Looks like you are either in zone 6 or 7, so (surprisingly enough) not that different from me here in Ohio in zone 6b. And it also looks like your average last frost date may be about the same as mine, around mid April:
I like to get a jump on the season, so I start pepper seeds around beginning of February, tomatoes around Valentine's Day. I'm impatient and push the season, so you probably would not want to go earlier, could be later.
Here's a thread where we've been discussing these issues: