There has been many questions about how late the snow pack remains, so I've edited a past comment of mine focused on the Black Tusk to help provide some general context.
Snow changes a lot with the seasons. Some years we get meters of snow, or week long high elevation rain that washes things away quickly. Other years the snow remains. So this is all general in terms of coverage. But how the snow itself changes is much more consistent, and very important to consider when planning trips.
Late Summer ( August to September)
By late July and August we have hardly any snow anywhere in this area. You'll find isolated patches in North facing gulleys and bowls. Glaciers are often fully clear. Snowfall is rare. Small "isothermic"
Fall (Late September to November)
Come September we will see the odd flurry of snow in the alpine in the Coquihalla, and North of Vancouver. Often it will snow as much as a foot. In the trees the branches tend to catch the snow, and you get little on the ground. Rocks, with their dark colours tend to heat quickly, and so the snow melts rapidly. Patches of snow can remain on grassy or muddy sections. Into October these snow bursts tend to melt as the daytime temperatures are still warm and the days longer. By late October it is a good idea to expect frozen trails or patches of icy snow. When there is a dusting its good to watch out for rocks, especially in talus fields, as they can be hidden, slippery and hide ankle snapping gaps between them. Trekking poles are quite handy for testing, and knocking snow away.
Come November the snows start in earnest. Generally for the first few weeks the snows are maximum knee deep, but unconsolidated (loose). So when you go to put a foot or snowshoe down you often are finding rocks and undergrowth just beneath the surface. It makes for tricky walking off trail , and popular trails like Dog mountain or Hollyburn will be icy and or muddy or both. Glaciers are at their most dangerous as snowbridges start to form, but are far from being consolidated. In the trees we rarely see snow deeper than foot until December.
Winter (November to March)
As the snows falls through December we get our winter snowpack. Avalanche danger increases, with terrain between 25˚ - 45˚ the riskiest. Even in the trees avalanches can occur from storm slabs, recent snow that bonds into larger layers of snow. While not that risky in the trees, they can still carry walkers into treewells or gullys (terrain traps in avalanche parlance). If you brush you hand on a small steep pile of fresh snow, and more than a foot of snow slides away, that is a good indication you should avoid anything steeper than 20˚
The snow is weather dependent. On long periods of clear days it can be crusty, and icy making travel with microspikes easy. But when it dumps powder it can be up to a meter of loose wet snow. Freezing level elevation have been fluctuating more in recent years, so conditions change rapidly. Towards whistler things are more consistent with powder snow being the norm most of the time.
Snowshoes are generally necessary on most trails that don't get compacted by very regular walkers. On these compacted trails microspikes are preferred since they are lighter, and less bothersome on punched out and rough snow. Powder snow is generally best travelled with snowshoes , or backcountry skis/boards for better efficiency.
The North Shore tends to get very inconsistent temperatures leading to rapid changes in snow conditions. We do get the odd clear spell, sometimes with warmth. This melts the snow which then freezes at night. This creates a solid crust. Wind blown slopes above the trees also tend to develop crusts. Thin crusts can be punched through with only a little extra effort. Thick crusts can be supportive, meaning you can walk on them, but tend to be variable. Injuries are common from walkers suddenly plunging through a crust and hurting their legs or feet. Crusts also increase the risk of avalanches as they pull more snow down.
Over longer periods this consolidates the snow into an ice like hard pack generally referred to as neve. This hard pack makes for great walking, though microspikes and trekking poles are required. On steeper terrain crampons can be better as they have better steep stability, and an ice axe ( along with a helmet) is a good idea. The ice axe is primarily a balance aid, but if you slip, it can be used to arrest a fall. This technique takes practice, and should be learnt from an ACMG guide first.
Spring ( March to June)
Spring snow can be variable depending on where you go. Further past Pemberton winter conditions can last well into April. The now will often hover around 1100m this time of year. Avalanche risks start to become more a factor of time of day, but are generally more predictable.
Longer days causes a melt cycle, with soft, squishy, Slushy/ice cone like snow. By midday it warms, becoming isothermic (slushy). This can be great skiing, but this warming is a common trigger for avalanches. Overnight it freezes, and in the morning it can be hard packed, making for quick travel with traction devices or skis. This hardpack snow is called neve.
Leaving early for objectives and returning before the afternoon heat is a reliable way to reduce risk. For hikers snowshoes are preferable for slushy days, but microspikes are often needed in the early mornings to cross hardened snow fields in steep terrain. On terrain over 20 degrees crampons with their frontpoints become helpful. But these tools are dangerous to use without training as they are much more awkward than microspikes. Pant rips are guaranteed, and jabbing a spike into the back of the leg is more common than it should be.
Ski mountaineering is popular at this time of the year as avalanche conditions tend to be dictated by warmth. Glaciers are often covered completely this time of year with several meters of snow. Snow bridges tend to be especially strong in the mornings.
Late Spring/Early Summer ( May to mid July)
Snowline is variable with shaded sections in the trees or on north faces retaining snow at 1100m. By now the melt is happening rapidly, and many south facing alpine trails will be nearly snow free. Rocks melt fastest so many scrambles with snow on the approach will be clear on the more challenging sections.
Depending on the weather and snow pack a place like Black Tusk will be mostly snow free as early as the first week of July. Patches of snow might be found here and there, but not deep enough to cause significant inconvenience. Snowshoes would be only marginally helpful in the slush, while leaving early and walking on hard neve with microspikes would be far more pleasant.
Generally by mid July the snow is generally reduced to patches in the alpine. Microspikes can still be handy for crossing these sections. And the cycle starts anew.
Mountaineering is most popular through the summer as hard neve is fast and easy to travel on. The unpredictable winter snow has given way to freeze-thaw cycles which allow groups to rely on turn around times and avoiding being around melting snow in the afternoon for safety. Less skill is therefore required, but training is still highly recommended. Glaciers tend to still have descent coverage, so travelling across them roped up is a fast way to access certain peaks and routes.
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