Strong storms with damaging winds and hail pummeled north Texas on May 28, with widespread power outages reported Dallas and Fort Worth, where an oppressive, early-season heat wave added to the misery.

Nearly 800,000 customers lacked electricity Tuesday, including close to 390,000 in Dallas County, according to PowerOutage.us.

Dallas County Judge Clay Jenkins issued a disaster declaration, stating that it could be days until power is restored for a significant amount of Oncor customers.

"As the current estimate is that this will be a multi day power outage for a significant number of Oncor customers, I have instructed the civil Dallas DA to prepare a declaration of disaster for my signature," Jenkins tweeted.

Oncor said it has crews responding to outages but did not give an estimate for when power is expected to be restored.

Dallas Fort Worth International Airport recorded a wind gust of 77 mph early Tuesday as power outages in the region started to climb. Power went out at about 6 am.

Two downed Bradford pear trees off Gus Thomasson Road in Casa View.Teresa Gubbins

The east side of Dallas was especially hard hit, but trees, fences, and even roofs were damaged in neighborhoods from downtown to North Dallas to Irving, where residents reported 90 mph winds.

Greenville Avenue still had power but residential neighborhoods east of Greenville Avenue did not. Every coffeehouse, from the White Rock Coffee on Northwest Highway to the Starbucks on Greenville Ave to Well Grounded on Garland Road was jammed.

The storm in Dallas followed a May 25 tornado that swept through Collin County, hitting towns such as Celina and Valley View.

Late May is the peak of tornado season, but the recent storms have been exceptionally violent, producing very strong tornadoes, said Victor Gensini, a meteorology professor at Northern Illinois University.

“Over the weekend, we’ve had a lot of hot and humid air, a lot of gasoline, a lot of fuel for these storms. And we’ve had a really strong jet stream as well. That jet stream has been aiding in providing the wind shear necessary for these types of tornadoes,” Gensini said.

Harold Brooks, a senior scientist at the National Severe Storms Laboratory in Norman, Oklahoma, said a persistent pattern of warm, moist air is to blame for the string of tornadoes over the past two months. That air is at the northern edge of a heat dome bringing temperatures typically seen at the height of summer to late May.