After temperatures briefly climb to typical midsummer levels, cool air will roll into the Midwest and expand to the East for the last part of July.
Later this week into the end of July, the air forecast to settle in from the Midwest to the East Coast will not be as cool as that of last week.
According to AccuWeather Lead Long-Range Forecaster Paul Pastelok, "We are not looking at very many, if any, record lows being set, but for those who don't like 90-degree heat and high humidity this will be another nice air mass."
Home and business owners will continue to save on air conditioning and watering bills across the northern Plains, Great Lakes, Ohio Valley, Appalachians and parts of the South.
For example from July 1 to July 21, Chicagoians have used 35 percent less energy than the 30-year average to cool their homes and businesses. In Atlanta, that savings has been around 12 percent.
The cool July will offset some of the high energy demands from the past winter, which was much colder than average over much of the eastern two-thirds of the nation.
The waves of cool air have been due to the jet stream taking up a position unusually far to the south over the central and eastern part of the nation for July. Usually the jet stream takes up residence along or just north of the United States/Canada border.
"July will wind up averaging about 4 degrees below normal over the Upper Midwest, including around Minneapolis, Chicago and Detroit," Pastelok said.
The below-normal average for the Midwest will factor in the roller-coaster temperatures of this month, including cool weather during the first part of the month, record chill from last week, a spike in heat early this week and more cool air coming during the last part of the month.
Temperatures over much of the South will finish the month averaging 1 to 3 degrees below normal, while much of the coastal Northeast averages within a degree or so of normal for July.
Looking ahead into August, there may be a trend toward more warm and fewer cool days.
"We expect the Bermuda High to have more influence over the eastern third of the nation than has been the case during much of the season," Pastelok said.
The Bermuda High is a large fair weather system that hovers over Bermuda in the Atlantic Ocean. The clockwise flow around the high typically pumps warm, humid air northward over the eastern half of the nation during the summer.
If the Bermuda high were to strengthen, the jet stream would tend to retreat more to the north and the southward dip might decrease over the Midwest.
"The key will be how moist the soil remains from the Mississippi Valley to the Atlantic coast during August," Pastelok said.
"If the number of showers and thunderstorms diminish, the soil may have some chance to dry out and allow the sun's energy to heat the ground and nearby air."
When the soil is wet, a significant part of the sun's energy goes to evaporating moisture rather than heating the ground. As the moisture evaporates, the ground tends to cool.
According to the Climate Prediction Center, the soil was very moist over much of the eastern half of the nation as of July 20, 2014.
During August, the sun angle lowers and daylight hours decrease, both of which tend to lower evaporation rates. However, there is also somewhat less energy available to warm the ground.