As others have noted, learn to read the weather radar on your smart phone (assuming you're riding where there's cell phone coverage).

At least in my experience, it's pretty rare to have even one day of solid rain (unless a hurricane or similar tropical storm is coming through). Check the radar, check your route; does it look like you can get to the next town or campground before it starts raining? Go for it! Hunker down in the town library, wait out a shower, and you may get another window of clear weather an hour or two later -- go some more!

If it's warm to hot outside, make sure your rear light is blinking, wear the brightest top or jacket you have, and hit the road. Call it free sweat instead of rain, it keeps you cool just like sweat and you don't have to focus on drinking all day long. Just wipe off the chain, rims and spokes with a paper towel when you're done for the day.