Around here MOST washer fluid is labeled 'Winter' or 'Summer'. Never had any freeze solid, but have had slush in the bottle if I still had a lot of the higher temp stuff in when it gets too cold.
The other night when it got to like 15 here, I removed the radiator cap on the truck and it had ice slivers around the cap and around the cap opening, but the coolant on the tank was still liquid. I had measured it the day before and it went to -25.
People usually worry over nothing. It takes a LOT of cold to freeze coolant inside an engine.
