Zermatt and the surrounding Valais area in Switzerland has a varied Alpine climate. But a study of weather data back to the beginning of 2011 reveals distinct seasonal patterns in terms of air pressure and precipitation.

Although these patterns can’t be relied on completely in terms of planning a wintersport or summer climbing trip awareness of the extremes can be a big help. Knowing when pressure is usually highest can help mountaineers pick that ideal week in summer to tackle 4,000m peaks. Similarly pinpointing weeks with lowest pressure and highest precipitation is the holy grail for those hunting for powder snow.

Looking at the averages pressure is highest on December 23rd. Further scrutiny of rolling weekly averages shows this date coincides with the week commencing December 20th. Anyone who’s been to the Alps at Christmas time will know that this period can be very unreliable for deep snow cover. In terms of summer pressure is highest on August 21st.

Pressure is lowest on February 2nd. Again this date often coincides when the deepest snowfalls often arrive after weeks of dry weather. Despite the unsettled pattern at this time annual precipitation is usually greatest at the end of October / beginning of November. I’ve lost count of the number of times the press interpret these early snowfalls to be a sign of a bumper season ahead only for the skies to clear at the end of November and, sometimes, the arrival of unseasonably warm weather.

The second wettest period is usually the end of April / beginning of May. Again, this past week has seen some parts of the Alps record the best snowfalls this season.