I've never raised sweet peas but have done the vegetable peas, commonly called garden peas here. Those are started outside as early as the ground can be worked, usually early to mid March. I suspect that your flowering sweet peas will not do well due to our hot summers but nothing ventured, nothing gained.

You could try them in the coolest part of your yard and keep them well watered once the weather warms up and see what happens. You could start a few inside to get a head start but be careful when you put them outside if we get a hard freeze. Inside started plants may need some protection. I think they're beautiful. I'd love to know how they turn out.

Sandy

Sweet peas here did well in a fairly warm 2008 summer. They bloomed into July. I planted them on the east side of a grape trellis and mulched them with wood chips once they were climbing.

Of course, Hnbg is one zone colder and we are at 1200 feet.
David

If you mean sugar snap peas, I usually hand sow them around the first week in February here in Richmond, and try to do some successive sowings. I also try to get an Autumn crop by sowing around August 1 as well.

I'm a couple of hours from Richmond, in Orange, and I grew english peas, snap peas and snow peas last fall and got a great harvest. I'm going to put some seeds in the ground this weekend :)