We are wondering if its foolish to book Glacier Express between Zermatt and St Moritz for in early April. How likely is it to be too cloudy to see anything that time of year?
Can you predict the weather that far in advance? I don't know anyone who can. Took it 5 years ago in the middle of January and the weather was absolutely clear. This year on the same date, it would have been impossible as the tracks were shut down due to avalanche danger and a blizzard. You go up and down and it could be into the clouds, above the clouds, or a bluebird day. Ya pays your money and ya takes your chances.
I'm just wondering about typical weather patterns. I'm from Seattle Washington in the US and I'd bet on a clear day for sight seeing in July and August but I'd not even suggest such a trip in April.
I once took a train in Switzerland (sometime between very late May and late June), and it was so rainy and foggy that you really couldn't see the scenery at all. That was an ordinary Point A-to-Point B train ride, so not as big a deal. It's a tough position to be in since, unlike the Bernina Express, it doesn't sound like there's a convenient way to cover the Glacier Express route by cobbling together a series of ordinary trains you wouldn't have to book in advance. (I haven't researched this, however; it might pay off to see what Seat61 says.)
Actually, the entire route is plied by trains that run hourly and need no reservations. You will have to change trains a few times. Brig, Andermatt, Disentis/Muster, Chur.
The Swiss transportation system's web site is:
When you type in your "From" and "To" stations (Zermatt and St. Moritz), the red box that said "Search for connection" changes to say "add via." Click on "add via" and type in one of the stations that are on the way and on the Glacier Express route (use "Andermatt"). Make sure the date is a day in the future with an early morning daytime time setting. That will give you the trains on that route that day, including the same train as the Glacier Express, to take you over the same route, but doesn't require a reservation. It leaves at 8:52 a.m. and arrives at 4:39 p.m. (=16:39) and you get to stay on the same train the whole way (no connections needed). You can buy your train ticket and hop on, spur of the moment, depending on weather.
I am also from Seattle area and in July and August you would be extremely unlucky to get bad weather. In Europe it's different. Mornings are usually clear and by afternoon clouds, thunderstorms and rain are coming. When I went for high mountains hike I always made sure I started very early in the morning.
The mountains make their own weather, mini-climates. Often quite different than that in the lowlands.