Hottest Day in Each State: When Will It Happen Where You Live?

Summer is in full swing across the United States, and for some, the hottest day of the year has likely already passed, assuming the weather this year follows the same patterns past years have.

Climate norms from the National Centers for Environmental Information were used to create the map that shows when the hottest day would likely occur. That data set contains far more information than temperature: It also includes stats about precipitation, snowfall, frost and freeze days.

The data was collected from 1981 until 2010 and showed that in most areas, the hottest day of the year typically happen sometime between mid-July and the end of that month. But there are a few locations that see those high temperatures as early as June.

Parts of Arizona, New Mexico and Texas have historically seen the hottest day of the year sometime in June. While there's no way to know whether this trend holds true for this year until the year is up, the data suggests those same areas likely already saw the hottest day of the year.

warmest day of year map
A map of the time frame during which the hottest day of the year is expected in each state, and the regions in each of those states. The map was based on historical data of the hottest days of the year from 1981 through 2010. NOAA

The summer solstice is the day of the year in the Northern Hemisphere that gets the most solar radiation. This year, it fell on June 21, but it can fall in a span of a few days around that time of the year. It's known as the longest day of the year because it's the day with the most sunlight. But that doesn't necessarily make it the hottest day of the year, according to NOAA, the National Oceanic and Atmospheric Administration.

In many places across the U.S., temperatures keep increasing well after the solstice and don't start cooling down until around August. There are a few areas in select states where the hottest days of the year don't come until September.

There are numerous causes for the difference in timing. For example, the hottest days typically arrive in the southwest before monsoon season hits there, while on the Pacific coastline, there's a marine layer that can cause the cooler early summer temperatures to hang on longer than they do elsewhere, according to NOAA.

While the map from NOAA simply shows when the hottest day might happen based on averages, some areas can expect those hot days during a certain time period.

Those in New York City can expect the hottest day sometime between mid-July and the start of August, as can those in Boston. People in Washington, D.C., likely already experienced the hottest day—sometime in early July—though a hotter day could still come along.

Down south, in Houston, the hottest day might not happen until August. That will likely be the case for most of California, though the hottest day could come as late as September for some areas of that state.