Mountain weather

Mountain weather

Eryri / Snowdonia

Printable version

Confidence

Some uncertainty regarding shower details on Tuesday, notably regarding intensity and any associated thunder risk. Some uncertainty with regards timing and extent of rain moving through the area Wednesday night. Otherwise confidence fairly high, and also regarding the likelihood of temperatures starting to climb again from this weekend.

Mountain hazards

Mountain weather hazards

Hazards apply at or above 300m, reflecting the more severe conditions which can occur at altitude.

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.
Strong Sunlight
Harmful UV levels from sunlight increase with altitude giving a greater risk of sunburn and eye damage, even on some overcast days. On breezy days, the cooling effect of wind on exposed skin may disguise any feeling of sunburn until it is too late. If there is snow cover, glare increases the effect of UV rays especially on the eyes. It is advisable to wear sun block, protective clothing such as a long-sleeved top and hat and have good quality eye protection.

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.
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.
Updated: 
Mountain hazards explained

Mountain weather forecast

Mist and patchy rain giving way to heavy showers, with possible thunder. A drier evening with cloud shrouding summits.

Time
 Time
06:00
09:00
12:00
15:00
18:00
21:00
Weather
(at 800m)
 Weather symbols Light rain Heavy Rain Heavy Rain Fog Fog Fog
Chance of
precipitation
(at 800m)
 Chance of precipitation
40%
70%
90%
50%
30%
10%

Wind direction and speed

Altitude above mean sea level
Time
 Time
06:00
09:00
12:00
15:00
18:00
21:00
900m
 900m S 26mph knots
S
26mph
 S 29mph knots
S
29mph
 SW 27mph knots
SW
27mph
 SW 23mph knots
SW
23mph
 SW 16mph knots
SW
16mph
 W 14mph knots
W
14mph
600m
 600m S 20mph knots
S
20mph
 S 21mph knots
S
21mph
 SW 21mph knots
SW
21mph
 SW 18mph knots
SW
18mph
 SW 13mph knots
SW
13mph
 SW 10mph knots
SW
10mph
300m
 300m S 13mph knots
S
13mph
 S 16mph knots
S
16mph
 S 14mph knots
S
14mph
 SW 13mph knots
SW
13mph
 SW 9mph knots
SW
9mph
 SW 6mph knots
SW
6mph
Valley
 Valley S 13mph knots
S
13mph
 S 16mph knots
S
16mph
 S 14mph knots
S
14mph
 SW 12mph knots
SW
12mph
 SW 9mph knots
SW
9mph
 SW 6mph knots
SW
6mph

Wind gust

Altitude above mean sea level
Time
 Time
06:00
09:00
12:00
15:00
18:00
21:00
900m
 900m 30mph 36mph 35mph 30mph 22mph 18mph
600m
 600m 25mph 27mph 28mph 25mph 18mph 14mph
300m
 300m 22mph 27mph 25mph 22mph 16mph 13mph
Valley
 Valley 22mph 26mph 24mph 21mph 16mph 13mph

Altitude above mean sea level
Time
 Time
06:00
09:00
12:00
15:00
18:00
21:00
900m
 900m 4 degrees Celsius 5 degrees Celsius 6 degrees Celsius 6 degrees Celsius 7 degrees Celsius 7 degrees Celsius
600m
 600m 7 degrees Celsius 8 degrees Celsius 9 degrees Celsius 9 degrees Celsius 10 degrees Celsius 10 degrees Celsius
300m
 300m 11 degrees Celsius 11 degrees Celsius 12 degrees Celsius 13 degrees Celsius 13 degrees Celsius 13 degrees Celsius
Valley
 Valley 12 degrees Celsius 13 degrees Celsius 14 degrees Celsius 15 degrees Celsius 15 degrees Celsius 15 degrees Celsius
Freezing Level Freezing Level
2500m
2600m
2500m
2500m
2600m
2600m

Additional weather information

Meteorologist's view

Misty conditions at first, and fog patches during the evening are likely to give some difficult navigating conditions. There is a small risk of thunder and briefly gusty winds, accompanying the daytime showers. If the sun comes out in the afternoon UV levels are likely to be high.

Weather

Mostly cloudy with some drizzle and mist patches at first. Showery rain developing from the west during the morning. Some heavy bursts possible around the middle of the day, with the chance of thunder. Showers easing from mid-afternoon with some brighter breaks, then mostly dry in the evening with clear intervals, though some mist and fog patches also forming. Brisk south to southwesterly winds until the evening near the summits and heavy showers could give some brief gusty conditions elsewhere too during the day.

Chance of cloud-free hill tops

30% at first and as heavy showers develop during the morning/early afternoon. Increasing to around 70% mid to late afternoon, then dropping to 30% or less in the evening as cloud shrouds most summits.

Low cloud and visibility

Broken cloud bases around 600m with mist and drizzle giving some poor visibility at first especially near the summits. Moderate to poor visibility in heavy showers during the day, then improving moderate in brighter breaks later. Poor or very poor visibility in summit cloud during the evening.

Ground conditions

Please see - https://yrwyddfa.live/

Summit specific forecast

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.

Related links