Gothenburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gothenburg clear sky chart from 2005-11-06 to 2026-08-15.

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	8% 6% 2 5% 4 3 4 3 5% 7% 53%	152060
	Night	8% 6% 2 6% 4 4 4 3 5% 7% 51%	147240
Transparency	Day	31% 4 12% 27% 21% 5%	146880
	Night	32% 5% 12% 26% 20% 5%	143445
Seeing	Day	12% 8% 31% 32% 15% 2	18248
	Night	10% 8% 35% 37% 9%	28080

By Month

Percentage Cloud Cover SW (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	8% 11% 3 7% 4 3 4 2 4 5% 49%	4720
	11th to 20th	Day	4 8% 3 7% 4 4 5% 4 5% 6% 49%	4740
	21st to end	Day	4 7% 3 8% 5% 5% 5% 3 5% 7% 49%	5510
February	1st to 10th	Day	7% 8% 3 9% 7% 4 5% 3 6% 7% 42%	1995
	11th to 20th	Day	5% 7% 3 8% 4 3 5% 4 6% 7% 47%	2049
	21st to end	Day	6% 7% 3 5% 3 3 3 2 5% 6% 57%	1730
March	1st to 10th	Day	11% 7% 2 4 2 2 3 3 4 5% 56%	4600
	11th to 20th	Day	8% 6% 2 4 3 3 3 3 4 6% 58%	5034
	21st to end	Day	9% 7% 2 7% 4 3 4 4 6% 7% 47%	5626
April	1st to 10th	Day	10% 6% 2 5% 3 3 3 4 5% 7% 52%	2520
	11th to 20th	Day	13% 7% 2 5% 4 4 3 3 5% 7% 46%	2542
	21st to end	Day	16% 6% 2 5% 4 3 4 3 5% 6% 47%	2730
May	1st to 10th	Day	9% 5% 2 5% 4 4 4 4 6% 8% 50%	7655
	11th to 20th	Day	11% 4 2 4 3 3 3 3 4 6% 56%	7627
	21st to end	Day	16% 6% 2 6% 4 4 4 3 5% 7% 43%	8531
June	1st to 10th	Day	6% 3 1 3 4 3 3 4 7% 9% 56%	2940
	11th to 20th	Day	8% 4 1 4 4 4 4 4 6% 8% 54%	2940
	21st to end	Day	5% 4 1 4 3 4 4 4 6% 9% 56%	2940
July	1st to 10th	Day	6% 4 2 5% 3 4 4 4 6% 8% 56%	8249
	11th to 20th	Day	5% 4 1 3 2 3 3 3 5% 8% 62%	8250
	21st to end	Day	6% 5% 2 5% 4 4 4 4 7% 10% 50%	8626
August	1st to 10th	Day	9% 5% 2 6% 4 3 4 4 6% 8% 49%	5931
	11th to 20th	Day	8% 4 2 5% 4 4 4 4 6% 9% 51%	5874
	21st to end	Day	11% 6% 2 5% 4 4 4 3 5% 7% 49%	5996
September	1st to 10th	Day	9% 4 2 4 3 3 3 3 4 6% 58%	2347
	11th to 20th	Day	7% 4 2 5% 3 3 4 3 5% 7% 56%	2200
	21st to end	Day	10% 4 2 4 1 2 3 2 4 5% 64%	2200
October	1st to 10th	Day	7% 3 1 2 2 1 2 2 2 4 74%	3590
	11th to 20th	Day	6% 4 1 4 3 2 3 3 4 6% 64%	3266
	21st to end	Day	9% 5% 2 4 3 3 3 3 4 6% 58%	3190
November	1st to 10th	Day	7% 6% 2 4 3 4 3 3 5% 6% 57%	1853
	11th to 20th	Day	5% 7% 1 4 3 3 3 3 4 6% 62%	1890
	21st to end	Day	8% 7% 2 4 3 3 3 3 5% 7% 56%	1890
December	1st to 10th	Day	3 4 2 6% 4 3 3 3 4 7% 61%	3030
	11th to 20th	Day	4 6% 2 6% 4 3 3 3 4 6% 58%	3157
	21st to end	Day	9% 12% 3 9% 5% 4 3 3 4 6% 42%	4092
January	1st to 10th	Night	6% 10% 4 10% 5% 5% 4 3 4 6% 42%	8201
	11th to 20th	Night	2 6% 2 7% 4 4 4 4 6% 7% 52%	8250
	21st to end	Night	4 8% 3 7% 4 5% 4 3 5% 6% 49%	8689
February	1st to 10th	Night	8% 9% 4 7% 4 4 4 4 5% 7% 45%	2644
	11th to 20th	Night	4 9% 3 7% 5% 5% 4 4 5% 8% 46%	2458
	21st to end	Night	4 7% 2 6% 4 3 4 4 5% 5% 56%	2076
March	1st to 10th	Night	9% 7% 2 5% 3 3 3 3 4 5% 57%	5494
	11th to 20th	Night	9% 5% 2 4 3 3 3 3 4 7% 58%	5148
	21st to end	Night	10% 8% 3 7% 5% 5% 5% 5% 6% 8% 39%	5544
April	1st to 10th	Night	11% 7% 2 5% 4 4 4 3 6% 7% 47%	2100
	11th to 20th	Night	12% 5% 2 4 3 4 5% 4 6% 6% 49%	2026
	21st to end	Night	12% 7% 2 5% 4 4 4 4 6% 8% 46%	1890
May	1st to 10th	Night	14% 6% 2 5% 4 4 4 3 5% 6% 46%	5292
	11th to 20th	Night	7% 5% 2 6% 4 4 5% 3 6% 8% 51%	5265
	21st to end	Night	18% 7% 2 6% 4 4 3 3 4 7% 41%	5672
June	1st to 10th	Night	7% 3 2 5% 5% 4 4 4 6% 7% 54%	1680
	11th to 20th	Night	10% 4 1 4 4 3 4 3 5% 9% 52%	1680
	21st to end	Night	6% 4 1 5% 4 4 5% 5% 6% 9% 52%	1680
July	1st to 10th	Night	6% 4 2 5% 4 4 5% 5% 8% 10% 46%	4740
	11th to 20th	Night	6% 4 2 4 4 4 4 4 5% 8% 57%	4740
	21st to end	Night	7% 5% 2 5% 4 4 4 4 7% 10% 48%	5468
August	1st to 10th	Night	7% 5% 2 6% 5% 5% 5% 4 8% 12% 41%	4101
	11th to 20th	Night	8% 5% 2 5% 4 4 4 5% 7% 10% 46%	4064
	21st to end	Night	9% 6% 2 5% 4 4 5% 4 7% 8% 44%	4964
September	1st to 10th	Night	7% 5% 1 4 2 3 3 3 5% 6% 61%	2051
	11th to 20th	Night	6% 4 1 4 3 3 4 3 5% 7% 60%	2200
	21st to end	Night	8% 3 1 4 3 3 3 2 4 6% 62%	2200
October	1st to 10th	Night	8% 2 1 2 2 2 2 1 3 3 73%	3590
	11th to 20th	Night	7% 4 1 3 2 2 2 2 3 6% 66%	3837
	21st to end	Night	8% 5% 2 5% 3 3 3 3 4 6% 59%	4610
November	1st to 10th	Night	5% 4 2 4 3 3 3 3 5% 7% 61%	2665
	11th to 20th	Night	5% 6% 2 5% 3 3 3 4 5% 7% 58%	2730
	21st to end	Night	7% 7% 2 5% 3 3 3 3 5% 7% 56%	2730
December	1st to 10th	Night	3 4 2 4 3 2 3 3 5% 6% 64%	4380
	11th to 20th	Night	4 5% 2 5% 4 3 4 3 6% 7% 58%	5253
	21st to end	Night	10% 13% 3 6% 4 4 3 3 4 6% 43%	7128

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	40% 2 9% 30% 17% 1	4723
	11th to 20th	Day	35% 5% 10% 26% 19% 4	4740
	21st to end	Day	36% 4 12% 25% 19% 3	5510
February	1st to 10th	Day	41% 7% 15% 21% 14% 3	1995
	11th to 20th	Day	35% 5% 15% 25% 16% 4	2059
	21st to end	Day	29% 3 13% 29% 21% 6%	1730
March	1st to 10th	Day	31% 4 8% 23% 29% 6%	4600
	11th to 20th	Day	28% 3 9% 25% 29% 6%	5034
	21st to end	Day	34% 8% 18% 27% 11% 2	5626
April	1st to 10th	Day	31% 5% 17% 27% 18% 3	2520
	11th to 20th	Day	37% 5% 14% 23% 17% 4	2545
	21st to end	Day	37% 5% 11% 27% 17% 2	2730
May	1st to 10th	Day	31% 5% 11% 28% 21% 5%	7655
	11th to 20th	Day	29% 5% 10% 27% 23% 5%	7631
	21st to end	Day	41% 5% 13% 25% 14% 2	8532
June	1st to 10th	Day	23% 8% 20% 33% 14% 3	2940
	11th to 20th	Day	28% 6% 13% 27% 19% 7%	2940
	21st to end	Day	24% 7% 13% 29% 22% 6%	2940
July	1st to 10th	Day	27% 3 10% 31% 26% 3	8181
	11th to 20th	Day	22% 3 12% 29% 23% 10%	8175
	21st to end	Day	30% 4 19% 25% 18% 4	8435
August	1st to 10th	Day	34% 6% 15% 25% 19% 2	4350
	11th to 20th	Day	36% 6% 14% 25% 18% 1	4263
	21st to end	Day	24% 4 15% 26% 19% 11%	4323
September	1st to 10th	Day	27% 4 12% 25% 24% 9%	2347
	11th to 20th	Day	26% 6% 12% 27% 24% 5%	2200
	21st to end	Day	24% 3 9% 31% 27% 6%	2200
October	1st to 10th	Day	18% 2 5% 23% 37% 15%	3590
	11th to 20th	Day	22% 3 12% 36% 21% 5%	3266
	21st to end	Day	28% 3 7% 34% 23% 6%	3190
November	1st to 10th	Day	27% 4 13% 28% 23% 4	1853
	11th to 20th	Day	25% 3 11% 30% 25% 6%	1890
	21st to end	Day	29% 3 14% 27% 22% 4	1890
December	1st to 10th	Day	25% 3 11% 33% 24% 4	3030
	11th to 20th	Day	28% 3 18% 32% 17% 2	3155
	21st to end	Day	45% 3 8% 28% 14% 2	4092
January	1st to 10th	Night	43% 4 11% 22% 17% 3	8202
	11th to 20th	Night	31% 4 15% 27% 22% 2	8250
	21st to end	Night	36% 5% 9% 25% 20% 4	8689
February	1st to 10th	Night	38% 6% 13% 24% 16% 4	2644
	11th to 20th	Night	36% 6% 13% 27% 15% 3	2458
	21st to end	Night	30% 4 12% 26% 22% 7%	2076
March	1st to 10th	Night	30% 4 7% 24% 28% 7%	5494
	11th to 20th	Night	27% 4 8% 23% 27% 11%	5148
	21st to end	Night	40% 7% 18% 22% 12% 1	5544
April	1st to 10th	Night	34% 5% 14% 25% 18% 4	2100
	11th to 20th	Night	34% 7% 14% 25% 18% 3	2026
	21st to end	Night	35% 7% 15% 26% 16% 2	1890
May	1st to 10th	Night	37% 5% 10% 27% 20% 2	5293
	11th to 20th	Night	31% 6% 13% 28% 19% 4	5266
	21st to end	Night	43% 6% 13% 24% 12% 1	5674
June	1st to 10th	Night	28% 8% 21% 27% 14% 2	1680
	11th to 20th	Night	30% 5% 15% 26% 17% 6%	1680
	21st to end	Night	28% 7% 16% 26% 20% 3	1680
July	1st to 10th	Night	33% 4 16% 31% 15% 1	4700
	11th to 20th	Night	27% 4 14% 23% 22% 10%	4692
	21st to end	Night	31% 5% 17% 25% 17% 6%	5346
August	1st to 10th	Night	33% 6% 17% 26% 17% 2	3006
	11th to 20th	Night	36% 5% 16% 26% 15% 2	2951
	21st to end	Night	27% 4 15% 28% 19% 8%	3581
September	1st to 10th	Night	24% 5% 11% 25% 25% 10%	2051
	11th to 20th	Night	24% 6% 13% 28% 23% 6%	2200
	21st to end	Night	25% 4 9% 27% 29% 7%	2200
October	1st to 10th	Night	18% 3 5% 19% 45% 9%	3590
	11th to 20th	Night	22% 3 11% 30% 25% 10%	3837
	21st to end	Night	28% 2 10% 27% 27% 6%	4610
November	1st to 10th	Night	22% 4 12% 30% 24% 7%	2665
	11th to 20th	Night	25% 5% 11% 28% 25% 6%	2730
	21st to end	Night	28% 4 11% 28% 24% 5%	2730
December	1st to 10th	Night	21% 3 15% 37% 21% 3	4380
	11th to 20th	Night	25% 3 14% 37% 17% 3	5254
	21st to end	Night	42% 4 11% 29% 14% 1	7128

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	14% 7% 35% 32% 11% 2	330
	11th to 20th	Day	12% 14% 35% 32% 6% 1	330
	21st to end	Day	10% 8% 47% 21% 11% 3	363
February	1st to 10th	Day	9% 15% 44% 26% 5%	330
	11th to 20th	Day	11% 8% 43% 28% 8% 2	330
	21st to end	Day	11% 13% 44% 29% 3	273
March	1st to 10th	Day	12% 9% 43% 25% 10% 1	330
	11th to 20th	Day	14% 10% 38% 28% 9% 1	330
	21st to end	Day	19% 14% 40% 18% 8% 1	379
April	1st to 10th	Day	14% 20% 39% 21% 6%	540
	11th to 20th	Day	17% 19% 32% 26% 5%	583
	21st to end	Day	20% 15% 31% 24% 9% 1	750
May	1st to 10th	Day	12% 12% 35% 29% 11% 2	753
	11th to 20th	Day	19% 10% 29% 27% 13% 1	775
	21st to end	Day	16% 10% 32% 28% 12% 1	844
June	1st to 10th	Day	6% 7% 28% 32% 20% 7%	780
	11th to 20th	Day	9% 8% 35% 34% 13% 1	780
	21st to end	Day	9% 6% 29% 39% 16% 2	780
July	1st to 10th	Day	7% 4 24% 37% 25% 4	771
	11th to 20th	Day	6% 2 21% 40% 27% 5%	768
	21st to end	Day	6% 2 19% 42% 25% 6%	849
August	1st to 10th	Day	9% 4 19% 41% 24% 4	776
	11th to 20th	Day	9% 3 21% 43% 23% 2	736
	21st to end	Day	8% 3 23% 40% 22% 4	595
September	1st to 10th	Day	9% 3 24% 44% 17% 4	477
	11th to 20th	Day	5% 6% 25% 38% 22% 5%	330
	21st to end	Day	12% 9% 24% 30% 20% 4	330
October	1st to 10th	Day	18% 5% 24% 30% 18% 5%	330
	11th to 20th	Day	10% 11% 39% 28% 9% 2	330
	21st to end	Day	19% 11% 29% 27% 12% 1	363
November	1st to 10th	Day	13% 8% 39% 25% 13% 1	330
	11th to 20th	Day	12% 11% 36% 30% 11% 1	330
	21st to end	Day	17% 8% 37% 26% 10% 2	330
December	1st to 10th	Day	6% 10% 42% 32% 9% 1	330
	11th to 20th	Day	13% 9% 40% 28% 9% 1	330
	21st to end	Day	14% 11% 39% 28% 7% 1	363
January	1st to 10th	Night	10% 10% 36% 35% 8%	1050
	11th to 20th	Night	8% 13% 38% 34% 7% 1	1050
	21st to end	Night	8% 8% 45% 32% 7%	1155
February	1st to 10th	Night	12% 9% 43% 31% 6%	964
	11th to 20th	Night	9% 10% 42% 35% 4	824
	21st to end	Night	7% 11% 42% 34% 5%	692
March	1st to 10th	Night	11% 10% 42% 33% 5%	840
	11th to 20th	Night	13% 10% 40% 32% 5%	662
	21st to end	Night	15% 12% 40% 28% 5%	693
April	1st to 10th	Night	14% 14% 42% 28% 2	630
	11th to 20th	Night	15% 15% 42% 27% 2	623
	21st to end	Night	16% 12% 36% 30% 7%	630
May	1st to 10th	Night	16% 8% 37% 32% 7%	630
	11th to 20th	Night	16% 10% 35% 31% 7%	621
	21st to end	Night	18% 7% 36% 30% 9% 1	683
June	1st to 10th	Night	7% 7% 31% 42% 12%	630
	11th to 20th	Night	10% 7% 36% 37% 10%	630
	21st to end	Night	7% 5% 33% 46% 9%	630
July	1st to 10th	Night	6% 4 27% 44% 19%	615
	11th to 20th	Night	3 1 25% 54% 15% 1	612
	21st to end	Night	6% 2 21% 51% 20% 1	690
August	1st to 10th	Night	6% 2 20% 53% 18%	627
	11th to 20th	Night	8% 3 23% 50% 16%	606
	21st to end	Night	7% 2 23% 49% 18% 1	660
September	1st to 10th	Night	8% 3 28% 49% 11% 1	600
	11th to 20th	Night	7% 4 31% 43% 14% 1	600
	21st to end	Night	9% 6% 32% 36% 16% 1	600
October	1st to 10th	Night	15% 7% 32% 34% 12% 1	600
	11th to 20th	Night	12% 11% 34% 33% 10%	753
	21st to end	Night	15% 10% 32% 34% 9%	1100
November	1st to 10th	Night	8% 8% 37% 39% 8% 1	1025
	11th to 20th	Night	10% 8% 38% 36% 7%	1050
	21st to end	Night	10% 8% 33% 37% 11% 1	1050
December	1st to 10th	Night	9% 9% 40% 37% 5%	1050
	11th to 20th	Night	11% 9% 40% 32% 7%	1050
	21st to end	Night	15% 10% 35% 34% 6%	1155

Page generated at 2026-08-12 02:37:16. Version ac07

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