It's too warm outside when you're sweaty and exhausted before you start your workout.
For a while I was actually trying to get a reasonable amount of sleep. Usually it's my own fault when I stop. This time it's the heat. Now I just can't get to bed before two or three, because it takes that long for my house to cool off. Lying in bed when it's warm is pointless; I'll never fall asleep. When I was in Hawaii I was sometimes awake in bed for three hours or longer, unable to sleep due to heat. At least it's not that warm yet, and it's actually supposed to be cooler for the next couple days, which sounds fantastic.