I want to do my worm composting ourdoors. Luckily there's a nice location far from any buildings (in case people object) and luckily my landlord is all for it. The problem is that the climate in Ottawa, Ontario, Canada ranges from -15C (5F) to 30C (90F) and worms prefer 4C (40F) to 27C (80F).
There are a number of things that I do that do not require costly energy:
Some temperature measuring methods
Home Depot sells a handy remote thermometer. It consists of a hand control with the temperature readout and a long 10 foot wire which has the actual temperature sensor on the end. To monitor the temperature at the location near the bottom of the bin where the worms are, I bury the end of this wire. The readout is on the hand control which is outside the bin.