My 2000 WJ wipers were barely moving last night after driving all night at -18*. It was clear skies all night, so I didn't turn them on, but there was some frozen slush around the wiper arm shafts from the day before. When I tried to remove a little road film, I hit the washer, got the squirt, but the wipers just barely crept across the glass. I got out and helped them park!

This morning, I investigated and found ice like stone around the arms where they attach to the shafts and had to chip it away carefully. Then the wipers worked normally.

SO, if you know it's going into a deep freeze, clean off the slush unless you want the same problem. That is all!