Worm Compost Bin Heater – Buy or build your self a warm worm heater. The heater I use came with the worm wigwam and is made from a thermostat (so that it can turn itself on) and the heating coils used to heat seed trays in a greenhouse. The coil is stapled to a board that lays flat (heat side down) on top of my worm bin. If you are handy you can make your own. If not, the same effect can be achieved by purchasing seed tray warming mats and laying them on top of your worm bin. Be sure to buy the ones with a thermostat so you don’t have to run out in the cold to turn it on!
For more on regulating the temperature in your worm composting bin read: Regulating Temperature in Worm Bin