Too early for cukes outside?

In the past, I've sown cucumber seeds directly outside at the end of May. This year, I decided to start my cucumber seeds indoors, and since today was such a nice day I'm sorely tempted to put them in the ground. It's about 70 degrees out there now!

The only thing holding me back is that the last frost date in these parts is usually Mid-April, and today is only April 13th. What if in a few days it turns colder than usual and there is a frost? I can't take that chance, so I'll have to wait a couple of more weeks before I put my cukes in the ground.