Natural variability can produce the hottest day in any particular year on just about any summer date. Averaged over time, however, the hottest time of the year in our region is most often from early July through mid August. Solar heat is most direct in late June, but climate lags the solar peak by a few weeks. Other regions of the United States vary from this mid-summer peak.
For example, in the Gulf Coast region, the hottest days are in August and early September due to the influence of the Gulf of Mexico, where water temperatures peak around Labor Day. Across the desert southwest, the hottest days often come in late June or early July because of higher humidity later in the summer. The hottest days along the California coast are often in September or October when high pressure builds into the southern Rockies and sends dry winds over the coastal mountains from the Mojave Desert.