I want to order kindle 4 to poland, but recently weather here is pretty cold.
Low temperatures -20 to -30 Celsius degrees.
I agree, that is pretty cold

According to Kidnle specifications, storage temperature of kindle is max -10 degrees cold.
Maybe that just means they didn't have an easy way to test at colder temperatures. However, I don't see how we could override Amazon's recommendation.
If you were in the US, where they'll get you a replacement unit in two days, with free return shipping, it could be risked. But in your case, I'd wait until Spring. Or if that sounds cruel, what about 1 March?