Big Warmup Continues Heading Into Memorial Day Weekend

IF YOU THINK IT IS HOT ALREADY, JUST WAIT!
We’ve seen a tremendous jump in temperatures since Saturday. Here are the official high temperatures in Philadelphia:

Saturday: 62

Sunday: 66

Monday: 76

Tuesday: 83

Wednesday: 88

The average (or “normal”) high for this time of year is 77. So we’ve gone from 15 degrees below normal to about 15 degrees above normal (once we get to the predicted 92).

BUT AT LEAST IT’S NOT HUMID-YET
Relative humidity dropped to only 19% Wednesday afternoon, which is extremely low for this part of the country. For those who follow dewpoints, it was around 40. By Friday, the afternoon dewpoint should be around 60, or even higher. That would make the relative humidity closer to 40%. That’s still not up to July levels, but pretty close.

(Relative humidity is just that-relative-to the temperature. So, in the afternoon, when it gets most uncomfortable, the relative humidity is the lowest. That’s very confusing. And that’s why we normally don’t use relative humidity on TV. The dewpoint is much more consistent from day to night)

SHOWER CHANCES INCREASE TOWARD MONDAY
There isn’t any day of the weekend (Friday through Monday), when the chance of rain is zero. But it’s pretty low Friday and Saturday, and then it goes up Sunday. By Memorial Day itself, showers become likely. But even then, it’s not a washout. Here are the forecast weather maps for those days:

The maps show a generally dry pattern Friday, with HIGH pressure well offshore (the “Bermuda High”). That means a wind flow from the south, which will result in sea breezes at the shore, keeping temperatures much lower than those inland. The green in the rain area, but it doesn’t mean it’ll be raining everywhere at any given time Monday.

Forecast High Temps