Big Bay Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Big Bay Point clear sky chart from 2005-11-06 to 2024-01-13.

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
32%
24809
10%
75025
7%
24751
36%
24751
14%
57630

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
14%
950
5%
2648
1%
946
18%
946
6%
2310
January11th to 20thNight
14%
911
4%
2549
1%
911
16%
911
5%
2292
January21st to endNight
14%
990
5%
2772
1%
990
17%
990
5%
2488
February1st to 10thNight
18%
900
6%
2465
2%
900
21%
900
9%
2090
February11th to 20thNight
21%
766
10%
2162
4%
763
25%
763
12%
1738
February21st to endNight
23%
592
10%
1776
4%
592
28%
592
11%
1422
March1st to 10thNight
33%
718
13%
2160
8%
718
39%
718
18%
1579
March11th to 20thNight
29%
720
17%
2122
10%
720
35%
720
17%
1550
March21st to endNight
35%
602
16%
1988
14%
602
40%
602
15%
1439
April1st to 10thNight
33%
540
9%
1800
7%
540
37%
540
14%
1344
April11th to 20thNight
38%
533
15%
1740
12%
533
43%
533
18%
1230
April21st to endNight
39%
540
14%
1620
9%
540
43%
540
21%
1111
May1st to 10thNight
44%
540
13%
1504
11%
540
46%
540
20%
1113
May11th to 20thNight
45%
531
16%
1416
12%
531
48%
531
24%
1013
May21st to endNight
58%
583
13%
1552
9%
582
61%
582
29%
1045
June1st to 10thNight
57%
540
11%
1440
6%
540
59%
540
28%
962
June11th to 20thNight
54%
427
10%
1327
8%
427
55%
427
21%
921
June21st to endNight
55%
540
10%
1440
6%
540
56%
540
28%
980
July1st to 10thNight
65%
525
13%
1400
9%
525
67%
525
38%
853
July11th to 20thNight
58%
522
14%
1392
9%
522
60%
522
31%
912
July21st to endNight
65%
591
18%
1487
13%
558
66%
558
40%
878
August1st to 10thNight
64%
537
20%
1423
15%
534
67%
534
36%
884
August11th to 20thNight
61%
534
21%
1530
15%
534
66%
534
34%
924
August21st to endNight
55%
594
17%
1965
15%
594
59%
594
28%
1182
September1st to 10thNight
55%
540
18%
1800
17%
540
60%
540
28%
1097
September11th to 20thNight
48%
631
16%
1891
13%
631
52%
631
22%
1287
September21st to endNight
41%
720
13%
1980
10%
720
44%
720
20%
1435
October1st to 10thNight
36%
720
14%
2055
8%
720
40%
720
20%
1489
October11th to 20thNight
25%
720
10%
2258
5%
720
31%
720
13%
1729
October21st to endNight
22%
792
8%
2574
5%
792
27%
792
9%
2115
November1st to 10thNight
23%
740
12%
2406
8%
740
29%
740
11%
1878
November11th to 20thNight
15%
831
8%
2541
3%
831
20%
831
7%
2141
November21st to endNight
16%
950
5%
2660
4%
950
18%
950
7%
2323
December1st to 10thNight
13%
950
4%
2836
1%
950
16%
950
5%
2485
December11th to 20thNight
11%
950
4%
3476
1%
949
15%
949
4%
2966
December21st to endNight
8%
1039
3%
4870
1%
1026
12%
1026
2%
4425

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%10%5%8%7%45%5%5%7%31%
74426
Night
14%12%6%10%8%45%5%5%6%27%
75229
TransparencyDay
52%7%12%19%9%1
74131
Night
58%7%11%17%7%1
75058
SeeingDay
18%8%25%30%16%3
14733
Night
20%10%27%28%13%2
24818

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
10%15%10%15%11%6%8%445%12%
1517
11th to 20thDay
13%16%8%16%15%6%5%435%10%
1456
21st to endDay
10%15%8%15%15%6%6%5%5%412%
1584
February1st to 10thDay
8%12%7%12%14%7%9%5%5%415%
1494
11th to 20thDay
8%11%6%12%11%8%8%6%5%5%20%
1685
21st to endDay
11%12%7%12%10%37%6%6%6%18%
1480
March1st to 10thDay
9%11%6%11%8%5%7%45%7%25%
1798
11th to 20thDay
11%10%6%11%9%45%345%32%
1844
21st to endDay
15%12%5%10%7%45%5%6%7%25%
2376
April1st to 10thDay
14%11%5%7%6%46%5%5%8%28%
2160
11th to 20thDay
19%10%48%6%3445%7%30%
2167
21st to endDay
15%9%47%6%35%5%5%7%35%
2340
May1st to 10thDay
14%8%36%6%35%5%5%8%37%
2453
11th to 20thDay
13%7%37%5%35%46%7%39%
2479
21st to endDay
11%5%25%5%46%6%6%9%41%
2725
June1st to 10thDay
11%5%25%6%35%5%5%9%43%
2520
11th to 20thDay
14%5%25%5%36%5%7%8%41%
2574
21st to endDay
14%6%35%5%35%5%6%7%41%
2520
July1st to 10thDay
7%424436%5%6%10%49%
2520
11th to 20thDay
8%425%5%35%5%7%9%47%
2520
21st to endDay
9%324335%5%6%9%51%
2743
August1st to 10thDay
8%4245%345%6%10%49%
2507
11th to 20thDay
12%4345%445%6%8%46%
2369
21st to endDay
12%5%35%5%35%5%5%7%46%
2389
September1st to 10thDay
16%6%25%5%3446%7%41%
2160
11th to 20thDay
14%5%26%6%45%5%7%8%39%
2050
21st to endDay
20%8%46%6%36%5%6%6%31%
1980
October1st to 10thDay
19%10%36%6%35%46%8%29%
1904
11th to 20thDay
23%13%410%7%35%5%6%6%18%
1701
21st to endDay
22%21%6%9%6%4444416%
1782
November1st to 10thDay
18%17%5%9%5%345%7%6%22%
1672
11th to 20thDay
17%18%8%13%8%35%445%15%
1636
21st to endDay
15%19%10%16%8%4444313%
1520
December1st to 10thDay
10%17%11%16%9%5%6%45%5%12%
1337
11th to 20thDay
16%19%9%18%6%5%5%445%10%
1681
21st to endDay
19%21%12%15%10%45%4335%
2783
January1st to 10thNight
11%15%10%15%10%7%5%45%5%13%
2648
11th to 20thNight
12%16%9%16%13%8%5%43311%
2549
21st to endNight
12%13%8%16%13%6%8%6%4410%
2772
February1st to 10thNight
8%14%8%13%11%7%9%5%5%5%15%
2465
11th to 20thNight
11%11%5%10%15%5%7%6%5%6%20%
2161
21st to endNight
13%14%6%14%8%45%45%5%21%
1776
March1st to 10thNight
10%10%5%9%7%47%5%6%7%30%
2149
11th to 20thNight
12%11%6%11%6%45%5%5%5%32%
2122
21st to endNight
14%11%6%9%7%345%46%30%
1988
April1st to 10thNight
17%13%5%8%7%45%5%5%7%25%
1800
11th to 20thNight
20%9%45%5%25%45%8%31%
1740
21st to endNight
16%11%36%5%4445%7%35%
1620
May1st to 10thNight
15%10%47%6%5%5%5%5%6%32%
1504
11th to 20thNight
16%9%37%5%35%5%6%7%35%
1416
21st to endNight
11%5%36%5%36%5%7%9%41%
1551
June1st to 10thNight
14%6%25%6%36%45%7%42%
1440
11th to 20thNight
12%5%27%7%48%5%6%9%35%
1327
21st to endNight
16%5%25%5%35%5%6%9%39%
1440
July1st to 10thNight
8%5%345%45%5%5%8%49%
1440
11th to 20thNight
12%425%4446%7%7%45%
1440
21st to endNight
8%32342447%10%53%
1575
August1st to 10thNight
9%424435%5%6%8%48%
1432
11th to 20thNight
9%5%15%425%5%5%8%51%
1530
21st to endNight
12%7%25%344346%50%
1965
September1st to 10thNight
13%6%25%5%34447%48%
1800
11th to 20thNight
14%7%36%6%35%45%7%39%
1891
21st to endNight
20%7%36%7%4445%7%34%
1980
October1st to 10thNight
20%9%35%7%3446%6%34%
2055
11th to 20thNight
20%13%47%6%35%45%7%25%
2258
21st to endNight
22%18%5%8%6%445%4419%
2574
November1st to 10thNight
17%18%48%6%4445%6%23%
2406
11th to 20thNight
16%20%8%12%8%4444417%
2541
21st to endNight
15%18%11%15%8%34445%14%
2660
December1st to 10thNight
12%17%10%15%9%6%5%5%45%12%
2836
11th to 20thNight
13%15%9%18%9%5%6%445%14%
3494
21st to endNight
19%21%12%13%9%444347%
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
75%6%7%10%2
1518
11th to 20thDay
80%47%8%1
1456
21st to endDay
74%6%8%8%3
1584
February1st to 10thDay
69%6%11%11%3
1494
11th to 20thDay
64%7%11%13%5%
1694
21st to endDay
63%8%9%12%7%1
1480
March1st to 10thDay
58%7%12%13%10%1
1800
11th to 20thDay
55%5%13%17%9%2
1844
21st to endDay
57%6%14%16%7%1
2376
April1st to 10thDay
52%7%11%21%7%1
2160
11th to 20thDay
55%6%8%20%9%2
2167
21st to endDay
48%6%10%20%13%3
2340
May1st to 10thDay
45%7%11%22%13%1
2453
11th to 20thDay
43%7%10%25%13%1
2483
21st to endDay
39%9%15%22%14%1
2725
June1st to 10thDay
38%7%15%26%13%2
2520
11th to 20thDay
39%8%14%24%14%1
2574
21st to endDay
41%7%14%25%12%1
2520
July1st to 10thDay
29%7%16%31%15%1
2451
11th to 20thDay
31%8%14%29%15%2
2445
21st to endDay
29%8%16%31%16%1
2591
August1st to 10thDay
30%9%18%31%11%2
2492
11th to 20thDay
36%8%16%28%11%1
2369
21st to endDay
37%8%16%26%13%1
2389
September1st to 10thDay
41%8%11%30%10%
2160
11th to 20thDay
41%10%19%24%6%
2050
21st to endDay
51%8%15%21%6%
1980
October1st to 10thDay
51%9%12%23%6%
1904
11th to 20thDay
66%7%11%13%4
1701
21st to endDay
71%6%8%10%4
1782
November1st to 10thDay
62%6%10%15%6%
1672
11th to 20thDay
73%6%9%9%4
1636
21st to endDay
76%7%8%7%2
1520
December1st to 10thDay
75%6%9%8%2
1337
11th to 20thDay
78%7%7%7%2
1681
21st to endDay
83%7%6%41
2783
January1st to 10thNight
74%6%8%10%1
2648
11th to 20thNight
79%5%8%7%1
2549
21st to endNight
77%6%7%7%2
2772
February1st to 10thNight
69%6%9%11%3
2465
11th to 20thNight
64%6%11%14%4
2162
21st to endNight
65%6%10%13%6%
1776
March1st to 10thNight
52%7%13%19%8%1
2160
11th to 20thNight
54%5%9%19%12%1
2123
21st to endNight
55%6%10%20%8%1
1988
April1st to 10thNight
58%5%11%16%10%1
1800
11th to 20thNight
51%6%9%20%11%2
1740
21st to endNight
48%6%10%20%14%2
1620
May1st to 10thNight
53%6%8%18%13%3
1504
11th to 20thNight
47%7%7%25%12%2
1417
21st to endNight
39%9%13%24%15%2
1552
June1st to 10thNight
41%6%11%26%14%2
1440
11th to 20thNight
45%9%10%21%13%1
1327
21st to endNight
41%8%14%23%13%1
1440
July1st to 10thNight
30%7%14%31%16%2
1400
11th to 20thNight
36%9%12%27%14%1
1392
21st to endNight
27%9%16%30%17%2
1487
August1st to 10thNight
32%7%15%32%11%3
1423
11th to 20thNight
31%8%15%32%13%1
1530
21st to endNight
36%7%14%27%15%2
1965
September1st to 10thNight
37%6%14%29%14%1
1800
11th to 20thNight
43%9%14%27%6%1
1891
21st to endNight
50%7%14%22%7%
1980
October1st to 10thNight
50%7%12%22%7%1
2055
11th to 20thNight
59%6%12%16%6%
2258
21st to endNight
67%7%11%11%4
2574
November1st to 10thNight
63%5%11%13%7%
2406
11th to 20thNight
72%5%9%8%5%
2541
21st to endNight
74%6%10%8%2
2660
December1st to 10thNight
75%7%8%8%1
2836
11th to 20thNight
74%6%10%7%3
3493
21st to endNight
80%7%5%6%1
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
19%16%29%28%8%1
270
11th to 20thDay
22%11%34%24%6%4
246
21st to endDay
23%8%36%29%31
264
February1st to 10thDay
14%16%40%25%5%
240
11th to 20thDay
11%17%42%25%5%
240
21st to endDay
19%19%34%23%5%
198
March1st to 10thDay
13%13%38%29%8%1
240
11th to 20thDay
15%13%29%31%11%1
276
21st to endDay
20%11%33%23%11%2
462
April1st to 10thDay
20%11%30%30%7%1
420
11th to 20thDay
25%10%24%27%11%3
412
21st to endDay
22%8%26%27%14%3
420
May1st to 10thDay
18%6%29%31%14%2
536
11th to 20thDay
17%423%36%15%5%
625
21st to endDay
14%421%37%20%4
679
June1st to 10thDay
11%5%22%39%19%4
630
11th to 20thDay
16%417%40%20%3
630
21st to endDay
17%317%37%22%5%
630
July1st to 10thDay
8%216%40%28%6%
621
11th to 20thDay
12%318%35%26%4
618
21st to endDay
10%218%40%25%6%
684
August1st to 10thDay
11%318%38%25%4
626
11th to 20thDay
15%5%13%31%28%8%
505
21st to endDay
19%7%17%31%21%5%
495
September1st to 10thDay
19%6%24%25%19%7%
450
11th to 20thDay
14%5%27%29%20%5%
450
21st to endDay
22%8%23%25%18%3
450
October1st to 10thDay
26%7%26%22%14%4
374
11th to 20thDay
29%14%27%24%6%
270
21st to endDay
35%15%27%19%4
297
November1st to 10thDay
20%16%26%29%8%2
270
11th to 20thDay
23%19%39%14%41
270
21st to endDay
22%22%31%20%4
270
December1st to 10thDay
21%14%35%19%10%1
183
11th to 20thDay
27%21%37%9%42
185
21st to endDay
26%21%30%18%6%
297
January1st to 10thNight
18%17%36%23%5%1
950
11th to 20thNight
21%14%36%21%8%
911
21st to endNight
19%15%35%25%5%1
990
February1st to 10thNight
16%17%34%25%7%1
900
11th to 20thNight
16%13%37%24%10%1
766
21st to endNight
20%9%33%30%7%1
592
March1st to 10thNight
14%10%31%30%13%1
720
11th to 20thNight
18%12%32%27%10%1
720
21st to endNight
20%9%26%32%11%2
602
April1st to 10thNight
23%6%28%34%9%1
540
11th to 20thNight
25%5%24%32%12%2
533
21st to endNight
21%6%25%30%15%3
540
May1st to 10thNight
19%423%32%17%4
540
11th to 20thNight
18%324%35%16%4
531
21st to endNight
14%318%37%25%3
584
June1st to 10thNight
16%415%38%24%3
540
11th to 20thNight
15%317%38%25%2
427
21st to endNight
19%314%35%24%5%
540
July1st to 10thNight
11%214%38%30%5%
525
11th to 20thNight
14%218%35%25%6%
522
21st to endNight
11%118%38%27%6%
591
August1st to 10thNight
13%216%38%29%3
537
11th to 20thNight
12%216%29%32%7%
534
21st to endNight
16%419%38%21%2
594
September1st to 10thNight
14%419%33%23%6%
540
11th to 20thNight
18%5%22%34%18%2
631
21st to endNight
24%5%22%29%18%3
720
October1st to 10thNight
26%7%26%25%14%2
720
11th to 20thNight
26%12%30%23%8%
720
21st to endNight
33%13%25%22%6%1
792
November1st to 10thNight
28%13%29%25%6%
740
11th to 20thNight
27%16%34%16%7%
831
21st to endNight
25%18%31%20%6%
950
December1st to 10thNight
22%19%36%17%5%1
950
11th to 20thNight
22%17%35%20%5%2
950
21st to endNight
29%15%35%17%4
1045
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