Traverse City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Traverse City clear sky chart from 2005-11-06 to 2024-03-28.

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
32%
24975
10%
81513
8%
24879
36%
24879
14%
62526

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
13%
945
3%
4406
1%
926
15%
926
3%
3897
January11th to 20thNight
14%
945
2%
4440
2%
930
16%
930
3%
4120
January21st to endNight
16%
1032
1%
4881
2%
1023
17%
1023
3%
4422
February1st to 10thNight
17%
851
6%
2549
3%
851
20%
851
7%
2188
February11th to 20thNight
16%
742
8%
2219
3%
740
21%
740
9%
1850
February21st to endNight
19%
628
8%
1884
2%
628
25%
628
11%
1511
March1st to 10thNight
30%
760
15%
2280
9%
760
35%
760
19%
1641
March11th to 20thNight
29%
760
17%
2155
10%
760
35%
760
20%
1549
March21st to endNight
32%
748
16%
2183
11%
748
37%
748
19%
1578
April1st to 10thNight
28%
540
12%
1800
7%
540
35%
540
15%
1280
April11th to 20thNight
32%
533
18%
1692
12%
533
40%
533
19%
1184
April21st to endNight
37%
540
17%
1620
10%
540
43%
540
23%
1100
May1st to 10thNight
38%
540
15%
1620
10%
540
42%
540
22%
1122
May11th to 20thNight
39%
531
16%
1507
11%
531
45%
531
22%
1058
May21st to endNight
51%
583
14%
1552
9%
582
56%
582
32%
988
June1st to 10thNight
46%
540
14%
1440
8%
540
51%
540
31%
943
June11th to 20thNight
53%
456
16%
1356
13%
456
56%
456
29%
833
June21st to endNight
54%
540
15%
1440
9%
540
58%
540
33%
911
July1st to 10thNight
66%
525
17%
1400
11%
525
70%
525
43%
807
July11th to 20thNight
59%
522
17%
1392
12%
522
62%
522
37%
846
July21st to endNight
59%
591
18%
1487
13%
558
60%
558
36%
922
August1st to 10thNight
63%
537
18%
1512
14%
534
66%
534
33%
917
August11th to 20thNight
62%
534
20%
1598
15%
534
67%
534
34%
947
August21st to endNight
56%
594
18%
1896
16%
594
58%
594
27%
1172
September1st to 10thNight
53%
540
18%
1800
16%
540
57%
540
28%
1091
September11th to 20thNight
53%
720
22%
1980
18%
720
56%
720
32%
1265
September21st to endNight
45%
720
18%
1980
14%
720
47%
720
25%
1354
October1st to 10thNight
40%
720
17%
1980
12%
720
44%
720
23%
1379
October11th to 20thNight
27%
720
10%
2253
7%
720
32%
720
13%
1730
October21st to endNight
22%
792
10%
2574
7%
792
27%
792
11%
2038
November1st to 10thNight
26%
740
14%
2406
10%
740
32%
740
14%
1770
November11th to 20thNight
18%
760
9%
2470
7%
760
22%
760
9%
2001
November21st to endNight
18%
807
6%
2540
4%
807
21%
807
8%
2158
December1st to 10thNight
12%
950
2%
2850
1%
950
14%
950
5%
2544
December11th to 20thNight
14%
950
2%
3491
1%
949
15%
949
5%
3108
December21st to endNight
9%
1039
2%
4880
1%
1026
12%
1026
3%
4302

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%11%5%8%7%45%45%6%31%
78222
Night
15%13%6%10%8%44446%26%
81726
TransparencyDay
54%6%10%19%10%1
77922
Night
60%5%11%16%8%1
81547
SeeingDay
18%11%28%25%13%4
14813
Night
20%9%29%30%11%1
25006

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
12%24%16%18%9%442236%
2527
11th to 20thDay
13%17%9%19%17%9%5%3224
2530
21st to endDay
18%20%12%13%9%46%4348%
2783
February1st to 10thDay
8%17%8%13%18%5%6%44313%
1626
11th to 20thDay
12%14%8%14%14%6%5%5%4415%
1848
21st to endDay
12%15%9%11%10%45%45%5%19%
1570
March1st to 10thDay
12%12%5%11%10%45%45%6%27%
1900
11th to 20thDay
11%10%7%10%7%45%5%46%32%
2024
21st to endDay
17%12%5%7%7%44447%29%
2343
April1st to 10thDay
18%13%5%7%5%35%446%29%
2160
11th to 20thDay
20%12%46%434446%34%
2217
21st to endDay
15%11%47%5%3446%7%33%
2340
May1st to 10thDay
15%9%36%6%3445%6%40%
2340
11th to 20thDay
15%7%36%4345%47%41%
2386
21st to endDay
10%6%345%36%5%5%8%45%
2725
June1st to 10thDay
13%5%25%435%46%7%45%
2520
11th to 20thDay
11%6%25%6%345%5%9%44%
2520
21st to endDay
12%5%25%5%35%5%6%9%43%
2520
July1st to 10thDay
8%423425%46%9%53%
2520
11th to 20thDay
11%5%34435%5%6%9%46%
2520
21st to endDay
9%5%245%245%6%10%49%
2743
August1st to 10thDay
9%5%246%35%6%6%9%45%
2417
11th to 20thDay
11%5%245%35%6%6%7%46%
2303
21st to endDay
14%6%25%42445%7%46%
2458
September1st to 10thDay
15%435%5%35%46%7%43%
2142
11th to 20thDay
14%5%25%4345%5%8%45%
1980
21st to endDay
16%6%27%435%5%7%8%36%
1980
October1st to 10thDay
19%8%36%5%4345%7%35%
1980
11th to 20thDay
24%15%47%6%46%446%20%
1706
21st to endDay
24%16%5%9%7%45%45%5%16%
1782
November1st to 10thDay
16%17%5%7%5%34447%27%
1672
11th to 20thDay
13%21%7%11%6%5%5%45%6%16%
1710
21st to endDay
17%23%9%12%7%34345%15%
1633
December1st to 10thDay
15%21%13%16%9%45%3339%
1330
11th to 20thDay
14%19%10%15%10%5%5%445%10%
1684
21st to endDay
19%22%12%12%9%444349%
2783
January1st to 10thNight
13%24%10%17%9%4432311%
4428
11th to 20thNight
11%17%9%18%17%7%43337%
4440
21st to endNight
16%22%11%12%10%5%5%4438%
4884
February1st to 10thNight
10%16%9%13%15%6%6%44313%
2549
11th to 20thNight
12%13%8%15%11%5%45%5%5%18%
2218
21st to endNight
14%15%6%14%8%35%345%21%
1884
March1st to 10thNight
12%11%5%9%7%35%45%5%34%
2280
11th to 20thNight
11%12%5%8%8%34445%35%
2155
21st to endNight
16%10%48%7%345%5%6%32%
2183
April1st to 10thNight
18%13%38%5%345%5%6%30%
1800
11th to 20thNight
21%9%46%5%23447%35%
1692
21st to endNight
17%9%36%5%335%46%38%
1620
May1st to 10thNight
15%7%37%6%35%5%6%7%35%
1620
11th to 20thNight
16%8%37%6%36%5%5%6%35%
1506
21st to endNight
11%6%25%4345%6%9%44%
1551
June1st to 10thNight
14%5%26%5%245%5%7%44%
1440
11th to 20thNight
12%6%26%435%6%6%10%43%
1356
21st to endNight
10%5%25%6%35%45%8%47%
1440
July1st to 10thNight
9%31432445%11%53%
1440
11th to 20thNight
7%5%25%435%5%5%9%49%
1440
21st to endNight
9%5%345%3445%8%50%
1575
August1st to 10thNight
8%426%5%45%47%9%46%
1521
11th to 20thNight
9%425%5%345%6%7%49%
1598
21st to endNight
12%6%36%5%3435%7%46%
1896
September1st to 10thNight
11%7%36%43345%6%49%
1800
11th to 20thNight
15%5%25%5%3345%6%46%
1980
21st to endNight
18%6%27%6%3445%7%38%
1980
October1st to 10thNight
17%9%37%5%34446%38%
1980
11th to 20thNight
23%11%47%6%35%5%5%6%25%
2253
21st to endNight
24%14%5%9%7%34345%22%
2574
November1st to 10thNight
14%15%48%6%35%5%5%6%28%
2406
11th to 20thNight
15%20%6%10%7%46%5%45%18%
2470
21st to endNight
17%19%9%11%7%445%35%15%
2540
December1st to 10thNight
14%20%12%15%9%45%44410%
2850
11th to 20thNight
13%19%9%18%10%45%45%410%
3493
21st to endNight
23%21%10%11%7%4443410%
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
87%35%41
2528
11th to 20thDay
89%3431
2530
21st to endDay
81%5%9%41
2783
February1st to 10thDay
77%48%9%2
1626
11th to 20thDay
73%5%9%9%4
1858
21st to endDay
67%5%9%15%31
1570
March1st to 10thDay
58%7%11%17%7%1
1900
11th to 20thDay
53%6%11%20%8%2
2024
21st to endDay
56%6%10%20%7%1
2343
April1st to 10thDay
58%5%9%18%10%
2160
11th to 20thDay
53%48%19%15%1
2217
21st to endDay
49%7%11%15%16%3
2340
May1st to 10thDay
46%5%9%25%13%2
2340
11th to 20thDay
43%6%10%22%17%3
2390
21st to endDay
38%7%13%25%16%2
2725
June1st to 10thDay
37%7%10%27%16%2
2520
11th to 20thDay
38%6%12%23%20%2
2520
21st to endDay
38%7%13%25%15%1
2520
July1st to 10thDay
28%6%13%32%20%2
2451
11th to 20thDay
35%8%11%28%17%2
2445
21st to endDay
32%7%11%28%20%2
2591
August1st to 10thDay
35%7%14%31%12%1
2402
11th to 20thDay
35%8%11%30%14%2
2303
21st to endDay
38%7%13%25%16%2
2458
September1st to 10thDay
40%7%12%25%15%2
2142
11th to 20thDay
36%7%14%30%11%1
1980
21st to endDay
44%7%15%25%9%
1980
October1st to 10thDay
49%6%11%23%10%1
1980
11th to 20thDay
66%5%10%15%4
1706
21st to endDay
70%6%11%9%4
1782
November1st to 10thDay
58%6%10%19%8%
1672
11th to 20thDay
69%5%12%10%4
1710
21st to endDay
73%5%12%8%1
1633
December1st to 10thDay
83%46%6%1
1330
11th to 20thDay
79%5%9%6%1
1680
21st to endDay
80%7%7%42
2783
January1st to 10thNight
81%47%8%1
4428
11th to 20thNight
85%46%41
4440
21st to endNight
82%6%7%5%1
4884
February1st to 10thNight
75%38%10%4
2549
11th to 20thNight
69%6%9%13%3
2219
21st to endNight
65%5%11%15%4
1884
March1st to 10thNight
51%6%14%20%8%
2280
11th to 20thNight
51%6%11%20%11%1
2155
21st to endNight
53%5%11%21%10%1
2183
April1st to 10thNight
55%5%10%20%11%1
1800
11th to 20thNight
51%47%20%14%3
1692
21st to endNight
47%411%21%14%3
1620
May1st to 10thNight
47%6%11%20%12%4
1620
11th to 20thNight
49%5%8%20%15%3
1507
21st to endNight
36%7%15%26%15%2
1552
June1st to 10thNight
39%6%11%28%15%1
1440
11th to 20thNight
36%7%13%25%16%3
1356
21st to endNight
36%6%13%26%17%2
1440
July1st to 10thNight
27%6%14%31%19%4
1400
11th to 20thNight
32%6%15%26%21%2
1392
21st to endNight
33%6%14%29%17%1
1487
August1st to 10thNight
33%7%17%29%12%2
1512
11th to 20thNight
32%6%16%29%16%1
1598
21st to endNight
38%6%13%25%17%1
1896
September1st to 10thNight
36%7%12%23%21%1
1800
11th to 20thNight
38%5%14%30%12%
1980
21st to endNight
45%6%15%26%8%1
1980
October1st to 10thNight
48%411%23%13%1
1980
11th to 20thNight
60%5%12%17%5%
2253
21st to endNight
65%5%11%14%5%
2574
November1st to 10thNight
56%6%12%18%7%1
2406
11th to 20thNight
68%5%12%10%5%1
2470
21st to endNight
73%5%12%9%2
2540
December1st to 10thNight
79%5%7%7%1
2850
11th to 20thNight
78%6%10%42
3496
21st to endNight
79%6%10%41
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
18%15%38%21%7%1
270
11th to 20thDay
21%13%40%20%6%
270
21st to endDay
24%14%31%25%6%1
297
February1st to 10thDay
17%23%37%17%43
270
11th to 20thDay
19%22%37%19%4
270
21st to endDay
21%25%40%12%2
225
March1st to 10thDay
21%20%39%17%3
270
11th to 20thDay
24%13%30%24%9%2
394
21st to endDay
27%13%28%22%9%1
490
April1st to 10thDay
27%12%30%24%5%2
420
11th to 20thDay
25%19%26%17%10%3
412
21st to endDay
21%14%26%25%10%3
420
May1st to 10thDay
21%15%30%19%11%4
423
11th to 20thDay
15%10%31%29%11%4
532
21st to endDay
13%9%28%29%17%5%
679
June1st to 10thDay
15%8%29%30%15%4
630
11th to 20thDay
14%9%28%32%13%4
630
21st to endDay
14%6%27%32%16%4
630
July1st to 10thDay
8%5%27%32%21%7%
621
11th to 20thDay
12%7%24%32%17%7%
618
21st to endDay
8%5%28%34%19%6%
684
August1st to 10thDay
11%5%21%31%23%9%
536
11th to 20thDay
12%5%18%29%24%12%
439
21st to endDay
17%8%20%28%21%6%
495
September1st to 10thDay
17%7%22%28%17%9%
450
11th to 20thDay
13%6%20%30%22%8%
450
21st to endDay
19%10%18%26%20%6%
450
October1st to 10thDay
22%11%24%25%14%4
450
11th to 20thDay
28%16%29%21%5%
333
21st to endDay
32%15%32%15%5%1
297
November1st to 10thDay
25%17%32%16%10%
270
11th to 20thDay
19%20%41%16%4
270
21st to endDay
24%23%36%14%3
257
December1st to 10thDay
29%16%33%16%6%1
180
11th to 20thDay
22%22%36%16%31
184
21st to endDay
23%20%38%15%31
297
January1st to 10thNight
20%13%34%24%7%1
950
11th to 20thNight
23%13%34%23%7%1
950
21st to endNight
18%10%34%29%8%1
1045
February1st to 10thNight
17%11%37%28%7%1
851
11th to 20thNight
20%14%36%24%6%
743
21st to endNight
23%15%33%24%5%
628
March1st to 10thNight
16%10%34%28%10%1
760
11th to 20thNight
17%12%34%31%5%1
760
21st to endNight
20%10%29%33%7%1
748
April1st to 10thNight
24%8%32%29%6%1
540
11th to 20thNight
23%11%28%27%9%1
533
21st to endNight
19%8%30%33%9%1
540
May1st to 10thNight
18%6%31%34%11%1
540
11th to 20thNight
20%6%26%35%13%
531
21st to endNight
14%425%36%19%1
584
June1st to 10thNight
17%426%36%15%1
540
11th to 20thNight
13%5%22%45%14%1
456
21st to endNight
12%324%38%21%1
540
July1st to 10thNight
10%316%42%27%2
525
11th to 20thNight
11%321%38%25%2
522
21st to endNight
11%319%41%24%2
591
August1st to 10thNight
9%117%44%27%1
537
11th to 20thNight
9%318%38%28%4
534
21st to endNight
13%419%40%22%2
594
September1st to 10thNight
15%422%33%22%4
540
11th to 20thNight
17%321%33%22%4
720
21st to endNight
21%7%20%31%18%4
720
October1st to 10thNight
21%7%25%29%17%1
720
11th to 20thNight
30%9%28%27%6%1
720
21st to endNight
31%12%27%23%6%1
792
November1st to 10thNight
25%11%30%27%6%
740
11th to 20thNight
24%15%35%22%4
760
21st to endNight
27%12%36%22%3
807
December1st to 10thNight
24%15%36%21%4
950
11th to 20thNight
22%15%36%21%41
950
21st to endNight
27%12%37%21%3
1045
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