What about doing the walking in place videos? You get the same benefits except for the fresh air and scenery.
I've found that waiting till after sunset works. It's a lot cooler and there's still light to see. Come July and August, I might have to try the videos, or sign up to workout at the PT department at the local hospital. Then it might be too hot even at night. Tomorrow it's supposed to be cooler, but there's rain in the forecast. As long as it's not violent thunderstorms, I may just put on my rain jacket and rubber boots and walk in the rain.