You can get a cheap hygrometer to check humidity, and a cheap thermometer to check temperature.. And then check once in a while to see how things change.
- Or you can spend a ton of money on a wireless that either measures both of those, or extra money on one that measures co2 as well, if you want to know exactly what's going on.
I got myself a wireless with 3 frequencies since I have 2 tents and a drying closet, and I'm not regretting it one bit.