Seagrape Drive
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Seagrape Drive clear sky chart from 2005-11-06 to 2024-03-06.

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
66%
24986
18%
80026
17%
24896
69%
24896
28%
49963

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
59%
751
19%
4054
22%
737
66%
737
19%
2321
January11th to 20thNight
53%
753
13%
4107
18%
740
60%
740
14%
2905
January21st to endNight
52%
825
18%
4203
20%
814
60%
814
20%
2366
February1st to 10thNight
55%
760
26%
2280
21%
760
62%
760
35%
1322
February11th to 20thNight
60%
741
28%
2191
21%
739
68%
739
42%
1194
February21st to endNight
68%
628
34%
1727
27%
628
74%
628
49%
912
March1st to 10thNight
61%
743
31%
2042
22%
743
69%
743
48%
1084
March11th to 20thNight
65%
720
28%
1980
21%
720
71%
720
45%
1077
March21st to endNight
65%
792
32%
2178
24%
792
71%
792
48%
1157
April1st to 10thNight
68%
720
26%
1980
21%
720
71%
720
47%
1063
April11th to 20thNight
68%
711
22%
1946
18%
711
72%
711
43%
1105
April21st to endNight
65%
720
28%
1800
19%
720
68%
720
46%
1050
May1st to 10thNight
78%
720
29%
1800
20%
720
79%
720
54%
980
May11th to 20thNight
72%
581
14%
1642
10%
581
73%
581
35%
1018
May21st to endNight
75%
582
19%
1745
17%
582
75%
582
33%
1067
June1st to 10thNight
59%
540
9%
1620
8%
540
59%
540
17%
1220
June11th to 20thNight
73%
540
9%
1620
8%
540
73%
540
23%
1140
June21st to endNight
75%
540
7%
1620
6%
540
75%
540
21%
1200
July1st to 10thNight
75%
525
5%
1575
5%
525
75%
525
21%
1142
July11th to 20thNight
80%
522
6%
1566
6%
522
80%
522
24%
1111
July21st to endNight
80%
591
7%
1672
8%
558
80%
558
24%
1187
August1st to 10thNight
78%
537
5%
1600
5%
534
78%
534
23%
1141
August11th to 20thNight
77%
651
5%
1842
5%
651
77%
651
20%
1344
August21st to endNight
66%
792
5%
2178
4%
792
66%
792
16%
1648
September1st to 10thNight
74%
720
6%
1980
7%
720
74%
720
22%
1425
September11th to 20thNight
66%
720
6%
1980
7%
720
66%
720
17%
1501
September21st to endNight
60%
720
7%
1980
7%
720
60%
720
15%
1533
October1st to 10thNight
64%
720
15%
1993
15%
720
65%
720
25%
1353
October11th to 20thNight
66%
720
20%
2160
20%
720
69%
720
31%
1359
October21st to endNight
63%
792
22%
2376
24%
792
65%
792
30%
1492
November1st to 10thNight
62%
740
26%
2221
22%
740
69%
740
37%
1282
November11th to 20thNight
61%
760
25%
2280
23%
760
66%
760
30%
1420
November21st to endNight
62%
760
28%
2280
23%
760
68%
760
33%
1347
December1st to 10thNight
65%
760
25%
2403
23%
760
71%
760
36%
1342
December11th to 20thNight
64%
760
26%
2922
25%
758
67%
758
31%
1534
December21st to endNight
61%
829
14%
4483
23%
817
66%
817
19%
2621

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%5%36%7%47%7%7%10%37%
78950
Night
7%5%25%6%45%6%7%10%44%
80567
TransparencyDay
38%12%17%18%12%3
78673
Night
33%11%18%20%14%3
80363
SeeingDay
6%315%28%28%20%
14838
Night
7%214%33%31%12%
25024

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
9%8%36%5%345%6%10%41%
2836
11th to 20thDay
15%6%36%5%45%6%6%10%33%
2840
21st to endDay
7%6%37%7%46%6%6%7%43%
3352
February1st to 10thDay
8%5%35%5%36%5%6%9%45%
1900
11th to 20thDay
6%223335%46%9%58%
1872
21st to endDay
5%3244245%6%9%56%
1727
March1st to 10thDay
33235%346%6%9%55%
2035
11th to 20thDay
5%4245%35%6%7%8%51%
1980
21st to endDay
4325%5%345%5%8%57%
2178
April1st to 10thDay
43245%35%6%6%11%52%
1980
11th to 20thDay
6%3245%46%5%7%11%47%
1960
21st to endDay
5%425%5%346%5%10%51%
2160
May1st to 10thDay
4223425%5%5%10%58%
2160
11th to 20thDay
8%6%36%6%46%7%7%8%38%
2264
21st to endDay
9%6%46%8%46%6%7%10%34%
2531
June1st to 10thDay
14%8%48%8%5%8%8%7%11%19%
2340
11th to 20thDay
7%6%39%8%5%9%8%10%12%22%
2340
21st to endDay
8%6%38%8%5%9%8%10%11%23%
2340
July1st to 10thDay
6%6%47%9%7%11%9%9%10%22%
2340
11th to 20thDay
8%6%28%8%7%11%9%9%12%21%
2340
21st to endDay
6%6%38%8%5%10%9%9%13%22%
2547
August1st to 10thDay
5%5%37%10%5%9%10%10%12%23%
2327
11th to 20thDay
6%5%27%8%6%9%9%12%13%24%
2031
21st to endDay
8%6%310%9%5%9%8%9%10%22%
2178
September1st to 10thDay
7%6%38%9%5%8%8%9%12%24%
1980
11th to 20thDay
9%6%49%9%6%9%7%8%10%24%
1980
21st to endDay
12%7%5%8%9%5%8%8%8%8%22%
1980
October1st to 10thDay
7%6%37%8%47%8%8%11%31%
1966
11th to 20thDay
9%5%26%7%47%7%8%10%36%
1800
21st to endDay
9%5%26%6%45%5%7%8%42%
1980
November1st to 10thDay
6%425%6%45%5%6%8%49%
1857
11th to 20thDay
9%435%5%46%7%6%8%42%
1900
21st to endDay
7%425%6%35%6%7%9%47%
1900
December1st to 10thDay
7%435%5%35%5%6%9%49%
1772
11th to 20thDay
8%425%6%35%5%6%9%47%
2153
21st to endDay
10%5%26%6%46%6%7%10%37%
3124
January1st to 10thNight
8%6%27%6%46%6%6%10%40%
4109
11th to 20thNight
16%10%48%7%36%5%6%7%29%
4120
21st to endNight
6%6%37%6%46%5%6%8%43%
4299
February1st to 10thNight
8%435%5%35%5%6%9%49%
2280
11th to 20thNight
7%31442445%8%58%
2191
21st to endNight
431342446%7%62%
1727
March1st to 10thNight
3323435%45%7%60%
2042
11th to 20thNight
6%3243335%6%9%57%
1980
21st to endNight
422343446%8%60%
2178
April1st to 10thNight
431333447%9%60%
1980
11th to 20thNight
5%31343445%10%56%
1946
21st to endNight
6%41443446%9%55%
1800
May1st to 10thNight
321332346%10%62%
1800
11th to 20thNight
7%5%15%6%36%5%6%10%46%
1642
21st to endNight
7%5%36%5%25%5%7%12%43%
1744
June1st to 10thNight
13%9%46%8%45%7%6%9%28%
1620
11th to 20thNight
6%5%37%7%46%6%10%13%32%
1620
21st to endNight
6%6%36%7%46%8%9%12%32%
1620
July1st to 10thNight
5%5%26%7%46%7%9%12%34%
1620
11th to 20thNight
5%435%6%5%8%8%11%12%34%
1620
21st to endNight
4425%7%47%9%10%12%35%
1771
August1st to 10thNight
5%5%36%7%5%7%8%10%15%30%
1611
11th to 20thNight
45%26%7%5%8%9%8%13%33%
1842
21st to endNight
6%5%37%9%5%7%9%8%13%28%
2178
September1st to 10thNight
6%426%6%47%8%11%15%33%
1980
11th to 20thNight
8%6%37%8%47%8%8%11%31%
1980
21st to endNight
10%7%38%9%47%8%7%9%28%
1980
October1st to 10thNight
7%6%37%7%46%6%7%11%36%
1993
11th to 20thNight
8%5%26%5%35%5%7%10%43%
2160
21st to endNight
9%5%25%6%45%5%6%7%45%
2376
November1st to 10thNight
8%4234345%5%8%54%
2221
11th to 20thNight
8%6%35%6%45%5%6%9%44%
2280
21st to endNight
7%5%25%5%35%45%8%50%
2280
December1st to 10thNight
6%425%4346%6%8%51%
2403
11th to 20thNight
9%4244345%5%9%51%
3042
21st to endNight
8%7%36%6%45%6%7%9%39%
4532

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
36%7%14%23%15%5%
2837
11th to 20thDay
45%10%13%18%10%4
2840
21st to endDay
38%6%11%22%18%5%
3352
February1st to 10thDay
34%6%13%24%17%6%
1900
11th to 20thDay
21%6%14%26%23%10%
1882
21st to endDay
22%8%14%21%27%9%
1727
March1st to 10thDay
22%7%14%27%24%6%
2035
11th to 20thDay
27%7%14%27%18%6%
1980
21st to endDay
24%6%14%27%21%8%
2178
April1st to 10thDay
23%8%20%29%15%4
1980
11th to 20thDay
28%9%19%25%15%3
1960
21st to endDay
27%8%15%25%21%4
2160
May1st to 10thDay
19%8%16%30%21%6%
2160
11th to 20thDay
39%9%18%21%12%
2268
21st to endDay
40%11%18%18%11%1
2531
June1st to 10thDay
54%14%18%12%2
2340
11th to 20thDay
47%17%22%12%1
2340
21st to endDay
49%19%22%9%1
2340
July1st to 10thDay
48%21%24%7%
2275
11th to 20thDay
49%19%23%8%
2271
21st to endDay
46%20%25%8%1
2405
August1st to 10thDay
46%19%25%10%1
2314
11th to 20thDay
43%21%26%10%
2031
21st to endDay
51%20%21%7%1
2178
September1st to 10thDay
46%19%23%10%1
1980
11th to 20thDay
50%17%20%11%2
1980
21st to endDay
55%16%14%10%41
1980
October1st to 10thDay
40%16%16%14%11%2
1966
11th to 20thDay
39%10%16%19%13%4
1800
21st to endDay
35%9%13%18%18%7%
1980
November1st to 10thDay
30%8%14%19%19%10%
1857
11th to 20thDay
35%9%12%21%15%8%
1900
21st to endDay
29%8%16%20%22%5%
1900
December1st to 10thDay
30%7%14%24%21%4
1772
11th to 20thDay
31%7%14%20%19%8%
2150
21st to endDay
39%8%17%18%15%3
3124
January1st to 10thNight
37%8%13%23%16%3
4109
11th to 20thNight
51%9%12%17%9%3
4120
21st to endNight
37%7%11%22%19%5%
4299
February1st to 10thNight
31%6%13%25%20%5%
2280
11th to 20thNight
25%6%12%25%23%10%
2192
21st to endNight
20%6%13%23%30%8%
1727
March1st to 10thNight
22%5%12%31%24%6%
2042
11th to 20thNight
23%7%16%30%19%5%
1980
21st to endNight
20%7%13%30%25%5%
2178
April1st to 10thNight
21%7%19%33%16%4
1980
11th to 20thNight
23%8%17%26%21%4
1946
21st to endNight
23%8%16%27%22%4
1800
May1st to 10thNight
17%8%15%35%21%4
1800
11th to 20thNight
31%9%24%23%13%
1643
21st to endNight
31%9%21%22%15%
1745
June1st to 10thNight
49%13%21%15%2
1620
11th to 20thNight
37%16%28%15%3
1620
21st to endNight
41%18%30%10%2
1620
July1st to 10thNight
37%20%32%11%1
1575
11th to 20thNight
36%17%34%12%1
1566
21st to endNight
33%21%32%13%1
1672
August1st to 10thNight
36%19%30%15%
1600
11th to 20thNight
37%21%30%11%1
1842
21st to endNight
42%21%27%9%1
2178
September1st to 10thNight
34%22%31%13%1
1980
11th to 20thNight
44%19%22%13%2
1980
21st to endNight
47%18%19%11%5%
1980
October1st to 10thNight
38%13%22%17%9%2
1993
11th to 20thNight
34%9%19%20%15%3
2160
21st to endNight
36%8%14%18%18%7%
2376
November1st to 10thNight
27%9%15%21%20%8%
2221
11th to 20thNight
35%8%11%24%16%6%
2280
21st to endNight
31%8%13%20%23%5%
2280
December1st to 10thNight
28%8%16%27%18%4
2403
11th to 20thNight
28%6%13%24%20%9%
3044
21st to endNight
38%8%19%17%15%2
4532

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
9%7%29%37%17%2
270
11th to 20thDay
11%9%30%35%14%1
270
21st to endDay
9%10%38%33%9%1
297
February1st to 10thDay
5%8%27%40%17%2
270
11th to 20thDay
5%5%25%43%18%4
294
21st to endDay
35%21%42%27%2
382
March1st to 10thDay
4428%43%19%2
440
11th to 20thDay
6%5%25%34%27%3
420
21st to endDay
3223%42%26%5%
462
April1st to 10thDay
4329%39%21%5%
420
11th to 20thDay
5%426%36%24%5%
412
21st to endDay
4221%36%31%5%
420
May1st to 10thDay
4113%37%35%11%
423
11th to 20thDay
10%216%29%28%15%
447
21st to endDay
7%25%27%33%25%
485
June1st to 10thDay
16%29%20%32%21%
450
11th to 20thDay
8%3416%33%36%
450
21st to endDay
5%2212%30%50%
450
July1st to 10thDay
4129%29%56%
445
11th to 20thDay
5%119%34%49%
444
21st to endDay
7%1313%31%46%
488
August1st to 10thDay
4411%35%47%
446
11th to 20thDay
4129%37%48%
439
21st to endDay
8%17%18%29%38%
495
September1st to 10thDay
6%1413%32%43%
450
11th to 20thDay
6%15%12%33%42%
450
21st to endDay
10%2417%32%35%
450
October1st to 10thDay
6%112%32%37%12%
450
11th to 20thDay
8%311%32%33%14%
450
21st to endDay
8%315%35%30%9%
495
November1st to 10thDay
7%319%34%29%8%
455
11th to 20thDay
8%5%23%32%25%7%
460
21st to endDay
5%222%41%25%6%
460
December1st to 10thDay
7%5%21%37%26%4
332
11th to 20thDay
8%6%23%35%21%7%
270
21st to endDay
6%6%21%38%24%5%
297
January1st to 10thNight
8%5%20%44%22%2
760
11th to 20thNight
9%425%43%19%1
760
21st to endNight
8%5%28%43%16%
836
February1st to 10thNight
8%426%44%18%
760
11th to 20thNight
7%423%44%21%2
743
21st to endNight
4319%48%25%1
628
March1st to 10thNight
4425%46%19%1
743
11th to 20thNight
7%220%46%24%1
720
21st to endNight
5%322%47%22%1
792
April1st to 10thNight
4319%46%27%1
720
11th to 20thNight
5%317%51%22%1
711
21st to endNight
6%219%44%28%1
720
May1st to 10thNight
3112%49%33%3
720
11th to 20thNight
6%112%41%35%5%
581
21st to endNight
8%25%29%48%9%
584
June1st to 10thNight
14%27%19%44%14%
540
11th to 20thNight
6%1213%49%30%
540
21st to endNight
5%2210%42%39%
540
July1st to 10thNight
5%128%41%44%
525
11th to 20thNight
4127%41%45%
522
21st to endNight
4210%34%51%
591
August1st to 10thNight
6%29%44%38%
537
11th to 20thNight
4128%43%43%
651
21st to endNight
7%16%15%40%30%
792
September1st to 10thNight
6%1411%43%35%
720
11th to 20thNight
8%25%16%40%29%
720
21st to endNight
11%26%18%40%22%
720
October1st to 10thNight
9%210%35%35%10%
720
11th to 20thNight
9%310%32%36%11%
720
21st to endNight
11%214%37%29%6%
792
November1st to 10thNight
8%222%38%28%3
740
11th to 20thNight
8%220%38%30%3
760
21st to endNight
9%317%43%27%1
760
December1st to 10thNight
6%218%41%31%2
760
11th to 20thNight
8%317%40%29%3
760
21st to endNight
6%421%38%28%2
836
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