At 74.3 degrees, coolest summer in a decade
After four straight years of sometimes punishing summer temperatures, Rehoboth Toy & Kite Co. co-owner Rachel Webster looked back Thursday on the summer of 2014 as the season when heat took a vacation.
"We feel honestly that the weather has been fantastic. It could not have cooperated more," Webster said as she prepared for the long Labor Day weekend. "We've had Augusts where you can barely walk around in Rehoboth and people are cranky – it's just hot."
Preliminary weather records only partly support Webster's widely shared view that 2014 delivered a cool summer. Forecasts released Thursday show warm-to-hot weather rolling in by the end of the holiday, with Wilmington reaching 90 degrees on Monday.
Delaware's June-July-August average temperature now appears likely to hit only 74.3 degrees, the lowest since 2004. But that's still a full degree above the 120-year average for the state. It also should come in only slightly below a century-long trend that has been rising at two-tenths of a degree every decade.
The moisture report is similar. Despite a relatively green summer, statewide rainfall was nearly an inch below average for the summer. It would have proven even drier but for three big, intense downpours in southern Delaware in the first half of July.
A federal crop progress report released late last week noted that about 20 percent of Delaware soils are short of moisture.
"The fact is, the last four summers all ranked among the top 15 [hottest], and that goes back 120 years," said David A. Robinson, a Rutgers University professor and New Jersey's state climatologist. "We've been baking the last four summers, which makes this summer feel all the more comfortable."
Some credit might go to the same sort of repeated jet stream dips from the north that went by the name "Polar Vortex" last winter.
In more-recent months, the cooler air flows managed to beat back or divert warmer air from the southeast that would have turned one or two days of 90 degree temperatures into heat waves lasting three or more days.
Gerald J. Kauffman, a University of Delaware professor and director of the state Water Resources Agency, said northern Delaware creeks that supply most of the area's drinking water are only now slipping toward the dry side.
White Clay Creek near Stanton, an essential source for United Water Delaware, clocked in late Thursday very near the exact middle of flows recorded for late August over the last 74 years.
The Nanticoke River south of Bridgeville was even lower, running at only about one third of the late August average for the past 71 years.
"There hasn't been the blazing heat we've seen over the last few years. It's beautiful beach weather. I'm looking out at the campus right now and it's like a postcard." Kauffman said. "Soil moisture is declining, but we'll be getting into the cooler part of the year now, so things are holding steady right now."
Robinson said that on a more-recent scale, the average temperature for the summer now ending is about about 0.7 degrees below the average for the past 30 years. Delaware fell about .85 below the average over that shorter time frame as well, although the 30-year span obscures the overall steady rise of the past century.
"We can enjoy this locally, but for January through July, the first seven months of the year globally, this is the third-warmest on record for about 140 years," Robinson said. "Generally, when the globe is baking, we're baking here. But there are always exceptions to the global rule, simply because weather patterns zig and zag."
"Enjoy it," Robinson added. "Don't get the idea that this will be the last time we're ever going to see something like this. But more often than not, summers are likely to continue to get warmer."
American and United Nations researchers have reported with rising certainty that global temperatures are climbing, pushed upward by human fossil-fuel burning and releases of heat-trapping greenhouse gases.
One climate change outlook prepared for the state last year projected that Delaware could see a big increase in heat waves, with about 65 days of 95-degree-plus temperatures by the end of the century, if emissions continue unchecked.
By 2100, the state's climate could have more in common with present-day Savannah, Ga.
The National Oceanic and Atmospheric Administration's Climate Prediction Center underscored that point Thursday, releasing an outlook showing Delaware having a 60 percent to 70 percent chance of above normal temperatures for roughly the first week of September. Similar conditions are expected across much of the eastern United States.
Contact Jeff Montgomery at (302) 463-3344 or jmontgomery@delawareonline.com