Mountain Passes
 

Obiviously every year is different depending onweather conditions etc...

But traditionally at what time of year do the high mountain passes:freezing: (stelvio, grimsel, etc..) of the alps open for vehicles??

Just looking at options for crossing europe at the start of our RTW trip in april.

You might be a bit early in April. As you say things are weather dependent but things seem to gradually roll into life from the begining of May.

If all you want to do is travel south there's lots of choice as all of the main alpine passes (Brenner etc) are kept open through the winter. If the idea was to take some of the more scenic routes and ride the high passes that are normally left blocked during the winter then April is probably too early. It varies year on year depending on how much snowfall there has been but it's rare to see many of the high passes in our area of the French Alps open before the middle / end of May.

This is the best page showning when the passes are open or closed
ALPENPORTAL | Straßenbericht Alpenpässe

And this link goes to another page with waypoints and other information on passes in Europe
Alpenpässe, Schotterpisten und andere Ziele (nicht nur) für Motorradfahrer - Alpen-Motorrad-Guide

-Juuso-

I was near Stelvio in early May this year, and it was still blocked; I found a webcam which showed rather large amounts of snow across the road.

I was able to re-route via Tonale and passo de Aprica (?), but I think that the higher passes I think are closed until late May.

I used to visit Innertkirchen every June, (around 2004 - 2008) at the bottom of Grimsel and Susten passes.
Those two usually opened around end of 1st week of June. Usually Susten before Grimsel.

A fixed date is never set, the road opens when an inspection deems it safe.

One year for Grimsel they said "tomorrow!"
But when tomorrow came, they found avalanches posed a danger.
I think it was another 2 days.

It's not only the road being clear, but no avalanche danger as well.
You can find webcams sited in Innertkirchen and up on Susten, on google I should think.

If you arrive in Innertkirchen and have to wait, well, I think it's a very nice place to do so. In that there's not a lot there, a few hotels, Post Office and a couple of grocery stores.
Plus plenty of alpine countryside all around.
The alpine meadows going up towards Engstlenalp are wonderful.
And Innertkirchen is a 'bikers welcome' town. One hotel is called 'Bikers Hotel'.
All very welcoming.