I don't think there's a 'too hot' to be outdoors. Appropriate dress, sunscreen and lots of water. In fact, I'd opt for water play and stuff in the shade. There have been times when it's been flat out too hot to play on the playground because all the equipment was hot.. but we just got out the sidewalk chalk and did that instead. (unless of course, you live in an area that is seriously too hot, like Death Valley, and then okay).
as far as cold.. I don't really think there's a 'too cold' that I've encountered. We just bundle up. But, like today and yesterday, we didn't go outside because I didn't feel like bundling up, but that's more mom's laziness
it's not quite as damp today, so maybe I'll bundle her up after naptime.
wet and such.. depends on if I have good shoes and if it's cold or hot. I am better with wet and hot than I am with cold and wet. I don't want her getting sick.. but if it's cold enough to bundle her, then it'll be okay. snow is just as wet as rain in a way.
Muddy? I'm pretty okay with mud. I've let her cover herself in mud just after a graduation ceremony when she was wearing a nice dress. It probably depends on HOW nice of a dress... but I'm fairly flexible as long as I have a change of clothes within a short distance.