Mountain weather
Eryri / Snowdonia Mountain weather forecast table
Confidence
High confidence for an unsettled and changeable period of weather. Lower for rain or snow detail so please keep updated on the forecast.
Mountain weather hazards
Hazards apply at or above 300m, reflecting the more severe conditions which can occur at altitude.
Gales
Gale force winds (gusts over 50mph) make walking difficult and strenuous with a potential to be blown over by gusts. There is often a marked increase in winds through cols or on exposed ridges and summits. Distances can take longer to cover and compass bearings become harder to follow accurately.
Severe Chill Effect
Wind significantly lowers the ‘feels-like’ temperature relative to the actual temperature, with even moderate winds significantly adding to the chilling effect. Strong winds can result in a severe and debilitating wind chill many degrees below the actual temperature. This effect will be enhanced in rain or wet snow. Without protection, prolonged exposure could result in frost nip or frostbite on exposed parts of the body and/or hypothermia.
Poor Visibility
Poor visibility presents challenging route finding conditions. Visibility could be significantly less than 50 metres in all directions with few or no visual references, especially on featureless moors or plateaux. Distances become hard to judge and cliff or cornice edges can be difficult to recognise. These conditions require good navigational skills. There is a risk of white-out conditions when mist or fog is combined with extensive snow cover.
Heavy Persistent Rain
Heavy and persistent rain can lead to drenched clothing and footwear with waterproofs often becoming soaked through, especially if accompanied by strong winds. This can lead to significant loss of body heat and an increased likelihood of hypothermia. Terrain may turn increasingly boggy underfoot while streams can flood and become impassable. There may also be a risk of flooding in valleys or glens. If there is snow cover, a heightened avalanche hazard is possible and avalanche reports should be consulted where available.
Blizzards
Blizzards and whiteouts present challenging and serious conditions due to a combination of falling or blowing snow, strong winds and cold temperatures. They can be highly disorientating, often resulting in near-zero visibility with limited or no visual references and no distinction between ground and sky. Cliff edges and cornices may not be apparent, even close up. These conditions require very good navigational skills.
Heavy Persistent Snow
Heavy snow can lead to rapid changes in underfoot conditions and paths may become treacherous or hidden. It also brings very poor visibility and often makes navigation much more challenging. When deep snow accumulates progress is often time consuming and strenuous, significantly affecting the distance one can travel on foot. Deep drifts can develop if snow is combined with strong winds. A heightened avalanche risk is possible and avalanche reports should be consulted where available.
Storm Force Winds
Storm force winds (gusts over 70mph) make walking very strenuous with any mobility virtually impossible over exposed ground. Where these conditions occur there is a high risk of being blown over and even standing may be impossible at times with a risk of being blown off one’s feet. Basic tasks such as using a map, eating, putting on extra clothing or communication become extremely difficult away from any shelter.
Thunderstorms
Lightning is a significant mountain hazard which can result in serious injury or death. Mountain terrain often leaves one highly exposed to lightning strikes. Hail may give unpleasant conditions with torrential rain and localised flash flooding also possible, mainly in Summer months.
Mountain weather forecast
Mostly dry morning. Rain, sleet and summit snow arriving with very strong winds in afternoon.
| Time | 06:00 | 09:00 | 12:00 | 15:00 | 18:00 | 21:00 |
|---|---|---|---|---|---|---|
Weather (at 800m) |
|
|
|
|
|
|
Chance of precipitation (at 800m) |
30% | 10% | 50% | >95% | >95% | 80% |
Wind direction and speed (mph)
Altitude above mean sea level
| Time | 06:00 | 09:00 | 12:00 | 15:00 | 18:00 | 21:00 |
|---|---|---|---|---|---|---|
| 900m |
S
22
|
S
34
|
S
48
|
SE
53
|
S
49
|
SW
40
|
| 600m |
S
18
|
S
25
|
S
36
|
SE
40
|
S
34
|
S
29
|
| 300m |
S
12
|
S
16
|
S
25
|
SE
30
|
SE
24
|
S
18
|
| Valley |
S
12
|
S
17
|
S
25
|
SE
30
|
SE
25
|
S
17
|
Wind gust (mph)
Altitude above mean sea level
| Time | 06:00 | 09:00 | 12:00 | 15:00 | 18:00 | 21:00 |
|---|---|---|---|---|---|---|
| 900m | 27 | 41 | 59 | 66 | 60 | 50 |
| 600m | 22 | 32 | 46 | 52 | 45 | 38 |
| 300m | 21 | 29 | 42 | 49 | 41 | 33 |
| Valley | 21 | 29 | 42 | 50 | 42 | 31 |
Altitude above mean sea level
| Time | 06:00 | 09:00 | 12:00 | 15:00 | 18:00 | 21:00 |
|---|---|---|---|---|---|---|
| 900m |
1°
|
1°
|
1°
|
1°
|
2°
|
4°
|
| 600m |
3°
|
3°
|
3°
|
3°
|
4°
|
6°
|
| 300m |
5°
|
5°
|
6°
|
5°
|
6°
|
8°
|
| Valley |
6°
|
6°
|
7°
|
7°
|
8°
|
9°
|
| Freezing Level |
1,000m
|
1,000m
|
1,000m
|
1,600m
|
1,700m
|
1,500m
|
Altitude above mean sea level
| Time | 06:00 | 09:00 | 12:00 | 15:00 | 18:00 | 21:00 |
|---|---|---|---|---|---|---|
| 900m |
-5°
|
-7°
|
-9°
|
-9°
|
-6°
|
-4°
|
| 600m |
-2°
|
-3°
|
-4°
|
-5°
|
-3°
|
0°
|
| 300m |
1°
|
1°
|
0°
|
-1°
|
1°
|
4°
|
| Valley |
2°
|
2°
|
2°
|
1°
|
3°
|
6°
|
Additional weather information
Meteorologist's view
Temporarily fair conditions at first but note the quick deterioration this afternoon. A severe wind chill develops, with walking becoming very difficult or dangerous on higher slopes and ridges in the severe gales or storm force winds.
Weather
Mainly dry and cloudy this morning with perhaps some bright spells but also a few early showers. Outbreaks of rain will arrive from the west late morning to early afternoon, with the rain becoming persistent and heavy at times this afternoon as severe gales or storm force winds develop over the summits. As the rain arrives and then becomes persistent there will be a couple of hours of sleet or snow above 600m, before turning to rain at all levels by this evening. Heavy showers follow this evening, with a low risk of hail and thunder.
Chance of cloud-free hill tops
70%, becoming 10% this afternoon.
Low cloud and visibility
Patchy cloud above 500m at first, this lifting this morning with mostly good visibility for a few hours. However, conditions deteriorate rapidly this afternoon with extensive cloud developing giving poor visibility above 500m.
Ground conditions
Please see - https://yrwyddfa.live/
Mountain weather information
Weather
A mixture of clear or bright intervals and rain showers, heavy at times with a small chance of hail and thunder overnight and through the morning. Showers become lighter and isolated through the afternoon, followed by a dry evening with clear spells and temperatures quickly falling.
Chance of cloud-free hill tops
30%.
Maximum wind speed expected
Southwest 30-40mph gusts 50-60mph at first.
Temperature
- At 800m Plus 4 or 5C.
- Valley Plus 7 to 9C.
- Freezing level Above summits.
Low cloud and visibility
Areas of cloud with bases 500 to 700m giving periods of very poor visibility. Good visibility on lower slopes but occasionally few km in showers.
Mountain weather information
Sun 7 Dec
Sunrise:
Sunset:
A band of rain moves northeast accompanied by strong winds. Drier and brighter conditions follow early to mid-afternoon. Freezing level above summits, falling to 1000m in the afternoon.
Mon 8 Dec
Sunrise:
Sunset:
This is likely to be a mostly bright day with possibly a few sharp showers. Strong to gale force southerly winds on the tops. Wet, stormy conditions perhaps arriving in evening. Freezing level 1000m rising above summits.
Tue 9 Dec
Sunrise:
Sunset:
A lot of uncertainty by this stage but a spell of wet and very windy conditions is likely followed by brighter weather from the southwest. Mild with freezing level above summits.
Updated at:
Summit specific forecast
Mountain summit forecast map
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Key
Mountain summits
Other points of interest
Cluster of multiple stations
The Eryri (Snowdonia) mountains are made up of 90 mountain peaks including the tallest mountain in Wales, Yr Wyddfa (Snowdon), standing at 1,085 metres.