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Boise
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Boise 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
56%
23040
19%
80856
19%
22971
60%
22971
26%
49481

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
40%
749
8%
4378
7%
736
42%
736
8%
3161
January11th to 20thNight
43%
754
7%
4409
10%
740
46%
740
8%
3441
January21st to endNight
45%
826
6%
4791
10%
814
49%
814
9%
3415
February1st to 10thNight
42%
760
11%
2498
9%
760
47%
760
19%
1773
February11th to 20thNight
48%
740
17%
2219
13%
740
54%
740
25%
1485
February21st to endNight
44%
628
15%
1884
14%
628
48%
628
20%
1319
March1st to 10thNight
41%
760
15%
2280
12%
760
47%
760
21%
1589
March11th to 20thNight
49%
760
18%
2175
14%
760
54%
760
26%
1434
March21st to endNight
43%
820
15%
2151
9%
820
45%
820
24%
1502
April1st to 10thNight
51%
720
22%
1800
11%
720
55%
720
31%
1191
April11th to 20thNight
47%
669
25%
1737
11%
669
53%
669
31%
1125
April21st to endNight
55%
540
26%
1620
17%
540
60%
540
37%
911
May1st to 10thNight
57%
540
26%
1620
19%
540
62%
540
41%
880
May11th to 20thNight
58%
457
22%
1519
22%
457
63%
457
31%
874
May21st to endNight
60%
388
16%
1552
22%
388
63%
388
23%
873
June1st to 10thNight
61%
360
16%
1440
22%
360
66%
360
26%
796
June11th to 20thNight
59%
360
22%
1440
29%
360
68%
360
36%
672
June21st to endNight
71%
360
25%
1440
38%
360
77%
360
46%
603
July1st to 10thNight
81%
350
26%
1400
39%
350
85%
350
55%
525
July11th to 20thNight
81%
348
32%
1392
44%
348
86%
348
62%
484
July21st to endNight
81%
394
34%
1488
46%
372
85%
372
51%
583
August1st to 10thNight
75%
455
32%
1521
31%
453
78%
453
49%
700
August11th to 20thNight
84%
534
38%
1602
31%
534
87%
534
67%
686
August21st to endNight
78%
775
36%
1963
23%
775
80%
775
64%
978
September1st to 10thNight
80%
720
38%
1800
24%
720
83%
720
66%
897
September11th to 20thNight
76%
720
36%
1966
28%
720
79%
720
54%
1022
September21st to endNight
71%
720
36%
1980
31%
720
75%
720
51%
1043
October1st to 10thNight
66%
720
28%
1980
22%
720
72%
720
45%
1100
October11th to 20thNight
65%
720
30%
2215
28%
720
71%
720
40%
1201
October21st to endNight
58%
792
26%
2574
23%
792
65%
792
33%
1449
November1st to 10thNight
55%
740
23%
2405
24%
740
59%
740
27%
1497
November11th to 20thNight
49%
760
19%
2470
17%
760
53%
760
23%
1607
November21st to endNight
55%
760
16%
2493
15%
760
58%
760
26%
1559
December1st to 10thNight
47%
760
11%
2660
10%
760
50%
760
18%
1830
December11th to 20thNight
43%
758
10%
3207
10%
758
45%
758
12%
2356
December21st to endNight
33%
823
7%
4787
9%
817
38%
817
9%
2920

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
9%7%35%5%3445%7%48%
78720
Night
12%8%35%5%3445%7%45%
81293
TransparencyDay
36%5%12%20%17%10%
78424
Night
40%5%12%20%15%8%
81110
SeeingDay
11%8%23%29%22%7%
13604
Night
14%417%38%23%4
23087

By Month

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 10thDay
15%17%48%7%45%6%7%7%20%
2539
11th to 20thDay
15%16%6%11%8%46%5%5%6%18%
2540
21st to endDay
18%12%5%11%9%5%6%45%7%18%
2794
February1st to 10thDay
13%11%47%6%45%6%6%7%31%
1679
11th to 20thDay
11%13%37%6%35%5%5%8%34%
1850
21st to endDay
12%10%5%6%6%45%5%5%7%34%
1570
March1st to 10thDay
12%11%47%6%46%6%5%8%32%
1900
11th to 20thDay
12%8%36%435%5%5%7%40%
2004
21st to endDay
12%10%47%5%5%5%6%6%8%33%
2356
April1st to 10thDay
11%8%35%5%36%6%5%9%39%
2160
11th to 20thDay
7%9%346%46%5%5%8%44%
2169
21st to endDay
9%6%35%5%345%6%7%48%
2340
May1st to 10thDay
6%5%145%35%5%6%8%52%
2340
11th to 20thDay
10%6%25%5%3446%8%47%
2370
21st to endDay
8%7%25%5%36%5%6%10%43%
2723
June1st to 10thDay
9%5%36%5%35%5%6%9%43%
2520
11th to 20thDay
7%42433445%8%56%
2520
21st to endDay
3313223445%72%
2520
July1st to 10thDay
2313213446%72%
2520
11th to 20thDay
22121223479%
2520
21st to endDay
421332234473%
2741
August1st to 10thDay
4313323447%66%
2410
11th to 20thDay
2212222345%76%
2299
21st to endDay
2312222345%74%
2390
September1st to 10thDay
3212212336%75%
2160
11th to 20thDay
4423323346%65%
1994
21st to endDay
7%423223436%65%
1980
October1st to 10thDay
8%6%25%324446%55%
1980
11th to 20thDay
8%42343445%8%55%
1742
21st to endDay
9%6%35%4235%5%8%49%
1782
November1st to 10thDay
14%9%245%3445%7%41%
1674
11th to 20thDay
16%8%25%6%45%5%6%7%35%
1710
21st to endDay
13%7%37%6%5%7%5%6%10%32%
1682
December1st to 10thDay
17%10%38%6%35%5%5%6%33%
1520
11th to 20thDay
16%12%49%8%46%5%7%8%20%
1928
21st to endDay
13%10%49%7%45%5%6%9%27%
2794
January1st to 10thNight
16%15%5%9%7%45%45%7%25%
4406
11th to 20thNight
21%17%5%8%6%44445%21%
4420
21st to endNight
17%13%38%7%35%446%29%
4862
February1st to 10thNight
16%10%37%6%35%45%7%34%
2498
11th to 20thNight
13%11%35%435%46%8%38%
2218
21st to endNight
14%12%45%6%45%5%5%7%32%
1884
March1st to 10thNight
14%12%36%6%35%45%6%35%
2280
11th to 20thNight
12%9%35%6%3446%7%39%
2175
21st to endNight
13%9%36%6%36%5%5%7%36%
2151
April1st to 10thNight
11%7%35%5%36%5%6%6%44%
1800
11th to 20thNight
11%7%36%6%345%5%6%46%
1737
21st to endNight
8%6%2443447%7%52%
1620
May1st to 10thNight
7%5%2343446%8%55%
1620
11th to 20thNight
9%5%25%5%35%5%7%9%46%
1519
21st to endNight
7%6%36%6%45%6%7%8%42%
1552
June1st to 10thNight
11%4246%3445%9%46%
1440
11th to 20thNight
7%5%14324347%59%
1440
21st to endNight
3213324446%67%
1440
July1st to 10thNight
211322335%8%70%
1440
11th to 20thNight
1212213345%78%
1440
21st to endNight
221332335%5%70%
1576
August1st to 10thNight
4324423347%65%
1529
11th to 20thNight
2111223346%75%
1602
21st to endNight
321222334474%
1963
September1st to 10thNight
331221233475%
1800
11th to 20thNight
5%32332335%6%65%
1966
21st to endNight
7%313323336%66%
1980
October1st to 10thNight
7%5%24433446%59%
1980
11th to 20thNight
9%41443445%6%57%
2215
21st to endNight
10%6%25%4336%6%7%49%
2574
November1st to 10thNight
14%7%36%5%3445%7%43%
2405
11th to 20thNight
18%7%36%5%3445%6%39%
2470
21st to endNight
14%9%35%424447%43%
2493
December1st to 10thNight
16%10%36%7%3445%7%35%
2660
11th to 20thNight
17%11%38%7%35%5%6%7%26%
3276
21st to endNight
15%10%37%6%35%46%9%33%
4862

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
61%8%18%12%1
2539
11th to 20thDay
65%8%14%12%2
2540
21st to endDay
62%8%18%10%1
2794
February1st to 10thDay
51%8%20%17%31
1679
11th to 20thDay
48%8%17%21%6%
1860
21st to endDay
49%6%16%20%8%1
1570
March1st to 10thDay
48%7%16%21%7%1
1900
11th to 20thDay
43%5%15%25%10%1
2004
21st to endDay
48%6%17%20%9%1
2356
April1st to 10thDay
41%5%15%23%13%2
2160
11th to 20thDay
38%5%11%27%16%3
2172
21st to endDay
35%414%28%18%2
2340
May1st to 10thDay
30%411%29%23%4
2340
11th to 20thDay
35%410%30%17%4
2373
21st to endDay
36%5%15%24%16%3
2724
June1st to 10thDay
36%6%12%27%18%2
2520
11th to 20thDay
26%38%26%28%9%
2520
21st to endDay
15%26%19%33%24%
2520
July1st to 10thDay
14%3416%30%33%
2451
11th to 20thDay
10%239%28%48%
2445
21st to endDay
15%338%28%44%
2589
August1st to 10thDay
20%26%16%27%28%
2393
11th to 20thDay
12%2318%35%31%
2299
21st to endDay
14%2417%36%27%
2390
September1st to 10thDay
13%2417%31%33%
2160
11th to 20thDay
20%38%24%28%17%
1994
21st to endDay
22%36%26%31%11%
1980
October1st to 10thDay
31%312%25%24%5%
1980
11th to 20thDay
27%412%32%22%3
1742
21st to endDay
34%5%17%28%15%2
1782
November1st to 10thDay
42%6%15%24%13%
1674
11th to 20thDay
46%7%19%22%5%
1710
21st to endDay
46%8%19%21%6%
1682
December1st to 10thDay
50%9%19%16%5%
1520
11th to 20thDay
57%11%20%10%1
1928
21st to endDay
52%9%17%18%4
2794
January1st to 10thNight
60%6%19%14%1
4406
11th to 20thNight
65%6%13%13%2
4420
21st to endNight
56%8%18%16%2
4862
February1st to 10thNight
50%7%18%21%31
2498
11th to 20thNight
44%6%17%23%10%1
2219
21st to endNight
50%5%13%20%10%1
1884
March1st to 10thNight
50%5%12%22%10%2
2280
11th to 20thNight
44%411%27%14%1
2175
21st to endNight
47%5%15%24%9%1
2151
April1st to 10thNight
40%411%25%16%4
1800
11th to 20thNight
38%5%10%25%19%3
1737
21st to endNight
31%311%28%24%2
1620
May1st to 10thNight
27%49%28%29%4
1620
11th to 20thNight
34%5%9%29%20%4
1519
21st to endNight
36%7%13%26%16%3
1552
June1st to 10thNight
36%413%25%20%2
1440
11th to 20thNight
26%38%23%32%8%
1440
21st to endNight
20%36%17%30%24%
1440
July1st to 10thNight
14%3415%29%37%
1400
11th to 20thNight
10%2310%26%48%
1392
21st to endNight
16%238%24%47%
1488
August1st to 10thNight
21%25%14%25%33%
1521
11th to 20thNight
12%2413%31%39%
1602
21st to endNight
15%2414%30%34%
1963
September1st to 10thNight
15%2313%30%38%
1800
11th to 20thNight
21%25%19%27%26%
1966
21st to endNight
22%3420%32%19%
1980
October1st to 10thNight
27%38%26%25%11%
1980
11th to 20thNight
29%310%29%25%5%
2215
21st to endNight
33%413%26%21%3
2574
November1st to 10thNight
42%312%22%19%2
2405
11th to 20thNight
45%5%13%27%10%
2470
21st to endNight
42%416%28%10%1
2493
December1st to 10thNight
49%8%19%16%8%
2660
11th to 20thNight
56%7%17%17%3
3276
21st to endNight
49%6%22%18%5%
4862

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
26%6%20%25%19%5%
180
11th to 20thDay
18%9%21%24%21%8%
180
21st to endDay
19%421%32%15%10%
198
February1st to 10thDay
21%11%27%22%16%4
286
11th to 20thDay
17%11%29%25%14%3
455
21st to endDay
17%12%30%26%13%2
382
March1st to 10thDay
17%11%30%29%12%1
460
11th to 20thDay
13%9%31%27%16%4
460
21st to endDay
16%12%33%24%13%2
491
April1st to 10thDay
13%18%26%22%16%5%
420
11th to 20thDay
11%17%30%24%13%5%
412
21st to endDay
12%15%32%24%13%4
420
May1st to 10thDay
6%14%30%29%17%4
423
11th to 20thDay
17%7%23%27%19%7%
448
21st to endDay
9%8%20%32%18%14%
485
June1st to 10thDay
10%7%24%27%23%9%
450
11th to 20thDay
8%12%26%33%16%5%
450
21st to endDay
46%23%32%27%7%
450
July1st to 10thDay
2420%38%28%8%
446
11th to 20thDay
2322%39%27%7%
444
21st to endDay
4216%38%31%9%
487
August1st to 10thDay
4420%35%28%9%
447
11th to 20thDay
3216%32%33%14%
437
21st to endDay
4418%30%31%14%
495
September1st to 10thDay
5%414%29%36%13%
450
11th to 20thDay
6%418%29%28%14%
450
21st to endDay
7%5%20%32%30%7%
450
October1st to 10thDay
7%10%18%24%30%11%
450
11th to 20thDay
10%6%22%26%25%10%
346
21st to endDay
14%7%25%27%24%3
297
November1st to 10thDay
17%8%21%34%17%3
270
11th to 20thDay
14%8%18%35%19%6%
270
21st to endDay
15%7%15%33%25%5%
257
December1st to 10thDay
23%5%21%24%18%9%
180
11th to 20thDay
26%423%28%14%4
180
21st to endDay
18%10%25%26%17%4
198
January1st to 10thNight
22%6%18%30%20%3
760
11th to 20thNight
21%5%17%31%22%4
760
21st to endNight
19%416%32%25%4
836
February1st to 10thNight
22%421%34%16%3
760
11th to 20thNight
18%323%35%18%2
744
21st to endNight
16%7%24%37%14%3
628
March1st to 10thNight
18%8%24%34%15%2
760
11th to 20thNight
16%6%20%39%17%2
760
21st to endNight
17%8%24%36%12%2
820
April1st to 10thNight
14%7%19%38%19%2
720
11th to 20thNight
12%8%25%36%16%3
669
21st to endNight
9%8%24%41%15%2
540
May1st to 10thNight
10%6%22%40%19%2
540
11th to 20thNight
11%5%19%34%28%4
457
21st to endNight
9%5%17%33%30%6%
389
June1st to 10thNight
12%5%13%38%28%4
360
11th to 20thNight
10%6%21%36%26%2
360
21st to endNight
3117%44%31%3
360
July1st to 10thNight
3111%50%34%2
350
11th to 20thNight
1114%56%27%1
348
21st to endNight
2111%49%34%4
394
August1st to 10thNight
4211%47%34%2
455
11th to 20thNight
128%48%39%2
534
21st to endNight
4212%46%32%5%
775
September1st to 10thNight
3111%42%37%6%
720
11th to 20thNight
5%210%38%38%6%
720
21st to endNight
9%214%37%29%10%
720
October1st to 10thNight
9%315%40%27%5%
720
11th to 20thNight
10%315%38%27%6%
720
21st to endNight
13%418%37%23%5%
792
November1st to 10thNight
16%5%16%36%23%3
740
11th to 20thNight
21%418%36%19%3
760
21st to endNight
19%216%37%22%5%
760
December1st to 10thNight
21%317%37%19%3
760
11th to 20thNight
24%416%38%16%3
760
21st to endNight
28%5%21%32%13%2
836
Page generated at 2024-03-24 21:37:04. Version ac07

Copyright © 2024 Attilla Danko.


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