Training in the Summer Heat Safely

By 4Football Staff · October 29, 2026 · 10 min read

Summer conditioning can be dangerous if the heat is ignored. Learn how acclimatization works, how to judge conditions, how to spot heat illness and what to do in an emergency.

Football players are asked to do their hardest running in the hottest months of the year. The first practices of the season, and the conditioning that comes before them, often fall in late July and August, in helmets and pads, on fields that can be much hotter than the air above them. Most players come through the summer fine. A small number do not, and the cause is almost always the same: a body that was pushed too hard in heat it was not ready for.

Heat illness is one of the most preventable serious problems in sport. This article explains how the body copes with heat, how to ease into hot-weather training, how to judge conditions, how to recognize trouble and what to do about it. It is general education and not medical advice. For decisions about your own health, talk to a doctor or an athletic trainer, and follow the heat policy of your school, league or state association.

Why heat is dangerous

Muscles working hard produce a lot of heat. The body gets rid of it mostly by sweating, with the sweat evaporating from the skin, and by moving blood toward the skin. In hot, humid air the sweat evaporates poorly, so the body cools less effectively. Heavy equipment makes it worse. A helmet and shoulder pads trap heat and cover much of the area that would normally release it.

As the body temperature rises, performance drops. Beyond a point, the body's cooling systems start to fail, and a person can slide from tired to seriously ill within a short time. Several things make this more likely:

• Not being used to the heat. An unacclimatized athlete sweats later, loses more salt, and has a faster heart rate for the same work.
• High humidity. Even moderate temperatures can be dangerous if the air is saturated.
• Direct sun and hot surfaces. Artificial turf and blacktop can be much hotter than the air.
• Dehydration. Being short of fluid makes it harder to sweat and cool.
• Equipment. Full pads and helmet raise the risk. Many of the worst cases happen in the first days of practice with equipment.
• Illness, poor sleep or recent fever. A body that is already stressed copes less well.
• Body size and fitness. Larger athletes generate more heat, and a low fitness level makes work feel harder.
• Certain medications and supplements. Some medicines and stimulants can affect temperature regulation. Ask a doctor or pharmacist about anything you take.

Acclimatization: the single biggest protection

When people spend days exercising in the heat, the body adapts. Sweating starts earlier and is more efficient, sweat loses less salt, heart rate drops for a given effort and blood volume expands. This process is called heat acclimatization, and it typically takes around one to two weeks of gradual exposure to develop most of its benefits. Exact guidelines vary, but the principle is stable: start light, build slowly and give the body days, not hours.

This is why governing bodies have rules about the first days of preseason practice. Many state high school associations, the NCAA and the NFL have limits on how many hours and how much equipment are allowed during the first practices, with the early days using helmets only, then adding shoulder pads, then full pads. The details differ by level and by state and change over time, so check your own association. Our article on preseason practice limits and heat acclimatization rules explains what these schedules look like at the high school level.

If you train on your own, borrow the same logic:

1. Begin with short, easy sessions. In the first few days, cut back the length and the intensity compared with what you would do in cool weather.
2. Add time before adding intensity. Let the body get used to being outside before pushing hard.
3. Add equipment last. Do not start with the heaviest gear on the hottest day.
4. Keep rest days and breaks. Plan shade breaks in every session.
5. Do not skip steps after a break. If you spent a week indoors, sick or on vacation in a cool place, you lose part of your acclimatization and should ease back.

A hypothetical first week

Imagine a lineman who spent the early summer in an air-conditioned gym and now begins outdoor conditioning in late July. A sensible week might look like this, shown only to illustrate the build, since a real plan should come from a coach or athletic trainer:

By the end of the week the same work typically feels easier, which is the visible sign that adaptation is under way. If it does not feel easier, or if it feels worse, the plan was too aggressive or something else, such as poor sleep or illness, is interfering.

Myths that cause trouble

• "Toughness means going without water." Water restriction was once common in football practices and is now recognized as dangerous.
• "If you are not sweating, you are not hot." Some people with serious heat illness have dry skin or sweat very little, and others sweat heavily until they collapse.
• "I'm fit, so I'm safe." Fitness helps, but acclimatization to heat is separate. A very fit athlete moved suddenly from cold to heat is still at risk.
• "One big drink before practice is enough." Hydration is built over a day or more.
• "Salt tablets fix everything." Salt can be part of a plan for heavy sweaters, but taking it in large doses without fluid can backfire. Ask a doctor or dietitian before using supplements.
• "A good coach pushes through." A good coach adjusts the practice and listens to athletes.

Judging the conditions

Air temperature alone is a weak guide because humidity, sun and wind all change the load on the body. Many athletic programs use a measure called the wet bulb globe temperature, abbreviated WBGT, which combines temperature, humidity, sun and wind into a single reading from a special meter. Programs that follow safety guidelines often adjust practice based on WBGT readings, for example by lengthening breaks, removing equipment or moving or canceling sessions when readings reach high levels. The specific cutoffs differ among associations and change over time, so ask your coaches what policy their program follows.

Without a meter, you can still use common sense:

• Check the heat index and the forecast, not just the air temperature. Look for humid mornings as well as hot afternoons.
• Train earlier or later. Early morning and evening are usually cooler than midday.
• Move to shade or indoors when the weather is extreme.
• Remember the surface. A synthetic field in direct sun can be uncomfortably hot at the surface even when the air seems tolerable.
• Respect your own signals. If you feel unusually bad, the day is probably unusually dangerous.

Players and parents should not be shy about asking a coach what the plan is for a hot day. A responsible program will have a plan and will explain it. Our schedule page can help you see when games and events fall if you are planning around the season, and programs listed on our high school pages can usually be reached through their athletic offices.

Fluids and fuel

Hydration is an everyday habit, not something to start at practice.

Before

Show up already hydrated. Drink water or another fluid in the hours before training, and drink with meals. Pale yellow urine is a rough sign of reasonable hydration, while dark urine suggests you need more fluid. It is not a perfect test, and some vitamins change urine color, but it is a quick check.

During

Drink at breaks. Water is enough for short sessions. For longer or very sweaty sessions, a drink that contains sodium and some carbohydrate can help replace what is lost and may help you keep drinking. Do not wait until you are very thirsty, but also avoid forcing down huge amounts at once; drinking far too much plain water over a short time can dilute the body's sodium, a rare but serious condition. A steady pattern is best.

After

Weighing yourself before and after a session shows how much fluid you lost. A common guideline is to replace fluid over the following hours, with roughly 16 to 24 ounces of fluid for each pound lost, along with food that contains some salt. A large loss of body weight in a single session is a warning that you did not drink enough or that the conditions were too severe. If you notice the same large losses day after day, talk to your athletic trainer.

Food

Training in heat is tiring. Meals with carbohydrates, protein and some salt support recovery. Our guide on hydration and heat safety for athletes covers fluids in more detail and is a good companion to this one.

Dress and equipment

• Wear light clothing in light colors that breathes when training without pads.
• Remove helmets and pads during breaks. Taking them off lets heat escape.
• Use shade and cooling aids such as damp towels on the neck, fans and cold water.
• Avoid rubber or plastic "sweat suits." Clothing designed to make you sweat more does not make you fitter and raises the risk of overheating.
• Do not use extra layers to cut weight. Rapid weight loss through sweating can dehydrate you.

Recognizing heat illness

Heat illnesses range from mild to life-threatening. Knowing the differences helps you act fast.

Two warnings. First, the signs are not always clear: someone with heat stroke may still be sweating, and confusion can be subtle at first. A player who becomes unusually irritable, unsteady, or out of sorts in the heat should be taken seriously. Second, do not assume a collapse is "just cramps" or "just a fainting spell."

What to do in an emergency

For a suspected heat stroke, speed matters. Athletic trainers and sports medicine organizations teach the principle "cool first, transport second." The steps are:

1. Call emergency services (911 in the United States). Do it immediately if the athlete is confused, collapses or has a very high temperature.
2. Begin cooling at once. The most effective method is immersion in a tub or container of cold water, with ice if it is available, up to the neck, while monitoring the athlete. If immersion is not available, use cold wet towels or ice packs on the body, especially the neck, armpits and groin, and fans to help.
3. Remove equipment and extra clothing.
4. Stay with the athlete and keep watching breathing and responsiveness until help arrives.
5. Do not give fluids by mouth to someone who is confused or unconscious.

Guidance for lesser conditions is gentler: move the person to shade or indoors, remove excess clothing and equipment, cool with towels or fans, offer fluids if they are alert and able to drink, and have them rest. Anyone with heat exhaustion should be monitored, and if they do not improve quickly or their symptoms worsen, treat it as an emergency.

Programs with athletic trainers often have plans and cold-water tubs on site. If your team lacks an athletic trainer, ask the coach and the school what the emergency plan is. This is a fair question, and the answer should be a clear one. Parents who coach youth or recreational football through our Play section should also have a plan for summer sessions that includes water, shade, rest breaks and a phone.

Return to play

After a heat illness, an athlete should not return to full activity on their own timetable. Doctors and athletic trainers decide when it is safe, and the return usually involves a gradual return to activity with attention to acclimatization again. A previous heat illness can mean a higher chance of a future problem, so these athletes need extra attention in the next hot spell.

Planning a summer of conditioning

If you are designing a summer program, whether for yourself or for a team, a few structural choices reduce risk:

• Schedule the hard work in the cooler parts of the day.
• Start with lower volume and build. Our guide to interval conditioning for football discusses how to layer intensity.
• Use work-to-rest ratios that include real rest and shade.
• Monitor. Coaches and athletes should check in about symptoms, sleep and body weight changes.
• Do not use exercise as punishment in heat. Extra running as a penalty on a hot day has caused harm and has no training value.
• Create a culture where saying "I'm struggling" is encouraged. Players who hide symptoms are in more danger than those who speak up.

The short version

• Heat illness is largely preventable, and equipment, humidity and fitness all raise the risk.
• Acclimatize gradually over about one to two weeks, and add intensity, duration and equipment in stages.
• Judge the day by humidity, sun and surface, not only air temperature; ask whether your program uses WBGT.
• Drink steadily before, during and after; use weight changes and urine color as rough checks.
• Know the signs of heat cramps, heat exhaustion and heat stroke.
• For suspected heat stroke, call 911 and cool the athlete immediately, ideally in cold water.
• Follow your association's heat rules and your athletic trainer's directions, and speak up if you feel bad.