It's not just rain, thunder, lightning, and snow that can wreak havoc on an MLS match. Major League Soccer has policies in place for heat, too, and extreme conditions may lead to water breaks or even match postponement. More details on the league's policies and guidelines follow below.

How is the temperature measured?

It’s measured by Wet Bulb Globe Temperature (WBGT), and not “regular” temperature or heat index. The WBGT is a more involved measurement, which takes into account how stressful the heat would actually be for a player. It includes temperature, humidity, wind speed, sun angle, and cloud cover (solar radiation).

How does that differ from the heat index?

The heat index only takes into account temperature and humidity. WGBT considers even more factors that could make playing physically difficult or even dangerous. As such, a WGBT measurement could be much lower than a regular heat index measurement, but still necessitate special heat procedures.

How many water breaks will there be in a match?



The threshold for mandatory hydration breaks occurs at 82 F on the WBGT and will take place at approximately the 30th and 75th minute of the match. The referee can also call extra breaks whenever he deems appropriate.



Could heat delay the match?

The WGBT is usually measured twice during the match; in extreme heat, the referee will add a third measurement. The first measurement will occur approximately 60 minutes prior to the start of the match.

Here’s how that measurement could affect the game’s timeline: