Hike Day: Planning, Start and Turnaround Times, Water and Fuel per Hour, Weather

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4:45 a.m. The trailhead parking lot is dark except for headlamps bobbing toward the sign-in box. Somebody’s stove hisses for one last coffee. By sunrise you’re above the trees, by 10 a.m. you’re on the summit with a sandwich, and by the time the first thunderheads build over the ridge, you’re halfway down and smiling. That’s a good hike day, and it rarely happens by luck. Whether it’s a family waterfall walk, a Scout troop’s first big peak, a 14er in Colorado or a rim-to-rim of the Grand Canyon, the day comes down to a plan: when to start, when to turn around, what to eat and drink each hour, and how to read the weather.

General guidance for healthy hikers. If you have diabetes, a heart or kidney condition, high blood pressure or a special diet, follow your doctor’s or a registered dietitian’s advice. Back to the hiking hub.

The night before: plan and tell someone

• Know the route: distance, total climb, water sources, bail-out points and whether there’s cell service. Download offline maps.
• Leave a trip plan with someone who isn’t coming. The National Park Service (NPS) says to include where you’ll hike, who is with you, your contact details and when you plan to start and return.
• Check the forecast and conditions (park or forest alerts, trail closures, fire, snow), and have a backup plan.
• Pack the Ten Essentials (NPS): navigation, sun protection, extra clothing, a headlamp, first-aid supplies, fire, a repair kit and tools, extra food, water and a way to treat it, and emergency shelter.
• Charge everything: phone, watch, headlamp, satellite messenger or check your PLB.

Start times and turnaround times

Start early. In the mountains, the National Weather Service says thunderstorms typically develop in the early afternoon, so “plan to hike early in the day and be down the mountain by noon.” In desert canyons, start early for the heat: Grand Canyon National Park says most people who need emergency help for heat illness there are hiking between 10 a.m. and 4 p.m.

Set a turnaround time and keep it. The NPS calls for a firm turnaround time. Work backward: when must you be back at the car (before dark, before storms)? How long will the return take? The NPS adds that if any part of the hike is uphill on the way back, plan for it to take at least double the time it took to go down, and Grand Canyon rangers suggest using a third of your time to descend and two-thirds to climb out. Then pick the time at which you turn around no matter where you are, summit included. The mountain will be there next time.

Pace for the slowest person. The NPS suggests letting the slowest hiker lead so the group stays together, and offers a simple pace check: if you can talk while you walk, you’re at the right speed.

Water per hour

There’s no single number, because sweat rates vary hugely. The American College of Sports Medicine (ACSM) joint position on sports nutrition gives sweat losses of about 0.3 to 2.4 liters an hour in exercise, and Grand Canyon rangers say hikers in the heat can lose one to two quarts (liters) an hour. The practical rules:

• Start hydrated: ACSM suggests about 5–10 mL per kg of body weight 2–4 hours before, aiming for pale yellow urine.
• Drink regularly, guided by thirst. The NPS says drink as you are thirsty; the National Athletic Trainers’ Association (NATA) says drinking to thirst is reasonable when you don’t know your sweat rate, and warns against drinking so much you gain weight.
• Add salt: Grand Canyon rangers recommend salty snacks plus water or a sports drink on any hike longer than 30 minutes. Drinking lots of plain water without salt can lead to hyponatremia, which looks like heat exhaustion.
• Know your water sources and carry enough to reach the next one, plus a way to treat it (see hiking nutrition).

Fuel per hour

Hiking is long and steady, so small, frequent snacks beat one big lunch. ACSM’s guidance for endurance exercise is about 30–60 grams of carbohydrate an hour for 1 to 2.5 hours, and up to 90 grams an hour beyond 2.5–3 hours, written for harder efforts like races. On a relaxed walk you’ll need less; on a long, steep day with a pack, closer to those numbers. Grand Canyon rangers put it simply: you need to eat about twice as much as you normally would when hiking in the canyon. The NPS suggests trail mix, nuts and granola bars. A practical rhythm: a real breakfast, then a snack every hour (a bar, a handful of trail mix, dried fruit, crackers, a gel on steep climbs), and lunch at the top.

Hike	Water	Food
Short (under 2 h), cool	Drink to thirst; carry a bottle	A snack in the pack
Half day (2–5 h)	Regular sips; electrolytes or salty snacks	Snack every hour (ACSM: 30–60 g carbs/h for hard efforts)
Long day (5+ h), climbing or heat	Plan by sweat rate and sources; treat water; electrolytes	Snack every hour, up to ACSM’s 90 g/h on very long, hard days; a real lunch

Weather on the trail

• Thunderstorms: if you hear thunder, lightning is close enough to strike. Get off peaks and ridges, avoid isolated tall trees, open meadows and water, spread a group out, and wait 30 minutes after the last thunder (NWS, NATA). A tent offers no protection.
• Heat: start before dawn, rest in shade, wet your hat or shirt, and know the signs of heat exhaustion and heat stroke (hiking injuries).
• Cold, wind and rain: the CDC notes hypothermia can happen above 40°F when you’re wet; put on layers before you’re cold and keep a dry set.
• Flash floods: the NPS lists them with lightning as hazards to plan for. Stay out of narrow canyons when storms are possible upstream.
• Altitude: above 8,000 feet, a headache plus nausea or fatigue may be acute mountain sickness. Slow down and turn back if it’s getting worse.

On the trail: small habits that matter

• Stop at the first hot spot on your feet and tape it.
• Adjust layers before you sweat through them or get chilled.
• Check the time at every junction against your turnaround.
• Lengthen your trekking poles and shorten your steps for the descent.
• Stay on marked trails and watch your footing near water and cliffs (NPS).
• Sign out, and tell your contact you’re back.

After the hike, start recovering on the drive home: see hiking recovery. For more on electrolytes, compare drink mixes in our electrolyte powder guide; for how team athletes handle game day, see soccer game day.

Hike Day: FAQs

How much water should I bring on a hike?

It depends on heat, climbing, your size and sweat rate, and water sources. Sweat losses range from about 0.3 to 2.4 liters an hour (ACSM); Grand Canyon rangers say one to two liters an hour in the heat. Carry enough to reach the next reliable source, plus a way to treat water.

What is a turnaround time?

The time you’ll turn back wherever you are, even short of the summit, so you finish before dark, storms or your water runs out. The NPS says to set one and stick to it, and to plan for uphill return sections taking at least twice as long as the way down.

What time should I start a mountain hike?

Early. The National Weather Service says mountain thunderstorms typically develop in the early afternoon and advises being down by noon. Many hikers on big peaks start before sunrise with a headlamp.

What should I eat during a long hike?

Small, frequent snacks with carbohydrate and some salt: trail mix, nuts, bars, dried fruit, crackers, pretzels, plus a real lunch. On long, hard days, ACSM’s 30–60 grams of carbohydrate an hour (more on very long efforts) is a useful guide.

Can you drink too much water while hiking?

Yes. Drinking large amounts of plain water while losing salt in sweat can cause hyponatremia, which Grand Canyon rangers note looks like heat exhaustion. Drink to thirst and eat salty snacks or use an electrolyte drink.