Kodiak
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kodiak 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	24% 14% 4 8% 5% 5% 5% 4 5% 5% 21%	135441
	Night	24% 15% 4 8% 5% 4 4 3 5% 5% 24%	134850
Transparency	Day	61% 9% 12% 12% 5% 1	135113
	Night	62% 7% 11% 13% 7% 1	134761
Seeing	Day	29% 11% 20% 21% 14% 4	20288
	Night	32% 12% 20% 20% 13% 4	24915

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	22% 18% 4 9% 5% 6% 5% 4 5% 4 18%	3525
	11th to 20th	Day	19% 21% 4 9% 6% 5% 4 3 4 5% 21%	3556
	21st to end	Day	20% 18% 3 8% 7% 6% 4 2 4 5% 23%	4494
February	1st to 10th	Day	22% 18% 3 7% 5% 4 4 4 5% 5% 23%	1510
	11th to 20th	Day	21% 17% 3 7% 5% 4 4 4 6% 7% 22%	1761
	21st to end	Day	19% 14% 2 7% 6% 4 4 4 5% 6% 29%	1557
March	1st to 10th	Day	16% 17% 4 8% 7% 5% 5% 4 5% 6% 24%	4432
	11th to 20th	Day	9% 16% 6% 13% 7% 5% 6% 5% 5% 5% 23%	5000
	21st to end	Day	15% 22% 5% 9% 5% 5% 5% 4 5% 5% 19%	5755
April	1st to 10th	Day	21% 18% 4 8% 5% 5% 5% 3 4 4 24%	2446
	11th to 20th	Day	24% 18% 3 8% 5% 4 4 3 5% 4 23%	2652
	21st to end	Day	32% 19% 3 6% 5% 4 3 3 4 3 17%	2800
May	1st to 10th	Day	24% 23% 5% 10% 6% 5% 6% 3 4 4 12%	6588
	11th to 20th	Day	22% 16% 4 9% 5% 6% 5% 4 5% 6% 19%	7206
	21st to end	Day	32% 18% 4 7% 5% 4 4 3 4 5% 15%	7929
June	1st to 10th	Day	33% 11% 3 7% 5% 5% 4 3 5% 4 19%	3235
	11th to 20th	Day	30% 10% 3 7% 4 4 5% 3 5% 6% 24%	3400
	21st to end	Day	30% 13% 3 9% 5% 5% 5% 4 5% 5% 15%	3400
July	1st to 10th	Day	38% 12% 3 8% 5% 5% 4 4 5% 5% 12%	7656
	11th to 20th	Day	27% 14% 4 10% 6% 6% 6% 4 4 5% 14%	7260
	21st to end	Day	20% 10% 4 9% 6% 5% 5% 4 5% 6% 24%	7691
August	1st to 10th	Day	34% 9% 3 8% 4 5% 4 3 5% 6% 20%	4887
	11th to 20th	Day	18% 8% 3 7% 5% 5% 5% 4 5% 7% 33%	4496
	21st to end	Day	23% 8% 3 7% 5% 5% 6% 4 6% 7% 25%	4812
September	1st to 10th	Day	27% 9% 3 9% 5% 6% 5% 3 6% 6% 21%	2446
	11th to 20th	Day	29% 7% 2 7% 5% 4 5% 3 6% 6% 26%	2400
	21st to end	Day	26% 8% 4 9% 5% 5% 4 3 4 5% 26%	2110
October	1st to 10th	Day	20% 9% 3 8% 5% 6% 6% 5% 6% 7% 27%	3260
	11th to 20th	Day	25% 10% 3 7% 4 4 4 3 4 4 31%	3063
	21st to end	Day	21% 10% 2 6% 3 4 4 3 5% 6% 34%	2831
November	1st to 10th	Day	25% 10% 3 6% 5% 5% 3 3 5% 6% 28%	1622
	11th to 20th	Day	20% 10% 3 8% 5% 3 6% 4 4 7% 30%	1343
	21st to end	Day	21% 12% 2 7% 6% 6% 5% 4 5% 5% 26%	1260
December	1st to 10th	Day	36% 20% 4 8% 4 3 4 2 3 3 15%	2020
	11th to 20th	Day	25% 16% 3 7% 4 4 4 4 4 6% 24%	2315
	21st to end	Day	24% 17% 4 7% 4 4 3 4 4 4 23%	2723
January	1st to 10th	Night	24% 16% 3 7% 5% 5% 5% 4 6% 7% 19%	9400
	11th to 20th	Night	26% 20% 4 8% 4 4 3 3 4 4 22%	9370
	21st to end	Night	22% 19% 4 8% 6% 5% 4 3 4 5% 20%	9719
February	1st to 10th	Night	25% 21% 3 7% 5% 3 3 2 4 5% 23%	3110
	11th to 20th	Night	23% 17% 3 7% 5% 4 4 3 4 5% 23%	2743
	21st to end	Night	20% 13% 2 5% 4 4 4 4 5% 6% 32%	2249
March	1st to 10th	Night	18% 16% 4 10% 6% 5% 4 4 4 5% 24%	5642
	11th to 20th	Night	9% 15% 6% 12% 6% 5% 4 4 5% 6% 26%	5111
	21st to end	Night	17% 20% 5% 11% 6% 5% 5% 3 5% 5% 18%	5175
April	1st to 10th	Night	21% 16% 3 8% 5% 4 4 4 4 5% 27%	1951
	11th to 20th	Night	21% 19% 4 8% 4 4 3 2 4 5% 27%	1697
	21st to end	Night	33% 18% 3 6% 4 2 2 2 3 5% 21%	1600
May	1st to 10th	Night	22% 27% 5% 9% 5% 5% 4 3 3 4 15%	3390
	11th to 20th	Night	24% 15% 4 8% 4 3 5% 4 5% 5% 23%	2708
	21st to end	Night	32% 19% 4 6% 4 4 4 2 3 4 19%	2968
June	1st to 10th	Night	33% 11% 2 7% 5% 4 4 3 4 5% 22%	1162
	11th to 20th	Night	31% 10% 2 4 3 4 3 4 5% 6% 29%	1000
	21st to end	Night	32% 12% 3 8% 5% 5% 4 4 6% 5% 17%	1000
July	1st to 10th	Night	39% 15% 4 8% 4 3 3 2 4 4 14%	2338
	11th to 20th	Night	31% 13% 3 9% 5% 5% 4 3 5% 5% 18%	2720
	21st to end	Night	22% 9% 2 6% 4 5% 4 4 6% 8% 30%	3174
August	1st to 10th	Night	32% 11% 3 7% 4 4 4 3 4 4 24%	2273
	11th to 20th	Night	18% 6% 2 5% 4 4 5% 4 6% 7% 38%	2561
	21st to end	Night	26% 8% 3 8% 4 4 4 3 6% 8% 26%	3087
September	1st to 10th	Night	27% 8% 3 7% 5% 4 5% 4 5% 6% 25%	1953
	11th to 20th	Night	26% 8% 3 7% 5% 4 4 4 6% 6% 28%	2000
	21st to end	Night	28% 8% 3 7% 4 4 5% 3 5% 6% 28%	2289
October	1st to 10th	Night	22% 10% 4 9% 5% 4 5% 4 6% 7% 26%	3920
	11th to 20th	Night	22% 11% 3 6% 3 3 3 3 4 4 37%	4076
	21st to end	Night	24% 11% 3 7% 4 4 4 3 4 5% 32%	4970
November	1st to 10th	Night	23% 10% 3 7% 4 4 4 4 5% 6% 29%	2895
	11th to 20th	Night	19% 10% 3 7% 5% 4 5% 4 5% 6% 30%	3276
	21st to end	Night	19% 13% 3 7% 5% 5% 5% 4 6% 6% 26%	3360
December	1st to 10th	Night	33% 21% 4 7% 4 3 3 3 3 4 14%	5390
	11th to 20th	Night	24% 15% 4 7% 5% 5% 4 4 5% 5% 23%	6121
	21st to end	Night	21% 15% 4 8% 4 4 5% 4 5% 5% 26%	8452

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	66% 6% 6% 10% 12% 1	3526
	11th to 20th	Day	65% 6% 6% 12% 9% 2	3574
	21st to end	Day	65% 5% 6% 13% 8% 3	4495
February	1st to 10th	Day	62% 8% 10% 9% 8% 2	1510
	11th to 20th	Day	62% 7% 9% 13% 8% 1	1768
	21st to end	Day	54% 9% 15% 13% 7% 2	1557
March	1st to 10th	Day	58% 8% 6% 14% 12% 2	4432
	11th to 20th	Day	56% 9% 8% 15% 9% 2	5000
	21st to end	Day	63% 11% 9% 10% 6% 1	5755
April	1st to 10th	Day	60% 9% 9% 12% 7% 2	2446
	11th to 20th	Day	63% 8% 11% 13% 6%	2652
	21st to end	Day	68% 8% 9% 9% 4 1	2800
May	1st to 10th	Day	67% 9% 9% 11% 3	6588
	11th to 20th	Day	58% 12% 13% 11% 6%	7209
	21st to end	Day	68% 10% 12% 9% 1	7930
June	1st to 10th	Day	62% 12% 13% 11% 2	3235
	11th to 20th	Day	57% 12% 16% 13% 2	3400
	21st to end	Day	66% 15% 13% 5%	3400
July	1st to 10th	Day	70% 9% 16% 5%	7573
	11th to 20th	Day	64% 11% 17% 7%	7173
	21st to end	Day	56% 10% 19% 13% 1	7475
August	1st to 10th	Day	63% 11% 15% 11% 1	4869
	11th to 20th	Day	46% 9% 19% 20% 5%	4538
	21st to end	Day	55% 10% 15% 15% 5%	4811
September	1st to 10th	Day	59% 13% 14% 11% 3	2446
	11th to 20th	Day	56% 11% 14% 14% 5%	2400
	21st to end	Day	57% 10% 14% 13% 6%	2110
October	1st to 10th	Day	53% 9% 12% 19% 8%	3260
	11th to 20th	Day	50% 7% 14% 24% 6%	3063
	21st to end	Day	50% 7% 12% 20% 8% 3	2831
November	1st to 10th	Day	56% 8% 13% 14% 7% 1	1622
	11th to 20th	Day	56% 10% 10% 16% 8% 1	1343
	21st to end	Day	58% 9% 10% 13% 10% 1	1260
December	1st to 10th	Day	77% 4 7% 6% 4 2	2020
	11th to 20th	Day	63% 6% 9% 9% 12% 1	2319
	21st to end	Day	60% 6% 9% 16% 8% 1	2723
January	1st to 10th	Night	65% 6% 8% 12% 9% 1	9400
	11th to 20th	Night	68% 4 6% 13% 8% 2	9415
	21st to end	Night	67% 6% 6% 11% 9% 1	9719
February	1st to 10th	Night	66% 6% 9% 11% 7% 1	3110
	11th to 20th	Night	65% 7% 7% 10% 8% 1	2747
	21st to end	Night	52% 8% 12% 17% 9% 2	2249
March	1st to 10th	Night	60% 8% 8% 11% 12% 1	5642
	11th to 20th	Night	54% 11% 8% 16% 10% 1	5113
	21st to end	Night	66% 9% 10% 9% 5% 1	5175
April	1st to 10th	Night	60% 8% 10% 14% 6% 2	1951
	11th to 20th	Night	61% 7% 10% 15% 6%	1697
	21st to end	Night	67% 7% 8% 12% 6%	1600
May	1st to 10th	Night	71% 7% 8% 11% 2	3387
	11th to 20th	Night	61% 8% 10% 17% 4	2709
	21st to end	Night	69% 6% 13% 10% 1	2968
June	1st to 10th	Night	64% 9% 14% 10% 3	1162
	11th to 20th	Night	56% 13% 16% 14% 1	1000
	21st to end	Night	68% 11% 14% 7%	1000
July	1st to 10th	Night	76% 5% 13% 5%	2312
	11th to 20th	Night	68% 10% 15% 6% 2	2684
	21st to end	Night	51% 9% 26% 13%	3085
August	1st to 10th	Night	63% 8% 15% 13% 1	2266
	11th to 20th	Night	43% 8% 23% 22% 3	2585
	21st to end	Night	56% 8% 17% 16% 3	3087
September	1st to 10th	Night	58% 12% 16% 11% 3	1953
	11th to 20th	Night	56% 9% 15% 16% 4	2000
	21st to end	Night	57% 8% 15% 14% 6%	2289
October	1st to 10th	Night	59% 7% 12% 18% 4	3920
	11th to 20th	Night	48% 7% 14% 22% 10%	4076
	21st to end	Night	56% 6% 11% 16% 11% 1	4970
November	1st to 10th	Night	55% 9% 13% 14% 8% 1	2895
	11th to 20th	Night	54% 8% 12% 17% 7% 1	3276
	21st to end	Night	58% 9% 11% 13% 7% 1	3360
December	1st to 10th	Night	76% 5% 7% 6% 4 1	5390
	11th to 20th	Night	63% 6% 9% 12% 9% 1	6117
	21st to end	Night	56% 8% 10% 16% 8% 2	8452

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	28% 16% 21% 19% 12% 4	320
	11th to 20th	Day	33% 16% 23% 17% 9% 3	320
	21st to end	Day	34% 16% 30% 15% 3 2	352
February	1st to 10th	Day	29% 13% 25% 19% 7% 7%	342
	11th to 20th	Day	32% 20% 23% 18% 6% 1	425
	21st to end	Day	25% 28% 23% 15% 8% 1	355
March	1st to 10th	Day	26% 19% 28% 15% 9% 3	430
	11th to 20th	Day	20% 14% 27% 24% 11% 4	597
	21st to end	Day	27% 13% 25% 21% 11% 3	660
April	1st to 10th	Day	28% 17% 21% 19% 13% 2	600
	11th to 20th	Day	30% 9% 22% 23% 13% 3	633
	21st to end	Day	38% 13% 18% 16% 12% 3	700
May	1st to 10th	Day	35% 13% 17% 20% 13% 2	703
	11th to 20th	Day	32% 10% 20% 22% 13% 3	725
	21st to end	Day	34% 8% 16% 21% 16% 5%	790
June	1st to 10th	Day	32% 7% 14% 19% 23% 5%	765
	11th to 20th	Day	28% 5% 14% 23% 23% 7%	930
	21st to end	Day	31% 6% 14% 23% 18% 8%	930
July	1st to 10th	Day	32% 7% 11% 21% 22% 7%	892
	11th to 20th	Day	28% 4 16% 27% 21% 4	718
	21st to end	Day	26% 6% 19% 24% 20% 5%	794
August	1st to 10th	Day	27% 7% 19% 26% 18% 3	726
	11th to 20th	Day	22% 8% 24% 25% 17% 4	715
	21st to end	Day	25% 10% 21% 29% 13% 3	729
September	1st to 10th	Day	25% 9% 23% 22% 16% 4	620
	11th to 20th	Day	28% 10% 22% 20% 15% 5%	620
	21st to end	Day	29% 12% 25% 17% 12% 5%	495
October	1st to 10th	Day	29% 13% 25% 20% 11% 2	420
	11th to 20th	Day	30% 11% 23% 23% 11% 2	420
	21st to end	Day	29% 13% 24% 21% 10% 3	462
November	1st to 10th	Day	31% 16% 24% 20% 6% 3	425
	11th to 20th	Day	28% 21% 27% 16% 7% 1	363
	21st to end	Day	30% 20% 21% 18% 9% 2	320
December	1st to 10th	Day	35% 18% 26% 12% 8% 1	320
	11th to 20th	Day	31% 17% 24% 20% 4 4	320
	21st to end	Day	32% 16% 23% 17% 8% 3	352
January	1st to 10th	Night	30% 12% 22% 21% 13% 2	950
	11th to 20th	Night	37% 13% 20% 20% 8% 2	950
	21st to end	Night	36% 16% 22% 19% 6% 1	1045
February	1st to 10th	Night	37% 10% 20% 19% 9% 4	950
	11th to 20th	Night	36% 16% 19% 19% 8% 2	808
	21st to end	Night	28% 23% 22% 16% 10% 2	610
March	1st to 10th	Night	25% 20% 25% 19% 9% 2	740
	11th to 20th	Night	20% 12% 26% 24% 13% 4	728
	21st to end	Night	30% 11% 18% 23% 13% 4	707
April	1st to 10th	Night	31% 11% 21% 19% 15% 4	600
	11th to 20th	Night	30% 9% 19% 21% 17% 5%	593
	21st to end	Night	41% 9% 15% 18% 14% 4	600
May	1st to 10th	Night	33% 8% 15% 19% 17% 7%	500
	11th to 20th	Night	33% 9% 13% 23% 18% 5%	394
	21st to end	Night	40% 5% 8% 19% 23% 4	433
June	1st to 10th	Night	34% 7% 6% 21% 24% 9%	400
	11th to 20th	Night	33% 5% 9% 20% 24% 11%	400
	21st to end	Night	35% 4 11% 18% 21% 12%	400
July	1st to 10th	Night	34% 3 11% 15% 26% 10%	390
	11th to 20th	Night	28% 4 11% 22% 25% 10%	388
	21st to end	Night	31% 4 12% 21% 25% 8%	438
August	1st to 10th	Night	31% 6% 16% 20% 24% 4	398
	11th to 20th	Night	27% 6% 17% 22% 22% 5%	587
	21st to end	Night	32% 7% 14% 24% 18% 6%	660
September	1st to 10th	Night	29% 9% 14% 27% 15% 6%	600
	11th to 20th	Night	30% 7% 17% 23% 19% 5%	600
	21st to end	Night	33% 8% 19% 21% 15% 5%	691
October	1st to 10th	Night	31% 13% 19% 21% 12% 4	710
	11th to 20th	Night	29% 10% 21% 23% 14% 3	800
	21st to end	Night	31% 13% 22% 18% 11% 4	1001
November	1st to 10th	Night	31% 14% 21% 23% 9% 2	930
	11th to 20th	Night	25% 20% 28% 18% 8% 2	950
	21st to end	Night	26% 16% 27% 21% 9% 1	950
December	1st to 10th	Night	40% 15% 22% 16% 6% 1	950
	11th to 20th	Night	30% 14% 28% 20% 6% 2	950
	21st to end	Night	35% 16% 21% 16% 9% 2	1114

Page generated at 2026-03-14 22:23:56. Version ac07

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