Bolton Landing
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bolton Landing clear sky chart from 2005-11-06 to 2024-03-06.

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
31%
22964
13%
80809
9%
22879
38%
22879
16%
56580

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%
750
11%
4396
6%
737
27%
737
7%
3052
January11th to 20thNight
19%
756
10%
4391
4%
740
27%
740
6%
3263
January21st to endNight
22%
831
8%
4836
7%
814
32%
814
8%
3592
February1st to 10thNight
15%
760
11%
2470
4%
760
24%
760
11%
1897
February11th to 20thNight
17%
743
14%
2258
3%
740
30%
740
15%
1633
February21st to endNight
19%
628
14%
1884
5%
628
31%
628
16%
1353
March1st to 10thNight
22%
743
15%
2227
9%
743
32%
743
16%
1611
March11th to 20thNight
24%
720
14%
2094
6%
720
32%
720
16%
1507
March21st to endNight
24%
792
20%
1980
7%
792
33%
792
21%
1421
April1st to 10thNight
24%
720
16%
1800
4%
720
31%
720
21%
1307
April11th to 20thNight
24%
711
15%
1775
4%
711
30%
711
22%
1280
April21st to endNight
25%
612
16%
1692
6%
612
32%
612
19%
1200
May1st to 10thNight
28%
489
14%
1569
10%
489
33%
489
15%
1132
May11th to 20thNight
30%
354
18%
1416
13%
354
42%
354
18%
901
May21st to endNight
43%
388
14%
1551
14%
388
50%
388
20%
968
June1st to 10thNight
39%
360
13%
1440
13%
360
48%
360
17%
943
June11th to 20thNight
42%
360
12%
1440
13%
360
50%
360
19%
902
June21st to endNight
44%
360
12%
1440
13%
360
51%
360
18%
922
July1st to 10thNight
55%
350
12%
1400
17%
350
61%
350
22%
847
July11th to 20thNight
53%
348
14%
1392
17%
348
59%
348
23%
835
July21st to endNight
54%
394
17%
1486
20%
372
60%
372
25%
865
August1st to 10thNight
61%
358
17%
1422
19%
356
65%
356
26%
807
August11th to 20thNight
53%
645
15%
1709
9%
645
55%
645
27%
1158
August21st to endNight
53%
792
18%
1980
9%
792
55%
792
31%
1313
September1st to 10thNight
51%
720
16%
1800
8%
720
53%
720
33%
1191
September11th to 20thNight
50%
720
24%
1885
15%
720
54%
720
35%
1177
September21st to endNight
44%
720
23%
1980
15%
720
49%
720
29%
1272
October1st to 10thNight
35%
720
14%
2076
11%
720
40%
720
18%
1513
October11th to 20thNight
36%
720
16%
2170
11%
720
43%
720
21%
1506
October21st to endNight
26%
792
12%
2574
7%
792
33%
792
14%
1916
November1st to 10thNight
30%
740
17%
2407
11%
740
39%
740
19%
1614
November11th to 20thNight
29%
760
19%
2470
11%
760
39%
760
18%
1681
November21st to endNight
24%
760
13%
2645
7%
760
33%
760
15%
1853
December1st to 10thNight
18%
760
9%
2660
4%
760
23%
760
10%
2050
December11th to 20thNight
21%
759
11%
3243
4%
759
30%
759
10%
2329
December21st to endNight
17%
829
6%
4851
3%
817
25%
817
6%
3769

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
16%9%47%6%45%5%5%7%33%
78361
Night
17%9%47%6%35%45%6%33%
81152
TransparencyDay
49%7%13%19%11%1
78066
Night
50%7%13%18%10%1
80981
SeeingDay
21%16%31%21%9%2
13798
Night
20%11%31%28%9%1
22992

By Month

Percentage Cloud Cover NE (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
12%14%5%9%7%45%5%5%5%27%
2517
11th to 20thDay
15%14%7%11%10%4444422%
2520
21st to endDay
16%13%410%8%5%5%6%6%6%22%
2804
February1st to 10thDay
13%13%5%7%8%46%5%5%7%26%
1710
11th to 20thDay
11%12%7%10%7%45%5%5%6%29%
1809
21st to endDay
18%11%48%6%44446%31%
1570
March1st to 10thDay
14%10%49%7%35%5%5%7%30%
1847
11th to 20thDay
17%11%5%7%6%35%5%5%5%32%
1862
21st to endDay
17%11%47%5%34435%37%
2376
April1st to 10thDay
19%10%46%5%3435%5%36%
2160
11th to 20thDay
17%7%36%6%35%45%6%37%
2134
21st to endDay
22%9%37%5%45%46%6%29%
2267
May1st to 10thDay
21%9%46%6%3445%6%32%
2405
11th to 20thDay
18%7%36%6%35%5%5%6%38%
2478
21st to endDay
15%6%26%6%446%6%7%38%
2725
June1st to 10thDay
17%6%36%7%46%6%7%8%30%
2520
11th to 20thDay
17%6%36%5%35%6%6%8%35%
2520
21st to endDay
16%6%37%6%45%6%7%8%31%
2520
July1st to 10thDay
13%6%35%6%36%6%6%9%37%
2520
11th to 20thDay
12%6%26%6%45%6%7%10%36%
2520
21st to endDay
14%5%25%6%46%6%8%8%36%
2744
August1st to 10thDay
11%5%35%6%46%7%7%9%38%
2506
11th to 20thDay
14%5%25%6%5%5%6%7%10%33%
2172
21st to endDay
13%5%35%5%46%6%6%8%40%
2376
September1st to 10thDay
14%4345%35%5%7%9%42%
2160
11th to 20thDay
14%5%2442435%7%49%
2075
21st to endDay
16%6%244345%5%8%42%
1980
October1st to 10thDay
22%9%36%6%34445%33%
1882
11th to 20thDay
16%8%36%6%35%5%6%8%35%
1788
21st to endDay
25%10%37%6%35%447%26%
1782
November1st to 10thDay
14%9%37%6%35%5%6%9%35%
1671
11th to 20thDay
17%9%46%6%445%6%7%33%
1710
21st to endDay
17%9%47%6%35%5%6%7%31%
1533
December1st to 10thDay
21%12%5%9%7%4445%6%22%
1520
11th to 20thDay
23%10%48%6%34446%28%
1906
21st to endDay
25%17%6%9%5%3333422%
2772
January1st to 10thNight
15%14%5%8%6%3445%5%30%
4429
11th to 20thNight
12%13%7%12%9%5%6%45%6%22%
4440
21st to endNight
20%15%5%8%6%34445%26%
4848
February1st to 10thNight
13%12%6%10%8%46%5%5%6%25%
2470
11th to 20thNight
11%10%49%9%45%5%5%6%31%
2256
21st to endNight
15%11%47%6%36%45%6%33%
1884
March1st to 10thNight
14%11%48%7%36%5%5%6%31%
2217
11th to 20thNight
16%10%5%6%6%345%5%6%34%
2093
21st to endNight
17%8%36%5%345%5%6%38%
1980
April1st to 10thNight
19%8%47%5%445%5%6%35%
1800
11th to 20thNight
19%7%47%5%3445%7%36%
1775
21st to endNight
21%9%36%5%345%47%35%
1692
May1st to 10thNight
23%8%48%43445%6%32%
1569
11th to 20thNight
18%8%46%5%3445%7%38%
1415
21st to endNight
15%6%35%5%25%6%7%8%39%
1550
June1st to 10thNight
20%5%35%435%5%6%7%37%
1440
11th to 20thNight
19%6%25%6%2445%8%39%
1440
21st to endNight
16%6%26%6%45%5%5%7%39%
1440
July1st to 10thNight
13%4346%35%6%6%9%40%
1440
11th to 20thNight
13%5%245%35%5%6%9%44%
1440
21st to endNight
11%5%35%5%35%46%9%45%
1574
August1st to 10thNight
10%425%5%35%6%6%9%44%
1432
11th to 20thNight
13%5%27%7%46%5%6%8%38%
1709
21st to endNight
14%5%244246%5%8%45%
1980
September1st to 10thNight
13%5%2444346%7%46%
1800
11th to 20thNight
13%5%25%424446%52%
1885
21st to endNight
16%5%234245%46%46%
1980
October1st to 10thNight
21%8%36%6%345%5%5%33%
2076
11th to 20thNight
17%7%27%6%45%45%6%36%
2170
21st to endNight
23%10%46%6%3445%7%28%
2574
November1st to 10thNight
15%9%47%6%3445%6%38%
2407
11th to 20thNight
19%8%36%6%3445%7%36%
2470
21st to endNight
17%10%46%6%3446%7%33%
2645
December1st to 10thNight
19%14%5%8%6%45%45%7%23%
2660
11th to 20thNight
21%11%46%6%2446%6%29%
3288
21st to endNight
26%14%6%8%5%34345%22%
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
53%8%14%19%5%1
2518
11th to 20thDay
65%6%10%13%5%1
2520
21st to endDay
62%7%12%12%6%1
2804
February1st to 10thDay
55%8%13%16%6%1
1710
11th to 20thDay
55%7%11%15%11%1
1818
21st to endDay
55%6%12%14%13%2
1570
March1st to 10thDay
53%7%13%15%10%3
1850
11th to 20thDay
53%6%12%13%14%3
1862
21st to endDay
50%5%9%18%15%4
2376
April1st to 10thDay
50%5%11%19%12%3
2160
11th to 20thDay
47%6%11%19%15%2
2134
21st to endDay
53%7%10%15%11%3
2267
May1st to 10thDay
52%6%9%19%13%2
2405
11th to 20thDay
46%6%9%20%16%3
2482
21st to endDay
42%9%15%20%12%1
2725
June1st to 10thDay
49%9%15%16%9%1
2520
11th to 20thDay
45%7%14%19%13%1
2520
21st to endDay
49%9%13%18%11%1
2520
July1st to 10thDay
40%9%14%23%13%1
2450
11th to 20thDay
40%9%16%27%8%
2445
21st to endDay
42%9%15%22%11%1
2591
August1st to 10thDay
39%10%17%23%10%1
2492
11th to 20thDay
42%10%17%23%8%
2172
21st to endDay
39%9%15%24%13%1
2376
September1st to 10thDay
37%9%14%27%13%1
2160
11th to 20thDay
35%5%13%28%18%1
2075
21st to endDay
39%8%14%24%13%1
1980
October1st to 10thDay
53%6%10%19%11%1
1882
11th to 20thDay
45%8%17%23%7%1
1788
21st to endDay
58%5%13%15%8%1
1782
November1st to 10thDay
45%8%15%21%11%
1671
11th to 20thDay
48%7%13%17%13%2
1710
21st to endDay
51%8%17%17%7%1
1533
December1st to 10thDay
60%7%14%12%6%
1520
11th to 20thDay
56%8%15%15%6%1
1906
21st to endDay
67%5%8%13%7%
2772
January1st to 10thNight
54%9%15%14%8%1
4429
11th to 20thNight
61%7%13%12%7%1
4440
21st to endNight
61%6%12%13%7%1
4848
February1st to 10thNight
57%9%12%14%7%1
2470
11th to 20thNight
52%7%11%19%11%1
2258
21st to endNight
51%6%13%18%8%2
1884
March1st to 10thNight
53%6%11%18%10%2
2227
11th to 20thNight
51%6%11%17%12%2
2094
21st to endNight
48%5%10%17%16%4
1980
April1st to 10thNight
50%5%11%20%13%2
1800
11th to 20thNight
49%5%10%22%13%1
1775
21st to endNight
49%6%11%17%13%4
1692
May1st to 10thNight
54%6%7%16%15%2
1569
11th to 20thNight
47%5%11%19%16%2
1416
21st to endNight
41%9%15%21%13%2
1551
June1st to 10thNight
46%8%14%19%12%2
1440
11th to 20thNight
44%6%16%20%13%2
1440
21st to endNight
44%8%13%24%11%1
1440
July1st to 10thNight
38%9%16%23%14%1
1400
11th to 20thNight
36%10%15%27%11%1
1392
21st to endNight
35%8%16%27%12%2
1486
August1st to 10thNight
33%9%19%27%12%
1422
11th to 20thNight
41%8%17%24%10%
1709
21st to endNight
37%8%15%27%13%1
1980
September1st to 10thNight
36%8%16%28%12%1
1800
11th to 20thNight
34%5%13%29%18%1
1885
21st to endNight
37%7%13%25%15%2
1980
October1st to 10thNight
51%7%11%18%12%1
2076
11th to 20thNight
47%7%15%22%9%1
2170
21st to endNight
56%6%12%15%10%1
2574
November1st to 10thNight
47%6%14%19%12%2
2407
11th to 20thNight
47%7%13%19%12%2
2470
21st to endNight
49%8%16%18%8%
2645
December1st to 10thNight
60%8%14%14%4
2660
11th to 20thNight
54%8%14%14%9%1
3288
21st to endNight
64%7%10%14%4
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
21%27%26%22%5%
180
11th to 20thDay
27%27%27%16%21
180
21st to endDay
17%26%35%17%4
207
February1st to 10thDay
28%32%29%9%1
270
11th to 20thDay
24%27%34%13%2
417
21st to endDay
29%19%33%17%3
382
March1st to 10thDay
27%14%35%21%3
440
11th to 20thDay
27%23%30%17%31
420
21st to endDay
29%21%26%16%6%2
462
April1st to 10thDay
32%18%26%16%8%
420
11th to 20thDay
30%20%27%13%8%2
412
21st to endDay
29%18%33%12%6%2
420
May1st to 10thDay
29%18%29%14%9%2
423
11th to 20thDay
19%16%36%20%7%2
447
21st to endDay
18%14%32%22%12%2
485
June1st to 10thDay
18%16%34%21%9%1
450
11th to 20thDay
19%13%33%23%9%2
450
21st to endDay
18%12%36%24%8%2
450
July1st to 10thDay
15%9%28%29%16%2
445
11th to 20thDay
13%10%31%29%15%3
444
21st to endDay
14%7%36%31%10%2
488
August1st to 10thDay
11%8%29%31%16%4
446
11th to 20thDay
17%6%27%30%15%5%
439
21st to endDay
11%13%28%27%17%4
495
September1st to 10thDay
14%9%27%27%16%7%
450
11th to 20thDay
14%10%29%22%16%9%
450
21st to endDay
17%10%32%22%12%7%
450
October1st to 10thDay
26%15%24%20%12%4
450
11th to 20thDay
18%16%32%24%9%1
444
21st to endDay
31%13%28%22%6%
396
November1st to 10thDay
22%17%27%21%12%1
365
11th to 20thDay
24%20%31%17%6%1
370
21st to endDay
23%18%35%20%4
193
December1st to 10thDay
26%23%29%17%5%
180
11th to 20thDay
29%22%36%12%1
180
21st to endDay
28%21%33%15%31
198
January1st to 10thNight
20%15%37%25%3
760
11th to 20thNight
23%16%34%24%3
760
21st to endNight
16%15%37%28%4
836
February1st to 10thNight
19%16%42%22%2
760
11th to 20thNight
17%17%42%22%2
743
21st to endNight
22%16%39%21%3
628
March1st to 10thNight
21%15%34%26%3
743
11th to 20thNight
22%17%33%24%4
720
21st to endNight
21%17%32%22%7%
792
April1st to 10thNight
25%14%32%25%4
720
11th to 20thNight
24%16%32%21%8%
711
21st to endNight
25%15%30%25%6%
612
May1st to 10thNight
27%13%25%25%9%
489
11th to 20thNight
21%8%36%28%6%
354
21st to endNight
16%7%28%36%12%1
389
June1st to 10thNight
20%429%33%13%
360
11th to 20thNight
18%8%26%38%11%
360
21st to endNight
15%429%39%12%1
360
July1st to 10thNight
14%321%44%17%2
350
11th to 20thNight
12%422%43%18%1
348
21st to endNight
10%323%47%16%1
394
August1st to 10thNight
11%120%45%22%1
358
11th to 20thNight
15%320%39%21%3
645
21st to endNight
15%5%21%39%21%1
792
September1st to 10thNight
15%5%23%38%17%3
720
11th to 20thNight
17%7%23%31%19%4
720
21st to endNight
18%7%27%29%17%2
720
October1st to 10thNight
24%10%23%28%14%1
720
11th to 20thNight
20%9%29%31%10%1
720
21st to endNight
28%10%29%27%5%
792
November1st to 10thNight
20%13%32%29%7%
740
11th to 20thNight
23%13%31%26%7%1
760
21st to endNight
22%13%34%25%6%
760
December1st to 10thNight
26%13%35%22%4
760
11th to 20thNight
25%12%34%25%4
760
21st to endNight
28%13%36%21%2
836
Page generated at 2024-03-03 06:28:53. Version ac07

Copyright © 2024 Attilla Danko.


Bolton Landing Clear Sky Chart |Charts Home