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Rule Fog Hunter

Sapa - Fog Hunter - Vietnam

Sa Pa, Lào Cai Province, Vietnam

Thick, moody fog for atmospheric forest and landscape shots

Currently

Real-time conditions
Dewpoint Spread0.3°C
Visibility17370 (Clear)
Relative Humidity99%
Wind Speed0.3m/s (calm conditions)

Upcoming Opportunities

When all conditions match, PhotoWeather marks an opportunity window.

Times shown in Asia/Bangkok
fog weather icon
Next opportunity
Dense Fog
Sapa
Tomorrow · 24:00–05:00 · 5h window
High confidence
89%
🌫️Fog Probability82.2-100%
Dewpoint Spread: 0.1°C
Visibility: 358 (Fog)
Relative Humidity: 99%
Wind Speed: 0.6m/s (calm conditions)
fog weather icon
Dense Fog at Sunrise
Sapa
Tomorrow · 05:00–06:00
🌫️Fog Probability:100%
High
fog weather icon
Dense Fog
Sapa
Tomorrow · 06:00–09:00
🌫️Fog Probability:94.3-100%
High
fog weather icon
Moderate Fog
Sapa
Tomorrow · 20:00–23:00
🌫️Fog Probability:82.2%
Low
fog weather icon
Dense Fog
Sapa
Fri, Jul 10 · 02:00–04:00
🌫️Fog Probability:100%
High
fog weather icon
Dense Fog
Sapa
Fri, Jul 10 · 20:00–02:00
🌫️Fog Probability:100%
High

What this forecast looks for

Plain-language explanation from the rule

This forecast predicts when temperature inversions and morning mist create atmospheric conditions across Vietnam's mountain valleys, rice terraces, and karst landscapes. We track overnight cooling, humidity, topography, and seasonal patterns to identify when fog transforms Vietnam's highland regions into ethereal scenes.

Vietnam's dramatic elevation changes—from sea level to 10,000-foot peaks—create ideal conditions for fog formation in mountain valleys. Northern highlands around Sapa and Mu Cang Chai experience frequent morning fog, particularly during the transition between dry and wet seasons. Hill stations like Da Lat maintain cooler temperatures that promote mist formation even in tropical latitudes. The limestone karsts of Ha Long Bay and Ninh Binh develop ethereal fog conditions during cooler months.

What makes Vietnam fog photography special:

  • Terraced valleys - Sapa and Mu Cang Chai rice terraces emerge layer by layer as fog burns off, creating depth and mystery
  • Karst landscapes - Ha Long Bay limestone islands pierce through low-lying fog like ancient towers floating on clouds
  • Mountain village life - Traditional H'mong and Dao villages in Sapa appear and disappear through drifting mist during morning hours
  • Highland agriculture - Da Lat's flower farms and strawberry fields gain dreamlike quality under morning fog blankets

Sapa experiences its most reliable fog from September through November and March through May—transition seasons when temperature differentials are greatest. Early morning (5-8 AM) provides peak conditions as fog fills valleys while higher villages remain clear. Mu Cang Chai's deep valleys create spectacular inversions, especially during harvest season (late September) when golden rice terraces emerge through fog layers. Da Lat's elevation (1,500 meters) generates morning mist year-round, peaking December through March. Ninh Binh's karsts become most atmospheric during cooler months (November-February) when mist drifts through limestone formations. Arrive at viewpoints well before dawn—fog often dissipates quickly after sunrise.

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72-hour requirements breakdown

What passed or failed, hour by hour
20matching hours in the next 80 hoursJump to next match
AND logic: all conditions required
Meets requirement
Misses requirement
Time
Asia/Bangkok
Fog Probability
≥ 75.0%
Wed, Jul 8
12:000%
13:000%
14:0034%
15:0033%
16:0033%
17:0034%
18:0041%
19:0042%
20:0073%
21:0073%
22:0073%
23:0073%
Thu, Jul 9
24:0082%
01:0091%
02:00100%
03:00100%
04:00100%
05:00100%
06:00100%
07:00100%
08:0094%
09:0029%
10:000%
11:000%
12:000%
13:000%
14:000%
15:000%
16:000%
17:000%
18:000%
19:000%
20:0082%
21:0082%
22:0082%
23:0042%
Fri, Jul 10
24:0046%
01:0068%
02:00100%
03:00100%
04:0069%
05:0069%
06:0069%
07:0061%
08:0069%
09:0054%
10:0054%
11:0054%
12:0053%
13:000%
14:0050%
15:000%
16:0046%
17:000%
18:000%
19:000%
20:00100%
21:00100%
22:00100%
23:00100%
Sat, Jul 11
24:00100%
01:00100%
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%
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
Asia/Bangkok
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
Wed, Jul 8 Sunrise 05:26 Sunset 18:52
21:00
6% 19°C 0mm 99% 0cm -26° 19°C 0mm 0.03kPa 17370m 0.82m/s 0.31m/s
22:00
9% 18°C 0mm 98% 0cm -35° 19°C 0mm 0.03kPa 17348m 0.81m/s 0.43m/s
23:00
7% 19°C 0mm 99% 0cm -42° 19°C 0mm 0.02kPa 17307m 1.1m/s 0.66m/s
Thu, Jul 9 Sunrise 05:26 Sunset 18:52
24:00
5% 18°C 0mm 99% 0cm -45° 19°C 0mm 0.02kPa 9549m 1.1m/s 0.51m/s
01:00
3% 18°C 0mm 99% 0cm -44° 19°C 0.13mm 0.02kPa 5529m 1.1m/s 0.61m/s
02:00
3% 18°C 0mm 99% 0cm -38° 18°C 0mm 0.01kPa 358m 1.2m/s 0.64m/s
03:00
4% 18°C 0mm 99% 0cm -29° 19°C 0mm 0.01kPa 224m 1.2m/s 0.56m/s
04:00
4% 18°C 0mm 99% 0cm -18° 19°C 0mm 0.01kPa 201m 1m/s 0.62m/s
05:00
4% 18°C 0mm 100% 0cm -6.4° 18°C 0mm 0.01kPa 160m 1.1m/s 0.59m/s
06:00
3% 18°C 0.01mm 99% 0cm 6.3° 19°C 0mm 0.01kPa 144m 1.1m/s 0.56m/s
07:00
3% 19°C 0mm 99% 0cm 19° 19°C 0.06mm 0.02kPa 106m 1.2m/s 0.87m/s
08:00
3% 19°C 0mm 98% 0cm 33° 20°C 0.13mm 0.05kPa 120m 1.4m/s 1.1m/s
09:00
3% 20°C 0mm 95% 0cm 46° 20°C 0.38mm 0.11kPa 3593m 1.4m/s 1.2m/s
10:00
3% 20°C 0mm 96% 0cm 60° 21°C 1.1mm 0.11kPa 765m 1.8m/s 1.6m/s
11:00
3% 20°C 0mm 97% 0cm 74° 21°C 2mm 0.08kPa 262m 1.9m/s 1.6m/s
12:00
2% 21°C 0mm 95% 0cm 88° 21°C 2.7mm 0.13kPa 3406m 2.2m/s 1.9m/s
13:00
2% 21°C 0mm 94% 0cm 78° 22°C 3.8mm 0.15kPa 7963m 2.5m/s 1.9m/s
14:00
3% 21°C 0mm 92% 0cm 65° 22°C 0.75mm 0.21kPa 8080m 2.5m/s 1.9m/s
15:00
4% 21°C 0mm 94% 0cm 51° 21°C 1.4mm 0.14kPa 16493m 2.3m/s 1.8m/s
16:00
5% 20°C 0mm 90% 0cm 37° 22°C 1.6mm 0.26kPa 24135m 2.2m/s 1.7m/s
17:00
5% 19°C 0mm 86% 0cm 24° 22°C 1.8mm 0.35kPa 24134m 2.3m/s 1.7m/s
18:00
6% 20°C 0mm 92% 0cm 11° 21°C 1.9mm 0.19kPa 19506m 2.4m/s 1.5m/s
19:00
6% 19°C 0mm 99% 0cm -2.2° 19°C 2.2mm 0.03kPa 20236m 1.7m/s 1.2m/s
20:00
8% 19°C 0mm 99% 0cm -15° 19°C 0.13mm 0.02kPa 9546m 1.3m/s 0.79m/s
21:00
10% 19°C 0mm 99% 0cm -26° 19°C 0.19mm 0.01kPa 9401m 1.4m/s 0.63m/s
22:00
12% 18°C 0mm 99% 0cm -35° 18°C 0.19mm 0.01kPa 11646m 1.3m/s 0.67m/s
23:00
11% 18°C 0mm 99% 0cm -42° 18°C 0.25mm 0.02kPa 12955m 1.3m/s 0.71m/s
Fri, Jul 10 Sunrise 05:27 Sunset 18:52
24:00
11% 18°C 0.01mm 99% 0cm -45° 18°C 0.25mm 0.01kPa 9361m 1.3m/s 0.75m/s
01:00
10% 18°C 0mm 100% 0cm -44° 18°C 0.31mm 0.01kPa 310m 1.5m/s 0.96m/s
02:00
8% 19°C 0mm 100% 0cm -38° 18°C 0.06mm 0kPa 142m 1.7m/s 1m/s
03:00
6% 19°C 0mm 100% 0cm -29° 19°C 0.13mm 0.01kPa 94m 1.7m/s 1m/s
04:00
4% 19°C 0mm 100% 0cm -18° 19°C 0.25mm 0.01kPa 72m 1.8m/s 1.1m/s
05:00
4% 19°C 0mm 100% 0cm -6.4° 19°C 0.38mm 0.01kPa 57m 2m/s 1.1m/s
06:00
4% 19°C 0mm 100% 0cm 6.3° 19°C 0.44mm 0.01kPa 52m 1.9m/s 1.2m/s
07:00
4% 19°C 0mm 99% 0cm 19° 19°C 0.5mm 0.01kPa 48m 1.8m/s 1.2m/s
08:00
5% 19°C 0mm 99% 0cm 33° 19°C 0.13mm 0.02kPa 44m 1.9m/s 1.4m/s
09:00
5% 19°C 0mm 99% 0cm 46° 20°C 0.31mm 0.02kPa 46m 1.9m/s 1.4m/s
10:00
6% 20°C 0mm 99% 0cm 60° 20°C 0.5mm 0.03kPa 50m 2m/s 1.6m/s
11:00
5% 20°C 0mm 98% 0cm 74° 20°C 0.75mm 0.04kPa 59m 2m/s 1.6m/s
12:00
3% 20°C 0mm 98% 0cm 88° 20°C 0.88mm 0.05kPa 69m 1.9m/s 1.6m/s
13:00
2% 20°C 0mm 97% 0cm 78° 20°C 1.1mm 0.07kPa 106m 2.1m/s 1.6m/s
14:00
2% 20°C 0mm 96% 0cm 65° 21°C 0.25mm 0.11kPa 176m 2.3m/s 1.9m/s
15:00
1% 20°C 0mm 95% 0cm 51° 21°C 0.56mm 0.12kPa 5680m 2.3m/s 2m/s
16:00
1% 20°C 0mm 97% 0cm 37° 20°C 0.81mm 0.08kPa 1126m 2.3m/s 1.9m/s
17:00
2% 19°C 0mm 98% 0cm 24° 20°C 1mm 0.06kPa 9299m 2.2m/s 1.7m/s
18:00
2% 19°C 0mm 99% 0cm 11° 19°C 1.1mm 0.03kPa 1252m 2m/s 1.4m/s
19:00
3% 19°C 0mm 100% 0cm -2.2° 19°C 1.1mm 0.01kPa 395m 1.7m/s 1.1m/s
20:00
4% 18°C 0mm 100% 0cm -15° 18°C 0mm 0.01kPa 331m 1.4m/s 0.93m/s
21:00
4% 18°C 0mm 100% 0cm -26° 18°C 0mm 0.01kPa 187m 1.4m/s 0.76m/s
22:00
5% 18°C 0mm 100% 0cm -35° 18°C 0mm 0.01kPa 146m 1.5m/s 0.88m/s
23:00
4% 18°C 0mm 100% 0cm -42° 18°C 0.06mm 0.01kPa 127m 1.1m/s 0.58m/s
Sat, Jul 11 Sunrise 05:27 Sunset 18:52
24:00
2% 18°C 0.01mm 100% 0cm -45° 18°C 0.06mm 0.01kPa 110m 1.3m/s 0.75m/s
01:00
1% 18°C 0.01mm 100% 0cm -44° 18°C 0.06mm 0.01kPa 108m 1.4m/s 0.81m/s
02:00
3% 19°C 0.007mm 86% 0cm -38° 22°C 0.08mm 0.38kPa 8117m 1.5m/s 0.85m/s
03:00
5% 21°C 0.003mm 72% 0cm -29° 26°C 0.1mm 0.96kPa 16126m 1.5m/s 0.89m/s
04:00
7% 21°C 0mm 58% 0cm -18° 30°C 0.13mm 1.8kPa 24135m 1.6m/s 0.93m/s
05:00
7% 21°C 0mm 54% 0cm -6.5° 32°C 0.29mm 2.1kPa 22554m 1.6m/s 0.87m/s
06:00
6% 21°C 0mm 51% 0cm 6.2° 33°C 0.46mm 2.4kPa 20974m 1.5m/s 0.81m/s
07:00
6% 22°C 0mm 48% 0cm 19° 34°C 0.63mm 2.8kPa 19393m 1.4m/s 0.75m/s
08:00
13% 22°C 0.007mm 49% 0cm 33° 34°C 0.52mm 2.7kPa 20974m 1.6m/s 1.1m/s
09:00
19% 22°C 0.01mm 51% 0cm 46° 34°C 0.42mm 2.5kPa 22554m 1.7m/s 1.4m/s
10:00
26% 22°C 0.02mm 53% 0cm 60° 33°C 0.31mm 2.4kPa 24135m 1.8m/s 1.8m/s
11:00
23% 23°C 0.01mm 61% 0cm 74° 31°C 0.56mm 1.8kPa 22030m 1.7m/s 1.5m/s
12:00
20% 23°C 0.007mm 69% 0cm 88° 29°C 0.81mm 1.3kPa 19924m 1.6m/s 1.2m/s
13:00
17% 23°C 0mm 77% 0cm 78° 27°C 1.1mm 0.84kPa 17819m 1.4m/s 0.95m/s
14:00
13% 23°C 0.2mm 83% 0cm 65° 26°C 2mm 0.56kPa 19480m 1.6m/s 1m/s
15:00
9% 23°C 0.41mm 90% 0cm 51° 25°C 3mm 0.31kPa 21141m 1.8m/s 1.1m/s
16:00
5% 23°C 0.61mm 97% 0cm 37° 24°C 3.9mm 0.09kPa 22803m 1.9m/s 1.3m/s
17:00
7% 23°C 0.41mm 97% 0cm 24° 24°C 4.6mm 0.09kPa 23247m 1.7m/s 1.2m/s
18:00
9% 23°C 0.21mm 97% 0cm 11° 24°C 5.2mm 0.08kPa 23691m 1.4m/s 1.1m/s
19:00
11% 23°C 0.01mm 98% 0cm -2.3° 23°C 5.9mm 0.07kPa 24135m 1.1m/s 1m/s
20:00
16% 23°C 0.007mm 97% 0cm -15° 23°C 3.9mm 0.08kPa 24135m 1.2m/s 0.99m/s
How to read: these inputs help produce the derived score; they are not requirements by themselves.

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