Steff, I went to a pet store and bought a terrarium thermometer/hygrometer for reptiles. it seems to be working pretty well, but had to be adjusted because the thing that registers the temps (not digital, obviously) are on a piece of plastic that slips inside the base that has the numbers on it. I think that's why my last hatch went south, because it wasn't reading right, and I didn't realize it until the end. I'm not sure what it's called, but I could take a picture next time I lift the lid to add water. I find keeping the humidity up is the real problem here in Utah. I imagine it's the same in your area, unless you live way closer to the lake then my sister did in Stansbury.
Cute kids on your blog, by the way.