Itinerary Planning Help for Northern Italy Trip

I would shoot for April if you are counting on Lake Como (stay in Varenna) and the Cinque Terre. What is your plan for where to fly into and out of? I hope into Venice and out of, perhaps, Pisa, Genoa, or Milan?

I agree with Laurel, April would be better if planning to go to Lake Como or Cinque Terre.

When my mom and I traveled to Northern Italy, we visited Padua, Venice, Ravenna, Verona (day trip to Lake Garda)
and Varenna (Lake Como).

As much as I loved my visit to Assisi (separate trip) I think it’s the outlier on your list of desired destinations.

Wishing you a wonderful trip!

Save Assisi for a trip to Umbria.
I would choose from Venice Verona Lake Garda Bologna Lake Como Cinque Terre Milan.
You could easily add Lake Maggiore as it is very near Milan Malpensa. If so, drop Lake Garda.
April rather than March. Go south if it must be in March.

Even mid-April can have bad weather. I’ll never forget the day, 4/12, when we arrived in Rome to a temperature of 32 F, literally freezing. It got only slightly warmer as the day progressed. The next day the temp reached 40, but it was raining. If you go to Como and CT, I advise you to plan some alternates to outdoor activities, just in case of bad weather.

It looks like you've taken into account that Easter 2020 is on April 12, so your trip would be before that week or after it. Weather is more likely to be better later than earlier. To get an idea, go to this site and look at historical daily weather data for the places you are planning mostly outdoor activities. There's data by month for the last 10 years.

You can see a lot of Verona on the way to or from Venice. There's luggage storage at the train station. It's a lovely town with quite a few sights so it is worth at least one night. If you spend a few nights in Bologna, you can day trip to Padua, Modena, Ravenna (wonderful 5th=7th century churches and mosaics unlike anywhere else in Italy), Ferrara and more. It will take a long time to get to Assisi, not worth it with the time you have. The CT will also take a lot of time. You'll probably have to change trains in Florence and again in La Spezia. There are several trains a day to Milan that take about 3 hours. One of the problems with the CT mentioned a lot is that some of the hiking trails may be badly damaged over the winter and may not be open for hiking. If you are considering March, check if the ferries are running then. Some of the best views are from the water. My nightmare would be stuck in the CT for 2 days in bad weather. I'd arrange for 24 or 48 hours cancellation and have an alternative plan. I have no idea what Como is like in poor weather.

Thank you everyone for your thoughtful comments and advice. I will definitely take this all into consideration when planning this trip. I have been to Florence recently so will not be returning on this trip. As a few people mentioned leaving Assisi for another time, I will heed that advice. The plan is to travel in/out of Milan or fly into Venice and leave from MIlan. I will look into all towns and cities mentioned (and check the historical weather). Thanks again!