Pioneer Scout Reservation
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pioneer Scout Reservation clear sky chart from 2005-11-06 to 2024-11-05.

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
37%
25353
15%
96990
11%
25074
43%
25074
17%
65279

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
19%
944
11%
4401
5%
926
27%
926
8%
3368
January11th to 20thNight
17%
948
7%
4415
4%
930
21%
930
6%
3577
January21st to endNight
19%
928
5%
4678
4%
912
25%
912
6%
3916
February1st to 10thNight
19%
760
10%
2428
5%
760
25%
760
12%
1846
February11th to 20thNight
23%
740
15%
2219
7%
740
31%
740
15%
1632
February21st to endNight
17%
628
14%
1884
3%
628
28%
628
15%
1394
March1st to 10thNight
26%
757
18%
3696
10%
745
32%
745
12%
2379
March11th to 20thNight
27%
757
22%
3438
9%
740
38%
740
18%
1840
March21st to endNight
27%
830
10%
3756
9%
814
35%
814
13%
2471
April1st to 10thNight
31%
580
17%
1910
9%
580
41%
580
21%
1271
April11th to 20thNight
30%
563
20%
1792
10%
563
41%
563
21%
1195
April21st to endNight
32%
570
17%
1710
6%
570
40%
570
23%
1147
May1st to 10thNight
34%
565
16%
2765
7%
559
40%
559
12%
1833
May11th to 20thNight
38%
551
13%
2750
10%
541
45%
541
15%
1684
May21st to endNight
52%
605
11%
2965
10%
593
57%
593
20%
1575
June1st to 10thNight
54%
570
18%
1520
11%
570
60%
570
37%
937
June11th to 20thNight
54%
570
18%
1520
14%
570
57%
570
32%
979
June21st to endNight
55%
570
18%
1520
13%
570
60%
570
36%
947
July1st to 10thNight
64%
544
20%
2331
15%
535
67%
535
26%
1261
July11th to 20thNight
65%
541
18%
2216
18%
533
68%
533
31%
1134
July21st to endNight
66%
608
15%
2648
16%
569
71%
569
25%
1472
August1st to 10thNight
67%
555
19%
2653
18%
545
71%
545
22%
1547
August11th to 20thNight
66%
551
20%
2478
19%
543
71%
543
25%
1389
August21st to endNight
65%
608
17%
3041
21%
605
68%
605
22%
1721
September1st to 10thNight
59%
634
25%
1964
22%
634
64%
634
33%
1138
September11th to 20thNight
65%
760
30%
2090
25%
760
68%
760
40%
1205
September21st to endNight
50%
760
23%
2090
18%
760
55%
760
30%
1367
October1st to 10thNight
48%
760
21%
2201
17%
740
55%
740
30%
1377
October11th to 20thNight
33%
760
14%
2818
10%
740
41%
740
16%
1976
October21st to endNight
28%
836
16%
3121
13%
814
38%
814
15%
2166
November1st to 10thNight
36%
760
21%
2470
16%
760
44%
760
23%
1560
November11th to 20thNight
27%
760
18%
2470
11%
760
37%
760
17%
1709
November21st to endNight
27%
760
14%
2470
10%
760
33%
760
15%
1809
December1st to 10thNight
20%
760
9%
2470
6%
760
25%
760
11%
1902
December11th to 20thNight
19%
920
9%
3222
4%
919
25%
919
11%
2471
December21st to endNight
16%
1040
5%
4870
3%
1026
21%
1026
5%
4084

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
13%9%48%5%5%5%46%8%34%
101156
Night
15%10%48%5%4445%7%35%
97911
TransparencyDay
46%6%12%22%13%1
104771
Night
47%6%12%21%14%1
102436
SeeingDay
17%9%27%25%15%7%
15673
Night
18%8%29%30%13%1
25497

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
16%17%7%13%6%5%5%35%5%18%
2527
11th to 20thDay
15%16%7%14%6%5%6%6%6%5%13%
2530
21st to endDay
24%20%9%13%6%4322413%
2951
February1st to 10thDay
14%16%5%11%8%6%5%446%21%
1752
11th to 20thDay
15%11%412%8%5%446%5%25%
1848
21st to endDay
16%13%5%12%6%4446%7%25%
1570
March1st to 10thDay
18%15%49%7%45%446%24%
3120
11th to 20thDay
12%8%39%6%5%6%46%8%32%
3468
21st to endDay
20%12%5%9%5%5%445%6%25%
3832
April1st to 10thDay
17%12%47%5%5%5%46%7%29%
2280
11th to 20thDay
17%9%37%5%5%5%45%6%36%
2335
21st to endDay
17%9%37%5%5%435%8%33%
2470
May1st to 10thDay
18%8%37%5%5%5%46%7%31%
4082
11th to 20thDay
15%7%26%45%5%47%9%35%
4081
21st to endDay
9%6%37%45%5%46%9%43%
4562
June1st to 10thDay
10%7%26%5%5%6%5%6%8%41%
2660
11th to 20thDay
9%6%26%5%5%5%47%9%43%
2660
21st to endDay
10%5%27%5%5%6%5%7%10%37%
2660
July1st to 10thDay
11%7%27%5%5%5%5%7%10%38%
4440
11th to 20thDay
7%425%445%47%11%47%
4440
21st to endDay
6%5%37%6%6%6%47%9%41%
4634
August1st to 10thDay
10%5%26%445%47%8%46%
4104
11th to 20thDay
9%6%26%45%5%46%9%43%
4044
21st to endDay
7%5%36%45%446%11%45%
4290
September1st to 10thDay
11%7%26%5%4446%7%44%
2196
11th to 20thDay
10%425%346%47%9%46%
2090
21st to endDay
13%8%27%445%36%8%40%
2090
October1st to 10thDay
12%7%27%5%4435%7%44%
2090
11th to 20thDay
16%7%37%5%45%45%7%36%
1906
21st to endDay
18%11%37%5%5%5%47%8%29%
1881
November1st to 10thDay
12%8%37%43336%7%42%
1708
11th to 20thDay
15%14%48%6%45%347%29%
1710
21st to endDay
20%14%49%6%4435%5%25%
1710
December1st to 10thDay
15%16%7%12%7%5%435%5%22%
1710
11th to 20thDay
15%15%6%12%6%45%45%6%22%
1942
21st to endDay
22%22%9%11%6%44345%11%
2783
January1st to 10thNight
16%15%7%12%6%5%4446%21%
4428
11th to 20thNight
15%17%8%15%6%5%5%6%5%5%14%
4440
21st to endNight
24%18%7%11%6%5%434414%
4695
February1st to 10thNight
17%15%49%7%6%435%6%24%
2428
11th to 20thNight
14%12%49%7%6%5%45%6%28%
2218
21st to endNight
20%11%48%5%5%5%35%5%29%
1884
March1st to 10thNight
16%12%48%44435%6%34%
3733
11th to 20thNight
9%7%36%5%5%446%8%44%
3490
21st to endNight
17%9%49%5%4435%6%34%
3817
April1st to 10thNight
15%9%37%5%4345%8%37%
1910
11th to 20thNight
19%8%35%5%4435%6%37%
1792
21st to endNight
18%8%36%5%3445%6%37%
1710
May1st to 10thNight
16%9%48%5%5%5%46%8%31%
2813
11th to 20thNight
19%8%36%34335%6%40%
2812
21st to endNight
12%5%26%44446%9%44%
2992
June1st to 10thNight
10%5%25%44446%9%47%
1520
11th to 20thNight
8%5%27%5%45%47%7%45%
1520
21st to endNight
8%5%36%5%4448%9%46%
1520
July1st to 10thNight
8%425%5%4447%10%48%
2530
11th to 20thNight
7%415%43435%8%56%
2530
21st to endNight
6%5%26%5%45%47%9%46%
2921
August1st to 10thNight
10%6%26%43446%9%44%
2825
11th to 20thNight
8%5%15%45%5%46%8%49%
2785
21st to endNight
8%5%26%45%445%8%47%
3362
September1st to 10thNight
10%6%26%34436%5%52%
1964
11th to 20thNight
9%5%14424347%56%
2090
21st to endNight
14%7%27%444346%45%
2090
October1st to 10thNight
11%7%25%34335%7%49%
2090
11th to 20thNight
17%8%36%5%4435%6%37%
2271
21st to endNight
19%9%27%44435%6%37%
2717
November1st to 10thNight
11%9%37%5%4435%7%42%
2470
11th to 20thNight
16%11%39%5%4445%7%32%
2470
21st to endNight
18%13%5%7%5%5%4446%28%
2470
December1st to 10thNight
18%13%5%11%6%5%446%6%21%
2470
11th to 20thNight
17%13%6%11%7%5%5%35%6%23%
3250
21st to endNight
26%18%6%11%6%4435%5%13%
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
67%6%10%12%5%
2528
11th to 20thDay
69%5%12%9%6%
2530
21st to endDay
77%47%9%3
2951
February1st to 10thDay
64%5%10%13%7%1
1752
11th to 20thDay
59%5%10%16%9%1
1858
21st to endDay
57%5%13%16%6%2
1570
March1st to 10thDay
61%5%9%18%6%
3120
11th to 20thDay
46%6%16%22%9%1
3468
21st to endDay
59%6%11%17%6%1
3832
April1st to 10thDay
52%6%11%19%11%
2280
11th to 20thDay
48%6%11%22%12%2
2335
21st to endDay
49%5%13%18%13%2
2470
May1st to 10thDay
49%6%12%21%10%
4120
11th to 20thDay
43%8%14%24%10%1
4085
21st to endDay
36%7%11%20%22%4
4575
June1st to 10thDay
39%8%10%26%15%2
2660
11th to 20thDay
36%7%13%24%18%2
2660
21st to endDay
40%8%13%21%15%3
2660
July1st to 10thDay
40%6%14%21%16%3
4371
11th to 20thDay
28%7%13%32%18%1
4365
21st to endDay
37%8%14%19%20%2
4487
August1st to 10thDay
34%8%16%25%17%1
4091
11th to 20thDay
35%8%11%29%16%1
4083
21st to endDay
33%6%12%34%13%3
4289
September1st to 10thDay
38%7%14%22%17%3
2196
11th to 20thDay
32%7%12%28%21%1
2090
21st to endDay
40%5%13%23%18%
2090
October1st to 10thDay
28%412%35%20%1
3480
11th to 20thDay
38%5%9%26%21%
3134
21st to endDay
43%5%13%26%12%1
3081
November1st to 10thDay
39%5%13%27%15%1
1708
11th to 20thDay
55%5%11%18%10%1
1710
21st to endDay
60%412%16%7%
1710
December1st to 10thDay
66%5%11%12%5%
1710
11th to 20thDay
60%7%13%15%5%
1939
21st to endDay
77%5%7%6%5%
2783
January1st to 10thNight
62%6%10%15%6%
4428
11th to 20thNight
70%412%10%4
4440
21st to endNight
73%5%9%9%3
4695
February1st to 10thNight
60%5%11%16%6%1
2428
11th to 20thNight
55%5%8%21%9%1
2219
21st to endNight
56%5%10%18%9%2
1884
March1st to 10thNight
51%5%11%24%9%1
3733
11th to 20thNight
36%6%15%23%18%2
3490
21st to endNight
50%5%13%22%8%1
3817
April1st to 10thNight
45%6%10%23%14%2
1910
11th to 20thNight
47%5%10%19%18%2
1792
21st to endNight
46%5%11%20%16%2
1710
May1st to 10thNight
49%8%10%19%13%1
2840
11th to 20thNight
44%7%9%27%12%1
2813
21st to endNight
36%6%14%22%20%2
3000
June1st to 10thNight
33%5%13%27%19%3
1520
11th to 20thNight
36%8%13%23%18%2
1520
21st to endNight
32%8%17%25%17%2
1520
July1st to 10thNight
32%5%13%26%17%6%
2490
11th to 20thNight
26%6%16%27%24%2
2482
21st to endNight
32%7%16%18%21%5%
2828
August1st to 10thNight
35%8%14%27%15%1
2814
11th to 20thNight
30%7%14%32%16%2
2812
21st to endNight
34%6%12%29%18%2
3362
September1st to 10thNight
32%6%11%27%20%4
1964
11th to 20thNight
28%6%9%30%26%2
2090
21st to endNight
40%5%10%27%16%1
2090
October1st to 10thNight
23%48%34%30%1
3480
11th to 20thNight
39%410%23%23%1
3782
21st to endNight
36%49%33%18%1
4467
November1st to 10thNight
41%6%11%25%16%1
2470
11th to 20thNight
51%412%21%10%2
2470
21st to endNight
56%5%12%20%7%
2470
December1st to 10thNight
61%6%11%15%7%
2470
11th to 20thNight
62%413%13%7%1
3252
21st to endNight
73%5%11%8%3
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
25%16%31%21%6%1
270
11th to 20thDay
23%13%45%15%41
270
21st to endDay
27%13%30%23%7%1
297
February1st to 10thDay
23%15%31%24%42
270
11th to 20thDay
23%15%37%20%4
270
21st to endDay
24%17%39%17%3
225
March1st to 10thDay
20%17%40%18%4
270
11th to 20thDay
21%12%35%24%7%2
448
21st to endDay
31%11%31%19%7%1
506
April1st to 10thDay
20%15%33%22%11%
460
11th to 20thDay
25%14%30%19%9%3
452
21st to endDay
22%12%34%18%10%3
460
May1st to 10thDay
22%11%31%21%12%3
463
11th to 20thDay
21%8%27%22%16%7%
487
21st to endDay
11%6%25%28%19%11%
576
June1st to 10thDay
11%7%28%28%20%5%
680
11th to 20thDay
12%6%26%30%19%6%
680
21st to endDay
12%5%30%29%17%7%
680
July1st to 10thDay
9%319%30%24%15%
671
11th to 20thDay
10%421%30%22%13%
668
21st to endDay
7%321%29%30%11%
635
August1st to 10thDay
10%216%29%23%20%
486
11th to 20thDay
10%5%19%27%24%14%
479
21st to endDay
9%315%29%29%16%
539
September1st to 10thDay
14%5%17%28%22%14%
490
11th to 20thDay
9%316%22%33%17%
490
21st to endDay
18%8%20%24%21%9%
490
October1st to 10thDay
13%7%23%31%18%8%
490
11th to 20thDay
18%14%28%29%10%2
482
21st to endDay
24%13%38%18%5%1
330
November1st to 10thDay
13%12%33%28%10%4
282
11th to 20thDay
21%21%30%20%8%1
270
21st to endDay
26%11%41%19%3
270
December1st to 10thDay
21%19%35%16%9%1
270
11th to 20thDay
22%16%38%20%4
270
21st to endDay
25%20%32%20%2
297
January1st to 10thNight
21%16%35%22%6%1
950
11th to 20thNight
24%13%36%22%5%1
950
21st to endNight
22%11%35%26%5%
934
February1st to 10thNight
23%11%38%24%4
760
11th to 20thNight
21%13%35%27%3
743
21st to endNight
27%11%38%21%3
628
March1st to 10thNight
20%11%34%27%7%1
760
11th to 20thNight
17%13%38%25%7%1
760
21st to endNight
24%9%33%26%7%1
836
April1st to 10thNight
18%11%36%29%6%
580
11th to 20thNight
22%8%35%26%9%1
563
21st to endNight
23%8%33%27%9%
570
May1st to 10thNight
21%7%30%33%9%1
570
11th to 20thNight
24%5%26%29%16%1
561
21st to endNight
13%324%38%19%3
617
June1st to 10thNight
12%224%46%16%1
570
11th to 20thNight
9%5%24%43%18%1
570
21st to endNight
9%423%40%22%2
570
July1st to 10thNight
8%315%41%27%6%
555
11th to 20thNight
9%216%40%29%4
552
21st to endNight
6%216%44%31%1
624
August1st to 10thNight
7%215%41%31%4
567
11th to 20thNight
9%114%41%30%5%
564
21st to endNight
10%215%35%34%4
627
September1st to 10thNight
11%416%34%31%5%
634
11th to 20thNight
11%314%35%33%4
760
21st to endNight
17%6%21%32%21%4
760
October1st to 10thNight
13%6%26%33%21%2
760
11th to 20thNight
22%11%29%27%10%1
760
21st to endNight
22%12%33%26%8%
836
November1st to 10thNight
15%11%33%27%13%1
760
11th to 20thNight
22%12%31%28%6%1
760
21st to endNight
23%10%32%28%6%
760
December1st to 10thNight
24%14%34%22%6%
760
11th to 20thNight
24%12%35%24%41
921
21st to endNight
30%11%32%24%3
1045
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