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 2005-11-05 to 2017-09-16.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
35%
13082
8%
46470
5%
13049
39%
13049
13%
34253

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
33%
779
10%
3187
7%
776
38%
776
13%
2203
January16th to endNight
28%
802
13%
3084
7%
802
33%
802
14%
2149
February1st to 15thNight
31%
734
13%
2608
7%
730
37%
730
18%
1729
February16th to endNight
26%
605
12%
2158
6%
605
31%
605
13%
1538
March1st to 15thNight
36%
570
17%
2172
11%
570
47%
570
18%
1374
March16th to endNight
49%
585
14%
2005
14%
584
53%
584
20%
1313
April1st to 15thNight
40%
539
4%
1648
2%
539
42%
539
13%
1291
April16th to endNight
44%
540
1%
1407
0%
540
45%
540
21%
1037
May1st to 15thNight
44%
389
0%
1110
0%
389
44%
389
15%
857
May16th to endNight
52%
242
0%
936
0%
241
52%
241
15%
654
June1st to 15thNight
43%
180
0%
720
0%
180
43%
180
9%
565
June16th to endNight
45%
180
0%
720
0%
180
45%
180
6%
590
July1st to 15thNight
42%
170
0%
680
0%
170
42%
170
7%
558
July16th to endNight
35%
344
0%
971
0%
322
33%
322
7%
842
August1st to 15thNight
32%
394
0%
1158
0%
392
32%
392
8%
997
August16th to endNight
32%
573
1%
1528
0%
573
32%
573
8%
1325
September1st to 15thNight
29%
540
3%
1751
2%
540
30%
540
6%
1499
September16th to endNight
35%
497
4%
1795
4%
497
36%
497
10%
1419
October1st to 15thNight
35%
599
8%
2054
7%
599
37%
599
12%
1578
October16th to endNight
40%
736
10%
2443
8%
736
42%
736
14%
1809
November1st to 15thNight
30%
730
8%
2681
4%
730
34%
730
11%
2040
November16th to endNight
35%
750
15%
3006
11%
750
44%
750
15%
2001
December1st to 15thNight
33%
772
9%
3192
8%
772
38%
772
10%
2347
December16th to endNight
30%
832
7%
3456
4%
832
34%
832
9%
2538

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 ForecastData
Points
Cloud CoverDay
14%10%47%7%45%5%6%7%26%
48355
Night
10%10%47%7%35%5%6%7%30%
46572
TransparencyDay
57%10%15%11%4
47958
Night
53%9%13%13%7%1
46475
SeeingDay
19%11%27%26%13%1
8451
Night
15%9%29%28%15%1
13084

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
6%11%48%7%25%45%6%36%
749
16th to endDay
5%11%6%9%6%45%7%6%8%28%
1140
February1st to 15thDay
412%46%6%35%5%47%37%
1255
16th to endDay
5%10%410%6%36%6%5%7%33%
1313
March1st to 15thDay
36%36%5%45%46%6%44%
1788
16th to endDay
310%47%7%36%6%6%8%35%
2211
April1st to 15thDay
414%7%8%8%46%7%7%5%26%
2297
16th to endDay
310%48%6%46%6%6%9%31%
2553
May1st to 15thDay
10%10%48%7%45%5%6%7%27%
2841
16th to endDay
12%8%36%5%35%5%5%7%35%
3178
June1st to 15thDay
16%10%47%7%46%6%6%7%22%
3240
16th to endDay
18%9%37%7%46%6%6%7%21%
3240
July1st to 15thDay
17%10%5%9%7%35%6%6%7%20%
3240
16th to endDay
23%8%47%7%46%5%5%6%20%
3128
August1st to 15thDay
26%8%5%7%7%46%5%5%6%17%
2795
16th to endDay
27%9%48%6%35%45%5%18%
2674
September1st to 15thDay
26%11%27%7%35%5%45%18%
2208
16th to endDay
22%11%36%7%45%5%4424%
1838
October1st to 15thDay
19%11%46%5%35%46%6%27%
1576
16th to endDay
8%10%36%6%345%6%10%33%
1427
November1st to 15thDay
7%13%6%7%5%45%7%5%8%28%
1177
16th to endDay
5%10%5%8%5%436%5%6%38%
954
December1st to 15thDay
9%12%47%6%5%4449%30%
765
16th to endDay
28%410%8%37%7%8%11%26%
768
January1st to 15thNight
6%9%5%7%8%46%5%6%6%34%
3187
16th to endNight
5%12%5%7%6%35%5%6%9%31%
3084
February1st to 15thNight
49%6%6%6%3445%7%40%
2596
16th to endNight
6%10%5%8%7%45%5%7%9%29%
2158
March1st to 15thNight
47%46%7%35%46%6%41%
2172
16th to endNight
310%47%5%445%6%7%39%
2005
April1st to 15thNight
6%18%5%7%7%5%6%6%5%6%24%
1648
16th to endNight
48%47%7%36%7%7%7%35%
1407
May1st to 15thNight
10%9%48%7%46%6%6%6%29%
1109
16th to endNight
11%9%36%425%5%5%8%35%
935
June1st to 15thNight
18%10%47%6%36%5%45%26%
720
16th to endNight
18%9%37%5%46%6%7%7%21%
720
July1st to 15thNight
22%11%5%8%5%25%5%5%7%20%
720
16th to endNight
26%8%48%5%35%5%5%6%18%
1041
August1st to 15thNight
24%9%38%7%46%46%5%19%
1164
16th to endNight
29%9%37%6%435%4419%
1528
September1st to 15thNight
26%11%37%7%45%5%5%6%17%
1751
16th to endNight
23%11%26%6%345%5%6%23%
1795
October1st to 15thNight
17%13%46%7%3434429%
2054
16th to endNight
9%12%47%6%36%5%5%7%30%
2443
November1st to 15thNight
6%13%38%7%46%6%5%7%29%
2681
16th to endNight
6%9%37%7%345%6%7%36%
3006
December1st to 15thNight
9%12%5%8%6%35%5%6%6%30%
3192
16th to endNight
410%6%9%7%46%6%7%8%27%
3456

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
49%7%10%16%11%3
749
16th to endDay
52%10%10%15%10%
1140
February1st to 15thDay
45%9%13%16%12%2
1255
16th to endDay
50%8%14%16%9%1
1313
March1st to 15thDay
38%9%9%15%18%8%
1788
16th to endDay
47%9%13%15%12%1
2211
April1st to 15thDay
59%9%13%13%4
2297
16th to endDay
49%10%18%18%3
2553
May1st to 15thDay
58%8%14%13%4
2841
16th to endDay
48%9%18%19%3
3182
June1st to 15thDay
62%10%15%9%1
3240
16th to endDay
63%11%17%5%2
3240
July1st to 15thDay
64%11%18%3
3051
16th to endDay
66%12%17%2
2935
August1st to 15thDay
69%11%14%3
2776
16th to endDay
68%10%12%6%1
2674
September1st to 15thDay
68%10%12%7%1
2208
16th to endDay
63%9%14%9%3
1838
October1st to 15thDay
57%10%15%11%31
1576
16th to endDay
47%14%16%13%5%1
1427
November1st to 15thDay
55%10%14%12%6%
1177
16th to endDay
47%8%14%16%11%1
954
December1st to 15thDay
53%12%13%10%9%1
765
16th to endDay
52%13%13%14%3
768
January1st to 15thNight
49%9%11%15%8%4
3187
16th to endNight
49%8%13%17%9%1
3084
February1st to 15thNight
43%9%10%19%14%2
2608
16th to endNight
50%9%12%15%9%2
2158
March1st to 15thNight
42%7%8%14%17%9%
2172
16th to endNight
42%9%15%17%13%2
2010
April1st to 15thNight
59%8%14%13%4
1648
16th to endNight
44%12%21%17%3
1407
May1st to 15thNight
55%9%15%15%3
1110
16th to endNight
49%9%19%18%3
936
June1st to 15thNight
60%10%18%9%1
720
16th to endNight
61%15%16%5%1
720
July1st to 15thNight
64%11%20%21
680
16th to endNight
65%14%17%2
971
August1st to 15thNight
67%11%16%4
1158
16th to endNight
68%9%13%5%2
1528
September1st to 15thNight
68%10%12%7%
1751
16th to endNight
63%7%15%10%3
1795
October1st to 15thNight
58%8%14%11%6%
2054
16th to endNight
52%10%15%13%6%1
2443
November1st to 15thNight
55%11%13%14%5%
2681
16th to endNight
46%8%11%20%10%1
3006
December1st to 15thNight
55%9%13%10%9%
3192
16th to endNight
54%11%13%14%5%
3456

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
20%17%22%19%15%4
63
16th to endDay
12%12%33%29%11%
224
February1st to 15thDay
6%14%32%23%15%6%
217
16th to endDay
8%18%33%24%12%1
211
March1st to 15thDay
6%12%37%31%12%
240
16th to endDay
8%11%27%25%23%2
412
April1st to 15thDay
10%15%30%28%14%1
435
16th to endDay
10%10%31%34%12%
450
May1st to 15thDay
15%12%31%26%12%
468
16th to endDay
15%13%31%27%11%1
572
June1st to 15thDay
21%10%30%25%10%
675
16th to endDay
21%8%21%29%17%2
675
July1st to 15thDay
23%5%22%29%17%1
645
16th to endDay
27%8%23%27%12%1
574
August1st to 15thDay
29%12%21%22%12%1
494
16th to endDay
32%12%22%23%8%
523
September1st to 15thDay
31%14%25%19%7%1
460
16th to endDay
27%12%21%21%15%1
276
October1st to 15thDay
25%10%23%23%16%1
225
16th to endDay
14%11%26%25%18%5%
240
November1st to 15thDay
16%8%33%21%16%3
226
16th to endDay
11%10%21%29%21%4
84
December1st to 15thDay
6%6%50%30%6%
30
16th to endDay
15%18%34%6%21%3
32
January1st to 15thNight
8%15%32%28%12%1
780
16th to endNight
12%11%39%26%10%
802
February1st to 15thNight
5%13%41%27%9%1
734
16th to endNight
11%11%40%26%8%
605
March1st to 15thNight
7%10%37%34%10%
570
16th to endNight
7%7%24%34%24%1
585
April1st to 15thNight
11%9%25%30%21%
539
16th to endNight
8%7%28%32%22%
540
May1st to 15thNight
13%5%24%36%18%1
390
16th to endNight
13%5%22%36%19%2
242
June1st to 15thNight
18%325%33%17%1
180
16th to endNight
22%416%30%25%1
180
July1st to 15thNight
25%5%14%24%30%1
170
16th to endNight
31%6%17%19%23%1
344
August1st to 15thNight
31%5%21%22%16%1
394
16th to endNight
32%5%20%26%14%1
573
September1st to 15thNight
33%7%21%22%13%1
540
16th to endNight
29%7%19%23%17%1
497
October1st to 15thNight
22%9%26%21%20%1
599
16th to endNight
15%8%26%28%19%1
736
November1st to 15thNight
14%7%37%28%10%1
730
16th to endNight
11%11%32%30%12%1
750
December1st to 15thNight
14%11%30%25%13%5%
772
16th to endNight
9%13%35%27%12%1
832
Page generated at 2017-09-16 14:06:59. Version ac04

Copyright 2017 A. Danko


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