Mountain weather
Snowdonia Mountain weather forecast table
Confidence
High for cool and largely unsettled conditions continuing this week. Moderate for a brief drier interlude during the middle of the week. Low for developments towards the end of the week, particularly with respect to wind strengths in association with a developing area of low pressure to the west.
Mountain weather hazards
Hazards apply at or above 300m, reflecting the more severe conditions which can occur at altitude.
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.
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.
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.
Mountain weather forecast
Sunny spells and showers. Low chance of thundery downpours.
| 06:00 | 09:00 | 12:00 | 15:00 | 18:00 | 21:00 | |
|---|---|---|---|---|---|---|
Weather (at 800m) |
|
|
|
|
|
|
Chance of precipitation (at 800m) |
20% | 20% | 40% | 40% | 20% | 10% |
Wind direction and speed (mph)
Altitude above mean sea level
| 06:00 | 09:00 | 12:00 | 15:00 | 18:00 | 21:00 | |
|---|---|---|---|---|---|---|
| 900m |
W
12
|
W
10
|
W
10
|
W
10
|
W
9
|
W
10
|
| 600m |
SW
8
|
W
9
|
W
9
|
SW
9
|
W
8
|
W
5
|
| 300m |
W
3
|
W
7
|
W
8
|
W
7
|
W
6
|
SW
3
|
| Valley |
W
4
|
W
7
|
W
7
|
W
7
|
NW
6
|
SE
2
|
Wind gust (mph)
Altitude above mean sea level
| 06:00 | 09:00 | 12:00 | 15:00 | 18:00 | 21:00 | |
|---|---|---|---|---|---|---|
| 900m | 14 | 16 | 16 | 16 | 14 | 12 |
| 600m | 10 | 14 | 15 | 14 | 12 | 7 |
| 300m | 6 | 12 | 14 | 13 | 11 | 5 |
| Valley | 7 | 12 | 13 | 13 | 11 | 5 |
Altitude above mean sea level
| 06:00 | 09:00 | 12:00 | 15:00 | 18:00 | 21:00 | |
|---|---|---|---|---|---|---|
| 900m |
3°
|
4°
|
5°
|
5°
|
4°
|
3°
|
| 600m |
5°
|
7°
|
7°
|
8°
|
6°
|
5°
|
| 300m |
7°
|
9°
|
10°
|
11°
|
9°
|
7°
|
| Valley |
8°
|
11°
|
11°
|
12°
|
10°
|
8°
|
| Freezing Level |
1,200m
|
1,200m
|
1,200m
|
1,200m
|
1,200m
|
1,200m
|
Altitude above mean sea level
| 06:00 | 09:00 | 12:00 | 15:00 | 18:00 | 21:00 | |
|---|---|---|---|---|---|---|
| 900m |
-1°
|
1°
|
1°
|
2°
|
1°
|
0°
|
| 600m |
2°
|
4°
|
5°
|
5°
|
4°
|
3°
|
| 300m |
6°
|
8°
|
8°
|
9°
|
8°
|
6°
|
| Valley |
8°
|
9°
|
10°
|
10°
|
9°
|
8°
|
Additional weather information
Meteorologist's view
Moderate UV levels during sunny spells, so sun protection is recommended. Plenty of fine conditions are expected, however be prepared to be caught in heavy showers, with the low chance of the odd tumble of thunder. Still feeling chilly on the tops, especially when caught in showers.
Weather
Often cloudy, particularly across the west of Snowdonia, with clear spells further east. During the morning showers will develop giving locally heavy bursts. There is also a small risk of hail and thunder during the afternoon. Showers should gradually die out towards the end of the afternoon with clear spells developing.
Chance of cloud-free mountain/hill tops at 800m
30% becoming 70% by the late evening as showers clear.
Visibility
Generally very good, however areas of cloud above 700m during the first part of the morning will give some temporarily poor visibilities over the tops. Slow improvements are expected from mid-morning with cloud breaking as it lifts to around 1000m, above all except the highest summits. Sudden deterioration in the visibility remain possible in any showers however, with cloud descending again to 700m.
Ground conditions
Please see - https://www.eryri.llyw.cymru/visiting/walking/ground-conditions
Mountain weather information
Weather
A cloudy start, giving way to a mixture of sunshine and showers from mid-morning. Showers quickly developing, but likely less frequent than of late. Despite this, there will remain the risk of the odd one turning heavy, with chance of thunder. Showers then fading during the afternoon
Chance of cloud-free mountain/hill tops at 800m
40% gradually rising to 80% through the day.
Maximum wind speed expected
Westerly 10-15 mph gusting 20-25 mph.
Temperature
- At 800m Plus 5 Celsius rising to Plus 7 Celsius.
- Valley Plus 7 Celsius rising to Plus 10 Celsius.
- Freezing level Above summits.
Visibility
Generally very good, however areas of cloud above 800m at first will give some temporarily poor visibilities over the summits. Improvements from mid-morning with cloud lifting to 1000m, although sudden deterioration in the visibility are possible in any showers. Visibilities improving further during the afternoon as cloud clears.
Mountain weather information
Thursday 20 May
Sunrise:
Sunset:
Cloudy with showers or longer spells of rain. This persistent on the highest hills, and obscuring views. Strong southwesterly winds, severe gales on summits and ridges. Freezing level above the summits.
Friday 21 May
Sunrise:
Sunset:
Windy, with southwesterly gales, severe on higher routes and cloud obscuring summits. Outbreaks of rain expected throughout, persistent and heavy at times. Freezing level above the tops.
Saturday 22 May
Sunrise:
Sunset:
Very windy with a mixture of sunny spells and showers. These locally heavy with hail and thunder at times. Perhaps snow on highest hills. Feeling cold, with brisk winds and freezing levels falling to 900m.
Updated at:
Mountain summits
Other points of interest
Cluster of multiple stations
The Snowdonia mountains are made up of 90 mountain peaks including the tallest mountain in Wales, Snowdon, standing at 1,085 metres.
The region can be divided into four areas with the northernmost area the most popular, including peaks such as Moel Hebog, Mynydd Mawr and the Nantlle Ridge. Many hikers tend to concentrate on Snowdon itself regarding it as a fine mountain. However it can become quite crowded, with the peak welcoming around half a million visitors every year, of which four fifths scale the peak on foot, while the remainder choose to take the train instead.
One of Snowdon’s main attractions is the sheer number and variety of paths that reach the peak. This means that everyone from mountaineering novices to climbing experts should find a way up the mountain that will suit their abilities or provide them with a sufficient test. The easiest is the Llanberis path which, being the longest, has the most shallow ascent. In contrast, the Watkin Path is widely seen as being the most demanding ascent, despite also being considered the prettiest.