A Quick Guide to Mountain Weather
Mountain weather is notoriously volatile and difficult to predict. As conditions change rapidly and so many different environmental factors influence the weather, forecasting is a significant challenge. However, thanks to developments in technology and our understanding of mountain weather, organisations like the Mountain Weather Information Service (MWIS) now play a vital role in keeping outdoor enthusiasts safe.
Understanding mountain weather is crucial for hikers, climbers, skiers and anyone else venturing into these extraordinary landscapes. With this in mind, we put together a quick guide to help you better understand mountain weather.
Topography’s influence on weather
Two of the core reasons mountains influence weather patterns are their elevation and complex topography (i.e. the shape of the ground). When air masses move across the landscape and encounter a mountain, the air must move from a low elevation to a higher elevation. This is known as orographic lift.
As the air mass gains elevation, it cools quickly and condenses, causing cloud formation and precipitation. This most often occurs on the windward side of the mountain. The opposite happens on the leeward side (the side sheltered from the wind). The air mass warms up as it descends, resulting in drier conditions.
However, this cooling and warming process can lead to sudden changes in temperature and weather conditions on the leeward side. When this occurs, it is known as a Foehn wind. These are particularly notorious amongst climbers, as they can destabilise snow and obscure visibility.
Altitude and temperature
A general rule of thumb states that the temperature decreases with altitude at a rate of around 10℃ every 1,000 metres. We call this the lapse rate. Understanding the lapse rate is crucial for planning outdoor activities, as conditions can vary significantly between the base and the summit of a mountain.
Lower temperatures at higher altitudes can pose risks of hypothermia and frostbite, even in moderate weather conditions. That is why we always suggest you prepare and pack for the worst. Layering is an excellent way to maintain a good temperature in changing conditions, while insulated clothing makes a big difference to mountain comfort and safety.
Understanding microclimates
Mountains create microclimates due to sudden and sharp changes in altitude. For instance, valleys and sheltered areas may trap cold air, leading to temperature inversions and the accumulation of cold air pockets. Exposed peaks may be far windier than the valleys below and areas that receive no sun because they are in the shadow of a mountain will also be considerably cooler, and may even hold snow patches well into spring, or even year-round in Scotland!
Before heading into the mountains, it is always a good idea to seek advice from a trusted source and learn more about local microclimates and whether they pose any risk or danger. You are always safer when you are better informed.
Rain and snow in the mountains
At higher elevations, the colder temperatures are more likely to result in snowfall than rain. Understanding snow accumulation and potential avalanche hazards is essential for anyone entering the high mountains.
Heavy snowfall can lead to unstable snowpack and an increased risk of avalanches, especially on steep slopes. However, snowmelt is also dangerous as it destabilises the snow and makes climbing more treacherous.
Rain at high elevations also leads to greater risk. Slippery conditions, run-off, and increased river and stream flow are all things to watch out for.
The challenges of wind
The wind is a significant factor in mountain weather, especially at higher elevations. Strong winds can make temperatures feel much colder, posing a risk of hypothermia. One of the best ways to assess this risk is by paying attention to the wind chill forecasts.
Wind chill is the perceived temperature on exposed skin due to the combined effect of wind and cold temperatures. Ensuring you have adequate apparel is the best way to mitigate wind chill. Pay particular attention to your extremities – check out these guides to buying the right socks and gloves – as they are especially exposed.
For accurate wind forecasts, we recommend checking out Windy.com. It is a fantastic resource for anyone looking to stay safe in the mountains.
Storms, thunder and lightning
Thunderstorms develop quickly in mountainous areas and are a serious threat. Orographic lift means these storms are intense and often bring heavy rain, lightning and strong winds. You do not want to be on the mountainside when a storm hits, so if you have any doubt as to whether the weather will turn stormy during your hike, always play it safe.
Lightning is a significant risk in mountain thunderstorms. So if you find yourself high up in a storm, avoid exposed ridges, high points and isolated trees. If possible, seek shelter in lower-elevation areas away from the storm.
Mountain weather forecasts
Accurate weather forecasting is essential for safe mountain activities. However, predicting mountain weather can be challenging due to the complex terrain and the influence of nearby weather systems.
Check websites tailored to mountain regions for more accurate forecasts. Our favourite is MWIS, though local weather reports are also valuable. You want clear advice and guidance, so look for forecasts that communicate essential information well.
Respecting mountain weather is central to safety
Understanding mountain weather is essential to your safety and the success and enjoyment of your outdoor adventures. While poor weather may put a big dampener on your hike, it could also result in much more serious consequences and endanger your entire group.
Be prepared for rapid weather changes and always check reliable forecasts before heading out. Remember that the mountains are often home to unique microclimates, with significant variations in temperature, rain and wind patterns. Just because it is dry and warm at the bottom of the mountain does not mean that will be the case at the top.
If you stay informed, use proper gear and make educated decisions, you can enjoy the mountains safely. To learn more about mountain weather and how it is forecast, you can spend a day with MWIS, during which you will develop your understanding of mountain weather and even have a go at making a forecast yourself.
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