Anyone interested in winter recreation cares deeply whether they are in rain or snow, snow generally being preferred, of course. So it is important to know the current and future elevations of the snow level, the height separating snow from rain.

And there is another closely related term that is used in weather forecasts: the freezing level, the altitude at which the temperature drops to freezing.

Freezing level:  The freezing level is the elevation at which the temperature drops to 0°C.  As the snow falls from the colder upper atmosphere into the warmer air below, it often reaches a level at which temperature warms to freezing (0 degrees C), the freezing level.

Snow level: Snow levels is lower than freezing levels because snow can still fall at temperatures slightly above freezing. The elevation where the snow turns to rain is the snow level. It takes time for the snow to melt, and that is why we will often see precipitation falling as snow even when it is +1°C or +2°C (and sometimes even more) at the surface. If the snow level is above the ground, it will still be lower than the freezing level as snow often takes a few hundred metres to melt as it falls toward the ground.

Both the freezing level and snow level can change in time as precipitation falls, and the direction is usually down. The reason? Cooling due to evaporation and melting.

First, evaporation: The air below the cloud is often unsaturated, which means the relative humidity is less than 100%. As the snow falls into that layer there is evaporation (actually sublimation), which results in cooling. If the snow turns into rain there still can be evaporation and cooling. Such cooling continues until the air is saturated, and can cause the freezing and snow levels to drop quickly and substantially (hundreds to even thousands of feet).

And then there is melting: When snow falls into air warmer than freezing, it melts. But it takes energy to melt the snow, and thus as melting occurs the surrounding air cools. Heavier precipitation results in more melting and more cooling. Such cooling can occur even after evaporation has stopped (because the air becomes saturated). Melting thus causes the freezing and snow levels to fall. The good news about this: If you are up in the mountains and it starts to rain on you, there is a good chance, particularly if you are near the snow level, for the rain to turn into snow!

Ski resorts are big travel business, and in the battle for winter sport tourists, size is everything. Adding extra runs and lifts, or connecting into other areas of the mountain are all part of the alpine arms race to be the biggest and best.

Most of us on a week’s ski holiday can make do with some 80km of slopes, but as ski areas have grown and interconnected with one another over the years, you can now access vast ski regions – some so big you need never ski the same slope twice!

The biggest ski areas in Europe are mostly of interest to experienced skiers who have direct access to more challenging terrain than they’re likely to find at any standalone resort – all accessible on one ticket.

However, most of the interlinked ski areas are among the more expensive lift passes in Europe and it’s worth considering whether you’re likely to make full use of what is available. Is it good value for you?

Beginners are unlikely to get good value from one of the big area passes, but, if money is no object, then why not enjoy sampling the blue runs in different resorts?

The most popular of the interconnected ski areas are the largely lift-linked ones, where you don’t need to take off your skis to catch a bus between sectors.

Here’s the biggest and best ski areas in Europe . . .

  1. The 3 Valleys, France, 600km

Good for all abilities, snow-sure skiing, gourmet dining

Six-day adult pass: €312

The titanic 3 Vallees is the top dog, the world’s biggest ski area with 600 kilometers of runs spread between the three main resorts of Courchevel, Meribel and Val Thorens. Les 3 Valleys is a ski region of spectacular statistics as well as superb skiing with more than 2,000m of lift-served vertical. Among the big-name resorts here is Europe’s highest, Val Thorens, as well as Courchevel, home of the world’s most expensive chalet holidays and Brits favourite, Meribel.

  1. Sella Ronda, Italy, unofficially 500km

Spectacular scenery, traditional villages, easy runs

Six-day adult pass: €250

It doesn’t shout it from the rooftops, but the extended Sella Ronda region in Italy’s Dolomites could be right up there as one of the world’s biggest connected ski areas. The Sella Ronda is a celebrated circuit around the Sella massif. It’s part of the giant Dolomiti Superski region (1200km), which is always keen to promote the Sella Ronda circuit of 40km of pistes but does not make much of the fact that the Sella Ronda is a hub with valleys like Gardena, Badia and Fassa radiating off it.

  1. Les Portes Du Soleil, France & Switzerland, 650km

Cross-border skiing & choice of modern or traditional resort

Six-day adult pass: €285

The Portes du Soleil is a vast region spanning 12 resorts between Mont Blanc in France and Lake Geneva in Switzerland, although several gaps in the lift system means it trails the 3 Vallees in size despite the advertised 650 kilometers of pistes.

About a dozen villages are linked on the pass, two thirds of them in France, the others in Switzerland. The ski area includes modern, snow-sure Avoriaz, market town Morzine, family-favorite Les Gets and traditional Chatel are the big-name French resorts, while Champery stands out as a traditional village on the Swiss side.

  1. Paradiski, France, 425km

Family-friendly, good intermediate cruising, easy rail access

Six-day adult pass: €310

When the double-decker Vanoise Express cable car opened in 2003 it brought together Les Arcs and La Plagne to form a massive new interlinked area called “Paradiski” above the Tarentaise valley. Paradiski instantly became one of the world’s five biggest ski areas. There’s a mixture of traditional valley resorts and high-altitude, snow-sure purpose built centres.

Multilevel La Plagne is a beginner and intermediate heaven, while experts are served by some challenging terrain on the north-facing slopes of the Bellecote (3417 meters). Les Arcs contains various satellites named by altitude — Arc 1600, Arc 1800, Arc 2000 — with myriad runs for all levels reaching up to the Aiguille Rouge at 3,226 meters.

Peisey Vallandry, which lies in a key location between the two giant resorts, has a reputation as a Nordic ski centre close to the Vanoise national park. Located above Bourg St Maurice, the ski area can be reached by Eurostar direct from London St Pancras.

  1. Quatre Vallees Switzerland, 412km

Luxury accommodation, snow-sure skiing, awesome off-piste

Six-day adult pass: CHF 355

The 4 Vallees is Switzerland’s biggest linked ski area with jet-set favorite Verbier at its heart.
Stretching to 412 kilometers of linked runs. Verbier, the most famous member of the biggest ski area in Switzerland, is known for its exciting terrain and après-ski vibe. The area also encompasses the smaller resorts of Bruson opposite Verbier, and Nendaz, Veysonnaz, Thyon and La Tzoumaz overlooking the Rhone Valley.
The high point of the lift system is Mont Fort at 3330 meters with its far-reaching views of the Matterhorn, the Grand Combin and Mont Blanc

  1. Milky Way, France – Italy, 400km

Cross-border skiing, intermediate runs, extensive snowmaking

Six-day adult pass: €252

The ski resorts within the Milky Way, or the ‘Via Lattea’, vary from wooded, characterful Claviere to party-starting Sauze d’Oulx, with a drop into Montgenevre in France to add an international flavor. The highest lift reaches almost to the summit of Mt. Motta at 2823 meters with spectacular views above Sestriere, a fixture on the World Cup downhill circuit. The 2006 Winter Olympics brought huge lift investment on the Italian side and has led to what’s now a hi-tech area where you can zip from end to end and back within the day.

  1. Matterhorn Ski Paradise, Switzerland – Italy, 360km

Stunning views of the Matterhorn, long descents, year-round glacier skiing

Six-day adult pass: CHF 439

World-renowned Zermatt, a historic center for alpinism has 200 kilometers of trails with skiing up to the Matterhorn glacier paradise at 3,889 meters. Combined with the 160 kilometers in Italy, it makes for a vast mountain playground surrounded by some of the Alps’ highest peaks, including Monte Rosa (4634 meters), the Weisshorn (4506 meters) and the Dent Blanche (4,357 meters). Europe’s highest ski lifts take you up from Zermatt into the heart of one of the world’s biggest ski areas – crossing the Swiss border to the Italian resort of Cervinia and also including Valtournenche in the Aosta Valley. The area includes incredible runs for all standards, with the world’s second biggest lift-served vertical drop (2379m), and an epic 20km descent down to Valtournenche.

  1. Ski Arlberg, Austria, 305km

Reliable snow, off-piste adventures, vibrant apres-ski, royalty spotting

Six-day adult pass: €313

The Arlberg has long been one of world skiing’s crown jewels but took on an extra shimmer in the 2016-17 season with a new lift forming the final link in the chain to make it Austria’s largest connected area. The flash Flexenbahn gondola joins Stuben with Zurs to provide 305 kilometers of linked ski runs stretching from St. Anton, through St. Christoph, Zurs, Lech and the recently linked area of Warth-Schrocken.
The White Ring ski route and recent Run of Fame circuit are good ways to see the area, from challenging skiing and hard-partying in St. Anton

  1. Espace Killy, France, 300km

Challenging terrain, snow-sure glacier, ski-in/out accommodation

Six-day adult pass: €294

Espace Killy connects the two world-famous resorts of Val d’Isere and Tignes. Regarded by many as one of the most exciting ski areas in the world thanks to its famous steep terrain including the Olympic Downhill run on the Bellevarde face, masses of off piste opportunities and also having one of the planet’s biggest lift-served verticals of more than 2.000m.

Val d’Isere offers skiing for all abilities on its Le Fornet, Pissaillas, Solaise and Bellevarde sectors, including the challenging 1992 Olympic downhill run, “La Face”. The various hamlets that make up Tignes sit in a high treeless bowl below the Grande Motte (3656 meters) with skiing on the glacier — reached by underground funicular railway and cable car — from 3456 meters.

  1. Le Grand Massif, France, 265km

Family friendly, deep snow, easy access from Geneva

Six-day adult pass: €230

The Grand Massif is one of the closest ski areas to Geneva and has a reputation for excellent snow conditions, all season long, thanks to its proximity to Mont Blanc. The area is centred on the modern resort of Flaine, surrounded by small traditional villages with long pistes, some up to 13km in length.

  1. Le Grand Serre Chevalier, France, 250km

Sunny skiing, lowest prices of the big areas, relaxed atmosphere

Six-day adult pass: €249

The leading resort in the Southern Alps, Serre Chevalier is made up of 13 villages (three connected to the ski area) that are spread over 6km of the Guisane Valley floor from the old town of Briançon, the highest town in Europe. The area was created when Briançon was connected by a six-seater lift to the rest of the network in 1989.

  1. Alpe d’Huez and Les Deux Alpes, France, 475km

Short transfer from Grenoble, purpose-built convenience, runs for all standards, glacier skiing

Six-day adult pass: ?

Not quite a behemoth yet, but the proposed link between Alpe d’Huez and Les Deux Alpes will create a ski area of about 475 kilometers when it’s completed by 2021. The two resorts announced a 350 million euro investment over the next five years, which will include an 18-minute gondola spanning a deep valley between the two areas.

Purpose-built Alpe’d’Huez sits at 1860 meters in a south-facing bowl with 250 kilometers of varied pistes, including the world’s longest black run, the 16-kilometer Sarenne descent. Les Deux Alpes climbs a ridge radiating from La Meije (3864 meters) with skiing on the glacier at 3568 meters virtually all year round.