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Blackfoot
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blackfoot clear sky chart from 2005-11-06 to 2024-01-16.

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
41%
23497
11%
74697
7%
23468
45%
23468
19%
51188

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
32%
946
9%
2836
4%
946
36%
946
15%
2144
January11th to 20thNight
32%
926
14%
2776
7%
926
40%
926
18%
1977
January21st to endNight
26%
932
12%
2912
5%
932
34%
932
13%
2207
February1st to 10thNight
38%
720
11%
2520
8%
720
43%
720
14%
1838
February11th to 20thNight
38%
700
12%
2300
10%
700
43%
700
17%
1615
February21st to endNight
44%
592
15%
1902
13%
592
50%
592
20%
1294
March1st to 10thNight
40%
720
13%
2160
11%
720
43%
720
18%
1577
March11th to 20thNight
41%
720
15%
1980
9%
720
45%
720
21%
1421
March21st to endNight
42%
792
11%
2175
6%
792
44%
792
20%
1610
April1st to 10thNight
47%
608
14%
1688
8%
608
51%
608
24%
1171
April11th to 20thNight
39%
533
13%
1601
10%
533
43%
533
18%
1148
April21st to endNight
46%
540
12%
1620
12%
540
48%
540
22%
1099
May1st to 10thNight
47%
414
10%
1325
8%
414
49%
414
19%
915
May11th to 20thNight
47%
354
6%
1239
4%
354
48%
354
22%
795
May21st to endNight
46%
388
0%
1358
0%
388
46%
388
16%
943
June1st to 10thNight
47%
360
0%
1260
0%
360
47%
360
17%
876
June11th to 20thNight
40%
360
0%
1260
0%
360
40%
360
12%
944
June21st to endNight
56%
360
0%
1260
0%
360
56%
360
22%
799
July1st to 10thNight
58%
350
0%
1225
0%
350
58%
350
23%
767
July11th to 20thNight
56%
348
0%
1218
0%
348
56%
348
21%
778
July21st to endNight
62%
394
5%
1302
4%
372
64%
372
31%
722
August1st to 10thNight
61%
358
7%
1321
9%
356
63%
356
23%
801
August11th to 20thNight
59%
482
10%
1550
11%
482
60%
482
29%
954
August21st to endNight
55%
594
16%
1782
13%
594
57%
594
28%
1145
September1st to 10thNight
54%
548
15%
1659
11%
548
56%
548
29%
1033
September11th to 20thNight
54%
720
18%
1980
12%
720
57%
720
33%
1249
September21st to endNight
49%
720
20%
1980
13%
720
55%
720
32%
1263
October1st to 10thNight
45%
720
16%
2109
11%
720
49%
720
26%
1382
October11th to 20thNight
40%
720
17%
2281
11%
720
47%
720
24%
1480
October21st to endNight
35%
823
15%
2605
8%
823
43%
823
19%
1788
November1st to 10thNight
31%
925
14%
2590
8%
925
36%
925
16%
1964
November11th to 20thNight
29%
950
13%
2783
6%
950
35%
950
16%
2104
November21st to endNight
30%
950
10%
2850
4%
950
34%
950
17%
2082
December1st to 10thNight
31%
950
13%
2850
7%
950
37%
950
16%
2095
December11th to 20thNight
33%
949
12%
3478
7%
949
38%
949
13%
2566
December21st to endNight
35%
1031
8%
4962
5%
1026
41%
1026
14%
2642

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
10%9%48%7%46%6%6%8%34%
74660
Night
8%9%48%7%46%6%6%8%33%
75141
TransparencyDay
46%8%17%21%7%1
74341
Night
47%7%16%20%9%1
74978
SeeingDay
12%6%25%31%19%6%
14330
Night
12%6%28%36%16%2
23521

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 10thDay
5%11%5%11%10%6%9%6%6%6%25%
1329
11th to 20thDay
5%12%5%9%9%46%5%6%9%29%
1295
21st to endDay
5%12%6%12%10%6%7%5%5%7%24%
1461
February1st to 10thDay
8%11%6%10%11%6%5%5%6%8%24%
1440
11th to 20thDay
5%12%7%12%6%46%7%7%8%25%
1548
21st to endDay
5%11%6%10%9%47%7%6%8%26%
1353
March1st to 10thDay
6%13%6%10%9%6%8%7%5%8%22%
1800
11th to 20thDay
8%12%5%8%7%35%46%9%34%
1979
21st to endDay
9%11%7%12%9%36%5%6%8%23%
2178
April1st to 10thDay
9%11%5%8%7%5%6%6%7%7%30%
2272
11th to 20thDay
12%12%48%6%36%5%6%7%31%
2310
21st to endDay
12%10%37%7%45%6%6%9%32%
2340
May1st to 10thDay
10%9%48%8%5%6%7%6%7%31%
2630
11th to 20thDay
8%7%36%6%46%5%6%8%40%
2654
21st to endDay
16%9%46%6%35%5%6%8%33%
2917
June1st to 10thDay
14%8%48%6%46%6%5%7%31%
2700
11th to 20thDay
18%9%49%7%5%5%6%6%8%23%
2700
21st to endDay
11%6%26%6%47%6%8%9%36%
2700
July1st to 10thDay
10%6%26%7%5%5%5%6%9%39%
2700
11th to 20thDay
10%6%25%6%45%7%8%10%36%
2700
21st to endDay
8%5%25%5%35%6%7%10%44%
2938
August1st to 10thDay
10%5%25%6%46%6%8%11%38%
2608
11th to 20thDay
10%5%245%35%6%7%10%43%
2350
21st to endDay
10%5%25%5%35%5%7%9%43%
2574
September1st to 10thDay
12%7%16%6%45%5%6%8%40%
2299
11th to 20thDay
14%7%36%5%345%5%8%40%
1980
21st to endDay
8%7%26%6%45%5%6%9%43%
1980
October1st to 10thDay
12%8%49%7%45%45%6%36%
1850
11th to 20thDay
9%10%46%7%3445%8%40%
1675
21st to endDay
9%10%48%8%46%6%7%6%32%
1733
November1st to 10thDay
8%13%6%9%8%45%6%6%8%27%
1488
11th to 20thDay
6%10%6%13%8%5%6%5%5%7%30%
1395
21st to endDay
5%9%7%12%8%445%5%9%32%
1330
December1st to 10thDay
5%11%6%8%10%7%7%6%5%8%26%
1330
11th to 20thDay
6%9%5%11%8%6%6%6%7%10%27%
1682
21st to endDay
37%38%7%45%5%5%8%43%
2442
January1st to 10thNight
6%9%5%12%11%6%7%7%7%7%24%
2836
11th to 20thNight
49%6%10%8%47%6%7%8%31%
2776
21st to endNight
6%13%6%12%8%5%7%6%6%7%25%
2912
February1st to 10thNight
6%8%5%12%10%7%7%6%6%8%26%
2520
11th to 20thNight
5%11%5%9%8%5%7%6%7%8%29%
2299
21st to endNight
48%411%8%5%7%7%7%9%31%
1902
March1st to 10thNight
6%11%5%10%9%46%6%6%8%28%
2160
11th to 20thNight
8%9%410%7%46%6%7%8%29%
1980
21st to endNight
8%12%6%9%7%35%6%7%9%27%
2175
April1st to 10thNight
7%9%48%6%5%7%6%7%7%34%
1688
11th to 20thNight
10%10%5%9%8%46%7%6%6%29%
1601
21st to endNight
13%10%37%5%35%5%6%8%35%
1620
May1st to 10thNight
13%9%36%8%5%7%7%6%6%30%
1325
11th to 20thNight
9%9%36%8%45%6%6%7%38%
1239
21st to endNight
17%9%36%6%35%5%5%7%31%
1358
June1st to 10thNight
15%8%47%7%45%6%8%7%29%
1260
11th to 20thNight
17%8%38%9%5%8%6%5%8%23%
1260
21st to endNight
10%6%36%5%5%5%6%7%10%38%
1260
July1st to 10thNight
11%5%25%7%36%6%7%9%39%
1260
11th to 20thNight
10%6%25%6%47%7%6%10%37%
1260
21st to endNight
8%425%445%5%7%9%47%
1379
August1st to 10thNight
8%5%25%6%46%6%7%9%41%
1328
11th to 20thNight
10%7%15%6%35%46%8%45%
1550
21st to endNight
10%7%25%6%445%6%8%42%
1782
September1st to 10thNight
11%5%36%5%44448%45%
1659
11th to 20thNight
12%6%25%43445%8%47%
1980
21st to endNight
8%5%26%5%35%5%6%9%45%
1980
October1st to 10thNight
11%8%48%5%35%5%5%8%40%
2109
11th to 20thNight
8%8%37%7%45%6%7%8%38%
2281
21st to endNight
7%10%410%7%46%6%6%8%33%
2605
November1st to 10thNight
12%15%5%8%7%45%5%5%7%27%
2590
11th to 20thNight
7%12%6%10%9%5%6%5%5%7%28%
2783
21st to endNight
5%9%6%10%10%46%6%6%8%30%
2850
December1st to 10thNight
7%11%410%10%46%6%5%7%28%
2850
11th to 20thNight
6%11%5%12%9%5%6%6%6%9%25%
3510
21st to endNight
46%37%7%46%6%6%8%43%
5214

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
57%7%12%17%7%1
1329
11th to 20thDay
51%6%16%16%9%2
1295
21st to endDay
58%7%10%18%6%
1461
February1st to 10thDay
57%5%15%15%7%
1440
11th to 20thDay
53%8%17%15%7%
1557
21st to endDay
52%8%13%20%8%
1353
March1st to 10thDay
57%8%16%15%4
1800
11th to 20thDay
47%6%15%21%10%
1980
21st to endDay
57%9%14%16%4
2178
April1st to 10thDay
50%8%16%18%8%1
2272
11th to 20thDay
49%7%15%21%8%
2310
21st to endDay
47%7%15%22%7%1
2340
May1st to 10thDay
49%7%15%20%8%1
2630
11th to 20thDay
40%7%12%28%12%1
2658
21st to endDay
48%7%13%21%11%
2918
June1st to 10thDay
50%7%14%21%8%
2700
11th to 20thDay
56%9%16%15%4
2700
21st to endDay
40%11%21%21%6%1
2700
July1st to 10thDay
39%8%21%26%5%1
2626
11th to 20thDay
39%12%25%22%2
2619
21st to endDay
33%10%28%26%3
2775
August1st to 10thDay
37%10%28%22%3
2590
11th to 20thDay
33%10%26%25%6%
2350
21st to endDay
35%8%21%27%7%1
2574
September1st to 10thDay
38%8%21%24%7%2
2299
11th to 20thDay
41%6%19%27%7%
1980
21st to endDay
37%9%18%26%8%2
1980
October1st to 10thDay
48%6%17%20%9%
1850
11th to 20thDay
42%7%17%24%10%
1675
21st to endDay
49%9%12%23%6%
1733
November1st to 10thDay
54%8%16%15%6%1
1488
11th to 20thDay
54%6%17%19%4
1395
21st to endDay
49%8%18%19%5%1
1330
December1st to 10thDay
55%9%11%16%8%1
1330
11th to 20thDay
50%7%19%17%7%
1684
21st to endDay
39%5%11%29%14%2
2442
January1st to 10thNight
56%8%15%14%7%1
2836
11th to 20thNight
48%9%17%17%8%1
2776
21st to endNight
56%8%13%15%7%1
2912
February1st to 10thNight
55%7%14%16%8%1
2520
11th to 20thNight
50%7%16%17%9%
2300
21st to endNight
47%6%14%21%10%1
1902
March1st to 10thNight
52%7%15%19%7%1
2160
11th to 20thNight
49%7%13%20%10%1
1980
21st to endNight
51%7%15%18%7%1
2175
April1st to 10thNight
44%8%15%20%13%1
1688
11th to 20thNight
51%7%12%18%9%2
1601
21st to endNight
45%8%13%22%11%2
1620
May1st to 10thNight
49%7%12%22%9%1
1325
11th to 20thNight
43%7%12%24%14%1
1239
21st to endNight
51%7%11%20%10%1
1358
June1st to 10thNight
50%8%14%21%7%1
1260
11th to 20thNight
57%8%14%16%5%
1260
21st to endNight
38%11%24%22%5%1
1260
July1st to 10thNight
38%10%20%24%7%1
1225
11th to 20thNight
41%10%23%22%5%
1218
21st to endNight
29%9%27%30%5%
1302
August1st to 10thNight
36%11%25%25%3
1321
11th to 20thNight
37%7%24%26%6%1
1550
21st to endNight
37%9%17%28%9%
1782
September1st to 10thNight
36%7%20%25%9%2
1659
11th to 20thNight
35%7%18%29%10%2
1980
21st to endNight
34%8%15%27%13%2
1980
October1st to 10thNight
42%6%16%25%10%1
2109
11th to 20thNight
41%7%17%25%8%1
2281
21st to endNight
46%8%16%23%7%1
2605
November1st to 10thNight
55%7%12%19%7%
2590
11th to 20thNight
55%7%13%18%6%1
2783
21st to endNight
51%8%16%18%6%1
2850
December1st to 10thNight
54%6%12%17%9%1
2850
11th to 20thNight
55%8%16%15%6%
3507
21st to endNight
38%5%18%19%17%3
5214

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
10%328%35%20%3
180
11th to 20thDay
9%9%25%35%18%4
170
21st to endDay
8%9%34%31%14%5%
176
February1st to 10thDay
8%9%30%38%13%3
160
11th to 20thDay
11%7%31%33%16%3
228
21st to endDay
8%429%31%19%10%
219
March1st to 10thDay
9%7%29%34%19%3
420
11th to 20thDay
10%431%32%16%7%
420
21st to endDay
13%426%35%18%5%
462
April1st to 10thDay
10%8%30%32%17%4
420
11th to 20thDay
17%7%17%34%18%7%
412
21st to endDay
16%8%23%32%16%5%
420
May1st to 10thDay
12%8%23%31%19%6%
591
11th to 20thDay
11%423%32%23%7%
625
21st to endDay
16%5%20%30%20%8%
679
June1st to 10thDay
16%7%24%31%18%4
630
11th to 20thDay
21%7%21%26%17%8%
630
21st to endDay
12%5%18%30%23%12%
630
July1st to 10thDay
11%317%32%28%10%
621
11th to 20thDay
11%421%31%25%8%
618
21st to endDay
8%419%33%25%11%
684
August1st to 10thDay
11%319%29%24%13%
548
11th to 20thDay
8%5%24%32%24%7%
437
21st to endDay
12%7%18%29%24%10%
495
September1st to 10thDay
13%7%29%28%18%4
450
11th to 20thDay
18%8%23%31%17%3
450
21st to endDay
11%14%30%27%16%3
450
October1st to 10thDay
16%7%31%25%17%5%
320
11th to 20thDay
14%7%30%32%16%2
270
21st to endDay
14%10%37%25%12%2
297
November1st to 10thDay
16%433%34%11%3
270
11th to 20thDay
11%6%38%31%12%1
210
21st to endDay
47%43%29%12%4
180
December1st to 10thDay
11%6%33%31%13%6%
180
11th to 20thDay
7%9%31%33%18%1
180
21st to endDay
7%5%25%40%18%5%
198
January1st to 10thNight
9%6%35%35%13%2
950
11th to 20thNight
9%8%36%32%14%1
926
21st to endNight
13%9%35%31%11%2
932
February1st to 10thNight
8%8%28%35%18%3
720
11th to 20thNight
9%5%35%35%14%1
704
21st to endNight
6%429%37%18%5%
592
March1st to 10thNight
9%6%28%40%15%3
720
11th to 20thNight
11%429%38%15%3
720
21st to endNight
13%6%26%36%17%3
792
April1st to 10thNight
10%6%25%36%20%3
608
11th to 20thNight
13%5%30%34%17%1
533
21st to endNight
15%7%23%38%16%1
540
May1st to 10thNight
14%7%21%36%19%3
414
11th to 20thNight
12%5%23%39%19%3
354
21st to endNight
21%5%18%34%20%2
389
June1st to 10thNight
17%7%19%40%14%2
360
11th to 20thNight
22%6%18%31%22%1
360
21st to endNight
12%416%38%26%4
360
July1st to 10thNight
12%316%43%26%1
350
11th to 20thNight
11%319%44%22%1
348
21st to endNight
9%219%40%27%3
394
August1st to 10thNight
11%317%33%31%5%
358
11th to 20thNight
11%418%39%24%3
482
21st to endNight
12%220%39%25%1
594
September1st to 10thNight
13%321%36%25%2
548
11th to 20thNight
13%422%41%18%1
720
21st to endNight
11%5%27%40%15%2
720
October1st to 10thNight
15%427%38%15%1
720
11th to 20thNight
13%5%31%36%13%2
720
21st to endNight
13%8%34%34%11%
823
November1st to 10thNight
18%7%33%31%9%2
925
11th to 20thNight
12%8%35%31%11%3
950
21st to endNight
8%7%39%33%11%1
950
December1st to 10thNight
12%9%33%30%13%3
950
11th to 20thNight
10%8%33%35%12%2
950
21st to endNight
9%5%31%35%16%3
1045
Page generated at 2024-01-12 23:38:12. Version ac07

Copyright 2024 Attilla Danko


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