Spirit Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Spirit Lake clear sky chart from 2005-11-05 to 2017-09-24.

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
49%
14980
13%
46917
12%
14948
51%
14948
20%
32352

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
26%
726
6%
2512
5%
722
28%
722
7%
2088
January16th to endNight
36%
768
6%
2688
6%
768
37%
768
10%
2121
February1st to 15thNight
36%
702
6%
2405
6%
698
38%
698
11%
1863
February16th to endNight
40%
632
13%
1895
12%
632
42%
632
16%
1420
March1st to 15thNight
41%
720
6%
2160
5%
720
42%
720
15%
1652
March16th to endNight
39%
768
8%
2025
4%
768
41%
768
15%
1619
April1st to 15thNight
48%
719
11%
1799
6%
719
49%
719
23%
1300
April16th to endNight
49%
543
15%
1623
13%
543
51%
543
22%
1107
May1st to 15thNight
60%
402
18%
1482
23%
402
62%
402
28%
833
May16th to endNight
57%
374
12%
1442
17%
374
60%
374
21%
891
June1st to 15thNight
59%
360
9%
1260
9%
360
60%
360
25%
758
June16th to endNight
64%
360
13%
1260
12%
360
65%
360
29%
706
July1st to 15thNight
81%
340
17%
1294
21%
340
84%
340
54%
509
July16th to endNight
85%
376
26%
1416
42%
354
87%
354
62%
491
August1st to 15thNight
84%
378
28%
1450
38%
376
87%
376
53%
558
August16th to endNight
78%
648
32%
1794
24%
648
80%
648
55%
902
September1st to 15thNight
77%
720
29%
1818
18%
720
79%
720
58%
957
September16th to endNight
64%
692
24%
1914
20%
692
66%
692
36%
1167
October1st to 15thNight
56%
660
19%
1921
17%
660
58%
660
29%
1220
October16th to endNight
50%
704
14%
2288
15%
704
52%
704
19%
1593
November1st to 15thNight
36%
700
9%
2275
9%
700
38%
700
12%
1783
November16th to endNight
37%
828
6%
2616
5%
828
38%
828
11%
2075
December1st to 15thNight
32%
900
6%
2700
4%
900
33%
900
10%
2248
December16th to endNight
25%
960
4%
2880
2%
960
27%
960
7%
2491

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%10%35%5%24445%38%
48023
Night
15%10%36%5%34446%36%
47086
Cloud CoverDay
14%9%35%5%34446%38%
48024
Night
15%10%36%5%2445%6%36%
47089
TransparencyDay
47%6%12%20%11%2
47694
Night
48%6%12%18%11%3
46918
SeeingDay
16%11%23%25%17%4
5768
Night
21%5%15%31%22%3
14984

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
26%17%5%6%6%24335%16%
1432
16th to endDay
21%18%6%9%4235%5%5%18%
1536
February1st to 15thDay
18%20%5%7%5%245%5%419%
1456
16th to endDay
17%20%6%7%6%3342422%
1579
March1st to 15thDay
21%20%5%8%5%3423418%
1800
16th to endDay
24%16%48%7%35%335%18%
2197
April1st to 15thDay
18%12%5%8%6%35%5%5%6%21%
2149
16th to endDay
14%11%47%7%35%446%30%
2337
May1st to 15thDay
9%7%36%5%45%6%5%6%40%
2466
16th to endDay
13%7%37%6%35%5%6%8%30%
2669
June1st to 15thDay
19%5%346%24446%36%
2700
16th to endDay
14%414435%5%5%6%44%
2700
July1st to 15thDay
421232344465%
2585
16th to endDay
11121233474%
2657
August1st to 15thDay
322222347%66%
2502
16th to endDay
431331335%7%62%
2405
September1st to 15thDay
331331335%6%63%
2142
16th to endDay
11%5%2443446%6%45%
1904
October1st to 15thDay
17%8%25%5%24235%41%
1706
16th to endDay
20%10%37%6%23345%31%
1584
November1st to 15thDay
25%15%44434435%23%
1584
16th to endDay
18%19%6%9%6%3443320%
1326
December1st to 15thDay
19%18%6%9%435%445%18%
1260
16th to endDay
22%21%6%9%6%3423414%
1347
January1st to 15thNight
26%17%6%7%6%3332417%
2512
16th to endNight
21%15%5%7%6%24445%23%
2688
February1st to 15thNight
20%16%46%5%23345%26%
2394
16th to endNight
15%14%47%5%34436%29%
1895
March1st to 15thNight
18%11%47%7%35%45%6%26%
2160
16th to endNight
18%10%46%6%36%5%5%7%24%
2022
April1st to 15thNight
11%9%46%7%35%5%6%6%33%
1799
16th to endNight
10%8%37%6%45%5%45%39%
1623
May1st to 15thNight
8%415%435%5%6%9%43%
1482
16th to endNight
11%6%35%5%346%7%8%35%
1442
June1st to 15thNight
13%324435%5%5%8%42%
1260
16th to endNight
10%426%4345%6%6%47%
1260
July1st to 15thNight
2112222446%70%
1373
16th to endNight
111212236%75%
1512
August1st to 15thNight
212123347%69%
1458
16th to endNight
1213323345%68%
1794
September1st to 15thNight
321221335%6%66%
1818
16th to endNight
9%425%5%2445%8%47%
1914
October1st to 15thNight
13%425%5%34347%45%
1921
16th to endNight
17%8%35%5%3346%6%34%
2288
November1st to 15thNight
22%13%45%6%2445%6%23%
2275
16th to endNight
24%13%46%6%34435%23%
2616
December1st to 15thNight
18%18%6%8%5%34445%20%
2700
16th to endNight
24%19%6%9%5%2334416%
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
26%18%5%6%5%3434416%
1432
16th to endDay
20%18%5%8%5%2345%5%18%
1536
February1st to 15thDay
19%20%6%7%5%3444419%
1456
16th to endDay
16%19%6%8%6%2443422%
1579
March1st to 15thDay
21%19%5%8%7%33235%18%
1800
16th to endDay
23%16%47%7%34345%18%
2198
April1st to 15thDay
17%12%48%7%35%6%5%6%22%
2149
16th to endDay
14%10%47%6%45%446%31%
2337
May1st to 15thDay
9%6%35%5%36%5%6%6%40%
2466
16th to endDay
13%7%36%6%35%5%6%9%31%
2669
June1st to 15thDay
19%5%35%5%35%446%37%
2700
16th to endDay
13%4245%35%45%7%44%
2700
July1st to 15thDay
4212323445%65%
2585
16th to endDay
11121334474%
2657
August1st to 15thDay
3212222346%67%
2502
16th to endDay
421332345%7%62%
2405
September1st to 15thDay
3213323346%64%
2142
16th to endDay
11%5%25%4345%5%7%44%
1904
October1st to 15thDay
17%7%26%5%23245%41%
1706
16th to endDay
21%9%36%6%34335%32%
1584
November1st to 15thDay
26%13%45%43435%423%
1584
16th to endDay
19%17%5%9%7%3343320%
1326
December1st to 15thDay
20%17%7%9%5%24445%17%
1260
16th to endDay
22%22%5%9%7%2443214%
1347
January1st to 15thNight
27%17%6%7%5%3333417%
2512
16th to endNight
21%15%5%7%5%35%446%22%
2688
February1st to 15thNight
20%16%46%5%23345%26%
2394
16th to endNight
15%14%47%5%34447%29%
1895
March1st to 15thNight
17%10%46%6%35%45%6%26%
2160
16th to endNight
18%10%36%6%36%5%6%6%24%
2025
April1st to 15thNight
11%8%46%7%35%6%6%6%34%
1799
16th to endNight
11%7%36%6%445%45%39%
1623
May1st to 15thNight
7%5%15%4345%7%8%45%
1482
16th to endNight
11%6%45%5%45%6%7%8%36%
1442
June1st to 15thNight
12%414426%6%6%7%43%
1260
16th to endNight
9%5%25%425%5%6%7%46%
1260
July1st to 15thNight
212213346%70%
1373
16th to endNight
11211336%75%
1512
August1st to 15thNight
212213347%69%
1458
16th to endNight
2223323335%68%
1794
September1st to 15thNight
321232345%6%66%
1818
16th to endNight
9%3245%3446%7%48%
1914
October1st to 15thNight
13%425%5%34446%45%
1921
16th to endNight
17%7%36%5%3445%6%35%
2288
November1st to 15thNight
22%13%36%5%2445%6%23%
2275
16th to endNight
24%13%37%5%34445%22%
2616
December1st to 15thNight
19%17%6%8%6%34446%19%
2700
16th to endNight
24%20%5%8%5%2344316%
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
71%7%10%7%3
1432
16th to endDay
66%8%12%8%3
1536
February1st to 15thDay
67%7%12%7%3
1456
16th to endDay
66%6%10%13%4
1579
March1st to 15thDay
69%6%12%9%1
1800
16th to endDay
69%6%12%9%1
2198
April1st to 15thDay
60%7%13%13%3
2149
16th to endDay
53%6%15%18%4
2337
May1st to 15thDay
41%6%15%25%10%
2466
16th to endDay
47%7%18%21%4
2673
June1st to 15thDay
47%6%12%22%9%2
2700
16th to endDay
38%6%13%27%12%1
2700
July1st to 15thDay
21%49%30%22%10%
2435
16th to endDay
12%48%24%38%11%
2490
August1st to 15thDay
17%39%32%28%7%
2485
16th to endDay
20%411%31%27%5%
2405
September1st to 15thDay
21%312%30%25%6%
2142
16th to endDay
37%6%17%22%12%3
1904
October1st to 15thDay
46%413%26%9%
1706
16th to endDay
55%5%14%20%4
1584
November1st to 15thDay
63%7%13%10%31
1584
16th to endDay
67%6%12%9%3
1326
December1st to 15thDay
69%7%11%10%1
1260
16th to endDay
76%49%8%1
1347
January1st to 15thNight
71%411%9%2
2512
16th to endNight
63%7%15%10%21
2688
February1st to 15thNight
60%7%15%11%4
2405
16th to endNight
56%6%13%16%7%
1895
March1st to 15thNight
57%6%16%14%4
2160
16th to endNight
57%9%12%14%5%
2025
April1st to 15thNight
48%6%16%20%7%
1799
16th to endNight
46%5%12%25%9%
1623
May1st to 15thNight
33%6%13%30%14%1
1483
16th to endNight
41%6%17%23%10%
1442
June1st to 15thNight
37%7%11%23%16%4
1260
16th to endNight
34%410%27%18%4
1260
July1st to 15thNight
15%27%23%33%17%
1294
16th to endNight
10%26%20%36%23%
1416
August1st to 15thNight
14%38%22%39%12%
1450
16th to endNight
18%37%27%31%11%
1794
September1st to 15thNight
17%47%29%30%10%
1818
16th to endNight
33%5%14%23%16%6%
1914
October1st to 15thNight
39%411%29%13%1
1921
16th to endNight
48%6%13%22%7%
2288
November1st to 15thNight
60%8%12%13%31
2275
16th to endNight
63%6%14%11%3
2616
December1st to 15thNight
66%8%11%11%1
2700
16th to endNight
72%7%10%8%1
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
21%320%30%18%6%
60
16th to endDay
43%418%21%6%4
64
February1st to 15thDay
28%18%19%19%13%2
99
16th to endDay
34%15%21%17%10%2
238
March1st to 15thDay
34%22%24%14%4
270
16th to endDay
30%15%29%17%5%
288
April1st to 15thDay
19%20%27%18%10%2
269
16th to endDay
20%17%27%21%11%2
270
May1st to 15thDay
13%17%26%25%15%2
288
16th to endDay
14%9%19%28%22%7%
384
June1st to 15thDay
14%8%25%27%18%4
495
16th to endDay
12%9%23%27%21%6%
495
July1st to 15thDay
5%425%32%26%4
369
16th to endDay
210%29%33%16%7%
327
August1st to 15thDay
5%420%31%27%10%
315
16th to endDay
38%23%32%21%10%
332
September1st to 15thDay
7%9%24%25%22%8%
315
16th to endDay
13%12%22%24%21%4
288
October1st to 15thDay
22%12%23%26%13%1
231
16th to endDay
42%5%16%21%8%5%
96
November1st to 15thDay
27%10%16%30%14%1
90
16th to endDay
31%421%22%16%3
61
December1st to 15thDay
38%15%20%16%6%3
60
16th to endDay
37%420%26%10%
64
January1st to 15thNight
37%8%14%23%14%1
726
16th to endNight
29%5%15%30%16%1
768
February1st to 15thNight
31%8%14%29%13%2
704
16th to endNight
24%7%17%28%19%2
632
March1st to 15thNight
23%9%17%34%14%1
720
16th to endNight
24%8%17%33%14%1
768
April1st to 15thNight
15%7%19%34%22%1
719
16th to endNight
15%6%21%33%21%2
543
May1st to 15thNight
9%6%16%33%29%4
403
16th to endNight
13%414%27%33%6%
375
June1st to 15thNight
14%314%38%24%5%
360
16th to endNight
11%213%37%31%3
360
July1st to 15thNight
2110%39%41%4
340
16th to endNight
118%39%45%3
376
August1st to 15thNight
315%29%51%7%
378
16th to endNight
329%35%41%7%
648
September1st to 15thNight
4111%32%38%10%
720
16th to endNight
11%214%32%32%6%
692
October1st to 15thNight
16%414%35%25%3
660
16th to endNight
21%5%16%29%25%2
704
November1st to 15thNight
32%7%17%30%11%
700
16th to endNight
33%7%12%25%17%2
828
December1st to 15thNight
30%6%17%31%13%
900
16th to endNight
36%7%17%29%8%
960
Page generated at 2017-09-25 06:02:20. Version ac04

Copyright 2017 A. Danko


Spirit Lake Clear Sky Chart | Charts Home