Should I put the tomatoes out?

I have some tomato plants that have sprouted a couple of days ago (indoors, in a heated propagator). They're now on a windowsill, surrounded by tinfoil, but I'm wondering if I can put them outside during the day, since it's supposed to be around 18 degrees in the next few days. I thought they'd get much more light, but I'm not sure if they're too young to be put outside.

I suspect that they are still a bit small to go outside.
If they were a bit bigger I would agree, as long as you keep an eye on the temps and bring them in fairly early before the temp drops too much.

Mine tom plants (3 Roma plum & 4 Gardeners Delight) are all over a foot tall now and I believe I've managed to avoid leggyness. Anyway,I put mine outside all day long now and have done for the past four days. No adverse effects to report so all should be fine as long as you keep an eye on any strong winds

Neston, Wirral