Wooden window won't close

[chopc]

I think the wood has expanded due to the cold and now one of the windows won't close. Can anyone suggest any solutions?

Is it so cold that ice could be holding it open?

How long has it been like that?

I only noticed it a day ago . It's icy in the mornings .......

Try warming around the sides with a hair dryer - don't get the glass too hot though as it may break

Is it a wooden frame?

Does it ever get any sun? if so try shutting it straight afterwards (if there's any sun at all)

Yes it's a wooden frame. No chance of sun at the moment although it is on the south facing side of the house!