Darwin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Darwin clear sky chart from 2005-11-06 to 2024-01-17.

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
36%
24880
17%
74314
9%
24823
43%
24823
24%
49489

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
28%
950
13%
2714
5%
946
36%
946
20%
1933
January11th to 20thNight
27%
933
11%
2539
6%
933
31%
933
16%
1944
January21st to endNight
23%
990
13%
2574
4%
990
29%
990
16%
1967
February1st to 10thNight
28%
900
14%
2340
3%
900
35%
900
23%
1661
February11th to 20thNight
29%
879
17%
2274
5%
875
36%
875
25%
1537
February21st to endNight
31%
736
16%
1920
5%
736
39%
736
23%
1372
March1st to 10thNight
30%
542
13%
1982
9%
542
37%
542
18%
1312
March11th to 20thNight
31%
540
19%
1980
11%
540
44%
540
20%
1259
March21st to endNight
32%
594
14%
2178
12%
594
39%
594
16%
1488
April1st to 10thNight
30%
540
16%
1822
10%
540
40%
540
21%
1186
April11th to 20thNight
32%
533
20%
1698
16%
533
41%
533
20%
1160
April21st to endNight
31%
540
17%
1620
11%
540
39%
540
20%
1128
May1st to 10thNight
34%
540
14%
1580
9%
540
39%
540
24%
1054
May11th to 20thNight
37%
531
18%
1417
7%
531
43%
531
28%
943
May21st to endNight
45%
584
15%
1552
6%
582
49%
582
31%
998
June1st to 10thNight
51%
540
15%
1440
6%
540
54%
540
39%
872
June11th to 20thNight
47%
540
16%
1265
6%
540
52%
540
40%
819
June21st to endNight
58%
540
18%
1260
7%
540
61%
540
46%
788
July1st to 10thNight
62%
525
19%
1225
8%
525
64%
525
50%
723
July11th to 20thNight
62%
522
21%
1354
9%
522
65%
522
50%
749
July21st to endNight
66%
591
21%
1576
13%
558
68%
558
48%
837
August1st to 10thNight
64%
537
20%
1601
15%
534
68%
534
35%
929
August11th to 20thNight
61%
534
22%
1600
21%
534
67%
534
37%
929
August21st to endNight
59%
594
25%
1842
22%
594
66%
594
41%
975
September1st to 10thNight
57%
540
23%
1800
22%
540
64%
540
35%
964
September11th to 20thNight
48%
540
25%
1891
21%
540
58%
540
33%
1032
September21st to endNight
40%
565
24%
2005
15%
565
54%
565
30%
1116
October1st to 10thNight
38%
720
22%
2160
14%
720
45%
720
30%
1338
October11th to 20thNight
30%
720
22%
2160
9%
720
40%
720
24%
1391
October21st to endNight
30%
792
19%
2376
9%
792
38%
792
21%
1599
November1st to 10thNight
34%
912
20%
2546
10%
912
42%
912
27%
1646
November11th to 20thNight
26%
950
17%
2660
7%
950
34%
950
19%
1921
November21st to endNight
27%
950
16%
2660
7%
950
34%
950
23%
1816
December1st to 10thNight
27%
950
11%
2660
4%
950
33%
950
19%
1940
December11th to 20thNight
22%
949
12%
3219
3%
949
30%
949
13%
2389
December21st to endNight
20%
1037
7%
4824
3%
1026
27%
1026
7%
3774

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
13%8%37%6%35%5%6%7%38%
75147
Night
12%8%37%5%3445%7%41%
74628
TransparencyDay
44%7%14%23%10%1
74845
Night
43%6%14%24%12%2
74450
SeeingDay
16%9%31%28%14%3
14852
Night
15%9%33%32%11%1
24889

By Month

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 10thDay
7%12%5%9%8%5%7%6%6%8%27%
1429
11th to 20thDay
10%13%5%12%9%5%7%5%5%6%26%
1558
21st to endDay
7%13%6%10%10%6%8%6%6%7%21%
1782
February1st to 10thDay
8%10%5%9%7%5%6%5%6%8%30%
1620
11th to 20thDay
9%10%5%9%8%46%6%5%7%32%
1574
21st to endDay
10%11%48%9%47%47%7%29%
1349
March1st to 10thDay
13%12%6%7%7%3445%7%32%
1980
11th to 20thDay
14%8%48%5%35%45%7%37%
1980
21st to endDay
18%10%48%6%45%45%7%29%
2178
April1st to 10thDay
18%9%37%5%245%6%6%36%
2137
11th to 20thDay
19%10%47%6%3445%6%32%
2210
21st to endDay
24%10%36%5%3435%6%32%
2340
May1st to 10thDay
18%7%36%6%36%5%5%7%35%
2380
11th to 20thDay
16%7%36%6%3445%7%38%
2479
21st to endDay
15%6%36%6%35%5%6%8%37%
2725
June1st to 10thDay
11%5%345%45%5%6%9%44%
2520
11th to 20thDay
13%6%35%6%35%6%6%9%39%
2690
21st to endDay
9%425%5%346%7%11%44%
2700
July1st to 10thDay
6%3234346%7%11%52%
2700
11th to 20thDay
8%42443446%8%54%
2558
21st to endDay
5%425%4345%7%9%51%
2646
August1st to 10thDay
9%5%36%5%45%6%7%8%42%
2328
11th to 20thDay
12%6%245%35%47%8%45%
2301
21st to endDay
9%5%2442346%8%54%
2513
September1st to 10thDay
10%426%4345%5%7%50%
2160
11th to 20thDay
12%425%435%5%6%8%45%
2066
21st to endDay
16%7%2442445%7%45%
1936
October1st to 10thDay
17%7%35%5%34447%41%
1800
11th to 20thDay
15%9%35%5%345%5%7%41%
1800
21st to endDay
17%10%47%5%2335%7%37%
1980
November1st to 10thDay
13%9%47%5%445%5%7%38%
1529
11th to 20thDay
9%11%7%11%8%35%45%6%30%
1520
21st to endDay
14%10%36%7%35%5%5%9%33%
1520
December1st to 10thDay
9%11%5%11%7%5%6%6%6%6%27%
1520
11th to 20thDay
10%13%7%10%7%45%45%6%29%
1918
21st to endDay
22%14%5%15%6%33346%20%
2721
January1st to 10thNight
8%8%5%11%8%45%5%6%7%32%
2714
11th to 20thNight
9%12%5%10%8%5%6%5%7%7%26%
2539
21st to endNight
11%13%6%10%8%45%5%6%7%26%
2574
February1st to 10thNight
7%10%5%7%7%5%6%5%5%6%36%
2340
11th to 20thNight
7%8%47%5%45%5%6%8%40%
2273
21st to endNight
12%9%37%6%45%5%6%7%35%
1920
March1st to 10thNight
12%9%48%7%35%5%5%8%37%
1982
11th to 20thNight
12%10%5%7%433446%42%
1980
21st to endNight
18%9%46%6%3445%7%34%
2178
April1st to 10thNight
14%9%37%5%345%5%6%40%
1822
11th to 20thNight
19%11%46%5%3445%5%36%
1698
21st to endNight
19%9%35%5%3445%6%37%
1620
May1st to 10thNight
15%7%25%6%245%5%6%42%
1580
11th to 20thNight
14%6%25%5%345%5%8%43%
1416
21st to endNight
13%435%4345%6%8%46%
1551
June1st to 10thNight
11%324425%46%9%50%
1440
11th to 20thNight
9%425%425%5%7%9%49%
1265
21st to endNight
8%3133245%6%7%56%
1260
July1st to 10thNight
43234235%6%10%58%
1260
11th to 20thNight
5%32443345%9%60%
1399
21st to endNight
5%21333447%8%60%
1669
August1st to 10thNight
6%425%435%6%6%8%51%
1611
11th to 20thNight
9%43433445%7%54%
1600
21st to endNight
7%324423446%62%
1842
September1st to 10thNight
8%42442446%8%56%
1800
11th to 20thNight
10%42442445%7%54%
1891
21st to endNight
11%5%25%423447%53%
2005
October1st to 10thNight
16%6%24434447%48%
2160
11th to 20thNight
16%8%35%433447%43%
2160
21st to endNight
17%10%36%42435%6%40%
2376
November1st to 10thNight
12%7%36%5%445%6%7%43%
2546
11th to 20thNight
12%11%5%9%6%34445%36%
2660
21st to endNight
12%8%37%6%3445%7%40%
2660
December1st to 10thNight
9%9%5%10%8%45%45%7%33%
2660
11th to 20thNight
11%10%5%9%8%5%5%6%6%6%28%
3279
21st to endNight
21%14%5%11%7%44445%22%
4898

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
53%8%15%18%6%
1430
11th to 20thDay
59%6%13%15%7%1
1558
21st to endDay
60%7%13%13%6%
1782
February1st to 10thDay
50%6%14%20%8%1
1620
11th to 20thDay
51%7%15%19%8%1
1583
21st to endDay
52%7%11%19%11%
1349
March1st to 10thDay
52%7%14%19%7%1
1980
11th to 20thDay
48%6%15%23%8%1
1980
21st to endDay
54%7%12%22%5%
2178
April1st to 10thDay
48%6%12%22%11%1
2137
11th to 20thDay
53%6%11%18%11%2
2210
21st to endDay
53%6%12%19%9%1
2340
May1st to 10thDay
49%8%13%20%10%1
2380
11th to 20thDay
45%7%12%23%12%
2483
21st to endDay
43%8%13%23%11%1
2725
June1st to 10thDay
35%9%16%28%11%1
2520
11th to 20thDay
40%9%15%21%14%1
2690
21st to endDay
32%10%19%28%10%2
2700
July1st to 10thDay
25%8%18%32%16%1
2626
11th to 20thDay
28%8%15%27%19%4
2480
21st to endDay
26%9%17%30%15%2
2499
August1st to 10thDay
36%10%17%25%10%3
2314
11th to 20thDay
35%8%16%29%11%
2301
21st to endDay
28%6%17%32%15%2
2513
September1st to 10thDay
34%6%13%34%13%
2160
11th to 20thDay
36%7%17%30%9%1
2066
21st to endDay
39%6%12%33%10%1
1936
October1st to 10thDay
43%5%12%26%13%1
1800
11th to 20thDay
42%6%13%24%12%2
1800
21st to endDay
48%414%24%9%1
1980
November1st to 10thDay
45%7%14%19%13%3
1529
11th to 20thDay
53%7%12%17%10%1
1520
21st to endDay
47%6%16%22%7%2
1520
December1st to 10thDay
56%8%14%15%7%
1520
11th to 20thDay
56%5%17%17%5%
1915
21st to endDay
66%5%11%13%5%
2721
January1st to 10thNight
50%5%13%22%9%1
2714
11th to 20thNight
56%7%14%16%7%
2539
21st to endNight
56%6%13%17%8%1
2574
February1st to 10thNight
48%5%14%20%11%1
2340
11th to 20thNight
41%6%17%23%11%2
2274
21st to endNight
47%6%12%20%13%2
1920
March1st to 10thNight
47%6%16%23%7%
1982
11th to 20thNight
45%5%13%23%13%1
1980
21st to endNight
51%5%12%23%7%1
2178
April1st to 10thNight
44%6%13%25%11%1
1822
11th to 20thNight
49%6%8%21%15%2
1698
21st to endNight
48%6%10%20%14%2
1620
May1st to 10thNight
42%8%13%24%13%1
1580
11th to 20thNight
39%8%13%22%16%2
1417
21st to endNight
37%6%16%23%16%2
1552
June1st to 10thNight
29%7%16%30%15%2
1440
11th to 20thNight
31%8%16%26%17%3
1265
21st to endNight
25%8%16%30%17%3
1260
July1st to 10thNight
22%7%17%34%20%1
1225
11th to 20thNight
22%5%17%34%17%4
1354
21st to endNight
20%7%17%34%16%5%
1576
August1st to 10thNight
30%7%16%28%14%4
1601
11th to 20thNight
29%7%17%31%15%1
1600
21st to endNight
24%7%15%31%20%4
1842
September1st to 10thNight
27%7%15%32%19%1
1800
11th to 20thNight
30%6%16%30%17%1
1891
21st to endNight
32%5%13%33%16%1
2005
October1st to 10thNight
37%5%10%30%15%2
2160
11th to 20thNight
42%6%12%24%15%2
2160
21st to endNight
46%6%12%24%12%1
2376
November1st to 10thNight
39%7%15%24%14%2
2546
11th to 20thNight
51%6%12%18%12%1
2660
21st to endNight
44%6%17%23%7%1
2660
December1st to 10thNight
51%6%16%20%7%
2660
11th to 20thNight
53%9%13%18%6%1
3281
21st to endNight
64%7%10%15%4
4898

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
14%10%35%25%14%2
270
11th to 20thDay
16%10%35%33%41
258
21st to endDay
16%10%39%24%8%2
264
February1st to 10thDay
14%13%44%27%3
240
11th to 20thDay
15%18%35%26%5%1
240
21st to endDay
19%9%41%25%6%
198
March1st to 10thDay
19%13%38%24%5%2
240
11th to 20thDay
17%9%41%23%8%2
240
21st to endDay
28%12%23%24%11%2
264
April1st to 10thDay
25%14%31%23%6%
397
11th to 20thDay
26%13%27%23%10%2
488
21st to endDay
25%11%33%19%11%2
600
May1st to 10thDay
21%10%35%25%7%2
603
11th to 20thDay
20%10%29%25%13%3
625
21st to endDay
18%8%30%28%13%3
679
June1st to 10thDay
10%7%26%31%22%4
630
11th to 20thDay
16%7%33%32%11%2
630
21st to endDay
10%7%33%30%17%4
630
July1st to 10thDay
8%422%36%22%8%
621
11th to 20thDay
9%6%27%30%22%6%
618
21st to endDay
7%424%38%23%5%
684
August1st to 10thDay
12%222%35%26%3
626
11th to 20thDay
13%5%21%33%23%5%
615
21st to endDay
8%5%28%33%22%4
632
September1st to 10thDay
12%9%29%34%12%5%
450
11th to 20thDay
13%5%28%30%18%5%
356
21st to endDay
21%11%30%22%11%4
270
October1st to 10thDay
20%10%31%21%14%5%
270
11th to 20thDay
13%20%36%21%9%1
270
21st to endDay
25%14%36%16%8%1
297
November1st to 10thDay
17%14%32%25%9%2
270
11th to 20thDay
13%17%43%24%4
270
21st to endDay
20%14%41%20%4
270
December1st to 10thDay
13%10%43%24%10%
270
11th to 20thDay
17%13%37%28%4
270
21st to endDay
28%12%37%20%3
297
January1st to 10thNight
11%12%38%29%9%1
950
11th to 20thNight
14%11%36%31%7%1
933
21st to endNight
17%11%37%29%6%
990
February1st to 10thNight
12%10%40%29%7%1
900
11th to 20thNight
11%12%41%29%6%1
879
21st to endNight
16%12%35%28%9%1
736
March1st to 10thNight
17%9%37%25%11%1
542
11th to 20thNight
18%9%37%30%5%1
540
21st to endNight
22%10%30%26%10%2
594
April1st to 10thNight
19%8%38%27%7%
540
11th to 20thNight
22%13%28%28%9%1
533
21st to endNight
24%10%30%27%8%1
540
May1st to 10thNight
19%9%33%31%8%1
540
11th to 20thNight
17%8%34%30%10%1
531
21st to endNight
16%7%27%37%11%1
584
June1st to 10thNight
12%5%28%38%17%
540
11th to 20thNight
10%435%41%10%
540
21st to endNight
8%326%45%17%
540
July1st to 10thNight
5%225%42%25%2
525
11th to 20thNight
6%226%49%16%1
522
21st to endNight
5%223%47%21%2
591
August1st to 10thNight
7%417%48%22%2
537
11th to 20thNight
10%419%40%25%3
534
21st to endNight
7%426%38%23%2
594
September1st to 10thNight
10%426%39%18%2
540
11th to 20thNight
11%7%30%33%17%2
540
21st to endNight
12%10%34%31%12%2
565
October1st to 10thNight
19%6%32%29%12%1
720
11th to 20thNight
19%11%35%25%8%1
720
21st to endNight
23%13%30%28%6%
792
November1st to 10thNight
16%10%35%31%9%
912
11th to 20thNight
16%13%37%26%7%1
950
21st to endNight
17%12%38%26%7%
950
December1st to 10thNight
15%11%36%30%8%1
950
11th to 20thNight
19%9%38%26%7%1
950
21st to endNight
24%11%33%27%5%
1045
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