Self Reliance Exchange has a great article on what items to keep in your car in case of emergencies when you may be driving in extreme conditions:

Many things should be in all vehicles, but there more things that can be needed or required for extreme conditions. Recently, I have been researching 4×4 off-roading and beach buggying and discovered there are tools and equipment that are either required or needed that could benefit people even in everyday conditions.

Read the whole thing. Many of those items don’t seem all that extreme to me. But then I live in the northwest where during winter just getting across town can be extreme conditions.