You may have planned your ultramarathon around a set of splits, expected arrival times and the supplies waiting at each aid station. Then the forecast changes, or you reach an exposed stretch and realize the day is hotter than you prepared for. The course is still the same, but the plan needs to change while you are on it.
Running an ultra in extreme heat means reconsidering what you carry, how you use each stop and when you let go of a time goal. You need enough options to handle the conditions you actually get, especially when the next opportunity to refill or see your crew is farther away than you would like.
Why Effort Replaces Pace on a Hot Day
A split plan helps you organize an ultra, but it cannot tell you what effort is appropriate once the heat arrives. If a section takes longer than expected, trying to recover that time on the next climb can turn a manageable adjustment into a race you cannot continue.
Use your perceived effort to decide whether to keep running, shorten your stride or walk. Make that decision for the terrain and conditions you are in, rather than the pace written beside that section of your plan. When maintaining your predicted split requires pushing harder than you intended, revise the split.
If you want the explanation behind the adjustment, read why running feels harder in the heat. During the race, your job is to act on it. Let your crew know that later arrivals may reflect a sensible change of effort, and update your expected time to the next stop before leaving.
Coach’s Habit: At Western States 100, Javelina Jundred and Tahoe Rim Trail 100, I have had to let the heat change my predictions for a section. I slow down and use the effort that fits that day and that moment, even when it means letting the clock move beyond my original plan.
Keep checking that decision after the terrain changes. Walking a climb does not mean you should immediately chase your old pace when the trail levels out. Settle into an effort you can manage, then reassess as you continue.
Training Through Heat Before a Hot Race
If your race will be hot, some of your long runs need to include heat. A 100 miler can keep you moving through heat for far longer than a shorter race, and race day is too late to discover that your carrying setup or cooling supplies are difficult to use. For how to build that exposure through a whole summer rather than just before a race, our guide to running in hot weather covers the wider picture.
Use those runs to practice the decisions you will need between aid stations. Check whether you can reach your bottles without stopping, whether your bandana holds ice comfortably and whether the supplies you leave at your car give you useful choices when you return.
Begin those runs regularly hydrated, and adjust the effort to the day rather than forcing the planned pace. Your ultramarathon training plan provides the structure, while these rehearsals help you work out how to carry out that training when the conditions demand changes.
Hydration Between Aid Stations
Before race week, identify the longest gap between reliable aid stations and estimate how long it could take at a slower hot-day effort. Distance alone is not enough. Look at the climbing, exposure and trail conditions, then check whether your bottles or reservoir can cover that stretch with a reserve.
Base your drinking plan on what you have learned about your own needs in training, using this guide to hydration for running in the heat to work through the details. Here, the decision is how to get that fluid across the course. Carry more than you expect to drink so you have spare water for cooling and unexpected delays, without treating that reserve as an instruction to drink more.
Keep drinking water available when you cool yourself. If you pour water over your head early in a long gap, you still need enough to reach the next reliable refill. Decide before leaving the station how you will divide your supply.
On remote trail, locate possible water sources and creek crossings in advance, and check current information from the race. Planned sources are not guaranteed. Creeks can be dry or inaccessible, and runners do get caught out when the water they expected is unavailable. Do not count untreated creek water as a guaranteed drinking refill.
Before every departure, confirm where the next reliable water is and check your actual supply. If the previous stretch took longer than planned, use that information to revise what you carry for the next one, even if it means stopping to repack.
Cooling Before and During the Race
Give yourself somewhere shaded to wait before the start, and keep your cooling supplies accessible rather than buried in a bag already handed to your crew. Starting a hot race already hot makes the opening miles harder to manage, so avoid spending your waiting time standing in direct sunlight.
A review of pre-cooling research found it most promising for endurance exercise in hot conditions, while noting the overall evidence is mixed, and a study of ice slurry before running found that it lowered pre-exercise core temperature and extended running time compared with cold water. Practice anything you intend to ingest before race day, and arrange how you will keep it cold at the start.
Once you are moving, use the cooling options the course provides. Put ice in a suitable hat or bandana, mist your face, chest and shoulders and use sponges or ice buckets where the race offers them. Where the course crosses a creek, take the chance to wet your skin.
Cooling can also lower how hard the effort feels, which matters when effort is guiding your pace. Use that relief to settle back into manageable running, and reassess before increasing your effort. Feeling better after cooling does not require you to recover lost time.
Check the race information for where ice and cooling stations are expected, then place your own supplies at the stops your crew can reach. Keep an alternative available so an empty ice bucket does not leave you without any way to cool yourself.
Working an Aid Station in the Heat
When you arrive, get into shade first and take a few calm moments out of direct sunlight. Tell a volunteer or your crew what you need, then consider what happened over the stretch you just completed. That gives you a better starting point than automatically repeating the same routine at every station.
If you have gone without the electrolyte drink you planned to use, address that gap. If you feel hydrated but have fallen behind on food, choose something familiar that you can manage. Keep your broader eating plan grounded in your practiced trail and ultramarathon fueling choices, rather than trying every available option because it is on the table.
Coach’s Habit: I get into shade before deciding what to replenish. If I have missed electrolyte drinks, I start there, while low energy may lead me toward Coke or Red Bull. I keep ginger options, cold water and ice available because what I choose depends on how I feel when I stop.
Give your crew options they can offer without making you search through everything yourself. Keep familiar drinks, stomach-friendly choices and cooling supplies easy to find, and include anti-chafing lube so you can address that problem before leaving. On remote sections, carry smaller versions of the same supplies.
Before you go, check that the problem you stopped to address has actually been addressed. Confirm your water, take the cooling supplies you need and tell your crew about any changed arrival expectations. If you still feel unwell, tell someone instead of leaving simply because your bottles are full.
Planning for the Temperature Swing
An ultra that continues into the night can take you from dangerous heat into conditions that feel genuinely cold. Plan for that transition before packing your drop bags, using the course profile and your likely progress to identify where you might need different clothing or supplies.
Work from a range of possible arrival times. If heat slows you down, darkness may reach you earlier on the course than expected. If you move faster than planned, you may reach your intended clothing stop while you still need your hot-weather setup.
Spread useful layers and replacement supplies across 2 or 3 drop bags or crew stops. Picking everything up too early can leave you carrying gear you do not yet need, and putting it on too soon can make you overheat. Waiting too long can leave you cold with no suitable layer available.
Coach’s Habit: I spread what I may need for the temperature change across 2 or 3 drop bags or crew stops. Having extras farther along lets me pass a stop when I am early, because I know I can reach similar supplies later instead of carrying everything before I need it.
Label the bags so you and your crew can find those options without guessing. At each stop, decide what belongs with you for the next stretch based on the conditions and your progress. Before skipping a bag, confirm that the next opportunity really contains what you may need, rather than assuming you packed a duplicate.
Knowing When Heat Has Become Dangerous
Pay attention to dizziness, nausea, chills or sweating that stops while you are still working hard in the heat. You do not need to work out what is causing it before you act, and you should not wait for several signs to show up together.
Chills are the one that catches people out, because feeling cold on a brutally hot day reads as relief rather than a warning. Treat it as a reason to stop, not a sign that things are improving.
Stop running, get into shade and tell someone. Ask another runner or your crew to get race staff and tell them where you are, rather than pushing on alone to the next aid station because it is only a couple of miles. A finish time is not worth running through any of this, and that is a decision worth making before the race rather than during it.
Give Yourself Room to Change the Race Plan
Heat does not have to end your race, but it changes what you carry, what you decide at each stop and what you are willing to let the clock do. Prepare enough options that you can respond to the day you get, and leave yourself permission to use them. Get that right and the finish takes care of itself, whether you mark it with a buckle or with a 50K sticker on the back of the car.
Our running plans run from 5K to a 100 mile ultramarathon and are delivered through Final Surge. Use that structure to prepare consistently, then bring the same care to your course planning, crew instructions and decisions when race day arrives.
