Skip to content
PhotoWeather
Get started
More Fog Hunter in Snowdonia (Eryri)
Create your own alerts
Rule Fog Hunter

Cwm Idwal - Fog Hunter - Snowdonia (Eryri)

Bethesda, Wales, United Kingdom

Thick, moody fog for atmospheric forest and landscape shots

Currently

Real-time conditions
Fog Probability
0%
Dewpoint Spread6.0°C
Visibility24134 (Clear)
Relative Humidity66%
Wind Speed1.9m/s (calm conditions)

Upcoming Opportunities

When all conditions match, PhotoWeather marks an opportunity window.

Times shown in Europe/London
fog weather icon
Next opportunity
Dense Fog at Dusk
Cwm Idwal
Fri, May 22 · 22:00–23:00 · 1h window
Medium confidence
65%
🌫️Fog Probability100%
Dewpoint Spread: 0.1°C
Visibility: 113 (Dense fog)
Relative Humidity: 99%
Wind Speed: 2.5m/s (calm conditions)
fog weather icon
Dense Fog
Cwm Idwal
Fri, May 22 · 23:00–02:00
🌫️Fog Probability:86-100%
High

What this forecast looks for

Plain-language explanation from the rule

This forecast tracks when valley inversions and mountain mist create atmospheric conditions for photography in Snowdonia's glacial valleys. We monitor temperature inversions, humidity patterns, and wind conditions to predict optimal fog photography opportunities.

Snowdonia's deep glacial valleys—Nant Gwynant, Llanberis Pass, and Ogwen Valley—act as natural fog bowls where cold air settles overnight, creating spectacular valley inversions with mountain peaks rising through cloud seas. The region's high rainfall and numerous lakes add moisture to the atmosphere, producing frequent mist conditions that transform slate landscapes and mountain tarns into ethereal scenes.

What makes Snowdonia fog photography distinctive:

  • Valley inversions - Nant Gwynant and Ogwen Valley trap cold air, creating cloud seas with peaks emerging above
  • Lake mist - Llyn Padarn and Llyn Ogwen generate morning mist that drifts across mirror-still water
  • Slate atmosphere - Historic slate quarries at Llanberis create moody industrial landscapes in fog
  • Glacial cwms - Cwm Idwal's enclosed cirque traps mist, creating atmospheric waterfall scenes at Devil's Kitchen

The most reliable fog conditions occur during settled high-pressure periods in autumn and winter (September-February) when clear skies allow overnight cooling to create temperature inversions. Nant Gwynant valley is particularly prone to inversions—position yourself at higher viewpoints like Pen-y-Gwryd or along the A498 to capture peaks rising through cloud. Llyn Padarn generates morning mist that drifts past Dolbadarn Castle's tower, creating atmospheric castle scenes. Cwm Idwal's enclosed glacial bowl traps mist against the dramatic headwall of Devil's Kitchen. The timing is critical—arrive before dawn as mist typically burns off within an hour or two of sunrise. Wales's wet climate means fog is common, but our forecast identifies the photogenic conditions when visibility is just right—not too thick to lose definition, not too thin to lack atmosphere.

Create your own Fog Hunter alerts

Get notified when these conditions match at your own locations.

Get this template

72-hour requirements breakdown

What passed or failed, hour by hour
0matching hours in the next 95 hours
AND logic: all conditions required
Meets requirement
Misses requirement
Time
Europe/London
Fog Probability
≥ 75.0%
Sun, May 17
15:000%
16:000%
17:000%
18:000%
19:000%
20:000%
21:000%
22:000%
23:000%
Mon, May 18
24:000%
01:000%
02:000%
03:000%
04:000%
05:000%
06:000%
07:000%
08:000%
09:000%
10:000%
11:000%
12:000%
13:000%
14:000%
15:000%
16:000%
17:000%
18:000%
19:000%
20:000%
21:000%
22:000%
23:000%
Tue, May 19
24:000%
01:000%
02:000%
03:000%
04:000%
05:000%
06:000%
07:000%
08:000%
09:000%
10:000%
11:000%
12:000%
13:000%
14:000%
15:000%
16:000%
17:000%
18:000%
19:000%
20:000%
21:000%
22:000%
23:000%
Wed, May 20
24:000%
01:000%
02:000%
03:000%
04:000%
05:000%
06:000%
07:000%
08:000%
09:000%
10:000%
11:000%
12:000%
13:000%
14:000%
15:000%
16:000%
17:000%
18:000%
19:000%
20:000%
21:000%
22:000%
23:000%
Thu, May 21
24:000%
01:000%
02:000%
03:000%
04:0033%
05:000%
06:000%
07:000%
08:000%
09:000%
10:000%
11:000%
12:000%
13:000%
How to read: colored cells show whether each predicate requirement is met; highlighted rows mean the full rule matched (an opportunity).

What does Fog Probability mean?

Inputs that drive the score

This derived score summarizes multiple raw weather signals. The table below shows the supporting inputs hour by hour, so you can see what's pushing the score up or down.

Time
Europe/London
Clear Sky Probability (Ensemble)
%
Dew Point
°C
Rainfall
mm
Relative Humidity
%
Snowfall
cm
Solar Elevation
°
Temperature
°C
Total Precipitation
mm
Vapor Pressure Deficit
kPa
Visibility
m
Wind Gusts
m/s
Wind Speed
m/s
Mon, May 18 Sunrise 05:13 Sunset 21:13
15:00
3% 6°C 0mm 66% 0cm 51° 12°C 0mm 0.47kPa 24134m 3.3m/s 1.9m/s
16:00
4% 6.5°C 0.01mm 68% 0cm 44° 12°C 0mm 0.45kPa 24134m 2.8m/s 1.4m/s
17:00
3% 7.2°C 0mm 73% 0cm 35° 12°C 0.13mm 0.38kPa 22468m 3.3m/s 1.8m/s
18:00
1% 6.9°C 0mm 72% 0cm 26° 12°C 0.25mm 0.38kPa 24134m 4.4m/s 2.1m/s
19:00
0% 7.1°C 0mm 74% 0cm 18° 11°C 0.31mm 0.35kPa 24095m 4.9m/s 2.8m/s
20:00
0% 7.2°C 0mm 78% 0cm 9° 11°C 0mm 0.29kPa 24135m 3.9m/s 2.1m/s
21:00
0% 7.2°C 0mm 80% 0cm 1.2° 11°C 0.06mm 0.26kPa 24135m 3.4m/s 2.5m/s
22:00 ☾
0% 7.5°C 0.04mm 83% 0cm -6.1° 10°C 0.13mm 0.21kPa 24135m 4.1m/s 3m/s
23:00 ☾
0% 7.1°C 0.15mm 82% 0cm -12° 10°C 0.19mm 0.23kPa 24134m 5m/s 3.2m/s
Tue, May 19 Sunrise 05:13 Sunset 21:13
24:00 ☾
0% 7.1°C 0.06mm 83% 0cm -15° 9.9°C 0.31mm 0.21kPa 24134m 5.4m/s 3.8m/s
01:00 ☾
0% 7.2°C 0.02mm 84% 0cm -17° 9.9°C 0.38mm 0.2kPa 24134m 5.7m/s 4.1m/s
02:00 ☾
0% 7.5°C 0.06mm 85% 0cm -16° 9.9°C 0.06mm 0.18kPa 24134m 6.1m/s 4.4m/s
03:00 ☾
0% 7.8°C 0.55mm 88% 0cm -13° 9.6°C 0.5mm 0.14kPa 15026m 6.9m/s 4.6m/s
04:00 ☾
0% 8.1°C 0.72mm 90% 0cm -8.6° 9.6°C 1mm 0.12kPa 16754m 6.4m/s 4.4m/s
05:00 ☾
0% 8.4°C 0.38mm 91% 0cm -2° 9.8°C 1.8mm 0.11kPa 16370m 6.3m/s 4.4m/s
06:00
0% 8.6°C 0.12mm 92% 0cm 5.6° 9.9°C 2.1mm 0.1kPa 22429m 5.7m/s 3.7m/s
07:00
0% 9°C 0mm 91% 0cm 14° 10°C 2.2mm 0.11kPa 24134m 7.5m/s 4.7m/s
08:00
0% 9.6°C 0.01mm 88% 0cm 23° 11°C 0.06mm 0.16kPa 24134m 7.3m/s 4.3m/s
09:00
0% 9.6°C 0.4mm 89% 0cm 32° 11°C 0.44mm 0.14kPa 15306m 5.9m/s 3.2m/s
10:00
0% 9.7°C 1.2mm 92% 0cm 40° 11°C 1.3mm 0.1kPa 8394m 5.4m/s 2.8m/s
11:00
0% 9.9°C 0.23mm 94% 0cm 48° 11°C 2.3mm 0.08kPa 2386m 6.4m/s 3.2m/s
12:00
0% 10°C 0mm 89% 0cm 54° 12°C 2.8mm 0.16kPa 11498m 8.5m/s 5.1m/s
13:00
0% 9.8°C 0mm 87% 0cm 57° 12°C 3.4mm 0.17kPa 22746m 10m/s 6m/s
14:00
2% 9°C 0mm 81% 0cm 55° 12°C 0.13mm 0.28kPa 23984m 13m/s 7.9m/s
15:00
3% 9.3°C 0mm 82% 0cm 51° 12°C 0.31mm 0.25kPa 23510m 13m/s 8.4m/s
16:00
5% 9.3°C 0mm 83% 0cm 44° 12°C 0.38mm 0.23kPa 24134m 14m/s 8.3m/s
17:00
4% 9.4°C 0mm 84% 0cm 36° 12°C 0.56mm 0.22kPa 24135m 15m/s 8.5m/s
18:00
3% 9.4°C 0mm 87% 0cm 27° 11°C 0.69mm 0.17kPa 24134m 16m/s 8.8m/s
19:00
2% 9.3°C 0.01mm 88% 0cm 18° 11°C 0.88mm 0.15kPa 24135m 17m/s 9.7m/s
20:00
1% 9.1°C 0.24mm 89% 0cm 9.1° 11°C 0.13mm 0.15kPa 19987m 17m/s 9.5m/s
21:00
1% 9°C 0.3mm 90% 0cm 1.4° 11°C 0.63mm 0.13kPa 5278m 17m/s 9.7m/s
22:00 ☾
0% 9°C 0.07mm 89% 0cm -5.9° 11°C 0.81mm 0.14kPa 6993m 16m/s 9.9m/s
23:00 ☾
0% 8.7°C 0.11mm 88% 0cm -11° 11°C 0.94mm 0.15kPa 24135m 16m/s 9.9m/s
Wed, May 20 Sunrise 05:11 Sunset 21:14
24:00 ☾
0% 8.9°C 0.27mm 90% 0cm -15° 10°C 1.4mm 0.13kPa 24134m 15m/s 9.9m/s
01:00 ☾
0% 8.8°C 0mm 89% 0cm -17° 11°C 1.5mm 0.15kPa 24134m 15m/s 9.4m/s
02:00 ☾
0% 8.6°C 0mm 88% 0cm -16° 11°C 0mm 0.15kPa 24135m 15m/s 8.7m/s
03:00 ☾
0% 8.8°C 0mm 89% 0cm -13° 11°C 0.06mm 0.14kPa 24135m 13m/s 7.6m/s
04:00 ☾
0% 9.1°C 0mm 90% 0cm -8.4° 11°C 0.06mm 0.13kPa 24135m 13m/s 7.4m/s
05:00 ☾
0% 9.1°C 0mm 89% 0cm -1.8° 11°C 0.19mm 0.14kPa 24135m 13m/s 7.7m/s
06:00
0% 8.7°C 0mm 89% 0cm 5.8° 11°C 0.19mm 0.15kPa 24135m 12m/s 7.2m/s
07:00
0% 8.9°C 0mm 89% 0cm 14° 11°C 0.25mm 0.14kPa 24134m 12m/s 7.1m/s
08:00
0% 8.8°C 0mm 86% 0cm 23° 11°C 0mm 0.19kPa 24134m 12m/s 7.7m/s
09:00
0% 9.6°C 0mm 87% 0cm 32° 12°C 0.06mm 0.17kPa 24134m 13m/s 8.7m/s
10:00
0% 9.2°C 0mm 83% 0cm 41° 12°C 0.06mm 0.24kPa 24135m 14m/s 9.6m/s
11:00
0% 9.8°C 0mm 83% 0cm 48° 13°C 0.13mm 0.24kPa 24135m 16m/s 11m/s
12:00
0% 11°C 0mm 88% 0cm 54° 13°C 0.19mm 0.18kPa 24135m 16m/s 11m/s
13:00
0% 11°C 0mm 88% 0cm 57° 13°C 0.25mm 0.18kPa 24134m 16m/s 11m/s
14:00
2% 11°C 0.01mm 84% 0cm 56° 13°C 0mm 0.24kPa 24135m 15m/s 10m/s
15:00
4% 11°C 0mm 86% 0cm 51° 13°C 0mm 0.22kPa 24135m 14m/s 9m/s
16:00
6% 10°C 0mm 80% 0cm 44° 14°C 0mm 0.32kPa 24134m 13m/s 8.8m/s
17:00
5% 10°C 0mm 80% 0cm 36° 14°C 0mm 0.31kPa 24135m 13m/s 8.2m/s
18:00
4% 10°C 0mm 82% 0cm 27° 13°C 0.06mm 0.28kPa 24135m 12m/s 8m/s
19:00
3% 10°C 0mm 82% 0cm 18° 13°C 0.06mm 0.27kPa 24134m 12m/s 7.5m/s
20:00
3% 10°C 0.21mm 88% 0cm 9.3° 12°C 0.21mm 0.18kPa 16211m 13m/s 6.9m/s
21:00
4% 10°C 0.42mm 93% 0cm 1.6° 11°C 0.35mm 0.09kPa 8288m 13m/s 6.4m/s
22:00 ☾
4% 10°C 0.63mm 98% 0cm -5.7° 11°C 0.5mm 0.02kPa 364m 14m/s 5.8m/s
23:00 ☾
3% 11°C 0.44mm 98% 0cm -11° 11°C 0.6mm 0.02kPa 774m 14m/s 5.9m/s
Thu, May 21 Sunrise 05:10 Sunset 21:16
24:00 ☾
1% 11°C 0.24mm 98% 0cm -15° 11°C 0.71mm 0.02kPa 1184m 13m/s 5.9m/s
01:00 ☾
0% 11°C 0.05mm 98% 0cm -17° 11°C 0.81mm 0.02kPa 1594m 13m/s 6m/s
02:00 ☾
0% 11°C 0.03mm 97% 0cm -16° 12°C 0.58mm 0.04kPa 9108m 13m/s 5.8m/s
03:00 ☾
1% 11°C 0.02mm 96% 0cm -13° 12°C 0.35mm 0.05kPa 16621m 12m/s 5.6m/s
04:00 ☾
1% 11°C 0mm 95% 0cm -8.2° 12°C 0.13mm 0.07kPa 24135m 12m/s 5.5m/s
05:00 ☾
1% 12°C 0mm 89% 0cm -1.6° 13°C 0.13mm 0.17kPa 24135m 11m/s 5.7m/s
06:00
0% 12°C 0mm 82% 0cm 5.9° 14°C 0.13mm 0.29kPa 24135m 11m/s 6m/s
07:00
0% 11°C 0mm 76% 0cm 14° 16°C 0.13mm 0.43kPa 24135m 10m/s 6.2m/s
08:00
1% 11°C 0mm 75% 0cm 23° 16°C 0.08mm 0.44kPa 24135m 10m/s 5.9m/s
09:00
3% 11°C 0mm 74% 0cm 32° 16°C 0.04mm 0.46kPa 24135m 10m/s 5.7m/s
10:00
4% 11°C 0mm 74% 0cm 41° 16°C 0mm 0.48kPa 24135m 10m/s 5.4m/s
11:00
4% 12°C 0mm 76% 0cm 48° 16°C 0mm 0.44kPa 24135m 8.5m/s 4.6m/s
12:00
4% 12°C 0mm 78% 0cm 54° 16°C 0mm 0.39kPa 24135m 7.1m/s 3.7m/s
13:00
4% 12°C 0mm 80% 0cm 57° 16°C 0mm 0.35kPa 24135m 5.6m/s 2.9m/s
14:00
8% 12°C 0mm 83% 0cm 56° 14°C 0mm 0.28kPa 24135m 4.4m/s 2.6m/s
How to read: these inputs help produce the derived score; they are not requirements by themselves.

Get Notified of Opportunities

Create your own custom alerts for this location and more.

Create Free Account