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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 Spread0.9°C
Visibility24135 (Clear)
Relative Humidity94%
Wind Speed1.1m/s (calm conditions)

Upcoming Opportunities

When all conditions match, PhotoWeather marks an opportunity window.

Times shown in Asia/Bangkok
fog weather icon
Next opportunity
Moderate Fog
Sapa
Tomorrow · 03:00–04:00 · 1h window
Medium confidence
54%
🌫️Fog Probability79.7%
Dewpoint Spread: 0.2°C
Visibility: 9827 (Moderate)
Relative Humidity: 99%
Wind Speed: 1.0m/s (calm conditions)
fog weather icon
Moderate Fog at Dawn
Sapa
Tomorrow · 04:00–05:00
🌫️Fog Probability:82.2%
Medium

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
2matching hours in the next 79 hoursJump to next match
AND logic: all conditions required
Meets requirement
Misses requirement
Time
Asia/Bangkok
Fog Probability
≥ 75.0%
Sun, May 24
12:000%
13:000%
14:000%
15:000%
16:000%
17:000%
18:000%
19:000%
20:000%
21:000%
22:000%
23:000%
Mon, May 25
24:0029%
01:0039%
02:0071%
03:0080%
04:0082%
05:0046%
06:0044%
07:0038%
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 26
24:000%
01:000%
02:000%
03:0029%
04:0039%
05:0041%
06:0044%
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 27
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%
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
Sun, May 24 Sunrise 05:21 Sunset 18:41
20:00
35% 19°C 0mm 94% 0cm -17° 20°C 0.06mm 0.14kPa 24135m 1.6m/s 1.1m/s
21:00
32% 19°C 0mm 94% 0cm -28° 20°C 0.19mm 0.15kPa 24135m 1.4m/s 0.99m/s
22:00
28% 19°C 0mm 94% 0cm -38° 20°C 0.25mm 0.14kPa 24134m 1.4m/s 1.1m/s
23:00
28% 19°C 0mm 95% 0cm -44° 20°C 0.38mm 0.12kPa 22583m 1.3m/s 1m/s
Mon, May 25 Sunrise 05:21 Sunset 18:41
24:00
27% 19°C 0.01mm 95% 0cm -47° 19°C 0.5mm 0.11kPa 24134m 1.4m/s 1.2m/s
01:00
27% 18°C 0mm 97% 0cm -44° 19°C 0.56mm 0.06kPa 24134m 1.3m/s 0.93m/s
02:00
31% 18°C 0mm 98% 0cm -38° 19°C 0.06mm 0.04kPa 24135m 1.6m/s 1m/s
03:00
34% 18°C 0mm 99% 0cm -29° 18°C 0.13mm 0.03kPa 9827m 1.6m/s 1m/s
04:00
38% 18°C 0mm 99% 0cm -18° 18°C 0.19mm 0.02kPa 9420m 1.8m/s 0.95m/s
05:00
36% 18°C 0mm 99% 0cm -5.3° 18°C 0.25mm 0.01kPa 9325m 1.9m/s 1m/s
06:00
35% 19°C 0mm 99% 0cm 7.6° 19°C 0.38mm 0.02kPa 9331m 2.1m/s 1.4m/s
07:00
33% 19°C 0mm 98% 0cm 21° 20°C 0.5mm 0.06kPa 8750m 2.6m/s 1.8m/s
08:00
26% 20°C 0mm 95% 0cm 34° 21°C 0.25mm 0.13kPa 4958m 2.9m/s 2.1m/s
09:00
18% 20°C 0mm 89% 0cm 48° 22°C 0.44mm 0.28kPa 24135m 3.2m/s 2.4m/s
10:00
11% 20°C 0mm 83% 0cm 62° 23°C 0.63mm 0.49kPa 21030m 3.3m/s 2.6m/s
11:00
9% 20°C 0mm 77% 0cm 76° 24°C 0.88mm 0.7kPa 21134m 3.4m/s 2.6m/s
12:00
7% 20°C 0mm 73% 0cm 89° 25°C 1.1mm 0.85kPa 20655m 3.5m/s 2.5m/s
13:00
5% 20°C 0mm 70% 0cm 76° 26°C 1.3mm 0.99kPa 21941m 3.6m/s 2.6m/s
14:00
29% 20°C 0mm 69% 0cm 62° 26°C 0.19mm 1kPa 21437m 3.6m/s 2.5m/s
15:00
54% 20°C 0mm 70% 0cm 49° 25°C 0.44mm 0.96kPa 20972m 3.3m/s 2.4m/s
16:00
78% 20°C 0mm 80% 0cm 35° 24°C 0.75mm 0.6kPa 12742m 2.9m/s 1.9m/s
17:00
83% 21°C 0.01mm 82% 0cm 21° 24°C 1mm 0.52kPa 15045m 2.4m/s 1.3m/s
18:00
87% 20°C 0mm 89% 0cm 8.3° 22°C 1.2mm 0.29kPa 23255m 1.6m/s 0.65m/s
19:00
92% 19°C 0mm 88% 0cm -4.6° 21°C 1.2mm 0.29kPa 24135m 1.1m/s 0.27m/s
20:00
92% 18°C 0mm 90% 0cm -17° 20°C 0.06mm 0.24kPa 24134m 1m/s 0.15m/s
21:00
93% 18°C 0mm 90% 0cm -28° 20°C 0.06mm 0.22kPa 24134m 0.93m/s 0.29m/s
22:00
93% 18°C 0mm 91% 0cm -37° 20°C 0.13mm 0.21kPa 24134m 0.91m/s 0.11m/s
23:00
92% 19°C 0mm 92% 0cm -44° 20°C 0.13mm 0.17kPa 24134m 1.1m/s 0.39m/s
Tue, May 26 Sunrise 05:21 Sunset 18:41
24:00
91% 19°C 0mm 94% 0cm -47° 20°C 0.19mm 0.14kPa 24135m 1.1m/s 0.56m/s
01:00
90% 19°C 0mm 94% 0cm -44° 20°C 0.31mm 0.13kPa 23339m 1.1m/s 0.55m/s
02:00
89% 19°C 0mm 95% 0cm -38° 20°C 0.13mm 0.12kPa 22765m 1m/s 0.82m/s
03:00
88% 19°C 0mm 96% 0cm -29° 20°C 0.25mm 0.1kPa 23818m 1.1m/s 0.93m/s
04:00
87% 19°C 0mm 98% 0cm -17° 19°C 0.25mm 0.05kPa 24135m 1m/s 0.73m/s
05:00
86% 18°C 0mm 98% 0cm -5.3° 19°C 0.25mm 0.03kPa 24134m 1.1m/s 0.71m/s
06:00
85% 19°C 0mm 98% 0cm 7.6° 19°C 0.25mm 0.04kPa 10005m 1.5m/s 0.61m/s
07:00
84% 20°C 0mm 94% 0cm 21° 21°C 0.25mm 0.14kPa 24135m 1.6m/s 1.1m/s
08:00
85% 20°C 0mm 86% 0cm 34° 22°C 0mm 0.36kPa 24134m 2.3m/s 1.8m/s
09:00
86% 19°C 0mm 75% 0cm 48° 24°C 0.06mm 0.74kPa 24135m 2.5m/s 2.1m/s
10:00
87% 19°C 0mm 66% 0cm 62° 26°C 0.06mm 1.1kPa 24134m 2.7m/s 2.4m/s
11:00
84% 19°C 0mm 62% 0cm 76° 27°C 0.13mm 1.3kPa 24134m 2.8m/s 2.5m/s
12:00
82% 19°C 0mm 60% 0cm 89° 27°C 0.13mm 1.4kPa 24134m 2.9m/s 2.4m/s
13:00
79% 18°C 0mm 55% 0cm 76° 28°C 0.13mm 1.7kPa 24135m 3.1m/s 2.4m/s
14:00
75% 18°C 0mm 57% 0cm 63° 27°C 0.06mm 1.6kPa 24134m 3.1m/s 2.3m/s
15:00
72% 19°C 0mm 68% 0cm 49° 26°C 0.06mm 1kPa 23499m 2.9m/s 1.8m/s
16:00
68% 19°C 0mm 71% 0cm 35° 25°C 0.19mm 0.92kPa 24134m 2.6m/s 1.6m/s
17:00
72% 20°C 0mm 76% 0cm 22° 25°C 0.25mm 0.76kPa 24085m 1.6m/s 0.99m/s
18:00
76% 20°C 0mm 82% 0cm 8.4° 23°C 0.25mm 0.51kPa 24134m 0.9m/s 0.48m/s
19:00
80% 19°C 0mm 83% 0cm -4.5° 22°C 0.25mm 0.43kPa 24134m 0.82m/s 0.35m/s
20:00
86% 18°C 0mm 83% 0cm -17° 21°C 0mm 0.42kPa 24134m 0.8m/s 0.29m/s
21:00
92% 18°C 0mm 84% 0cm -28° 21°C 0mm 0.38kPa 24135m 0.73m/s 0.45m/s
22:00
98% 18°C 0mm 85% 0cm -37° 20°C 0mm 0.37kPa 24135m 0.91m/s 0.56m/s
23:00
98% 18°C 0mm 84% 0cm -44° 21°C 0mm 0.38kPa 24134m 0.83m/s 0.52m/s
Wed, May 27 Sunrise 05:21 Sunset 18:42
24:00
97% 18°C 0mm 84% 0cm -46° 20°C 0mm 0.38kPa 24135m 0.81m/s 0.5m/s
01:00
97% 18°C 0mm 85% 0cm -44° 20°C 0mm 0.36kPa 24134m 0.82m/s 0.39m/s
02:00
95% 19°C 0.003mm 72% 0cm -38° 25°C 0mm 0.87kPa 24134m 1.1m/s 0.75m/s
03:00
93% 20°C 0.007mm 59% 0cm -28° 29°C 0mm 1.7kPa 24135m 1.4m/s 1.1m/s
04:00
91% 21°C 0.01mm 46% 0cm -17° 34°C 0mm 2.8kPa 24135m 1.7m/s 1.5m/s
05:00
91% 21°C 0.007mm 43% 0cm -5.2° 35°C 0.02mm 3.2kPa 24135m 2.2m/s 1.7m/s
06:00
91% 21°C 0.003mm 40% 0cm 7.7° 36°C 0.04mm 3.6kPa 24135m 2.6m/s 1.8m/s
07:00
91% 20°C 0mm 37% 0cm 21° 37°C 0.06mm 4kPa 24135m 3.1m/s 2m/s
08:00
90% 21°C 0mm 39% 0cm 34° 37°C 0.06mm 3.8kPa 24135m 3.1m/s 1.9m/s
09:00
89% 21°C 0mm 41% 0cm 48° 36°C 0.06mm 3.6kPa 24135m 3.1m/s 1.8m/s
10:00
88% 21°C 0mm 43% 0cm 62° 36°C 0.06mm 3.4kPa 24135m 3.1m/s 1.7m/s
11:00
81% 22°C 0mm 51% 0cm 76° 34°C 0.08mm 2.5kPa 24135m 2.5m/s 1.5m/s
12:00
75% 23°C 0mm 59% 0cm 89° 31°C 0.1mm 1.9kPa 24135m 1.9m/s 1.2m/s
13:00
68% 23°C 0mm 67% 0cm 76° 29°C 0.13mm 1.3kPa 24135m 1.2m/s 1m/s
14:00
47% 23°C 0.02mm 73% 0cm 63° 28°C 0.52mm 0.99kPa 24135m 1.1m/s 0.91m/s
15:00
27% 23°C 0.03mm 79% 0cm 49° 26°C 0.92mm 0.7kPa 24135m 1m/s 0.81m/s
16:00
6% 22°C 0.05mm 86% 0cm 35° 25°C 1.3mm 0.46kPa 24135m 0.93m/s 0.71m/s
17:00
7% 22°C 0.1mm 88% 0cm 22° 25°C 2.1mm 0.37kPa 24135m 0.81m/s 0.66m/s
18:00
9% 23°C 0.16mm 91% 0cm 8.4° 24°C 3mm 0.28kPa 24135m 0.69m/s 0.6m/s
19:00
10% 23°C 0.21mm 93% 0cm -4.4° 24°C 3.8mm 0.2kPa 24135m 0.57m/s 0.55m/s
How to read: these inputs help produce the derived score; they are not requirements by themselves.

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