The message from Duncanwood contains these words:
Quite. I just use water from the hot tap though, 'cos it's plenty hot enough to do the job. It's a hell of a lot easier than scraping or spraying.
Trick to remember though is to add a drop (and it really only takes a drop) of dishwasher rinse-aid to the water. It's an anti-surfactant and makes the water run off the screen leaving it dry so there's nothing to refreeze.