It is normal. It is relative humidity. Minus 20 degree you need to lower your humidity to around 15-25% or turn off your humidifier completely. I have a brand new house. Not only my window is like this,
-jeffrey815(Smartiecat);
2020-2-15{134}(#12685853@0)+1
my solid wood front door is cover in 冰霜,the lock and door handle is cover in ice. Lower your humidity more.