Portage (MI)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Portage (MI) clear sky chart from 2005-11-05 to 2017-09-18.

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%
15944
15%
46823
10%
15902
40%
15902
20%
32858

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
14%
900
8%
2506
3%
895
18%
895
10%
2059
January16th to endNight
16%
954
5%
2682
2%
954
19%
954
9%
2251
February1st to 15thNight
17%
701
9%
2181
3%
701
23%
701
11%
1716
February16th to endNight
25%
631
13%
1893
6%
631
32%
631
13%
1431
March1st to 15thNight
27%
720
14%
2133
9%
720
32%
720
19%
1510
March16th to endNight
30%
732
17%
2076
10%
732
37%
732
20%
1471
April1st to 15thNight
29%
539
14%
1797
9%
539
36%
539
19%
1227
April16th to endNight
33%
540
20%
1650
10%
540
43%
540
24%
1082
May1st to 15thNight
34%
540
14%
1620
7%
540
40%
540
22%
1120
May16th to endNight
46%
562
16%
1582
10%
561
51%
561
30%
994
June1st to 15thNight
51%
540
16%
1440
10%
540
57%
540
38%
880
June16th to endNight
57%
540
15%
1440
11%
540
60%
540
35%
897
July1st to 15thNight
64%
510
16%
1360
13%
510
66%
510
41%
797
July16th to endNight
68%
564
22%
1423
16%
531
70%
531
42%
821
August1st to 15thNight
68%
539
22%
1609
17%
536
71%
536
38%
896
August16th to endNight
64%
573
21%
1837
20%
573
67%
573
32%
1067
September1st to 15thNight
62%
612
27%
1872
24%
612
67%
612
36%
1064
September16th to endNight
56%
669
25%
1848
19%
669
59%
669
34%
1139
October1st to 15thNight
46%
660
24%
1840
18%
660
52%
660
29%
1192
October16th to endNight
25%
704
15%
2276
9%
704
34%
704
17%
1593
November1st to 15thNight
32%
700
19%
2276
16%
700
39%
700
20%
1502
November16th to endNight
23%
720
13%
2340
9%
720
29%
720
13%
1792
December1st to 15thNight
14%
834
6%
2454
2%
834
17%
834
9%
2049
December16th to endNight
12%
960
6%
2688
2%
960
17%
960
8%
2308

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%45%7%33%
47980
Night
15%9%47%5%34446%33%
46993
Cloud CoverDay
13%9%47%6%35%45%7%33%
47989
Night
15%9%47%5%34446%33%
46998
TransparencyDay
50%411%20%11%1
47668
Night
50%411%20%11%1
46823
SeeingDay
16%9%26%25%16%6%
5944
Night
20%8%28%29%12%1
15948

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
17%16%7%10%9%45%5%4414%
1432
16th to endDay
13%18%10%12%10%35%43412%
1541
February1st to 15thDay
13%13%7%14%10%5%6%34416%
1681
16th to endDay
14%13%8%13%7%45%345%18%
1580
March1st to 15thDay
14%11%5%9%6%45%447%25%
1816
16th to endDay
17%9%47%6%34446%31%
2157
April1st to 15thDay
19%12%45%5%23346%31%
2151
16th to endDay
17%7%34425%35%6%38%
2310
May1st to 15thDay
19%8%36%6%345%5%6%31%
2331
16th to endDay
12%6%25%4345%5%7%41%
2531
June1st to 15thDay
10%5%25%6%245%6%7%42%
2520
16th to endDay
9%5%245%35%6%7%9%38%
2520
July1st to 15thDay
7%325%5%35%46%10%46%
2520
16th to endDay
7%424435%6%7%10%43%
2649
August1st to 15thDay
7%415%7%26%6%6%9%42%
2340
16th to endDay
11%426%6%35%5%5%7%41%
2363
September1st to 15thDay
12%5%246%2445%6%44%
2075
16th to endDay
10%6%25%5%3445%9%41%
1837
October1st to 15thDay
15%7%26%6%34446%38%
1790
16th to endDay
22%9%36%5%25%446%28%
1595
November1st to 15thDay
14%9%36%435%35%6%37%
1582
16th to endDay
18%17%5%10%7%32445%20%
1620
December1st to 15thDay
17%17%11%11%6%2424317%
1503
16th to endDay
21%17%9%12%7%33335%11%
1536
January1st to 15thNight
19%15%8%10%7%3434418%
2506
16th to endNight
14%13%9%13%9%5%5%445%13%
2682
February1st to 15thNight
14%16%6%11%7%44345%21%
2179
16th to endNight
16%11%6%9%6%45%445%25%
1893
March1st to 15thNight
17%10%5%6%5%23346%33%
2120
16th to endNight
15%7%47%6%35%447%33%
2076
April1st to 15thNight
18%8%45%5%25%35%7%33%
1797
16th to endNight
18%6%35%42345%6%40%
1650
May1st to 15thNight
19%8%26%5%25%348%33%
1620
16th to endNight
12%6%2443345%9%42%
1580
June1st to 15thNight
10%4245%2335%10%46%
1440
16th to endNight
7%425%425%5%6%11%42%
1440
July1st to 15thNight
5%2245%3346%8%52%
1440
16th to endNight
6%4133235%7%9%51%
1519
August1st to 15thNight
5%3235%345%5%9%50%
1620
16th to endNight
10%4245%2445%6%49%
1837
September1st to 15thNight
11%42431345%7%51%
1872
16th to endNight
11%6%24424446%47%
1848
October1st to 15thNight
15%6%25%433345%44%
1840
16th to endNight
22%8%36%434345%32%
2276
November1st to 15thNight
15%10%36%5%23345%38%
2276
16th to endNight
20%13%5%8%7%23445%23%
2340
December1st to 15thNight
21%18%9%10%6%3333316%
2454
16th to endNight
22%17%8%10%6%3444412%
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
17%16%7%10%9%45%44413%
1432
16th to endDay
13%18%10%12%10%45%43312%
1541
February1st to 15thDay
13%13%8%14%10%5%6%34416%
1681
16th to endDay
14%13%8%13%7%45%345%18%
1580
March1st to 15thDay
14%11%5%9%6%35%447%24%
1826
16th to endDay
17%9%47%6%34446%31%
2156
April1st to 15thDay
19%12%46%5%23336%31%
2151
16th to endDay
17%7%34425%35%6%38%
2310
May1st to 15thDay
18%8%26%6%3445%7%31%
2331
16th to endDay
12%6%25%425%45%7%41%
2531
June1st to 15thDay
10%5%25%5%25%5%6%7%42%
2520
16th to endDay
9%5%245%35%7%7%10%37%
2520
July1st to 15thDay
6%425%5%35%46%10%46%
2520
16th to endDay
7%424435%6%7%10%42%
2649
August1st to 15thDay
7%415%6%36%6%6%9%42%
2340
16th to endDay
11%426%7%35%5%47%41%
2363
September1st to 15thDay
12%5%246%245%46%44%
2075
16th to endDay
10%6%25%5%2445%9%41%
1837
October1st to 15thDay
15%7%26%6%34446%38%
1790
16th to endDay
22%9%36%5%25%446%28%
1595
November1st to 15thDay
14%9%46%5%3445%5%37%
1582
16th to endDay
18%17%5%10%7%33345%20%
1620
December1st to 15thDay
16%18%11%11%6%2433318%
1503
16th to endDay
21%17%9%12%7%33235%11%
1536
January1st to 15thNight
19%15%8%10%7%3434418%
2506
16th to endNight
14%14%9%12%9%5%6%445%13%
2682
February1st to 15thNight
13%16%6%11%7%44345%21%
2172
16th to endNight
16%10%6%9%6%45%45%5%25%
1893
March1st to 15thNight
17%11%46%5%33436%33%
2133
16th to endNight
15%6%5%6%6%25%447%33%
2076
April1st to 15thNight
18%8%45%43436%7%33%
1797
16th to endNight
17%6%35%42445%6%40%
1650
May1st to 15thNight
19%8%26%5%34347%34%
1619
16th to endNight
12%6%2443346%9%42%
1580
June1st to 15thNight
10%415%5%1436%9%47%
1440
16th to endNight
7%425%425%5%6%11%43%
1440
July1st to 15thNight
5%2245%3346%9%52%
1440
16th to endNight
5%4233235%6%9%51%
1519
August1st to 15thNight
5%3235%25%5%6%9%50%
1620
16th to endNight
9%425%5%2445%6%49%
1837
September1st to 15thNight
11%42432345%7%51%
1872
16th to endNight
11%6%34424447%47%
1848
October1st to 15thNight
15%5%25%43335%5%44%
1840
16th to endNight
22%8%36%434345%33%
2276
November1st to 15thNight
15%10%37%5%23345%38%
2276
16th to endNight
20%13%5%8%6%23446%23%
2340
December1st to 15thNight
21%17%9%10%6%3333316%
2454
16th to endNight
22%17%8%10%6%3444412%
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
72%311%9%2
1433
16th to endDay
75%39%8%2
1541
February1st to 15thDay
70%37%13%4
1683
16th to endDay
68%49%12%4
1580
March1st to 15thDay
58%412%17%7%
1826
16th to endDay
54%411%22%6%1
2157
April1st to 15thDay
54%39%20%11%
2151
16th to endDay
46%313%18%14%3
2310
May1st to 15thDay
52%412%22%8%
2331
16th to endDay
40%413%27%12%1
2535
June1st to 15thDay
38%312%26%17%
2520
16th to endDay
39%5%14%21%17%1
2520
July1st to 15thDay
34%410%25%21%3
2371
16th to endDay
34%5%15%24%17%2
2482
August1st to 15thDay
36%5%14%26%15%2
2327
16th to endDay
40%411%26%14%2
2363
September1st to 15thDay
39%311%25%17%2
2075
16th to endDay
39%410%28%16%
1837
October1st to 15thDay
45%311%24%14%
1790
16th to endDay
55%412%19%7%
1595
November1st to 15thDay
47%310%23%12%1
1582
16th to endDay
65%310%15%3
1620
December1st to 15thDay
70%29%13%2
1503
16th to endDay
75%310%7%2
1536
January1st to 15thNight
68%310%12%4
2506
16th to endNight
71%313%8%2
2682
February1st to 15thNight
64%310%14%5%
2181
16th to endNight
60%311%18%41
1893
March1st to 15thNight
52%313%19%9%1
2133
16th to endNight
51%312%22%9%1
2076
April1st to 15thNight
49%411%20%13%
1797
16th to endNight
44%49%21%16%3
1650
May1st to 15thNight
49%312%22%10%2
1620
16th to endNight
38%414%24%15%2
1582
June1st to 15thNight
32%412%30%18%1
1440
16th to endNight
33%6%18%23%16%1
1440
July1st to 15thNight
28%5%15%26%21%2
1360
16th to endNight
27%5%15%25%21%3
1423
August1st to 15thNight
28%5%13%28%21%2
1609
16th to endNight
33%5%9%26%20%4
1837
September1st to 15thNight
31%49%30%21%2
1872
16th to endNight
36%38%29%20%1
1848
October1st to 15thNight
40%48%26%18%
1840
16th to endNight
53%210%22%9%
2276
November1st to 15thNight
47%310%22%13%2
2276
16th to endNight
61%411%18%3
2340
December1st to 15thNight
71%39%11%4
2454
16th to endNight
73%310%9%2
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
21%18%41%14%4
90
16th to endDay
26%11%38%18%41
96
February1st to 15thDay
22%23%34%16%3
90
16th to endDay
18%13%38%22%6%1
81
March1st to 15thDay
31%15%30%18%5%
116
16th to endDay
25%12%31%20%8%1
288
April1st to 15thDay
27%8%32%21%8%1
270
16th to endDay
21%9%31%20%12%5%
270
May1st to 15thDay
24%12%24%24%10%4
288
16th to endDay
17%9%26%25%15%5%
431
June1st to 15thDay
12%6%30%32%14%5%
495
16th to endDay
12%10%30%27%15%4
495
July1st to 15thDay
10%326%27%21%9%
475
16th to endDay
8%221%33%23%10%
509
August1st to 15thDay
8%219%23%27%18%
313
16th to endDay
14%317%27%23%12%
332
September1st to 15thDay
11%6%15%25%27%13%
315
16th to endDay
13%6%16%25%30%8%
262
October1st to 15thDay
17%9%22%27%19%4
255
16th to endDay
22%14%35%25%2
107
November1st to 15thDay
10%13%23%36%13%3
90
16th to endDay
32%21%32%10%4
90
December1st to 15thDay
26%30%25%14%3
90
16th to endDay
20%34%40%31
96
January1st to 15thNight
26%13%35%19%4
900
16th to endNight
19%12%36%27%3
954
February1st to 15thNight
21%12%37%23%4
704
16th to endNight
21%13%31%28%4
631
March1st to 15thNight
24%10%31%25%7%
720
16th to endNight
18%10%33%29%7%
732
April1st to 15thNight
21%10%32%28%6%
539
16th to endNight
22%6%33%28%7%1
540
May1st to 15thNight
24%5%29%30%9%
540
16th to endNight
16%426%36%14%1
563
June1st to 15thNight
13%225%42%16%
540
16th to endNight
9%223%43%20%1
540
July1st to 15thNight
8%118%44%24%3
510
16th to endNight
7%215%40%30%3
564
August1st to 15thNight
8%15%44%27%3
539
16th to endNight
12%310%37%30%5%
573
September1st to 15thNight
13%215%36%26%5%
612
16th to endNight
14%5%18%29%27%4
669
October1st to 15thNight
18%5%23%32%18%1
660
16th to endNight
26%12%30%21%7%
704
November1st to 15thNight
22%10%28%26%11%
700
16th to endNight
27%11%28%24%6%
720
December1st to 15thNight
30%12%34%18%4
834
16th to endNight
32%12%34%17%2
960
Page generated at 2017-09-19 07:32:21. Version ac04

Copyright 2017 A. Danko


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