How do icicles form?

Answer 1

icicles form like so:

The temperature must be below 0, but it must also be raining.
As soon as one drop starts to freeze another will attach to it and freeze wider and longer.. repeat repeat repeat..
an easy way to do this at home would be to turn your freezer on really cold, get a slanted piece of metal or something, and support it in a plastic container, then pour a bit of water down it and come back in 10 minutes and do it again
do this every 10 minutes until you make your very own icicle!

Answer 2

When temperatures warm or a building is losing heat thru the roof, the snow changes to water. It runs down the roof and off the eaves where it is refroze by the cold air. As more water runs down the icicle the larger and longer it becomes.

Answer 3

If the building is poorly insulated, or if the sun is shining warmly enough on snow on the roof, some of it will melt and drip down, and then freeze again.

If you have really big icicles hanging off your roof, that denotes a poorly insulated upstairs.