At the last time that I day hiked there in mid-March, it was warm but not hot. I hiked 16 miles RT that day, starting at 8 a.m. I had assumed that 2.5 quarts of water would be plenty. However, by the time I dragged back to my car late that afternoon, I had been dry for the last mile or so. It's deceptive there, because even when the weather is not quite hot, it is still very dry.
When hiking there, it is best to find the springs so that you can replenish as you go along. Further south, there are some springs that are absolutely phenomenal.