North Pole
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the North Pole clear sky chart from 2005-11-06 to 2026-03-18.

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	13% 11% 4 10% 6% 6% 6% 5% 6% 7% 26%	134392
	Night	8% 13% 5% 12% 7% 6% 5% 4 6% 7% 28%	135927
Transparency	Day	56% 4 16% 18% 6% 1	133996
	Night	55% 3 14% 18% 9% 1	135903
Seeing	Day	17% 2 9% 22% 28% 22%	20298
	Night	16% 2 10% 31% 31% 10%	24877

By Month

Percentage Cloud Cover NW (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	4 12% 5% 11% 6% 5% 3 4 4 5% 42%	1824
	11th to 20th	Day	4 17% 7% 14% 7% 6% 4 4 4 6% 27%	2358
	21st to end	Day	5% 10% 4 10% 10% 9% 9% 7% 8% 6% 22%	3226
February	1st to 10th	Day	4 13% 6% 11% 5% 5% 4 4 5% 5% 38%	1260
	11th to 20th	Day	4 15% 6% 12% 7% 6% 7% 4 6% 8% 24%	1557
	21st to end	Day	5% 16% 5% 12% 6% 6% 7% 4 5% 5% 27%	1384
March	1st to 10th	Day	3 16% 7% 14% 6% 6% 5% 4 5% 5% 30%	4480
	11th to 20th	Day	3 11% 7% 15% 8% 7% 6% 4 6% 8% 27%	4697
	21st to end	Day	6% 14% 5% 10% 5% 5% 5% 4 6% 6% 33%	5964
April	1st to 10th	Day	6% 16% 6% 11% 7% 6% 5% 5% 7% 6% 26%	2553
	11th to 20th	Day	5% 9% 4 8% 7% 6% 5% 5% 5% 8% 38%	2766
	21st to end	Day	6% 7% 3 7% 7% 7% 5% 6% 7% 7% 39%	3044
May	1st to 10th	Day	10% 12% 4 11% 7% 7% 6% 5% 7% 7% 23%	7389
	11th to 20th	Day	5% 7% 3 9% 7% 6% 7% 5% 6% 7% 39%	7832
	21st to end	Day	11% 10% 4 10% 7% 7% 7% 6% 8% 8% 22%	9157
June	1st to 10th	Day	11% 8% 3 10% 8% 6% 6% 5% 8% 9% 25%	3910
	11th to 20th	Day	12% 7% 3 8% 6% 6% 6% 5% 7% 9% 31%	4000
	21st to end	Day	13% 7% 3 8% 6% 6% 6% 5% 8% 10% 29%	4000
July	1st to 10th	Day	24% 8% 3 7% 5% 5% 5% 4 5% 7% 27%	9025
	11th to 20th	Day	14% 9% 3 8% 6% 6% 7% 5% 8% 10% 24%	8284
	21st to end	Day	20% 9% 3 8% 6% 5% 6% 5% 7% 8% 25%	8798
August	1st to 10th	Day	26% 10% 3 9% 5% 4 5% 4 6% 6% 22%	5221
	11th to 20th	Day	21% 10% 3 9% 6% 6% 5% 5% 7% 8% 19%	4958
	21st to end	Day	24% 12% 4 10% 6% 5% 5% 4 6% 7% 17%	5038
September	1st to 10th	Day	18% 12% 4 10% 6% 5% 6% 4 6% 6% 24%	2600
	11th to 20th	Day	23% 13% 5% 10% 6% 4 5% 4 5% 6% 19%	2360
	21st to end	Day	21% 13% 4 10% 6% 5% 4 4 4 5% 24%	2175
October	1st to 10th	Day	13% 16% 5% 10% 6% 4 4 3 5% 5% 28%	3078
	11th to 20th	Day	8% 21% 7% 13% 8% 5% 5% 3 5% 5% 20%	2864
	21st to end	Day	13% 19% 6% 13% 6% 6% 5% 3 4 6% 19%	2520
November	1st to 10th	Day	10% 17% 6% 11% 7% 6% 5% 6% 6% 6% 21%	1284
	11th to 20th	Day	9% 13% 8% 13% 8% 4 6% 4 5% 5% 25%	1050
	21st to end	Day	10% 15% 6% 12% 8% 5% 5% 3 5% 7% 23%	806
December	1st to 10th	Day	9% 12% 4 8% 4 5% 6% 5% 6% 8% 32%	1010
	11th to 20th	Day	4 17% 6% 13% 6% 6% 6% 5% 5% 4 28%	886
	21st to end	Day	2 11% 4 12% 7% 6% 6% 4 5% 7% 35%	1034
January	1st to 10th	Night	3 10% 4 11% 6% 4 4 3 5% 5% 44%	11157
	11th to 20th	Night	4 14% 6% 11% 6% 5% 5% 5% 7% 8% 28%	10570
	21st to end	Night	5% 11% 4 10% 8% 8% 6% 5% 7% 10% 27%	10985
February	1st to 10th	Night	2 14% 6% 12% 5% 4 4 4 4 6% 37%	3360
	11th to 20th	Night	4 12% 5% 11% 7% 6% 6% 6% 7% 7% 28%	2949
	21st to end	Night	6% 16% 6% 12% 7% 7% 5% 5% 5% 6% 25%	2422
March	1st to 10th	Night	4 15% 7% 15% 7% 5% 5% 3 5% 7% 27%	5596
	11th to 20th	Night	4 10% 6% 15% 9% 7% 6% 5% 5% 7% 25%	5416
	21st to end	Night	7% 14% 4 8% 6% 5% 5% 5% 6% 9% 31%	4967
April	1st to 10th	Night	6% 15% 6% 11% 6% 6% 6% 5% 6% 7% 25%	1844
	11th to 20th	Night	5% 11% 3 10% 7% 5% 6% 4 6% 7% 37%	1583
	21st to end	Night	7% 7% 4 9% 6% 6% 5% 5% 7% 7% 38%	1355
May	1st to 10th	Night	9% 9% 4 11% 8% 8% 7% 5% 8% 8% 23%	2585
	11th to 20th	Night	8% 7% 2 7% 6% 5% 5% 5% 8% 8% 39%	2057
	21st to end	Night	12% 11% 4 10% 8% 7% 8% 5% 6% 8% 21%	1740
June	1st to 10th	Night	10% 10% 3 8% 8% 5% 7% 7% 9% 9% 24%	488
	11th to 20th	Night	11% 11% 2 8% 7% 7% 8% 5% 7% 9% 27%	400
	21st to end	Night	13% 9% 2 7% 7% 8% 4 7% 11% 10% 24%	400
July	1st to 10th	Night	26% 8% 4 9% 5% 6% 4 4 6% 5% 23%	954
	11th to 20th	Night	16% 11% 3 10% 7% 6% 6% 5% 6% 7% 23%	1682
	21st to end	Night	20% 10% 3 9% 6% 5% 5% 4 6% 7% 24%	2062
August	1st to 10th	Night	27% 9% 4 10% 6% 5% 5% 4 6% 6% 19%	1937
	11th to 20th	Night	26% 13% 4 11% 6% 6% 5% 3 5% 5% 17%	2098
	21st to end	Night	23% 13% 4 11% 6% 5% 5% 4 5% 5% 17%	2871
September	1st to 10th	Night	18% 9% 3 11% 6% 6% 6% 4 7% 6% 24%	1800
	11th to 20th	Night	20% 14% 5% 11% 7% 5% 5% 4 5% 6% 20%	2040
	21st to end	Night	20% 14% 4 9% 5% 5% 5% 4 4 5% 24%	2224
October	1st to 10th	Night	12% 15% 4 10% 6% 6% 5% 4 6% 7% 25%	4108
	11th to 20th	Night	10% 18% 5% 13% 8% 6% 5% 4 5% 6% 18%	4283
	21st to end	Night	10% 18% 7% 17% 7% 5% 4 3 4 5% 20%	5281
November	1st to 10th	Night	11% 18% 5% 11% 6% 5% 5% 5% 5% 6% 24%	3230
	11th to 20th	Night	8% 15% 7% 15% 8% 5% 4 3 5% 6% 24%	3570
	21st to end	Night	9% 16% 6% 12% 7% 6% 5% 5% 5% 6% 23%	3793
December	1st to 10th	Night	7% 11% 4 11% 7% 6% 5% 5% 6% 8% 29%	6400
	11th to 20th	Night	5% 16% 6% 11% 6% 6% 6% 4 6% 6% 28%	7534
	21st to end	Night	3 12% 5% 12% 6% 5% 6% 4 6% 8% 31%	10186

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	46% 3 9% 18% 21% 2	1824
	11th to 20th	Day	59% 3 15% 16% 5% 2	2370
	21st to end	Day	59% 4 11% 16% 8% 3	3227
February	1st to 10th	Day	48% 2 8% 21% 17% 5%	1260
	11th to 20th	Day	58% 3 12% 18% 9% 1	1564
	21st to end	Day	58% 3 10% 18% 10% 1	1384
March	1st to 10th	Day	57% 2 9% 19% 12% 1	4480
	11th to 20th	Day	57% 1 9% 18% 12% 2	4697
	21st to end	Day	51% 2 15% 20% 11% 1	5964
April	1st to 10th	Day	57% 3 14% 18% 8% 1	2553
	11th to 20th	Day	44% 3 14% 29% 8% 2	2766
	21st to end	Day	42% 3 11% 33% 11%	3044
May	1st to 10th	Day	59% 2 8% 24% 7%	7389
	11th to 20th	Day	45% 2 9% 26% 15% 4	7835
	21st to end	Day	56% 4 14% 21% 5%	9158
June	1st to 10th	Day	53% 4 17% 23% 4	3910
	11th to 20th	Day	48% 4 19% 25% 4	4000
	21st to end	Day	49% 5% 22% 21% 3	4000
July	1st to 10th	Day	56% 5% 19% 16% 3	8926
	11th to 20th	Day	53% 7% 24% 16% 1	8182
	21st to end	Day	56% 6% 24% 12% 3	8550
August	1st to 10th	Day	62% 4 21% 10% 2	5201
	11th to 20th	Day	61% 5% 23% 10%	5006
	21st to end	Day	66% 6% 19% 9%	5037
September	1st to 10th	Day	60% 4 23% 12% 1	2600
	11th to 20th	Day	65% 4 18% 13% 1	2360
	21st to end	Day	63% 4 15% 15% 3	2175
October	1st to 10th	Day	58% 3 13% 21% 4	3078
	11th to 20th	Day	66% 3 14% 14% 2	2864
	21st to end	Day	67% 3 15% 13% 1	2520
November	1st to 10th	Day	62% 5% 17% 13% 4	1284
	11th to 20th	Day	61% 4 13% 18% 4	1050
	21st to end	Day	62% 2 13% 17% 5%	806
December	1st to 10th	Day	49% 5% 19% 21% 5% 1	1010
	11th to 20th	Day	59% 4 15% 14% 4 5%	888
	21st to end	Day	50% 3 16% 17% 13% 1	1034
January	1st to 10th	Night	43% 2 11% 20% 21% 4	11158
	11th to 20th	Night	53% 3 17% 18% 8%	10620
	21st to end	Night	52% 3 11% 18% 11% 4	10985
February	1st to 10th	Night	49% 2 8% 18% 20% 3	3360
	11th to 20th	Night	52% 4 11% 22% 10%	2953
	21st to end	Night	60% 3 10% 19% 8% 1	2422
March	1st to 10th	Night	57% 2 7% 23% 9% 1	5596
	11th to 20th	Night	59% 2 11% 16% 12% 1	5418
	21st to end	Night	51% 2 16% 18% 13% 1	4967
April	1st to 10th	Night	56% 3 13% 20% 7% 1	1844
	11th to 20th	Night	46% 3 19% 24% 7% 1	1583
	21st to end	Night	42% 2 12% 32% 11%	1355
May	1st to 10th	Night	57% 3 10% 26% 4	2582
	11th to 20th	Night	42% 2 10% 30% 15% 2	2057
	21st to end	Night	59% 5% 9% 20% 7%	1740
June	1st to 10th	Night	53% 3 19% 22% 3	488
	11th to 20th	Night	53% 4 17% 22% 5%	400
	21st to end	Night	51% 8% 20% 21% 1	400
July	1st to 10th	Night	63% 4 14% 13% 5%	944
	11th to 20th	Night	58% 6% 19% 15% 1	1661
	21st to end	Night	60% 6% 19% 13% 3	2005
August	1st to 10th	Night	65% 4 19% 10% 2	1932
	11th to 20th	Night	69% 5% 16% 9%	2116
	21st to end	Night	68% 6% 17% 9% 1	2871
September	1st to 10th	Night	59% 3 21% 14% 2	1800
	11th to 20th	Night	66% 2 15% 15% 2	2040
	21st to end	Night	63% 4 14% 16% 3	2224
October	1st to 10th	Night	57% 4 12% 22% 4	4108
	11th to 20th	Night	66% 5% 16% 12% 2	4283
	21st to end	Night	66% 4 14% 15% 1	5281
November	1st to 10th	Night	62% 3 16% 15% 4	3230
	11th to 20th	Night	61% 3 14% 18% 3	3570
	21st to end	Night	61% 4 10% 20% 6%	3793
December	1st to 10th	Night	51% 5% 17% 20% 6% 1	6400
	11th to 20th	Night	56% 4 17% 15% 5% 4	7531
	21st to end	Night	51% 4 15% 16% 13% 1	10186

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	6% 1 13% 40% 29% 11%	110
	11th to 20th	Day	10% 3 6% 45% 31% 5%	110
	21st to end	Day	11% 2 8% 33% 28% 19%	237
February	1st to 10th	Day	9% 3 7% 29% 31% 22%	320
	11th to 20th	Day	12% 3 13% 31% 26% 15%	397
	21st to end	Day	12% 4 14% 28% 28% 15%	355
March	1st to 10th	Day	9% 1 9% 31% 34% 16%	430
	11th to 20th	Day	8% 1 9% 29% 27% 26%	422
	21st to end	Day	9% 2 11% 23% 34% 21%	655
April	1st to 10th	Day	13% 3 11% 31% 25% 17%	667
	11th to 20th	Day	10% 3 13% 25% 28% 21%	690
	21st to end	Day	8% 3 7% 22% 34% 27%	700
May	1st to 10th	Day	12% 3 10% 25% 30% 18%	703
	11th to 20th	Day	9% 2 11% 26% 29% 21%	803
	21st to end	Day	16% 4 10% 23% 28% 19%	1109
June	1st to 10th	Day	14% 1 8% 25% 29% 23%	1130
	11th to 20th	Day	13% 1 7% 19% 31% 29%	1130
	21st to end	Day	14% 1 5% 18% 33% 29%	1130
July	1st to 10th	Day	17% 2 6% 18% 33% 24%	1111
	11th to 20th	Day	22% 1 5% 17% 31% 23%	968
	21st to end	Day	18% 2 5% 19% 28% 28%	983
August	1st to 10th	Day	27% 2 8% 16% 26% 21%	726
	11th to 20th	Day	27% 2 8% 20% 23% 20%	715
	21st to end	Day	30% 2 8% 18% 21% 21%	803
September	1st to 10th	Day	22% 2 10% 21% 23% 22%	713
	11th to 20th	Day	32% 2 8% 21% 20% 17%	580
	21st to end	Day	30% 2 8% 17% 19% 23%	420
October	1st to 10th	Day	28% 3 11% 20% 21% 17%	420
	11th to 20th	Day	20% 4 11% 19% 23% 25%	420
	21st to end	Day	20% 2 8% 18% 29% 22%	462
November	1st to 10th	Day	22% 3 6% 21% 27% 20%	318
	11th to 20th	Day	15% 4 5% 22% 29% 25%	110
	21st to end	Day	10% 4 10% 27% 35% 15%	110
December	1st to 10th	Day	20% 1 14% 32% 22% 12%	110
	11th to 20th	Day	10% 3 16% 35% 24% 12%	110
	21st to end	Day	6% 5% 17% 34% 29% 10%	121
January	1st to 10th	Night	9% 1 8% 35% 33% 14%	1223
	11th to 20th	Night	12% 3 11% 39% 26% 9%	1060
	21st to end	Night	10% 3 7% 42% 29% 9%	1108
February	1st to 10th	Night	8% 3 12% 36% 29% 12%	950
	11th to 20th	Night	9% 3 15% 38% 28% 7%	934
	21st to end	Night	13% 2 13% 36% 30% 6%	783
March	1st to 10th	Night	12% 1 10% 40% 30% 6%	761
	11th to 20th	Night	9% 1 15% 27% 36% 12%	707
	21st to end	Night	12% 2 13% 33% 30% 10%	660
April	1st to 10th	Night	12% 2 13% 39% 28% 6%	600
	11th to 20th	Night	12% 3 9% 34% 34% 8%	593
	21st to end	Night	9% 1 7% 33% 43% 8%	555
May	1st to 10th	Night	12% 2 10% 28% 39% 8%	343
	11th to 20th	Night	9% 2 13% 38% 35% 4	197
	21st to end	Night	18% 3 6% 32% 36% 5%	217
June	1st to 10th	Night	15% 2 8% 26% 42% 8%	200
	11th to 20th	Night	18% 2 5% 27% 40% 10%	200
	21st to end	Night	18% 1 3 24% 44% 11%	200
July	1st to 10th	Night	16% 3 6% 30% 39% 6%	195
	11th to 20th	Night	26% 2 4 26% 32% 9%	194
	21st to end	Night	21% 1 5% 26% 39% 9%	219
August	1st to 10th	Night	32% 2 4 21% 34% 7%	381
	11th to 20th	Night	29% 3 7% 24% 30% 8%	480
	21st to end	Night	31% 2 5% 20% 29% 13%	660
September	1st to 10th	Night	24% 2 8% 23% 33% 10%	600
	11th to 20th	Night	28% 2 8% 27% 30% 6%	600
	21st to end	Night	28% 1 9% 22% 30% 9%	614
October	1st to 10th	Night	26% 2 14% 25% 27% 7%	820
	11th to 20th	Night	21% 3 10% 25% 28% 13%	910
	21st to end	Night	17% 3 8% 29% 32% 11%	1001
November	1st to 10th	Night	21% 2 8% 31% 30% 8%	930
	11th to 20th	Night	16% 1 7% 27% 32% 18%	950
	21st to end	Night	15% 2 9% 31% 29% 14%	1095
December	1st to 10th	Night	16% 2 12% 33% 26% 11%	1270
	11th to 20th	Night	14% 3 10% 29% 32% 12%	1270
	21st to end	Night	10% 4 9% 35% 30% 13%	1397

Page generated at 2026-03-14 22:23:57. Version ac07

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