Baltic Corners
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Baltic Corners clear sky chart from 2005-11-06 to 2025-09-04.

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	17% 10% 4 8% 5% 4 4 4 5% 7% 31%	126437
	Night	17% 12% 4 9% 5% 4 4 3 5% 6% 30%	122262
Transparency	Day	51% 6% 12% 20% 9% 1	129878
	Night	54% 6% 12% 18% 10% 1	126908
Seeing	Day	23% 16% 29% 20% 9% 2	15563
	Night	23% 12% 30% 25% 9% 1	24539

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	15% 20% 6% 15% 5% 4 4 3 4 4 20%	3597
	11th to 20th	Day	12% 16% 7% 14% 7% 4 5% 4 5% 5% 22%	3570
	21st to end	Day	12% 19% 7% 11% 5% 6% 5% 4 5% 6% 21%	4006
February	1st to 10th	Day	15% 17% 5% 11% 5% 4 4 3 5% 6% 25%	1800
	11th to 20th	Day	15% 14% 5% 12% 7% 5% 3 4 4 5% 26%	1808
	21st to end	Day	20% 14% 5% 8% 5% 5% 4 3 5% 5% 25%	1650
March	1st to 10th	Day	18% 13% 5% 12% 6% 5% 4 3 4 5% 25%	4476
	11th to 20th	Day	12% 14% 4 9% 5% 5% 5% 4 6% 6% 30%	4837
	21st to end	Day	19% 10% 3 9% 5% 4 4 3 4 5% 35%	5870
April	1st to 10th	Day	22% 13% 3 6% 4 4 4 3 3 5% 33%	2400
	11th to 20th	Day	21% 11% 3 7% 5% 3 3 2 4 6% 35%	2374
	21st to end	Day	23% 10% 3 8% 5% 4 4 3 4 5% 31%	2525
May	1st to 10th	Day	26% 10% 3 9% 5% 4 5% 4 5% 6% 23%	6346
	11th to 20th	Day	19% 9% 4 10% 5% 5% 4 4 5% 6% 30%	6318
	21st to end	Day	22% 8% 3 7% 4 4 5% 4 5% 7% 31%	6949
June	1st to 10th	Day	23% 9% 3 7% 5% 4 4 4 5% 7% 29%	2800
	11th to 20th	Day	14% 7% 2 6% 5% 6% 5% 4 6% 9% 37%	2800
	21st to end	Day	20% 7% 3 6% 4 5% 5% 4 6% 9% 30%	2800
July	1st to 10th	Day	13% 7% 3 8% 6% 6% 5% 4 7% 8% 33%	6360
	11th to 20th	Day	12% 6% 2 6% 5% 5% 5% 4 6% 8% 41%	6360
	21st to end	Day	11% 5% 2 5% 4 4 4 4 6% 10% 45%	6926
August	1st to 10th	Day	15% 7% 3 7% 5% 4 5% 4 6% 8% 35%	4563
	11th to 20th	Day	15% 7% 2 6% 4 4 4 4 6% 8% 39%	4080
	21st to end	Day	15% 5% 2 6% 4 5% 5% 4 6% 8% 38%	4312
September	1st to 10th	Day	13% 7% 2 5% 4 4 5% 4 6% 8% 43%	2316
	11th to 20th	Day	14% 5% 2 5% 3 4 4 3 5% 7% 48%	2242
	21st to end	Day	19% 6% 2 5% 4 4 3 3 6% 7% 41%	2089
October	1st to 10th	Day	21% 7% 2 6% 4 4 5% 4 5% 7% 36%	1900
	11th to 20th	Day	21% 10% 4 9% 5% 4 3 4 4 6% 30%	1900
	21st to end	Day	25% 11% 3 7% 4 4 5% 3 5% 5% 28%	1891
November	1st to 10th	Day	16% 9% 5% 8% 4 4 4 5% 5% 6% 33%	1761
	11th to 20th	Day	17% 13% 3 8% 5% 4 5% 4 5% 6% 30%	1665
	21st to end	Day	22% 15% 4 10% 5% 5% 5% 3 5% 5% 22%	1600
December	1st to 10th	Day	22% 21% 6% 9% 5% 5% 5% 4 5% 5% 14%	2600
	11th to 20th	Day	19% 16% 5% 11% 5% 4 4 3 4 5% 23%	2986
	21st to end	Day	23% 16% 4 10% 5% 4 4 3 4 4 23%	3960
January	1st to 10th	Night	15% 21% 8% 13% 5% 4 4 3 4 4 19%	6349
	11th to 20th	Night	11% 17% 7% 16% 7% 6% 5% 4 5% 5% 18%	6315
	21st to end	Night	14% 17% 6% 12% 7% 5% 4 3 4 5% 21%	6932
February	1st to 10th	Night	15% 14% 5% 12% 7% 6% 4 4 5% 6% 23%	2600
	11th to 20th	Night	14% 13% 4 12% 7% 5% 4 4 5% 5% 27%	2477
	21st to end	Night	15% 15% 5% 10% 6% 4 4 3 4 5% 29%	1980
March	1st to 10th	Night	21% 14% 4 9% 4 4 4 2 4 4 29%	5364
	11th to 20th	Night	14% 13% 4 8% 6% 5% 5% 4 6% 8% 29%	5117
	21st to end	Night	18% 11% 4 8% 5% 4 4 3 5% 5% 32%	5061
April	1st to 10th	Night	23% 11% 3 7% 4 5% 4 3 4 7% 30%	2000
	11th to 20th	Night	21% 10% 3 7% 5% 3 4 3 4 5% 35%	1975
	21st to end	Night	22% 9% 3 7% 4 4 3 3 4 6% 34%	1891
May	1st to 10th	Night	23% 9% 3 9% 6% 5% 5% 4 6% 7% 23%	3594
	11th to 20th	Night	19% 10% 3 7% 4 4 5% 4 6% 6% 34%	3575
	21st to end	Night	17% 11% 4 8% 5% 4 5% 4 6% 7% 31%	3926
June	1st to 10th	Night	18% 9% 2 6% 6% 5% 6% 5% 6% 9% 29%	1600
	11th to 20th	Night	16% 6% 2 6% 5% 4 5% 4 6% 7% 40%	1600
	21st to end	Night	19% 7% 3 6% 4 5% 4 4 6% 7% 35%	1600
July	1st to 10th	Night	15% 7% 3 7% 5% 5% 5% 5% 7% 9% 33%	3600
	11th to 20th	Night	13% 6% 3 7% 4 4 4 4 5% 7% 43%	3600
	21st to end	Night	10% 6% 2 6% 5% 4 4 4 6% 8% 46%	3926
August	1st to 10th	Night	14% 8% 3 7% 4 4 4 4 6% 8% 39%	2586
	11th to 20th	Night	15% 7% 2 6% 4 4 4 3 5% 8% 41%	2932
	21st to end	Night	13% 6% 2 7% 5% 4 5% 4 5% 8% 41%	3586
September	1st to 10th	Night	11% 6% 2 8% 5% 4 5% 4 6% 6% 44%	1931
	11th to 20th	Night	14% 6% 1 5% 4 2 3 3 4 7% 50%	1938
	21st to end	Night	17% 5% 2 6% 3 5% 5% 3 5% 6% 43%	2090
October	1st to 10th	Night	20% 7% 3 6% 4 4 4 3 4 6% 38%	2279
	11th to 20th	Night	20% 9% 3 7% 5% 4 5% 3 4 6% 33%	2280
	21st to end	Night	23% 10% 3 9% 4 4 4 3 5% 5% 29%	2707
November	1st to 10th	Night	21% 10% 3 7% 4 3 4 3 5% 6% 33%	2537
	11th to 20th	Night	18% 10% 4 9% 5% 4 5% 4 4 5% 32%	2730
	21st to end	Night	22% 14% 4 10% 5% 4 4 3 4 6% 23%	2800
December	1st to 10th	Night	18% 18% 7% 12% 7% 5% 5% 3 5% 5% 16%	4580
	11th to 20th	Night	24% 15% 5% 10% 5% 4 4 3 3 3 25%	5208
	21st to end	Night	26% 18% 4 10% 4 3 3 3 4 5% 21%	6996

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	67% 6% 10% 13% 4	3598
	11th to 20th	Day	63% 6% 11% 12% 8% 1	3600
	21st to end	Day	63% 6% 12% 10% 8% 1	4006
February	1st to 10th	Day	61% 5% 9% 18% 5% 2	1800
	11th to 20th	Day	59% 6% 12% 15% 7% 1	1817
	21st to end	Day	61% 4 11% 13% 9% 1	1650
March	1st to 10th	Day	60% 6% 9% 14% 9% 3	4479
	11th to 20th	Day	52% 7% 16% 14% 9% 1	4837
	21st to end	Day	52% 5% 7% 16% 18% 2	5870
April	1st to 10th	Day	54% 5% 8% 19% 12% 3	2400
	11th to 20th	Day	51% 5% 7% 20% 15% 2	2374
	21st to end	Day	54% 6% 8% 15% 13% 4	2525
May	1st to 10th	Day	60% 7% 9% 16% 7% 1	6357
	11th to 20th	Day	53% 7% 13% 17% 9% 1	6322
	21st to end	Day	50% 7% 12% 19% 11% 1	6949
June	1st to 10th	Day	53% 6% 11% 18% 12% 1	2800
	11th to 20th	Day	43% 7% 13% 23% 13% 2	2800
	21st to end	Day	49% 9% 13% 20% 9% 1	2800
July	1st to 10th	Day	45% 7% 14% 25% 9%	6290
	11th to 20th	Day	38% 8% 13% 29% 12%	6285
	21st to end	Day	33% 7% 15% 36% 9%	6728
August	1st to 10th	Day	44% 7% 17% 23% 8%	4549
	11th to 20th	Day	40% 7% 17% 29% 6%	4120
	21st to end	Day	42% 7% 17% 22% 11% 1	4312
September	1st to 10th	Day	37% 8% 15% 27% 12%	2316
	11th to 20th	Day	35% 6% 14% 31% 14% 1	2242
	21st to end	Day	42% 8% 14% 26% 10%	2089
October	1st to 10th	Day	45% 6% 12% 29% 8%	3160
	11th to 20th	Day	47% 5% 16% 25% 7%	3140
	21st to end	Day	47% 6% 18% 22% 6%	3091
November	1st to 10th	Day	50% 7% 14% 21% 7% 1	1761
	11th to 20th	Day	54% 6% 13% 16% 11%	1665
	21st to end	Day	64% 6% 14% 11% 5%	1600
December	1st to 10th	Day	70% 8% 11% 10% 2	2600
	11th to 20th	Day	64% 6% 9% 15% 6%	2986
	21st to end	Day	65% 5% 9% 16% 6%	3960
January	1st to 10th	Night	70% 5% 11% 11% 3	6349
	11th to 20th	Night	67% 7% 11% 10% 5%	6360
	21st to end	Night	64% 5% 10% 10% 11% 1	6932
February	1st to 10th	Night	62% 6% 10% 15% 6% 1	2600
	11th to 20th	Night	58% 6% 11% 18% 7%	2479
	21st to end	Night	57% 4 9% 18% 11% 1	1980
March	1st to 10th	Night	59% 4 8% 14% 12% 3	5374
	11th to 20th	Night	51% 7% 15% 16% 8% 3	5118
	21st to end	Night	53% 5% 6% 22% 12% 2	5061
April	1st to 10th	Night	54% 5% 8% 18% 13% 2	2000
	11th to 20th	Night	51% 6% 8% 19% 14% 1	1975
	21st to end	Night	50% 5% 9% 17% 15% 4	1891
May	1st to 10th	Night	57% 8% 10% 15% 7% 2	3600
	11th to 20th	Night	48% 9% 11% 18% 13% 1	3576
	21st to end	Night	50% 8% 11% 17% 13% 1	3927
June	1st to 10th	Night	48% 8% 14% 18% 11% 1	1600
	11th to 20th	Night	42% 7% 12% 22% 17% 2	1600
	21st to end	Night	47% 7% 13% 19% 14% 1	1600
July	1st to 10th	Night	44% 8% 16% 21% 10%	3560
	11th to 20th	Night	39% 7% 14% 30% 11%	3552
	21st to end	Night	35% 7% 14% 29% 15%	3809
August	1st to 10th	Night	42% 7% 16% 26% 9%	2576
	11th to 20th	Night	41% 7% 16% 28% 8%	2958
	21st to end	Night	40% 7% 15% 24% 12% 1	3586
September	1st to 10th	Night	39% 7% 11% 27% 15% 1	1931
	11th to 20th	Night	35% 6% 13% 33% 12% 1	1938
	21st to end	Night	41% 6% 13% 27% 12%	2090
October	1st to 10th	Night	43% 6% 15% 27% 9%	3799
	11th to 20th	Night	45% 6% 14% 26% 9%	3779
	21st to end	Night	48% 5% 17% 19% 10%	4457
November	1st to 10th	Night	51% 5% 15% 20% 8% 1	2537
	11th to 20th	Night	52% 7% 12% 18% 9% 1	2730
	21st to end	Night	62% 6% 12% 15% 5%	2800
December	1st to 10th	Night	70% 6% 12% 11% 2	4580
	11th to 20th	Night	65% 4 6% 15% 9% 1	5208
	21st to end	Night	66% 4 7% 13% 10%	6996

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	26% 22% 32% 19% 3	200
	11th to 20th	Day	26% 27% 31% 13% 4 1	200
	21st to end	Day	17% 21% 39% 18% 5%	230
February	1st to 10th	Day	30% 30% 28% 11% 2	300
	11th to 20th	Day	27% 26% 37% 10% 1	355
	21st to end	Day	30% 20% 32% 17% 1	414
March	1st to 10th	Day	26% 21% 32% 17% 4	500
	11th to 20th	Day	22% 27% 32% 16% 2 1	500
	21st to end	Day	32% 21% 24% 15% 7% 1	550
April	1st to 10th	Day	31% 19% 30% 15% 5%	500
	11th to 20th	Day	32% 21% 24% 14% 8% 2	492
	21st to end	Day	30% 21% 26% 14% 8% 1	500
May	1st to 10th	Day	26% 15% 34% 17% 6% 2	503
	11th to 20th	Day	19% 17% 33% 19% 10% 2	527
	21st to end	Day	20% 18% 31% 22% 9% 1	573
June	1st to 10th	Day	26% 12% 29% 23% 7% 2	530
	11th to 20th	Day	15% 15% 31% 27% 10% 2	530
	21st to end	Day	24% 12% 31% 20% 10% 2	530
July	1st to 10th	Day	14% 11% 30% 28% 15% 3	525
	11th to 20th	Day	13% 10% 32% 29% 14% 2	524
	21st to end	Day	15% 10% 31% 30% 12% 2	576
August	1st to 10th	Day	15% 8% 26% 32% 16% 3	526
	11th to 20th	Day	14% 7% 24% 31% 17% 7%	519
	21st to end	Day	15% 11% 28% 26% 14% 6%	583
September	1st to 10th	Day	15% 12% 27% 21% 16% 8%	502
	11th to 20th	Day	12% 10% 22% 24% 20% 11%	490
	21st to end	Day	18% 13% 30% 18% 16% 4	490
October	1st to 10th	Day	23% 15% 26% 20% 12% 3	490
	11th to 20th	Day	25% 19% 29% 18% 9% 1	490
	21st to end	Day	32% 13% 31% 20% 5%	434
November	1st to 10th	Day	27% 18% 27% 20% 6% 1	395
	11th to 20th	Day	25% 21% 33% 15% 5%	265
	21st to end	Day	31% 23% 28% 15% 5% 1	200
December	1st to 10th	Day	29% 18% 32% 17% 5%	200
	11th to 20th	Day	29% 27% 31% 12% 1 1	200
	21st to end	Day	30% 23% 30% 14% 3	220
January	1st to 10th	Night	27% 17% 36% 16% 4	800
	11th to 20th	Night	27% 15% 32% 21% 5% 1	800
	21st to end	Night	20% 14% 35% 25% 5%	880
February	1st to 10th	Night	21% 17% 36% 22% 3	800
	11th to 20th	Night	22% 19% 37% 19% 4	783
	21st to end	Night	25% 15% 33% 25% 3	660
March	1st to 10th	Night	24% 17% 34% 22% 4	800
	11th to 20th	Night	25% 17% 33% 21% 3	800
	21st to end	Night	24% 15% 29% 25% 6%	880
April	1st to 10th	Night	30% 13% 30% 24% 3	800
	11th to 20th	Night	26% 15% 32% 20% 6%	791
	21st to end	Night	29% 13% 29% 22% 7%	691
May	1st to 10th	Night	27% 8% 31% 25% 7% 2	400
	11th to 20th	Night	22% 10% 31% 27% 9% 1	394
	21st to end	Night	16% 8% 37% 29% 9%	433
June	1st to 10th	Night	19% 9% 30% 36% 7% 1	400
	11th to 20th	Night	19% 7% 29% 33% 11% 1	400
	21st to end	Night	19% 6% 30% 30% 16% 1	400
July	1st to 10th	Night	11% 7% 28% 36% 16% 1	390
	11th to 20th	Night	13% 4 29% 40% 14%	388
	21st to end	Night	13% 5% 29% 38% 13% 1	438
August	1st to 10th	Night	13% 3 24% 40% 19% 1	398
	11th to 20th	Night	14% 4 22% 35% 22% 2	624
	21st to end	Night	15% 6% 27% 34% 17% 2	880
September	1st to 10th	Night	14% 5% 28% 35% 16% 1	773
	11th to 20th	Night	17% 7% 21% 32% 21% 3	760
	21st to end	Night	19% 7% 28% 25% 19% 2	760
October	1st to 10th	Night	23% 8% 30% 26% 13% 1	760
	11th to 20th	Night	24% 12% 30% 25% 10%	760
	21st to end	Night	27% 14% 31% 24% 5%	836
November	1st to 10th	Night	27% 14% 27% 24% 7% 1	780
	11th to 20th	Night	23% 17% 33% 18% 9%	800
	21st to end	Night	27% 18% 28% 21% 7%	800
December	1st to 10th	Night	29% 15% 32% 19% 5%	800
	11th to 20th	Night	31% 18% 28% 18% 4 1	800
	21st to end	Night	34% 17% 29% 16% 4	880

Page generated at 2025-09-01 01:51:08. Version ac07

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