Kenai
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kenai clear sky chart from 2005-11-06 to 2024-11-11.

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	20% 12% 4 9% 5% 5% 5% 4 5% 6% 26%	106465
	Night	17% 14% 4 9% 6% 5% 4 4 5% 6% 26%	101349
Transparency	Day	58% 7% 14% 14% 5% 1	106163
	Night	58% 6% 12% 14% 8% 2	101300
Seeing	Day	23% 5% 11% 23% 26% 12%	18342
	Night	25% 6% 15% 26% 21% 7%	22564

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	9% 17% 4 12% 8% 9% 6% 5% 6% 6% 19%	1493
	11th to 20th	Day	13% 13% 4 9% 6% 5% 5% 4 4 8% 29%	1677
	21st to end	Day	11% 13% 4 8% 5% 4 4 4 5% 5% 38%	2158
February	1st to 10th	Day	14% 18% 4 9% 6% 5% 4 5% 4 5% 25%	1330
	11th to 20th	Day	19% 20% 6% 10% 6% 5% 3 3 4 5% 20%	1471
	21st to end	Day	12% 12% 2 8% 5% 6% 6% 3 5% 6% 35%	1413
March	1st to 10th	Day	11% 19% 6% 9% 4 3 3 3 3 4 34%	3017
	11th to 20th	Day	10% 12% 5% 11% 5% 6% 5% 4 5% 7% 31%	3347
	21st to end	Day	21% 20% 5% 9% 5% 4 4 2 4 5% 21%	4087
April	1st to 10th	Day	10% 14% 4 9% 6% 5% 5% 4 6% 7% 29%	2332
	11th to 20th	Day	11% 16% 3 9% 6% 4 4 3 4 6% 34%	2599
	21st to end	Day	11% 15% 4 8% 7% 5% 5% 4 6% 7% 28%	2660
May	1st to 10th	Day	19% 19% 5% 12% 7% 5% 5% 4 4 4 16%	4969
	11th to 20th	Day	13% 13% 4 9% 5% 4 4 3 5% 6% 33%	5023
	21st to end	Day	23% 12% 4 9% 5% 4 5% 4 5% 6% 23%	5748
June	1st to 10th	Day	17% 12% 3 8% 5% 5% 4 4 7% 8% 26%	3420
	11th to 20th	Day	17% 10% 3 9% 6% 5% 5% 4 6% 8% 28%	3420
	21st to end	Day	19% 9% 3 7% 6% 5% 5% 4 7% 8% 27%	3420
July	1st to 10th	Day	23% 11% 4 8% 5% 6% 5% 5% 6% 6% 21%	5642
	11th to 20th	Day	29% 10% 3 7% 5% 4 3 4 5% 6% 24%	5390
	21st to end	Day	26% 8% 3 6% 4 3 4 4 4 7% 31%	5505
August	1st to 10th	Day	29% 7% 3 8% 6% 4 4 3 6% 7% 23%	4893
	11th to 20th	Day	28% 8% 3 7% 4 4 4 3 4 6% 30%	4451
	21st to end	Day	28% 9% 3 8% 4 4 4 4 5% 5% 25%	4834
September	1st to 10th	Day	30% 12% 3 9% 5% 5% 4 4 4 5% 18%	2332
	11th to 20th	Day	33% 10% 3 8% 5% 4 4 4 4 5% 20%	2280
	21st to end	Day	22% 12% 3 9% 4 5% 5% 3 6% 6% 27%	2014
October	1st to 10th	Day	19% 11% 4 10% 7% 6% 6% 4 6% 6% 20%	3160
	11th to 20th	Day	14% 10% 3 7% 4 4 5% 4 6% 6% 37%	2799
	21st to end	Day	19% 12% 3 7% 4 3 4 3 4 5% 36%	2743
November	1st to 10th	Day	20% 16% 4 9% 5% 5% 5% 3 4 5% 23%	1387
	11th to 20th	Day	16% 9% 4 7% 4 5% 5% 4 7% 5% 34%	1141
	21st to end	Day	18% 17% 5% 9% 6% 6% 6% 5% 4 4 21%	1107
December	1st to 10th	Day	20% 16% 6% 9% 8% 6% 6% 2 5% 4 18%	839
	11th to 20th	Day	16% 20% 8% 12% 4 4 4 4 4 5% 19%	967
	21st to end	Day	11% 15% 5% 10% 7% 6% 5% 5% 6% 13% 16%	1397
January	1st to 10th	Night	11% 17% 5% 11% 9% 8% 6% 4 4 5% 19%	5469
	11th to 20th	Night	15% 14% 5% 9% 5% 5% 4 3 5% 6% 27%	5236
	21st to end	Night	13% 12% 3 6% 4 4 4 3 4 6% 40%	5506
February	1st to 10th	Night	15% 16% 4 9% 6% 5% 4 3 5% 5% 28%	2850
	11th to 20th	Night	20% 20% 5% 10% 6% 5% 4 4 4 4 19%	2593
	21st to end	Night	12% 15% 5% 8% 5% 4 4 4 5% 4 32%	2041
March	1st to 10th	Night	11% 17% 5% 9% 5% 4 4 3 5% 5% 31%	3837
	11th to 20th	Night	10% 13% 5% 11% 6% 6% 5% 5% 7% 6% 28%	3610
	21st to end	Night	16% 23% 6% 10% 6% 4 4 3 3 3 21%	3544
April	1st to 10th	Night	13% 18% 4 9% 6% 4 4 3 4 5% 30%	1847
	11th to 20th	Night	13% 14% 4 8% 6% 4 3 3 4 6% 34%	1530
	21st to end	Night	10% 16% 4 10% 4 4 4 5% 6% 7% 30%	1520
May	1st to 10th	Night	20% 19% 5% 11% 6% 5% 5% 3 5% 4 18%	1999
	11th to 20th	Night	14% 18% 5% 8% 4 3 3 3 5% 5% 32%	1882
	21st to end	Night	16% 11% 5% 11% 6% 5% 4 4 6% 7% 24%	1839
June	1st to 10th	Night	21% 13% 4 6% 5% 6% 5% 3 5% 10% 23%	760
	11th to 20th	Night	15% 11% 3 9% 5% 5% 5% 5% 7% 8% 27%	760
	21st to end	Night	20% 9% 3 6% 5% 4 5% 6% 9% 8% 24%	760
July	1st to 10th	Night	24% 11% 3 10% 6% 6% 5% 4 5% 5% 20%	1328
	11th to 20th	Night	30% 9% 3 8% 5% 5% 4 3 4 6% 24%	1590
	21st to end	Night	26% 7% 2 7% 5% 5% 3 3 6% 7% 31%	2059
August	1st to 10th	Night	28% 9% 2 7% 5% 4 5% 3 4 6% 27%	2044
	11th to 20th	Night	29% 5% 2 5% 4 3 3 4 5% 6% 35%	2387
	21st to end	Night	28% 9% 3 7% 5% 4 4 3 5% 5% 26%	2830
September	1st to 10th	Night	31% 12% 4 10% 5% 6% 4 2 4 5% 18%	1848
	11th to 20th	Night	30% 10% 3 8% 4 4 5% 4 4 6% 22%	1900
	21st to end	Night	26% 11% 4 8% 4 4 4 2 4 5% 27%	2166
October	1st to 10th	Night	23% 12% 4 9% 7% 6% 7% 4 4 5% 18%	3800
	11th to 20th	Night	15% 9% 3 9% 5% 4 4 3 4 6% 38%	4125
	21st to end	Night	18% 13% 3 9% 5% 4 3 3 4 5% 34%	4816
November	1st to 10th	Night	21% 16% 5% 9% 5% 5% 4 3 4 5% 24%	2908
	11th to 20th	Night	14% 12% 3 8% 5% 4 4 4 7% 6% 32%	3045
	21st to end	Night	16% 17% 5% 10% 7% 5% 5% 3 4 4 23%	3071
December	1st to 10th	Night	22% 16% 5% 10% 7% 5% 4 3 5% 5% 19%	3339
	11th to 20th	Night	13% 19% 6% 13% 8% 5% 5% 4 4 5% 19%	4240
	21st to end	Night	12% 16% 5% 13% 9% 6% 5% 4 6% 11% 14%	6270

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	63% 6% 10% 12% 8% 1	1493
	11th to 20th	Day	52% 5% 8% 20% 14% 2	1692
	21st to end	Day	48% 4 9% 11% 23% 5%	2158
February	1st to 10th	Day	58% 7% 8% 12% 11% 3	1330
	11th to 20th	Day	68% 5% 9% 11% 6% 2	1478
	21st to end	Day	48% 7% 12% 18% 13% 1	1413
March	1st to 10th	Day	54% 3 8% 12% 17% 5%	3017
	11th to 20th	Day	50% 6% 13% 13% 16% 2	3347
	21st to end	Day	66% 7% 8% 10% 8% 1	4087
April	1st to 10th	Day	54% 7% 13% 15% 9% 2	2332
	11th to 20th	Day	53% 7% 12% 19% 10%	2599
	21st to end	Day	55% 7% 10% 19% 8%	2660
May	1st to 10th	Day	71% 7% 10% 10% 3	4969
	11th to 20th	Day	52% 9% 10% 22% 7%	5026
	21st to end	Day	58% 10% 14% 16% 3	5749
June	1st to 10th	Day	55% 10% 18% 16% 1	3420
	11th to 20th	Day	54% 10% 16% 16% 3 1	3420
	21st to end	Day	55% 12% 22% 11%	3420
July	1st to 10th	Day	63% 9% 20% 7%	5554
	11th to 20th	Day	63% 8% 20% 9% 1	5297
	21st to end	Day	54% 8% 24% 14% 1	5331
August	1st to 10th	Day	62% 9% 19% 10%	4874
	11th to 20th	Day	56% 6% 16% 20% 2	4495
	21st to end	Day	61% 7% 13% 16% 3	4833
September	1st to 10th	Day	70% 6% 13% 9% 2	2332
	11th to 20th	Day	67% 7% 11% 13% 2	2280
	21st to end	Day	60% 8% 12% 17% 3	2014
October	1st to 10th	Day	63% 6% 14% 15% 2	3160
	11th to 20th	Day	48% 6% 15% 20% 11%	2799
	21st to end	Day	50% 7% 9% 28% 6%	2743
November	1st to 10th	Day	63% 8% 11% 11% 6% 1	1387
	11th to 20th	Day	49% 7% 13% 24% 7%	1141
	21st to end	Day	65% 5% 8% 12% 9% 1	1107
December	1st to 10th	Day	69% 6% 8% 10% 7%	839
	11th to 20th	Day	65% 5% 10% 13% 7%	970
	21st to end	Day	56% 5% 12% 10% 13% 4	1397
January	1st to 10th	Night	63% 8% 10% 9% 8% 1	5469
	11th to 20th	Night	56% 6% 6% 18% 12% 2	5284
	21st to end	Night	46% 3 8% 13% 21% 9%	5506
February	1st to 10th	Night	58% 5% 7% 13% 13% 4	2850
	11th to 20th	Night	67% 6% 9% 10% 6% 1	2597
	21st to end	Night	53% 6% 10% 19% 11% 2	2041
March	1st to 10th	Night	54% 4 9% 12% 12% 8%	3837
	11th to 20th	Night	51% 7% 13% 12% 15% 2	3612
	21st to end	Night	66% 8% 9% 10% 6% 2	3544
April	1st to 10th	Night	57% 5% 11% 17% 7% 2	1847
	11th to 20th	Night	52% 7% 11% 19% 12%	1530
	21st to end	Night	52% 7% 14% 19% 9%	1520
May	1st to 10th	Night	68% 7% 9% 12% 4	1999
	11th to 20th	Night	54% 9% 9% 22% 5%	1883
	21st to end	Night	54% 9% 15% 18% 4	1839
June	1st to 10th	Night	58% 8% 19% 14% 1	760
	11th to 20th	Night	51% 11% 20% 15% 2 1	760
	21st to end	Night	55% 14% 24% 8%	760
July	1st to 10th	Night	65% 10% 19% 6%	1307
	11th to 20th	Night	63% 8% 21% 8%	1560
	21st to end	Night	53% 6% 27% 14% 1	1994
August	1st to 10th	Night	59% 7% 21% 12% 1	2038
	11th to 20th	Night	51% 6% 20% 21% 2	2409
	21st to end	Night	61% 6% 12% 17% 3	2830
September	1st to 10th	Night	69% 8% 12% 9% 2	1848
	11th to 20th	Night	63% 9% 13% 13% 2	1900
	21st to end	Night	60% 8% 13% 16% 4	2166
October	1st to 10th	Night	65% 7% 10% 16% 2	3800
	11th to 20th	Night	49% 6% 16% 18% 10%	4125
	21st to end	Night	54% 5% 9% 24% 8% 1	4816
November	1st to 10th	Night	63% 6% 12% 12% 6% 1	2908
	11th to 20th	Night	50% 7% 13% 20% 10%	3045
	21st to end	Night	62% 5% 10% 11% 10% 2	3071
December	1st to 10th	Night	67% 5% 10% 10% 8%	3339
	11th to 20th	Night	67% 5% 8% 12% 7%	4236
	21st to end	Night	62% 5% 10% 9% 8% 6%	6270

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	15% 5% 13% 37% 20% 11%	223
	11th to 20th	Day	22% 6% 18% 30% 16% 7%	280
	21st to end	Day	29% 5% 14% 31% 15% 6%	308
February	1st to 10th	Day	23% 5% 15% 31% 16% 10%	280
	11th to 20th	Day	28% 9% 15% 28% 14% 6%	358
	21st to end	Day	15% 7% 16% 39% 15% 8%	307
March	1st to 10th	Day	19% 5% 15% 29% 20% 12%	370
	11th to 20th	Day	13% 5% 11% 33% 26% 11%	479
	21st to end	Day	16% 5% 15% 27% 26% 11%	616
April	1st to 10th	Day	17% 6% 13% 31% 23% 11%	560
	11th to 20th	Day	18% 5% 8% 20% 31% 17%	628
	21st to end	Day	17% 4 10% 21% 30% 18%	650
May	1st to 10th	Day	20% 6% 13% 24% 28% 9%	653
	11th to 20th	Day	20% 3 11% 23% 31% 11%	675
	21st to end	Day	22% 4 10% 23% 30% 11%	819
June	1st to 10th	Day	17% 4 10% 19% 33% 18%	870
	11th to 20th	Day	15% 3 7% 22% 37% 15%	870
	21st to end	Day	20% 3 6% 19% 35% 18%	870
July	1st to 10th	Day	22% 3 7% 18% 33% 17%	856
	11th to 20th	Day	24% 4 7% 23% 30% 12%	852
	21st to end	Day	28% 2 6% 23% 26% 14%	745
August	1st to 10th	Day	29% 5% 8% 20% 28% 10%	676
	11th to 20th	Day	26% 4 14% 21% 26% 9%	665
	21st to end	Day	29% 4 11% 20% 23% 13%	735
September	1st to 10th	Day	31% 6% 12% 18% 23% 10%	580
	11th to 20th	Day	36% 6% 7% 15% 24% 12%	580
	21st to end	Day	26% 4 14% 16% 24% 16%	433
October	1st to 10th	Day	32% 4 13% 23% 20% 9%	390
	11th to 20th	Day	26% 7% 15% 25% 19% 8%	390
	21st to end	Day	28% 7% 13% 24% 19% 9%	429
November	1st to 10th	Day	28% 8% 20% 23% 17% 4	388
	11th to 20th	Day	20% 6% 22% 29% 20% 2	281
	21st to end	Day	25% 7% 23% 22% 19% 4	247
December	1st to 10th	Day	28% 8% 13% 30% 21%	90
	11th to 20th	Day	31% 7% 18% 33% 9% 2	90
	21st to end	Day	24% 12% 21% 25% 12% 5%	99
January	1st to 10th	Night	17% 6% 17% 34% 21% 5%	940
	11th to 20th	Night	25% 6% 20% 27% 17% 5%	908
	21st to end	Night	27% 5% 17% 31% 17% 4	935
February	1st to 10th	Night	21% 6% 18% 32% 17% 6%	850
	11th to 20th	Night	32% 6% 15% 29% 15% 3	823
	21st to end	Night	19% 7% 18% 32% 18% 6%	546
March	1st to 10th	Night	21% 5% 21% 27% 20% 5%	660
	11th to 20th	Night	14% 5% 16% 32% 23% 10%	660
	21st to end	Night	18% 5% 14% 30% 22% 12%	651
April	1st to 10th	Night	21% 7% 12% 27% 23% 10%	570
	11th to 20th	Night	20% 4 11% 24% 29% 12%	563
	21st to end	Night	15% 5% 14% 21% 31% 14%	570
May	1st to 10th	Night	22% 8% 12% 20% 31% 7%	399
	11th to 20th	Night	22% 4 9% 26% 30% 8%	374
	21st to end	Night	21% 5% 10% 26% 30% 8%	368
June	1st to 10th	Night	25% 2 4 19% 39% 11%	190
	11th to 20th	Night	17% 3 6% 28% 40% 6%	190
	21st to end	Night	23% 2 8% 18% 37% 12%	190
July	1st to 10th	Night	27% 2 7% 20% 33% 10%	216
	11th to 20th	Night	25% 2 7% 23% 33% 10%	368
	21st to end	Night	31% 2 6% 21% 27% 13%	416
August	1st to 10th	Night	31% 4 12% 23% 23% 7%	378
	11th to 20th	Night	31% 4 12% 23% 24% 6%	499
	21st to end	Night	31% 4 11% 20% 23% 10%	627
September	1st to 10th	Night	36% 4 13% 22% 20% 6%	570
	11th to 20th	Night	34% 5% 9% 18% 23% 11%	570
	21st to end	Night	30% 5% 12% 20% 22% 10%	633
October	1st to 10th	Night	37% 5% 10% 25% 16% 7%	670
	11th to 20th	Night	28% 6% 14% 23% 20% 9%	827
	21st to end	Night	27% 5% 18% 24% 20% 6%	946
November	1st to 10th	Night	29% 7% 19% 23% 18% 4	880
	11th to 20th	Night	21% 7% 22% 30% 18% 2	852
	21st to end	Night	27% 7% 20% 25% 18% 3	850
December	1st to 10th	Night	30% 8% 19% 27% 14% 3	901
	11th to 20th	Night	26% 7% 17% 31% 15% 3	940
	21st to end	Night	25% 7% 21% 26% 15% 5%	1034

Page generated at 2024-11-08 02:44:48. Version ac07

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