Your heater,..is it a submersible for water or another kind? Mine are in a constant temp (have this heater for their water) and tank is pretty constant and I control humidity. Being in California you probably don't have a winter like we do with snow and ice storms. To make it worse we have bad drivers, too. When we are going to get snowed in I prepare ahead of time. And you have a screened lid? I do, and put saran wrap over maybe 1/2 the top depending on temp outside and if its night. My tank is by a window for natural light so I use saran wrap when sun is not out and its cloudy. This works wonderful and adds just enough humidity. The heater is pre-set to 76 degrees by Tetra. Then I have a small lamp next to tank with either 15 or 25 w bulb. Hope this helps, write if you have questions.I'm taking a break...I just cleaned my fish tank and sat down with some tea.