cold temp steering problem?

[72K10]

In the last couple of days, my pickup's steering has been acting up. At low speeds, it pulls hard to the right - sometimes. I'll be driving along and all of a sudden, the wheel is turning by itself and I'm veering towards the ditch. This doesn't happen at high speeds (above 30 miles an hour) and only began three days ago. What I have noticed is when it's veeerrrrryyyy cold (10 degrees or so), it's bad. Anyone here ever hear of cold temps causing steering problems? What is it that's affected by the cold?