A virtual sauna bath is what USA Today called the weather along the I-95 corridor today. And I thought it was hot yesterday.
So drink plenty of water, or seltzer in my case, and minimize outside physical labor.
A high pressure means sinking air, where it then sprays out along the surface drawn toward a low pressure. There are two mainland lows in the US: one in Nevada and one in southern Texas.
You can get some pretty neat (and detailed) weather analysis at the AMS Datastreme Atmosphere Project.
Here is the current isobar (lines of equal pressure) map.