Expect a Hot Official Start to Summer

While 2012 started out on a hot note overall, June has not.  In fact, June so far has had temperatures around a degree below normal through the month's first two-plus weeks.  It's been a welcome respite from buzzing air conditioners and sweating at the drop of a hat.

The bad news for those of us who like our summers not-so-hot is that things will change for the "official" start of summer on Wednesday. A ridge of high pressure will build overhead for a couple of days, allowing temperatures to reach or breach the season's highest mark so far (94, last Sunday) on Thursday afternoon.

Before that heat, Monday and Tuesday will provide a fair bit of cloud cover and perhaps even a few thunderstorms each afternoon.  Odds don't favor much thunder locally as the best support and energy for thunderstorms stays back over Western Pennsylvania.  Monday likely ends up the coolest day of the week as temperatures stay in the 70s although humidity will be creeping higher.  Tuesday marks the transition to heat, with a noticeable spike in humidity before Wednesday and Thursday's heat event.  With high temperatures in the middle 90s and dew point levels near 70, heat index values are poised to approach 100 degrees midweek.

The question then turns to how quickly the heat will last. A cool front will push through Thursday night or Friday ― the later the frontal passage, the better the chances for a high temperature at or above 90 on Friday.  As of now though, odds favor the front pushing through Thursday night.  There could be some thunderstorms with the front but odds don't favor a widespread soaking of rain for the entire region as it passes through.

Next weekend looks nice to start, but there's a chance for more thunderstorms next Sunday.

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Tom Thunstrom is the editor and publisher of Phillyweather.net. You can also follow Phillyweather.net on twitter at @phillywx or on Facebook.