When it comes to heat and record highs, most of us associate the word “record” with the heat that happens in the afternoon, or the hottest part of the day. However, record low maximum temperatures can be just as important.

The record low maximum temperature is when a city’s overnight low temperature is at a record high. It may not be as hot as the afternoon temperature, but the overnight hours are when our bodies recover from the heat to avoid heat-related illnesses.

If that overnight temperature doesn’t drop enough, it puts added stress on our bodies and makes us more susceptible to heat illnesses (for those who don’t have air conditioners).

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According to Climate Central, overnight lows are warming twice as fast as daytime highs. Just since 1970, the overnight low temperature has warmed by roughly 3 degrees Fahrenheit.

Heat is the No. 1 killer when it comes to weather, so paying attention to not only the afternoon highs, but the morning lows as well, could help protect you from those sweltering summer nights.

Jennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.