Well its started already, lost 5 kits to the heat yesterday, very unexpected. I haven't lost kits to heat in eons, but the two that got out of the nestbox were fine, the 5 in it were dead. There must have been a buildup of heat in that one cage, because everyone esle was fine. Cheeses me off, its always the biggest ones, and they were old enough to get out of the box too. So be careful, even if it doesn't seem hot to you it may be hot enough to kill kits. Its been cool here, and then the one day of higher heat, so it must have been too much. If you have stackable cages, move your litters out of the top cages, remove excess fur that make them too warm, or bring the nestboxes inside if it seems like its going to be a hot day. Check your nestboxes every day, a dead kit can rot fast in hot weather and poison the nest. Thats my community service announcement for the month.