Newmarket
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Newmarket clear sky chart from 2005-11-06 to 2024-02-25.

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%
22944
13%
80379
8%
22846
36%
22846
15%
57605

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
14%
753
7%
4413
3%
737
23%
737
5%
3325
January11th to 20thNight
15%
757
6%
4210
3%
740
20%
740
4%
3367
January21st to endNight
18%
833
6%
4527
5%
814
25%
814
6%
3657
February1st to 10thNight
15%
760
10%
2470
3%
760
23%
760
9%
1944
February11th to 20thNight
16%
740
11%
2405
3%
740
25%
740
11%
1817
February21st to endNight
17%
611
11%
1937
4%
611
25%
611
12%
1423
March1st to 10thNight
18%
720
15%
1980
5%
720
27%
720
17%
1430
March11th to 20thNight
21%
720
17%
1980
6%
720
30%
720
16%
1449
March21st to endNight
26%
792
18%
2178
8%
792
34%
792
21%
1528
April1st to 10thNight
20%
720
14%
1832
4%
720
26%
720
19%
1366
April11th to 20thNight
27%
653
17%
1717
7%
653
33%
653
22%
1215
April21st to endNight
28%
540
16%
1620
7%
540
36%
540
21%
1134
May1st to 10thNight
39%
540
16%
1620
10%
540
44%
540
23%
1071
May11th to 20thNight
38%
356
21%
1418
16%
356
52%
356
22%
828
May21st to endNight
48%
388
17%
1551
17%
388
58%
388
27%
835
June1st to 10thNight
38%
360
14%
1440
12%
360
50%
360
20%
856
June11th to 20thNight
42%
360
15%
1425
16%
360
51%
360
23%
827
June21st to endNight
44%
360
15%
1260
15%
360
51%
360
24%
762
July1st to 10thNight
56%
350
17%
1323
19%
350
63%
350
34%
680
July11th to 20thNight
53%
348
19%
1392
25%
348
59%
348
29%
754
July21st to endNight
56%
546
17%
1630
14%
516
60%
516
33%
962
August1st to 10thNight
58%
537
17%
1600
13%
534
62%
534
34%
957
August11th to 20thNight
63%
534
22%
1598
14%
534
68%
534
36%
918
August21st to endNight
49%
666
20%
1854
11%
666
54%
666
31%
1176
September1st to 10thNight
49%
720
16%
1800
8%
720
52%
720
33%
1169
September11th to 20thNight
50%
720
26%
1898
14%
720
56%
720
37%
1146
September21st to endNight
45%
720
19%
2017
14%
720
49%
720
26%
1350
October1st to 10thNight
36%
720
15%
2160
12%
720
41%
720
20%
1514
October11th to 20thNight
26%
720
12%
2160
6%
720
35%
720
16%
1574
October21st to endNight
19%
792
13%
2376
7%
792
27%
792
13%
1831
November1st to 10thNight
28%
740
16%
2483
12%
740
35%
740
18%
1670
November11th to 20thNight
20%
760
13%
2660
7%
760
29%
760
12%
1964
November21st to endNight
20%
760
8%
2660
5%
760
25%
760
10%
2076
December1st to 10thNight
13%
760
5%
2660
2%
760
17%
760
7%
2182
December11th to 20thNight
13%
760
6%
3255
1%
758
19%
758
5%
2612
December21st to endNight
9%
828
3%
4870
0%
817
15%
817
3%
4236

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%10%48%7%45%5%5%7%30%
78614
Night
15%11%48%7%45%5%5%6%31%
80651
TransparencyDay
51%8%13%18%9%1
78328
Night
51%8%12%18%9%1
80471
SeeingDay
19%15%31%22%10%3
13659
Night
19%13%32%25%9%1
22969

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 10thDay
16%14%6%8%8%35%5%46%25%
2517
11th to 20thDay
11%18%8%14%11%5%5%445%15%
2724
21st to endDay
20%19%8%11%7%35%335%15%
3124
February1st to 10thDay
14%16%5%14%8%46%5%46%18%
1710
11th to 20thDay
12%15%6%13%9%445%46%22%
1663
21st to endDay
17%15%7%10%7%34445%25%
1410
March1st to 10thDay
13%13%410%7%5%5%45%6%28%
1977
11th to 20thDay
12%13%6%9%7%5%5%445%30%
1980
21st to endDay
18%12%37%6%34445%33%
2178
April1st to 10thDay
17%13%48%6%4446%5%27%
2128
11th to 20thDay
19%10%46%5%2345%6%35%
2208
21st to endDay
20%10%47%6%34446%33%
2340
May1st to 10thDay
16%9%46%6%345%5%8%34%
2340
11th to 20thDay
15%7%35%6%4445%6%40%
2473
21st to endDay
12%6%36%5%45%5%7%7%42%
2725
June1st to 10thDay
16%6%35%5%35%5%7%8%37%
2520
11th to 20thDay
13%6%35%5%346%6%9%39%
2524
21st to endDay
14%5%35%5%45%46%8%39%
2700
July1st to 10thDay
10%425%5%45%5%7%9%45%
2588
11th to 20thDay
10%6%35%6%46%5%8%10%37%
2520
21st to endDay
9%6%36%7%46%6%8%10%34%
2590
August1st to 10thDay
10%5%27%6%46%6%7%10%38%
2327
11th to 20thDay
8%6%36%7%46%6%8%9%37%
2303
21st to endDay
13%7%25%6%45%5%6%9%38%
2482
September1st to 10thDay
14%6%27%5%35%6%6%8%39%
2160
11th to 20thDay
12%6%35%5%35%5%6%8%42%
2057
21st to endDay
13%7%37%7%45%5%5%7%37%
1941
October1st to 10thDay
19%9%37%6%45%45%6%34%
1800
11th to 20thDay
21%11%47%7%35%446%27%
1800
21st to endDay
26%14%37%6%345%5%5%20%
1980
November1st to 10thDay
14%14%48%5%35%5%5%7%30%
1587
11th to 20thDay
14%14%5%8%8%5%5%6%5%8%22%
1520
21st to endDay
18%15%7%11%8%45%445%19%
1520
December1st to 10thDay
15%18%8%13%7%46%5%46%13%
1520
11th to 20thDay
17%14%5%9%8%46%6%5%7%19%
1906
21st to endDay
25%17%7%14%8%4443311%
2772
January1st to 10thNight
16%15%7%11%8%45%45%6%19%
4429
11th to 20thNight
13%13%7%13%11%6%6%5%5%5%15%
4234
21st to endNight
19%14%7%9%11%5%5%45%5%17%
4532
February1st to 10thNight
13%15%5%10%8%46%6%5%6%21%
2470
11th to 20thNight
13%13%7%10%7%45%5%5%6%24%
2403
21st to endNight
13%12%5%10%6%45%5%5%6%27%
1937
March1st to 10thNight
13%9%5%8%8%46%446%33%
1970
11th to 20thNight
15%13%48%6%34445%34%
1979
21st to endNight
15%9%46%6%3445%5%37%
2178
April1st to 10thNight
18%11%46%6%36%45%5%31%
1832
11th to 20thNight
16%9%36%6%35%45%6%39%
1717
21st to endNight
16%11%37%6%335%5%6%35%
1620
May1st to 10thNight
17%6%25%5%346%5%8%39%
1620
11th to 20thNight
14%6%235%45%35%8%45%
1417
21st to endNight
10%5%244345%5%8%51%
1550
June1st to 10thNight
13%5%26%5%45%6%5%7%42%
1440
11th to 20thNight
11%5%35%6%45%5%6%9%43%
1425
21st to endNight
12%6%26%6%2445%9%44%
1260
July1st to 10thNight
6%425%5%2346%7%56%
1363
11th to 20thNight
10%424435%45%8%50%
1440
21st to endNight
8%424435%6%6%8%49%
1726
August1st to 10thNight
8%6%245%3445%8%50%
1611
11th to 20thNight
7%5%25%3345%6%10%50%
1598
21st to endNight
10%6%25%5%345%6%8%46%
1854
September1st to 10thNight
10%6%25%5%36%5%6%8%46%
1800
11th to 20thNight
13%42443335%6%52%
1898
21st to endNight
15%7%35%5%44447%42%
2017
October1st to 10thNight
16%8%36%6%35%45%6%37%
2160
11th to 20thNight
19%9%37%6%345%5%6%31%
2160
21st to endNight
23%10%47%7%35%5%5%7%26%
2376
November1st to 10thNight
19%10%45%425%5%6%7%34%
2483
11th to 20thNight
17%12%5%7%6%35%5%6%7%27%
2660
21st to endNight
18%14%5%9%6%45%5%5%6%23%
2660
December1st to 10thNight
18%15%7%10%8%46%5%5%5%18%
2660
11th to 20thNight
15%17%7%10%7%46%5%5%6%19%
3288
21st to endNight
26%17%6%13%6%45%5%45%11%
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
56%10%16%13%5%
2518
11th to 20thDay
70%8%9%10%3
2724
21st to endDay
71%8%9%9%31
3124
February1st to 10thDay
65%7%10%13%41
1710
11th to 20thDay
60%7%10%15%6%1
1672
21st to endDay
62%6%10%14%7%1
1410
March1st to 10thDay
55%8%13%15%9%1
1980
11th to 20thDay
55%6%10%16%11%2
1980
21st to endDay
52%6%10%16%14%2
2178
April1st to 10thDay
56%6%11%17%9%1
2128
11th to 20thDay
49%6%11%20%14%1
2208
21st to endDay
51%7%11%17%11%3
2340
May1st to 10thDay
49%6%10%19%14%2
2340
11th to 20thDay
44%7%11%24%14%1
2477
21st to endDay
39%8%15%23%13%2
2725
June1st to 10thDay
43%8%15%18%15%1
2520
11th to 20thDay
39%8%13%22%16%1
2524
21st to endDay
42%8%14%23%13%1
2700
July1st to 10thDay
34%9%13%24%18%2
2518
11th to 20thDay
37%10%16%25%10%1
2445
21st to endDay
41%11%16%19%12%1
2445
August1st to 10thDay
38%10%18%22%12%1
2314
11th to 20thDay
38%11%17%24%11%
2303
21st to endDay
41%8%15%24%11%1
2482
September1st to 10thDay
40%9%15%25%10%2
2160
11th to 20thDay
37%9%14%27%12%
2057
21st to endDay
45%8%14%25%8%
1941
October1st to 10thDay
50%7%12%18%11%1
1800
11th to 20thDay
56%8%13%17%6%1
1800
21st to endDay
63%8%11%13%5%
1980
November1st to 10thDay
51%9%14%18%8%1
1587
11th to 20thDay
57%11%12%13%7%1
1520
21st to endDay
65%8%13%13%2
1520
December1st to 10thDay
69%10%10%9%2
1520
11th to 20thDay
62%11%13%12%3
1906
21st to endDay
76%8%7%8%1
2772
January1st to 10thNight
61%9%14%12%3
4429
11th to 20thNight
65%10%12%9%2
4234
21st to endNight
65%10%11%10%31
4532
February1st to 10thNight
61%9%10%17%4
2470
11th to 20thNight
57%8%12%16%6%
2405
21st to endNight
54%7%14%17%7%1
1937
March1st to 10thNight
50%7%14%19%9%1
1980
11th to 20thNight
51%7%10%19%11%2
1980
21st to endNight
47%6%10%21%14%2
2178
April1st to 10thNight
53%5%11%19%11%1
1832
11th to 20thNight
46%6%10%20%15%2
1717
21st to endNight
48%7%11%18%14%2
1620
May1st to 10thNight
43%6%11%21%16%3
1620
11th to 20thNight
38%6%11%24%18%3
1418
21st to endNight
30%8%16%25%17%4
1551
June1st to 10thNight
39%8%12%24%16%2
1440
11th to 20thNight
37%7%12%22%21%2
1425
21st to endNight
37%8%14%23%16%1
1260
July1st to 10thNight
27%6%13%28%23%3
1323
11th to 20thNight
32%6%13%31%17%1
1392
21st to endNight
30%9%15%29%14%2
1630
August1st to 10thNight
31%7%18%29%13%1
1600
11th to 20thNight
28%8%18%31%14%1
1598
21st to endNight
35%8%13%28%14%1
1854
September1st to 10thNight
35%7%18%26%13%1
1800
11th to 20thNight
31%6%13%33%16%1
1898
21st to endNight
40%8%13%28%11%
2017
October1st to 10thNight
46%8%11%18%15%1
2160
11th to 20thNight
51%9%14%20%7%
2160
21st to endNight
56%9%12%14%9%
2376
November1st to 10thNight
47%6%14%22%10%1
2483
11th to 20thNight
54%9%13%15%8%1
2660
21st to endNight
58%10%16%12%2
2660
December1st to 10thNight
65%10%12%11%3
2660
11th to 20thNight
64%10%11%13%3
3288
21st to endNight
73%10%9%6%2
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
21%22%33%19%5%1
180
11th to 20thDay
22%29%29%14%5%1
240
21st to endDay
22%23%37%15%3
297
February1st to 10thDay
23%26%37%11%3
270
11th to 20thDay
23%24%43%8%1
270
21st to endDay
33%25%31%11%
223
March1st to 10thDay
23%19%38%16%4
420
11th to 20thDay
21%21%36%16%5%1
420
21st to endDay
29%18%31%17%5%1
462
April1st to 10thDay
24%20%35%14%7%
420
11th to 20thDay
27%19%25%17%8%3
412
21st to endDay
24%16%34%17%7%1
420
May1st to 10thDay
21%15%30%21%10%4
423
11th to 20thDay
20%12%30%25%9%4
447
21st to endDay
15%12%28%27%13%5%
485
June1st to 10thDay
14%15%30%28%11%1
450
11th to 20thDay
15%14%26%29%14%3
454
21st to endDay
16%10%33%28%10%2
630
July1st to 10thDay
10%7%29%31%19%4
513
11th to 20thDay
12%7%27%31%16%8%
444
21st to endDay
8%7%32%35%12%6%
488
August1st to 10thDay
9%6%28%29%17%10%
446
11th to 20thDay
10%7%24%29%22%9%
439
21st to endDay
13%9%29%24%17%8%
495
September1st to 10thDay
13%8%28%26%16%8%
450
11th to 20thDay
9%9%28%23%20%12%
450
21st to endDay
13%11%32%23%15%6%
450
October1st to 10thDay
23%12%27%19%15%4
450
11th to 20thDay
22%21%34%16%6%1
450
21st to endDay
29%19%32%16%4
495
November1st to 10thDay
22%23%28%20%7%
248
11th to 20thDay
23%26%30%17%31
180
21st to endDay
29%20%37%11%2
180
December1st to 10thDay
23%23%36%14%4
180
11th to 20thDay
28%23%31%13%41
180
21st to endDay
26%22%39%11%2
198
January1st to 10thNight
22%21%36%15%5%1
760
11th to 20thNight
24%18%33%20%41
760
21st to endNight
19%14%41%21%6%
836
February1st to 10thNight
21%18%39%21%1
760
11th to 20thNight
22%17%38%20%3
743
21st to endNight
20%20%37%19%4
611
March1st to 10thNight
19%19%37%21%4
720
11th to 20thNight
22%18%34%19%5%1
720
21st to endNight
20%15%35%23%7%
792
April1st to 10thNight
25%15%35%22%3
720
11th to 20thNight
18%16%35%22%8%1
653
21st to endNight
20%13%34%26%8%
540
May1st to 10thNight
18%7%30%32%11%1
540
11th to 20thNight
16%6%33%33%11%1
356
21st to endNight
12%6%29%36%17%1
389
June1st to 10thNight
14%6%34%34%12%
360
11th to 20thNight
12%8%29%36%14%1
360
21st to endNight
13%7%28%40%12%
360
July1st to 10thNight
6%6%27%41%20%1
350
11th to 20thNight
9%5%28%37%20%1
348
21st to endNight
7%5%27%41%19%1
546
August1st to 10thNight
10%321%36%28%1
537
11th to 20thNight
6%417%44%25%3
534
21st to endNight
12%5%26%34%21%2
666
September1st to 10thNight
11%7%27%32%19%4
720
11th to 20thNight
13%6%24%31%21%4
720
21st to endNight
16%10%23%31%17%4
720
October1st to 10thNight
18%9%30%25%16%1
720
11th to 20thNight
22%14%32%23%7%1
720
21st to endNight
28%13%33%22%4
792
November1st to 10thNight
23%13%32%23%9%1
740
11th to 20thNight
22%18%33%20%6%1
760
21st to endNight
24%16%34%22%4
760
December1st to 10thNight
27%16%38%16%3
760
11th to 20thNight
21%19%39%18%31
760
21st to endNight
30%15%37%16%2
836
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