Growing up in Colorado, I am used to the very dry air and hotter temperatures while training during the summer. But when you throw in a bit of humidity, my body feels like it is melting, literally.

No matter where you live, you will likely be faced with adapting your fluid and electrolyte strategy to meet the environmental conditions. 

Let’s get more into these differences so you know how to handle each of these challenges.

Hot and Humid

In a hot, humid environment, the body produces sweat to cool itself but high humidity makes it difficult for sweat to evaporate from the skin. As a result, you may sweat heavily without receiving much cooling benefit.

This can create a challenging combination: high sweat rates + poor evaporative cooling.

Hydration should therefore focus on replacing enough fluid to limit excessive body-mass loss while also replacing sodium lost through sweat.

For longer or harder training sessions, use an individualized strategy based on your sweat rate (this means you have to weigh yourself before and after a training session). 

A practical starting point is to consume approximately 16 - 28 ounces of fluid per hour. Adjust this amount upward or downward based on your measured sweat losses from sweat rate testing. Sodium intake may also need to increase, particularly if you are a salty sweater.

Because humidity reduces evaporation, don't assume that drinking more and more water will solve the problem. Cooling strategies such as ice, cold fluids, shade, appropriate clothing and reducing intensity when necessary, become particularly important.

Hot and Dry

Hot, dry environments present a different challenge. Your sweat can evaporate so rapidly that you may not realize how much fluid you're losing.

You may finish a workout feeling relatively dry while having experienced substantial fluid loss.

In this environment, hydration should focus on consistent fluid consumption throughout the session rather than waiting until you feel thirsty. Set a timer on your watch or use the “nutrition alert” like I do on my GPS watch. It’s super helpful! Sodium is also still very important, particularly during prolonged exercise or when sweat losses are high.

Because sweat evaporates quickly, you should really know your sweat rate (shout out again to weighing yourself before and after training so you know your numbers). This can help you dial in your actual fluid losses rather than relying solely on thirst or how wet your clothing is.

Think of it this way:

Hot and humid - you sweat a lot but sweat doesn't evaporate efficiently. Cooling becomes the major challenge.

Hot and dry - sweat evaporates efficiently, so you may not notice how much you're losing. Fluid replacement becomes easier to underestimate.

In both environments, the goal isn't to replace every ounce of sweat. A good general target during prolonged exercise is to limit body-mass loss to roughly 2% or less, while avoiding excessive drinking that causes body weight to increase during exercise.

Let’s not forget sodium!

Fluid is only part of the equation. Sweat contains sodium, and sodium losses can become significant during prolonged exercise in the heat.

A personalized strategy based on your sweat rate AND sweat sodium concentration is much more useful than simply following a universal hydration formula. Shout out to get your sweat sodium concentration measured. It’s usually pretty easy and is a “one and done” test.

The best approach is simple if you remember my mantra: "test, don't guess”. 

Weigh yourself before and after training sessions, account for fluid consumed and urine losses, get your sweat sodium concentration tested and use that information to develop an individualized hydration and electrolyte plan.

The bottom line is that you want to combine appropriate fluid and sodium intake with environmental cooling, pacing and an individualized sweat-rate strategy. 

The goal isn't to drink as much as possible - it's to replace enough of what you lose while maintaining the ability to thermoregulate and perform.