I'm not so sure about that. We had a horrible drought this past summer...one of the worst on record and there was no EHD. We went weeks on end without a drop of rain. After the winter of 2012 (which was a bad one), we had a lot of flooding in the spring...lots of rain as well and EHD hit the deer hard. The F&G estimated we lost up to 75% of our whitetails that year, but I think that was a conservative estimate... I think we lost more. We have lots of drought years here... It's a very dry climate. Our annual precipitation is only around 13 inches, but EHD only seems to hit once every 8 to 10 years or so. It appears to be more related to the overall health of the deer herd. When populations get high, which often happens as access is very difficult on private land here, Mother Nature seems to take care of the overpopulation via EHD. But again..I'm no authority by any means...I'm just sharing what I've observed in the 40 years I've lived here.