Hartford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hartford clear sky chart from 2005-11-05 to 2018-02-22.

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
29%
15576
18%
48876
8%
15544
40%
15544
20%
32135

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%
780
20%
2716
7%
776
35%
776
17%
1728
January16th to endNight
17%
832
19%
2892
6%
832
36%
832
16%
1857
February1st to 15thNight
15%
764
17%
2373
5%
761
30%
761
16%
1625
February16th to endNight
17%
659
23%
1976
7%
659
37%
659
18%
1306
March1st to 15thNight
17%
720
16%
2160
5%
720
31%
720
16%
1495
March16th to endNight
21%
768
24%
2007
8%
768
34%
768
23%
1336
April1st to 15thNight
20%
718
16%
1796
4%
718
27%
718
21%
1309
April16th to endNight
22%
642
17%
1722
4%
642
31%
642
21%
1188
May1st to 15thNight
22%
540
16%
1620
7%
540
31%
540
17%
1154
May16th to endNight
33%
375
12%
1497
9%
374
40%
374
17%
970
June1st to 15thNight
35%
360
13%
1440
8%
360
48%
360
15%
961
June16th to endNight
42%
360
14%
1440
14%
360
50%
360
23%
853
July1st to 15thNight
46%
340
12%
1360
15%
340
50%
340
21%
841
July16th to endNight
52%
376
14%
1418
16%
354
58%
354
21%
880
August1st to 15thNight
47%
501
17%
1572
11%
499
52%
499
28%
966
August16th to endNight
54%
764
20%
1910
11%
764
56%
764
33%
1255
September1st to 15thNight
41%
720
20%
1827
10%
720
47%
720
29%
1215
September16th to endNight
47%
717
26%
1980
18%
717
52%
717
31%
1241
October1st to 15thNight
37%
720
21%
2051
12%
720
47%
720
25%
1356
October16th to endNight
26%
768
17%
2454
8%
768
39%
768
21%
1603
November1st to 15thNight
30%
760
19%
2472
9%
760
45%
760
21%
1589
November16th to endNight
26%
780
22%
2551
10%
780
41%
780
19%
1651
December1st to 15thNight
23%
780
16%
2730
5%
780
37%
780
17%
1810
December16th to endNight
17%
832
19%
2912
5%
832
34%
832
15%
1946

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%5%25%42445%7%40%
49378
Night
17%6%24424446%41%
49046
Cloud CoverDay
17%5%25%5%2445%7%40%
49388
Night
17%6%25%424446%41%
49051
TransparencyDay
43%6%11%21%15%2
49066
Night
43%6%11%21%15%2
48876
SeeingDay
22%13%29%21%9%3
6294
Night
22%12%32%24%7%
15576

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%5%334235%5%7%42%
1552
16th to endDay
16%7%2332446%7%42%
1681
February1st to 15thDay
16%6%36%5%26%5%5%6%34%
1816
16th to endDay
17%6%25%4245%46%38%
1644
March1st to 15thDay
19%6%35%5%24447%37%
1790
16th to endDay
17%6%345%23336%43%
2214
April1st to 15thDay
19%6%35%43345%5%39%
2152
16th to endDay
17%424424346%44%
2238
May1st to 15thDay
24%5%25%424446%33%
2341
16th to endDay
17%5%2442445%8%39%
2618
June1st to 15thDay
22%6%2442445%7%35%
2520
16th to endDay
13%5%25%5%35%5%5%10%36%
2520
July1st to 15thDay
11%5%25%6%46%5%6%8%37%
2520
16th to endDay
12%5%25%6%35%6%5%8%37%
2654
August1st to 15thDay
11%6%35%6%35%5%6%7%37%
2362
16th to endDay
10%436%4245%5%7%44%
2292
September1st to 15thDay
13%5%26%5%24446%45%
2132
16th to endDay
14%424324345%49%
1980
October1st to 15thDay
18%6%34433346%42%
1908
16th to endDay
17%5%24434446%42%
1769
November1st to 15thDay
18%6%35%323336%43%
1716
16th to endDay
18%424424346%44%
1735
December1st to 15thDay
18%5%26%423446%39%
1560
16th to endDay
21%7%3442445%6%35%
1664
January1st to 15thNight
18%6%24424446%41%
2716
16th to endNight
16%8%35%323346%41%
2892
February1st to 15thNight
16%8%35%5%34446%37%
2372
16th to endNight
17%7%25%423435%41%
1976
March1st to 15thNight
19%7%3442445%6%37%
2147
16th to endNight
17%5%34313336%45%
2007
April1st to 15thNight
17%7%36%5%24445%37%
1796
16th to endNight
21%5%245%13445%41%
1722
May1st to 15thNight
20%7%25%434446%36%
1620
16th to endNight
18%6%2333446%9%37%
1495
June1st to 15thNight
22%42442445%6%37%
1440
16th to endNight
14%4143345%6%8%44%
1440
July1st to 15thNight
12%6%2443446%11%38%
1440
16th to endNight
9%5%25%5%45%5%7%8%39%
1514
August1st to 15thNight
11%41443446%8%45%
1582
16th to endNight
12%3145%36%46%7%44%
1910
September1st to 15thNight
14%424424445%45%
1827
16th to endNight
13%5%25%322445%50%
1980
October1st to 15thNight
17%5%245%34335%45%
2051
16th to endNight
20%5%245%23445%40%
2454
November1st to 15thNight
18%6%25%323345%43%
2472
16th to endNight
18%6%24423445%41%
2551
December1st to 15thNight
20%7%25%434346%38%
2730
16th to endNight
21%7%24424446%37%
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%5%3342445%6%42%
1552
16th to endDay
16%7%2431446%7%41%
1681
February1st to 15thDay
17%6%25%5%36%5%47%34%
1816
16th to endDay
17%6%15%435%446%39%
1644
March1st to 15thDay
20%5%25%434447%37%
1800
16th to endDay
17%6%25%424335%43%
2214
April1st to 15thDay
19%7%25%423445%38%
2152
16th to endDay
18%414425%346%44%
2238
May1st to 15thDay
24%5%34424447%33%
2341
16th to endDay
18%5%235%24447%40%
2618
June1st to 15thDay
23%5%25%42445%6%35%
2520
16th to endDay
12%5%25%6%35%46%9%37%
2520
July1st to 15thDay
12%5%35%6%36%5%5%8%37%
2520
16th to endDay
13%425%5%36%5%5%8%38%
2654
August1st to 15thDay
12%5%26%6%35%5%6%8%37%
2362
16th to endDay
11%426%42446%6%44%
2292
September1st to 15thDay
14%5%245%25%35%5%45%
2132
16th to endDay
15%424323346%49%
1980
October1st to 15thDay
18%6%24423346%43%
1908
16th to endDay
17%5%24423445%42%
1769
November1st to 15thDay
19%6%25%423335%43%
1716
16th to endDay
18%424423446%44%
1735
December1st to 15thDay
18%7%25%5%13446%39%
1560
16th to endDay
21%7%25%41445%6%35%
1664
January1st to 15thNight
18%7%25%42335%5%41%
2716
16th to endNight
17%8%35%422346%41%
2892
February1st to 15thNight
16%8%35%5%35%445%37%
2365
16th to endNight
18%6%25%424435%41%
1976
March1st to 15thNight
19%6%34434446%37%
2160
16th to endNight
17%6%23413336%44%
2006
April1st to 15thNight
18%6%35%5%34445%38%
1796
16th to endNight
22%425%423345%41%
1722
May1st to 15thNight
21%6%25%5%24346%36%
1620
16th to endNight
18%42433346%8%38%
1495
June1st to 15thNight
22%6%1442445%6%37%
1440
16th to endNight
13%425%42445%7%45%
1440
July1st to 15thNight
12%5%25%43447%10%38%
1440
16th to endNight
10%425%5%45%6%6%9%38%
1514
August1st to 15thNight
11%4234345%5%7%45%
1582
16th to endNight
13%315%5%25%5%5%7%45%
1910
September1st to 15thNight
14%425%42445%6%45%
1827
16th to endNight
14%425%323445%49%
1980
October1st to 15thNight
17%5%24434345%45%
2051
16th to endNight
20%6%25%422445%41%
2454
November1st to 15thNight
18%6%24412345%44%
2472
16th to endNight
19%6%24424345%41%
2551
December1st to 15thNight
20%6%25%423446%38%
2730
16th to endNight
21%7%245%24346%37%
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
41%6%13%24%11%3
1553
16th to endDay
40%6%12%24%14%1
1681
February1st to 15thDay
47%7%11%19%12%1
1819
16th to endDay
44%5%10%22%13%2
1644
March1st to 15thDay
47%5%12%22%9%2
1800
16th to endDay
43%39%20%16%4
2214
April1st to 15thDay
46%5%10%19%16%2
2152
16th to endDay
41%49%21%18%3
2238
May1st to 15thDay
50%6%8%19%12%2
2341
16th to endDay
42%8%12%19%14%2
2622
June1st to 15thDay
49%6%11%20%10%1
2520
16th to endDay
42%8%13%21%14%
2520
July1st to 15thDay
44%8%11%19%15%1
2371
16th to endDay
41%8%13%20%13%2
2487
August1st to 15thDay
43%7%13%19%14%
2348
16th to endDay
36%8%9%25%18%1
2292
September1st to 15thDay
39%6%11%20%19%2
2132
16th to endDay
36%5%7%22%25%2
1980
October1st to 15thDay
43%5%10%23%14%2
1908
16th to endDay
42%5%10%23%15%2
1769
November1st to 15thDay
44%412%19%16%2
1716
16th to endDay
42%39%26%15%2
1735
December1st to 15thDay
44%5%15%17%14%1
1560
16th to endDay
48%6%14%17%11%
1664
January1st to 15thNight
44%412%22%14%2
2716
16th to endNight
44%5%11%20%16%2
2892
February1st to 15thNight
47%5%12%19%12%2
2373
16th to endNight
44%410%22%15%2
1976
March1st to 15thNight
46%6%11%19%13%2
2160
16th to endNight
41%49%21%18%4
2007
April1st to 15thNight
47%6%9%18%15%2
1796
16th to endNight
44%5%7%21%16%4
1722
May1st to 15thNight
48%7%8%17%14%3
1620
16th to endNight
42%9%16%17%11%1
1497
June1st to 15thNight
47%7%12%18%12%1
1440
16th to endNight
37%7%13%26%14%
1440
July1st to 15thNight
38%9%12%22%15%
1360
16th to endNight
39%9%15%22%11%2
1418
August1st to 15thNight
35%8%14%25%14%2
1572
16th to endNight
36%7%10%27%17%
1910
September1st to 15thNight
38%6%11%22%19%
1827
16th to endNight
36%5%6%22%26%1
1980
October1st to 15thNight
42%5%10%21%17%2
2051
16th to endNight
44%413%22%14%
2454
November1st to 15thNight
42%5%11%19%18%2
2472
16th to endNight
44%411%23%13%2
2551
December1st to 15thNight
47%5%14%19%12%
2730
16th to endNight
48%411%20%13%
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
21%32%28%15%2
90
16th to endDay
26%19%42%10%
101
February1st to 15thDay
26%26%30%15%1
242
16th to endDay
22%23%33%15%4
265
March1st to 15thDay
29%19%30%18%2
270
16th to endDay
22%21%32%15%5%1
288
April1st to 15thDay
27%14%32%18%6%
270
16th to endDay
23%13%32%19%7%3
270
May1st to 15thDay
37%12%24%15%8%1
288
16th to endDay
22%13%30%22%9%1
331
June1st to 15thDay
24%15%23%22%11%1
315
16th to endDay
15%15%31%28%8%1
315
July1st to 15thDay
20%7%28%27%13%2
305
16th to endDay
15%5%30%28%15%3
326
August1st to 15thDay
14%7%28%30%12%7%
313
16th to endDay
14%426%27%18%8%
332
September1st to 15thDay
16%9%29%21%13%8%
315
16th to endDay
20%6%24%20%14%14%
314
October1st to 15thDay
21%7%25%24%13%6%
315
16th to endDay
20%16%29%22%9%1
298
November1st to 15thDay
23%12%28%21%10%2
280
16th to endDay
25%14%28%20%9%1
265
December1st to 15thDay
22%20%41%11%5%
90
16th to endDay
30%28%30%10%1
96
January1st to 15thNight
23%18%35%19%3
780
16th to endNight
24%16%36%20%1
832
February1st to 15thNight
21%18%39%20%1
764
16th to endNight
25%16%36%18%2
659
March1st to 15thNight
25%19%34%18%2
720
16th to endNight
21%17%35%20%4
768
April1st to 15thNight
22%17%37%19%3
718
16th to endNight
25%16%33%19%5%
642
May1st to 15thNight
26%14%34%20%4
540
16th to endNight
21%8%32%30%6%
375
June1st to 15thNight
24%6%30%30%7%
360
16th to endNight
15%335%36%9%
360
July1st to 15thNight
16%328%37%14%
340
16th to endNight
11%326%41%15%
376
August1st to 15thNight
13%426%40%13%
501
16th to endNight
14%221%40%19%1
764
September1st to 15thNight
18%5%29%32%13%
720
16th to endNight
17%5%24%27%20%3
717
October1st to 15thNight
21%7%28%27%12%1
720
16th to endNight
24%13%32%22%7%
768
November1st to 15thNight
22%12%30%23%9%1
760
16th to endNight
23%13%33%21%7%
780
December1st to 15thNight
26%11%35%21%5%
780
16th to endNight
26%15%36%18%2
832
Page generated at 2018-02-23 11:21:40. Version ac04

Copyright 2018 A. Danko


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