Allentown(PA)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Allentown(PA) 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
36%
15516
20%
48376
11%
15483
46%
15483
25%
30584

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
24%
765
19%
2662
9%
761
38%
761
20%
1684
January16th to endNight
22%
768
22%
2532
8%
768
39%
768
22%
1594
February1st to 15thNight
18%
704
17%
2274
5%
701
34%
701
19%
1462
February16th to endNight
19%
631
26%
1893
8%
631
40%
631
23%
1184
March1st to 15thNight
24%
720
20%
2091
9%
720
37%
720
23%
1358
March16th to endNight
26%
768
22%
2034
9%
768
38%
768
27%
1347
April1st to 15thNight
26%
718
17%
1796
6%
718
31%
718
27%
1212
April16th to endNight
34%
720
19%
1800
6%
720
41%
720
31%
1192
May1st to 15thNight
35%
484
18%
1564
9%
484
43%
484
22%
1026
May16th to endNight
48%
374
15%
1497
13%
374
54%
374
21%
921
June1st to 15thNight
45%
360
15%
1440
14%
360
55%
360
21%
878
June16th to endNight
58%
360
17%
1440
21%
360
62%
360
27%
797
July1st to 15thNight
56%
340
13%
1360
17%
340
58%
340
21%
840
July16th to endNight
65%
397
16%
1438
18%
374
70%
374
28%
797
August1st to 15thNight
63%
566
19%
1636
14%
563
65%
563
31%
1031
August16th to endNight
61%
764
20%
1910
11%
764
62%
764
33%
1255
September1st to 15thNight
50%
720
24%
1800
11%
720
56%
720
35%
1172
September16th to endNight
56%
717
27%
1943
21%
717
61%
717
36%
1211
October1st to 15thNight
46%
720
21%
2160
17%
720
53%
720
28%
1356
October16th to endNight
36%
768
26%
2346
15%
768
52%
768
31%
1392
November1st to 15thNight
37%
760
21%
2472
13%
760
48%
760
27%
1498
November16th to endNight
31%
780
22%
2646
13%
780
44%
780
21%
1629
December1st to 15thNight
24%
780
15%
2730
7%
780
35%
780
16%
1840
December16th to endNight
20%
832
18%
2912
5%
832
37%
832
18%
1908

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
15%5%25%5%3445%7%39%
48971
Night
15%5%2442445%7%42%
48547
Cloud CoverDay
15%5%25%5%3445%7%39%
48980
Night
15%5%2442445%7%42%
48553
TransparencyDay
42%5%11%23%15%1
48661
Night
41%412%23%16%2
48376
SeeingDay
18%9%24%24%15%6%
6045
Night
18%8%30%30%11%
15517

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
14%5%36%6%3445%5%38%
1520
16th to endDay
13%7%35%5%25%5%47%38%
1689
February1st to 15thDay
15%7%35%5%25%35%7%36%
1588
16th to endDay
14%7%25%6%345%6%6%38%
1580
March1st to 15thDay
15%7%25%5%36%5%5%6%36%
1858
16th to endDay
18%6%25%33435%6%40%
2190
April1st to 15thDay
18%6%35%42345%8%38%
2152
16th to endDay
15%3245%3345%6%43%
2160
May1st to 15thDay
21%5%24425%5%5%7%35%
2396
16th to endDay
17%5%25%435%5%6%8%35%
2618
June1st to 15thDay
14%5%24445%5%7%10%34%
2520
16th to endDay
13%4145%35%5%6%9%39%
2520
July1st to 15thDay
10%5%25%6%45%6%7%9%36%
2520
16th to endDay
9%425%6%35%5%7%10%38%
2630
August1st to 15thDay
13%5%245%35%5%6%8%36%
2301
16th to endDay
14%5%2443445%7%43%
2292
September1st to 15thDay
15%415%43436%7%43%
2160
16th to endDay
14%414425%445%46%
2016
October1st to 15thDay
17%6%243345%46%42%
1800
16th to endDay
18%42442445%6%42%
1878
November1st to 15thDay
17%7%24324345%45%
1716
16th to endDay
17%5%2431235%7%44%
1643
December1st to 15thDay
16%6%35%4345%5%7%36%
1560
16th to endDay
19%7%35%4245%6%6%34%
1664
January1st to 15thNight
15%6%25%5%2435%6%40%
2662
16th to endNight
15%7%35%424447%41%
2532
February1st to 15thNight
15%6%35%5%24446%40%
2272
16th to endNight
15%5%24314446%45%
1893
March1st to 15thNight
17%6%2442335%5%43%
2078
16th to endNight
17%7%23424336%44%
2034
April1st to 15thNight
16%5%24325%5%5%7%40%
1796
16th to endNight
18%323424446%45%
1800
May1st to 15thNight
19%6%25%42435%6%38%
1564
16th to endNight
15%6%25%5%2445%7%41%
1495
June1st to 15thNight
17%5%14424447%43%
1440
16th to endNight
10%3244346%6%10%43%
1440
July1st to 15thNight
11%4246%4447%7%40%
1440
16th to endNight
8%314435%5%6%10%44%
1535
August1st to 15thNight
11%5%245%3446%7%44%
1647
16th to endNight
12%425%4245%5%8%43%
1910
September1st to 15thNight
14%42343335%6%48%
1800
16th to endNight
11%5%245%2435%6%49%
1943
October1st to 15thNight
18%5%24323346%45%
2160
16th to endNight
18%413212346%49%
2346
November1st to 15thNight
15%5%24423445%47%
2472
16th to endNight
17%5%245%2445%6%42%
2646
December1st to 15thNight
19%5%35%5%35%5%5%7%32%
2730
16th to endNight
17%7%35%435%45%6%38%
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
14%6%36%7%2445%5%38%
1520
16th to endDay
13%8%45%5%25%447%38%
1689
February1st to 15thDay
15%7%35%435%45%7%36%
1588
16th to endDay
14%7%26%6%345%6%6%37%
1580
March1st to 15thDay
15%8%346%35%45%7%36%
1868
16th to endDay
18%7%24424446%40%
2189
April1st to 15thDay
18%5%35%42345%8%38%
2152
16th to endDay
15%425%42446%6%42%
2160
May1st to 15thDay
20%6%24435%45%7%35%
2396
16th to endDay
17%5%25%5%35%46%8%35%
2618
June1st to 15thDay
13%5%25%435%5%7%9%34%
2520
16th to endDay
13%4245%35%5%6%9%38%
2520
July1st to 15thDay
9%5%15%6%37%6%7%9%36%
2520
16th to endDay
9%435%5%36%5%6%10%38%
2630
August1st to 15thDay
13%5%25%6%35%5%6%8%36%
2301
16th to endDay
13%5%2443445%8%43%
2292
September1st to 15thDay
15%42443445%8%43%
2160
16th to endDay
14%424434446%45%
2016
October1st to 15thDay
16%5%143335%5%7%42%
1800
16th to endDay
18%42342445%6%43%
1878
November1st to 15thDay
16%7%34323346%44%
1716
16th to endDay
17%43332235%6%45%
1643
December1st to 15thDay
16%6%25%4345%5%8%36%
1560
16th to endDay
18%8%35%5%2445%6%35%
1664
January1st to 15thNight
15%6%25%5%34447%39%
2662
16th to endNight
15%8%24434346%41%
2532
February1st to 15thNight
14%7%26%5%24447%39%
2265
16th to endNight
16%5%2442445%5%44%
1893
March1st to 15thNight
17%6%2442435%6%42%
2091
16th to endNight
17%7%23423336%44%
2034
April1st to 15thNight
16%5%25%325%46%7%40%
1796
16th to endNight
17%42342445%6%45%
1800
May1st to 15thNight
18%7%345%3345%5%39%
1564
16th to endNight
14%6%3442445%7%41%
1495
June1st to 15thNight
17%5%1442435%7%42%
1440
16th to endNight
9%3235%346%7%9%43%
1440
July1st to 15thNight
11%4246%35%5%6%8%40%
1440
16th to endNight
8%324326%5%6%11%43%
1535
August1st to 15thNight
10%5%25%5%245%7%7%44%
1647
16th to endNight
12%5%25%5%235%6%8%43%
1910
September1st to 15thNight
14%424333446%47%
1800
16th to endNight
11%5%1442435%6%49%
1943
October1st to 15thNight
17%5%24423346%45%
2160
16th to endNight
18%5%13213446%49%
2346
November1st to 15thNight
14%5%25%424346%46%
2472
16th to endNight
16%5%245%2445%6%41%
2646
December1st to 15thNight
18%6%25%5%35%5%5%7%33%
2730
16th to endNight
17%7%25%5%2445%5%38%
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
46%412%23%10%3
1521
16th to endDay
46%313%22%12%1
1689
February1st to 15thDay
46%413%21%12%1
1590
16th to endDay
45%411%26%11%1
1580
March1st to 15thDay
46%413%23%10%1
1868
16th to endDay
45%39%21%17%2
2190
April1st to 15thDay
44%39%24%13%4
2152
16th to endDay
38%49%22%20%4
2160
May1st to 15thDay
47%49%19%15%2
2396
16th to endDay
45%5%12%21%13%1
2622
June1st to 15thDay
42%7%14%24%10%
2520
16th to endDay
40%6%14%25%11%1
2520
July1st to 15thDay
41%7%10%23%15%1
2371
16th to endDay
37%6%13%26%13%2
2465
August1st to 15thDay
42%6%12%21%16%
2288
16th to endDay
38%5%8%24%20%2
2292
September1st to 15thDay
38%410%21%22%1
2160
16th to endDay
39%37%23%23%2
2016
October1st to 15thDay
40%412%22%17%1
1800
16th to endDay
41%310%26%16%1
1878
November1st to 15thDay
41%313%21%16%2
1716
16th to endDay
38%310%30%15%1
1643
December1st to 15thDay
45%5%17%20%10%1
1560
16th to endDay
48%316%19%10%
1664
January1st to 15thNight
44%312%22%14%3
2662
16th to endNight
43%211%27%13%1
2532
February1st to 15thNight
44%313%23%12%2
2274
16th to endNight
40%39%26%17%2
1893
March1st to 15thNight
43%312%23%14%2
2091
16th to endNight
42%310%22%17%3
2034
April1st to 15thNight
41%411%22%16%2
1796
16th to endNight
39%49%20%21%3
1800
May1st to 15thNight
45%410%18%17%2
1564
16th to endNight
41%6%15%17%16%3
1497
June1st to 15thNight
41%6%12%22%16%
1440
16th to endNight
33%6%13%31%13%
1440
July1st to 15thNight
41%6%12%21%15%2
1360
16th to endNight
31%7%17%25%14%2
1438
August1st to 15thNight
35%7%13%22%18%2
1636
16th to endNight
37%5%10%21%22%2
1910
September1st to 15thNight
36%5%10%22%22%2
1800
16th to endNight
35%36%24%26%2
1943
October1st to 15thNight
40%410%26%15%2
2160
16th to endNight
36%212%29%16%1
2346
November1st to 15thNight
39%312%22%16%4
2472
16th to endNight
42%311%26%14%1
2646
December1st to 15thNight
49%414%19%10%1
2730
16th to endNight
47%413%22%11%
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
19%29%30%15%31
82
16th to endDay
21%15%39%16%6%
89
February1st to 15thDay
14%27%42%11%3
104
16th to endDay
20%16%38%23%2
239
March1st to 15thDay
20%17%32%24%5%
270
16th to endDay
20%17%30%19%8%2
288
April1st to 15thDay
20%15%30%20%12%2
270
16th to endDay
20%8%30%23%10%7%
270
May1st to 15thDay
32%14%20%17%12%4
288
16th to endDay
22%6%19%24%20%6%
331
June1st to 15thDay
16%11%23%21%21%5%
315
16th to endDay
17%6%26%27%16%5%
315
July1st to 15thDay
14%220%32%22%6%
305
16th to endDay
14%216%31%24%11%
326
August1st to 15thDay
16%215%28%23%12%
313
16th to endDay
14%114%28%23%17%
332
September1st to 15thDay
15%6%21%22%19%13%
315
16th to endDay
17%316%24%19%19%
314
October1st to 15thDay
21%319%26%21%7%
315
16th to endDay
16%8%35%23%15%1
325
November1st to 15thDay
20%7%27%27%13%2
280
16th to endDay
14%21%30%24%6%1
173
December1st to 15thDay
23%25%23%14%11%2
90
16th to endDay
31%20%36%10%1
96
January1st to 15thNight
19%13%37%25%4
765
16th to endNight
21%12%38%25%2
768
February1st to 15thNight
17%15%41%24%1
704
16th to endNight
18%16%41%21%2
631
March1st to 15thNight
21%12%36%24%4
720
16th to endNight
21%9%37%23%7%
768
April1st to 15thNight
18%11%40%23%5%
718
16th to endNight
20%6%34%28%9%
720
May1st to 15thNight
21%5%30%30%10%
484
16th to endNight
18%322%40%14%1
375
June1st to 15thNight
18%423%34%18%
360
16th to endNight
10%221%51%13%
360
July1st to 15thNight
12%118%45%21%
340
16th to endNight
9%215%41%28%2
397
August1st to 15thNight
14%113%44%24%2
566
16th to endNight
14%212%38%29%2
764
September1st to 15thNight
16%321%35%21%1
720
16th to endNight
15%118%32%26%5%
717
October1st to 15thNight
20%323%31%18%2
720
16th to endNight
20%7%32%29%10%
768
November1st to 15thNight
18%5%33%29%12%1
760
16th to endNight
18%11%31%27%9%
780
December1st to 15thNight
23%10%34%24%7%
780
16th to endNight
20%12%40%22%3
832
Page generated at 2018-01-12 22:01:35. Version ac04

Copyright 2018 A. Danko


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