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 2024-03-08.

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% 11% 5% 8% 7% 4 6% 6% 6% 7% 27%	76754
	Night	10% 12% 5% 8% 7% 4 5% 5% 6% 7% 30%	82803
Transparency	Day	56% 10% 15% 12% 6% 1	76403
	Night	52% 10% 13% 13% 10% 3	82738
Seeing	Day	21% 13% 26% 25% 13% 3	16843
	Night	18% 12% 28% 27% 14% 2	21695

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 10% 4 8% 8% 5% 7% 6% 6% 7% 35%	1269
	11th to 20th	Day	6% 13% 4 6% 5% 3 4 5% 5% 7% 42%	1631
	21st to end	Day	4 10% 8% 10% 8% 6% 6% 6% 6% 7% 31%	2090
February	1st to 10th	Day	5% 13% 5% 8% 6% 4 4 4 4 7% 40%	1287
	11th to 20th	Day	6% 21% 7% 10% 7% 3 6% 6% 4 6% 25%	1479
	21st to end	Day	6% 12% 5% 10% 7% 4 6% 5% 5% 6% 34%	1338
March	1st to 10th	Day	6% 12% 6% 9% 6% 3 5% 4 5% 5% 38%	1855
	11th to 20th	Day	2 8% 3 6% 7% 5% 6% 5% 8% 8% 41%	1838
	21st to end	Day	4 12% 5% 9% 7% 4 6% 5% 6% 8% 34%	2376
April	1st to 10th	Day	4 15% 7% 10% 8% 4 6% 7% 7% 6% 26%	2201
	11th to 20th	Day	5% 11% 4 7% 6% 4 6% 7% 7% 8% 35%	2486
	21st to end	Day	6% 14% 5% 9% 8% 4 6% 6% 6% 7% 30%	2569
May	1st to 10th	Day	11% 14% 6% 11% 8% 4 6% 6% 7% 7% 22%	2834
	11th to 20th	Day	11% 11% 4 7% 6% 4 6% 6% 6% 8% 31%	2837
	21st to end	Day	15% 9% 4 7% 6% 3 5% 6% 5% 7% 31%	3385
June	1st to 10th	Day	15% 10% 4 8% 8% 5% 7% 7% 6% 8% 24%	3240
	11th to 20th	Day	18% 11% 3 8% 7% 4 6% 6% 7% 8% 22%	3240
	21st to end	Day	20% 10% 4 8% 7% 5% 7% 6% 7% 7% 20%	3240
July	1st to 10th	Day	17% 9% 4 8% 8% 4 5% 6% 6% 9% 23%	3240
	11th to 20th	Day	22% 9% 4 9% 8% 3 6% 6% 6% 7% 19%	3200
	21st to end	Day	22% 10% 4 8% 6% 5% 6% 5% 5% 7% 23%	3137
August	1st to 10th	Day	27% 9% 5% 8% 7% 4 6% 4 5% 6% 19%	2865
	11th to 20th	Day	27% 11% 4 7% 7% 4 6% 5% 6% 6% 17%	2527
	21st to end	Day	27% 10% 4 8% 7% 4 5% 5% 5% 6% 19%	2772
September	1st to 10th	Day	25% 11% 4 8% 8% 4 6% 5% 6% 6% 17%	2234
	11th to 20th	Day	26% 13% 4 8% 7% 3 4 5% 4 4 21%	2151
	21st to end	Day	21% 11% 4 7% 7% 4 5% 5% 4 6% 26%	1931
October	1st to 10th	Day	23% 14% 4 7% 6% 3 5% 5% 6% 6% 21%	1769
	11th to 20th	Day	12% 12% 6% 9% 7% 3 5% 6% 5% 8% 27%	1620
	21st to end	Day	10% 12% 5% 7% 6% 3 4 4 6% 9% 34%	1526
November	1st to 10th	Day	7% 13% 6% 7% 7% 5% 5% 6% 6% 8% 29%	1301
	11th to 20th	Day	8% 11% 4 6% 6% 4 5% 5% 5% 6% 39%	1140
	21st to end	Day	6% 12% 7% 12% 8% 5% 3 6% 5% 7% 30%	950
December	1st to 10th	Day	12% 12% 4 9% 9% 6% 4 6% 5% 8% 25%	832
	11th to 20th	Day	4 19% 9% 11% 5% 4 6% 5% 6% 9% 23%	967
	21st to end	Day	3 8% 5% 10% 8% 4 5% 6% 7% 8% 36%	1397
January	1st to 10th	Night	5% 10% 4 8% 8% 5% 7% 7% 8% 8% 32%	5686
	11th to 20th	Night	8% 11% 5% 8% 7% 4 4 4 4 5% 41%	5277
	21st to end	Night	4 11% 6% 9% 7% 4 6% 5% 6% 7% 36%	5577
February	1st to 10th	Night	5% 12% 6% 7% 5% 3 4 4 5% 7% 42%	2891
	11th to 20th	Night	9% 18% 6% 9% 8% 4 5% 5% 6% 6% 24%	2588
	21st to end	Night	5% 11% 6% 11% 9% 5% 5% 5% 6% 8% 30%	2113
March	1st to 10th	Night	6% 11% 5% 9% 7% 4 4 4 6% 6% 37%	2264
	11th to 20th	Night	2 10% 4 8% 8% 4 5% 6% 6% 8% 39%	2117
	21st to end	Night	5% 13% 5% 8% 6% 4 4 4 5% 7% 38%	1980
April	1st to 10th	Night	6% 16% 7% 10% 7% 5% 6% 6% 5% 6% 25%	1755
	11th to 20th	Night	7% 13% 3 5% 7% 4 6% 6% 6% 7% 36%	1423
	21st to end	Night	4 12% 6% 8% 8% 4 6% 6% 6% 6% 35%	1391
May	1st to 10th	Night	10% 12% 5% 11% 8% 5% 5% 8% 7% 7% 22%	1126
	11th to 20th	Night	12% 12% 5% 7% 5% 4 7% 5% 5% 8% 30%	1058
	21st to end	Night	16% 9% 2 6% 5% 2 5% 5% 7% 9% 32%	889
June	1st to 10th	Night	17% 11% 5% 8% 8% 4 6% 5% 4 9% 23%	720
	11th to 20th	Night	21% 11% 4 7% 8% 4 6% 5% 6% 7% 22%	720
	21st to end	Night	22% 9% 3 8% 6% 5% 6% 7% 6% 7% 21%	720
July	1st to 10th	Night	23% 11% 4 7% 4 4 6% 5% 5% 9% 22%	720
	11th to 20th	Night	29% 8% 5% 9% 6% 3 4 5% 5% 7% 19%	759
	21st to end	Night	27% 9% 5% 8% 5% 4 5% 6% 5% 7% 19%	1181
August	1st to 10th	Night	28% 9% 3 7% 7% 5% 6% 4 5% 6% 20%	1074
	11th to 20th	Night	29% 11% 4 9% 8% 4 5% 5% 6% 4 16%	1372
	21st to end	Night	28% 10% 4 8% 7% 5% 5% 5% 5% 5% 19%	1584
September	1st to 10th	Night	29% 12% 3 7% 7% 5% 7% 5% 5% 5% 16%	1723
	11th to 20th	Night	26% 14% 3 7% 6% 3 4 4 5% 6% 20%	1808
	21st to end	Night	22% 12% 3 8% 7% 4 5% 5% 5% 7% 22%	2028
October	1st to 10th	Night	23% 15% 4 7% 7% 4 5% 4 4 5% 21%	2191
	11th to 20th	Night	11% 13% 4 8% 9% 4 6% 5% 6% 6% 28%	2340
	21st to end	Night	10% 15% 5% 9% 6% 4 6% 5% 5% 7% 29%	2826
November	1st to 10th	Night	8% 14% 4 8% 7% 5% 6% 5% 5% 6% 31%	2777
	11th to 20th	Night	6% 11% 4 7% 7% 4 5% 6% 6% 7% 38%	3040
	21st to end	Night	7% 12% 5% 9% 9% 4 6% 5% 6% 7% 29%	3230
December	1st to 10th	Night	10% 15% 6% 10% 7% 4 5% 6% 6% 7% 26%	3345
	11th to 20th	Night	4 16% 8% 13% 7% 4 6% 5% 6% 6% 24%	4240
	21st to end	Night	4 11% 5% 9% 8% 4 6% 6% 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	47% 8% 10% 15% 15% 6%	1855
	11th to 20th	Day	39% 10% 12% 19% 16% 4	1838
	21st to end	Day	49% 10% 14% 12% 12% 3	2376
April	1st to 10th	Day	58% 9% 13% 14% 5% 1	2201
	11th to 20th	Day	44% 12% 16% 19% 9%	2486
	21st to end	Day	53% 8% 14% 15% 8% 1	2569
May	1st to 10th	Day	61% 9% 15% 11% 3	2834
	11th to 20th	Day	51% 11% 14% 19% 5%	2840
	21st to end	Day	51% 10% 18% 18% 3	3386
June	1st to 10th	Day	59% 12% 17% 11% 2	3240
	11th to 20th	Day	62% 11% 15% 9% 3	3240
	21st to end	Day	63% 12% 19% 6%	3240
July	1st to 10th	Day	59% 11% 20% 10% 1	3151
	11th to 20th	Day	67% 12% 19% 3	3101
	21st to end	Day	61% 14% 19% 6%	2963
August	1st to 10th	Day	68% 11% 15% 5% 1	2846
	11th to 20th	Day	68% 11% 13% 6% 1	2527
	21st to end	Day	67% 11% 13% 7% 1	2772
September	1st to 10th	Day	69% 11% 10% 7% 2	2234
	11th to 20th	Day	68% 9% 12% 10% 1	2151
	21st to end	Day	61% 9% 14% 13% 4	1931
October	1st to 10th	Day	65% 10% 13% 8% 3 1	1769
	11th to 20th	Day	56% 12% 14% 13% 4 1	1620
	21st to end	Day	49% 11% 15% 15% 8% 2	1526
November	1st to 10th	Day	53% 9% 14% 14% 7% 3	1301
	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	47% 7% 10% 14% 15% 7%	2264
	11th to 20th	Night	40% 8% 12% 17% 19% 4	2119
	21st to end	Night	45% 9% 16% 13% 13% 4	1980
April	1st to 10th	Night	58% 8% 13% 14% 6%	1755
	11th to 20th	Night	44% 11% 17% 19% 8%	1423
	21st to end	Night	48% 9% 18% 17% 9%	1391
May	1st to 10th	Night	57% 11% 18% 12% 2	1126
	11th to 20th	Night	53% 8% 14% 19% 5%	1059
	21st to end	Night	49% 11% 21% 17% 2	889
June	1st to 10th	Night	58% 13% 18% 9% 2	720
	11th to 20th	Night	63% 10% 17% 8% 2	720
	21st to end	Night	62% 15% 18% 5%	720
July	1st to 10th	Night	59% 12% 19% 8% 1	700
	11th to 20th	Night	66% 11% 21% 2	735
	21st to end	Night	63% 17% 16% 4	1116
August	1st to 10th	Night	66% 12% 17% 3 1	1068
	11th to 20th	Night	70% 10% 13% 6% 1	1372
	21st to end	Night	68% 10% 13% 7% 2	1584
September	1st to 10th	Night	69% 11% 11% 6% 2	1723
	11th to 20th	Night	66% 8% 15% 9% 1	1808
	21st to end	Night	63% 8% 14% 12% 3	2028
October	1st to 10th	Night	66% 8% 12% 10% 4	2191
	11th to 20th	Night	56% 9% 16% 12% 6% 1	2340
	21st to end	Night	55% 9% 12% 14% 9% 1	2826
November	1st to 10th	Night	54% 9% 12% 15% 9% 2	2777
	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% 35% 25% 12% 3	362
	11th to 20th	Day	8% 13% 32% 26% 16% 5%	376
	21st to end	Day	10% 16% 29% 24% 20% 2	572
April	1st to 10th	Day	10% 18% 36% 23% 11% 1	538
	11th to 20th	Day	13% 11% 24% 33% 15% 3	590
	21st to end	Day	16% 11% 30% 30% 12% 1	600
May	1st to 10th	Day	19% 18% 30% 26% 8%	603
	11th to 20th	Day	18% 15% 30% 22% 13% 1	625
	21st to end	Day	23% 14% 28% 26% 8% 1	760
June	1st to 10th	Day	20% 12% 24% 26% 15% 3	810
	11th to 20th	Day	20% 11% 25% 29% 13% 3	810
	21st to end	Day	21% 11% 23% 30% 14% 2	810
July	1st to 10th	Day	20% 9% 26% 29% 14% 1	796
	11th to 20th	Day	25% 8% 23% 29% 13% 1	792
	21st to end	Day	26% 8% 23% 25% 16% 2	684
August	1st to 10th	Day	29% 13% 23% 23% 10% 2	626
	11th to 20th	Day	28% 15% 25% 19% 11% 2	615
	21st to end	Day	33% 11% 20% 23% 12% 1	693
September	1st to 10th	Day	28% 17% 22% 21% 10% 2	570
	11th to 20th	Day	33% 16% 20% 18% 11% 2	531
	21st to end	Day	30% 13% 19% 21% 13% 4	360
October	1st to 10th	Day	33% 14% 22% 18% 11% 2	360
	11th to 20th	Day	19% 11% 24% 26% 16% 4	360
	21st to end	Day	22% 12% 21% 24% 17% 3	396
November	1st to 10th	Day	18% 11% 25% 22% 17% 7%	365
	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% 1	649
	11th to 20th	Night	8% 11% 30% 30% 19% 2	618
	21st to end	Night	10% 8% 33% 28% 20% 2	594
April	1st to 10th	Night	13% 12% 26% 31% 18%	540
	11th to 20th	Night	12% 7% 25% 32% 23% 1	533
	21st to end	Night	10% 7% 30% 37% 15% 1	540
May	1st to 10th	Night	16% 9% 28% 30% 17%	406
	11th to 20th	Night	14% 9% 27% 33% 16% 1	350
	21st to end	Night	19% 9% 23% 33% 15% 1	195
June	1st to 10th	Night	18% 9% 22% 32% 19%	180
	11th to 20th	Night	24% 5% 21% 33% 16% 1	180
	21st to end	Night	22% 8% 17% 30% 21% 2	180
July	1st to 10th	Night	26% 6% 17% 20% 31% 1	175
	11th to 20th	Night	31% 5% 18% 21% 23% 1	213
	21st to end	Night	29% 8% 16% 23% 21% 3	394
August	1st to 10th	Night	33% 8% 18% 25% 14% 2	358
	11th to 20th	Night	34% 9% 24% 21% 11% 1	500
	21st to end	Night	33% 7% 19% 22% 17% 2	594
September	1st to 10th	Night	34% 11% 19% 22% 12% 1	540
	11th to 20th	Night	34% 8% 19% 23% 15% 1	540
	21st to end	Night	30% 9% 19% 20% 19% 2	564
October	1st to 10th	Night	31% 12% 23% 18% 14% 2	661
	11th to 20th	Night	18% 8% 25% 28% 19% 3	810
	21st to end	Night	19% 12% 24% 27% 17% 1	891
November	1st to 10th	Night	19% 8% 32% 27% 13% 2	830
	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 2024-03-05 03:23:58. Version ac07

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