Before you ever head into the hills or the mountains, your last and final check should be to check the weather. Knowing what weather is forecast gives us information, and with this information you are in a better place to make good decisions. Decisions about suitability of route choice, crag venue, what kit to pack and so on are all affected by the mountain weather to come.
Some basics to understanding our mountain weather
Have you ever wondered why America and Russia (on the same lines of latitude as us here in the UK) seem to have massively colder winters and massively hotter summers than us? Here’s why …
Consider placing 1Kg of soil and the same mass of water into an oven. You turn the heat right up. Which of these will reach boiling point first and which will cool fastest?
The answer is that the soil will heat up fastest and then will cool quickest. Knowing this helps us to understand some basics around the UK weather. America and Russia are big land masses which quickly gain heat in the summer and lose it fast in the winter.
The UK on the other hand is a small island (of soil) surrounded by a whole load of water. We have the Atlantic Ocean on our western shore and then not so far away, Europe to the east. The Atlantic takes all summer to heat up and then takes all winter to cool down again.
This in turn means that during the summer months the sea around us is slowly warming up. Then by around autumn, it will be at its peak temperature before it slowly loses heat through the winter months. Most of our weather comes from the south-west and also from the warm water called the Gulf Stream (which originates in the Gulf of Mexico). Similarly, during the summer, the ground quickly warms up, and then as the weather gets cooler the ground begins to haemorrhage heat too.
The effect of all this is that during winter we have warm seas around us making our temperatures higher relative to say the USA and Russia. In turn we have less snow and less harsh winter conditions. During the summer months that same water which has chilled during the winter months now acts as a cooling influence allowing our summers to be cooler than say the USA and Russia.
More on the Gulf Stream … Sometimes factors skew the normal path of the Gulf Stream so that it bends further to the south during the winter months and so misses the UK altogether. When this occurs it gets cold really fast and we can expect a good dump of snow!
Where the weather comes from tells us lots …
Ok so knowing the above gives us a brief idea of what to expect if we know where the weather is coming from … We know that to the north of the UK is the Arctic and to the south is Africa. So, if we have weather coming from the north we expect it to be cold and dry. From the south, warm and dry. If it comes from the west it will be wet. From the north-west, cold and wet and so on. If it’s summer and the weather comes from the east it will be hot and dry, and in the winter cold and dry.
As a rock climber I also use this information to help guide me and to get the best from a day on the crag on wet-weather days. I know that as the winds from the west push the air upwards over the hills and mountains that the air will no longer hold any moisture and it will fall as rain. This is because as the moist air is pushed uphill and as the air pressure decreases, clouds will form and the rain is released.
Hence, I know that often when it’s raining in the Peak District, that it could well be dry further to the east, closer to Sheffield. Similarly I know that if it is raining in the mountains of Snowdonia it could well be dry at Tremadog on the coast – since these crags lie much lower down and the rain is yet to be released.
Wind speed and direction
Knowing the wind speed and direction is vital information to have before heading out to the mountains for the day. On a dry day we might not want to choose to traverse precipitous ridge lines if we know that the wind speeds will be in excess of 30mph and perpendicular to our direction of travel for example. During the winter months wind will blow snow onto the lee slopes of the hills: knowing where the prevailing winds have been blowing will tell us which slopes may have a build up of snow (avalanche risk) and which are scoured of snow. (Be avalanche aware – learn more here).
Out mountain biking I look at the wind speed and direction and sometimes decide which way I will head round a route, so that the wind pushes me up the hills!
If you have no concept of what different wind speeds will feel like try putting your hand out of the window the next time you’re in a moving car as a passenger. How much resistance is there at 30mph? And at 50mph!?
When planning a day out in the hills it also worth getting a dedicated mountain forecast that will give you information in greater detail including temperature changes due to height and/or wind speed. Knowing for example that above a certain altitude that temperatures could be reliably below zero will tell you not to go too high without be adequately equipped with crampons for example.
Mountain Weather on the Web
Some excellent online resources for getting an accurate forecast for the UK and worldwide are now widely available. For me when I look at a weather forecast i try and make my research as localised as possible. For example if I’m heading to the Lake District, I don’t just look at the forecast for the Lakes, but specifically for Scafell Pike since I know that, that as the highest peak, will be getting it worst that day.
Mountaincraft and Leadership, fourth edition Paperback by Eric Langmuir
Hill Walking: The Official Handbook of the Mountain Leader and Walking Group Leader Schemes Paperback by Steve Long
Chasing The Ephemeral – be in the right place at the right time for your next Scottish winter adventure
A Stitch in Time – preparing for a rainy day in the hills
Ten ways to be better at map reading
Five Top Tips to Help You Pass ML Assessment
Free training resources for navigation practice
Grade 1 Scrambles for Aspirant Mountain Leaders
Map and Compass beats a GPS Device Every Time. Here’s Why
Training for challenge walks – guide to get fit
Outdoor First Aid – Five items of essential first aid kit for the outdoors
What to do in an Emergency Outdoors