Willow Slough Fish and Wildlife Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Willow Slough Fish and Wildlife Area clear sky chart from 2005-11-05 to

2017-09-12
.

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
38%
15896
17%
46774
11%
15854
44%
15854
23%
31517

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
18%
900
13%
2506
5%
895
26%
895
16%
1879
January16th to endNight
22%
960
12%
2661
5%
960
27%
960
15%
2018
February1st to 15thNight
22%
752
13%
2163
4%
752
29%
752
18%
1550
February16th to endNight
25%
631
16%
1893
7%
631
34%
631
17%
1366
March1st to 15thNight
24%
720
12%
2160
8%
720
28%
720
17%
1557
March16th to endNight
28%
651
15%
2022
8%
651
36%
651
20%
1411
April1st to 15thNight
27%
539
15%
1797
10%
539
37%
539
21%
1181
April16th to endNight
33%
540
19%
1725
12%
540
42%
540
22%
1167
May1st to 15thNight
37%
540
15%
1620
9%
540
42%
540
21%
1131
May16th to endNight
53%
562
17%
1529
10%
561
58%
561
30%
1016
June1st to 15thNight
54%
540
18%
1440
12%
540
58%
540
38%
889
June16th to endNight
53%
540
17%
1440
10%
540
58%
540
32%
927
July1st to 15thNight
63%
510
17%
1360
13%
510
65%
510
38%
823
July16th to endNight
71%
564
23%
1417
17%
531
74%
531
43%
834
August1st to 15thNight
74%
539
21%
1607
20%
536
75%
536
39%
926
August16th to endNight
68%
573
21%
1910
22%
573
72%
573
32%
1098
September1st to 15thNight
65%
552
28%
1789
28%
552
69%
552
35%
1002
September16th to endNight
62%
657
28%
1815
21%
657
65%
657
37%
1075
October1st to 15thNight
51%
660
28%
1865
21%
660
58%
660
35%
1119
October16th to endNight
30%
704
19%
2249
12%
704
38%
704
21%
1467
November1st to 15thNight
34%
700
24%
2276
16%
700
45%
700
25%
1379
November16th to endNight
29%
720
17%
2340
11%
720
36%
720
19%
1596
December1st to 15thNight
20%
882
12%
2502
5%
882
27%
882
15%
1902
December16th to endNight
17%
960
10%
2688
3%
960
24%
960
11%
2204

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%7%36%5%3445%7%36%
47895
Night
14%8%36%5%24446%39%
46942
Cloud CoverDay
13%7%36%5%345%5%7%36%
47904
Night
14%8%36%5%34446%39%
46947
TransparencyDay
46%6%12%20%12%1
47581
Night
45%5%11%21%14%2
46774
SeeingDay
15%6%26%25%18%7%
5907
Night
18%8%28%29%13%1
15900

By Month

Percentage Cloud Cover NE (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
18%14%5%7%7%45%345%24%
1432
16th to endDay
14%15%8%8%434437%25%
1562
February1st to 15thDay
16%11%5%8%5%35%446%28%
1698
16th to endDay
15%11%48%6%3445%5%30%
1580
March1st to 15thDay
19%12%47%5%24446%27%
1790
16th to endDay
18%8%47%5%25%5%47%29%
2211
April1st to 15thDay
18%9%35%5%24346%35%
2151
16th to endDay
19%7%245%3445%6%35%
2234
May1st to 15thDay
19%9%35%5%33446%31%
2331
16th to endDay
12%6%36%5%35%5%6%8%37%
2584
June1st to 15thDay
10%425%5%345%5%8%43%
2520
16th to endDay
9%335%6%35%6%6%11%37%
2520
July1st to 15thDay
8%5%15%5%36%5%6%8%42%
2520
16th to endDay
6%3245%45%6%7%10%42%
2655
August1st to 15thDay
6%425%6%35%5%6%9%45%
2342
16th to endDay
8%5%25%6%245%6%8%43%
2292
September1st to 15thDay
11%5%245%2445%7%45%
2079
16th to endDay
9%5%24425%45%7%46%
1815
October1st to 15thDay
14%6%25%43445%6%43%
1763
16th to endDay
18%8%36%5%3445%6%33%
1623
November1st to 15thDay
15%7%33413346%46%
1582
16th to endDay
18%8%46%5%24346%35%
1620
December1st to 15thDay
19%12%48%5%25%445%25%
1455
16th to endDay
22%15%7%6%5%23436%22%
1536
January1st to 15thNight
19%11%47%5%2435%430%
2506
16th to endNight
14%13%6%8%6%34436%28%
2661
February1st to 15thNight
16%11%5%7%5%24336%34%
2161
16th to endNight
15%12%5%7%5%2445%5%32%
1893
March1st to 15thNight
18%11%46%5%23445%32%
2147
16th to endNight
15%8%26%5%35%5%5%7%34%
2022
April1st to 15thNight
16%7%36%5%24436%38%
1797
16th to endNight
17%7%36%434346%38%
1725
May1st to 15thNight
19%6%25%5%25%45%7%35%
1620
16th to endNight
9%426%5%35%46%8%43%
1527
June1st to 15thNight
10%5%2442345%8%49%
1440
16th to endNight
7%5%25%5%3446%9%43%
1440
July1st to 15thNight
7%314425%45%9%51%
1440
16th to endNight
43145%25%45%9%52%
1513
August1st to 15thNight
43145%25%5%6%11%50%
1616
16th to endNight
8%4244245%5%7%50%
1910
September1st to 15thNight
11%413333346%53%
1789
16th to endNight
8%32433445%9%49%
1815
October1st to 15thNight
12%425%223336%52%
1865
16th to endNight
18%7%36%423245%41%
2249
November1st to 15thNight
13%7%2443335%6%45%
2276
16th to endNight
19%8%35%43335%6%35%
2340
December1st to 15thNight
21%12%48%424335%29%
2502
16th to endNight
22%15%5%9%6%35%43421%
2688

Percentage Cloud Cover SE (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
18%15%47%7%45%34424%
1432
16th to endDay
14%15%8%8%5%24446%25%
1562
February1st to 15thDay
16%11%5%8%5%35%45%6%27%
1698
16th to endDay
15%12%48%6%34345%30%
1580
March1st to 15thDay
19%13%48%424446%27%
1800
16th to endDay
17%8%47%5%25%5%47%29%
2210
April1st to 15thDay
18%9%35%5%24446%35%
2151
16th to endDay
19%7%35%6%2445%6%34%
2234
May1st to 15thDay
20%9%36%43445%6%31%
2331
16th to endDay
11%6%36%5%35%5%6%8%37%
2584
June1st to 15thDay
10%4246%345%5%8%43%
2520
16th to endDay
9%426%5%46%6%7%10%37%
2520
July1st to 15thDay
8%425%5%36%5%6%8%42%
2520
16th to endDay
6%3245%45%7%7%10%41%
2655
August1st to 15thDay
6%4246%35%5%6%8%45%
2342
16th to endDay
8%5%246%35%5%6%8%43%
2292
September1st to 15thDay
11%5%244245%6%6%45%
2079
16th to endDay
9%5%25%435%45%8%46%
1815
October1st to 15thDay
14%6%25%42445%6%43%
1763
16th to endDay
18%8%26%6%2445%7%33%
1623
November1st to 15thDay
15%7%24422346%46%
1582
16th to endDay
18%9%46%434337%35%
1620
December1st to 15thDay
18%12%5%8%6%34445%25%
1455
16th to endDay
21%15%6%7%5%23336%22%
1536
January1st to 15thNight
19%11%47%5%3335%430%
2506
16th to endNight
14%13%7%8%6%34436%27%
2661
February1st to 15thNight
16%11%5%7%5%23336%34%
2154
16th to endNight
15%11%47%5%2445%5%32%
1893
March1st to 15thNight
18%11%46%5%24445%32%
2160
16th to endNight
15%8%36%5%3446%7%34%
2022
April1st to 15thNight
15%7%36%5%25%446%37%
1797
16th to endNight
17%7%36%5%3435%5%38%
1725
May1st to 15thNight
19%6%35%5%3445%7%34%
1619
16th to endNight
9%426%6%35%45%8%43%
1527
June1st to 15thNight
9%5%2342335%8%50%
1440
16th to endNight
7%435%6%445%5%10%43%
1440
July1st to 15thNight
7%32442435%9%51%
1440
16th to endNight
43145%25%45%8%53%
1513
August1st to 15thNight
33144445%6%11%49%
1616
16th to endNight
8%325%4245%5%7%50%
1910
September1st to 15thNight
11%413323347%53%
1789
16th to endNight
7%42442445%9%49%
1815
October1st to 15thNight
12%5%24323336%52%
1865
16th to endNight
18%7%36%5%23335%41%
2249
November1st to 15thNight
13%7%2433335%7%44%
2276
16th to endNight
19%8%35%5%34346%35%
2340
December1st to 15thNight
20%12%5%8%424335%29%
2502
16th to endNight
21%15%5%8%6%3443421%
2688

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
62%411%12%8%
1433
16th to endDay
59%5%12%15%6%
1562
February1st to 15thDay
57%5%12%16%7%1
1700
16th to endDay
55%5%11%21%5%1
1580
March1st to 15thDay
56%5%12%17%6%
1800
16th to endDay
54%5%13%21%5%
2211
April1st to 15thDay
48%5%10%20%13%
2151
16th to endDay
48%6%11%17%11%4
2234
May1st to 15thDay
52%6%11%21%8%
2331
16th to endDay
42%7%11%19%15%2
2588
June1st to 15thDay
36%7%11%23%18%1
2520
16th to endDay
38%8%13%19%17%2
2520
July1st to 15thDay
39%7%11%21%17%3
2371
16th to endDay
34%9%16%23%13%2
2488
August1st to 15thDay
34%8%13%25%17%1
2327
16th to endDay
36%7%13%21%16%4
2292
September1st to 15thDay
35%7%10%23%16%6%
2079
16th to endDay
35%5%8%26%21%1
1815
October1st to 15thDay
40%5%11%24%16%2
1763
16th to endDay
49%5%12%21%10%
1623
November1st to 15thDay
39%411%23%17%3
1582
16th to endDay
50%412%21%9%
1620
December1st to 15thDay
59%5%10%17%5%
1455
16th to endDay
64%5%11%11%5%
1536
January1st to 15thNight
56%410%17%10%
2506
16th to endNight
57%413%15%7%
2661
February1st to 15thNight
53%312%19%8%1
2163
16th to endNight
52%5%11%19%9%
1893
March1st to 15thNight
53%412%17%9%2
2160
16th to endNight
47%7%14%20%9%1
2022
April1st to 15thNight
46%311%21%14%1
1797
16th to endNight
46%5%8%19%13%4
1725
May1st to 15thNight
47%6%11%21%11%
1620
16th to endNight
38%8%12%18%18%3
1529
June1st to 15thNight
32%5%12%24%22%2
1440
16th to endNight
35%7%13%22%17%3
1440
July1st to 15thNight
31%5%13%26%19%3
1360
16th to endNight
27%5%15%27%19%3
1417
August1st to 15thNight
26%8%15%25%20%2
1607
16th to endNight
31%7%10%24%20%5%
1910
September1st to 15thNight
31%49%25%21%6%
1789
16th to endNight
30%6%8%27%23%3
1815
October1st to 15thNight
33%48%27%24%1
1865
16th to endNight
45%39%26%13%1
2249
November1st to 15thNight
38%49%24%17%4
2276
16th to endNight
49%413%22%10%
2340
December1st to 15thNight
59%39%16%9%
2502
16th to endNight
66%48%13%5%
2688

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
28%8%36%18%6%
90
16th to endDay
20%14%33%27%4
96
February1st to 15thDay
16%23%44%14%1
90
16th to endDay
22%12%30%20%11%2
81
March1st to 15thDay
34%20%22%22%1
90
16th to endDay
28%9%27%24%8%1
261
April1st to 15thDay
23%10%30%21%11%2
270
16th to endDay
23%7%28%22%12%4
270
May1st to 15thDay
24%9%29%20%12%3
288
16th to endDay
16%6%31%24%15%5%
484
June1st to 15thDay
11%428%30%18%6%
495
16th to endDay
12%6%32%27%16%5%
495
July1st to 15thDay
10%326%28%17%13%
475
16th to endDay
6%118%32%26%13%
515
August1st to 15thDay
8%115%26%28%19%
357
16th to endDay
11%119%24%28%15%
332
September1st to 15thDay
13%415%26%31%9%
299
16th to endDay
9%5%15%27%31%9%
254
October1st to 15thDay
12%5%27%24%25%5%
203
16th to endDay
23%11%34%27%3
96
November1st to 15thDay
13%7%25%23%22%7%
90
16th to endDay
33%14%34%12%5%
90
December1st to 15thDay
18%18%37%17%6%
90
16th to endDay
28%25%38%5%3
96
January1st to 15thNight
25%14%35%19%4
900
16th to endNight
21%14%33%27%3
960
February1st to 15thNight
23%10%36%24%5%
755
16th to endNight
21%11%34%26%5%
631
March1st to 15thNight
24%11%35%23%5%
720
16th to endNight
18%9%38%24%8%
651
April1st to 15thNight
18%11%36%25%6%
539
16th to endNight
20%7%34%27%9%
540
May1st to 15thNight
21%430%32%9%
540
16th to endNight
9%326%39%19%1
563
June1st to 15thNight
10%323%45%15%
540
16th to endNight
9%325%40%19%1
540
July1st to 15thNight
9%218%40%27%1
510
16th to endNight
5%114%40%34%3
564
August1st to 15thNight
5%10%47%30%5%
539
16th to endNight
9%112%36%35%4
573
September1st to 15thNight
12%313%36%30%3
552
16th to endNight
9%318%32%32%3
657
October1st to 15thNight
15%6%22%34%19%1
660
16th to endNight
21%11%32%25%8%
704
November1st to 15thNight
16%10%34%26%10%1
700
16th to endNight
23%12%31%24%8%
720
December1st to 15thNight
27%12%31%22%5%
882
16th to endNight
31%11%31%21%3
960
Page generated at 2017-09-13 06:39:22. Version ac04

Copyright 2017 A. Danko


Willow Slough Fish and Wildlife Area Clear Sky Chart | Charts Home