Here in the pacific northwest we usually take our raincoats out around the middle of October and can safely put them away around June. That is about 8 months of rain. That being said, our water repellant wear probably get more wear than any other jacket or coat we own. A lot of the reason these jackets are so effective is because the back side of the outer shell is coated with some level of a polyurathane resin.
Fortunately, this fabric is easy to care for, as long as you follow the instructions on the label. I use a spot remover or sometimes just dawn dish soap and water and give the cuffs a good scrub with a brush and toss it in the wash on a cold water wash cycle. Sometimes, it may take an extra spin cycle to get all the water out. The step that most skip is the most crucial.
DO NOT put your jacket with water repellant properties in the dryer. It may be ok once, but over time the heat from the dryer melts the resin coating. The result is a jacket that starts to get that puckered look from the breakdown of the polyurathane and loss of water repellancy much sooner than necessary.
The color will stay more vibrant, the water repellency will last much longer and you’ve saved a lot of money in the long run.