Marengo
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Marengo clear sky chart from 2005-11-05 to 2017-12-02.

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
37%
16305
18%
47788
11%
16263
44%
16263
24%
31942

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
21%
900
15%
2506
5%
895
29%
895
18%
1838
January16th to endNight
21%
960
12%
2646
5%
960
28%
960
16%
1975
February1st to 15thNight
23%
821
14%
2232
4%
821
30%
821
20%
1599
February16th to endNight
25%
631
18%
1893
8%
631
34%
631
18%
1318
March1st to 15thNight
30%
720
14%
2160
7%
720
36%
720
19%
1492
March16th to endNight
32%
603
15%
2005
11%
603
38%
603
18%
1400
April1st to 15thNight
30%
539
15%
1797
10%
539
39%
539
19%
1219
April16th to endNight
33%
540
19%
1746
11%
540
43%
540
22%
1171
May1st to 15thNight
36%
540
15%
1563
8%
540
42%
540
22%
1101
May16th to endNight
47%
562
18%
1497
10%
561
53%
561
31%
973
June1st to 15thNight
53%
540
16%
1440
10%
540
56%
540
34%
902
June16th to endNight
51%
540
16%
1440
8%
540
55%
540
31%
965
July1st to 15thNight
63%
510
17%
1360
11%
510
66%
510
39%
810
July16th to endNight
67%
564
21%
1417
15%
531
71%
531
41%
838
August1st to 15thNight
75%
539
22%
1562
22%
536
76%
536
42%
852
August16th to endNight
68%
573
21%
1910
22%
573
71%
573
34%
1068
September1st to 15thNight
62%
540
29%
1800
28%
540
68%
540
37%
971
September16th to endNight
57%
707
28%
1970
20%
707
63%
707
36%
1168
October1st to 15thNight
43%
720
23%
2094
16%
720
50%
720
30%
1304
October16th to endNight
30%
768
19%
2431
11%
768
40%
768
21%
1585
November1st to 15thNight
32%
760
23%
2471
15%
760
42%
760
24%
1547
November16th to endNight
25%
858
17%
2613
8%
858
36%
858
20%
1760
December1st to 15thNight
22%
910
13%
2547
5%
910
30%
910
17%
1909
December16th to endNight
16%
960
11%
2688
3%
960
24%
960
11%
2177

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%8%36%5%3445%7%36%
48665
Night
14%7%35%424446%40%
47957
Cloud CoverDay
13%8%36%5%3445%7%36%
48674
Night
14%8%35%424446%40%
47962
TransparencyDay
45%6%12%21%11%1
48351
Night
44%5%11%22%14%1
47789
SeeingDay
15%6%28%26%16%6%
6245
Night
17%7%30%30%12%1
16309

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
14%13%46%6%36%5%5%7%26%
1432
16th to endDay
12%13%7%11%6%25%445%25%
1575
February1st to 15thDay
13%14%5%8%6%35%445%28%
1628
16th to endDay
14%12%37%7%24346%33%
1580
March1st to 15thDay
15%11%46%424446%34%
1790
16th to endDay
18%9%37%5%24446%31%
2227
April1st to 15thDay
18%10%46%6%34445%30%
2151
16th to endDay
19%9%25%433447%33%
2214
May1st to 15thDay
19%7%46%6%35%45%7%28%
2385
16th to endDay
13%6%36%5%25%5%5%7%37%
2617
June1st to 15thDay
12%5%25%4245%6%8%41%
2520
16th to endDay
9%5%36%5%35%5%6%9%39%
2520
July1st to 15thDay
8%4245%35%6%7%8%43%
2520
16th to endDay
6%5%26%5%46%5%6%9%42%
2655
August1st to 15thDay
7%4245%35%6%6%9%43%
2388
16th to endDay
11%5%25%5%35%45%7%43%
2292
September1st to 15thDay
12%313424447%51%
2157
16th to endDay
9%5%25%5%3435%7%45%
1980
October1st to 15thDay
17%6%25%423346%42%
1863
16th to endDay
18%8%25%43435%6%37%
1791
November1st to 15thDay
14%8%46%43445%6%38%
1717
16th to endDay
17%9%36%5%23336%38%
1677
December1st to 15thDay
17%12%5%7%6%34346%27%
1450
16th to endDay
19%14%6%9%6%35%435%21%
1536
January1st to 15thNight
15%12%47%5%24245%34%
2506
16th to endNight
12%11%6%10%6%25%446%29%
2646
February1st to 15thNight
13%13%5%6%433435%36%
2230
16th to endNight
16%11%45%6%24346%34%
1893
March1st to 15thNight
16%8%45%434446%37%
2147
16th to endNight
17%8%45%4445%47%33%
2005
April1st to 15thNight
19%7%45%425%436%35%
1797
16th to endNight
19%7%35%423345%41%
1746
May1st to 15thNight
18%5%35%435%5%5%7%35%
1563
16th to endNight
11%425%5%245%5%10%42%
1496
June1st to 15thNight
11%4235%2345%7%48%
1440
16th to endNight
8%5%246%46%6%6%8%42%
1440
July1st to 15thNight
7%313325%5%6%10%51%
1440
16th to endNight
6%3143245%6%10%50%
1513
August1st to 15thNight
42134235%7%10%53%
1571
16th to endNight
9%32431446%8%51%
1910
September1st to 15thNight
9%324423335%58%
1800
16th to endNight
9%3235%24347%52%
1970
October1st to 15thNight
14%5%25%423345%48%
2094
16th to endNight
19%8%25%423345%42%
2431
November1st to 15thNight
14%8%24424346%45%
2471
16th to endNight
16%9%36%424346%37%
2613
December1st to 15thNight
20%9%47%5%34445%31%
2547
16th to endNight
23%13%5%8%5%3434422%
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
14%13%5%6%6%36%46%6%26%
1432
16th to endDay
12%13%7%11%6%245%45%25%
1575
February1st to 15thDay
13%13%5%8%6%35%5%35%27%
1628
16th to endDay
13%12%36%7%3435%6%32%
1580
March1st to 15thDay
16%11%46%5%245%46%33%
1800
16th to endDay
18%9%37%6%2445%6%31%
2226
April1st to 15thDay
18%10%46%6%3435%5%30%
2151
16th to endDay
19%9%25%434447%33%
2214
May1st to 15thDay
18%8%36%6%35%5%5%7%28%
2385
16th to endDay
12%6%35%5%35%5%6%7%37%
2617
June1st to 15thDay
11%5%35%4345%6%8%41%
2520
16th to endDay
9%5%36%5%35%5%6%10%39%
2520
July1st to 15thDay
7%4245%35%6%7%8%43%
2520
16th to endDay
6%435%5%36%5%6%9%41%
2655
August1st to 15thDay
6%5%245%35%6%6%9%43%
2388
16th to endDay
11%5%245%35%448%42%
2292
September1st to 15thDay
12%31342445%7%51%
2157
16th to endDay
9%6%245%2436%7%46%
1980
October1st to 15thDay
17%7%25%423346%42%
1863
16th to endDay
19%8%25%5%34345%37%
1791
November1st to 15thDay
13%9%46%4245%5%6%38%
1717
16th to endDay
17%10%36%5%23336%38%
1677
December1st to 15thDay
16%12%5%8%6%35%35%6%26%
1450
16th to endDay
19%14%6%9%6%3444421%
1536
January1st to 15thNight
15%11%47%5%34245%33%
2506
16th to endNight
12%11%6%10%6%345%46%28%
2646
February1st to 15thNight
13%13%46%5%23445%35%
2223
16th to endNight
15%11%45%6%24346%34%
1893
March1st to 15thNight
16%9%45%5%34346%37%
2160
16th to endNight
17%8%35%444447%33%
2005
April1st to 15thNight
19%7%45%4245%45%35%
1797
16th to endNight
19%8%35%414445%40%
1746
May1st to 15thNight
17%6%35%435%5%5%7%35%
1562
16th to endNight
11%5%145%345%6%10%41%
1496
June1st to 15thNight
10%5%235%2445%7%48%
1440
16th to endNight
8%4246%36%5%7%7%42%
1440
July1st to 15thNight
7%33425%5%5%10%51%
1440
16th to endNight
6%2144245%6%10%50%
1513
August1st to 15thNight
322342347%10%53%
1571
16th to endNight
9%31432445%9%51%
1910
September1st to 15thNight
9%314413335%57%
1800
16th to endNight
9%3235%2435%7%52%
1970
October1st to 15thNight
13%6%25%423345%48%
2094
16th to endNight
18%8%25%423345%41%
2431
November1st to 15thNight
13%8%35%424346%45%
2471
16th to endNight
15%10%36%42435%6%37%
2613
December1st to 15thNight
20%9%47%5%34445%30%
2547
16th to endNight
22%13%6%8%5%35%34422%
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
56%5%14%15%8%
1433
16th to endDay
59%6%12%13%7%
1575
February1st to 15thDay
58%5%10%17%7%1
1630
16th to endDay
51%7%11%20%8%
1580
March1st to 15thDay
51%6%13%20%7%
1800
16th to endDay
53%7%12%19%6%
2227
April1st to 15thDay
55%49%20%8%
2151
16th to endDay
50%5%12%17%12%2
2214
May1st to 15thDay
53%7%11%21%5%
2385
16th to endDay
43%7%12%21%12%1
2621
June1st to 15thDay
37%7%11%25%15%1
2520
16th to endDay
38%8%12%21%16%1
2520
July1st to 15thDay
34%7%13%26%15%1
2371
16th to endDay
34%8%17%21%13%3
2488
August1st to 15thDay
34%8%13%27%13%1
2373
16th to endDay
37%6%11%24%17%2
2292
September1st to 15thDay
32%6%11%26%21%3
2157
16th to endDay
35%5%11%29%16%1
1980
October1st to 15thDay
41%5%11%24%15%
1863
16th to endDay
48%412%22%10%1
1791
November1st to 15thDay
44%5%13%21%12%1
1717
16th to endDay
49%412%26%7%
1677
December1st to 15thDay
57%5%14%16%6%
1450
16th to endDay
65%5%9%10%7%
1536
January1st to 15thNight
53%410%19%11%
2506
16th to endNight
55%5%13%15%10%
2646
February1st to 15thNight
51%411%20%12%
2232
16th to endNight
51%311%22%7%2
1893
March1st to 15thNight
48%5%13%17%12%2
2160
16th to endNight
50%6%12%21%8%1
2005
April1st to 15thNight
47%5%9%21%14%1
1797
16th to endNight
45%5%9%23%11%4
1746
May1st to 15thNight
46%7%12%22%10%
1563
16th to endNight
36%7%12%22%17%2
1498
June1st to 15thNight
34%6%11%25%19%2
1440
16th to endNight
37%8%12%19%19%2
1440
July1st to 15thNight
29%6%12%29%19%2
1360
16th to endNight
26%7%15%28%17%3
1417
August1st to 15thNight
22%8%13%33%19%1
1562
16th to endNight
29%6%13%28%18%4
1910
September1st to 15thNight
29%48%27%28%2
1800
16th to endNight
31%5%10%33%18%1
1970
October1st to 15thNight
37%49%26%19%2
2094
16th to endNight
45%410%25%13%1
2431
November1st to 15thNight
41%49%23%17%3
2471
16th to endNight
47%413%23%10%
2613
December1st to 15thNight
55%5%9%21%7%
2547
16th to endNight
65%48%13%6%
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
26%8%36%25%2
90
16th to endDay
20%6%35%29%6%2
96
February1st to 15thDay
20%13%47%16%2
90
16th to endDay
27%11%30%20%8%1
81
March1st to 15thDay
33%14%35%12%31
90
16th to endDay
30%5%31%18%11%2
229
April1st to 15thDay
25%10%30%24%7%1
270
16th to endDay
22%10%26%26%9%4
270
May1st to 15thDay
23%11%28%23%11%3
342
16th to endDay
16%9%32%22%13%4
517
June1st to 15thDay
10%431%32%15%5%
495
16th to endDay
10%7%33%27%13%6%
495
July1st to 15thDay
6%329%30%19%10%
475
16th to endDay
7%123%34%21%11%
515
August1st to 15thDay
8%19%31%24%15%
427
16th to endDay
11%315%28%27%13%
332
September1st to 15thDay
9%315%32%27%11%
315
16th to endDay
9%420%28%28%8%
314
October1st to 15thDay
17%10%23%26%18%4
198
16th to endDay
23%13%28%27%6%
144
November1st to 15thDay
17%6%35%22%14%4
135
16th to endDay
24%14%39%13%8%
135
December1st to 15thDay
17%15%36%24%6%
94
16th to endDay
29%15%46%6%2
96
January1st to 15thNight
21%12%38%20%6%
900
16th to endNight
17%11%37%28%4
960
February1st to 15thNight
21%9%38%25%5%
824
16th to endNight
21%10%35%25%6%
631
March1st to 15thNight
21%8%34%27%7%
720
16th to endNight
20%6%33%28%9%1
603
April1st to 15thNight
22%11%31%28%5%
539
16th to endNight
23%5%33%27%8%
540
May1st to 15thNight
20%5%32%29%11%
540
16th to endNight
12%6%28%36%16%
563
June1st to 15thNight
11%323%45%14%
540
16th to endNight
7%5%29%39%17%
540
July1st to 15thNight
8%20%41%25%2
510
16th to endNight
6%118%45%27%1
564
August1st to 15thNight
410%50%29%4
539
16th to endNight
9%14%39%30%4
573
September1st to 15thNight
9%217%37%27%5%
540
16th to endNight
11%420%33%26%2
707
October1st to 15thNight
16%7%27%29%17%1
720
16th to endNight
23%10%32%24%9%
768
November1st to 15thNight
19%8%35%24%11%
760
16th to endNight
19%11%36%25%6%
858
December1st to 15thNight
26%9%36%23%4
910
16th to endNight
29%9%34%22%3
960
Page generated at 2017-12-03 10:16:47. Version ac04

Copyright 2017 A. Danko


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