Hi serv. Just out of interest, (considering that it gets hot here, too...25º upward during the day in winter) mine sit on their eggs all the time even in the heat, it gets v hot, they pant, and they´ll stand for a bit over the eggs to cool down, then sit again, and they´ll come off the eggs every day, usually late afternoon, to eat, drink and swim about, then go back on.You know when a goose is broody she stays on the eggs all day for 30-33 days and only comes off her eggs maybe every 2-5 days! Some never come off but the weather may be hot but she would still have to sit on the eggs all the time
So, even in a hot climate, they sit tight.