Mid-Atlantic derecho's 90-mph winds cut power to millions

A complex of thunderstorms on June 3, 2020, caused wind gusts over 90 mph and cut power to over 550,000 customers (approximately 1.5 million people) in Pennsylvania and New Jersey. At least four people were killed, according to our news story.

This map shows hundreds of wind damage reports through the area, as reported by National Weather Service spotters.

A basic GIF radar loop showing the derecho traveling from Pennsylvania to New Jersey on June 3, 2020.

The derecho began over Lake Erie around 6 a.m., causing significant wind damage and gusts starting around Reading, Pennsylvania.

By the time it got to Philadelphia, it had a history of high wind gusts and tree damage.

The derecho finally moved off the coast of New Jersey around 2 p.m. on June 3, 2020.

Four locations recorded gusts over 80 mph, including a 93-mph gust on the New Jersey coast!

A list of wind gusts from the June 3 derecho.

Reading, Pennsylvania, ended up getting two rounds of more than a dozen wind damage reports, around noon with the derecho, then again at 7 p.m. when additional storms came through!

Was this wind event a derecho? The National Weather Service defines the length of a derecho to be 250 miles* which this event exceeded. The NWS office in Philadelphia (Mount Holly) declared this event a derecho. Electric service was slow to return, with about half the customers restored by the next day and 90% by the end of the next day.

According to PowerOutage.US, there were still over 40,000 customers without power in the mid-Atlantic on June 7, four days after the derecho.

The storm didn't look too photogenic here in State College, Pennsylvania, but more of a shelf cloud developed in Carlisle, then the storm really doused Philadelphia with heavy rain and high winds, as the webcam timelapse videos below show:

The wind gust of 93 mph at Reading, Pennsylvania, may well be a state record (which doesn't officially exist and unofficially was 81 mph during Superstorm Sandy) or at least a record for the county (previous record 82 mph in 1954), according to our news story.

*The SPC "Derecho FAQ" page and initial NWS Mt. Holly statement had identified incorrectly the definition of the length of a derecho at 240 miles. After speaking with NOAA's Stephen Corfidi, we realized that the 240 was a typo on SPC's end. We also uncovered a bad conversion in the Johns and Hirt 1987 paper where they equated 400 km to 250 nautical miles, whereas in reality, it converts to 215 nautical miles, or 248.548 (249) statute miles. Separately, the American Meteorological Society redefined "derecho" in March 2019. Their definition page previously did not specify a length but as of this year says "a swath of at least 650 km (~400 mi) and a width of approximately 100 km (~60 mi) or more." Generally, the NWS is the standard for meteorological queries, AccuWeather believes, so you will typically see our staff, including me, going with the 250-mile definition.