Perhaps on smaller ones, but I think on the longer ones, the lack of rain further north in their watersheds would offset the gain from the heavy rain in the southern portion.
But of course, I have no idea what I'm talking about.
Or stage left. (I think that was a big debate last year).
Take away from this is that unless you're talking about Irene-type flooding, rain storms are utterly forgettable.
I'm counting on them all being there already and not driving up with the rain. The bulk of traffic is really just Mass folks coming home from work and clogging up 495/93/3. Other than that, it's typically nbd.
Decided to take the dog out for her morning walk as it was only raining lightly. Alas, that didn't hold--became heavy about 1/3 of the way into the 1-mile loop. At least she got her dump in.