Is the Northern Lake region-Como, Bellagio too cold in mid October

Depends on whether you consider average in 60’s too cold.

I dont know what you consider too cool. That will differ from one person to the next. And given the variability due to climate change, last October's weather may bear no resemblance to what happens this year. However there are several websites that can give you historic averages. This is just one: https://weatherspark.com/m/62782/10/Average-Weather-in-October-in-Bellagio-Italy

Yes, it's going to be pretty cold. You'll be right next to the Alps so you might even get some snow.

I spent 3 night in Varenna with a day trip on the Bernina train in mid October 2024. I get cold easily but was always comfortable. My layers of clothing included a lightweight puffer jacket over a sweatshirt or sweater. It was rainy some of the time but with a waterproof rain jacket over the other layers, I was never cold. The lack of crowds in Varenna was really lovely. I also had packed a long underwear base layer top but didn't need it.

I lived in northern Italy for about a year back in 2012-13, in that area (Lecco/Bergamo) and while it wasn’t exactly the warmest time of year, it certainly is very pretty. There are also a lot less ferries running between Bellagio, Varenna and the other towns and villages. Nowadays, though, daytime temperatures can reach 25c or more. The month of the year isn’t anymore a sign of what kind of weather will appear when one visits. I was there last October and it didn’t go below 22 the entire time. It varies. At night it will be cool, no doubt about that