We've made a goal of getting the kids out of the house for several hours each day. This has usually entailed taking walks in the morning before it gets too hot, though the past two days it's been a lot cooler. Before it started to cool off however, it was a LOT of work getting the kids out and worn out enough to not go stir crazy at home, so I changed it up and got a big stock pot, filled it with water, added some big spoons and cups and whisks, then put it out on the balcony for the kids to play with. Then, while they were playing, I added ice cubes periodically.
My daughter threw ice cubes off the balcony and yelled "It's hailing!" They had a LOT of fun with this, so that night I froze water in some cleaned out cans and a big yogurt container and then when we went out on the balcony the next day I also got some string and some salt and we made ice trains by sprinkling salt on some ice cubes and laying the string on it and waited a few minutes and then we could pulled it along by the string. Since it was so hot, we could only do this for a few minutes because then the ice cubes would melt down enough that the salt and string were completely melted off.
The kids had a lot of fun and were really happy that they not only got to get outside, but also do something new!