We will be in Grindelwald in late September and I sure hope we get three good days to do the mountain hikes I have planned, but if there is significant cloud cover or rain, I'm looking for a nice optional day activity. From Grindelwald to the Giessbach Falls it looks to be about a 1.5 hour train/boat trip and then a quick funicular up to the Grand hotel. Brienz also looks like a quaint village to walk around. We don't mind walking around in light rain, so wondering if this side trip would be a good one if weather not cooperating in the Grindelwald area? Any other good rainy day options?
That’s a good option. I combined the Ballenberg open-air museum with Brienz and Giessbach Falls.
Other rainy day options are Trummelbach Falls and Thun to see the castle with or without the boat ride on Lake Thun.
Also, some of my best pictures are from cloudy days so still a great time to be out walking.
I'm headed there in a couple weeks. Wengen is about an hour away from Grindelwald by train/rail/cable car. I have spas on my list to enjoy in case it's rainy. One of them is at Beausite Park Hotel Wengen AG. You can buy a spa day pass and you don't need to stay at the hotel. It's CHF 32.00 including bathrobe, complimentary towels and changing room with lockers. No pre-reservation is required.
It might seem like a waste to go all the way to Switzerland just to dip in a hot tub. But when it's miserable outdoors, you might as well treat yourself to something relaxing.
If spas aren't your thing, there are lots of museums and castles in and around Interlaken you could check out. Or if you can book last minute, a cooking class or cheese tour (not sure if any of these are close to Grindelwald though).