I’m starting to get a little worried because the weather forecast looks like rain every day while we are on our trip. Are the forecasts usually accurate and does it rain all day? We are going to Grindelwald and Zermatt and I will be so bummed if it rains the entire time. :(
Bring the right clothing (ie a raincoat and enjoy the weather. It's summer. Rain "all day" and every day is not likely and forecast amounts of precipitation are measured in millimeters, not inches and temperatures in the mid-teens (C).
https://www.yr.no/place/Switzerland/Bern/Grindelwald/long.html
https://www.yr.no/place/Switzerland/Valais/Zermatt~2657928/long.html
And thinking positively, temperatures of 16C are better than 36C. It's easier to put on a jacket than strip down to shorts.
You don't say how far out you are looking. I don't find weather forecasting to be very accurate more than a day or so out. We spent 4 weeks last September in Germany, Switzerland and Austria. It looked like we would be going into rain the whole trip...but we actually had great weather. For example, it looked like rain the whole 3 days we were going to be in Stubital area (for hiking) and we actually had one rain storm late afternoon. The 3 days we were in the Garmisch area looked bad, but we had awesome views, great hikes and yes, some rain. It started at 5:00 PM one evening and went through about 10 AM the next day. We also had some blue skies, hot weather. This continued in Switzerland too. (Looked like rain, we ended up with one rain shower that lasted about 10 minutes...it quit as soon as we got our raincoats out).
Having said that, you can get bad weather in any mountain area. Our first trip to Lauterbrunnen, we had bad weather. (Actually was snowing when we visited Kleine Scheidegg.) Even then, the clouds would clear and we get glimpses of mountains. We still had a great time, even though there was an element of disappointment. (We actually went to Grindelwald one day and the mountains were much clearer over there). Zermatt had good weather for us that trip, so you just never know.
One thing I do is look at what the chance of rain is. If it says 80-100% a day or so out....I have less hope. If it says anything below 60%, I figure at least part of the day will probably be rain free. Once again...no guarantees. You can't control the weather, so just go and hope for the best. I am talking to myself as well. We leave next week for Alaska to hike and it is showing we may get some rain.
After spectacular weather in France, I just made it to Lucerne and there were heavy storms right after I arrived at my hotel and there is a 90 % chance of rain for the whole time that I'm here. I had planned to go hiking but we shall see. I don't mind normal rain but I don't want to be on a hike with thunderstorms and high winds!