Black Forest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Black Forest clear sky chart from 2005-11-06 to 2026-06-16.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	19% 13% 5% 9% 5% 4 4 3 5% 6% 27%	137970
	Night	19% 14% 5% 11% 5% 4 4 3 4 5% 25%	134032
Transparency	Day	58% 4 10% 18% 8% 1	141437
	Night	62% 4 9% 16% 8% 1	138654
Seeing	Day	29% 17% 28% 17% 7% 2	16676
	Night	27% 16% 27% 21% 7% 1	25824

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	12% 19% 9% 24% 10% 5% 3 2 2 3 11%	4661
	11th to 20th	Day	11% 19% 11% 22% 11% 6% 2 2 2 3 11%	4650
	21st to end	Day	12% 16% 9% 15% 9% 8% 5% 3 4 4 16%	5441
February	1st to 10th	Day	15% 20% 6% 15% 8% 5% 5% 3 3 4 15%	1890
	11th to 20th	Day	15% 19% 8% 16% 7% 4 2 3 3 4 19%	1932
	21st to end	Day	18% 18% 7% 13% 8% 4 4 3 3 4 18%	1730
March	1st to 10th	Day	20% 18% 9% 14% 4 3 3 2 3 4 21%	4576
	11th to 20th	Day	12% 21% 7% 8% 4 4 4 3 4 5% 29%	4996
	21st to end	Day	21% 15% 6% 10% 4 3 3 2 3 4 29%	5961
April	1st to 10th	Day	22% 16% 4 8% 4 3 3 2 3 6% 28%	2520
	11th to 20th	Day	21% 14% 3 7% 5% 3 3 3 5% 5% 31%	2494
	21st to end	Day	22% 16% 3 7% 3 4 4 3 3 6% 29%	2567
May	1st to 10th	Day	31% 12% 3 7% 4 4 4 3 4 4 24%	8135
	11th to 20th	Day	20% 10% 3 7% 5% 5% 5% 4 5% 7% 29%	8221
	21st to end	Day	25% 9% 3 6% 4 4 5% 4 6% 7% 28%	9060
June	1st to 10th	Day	23% 8% 3 6% 5% 5% 4 4 6% 7% 29%	2940
	11th to 20th	Day	22% 7% 2 6% 5% 5% 5% 5% 6% 8% 30%	2870
	21st to end	Day	22% 8% 3 7% 4 5% 4 3 6% 8% 30%	2800
July	1st to 10th	Day	14% 6% 3 7% 5% 5% 5% 5% 7% 10% 35%	6360
	11th to 20th	Day	15% 8% 2 6% 5% 5% 5% 5% 7% 9% 33%	6360
	21st to end	Day	16% 6% 2 6% 4 5% 5% 4 6% 7% 40%	6926
August	1st to 10th	Day	20% 7% 2 6% 4 5% 5% 4 6% 8% 33%	4447
	11th to 20th	Day	19% 8% 3 7% 5% 4 5% 4 6% 8% 31%	3982
	21st to end	Day	20% 6% 2 6% 4 4 4 4 6% 9% 36%	4312
September	1st to 10th	Day	18% 5% 2 5% 4 4 5% 4 6% 8% 38%	2400
	11th to 20th	Day	17% 6% 2 6% 3 4 4 3 5% 7% 43%	2365
	21st to end	Day	21% 7% 2 5% 5% 4 4 3 6% 6% 35%	2196
October	1st to 10th	Day	25% 10% 3 8% 5% 4 4 3 4 5% 31%	2000
	11th to 20th	Day	23% 12% 3 6% 4 4 4 4 5% 5% 30%	2000
	21st to end	Day	28% 12% 4 7% 4 4 3 4 4 5% 24%	2037
November	1st to 10th	Day	19% 15% 5% 8% 5% 5% 4 3 5% 5% 27%	1851
	11th to 20th	Day	18% 19% 5% 8% 5% 3 4 3 4 5% 27%	1816
	21st to end	Day	20% 22% 7% 10% 4 5% 3 3 4 4 18%	1680
December	1st to 10th	Day	19% 27% 9% 16% 5% 3 3 3 3 3 10%	2680
	11th to 20th	Day	20% 21% 10% 16% 6% 3 3 2 3 3 14%	3066
	21st to end	Day	20% 19% 8% 13% 5% 4 3 2 3 4 20%	4048
January	1st to 10th	Night	13% 20% 9% 21% 9% 5% 3 2 2 3 12%	8234
	11th to 20th	Night	11% 19% 10% 26% 11% 5% 3 2 2 2 8%	8235
	21st to end	Night	12% 14% 7% 17% 9% 8% 5% 3 4 5% 14%	8726
February	1st to 10th	Night	16% 18% 7% 17% 8% 5% 4 2 4 4 15%	2730
	11th to 20th	Night	14% 15% 8% 17% 9% 5% 4 3 4 4 17%	2573
	21st to end	Night	16% 17% 7% 12% 8% 5% 4 3 4 6% 18%	2076
March	1st to 10th	Night	19% 15% 6% 14% 6% 5% 3 2 3 4 22%	5484
	11th to 20th	Night	17% 18% 6% 8% 4 3 3 3 4 6% 29%	5167
	21st to end	Night	23% 14% 6% 13% 4 3 3 2 4 4 24%	5213
April	1st to 10th	Night	23% 16% 4 8% 3 4 3 3 4 5% 27%	2100
	11th to 20th	Night	22% 13% 3 6% 5% 4 4 3 4 5% 30%	2075
	21st to end	Night	22% 11% 3 5% 3 4 4 3 4 6% 34%	2053
May	1st to 10th	Night	31% 13% 3 7% 4 4 4 3 4 5% 23%	4805
	11th to 20th	Night	20% 12% 3 7% 4 4 4 3 5% 6% 32%	4639
	21st to end	Night	23% 10% 2 7% 4 4 5% 3 5% 7% 30%	5114
June	1st to 10th	Night	22% 6% 3 5% 4 4 4 4 6% 6% 36%	1680
	11th to 20th	Night	24% 6% 2 4 3 3 3 4 5% 8% 37%	1640
	21st to end	Night	20% 7% 2 6% 4 4 4 4 5% 7% 37%	1600
July	1st to 10th	Night	15% 7% 3 7% 5% 5% 4 5% 6% 8% 36%	3600
	11th to 20th	Night	20% 7% 3 5% 3 3 4 3 5% 7% 40%	3600
	21st to end	Night	12% 7% 2 5% 4 3 3 4 6% 7% 47%	3926
August	1st to 10th	Night	24% 8% 2 6% 4 4 3 3 4 6% 37%	2684
	11th to 20th	Night	22% 8% 2 6% 4 3 4 3 4 6% 38%	3033
	21st to end	Night	16% 7% 2 5% 4 4 4 4 5% 7% 41%	3586
September	1st to 10th	Night	17% 7% 2 5% 4 4 4 4 5% 6% 42%	2000
	11th to 20th	Night	17% 6% 2 6% 3 3 3 3 4 6% 48%	2035
	21st to end	Night	21% 7% 2 5% 4 4 5% 3 6% 7% 38%	2200
October	1st to 10th	Night	25% 8% 3 7% 4 4 4 3 4 4 34%	2400
	11th to 20th	Night	23% 10% 3 6% 4 4 4 4 5% 6% 32%	2400
	21st to end	Night	27% 13% 4 8% 4 3 4 3 4 6% 23%	2801
November	1st to 10th	Night	19% 15% 4 8% 5% 3 4 3 4 5% 30%	2667
	11th to 20th	Night	20% 17% 5% 7% 5% 4 4 3 4 5% 27%	2798
	21st to end	Night	19% 22% 6% 10% 4 3 4 3 5% 5% 19%	2940
December	1st to 10th	Night	18% 25% 11% 16% 4 3 3 3 3 3 10%	4720
	11th to 20th	Night	23% 21% 7% 15% 5% 3 3 2 2 3 15%	5348
	21st to end	Night	23% 20% 6% 12% 4 4 3 2 3 4 19%	7150

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	81% 2 5% 8% 3	4662
	11th to 20th	Day	82% 2 4 5% 6% 2	4680
	21st to end	Day	72% 3 8% 11% 5% 1	5441
February	1st to 10th	Day	74% 3 6% 12% 5% 1	1890
	11th to 20th	Day	70% 4 6% 12% 7% 1	1941
	21st to end	Day	71% 4 7% 10% 7%	1730
March	1st to 10th	Day	69% 2 8% 10% 8% 2	4579
	11th to 20th	Day	59% 3 17% 11% 7% 3	4996
	21st to end	Day	61% 3 6% 13% 16% 2	5961
April	1st to 10th	Day	60% 3 7% 18% 10% 2	2520
	11th to 20th	Day	56% 4 8% 19% 11% 1	2494
	21st to end	Day	58% 4 8% 16% 11% 3	2567
May	1st to 10th	Day	65% 3 8% 15% 8% 1	8147
	11th to 20th	Day	55% 5% 11% 21% 8% 1	8225
	21st to end	Day	55% 5% 10% 23% 7%	9061
June	1st to 10th	Day	53% 4 12% 20% 10%	2940
	11th to 20th	Day	51% 5% 13% 22% 8% 1	2870
	21st to end	Day	53% 5% 13% 19% 9% 1	2800
July	1st to 10th	Day	42% 6% 17% 24% 11%	6290
	11th to 20th	Day	45% 7% 13% 25% 10%	6285
	21st to end	Day	42% 6% 12% 32% 8%	6728
August	1st to 10th	Day	47% 6% 15% 20% 12%	4433
	11th to 20th	Day	50% 6% 16% 23% 6%	4021
	21st to end	Day	44% 5% 15% 28% 6%	4312
September	1st to 10th	Day	43% 6% 11% 28% 11%	2400
	11th to 20th	Day	42% 4 10% 28% 15% 1	2365
	21st to end	Day	50% 5% 10% 23% 12% 1	2196
October	1st to 10th	Day	53% 4 9% 24% 9% 1	3260
	11th to 20th	Day	50% 3 13% 18% 15% 1	3240
	21st to end	Day	50% 4 15% 23% 7% 1	3262
November	1st to 10th	Day	59% 4 11% 16% 9%	1851
	11th to 20th	Day	60% 4 9% 15% 10% 2	1816
	21st to end	Day	69% 5% 12% 9% 5% 1	1680
December	1st to 10th	Day	82% 4 6% 6% 2	2680
	11th to 20th	Day	78% 3 5% 11% 3	3066
	21st to end	Day	71% 2 6% 8% 12% 1	4048
January	1st to 10th	Night	80% 2 6% 8% 4	8234
	11th to 20th	Night	86% 2 4 4 4 1	8280
	21st to end	Night	74% 3 8% 9% 5% 1	8726
February	1st to 10th	Night	74% 3 7% 10% 6%	2730
	11th to 20th	Night	71% 5% 6% 13% 6%	2575
	21st to end	Night	68% 4 9% 12% 7% 1	2076
March	1st to 10th	Night	68% 3 8% 12% 8% 2	5494
	11th to 20th	Night	58% 4 15% 15% 6% 3	5168
	21st to end	Night	65% 2 5% 17% 10% 1	5213
April	1st to 10th	Night	60% 4 9% 18% 8% 1	2100
	11th to 20th	Night	56% 5% 8% 18% 12%	2075
	21st to end	Night	53% 3 10% 18% 13% 2	2053
May	1st to 10th	Night	65% 3 8% 12% 11% 1	4811
	11th to 20th	Night	54% 5% 10% 22% 9% 1	4640
	21st to end	Night	55% 4 10% 21% 9% 1	5115
June	1st to 10th	Night	47% 5% 12% 22% 13% 1	1680
	11th to 20th	Night	46% 5% 14% 23% 11% 1	1640
	21st to end	Night	47% 6% 13% 24% 10% 1	1600
July	1st to 10th	Night	45% 6% 16% 20% 12% 1	3560
	11th to 20th	Night	46% 5% 12% 23% 14%	3552
	21st to end	Night	36% 5% 13% 34% 11%	3809
August	1st to 10th	Night	50% 5% 14% 23% 8%	2674
	11th to 20th	Night	48% 4 12% 28% 7%	3060
	21st to end	Night	41% 5% 15% 31% 8%	3586
September	1st to 10th	Night	43% 5% 13% 27% 12% 1	2000
	11th to 20th	Night	38% 4 10% 31% 16% 1	2035
	21st to end	Night	45% 5% 12% 25% 12% 2	2200
October	1st to 10th	Night	55% 4 10% 20% 10% 1	3920
	11th to 20th	Night	47% 4 13% 20% 11% 5%	3899
	21st to end	Night	53% 5% 11% 23% 6% 1	4526
November	1st to 10th	Night	56% 5% 11% 16% 10% 2	2667
	11th to 20th	Night	61% 4 9% 16% 9% 2	2798
	21st to end	Night	67% 4 9% 14% 4 1	2940
December	1st to 10th	Night	80% 5% 6% 7% 2	4720
	11th to 20th	Night	77% 3 6% 10% 4	5348
	21st to end	Night	71% 2 7% 7% 11% 2	7150

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	34% 20% 32% 11% 3	220
	11th to 20th	Day	37% 28% 28% 5% 2	220
	21st to end	Day	29% 26% 33% 9% 2	300
February	1st to 10th	Day	40% 29% 27% 5%	330
	11th to 20th	Day	38% 28% 28% 5% 1	419
	21st to end	Day	35% 25% 32% 7% 1	446
March	1st to 10th	Day	32% 26% 28% 12% 2	540
	11th to 20th	Day	33% 26% 28% 10% 3	540
	21st to end	Day	36% 24% 24% 12% 3 1	594
April	1st to 10th	Day	39% 24% 21% 10% 4 1	540
	11th to 20th	Day	38% 22% 21% 12% 6% 1	532
	21st to end	Day	35% 20% 27% 13% 4 2	540
May	1st to 10th	Day	37% 18% 26% 11% 5% 3	543
	11th to 20th	Day	26% 16% 31% 20% 6% 2	567
	21st to end	Day	26% 14% 30% 18% 10% 2	617
June	1st to 10th	Day	26% 15% 30% 19% 7% 1	570
	11th to 20th	Day	25% 14% 28% 24% 7% 2	550
	21st to end	Day	28% 13% 32% 18% 7% 2	530
July	1st to 10th	Day	19% 8% 30% 27% 12% 3	525
	11th to 20th	Day	19% 7% 31% 30% 10% 3	524
	21st to end	Day	19% 9% 36% 26% 8% 2	576
August	1st to 10th	Day	19% 8% 24% 29% 14% 5%	526
	11th to 20th	Day	23% 8% 24% 24% 15% 6%	519
	21st to end	Day	19% 14% 28% 21% 12% 5%	583
September	1st to 10th	Day	21% 11% 24% 23% 15% 6%	530
	11th to 20th	Day	17% 9% 25% 20% 18% 10%	530
	21st to end	Day	23% 10% 31% 22% 11% 3	530
October	1st to 10th	Day	31% 12% 24% 18% 13% 3	530
	11th to 20th	Day	30% 18% 31% 15% 5% 1	530
	21st to end	Day	36% 17% 24% 20% 3	492
November	1st to 10th	Day	36% 16% 25% 15% 8%	425
	11th to 20th	Day	32% 25% 25% 13% 3 1	356
	21st to end	Day	42% 25% 25% 7% 1	220
December	1st to 10th	Day	36% 24% 28% 8% 4	220
	11th to 20th	Day	39% 27% 25% 6% 3	220
	21st to end	Day	37% 22% 29% 10% 2	242
January	1st to 10th	Night	30% 27% 30% 11% 1	840
	11th to 20th	Night	34% 22% 28% 13% 2	840
	21st to end	Night	22% 25% 33% 16% 3	924
February	1st to 10th	Night	28% 25% 33% 13% 1	840
	11th to 20th	Night	27% 27% 32% 12% 2	823
	21st to end	Night	29% 23% 33% 13% 2	692
March	1st to 10th	Night	27% 23% 33% 16% 2	840
	11th to 20th	Night	31% 21% 31% 15% 3	840
	21st to end	Night	28% 23% 29% 14% 5% 1	924
April	1st to 10th	Night	30% 19% 31% 17% 2	840
	11th to 20th	Night	30% 18% 29% 16% 6%	831
	21st to end	Night	31% 15% 26% 21% 6%	793
May	1st to 10th	Night	33% 9% 28% 23% 7% 1	474
	11th to 20th	Night	23% 14% 31% 26% 7%	414
	21st to end	Night	20% 5% 29% 34% 10% 1	455
June	1st to 10th	Night	25% 6% 22% 36% 10% 1	420
	11th to 20th	Night	25% 8% 24% 29% 13%	410
	21st to end	Night	23% 6% 29% 32% 11%	400
July	1st to 10th	Night	18% 4 21% 39% 17% 1	390
	11th to 20th	Night	16% 4 21% 39% 17% 2	388
	21st to end	Night	16% 6% 21% 43% 13% 1	438
August	1st to 10th	Night	20% 3 18% 39% 19% 1	457
	11th to 20th	Night	22% 4 20% 30% 22% 2	687
	21st to end	Night	20% 6% 20% 35% 17% 1	880
September	1st to 10th	Night	20% 8% 23% 32% 16% 2	800
	11th to 20th	Night	21% 5% 21% 30% 19% 4	800
	21st to end	Night	24% 8% 25% 28% 14% 2	800
October	1st to 10th	Night	29% 10% 24% 23% 13% 2	800
	11th to 20th	Night	29% 13% 29% 23% 6% 1	800
	21st to end	Night	35% 15% 28% 19% 2	880
November	1st to 10th	Night	27% 18% 29% 19% 6%	820
	11th to 20th	Night	31% 19% 29% 14% 6% 1	840
	21st to end	Night	30% 23% 28% 16% 3 1	840
December	1st to 10th	Night	35% 22% 27% 13% 3	840
	11th to 20th	Night	34% 25% 25% 13% 3	840
	21st to end	Night	35% 26% 25% 12% 2	924

Page generated at 2026-06-13 02:31:40. Version ac07

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