Lukewarm tub

I found an issue with the solar "hot" tub. It's only hot when it's really hot outside. Go figure! It was a bit relaxing this afternoon at the balmy temperature of 83 degrees (the water temp) but isn't a hot tub supposed to be at least 100 degrees. When this thing worked like a hot tub I heated it to 102 usually. Oh well, it's just a bubbly tub-o-fun. Still refreshing!