THE FOLLOWING HAS BEEN UPDATED SINCE ORIGINALLY POSTED.
The standard issue goat skin bee gloves can get sweaty. Here’s a photo of my hand after beekeeping in 20°C heat (68°F) for about half an hour — and it usually gets a lot sweatier than this:
I recently experimented with using heavy duty rubber gloves, slightly thicker than dish washing gloves. They don’t breathe at all but provide a better feel than goat coat skin. NOTE: Gloves that don’t have long cuffs and therefore don’t provide wrist protection aren’t so great. Blue medical examination gloves, the kind dentists use, are even thinner than dish washing gloves. The bees can easily sting through them and they offer no wrist protection. I’ve gone barehanded at times, too, but only when I’m not digging too deep into a hive.
ADDENDUM (August 02/14): I’ve been using heavy duty rubber gloves for about two months now and I haven’t had any problems with them other than the fact that my hands get instantly sweaty and the sweat accumulates in the fingers of the gloves after about an hour. For hygienic reasons, they should be soaked in soapy water after every use, then hung up to dry. I’d buy a few pairs. The bees, when determined, can sting through them. I got stung today for the first time. It wasn’t a deep sting but a surprising sting nonetheless. I wouldn’t use rubber gloves with defensive bees or during any kind of beekeeping that could rile up the bees. But for everyday maintenance and poking around, the heavy duty rubber gloves are the gloves for me. They’re more tactile, and even though they’re sweaty, I don’t get nearly as hot wearing them as I do with goat skin gloves. I’m not trying to advertise a specific brand of rubber gloves, but the ones I bought from a big box hardware store are described as “Long Cuff Neoprene Gloves.”