Training in Jeddah Humidity: Why It Is Harder Than Heat

Why humidity is harder than dry heat

Your body has one dominant tool for shedding heat during exercise: sweat that evaporates off your skin. As soon as the air gets close to your skin temperature, evaporation is doing almost all of the cooling. The catch is that evaporation only works when the surrounding air has room to accept more moisture. Hot, dry desert air pulls sweat off you quickly. Hot, humid coastal air is already near saturation, so the sweat has nowhere to go: it sits on your skin and drips off, carrying almost no heat with it. Same thermometer reading, a completely different experience, and that is why a humid 38°C can flatten you when a dry 42°C did not.

What it does to your sweat rate and your pace

Humidity does not make you sweat less. It makes your sweat useless. In a 2025 study, whole-body sweat rate stayed around 1.9 to 2.0 litres an hour whether humidity was low or very high, but the share of that sweat that actually evaporated collapsed as the air got wetter. In plain terms: you keep losing fluid and salt, but you stop getting the cooling you paid for. That is the worst of both worlds, dehydration without the temperature relief.

Your core temperature pays for it. In the same study, riders held at 33°C hit a peak core temperature of 39.49°C in very humid air versus 38.97°C in dry air, and their self-paced power output dropped by roughly 5% in high humidity and about 16% in very high humidity. Your body is not being weak; it is protecting itself by forcing you to slow down. Push through it and core temperature keeps climbing, which is exactly when heat illness becomes a genuine risk.

How to train through a humid Jeddah week

Jeddah sits on the Red Sea, so its summers are hot and humid together, roughly 31°C to 45°C in August with humidity that can climb past 80%. You can still train well, you just have to respect the conditions.

Slow down on purpose

Plan to hold back 15 to 20% on effort in the worst heat, especially early in a session. Going out at your normal pace is the classic mistake, because once core temperature spikes you cannot claw it back without stopping. A slower run that you finish beats a fast one that ends in a wall.

Hydrate before, not just during

Start every session already properly hydrated rather than trying to catch up mid-workout, and replace salt as well as water on long or very sweaty sessions. Because your sweat rate stays high in humidity, fluid loss adds up faster than the cooling would ever suggest.

Acclimatise gradually

If you are new to the Jeddah summer or coming back from time away, build your exposure over about two weeks; most of the adaptation arrives in the first handful of sessions. Do not try to be a hero on day one.

The indoor option that simply removes the problem

Here is the honest shortcut: air conditioning fixes the exact thing humidity breaks. Cool, dry indoor air lets your sweat evaporate again, so your body cools normally and you can train at full effort instead of nursing a slow outdoor session. On the stickiest days, moving your workout indoors is not giving up, it is the smart call. A treadmill or bike gives you your run without the saturated air, a HIIT session lets you push intensity safely, and the whole floor of equipment at our gyms in Jeddah is climate-controlled. If you would rather train alongside other people with a coach setting the pace, a group fitness class keeps you honest, and you can refine any movement in our exercise library.

Beat the humidity this week

Humid Jeddah days do not have to cost you a workout, they just move it to where the air works with you instead of against you. Come and feel the difference on an air-conditioned floor and keep your training on track no matter what the coast is doing outside. Try GymNation with a free day pass and train in comfort today.

Sources:
pmc.ncbi.nlm.nih.gov
precisionhydration.com
journals.physiology.org
climatestotravel.com

The opinions shared in the GymNation blog articles are solely those of the respective authors and may not represent the perspectives of GymNation or any member of the GymNation team.