Knik River Swimming Hole
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Knik River Swimming Hole clear sky chart from 2005-11-06 to 2026-09-29.

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	15% 13% 4 10% 6% 6% 6% 4 6% 7% 23%	156334
	Night	11% 14% 5% 10% 6% 5% 5% 4 6% 7% 27%	143978
Transparency	Day	57% 10% 15% 12% 5% 1	155979
	Night	53% 9% 13% 14% 9% 2	143918
Seeing	Day	21% 12% 25% 25% 13% 3	20524
	Night	18% 11% 28% 27% 14% 2	24742

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	2 15% 4 10% 7% 7% 5% 3 5% 6% 36%	2361
	11th to 20th	Day	7% 14% 4 10% 6% 6% 5% 4 5% 6% 31%	3059
	21st to end	Day	7% 13% 6% 10% 7% 6% 5% 4 5% 7% 30%	3871
February	1st to 10th	Day	5% 13% 4 8% 6% 5% 4 3 5% 7% 40%	1423
	11th to 20th	Day	6% 21% 7% 11% 6% 4 5% 5% 5% 7% 24%	1639
	21st to end	Day	6% 12% 4 11% 6% 6% 6% 4 5% 6% 34%	1475
March	1st to 10th	Day	3 16% 7% 12% 7% 6% 6% 4 5% 6% 29%	4541
	11th to 20th	Day	2 9% 5% 13% 8% 7% 7% 5% 8% 8% 28%	4744
	21st to end	Day	7% 15% 5% 10% 6% 5% 6% 5% 6% 8% 28%	6101
April	1st to 10th	Day	4 17% 6% 11% 6% 6% 6% 6% 6% 6% 26%	2570
	11th to 20th	Day	6% 13% 4 8% 6% 5% 6% 5% 6% 7% 33%	2906
	21st to end	Day	6% 15% 5% 10% 7% 6% 6% 5% 6% 7% 28%	2998
May	1st to 10th	Day	13% 20% 6% 12% 7% 5% 5% 4 5% 6% 17%	9277
	11th to 20th	Day	12% 16% 5% 11% 6% 6% 6% 5% 6% 7% 20%	9398
	21st to end	Day	14% 16% 5% 11% 6% 6% 6% 5% 6% 7% 18%	11237
June	1st to 10th	Day	16% 11% 4 9% 6% 6% 6% 5% 7% 8% 23%	3780
	11th to 20th	Day	16% 11% 2 9% 6% 5% 6% 4 7% 8% 26%	3780
	21st to end	Day	18% 11% 3 8% 6% 7% 7% 5% 7% 7% 21%	3780
July	1st to 10th	Day	20% 11% 4 9% 6% 6% 5% 5% 7% 8% 20%	10620
	11th to 20th	Day	24% 12% 4 10% 7% 6% 6% 4 6% 7% 14%	10489
	21st to end	Day	22% 10% 3 8% 5% 5% 5% 4 6% 7% 23%	10251
August	1st to 10th	Day	27% 10% 3 8% 5% 4 5% 4 5% 7% 22%	7396
	11th to 20th	Day	23% 10% 3 8% 5% 5% 5% 4 6% 8% 22%	6527
	21st to end	Day	22% 11% 4 9% 5% 5% 5% 4 7% 7% 19%	7103
September	1st to 10th	Day	25% 11% 4 10% 6% 6% 6% 4 6% 6% 17%	2604
	11th to 20th	Day	26% 14% 4 10% 6% 4 4 4 4 4 20%	2508
	21st to end	Day	19% 12% 4 9% 6% 6% 6% 4 5% 6% 25%	2233
October	1st to 10th	Day	14% 13% 4 9% 6% 6% 6% 5% 7% 7% 23%	3201
	11th to 20th	Day	8% 9% 5% 8% 4 4 4 4 6% 8% 39%	2924
	21st to end	Day	11% 14% 4 8% 4 4 5% 3 5% 8% 33%	2721
November	1st to 10th	Day	7% 13% 5% 9% 7% 7% 6% 4 6% 8% 28%	1441
	11th to 20th	Day	7% 11% 4 8% 4 5% 5% 4 6% 7% 38%	1258
	21st to end	Day	5% 13% 7% 13% 6% 6% 4 5% 5% 7% 29%	1050
December	1st to 10th	Day	13% 13% 4 9% 7% 6% 5% 5% 5% 8% 26%	1465
	11th to 20th	Day	3 21% 7% 10% 4 5% 5% 4 6% 8% 26%	1557
	21st to end	Day	2 9% 4 12% 7% 5% 5% 4 6% 8% 37%	2046
January	1st to 10th	Night	4 13% 4 9% 6% 6% 5% 4 6% 7% 35%	10564
	11th to 20th	Night	9% 15% 5% 11% 7% 6% 5% 4 5% 5% 27%	9877
	21st to end	Night	7% 12% 4 9% 6% 5% 6% 4 6% 8% 31%	10342
February	1st to 10th	Night	5% 12% 5% 8% 5% 4 3 4 5% 7% 43%	3194
	11th to 20th	Night	8% 19% 6% 11% 6% 5% 4 4 5% 6% 24%	2868
	21st to end	Night	5% 11% 5% 12% 7% 6% 5% 5% 6% 7% 31%	2328
March	1st to 10th	Night	3 16% 6% 13% 7% 5% 4 3 6% 6% 32%	5532
	11th to 20th	Night	2 14% 6% 11% 6% 5% 6% 5% 6% 8% 31%	5431
	21st to end	Night	6% 16% 5% 9% 5% 5% 5% 4 6% 9% 31%	5072
April	1st to 10th	Night	5% 17% 6% 11% 6% 7% 5% 4 6% 7% 25%	2046
	11th to 20th	Night	7% 15% 4 7% 6% 6% 5% 5% 6% 6% 33%	1663
	21st to end	Night	6% 13% 5% 9% 6% 5% 5% 5% 6% 6% 33%	1622
May	1st to 10th	Night	15% 19% 4 11% 7% 6% 6% 5% 6% 6% 16%	3672
	11th to 20th	Night	18% 21% 5% 9% 5% 4 5% 3 4 6% 20%	3492
	21st to end	Night	21% 16% 4 10% 5% 6% 5% 4 6% 7% 17%	2934
June	1st to 10th	Night	15% 13% 5% 9% 7% 7% 6% 3 5% 8% 23%	840
	11th to 20th	Night	18% 11% 3 9% 7% 5% 6% 4 7% 7% 23%	840
	21st to end	Night	20% 9% 3 9% 6% 7% 5% 6% 7% 7% 21%	840
July	1st to 10th	Night	29% 14% 5% 11% 5% 5% 5% 3 4 6% 13%	2370
	11th to 20th	Night	32% 10% 3 9% 6% 6% 5% 4 5% 5% 15%	2507
	21st to end	Night	30% 10% 4 8% 5% 4 5% 4 5% 6% 20%	3851
August	1st to 10th	Night	28% 10% 3 8% 5% 4 5% 3 5% 7% 22%	2774
	11th to 20th	Night	26% 10% 4 10% 6% 5% 6% 4 6% 6% 17%	3525
	21st to end	Night	30% 14% 4 10% 6% 6% 4 4 4 3 14%	4045
September	1st to 10th	Night	30% 13% 3 8% 5% 6% 6% 4 6% 5% 15%	2012
	11th to 20th	Night	27% 15% 3 9% 5% 5% 4 3 5% 5% 18%	2111
	21st to end	Night	21% 13% 3 9% 6% 5% 5% 4 6% 6% 22%	2343
October	1st to 10th	Night	15% 14% 4 9% 7% 7% 7% 5% 6% 7% 20%	3981
	11th to 20th	Night	7% 9% 3 8% 6% 6% 5% 4 7% 7% 38%	4224
	21st to end	Night	11% 15% 3 10% 6% 6% 5% 3 5% 7% 27%	5076
November	1st to 10th	Night	7% 14% 4 11% 6% 6% 6% 5% 5% 6% 29%	3077
	11th to 20th	Night	6% 12% 3 8% 6% 5% 5% 4 6% 7% 38%	3362
	21st to end	Night	7% 13% 4 11% 8% 6% 6% 4 7% 7% 29%	3570
December	1st to 10th	Night	10% 16% 6% 10% 5% 5% 5% 4 6% 7% 24%	5939
	11th to 20th	Night	3 16% 7% 13% 6% 6% 6% 4 7% 7% 26%	6880
	21st to end	Night	3 10% 5% 11% 6% 6% 6% 5% 6% 8% 35%	9174

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	45% 8% 11% 12% 19% 5%	2361
	11th to 20th	Day	51% 8% 10% 16% 13% 2	3075
	21st to end	Day	50% 9% 7% 16% 15% 4	3872
February	1st to 10th	Day	43% 7% 12% 17% 14% 6%	1423
	11th to 20th	Day	57% 10% 12% 10% 9% 2	1646
	21st to end	Day	50% 7% 11% 16% 14% 3	1475
March	1st to 10th	Day	51% 8% 8% 13% 15% 4	4541
	11th to 20th	Day	46% 11% 11% 15% 15% 2	4744
	21st to end	Day	50% 10% 12% 16% 10% 1	6101
April	1st to 10th	Day	57% 9% 14% 16% 5% 1	2570
	11th to 20th	Day	47% 12% 16% 18% 8%	2906
	21st to end	Day	54% 8% 14% 16% 7% 1	2998
May	1st to 10th	Day	65% 7% 8% 15% 5%	9277
	11th to 20th	Day	57% 11% 13% 17% 2	9401
	21st to end	Day	61% 10% 14% 14% 1	11238
June	1st to 10th	Day	58% 12% 16% 13% 2	3780
	11th to 20th	Day	58% 10% 19% 11% 2	3780
	21st to end	Day	61% 12% 20% 7%	3780
July	1st to 10th	Day	60% 12% 20% 8%	10531
	11th to 20th	Day	68% 10% 16% 6%	10390
	21st to end	Day	58% 11% 21% 10%	10030
August	1st to 10th	Day	61% 10% 22% 7%	7377
	11th to 20th	Day	60% 10% 21% 8% 1	6570
	21st to end	Day	63% 9% 20% 7% 1	7102
September	1st to 10th	Day	68% 11% 11% 7% 2	2604
	11th to 20th	Day	68% 8% 13% 10% 1	2508
	21st to end	Day	61% 9% 14% 13% 3	2233
October	1st to 10th	Day	58% 10% 15% 15% 3	3201
	11th to 20th	Day	42% 9% 15% 21% 12% 1	2924
	21st to end	Day	49% 8% 13% 24% 5% 1	2721
November	1st to 10th	Day	54% 9% 14% 13% 7% 3	1441
	11th to 20th	Day	43% 9% 13% 21% 13% 1	1258
	21st to end	Day	53% 9% 10% 13% 13% 2	1050
December	1st to 10th	Day	55% 11% 11% 17% 5% 1	1465
	11th to 20th	Day	55% 9% 13% 16% 7% 1	1560
	21st to end	Day	41% 8% 15% 19% 10% 7%	2046
January	1st to 10th	Night	45% 8% 10% 12% 18% 7%	10564
	11th to 20th	Night	56% 8% 10% 13% 11% 2	9924
	21st to end	Night	45% 9% 9% 16% 16% 5%	10342
February	1st to 10th	Night	41% 8% 9% 20% 15% 7%	3194
	11th to 20th	Night	59% 8% 11% 11% 9% 2	2872
	21st to end	Night	50% 9% 10% 14% 13% 3	2328
March	1st to 10th	Night	49% 7% 8% 15% 15% 5%	5532
	11th to 20th	Night	45% 8% 12% 15% 18% 2	5433
	21st to end	Night	47% 8% 14% 18% 11% 2	5072
April	1st to 10th	Night	57% 8% 14% 16% 5%	2046
	11th to 20th	Night	47% 11% 16% 19% 8%	1663
	21st to end	Night	48% 9% 16% 18% 8%	1622
May	1st to 10th	Night	61% 11% 9% 15% 4	3669
	11th to 20th	Night	63% 7% 15% 13% 2	3493
	21st to end	Night	59% 11% 15% 14% 1	2938
June	1st to 10th	Night	58% 12% 18% 10% 1	840
	11th to 20th	Night	58% 12% 18% 10% 2	840
	21st to end	Night	58% 15% 21% 6%	840
July	1st to 10th	Night	68% 11% 15% 6%	2350
	11th to 20th	Night	66% 13% 16% 5%	2483
	21st to end	Night	65% 9% 18% 8% 1	3768
August	1st to 10th	Night	61% 11% 22% 5% 1	2768
	11th to 20th	Night	66% 11% 17% 6% 1	3547
	21st to end	Night	74% 8% 11% 6% 1	4045
September	1st to 10th	Night	70% 11% 11% 6% 2	2012
	11th to 20th	Night	67% 8% 15% 9% 1	2111
	21st to end	Night	63% 8% 15% 12% 3	2343
October	1st to 10th	Night	63% 8% 15% 11% 3	3981
	11th to 20th	Night	41% 9% 17% 20% 13%	4224
	21st to end	Night	57% 7% 13% 17% 5% 1	5076
November	1st to 10th	Night	55% 8% 12% 15% 8% 2	3077
	11th to 20th	Night	43% 11% 11% 22% 12% 1	3362
	21st to end	Night	52% 9% 11% 14% 11% 3	3570
December	1st to 10th	Night	55% 10% 10% 16% 7% 1	5939
	11th to 20th	Night	53% 10% 16% 14% 7% 1	6876
	21st to end	Night	42% 10% 16% 16% 10% 6%	9174

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	12% 15% 21% 28% 17% 7%	110
	11th to 20th	Day	17% 12% 32% 26% 10% 3	275
	21st to end	Day	14% 14% 26% 26% 16% 5%	352
February	1st to 10th	Day	11% 12% 25% 27% 16% 9%	328
	11th to 20th	Day	18% 15% 29% 23% 12% 2	425
	21st to end	Day	11% 18% 30% 26% 8% 7%	355
March	1st to 10th	Day	10% 13% 35% 24% 14% 4	430
	11th to 20th	Day	8% 13% 31% 26% 17% 5%	473
	21st to end	Day	10% 15% 28% 23% 20% 4	704
April	1st to 10th	Day	12% 19% 34% 23% 12% 2	666
	11th to 20th	Day	16% 12% 26% 30% 14% 3	740
	21st to end	Day	19% 11% 28% 30% 11% 1	750
May	1st to 10th	Day	20% 18% 28% 25% 8% 1	753
	11th to 20th	Day	21% 14% 29% 22% 13% 2	775
	21st to end	Day	22% 14% 29% 26% 9% 1	939
June	1st to 10th	Day	22% 12% 24% 26% 13% 2	990
	11th to 20th	Day	19% 10% 22% 32% 14% 3	990
	21st to end	Day	20% 9% 23% 30% 15% 3	990
July	1st to 10th	Day	21% 8% 26% 30% 13% 1	976
	11th to 20th	Day	26% 8% 24% 28% 12% 1	972
	21st to end	Day	26% 8% 24% 25% 15% 2	849
August	1st to 10th	Day	29% 12% 22% 24% 12% 2	776
	11th to 20th	Day	28% 14% 24% 21% 12% 2	765
	21st to end	Day	32% 10% 21% 23% 12% 1	858
September	1st to 10th	Day	30% 15% 24% 20% 9% 2	699
	11th to 20th	Day	34% 13% 21% 19% 11% 2	648
	21st to end	Day	27% 12% 18% 23% 14% 5%	445
October	1st to 10th	Day	30% 14% 24% 17% 12% 3	420
	11th to 20th	Day	19% 10% 25% 26% 16% 4	420
	21st to end	Day	22% 11% 23% 25% 16% 3	462
November	1st to 10th	Day	16% 10% 24% 25% 17% 8%	425
	11th to 20th	Day	14% 6% 24% 24% 24% 8%	313
	21st to end	Day	11% 15% 24% 21% 15% 15%	110
December	1st to 10th	Day	19% 14% 15% 29% 20% 3	110
	11th to 20th	Day	15% 10% 32% 26% 13% 4	110
	21st to end	Day	7% 22% 30% 23% 12% 6%	121
January	1st to 10th	Night	8% 15% 29% 30% 16% 2	1060
	11th to 20th	Night	15% 18% 32% 23% 11% 1	1016
	21st to end	Night	15% 11% 32% 26% 14% 1	1045
February	1st to 10th	Night	11% 12% 34% 29% 12% 2	950
	11th to 20th	Night	19% 16% 34% 22% 8%	934
	21st to end	Night	11% 13% 36% 25% 11% 3	689
March	1st to 10th	Night	11% 13% 31% 34% 10% 2	740
	11th to 20th	Night	8% 11% 28% 31% 19% 3	737
	21st to end	Night	10% 8% 32% 29% 19% 1	693
April	1st to 10th	Night	12% 12% 29% 30% 17% 1	630
	11th to 20th	Night	15% 9% 25% 30% 21% 1	623
	21st to end	Night	12% 8% 29% 37% 13% 1	630
May	1st to 10th	Night	18% 10% 28% 28% 15%	473
	11th to 20th	Night	17% 9% 26% 31% 16% 1	409
	21st to end	Night	20% 9% 24% 32% 14%	228
June	1st to 10th	Night	19% 10% 22% 33% 16%	210
	11th to 20th	Night	22% 5% 21% 35% 15% 2	210
	21st to end	Night	22% 7% 17% 33% 20% 1	210
July	1st to 10th	Night	26% 5% 18% 23% 27%	205
	11th to 20th	Night	34% 4 18% 21% 21% 1	250
	21st to end	Night	31% 7% 17% 24% 19% 2	460
August	1st to 10th	Night	33% 7% 17% 25% 16% 2	418
	11th to 20th	Night	33% 9% 24% 22% 11% 1	584
	21st to end	Night	34% 7% 19% 23% 15% 2	693
September	1st to 10th	Night	35% 10% 22% 21% 11% 1	630
	11th to 20th	Night	36% 7% 19% 23% 14% 1	630
	21st to end	Night	29% 9% 18% 21% 21% 2	655
October	1st to 10th	Night	29% 12% 24% 19% 14% 2	745
	11th to 20th	Night	18% 8% 25% 29% 18% 2	910
	21st to end	Night	18% 12% 23% 27% 18% 2	1001
November	1st to 10th	Night	18% 8% 31% 28% 14% 2	930
	11th to 20th	Night	10% 11% 27% 32% 17% 2	950
	21st to end	Night	15% 15% 28% 27% 12% 3	950
December	1st to 10th	Night	19% 13% 30% 24% 12% 2	1018
	11th to 20th	Night	11% 12% 34% 30% 10% 3	1060
	21st to end	Night	13% 15% 32% 25% 12% 2	1166

Page generated at 2026-09-26 00:18:39. Version ac07

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