Suffield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Suffield clear sky chart from 2005-11-06 to 2024-02-10.

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
39%
23806
15%
80473
9%
23742
45%
23742
23%
50261

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
31%
935
14%
4675
7%
926
36%
926
13%
2894
January11th to 20thNight
31%
942
17%
4615
7%
929
39%
929
13%
3047
January21st to endNight
29%
899
10%
4918
6%
893
39%
893
12%
2763
February1st to 10thNight
36%
758
13%
2508
11%
758
42%
758
18%
1733
February11th to 20thNight
33%
701
13%
2273
10%
700
39%
700
17%
1600
February21st to endNight
44%
592
14%
1916
10%
592
51%
592
20%
1307
March1st to 10thNight
36%
720
15%
2087
10%
720
41%
720
21%
1450
March11th to 20thNight
37%
720
18%
1980
9%
720
44%
720
24%
1341
March21st to endNight
37%
792
10%
2178
4%
792
42%
792
20%
1561
April1st to 10thNight
32%
586
15%
1768
7%
586
38%
586
20%
1230
April11th to 20thNight
36%
533
16%
1601
10%
533
41%
533
20%
1105
April21st to endNight
42%
540
14%
1620
12%
540
46%
540
24%
1079
May1st to 10thNight
49%
540
12%
1490
9%
540
53%
540
28%
988
May11th to 20thNight
50%
440
16%
1325
12%
440
53%
440
30%
809
May21st to endNight
43%
389
9%
1358
7%
388
46%
388
21%
876
June1st to 10thNight
41%
360
4%
1260
3%
360
42%
360
23%
790
June11th to 20thNight
41%
360
4%
1260
1%
360
42%
360
23%
774
June21st to endNight
55%
360
5%
1260
2%
360
57%
360
33%
668
July1st to 10thNight
63%
350
6%
1225
4%
350
65%
350
39%
604
July11th to 20thNight
55%
348
10%
1218
9%
348
59%
348
34%
653
July21st to endNight
66%
394
22%
1302
22%
372
74%
372
49%
571
August1st to 10thNight
61%
471
16%
1497
14%
469
66%
469
38%
800
August11th to 20thNight
63%
534
21%
1602
15%
534
69%
534
43%
859
August21st to endNight
57%
594
25%
1782
18%
594
62%
594
41%
965
September1st to 10thNight
53%
540
22%
1732
16%
540
58%
540
34%
974
September11th to 20thNight
52%
688
20%
1948
15%
688
57%
688
34%
1192
September21st to endNight
45%
720
24%
1980
14%
720
54%
720
37%
1168
October1st to 10thNight
43%
720
22%
2142
12%
720
53%
720
29%
1327
October11th to 20thNight
39%
720
22%
2160
10%
720
50%
720
28%
1342
October21st to endNight
34%
800
17%
2578
7%
800
44%
800
21%
1656
November1st to 10thNight
28%
925
16%
2590
6%
925
36%
925
21%
1835
November11th to 20thNight
30%
950
17%
2660
6%
950
40%
950
24%
1771
November21st to endNight
29%
950
13%
2743
5%
950
36%
950
24%
1846
December1st to 10thNight
30%
950
13%
2850
6%
950
36%
950
19%
1995
December11th to 20thNight
27%
949
12%
3469
5%
949
33%
949
18%
2197
December21st to endNight
29%
1036
10%
4903
6%
1026
37%
1026
15%
2491

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
8%8%36%6%35%5%6%8%42%
77715
Night
7%8%37%6%35%5%6%8%40%
81195
TransparencyDay
40%6%16%25%12%2
77417
Night
41%6%16%24%12%2
81073
SeeingDay
12%8%26%31%19%5%
14420
Night
11%8%31%33%14%2
23858

By Month

Percentage Cloud Cover NW (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
413%5%8%7%46%6%6%10%30%
2219
11th to 20thDay
5%7%411%9%48%9%6%6%30%
2199
21st to endDay
410%47%7%45%46%7%42%
2680
February1st to 10thDay
9%12%6%9%10%45%5%6%7%27%
1655
11th to 20thDay
8%12%6%9%8%6%7%7%8%7%23%
1575
21st to endDay
5%12%5%13%8%46%5%6%6%29%
1337
March1st to 10thDay
6%11%411%10%45%5%5%7%31%
1873
11th to 20thDay
8%9%49%6%37%6%6%9%34%
1979
21st to endDay
10%10%49%6%35%5%7%7%34%
2178
April1st to 10thDay
7%9%5%9%7%46%5%6%9%32%
2190
11th to 20thDay
9%12%5%8%7%35%5%5%7%34%
2310
21st to endDay
11%7%48%6%46%5%6%9%35%
2340
May1st to 10thDay
12%8%37%6%35%6%6%8%36%
2469
11th to 20thDay
9%6%26%6%345%6%9%43%
2565
21st to endDay
20%8%35%5%345%6%7%36%
2917
June1st to 10thDay
14%6%26%5%35%6%6%9%39%
2700
11th to 20thDay
17%7%25%5%46%6%7%8%32%
2700
21st to endDay
7%3245%35%6%6%10%49%
2700
July1st to 10thDay
43245%345%7%9%53%
2700
11th to 20thDay
6%42443446%8%55%
2700
21st to endDay
321342345%9%64%
2938
August1st to 10thDay
5%42343445%8%59%
2430
11th to 20thDay
7%4144245%6%9%54%
2299
21st to endDay
7%4134235%5%8%57%
2574
September1st to 10thDay
10%5%245%23446%56%
2228
11th to 20thDay
13%5%2442446%8%49%
2009
21st to endDay
9%6%25%33445%8%51%
1980
October1st to 10thDay
11%6%36%5%35%5%6%7%43%
1818
11th to 20thDay
8%7%37%6%26%6%6%7%42%
1800
21st to endDay
10%9%47%5%35%5%6%7%39%
1756
November1st to 10thDay
11%13%39%7%35%5%5%6%31%
1488
11th to 20thDay
6%9%5%8%7%46%46%8%37%
1520
21st to endDay
7%9%47%7%45%5%7%8%36%
1435
December1st to 10thDay
8%14%410%8%45%6%6%6%30%
1330
11th to 20thDay
5%11%5%11%8%46%5%5%6%34%
1682
21st to endDay
49%36%7%3445%6%48%
2442
January1st to 10thNight
49%5%9%8%46%6%7%9%32%
4726
11th to 20thNight
5%8%411%9%47%6%7%8%32%
4699
21st to endNight
49%410%7%45%5%6%8%40%
4993
February1st to 10thNight
8%10%49%8%5%5%6%6%8%30%
2508
11th to 20thNight
6%11%6%8%7%47%7%7%8%29%
2272
21st to endNight
6%9%5%8%7%47%6%7%9%32%
1916
March1st to 10thNight
5%9%411%9%36%6%6%9%33%
2087
11th to 20thNight
8%8%47%7%46%6%7%9%35%
1980
21st to endNight
7%10%47%9%46%6%8%10%30%
2178
April1st to 10thNight
9%10%49%7%36%5%6%9%32%
1768
11th to 20thNight
9%10%37%8%36%6%6%7%34%
1601
21st to endNight
11%8%46%7%36%5%6%9%36%
1620
May1st to 10thNight
12%7%37%5%4446%8%39%
1490
11th to 20thNight
8%5%35%5%36%6%5%7%45%
1325
21st to endNight
17%6%36%6%35%5%5%8%37%
1358
June1st to 10thNight
16%6%35%5%35%46%10%37%
1260
11th to 20thNight
13%425%6%36%6%8%10%37%
1260
21st to endNight
5%325%5%46%46%8%52%
1260
July1st to 10thNight
6%224335%5%6%10%54%
1260
11th to 20thNight
6%315%425%6%7%9%51%
1260
21st to endNight
321242335%9%65%
1379
August1st to 10thNight
6%415%6%245%6%9%53%
1504
11th to 20thNight
5%314425%47%11%54%
1602
21st to endNight
7%42343446%8%55%
1782
September1st to 10thNight
9%5%245%35%5%6%7%51%
1732
11th to 20thNight
12%5%25%43445%7%50%
1948
21st to endNight
7%5%245%245%6%8%50%
1980
October1st to 10thNight
11%7%26%5%3445%8%45%
2142
11th to 20thNight
8%7%37%5%36%46%9%43%
2160
21st to endNight
7%10%37%6%35%6%6%8%37%
2578
November1st to 10thNight
11%11%37%7%445%5%7%35%
2590
11th to 20thNight
5%8%48%7%45%6%6%8%39%
2660
21st to endNight
6%11%5%8%6%45%5%6%8%38%
2743
December1st to 10thNight
6%12%5%9%8%46%5%5%7%34%
2850
11th to 20thNight
49%410%7%45%5%7%9%35%
3510
21st to endNight
5%7%36%5%35%6%6%7%46%
5214

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
48%7%18%21%5%1
2219
11th to 20thDay
52%7%12%15%14%1
2220
21st to endDay
40%5%24%25%5%
2680
February1st to 10thDay
56%5%13%17%7%1
1655
11th to 20thDay
55%7%15%17%6%
1584
21st to endDay
54%6%10%19%10%1
1337
March1st to 10thDay
51%8%15%20%7%
1873
11th to 20thDay
45%7%17%23%7%1
1980
21st to endDay
48%8%19%17%8%
2178
April1st to 10thDay
47%7%15%22%9%
2190
11th to 20thDay
49%5%11%25%8%1
2310
21st to endDay
46%6%14%24%9%1
2340
May1st to 10thDay
45%6%15%23%11%1
2469
11th to 20thDay
36%6%14%29%13%1
2569
21st to endDay
48%6%14%23%9%
2918
June1st to 10thDay
41%7%16%24%10%2
2700
11th to 20thDay
46%7%15%22%10%1
2700
21st to endDay
29%7%19%31%12%3
2700
July1st to 10thDay
24%7%18%32%15%3
2626
11th to 20thDay
26%6%15%33%18%2
2619
21st to endDay
18%5%15%34%23%5%
2775
August1st to 10thDay
24%5%16%32%17%5%
2412
11th to 20thDay
27%7%17%32%15%3
2299
21st to endDay
24%415%31%21%4
2574
September1st to 10thDay
31%413%27%18%7%
2228
11th to 20thDay
33%6%12%32%14%3
2009
21st to endDay
32%5%15%31%14%3
1980
October1st to 10thDay
38%6%17%27%11%1
1818
11th to 20thDay
40%5%16%26%11%2
1800
21st to endDay
42%6%16%24%12%
1756
November1st to 10thDay
54%6%13%18%7%1
1488
11th to 20thDay
45%5%18%23%8%
1520
21st to endDay
44%7%18%23%7%1
1435
December1st to 10thDay
52%5%17%18%6%2
1330
11th to 20thDay
50%5%18%22%41
1684
21st to endDay
36%416%25%16%2
2442
January1st to 10thNight
46%6%22%21%41
4726
11th to 20thNight
49%6%13%17%13%2
4740
21st to endNight
42%6%19%26%7%1
4993
February1st to 10thNight
49%5%15%19%10%1
2508
11th to 20thNight
50%7%15%19%8%
2273
21st to endNight
47%6%14%21%10%2
1916
March1st to 10thNight
45%8%16%25%6%
2087
11th to 20thNight
42%7%16%22%11%1
1980
21st to endNight
47%8%18%19%7%1
2178
April1st to 10thNight
48%7%11%24%10%
1768
11th to 20thNight
48%7%11%21%12%1
1601
21st to endNight
44%6%14%26%10%1
1620
May1st to 10thNight
42%5%13%24%15%1
1490
11th to 20thNight
34%8%12%27%18%1
1325
21st to endNight
45%5%15%22%11%2
1358
June1st to 10thNight
42%6%17%24%9%2
1260
11th to 20thNight
39%7%15%26%12%1
1260
21st to endNight
29%6%17%32%13%3
1260
July1st to 10thNight
24%5%19%31%18%3
1225
11th to 20thNight
28%7%16%23%20%6%
1218
21st to endNight
17%5%12%33%26%8%
1302
August1st to 10thNight
26%6%17%31%16%4
1497
11th to 20thNight
24%6%16%29%21%5%
1602
21st to endNight
26%5%11%26%26%6%
1782
September1st to 10thNight
31%5%13%26%18%7%
1732
11th to 20thNight
35%5%12%28%15%5%
1948
21st to endNight
30%6%14%31%17%3
1980
October1st to 10thNight
37%5%16%27%13%2
2142
11th to 20thNight
38%5%13%29%12%2
2160
21st to endNight
43%6%16%26%10%1
2578
November1st to 10thNight
48%7%15%21%9%1
2590
11th to 20thNight
42%6%20%21%11%
2660
21st to endNight
44%5%23%19%8%1
2743
December1st to 10thNight
50%5%17%19%8%1
2850
11th to 20thNight
44%6%25%20%4
3507
21st to endNight
35%5%15%25%16%4
5214

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
8%8%32%29%18%6%
180
11th to 20thDay
12%8%31%33%12%3
180
21st to endDay
10%10%35%28%14%4
198
February1st to 10thDay
18%14%32%26%9%2
246
11th to 20thDay
11%8%33%34%13%2
240
21st to endDay
6%9%27%37%16%4
203
March1st to 10thDay
11%10%32%28%15%3
420
11th to 20thDay
9%7%34%31%13%6%
420
21st to endDay
13%11%32%26%14%4
462
April1st to 10thDay
10%13%33%30%12%2
420
11th to 20thDay
14%10%31%30%14%1
412
21st to endDay
15%10%27%29%15%3
420
May1st to 10thDay
14%8%21%31%18%8%
552
11th to 20thDay
14%6%20%33%21%7%
625
21st to endDay
19%419%25%22%9%
679
June1st to 10thDay
13%10%22%31%20%4
630
11th to 20thDay
17%10%29%28%15%2
630
21st to endDay
9%5%23%33%21%8%
630
July1st to 10thDay
5%423%37%25%7%
621
11th to 20thDay
8%6%25%35%22%4
618
21st to endDay
46%18%33%30%9%
684
August1st to 10thDay
6%5%18%38%26%8%
485
11th to 20thDay
7%221%31%29%10%
437
21st to endDay
7%6%20%31%28%8%
495
September1st to 10thDay
12%9%26%28%23%3
450
11th to 20thDay
14%5%22%32%22%6%
450
21st to endDay
15%7%29%30%14%4
450
October1st to 10thDay
16%6%24%29%20%5%
288
11th to 20thDay
10%9%32%29%19%2
270
21st to endDay
20%12%31%23%12%2
297
November1st to 10thDay
21%11%31%27%9%1
270
11th to 20thDay
13%13%35%31%8%1
270
21st to endDay
9%10%39%27%7%7%
230
December1st to 10thDay
10%11%43%23%12%1
180
11th to 20thDay
11%13%42%26%9%
180
21st to endDay
15%9%21%37%15%3
198
January1st to 10thNight
10%13%35%29%12%1
950
11th to 20thNight
12%10%35%33%9%1
950
21st to endNight
10%12%36%29%11%2
915
February1st to 10thNight
14%9%28%31%15%3
758
11th to 20thNight
12%11%32%35%10%1
704
21st to endNight
9%6%26%36%19%3
592
March1st to 10thNight
8%7%37%34%11%3
720
11th to 20thNight
11%10%32%32%12%2
720
21st to endNight
10%11%29%36%13%2
792
April1st to 10thNight
12%11%34%28%13%2
586
11th to 20thNight
15%8%31%34%12%1
533
21st to endNight
15%8%25%38%12%1
540
May1st to 10thNight
14%8%21%34%21%2
540
11th to 20thNight
10%7%26%35%20%3
440
21st to endNight
20%424%29%21%2
389
June1st to 10thNight
18%9%26%28%18%2
360
11th to 20thNight
16%7%32%33%12%
360
21st to endNight
7%426%41%19%2
360
July1st to 10thNight
6%322%47%21%1
350
11th to 20thNight
7%425%43%20%1
348
21st to endNight
4421%46%22%3
394
August1st to 10thNight
7%323%37%28%2
471
11th to 20thNight
6%321%41%27%1
534
21st to endNight
8%426%38%24%1
594
September1st to 10thNight
11%5%26%42%15%2
540
11th to 20thNight
14%5%22%40%18%1
688
21st to endNight
10%7%32%34%14%3
720
October1st to 10thNight
16%6%27%34%16%1
720
11th to 20thNight
11%8%35%31%13%2
720
21st to endNight
11%14%33%32%9%
800
November1st to 10thNight
16%10%38%28%8%
925
11th to 20thNight
12%13%39%27%7%2
950
21st to endNight
10%10%41%30%8%1
950
December1st to 10thNight
13%9%36%28%13%2
950
11th to 20thNight
9%11%40%28%11%1
950
21st to endNight
13%9%34%33%10%2
1045
Page generated at 2024-02-07 04:11:57. Version ac07

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