How does "wet heat" negatively affect a man's fertility?

There are a number of things that a man can do to optimize his reproductive health. Simple things, like avoiding what we call “wet heat,” in other words, hot tubs, saunas, steam baths—these environments with very elevated heat temperatures can lead to diminishment in sperm production and even sperm death. It’s very important for men to realize this—even one exposure to a hot tub or a sauna can then lead to impaired sperm production for three months down the road. Men should be aware of the fact that if they want to optimize their fertility potential, they should avoid Jacuzzis, hot tubs, steam baths, and these sorts of exposures to wet heat.