The last couple of years, Disneyland has had some very unusual amounts of rain in Jan-Feb. This last year 2017 being more extreme that usual. But Feb is when it rains the most in Disneyland. What we love the most is when it looks like it’s going to rain a bunch in the morning/early afternoon & then only sprinkles. That will keep crowds away without us having to get soggy in the rain. We usually have ponchos with us, but the tougher obstacle is definitely keeping the stroller dry.
In our experience with rain, TSMM has almost always been one of the few rides open during the rain since it has an all indoor track. But because everything around it has exposed tracks to rain or is an outside ride, it becomes the only one running & waits fill up.
Most cast members & locals do bundle up when it gets below 60 degrees. Often we’ll be in t-shirts or light jackets when they are all bundled up, but we are also from Utah where winters are full of snow & cold temps. I remember as a teenager being in Disneyland over Martin Luther King Jr. weekend in jeans & a tee-shirt & standing next to the Rivers of America waiting for Fantasmic with all the people around us looking like they were ready to go skiing.