Enter the conditions and your planned session to see what the environment screens as, and what the screen cannot see.
Estimates are for general guidance only and are not medical advice. For a personalised plan, book a free guided tour at RPM Gym.
The category describes the air, not you. It is a screening band from the US National Weather Service heat index, and it is the same band whether the person reading it is a heat-adapted twenty-five-year-old or someone who landed from Europe on Tuesday. Nothing here clears anyone to train.
The heat index assumes shade and light wind, which is the assumption most likely to mislead you here. Step into direct sun and the strain is materially higher than the number shows — the NWS puts it as much as 15°F higher — and that is a limitation of the measure, not a correction you can add on. The same goes for still air.
The additional factors are listed rather than scored. Direct sun, a hard session, a long exposure and a lack of acclimatisation all raise heat strain, and there is no published way to combine them into one number. Anything that gave you Risk: 78 would be inventing the arithmetic.
Below about 27°C the table does not classify the conditions at all. That is an absence of a category, not a verdict — a hard hour in full sun at 26°C is still a hard hour in full sun.
Simple form: HI = 0.5 × (T + 61 + (T − 68) × 1.2 + RH × 0.094), T in °F That result is averaged with the temperature. Below 80°F the average is the answer. At or above 80°F the Rothfusz regression applies, plus the published low-humidity adjustment (RH under 13%, 80-112°F) and high-humidity adjustment (RH over 85%, 80-87°F). Categories: Caution 80-90°F · Extreme Caution 90-103°F · Danger 103-124°F · Extreme Danger 125°F and above.
An August afternoon in Abu Dhabi: 42°C, 55% relative humidity, a 45-minute run in direct sun, not heat acclimatised.
Extreme Danger on the screen, with three factors the screen cannot account for stacked on top of it. This is the condition the indoor floor exists for.
There is no published temperature that answers that for an individual, and any tool giving you one is making it up. Heat strain depends on humidity, sun, wind, how hard you are working, what you are wearing and how adapted you are. The screen here tells you what the conditions are; the decision stays yours.
An apparent-temperature figure from the US National Weather Service: what the air feels like once humidity is accounted for, because sweat evaporates more slowly in humid air. It is computed for shade and light wind.
Because it measures more of what actually loads you. The heat index only knows temperature and humidity and assumes shade. WBGT also captures radiant heat from the sun and the effect of air movement, which is why occupational and athletic guidance is written around it rather than around the heat index.
Because the published thresholds are not written for you. They come from workplace exposure programmes with defined work-rest cycles and medical monitoring, or from supervised sport with a trainer and an emergency plan on site. They also vary by climate, so a figure derived in a temperate country would rule out most of an Abu Dhabi summer. Showing you a number honestly beats showing you a threshold that does not apply.
No, and that is a common misreading. The NWS says full sunshine can increase the apparent heat by up to 15°F — an upper bound describing how badly the shade assumption can fail, not a constant to add. The real figure depends on the angle of the sun, cloud, surface and what you are wearing.
A substantial one. Repeated exposure over one to two weeks improves sweat rate and cardiovascular stability in heat. It is also why someone who has trained through a Gulf summer and someone who arrived last week face genuinely different conditions at the same reading.
Abu Dhabi summer removes the outdoor option for most people most days, and an air-conditioned floor is the whole reason RPM's is where it is. Come and see the space on a free guided tour.