North Falmouth
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the North Falmouth 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
33%
15441
17%
48292
9%
15406
43%
15406
21%
32037

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
19%
765
17%
2662
5%
761
33%
761
18%
1702
January16th to endNight
17%
768
17%
2668
5%
768
34%
768
15%
1758
February1st to 15thNight
19%
704
16%
2168
4%
701
34%
701
17%
1494
February16th to endNight
17%
631
23%
1893
5%
631
38%
631
23%
1233
March1st to 15thNight
25%
720
17%
2133
8%
720
36%
720
21%
1442
March16th to endNight
28%
768
20%
2064
8%
768
38%
768
24%
1414
April1st to 15thNight
30%
718
17%
1796
5%
718
36%
718
24%
1285
April16th to endNight
34%
576
17%
1656
7%
576
41%
576
23%
1143
May1st to 15thNight
33%
540
15%
1620
7%
540
39%
540
19%
1154
May16th to endNight
39%
478
10%
1600
8%
477
43%
477
16%
1137
June1st to 15thNight
40%
360
11%
1440
13%
360
45%
360
15%
980
June16th to endNight
53%
360
11%
1440
15%
360
57%
360
21%
864
July1st to 15thNight
52%
340
12%
1360
15%
340
55%
340
20%
832
July16th to endNight
54%
395
13%
1436
17%
372
55%
372
19%
933
August1st to 15thNight
58%
539
16%
1608
11%
535
60%
535
28%
1021
August16th to endNight
61%
702
21%
1848
13%
702
62%
702
34%
1188
September1st to 15thNight
52%
720
19%
1886
12%
720
56%
720
34%
1211
September16th to endNight
49%
717
23%
1980
17%
717
54%
717
28%
1309
October1st to 15thNight
39%
720
20%
2001
12%
720
47%
720
24%
1357
October16th to endNight
31%
768
18%
2478
10%
768
42%
768
22%
1600
November1st to 15thNight
34%
760
15%
2472
10%
760
42%
760
19%
1663
November16th to endNight
27%
780
21%
2535
8%
780
42%
780
20%
1593
December1st to 15thNight
22%
780
17%
2636
6%
780
35%
780
17%
1762
December16th to endNight
16%
832
18%
2912
5%
832
33%
832
14%
1962

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
17%6%2442445%7%40%
49042
Night
17%7%35%424446%38%
48465
Cloud CoverDay
17%6%2442445%7%40%
49052
Night
17%7%25%424446%38%
48470
TransparencyDay
43%5%12%23%13%1
48733
Night
45%412%21%13%1
48292
SeeingDay
20%6%26%27%15%3
6351
Night
21%9%28%28%11%1
15441

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
16%8%24323446%42%
1520
16th to endDay
16%6%35%43345%5%41%
1554
February1st to 15thDay
17%8%3442445%7%38%
1692
16th to endDay
15%7%34424447%41%
1580
March1st to 15thDay
19%7%35%33335%6%38%
1815
16th to endDay
16%7%35%324346%42%
2157
April1st to 15thDay
19%6%244145%46%39%
2152
16th to endDay
18%6%24423447%40%
2302
May1st to 15thDay
25%7%35%413446%32%
2332
16th to endDay
16%7%24425%35%7%39%
2524
June1st to 15thDay
24%6%2442445%8%32%
2520
16th to endDay
13%5%2433446%10%40%
2520
July1st to 15thDay
13%5%25%4245%6%7%41%
2520
16th to endDay
12%5%25%5%245%6%9%38%
2621
August1st to 15thDay
12%5%15%43446%8%43%
2340
16th to endDay
11%5%144235%5%8%46%
2351
September1st to 15thDay
14%5%14433346%47%
2073
16th to endDay
17%5%15%322446%46%
1980
October1st to 15thDay
18%6%23423446%43%
1958
16th to endDay
16%5%24423346%45%
1745
November1st to 15thDay
22%7%2442444438%
1716
16th to endDay
17%6%25%414447%41%
1755
December1st to 15thDay
19%7%36%424336%38%
1651
16th to endDay
21%10%34433335%34%
1664
January1st to 15thNight
17%8%3442345%5%40%
2662
16th to endNight
18%11%35%423345%38%
2668
February1st to 15thNight
16%7%46%5%24336%37%
2167
16th to endNight
14%8%25%6%23345%42%
1893
March1st to 15thNight
18%7%35%423447%38%
2120
16th to endNight
16%8%35%434345%40%
2064
April1st to 15thNight
18%8%35%424346%36%
1796
16th to endNight
22%5%35%324445%37%
1656
May1st to 15thNight
21%9%36%5%2235%6%32%
1620
16th to endNight
18%8%46%6%3445%6%30%
1598
June1st to 15thNight
22%8%46%32445%7%31%
1440
16th to endNight
19%5%2432435%10%38%
1440
July1st to 15thNight
15%8%2442445%8%38%
1440
16th to endNight
12%7%36%6%25%6%7%8%32%
1533
August1st to 15thNight
9%6%25%425%5%7%8%40%
1620
16th to endNight
13%5%145%2446%7%44%
1848
September1st to 15thNight
13%5%15%42436%7%45%
1886
16th to endNight
16%7%2442334445%
1980
October1st to 15thNight
17%6%25%5%33345%41%
2001
16th to endNight
17%7%2442435%6%41%
2478
November1st to 15thNight
19%6%25%425%5%35%39%
2472
16th to endNight
16%6%25%323347%41%
2535
December1st to 15thNight
20%6%25%5%23345%37%
2636
16th to endNight
19%8%4442435%6%36%
2912

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
16%8%24413447%41%
1520
16th to endDay
16%6%35%42445%5%42%
1554
February1st to 15thDay
17%7%3442445%7%38%
1692
16th to endDay
15%7%34424447%40%
1580
March1st to 15thDay
20%7%2443335%6%37%
1825
16th to endDay
17%7%35%323346%42%
2157
April1st to 15thDay
19%6%344235%46%39%
2152
16th to endDay
18%6%2442445%6%40%
2302
May1st to 15thDay
25%7%35%5%23346%32%
2332
16th to endDay
17%6%34425%347%39%
2524
June1st to 15thDay
24%6%245%2445%7%33%
2520
16th to endDay
14%42442446%9%41%
2520
July1st to 15thDay
14%5%244345%6%7%41%
2520
16th to endDay
13%5%25%425%5%6%9%38%
2621
August1st to 15thDay
12%5%24425%46%7%44%
2340
16th to endDay
11%5%1442346%7%46%
2351
September1st to 15thDay
14%5%145%23346%46%
2073
16th to endDay
17%5%14322446%46%
1980
October1st to 15thDay
18%6%24424346%43%
1958
16th to endDay
16%5%25%423346%45%
1745
November1st to 15thDay
22%7%24423445%38%
1716
16th to endDay
16%6%25%42435%8%40%
1755
December1st to 15thDay
19%7%35%424336%37%
1651
16th to endDay
21%10%34424335%34%
1664
January1st to 15thNight
17%7%34424346%39%
2662
16th to endNight
18%11%35%323345%38%
2668
February1st to 15thNight
16%8%36%5%24436%37%
2160
16th to endNight
14%8%25%5%33346%41%
1893
March1st to 15thNight
19%7%25%424447%38%
2133
16th to endNight
16%7%35%424435%40%
2063
April1st to 15thNight
18%9%35%433336%36%
1796
16th to endNight
22%6%35%324345%37%
1656
May1st to 15thNight
22%8%35%5%2235%5%32%
1620
16th to endNight
18%9%46%6%3445%6%30%
1598
June1st to 15thNight
23%9%35%32335%6%31%
1440
16th to endNight
18%5%2342435%9%38%
1440
July1st to 15thNight
16%7%25%4235%6%7%38%
1440
16th to endNight
12%7%36%6%35%6%6%8%33%
1533
August1st to 15thNight
10%6%15%5%35%5%7%8%40%
1620
16th to endNight
13%5%1343445%8%44%
1848
September1st to 15thNight
14%42432435%7%45%
1886
16th to endNight
16%7%25%42344445%
1980
October1st to 15thNight
17%6%345%2444441%
2001
16th to endNight
17%6%24433447%41%
2478
November1st to 15thNight
19%6%244245%45%39%
2472
16th to endNight
16%7%25%42335%7%41%
2535
December1st to 15thNight
20%6%25%5%23345%37%
2636
16th to endNight
19%9%3442435%6%36%
2912

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
42%5%13%23%11%3
1521
16th to endDay
44%312%25%12%1
1554
February1st to 15thDay
45%5%14%21%12%1
1695
16th to endDay
43%313%24%13%1
1580
March1st to 15thDay
47%415%22%9%2
1825
16th to endDay
43%310%23%14%3
2157
April1st to 15thDay
44%5%8%22%16%2
2152
16th to endDay
43%49%23%15%3
2302
May1st to 15thDay
52%48%17%14%2
2332
16th to endDay
44%5%14%23%10%1
2528
June1st to 15thDay
49%6%13%19%10%
2520
16th to endDay
38%5%15%23%15%
2520
July1st to 15thDay
39%7%12%24%14%1
2371
16th to endDay
39%7%15%24%11%2
2456
August1st to 15thDay
37%5%16%25%14%1
2327
16th to endDay
34%5%11%27%18%1
2351
September1st to 15thDay
37%5%11%22%21%1
2073
16th to endDay
38%48%25%19%3
1980
October1st to 15thDay
42%310%25%14%2
1958
16th to endDay
39%312%26%14%2
1745
November1st to 15thDay
48%5%12%19%11%1
1716
16th to endDay
43%413%24%12%2
1755
December1st to 15thDay
48%316%16%13%
1651
16th to endDay
53%413%19%9%
1664
January1st to 15thNight
44%415%22%11%1
2662
16th to endNight
48%310%22%12%1
2668
February1st to 15thNight
48%5%11%22%10%1
2168
16th to endNight
44%311%24%14%1
1893
March1st to 15thNight
46%413%20%12%2
2133
16th to endNight
46%39%18%17%4
2064
April1st to 15thNight
49%47%19%15%2
1796
16th to endNight
47%49%20%13%4
1656
May1st to 15thNight
52%49%17%13%2
1620
16th to endNight
53%5%12%18%8%2
1600
June1st to 15thNight
52%5%11%17%12%
1440
16th to endNight
42%413%23%15%1
1440
July1st to 15thNight
43%5%12%24%13%
1360
16th to endNight
45%7%13%23%7%2
1436
August1st to 15thNight
37%7%14%24%14%1
1608
16th to endNight
36%5%12%26%17%1
1848
September1st to 15thNight
37%413%25%17%1
1886
16th to endNight
41%46%21%23%1
1980
October1st to 15thNight
45%48%23%14%2
2001
16th to endNight
42%5%14%23%13%1
2478
November1st to 15thNight
46%6%12%20%13%2
2472
16th to endNight
42%313%24%12%2
2535
December1st to 15thNight
48%315%20%11%
2636
16th to endNight
48%5%13%20%10%
2912

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
15%15%45%14%8%
82
16th to endDay
19%12%39%25%3
82
February1st to 15thDay
24%12%36%23%3
257
16th to endDay
14%12%46%22%5%
239
March1st to 15thDay
24%12%35%21%5%
270
16th to endDay
20%13%33%22%9%1
288
April1st to 15thDay
23%6%32%29%7%1
270
16th to endDay
24%8%28%25%8%4
270
May1st to 15thDay
32%5%22%23%12%3
288
16th to endDay
23%220%32%19%2
331
June1st to 15thDay
24%123%30%16%2
315
16th to endDay
15%322%37%17%3
315
July1st to 15thDay
20%110%35%28%3
305
16th to endDay
13%117%33%27%5%
326
August1st to 15thDay
14%113%42%23%4
313
16th to endDay
12%113%32%28%10%
332
September1st to 15thDay
15%125%26%24%6%
315
16th to endDay
25%220%23%14%14%
314
October1st to 15thDay
22%5%22%24%18%6%
309
16th to endDay
17%9%34%25%12%1
288
November1st to 15thDay
23%8%28%26%11%1
280
16th to endDay
18%16%28%23%11%1
285
December1st to 15thDay
22%11%34%24%7%
181
16th to endDay
30%19%36%10%3
96
January1st to 15thNight
21%14%40%19%3
765
16th to endNight
24%17%34%19%2
768
February1st to 15thNight
21%14%39%23%1
704
16th to endNight
19%12%45%19%3
631
March1st to 15thNight
23%9%35%24%6%
720
16th to endNight
20%10%35%24%8%
768
April1st to 15thNight
22%7%32%33%4
718
16th to endNight
23%6%28%30%10%
576
May1st to 15thNight
25%5%26%29%10%2
540
16th to endNight
23%421%36%12%
478
June1st to 15thNight
26%420%32%16%
360
16th to endNight
21%313%41%19%
360
July1st to 15thNight
19%215%42%18%
340
16th to endNight
16%215%38%25%2
395
August1st to 15thNight
12%18%43%23%1
539
16th to endNight
17%111%37%28%3
702
September1st to 15thNight
16%121%38%19%2
720
16th to endNight
19%417%29%23%5%
717
October1st to 15thNight
22%6%24%27%15%3
720
16th to endNight
21%12%30%24%9%
768
November1st to 15thNight
22%10%26%27%12%1
760
16th to endNight
19%14%31%25%8%1
780
December1st to 15thNight
25%13%33%21%5%
780
16th to endNight
22%18%38%18%2
832
Page generated at 2018-01-12 22:01:28. Version ac04

Copyright 2018 A. Danko


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