Snowdon Weather and Conditions

Snowdon has its own microclimate. At 1,085 metres, the summit is frequently in cloud, and conditions can change rapidly. Understanding the weather is essential for a safe and enjoyable ascent of Wales's highest mountain.

Weather Forecasts

Standard weather apps are designed for lowland areas and don't accurately reflect mountain conditions. For Snowdon, use specialist mountain forecasts:

These forecasts provide summit-specific information including temperature, wind speed, wind chill, cloud base, visibility and precipitation.

Snowdon Mountain Railway Indicator

The Snowdon Mountain Railway operates from Llanberis to the summit when conditions allow. If the railway is not running to the summit due to weather, it is a good indicator that conditions on the mountain are poor. Check the railway website for current running information.

Summit vs Valley Conditions

The difference between Llanberis and the summit of Snowdon can be dramatic:

Llanberis (100m) Snowdon Summit (1,085m)
Temperature 15°C (summer typical) 8-9°C (6-7°C colder typical)
Wind Light breeze Often 20-40 mph, gusts higher
Visibility Clear Frequently in cloud
Precipitation Dry May be raining or snowing when valley is dry

As a rough guide, temperature drops approximately 1°C for every 150 metres of altitude gained. Wind chill can make it feel much colder.

Conditions by Season

Winter (December - March)

Snowdon in winter is a serious mountain. Snow and ice cover the upper paths, and the summit ridge can be dangerous in high winds.

  • Snow and ice on paths above 600m likely
  • Ice axe and crampons may be essential for upper sections
  • Daylight limited to 7-8 hours
  • Summit temperatures regularly below -5°C
  • High winds common, particularly on exposed ridges

Three Peaks Challenges do not run in winter conditions.

Spring (April - May)

A transitional period with improving conditions. Snow can persist on sheltered north-facing slopes into late spring.

  • Residual snow patches possible on upper slopes
  • Weather improving but still changeable
  • Days lengthening significantly
  • Summit temperatures typically 2-7°C

Early season Three Peaks Challenges may encounter residual snow. Check forecasts carefully.

Summer (June - August)

The most favourable conditions and the peak season for climbing Snowdon. However, the summit is frequently in cloud and conditions can change quickly.

  • Snow very unlikely
  • Longest days
  • Best chance of clear summit views
  • Summit temperatures typically 8-12°C
  • Busiest period on all routes

This is the main Three Peaks Challenge season. Even in summer, take warm and waterproof clothing.

Autumn (September - November)

Days shorten and weather becomes more unsettled. Early snow is possible from October on the highest ground.

  • Increasing chance of frost and early snow from October
  • Shorter daylight hours
  • More frequent rain and strong winds
  • Summit temperatures dropping, often below 5°C
  • Quieter on the paths

Cloud and Visibility

Like all high mountains, Snowdon attracts cloud regularly. The summit is in cloud on a significant proportion of days throughout the year. In poor visibility, navigation on the summit area requires care - multiple paths converge near the top and the terrain is rocky.

See our routes page for navigation advice.

Wind

Snowdon's ridges are particularly exposed to wind. The Pyg Track crosses exposed ground above Bwlch y Moch, and the summit ridge is unsheltered. Wind chill can make conditions feel significantly colder than the actual temperature.

Rain

North Wales receives significant rainfall, particularly on the western slopes of Eryri (Snowdonia). Rain is possible in any month and can be heavy and persistent.

Waterproof jacket and trousers are essential kit for any ascent of Snowdon.

Night Conditions

For Three Peaks Challenge participants climbing Snowdon in the early morning:

  • Temperatures will be near their lowest
  • Wind chill more significant
  • First light provides improving visibility as you climb
  • Cloud may lift in the morning, offering better summit views

As the final peak of a Three Peaks Challenge, fatigue will be a factor. Take extra care on the rocky sections of the Pyg Track.

What to Wear

Based on typical conditions, recommended clothing for a summer Three Peaks Challenge includes:

  • Moisture-wicking base layer
  • Insulating mid-layer (fleece or similar)
  • Waterproof and windproof jacket
  • Waterproof trousers
  • Warm hat and gloves (even in summer)
  • Spare warm layer

See our kit list for full equipment requirements on guided events.

Snowdon maps