Weather Outlook

Posted: July 3, 2012

June was a very dry month across Pennsylvania. Only portions of Lancaster and York counties tallied above average rainfall. The largest deficits were in the western quarter of the state where less than a 30% of the normal rain fell.

While the second half of June had several heat spells, overall, temperatures averaged near seasonal levels. More clouds will mark the return of very warm, humid conditions along with embedded thunderstorms on Wednesday, though only about half the state will receive an appreciable rainfall (>.10”). As sultry weather resumes on Thursday through Saturday, readings in many areas will rise well into the 80’s and 90’s with moderately high levels of moisture in the air. Only isolated afternoon and evening thunderstorms will develop, mainly over the higher terrain. A cold front should slip through Pennsylvania on Sunday curtailing the heat wave and causing a few extra storms, but some areas will miss any rain. Notably drier and more seasonable air will return for much of next week with no significant rain during that period. Odds favor a resurgence of near record heat during the middle or later part of July for at least a few days. Unfortunately, without a substantial shift in the weather regime soon, the region is on the verge of a ‘flash drought’ - that is a prolonged period with well below normal rainfall accompanied by periods of very high evaporation rates. There is a 30% chance of a break in the dry spell between July 16–21 as a disturbance forms over the Southeast states.

Odds still favor the center of summer heat to stay in the middle of the country so that hot spells in the eastern states should be short-lived. There are indications that a category 3 or 4 hurricane will strike the United States coastline, probably in August either in Florida (panhandle) or Texas, ending the long period (7 years) without a powerful hurricane hitting the nation. Barring a substantial change in the weather regime, dry conditions are likely to intensify in September.

Contact Information

Paul Knight
  • PA State Climatologist