If you saucer feeder isn't an open dish, I don't think that much rain would get in through the ports to significantly dilute the nectar. Several of the saucer ones I've seen have the ports on a small slant which helps with triggering some runoff.

Some folks will either buy or make an umbrella (or often dubbed a "humbrella"...lol) to put over the saucer to help stave off torrential rains. Often simply hanging under a tree can help too...

I use home made humbrellas but they do sell them at a lot of places that stcck hummer feeders. I also make my solution just a big stronger than the 1:4 ratio during really rainy weather (maybe a teaspoon or 2 extra to a quart of nectar at the most. If it is a light drizzle I don't worry about it.

Penny

Only when we have serious downpours and I mean downpours is it ever an issue. One time after a rain the feeder had 8 oz in it but I only fill it to 2oz hehe. But like I said this was some serious rain. Otherwise everyday rain is fine.