Unfortunately, it's about more than any single factor (altitude) although that one is a significant factor.
It's reputed to be the coldest Spring in Europe in 100 years according to some recent meteo reporting.
There are a couple of links in this thread that might shed some light and they are interesting in any case>
Such as at the end of this page>
Alpenpässe, Schotterpisten und andere Ziele (nicht nur) für Motorradfahrer - Alpen-Motorrad-Guide
there is some information about that route.
But, the weather hasn't given up just yet>
Slopes open for rare June weekend
I've just read the second link above and one of the posts comes out as this in the translation>
"LGKS in May nypdcollector, 17.04.2013, 23:21
it is not really sooooo hard to read, right?
LGKS is from the 01 Open in July each year.
constantly so what are the questions to Mai?
Forget it easy. First snow still impassable, effectively and secondly prohibited. If the authorities are so nice and the road can at least free for motorcycles, then please respect but also the official closures, so we still have some of that road as long as possible."
ask of final edition raiw, 17.04.2013, 22:1
Last edited by Walkabout; 2 Jun 2013 at 00:06.