Roxbury Airport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Roxbury Airport clear sky chart from 2005-11-05 to 2017-09-18.

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
28%
14965
18%
46849
8%
14933
39%
14933
20%
30397

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
16%
720
20%
2506
7%
716
33%
716
17%
1569
January16th to endNight
15%
768
20%
2643
5%
768
36%
768
16%
1658
February1st to 15thNight
14%
704
17%
2207
3%
701
30%
701
15%
1469
February16th to endNight
16%
631
23%
1893
6%
631
35%
631
17%
1217
March1st to 15thNight
16%
720
17%
2160
5%
720
30%
720
16%
1461
March16th to endNight
20%
768
24%
1998
7%
768
33%
768
20%
1315
April1st to 15thNight
19%
718
16%
1796
3%
718
27%
718
20%
1278
April16th to endNight
22%
666
17%
1746
2%
666
32%
666
22%
1204
May1st to 15thNight
23%
519
16%
1599
6%
519
33%
519
16%
1108
May16th to endNight
32%
375
14%
1497
11%
374
40%
374
17%
949
June1st to 15thNight
32%
360
13%
1440
9%
360
45%
360
16%
951
June16th to endNight
46%
360
14%
1440
13%
360
56%
360
24%
830
July1st to 15thNight
47%
340
11%
1360
13%
340
51%
340
21%
834
July16th to endNight
51%
376
15%
1418
17%
354
56%
354
21%
858
August1st to 15thNight
47%
515
16%
1586
9%
513
53%
513
29%
972
August16th to endNight
55%
764
18%
1910
9%
764
57%
764
31%
1279
September1st to 15thNight
40%
720
21%
1812
10%
720
46%
720
31%
1183
September16th to endNight
47%
669
25%
1847
17%
669
52%
669
30%
1152
October1st to 15thNight
32%
660
21%
1900
11%
660
43%
660
24%
1235
October16th to endNight
24%
704
17%
2231
6%
704
38%
704
19%
1454
November1st to 15thNight
28%
700
21%
2277
9%
700
44%
700
21%
1439
November16th to endNight
25%
720
20%
2375
10%
720
38%
720
18%
1539
December1st to 15thNight
22%
720
16%
2520
6%
720
35%
720
15%
1666
December16th to endNight
14%
768
18%
2688
4%
768
31%
768
13%
1777

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%6%245%3445%7%39%
47948
Night
17%6%24424446%41%
47019
Cloud CoverDay
16%6%2443445%7%39%
47958
Night
17%6%24424446%41%
47024
TransparencyDay
43%6%12%21%14%1
47636
Night
42%5%12%22%14%2
46849
SeeingDay
21%14%29%21%10%3
5808
Night
22%14%31%23%7%
14965

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%6%33335%45%5%40%
1432
16th to endDay
16%6%25%4145%5%7%40%
1578
February1st to 15thDay
15%6%36%5%35%5%47%36%
1654
16th to endDay
16%7%25%5%24446%39%
1580
March1st to 15thDay
17%7%25%435%446%36%
1790
16th to endDay
18%7%25%423345%41%
2221
April1st to 15thDay
20%6%23434445%39%
2152
16th to endDay
17%425%424346%45%
2214
May1st to 15thDay
23%6%2443435%6%34%
2361
16th to endDay
18%5%245%25%5%5%6%39%
2618
June1st to 15thDay
23%5%24425%5%5%7%33%
2520
16th to endDay
13%5%25%6%345%6%10%35%
2520
July1st to 15thDay
13%6%25%5%35%5%6%7%37%
2520
16th to endDay
12%5%245%35%5%6%9%37%
2654
August1st to 15thDay
14%425%5%25%6%6%8%37%
2349
16th to endDay
11%5%25%5%3446%8%42%
2292
September1st to 15thDay
13%425%5%345%5%6%43%
2148
16th to endDay
14%414423446%47%
1838
October1st to 15thDay
18%7%25%42235%442%
1727
16th to endDay
17%5%146%345%5%441%
1639
November1st to 15thDay
18%5%23323347%43%
1581
16th to endDay
18%5%2432335%6%42%
1584
December1st to 15thDay
17%7%24425%35%7%38%
1440
16th to endDay
20%9%245%2445%6%33%
1536
January1st to 15thNight
18%6%15%42336%6%41%
2506
16th to endNight
15%8%3432335%6%42%
2643
February1st to 15thNight
15%7%35%434445%39%
2206
16th to endNight
16%6%34423346%43%
1893
March1st to 15thNight
18%7%25%424446%39%
2147
16th to endNight
16%6%34413347%44%
1998
April1st to 15thNight
18%6%34425%447%37%
1796
16th to endNight
19%5%25%433335%42%
1746
May1st to 15thNight
20%7%25%43435%6%36%
1599
16th to endNight
18%6%2442435%7%39%
1495
June1st to 15thNight
21%5%34414436%38%
1440
16th to endNight
13%42343445%9%45%
1440
July1st to 15thNight
13%425%4246%7%8%40%
1440
16th to endNight
10%5%25%6%35%5%7%8%40%
1514
August1st to 15thNight
12%4135%345%6%7%45%
1596
16th to endNight
14%4235%25%45%8%44%
1910
September1st to 15thNight
15%423334336%48%
1812
16th to endNight
13%5%24323435%50%
1847
October1st to 15thNight
16%5%35%422346%44%
1900
16th to endNight
19%5%24424445%41%
2231
November1st to 15thNight
16%7%25%313345%44%
2277
16th to endNight
18%7%25%424345%40%
2375
December1st to 15thNight
21%6%2442445%6%36%
2520
16th to endNight
21%6%2442335%7%36%
2688

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%6%24335%5%46%41%
1432
16th to endDay
15%6%35%4245%5%7%39%
1578
February1st to 15thDay
15%6%36%435%5%47%36%
1654
16th to endDay
16%7%25%5%24446%39%
1580
March1st to 15thDay
17%7%25%435%447%36%
1800
16th to endDay
18%7%24424345%42%
2221
April1st to 15thDay
20%6%24424445%39%
2152
16th to endDay
17%5%25%424347%44%
2214
May1st to 15thDay
22%7%24433446%35%
2361
16th to endDay
18%5%34425%5%5%7%38%
2618
June1st to 15thDay
23%5%24435%45%7%32%
2520
16th to endDay
13%5%246%445%7%9%36%
2520
July1st to 15thDay
13%5%345%36%5%5%8%37%
2520
16th to endDay
11%5%25%5%36%6%6%8%37%
2654
August1st to 15thDay
14%5%245%346%6%9%37%
2349
16th to endDay
11%5%35%5%345%5%7%42%
2292
September1st to 15thDay
13%5%246%345%46%43%
2148
16th to endDay
14%4245%235%46%46%
1838
October1st to 15thDay
18%6%3442335%5%42%
1727
16th to endDay
17%5%245%345%5%5%41%
1639
November1st to 15thDay
17%6%34223347%43%
1581
16th to endDay
19%5%2432336%6%42%
1584
December1st to 15thDay
17%6%245%34446%39%
1440
16th to endDay
20%9%244245%5%5%34%
1536
January1st to 15thNight
17%6%25%42445%6%41%
2506
16th to endNight
15%8%3432345%6%42%
2643
February1st to 15thNight
14%7%35%5%25%446%39%
2199
16th to endNight
16%6%35%32335%6%42%
1893
March1st to 15thNight
18%6%25%4245%46%39%
2160
16th to endNight
16%6%24323338%44%
1997
April1st to 15thNight
18%6%34435%446%38%
1796
16th to endNight
19%435%423435%42%
1746
May1st to 15thNight
19%8%25%5%23446%36%
1599
16th to endNight
18%7%245%335%47%38%
1495
June1st to 15thNight
21%6%24424446%38%
1440
16th to endNight
12%5%1432345%9%45%
1440
July1st to 15thNight
13%425%4345%7%9%39%
1440
16th to endNight
10%5%35%6%345%6%9%40%
1514
August1st to 15thNight
12%3145%345%5%7%45%
1596
16th to endNight
14%3234345%5%8%43%
1910
September1st to 15thNight
15%424324437%48%
1812
16th to endNight
13%5%24424335%51%
1847
October1st to 15thNight
16%6%25%423346%44%
1900
16th to endNight
19%5%2442445%5%41%
2231
November1st to 15thNight
16%7%25%32334445%
2277
16th to endNight
18%6%34434345%40%
2375
December1st to 15thNight
21%6%2442445%6%37%
2520
16th to endNight
21%6%2442335%7%36%
2688

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
43%5%13%23%11%3
1433
16th to endDay
42%5%13%24%12%1
1578
February1st to 15thDay
46%6%12%19%13%1
1657
16th to endDay
44%411%24%12%1
1580
March1st to 15thDay
47%5%13%21%9%2
1800
16th to endDay
44%410%18%17%3
2221
April1st to 15thDay
45%5%10%20%14%3
2152
16th to endDay
40%5%9%22%18%3
2214
May1st to 15thDay
49%5%9%19%14%1
2361
16th to endDay
44%8%13%18%13%1
2622
June1st to 15thDay
49%6%13%19%9%1
2520
16th to endDay
41%8%14%22%11%
2520
July1st to 15thDay
44%7%10%20%14%1
2371
16th to endDay
41%7%14%20%13%2
2487
August1st to 15thDay
41%8%14%21%13%
2335
16th to endDay
38%6%11%24%17%
2292
September1st to 15thDay
39%7%10%20%19%1
2148
16th to endDay
37%5%9%21%23%2
1838
October1st to 15thDay
43%5%10%23%14%2
1727
16th to endDay
43%412%23%13%1
1639
November1st to 15thDay
41%413%21%16%2
1581
16th to endDay
41%312%26%13%2
1584
December1st to 15thDay
45%5%16%19%12%
1440
16th to endDay
49%5%14%19%10%
1536
January1st to 15thNight
42%414%22%12%2
2506
16th to endNight
42%411%24%14%2
2643
February1st to 15thNight
46%5%13%20%12%2
2207
16th to endNight
42%410%23%15%3
1893
March1st to 15thNight
44%6%12%21%12%2
2160
16th to endNight
41%39%21%18%4
1998
April1st to 15thNight
45%5%11%21%14%1
1796
16th to endNight
43%5%8%20%17%3
1746
May1st to 15thNight
48%6%10%18%13%2
1599
16th to endNight
44%6%16%18%12%1
1497
June1st to 15thNight
46%6%12%20%12%1
1440
16th to endNight
35%7%15%25%14%
1440
July1st to 15thNight
38%9%14%22%13%1
1360
16th to endNight
39%7%15%23%11%3
1418
August1st to 15thNight
35%7%15%25%14%1
1586
16th to endNight
36%8%12%23%17%
1910
September1st to 15thNight
37%5%11%25%19%1
1812
16th to endNight
36%5%6%23%26%1
1847
October1st to 15thNight
41%5%11%22%16%2
1900
16th to endNight
43%5%14%22%13%
2231
November1st to 15thNight
42%411%20%17%3
2277
16th to endNight
45%312%23%11%2
2375
December1st to 15thNight
46%6%14%20%12%
2520
16th to endNight
47%413%21%12%
2688

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
26%28%26%15%3
60
16th to endDay
28%22%38%11%
71
February1st to 15thDay
26%29%28%15%
170
16th to endDay
22%23%34%15%4
239
March1st to 15thDay
29%18%31%16%4
270
16th to endDay
25%22%33%13%41
288
April1st to 15thDay
29%17%29%14%7%1
270
16th to endDay
23%14%34%16%8%2
270
May1st to 15thDay
36%14%25%13%7%2
288
16th to endDay
19%11%32%25%9%1
331
June1st to 15thDay
26%11%26%20%13%1
315
16th to endDay
17%10%33%25%11%1
315
July1st to 15thDay
18%6%32%26%13%1
305
16th to endDay
12%7%30%28%19%2
326
August1st to 15thDay
16%5%28%30%12%7%
313
16th to endDay
12%425%29%17%9%
332
September1st to 15thDay
14%11%29%21%14%8%
315
16th to endDay
16%9%24%20%14%14%
262
October1st to 15thDay
23%10%27%20%13%5%
255
16th to endDay
21%18%29%24%7%
250
November1st to 15thDay
22%15%25%24%9%1
235
16th to endDay
21%24%25%18%8%1
204
December1st to 15thDay
26%25%31%13%3
60
16th to endDay
35%28%23%12%
64
January1st to 15thNight
24%19%35%17%3
720
16th to endNight
24%21%34%17%2
768
February1st to 15thNight
22%20%37%17%1
704
16th to endNight
25%21%33%16%2
631
March1st to 15thNight
25%21%33%16%2
720
16th to endNight
22%23%29%19%4
768
April1st to 15thNight
23%20%34%17%2
718
16th to endNight
23%18%32%19%5%
666
May1st to 15thNight
24%15%33%20%5%
519
16th to endNight
20%9%31%30%6%1
375
June1st to 15thNight
23%6%31%27%11%
360
16th to endNight
16%329%41%9%
360
July1st to 15thNight
15%328%35%15%
340
16th to endNight
11%326%38%19%1
376
August1st to 15thNight
14%328%38%13%1
515
16th to endNight
15%318%37%21%2
764
September1st to 15thNight
16%6%30%30%13%1
720
16th to endNight
17%7%23%27%20%4
669
October1st to 15thNight
19%10%32%24%10%1
660
16th to endNight
24%15%33%20%5%
704
November1st to 15thNight
22%15%30%21%8%1
700
16th to endNight
24%16%29%20%8%
720
December1st to 15thNight
28%16%29%20%4
720
16th to endNight
28%20%33%14%2
768
Page generated at 2017-09-19 07:32:31. Version ac04

Copyright 2017 A. Danko


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