At the U.S. Open, Stifling Heat Causes Some Players to Lose Their Cool

In a quarterfinal match on Wednesday, he struggled to see the ball and relied on instinct to survive a grinding battle with his countryman and close friend, Andrey Rublev. For the second consecutive day, organizers used a new measure to bring relief — partially closing the roof of Arthur Ashe Stadium to shade the court. “One player gonna die, and they gonna see,” Medvedev muttered in the middle of the match.

Current heat warning systems are woefully inadequate in an age of climate change

We need effective heat warning systems to properly inform people at risk when they should take caution. The first step is to revisit and redesign our current systems, which are deeply inadequate. Health problems from heat occur at temperatures significantly lower than when warnings are issued. This is because, for the most part, weather warnings for heat are issued based on the probability and magnitude of the heat event itself, rather than health outcomes.

To Keep Clear of Heatstroke, Pay Attention to This Metric

As the wet-bulb temperature climbs, the body loses its ability to cool itself with sweat. Heat index approximates how the combination of heat and humidity feels and is calculated based on air temperature and relative humidity. Wet-bulb temperature is measured by wrapping the bulb of a thermometer in a water-soaked cloth and then passing air over it until the water evaporates.

A Guide to the Hottest Measurements in Temperature

In order to better specify how hot “hot” is, a number of different equations and techniques have been developed around the world. In general, this math takes into account two main variables: temperature (the one we all use, also known as “dry bulb” or “ambient air temperature,” which is typically measured five feet above the ground in the shade) and relative humidity (the percentage of air saturated with water vapor, also known as the ugly cousin of the trendier dew point; notably Canada’s heat index equivalent, the Humidex, is calculated from the dew point rather than the relative humidity).

Are weather apps lying? The truth is in the dew point.

When a 72-degree day feels like a swampy armpit, I start to realize that everything I’ve ever thought I understood about weather, mainly temperature, is a lie. Sweating through my shirt, wiping my brow, and staring in disbelief at my weather app wondering, “How could this be the 72°F I know and love?” Thankfully, I’ve found a better number to tell me how it’s going to feel outside — and it’s not the relative humidity, which is also a sham. It’s the dew point.

Ask Anything: Wind Chill? Heat Index? Can’t We Combine Them?

More than 100 weather indices have been proposed over the past century in an effort to translate environmental conditions—how cold it is, how windy, how sunny, how wet—into felt experience and physiological risk. Many of these, like the wind chill and the heat index, focus on specific subsets of the variables in play.

Disaster experts say heat warning systems are falling short

What does the National Weather Service say about the idea that the current heat index is not useful enough? They told me they're reviewing that study, and they're committed to making the heat warning system better. They're also piloting a new system in the West that's called heat risk. It has a tiered warning system that has more specific information for vulnerable groups.

How Hot Is It, Really? The Number You See Isn’t What You Feel

Alternative measures that factor in humidity, sunlight and wind speed can be misleading.

How hot is too hot for the human body? Our lab found heat + humidity gets dangerous faster than many people realize

That combination of temperature and humidity whereby the person’s core temperature starts to rise is called the “critical environmental limit.” Below those limits, the body is able to maintain a relatively stable core temperature over time. Above those limits, core temperature rises continuously and risk of heat-related illnesses with prolonged exposures is increased.

What Is the Heat Index—and How Is That Different from the RealFeel Temperature?

The “feels like” temperature you’ll find on a weather app is pretty accurate, but RealFeel goes a few steps further. Created in the 1990s by AccuWeather, RealFeel helps people understand all the components (besides temperature and humidity) that go into what the air feels like by taking into consideration cloud cover, sun intensity, wind speed, precipitation and other factors.