I keep a light colored beach towel with me for hot days when we have to play in direct sunlight, and just drape it over my rack. You'd be shocked at how much cooler it is under that little tent from direct sunlight than are the other black metal items out in the open. You can't always get coverage for your MFC (or other pedal) while playing, so I cover them right up to gig time and haven't had a problem. I don't know 100% it makes a mechanical difference, but it sure makes me feel better that I have given myself the best chance of surviving the heat without a failure.
As for the condensation, I agree with those who have suggested a gradual acclimation for your guitars to changing temperatures. This is especially true of some guitar finishes which can not only experience condensation, but also finish checking (cracking) on exposure to extreme temperature changes. Make sure your guitars have time to come up to ambient temperature before yanking them from the case. One trick I learned as a young player was to unlock the case, and post the top slightly open by putting a latch in the way of the lid closing. That lets air through in smaller amounts and allows a gradual warm up. This also works well in the winter, bringing a guitar in from outside to a warmer gig space. 15 minutes or so seems to do fine, but I like to open the case top a little and leave it while we set up. Extra time can't hurt, so I try to use what time I have.
We have had the occasional gig where it was so humid (night time beach gigs, for example) that there is so much water in the air, you can't avoid the condensation. Lots of dry towels and regular wipe downs are the only answer there. Again, draping a towel over your rack can save it from this kind of moisture too. We have actually had powered speakers short out in extreme condensation, so I have no doubt it can hurt other electronics without some sort of protective practices. Just ignoring the environment is bad for equipment, and bad for business... gig failures will always be blamed on the band. It is best to do what you can to make sure the show does, in spite of the weather, go on.
I hope that is helpful to you.