Most of the U.S. sees temperatures increase into July even as the amount of solar radiation reaching Earth peaks in the Northern Hemisphere during the June 21 summer solstice, according to the National Oceanic and Atmospheric Administration's (NOAA) National Centers for Environmental Information (NCEI) "Warmest Day of the Year" maps, which are derived from the 1991–2020 U.S. Using 30-year averages of climatological variables – like daily average high temperatures – scientists are able to identify which day of the year is the "warmest" on average. "Similarly, the persistence of the marine layer along the Pacific Coast leads to cool temperatures in early summer with the warmest days on average later in the season." A map provided by NCEI shows much of the West with average temperatures later and later into the year based on the most recent update. Arizona and New Mexico are shown with their average warmest days in early to mid- June, whereas southern states and the Gulf Coast see their average warmest days during the beginning of August.

Source: Fox News July 28, 2021 19:18 UTC