Snow is ever present in the UK in most years though you have to look hard to find it in high summer.

A dedicated group of enthusiasts, led by Iain Cameron, chart and catalogue these snow patches – many of which are hidden or only seen as distant white dots during Scottish Highland walks.

Responding to an appeal in September I met up with Iain and other volunteers to chart the patches in Observatory Gully on Ben Nevis, the UK’s tallest mountain.

Our route up in the shadow of the magnificent north face of the Ben was a warm one; to our left a procession of ant-like figures were tracking the CMD arrete route to the summit, walkers making the most of the amazing weather.

Out of the sunshine it was noticeably colder in Observatory Gully; being north facing it sees very little of the sun even in mid June, slowing down the rate of melt of the snow which can be tens of feet thick by the end of the snowfall season. Being encased in snow for so long obviously has a chilling effect on the rock.

The walk up on the scree was hard work and I was surprised to see so many debris including parts of large parts of old galvanised chimney cowls, the legacy of the observatory that once sat proudly on top of the Ben. Not many people trek this way, being a bit of a cul-de-sac. To reach the 1,345m summit from here requires a 200m climb at the end.

As we edged higher the dot of snow grew ever larger and is surprisingly big by the time we reached it, Iain was surprised how hard the snow was. From Iain’s reports, published in the Royal Meteorological Society’s Weather magazine, I’d been fascinated by the images of the patches with naturally carved tunnels underneath them; the light inside the ‘cave’ has a gorgeous blue hue to it.

It was at this moment that I realised that this was a large part of the draw of tracking these patches; a fascination with snow in an area where the odds of it existing all year round seem to be forever diminishing.

Seasons of melt and snowfall

Snow has only vanished entirely in Scotland six times. Three of these occasions were in 2003, 2006 and 2017.

Mean temperature statistics from Cairngorm Summit show just how much the seasons can vary. Of course mean temperature is just one variable that affects snow survival rates. For example the Western Highlands saw huge amounts of snow fall in February and March above 300m, a factor that would have helped snow survive. Though the most recent melt season was 0.4C cooler than 2019 there was probably a far greater volume of snow.

* Because of the unreliable nature of mountain-top records the Met Office data for Cairngorm Summit has some large gaps, it is only the last 5 years that have complete records . I discounted any years that were missing more than 5% of data.