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 2024-12-06.

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%	107216
	Night	9% 14% 5% 12% 7% 6% 5% 4 6% 6% 27%	101092
Transparency	Day	57% 3 16% 18% 5%	106873
	Night	57% 3 14% 18% 7% 1	101082
Seeing	Day	17% 2 8% 22% 28% 22%	18732
	Night	16% 2 9% 31% 31% 10%	22978

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	5% 10% 5% 11% 6% 6% 3 3 4 5% 41%	962
	11th to 20th	Day	5% 14% 6% 11% 6% 6% 4 5% 6% 6% 32%	1258
	21st to end	Day	5% 10% 4 10% 7% 8% 8% 7% 9% 5% 26%	1725
February	1st to 10th	Day	4 12% 6% 11% 5% 4 4 4 5% 5% 39%	1140
	11th to 20th	Day	4 15% 6% 13% 7% 5% 7% 3 6% 8% 24%	1403
	21st to end	Day	5% 17% 5% 13% 6% 6% 7% 4 6% 5% 27%	1256
March	1st to 10th	Day	3 18% 8% 16% 7% 6% 5% 3 4 4 25%	3049
	11th to 20th	Day	4 13% 8% 14% 7% 6% 5% 4 5% 8% 27%	3238
	21st to end	Day	6% 13% 5% 10% 6% 5% 6% 5% 7% 7% 31%	4160
April	1st to 10th	Day	5% 16% 6% 11% 7% 6% 5% 5% 7% 7% 27%	2425
	11th to 20th	Day	5% 9% 4 8% 7% 6% 5% 5% 5% 8% 39%	2626
	21st to end	Day	6% 7% 3 7% 7% 7% 5% 5% 7% 7% 39%	2892
May	1st to 10th	Day	8% 13% 4 12% 8% 8% 7% 5% 7% 6% 21%	5160
	11th to 20th	Day	5% 7% 3 10% 7% 7% 7% 5% 7% 8% 34%	5456
	21st to end	Day	13% 9% 3 8% 6% 6% 6% 6% 8% 8% 27%	6381
June	1st to 10th	Day	11% 8% 3 10% 8% 7% 6% 5% 8% 9% 25%	3714
	11th to 20th	Day	12% 7% 3 8% 7% 6% 6% 5% 7% 9% 29%	3800
	21st to end	Day	14% 7% 3 8% 6% 6% 6% 5% 8% 10% 29%	3800
July	1st to 10th	Day	28% 9% 3 7% 5% 5% 5% 4 6% 7% 19%	6308
	11th to 20th	Day	16% 9% 4 9% 6% 6% 6% 5% 7% 8% 25%	5782
	21st to end	Day	21% 9% 3 8% 6% 5% 5% 4 6% 7% 28%	6130
August	1st to 10th	Day	26% 10% 3 9% 5% 4 5% 4 6% 6% 22%	5060
	11th to 20th	Day	21% 10% 3 9% 6% 6% 5% 5% 7% 8% 19%	4803
	21st to end	Day	23% 12% 4 10% 6% 5% 5% 4 6% 7% 17%	4884
September	1st to 10th	Day	18% 12% 4 10% 6% 5% 6% 4 6% 6% 25%	2471
	11th to 20th	Day	23% 13% 5% 10% 6% 4 5% 4 5% 6% 20%	2242
	21st to end	Day	19% 13% 4 10% 6% 5% 4 5% 4 5% 25%	2066
October	1st to 10th	Day	13% 16% 5% 10% 6% 4 4 3 5% 5% 29%	2984
	11th to 20th	Day	8% 20% 7% 13% 8% 5% 5% 4 5% 5% 20%	2776
	21st to end	Day	13% 19% 6% 12% 6% 6% 5% 3 4 6% 18%	2442
November	1st to 10th	Day	10% 17% 6% 11% 7% 6% 5% 6% 5% 6% 21%	1222
	11th to 20th	Day	10% 14% 8% 13% 8% 4 6% 4 5% 5% 25%	1000
	21st to end	Day	9% 15% 6% 12% 9% 5% 6% 3 5% 7% 23%	768
December	1st to 10th	Day	12% 15% 4 9% 6% 6% 4 4 7% 8% 25%	585
	11th to 20th	Day	3 20% 5% 18% 8% 5% 6% 4 5% 5% 21%	544
	21st to end	Day	3 11% 5% 11% 8% 7% 7% 5% 7% 7% 30%	704
January	1st to 10th	Night	4 11% 4 11% 6% 4 4 4 5% 6% 40%	6023
	11th to 20th	Night	4 14% 6% 12% 6% 4 5% 4 6% 7% 32%	5650
	21st to end	Night	3 10% 4 10% 8% 7% 6% 6% 7% 7% 31%	5939
February	1st to 10th	Night	2 13% 6% 13% 5% 5% 3 4 4 6% 38%	3040
	11th to 20th	Night	5% 12% 5% 11% 7% 6% 6% 6% 7% 7% 28%	2663
	21st to end	Night	6% 16% 6% 12% 7% 6% 5% 5% 5% 7% 25%	2198
March	1st to 10th	Night	4 18% 7% 17% 7% 5% 4 3 4 6% 26%	3806
	11th to 20th	Night	6% 12% 6% 14% 8% 7% 5% 4 4 6% 27%	3720
	21st to end	Night	7% 13% 4 7% 6% 6% 5% 5% 6% 9% 33%	3471
April	1st to 10th	Night	5% 15% 6% 11% 7% 6% 6% 5% 6% 7% 26%	1752
	11th to 20th	Night	5% 11% 3 10% 6% 5% 5% 4 6% 7% 38%	1503
	21st to end	Night	6% 7% 4 9% 6% 6% 5% 4 7% 8% 40%	1287
May	1st to 10th	Night	8% 11% 5% 13% 9% 9% 7% 5% 7% 7% 19%	1807
	11th to 20th	Night	6% 8% 3 8% 7% 6% 6% 6% 9% 9% 33%	1429
	21st to end	Night	14% 13% 4 9% 6% 6% 5% 4 5% 6% 28%	1205
June	1st to 10th	Night	10% 9% 3 8% 8% 4 7% 7% 9% 9% 24%	464
	11th to 20th	Night	12% 12% 2 8% 7% 7% 8% 4 7% 8% 26%	380
	21st to end	Night	13% 9% 2 7% 7% 7% 4 7% 11% 10% 23%	380
July	1st to 10th	Night	29% 9% 4 10% 6% 7% 5% 4 6% 4 15%	661
	11th to 20th	Night	18% 11% 3 9% 7% 6% 5% 4 6% 6% 26%	1174
	21st to end	Night	19% 10% 3 9% 5% 5% 5% 5% 6% 7% 26%	1431
August	1st to 10th	Night	27% 9% 4 10% 6% 5% 5% 4 6% 6% 19%	1878
	11th to 20th	Night	26% 12% 4 11% 6% 7% 5% 3 5% 5% 17%	2033
	21st to end	Night	23% 13% 4 11% 6% 5% 5% 5% 5% 5% 17%	2783
September	1st to 10th	Night	17% 9% 3 12% 6% 6% 6% 4 7% 6% 25%	1709
	11th to 20th	Night	19% 13% 5% 11% 6% 5% 5% 4 5% 6% 21%	1938
	21st to end	Night	19% 13% 4 9% 5% 5% 5% 4 5% 5% 25%	2113
October	1st to 10th	Night	11% 15% 4 9% 6% 6% 5% 4 7% 7% 26%	3982
	11th to 20th	Night	10% 17% 5% 14% 8% 6% 5% 4 5% 6% 19%	4151
	21st to end	Night	10% 18% 7% 17% 7% 5% 4 3 4 5% 20%	5117
November	1st to 10th	Night	11% 18% 5% 12% 7% 5% 5% 5% 4 6% 24%	3072
	11th to 20th	Night	8% 16% 7% 15% 8% 5% 4 3 5% 6% 23%	3400
	21st to end	Night	9% 16% 5% 12% 7% 6% 5% 5% 5% 5% 24%	3612
December	1st to 10th	Night	9% 14% 5% 12% 6% 6% 5% 4 6% 7% 26%	3712
	11th to 20th	Night	5% 19% 7% 15% 8% 7% 6% 4 6% 6% 18%	4646
	21st to end	Night	4 13% 5% 12% 7% 6% 6% 4 7% 7% 29%	6963

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	47% 3 11% 25% 13% 1	962
	11th to 20th	Day	52% 2 17% 18% 7% 4	1270
	21st to end	Day	57% 2 8% 14% 14% 5%	1725
February	1st to 10th	Day	47% 2 7% 22% 18% 5%	1140
	11th to 20th	Day	58% 3 12% 19% 8%	1410
	21st to end	Day	58% 3 10% 18% 11% 1	1256
March	1st to 10th	Day	64% 1 8% 14% 12% 1	3049
	11th to 20th	Day	58% 1 11% 20% 9% 1	3238
	21st to end	Day	52% 2 19% 17% 9% 1	4160
April	1st to 10th	Day	56% 2 14% 18% 8% 1	2425
	11th to 20th	Day	43% 3 15% 29% 8% 2	2626
	21st to end	Day	41% 3 11% 33% 12%	2892
May	1st to 10th	Day	62% 1 8% 23% 6%	5160
	11th to 20th	Day	48% 1 10% 33% 8%	5459
	21st to end	Day	54% 2 13% 24% 7%	6382
June	1st to 10th	Day	52% 4 18% 22% 4	3714
	11th to 20th	Day	50% 4 19% 23% 4	3800
	21st to end	Day	50% 5% 22% 21% 3	3800
July	1st to 10th	Day	64% 5% 18% 11% 2	6209
	11th to 20th	Day	55% 5% 18% 21% 1	5680
	21st to end	Day	55% 5% 20% 15% 5%	5936
August	1st to 10th	Day	63% 4 21% 10% 2	5040
	11th to 20th	Day	61% 5% 23% 10%	4851
	21st to end	Day	65% 6% 19% 9%	4883
September	1st to 10th	Day	60% 4 23% 13% 1	2471
	11th to 20th	Day	65% 4 18% 13% 1	2242
	21st to end	Day	62% 4 15% 16% 3	2066
October	1st to 10th	Day	57% 3 13% 22% 5%	2984
	11th to 20th	Day	66% 3 14% 14% 2	2776
	21st to end	Day	67% 3 15% 13% 1	2442
November	1st to 10th	Day	61% 5% 17% 13% 4	1222
	11th to 20th	Day	62% 4 14% 18% 3	1000
	21st to end	Day	63% 2 13% 16% 6%	768
December	1st to 10th	Day	56% 5% 17% 15% 6% 1	585
	11th to 20th	Day	64% 3 10% 18% 4	546
	21st to end	Day	54% 3 12% 19% 12% 1	704
January	1st to 10th	Night	45% 2 16% 27% 8% 1	6023
	11th to 20th	Night	52% 2 17% 18% 10% 1	5700
	21st to end	Night	51% 2 8% 15% 17% 6%	5939
February	1st to 10th	Night	48% 2 7% 19% 21% 3	3040
	11th to 20th	Night	52% 4 12% 22% 10%	2667
	21st to end	Night	60% 3 10% 18% 8% 1	2198
March	1st to 10th	Night	62% 1 6% 18% 12% 2	3806
	11th to 20th	Night	59% 2 12% 18% 9% 1	3722
	21st to end	Night	49% 1 22% 17% 11% 1	3471
April	1st to 10th	Night	56% 3 13% 21% 7% 1	1752
	11th to 20th	Night	44% 2 20% 25% 7% 1	1503
	21st to end	Night	41% 1 12% 34% 12%	1287
May	1st to 10th	Night	64% 2 10% 22% 3	1807
	11th to 20th	Night	46% 1 11% 35% 6%	1429
	21st to end	Night	58% 2 8% 22% 10%	1205
June	1st to 10th	Night	53% 3 20% 22% 3	464
	11th to 20th	Night	55% 3 17% 21% 4	380
	21st to end	Night	51% 8% 19% 21% 1	380
July	1st to 10th	Night	71% 4 14% 10% 2	651
	11th to 20th	Night	58% 5% 16% 20% 1	1153
	21st to end	Night	56% 5% 17% 18% 4	1386
August	1st to 10th	Night	66% 4 19% 10% 2	1873
	11th to 20th	Night	69% 5% 17% 9%	2051
	21st to end	Night	67% 6% 17% 9% 1	2783
September	1st to 10th	Night	59% 3 21% 15% 2	1709
	11th to 20th	Night	65% 2 16% 15% 2	1938
	21st to end	Night	61% 4 15% 17% 4	2113
October	1st to 10th	Night	57% 4 12% 23% 4	3982
	11th to 20th	Night	65% 5% 16% 12% 2	4151
	21st to end	Night	67% 3 14% 15% 1	5117
November	1st to 10th	Night	61% 3 16% 15% 4	3072
	11th to 20th	Night	63% 4 15% 17% 2	3400
	21st to end	Night	61% 4 10% 19% 6%	3612
December	1st to 10th	Night	55% 5% 16% 18% 6% 1	3712
	11th to 20th	Night	67% 4 10% 15% 4	4643
	21st to end	Night	54% 3 12% 18% 12% 1	6963

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	7% 1 12% 41% 29% 10%	90
	11th to 20th	Day	10% 2 3 42% 36% 7%	90
	21st to end	Day	11% 1 5% 34% 30% 19%	203
February	1st to 10th	Day	10% 2 6% 29% 30% 23%	280
	11th to 20th	Day	13% 3 10% 31% 26% 17%	341
	21st to end	Day	11% 4 14% 28% 29% 15%	307
March	1st to 10th	Day	9% 1 9% 31% 33% 17%	370
	11th to 20th	Day	9% 1 9% 28% 28% 24%	370
	21st to end	Day	9% 2 11% 24% 34% 20%	611
April	1st to 10th	Day	12% 3 11% 30% 26% 18%	620
	11th to 20th	Day	10% 3 12% 24% 30% 22%	640
	21st to end	Day	8% 2 6% 22% 34% 28%	650
May	1st to 10th	Day	12% 2 10% 26% 31% 19%	653
	11th to 20th	Day	10% 2 10% 27% 30% 22%	749
	21st to end	Day	16% 4 10% 24% 28% 18%	1038
June	1st to 10th	Day	13% 1 7% 25% 30% 24%	1060
	11th to 20th	Day	14% 1 7% 20% 30% 28%	1060
	21st to end	Day	14% 1 5% 18% 33% 29%	1060
July	1st to 10th	Day	17% 2 5% 18% 33% 24%	1041
	11th to 20th	Day	23% 1 6% 18% 30% 23%	905
	21st to end	Day	18% 2 5% 18% 28% 29%	919
August	1st to 10th	Day	27% 1 8% 17% 25% 22%	676
	11th to 20th	Day	26% 2 8% 20% 23% 20%	665
	21st to end	Day	29% 1 7% 18% 22% 22%	748
September	1st to 10th	Day	23% 2 9% 20% 23% 24%	665
	11th to 20th	Day	31% 2 9% 22% 19% 17%	542
	21st to end	Day	29% 2 9% 17% 19% 24%	390
October	1st to 10th	Day	28% 1 10% 20% 22% 18%	390
	11th to 20th	Day	18% 4 10% 19% 23% 26%	390
	21st to end	Day	20% 2 7% 19% 29% 23%	429
November	1st to 10th	Day	23% 3 6% 21% 26% 21%	296
	11th to 20th	Day	17% 4 5% 20% 30% 24%	100
	21st to end	Day	10% 4 9% 28% 34% 15%	100
December	1st to 10th	Day	21% 1 12% 33% 22% 12%	95
	11th to 20th	Day	12% 2 17% 32% 24% 12%	90
	21st to end	Day	7% 5% 18% 31% 27% 11%	99
January	1st to 10th	Night	9% 1 7% 34% 34% 15%	1088
	11th to 20th	Night	12% 2 8% 39% 28% 10%	940
	21st to end	Night	10% 2 6% 43% 30% 10%	987
February	1st to 10th	Night	8% 2 12% 36% 29% 13%	850
	11th to 20th	Night	10% 3 13% 38% 29% 7%	834
	21st to end	Night	13% 2 13% 35% 30% 7%	703
March	1st to 10th	Night	13% 1 10% 39% 29% 7%	679
	11th to 20th	Night	10% 1 15% 28% 35% 12%	641
	21st to end	Night	13% 2 13% 33% 30% 10%	627
April	1st to 10th	Night	12% 1 13% 38% 29% 7%	570
	11th to 20th	Night	11% 2 8% 34% 35% 9%	563
	21st to end	Night	9% 6% 32% 44% 8%	527
May	1st to 10th	Night	12% 2 9% 29% 40% 9%	326
	11th to 20th	Night	9% 2 12% 39% 35% 4	187
	21st to end	Night	17% 3 6% 33% 35% 5%	206
June	1st to 10th	Night	15% 1 8% 26% 42% 8%	190
	11th to 20th	Night	18% 1 5% 28% 37% 11%	190
	21st to end	Night	18% 1 3 23% 44% 11%	190
July	1st to 10th	Night	17% 3 5% 28% 41% 6%	185
	11th to 20th	Night	27% 2 4 26% 32% 9%	184
	21st to end	Night	21% 5% 26% 38% 10%	208
August	1st to 10th	Night	32% 2 4 21% 34% 7%	362
	11th to 20th	Night	29% 3 7% 25% 30% 8%	456
	21st to end	Night	31% 1 4 21% 30% 13%	627
September	1st to 10th	Night	24% 2 7% 23% 34% 10%	570
	11th to 20th	Night	28% 1 8% 27% 31% 6%	570
	21st to end	Night	27% 1 9% 23% 30% 9%	583
October	1st to 10th	Night	25% 2 13% 25% 28% 7%	774
	11th to 20th	Night	19% 2 10% 26% 29% 13%	860
	21st to end	Night	17% 3 7% 30% 32% 10%	946
November	1st to 10th	Night	21% 1 8% 32% 30% 8%	880
	11th to 20th	Night	16% 1 6% 27% 32% 17%	900
	21st to end	Night	16% 2 9% 30% 29% 14%	1034
December	1st to 10th	Night	16% 2 11% 33% 27% 11%	1168
	11th to 20th	Night	15% 2 10% 28% 33% 12%	1130
	21st to end	Night	10% 4 9% 34% 29% 14%	1243

Page generated at 2024-12-03 02:45:12. Version ac07

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