why is winter melon freezing in frostbite cave

and what I meant by freeze by the wind in this level it doesn't seem to freeze winter melon sometimes and thats why he isn't frozen in these images but I am tell you the truth here he also is very useful here too so why is he still able to freeze when he is a frozen melon.

 should he not freeze because the other ice plants were used as a wall to protect him form the snowball zombie if that were still to not freeze him ether that would be better.