Anakin and Obi-Wan ending up into some sort of weird tumble was far from a strange occurrence. He, himself, almost completely fell over. Maybe they both needed to lighten up a bit.

"Master, how many times have I told you to stop standing in my way. Sometimes I think you just want me to run you over."

If anything Obi-Wan distracted him from complaining about the cold. It probably won't last long, but it's a start.