Riverside
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Riverside clear sky chart from 2005-11-05 to 2017-04-24.

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%
15550
19%
45626
11%
15506
46%
15506
26%
29401

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
27%
900
15%
2506
6%
895
35%
895
22%
1743
January16th to endNight
23%
960
16%
2511
5%
960
32%
960
21%
1791
February1st to 15thNight
24%
877
14%
2288
4%
876
31%
876
22%
1627
February16th to endNight
30%
665
21%
1927
8%
665
41%
665
26%
1241
March1st to 15thNight
33%
621
20%
2061
12%
621
42%
621
25%
1272
March16th to endNight
29%
576
11%
2063
7%
576
36%
576
16%
1439
April1st to 15thNight
28%
539
18%
1797
12%
539
38%
539
22%
1148
April16th to endNight
37%
522
19%
1740
14%
522
47%
522
22%
1147
May1st to 15thNight
35%
495
18%
1391
9%
495
43%
495
25%
952
May16th to endNight
45%
515
19%
1369
9%
513
51%
513
32%
889
June1st to 15thNight
52%
495
17%
1320
9%
495
55%
495
33%
848
June16th to endNight
54%
495
17%
1320
8%
495
57%
495
38%
804
July1st to 15thNight
68%
465
19%
1240
12%
465
70%
465
45%
716
July16th to endNight
68%
522
21%
1347
15%
489
70%
489
43%
766
August1st to 15thNight
72%
494
23%
1475
26%
491
73%
491
40%
817
August16th to endNight
66%
525
21%
1729
23%
525
71%
525
33%
987
September1st to 15thNight
62%
495
28%
1650
29%
495
67%
495
35%
896
September16th to endNight
57%
574
27%
1791
18%
574
65%
574
37%
980
October1st to 15thNight
44%
660
26%
1980
19%
660
50%
660
33%
1173
October16th to endNight
34%
704
20%
2126
10%
704
43%
704
27%
1320
November1st to 15thNight
35%
700
25%
2276
16%
700
47%
700
30%
1298
November16th to endNight
29%
891
17%
2511
8%
891
37%
891
25%
1659
December1st to 15thNight
22%
900
14%
2520
5%
900
30%
900
18%
1825
December16th to endNight
23%
960
14%
2688
6%
960
31%
960
15%
2063

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%35%5%3445%7%38%
45993
Night
13%7%35%424346%43%
45800
Cloud CoverDay
14%7%35%5%3445%7%38%
46002
Night
13%7%35%424446%42%
45804
TransparencyDay
44%5%13%23%12%1
45684
Night
41%413%24%14%2
45627
SeeingDay
15%6%25%27%18%5%
5319
Night
16%7%29%31%13%1
15553

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
11%11%48%6%46%5%5%7%29%
1432
16th to endDay
13%14%6%8%7%4345%5%27%
1710
February1st to 15thDay
14%10%5%7%6%25%5%46%30%
1575
16th to endDay
13%8%47%5%35%347%35%
1545
March1st to 15thDay
13%9%36%434447%36%
1900
16th to endDay
20%10%45%5%24446%30%
2160
April1st to 15thDay
17%9%46%5%3344435%
2151
16th to endDay
23%8%25%423345%35%
2079
May1st to 15thDay
20%7%36%6%35%45%7%29%
2230
16th to endDay
13%5%36%6%35%5%5%7%36%
2393
June1st to 15thDay
14%5%35%5%25%5%6%8%37%
2310
16th to endDay
9%3245%35%6%6%8%43%
2310
July1st to 15thDay
7%324435%46%9%45%
2310
16th to endDay
7%4145%35%6%7%10%43%
2412
August1st to 15thDay
6%326%435%6%7%10%41%
2145
16th to endDay
11%5%25%434446%46%
2121
September1st to 15thDay
13%32342235%7%50%
1980
16th to endDay
10%3245%35%5%6%7%47%
1827
October1st to 15thDay
14%5%24423335%49%
1650
16th to endDay
17%6%15%5%33445%42%
1746
November1st to 15thDay
12%7%3442445%6%44%
1582
16th to endDay
19%8%35%313437%39%
1449
December1st to 15thDay
19%13%48%425%435%27%
1440
16th to endDay
19%15%6%8%6%24335%26%
1536
January1st to 15thNight
10%8%5%6%5%35%45%6%36%
2506
16th to endNight
11%11%6%7%5%23346%36%
2511
February1st to 15thNight
14%10%47%5%2335%6%35%
2285
16th to endNight
13%7%36%423345%44%
1927
March1st to 15thNight
15%6%34423346%44%
2049
16th to endNight
16%8%36%6%35%5%35%32%
2063
April1st to 15thNight
15%7%36%423346%40%
1797
16th to endNight
18%6%25%5%24446%38%
1740
May1st to 15thNight
17%5%35%435%36%7%37%
1391
16th to endNight
11%4335%25%45%8%44%
1368
June1st to 15thNight
9%6%25%43445%9%43%
1320
16th to endNight
7%325%4245%6%9%48%
1320
July1st to 15thNight
6%213325%46%9%55%
1320
16th to endNight
5%21442447%10%50%
1447
August1st to 15thNight
4413425%45%7%54%
1485
16th to endNight
10%423433446%51%
1729
September1st to 15thNight
10%413313448%53%
1650
16th to endNight
7%423334348%52%
1791
October1st to 15thNight
13%5%24423345%51%
1980
16th to endNight
14%5%26%433346%46%
2126
November1st to 15thNight
12%5%24323236%53%
2276
16th to endNight
17%7%24423346%41%
2511
December1st to 15thNight
17%12%47%5%2334433%
2520
16th to endNight
21%12%47%5%2433429%
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
11%11%48%6%46%45%7%29%
1432
16th to endDay
13%14%6%8%7%4345%5%27%
1710
February1st to 15thDay
14%10%5%8%6%3445%6%30%
1575
16th to endDay
13%8%47%5%35%347%36%
1545
March1st to 15thDay
14%9%36%434447%36%
1911
16th to endDay
20%10%35%5%34446%31%
2158
April1st to 15thDay
17%9%46%5%3444435%
2151
16th to endDay
23%8%26%423345%35%
2079
May1st to 15thDay
20%8%35%6%35%45%7%28%
2230
16th to endDay
13%5%36%6%35%5%5%7%36%
2393
June1st to 15thDay
14%6%35%5%25%46%8%37%
2310
16th to endDay
9%4245%35%6%6%8%43%
2310
July1st to 15thDay
7%415%435%5%6%10%45%
2310
16th to endDay
7%4245%35%6%7%10%43%
2412
August1st to 15thDay
6%325%435%6%7%10%41%
2145
16th to endDay
11%5%25%43445%6%46%
2121
September1st to 15thDay
13%31341345%7%50%
1980
16th to endDay
10%3244345%6%7%47%
1827
October1st to 15thDay
14%5%24423335%48%
1650
16th to endDay
17%6%25%5%33446%42%
1746
November1st to 15thDay
12%7%3442445%6%43%
1582
16th to endDay
20%7%35%323337%39%
1449
December1st to 15thDay
19%12%48%435%435%27%
1440
16th to endDay
19%15%6%8%6%24335%26%
1536
January1st to 15thNight
10%8%5%6%5%35%45%6%36%
2506
16th to endNight
11%11%6%7%5%23346%35%
2511
February1st to 15thNight
14%10%47%5%2435%6%35%
2278
16th to endNight
13%8%37%32335%5%43%
1927
March1st to 15thNight
16%6%24423346%44%
2061
16th to endNight
16%8%37%7%35%5%4432%
2063
April1st to 15thNight
15%7%36%423446%40%
1797
16th to endNight
18%6%25%424446%38%
1740
May1st to 15thNight
17%6%25%435%46%7%37%
1390
16th to endNight
11%4345%25%45%8%44%
1368
June1st to 15thNight
9%6%25%43445%9%43%
1320
16th to endNight
7%325%4245%6%9%47%
1320
July1st to 15thNight
6%213225%46%8%55%
1320
16th to endNight
5%2144245%7%10%50%
1447
August1st to 15thNight
44135%25%45%7%54%
1485
16th to endNight
10%41443335%7%51%
1729
September1st to 15thNight
11%413313448%53%
1650
16th to endNight
7%423334348%53%
1791
October1st to 15thNight
12%5%24423345%50%
1980
16th to endNight
14%6%25%423245%46%
2126
November1st to 15thNight
12%5%34313236%53%
2276
16th to endNight
17%8%24323346%41%
2511
December1st to 15thNight
17%11%47%5%23345%33%
2520
16th to endNight
21%12%47%5%2433429%
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
53%413%17%10%
1433
16th to endDay
58%412%16%7%
1710
February1st to 15thDay
53%414%21%5%
1576
16th to endDay
48%414%22%8%1
1545
March1st to 15thDay
47%416%21%9%
1911
16th to endDay
53%413%19%6%1
2160
April1st to 15thDay
51%310%24%9%
2151
16th to endDay
50%411%20%11%1
2079
May1st to 15thDay
54%5%11%20%8%
2230
16th to endDay
44%6%13%21%11%1
2397
June1st to 15thDay
42%5%14%24%11%1
2310
16th to endDay
34%7%13%23%17%2
2310
July1st to 15thDay
35%5%14%29%11%3
2161
16th to endDay
33%7%17%24%15%1
2249
August1st to 15thDay
34%8%14%26%15%1
2131
16th to endDay
37%412%26%16%3
2121
September1st to 15thDay
32%410%27%20%3
1980
16th to endDay
34%5%12%29%16%1
1827
October1st to 15thDay
38%310%24%21%1
1650
16th to endDay
42%412%24%13%1
1746
November1st to 15thDay
39%413%25%16%2
1582
16th to endDay
46%316%22%8%
1449
December1st to 15thDay
58%313%17%5%
1440
16th to endDay
62%411%13%8%
1536
January1st to 15thNight
47%414%18%13%
2506
16th to endNight
49%317%19%9%
2511
February1st to 15thNight
49%313%22%10%
2288
16th to endNight
42%313%27%12%
1927
March1st to 15thNight
41%314%26%12%1
2061
16th to endNight
52%414%17%9%1
2063
April1st to 15thNight
43%310%25%13%2
1797
16th to endNight
45%5%11%20%13%3
1740
May1st to 15thNight
45%413%23%12%
1391
16th to endNight
37%5%12%23%17%3
1370
June1st to 15thNight
37%5%14%26%15%2
1320
16th to endNight
30%6%14%22%20%4
1320
July1st to 15thNight
27%416%30%17%4
1240
16th to endNight
25%5%17%31%17%1
1347
August1st to 15thNight
27%5%15%30%17%3
1475
16th to endNight
32%5%11%25%19%6%
1729
September1st to 15thNight
30%49%26%25%3
1650
16th to endNight
29%311%32%20%2
1791
October1st to 15thNight
34%39%23%24%4
1980
16th to endNight
40%313%24%15%2
2126
November1st to 15thNight
34%312%25%19%4
2276
16th to endNight
44%313%27%11%
2511
December1st to 15thNight
53%313%21%8%
2520
16th to endNight
59%310%16%8%
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%16%8%
90
16th to endDay
20%10%37%22%7%1
96
February1st to 15thDay
14%23%35%15%11%
90
16th to endDay
17%13%35%14%16%2
81
March1st to 15thDay
25%16%40%12%5%
90
16th to endDay
29%9%27%22%9%2
144
April1st to 15thDay
20%9%35%24%10%
270
16th to endDay
30%427%22%11%3
243
May1st to 15thDay
21%13%30%23%9%2
385
16th to endDay
14%8%28%28%16%3
437
June1st to 15thDay
13%5%26%31%18%3
420
16th to endDay
9%428%31%19%6%
420
July1st to 15thDay
9%221%34%23%10%
400
16th to endDay
8%119%33%28%8%
445
August1st to 15thDay
7%117%34%30%7%
418
16th to endDay
10%312%32%32%8%
289
September1st to 15thDay
12%316%31%27%8%
255
16th to endDay
9%7%21%25%27%8%
194
October1st to 15thDay
313%28%32%11%11%
90
16th to endDay
21%7%30%31%9%
96
November1st to 15thDay
6%5%34%25%18%8%
90
16th to endDay
47%8%23%13%5%1
90
December1st to 15thDay
27%20%30%13%8%
90
16th to endDay
29%18%39%11%1
96
January1st to 15thNight
15%11%37%27%7%
900
16th to endNight
16%12%35%29%5%
960
February1st to 15thNight
18%11%35%27%6%
880
16th to endNight
18%8%38%28%4
665
March1st to 15thNight
19%10%32%27%8%1
621
16th to endNight
21%9%33%27%6%
576
April1st to 15thNight
18%11%35%28%5%
539
16th to endNight
21%6%28%32%10%
522
May1st to 15thNight
19%7%33%30%8%1
495
16th to endNight
13%330%35%15%
515
June1st to 15thNight
12%423%43%15%
495
16th to endNight
8%127%40%20%1
495
July1st to 15thNight
8%115%41%30%2
465
16th to endNight
5%115%43%31%2
522
August1st to 15thNight
6%19%47%32%2
494
16th to endNight
11%111%41%29%4
525
September1st to 15thNight
12%215%35%28%4
495
16th to endNight
8%423%34%26%3
574
October1st to 15thNight
16%6%26%29%19%1
660
16th to endNight
19%7%32%29%10%
704
November1st to 15thNight
15%11%34%28%10%
700
16th to endNight
20%12%33%25%7%
891
December1st to 15thNight
23%11%33%25%5%
900
16th to endNight
26%10%31%27%4
960
Page generated at 2017-04-25 06:48:26. Version ac04

Copyright 2017 A. Danko


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