[oldcow]

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.

[Composto]

They would be ok out of doors at these temperatures, but would not enjoy the cold if the temp drops too much, toms just don't like draughts. I won't be hardening my outdoor toms off until mid May here in the NW, as we can still get a frost up to the end of May

Don't forget to bring them in at night or an unexpected frost will see off all you efforts.

[mumofstig]

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.

[BabbyAnn]

and keep an eye on the wind - I've lost a lot of seedlings in the past that went outside to be hardened off and the wind picked up and damaged them    I have cold frames on my patio now which takes some of that stress out.

[iggyboy60]

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

[theakston_uk]

Composto, where about in the NW are you?

[Composto]

Neston, Wirral