Even if starting with seeds, I'd only do it now if you have a hoophouse or greenhouse. Clones I've been doing for years and years..Caretakerdad is spot on. I keep watching the forcast from May 10-20 for a nice stretch of three days good weather. Wind especially is tough on clones, so I get them at least in the ground and a couple of calm decent days before mother nature can throw a curve ball at them.
The seeds I have started are in a greenhouse until May as well. Under full spectrum florecents and a cheap but effective heater/fan made by Holmes that keeps the chill out of the air in my small greenhouse. It's on a tiumer with my lights..Comes on at 3AM with the lights. I've also toyed with the idea of throwing an outdoor rope light/light rope (Those christmas light things in a rubber tube) putting them in a box, covering with sand and placing my pots on top of the warmed sand to help keep the soil warmer.