Missoula
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Missoula clear sky chart from 2005-11-05 to

2017-09-12
.

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
50%
15192
13%
46754
12%
15163
51%
15163
23%
31296

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
35%
803
6%
2592
6%
802
36%
802
13%
2003
January16th to endNight
41%
768
12%
2688
11%
768
43%
768
17%
1891
February1st to 15thNight
33%
703
6%
2333
5%
699
35%
699
13%
1742
February16th to endNight
37%
632
9%
1923
9%
632
39%
632
16%
1439
March1st to 15thNight
42%
720
7%
2103
6%
720
44%
720
19%
1540
March16th to endNight
42%
768
7%
2112
5%
768
43%
768
18%
1594
April1st to 15thNight
46%
659
8%
1739
5%
659
47%
659
21%
1287
April16th to endNight
49%
540
14%
1620
11%
540
50%
540
22%
1101
May1st to 15thNight
50%
539
13%
1620
12%
539
52%
539
26%
1024
May16th to endNight
55%
374
9%
1349
12%
374
57%
374
19%
905
June1st to 15thNight
53%
360
7%
1260
7%
360
53%
360
21%
812
June16th to endNight
66%
360
15%
1260
17%
360
68%
360
35%
664
July1st to 15thNight
81%
340
19%
1204
24%
340
84%
340
53%
505
July16th to endNight
86%
376
27%
1416
42%
354
89%
354
59%
513
August1st to 15thNight
78%
488
25%
1561
27%
486
79%
486
49%
724
August16th to endNight
74%
573
29%
1719
25%
573
75%
573
49%
853
September1st to 15thNight
73%
691
25%
1837
18%
691
75%
691
49%
992
September16th to endNight
65%
656
24%
1815
20%
656
66%
656
36%
1094
October1st to 15thNight
55%
660
17%
1897
14%
660
58%
660
28%
1242
October16th to endNight
51%
704
14%
2274
12%
704
54%
704
22%
1535
November1st to 15thNight
41%
718
12%
2293
12%
718
44%
718
18%
1645
November16th to endNight
43%
900
7%
2559
6%
900
44%
900
20%
1851
December1st to 15thNight
37%
900
6%
2700
5%
900
38%
900
13%
2105
December16th to endNight
34%
960
6%
2880
4%
960
35%
960
14%
2235

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
7%8%37%6%35%5%5%7%37%
47928
Night
7%9%47%6%35%5%5%7%37%
46914
Cloud CoverDay
10%10%47%5%3445%6%37%
47929
Night
9%11%47%5%3445%6%36%
46917
TransparencyDay
45%5%14%20%11%3
47591
Night
45%5%17%20%8%2
46754
SeeingDay
14%11%24%28%16%3
5818
Night
13%6%19%40%19%1
15199

By Month

Percentage Cloud Cover NW (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
5%15%6%9%9%45%6%7%8%22%
1355
16th to endDay
6%15%6%9%7%35%436%29%
1536
February1st to 15thDay
6%13%5%10%8%5%8%5%6%6%23%
1530
16th to endDay
412%6%10%9%5%6%6%6%6%22%
1550
March1st to 15thDay
6%11%5%9%10%5%7%7%6%7%21%
1856
16th to endDay
8%13%5%10%10%5%6%7%6%6%19%
2111
April1st to 15thDay
8%11%5%11%8%46%5%7%8%21%
2207
16th to endDay
10%12%6%9%6%35%446%30%
2340
May1st to 15thDay
8%7%37%7%45%5%6%7%35%
2331
16th to endDay
15%8%47%8%35%5%6%7%26%
2758
June1st to 15thDay
15%6%36%6%36%5%5%7%32%
2700
16th to endDay
8%425%5%35%5%6%6%46%
2700
July1st to 15thDay
321342446%7%59%
2682
16th to endDay
211222335%5%69%
2657
August1st to 15thDay
3233235%5%8%60%
2391
16th to endDay
5%213313347%62%
2483
September1st to 15thDay
431442445%6%59%
2038
16th to endDay
8%5%26%42435%7%48%
1815
October1st to 15thDay
10%8%36%7%35%5%5%6%36%
1733
16th to endDay
9%9%38%8%5%6%5%5%8%29%
1598
November1st to 15thDay
7%13%5%10%9%5%6%5%5%7%23%
1552
16th to endDay
7%10%5%7%6%36%6%6%7%31%
1401
December1st to 15thDay
6%15%5%14%9%5%6%5%5%7%19%
1260
16th to endDay
6%13%5%13%8%5%7%5%6%7%18%
1344
January1st to 15thNight
7%13%6%10%7%47%6%5%6%23%
2592
16th to endNight
6%11%5%8%8%35%5%5%7%32%
2688
February1st to 15thNight
6%15%6%9%7%5%5%46%7%25%
2322
16th to endNight
412%5%9%9%46%6%6%6%26%
1923
March1st to 15thNight
5%10%47%7%47%7%7%8%28%
2103
16th to endNight
6%12%48%7%5%5%7%7%9%25%
2109
April1st to 15thNight
8%10%47%6%47%6%6%9%29%
1739
16th to endNight
10%9%37%5%3446%7%36%
1620
May1st to 15thNight
7%7%35%435%6%6%8%41%
1619
16th to endNight
13%8%36%5%35%5%5%9%32%
1349
June1st to 15thNight
16%445%435%5%5%7%38%
1260
16th to endNight
8%4133236%6%8%51%
1260
July1st to 15thNight
311111245%10%66%
1275
16th to endNight
1112212247%72%
1512
August1st to 15thNight
221322445%8%63%
1569
16th to endNight
322325%446%63%
1719
September1st to 15thNight
4313423346%61%
1837
16th to endNight
10%424434446%51%
1815
October1st to 15thNight
8%7%26%6%35%45%5%43%
1897
16th to endNight
10%8%36%5%35%5%5%7%36%
2274
November1st to 15thNight
9%11%5%8%5%45%5%5%7%31%
2293
16th to endNight
8%10%38%6%46%5%6%8%30%
2559
December1st to 15thNight
5%14%7%10%6%5%7%5%6%7%24%
2700
16th to endNight
7%14%6%11%8%36%6%6%6%22%
2880

Percentage Cloud Cover SW (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
9%20%7%10%7%2435%8%20%
1355
16th to endDay
9%19%5%10%5%2334429%
1536
February1st to 15thDay
10%19%6%10%7%35%445%21%
1530
16th to endDay
7%17%6%12%8%35%5%46%20%
1550
March1st to 15thDay
11%17%6%9%7%36%45%6%20%
1856
16th to endDay
12%16%6%10%7%45%5%5%5%19%
2112
April1st to 15thDay
11%15%6%10%6%46%5%5%6%21%
2207
16th to endDay
12%15%5%8%5%24446%29%
2340
May1st to 15thDay
9%9%47%5%46%45%7%35%
2331
16th to endDay
18%10%36%6%35%46%7%27%
2758
June1st to 15thDay
17%7%36%5%35%5%5%7%32%
2700
16th to endDay
9%5%245%245%6%6%46%
2700
July1st to 15thDay
321332445%6%59%
2682
16th to endDay
312222345%69%
2657
August1st to 15thDay
321242345%7%61%
2391
16th to endDay
5%312313447%62%
2483
September1st to 15thDay
6%314423337%58%
2038
16th to endDay
10%7%25%5%1335%6%47%
1815
October1st to 15thDay
13%9%36%5%345%48%35%
1733
16th to endDay
14%11%48%6%3445%8%27%
1598
November1st to 15thDay
14%16%7%9%5%35%35%5%23%
1552
16th to endDay
10%15%6%8%6%34346%30%
1401
December1st to 15thDay
10%18%7%11%6%46%5%35%19%
1260
16th to endDay
8%17%8%13%7%46%45%6%16%
1344
January1st to 15thNight
12%18%7%9%5%35%446%22%
2592
16th to endNight
9%15%6%8%5%24445%30%
2688
February1st to 15thNight
11%20%6%8%6%33445%24%
2322
16th to endNight
7%16%6%9%8%45%446%24%
1923
March1st to 15thNight
9%14%49%5%36%5%6%8%25%
2103
16th to endNight
10%14%5%8%6%46%5%7%7%24%
2112
April1st to 15thNight
9%11%46%7%46%5%6%8%28%
1739
16th to endNight
12%10%46%5%25%446%36%
1620
May1st to 15thNight
8%7%36%5%35%5%5%7%41%
1619
16th to endNight
13%7%36%6%36%5%6%7%32%
1349
June1st to 15thNight
16%6%346%2445%7%38%
1260
16th to endNight
8%41332446%8%51%
1260
July1st to 15thNight
31121245%8%66%
1275
16th to endNight
112221247%72%
1512
August1st to 15thNight
221221245%9%62%
1569
16th to endNight
4212323448%62%
1719
September1st to 15thNight
6%413313246%62%
1837
16th to endNight
12%41442435%7%50%
1815
October1st to 15thNight
10%7%36%5%35%5%5%5%41%
1897
16th to endNight
14%9%37%5%2445%6%36%
2274
November1st to 15thNight
15%14%47%6%33446%30%
2293
16th to endNight
11%13%5%8%6%3445%6%28%
2559
December1st to 15thNight
8%18%8%8%7%45%45%7%22%
2700
16th to endNight
10%18%8%11%7%35%5%5%6%19%
2880

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
59%7%19%11%1
1355
16th to endDay
54%5%16%16%42
1536
February1st to 15thDay
61%6%16%12%2
1530
16th to endDay
60%414%16%3
1550
March1st to 15thDay
59%6%19%11%3
1856
16th to endDay
62%7%15%12%2
2112
April1st to 15thDay
59%6%15%15%3
2207
16th to endDay
55%413%21%4
2340
May1st to 15thDay
45%417%23%8%
2331
16th to endDay
55%5%17%15%5%
2762
June1st to 15thDay
49%6%14%19%8%1
2700
16th to endDay
35%312%29%15%2
2700
July1st to 15thDay
24%310%25%27%8%
2524
16th to endDay
14%46%20%34%20%
2490
August1st to 15thDay
19%5%10%30%26%8%
2374
16th to endDay
21%310%30%26%6%
2483
September1st to 15thDay
26%310%31%21%6%
2038
16th to endDay
36%317%26%14%1
1815
October1st to 15thDay
46%5%18%23%5%
1733
16th to endDay
52%5%17%20%4
1598
November1st to 15thDay
59%6%16%13%4
1552
16th to endDay
49%7%23%17%2
1401
December1st to 15thDay
64%6%16%10%1
1260
16th to endDay
63%5%17%11%1
1344
January1st to 15thNight
59%6%18%11%2
2592
16th to endNight
51%5%18%18%41
2688
February1st to 15thNight
58%5%19%13%2
2333
16th to endNight
56%5%16%17%3
1923
March1st to 15thNight
50%8%22%15%3
2103
16th to endNight
53%8%19%16%2
2112
April1st to 15thNight
49%7%19%18%4
1739
16th to endNight
46%417%24%5%
1620
May1st to 15thNight
40%5%16%29%8%
1620
16th to endNight
46%7%20%17%7%
1349
June1st to 15thNight
44%5%16%23%8%1
1260
16th to endNight
28%5%15%32%15%2
1260
July1st to 15thNight
15%310%33%26%9%
1204
16th to endNight
12%27%28%31%17%
1416
August1st to 15thNight
18%5%10%32%25%9%
1561
16th to endNight
20%411%27%29%7%
1719
September1st to 15thNight
24%211%29%24%7%
1837
16th to endNight
32%5%15%25%17%2
1815
October1st to 15thNight
40%5%19%26%7%
1897
16th to endNight
46%5%18%22%6%
2274
November1st to 15thNight
52%5%17%18%4
2293
16th to endNight
51%5%23%17%3
2559
December1st to 15thNight
58%8%18%12%2
2700
16th to endNight
61%5%20%11%2
2880

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
6%116%33%26%15%
60
16th to endDay
15%7%10%39%17%9%
64
February1st to 15thDay
12%9%20%39%12%6%
83
16th to endDay
19%15%21%27%15%
209
March1st to 15thDay
24%17%29%21%6%
270
16th to endDay
22%17%31%22%5%
288
April1st to 15thDay
20%17%30%23%7%
269
16th to endDay
25%16%25%22%8%1
270
May1st to 15thDay
13%20%32%20%10%2
288
16th to endDay
21%9%18%27%16%5%
474
June1st to 15thDay
19%10%22%26%17%3
495
16th to endDay
12%10%24%29%20%2
495
July1st to 15thDay
6%8%22%29%28%3
458
16th to endDay
316%34%27%13%3
327
August1st to 15thDay
410%24%30%20%8%
315
16th to endDay
6%8%23%33%21%7%
332
September1st to 15thDay
9%11%27%24%21%7%
300
16th to endDay
12%10%21%29%20%5%
255
October1st to 15thDay
20%9%15%38%13%1
173
16th to endDay
17%319%35%17%6%
96
November1st to 15thDay
15%213%41%24%3
90
16th to endDay
13%322%44%15%
83
December1st to 15thDay
31%5%20%31%6%5%
60
16th to endDay
10%425%35%21%1
64
January1st to 15thNight
17%7%21%36%14%1
807
16th to endNight
14%6%24%35%16%1
768
February1st to 15thNight
16%9%25%36%11%1
704
16th to endNight
13%8%24%40%11%1
632
March1st to 15thNight
12%7%26%42%9%1
720
16th to endNight
15%7%22%42%11%
768
April1st to 15thNight
11%9%21%39%16%1
659
16th to endNight
16%6%19%42%15%
540
May1st to 15thNight
10%11%19%34%22%1
540
16th to endNight
17%213%30%33%2
375
June1st to 15thNight
17%415%38%22%3
360
16th to endNight
11%412%42%27%1
360
July1st to 15thNight
316%47%40%
340
16th to endNight
25%57%31%1
376
August1st to 15thNight
419%46%37%1
488
16th to endNight
5%411%41%35%1
573
September1st to 15thNight
7%19%40%34%4
691
16th to endNight
14%310%39%27%5%
656
October1st to 15thNight
12%417%43%20%1
660
16th to endNight
17%415%43%18%1
704
November1st to 15thNight
19%7%19%42%10%
718
16th to endNight
15%5%23%43%11%
900
December1st to 15thNight
15%7%24%40%12%1
900
16th to endNight
14%8%25%39%10%
960
Page generated at 2017-09-13 05:39:19. Version ac04

Copyright 2017 A. Danko


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