Mishuget

Hi everyone, I would like to know why water stays frozen during spring and summer in areas where I know the temperature is high. I have my base near a big lake, but when I use a boat to go somewhere fast (over this lake), the lake is still frozen in areas (far from my base, like a line in half of the lake), so I cannot use the boat to sail there, even in late-game summer. Is this a known issue of game mechanics, or do I need to change some setup, or anything? It is also present while walking somewhere far, but that is not so problematic. Ice in lakes in mountains is fine, but the lowland should not be frozen the whole year, right? I am new to this game and the forum, so please forgive me if the topic is already present. Kind regards Mishuget