Bad News For Fall Lovers: Peak Summer Temperatures Coming Later in Some Parts of the U.S.

Brian Donegan
Published: August 24,2016
After three months of hot, humid weather, many people anxiously await the cooler, more refreshing temperatures of fall. But do we have to wait longer to enjoy fall than in past years?
According to a map by Alaskan climatologist Brian Brettschneider, the answer is yes, for some parts of the United States.

Change in Date of Peak Summer Temperature

In the typically steamy Lower Mississippi Valley and parts of the southern Plains, the peak summer temperature now occurs six or more days later (1981-2010 averages) than it did between 1951-1980.
The reason for this is unknown, but Brettschneider reasons that it may be related to changes in sea-surface temperatures or ocean currents in the Gulf of Mexico. The amount of cloud cover earlier in the summer could also be a factor, with more outgoing longwave radiation (OLR) later in the summer.

In general, the Pacific Northwest is now seeing its peak summer temperature three to six days later than the 1951-1980 period. Seattle is actually seeing it six or more days later.
Areas from the Southeast through the mid-Atlantic states are seeing their peak summer temperature up to three days earlier than the 1951-1980 period.
Most of the Northeast now sees its peak summer temperature up to three days later as well. Parts of northern New England see it three to six days later than that period.
In the Great Lakes, the date of peak summer temperature hasn't changed much. Some places are up to three days later,  and others are up to three days earlier than 1951-1980.
In the Plains, Rockies and most of the West, the peak summer temperature is generally occurring up to three days later than the 1951-1980 period. Along coastal California, however, the peak summer temperature is actually happening six or more days earlier than that period.
Remember, this data shows the date of the average maximum temperature of the year, not the observed maximum temperature, which typically occurs earlier than the average.