It rains a lot in the UK but I still prefer the Twizy without windows. Snow is worst as it has to be removed before driving off.
The Driver does not get wet while driving even without windows, The inside of the doors do and the passenger might get wet but the driver is fine.
In fact it rains as much if not more in the UK and the temperatures here are a lot colder. I have often driven to and from work below 4c.