What to do when it rains in Lake Como area?

Milan, Como town, Bergamo, Lugano all make for good day trips if the weather is too bad to enjoy the lake attractions. Lugano is easily accessed by bus from Menaggio, Bergamo by train from Lecco. Milan and Como are easy from wherever.

Get wet.

Seriously, bring rain gear amd continue sightseeing. If you alter your plans every time it rains, you're going to miss out on a lot.

put up an umbrella, wear a rain hat and waterproof light jacket and keep going....

It will look different and still beautiful in a different way

Most likely the rain will be later in the day and if you’re lucky, you’ll have a thunder and lightning storm. We had a very beautiful one or two while we stayed in the area several years ago.