how long to warm up soil?

[Gillian]

I've put some plastic over a patch of earth to warm it up in preparation for sowing sweetcorn. How long will it take to warm up? Will it feel warm to the touch? Or will I need to use a thermometer, or should I just leave it for a few days?
Now that I've typed this it seems like a really stupid question.... sorry!

[Gillian]

[wivvles]

I was weeding last Sunday (in between the hail, rain, thunder etc) and thought then that the soil was warm. 

[philcooper]

Gillian,

You don't need a thermometer - the traditional method is the bare bottom test - if it feels warm to your bare bum, it's warm enough to plant in

Phil

[Gillian]

 :o