside the lean-to to bite—in which case you could protect yourself with an insect repellent or with an over the sleeping bag mesh bug net—but make sure you buy netting with very fine holes (some cheap bug nets on the market aren’t fine enough to keep out No Seeums). There are few fates more torturous than being bit all night by nearly invisible bugs. 

​If you do end up reacting to No-Seeum bites, consider anti-inflammatory creams containing Benadryl or other salves to reduce itchiness. ​

Thwarting Black Flies
Bug repellent is a must during black fly season (take it with you, as it will wear off when you sweat); I don’t find much difference between manufactured chemical repellents (DEET, Picaridin), or natural repellents (such as lemon-Eucalyptus concoctions, etc.) but I do find that I have to apply a lot of it to discourage black flies and re-apply it during the hike when I sweat it off. I apply it to all areas of exposed skin (except around my eyes, lips, and nostrils), on my hat, and around my collar and cuffs. Even this will not stop them from flying annoyingly around my head. I always wear a hat or keep handy a bandanna to cover my head, and I keep a mesh head net in my pack for the worse black fly days. 

Black flies are good enough reason to avoid some places altogether in the spring (in the arctic and subarctic spring they can be numerous enough to be life-threatening), but you can pick your days carefully: cold weather or a stiff wind will thwart them (but as soon as you take shelter from the wind, they will be waiting there for you).  Black flies are active only during the day and will avoid dark places—you can take refuge from them in the back of a lean-to, an overhang cave, or even a dense thicket of evergreens. They will mob you most when you are taking a break, and they tend to loiter in places where hikers congregate. The longer you stop, the more black flies will find you. Keeping up a good hiking pace can reduce biting—although black flies are fast, a moving target is harder for them to zero in on. When resting, I’ve sometimes succeeded in diverting some of their mob by placing my sweaty backpack as a scent decoy a few feet away from me and watching while they fruitlessly attack it. When camping, the smoke from a fire can discourage black flies (in old time outdoors language, lighting a fire for this purpose is called "smudging").

Because you will not be able to avoid getting bit by black flies if you hike in the northeast in the spring, it’s helpful to have a salve of some kind to coat your black fly bites and keep the itching down. ​

TICKS
Ticks (Ixodida) have eight legs and are closely related to spiders and scorpions. Few blood suckers inspire as much loathing as a tick—find just one crawling on you and you’ll be paranoid of every little itch. ​

​There is something inherently insidious and creepy about ticks, not the least of which is their ability to harbor and spread debilitating diseases—Lyme Disease, Anaplasmosis, Babesiosis, Ehrlichiosis, etc. Lyme Disease is particularly harsh; combating it can require several rounds of powerful antibiotics. Failing to treat it early can cause acute lifelong symptoms. 

​Lyme Disease is spread primarily by the Deer Tick also called the Black-Legged Tick (Ixodes scapularis), which is common in lower-elevation forests, fields, and shrubland across the Northeast. They are rare to non-existent in higher elevation boreal forests of northern New England. These ticks, identifiable by their reddish lower abdomens, come in a variety of sizes ranging from pencil-eraser-sized adults to pencil-dot larvae. All sizes will bite.

Other ticks: Lone Star Ticks (Amblyomma americanum), formerly a Midwestern and Southern tick, have been expanding their range with climate change and are now occasionally found in southern New England. Like Deer Ticks, Lone Start Ticks are vectors for many pathogens. They can be identified by the single white dot on their carapace. Asian Longhorned Ticks (Haemaphysalis longicornisare) are an invasive tick species from Asia that has been reported in parts of the United States (CT and NY in the northeast); they are less likely to bite human beings, but can transmit pathogens when they do. Winter Ticks (Dermacentor albipictus) inhabit the northeast but they almost exclusively host on hooved animals and are not known to feast on human beings. Winter ticks may infest moose in such great numbers that they can kill the animal.
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Season and Habitat: Ticks are particularly abundant in the spring, rare by mid-summer, and resurge in the fall. They can linger into winter in snow-free areas and emerge on thaw days. They like damp conditions—drought will force them into hiding. Ticks prefer grassy or shrubby areas; the action of an animal passing through dense vegetation makes it easier for a tick to attach to a host. They are therefore uncommon in woodlands with a clear understory, or on farmland where crops are grown and harvested before the ticks can complete their lifecycle. If you stay on trails (and don’t have a free-range tick-magnet dog with you), you’re a lot less likely to pick up ticks simply because the odds are against it: the entire tick population is spread out among many hikers, dogs and animals passing down the same linear corridor of trail. I rarely pick up ticks on popular, well-manicured trails but sometimes pick them up on seldom used, brushy, or poorly trimmed trails. 

Ecology and Behavior: Ticks procure blood as food and to produce eggs. They gorge themselves on blood, drop off, then molt or lay eggs. One tick can lay from several hundred to several thousand eggs. The ticks hatch, climb up a blade of grass or low shrub, and wait for a host to pass by. Contrary to folklore, they don’t climb trees and drop on people—doing so would be a waste of the tick’s energy. When they sense the host animal approaching, they reach out with their clingy limbs to hitch a ride on the lower parts of an animal. Sometimes many ticks from the same egg mass will climb the same bit of vegetation—if you’ve picked up a number of ticks over a short period of time this may be the cause. Ticks have acute senses and will sometimes notice and crawl toward a nearby stationary host.

Once attached, in order to avoid being dislodged, the tick will usually hunker down and cling tightly with its mouth (not biting) and all eight legs until the host slows its pace or stops to rest. In my experience with dog ticks and deer ticks, the ticks will rarely bite the feet or lower legs. Instead, they will climb to the groin, torso, or head—places where the blood flow is rich and strong. This may be a survival strategy—animals are more likely to notice and chew off ticks clinging to legs and other accessible body parts. Deer tick larvae are somewhat more likely to bite lower—although even they will usually crawl up at least as far as the thighs.
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Ticks have a flat shape and hard carapace, which makes it difficult to remove or crush them (they can be crushed—between fingernails, or with a rock, car-key, or coin, but you have to work at it).  They can survive months without feasting, as long as conditions are not too dry or too cold. They tend to linger where they are dislodged: I’ve found them waiting in my car headrest or steering wheel in the morning, where they crawled astray after I picked them up the day before, and I’ve found them lurking in my shower after dislodging them while cleaning up. 

Thwarting ticks: The best defense against ticks is to keep them off you, or remove them before they settle in. Contrary to popular advice, I don’t find wearing long pants to be a particularly good defense against ticks. Ticks cling more readily to fabric, less readily to skin, and I’m much more likely to feel or notice a tick crawling up my bare leg than I am to notice one crawling up my pant leg (where it will find its way to my head, burrow into my hair, and become harder to find and remove). Since the tick is usually aiming for at least my groin before it bites, I have a good chance of noticing it on my bare leg before it does any harm. When wearing pants (which I do when bushwhacking), a good coating of insect repellent on my footwear, upper socks, skin above my socks, pant legs, and belt-line helps discourage ticks from hitching a ride (I have had equal success with chemical and natural repellents: DEET, Picaridin, Lemon-Eucalyptus concoctions, etc.). If I’m wearing convertible pants with zip-off legs, I will often find ticks stuck under the zipper flap—a useful feature, and a good place to check for ticks. For that same reason, also check under pocket flaps. If your shoelaces are loose, you’re actively trolling for ticks by sending out lines which they can cling to. I tie my shoelaces up into tight knots for that reason. Some people tuck their pants into their socks, which means the ticks are going to have to crawl up to the head (if your shirt is tucked in) before they settle in (and before you feel them crawling on you)—in my mind, a sketchy practice especially if you have thick hair. In addition to insect repellents, I’ve used Permethrin which is an insecticide (not an insect repellent—do not apply it to your skin!), on my clothing, which is supposed to kill ticks on contact, but I’ve had mixed results with it.

The most important tick-thwarting strategy is vigilance. When I know I’m hiking in a ticky area in a ticky season, I check my legs and clothing during breaks and before returning to my car (remember: slowing or stopping one’s pace invites ticks to start climbing upward). When I get home, I check inside and outside my clothing and then my full body in a mirror, not forgetting my groin, bellybutton, genitals, armpits, and back. I shower then check again--every little speck of dirt is a suspect tiny deer tick larva. I will sometimes leave my clothing and footwear outside for the night, or throw it in the wash right away. Throwing your clothing in the dryer on an extended warm or hot cycle will desiccate and kill ticks.  It is wise to pre-treat your dog for ticks (dogs can contract Lyme Disease, too) but also check your dog before you get into your car and again before you enter your house --dogs are magnets for ticks and can transport them.

It’s important to remove the tick as gently as possible, making sure to get the tick’s tiny head as well as its body—squeezing the tick or stressing it too much can cause it to disgorge saliva-laden pathogens into your bloodstream.
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The sooner I get the tick off me, the less likely it will have time to infect me with a pathogen. The CDC suggests that a tick needs to be imbedded 36-48 hours before it passes Lyme Disease to its host, but it's wise to get them off  long before that. If you do find a tick embedded, and don’t know how long it has been there, consult your primary care physician about preemptive treatment. Pay close attention to any rashes or symptoms of illness over the next few weeks. Getting on treatment sooner than later can prevent debilitating chronic Lyme disease symptoms. ​