New Haven
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the New Haven clear sky chart from 2005-11-05 to 2017-09-16.

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
39%
15474
15%
46806
10%
15438
44%
15438
21%
32481

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
18%
895
10%
2506
4%
895
23%
895
13%
1986
January16th to endNight
21%
813
10%
2541
4%
813
27%
813
11%
2000
February1st to 15thNight
18%
701
9%
2286
2%
701
26%
701
12%
1756
February16th to endNight
25%
631
14%
1893
6%
631
33%
631
15%
1402
March1st to 15thNight
27%
720
14%
2058
9%
720
32%
720
17%
1521
March16th to endNight
36%
768
18%
2112
10%
768
42%
768
23%
1479
April1st to 15thNight
34%
617
15%
1817
7%
617
41%
617
21%
1275
April16th to endNight
40%
540
20%
1620
9%
540
48%
540
25%
1060
May1st to 15thNight
42%
540
14%
1620
9%
540
48%
540
23%
1115
May16th to endNight
52%
549
16%
1672
14%
549
56%
549
29%
1052
June1st to 15thNight
56%
360
17%
1292
17%
360
63%
360
27%
772
June16th to endNight
60%
366
19%
1266
20%
366
65%
366
29%
735
July1st to 15thNight
67%
510
17%
1360
15%
510
69%
510
41%
800
July16th to endNight
70%
564
17%
1531
15%
531
72%
531
38%
888
August1st to 15thNight
69%
539
19%
1609
16%
536
71%
536
34%
957
August16th to endNight
65%
573
24%
1719
19%
573
69%
573
34%
1020
September1st to 15thNight
59%
687
22%
1931
16%
687
63%
687
33%
1186
September16th to endNight
60%
661
22%
1826
17%
661
63%
661
33%
1130
October1st to 15thNight
47%
660
18%
1917
16%
660
51%
660
27%
1244
October16th to endNight
28%
704
14%
2181
8%
704
36%
704
17%
1577
November1st to 15thNight
39%
700
20%
2276
16%
700
46%
700
22%
1486
November16th to endNight
26%
720
13%
2457
9%
720
33%
720
14%
1765
December1st to 15thNight
18%
720
7%
2520
3%
720
23%
720
10%
1966
December16th to endNight
16%
936
7%
2796
2%
936
21%
936
9%
2309

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%8%47%6%35%5%5%7%33%
47933
Night
14%8%46%5%3445%6%35%
46987
Cloud CoverDay
13%8%47%6%35%5%5%7%33%
47943
Night
15%8%46%5%3445%6%36%
46991
TransparencyDay
47%7%12%20%10%1
47632
Night
47%6%12%21%11%1
46806
SeeingDay
16%423%28%18%7%
5780
Night
18%5%28%30%14%1
15484

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
18%13%6%10%8%35%445%19%
1432
16th to endDay
15%17%7%10%9%36%44415%
1680
February1st to 15thDay
15%13%7%10%8%45%446%18%
1575
16th to endDay
12%13%6%11%8%35%446%24%
1580
March1st to 15thDay
17%12%5%8%6%34446%26%
1891
16th to endDay
18%11%47%6%34446%28%
2112
April1st to 15thDay
18%9%47%5%2435%6%31%
2139
16th to endDay
16%8%35%6%23447%36%
2340
May1st to 15thDay
17%7%36%5%345%47%33%
2331
16th to endDay
12%5%35%5%35%448%39%
2440
June1st to 15thDay
9%436%5%35%5%7%10%38%
2665
16th to endDay
8%5%25%5%46%5%6%10%37%
2690
July1st to 15thDay
7%425%6%35%6%5%9%43%
2520
16th to endDay
7%435%5%36%6%7%11%38%
2528
August1st to 15thDay
7%426%6%36%6%7%10%37%
2340
16th to endDay
10%425%5%35%5%6%8%40%
2483
September1st to 15thDay
10%5%345%346%5%9%40%
2016
16th to endDay
11%5%35%5%35%5%5%8%39%
1824
October1st to 15thDay
12%8%37%5%34447%39%
1713
16th to endDay
20%10%46%5%24345%31%
1689
November1st to 15thDay
13%8%26%5%345%47%37%
1582
16th to endDay
17%10%47%6%345%5%6%27%
1501
December1st to 15thDay
17%12%6%10%7%3435%6%21%
1440
16th to endDay
20%16%6%9%6%2445%5%18%
1422
January1st to 15thNight
22%11%5%8%6%34445%23%
2506
16th to endNight
14%13%7%9%7%345%45%23%
2541
February1st to 15thNight
14%14%6%9%6%34445%25%
2284
16th to endNight
15%11%5%9%6%45%445%28%
1893
March1st to 15thNight
17%9%5%6%6%35%446%31%
2046
16th to endNight
17%7%25%5%345%5%7%35%
2112
April1st to 15thNight
19%8%25%43445%7%34%
1817
16th to endNight
14%6%3443446%8%40%
1620
May1st to 15thNight
16%6%35%6%3446%7%36%
1620
16th to endNight
10%426%42445%7%45%
1670
June1st to 15thNight
7%425%5%246%6%8%45%
1292
16th to endNight
8%5%244246%6%9%45%
1266
July1st to 15thNight
7%32342435%8%52%
1440
16th to endNight
5%3233245%7%9%51%
1637
August1st to 15thNight
5%425%4346%6%8%48%
1620
16th to endNight
7%5%245%33445%53%
1719
September1st to 15thNight
9%5%3443335%6%49%
1931
16th to endNight
10%425%42345%7%48%
1826
October1st to 15thNight
14%6%25%42445%6%43%
1917
16th to endNight
20%8%36%5%345%5%5%31%
2181
November1st to 15thNight
14%7%35%43445%7%38%
2276
16th to endNight
19%11%46%5%2445%6%29%
2457
December1st to 15thNight
20%12%5%8%5%245%46%24%
2520
16th to endNight
22%14%6%9%6%3444419%
2796

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
18%13%6%10%6%5%4445%19%
1432
16th to endDay
15%17%7%9%9%35%44416%
1680
February1st to 15thDay
15%13%7%9%8%45%446%19%
1575
16th to endDay
12%14%6%10%8%35%5%46%24%
1580
March1st to 15thDay
17%11%5%7%6%34446%26%
1902
16th to endDay
18%11%47%6%34445%28%
2111
April1st to 15thDay
18%9%47%6%2445%6%31%
2139
16th to endDay
17%7%26%5%33347%37%
2340
May1st to 15thDay
17%6%36%5%35%5%47%33%
2331
16th to endDay
12%5%36%5%35%45%8%40%
2440
June1st to 15thDay
9%436%5%35%47%9%39%
2665
16th to endDay
8%5%35%6%46%6%6%10%38%
2690
July1st to 15thDay
7%425%6%25%5%5%9%44%
2520
16th to endDay
7%425%5%36%6%8%10%39%
2528
August1st to 15thDay
7%427%5%35%7%7%10%37%
2340
16th to endDay
11%425%5%36%46%8%41%
2483
September1st to 15thDay
11%5%25%5%345%5%9%40%
2016
16th to endDay
11%5%35%436%5%6%8%40%
1824
October1st to 15thDay
12%8%36%5%35%447%39%
1713
16th to endDay
19%10%47%424435%32%
1689
November1st to 15thDay
14%7%36%4345%5%6%38%
1582
16th to endDay
17%10%47%6%3445%6%27%
1501
December1st to 15thDay
18%12%6%10%6%3445%5%22%
1440
16th to endDay
20%16%6%8%5%34446%17%
1422
January1st to 15thNight
21%11%5%8%6%34445%23%
2506
16th to endNight
14%14%8%9%7%34445%23%
2541
February1st to 15thNight
13%14%6%9%6%345%45%26%
2277
16th to endNight
16%11%5%8%6%35%445%28%
1893
March1st to 15thNight
18%10%46%6%34446%31%
2058
16th to endNight
18%7%25%5%335%5%7%36%
2112
April1st to 15thNight
19%8%344345%47%34%
1817
16th to endNight
14%6%344245%6%7%40%
1620
May1st to 15thNight
16%6%36%6%2445%7%36%
1619
16th to endNight
11%436%43445%7%45%
1670
June1st to 15thNight
7%425%5%345%5%8%46%
1292
16th to endNight
8%5%244236%5%9%45%
1266
July1st to 15thNight
8%3135%1445%8%52%
1440
16th to endNight
5%4233245%7%9%52%
1637
August1st to 15thNight
5%315%435%5%5%8%48%
1620
16th to endNight
8%5%24424446%52%
1719
September1st to 15thNight
9%5%3442435%6%49%
1931
16th to endNight
10%425%42345%7%48%
1826
October1st to 15thNight
14%6%26%424346%43%
1917
16th to endNight
20%8%36%5%345%46%31%
2181
November1st to 15thNight
14%6%36%43446%7%39%
2276
16th to endNight
20%11%46%5%2445%6%29%
2457
December1st to 15thNight
21%12%5%7%6%25%445%24%
2520
16th to endNight
22%14%6%9%5%35%44419%
2796

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
65%6%12%11%4
1433
16th to endDay
70%5%9%9%4
1680
February1st to 15thDay
65%5%8%14%4
1577
16th to endDay
60%6%10%15%5%1
1580
March1st to 15thDay
58%6%11%15%6%
1902
16th to endDay
55%6%10%19%7%1
2112
April1st to 15thDay
52%5%10%19%10%
2139
16th to endDay
46%5%12%17%14%2
2340
May1st to 15thDay
49%6%10%20%10%2
2331
16th to endDay
41%7%11%23%14%1
2444
June1st to 15thDay
38%8%13%24%13%1
2665
16th to endDay
39%8%15%21%14%1
2690
July1st to 15thDay
34%7%10%26%18%2
2371
16th to endDay
34%9%16%22%13%2
2371
August1st to 15thDay
35%10%14%24%12%1
2327
16th to endDay
37%8%12%25%14%1
2483
September1st to 15thDay
37%8%14%25%12%
2016
16th to endDay
38%7%12%28%12%
1824
October1st to 15thDay
43%5%13%22%12%1
1713
16th to endDay
53%6%14%17%7%
1689
November1st to 15thDay
43%8%12%23%10%1
1582
16th to endDay
56%7%13%15%6%
1501
December1st to 15thDay
63%7%11%12%4
1440
16th to endDay
67%6%11%10%3
1422
January1st to 15thNight
62%5%10%14%6%
2506
16th to endNight
62%6%12%14%4
2541
February1st to 15thNight
59%6%10%14%6%
2286
16th to endNight
56%5%11%19%6%
1893
March1st to 15thNight
53%6%9%19%9%1
2058
16th to endNight
47%5%11%23%10%1
2112
April1st to 15thNight
49%411%20%13%1
1817
16th to endNight
41%7%10%19%17%4
1620
May1st to 15thNight
45%6%11%19%13%2
1620
16th to endNight
37%6%11%23%17%3
1672
June1st to 15thNight
35%8%11%27%15%1
1292
16th to endNight
33%6%13%24%19%1
1266
July1st to 15thNight
29%5%10%30%21%2
1360
16th to endNight
26%9%17%24%19%3
1531
August1st to 15thNight
30%7%13%31%13%3
1609
16th to endNight
32%6%10%29%18%2
1719
September1st to 15thNight
34%5%12%28%16%1
1931
16th to endNight
34%6%11%31%14%1
1826
October1st to 15thNight
41%5%12%21%18%
1917
16th to endNight
51%6%13%20%6%
2181
November1st to 15thNight
43%6%12%24%11%1
2276
16th to endNight
54%5%14%19%6%
2457
December1st to 15thNight
61%7%13%12%5%
2520
16th to endNight
67%6%10%10%4
2796

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
23%8%42%17%6%1
90
16th to endDay
38%7%32%17%31
96
February1st to 15thDay
20%6%47%24%1
90
16th to endDay
12%13%43%24%6%
81
March1st to 15thDay
28%10%29%24%7%
192
16th to endDay
25%5%25%30%9%3
288
April1st to 15thDay
20%8%29%27%11%2
270
16th to endDay
24%425%23%14%7%
270
May1st to 15thDay
23%226%24%19%3
288
16th to endDay
17%321%30%19%8%
331
June1st to 15thDay
11%125%36%20%5%
460
16th to endDay
9%227%35%18%5%
495
July1st to 15thDay
8%118%35%24%10%
475
16th to endDay
7%215%34%27%11%
388
August1st to 15thDay
7%111%34%26%18%
313
16th to endDay
14%314%24%25%18%
332
September1st to 15thDay
10%220%18%31%17%
315
16th to endDay
15%312%26%28%14%
257
October1st to 15thDay
14%426%25%21%7%
255
16th to endDay
27%5%34%25%41
201
November1st to 15thDay
12%8%20%38%17%2
90
16th to endDay
24%24%24%20%7%
70
December1st to 15thDay
23%13%43%16%3
60
16th to endDay
27%17%42%12%
73
January1st to 15thNight
27%9%36%21%41
900
16th to endNight
20%8%36%28%6%
813
February1st to 15thNight
20%7%42%25%3
704
16th to endNight
21%8%33%30%5%
631
March1st to 15thNight
22%8%35%27%6%
720
16th to endNight
20%432%29%12%1
768
April1st to 15thNight
22%6%31%32%6%
617
16th to endNight
17%433%32%11%1
540
May1st to 15thNight
19%325%36%14%
540
16th to endNight
11%223%37%21%3
551
June1st to 15thNight
9%124%46%18%
360
16th to endNight
11%117%45%24%
366
July1st to 15thNight
9%114%39%31%4
510
16th to endNight
5%115%45%28%3
564
August1st to 15thNight
7%12%40%33%4
539
16th to endNight
9%114%36%33%4
573
September1st to 15thNight
11%317%32%27%6%
687
16th to endNight
13%215%34%27%6%
661
October1st to 15thNight
18%423%30%20%2
660
16th to endNight
25%8%33%26%5%
704
November1st to 15thNight
16%8%31%27%15%1
700
16th to endNight
26%12%29%22%8%
720
December1st to 15thNight
28%11%35%19%5%
720
16th to endNight
27%9%36%23%3
936
Page generated at 2017-09-17 12:05:45. Version ac04

Copyright 2017 A. Danko


New Haven Clear Sky Chart | Charts Home