Yes, I was upset with myself once when it was hot and I noticed my dwarf didn't have enough water. He had drank it all because of the heat!
From then on, I kept two bowls of water for him and later gave him a larger dish. My current dwarf has two water bottles (doesn't like bowls), but she's ignored one water bottle entirely.
Huh. No cold water for drinking? I know I put some little ice cubes onto a bowl. My dwarf liked licking it. They melted fast, though.
I leave one or two stone coasters bare in an enclosure. I haven't seen a hamster lie on it yet, but I think it's a good idea. However, during a really bad heat wave, I put in a small cold pack (about 4 inches by 2 inches?) that I kept in the freezer. I waited to see what my hamsters would do with them. The syrian didn't want to touch the cold pack (2 smalls or 1 medium), but he would keep on that side of the enclosure. The dwarf would nap on top of it!
Then he would lick the water off.
But I know some hamsters can bite plastics.
Something else you can do with cold packs is put them on top of the enclosure so that the cold air falls into the enclosure. I used a handheld temperature checker thing to test that it in fact did lower the temperature by 1 or 2 C for about an hour or so before you need to put the cold pack in the freezer again for several hours (which sucks). There is another problem: the cold packs work best when nothing is underneath them but they'll drip if a bit if nothing is underneath them (some cold packs drip more than others). If you put a piece of paper towel underneath the cold pack, it soaks up the water but the enclosure doesn't seem to cool as much that way but it still does cool! I tried putting a cold pack on a dish towel, but the dish towel seemed to almost completely block most of the cold air from going down into the enclosure.
I might have read on Hamster Hideout that aspen shavings make cooler dens, so I put a bunch of aspen in one side of the den, but my syrian didn't want to go into it. One time, it got so hot that my syrian fainted. I was able to move him to a cooler enclosure in the house.
Keeping curtains and blinds closed is so important when it's hot out! I also learned that light-coloured curtains were better than my black curtains. The best curtains were black-out curtains (slightly thicker and meant to block light) that were light-coloured.
The only other thing I can think to add is that I now put a table fan (that goes back and forth) on the floor near the enclosure to circulate the air. It really does help with the nearby window open a crack. Different houses and rooms will have different heat flow. The window may need to be closed. The air flow may also be different.
Great topic!
