What conditions does Dawn Crystals look for?

Time Window: Sunrise -45m to +90m. Frost Probability: ≥ 60.0%. Dewpoint Spread: ≤ 3.0°C. Relative Humidity: ≥ 85.0%. Wind Speed: ≤ 1.5m/s

How often do conditions match?

There are 16 upcoming opportunity windows in the next 14 days.

Rule Dawn Crystals

Morning Frost in Tuscany

Val d'Orcia, Italy

Morning dew drops or frost crystals on calm mornings

Upcoming Opportunities

When all conditions match, PhotoWeather marks an opportunity window.

Times shown in Europe/Rome

Next opportunity

Heavy Frost (radiative)

Sun, Jan 11 · 06:58–07:00 · 1h window

Medium confidence

57%

Moderate Frost at Sunrise

Sun, Jan 11 · 07:00–08:00

Medium

Heavy Frost (radiative) at Sunrise

Sun, Jan 11 · 08:00–09:00

Medium

Heavy Frost (radiative)

Sun, Jan 11 · 09:00–09:13

Medium

Moderate Frost (radiative)

Mon, Jan 12 · 06:58–07:00

Medium

Moderate Frost at Sunrise

Mon, Jan 12 · 07:00–08:00

Medium

+10 more windows in the next 14 days

What this forecast looks for

Plain-language explanation from the rule

Dawn Crystals detects conditions for dew drops and frost:

Frost Probability: Based on temperature and humidity
Dewpoint Spread: Close spread means moisture condensation
Wind Speed: Calm conditions let frost/dew form undisturbed
Timing: Around sunrise when conditions are most favorable

Perfect for macro photography of frost crystals and dew drops.

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72-hour requirements breakdown

What passed or failed, hour by hour

5matching hours in the next 72 hoursJump to next match

OR logic: one branch per group is enough

Meets requirement

Misses requirement

Time Europe/Rome	Time Window Sunrise -45m to +90m	Frost Probability OR1·B1 ≥ 60.0%	Dewpoint Spread OR1·B2 ≤ 3.0°C	Relative Humidity OR1·B2 ≥ 85.0%	Wind Speed ≤ 1.5m/s
Fri, Jan 9
07:00	✓	37%	3.4°C	79%	1.4m/s
08:00	✓	23%	2.5°C	84%	1.8m/s
09:00	✓	36%	3.6°C	78%	1.6m/s
10:00	✕	2.1%	2.6°C	84%	1.5m/s
11:00	✕	0%	2.8°C	83%	1.9m/s
12:00	✕	0%	4.7°C	73%	4.2m/s
13:00	✕	0%	4.9°C	72%	6.6m/s
14:00	✕	0%	6.4°C	65%	8.2m/s
15:00	✕	0%	5.5°C	69%	8.7m/s
16:00	✕	0%	5°C	71%	8.5m/s
17:00	✕	2.7%	4.2°C	75%	7.3m/s
18:00	✕	3%	3.2°C	80%	6.7m/s
19:00	✕	1.7%	2.7°C	83%	6.9m/s
20:00	✕	1.7%	2.5°C	84%	6.9m/s
21:00	✕	14%	2.5°C	84%	6.3m/s
22:00	✕	14%	2.9°C	82%	6.7m/s
23:00	✕	14%	1.8°C	88%	7.4m/s
Sat, Jan 10
24:00	✕	17%	1.7°C	89%	5.5m/s
01:00	✕	18%	2°C	87%	3m/s
02:00	✕	17%	1.7°C	89%	2m/s
03:00	✕	11%	1°C	93%	4.1m/s
04:00	✕	11%	1°C	93%	4.8m/s
05:00	✕	11%	0.9°C	94%	3.5m/s
06:00	✓	13%	0.7°C	95%	2.6m/s
07:00	✓	15%	0.7°C	95%	1.9m/s
08:00	✓	15%	0.4°C	97%	1.8m/s
09:00	✓	13%	0.7°C	95%	2.3m/s
10:00	✕	1.6%	1.2°C	92%	2.1m/s
11:00	✕	1.9%	2.3°C	85%	2.3m/s
12:00	✕	0%	3.6°C	78%	3m/s
13:00	✕	0%	4°C	76%	3.6m/s
14:00	✕	3%	4.9°C	71%	3.6m/s
15:00	✕	3.8%	6.4°C	64%	3.7m/s
16:00	✕	50%	6.1°C	65%	2.9m/s
17:00	✕	46%	4.4°C	73%	2.2m/s
18:00	✕	57%	5.4°C	68%	2.1m/s
19:00	✕	72%	5.3°C	68%	2m/s
20:00	✕	69%	4.2°C	74%	1.6m/s
21:00	✕	79%	3.6°C	77%	1.6m/s
22:00	✕	79%	3.3°C	79%	1.3m/s
23:00	✕	79%	4.2°C	74%	1.1m/s
Sun, Jan 11
24:00	✕	84%	5.3°C	68%	1.4m/s
01:00	✕	84%	5.1°C	69%	1.3m/s
02:00	✕	87%	5.1°C	69%	1.2m/s
03:00	✕	87%	5.7°C	66%	1.4m/s
04:00	✕	87%	5.7°C	66%	1.3m/s
05:00	✕	87%	5.9°C	65%	1.3m/s
06:00	✓	91%	6.3°C	63%	1m/s
07:00	✓	83%	6°C	64%	1.1m/s
08:00	✓	87%	5.6°C	66%	1.1m/s
09:00	✓	86%	5.8°C	65%	0.76m/s
10:00	✕	59%	5.3°C	68%	0.81m/s
11:00	✕	52%	9.8°C	49%	1m/s
12:00	✕	48%	12°C	43%	1.9m/s
13:00	✕	4.5%	13°C	39%	3.8m/s
14:00	✕	4.3%	11°C	44%	4.7m/s
15:00	✕	40%	12°C	42%	5m/s
16:00	✕	50%	9°C	52%	4.1m/s
17:00	✕	70%	5.9°C	65%	3m/s
18:00	✕	77%	4.5°C	72%	2.1m/s
19:00	✕	77%	3.6°C	77%	2m/s
20:00	✕	65%	2.9°C	81%	1.7m/s
21:00	✕	67%	2.5°C	83%	1.4m/s
22:00	✕	67%	2.5°C	83%	1.6m/s
23:00	✕	67%	2.4°C	84%	1.1m/s
Mon, Jan 12
24:00	✕	71%	2.1°C	86%	0.92m/s
01:00	✕	71%	1.9°C	87%	1.1m/s
02:00	✕	71%	1.9°C	87%	1.4m/s
03:00	✕	71%	2.2°C	85%	1.6m/s
04:00	✕	71%	2.7°C	82%	1.3m/s
05:00	✕	71%	2.7°C	82%	1.1m/s
06:00	✓	74%	2.8°C	81%	1.1m/s

How to read: colored cells show whether each predicate requirement is met; highlighted rows mean the full rule matched (an opportunity). For OR groups, only one branch is required, so some OR-branch predicates can be ✕ even in a matching hour.

What does Frost 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/Rome	Frost Probability %	Dew Point °C	Dewpoint Spread °C	Relative Humidity %	Surface Temperature °C	Temperature °C	Time Window	Total Cloud Coverage %	Vapor Pressure Deficit kPa
Fri, Jan 9 Sunrise 07:44 Sunset 16:56
08:00	23%	4.4°C	2.5°C	84%	3.7°C	6.9°C	-	64%	0.16kPa
09:00	36%	4.8°C	3.6°C	78%	5.4°C	8.4°C	-	62%	0.24kPa
10:00	2.1%	6.9°C	2.6°C	84%	7.8°C	9.5°C	-	81%	0.19kPa
11:00	0%	7.9°C	2.8°C	83%	9.5°C	11°C	-	86%	0.22kPa
12:00	0%	7.6°C	4.7°C	73%	11°C	12°C	-	67%	0.39kPa
13:00	0%	7.1°C	4.9°C	72%	10°C	12°C	-	66%	0.39kPa
14:00	0%	5.5°C	6.4°C	65%	11°C	12°C	-	54%	0.49kPa
15:00	0%	5.6°C	5.5°C	69%	10°C	11°C	-	54%	0.41kPa
16:00	0%	5°C	5°C	71%	8.5°C	10°C	-	72%	0.36kPa
17:00	2.7%	4.6°C	4.2°C	75%	7.1°C	8.8°C	-	74%	0.28kPa
18:00	3%	4.7°C	3.2°C	80%	6.4°C	7.9°C	-	47%	0.21kPa
19:00	1.7%	4.7°C	2.7°C	83%	6.3°C	7.4°C	-	59%	0.17kPa
20:00	1.7%	4.6°C	2.5°C	84%	6°C	7.1°C	-	49%	0.16kPa
21:00	14%	4.5°C	2.5°C	84%	5.7°C	7°C	-	96%	0.16kPa
22:00	14%	4.1°C	2.9°C	82%	5.8°C	7°C	-	100%	0.18kPa
23:00	14%	4.9°C	1.8°C	88%	5.8°C	6.7°C	-	100%	0.12kPa
Sat, Jan 10 Sunrise 07:44 Sunset 16:56
24:00	17%	4.7°C	1.7°C	89%	5.2°C	6.4°C	-	68%	0.11kPa
01:00	18%	4.2°C	2°C	87%	4.9°C	6.2°C	-	100%	0.12kPa
02:00	17%	3.9°C	1.7°C	89%	4.5°C	5.6°C	-	98%	0.1kPa
03:00	11%	4.1°C	1°C	93%	4.5°C	5.1°C	-	100%	0.06kPa
04:00	11%	3.8°C	1°C	93%	4°C	4.8°C	-	100%	0.06kPa
05:00	11%	3.7°C	0.9°C	94%	4.3°C	4.6°C	-	100%	0.05kPa
06:00	13%	4°C	0.7°C	95%	4.4°C	4.7°C	-	100%	0.04kPa
07:00	15%	3.8°C	0.7°C	95%	3.9°C	4.5°C	-	100%	0.04kPa
08:00	15%	3.8°C	0.4°C	97%	3.8°C	4.2°C	-	100%	0.02kPa
09:00	13%	4°C	0.7°C	95%	4.7°C	4.7°C	-	100%	0.04kPa
10:00	1.6%	4.3°C	1.2°C	92%	6.1°C	5.5°C	-	100%	0.07kPa
11:00	1.9%	4.2°C	2.3°C	85%	8°C	6.5°C	-	100%	0.15kPa
12:00	0%	3.5°C	3.6°C	78%	8.1°C	7.1°C	-	100%	0.22kPa
13:00	0%	3.5°C	4°C	76%	8.6°C	7.5°C	-	100%	0.25kPa
14:00	3%	2.5°C	4.9°C	71%	7.9°C	7.4°C	-	82%	0.3kPa
15:00	3.8%	1.4°C	6.4°C	64%	7.5°C	7.8°C	-	53%	0.38kPa
16:00	50%	0.8°C	6.1°C	65%	5.8°C	6.9°C	-	0%	0.35kPa
17:00	46%	0.9°C	4.4°C	73%	3.7°C	5.3°C	-	16%	0.24kPa
18:00	57%	-1.1°C	5.4°C	68%	2.7°C	4.3°C	-	0%	0.27kPa
19:00	72%	-1.8°C	5.3°C	68%	1.8°C	3.5°C	-	0%	0.25kPa
20:00	69%	-1.3°C	4.2°C	74%	1.2°C	2.9°C	-	0%	0.2kPa
21:00	79%	-1.2°C	3.6°C	77%	0.6°C	2.4°C	-	0%	0.17kPa
22:00	79%	-1.1°C	3.3°C	79%	0.2°C	2.2°C	-	0%	0.15kPa
23:00	79%	-1.9°C	4.2°C	74%	0.1°C	2.3°C	-	0%	0.19kPa
Sun, Jan 11 Sunrise 07:44 Sunset 16:57
24:00	84%	-2.8°C	5.3°C	68%	0.1°C	2.5°C	-	0%	0.23kPa
01:00	84%	-3.1°C	5.1°C	69%	0.1°C	2°C	-	0%	0.22kPa
02:00	87%	-3°C	5.1°C	69%	0°C	2.1°C	-	0%	0.22kPa
03:00	87%	-3.4°C	5.7°C	66%	-0.2°C	2.3°C	-	0%	0.25kPa
04:00	87%	-3.9°C	5.7°C	66%	-0.4°C	1.8°C	-	0%	0.24kPa
05:00	87%	-4.5°C	5.9°C	65%	-0.6°C	1.4°C	-	0%	0.24kPa
06:00	91%	-5°C	6.3°C	63%	-0.9°C	1.3°C	-	0%	0.25kPa
07:00	83%	-4.9°C	6°C	64%	-1°C	1.1°C	-	20%	0.24kPa
08:00	87%	-4.8°C	5.6°C	66%	-1°C	0.8°C	-	9%	0.22kPa
09:00	86%	-4.6°C	5.8°C	65%	0.1°C	1.2°C	-	0%	0.23kPa
10:00	59%	-2.3°C	5.3°C	68%	2.9°C	3°C	-	0%	0.24kPa
11:00	52%	-4.7°C	9.8°C	49%	4.5°C	5.1°C	-	0%	0.45kPa
12:00	48%	-5.5°C	12°C	43%	5.1°C	6.1°C	-	0%	0.54kPa
13:00	4.5%	-6.3°C	13°C	39%	6.9°C	6.7°C	-	0%	0.6kPa
14:00	4.3%	-4.8°C	11°C	44%	6.6°C	6.6°C	-	0%	0.55kPa
15:00	40%	-5.8°C	12°C	42%	5.5°C	6.2°C	-	15%	0.55kPa
16:00	50%	-4°C	9°C	52%	3.9°C	5°C	-	3%	0.42kPa
17:00	70%	-2.6°C	5.9°C	65%	1.8°C	3.3°C	-	0%	0.27kPa
18:00	77%	-2.3°C	4.5°C	72%	0.7°C	2.2°C	-	0%	0.2kPa
19:00	77%	-2.3°C	3.6°C	77%	0.1°C	1.3°C	-	3%	0.15kPa
20:00	65%	-2.1°C	2.9°C	81%	0.1°C	0.8°C	-	12%	0.12kPa
21:00	67%	-2°C	2.5°C	83%	0.1°C	0.5°C	-	11%	0.11kPa
22:00	67%	-2.3°C	2.5°C	83%	0.1°C	0.2°C	-	11%	0.11kPa
23:00	67%	-2.5°C	2.4°C	84%	-0.2°C	-0.1°C	-	12%	0.1kPa
Mon, Jan 12 Sunrise 07:43 Sunset 16:58
24:00	71%	-2.4°C	2.1°C	86%	-0.7°C	-0.3°C	-	0%	0.08kPa
01:00	71%	-2.5°C	1.9°C	87%	-1.1°C	-0.6°C	-	0%	0.08kPa
02:00	71%	-2.8°C	1.9°C	87%	-1.2°C	-0.9°C	-	0%	0.07kPa
03:00	71%	-3.4°C	2.2°C	85%	-1.2°C	-1.2°C	-	0%	0.08kPa
04:00	71%	-3.8°C	2.7°C	82%	-1.3°C	-1.1°C	-	0%	0.1kPa
05:00	71%	-3.9°C	2.7°C	82%	-1.3°C	-1.2°C	-	0%	0.1kPa
06:00	74%	-4.1°C	2.8°C	81%	-1.5°C	-1.3°C	-	9%	0.11kPa
07:00	0%	-4.6°C	3.2°C	79%	-1.7°C	-1.4°C	-	47%	0.12kPa

How to read: these inputs help produce the derived score; they are not requirements by themselves.

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