Riverdale
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Riverdale clear sky chart from 2005-11-05 to 2017-09-22.

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
44%
15845
27%
46977
16%
15799
54%
15799
38%
25989

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
35%
900
31%
2327
13%
895
48%
895
40%
1334
January16th to endNight
38%
960
34%
2496
14%
960
49%
960
43%
1411
February1st to 15thNight
32%
824
23%
2232
9%
820
42%
820
34%
1359
February16th to endNight
30%
632
29%
1894
10%
632
44%
632
35%
1036
March1st to 15thNight
35%
576
26%
2016
15%
576
48%
576
30%
1103
March16th to endNight
32%
576
19%
2112
13%
576
42%
576
25%
1223
April1st to 15thNight
28%
539
23%
1932
13%
539
45%
539
28%
1064
April16th to endNight
29%
540
23%
1620
13%
540
42%
540
30%
976
May1st to 15thNight
35%
539
23%
1620
15%
539
48%
539
33%
945
May16th to endNight
47%
562
20%
1684
17%
561
53%
561
36%
981
June1st to 15thNight
52%
540
19%
1620
11%
540
59%
540
42%
865
June16th to endNight
58%
540
25%
1620
16%
540
66%
540
54%
764
July1st to 15thNight
68%
510
19%
1530
16%
510
71%
510
45%
804
July16th to endNight
78%
564
26%
1594
28%
531
80%
531
46%
826
August1st to 15thNight
75%
539
25%
1610
29%
536
77%
536
44%
854
August16th to endNight
73%
573
27%
1777
30%
573
76%
573
42%
939
September1st to 15thNight
55%
540
24%
1980
23%
540
63%
540
33%
1054
September16th to endNight
54%
513
33%
1891
28%
513
65%
513
38%
924
October1st to 15thNight
47%
573
32%
1893
25%
573
54%
573
36%
1012
October16th to endNight
44%
704
35%
2112
17%
704
58%
704
49%
1026
November1st to 15thNight
41%
841
30%
2241
12%
841
53%
841
45%
1217
November16th to endNight
37%
900
31%
2340
12%
900
50%
900
41%
1342
December1st to 15thNight
37%
900
27%
2340
12%
900
48%
900
38%
1394
December16th to endNight
38%
960
30%
2496
14%
960
48%
960
34%
1536

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
9%42442445%7%51%
47907
Night
8%413323347%55%
47173
Cloud CoverDay
9%42442445%7%51%
47905
Night
9%413323347%55%
47173
TransparencyDay
31%412%27%19%4
47605
Night
28%311%27%22%5%
46978
SeeingDay
10%6%25%32%20%4
5842
Night
10%8%31%35%13%
15847

By Month

Percentage Cloud Cover SW (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
8%6%12422345%57%
1611
16th to endDay
8%6%25%313247%54%
1728
February1st to 15thDay
8%7%36%422345%50%
1639
16th to endDay
8%5%1332345%7%53%
1580
March1st to 15thDay
11%6%33324446%47%
1944
16th to endDay
16%6%25%424335%44%
2112
April1st to 15thDay
11%424424446%49%
2016
16th to endDay
16%6%2442335%6%45%
2340
May1st to 15thDay
13%5%34323447%47%
2331
16th to endDay
11%5%25%5%445%5%7%42%
2430
June1st to 15thDay
7%32342445%8%53%
2340
16th to endDay
5%21242446%9%57%
2340
July1st to 15thDay
8%413435%5%6%8%47%
2340
16th to endDay
4314425%5%7%10%51%
2466
August1st to 15thDay
5%314435%5%7%10%47%
2340
16th to endDay
6%4144235%5%8%53%
2421
September1st to 15thDay
9%5%25%42335%5%51%
1980
16th to endDay
7%4135%23346%57%
1881
October1st to 15thDay
12%41331334456%
1724
16th to endDay
7%5%13313346%59%
1760
November1st to 15thDay
5%313323446%61%
1616
16th to endDay
10%313212335%61%
1620
December1st to 15thDay
12%6%2432335%6%50%
1620
16th to endDay
12%7%25%424345%46%
1728
January1st to 15thNight
7%424323345%58%
2327
16th to endNight
7%32331333461%
2496
February1st to 15thNight
11%7%25%322246%51%
2222
16th to endNight
8%414413346%55%
1894
March1st to 15thNight
8%6%24424445%51%
2016
16th to endNight
15%6%23433336%47%
2112
April1st to 15thNight
12%423424348%50%
1932
16th to endNight
14%6%2432435%5%48%
1620
May1st to 15thNight
12%41432345%8%49%
1619
16th to endNight
7%4243245%8%9%47%
1683
June1st to 15thNight
5%32342446%10%53%
1620
16th to endNight
4112244411%62%
1620
July1st to 15thNight
5%3123245%6%11%52%
1620
16th to endNight
32134235%6%12%53%
1702
August1st to 15thNight
42135%245%6%11%53%
1620
16th to endNight
432332446%8%55%
1777
September1st to 15thNight
8%424423346%53%
1980
16th to endNight
6%31432345%6%58%
1891
October1st to 15thNight
12%313322335%57%
1893
16th to endNight
6%31121223469%
2112
November1st to 15thNight
6%313313345%62%
2241
16th to endNight
10%41322333460%
2340
December1st to 15thNight
11%5%2422335%7%52%
2340
16th to endNight
11%5%34423346%51%
2496

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
8%6%13313345%57%
1611
16th to endDay
7%6%25%312247%54%
1728
February1st to 15thDay
8%7%35%423345%50%
1639
16th to endDay
8%5%2332345%7%53%
1580
March1st to 15thDay
11%7%34324446%47%
1944
16th to endDay
16%6%25%424335%44%
2110
April1st to 15thDay
11%424424446%49%
2016
16th to endDay
17%5%24413347%45%
2340
May1st to 15thDay
14%5%2342335%7%46%
2331
16th to endDay
12%425%5%35%5%5%7%43%
2430
June1st to 15thDay
7%31333445%9%53%
2340
16th to endDay
5%21332445%9%57%
2340
July1st to 15thDay
8%3135%25%6%5%9%47%
2340
16th to endDay
4214425%5%7%9%51%
2466
August1st to 15thDay
6%314435%5%7%9%47%
2340
16th to endDay
6%4144235%5%8%53%
2421
September1st to 15thDay
9%5%24424345%51%
1980
16th to endDay
7%423423346%57%
1881
October1st to 15thDay
12%313323345%57%
1724
16th to endDay
7%5%13312346%59%
1760
November1st to 15thDay
5%312323346%61%
1616
16th to endDay
10%313212245%61%
1620
December1st to 15thDay
13%6%2332235%6%50%
1620
16th to endDay
12%7%35%424345%46%
1728
January1st to 15thNight
7%5%1431335%5%58%
2327
16th to endNight
7%33431333461%
2496
February1st to 15thNight
10%7%25%412246%51%
2222
16th to endNight
9%314413346%56%
1894
March1st to 15thNight
9%6%24424445%51%
2016
16th to endNight
15%5%24423445%48%
2112
April1st to 15thNight
12%413424347%50%
1932
16th to endNight
14%5%23314446%48%
1620
May1st to 15thNight
12%42332335%8%50%
1619
16th to endNight
7%4234246%7%9%48%
1683
June1st to 15thNight
5%31333445%10%54%
1620
16th to endNight
41121445%10%63%
1620
July1st to 15thNight
6%2123245%6%11%52%
1620
16th to endNight
42134235%6%11%53%
1702
August1st to 15thNight
42134235%6%11%53%
1620
16th to endNight
432332446%8%55%
1777
September1st to 15thNight
8%414424346%54%
1980
16th to endNight
6%31433335%7%58%
1891
October1st to 15thNight
12%313313335%57%
1893
16th to endNight
7%31121233469%
2112
November1st to 15thNight
7%313213346%62%
2241
16th to endNight
11%31322333460%
2340
December1st to 15thNight
11%5%24223347%52%
2340
16th to endNight
11%5%34323336%51%
2496

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
29%212%31%22%1
1612
16th to endDay
30%113%30%19%3
1728
February1st to 15thDay
36%314%27%13%4
1640
16th to endDay
29%312%28%20%4
1580
March1st to 15thDay
37%311%22%19%5%
1944
16th to endDay
43%49%24%16%2
2112
April1st to 15thDay
35%313%27%17%3
2016
16th to endDay
39%310%29%13%2
2340
May1st to 15thDay
37%412%21%21%2
2331
16th to endDay
39%5%15%24%13%1
2434
June1st to 15thDay
28%5%16%27%18%3
2340
16th to endDay
23%5%13%28%23%5%
2340
July1st to 15thDay
30%5%12%30%17%2
2201
16th to endDay
23%6%16%30%19%3
2311
August1st to 15thDay
29%6%17%25%16%5%
2326
16th to endDay
28%5%13%28%17%7%
2421
September1st to 15thDay
34%411%25%15%8%
1980
16th to endDay
27%310%30%22%5%
1881
October1st to 15thDay
29%39%26%25%4
1724
16th to endDay
25%29%29%26%5%
1760
November1st to 15thDay
23%210%25%27%9%
1616
16th to endDay
26%28%30%25%6%
1620
December1st to 15thDay
35%213%31%16%1
1620
16th to endDay
39%310%25%16%3
1728
January1st to 15thNight
27%38%32%24%4
2327
16th to endNight
27%29%31%23%5%
2496
February1st to 15thNight
35%213%26%17%5%
2232
16th to endNight
29%212%28%19%7%
1894
March1st to 15thNight
33%39%24%21%7%
2016
16th to endNight
38%312%25%16%3
2112
April1st to 15thNight
33%310%24%22%4
1932
16th to endNight
36%312%22%19%5%
1620
May1st to 15thNight
33%413%25%19%4
1620
16th to endNight
29%6%20%26%15%2
1685
June1st to 15thNight
25%418%28%20%3
1620
16th to endNight
17%415%31%24%7%
1620
July1st to 15thNight
23%413%29%24%3
1530
16th to endNight
22%5%12%31%23%3
1594
August1st to 15thNight
23%5%15%29%18%6%
1610
16th to endNight
25%5%12%27%23%6%
1777
September1st to 15thNight
30%411%25%18%9%
1980
16th to endNight
25%39%26%27%6%
1891
October1st to 15thNight
30%210%21%25%9%
1893
16th to endNight
20%26%28%33%7%
2112
November1st to 15thNight
24%210%22%29%9%
2241
16th to endNight
27%27%28%26%7%
2340
December1st to 15thNight
31%312%30%19%2
2340
16th to endNight
34%312%26%15%7%
2496

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
21%11%26%32%6%2
90
16th to endDay
13%11%47%25%11
96
February1st to 15thDay
6%21%42%24%5%
90
16th to endDay
6%16%48%23%41
81
March1st to 15thDay
13%17%50%17%1
90
16th to endDay
15%16%35%27%5%
96
April1st to 15thDay
13%14%34%29%7%
135
16th to endDay
21%12%38%20%6%1
450
May1st to 15thDay
14%11%34%25%11%2
468
16th to endDay
15%9%32%27%11%3
517
June1st to 15thDay
8%5%26%34%22%2
495
16th to endDay
5%222%41%22%4
495
July1st to 15thDay
9%214%38%29%5%
475
16th to endDay
410%39%35%8%
515
August1st to 15thDay
7%39%40%34%5%
493
16th to endDay
6%115%36%33%6%
461
September1st to 15thDay
314%44%31%5%
135
16th to endDay
5%30%26%25%10%
108
October1st to 15thDay
8%7%22%36%18%5%
90
16th to endDay
5%439%30%12%8%
96
November1st to 15thDay
6%435%27%18%6%
90
16th to endDay
24%20%32%15%5%2
90
December1st to 15thDay
13%7%47%21%7%2
90
16th to endDay
17%17%34%25%5%
96
January1st to 15thNight
9%13%36%32%8%
900
16th to endNight
10%9%37%35%6%
960
February1st to 15thNight
13%11%37%32%4
824
16th to endNight
10%14%39%31%4
632
March1st to 15thNight
12%11%36%33%5%
576
16th to endNight
18%10%36%28%5%
576
April1st to 15thNight
15%12%41%22%7%
539
16th to endNight
16%11%39%23%7%
540
May1st to 15thNight
14%6%38%28%10%1
540
16th to endNight
9%5%32%33%15%2
563
June1st to 15thNight
7%430%37%17%
540
16th to endNight
5%131%43%18%
540
July1st to 15thNight
6%17%50%22%1
510
16th to endNight
5%8%49%32%3
564
August1st to 15thNight
5%110%52%29%1
539
16th to endNight
5%112%41%37%1
573
September1st to 15thNight
10%123%37%24%2
540
16th to endNight
8%426%35%22%1
513
October1st to 15thNight
14%5%29%28%20%1
573
16th to endNight
7%9%35%34%12%
704
November1st to 15thNight
8%10%36%31%12%
841
16th to endNight
12%12%34%32%8%
900
December1st to 15thNight
15%10%34%34%6%
900
16th to endNight
14%10%31%37%5%
960
Page generated at 2017-09-23 06:43:34. Version ac04

Copyright 2017 A. Danko


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