Thanks to PSE's handy website I have daily numbers for my natural gas use. Much like last year I had fairly flat use during the warm months, and more irregular use in the colder seasons.
Comparing directly with temperature it seems that there are two different operating regions, both relatively linear. When the average temperature is above about 55 degrees my use is relatively flat. Below 55 degrees there's more variability but a clear trend of higher use as the temperature drops.