Caroline
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Caroline clear sky chart from 2005-11-06 to 2024-02-20.

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
41%
23464
13%
80698
8%
23413
46%
23413
19%
53883

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
36%
935
13%
4687
7%
926
41%
926
10%
3246
January11th to 20thNight
35%
938
19%
4602
10%
929
41%
929
12%
2993
January21st to endNight
32%
819
13%
4816
10%
815
45%
815
11%
2926
February1st to 10thNight
35%
760
13%
2660
11%
760
40%
760
15%
1901
February11th to 20thNight
33%
740
12%
2462
9%
738
39%
738
16%
1748
February21st to endNight
43%
592
18%
1803
14%
592
50%
592
24%
1200
March1st to 10thNight
40%
720
15%
2160
12%
720
45%
720
20%
1541
March11th to 20thNight
40%
720
16%
2034
9%
720
46%
720
24%
1404
March21st to endNight
39%
792
12%
2106
5%
792
43%
792
20%
1559
April1st to 10thNight
37%
684
13%
1764
5%
684
42%
684
22%
1298
April11th to 20thNight
29%
533
12%
1601
7%
533
33%
533
18%
1158
April21st to endNight
38%
540
10%
1620
7%
540
41%
540
19%
1147
May1st to 10thNight
39%
383
7%
1419
7%
383
43%
383
15%
993
May11th to 20thNight
47%
354
11%
1239
9%
354
50%
354
23%
788
May21st to endNight
44%
388
4%
1358
1%
388
44%
388
17%
956
June1st to 10thNight
42%
360
0%
1260
0%
360
42%
360
16%
899
June11th to 20thNight
40%
360
0%
1260
0%
360
40%
360
14%
934
June21st to endNight
56%
360
0%
1260
0%
360
56%
360
21%
818
July1st to 10thNight
57%
350
0%
1225
0%
350
57%
350
22%
787
July11th to 20thNight
54%
348
3%
1218
0%
348
54%
348
23%
774
July21st to endNight
64%
394
9%
1351
9%
372
67%
372
30%
763
August1st to 10thNight
59%
358
8%
1424
11%
356
61%
356
20%
893
August11th to 20thNight
62%
450
13%
1518
14%
450
65%
450
28%
903
August21st to endNight
56%
594
18%
1782
14%
594
59%
594
30%
1093
September1st to 10thNight
53%
652
16%
1732
10%
652
55%
652
33%
1106
September11th to 20thNight
50%
720
17%
1962
11%
720
53%
720
28%
1310
September21st to endNight
48%
720
20%
1980
12%
720
54%
720
31%
1263
October1st to 10thNight
45%
720
17%
2038
11%
720
50%
720
26%
1364
October11th to 20thNight
42%
720
15%
2340
9%
720
50%
720
23%
1534
October21st to endNight
37%
792
16%
2574
11%
792
45%
792
19%
1751
November1st to 10thNight
33%
840
16%
2505
9%
840
39%
840
19%
1793
November11th to 20thNight
30%
950
15%
2806
8%
950
38%
950
21%
1959
November21st to endNight
34%
950
12%
2850
6%
950
40%
950
21%
1961
December1st to 10thNight
37%
950
17%
2850
11%
950
42%
950
21%
1959
December11th to 20thNight
35%
949
14%
3467
8%
949
40%
949
15%
2471
December21st to endNight
35%
1029
11%
4965
8%
1026
42%
1026
15%
2690

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
10%9%47%7%46%6%7%8%34%
77800
Night
7%9%48%7%46%6%6%8%35%
81335
TransparencyDay
45%10%16%20%9%1
77505
Night
44%9%15%20%10%2
81211
SeeingDay
13%7%26%31%17%5%
14272
Night
12%6%29%36%15%2
23529

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
311%7%12%8%345%6%9%32%
2219
11th to 20thDay
48%5%9%7%37%7%7%8%36%
2213
21st to endDay
49%47%6%46%5%7%10%38%
2794
February1st to 10thDay
413%5%9%10%46%7%6%7%29%
1520
11th to 20thDay
5%12%412%8%5%5%7%7%8%27%
1591
21st to endDay
39%6%11%11%5%7%6%8%6%28%
1453
March1st to 10thDay
412%6%10%9%47%5%5%7%31%
1800
11th to 20thDay
6%8%49%7%36%6%9%8%34%
1925
21st to endDay
7%14%5%9%8%45%6%7%7%27%
2249
April1st to 10thDay
7%13%6%7%8%5%6%7%7%9%24%
2196
11th to 20thDay
12%15%5%8%6%45%6%6%7%25%
2310
21st to endDay
12%11%47%7%45%6%6%10%29%
2340
May1st to 10thDay
14%11%39%7%47%6%6%8%26%
2537
11th to 20thDay
10%8%37%7%46%5%5%9%35%
2654
21st to endDay
20%9%36%6%45%5%6%8%28%
2917
June1st to 10thDay
19%8%36%7%5%6%6%7%8%26%
2700
11th to 20thDay
21%9%47%7%47%6%6%7%23%
2700
21st to endDay
11%6%36%6%47%8%7%9%33%
2700
July1st to 10thDay
11%6%26%6%47%7%8%8%35%
2700
11th to 20thDay
12%5%35%5%36%7%8%9%36%
2700
21st to endDay
9%5%25%5%35%6%8%9%43%
2884
August1st to 10thDay
12%5%26%5%35%6%7%10%39%
2507
11th to 20thDay
10%424436%6%7%10%44%
2382
21st to endDay
11%5%25%5%35%6%6%10%41%
2574
September1st to 10thDay
13%6%25%435%5%6%9%42%
2226
11th to 20thDay
15%8%35%5%3445%6%42%
1998
21st to endDay
10%9%36%5%4446%8%41%
1980
October1st to 10thDay
12%9%35%5%346%6%7%39%
1919
11th to 20thDay
11%8%36%6%35%5%6%7%38%
1620
21st to endDay
8%10%5%8%7%36%6%6%8%34%
1782
November1st to 10thDay
7%15%7%8%7%5%5%5%5%6%31%
1553
11th to 20thDay
6%11%49%6%45%47%7%37%
1373
21st to endDay
5%12%38%7%45%6%7%8%35%
1330
December1st to 10thDay
6%11%411%9%47%5%5%8%29%
1330
11th to 20thDay
39%5%11%9%46%7%6%7%32%
1682
21st to endDay
49%48%8%445%7%7%40%
2442
January1st to 10thNight
311%7%12%8%5%6%6%6%8%27%
4726
11th to 20thNight
28%5%11%9%46%8%7%7%33%
4699
21st to endNight
410%48%8%5%6%6%7%10%32%
4863
February1st to 10thNight
6%11%6%12%9%47%6%5%8%28%
2660
11th to 20thNight
410%6%11%9%5%7%6%7%7%28%
2460
21st to endNight
29%6%11%8%5%6%5%5%7%36%
1803
March1st to 10thNight
411%5%8%9%5%5%7%7%8%31%
2160
11th to 20thNight
5%10%5%7%7%45%7%7%9%33%
2034
21st to endNight
6%12%410%8%46%5%7%9%29%
2106
April1st to 10thNight
8%10%5%9%8%46%5%6%9%29%
1764
11th to 20thNight
10%14%5%9%9%3436%7%30%
1601
21st to endNight
11%10%48%7%45%5%6%8%32%
1620
May1st to 10thNight
13%12%5%7%7%45%5%46%31%
1419
11th to 20thNight
11%7%36%5%345%7%9%39%
1239
21st to endNight
19%8%36%5%35%6%5%8%32%
1358
June1st to 10thNight
18%8%46%5%35%7%6%8%30%
1260
11th to 20thNight
17%9%48%7%47%6%7%7%25%
1260
21st to endNight
10%6%36%6%46%6%8%9%38%
1260
July1st to 10thNight
13%6%26%5%45%6%7%10%37%
1260
11th to 20thNight
12%6%36%5%35%7%7%9%39%
1260
21st to endNight
6%5%25%435%5%7%8%49%
1430
August1st to 10thNight
11%426%6%36%6%8%8%40%
1432
11th to 20thNight
10%5%245%245%7%10%45%
1518
21st to endNight
9%6%35%5%35%5%5%8%46%
1782
September1st to 10thNight
11%6%25%5%245%5%7%46%
1732
11th to 20thNight
15%7%35%5%335%6%7%40%
1962
21st to endNight
11%7%35%435%5%7%8%43%
1980
October1st to 10thNight
10%10%37%6%345%6%6%42%
2038
11th to 20thNight
8%9%37%5%45%5%6%10%37%
2340
21st to endNight
8%10%48%7%47%5%6%8%34%
2574
November1st to 10thNight
9%14%49%6%45%6%6%7%32%
2505
11th to 20thNight
5%10%5%9%6%5%7%5%7%8%33%
2806
21st to endNight
410%5%10%8%47%5%7%9%33%
2850
December1st to 10thNight
6%11%5%9%7%45%5%6%8%35%
2850
11th to 20thNight
310%5%9%10%5%7%7%6%9%29%
3510
21st to endNight
39%48%6%35%5%6%8%43%
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
46%6%11%23%11%2
2219
11th to 20thDay
43%9%9%16%20%4
2234
21st to endDay
36%11%14%30%8%1
2794
February1st to 10thDay
51%7%14%16%9%3
1520
11th to 20thDay
50%10%15%16%8%2
1599
21st to endDay
51%8%12%17%11%1
1453
March1st to 10thDay
50%9%16%16%9%1
1800
11th to 20thDay
42%9%16%22%11%1
1926
21st to endDay
54%10%16%14%6%1
2249
April1st to 10thDay
53%10%17%14%6%
2196
11th to 20thDay
55%7%12%17%8%
2310
21st to endDay
49%10%15%18%6%2
2340
May1st to 10thDay
53%10%16%16%6%
2537
11th to 20thDay
43%9%16%20%11%1
2658
21st to endDay
51%9%17%17%6%1
2918
June1st to 10thDay
54%9%15%15%5%1
2700
11th to 20thDay
57%10%15%13%41
2700
21st to endDay
42%12%19%20%6%1
2700
July1st to 10thDay
40%12%22%18%7%1
2626
11th to 20thDay
39%13%20%22%6%
2619
21st to endDay
32%11%22%26%7%1
2724
August1st to 10thDay
37%12%21%24%6%
2490
11th to 20thDay
31%11%25%23%9%1
2382
21st to endDay
36%11%19%24%9%1
2574
September1st to 10thDay
37%8%22%21%10%2
2226
11th to 20thDay
41%8%14%26%10%1
1998
21st to endDay
39%9%16%22%11%2
1980
October1st to 10thDay
42%8%16%23%10%1
1919
11th to 20thDay
42%8%18%20%10%2
1620
21st to endDay
46%9%12%20%11%1
1782
November1st to 10thDay
52%8%12%17%9%2
1553
11th to 20thDay
45%8%13%22%11%1
1373
21st to endDay
43%9%18%18%9%3
1330
December1st to 10thDay
52%7%12%15%12%2
1330
11th to 20thDay
46%10%17%18%8%1
1684
21st to endDay
37%8%11%20%18%5%
2442
January1st to 10thNight
52%9%13%16%8%2
4726
11th to 20thNight
46%8%10%16%13%6%
4740
21st to endNight
41%11%14%22%10%1
4863
February1st to 10thNight
52%8%11%17%10%2
2660
11th to 20thNight
52%7%14%15%11%1
2462
21st to endNight
45%5%13%22%13%2
1803
March1st to 10thNight
46%10%14%21%8%1
2160
11th to 20thNight
44%8%15%18%13%2
2034
21st to endNight
50%8%15%17%8%1
2106
April1st to 10thNight
48%9%14%19%10%1
1764
11th to 20thNight
52%7%14%18%8%1
1601
21st to endNight
48%9%16%20%6%1
1620
May1st to 10thNight
51%8%16%18%7%
1419
11th to 20thNight
39%9%14%25%12%
1239
21st to endNight
48%10%14%19%7%1
1358
June1st to 10thNight
49%10%14%18%9%
1260
11th to 20thNight
54%9%14%17%42
1260
21st to endNight
39%12%18%24%6%1
1260
July1st to 10thNight
38%12%21%24%6%1
1225
11th to 20thNight
38%11%22%20%9%1
1218
21st to endNight
30%10%20%30%11%
1351
August1st to 10thNight
36%13%22%22%6%
1424
11th to 20thNight
31%11%24%24%8%1
1518
21st to endNight
35%8%18%26%12%2
1782
September1st to 10thNight
35%7%19%24%13%2
1732
11th to 20thNight
40%8%15%25%10%4
1962
21st to endNight
36%7%17%24%13%3
1980
October1st to 10thNight
42%7%16%23%10%1
2038
11th to 20thNight
42%8%16%23%10%2
2340
21st to endNight
45%9%15%21%9%1
2574
November1st to 10thNight
49%8%12%19%11%2
2505
11th to 20thNight
45%9%16%17%11%1
2806
21st to endNight
44%9%16%19%8%4
2850
December1st to 10thNight
47%6%13%20%11%3
2850
11th to 20thNight
48%11%14%20%6%1
3507
21st to endNight
36%7%14%22%15%6%
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
6%429%32%18%11%
180
11th to 20thDay
6%435%34%17%4
180
21st to endDay
9%7%27%33%17%7%
198
February1st to 10thDay
10%11%27%36%10%6%
180
11th to 20thDay
11%6%30%34%16%3
235
21st to endDay
5%7%26%39%19%3
319
March1st to 10thDay
9%10%35%29%13%4
420
11th to 20thDay
8%7%33%32%14%5%
420
21st to endDay
15%10%32%26%13%5%
462
April1st to 10thDay
12%12%34%27%13%2
420
11th to 20thDay
17%10%26%27%15%5%
412
21st to endDay
17%12%25%28%14%4
420
May1st to 10thDay
19%11%23%27%15%4
466
11th to 20thDay
14%6%23%33%20%4
625
21st to endDay
19%5%19%30%20%6%
679
June1st to 10thDay
19%7%23%36%12%3
630
11th to 20thDay
22%7%25%28%15%4
630
21st to endDay
12%5%23%31%21%8%
630
July1st to 10thDay
14%419%34%22%8%
621
11th to 20thDay
16%5%20%32%23%4
618
21st to endDay
8%5%23%32%24%8%
630
August1st to 10thDay
11%5%25%34%17%9%
447
11th to 20thDay
8%5%24%34%24%5%
437
21st to endDay
11%7%23%31%21%7%
495
September1st to 10thDay
16%7%28%29%14%5%
450
11th to 20thDay
20%6%21%28%18%7%
450
21st to endDay
15%10%28%28%13%5%
450
October1st to 10thDay
16%8%25%28%16%8%
392
11th to 20thDay
16%7%30%28%14%5%
270
21st to endDay
14%14%30%27%12%3
297
November1st to 10thDay
16%5%24%38%13%4
270
11th to 20thDay
14%10%33%28%12%2
201
21st to endDay
48%29%38%13%7%
180
December1st to 10thDay
7%5%29%37%17%4
180
11th to 20thDay
6%12%34%33%12%3
180
21st to endDay
6%6%27%30%25%6%
198
January1st to 10thNight
10%8%33%34%13%1
950
11th to 20thNight
8%9%33%37%13%1
950
21st to endNight
11%10%33%33%11%2
837
February1st to 10thNight
11%9%29%33%16%3
760
11th to 20thNight
7%8%32%36%15%1
742
21st to endNight
7%428%36%19%6%
592
March1st to 10thNight
9%5%31%38%14%3
720
11th to 20thNight
8%5%33%39%13%2
720
21st to endNight
13%6%29%36%15%3
792
April1st to 10thNight
11%7%31%36%14%2
684
11th to 20thNight
16%6%34%33%10%1
533
21st to endNight
17%10%24%36%12%1
540
May1st to 10thNight
19%8%23%37%12%2
383
11th to 20thNight
14%5%24%42%15%1
354
21st to endNight
23%420%34%18%1
389
June1st to 10thNight
20%422%39%14%1
360
11th to 20thNight
19%5%24%35%15%2
360
21st to endNight
12%319%38%25%3
360
July1st to 10thNight
16%217%41%23%1
350
11th to 20thNight
15%319%44%18%1
348
21st to endNight
8%416%45%25%2
394
August1st to 10thNight
12%416%35%30%4
358
11th to 20thNight
12%5%14%41%26%2
450
21st to endNight
13%320%41%23%1
594
September1st to 10thNight
15%220%40%20%2
652
11th to 20thNight
18%321%33%21%3
720
21st to endNight
13%5%28%36%16%2
720
October1st to 10thNight
15%5%27%35%15%2
720
11th to 20thNight
12%430%36%15%3
720
21st to endNight
12%7%34%35%11%1
792
November1st to 10thNight
16%6%33%31%12%2
840
11th to 20thNight
11%8%40%31%8%1
950
21st to endNight
9%5%39%35%10%3
950
December1st to 10thNight
11%8%32%35%12%2
950
11th to 20thNight
8%6%36%37%12%1
950
21st to endNight
10%5%33%36%13%3
1045
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