Monroe
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Monroe clear sky chart from 2005-11-06 to 2024-01-14.

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%
24682
17%
74693
10%
24625
42%
24625
22%
50362

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 10thNight
22%
950
14%
2648
5%
946
30%
946
19%
1903
January11th to 20thNight
18%
918
11%
2569
4%
918
24%
918
14%
1988
January21st to endNight
19%
990
10%
2664
3%
990
25%
990
15%
2061
February1st to 10thNight
21%
900
11%
2340
3%
900
26%
900
18%
1756
February11th to 20thNight
22%
763
17%
2162
6%
763
31%
763
19%
1499
February21st to endNight
19%
592
17%
1776
5%
592
31%
592
17%
1245
March1st to 10thNight
22%
720
13%
2160
6%
720
29%
720
18%
1522
March11th to 20thNight
31%
608
19%
2048
11%
608
41%
608
22%
1282
March21st to endNight
27%
594
15%
2021
11%
594
34%
594
15%
1466
April1st to 10thNight
25%
540
14%
1800
7%
540
35%
540
19%
1211
April11th to 20thNight
30%
533
19%
1775
14%
533
40%
533
18%
1204
April21st to endNight
31%
540
15%
1763
9%
540
41%
540
21%
1180
May1st to 10thNight
33%
540
14%
1542
8%
540
38%
540
23%
1078
May11th to 20thNight
35%
531
17%
1417
9%
531
41%
531
24%
1005
May21st to endNight
46%
584
16%
1551
8%
582
52%
582
30%
1014
June1st to 10thNight
56%
540
16%
1440
9%
540
60%
540
35%
911
June11th to 20thNight
49%
540
19%
1440
11%
540
52%
540
35%
905
June21st to endNight
54%
540
18%
1440
10%
540
57%
540
35%
909
July1st to 10thNight
69%
525
17%
1400
12%
525
70%
525
44%
803
July11th to 20thNight
63%
522
22%
1392
15%
522
66%
522
42%
809
July21st to endNight
66%
591
22%
1487
16%
558
68%
558
43%
855
August1st to 10thNight
68%
537
22%
1485
21%
534
69%
534
38%
882
August11th to 20thNight
68%
534
22%
1724
23%
534
71%
534
37%
957
August21st to endNight
64%
594
22%
1980
23%
594
69%
594
34%
1098
September1st to 10thNight
59%
540
24%
1800
23%
540
64%
540
34%
1009
September11th to 20thNight
58%
571
31%
1831
27%
571
65%
571
35%
1021
September21st to endNight
49%
720
24%
1980
15%
720
55%
720
33%
1218
October1st to 10thNight
45%
720
22%
2131
16%
720
51%
720
31%
1296
October11th to 20thNight
33%
720
20%
2160
10%
720
43%
720
25%
1385
October21st to endNight
30%
792
16%
2524
10%
792
37%
792
20%
1709
November1st to 10thNight
30%
740
24%
2406
15%
740
43%
740
26%
1453
November11th to 20thNight
24%
764
17%
2474
9%
764
34%
764
18%
1685
November21st to endNight
26%
950
17%
2660
8%
950
34%
950
21%
1849
December1st to 10thNight
22%
950
12%
2660
4%
950
29%
950
17%
1968
December11th to 20thNight
22%
949
12%
3206
4%
948
29%
948
13%
2350
December21st to endNight
16%
1040
7%
4837
3%
1026
24%
1026
7%
3876

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
13%9%47%6%35%5%5%7%37%
74787
Night
14%9%46%5%3445%7%39%
74996
TransparencyDay
45%7%13%21%12%1
74487
Night
45%6%12%22%14%2
74816
SeeingDay
16%11%29%25%14%5%
14702
Night
17%10%31%30%11%1
24691

By Month

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 10thDay
11%12%6%8%7%45%45%7%32%
1517
11th to 20thDay
12%15%5%13%7%3445%6%24%
1464
21st to endDay
14%14%6%12%7%45%5%46%23%
1689
February1st to 10thDay
12%13%6%9%6%345%6%6%30%
1620
11th to 20thDay
14%11%5%7%6%36%446%35%
1684
21st to endDay
14%13%5%10%7%33346%32%
1480
March1st to 10thDay
14%11%6%7%6%345%5%7%32%
1800
11th to 20thDay
13%9%5%7%5%3345%8%39%
1926
21st to endDay
20%11%47%6%45%5%5%6%29%
2335
April1st to 10thDay
18%11%48%6%25%45%6%31%
2160
11th to 20thDay
17%9%47%6%4446%6%34%
2134
21st to endDay
20%10%47%5%3445%6%33%
2196
May1st to 10thDay
17%8%47%7%46%46%8%29%
2416
11th to 20thDay
18%8%36%5%45%5%5%7%35%
2479
21st to endDay
15%7%36%6%36%5%5%8%36%
2725
June1st to 10thDay
11%325%5%46%6%7%8%43%
2520
11th to 20thDay
12%5%25%5%35%5%7%8%43%
2520
21st to endDay
12%5%36%6%35%7%6%10%37%
2520
July1st to 10thDay
7%425%5%35%6%7%9%47%
2520
11th to 20thDay
7%5%25%5%36%6%8%9%44%
2520
21st to endDay
8%5%25%5%45%5%6%10%45%
2743
August1st to 10thDay
6%5%35%6%46%6%8%10%41%
2441
11th to 20thDay
10%5%35%5%35%5%6%8%44%
2176
21st to endDay
10%5%36%4335%5%8%47%
2376
September1st to 10thDay
12%6%25%5%35%46%7%45%
2160
11th to 20thDay
13%42442345%7%52%
2111
21st to endDay
12%8%26%5%345%47%44%
1980
October1st to 10thDay
13%7%35%5%24446%47%
1827
11th to 20thDay
20%8%37%6%2446%6%36%
1800
21st to endDay
19%10%345%2345%6%39%
1832
November1st to 10thDay
12%8%36%5%3445%6%44%
1672
11th to 20thDay
14%11%48%6%4445%6%34%
1703
21st to endDay
14%12%48%5%24346%37%
1520
December1st to 10thDay
14%13%5%8%435%45%5%33%
1520
11th to 20thDay
13%13%5%10%6%25%45%7%29%
1918
21st to endDay
20%20%10%10%7%345%4415%
2783
January1st to 10thNight
12%12%6%9%6%34345%36%
2648
11th to 20thNight
14%14%6%10%7%44445%27%
2569
21st to endNight
14%12%6%10%7%445%5%7%26%
2664
February1st to 10thNight
13%13%6%8%6%45%45%5%32%
2340
11th to 20thNight
12%10%47%6%4445%6%38%
2161
21st to endNight
17%11%5%6%5%2445%6%34%
1776
March1st to 10thNight
17%10%5%6%5%35%446%35%
2160
11th to 20thNight
12%8%36%6%45%45%8%41%
2048
21st to endNight
20%10%5%7%5%35%35%6%30%
2021
April1st to 10thNight
17%9%36%6%245%5%6%38%
1800
11th to 20thNight
20%9%36%5%33446%37%
1775
21st to endNight
16%8%36%6%345%5%8%36%
1763
May1st to 10thNight
15%8%26%7%25%5%6%8%35%
1542
11th to 20thNight
17%8%25%6%245%5%7%37%
1416
21st to endNight
11%6%36%5%35%6%5%10%42%
1551
June1st to 10thNight
8%5%235%45%6%6%8%47%
1440
11th to 20thNight
12%5%2443436%11%45%
1440
21st to endNight
10%5%25%42446%9%48%
1440
July1st to 10thNight
6%423425%5%7%11%53%
1440
11th to 20thNight
6%5%2342445%8%56%
1440
21st to endNight
7%32444446%9%53%
1575
August1st to 10thNight
5%425%5%35%5%6%9%51%
1494
11th to 20thNight
8%42443435%8%53%
1724
21st to endNight
8%425%4345%5%7%53%
1980
September1st to 10thNight
10%425%425%347%54%
1800
11th to 20thNight
11%42342445%7%54%
1831
21st to endNight
11%6%245%35%447%50%
1980
October1st to 10thNight
12%6%26%5%2435%6%50%
2131
11th to 20thNight
17%8%35%433446%43%
2160
21st to endNight
19%9%45%5%34446%38%
2524
November1st to 10thNight
12%7%36%423445%50%
2406
11th to 20thNight
14%10%37%6%45%446%37%
2474
21st to endNight
17%10%46%5%24346%38%
2660
December1st to 10thNight
15%12%48%7%45%5%5%5%31%
2660
11th to 20thNight
15%13%5%9%6%35%45%5%30%
3279
21st to endNight
21%16%7%10%7%34445%19%
4884

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 10thDay
52%6%15%16%11%
1518
11th to 20thDay
60%6%13%13%7%
1464
21st to endDay
61%6%11%13%8%1
1689
February1st to 10thDay
55%5%13%18%8%1
1620
11th to 20thDay
50%5%12%21%9%2
1693
21st to endDay
55%5%10%19%10%2
1480
March1st to 10thDay
50%7%14%20%8%1
1800
11th to 20thDay
44%7%13%22%13%2
1926
21st to endDay
55%7%10%19%7%1
2335
April1st to 10thDay
53%6%10%20%11%
2160
11th to 20thDay
50%7%10%20%12%2
2134
21st to endDay
51%7%11%18%12%2
2196
May1st to 10thDay
51%8%14%19%7%
2416
11th to 20thDay
48%7%13%20%11%
2483
21st to endDay
44%9%11%20%14%2
2725
June1st to 10thDay
36%8%15%25%15%1
2520
11th to 20thDay
35%9%14%22%18%2
2520
21st to endDay
40%10%15%22%13%1
2520
July1st to 10thDay
31%9%17%27%14%2
2451
11th to 20thDay
32%10%16%24%15%2
2445
21st to endDay
33%7%17%26%14%3
2591
August1st to 10thDay
33%10%18%27%12%1
2426
11th to 20thDay
37%8%14%26%14%1
2176
21st to endDay
33%7%12%27%18%3
2376
September1st to 10thDay
37%8%11%25%18%2
2160
11th to 20thDay
31%6%12%32%16%2
2111
21st to endDay
38%7%10%28%16%1
1980
October1st to 10thDay
38%7%11%29%15%1
1827
11th to 20thDay
48%5%11%23%12%1
1800
21st to endDay
46%6%11%22%13%1
1832
November1st to 10thDay
41%5%15%24%14%2
1672
11th to 20thDay
50%6%14%19%10%1
1703
21st to endDay
49%5%16%21%8%1
1520
December1st to 10thDay
53%7%14%17%8%1
1520
11th to 20thDay
54%6%16%15%8%2
1915
21st to endDay
72%6%9%8%5%
2783
January1st to 10thNight
50%5%11%20%12%1
2648
11th to 20thNight
59%6%13%13%8%
2569
21st to endNight
57%7%11%15%9%1
2664
February1st to 10thNight
54%6%11%17%11%1
2340
11th to 20thNight
47%6%12%20%13%1
2162
21st to endNight
50%5%12%19%10%3
1776
March1st to 10thNight
50%6%13%19%10%2
2160
11th to 20thNight
41%6%13%22%16%2
2048
21st to endNight
55%5%10%19%10%2
2021
April1st to 10thNight
46%6%12%21%14%2
1800
11th to 20thNight
48%5%7%18%17%4
1775
21st to endNight
45%6%14%21%12%2
1763
May1st to 10thNight
45%8%14%20%12%
1542
11th to 20thNight
46%7%11%21%14%1
1417
21st to endNight
36%9%15%22%16%1
1552
June1st to 10thNight
31%9%13%25%20%1
1440
11th to 20thNight
34%7%11%24%23%2
1440
21st to endNight
33%8%16%23%17%3
1440
July1st to 10thNight
24%8%17%31%17%3
1400
11th to 20thNight
26%7%14%29%21%3
1392
21st to endNight
25%8%20%26%18%4
1487
August1st to 10thNight
28%8%15%30%16%3
1485
11th to 20thNight
29%6%16%29%19%1
1724
21st to endNight
29%8%12%27%20%4
1980
September1st to 10thNight
30%7%13%25%23%2
1800
11th to 20thNight
29%7%12%32%18%2
1831
21st to endNight
34%6%10%30%19%1
1980
October1st to 10thNight
35%6%10%27%21%2
2131
11th to 20thNight
41%5%12%23%18%1
2160
21st to endNight
47%6%11%23%12%1
2524
November1st to 10thNight
37%5%11%26%18%3
2406
11th to 20thNight
49%5%14%20%11%1
2474
21st to endNight
47%5%13%23%10%1
2660
December1st to 10thNight
54%6%11%20%8%1
2660
11th to 20thNight
55%6%13%18%7%1
3281
21st to endNight
66%6%9%13%4
4884

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 10thDay
17%13%30%30%9%1
270
11th to 20thDay
21%15%38%20%41
249
21st to endDay
18%17%36%23%5%1
264
February1st to 10thDay
17%20%44%15%5%
240
11th to 20thDay
24%23%30%21%3
240
21st to endDay
25%22%38%14%1
198
March1st to 10thDay
14%24%42%16%5%
240
11th to 20thDay
19%23%34%17%5%2
240
21st to endDay
28%14%30%20%7%1
421
April1st to 10thDay
24%14%34%21%5%
420
11th to 20thDay
25%17%26%19%10%3
412
21st to endDay
23%12%30%22%10%1
420
May1st to 10thDay
22%11%31%26%8%2
499
11th to 20thDay
22%10%30%23%12%3
625
21st to endDay
17%8%28%22%17%8%
679
June1st to 10thDay
8%7%30%30%20%5%
630
11th to 20thDay
12%6%31%30%16%5%
630
21st to endDay
13%8%29%29%16%4
630
July1st to 10thDay
8%317%33%26%14%
621
11th to 20thDay
9%5%28%29%20%8%
618
21st to endDay
7%426%34%21%7%
684
August1st to 10thDay
8%219%35%27%10%
626
11th to 20thDay
11%5%20%26%23%14%
490
21st to endDay
11%6%20%29%23%9%
495
September1st to 10thDay
15%6%24%25%24%6%
450
11th to 20thDay
11%5%22%29%21%12%
450
21st to endDay
14%13%25%25%18%6%
450
October1st to 10thDay
15%12%29%25%17%2
297
11th to 20thDay
22%23%31%17%7%
270
21st to endDay
29%16%28%21%5%1
297
November1st to 10thDay
17%14%38%20%9%1
270
11th to 20thDay
19%20%35%17%9%1
270
21st to endDay
24%12%41%19%4
270
December1st to 10thDay
16%22%36%19%6%2
270
11th to 20thDay
20%13%39%20%8%
270
21st to endDay
26%17%41%15%2
297
January1st to 10thNight
18%15%36%25%6%1
950
11th to 20thNight
21%12%37%25%5%1
918
21st to endNight
19%13%36%27%4
990
February1st to 10thNight
20%12%38%24%6%
900
11th to 20thNight
17%16%39%24%5%
766
21st to endNight
24%15%38%20%4
592
March1st to 10thNight
21%12%38%23%6%
720
11th to 20thNight
17%11%35%30%8%
608
21st to endNight
24%11%31%27%6%1
594
April1st to 10thNight
20%14%36%25%5%
540
11th to 20thNight
26%13%26%28%7%
533
21st to endNight
21%9%34%27%9%1
540
May1st to 10thNight
17%8%36%31%8%
540
11th to 20thNight
20%6%32%31%11%
531
21st to endNight
12%431%35%17%1
584
June1st to 10thNight
9%6%25%45%15%1
540
11th to 20thNight
15%428%39%13%1
540
21st to endNight
11%424%44%16%1
540
July1st to 10thNight
7%215%38%34%4
525
11th to 20thNight
7%323%42%23%3
522
21st to endNight
7%120%45%25%2
591
August1st to 10thNight
5%216%46%28%3
537
11th to 20thNight
8%313%39%30%6%
534
21st to endNight
10%216%43%26%3
594
September1st to 10thNight
9%422%37%23%5%
540
11th to 20thNight
12%323%34%25%4
571
21st to endNight
13%8%25%33%19%2
720
October1st to 10thNight
15%6%29%31%18%1
720
11th to 20thNight
20%13%30%29%9%
720
21st to endNight
23%10%33%27%6%1
792
November1st to 10thNight
15%11%39%26%10%1
740
11th to 20thNight
19%15%36%24%5%
764
21st to endNight
21%13%35%24%7%
950
December1st to 10thNight
19%13%38%23%6%
950
11th to 20thNight
21%13%35%25%5%1
950
21st to endNight
27%15%34%22%2
1045
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