Rain in Venice

In general, I make sure I bring a seam taped packable waterproof jacket for my trips. Other types of jackets fail.

It’s also important to alternate indoor and outdoor activities when in urban rain weather.

I have found that rain pants (as ugly as they are) help tremendously for hard rains and hiking trips. My all time favorite is the Montbell Versalite pants. The women’s pants are a mere 2.9 oz and pack into a sack that is 1/2 the size of a soda can. They aren’t cheap, but last for years and provide excellent performance. They easily fit into my purse.

Deb,
I spent 2 days of rain in Venice and, in addition, it was an "acqua alta" event with flooding in St. Mark's Square. In October 2016. They are well-prepared for these natural events as they happen 2 or 3 times a year. A combination of winds, rain and near to/or full moon. Solid rain on my 17 days best of Italy tour - RS -. We did not have our gondola ride and other things that would have been easier in dry weather. Nonetheless, it was a fun visit. Going back to Venice is now on my bucket list.
There are still wonderful things to do and see so you won't lack for activities. Be prepared with an umbrella and rain jacket.

No acqua alta for me, but we did experience a rather sodden, unpleasant couple of days. As mentioned, a good rainproof jacket is a must, and consider that there are no cars, buses, or taxis to retreat to when the heavens unload. My boots were wet for several days, and my trouser legs were likewise drenched.

On a positive note, the museums were a wonderful refuge, along with churches, and most importantly, bars and cafeterias. Murano was less pleasant than the central city area, due in part to gusty winds and high waves hitting the vaporetto. Still, Venice is always wonderful. Hope for meaningful breaks in the weather.

The forecast I'm seeing for next week (weather.com) is for "showers" on three days, with 50-60% rain chance, highs in the 60s, and not especially windy. I'd prefer sunshine or partly cloudy, but it could be worse. As suggested, try to bring a hooded rain parka, preferably GoreTex or other breathable material. A baseball cap keeps the hood off your face and your face dry. If it's bad enough you might want to buy a cheap telescoping umbrella when you get there, and feel free to leave it in Italy. Good walking shoes, maybe you can put some waterproofing on them before you leave home. Maybe a few extra pairs of socks so you can change into dry ones after a wet day. Wool dries faster than cotton if your feet are comfortable wearing it. Rain pants sound appealing, but maybe not worth packing if it's just showers for parts of a few days.

Cities are much easier in wet weather than the countryside because there are so many things you can see and do indoors. The only thing I can think of to avoid in Venice rain would be a gondola ride, where you're really exposed, especially your legs.

I'm going to Italy in a few weeks and I'll check the forecast just before leaving. If my forecast looks like yours, I'll bring my hooded parka. If not, I'll bring a couple of very light disposable plastic ponchos as insurance.

Or, if it is raining when you are out, there likely will be vendors selling rain gear 'kits'. When my daughter was there there was rain and high water so she bought a boots and rain wear set from a vendor. Cheap enough that she left it behind when she left. ( not much need for it at home in PHX)

It won’t rain non-stop, in all likelihood, so plan for the worst and be ready to change plans if the weather is not as bad as forecast. The Natural History Museum is much overlooked and a break from art museums and churches,

Weather forecasts about precipitation are notoriously unreliable. It may well be much less wet than you are fearing.

Although I've had much better luck in recent years (climate change?), in the past I spent a lot of chilly, wet days in Europe, including some in Venice. Be sure you have a map showing sites of tourist interest so you know what is nearby if the heavens open. If you use a paper map, have some sort of plastic bag to slip it in, else it may disintegrate in the rain. A ZIP Lock bag will work, but a thinner plastic bag is more flexible.

Since all of my current trips include a bit of shoulder season as well as summer, I now travel with a pair of lightweight polypropylene long johns. I've found that the bottoms keep my legs more comfortable on chilly, rainy days when my slacks get soaked.

Do be sure the soles of your shoes are grippy. Wet pavement is slippery.

Rainy days can also be quite windy. A cheap foldable umbrella may be useless. Even a good foldable umbrella may keep turning inside out. A hooded rain jacket worn over a soft brimmed hat will serve its purpose even in high winds.

When you have good weather, use that time for the activities most dependent on sunny weather. Do not be a slave to a preplanned hour-by-hour itinerary.

When I was there in November 2016, I recall one night when it was pouring. I mean, literally pouring. I did end up getting a bit wet, but it wasn't a huge problem. The rain definitely thinned the crowds out around St. Mark's Square and other major spots.

I was there last year at this same time, and it was cool and rainy most of my 10 days.
As I'm from the PNW, I have lots of raingear!
I always take a waterproof jacket that comes almost to knee level and it has a hood that can be cinched in.
It's not terribly windy in Venice, but there are too many people walking about to add yet another umbrella to the ones already squeezing down the streets.
I don't take rain pants, but make sure you have a dry clothing option to change into after a day out.
A change of socks in your day bag is a great idea, and I also take a set of really light long underwear and a light toque and gloves; and I wore them all last year.
There were a couple of warm days in that mix, but not sandals and shorts warm.
If it is raining, duck into a café for a warming cappuccino.
We stayed in a café for two hours last year due to a torrential downpour outside.
Churches offer good, though cool, shelter as well.
Are you staying in an apartment or a hotel?
If an apartment, they can get cool; so after buying three hot water bottles in Italy, in three consecutive Fall visits, I now bring one with me!
Have a wonderful time, Venice is special!