In my experience the doors on my 2006 civic used to freeze shut all the time in UK winters (not hugely cold either: 0 to low negatives degrees-C). Also happens on my current 2010 Toyota if it gets cold enough. These have traditional door frames but the ice often builds up between the frames and seals I guess.

Bit of brute force was enough to pull them open. Windows need to be defrosted before you can open them too.