Peterborough
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Peterborough 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%
15388
14%
48951
8%
15354
37%
15354
17%
34200

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
13%
779
9%
2716
2%
776
21%
776
7%
2127
January16th to endNight
16%
832
12%
2736
5%
832
25%
832
10%
2111
February1st to 15thNight
12%
763
11%
2482
3%
761
23%
761
10%
1915
February16th to endNight
19%
659
15%
2101
5%
659
31%
659
13%
1518
March1st to 15thNight
19%
720
14%
2001
5%
720
27%
720
16%
1458
March16th to endNight
27%
768
21%
2101
8%
768
37%
768
24%
1408
April1st to 15thNight
24%
718
15%
1796
5%
718
30%
718
21%
1320
April16th to endNight
32%
600
19%
1680
8%
600
39%
600
25%
1118
May1st to 15thNight
39%
432
16%
1512
12%
432
47%
432
20%
1000
May16th to endNight
43%
375
17%
1497
13%
374
55%
374
24%
862
June1st to 15thNight
38%
360
11%
1440
9%
360
49%
360
18%
882
June16th to endNight
47%
360
11%
1440
12%
360
54%
360
20%
875
July1st to 15thNight
52%
340
16%
1360
20%
340
59%
340
29%
707
July16th to endNight
53%
415
16%
1454
15%
390
59%
390
30%
810
August1st to 15thNight
56%
539
16%
1609
11%
536
60%
536
33%
979
August16th to endNight
54%
651
22%
1797
10%
651
60%
651
34%
1089
September1st to 15thNight
45%
720
19%
1800
9%
720
49%
720
32%
1189
September16th to endNight
51%
717
24%
1992
16%
717
55%
717
31%
1270
October1st to 15thNight
34%
720
16%
2160
11%
720
41%
720
20%
1507
October16th to endNight
19%
768
14%
2304
6%
768
29%
768
13%
1748
November1st to 15thNight
28%
760
17%
2601
13%
760
35%
760
17%
1780
November16th to endNight
20%
780
10%
2730
5%
780
28%
780
10%
2067
December1st to 15thNight
13%
780
7%
2730
2%
780
20%
780
7%
2140
December16th to endNight
11%
832
9%
2912
2%
832
19%
832
7%
2320

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%9%36%5%3445%6%33%
49298
Night
15%8%36%5%3445%6%34%
49125
Cloud CoverDay
16%9%36%5%3445%6%33%
49308
Night
15%8%36%5%3445%6%35%
49130
TransparencyDay
49%6%11%19%10%1
48990
Night
49%6%11%19%11%1
48951
SeeingDay
20%13%29%20%10%5%
5829
Night
20%13%30%23%10%1
15390

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%15%5%8%6%14445%25%
1552
16th to endDay
14%14%5%11%8%35%435%22%
1838
February1st to 15thDay
13%14%6%12%8%35%345%22%
1710
16th to endDay
17%14%5%7%7%4434326%
1518
March1st to 15thDay
15%10%47%6%45%446%29%
1945
16th to endDay
16%9%35%434435%39%
2121
April1st to 15thDay
22%9%345%34345%33%
2152
16th to endDay
19%8%24433445%40%
2289
May1st to 15thDay
17%8%26%5%3445%6%33%
2439
16th to endDay
14%6%25%4345%5%8%39%
2618
June1st to 15thDay
18%6%35%5%345%6%8%32%
2520
16th to endDay
15%7%25%435%46%9%35%
2520
July1st to 15thDay
10%425%5%46%5%6%9%40%
2520
16th to endDay
9%5%26%6%47%7%6%8%36%
2612
August1st to 15thDay
10%6%26%5%35%6%6%7%38%
2340
16th to endDay
12%6%26%5%345%6%9%38%
2393
September1st to 15thDay
15%5%25%4345%47%40%
2160
16th to endDay
14%5%25%5%34445%44%
1963
October1st to 15thDay
20%8%36%5%34446%32%
1800
16th to endDay
24%10%47%5%3345%6%25%
1918
November1st to 15thDay
16%11%35%5%34447%33%
1586
16th to endDay
20%12%46%6%3445%5%25%
1560
December1st to 15thDay
16%16%6%8%7%4444422%
1560
16th to endDay
19%15%6%8%7%33345%20%
1664
January1st to 15thNight
20%13%5%8%7%35%445%22%
2716
16th to endNight
14%14%5%9%7%3435%6%24%
2736
February1st to 15thNight
12%14%5%9%7%36%5%5%5%24%
2480
16th to endNight
14%11%47%6%35%5%5%6%29%
2101
March1st to 15thNight
18%8%47%5%34345%33%
1989
16th to endNight
15%5%35%5%34345%42%
2101
April1st to 15thNight
19%7%35%4245%47%34%
1796
16th to endNight
14%7%2443435%6%42%
1680
May1st to 15thNight
15%5%16%5%35%5%47%38%
1512
16th to endNight
12%42344446%6%46%
1495
June1st to 15thNight
13%5%25%5%345%6%8%39%
1440
16th to endNight
10%426%5%35%5%5%8%41%
1440
July1st to 15thNight
6%3144345%5%7%52%
1440
16th to endNight
8%31343447%9%48%
1553
August1st to 15thNight
7%425%4245%5%9%47%
1620
16th to endNight
6%425%5%2445%7%50%
1797
September1st to 15thNight
14%5%2442346%7%45%
1800
16th to endNight
14%5%24313446%48%
1992
October1st to 15thNight
18%7%35%5%24346%37%
2160
16th to endNight
21%8%36%6%34446%28%
2304
November1st to 15thNight
18%9%35%5%34346%35%
2601
16th to endNight
21%9%46%6%35%5%5%6%25%
2730
December1st to 15thNight
19%13%5%7%5%35%5%5%6%21%
2730
16th to endNight
19%14%5%9%6%34445%19%
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
18%14%6%7%6%24445%25%
1552
16th to endDay
14%15%5%10%8%36%345%22%
1838
February1st to 15thDay
13%15%6%12%8%35%445%22%
1710
16th to endDay
17%14%47%7%45%34426%
1518
March1st to 15thDay
16%10%47%6%45%445%29%
1956
16th to endDay
16%8%35%5%34445%39%
2120
April1st to 15thDay
22%10%245%33445%33%
2152
16th to endDay
19%8%24423445%40%
2289
May1st to 15thDay
17%8%25%5%3445%6%33%
2439
16th to endDay
13%7%25%5%245%5%8%39%
2618
June1st to 15thDay
19%6%35%5%345%6%8%32%
2520
16th to endDay
15%6%24436%5%6%9%35%
2520
July1st to 15thDay
10%4245%36%5%6%9%40%
2520
16th to endDay
9%5%26%6%47%6%5%9%36%
2612
August1st to 15thDay
10%6%26%5%35%6%6%7%38%
2340
16th to endDay
12%6%25%4345%6%9%39%
2393
September1st to 15thDay
15%5%25%43445%7%41%
2160
16th to endDay
14%5%26%5%23445%44%
1963
October1st to 15thDay
20%8%35%6%34446%32%
1800
16th to endDay
25%9%47%5%32446%25%
1918
November1st to 15thDay
16%9%36%4345%47%33%
1586
16th to endDay
20%12%46%6%3445%5%25%
1560
December1st to 15thDay
17%16%6%7%6%44445%22%
1560
16th to endDay
19%15%6%8%7%34435%20%
1664
January1st to 15thNight
20%13%5%8%7%35%445%22%
2716
16th to endNight
14%14%5%9%7%3445%5%25%
2736
February1st to 15thNight
12%14%5%9%7%36%5%45%24%
2473
16th to endNight
14%10%47%6%35%5%5%6%29%
2101
March1st to 15thNight
18%9%46%5%24445%33%
2001
16th to endNight
15%5%35%5%24435%42%
2101
April1st to 15thNight
19%8%35%434446%35%
1796
16th to endNight
14%8%2442445%6%42%
1680
May1st to 15thNight
16%5%15%5%35%5%5%6%38%
1512
16th to endNight
11%42343436%6%46%
1495
June1st to 15thNight
13%6%345%25%45%8%39%
1440
16th to endNight
10%435%5%36%5%5%8%41%
1440
July1st to 15thNight
6%3244345%5%8%52%
1440
16th to endNight
8%324335%46%8%48%
1553
August1st to 15thNight
8%415%4235%6%9%48%
1620
16th to endNight
6%4245%3445%7%50%
1797
September1st to 15thNight
14%5%25%42245%7%45%
1800
16th to endNight
14%5%23323446%49%
1992
October1st to 15thNight
19%6%35%6%24346%37%
2160
16th to endNight
21%8%46%6%34446%29%
2304
November1st to 15thNight
18%8%345%24446%35%
2601
16th to endNight
21%9%46%6%35%5%5%6%25%
2730
December1st to 15thNight
20%13%5%7%5%35%5%5%6%21%
2730
16th to endNight
19%15%5%9%6%3445%5%20%
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
60%5%11%15%7%
1553
16th to endDay
64%5%8%11%8%1
1838
February1st to 15thDay
64%5%9%15%5%
1712
16th to endDay
61%49%13%11%
1518
March1st to 15thDay
56%5%13%15%7%1
1956
16th to endDay
46%5%8%20%16%2
2121
April1st to 15thDay
52%49%18%13%1
2152
16th to endDay
45%48%22%15%2
2289
May1st to 15thDay
49%6%8%20%13%1
2439
16th to endDay
42%7%12%21%14%1
2622
June1st to 15thDay
47%7%12%21%10%
2520
16th to endDay
43%8%13%20%13%
2520
July1st to 15thDay
36%7%13%26%14%
2371
16th to endDay
43%8%12%25%8%1
2448
August1st to 15thDay
41%9%14%21%12%1
2327
16th to endDay
39%7%13%27%11%1
2393
September1st to 15thDay
40%7%13%25%11%
2160
16th to endDay
40%7%11%29%10%
1963
October1st to 15thDay
52%6%9%21%9%1
1800
16th to endDay
58%7%13%14%6%
1918
November1st to 15thDay
49%8%13%16%10%1
1586
16th to endDay
58%7%13%12%6%
1560
December1st to 15thDay
64%6%11%11%4
1560
16th to endDay
66%49%13%5%
1664
January1st to 15thNight
64%5%8%12%7%1
2716
16th to endNight
60%6%8%16%7%
2736
February1st to 15thNight
60%6%9%16%6%
2482
16th to endNight
53%6%12%18%8%
2101
March1st to 15thNight
52%5%12%19%9%
2001
16th to endNight
43%49%22%17%2
2101
April1st to 15thNight
49%5%9%18%15%1
1796
16th to endNight
40%6%11%19%19%2
1680
May1st to 15thNight
44%7%10%19%14%3
1512
16th to endNight
36%6%12%26%16%2
1497
June1st to 15thNight
41%6%12%21%15%
1440
16th to endNight
39%8%13%22%15%1
1440
July1st to 15thNight
27%8%12%29%21%
1360
16th to endNight
31%7%13%31%15%1
1454
August1st to 15thNight
30%9%18%26%14%
1609
16th to endNight
31%7%12%31%15%
1797
September1st to 15thNight
36%6%15%25%13%1
1800
16th to endNight
35%6%10%31%14%
1992
October1st to 15thNight
47%7%10%21%12%
2160
16th to endNight
55%7%11%16%8%
2304
November1st to 15thNight
49%5%13%18%11%1
2601
16th to endNight
57%8%13%14%5%
2730
December1st to 15thNight
61%8%12%13%4
2730
16th to endNight
65%6%10%10%7%
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
22%30%32%10%41
90
16th to endDay
29%20%37%8%3
137
February1st to 15thDay
28%34%31%5%
135
16th to endDay
33%23%30%12%
139
March1st to 15thDay
22%17%33%21%4
270
16th to endDay
26%10%35%15%9%2
288
April1st to 15thDay
27%16%31%14%8%1
270
16th to endDay
22%18%28%17%8%4
270
May1st to 15thDay
29%10%26%17%8%7%
288
16th to endDay
17%11%34%22%9%4
331
June1st to 15thDay
21%8%34%22%11%1
315
16th to endDay
20%9%26%26%12%5%
315
July1st to 15thDay
13%6%26%29%14%9%
305
16th to endDay
9%6%30%30%15%7%
326
August1st to 15thDay
10%326%31%16%11%
313
16th to endDay
13%5%23%26%18%11%
332
September1st to 15thDay
14%8%24%21%17%13%
315
16th to endDay
15%8%22%23%18%11%
314
October1st to 15thDay
20%13%30%20%9%5%
315
16th to endDay
27%21%28%16%5%
335
November1st to 15thDay
24%13%29%25%7%
150
16th to endDay
22%23%33%18%2
90
December1st to 15thDay
20%32%28%14%4
90
16th to endDay
27%30%37%5%
96
January1st to 15thNight
26%23%28%14%5%
780
16th to endNight
23%16%32%21%4
832
February1st to 15thNight
20%20%39%16%2
764
16th to endNight
20%20%34%19%4
659
March1st to 15thNight
23%19%33%20%2
720
16th to endNight
19%13%35%20%10%1
768
April1st to 15thNight
23%16%31%22%5%
718
16th to endNight
19%12%31%25%9%1
600
May1st to 15thNight
20%5%29%29%13%2
432
16th to endNight
14%5%32%33%13%
375
June1st to 15thNight
15%7%29%33%11%1
360
16th to endNight
10%5%30%38%15%
360
July1st to 15thNight
7%5%28%37%20%
340
16th to endNight
7%132%36%21%1
415
August1st to 15thNight
10%321%35%25%3
539
16th to endNight
10%324%31%27%2
651
September1st to 15thNight
16%5%26%27%20%3
720
16th to endNight
16%7%21%27%23%5%
717
October1st to 15thNight
22%10%27%23%13%1
720
16th to endNight
27%16%29%20%5%
768
November1st to 15thNight
21%15%29%23%8%1
760
16th to endNight
25%19%29%18%6%
780
December1st to 15thNight
27%24%29%14%3
780
16th to endNight
28%19%32%16%2
832
Page generated at 2018-02-23 11:21:37. Version ac04

Copyright 2018 A. Danko


Peterborough Clear Sky Chart |Charts Home