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Harrington Beach State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Harrington Beach State Park clear sky chart from 2005-11-06 to 2024-01-16.

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
41%
24720
16%
74669
11%
24666
47%
24666
22%
51077

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
20%
950
13%
2648
3%
946
29%
946
15%
2021
January11th to 20thNight
20%
926
10%
2591
3%
926
27%
926
12%
2086
January21st to endNight
21%
990
11%
2772
3%
990
28%
990
14%
2157
February1st to 10thNight
23%
889
12%
2350
3%
889
30%
889
17%
1784
February11th to 20thNight
27%
700
18%
2098
7%
699
37%
699
19%
1442
February21st to endNight
24%
592
18%
1776
4%
592
36%
592
18%
1268
March1st to 10thNight
35%
720
14%
2160
6%
720
40%
720
19%
1498
March11th to 20thNight
39%
720
20%
2124
11%
720
47%
720
26%
1376
March21st to endNight
41%
596
18%
1982
15%
596
47%
596
18%
1386
April1st to 10thNight
35%
540
14%
1800
10%
540
44%
540
19%
1221
April11th to 20thNight
40%
533
19%
1775
17%
533
46%
533
20%
1185
April21st to endNight
48%
540
18%
1653
13%
540
54%
540
26%
1074
May1st to 10thNight
48%
540
15%
1620
12%
540
51%
540
22%
1121
May11th to 20thNight
49%
531
19%
1422
13%
531
53%
531
26%
979
May21st to endNight
59%
583
15%
1552
12%
582
60%
582
30%
1033
June1st to 10thNight
65%
540
16%
1440
12%
540
66%
540
35%
901
June11th to 20thNight
60%
540
18%
1440
12%
540
63%
540
33%
925
June21st to endNight
65%
540
17%
1440
11%
540
67%
540
34%
906
July1st to 10thNight
75%
525
17%
1400
13%
525
75%
525
42%
827
July11th to 20thNight
73%
522
20%
1392
15%
522
75%
522
41%
829
July21st to endNight
73%
591
21%
1487
17%
558
74%
558
44%
863
August1st to 10thNight
72%
537
22%
1435
17%
534
73%
534
39%
852
August11th to 20thNight
71%
534
21%
1688
20%
534
75%
534
37%
943
August21st to endNight
67%
594
22%
1980
23%
594
70%
594
33%
1104
September1st to 10thNight
62%
540
22%
1800
22%
540
66%
540
31%
1044
September11th to 20thNight
63%
641
30%
1901
26%
641
68%
641
36%
1111
September21st to endNight
50%
720
22%
1980
15%
720
54%
720
30%
1279
October1st to 10thNight
50%
720
22%
2024
15%
720
54%
720
31%
1280
October11th to 20thNight
37%
720
18%
2209
11%
720
45%
720
23%
1480
October21st to endNight
34%
792
14%
2574
10%
792
40%
792
18%
1781
November1st to 10thNight
40%
740
24%
2406
18%
740
49%
740
25%
1488
November11th to 20thNight
27%
760
17%
2470
9%
760
38%
760
17%
1720
November21st to endNight
27%
878
16%
2588
8%
878
36%
878
20%
1824
December1st to 10thNight
20%
950
12%
2660
4%
950
27%
950
14%
2030
December11th to 20thNight
20%
950
11%
3210
3%
948
27%
948
11%
2420
December21st to endNight
17%
1036
6%
4822
3%
1026
24%
1026
6%
3839

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
12%8%36%6%35%5%6%8%38%
74829
Night
14%9%36%5%35%5%5%7%37%
74984
TransparencyDay
44%6%14%23%12%1
74530
Night
46%6%11%22%13%2
74804
SeeingDay
15%419%33%23%6%
14737
Night
18%7%24%31%17%3
24733

By Month

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 10thDay
12%13%6%6%5%35%6%7%8%29%
1517
11th to 20thDay
14%14%6%10%7%45%6%7%7%20%
1480
21st to endDay
12%13%7%9%8%346%6%8%24%
1584
February1st to 10thDay
11%11%6%9%7%346%6%7%29%
1607
11th to 20thDay
14%10%47%6%45%5%5%5%36%
1748
21st to endDay
12%11%5%9%6%35%6%5%7%31%
1480
March1st to 10thDay
13%9%5%7%6%445%6%7%34%
1800
11th to 20thDay
12%8%46%6%35%5%6%7%38%
1848
21st to endDay
17%9%46%6%45%5%6%7%31%
2376
April1st to 10thDay
17%10%46%5%35%6%6%7%31%
2160
11th to 20thDay
16%8%46%6%45%5%5%6%34%
2134
21st to endDay
18%8%37%5%445%5%6%34%
2305
May1st to 10thDay
16%7%36%5%45%5%6%8%34%
2340
11th to 20thDay
15%7%36%5%45%46%7%38%
2469
21st to endDay
12%6%35%5%35%5%6%9%40%
2725
June1st to 10thDay
10%5%36%6%35%5%6%7%44%
2520
11th to 20thDay
11%6%36%5%35%46%9%43%
2520
21st to endDay
7%5%245%35%6%7%11%45%
2520
July1st to 10thDay
5%4245%346%7%10%50%
2520
11th to 20thDay
7%4245%35%5%6%10%50%
2520
21st to endDay
6%3245%35%6%7%10%50%
2743
August1st to 10thDay
7%3245%46%6%6%11%46%
2492
11th to 20thDay
9%425%6%35%45%8%49%
2210
21st to endDay
9%5%26%5%345%5%8%49%
2376
September1st to 10thDay
11%5%36%5%35%5%6%7%45%
2160
11th to 20thDay
12%5%25%5%3445%8%48%
2040
21st to endDay
11%7%26%6%346%6%9%42%
1980
October1st to 10thDay
14%6%35%435%45%6%44%
1932
11th to 20thDay
21%8%36%6%45%5%6%7%30%
1751
21st to endDay
16%8%37%6%445%5%6%36%
1782
November1st to 10thDay
12%7%36%6%35%5%5%7%42%
1672
11th to 20thDay
11%10%47%8%46%5%6%8%31%
1710
21st to endDay
17%10%37%434448%35%
1587
December1st to 10thDay
16%12%46%6%5%7%5%6%7%25%
1520
11th to 20thDay
13%12%48%7%46%5%7%8%27%
1918
21st to endDay
18%19%7%12%6%34445%17%
2783
January1st to 10thNight
13%13%6%8%6%3446%6%30%
2648
11th to 20thNight
16%13%5%10%6%45%6%6%6%23%
2591
21st to endNight
13%12%6%9%7%35%6%7%7%24%
2772
February1st to 10thNight
13%13%6%7%6%35%5%6%5%30%
2350
11th to 20thNight
12%9%5%7%6%35%46%5%38%
2098
21st to endNight
18%13%37%5%2345%5%34%
1776
March1st to 10thNight
15%8%5%6%6%45%5%5%5%36%
2160
11th to 20thNight
12%6%46%5%36%5%5%8%42%
2124
21st to endNight
18%10%36%5%35%5%5%6%34%
1982
April1st to 10thNight
17%10%46%5%345%5%6%37%
1800
11th to 20thNight
20%8%26%5%2445%5%39%
1775
21st to endNight
18%7%25%5%2445%7%40%
1653
May1st to 10thNight
16%7%37%6%36%5%6%8%33%
1620
11th to 20thNight
17%6%36%5%245%6%7%37%
1422
21st to endNight
12%6%36%5%36%5%5%10%41%
1551
June1st to 10thNight
11%425%435%5%5%9%46%
1440
11th to 20thNight
13%5%25%5%3446%8%44%
1440
21st to endNight
9%5%35%5%35%5%6%6%49%
1440
July1st to 10thNight
7%325%5%245%6%10%52%
1440
11th to 20thNight
6%425%435%5%7%7%52%
1440
21st to endNight
6%424425%5%7%10%52%
1575
August1st to 10thNight
6%3246%35%5%7%9%49%
1444
11th to 20thNight
7%4245%35%46%9%52%
1688
21st to endNight
10%424445%45%6%52%
1980
September1st to 10thNight
10%425%5%25%45%7%50%
1800
11th to 20thNight
11%42443445%6%53%
1901
21st to endNight
13%6%25%5%2446%7%45%
1980
October1st to 10thNight
14%6%25%5%3445%6%47%
2024
11th to 20thNight
19%7%25%43446%6%39%
2209
21st to endNight
20%8%35%5%345%6%7%34%
2574
November1st to 10thNight
12%8%34435%446%45%
2406
11th to 20thNight
14%9%47%6%45%6%5%6%34%
2470
21st to endNight
17%9%35%5%45%45%6%36%
2588
December1st to 10thNight
16%12%47%7%36%5%6%8%26%
2660
11th to 20thNight
15%14%47%6%46%5%5%6%27%
3279
21st to endNight
21%17%5%9%6%35%45%5%20%
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
51%10%11%18%9%
1518
11th to 20thDay
61%10%9%15%5%
1480
21st to endDay
58%9%11%14%8%
1584
February1st to 10thDay
54%8%11%19%7%1
1607
11th to 20thDay
50%5%11%21%12%2
1758
21st to endDay
53%5%10%19%11%2
1480
March1st to 10thDay
49%6%14%22%8%2
1800
11th to 20thDay
46%5%13%20%14%2
1848
21st to endDay
52%5%16%20%7%1
2376
April1st to 10thDay
50%6%14%19%11%
2160
11th to 20thDay
50%5%10%20%13%3
2134
21st to endDay
50%6%15%16%11%2
2305
May1st to 10thDay
47%6%13%24%10%1
2340
11th to 20thDay
45%6%12%23%12%2
2473
21st to endDay
39%8%13%24%14%2
2725
June1st to 10thDay
37%6%12%28%14%3
2520
11th to 20thDay
37%6%14%25%17%2
2520
21st to endDay
32%7%17%26%16%1
2520
July1st to 10thDay
28%7%16%32%14%3
2451
11th to 20thDay
30%7%16%28%16%2
2445
21st to endDay
27%7%18%28%16%4
2591
August1st to 10thDay
31%7%20%28%13%2
2477
11th to 20thDay
33%5%18%30%12%1
2210
21st to endDay
34%6%13%27%18%1
2376
September1st to 10thDay
37%7%13%27%14%2
2160
11th to 20thDay
35%6%13%30%14%1
2040
21st to endDay
38%6%14%30%11%
1980
October1st to 10thDay
41%5%12%28%14%1
1932
11th to 20thDay
52%6%13%19%10%1
1751
21st to endDay
49%5%14%20%11%1
1782
November1st to 10thDay
41%6%13%25%14%1
1672
11th to 20thDay
51%6%14%21%7%1
1710
21st to endDay
49%5%14%24%7%
1587
December1st to 10thDay
57%8%12%16%7%1
1520
11th to 20thDay
54%7%14%17%6%2
1915
21st to endDay
69%6%8%12%5%
2783
January1st to 10thNight
54%8%9%16%11%1
2648
11th to 20thNight
60%10%10%14%6%
2591
21st to endNight
57%8%11%15%8%
2772
February1st to 10thNight
55%6%8%19%10%2
2350
11th to 20thNight
49%5%10%21%13%2
2099
21st to endNight
52%5%10%18%13%2
1776
March1st to 10thNight
50%5%14%20%10%2
2160
11th to 20thNight
41%6%13%22%15%3
2124
21st to endNight
51%6%9%23%10%1
1982
April1st to 10thNight
49%5%9%19%17%1
1800
11th to 20thNight
48%5%7%20%17%4
1775
21st to endNight
43%5%14%23%14%2
1653
May1st to 10thNight
48%5%12%22%12%1
1620
11th to 20thNight
45%5%12%22%14%2
1423
21st to endNight
40%6%12%24%15%3
1552
June1st to 10thNight
34%6%12%29%17%2
1440
11th to 20thNight
37%5%9%26%20%2
1440
21st to endNight
34%8%14%25%18%2
1440
July1st to 10thNight
28%6%14%29%19%4
1400
11th to 20thNight
28%7%13%29%20%4
1392
21st to endNight
27%6%17%27%19%5%
1487
August1st to 10thNight
30%6%17%29%15%3
1435
11th to 20thNight
28%7%18%30%17%1
1688
21st to endNight
31%6%12%28%21%3
1980
September1st to 10thNight
33%7%10%26%22%2
1800
11th to 20thNight
31%5%9%37%15%2
1901
21st to endNight
39%6%10%31%14%1
1980
October1st to 10thNight
38%5%9%30%16%1
2024
11th to 20thNight
45%6%13%21%14%1
2209
21st to endNight
49%7%12%21%11%
2574
November1st to 10thNight
39%6%11%25%17%2
2406
11th to 20thNight
50%6%11%20%11%1
2470
21st to endNight
48%7%15%21%8%1
2588
December1st to 10thNight
55%8%11%19%7%1
2660
11th to 20thNight
57%7%11%16%9%1
3281
21st to endNight
66%6%9%14%5%
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
18%10%29%31%9%3
270
11th to 20thDay
16%9%31%31%12%
255
21st to endDay
19%6%27%36%11%2
264
February1st to 10thDay
16%8%38%30%8%
240
11th to 20thDay
18%10%35%28%8%
240
21st to endDay
20%5%39%33%21
198
March1st to 10thDay
13%7%39%33%8%
240
11th to 20thDay
19%430%30%15%2
275
21st to endDay
26%426%31%11%2
462
April1st to 10thDay
24%5%27%30%14%
420
11th to 20thDay
21%5%25%30%16%5%
412
21st to endDay
21%320%36%17%3
420
May1st to 10thDay
19%321%39%16%2
423
11th to 20thDay
19%217%35%22%4
615
21st to endDay
15%212%33%27%11%
679
June1st to 10thDay
10%212%37%31%7%
630
11th to 20thDay
14%212%39%26%8%
630
21st to endDay
11%211%39%31%7%
630
July1st to 10thDay
7%17%28%42%15%
621
11th to 20thDay
9%29%33%36%10%
618
21st to endDay
6%18%40%37%8%
684
August1st to 10thDay
7%27%35%36%12%
611
11th to 20thDay
11%18%28%35%16%
439
21st to endDay
11%39%34%33%11%
495
September1st to 10thDay
14%411%31%32%8%
450
11th to 20thDay
12%212%29%32%12%
450
21st to endDay
14%6%19%28%23%10%
450
October1st to 10thDay
20%418%27%24%7%
402
11th to 20thDay
20%9%27%31%11%2
270
21st to endDay
22%7%29%32%9%2
297
November1st to 10thDay
14%6%26%34%18%2
270
11th to 20thDay
14%11%35%28%12%
270
21st to endDay
23%7%28%32%10%
270
December1st to 10thDay
20%10%35%24%11%
270
11th to 20thDay
21%9%34%25%9%2
270
21st to endDay
25%11%33%24%6%1
297
January1st to 10thNight
20%14%36%23%7%
950
11th to 20thNight
23%11%32%26%6%1
926
21st to endNight
19%11%35%26%8%
990
February1st to 10thNight
19%11%34%30%5%
889
11th to 20thNight
18%10%37%26%8%
703
21st to endNight
25%9%34%27%5%
592
March1st to 10thNight
18%6%30%34%11%1
720
11th to 20thNight
14%8%31%33%12%2
720
21st to endNight
22%423%36%14%2
596
April1st to 10thNight
21%7%28%31%11%1
540
11th to 20thNight
25%422%32%13%3
533
21st to endNight
21%220%38%18%1
540
May1st to 10thNight
18%318%42%17%2
540
11th to 20thNight
20%317%34%24%3
531
21st to endNight
14%212%34%30%8%
584
June1st to 10thNight
12%210%43%26%7%
540
11th to 20thNight
14%112%38%27%7%
540
21st to endNight
10%311%38%33%5%
540
July1st to 10thNight
8%25%32%42%11%
525
11th to 20thNight
7%28%39%36%10%
522
21st to endNight
8%29%39%36%6%
591
August1st to 10thNight
7%17%39%37%9%
537
11th to 20thNight
8%210%34%33%12%
534
21st to endNight
10%311%34%37%5%
594
September1st to 10thNight
11%215%34%30%9%
540
11th to 20thNight
11%317%29%31%10%
641
21st to endNight
17%5%19%27%24%8%
720
October1st to 10thNight
18%421%29%23%5%
720
11th to 20thNight
23%9%26%28%13%1
720
21st to endNight
24%10%26%28%9%2
792
November1st to 10thNight
15%9%31%31%12%2
740
11th to 20thNight
20%12%33%27%8%
760
21st to endNight
21%11%34%27%7%
878
December1st to 10thNight
22%15%34%23%6%
950
11th to 20thNight
24%13%34%21%7%1
950
21st to endNight
29%11%32%24%4
1045
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