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 2017-03-14.

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
37%
15434
17%
45177
10%
15392
44%
15392
23%
30334

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
29%
716
14%
2148
7%
716
35%
716
19%
1488
March16th to endNight
33%
553
15%
1838
12%
553
38%
553
18%
1277
April1st to 15thNight
30%
494
15%
1647
10%
494
39%
494
20%
1112
April16th to endNight
33%
495
19%
1601
11%
495
43%
495
23%
1062
May1st to 15thNight
35%
495
16%
1433
8%
495
42%
495
22%
1022
May16th to endNight
48%
514
17%
1369
10%
513
53%
513
32%
886
June1st to 15thNight
50%
495
17%
1320
10%
495
54%
495
32%
845
June16th to endNight
52%
495
14%
1320
8%
495
55%
495
31%
889
July1st to 15thNight
64%
465
18%
1240
11%
465
66%
465
39%
741
July16th to endNight
68%
522
20%
1305
15%
489
70%
489
40%
778
August1st to 15thNight
75%
494
24%
1430
23%
491
77%
491
43%
775
August16th to endNight
67%
525
20%
1750
21%
525
71%
525
34%
982
September1st to 15thNight
61%
495
30%
1650
28%
495
67%
495
35%
907
September16th to endNight
56%
648
26%
1806
18%
648
61%
648
35%
1084
October1st to 15thNight
45%
660
25%
1919
18%
660
52%
660
31%
1176
October16th to endNight
30%
704
18%
2228
10%
704
40%
704
21%
1452
November1st to 15thNight
33%
700
23%
2276
16%
700
43%
700
25%
1403
November16th to endNight
25%
792
16%
2412
8%
792
34%
792
19%
1654
December1st to 15thNight
22%
900
13%
2520
5%
900
29%
900
17%
1894
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%
45535
Night
14%8%35%424446%40%
45346
Cloud CoverDay
13%8%36%5%35%45%7%36%
45544
Night
14%8%35%424446%39%
45351
TransparencyDay
46%6%12%21%11%1
45221
Night
44%5%11%22%13%1
45178
SeeingDay
15%6%27%27%16%6%
5176
Night
18%7%30%30%12%1
15438

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
16%11%46%424446%33%
1774
16th to endDay
17%9%37%5%25%447%32%
2041
April1st to 15thDay
18%11%46%5%34445%30%
1971
16th to endDay
19%9%25%433447%34%
2029
May1st to 15thDay
20%7%47%6%35%5%5%7%27%
2185
16th to endDay
12%6%36%5%25%5%6%7%38%
2393
June1st to 15thDay
13%5%35%4245%6%8%39%
2310
16th to endDay
10%5%36%425%5%6%10%39%
2310
July1st to 15thDay
8%4245%35%6%7%8%43%
2310
16th to endDay
7%5%26%5%46%5%6%9%40%
2459
August1st to 15thDay
7%4245%35%6%6%9%43%
2190
16th to endDay
11%425%435%5%5%7%43%
2100
September1st to 15thDay
13%314423447%49%
1977
16th to endDay
10%6%35%5%3436%8%43%
1815
October1st to 15thDay
16%6%25%423346%44%
1708
16th to endDay
19%8%25%5%34346%36%
1642
November1st to 15thDay
13%8%46%4345%5%5%39%
1582
16th to endDay
18%10%37%5%23336%35%
1548
December1st to 15thDay
17%12%5%7%6%34346%27%
1440
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
17%8%45%434446%37%
2135
16th to endNight
17%8%46%444437%34%
1838
April1st to 15thNight
19%7%45%424436%36%
1647
16th to endNight
19%8%3431334442%
1601
May1st to 15thNight
17%5%35%435%5%6%7%33%
1433
16th to endNight
11%4245%245%6%9%42%
1368
June1st to 15thNight
12%5%245%2345%7%45%
1320
16th to endNight
8%5%246%45%6%6%8%41%
1320
July1st to 15thNight
8%313425%46%10%51%
1320
16th to endNight
7%3143245%6%10%49%
1401
August1st to 15thNight
42134235%6%10%54%
1439
16th to endNight
9%32431446%8%50%
1750
September1st to 15thNight
10%424423335%57%
1650
16th to endNight
10%3235%24346%51%
1806
October1st to 15thNight
12%5%25%423345%49%
1919
16th to endNight
19%7%24423345%42%
2228
November1st to 15thNight
13%8%24424346%46%
2276
16th to endNight
16%10%36%5%24346%36%
2412
December1st to 15thNight
20%10%47%5%34445%30%
2520
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%
1784
16th to endDay
17%9%37%6%25%45%7%31%
2040
April1st to 15thDay
18%10%46%5%3435%5%30%
1971
16th to endDay
19%9%25%434446%33%
2029
May1st to 15thDay
19%8%46%6%35%5%5%7%26%
2185
16th to endDay
11%6%35%5%35%5%6%7%38%
2393
June1st to 15thDay
12%5%35%4345%6%9%39%
2310
16th to endDay
9%5%36%435%5%6%10%39%
2310
July1st to 15thDay
7%4245%35%6%7%8%43%
2310
16th to endDay
6%5%36%5%36%5%6%9%40%
2459
August1st to 15thDay
7%5%245%346%6%9%43%
2190
16th to endDay
11%5%245%35%5%48%43%
2100
September1st to 15thDay
13%41342345%7%49%
1977
16th to endDay
10%6%246%2436%8%43%
1815
October1st to 15thDay
15%7%25%423346%44%
1708
16th to endDay
19%8%35%5%34346%36%
1642
November1st to 15thDay
12%9%45%4245%5%6%39%
1582
16th to endDay
18%10%37%5%23336%35%
1548
December1st to 15thDay
17%12%5%8%6%35%35%6%26%
1440
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
17%9%45%5%34346%37%
2148
16th to endNight
17%8%35%45%4447%34%
1838
April1st to 15thNight
19%7%45%424445%36%
1647
16th to endNight
19%8%34413345%41%
1601
May1st to 15thNight
16%6%35%5%35%5%6%7%33%
1432
16th to endNight
11%5%145%2446%10%42%
1368
June1st to 15thNight
11%5%245%2445%7%45%
1320
16th to endNight
8%5%246%36%5%7%8%41%
1320
July1st to 15thNight
8%33425%5%5%10%51%
1320
16th to endNight
6%214425%5%6%10%49%
1401
August1st to 15thNight
322342347%10%53%
1439
16th to endNight
9%31432446%9%50%
1750
September1st to 15thNight
10%324413335%56%
1650
16th to endNight
10%3235%2435%6%51%
1806
October1st to 15thNight
11%6%25%413445%49%
1919
16th to endNight
19%7%25%323346%41%
2228
November1st to 15thNight
13%8%35%424346%46%
2276
16th to endNight
16%10%36%5%24346%36%
2412
December1st to 15thNight
20%9%47%5%34445%30%
2520
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
52%6%13%20%7%
1784
16th to endDay
52%6%13%20%6%
2041
April1st to 15thDay
55%48%21%8%
1971
16th to endDay
50%5%12%17%11%2
2029
May1st to 15thDay
55%7%11%20%5%
2185
16th to endDay
43%8%12%21%12%1
2397
June1st to 15thDay
40%7%11%25%14%1
2310
16th to endDay
38%8%12%21%16%1
2310
July1st to 15thDay
34%7%13%26%15%1
2161
16th to endDay
36%9%17%21%12%2
2292
August1st to 15thDay
33%8%13%28%13%1
2175
16th to endDay
37%7%11%24%17%2
2100
September1st to 15thDay
33%6%10%26%20%2
1977
16th to endDay
37%5%10%28%15%1
1815
October1st to 15thDay
40%5%12%26%15%
1708
16th to endDay
48%5%12%21%9%1
1642
November1st to 15thDay
43%5%12%22%13%1
1582
16th to endDay
51%412%24%6%
1548
December1st to 15thDay
57%5%14%16%6%
1440
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%11%2
2148
16th to endNight
50%5%12%22%8%1
1838
April1st to 15thNight
47%5%9%21%14%1
1647
16th to endNight
44%5%9%24%11%4
1601
May1st to 15thNight
47%7%12%21%10%
1433
16th to endNight
36%7%12%22%17%3
1370
June1st to 15thNight
37%5%11%26%17%1
1320
16th to endNight
38%7%13%18%19%2
1320
July1st to 15thNight
29%5%11%30%19%2
1240
16th to endNight
27%8%16%28%16%2
1305
August1st to 15thNight
23%7%14%32%20%1
1430
16th to endNight
29%6%12%28%18%4
1750
September1st to 15thNight
30%48%27%27%2
1650
16th to endNight
32%5%10%32%17%1
1806
October1st to 15thNight
35%5%10%27%19%1
1919
16th to endNight
44%410%25%12%1
2228
November1st to 15thNight
40%49%23%18%3
2276
16th to endNight
49%413%22%10%
2412
December1st to 15thNight
55%5%9%20%7%
2520
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
35%15%34%10%31
85
16th to endDay
28%5%29%20%12%2
170
April1st to 15thDay
24%10%30%24%8%1
210
16th to endDay
21%7%27%27%10%5%
210
May1st to 15thDay
25%11%28%21%10%3
277
16th to endDay
14%8%31%24%14%5%
437
June1st to 15thDay
12%5%32%30%14%5%
420
16th to endDay
11%6%30%30%14%7%
420
July1st to 15thDay
7%328%30%19%11%
400
16th to endDay
7%124%33%21%11%
445
August1st to 15thDay
8%18%32%24%15%
358
16th to endDay
12%313%28%30%12%
268
September1st to 15thDay
11%414%33%24%10%
255
16th to endDay
12%5%19%27%26%9%
254
October1st to 15thDay
10%10%25%27%20%5%
148
16th to endDay
23%11%30%29%5%
96
November1st to 15thDay
7%7%33%27%17%5%
90
16th to endDay
30%13%38%7%10%
90
December1st to 15thDay
17%16%36%23%5%
90
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%
716
16th to endNight
20%7%33%27%10%1
553
April1st to 15thNight
21%12%32%27%5%
494
16th to endNight
24%5%32%28%7%
495
May1st to 15thNight
19%5%33%28%11%
495
16th to endNight
12%5%27%36%17%
515
June1st to 15thNight
12%424%42%14%
495
16th to endNight
8%5%27%40%17%1
495
July1st to 15thNight
9%20%41%25%2
465
16th to endNight
6%117%45%27%1
522
August1st to 15thNight
411%51%28%3
494
16th to endNight
10%14%39%30%4
525
September1st to 15thNight
10%217%36%26%5%
495
16th to endNight
11%5%20%33%25%3
648
October1st to 15thNight
14%7%27%29%19%1
660
16th to endNight
23%10%31%24%9%
704
November1st to 15thNight
18%9%34%24%11%
700
16th to endNight
20%11%35%25%6%
792
December1st to 15thNight
26%9%36%22%4
900
16th to endNight
29%9%34%22%3
960
Page generated at 2017-03-15 10:32:39. Version ac04

Copyright 2017 A. Danko


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