Thinking about dress in north Switzerland during late March, any clues
As it is now the middle of March I can comment that in the last few weeks it has been "variable".
We have had a few days with 10-15°C and sun, but yesterday it snowed "down to the lowlands" (as the say here), i.e. down to the cities north of the Alps. A few days ago they had ½ metre of snow in Ticino (the part of Switzerland south of the Alps), but that was a 40-year record.
The higher you get up into the mountains, the cooler it will be. The high passes over the Alps (the ones that go from north of the Alps to Ticino) will be blocked by snow until mid May.
I suggest you look at your favourite weather website over the next few days and judge for yourself. It will make a big difference whether you select Zürich or somewhere high in the Alps.
Some of my Swiss friends use this:
I usually look at this one and look for historical weather in the area I plan to go to:
This is for Luzern, and I have already selected 'Historical', but you can do this for anywhere.
"North" Switzerland is generally at lower elevation than the more well known destinations to the south. No Alps, just the much lower Jura mountains and rolling hills. I would expect cloudy weather with cool to warm temperatures.