Bridgewater
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bridgewater clear sky chart from 2005-11-05 to 2018-01-12.

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
41%
16607
19%
48312
11%
16561
47%
16561
30%
30178

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
32%
956
14%
2662
8%
951
38%
951
23%
1855
January16th to endNight
30%
960
16%
2562
7%
960
36%
960
21%
1816
February1st to 15thNight
30%
879
11%
2288
4%
875
35%
875
22%
1648
February16th to endNight
38%
663
19%
1925
8%
663
47%
663
28%
1234
March1st to 15thNight
34%
612
18%
2052
10%
612
43%
612
24%
1274
March16th to endNight
30%
576
15%
2112
12%
576
39%
576
21%
1346
April1st to 15thNight
31%
539
17%
1805
11%
539
42%
539
25%
1112
April16th to endNight
29%
540
17%
1620
12%
540
39%
540
21%
1102
May1st to 15thNight
37%
540
18%
1620
10%
540
44%
540
31%
996
May16th to endNight
40%
562
15%
1601
6%
561
45%
561
29%
1029
June1st to 15thNight
47%
540
16%
1266
6%
540
50%
540
39%
818
June16th to endNight
59%
540
22%
1260
8%
540
62%
540
56%
713
July1st to 15thNight
66%
510
18%
1287
8%
510
67%
510
48%
733
July16th to endNight
67%
564
24%
1514
16%
531
70%
531
52%
768
August1st to 15thNight
66%
539
21%
1610
20%
536
69%
536
44%
856
August16th to endNight
59%
573
26%
1719
24%
573
67%
573
44%
911
September1st to 15thNight
57%
540
23%
1911
21%
540
66%
540
37%
993
September16th to endNight
48%
537
29%
1980
22%
537
62%
537
35%
995
October1st to 15thNight
37%
651
27%
2091
18%
651
46%
651
31%
1200
October16th to endNight
39%
846
25%
2382
14%
846
47%
846
33%
1457
November1st to 15thNight
39%
950
24%
2470
11%
950
47%
950
35%
1524
November16th to endNight
37%
975
23%
2718
13%
975
44%
975
32%
1684
December1st to 15thNight
31%
975
13%
2737
5%
975
37%
975
22%
1896
December16th to endNight
31%
1040
16%
3120
8%
1040
39%
1040
19%
2218

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
11%6%25%42445%7%43%
49009
Night
9%6%25%42445%7%47%
48488
Cloud CoverDay
11%6%25%42445%7%43%
49019
Night
9%6%25%42445%7%47%
48491
Cloud CoverDay
11%6%25%42445%7%43%
49020
Night
9%6%25%5%2445%7%47%
48492
Cloud CoverDay
11%6%25%42445%7%43%
49018
Night
9%6%25%42445%7%47%
48492
TransparencyDay
39%6%15%24%11%1
48704
Night
36%6%15%25%14%2
48312
SeeingDay
13%7%31%31%14%1
6429
Night
12%7%33%34%10%
16609

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 15thDay
6%8%48%7%45%7%6%6%33%
1517
16th to endDay
8%13%6%10%6%35%5%5%5%29%
1659
February1st to 15thDay
12%11%47%7%46%45%5%31%
1575
16th to endDay
8%8%36%6%47%5%6%7%34%
1558
March1st to 15thDay
12%8%48%43435%7%37%
1897
16th to endDay
16%9%46%5%3445%7%32%
2112
April1st to 15thDay
16%5%35%5%2445%7%41%
2139
16th to endDay
22%8%26%5%23346%33%
2340
May1st to 15thDay
15%5%3443446%6%41%
2331
16th to endDay
16%6%25%43445%8%37%
2511
June1st to 15thDay
14%4244245%5%9%41%
2691
16th to endDay
7%3243245%6%8%51%
2700
July1st to 15thDay
6%3133235%5%9%55%
2592
16th to endDay
421332445%8%57%
2546
August1st to 15thDay
8%425%4246%7%9%42%
2340
16th to endDay
8%41432435%6%55%
2483
September1st to 15thDay
12%423423347%51%
2046
16th to endDay
9%413323346%57%
1980
October1st to 15thDay
14%5%2432333452%
1857
16th to endDay
14%6%24312346%50%
1841
November1st to 15thDay
5%7%25%42445%7%48%
1718
16th to endDay
9%8%26%42346%8%42%
1570
December1st to 15thDay
11%10%47%6%25%45%6%34%
1550
16th to endDay
12%10%5%8%8%345%5%6%28%
1456
January1st to 15thNight
5%7%48%7%5%5%5%5%8%35%
2662
16th to endNight
6%10%47%6%45%5%5%7%36%
2562
February1st to 15thNight
11%10%47%5%25%445%37%
2285
16th to endNight
6%6%36%6%345%6%7%43%
1925
March1st to 15thNight
12%7%25%5%2435%7%43%
2040
16th to endNight
12%8%36%433446%41%
2112
April1st to 15thNight
13%6%3442445%7%44%
1805
16th to endNight
17%7%25%424446%39%
1620
May1st to 15thNight
15%423423446%49%
1620
16th to endNight
12%6%26%424448%44%
1599
June1st to 15thNight
8%6%3432445%8%49%
1266
16th to endNight
5%11232235%8%64%
1260
July1st to 15thNight
421331446%7%60%
1365
16th to endNight
22123235%5%8%62%
1619
August1st to 15thNight
3233335%8%9%55%
1620
16th to endNight
6%31332245%7%59%
1719
September1st to 15thNight
8%312423346%59%
1911
16th to endNight
8%313324345%60%
1980
October1st to 15thNight
15%413322345%52%
2091
16th to endNight
12%5%24412446%50%
2382
November1st to 15thNight
7%6%2442335%7%51%
2470
16th to endNight
7%6%25%42445%8%47%
2718
December1st to 15thNight
9%9%37%6%345%5%6%38%
2737
16th to endNight
12%10%47%6%345%45%35%
3120

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
7%8%48%7%45%6%6%6%34%
1518
16th to endDay
8%12%7%9%6%45%5%5%5%29%
1659
February1st to 15thDay
12%10%47%7%36%5%5%5%31%
1575
16th to endDay
8%7%47%5%46%6%6%8%35%
1558
March1st to 15thDay
12%8%47%42435%7%38%
1908
16th to endDay
16%9%46%5%3445%6%33%
2110
April1st to 15thDay
15%6%34424447%41%
2139
16th to endDay
22%8%25%5%23346%33%
2340
May1st to 15thDay
15%5%25%42445%6%41%
2331
16th to endDay
16%6%25%5%3445%7%38%
2511
June1st to 15thDay
14%425%4245%6%9%41%
2691
16th to endDay
7%32432446%9%51%
2700
July1st to 15thDay
6%31332446%8%54%
2592
16th to endDay
421332445%8%57%
2546
August1st to 15thDay
8%4245%346%6%10%43%
2340
16th to endDay
8%32332435%7%55%
2483
September1st to 15thDay
12%41342335%7%51%
2046
16th to endDay
9%413322336%57%
1980
October1st to 15thDay
14%5%2432333453%
1857
16th to endDay
14%7%24312336%49%
1841
November1st to 15thDay
6%7%2442445%7%48%
1718
16th to endDay
9%8%25%42445%8%43%
1570
December1st to 15thDay
11%10%5%7%5%44447%35%
1550
16th to endDay
11%11%5%8%7%345%5%6%29%
1456
January1st to 15thNight
5%8%39%7%46%5%5%7%35%
2662
16th to endNight
6%10%47%7%35%45%7%37%
2562
February1st to 15thNight
11%10%46%5%24446%37%
2278
16th to endNight
6%7%36%5%335%5%7%44%
1925
March1st to 15thNight
12%7%35%5%24447%43%
2052
16th to endNight
12%8%46%424446%41%
2110
April1st to 15thNight
12%6%2442445%7%43%
1805
16th to endNight
17%7%15%42435%5%39%
1620
May1st to 15thNight
14%413423446%49%
1619
16th to endNight
12%6%25%5%14448%44%
1600
June1st to 15thNight
8%6%2432445%8%49%
1266
16th to endNight
421132335%8%64%
1260
July1st to 15thNight
421332346%7%60%
1365
16th to endNight
21222346%8%63%
1619
August1st to 15thNight
32133246%6%10%54%
1620
16th to endNight
6%31232246%6%59%
1719
September1st to 15thNight
8%313322446%59%
1911
16th to endNight
7%313323335%60%
1980
October1st to 15thNight
14%423322345%52%
2091
16th to endNight
12%424423346%51%
2382
November1st to 15thNight
7%6%25%424347%51%
2470
16th to endNight
8%6%25%425%5%48%47%
2718
December1st to 15thNight
10%9%37%6%345%5%6%38%
2737
16th to endNight
12%10%47%6%345%45%35%
3120

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
6%8%48%7%45%7%6%6%33%
1517
16th to endDay
8%12%6%10%6%46%45%5%28%
1659
February1st to 15thDay
12%11%47%7%45%45%6%30%
1575
16th to endDay
8%8%36%6%46%5%6%7%34%
1558
March1st to 15thDay
12%8%48%43435%7%37%
1908
16th to endDay
16%9%46%6%2445%7%32%
2112
April1st to 15thDay
15%6%35%5%2445%7%41%
2139
16th to endDay
22%8%35%5%23346%33%
2340
May1st to 15thDay
15%6%2443445%6%41%
2331
16th to endDay
16%6%25%5%3445%7%37%
2511
June1st to 15thDay
14%4244245%5%9%40%
2691
16th to endDay
7%3244245%5%8%51%
2700
July1st to 15thDay
6%31332445%9%54%
2592
16th to endDay
42134245%5%8%57%
2546
August1st to 15thDay
7%425%425%6%7%9%42%
2340
16th to endDay
8%41332435%6%55%
2483
September1st to 15thDay
12%413423347%51%
2046
16th to endDay
9%413322346%57%
1980
October1st to 15thDay
14%5%2342333452%
1857
16th to endDay
14%6%24312346%49%
1841
November1st to 15thDay
6%7%25%42446%7%48%
1718
16th to endDay
9%8%26%42346%7%42%
1570
December1st to 15thDay
11%10%47%6%3445%7%34%
1550
16th to endDay
12%11%48%8%345%5%6%28%
1456
January1st to 15thNight
5%8%48%7%5%5%5%5%8%35%
2662
16th to endNight
6%10%47%6%35%5%5%7%36%
2562
February1st to 15thNight
12%10%47%5%24445%37%
2278
16th to endNight
6%7%35%6%345%6%7%44%
1925
March1st to 15thNight
11%8%25%5%2435%7%43%
2052
16th to endNight
12%9%36%424446%40%
2112
April1st to 15thNight
12%6%3442445%7%44%
1805
16th to endNight
17%7%25%424446%39%
1620
May1st to 15thNight
14%4243225%46%49%
1619
16th to endNight
12%5%26%424448%44%
1599
June1st to 15thNight
7%6%3431336%8%49%
1266
16th to endNight
4211313348%64%
1260
July1st to 15thNight
421331346%7%60%
1365
16th to endNight
2223235%5%9%62%
1619
August1st to 15thNight
3234235%8%9%55%
1620
16th to endNight
6%31332346%7%59%
1719
September1st to 15thNight
7%322423346%59%
1911
16th to endNight
7%313323345%59%
1980
October1st to 15thNight
14%414322346%52%
2091
16th to endNight
12%5%24422447%50%
2382
November1st to 15thNight
7%6%2442345%7%51%
2470
16th to endNight
7%6%25%5%3445%8%47%
2718
December1st to 15thNight
9%8%37%6%35%5%46%38%
2737
16th to endNight
12%10%47%6%345%45%35%
3120

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 15thDay
6%7%5%7%7%36%7%6%7%33%
1517
16th to endDay
8%12%6%10%6%35%5%5%5%29%
1659
February1st to 15thDay
12%11%47%6%45%5%46%31%
1575
16th to endDay
8%8%37%6%47%5%5%8%35%
1558
March1st to 15thDay
12%8%47%424447%38%
1908
16th to endDay
16%9%5%5%5%3445%7%32%
2110
April1st to 15thDay
16%5%25%42445%7%40%
2139
16th to endDay
22%8%35%5%23345%34%
2340
May1st to 15thDay
15%6%2442446%6%41%
2331
16th to endDay
16%6%25%425%45%7%38%
2511
June1st to 15thDay
15%4244345%5%8%41%
2691
16th to endDay
7%32342446%8%52%
2700
July1st to 15thDay
6%3133235%5%8%55%
2592
16th to endDay
5%21332446%7%57%
2546
August1st to 15thDay
8%425%435%6%8%9%43%
2340
16th to endDay
8%31332345%6%55%
2483
September1st to 15thDay
13%413323348%50%
2046
16th to endDay
10%314313336%57%
1980
October1st to 15thDay
14%5%2331323452%
1857
16th to endDay
14%7%24313346%49%
1841
November1st to 15thDay
6%7%25%4245%5%7%48%
1718
16th to endDay
9%8%26%43346%8%42%
1570
December1st to 15thDay
11%10%48%7%35%45%6%34%
1550
16th to endDay
12%10%5%9%8%445%46%28%
1456
January1st to 15thNight
5%8%48%8%45%46%8%35%
2662
16th to endNight
6%10%47%6%35%5%5%7%36%
2562
February1st to 15thNight
11%11%47%6%24446%37%
2278
16th to endNight
7%6%35%5%35%46%7%44%
1925
March1st to 15thNight
12%7%26%423447%43%
2052
16th to endNight
12%8%35%434346%41%
2112
April1st to 15thNight
13%6%3442435%7%44%
1805
16th to endNight
18%7%25%423446%39%
1620
May1st to 15thNight
15%32432345%7%48%
1619
16th to endNight
12%6%25%424348%44%
1599
June1st to 15thNight
8%6%3441435%8%49%
1266
16th to endNight
5%2221335%7%64%
1260
July1st to 15thNight
421322445%7%61%
1365
16th to endNight
21123135%5%8%63%
1619
August1st to 15thNight
321442448%10%55%
1620
16th to endNight
6%31332345%7%58%
1719
September1st to 15thNight
8%312323346%59%
1911
16th to endNight
8%313323435%59%
1980
October1st to 15thNight
14%5%13313345%53%
2091
16th to endNight
12%5%24323446%50%
2382
November1st to 15thNight
7%6%25%42335%6%51%
2470
16th to endNight
7%6%25%5%345%48%47%
2718
December1st to 15thNight
9%9%36%7%245%5%6%38%
2737
16th to endNight
13%9%47%6%34445%34%
3120

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
47%8%18%17%8%
1518
16th to endDay
55%7%14%17%5%
1659
February1st to 15thDay
53%6%16%17%6%
1576
16th to endDay
45%8%16%17%10%
1558
March1st to 15thDay
45%6%14%23%7%1
1908
16th to endDay
51%8%16%18%5%
2112
April1st to 15thDay
42%6%14%28%7%
2139
16th to endDay
51%6%13%18%9%
2340
May1st to 15thDay
41%6%14%22%14%
2331
16th to endDay
44%7%15%22%9%
2515
June1st to 15thDay
38%7%18%24%10%1
2691
16th to endDay
27%7%17%28%15%3
2700
July1st to 15thDay
26%7%17%31%13%4
2442
16th to endDay
23%7%15%28%20%3
2388
August1st to 15thDay
33%9%16%26%11%2
2326
16th to endDay
27%7%13%32%14%4
2483
September1st to 15thDay
33%5%14%28%16%2
2046
16th to endDay
29%5%12%33%17%1
1980
October1st to 15thDay
35%412%28%18%1
1857
16th to endDay
36%416%27%13%1
1841
November1st to 15thDay
33%6%16%26%15%1
1718
16th to endDay
39%5%18%24%10%
1570
December1st to 15thDay
49%6%17%18%7%
1550
16th to endDay
55%6%15%15%6%1
1456
January1st to 15thNight
45%7%14%21%11%
2662
16th to endNight
46%7%17%19%8%
2562
February1st to 15thNight
48%6%15%20%8%
2288
16th to endNight
38%6%16%24%11%2
1925
March1st to 15thNight
40%5%15%26%10%1
2052
16th to endNight
43%5%14%25%9%
2112
April1st to 15thNight
39%5%15%26%12%
1805
16th to endNight
45%6%12%22%11%1
1620
May1st to 15thNight
35%5%12%26%17%2
1620
16th to endNight
39%5%15%23%14%1
1601
June1st to 15thNight
32%6%17%26%14%2
1266
16th to endNight
19%5%15%30%24%4
1260
July1st to 15thNight
21%7%14%32%17%7%
1287
16th to endNight
17%6%14%30%25%5%
1514
August1st to 15thNight
21%7%18%29%20%2
1610
16th to endNight
23%5%15%29%19%6%
1719
September1st to 15thNight
26%6%14%28%21%3
1911
16th to endNight
26%5%11%32%21%2
1980
October1st to 15thNight
32%411%26%21%3
2091
16th to endNight
33%5%13%26%18%2
2382
November1st to 15thNight
32%5%13%24%20%3
2470
16th to endNight
34%5%16%26%15%
2718
December1st to 15thNight
45%6%17%21%7%
2737
16th to endNight
51%5%14%20%8%
3120

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
12%9%39%30%7%
123
16th to endDay
20%9%36%29%4
96
February1st to 15thDay
16%13%40%24%5%
90
16th to endDay
11%18%34%25%8%1
81
March1st to 15thDay
15%14%38%27%21
90
16th to endDay
19%6%35%25%8%5%
96
April1st to 15thDay
20%11%36%23%6%1
258
16th to endDay
27%12%31%17%9%1
450
May1st to 15thDay
17%9%33%26%11%1
468
16th to endDay
22%8%27%29%9%2
517
June1st to 15thDay
13%7%29%27%19%2
495
16th to endDay
6%5%34%35%14%2
495
July1st to 15thDay
6%226%40%20%3
475
16th to endDay
3127%46%19%1
515
August1st to 15thDay
7%323%38%23%2
493
16th to endDay
9%324%34%24%3
523
September1st to 15thDay
11%5%29%34%14%3
201
16th to endDay
18%237%27%13%1
135
October1st to 15thDay
18%6%37%23%12%1
135
16th to endDay
17%9%38%25%9%
144
November1st to 15thDay
8%7%31%32%17%2
135
16th to endDay
25%14%31%22%5%
135
December1st to 15thDay
21%14%39%14%8%
135
16th to endDay
15%16%43%22%2
144
January1st to 15thNight
10%10%37%31%8%1
956
16th to endNight
11%12%37%32%5%
960
February1st to 15thNight
16%10%35%29%7%
880
16th to endNight
10%7%37%31%10%1
663
March1st to 15thNight
15%8%34%36%4
612
16th to endNight
15%8%38%29%6%
576
April1st to 15thNight
15%11%39%28%5%
539
16th to endNight
21%8%37%23%8%
540
May1st to 15thNight
16%8%35%28%10%
540
16th to endNight
17%433%33%10%
563
June1st to 15thNight
12%430%39%12%
540
16th to endNight
5%330%47%13%
540
July1st to 15thNight
5%222%47%20%
510
16th to endNight
3123%56%15%
564
August1st to 15thNight
4123%51%18%
539
16th to endNight
6%327%39%21%1
573
September1st to 15thNight
7%328%39%17%3
540
16th to endNight
9%434%34%14%2
537
October1st to 15thNight
17%10%32%28%10%
651
16th to endNight
15%8%32%32%10%
846
November1st to 15thNight
11%9%36%32%9%1
950
16th to endNight
10%9%37%32%8%
975
December1st to 15thNight
15%9%36%31%6%
975
16th to endNight
17%8%33%31%8%
1040
Page generated at 2018-01-12 21:01:28. Version ac04

Copyright 2018 A. Danko


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