How to Read a Winter Weather Forecast for the Mountains (Snowdonia Edition)
Why Winter Weather Knowledge Matters in the Mountains
Winter transforms Snowdonia (Eryri) into one of the UK’s most beautiful mountain landscapes — but it also brings fast-changing, more serious conditions. Clear valleys can hide icy ridges, sudden whiteouts, and wind speeds strong enough to knock you off your feet.
Understanding a winter mountain weather forecast isn’t just useful — it’s essential.
At Yonder Adventure Company, we check professional forecasts every day before guiding groups across Snowdonia’s peaks, using this information to choose the safest and most rewarding routes. This guide breaks down what you should be looking for.
The Best Winter Forecast Sources for Snowdonia
Not all weather forecasts are made equal. In winter, these are the most reliable for mountain conditions:
🌬️ 1. MWIS (Mountain Weather Information Service)
The gold standard for UK mountain forecasting. It focuses on wind, visibility, freezing levels, ground conditions and hazards — not just general weather.
🏔️ 2. Met Office Mountain Forecasts
Includes detailed breakdowns for Snowdonia, showing temperature ranges, summit-level conditions and hazard warnings.
📡 3. Yr Wyddfa/Snowdon Live Data
Summit temperatures, wind speeds, and webcams (when available) can help you visualise conditions.
When you book with Yonder, we’ll send you weather expectations before your day — and adjust plans if conditions change.
How to Read a Winter Mountain Forecast (Key Sections Explained)
Forecasts can look technical, but once you know what to scan for, they become extremely useful.
❄️ 1. Freezing Level
This tells you the altitude where temperatures reach 0°C. Anything above this point may be icy or snow-covered.
In Snowdonia:
Freezing level around 600–900m → Expect ice/snow on Snowdon, Glyderau, and Carneddau summits.
Freezing level around 300–500m → Snow on lower passes (e.g., Ogwen, Pen-y-Pass).
Why it matters:
This determines whether you’ll need crampons, microspikes, or an ice axe.
🌬️ 2. Wind Speed & Gusts
Wind is the number one factor that turns people back in winter.
Guidelines:
0–20mph: Comfortable
25–35mph: Challenging but manageable
35–45mph: Difficult; expect balance issues on ridges
45mph+: Dangerous; high likelihood of abandoning summits
Wind chill also rapidly reduces body temperature — something a forecast will show separately.
🌫️ 3. Visibility
In winter, visibility changes fast. A clear morning can turn into a whiteout within an hour.
Look for words like:
“Cloud on summits”
“Very poor visibility in snow”
“Frequent fog”
“Whiteout conditions possible”
Navigation becomes significantly harder in winter, especially on featureless terrain like the Carneddau Plateau.
🌨️ 4. Precipitation & Snowfall
Rain at valley level can be snow or hail higher up. Check:
Snow depth
Probability of snowfall
Timing (arrival of new fronts)
Whether snow is drifting (linked to wind direction)
New snow can hide terrain hazards, steps and drops.
🧭 5. Ground Conditions
MWIS often gives extra detail such as:
Hard, frozen ground
Ice on paths
Fresh snow cover
Wind-slab or drifting snow
These can influence route choice or whether technical equipment is needed.
🌡️ 6. Temperature & Wind Chill
Wind chill in winter can be brutal.
For example:
Summit temp: -2°C
Wind: 35mph
→ Feels like -12°C
This affects clothing choices, layering, and pace.
Putting It All Together: A Realistic Example
Forecast snapshot for Snowdon (fictional example):
Freezing level: 750m
Summit temperature: -4°C (feels like -12°C)
Winds: 40mph gusting to 55mph
Visibility: poor in snow showers
Precipitation: Snowfall above 600m
Ground: Icy paths and drifting snow
Interpretation:
High ridges like Crib Goch: unsafe
Pyg/Miner’s Track: very icy, requires crampons
Llanberis Path: safer, but still cold and exposed
Navigation: difficult in poor visibility
Best choice: Lower-level route or full postponement unless with a qualified leader
This is exactly the kind of assessment our team carries out before every guided winter day.
Why Understanding Winter Forecasts Can Save Your Day (and Your Safety)
Winter conditions often catch out walkers who rely on basic phone weather apps. These don’t account for altitude, wind chill, or terrain-specific hazards.
By learning to read proper mountain forecasts, you can:
✔ Choose safer routes
✔ Avoid dangerous snow or ice conditions
✔ Pack the right equipment
✔ Prepare mentally and physically
✔ Make better decisions on the hill
But if you’re unsure — or want to build confidence — going with a qualified Mountain Leader is the safest option.
Join a Guided Winter Walk with Yonder Adventure Company
If you want to explore Snowdonia in winter but aren’t fully confident interpreting forecasts or assessing conditions, you’re not alone — and that’s exactly why we’re here.
Our guided winter adventures include:
Full weather and conditions assessment
Expert route planning
Advice on winter kit
Training in winter navigation
Qualified Mountain Leaders who know Snowdonia inside out
👉 Book Your Guided Winter Walk
Explore Snowdonia at its most magical — safely, confidently, and with people who love these mountains as much as you do.
