Yep I'm from Chicago! The weather has been great, I was so tired of the heat we'd been having. We can finally open the windows and turn off the a/c!
For overheating, check for their tongues hanging way out of their mouths, excessive panting, dry nose/mouth, noisy breathing, bright colored gums, drooling, and starting to slow or lag behind the bike a lot.
If you are still working on getting your dogs' stamina up for the biking, you also need to watch to not overdo things too much too quickly. Some dogs will keep running until they drop if you let them so if your dog is like this you may have to keep a closer eye on them for signs that you need to stop them. Other dogs are better about regulating themselves and will start to slow down and stop before that point.
I watch for them starting to lag behind more, for their tongues hanging, or panting in cooler weather, or if you give them a break and they are reluctant to get moving again. It's also a good idea to take breaks and check their paw pads for wear or abrasions, especially if you're biking on a hard surface or pavement and they're not used to running on those types of surfaces. Those breaks are also a good time to give them some water.Of course not TOO much water because you don't want a dog stopping to pee while you're biking (I've had that happen!)