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 2025-05-26.

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	14% 13% 4 10% 6% 5% 5% 4 6% 7% 25%	116235
	Night	10% 14% 5% 10% 6% 5% 5% 4 6% 7% 28%	121769
Transparency	Day	57% 10% 15% 12% 5% 1	115927
	Night	53% 9% 13% 14% 9% 2	121726
Seeing	Day	21% 13% 26% 25% 13% 3	18537
	Night	18% 12% 28% 27% 14% 2	23205

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	3 13% 4 10% 7% 7% 6% 4 6% 7% 33%	1819
	11th to 20th	Day	5% 16% 4 10% 5% 5% 5% 4 6% 7% 34%	2345
	21st to end	Day	9% 14% 6% 10% 8% 7% 6% 4 5% 5% 27%	2992
February	1st to 10th	Day	4 13% 4 8% 6% 5% 4 4 5% 7% 42%	1355
	11th to 20th	Day	6% 21% 7% 11% 6% 4 5% 5% 5% 7% 24%	1559
	21st to end	Day	6% 12% 4 11% 6% 6% 6% 4 6% 7% 33%	1407
March	1st to 10th	Day	3 16% 7% 12% 7% 6% 6% 4 5% 6% 29%	4442
	11th to 20th	Day	2 9% 5% 13% 7% 7% 7% 5% 8% 8% 28%	4642
	21st to end	Day	7% 15% 5% 10% 6% 5% 6% 5% 7% 8% 26%	5969
April	1st to 10th	Day	4 16% 6% 11% 7% 6% 6% 6% 7% 6% 25%	2448
	11th to 20th	Day	6% 12% 3 8% 6% 5% 6% 5% 6% 8% 34%	2766
	21st to end	Day	5% 15% 5% 10% 7% 6% 6% 5% 7% 7% 28%	2855
May	1st to 10th	Day	13% 21% 5% 12% 7% 6% 5% 4 5% 5% 17%	5154
	11th to 20th	Day	8% 14% 5% 11% 6% 6% 6% 5% 7% 7% 26%	5200
	21st to end	Day	20% 14% 4 9% 5% 5% 4 4 5% 6% 22%	6098
June	1st to 10th	Day	16% 11% 4 9% 6% 6% 6% 5% 7% 8% 23%	3420
	11th to 20th	Day	18% 11% 3 9% 6% 5% 6% 4 7% 7% 23%	3420
	21st to end	Day	18% 10% 3 9% 6% 7% 7% 4 7% 7% 22%	3420
July	1st to 10th	Day	22% 11% 4 9% 6% 5% 5% 4 6% 8% 19%	5700
	11th to 20th	Day	24% 12% 4 9% 7% 5% 5% 5% 7% 6% 17%	5621
	21st to end	Day	23% 10% 3 7% 5% 5% 5% 4 7% 7% 23%	5499
August	1st to 10th	Day	30% 11% 4 9% 5% 5% 5% 3 4 5% 18%	5046
	11th to 20th	Day	25% 10% 4 9% 5% 5% 5% 4 6% 8% 20%	4426
	21st to end	Day	22% 11% 4 9% 6% 5% 5% 4 6% 7% 20%	4884
September	1st to 10th	Day	25% 11% 3 10% 6% 6% 6% 4 6% 6% 17%	2357
	11th to 20th	Day	27% 14% 4 10% 6% 4 4 4 4 4 20%	2270
	21st to end	Day	19% 12% 4 8% 6% 5% 5% 4 4 6% 25%	2038
October	1st to 10th	Day	14% 13% 4 9% 6% 6% 7% 5% 7% 7% 23%	3103
	11th to 20th	Day	7% 8% 4 8% 5% 4 4 4 6% 9% 40%	2834
	21st to end	Day	11% 14% 4 8% 4 4 5% 3 5% 8% 34%	2636
November	1st to 10th	Day	7% 13% 5% 9% 6% 6% 6% 4 6% 8% 28%	1371
	11th to 20th	Day	7% 12% 4 8% 4 5% 5% 4 6% 6% 38%	1199
	21st to end	Day	5% 13% 7% 13% 6% 6% 4 5% 5% 7% 30%	1000
December	1st to 10th	Day	13% 13% 4 9% 7% 6% 5% 5% 5% 8% 26%	1421
	11th to 20th	Day	3 22% 7% 10% 4 5% 5% 4 6% 8% 24%	1517
	21st to end	Day	2 9% 4 12% 7% 5% 5% 4 6% 8% 37%	2002
January	1st to 10th	Night	4 14% 4 9% 6% 6% 6% 5% 7% 8% 33%	8146
	11th to 20th	Night	8% 16% 5% 11% 6% 5% 4 4 5% 5% 31%	7577
	21st to end	Night	9% 12% 5% 11% 6% 6% 6% 4 6% 6% 30%	7986
February	1st to 10th	Night	5% 12% 5% 8% 5% 4 3 3 5% 7% 44%	3042
	11th to 20th	Night	9% 19% 6% 11% 6% 5% 5% 4 5% 6% 24%	2728
	21st to end	Night	5% 11% 5% 13% 7% 6% 5% 5% 6% 7% 30%	2220
March	1st to 10th	Night	3 16% 6% 13% 7% 5% 4 3 6% 6% 32%	5411
	11th to 20th	Night	2 14% 6% 11% 6% 5% 6% 5% 6% 8% 31%	5313
	21st to end	Night	6% 16% 5% 9% 5% 5% 5% 4 6% 9% 30%	4962
April	1st to 10th	Night	5% 17% 6% 11% 6% 6% 6% 5% 6% 7% 25%	1948
	11th to 20th	Night	7% 14% 3 7% 7% 6% 5% 5% 6% 6% 34%	1583
	21st to end	Night	4 13% 5% 9% 6% 5% 5% 5% 6% 6% 34%	1545
May	1st to 10th	Night	14% 19% 4 11% 7% 5% 5% 5% 6% 5% 18%	2036
	11th to 20th	Night	12% 20% 5% 10% 5% 5% 6% 3 4 7% 23%	1924
	21st to end	Night	25% 12% 3 9% 5% 4 4 4 5% 8% 22%	1597
June	1st to 10th	Night	16% 13% 5% 9% 7% 6% 6% 3 5% 9% 23%	760
	11th to 20th	Night	20% 11% 3 8% 7% 6% 5% 4 7% 7% 22%	760
	21st to end	Night	21% 9% 3 9% 6% 7% 5% 6% 6% 7% 22%	760
July	1st to 10th	Night	30% 11% 5% 9% 4 5% 4 3 4 7% 17%	1270
	11th to 20th	Night	31% 10% 4 10% 5% 4 3 4 5% 6% 19%	1351
	21st to end	Night	30% 10% 4 7% 4 4 4 4 5% 7% 20%	2065
August	1st to 10th	Night	32% 11% 3 8% 5% 4 4 2 4 5% 21%	1894
	11th to 20th	Night	28% 12% 4 10% 5% 4 5% 4 7% 6% 16%	2399
	21st to end	Night	28% 12% 4 9% 7% 6% 5% 4 4 4 17%	2783
September	1st to 10th	Night	29% 13% 3 8% 6% 6% 6% 4 5% 5% 15%	1820
	11th to 20th	Night	27% 15% 3 8% 5% 5% 4 3 6% 5% 19%	1909
	21st to end	Night	21% 13% 3 9% 6% 5% 5% 4 5% 6% 22%	2141
October	1st to 10th	Night	15% 14% 4 9% 7% 7% 7% 5% 6% 7% 20%	3859
	11th to 20th	Night	6% 8% 3 8% 6% 6% 5% 4 7% 7% 39%	4094
	21st to end	Night	11% 16% 3 9% 6% 6% 5% 3 5% 7% 28%	4919
November	1st to 10th	Night	8% 15% 4 10% 6% 6% 6% 5% 5% 6% 30%	2927
	11th to 20th	Night	6% 12% 3 8% 5% 5% 5% 4 6% 7% 38%	3201
	21st to end	Night	7% 13% 4 11% 8% 6% 5% 4 7% 6% 29%	3400
December	1st to 10th	Night	10% 16% 6% 11% 5% 5% 5% 4 6% 7% 24%	5763
	11th to 20th	Night	3 17% 7% 13% 6% 6% 6% 4 7% 7% 24%	6700
	21st to end	Night	3 10% 5% 11% 6% 6% 6% 5% 7% 8% 35%	8976

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	44% 9% 15% 14% 14% 4	1819
	11th to 20th	Day	46% 9% 11% 17% 14% 2	2361
	21st to end	Day	54% 10% 6% 8% 17% 5%	2992
February	1st to 10th	Day	42% 8% 12% 17% 15% 6%	1355
	11th to 20th	Day	57% 10% 12% 10% 9% 2	1566
	21st to end	Day	50% 7% 11% 17% 12% 2	1407
March	1st to 10th	Day	51% 8% 8% 13% 15% 4	4442
	11th to 20th	Day	46% 11% 11% 15% 15% 2	4642
	21st to end	Day	51% 10% 12% 16% 9% 1	5969
April	1st to 10th	Day	58% 9% 14% 14% 5% 1	2448
	11th to 20th	Day	45% 12% 16% 18% 8%	2766
	21st to end	Day	53% 8% 14% 15% 8% 1	2855
May	1st to 10th	Day	68% 8% 11% 10% 3	5154
	11th to 20th	Day	52% 11% 15% 19% 3	5203
	21st to end	Day	62% 9% 15% 13% 2	6099
June	1st to 10th	Day	59% 12% 17% 11% 1	3420
	11th to 20th	Day	61% 10% 16% 10% 2	3420
	21st to end	Day	61% 12% 20% 7%	3420
July	1st to 10th	Day	62% 12% 19% 6% 1	5611
	11th to 20th	Day	66% 11% 19% 5%	5522
	21st to end	Day	60% 11% 21% 8%	5326
August	1st to 10th	Day	69% 9% 14% 7% 1	5027
	11th to 20th	Day	63% 10% 15% 11% 1	4469
	21st to end	Day	62% 10% 20% 7% 1	4883
September	1st to 10th	Day	69% 11% 11% 7% 2	2357
	11th to 20th	Day	69% 8% 12% 10% 1	2270
	21st to end	Day	61% 9% 14% 13% 3	2038
October	1st to 10th	Day	58% 9% 15% 15% 3	3103
	11th to 20th	Day	41% 9% 16% 22% 12% 1	2834
	21st to end	Day	49% 8% 12% 24% 5% 1	2636
November	1st to 10th	Day	53% 9% 15% 14% 7% 3	1371
	11th to 20th	Day	45% 8% 13% 20% 12% 1	1199
	21st to end	Day	54% 9% 11% 11% 13% 2	1000
December	1st to 10th	Day	55% 11% 11% 17% 5% 1	1421
	11th to 20th	Day	57% 9% 13% 16% 5%	1520
	21st to end	Day	41% 8% 15% 19% 10% 7%	2002
January	1st to 10th	Night	45% 9% 12% 15% 14% 5%	8146
	11th to 20th	Night	51% 9% 11% 14% 13% 3	7624
	21st to end	Night	47% 10% 8% 9% 20% 6%	7986
February	1st to 10th	Night	40% 8% 9% 20% 16% 7%	3042
	11th to 20th	Night	59% 8% 11% 12% 8% 2	2732
	21st to end	Night	52% 9% 10% 15% 12% 2	2220
March	1st to 10th	Night	50% 8% 8% 16% 14% 5%	5411
	11th to 20th	Night	45% 9% 13% 15% 17% 2	5315
	21st to end	Night	48% 8% 14% 17% 11% 2	4962
April	1st to 10th	Night	57% 8% 14% 15% 6%	1948
	11th to 20th	Night	45% 11% 17% 19% 8%	1583
	21st to end	Night	48% 9% 17% 18% 8%	1545
May	1st to 10th	Night	62% 10% 13% 12% 2	2036
	11th to 20th	Night	59% 9% 16% 14% 3	1925
	21st to end	Night	57% 10% 20% 13% 1	1597
June	1st to 10th	Night	58% 13% 18% 9% 1	760
	11th to 20th	Night	61% 11% 17% 9% 2	760
	21st to end	Night	59% 15% 19% 6%	760
July	1st to 10th	Night	66% 11% 17% 5% 1	1250
	11th to 20th	Night	65% 10% 20% 4	1327
	21st to end	Night	64% 11% 20% 6%	2000
August	1st to 10th	Night	67% 9% 17% 5% 1	1888
	11th to 20th	Night	68% 10% 14% 7% 1	2421
	21st to end	Night	70% 9% 13% 6% 2	2783
September	1st to 10th	Night	70% 11% 11% 6% 2	1820
	11th to 20th	Night	67% 8% 15% 9% 1	1909
	21st to end	Night	63% 8% 15% 12% 3	2141
October	1st to 10th	Night	63% 8% 15% 11% 3	3859
	11th to 20th	Night	40% 9% 18% 20% 13%	4094
	21st to end	Night	56% 7% 13% 17% 5% 1	4919
November	1st to 10th	Night	55% 9% 12% 15% 8% 2	2927
	11th to 20th	Night	44% 11% 12% 22% 11% 1	3201
	21st to end	Night	53% 9% 11% 13% 11% 3	3400
December	1st to 10th	Night	56% 11% 11% 17% 6% 1	5763
	11th to 20th	Night	54% 10% 16% 14% 6%	6696
	21st to end	Night	42% 10% 16% 16% 10% 5%	8976

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	11% 16% 23% 26% 17% 7%	100
	11th to 20th	Day	16% 12% 33% 25% 11% 3	257
	21st to end	Day	14% 14% 27% 27% 15% 3	330
February	1st to 10th	Day	10% 13% 25% 27% 16% 9%	307
	11th to 20th	Day	18% 16% 27% 23% 13% 3	395
	21st to end	Day	12% 17% 30% 25% 9% 8%	331
March	1st to 10th	Day	11% 13% 36% 24% 14% 3	400
	11th to 20th	Day	8% 14% 32% 25% 16% 5%	441
	21st to end	Day	11% 16% 28% 23% 19% 3	660
April	1st to 10th	Day	12% 20% 35% 23% 10% 1	624
	11th to 20th	Day	15% 12% 26% 31% 14% 3	690
	21st to end	Day	16% 11% 28% 31% 12% 1	700
May	1st to 10th	Day	19% 19% 28% 25% 8% 1	703
	11th to 20th	Day	19% 14% 28% 23% 13% 2	725
	21st to end	Day	23% 15% 27% 26% 9% 1	847
June	1st to 10th	Day	20% 13% 24% 26% 14% 3	870
	11th to 20th	Day	20% 10% 24% 30% 13% 3	870
	21st to end	Day	19% 10% 24% 30% 14% 3	870
July	1st to 10th	Day	21% 9% 27% 28% 13% 1	856
	11th to 20th	Day	25% 8% 23% 29% 13% 1	852
	21st to end	Day	26% 8% 23% 25% 15% 2	739
August	1st to 10th	Day	30% 13% 23% 23% 10% 2	676
	11th to 20th	Day	29% 15% 25% 19% 11% 2	665
	21st to end	Day	33% 11% 20% 23% 12% 1	748
September	1st to 10th	Day	29% 16% 22% 21% 10% 2	613
	11th to 20th	Day	35% 15% 20% 18% 11% 2	570
	21st to end	Day	29% 12% 18% 22% 14% 4	390
October	1st to 10th	Day	31% 14% 21% 18% 13% 3	390
	11th to 20th	Day	17% 11% 25% 27% 16% 4	390
	21st to end	Day	22% 11% 23% 24% 16% 3	429
November	1st to 10th	Day	17% 10% 26% 23% 17% 7%	395
	11th to 20th	Day	15% 6% 25% 24% 23% 7%	294
	21st to end	Day	11% 17% 23% 23% 13% 13%	100
December	1st to 10th	Day	20% 15% 15% 28% 20% 2	100
	11th to 20th	Day	17% 11% 29% 27% 12% 4	100
	21st to end	Day	7% 25% 28% 22% 13% 5%	110
January	1st to 10th	Night	8% 16% 29% 29% 15% 2	1000
	11th to 20th	Night	15% 19% 33% 21% 11% 1	960
	21st to end	Night	15% 12% 33% 27% 13% 1	990
February	1st to 10th	Night	11% 12% 34% 29% 12% 2	900
	11th to 20th	Night	20% 16% 33% 22% 8%	884
	21st to end	Night	11% 14% 36% 24% 11% 4	653
March	1st to 10th	Night	11% 13% 31% 34% 9% 1	700
	11th to 20th	Night	8% 12% 29% 30% 18% 2	697
	21st to end	Night	10% 8% 32% 28% 19% 2	660
April	1st to 10th	Night	12% 12% 29% 30% 17% 1	600
	11th to 20th	Night	14% 9% 25% 30% 22% 1	593
	21st to end	Night	11% 8% 28% 39% 14% 1	600
May	1st to 10th	Night	16% 11% 28% 29% 16%	450
	11th to 20th	Night	16% 9% 26% 32% 16% 2	389
	21st to end	Night	19% 9% 23% 33% 15%	211
June	1st to 10th	Night	18% 9% 22% 33% 18%	190
	11th to 20th	Night	23% 5% 21% 34% 16% 1	190
	21st to end	Night	21% 8% 17% 32% 21% 2	190
July	1st to 10th	Night	26% 5% 17% 21% 30% 1	185
	11th to 20th	Night	32% 4 18% 22% 23% 1	226
	21st to end	Night	31% 7% 16% 23% 20% 3	416
August	1st to 10th	Night	33% 7% 18% 26% 14% 2	378
	11th to 20th	Night	33% 10% 25% 21% 10% 1	528
	21st to end	Night	33% 7% 19% 22% 17% 2	627
September	1st to 10th	Night	35% 10% 20% 22% 12% 1	570
	11th to 20th	Night	36% 8% 18% 22% 15% 1	570
	21st to end	Night	29% 9% 19% 20% 20% 3	597
October	1st to 10th	Night	29% 12% 22% 19% 15% 2	703
	11th to 20th	Night	17% 8% 25% 29% 18% 3	860
	21st to end	Night	19% 12% 23% 28% 17% 1	946
November	1st to 10th	Night	19% 8% 32% 27% 13% 2	880
	11th to 20th	Night	11% 12% 27% 33% 16% 2	900
	21st to end	Night	15% 15% 28% 27% 12% 3	900
December	1st to 10th	Night	19% 14% 30% 24% 12% 2	962
	11th to 20th	Night	11% 12% 33% 30% 11% 3	1000
	21st to end	Night	14% 16% 32% 24% 12% 3	1100

Page generated at 2025-05-23 05:20:58. Version ac07

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