How much can our gear handle?

I am going stir crazy in this house due to the heatwave and I (crazy as it may be) have been thinking about driving around and trying to capture the effects of the drought and heatwave in my area (city folk and country farmland, etc.) but I am not sure how much my gear can handle for short periods at a time. I've been out in midwest blizzards and never experienced any problems but I'm sure I was pushing it to the limits.

I've even worried about having my gear out when it's 90 degrees and today is suppose to have a "real-feel" temp of 115 degrees! It's 9:30 a.m. now and already 106! I'd probably do most shooting very quickly from my air-conditioned car. With the window down, the gear would be briefly exposed to the heat & high humidity but there isn't much sun. Should one only do this if they have a lens coat & filter?

So, I was wondering at what temperature does it start possibly posing a risk to our gear for both cold and heat & humidity. In my area, temps go from one extreme to the other throughout the year.