Can my employer LEGALLY make me work in the rain?

I work at a gas station. A part of our daily duties includes filling propane tanks for customers. Our propane tank is located outside in the parking lot. My question is, is it legal (or fair) for my manager to make me fill tanks when there is excessive wind and rain outside? I told her that I have no issue filling them if it's just spinkling or not raining hard but I flat out refused to go out when it's storming. I am also very sick and feel like these are unsafe and unhealthy. I love in California , what are my rights?