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 2024-11-02.

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% 5% 5% 4 6% 7% 24%	103198
	Night	11% 14% 4 10% 6% 5% 5% 4 6% 6% 28%	95895
Transparency	Day	58% 10% 15% 11% 5% 1	102890
	Night	53% 9% 13% 13% 9% 2	95852
Seeing	Day	21% 13% 26% 25% 13% 3	17950
	Night	18% 12% 28% 27% 14% 2	22325

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 11% 3 9% 7% 7% 7% 5% 7% 7% 34%	1269
	11th to 20th	Day	6% 14% 3 7% 4 4 4 4 5% 6% 42%	1631
	21st to end	Day	3 11% 7% 11% 8% 7% 5% 5% 6% 7% 30%	2090
February	1st to 10th	Day	5% 13% 4 8% 6% 5% 4 4 5% 7% 40%	1287
	11th to 20th	Day	6% 22% 6% 11% 6% 4 5% 5% 4 6% 24%	1479
	21st to end	Day	6% 12% 4 11% 6% 6% 5% 4 5% 6% 34%	1338
March	1st to 10th	Day	4 14% 7% 12% 7% 5% 5% 3 5% 6% 31%	3096
	11th to 20th	Day	2 7% 3 10% 7% 7% 7% 6% 9% 9% 33%	3254
	21st to end	Day	10% 21% 7% 10% 5% 4 5% 3 5% 6% 22%	4165
April	1st to 10th	Day	4 17% 6% 11% 7% 6% 6% 6% 6% 6% 25%	2325
	11th to 20th	Day	6% 12% 3 8% 6% 5% 6% 5% 6% 8% 35%	2626
	21st to end	Day	5% 14% 5% 10% 7% 5% 6% 5% 7% 7% 30%	2712
May	1st to 10th	Day	13% 21% 5% 12% 7% 6% 5% 4 5% 5% 16%	4996
	11th to 20th	Day	8% 14% 5% 11% 6% 6% 6% 5% 7% 7% 26%	5040
	21st to end	Day	20% 14% 4 9% 5% 5% 4 4 5% 6% 22%	6007
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	22% 14% 4 8% 5% 5% 5% 4 7% 6% 22%	1867
	11th to 20th	Day	11% 12% 6% 10% 6% 5% 5% 4 5% 8% 28%	1710
	21st to end	Day	10% 13% 4 8% 5% 4 4 4 6% 9% 33%	1610
November	1st to 10th	Day	7% 14% 5% 9% 6% 6% 6% 5% 6% 8% 29%	1309
	11th to 20th	Day	8% 12% 4 8% 4 5% 5% 4 6% 6% 39%	1140
	21st to end	Day	6% 13% 6% 13% 6% 6% 4 5% 5% 7% 29%	950
December	1st to 10th	Day	12% 12% 4 10% 8% 7% 5% 5% 6% 8% 24%	832
	11th to 20th	Day	4 20% 9% 12% 4 5% 5% 4 6% 9% 23%	967
	21st to end	Day	3 9% 4 12% 6% 6% 5% 5% 7% 8% 36%	1397
January	1st to 10th	Night	5% 11% 3 9% 7% 6% 6% 5% 8% 8% 32%	5686
	11th to 20th	Night	8% 12% 4 9% 6% 4 3 4 4 5% 41%	5277
	21st to end	Night	4 12% 5% 11% 6% 5% 6% 4 6% 7% 36%	5577
February	1st to 10th	Night	5% 13% 5% 8% 5% 4 3 3 5% 7% 42%	2891
	11th to 20th	Night	9% 19% 6% 10% 6% 6% 4 4 5% 6% 23%	2588
	21st to end	Night	5% 11% 5% 13% 7% 6% 5% 4 6% 7% 30%	2113
March	1st to 10th	Night	4 15% 6% 13% 7% 5% 4 3 6% 6% 33%	3757
	11th to 20th	Night	3 11% 4 9% 6% 5% 6% 5% 7% 9% 35%	3701
	21st to end	Night	8% 21% 6% 9% 5% 4 4 3 5% 7% 29%	3466
April	1st to 10th	Night	6% 18% 6% 11% 6% 6% 6% 5% 6% 6% 24%	1851
	11th to 20th	Night	6% 14% 3 7% 7% 6% 5% 5% 6% 6% 35%	1503
	21st to end	Night	4 13% 5% 9% 6% 5% 5% 5% 6% 6% 36%	1468
May	1st to 10th	Night	15% 20% 4 12% 7% 5% 5% 5% 6% 5% 18%	1974
	11th to 20th	Night	11% 20% 5% 10% 5% 5% 6% 3 5% 7% 23%	1864
	21st to end	Night	25% 12% 3 8% 5% 4 4 3 5% 8% 23%	1572
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	22% 15% 4 8% 7% 5% 5% 3 4 5% 21%	2313
	11th to 20th	Night	10% 13% 4 10% 7% 6% 5% 4 6% 6% 29%	2470
	21st to end	Night	10% 16% 4 9% 5% 6% 5% 4 5% 7% 28%	2984
November	1st to 10th	Night	8% 14% 4 9% 6% 6% 6% 5% 5% 6% 31%	2803
	11th to 20th	Night	6% 12% 3 8% 6% 5% 5% 5% 6% 7% 38%	3040
	21st to end	Night	7% 13% 4 11% 8% 6% 5% 4 7% 6% 29%	3230
December	1st to 10th	Night	10% 16% 5% 11% 6% 5% 5% 4 6% 6% 25%	3345
	11th to 20th	Night	4 17% 8% 14% 6% 5% 6% 4 6% 6% 24%	4240
	21st to end	Night	4 12% 5% 11% 6% 5% 6% 4 6% 7% 34%	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	42% 9% 18% 16% 12% 3	1269
	11th to 20th	Day	41% 7% 10% 19% 20% 3	1647
	21st to end	Day	46% 12% 8% 10% 17% 7%	2090
February	1st to 10th	Day	44% 8% 12% 15% 14% 6%	1287
	11th to 20th	Day	57% 10% 13% 10% 8% 2	1486
	21st to end	Day	50% 7% 12% 16% 12% 3	1338
March	1st to 10th	Day	49% 8% 11% 12% 15% 6%	3096
	11th to 20th	Day	39% 12% 16% 17% 14% 2	3254
	21st to end	Day	59% 10% 13% 9% 7% 2	4165
April	1st to 10th	Day	58% 9% 14% 14% 5% 1	2325
	11th to 20th	Day	45% 11% 16% 19% 8%	2626
	21st to end	Day	52% 9% 14% 16% 8% 1	2712
May	1st to 10th	Day	69% 8% 11% 10% 2	4996
	11th to 20th	Day	51% 11% 15% 19% 3	5043
	21st to end	Day	62% 8% 15% 13% 2	6008
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	63% 9% 14% 10% 3 1	1867
	11th to 20th	Day	54% 12% 15% 14% 4 1	1710
	21st to end	Day	49% 10% 14% 16% 8% 2	1610
November	1st to 10th	Day	53% 9% 15% 14% 7% 3	1309
	11th to 20th	Day	45% 8% 13% 20% 12% 1	1140
	21st to end	Day	54% 9% 11% 11% 13% 2	950
December	1st to 10th	Day	57% 13% 10% 10% 9% 1	832
	11th to 20th	Day	57% 9% 12% 15% 7%	970
	21st to end	Day	40% 10% 14% 14% 13% 10%	1397
January	1st to 10th	Night	45% 10% 14% 17% 10% 4	5686
	11th to 20th	Night	43% 7% 11% 17% 18% 4	5324
	21st to end	Night	40% 11% 10% 11% 20% 8%	5577
February	1st to 10th	Night	42% 8% 9% 17% 16% 7%	2891
	11th to 20th	Night	59% 8% 11% 12% 8% 2	2592
	21st to end	Night	51% 9% 10% 14% 12% 3	2113
March	1st to 10th	Night	50% 7% 10% 14% 12% 7%	3757
	11th to 20th	Night	38% 10% 18% 15% 17% 2	3703
	21st to end	Night	52% 9% 17% 12% 8% 2	3466
April	1st to 10th	Night	58% 8% 14% 14% 6%	1851
	11th to 20th	Night	44% 11% 17% 19% 8%	1503
	21st to end	Night	46% 9% 17% 19% 9%	1468
May	1st to 10th	Night	63% 11% 13% 12% 2	1974
	11th to 20th	Night	58% 9% 16% 14% 3	1865
	21st to end	Night	57% 9% 20% 13% 1	1572
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	65% 8% 13% 10% 4	2313
	11th to 20th	Night	54% 9% 16% 13% 7% 1	2470
	21st to end	Night	55% 9% 12% 14% 8% 1	2984
November	1st to 10th	Night	54% 9% 12% 15% 9% 2	2803
	11th to 20th	Night	44% 11% 11% 22% 12%	3040
	21st to end	Night	54% 9% 11% 13% 11% 3	3230
December	1st to 10th	Night	58% 9% 12% 11% 10% 1	3345
	11th to 20th	Night	56% 11% 12% 13% 8%	4236
	21st to end	Night	44% 10% 12% 12% 14% 8%	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	9% 17% 24% 26% 18% 7%	90
	11th to 20th	Day	16% 12% 33% 24% 12% 3	239
	21st to end	Day	12% 15% 27% 27% 16% 4	308
February	1st to 10th	Day	11% 14% 27% 27% 13% 8%	286
	11th to 20th	Day	19% 18% 27% 22% 12% 2	365
	21st to end	Day	13% 18% 30% 23% 8% 7%	307
March	1st to 10th	Day	11% 13% 34% 25% 14% 4	370
	11th to 20th	Day	8% 14% 33% 24% 16% 5%	409
	21st to end	Day	12% 17% 28% 23% 19% 2	616
April	1st to 10th	Day	11% 19% 34% 23% 11% 1	581
	11th to 20th	Day	14% 12% 25% 31% 15% 3	640
	21st to end	Day	15% 11% 29% 31% 13% 1	650
May	1st to 10th	Day	20% 19% 28% 25% 8%	653
	11th to 20th	Day	18% 15% 29% 23% 13% 1	675
	21st to end	Day	23% 15% 28% 25% 8% 1	820
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	18% 11% 26% 22% 17% 7%	369
	11th to 20th	Day	16% 6% 25% 23% 22% 7%	275
	21st to end	Day	11% 19% 26% 21% 10% 13%	90
December	1st to 10th	Day	18% 17% 16% 28% 20% 2	90
	11th to 20th	Day	17% 12% 28% 26% 13% 4	90
	21st to end	Day	7% 27% 28% 21% 11% 5%	99
January	1st to 10th	Night	8% 16% 30% 29% 14% 3	940
	11th to 20th	Night	13% 19% 33% 22% 12% 1	904
	21st to end	Night	14% 12% 33% 27% 13% 1	935
February	1st to 10th	Night	11% 12% 35% 29% 10% 2	850
	11th to 20th	Night	20% 17% 33% 21% 8%	834
	21st to end	Night	11% 14% 36% 24% 10% 4	618
March	1st to 10th	Night	11% 13% 32% 34% 9% 2	660
	11th to 20th	Night	8% 12% 30% 30% 18% 2	657
	21st to end	Night	11% 8% 32% 28% 19% 2	627
April	1st to 10th	Night	12% 12% 27% 31% 18% 1	570
	11th to 20th	Night	12% 9% 25% 30% 23% 1	563
	21st to end	Night	10% 7% 29% 38% 14% 1	570
May	1st to 10th	Night	16% 11% 28% 29% 16%	428
	11th to 20th	Night	15% 9% 26% 33% 15% 1	369
	21st to end	Night	19% 10% 23% 33% 15%	206
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	839
	11th to 20th	Night	10% 12% 28% 33% 15% 2	850
	21st to end	Night	16% 16% 28% 25% 12% 3	850
December	1st to 10th	Night	19% 14% 30% 24% 12% 2	905
	11th to 20th	Night	11% 12% 33% 30% 11% 3	940
	21st to end	Night	15% 17% 31% 23% 12% 3	1034

Page generated at 2024-10-30 09:19:25. Version ac07

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