Posted: 18/04/2015 at 10:10
Ultimately it boils down to overnight temps, Bf. They have to be read alongside daytime temps. Overnight temps in single figures - within reason, obviously - won't hurt the plants (as written above) but their development will be slowed. Ideally, you'd want overnight temps into double figures.
I think I've posted before about my experiment years ago back in Sydney. I planted out a batch in early spring with overnight temps around 8 or 9C. I planted out the rest a month later with overnight temps around 12 or 13C. The two batches started their ripening process at the same time. The early planting just meant they took longer.
Obviously you're at the mercy of your local climate but, all boiled down, it depends how long you want to wait.