Greg's Happy Place
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Greg's Happy Place clear sky chart from 2005-11-06 to 2024-01-13.

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
34%
23629
16%
74878
10%
23579
41%
23579
19%
52440

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%
759
12%
2459
4%
757
23%
757
9%
1942
January11th to 20thNight
13%
732
8%
2378
3%
732
20%
732
8%
1922
January21st to endNight
15%
792
11%
2574
5%
792
22%
792
10%
2014
February1st to 10thNight
17%
720
10%
2340
5%
720
23%
720
10%
1823
February11th to 20thNight
13%
701
11%
2224
5%
700
20%
700
10%
1729
February21st to endNight
14%
592
13%
1776
5%
592
22%
592
10%
1388
March1st to 10thNight
20%
720
18%
1999
8%
720
29%
720
17%
1432
March11th to 20thNight
25%
720
19%
1980
9%
720
32%
720
18%
1412
March21st to endNight
22%
792
17%
2178
7%
792
31%
792
19%
1577
April1st to 10thNight
25%
720
15%
1938
6%
720
32%
720
21%
1384
April11th to 20thNight
29%
628
18%
1692
8%
628
35%
628
24%
1170
April21st to endNight
27%
540
18%
1620
6%
540
36%
540
22%
1096
May1st to 10thNight
33%
540
12%
1620
5%
540
39%
540
18%
1179
May11th to 20thNight
39%
531
16%
1592
10%
531
44%
531
22%
1099
May21st to endNight
55%
582
15%
1745
11%
582
59%
582
30%
1100
June1st to 10thNight
51%
396
17%
1476
17%
396
57%
396
24%
870
June11th to 20thNight
55%
360
18%
1440
19%
360
64%
360
24%
841
June21st to endNight
55%
448
17%
1528
16%
448
60%
448
28%
920
July1st to 10thNight
60%
525
14%
1575
11%
525
64%
525
29%
989
July11th to 20thNight
62%
522
19%
1566
15%
522
67%
522
34%
937
July21st to endNight
61%
591
16%
1672
14%
558
63%
558
26%
1083
August1st to 10thNight
64%
537
18%
1600
15%
534
65%
534
29%
1009
August11th to 20thNight
63%
534
20%
1598
16%
534
64%
534
28%
1023
August21st to endNight
62%
648
24%
1836
17%
648
66%
648
36%
1107
September1st to 10thNight
57%
720
24%
1877
15%
720
61%
720
34%
1195
September11th to 20thNight
63%
720
28%
1980
21%
720
68%
720
40%
1167
September21st to endNight
45%
720
24%
1980
17%
720
51%
720
28%
1296
October1st to 10thNight
48%
720
20%
2110
18%
720
54%
720
27%
1344
October11th to 20thNight
33%
720
20%
2160
12%
720
42%
720
23%
1434
October21st to endNight
28%
792
20%
2376
14%
792
37%
792
20%
1653
November1st to 10thNight
39%
740
24%
2352
18%
740
48%
740
26%
1422
November11th to 20thNight
26%
760
19%
2470
10%
760
38%
760
17%
1719
November21st to endNight
24%
760
15%
2647
10%
760
32%
760
14%
1913
December1st to 10thNight
17%
760
9%
2660
5%
760
23%
760
9%
2086
December11th to 20thNight
18%
759
10%
3243
5%
759
25%
759
9%
2418
December21st to endNight
15%
828
6%
4617
5%
817
23%
817
5%
3747

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
16%10%47%6%35%5%5%7%32%
74581
Night
16%10%47%6%3445%7%34%
75155
TransparencyDay
51%6%11%20%11%1
74302
Night
50%5%11%20%12%2
74953
SeeingDay
22%15%28%20%11%4
13599
Night
21%12%27%26%12%2
23643

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
18%15%8%11%8%34435%21%
1706
11th to 20thDay
18%21%8%11%5%3443419%
1644
21st to endDay
16%19%8%12%7%3435%5%18%
1782
February1st to 10thDay
21%17%6%9%7%34335%22%
1620
11th to 20thDay
16%13%8%12%6%3445%6%22%
1623
21st to endDay
19%15%5%9%6%34235%29%
1480
March1st to 10thDay
18%11%6%8%5%3445%5%33%
1959
11th to 20thDay
18%12%48%7%3445%6%29%
1980
21st to endDay
22%10%5%7%7%3445%5%28%
2178
April1st to 10thDay
14%12%5%7%6%3445%8%32%
2021
11th to 20thDay
16%10%37%6%45%45%7%35%
2231
21st to endDay
20%8%37%5%35%5%5%7%31%
2340
May1st to 10thDay
19%8%47%7%45%6%6%7%28%
2340
11th to 20thDay
21%8%36%6%35%5%6%7%30%
2301
21st to endDay
10%6%26%8%46%6%7%10%35%
2531
June1st to 10thDay
12%7%45%6%35%6%7%9%36%
2479
11th to 20thDay
12%7%26%6%46%6%7%10%34%
2520
21st to endDay
12%6%36%6%47%7%8%9%35%
2424
July1st to 10thDay
11%7%26%6%47%6%7%8%37%
2340
11th to 20thDay
11%6%26%6%46%5%6%10%37%
2340
21st to endDay
12%6%36%6%46%6%7%10%34%
2547
August1st to 10thDay
11%6%25%7%47%7%9%9%33%
2327
11th to 20thDay
12%6%35%6%46%8%7%10%33%
2303
21st to endDay
10%5%36%6%46%6%6%10%39%
2502
September1st to 10thDay
16%6%245%2445%8%44%
2080
11th to 20thDay
9%6%26%4445%5%8%46%
1980
21st to endDay
17%8%36%6%345%47%37%
1980
October1st to 10thDay
13%7%346%35%6%5%6%41%
1849
11th to 20thDay
17%9%36%6%345%6%5%36%
1800
21st to endDay
24%10%35%5%34346%33%
1980
November1st to 10thDay
11%9%46%5%34446%45%
1722
11th to 20thDay
17%12%5%6%5%35%35%6%33%
1710
21st to endDay
18%12%6%8%6%35%446%28%
1529
December1st to 10thDay
21%16%7%11%6%345%4420%
1520
11th to 20thDay
19%16%7%12%6%34445%22%
1910
21st to endDay
24%21%6%9%7%44335%14%
3003
January1st to 10thNight
18%15%7%9%7%45%5%4421%
2459
11th to 20thNight
20%17%6%11%7%44435%20%
2378
21st to endNight
17%16%6%11%8%33445%23%
2574
February1st to 10thNight
21%14%5%10%7%44345%24%
2340
11th to 20thNight
19%13%5%11%6%44445%23%
2222
21st to endNight
20%14%5%10%7%35%44424%
1776
March1st to 10thNight
17%10%48%6%3435%7%33%
1999
11th to 20thNight
18%11%46%5%34447%34%
1980
21st to endNight
20%10%47%5%3445%6%33%
2178
April1st to 10thNight
18%10%46%5%35%45%6%34%
1938
11th to 20thNight
16%7%46%5%345%5%9%36%
1692
21st to endNight
15%9%37%5%3445%9%36%
1620
May1st to 10thNight
18%9%26%7%36%5%7%7%29%
1620
11th to 20thNight
16%8%35%6%345%5%8%37%
1592
21st to endNight
8%5%26%6%35%6%7%11%41%
1744
June1st to 10thNight
8%6%36%5%36%6%5%9%44%
1476
11th to 20thNight
10%6%35%435%5%7%13%40%
1440
21st to endNight
11%5%246%35%5%6%9%45%
1528
July1st to 10thNight
8%6%35%6%35%5%6%8%44%
1620
11th to 20thNight
8%5%335%245%6%10%48%
1620
21st to endNight
8%6%25%7%46%6%8%9%39%
1771
August1st to 10thNight
6%436%5%45%7%8%10%42%
1611
11th to 20thNight
8%7%26%6%35%5%6%8%44%
1598
21st to endNight
8%5%245%346%7%9%47%
1836
September1st to 10thNight
12%5%25%5%3445%6%50%
1877
11th to 20thNight
10%4243245%6%8%52%
1980
21st to endNight
14%6%35%5%3445%6%44%
1980
October1st to 10thNight
13%6%25%5%345%5%7%44%
2110
11th to 20thNight
16%8%36%5%35%5%5%6%38%
2160
21st to endNight
24%9%25%434347%35%
2376
November1st to 10thNight
12%8%35%433447%46%
2352
11th to 20thNight
17%10%47%6%34446%33%
2470
21st to endNight
19%13%5%6%6%345%5%6%29%
2647
December1st to 10thNight
23%14%6%10%5%345%45%21%
2660
11th to 20thNight
17%17%7%9%5%3435%6%24%
3285
21st to endNight
22%19%8%9%7%3435%5%16%
4646

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
66%49%13%7%1
1707
11th to 20thDay
70%411%12%3
1644
21st to endDay
69%49%12%5%1
1782
February1st to 10thDay
66%39%13%8%1
1620
11th to 20thDay
63%5%9%16%7%1
1632
21st to endDay
61%39%17%8%3
1480
March1st to 10thDay
54%410%23%9%
1959
11th to 20thDay
56%410%17%10%2
1980
21st to endDay
58%49%17%11%2
2178
April1st to 10thDay
51%5%11%19%10%3
2021
11th to 20thDay
50%5%11%16%16%3
2231
21st to endDay
51%6%9%20%11%2
2340
May1st to 10thDay
53%6%11%19%9%1
2340
11th to 20thDay
52%8%10%17%11%1
2305
21st to endDay
42%8%16%23%9%1
2531
June1st to 10thDay
43%8%14%22%12%1
2479
11th to 20thDay
43%10%12%22%12%1
2520
21st to endDay
42%8%13%22%13%1
2424
July1st to 10thDay
44%8%13%20%14%2
2275
11th to 20thDay
42%8%10%23%15%1
2271
21st to endDay
42%9%14%23%12%1
2405
August1st to 10thDay
42%10%14%23%11%
2314
11th to 20thDay
43%9%14%24%10%1
2303
21st to endDay
39%8%12%24%13%4
2502
September1st to 10thDay
39%5%12%21%19%4
2080
11th to 20thDay
36%6%13%27%16%2
1980
21st to endDay
47%5%8%22%17%1
1980
October1st to 10thDay
42%6%11%22%18%1
1849
11th to 20thDay
48%5%12%23%12%1
1800
21st to endDay
53%411%20%11%1
1980
November1st to 10thDay
40%5%10%27%16%3
1722
11th to 20thDay
53%410%20%11%2
1710
21st to endDay
58%411%18%8%1
1529
December1st to 10thDay
68%5%9%15%4
1520
11th to 20thDay
66%39%17%5%
1906
21st to endDay
73%5%10%8%3
3003
January1st to 10thNight
65%47%15%7%1
2459
11th to 20thNight
68%411%12%41
2378
21st to endNight
65%39%16%5%1
2574
February1st to 10thNight
64%49%16%6%
2340
11th to 20thNight
63%49%16%8%1
2224
21st to endNight
63%48%15%8%2
1776
March1st to 10thNight
52%48%23%12%1
1999
11th to 20thNight
50%6%10%23%10%2
1980
21st to endNight
52%48%20%12%3
2178
April1st to 10thNight
50%410%19%13%2
1938
11th to 20thNight
45%6%12%17%17%4
1692
21st to endNight
46%5%12%20%15%2
1620
May1st to 10thNight
51%7%11%18%10%3
1620
11th to 20thNight
46%6%11%20%14%2
1593
21st to endNight
35%8%17%26%12%2
1745
June1st to 10thNight
37%7%12%24%17%3
1476
11th to 20thNight
35%8%15%24%16%2
1440
21st to endNight
35%8%13%25%17%2
1528
July1st to 10thNight
36%8%12%23%18%3
1575
11th to 20thNight
31%8%13%25%20%2
1566
21st to endNight
38%10%13%23%14%3
1672
August1st to 10thNight
34%11%13%27%16%
1600
11th to 20thNight
38%8%12%24%16%2
1598
21st to endNight
32%7%13%27%17%4
1836
September1st to 10thNight
35%6%10%22%21%6%
1877
11th to 20thNight
29%6%13%27%24%2
1980
21st to endNight
40%6%10%22%20%1
1980
October1st to 10thNight
39%6%12%23%18%2
2110
11th to 20thNight
45%49%25%15%1
2160
21st to endNight
50%49%22%12%2
2376
November1st to 10thNight
39%411%24%18%4
2352
11th to 20thNight
52%49%20%13%2
2470
21st to endNight
56%411%20%7%1
2647
December1st to 10thNight
65%5%9%15%5%1
2660
11th to 20thNight
62%412%18%5%
3288
21st to endNight
70%5%9%12%3
4646

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
31%25%30%10%4
270
11th to 20thDay
33%28%31%8%1
248
21st to endDay
33%31%30%33
264
February1st to 10thDay
36%25%31%8%1
240
11th to 20thDay
41%27%28%4
240
21st to endDay
37%31%28%5%
198
March1st to 10thDay
29%24%29%15%3
399
11th to 20thDay
30%21%31%13%41
420
21st to endDay
33%20%29%14%31
462
April1st to 10thDay
27%22%29%15%6%1
420
11th to 20thDay
26%20%26%16%8%3
412
21st to endDay
27%22%31%12%5%2
420
May1st to 10thDay
27%22%25%16%7%3
423
11th to 20thDay
22%15%33%18%9%4
447
21st to endDay
16%9%26%26%17%6%
485
June1st to 10thDay
15%9%30%29%14%3
450
11th to 20thDay
15%14%25%28%12%6%
450
21st to endDay
15%10%31%26%15%4
450
July1st to 10thDay
14%6%21%27%18%13%
445
11th to 20thDay
12%6%27%30%16%9%
444
21st to endDay
13%8%23%30%17%10%
488
August1st to 10thDay
14%419%31%22%9%
446
11th to 20thDay
15%7%21%30%18%10%
439
21st to endDay
9%6%26%27%22%9%
495
September1st to 10thDay
16%8%23%25%19%9%
450
11th to 20thDay
11%420%30%26%10%
450
21st to endDay
22%12%25%22%15%5%
450
October1st to 10thDay
14%11%29%26%16%4
450
11th to 20thDay
23%14%31%23%9%1
450
21st to endDay
31%15%31%16%7%
495
November1st to 10thDay
21%18%33%17%8%3
320
11th to 20thDay
30%17%32%14%6%1
270
21st to endDay
27%24%36%11%2
184
December1st to 10thDay
31%24%32%7%5%1
180
11th to 20thDay
29%25%33%11%2
180
21st to endDay
38%20%31%9%2
265
January1st to 10thNight
29%22%32%15%3
760
11th to 20thNight
31%19%31%17%3
732
21st to endNight
27%23%30%18%2
792
February1st to 10thNight
31%17%30%20%2
720
11th to 20thNight
30%21%33%15%1
703
21st to endNight
29%20%32%17%2
592
March1st to 10thNight
24%19%33%20%3
720
11th to 20thNight
25%18%29%21%5%1
720
21st to endNight
26%17%31%20%6%
792
April1st to 10thNight
25%16%31%22%6%
720
11th to 20thNight
19%15%35%20%11%1
628
21st to endNight
21%10%37%26%6%1
540
May1st to 10thNight
21%13%26%26%12%1
540
11th to 20thNight
22%8%26%32%12%1
531
21st to endNight
10%5%23%37%23%3
584
June1st to 10thNight
10%5%28%39%18%1
396
11th to 20thNight
12%5%24%39%18%1
360
21st to endNight
11%423%41%20%1
448
July1st to 10thNight
12%316%36%27%6%
525
11th to 20thNight
8%420%34%30%4
522
21st to endNight
10%418%38%28%3
591
August1st to 10thNight
8%215%41%30%3
537
11th to 20thNight
11%315%37%28%5%
534
21st to endNight
10%319%30%30%7%
648
September1st to 10thNight
13%5%18%29%30%5%
720
11th to 20thNight
10%417%35%29%5%
720
21st to endNight
17%7%26%27%20%4
720
October1st to 10thNight
16%8%21%32%19%4
720
11th to 20thNight
22%12%30%26%10%1
720
21st to endNight
28%12%28%24%7%1
792
November1st to 10thNight
18%13%28%29%12%
740
11th to 20thNight
24%17%29%22%7%1
760
21st to endNight
28%14%30%23%41
760
December1st to 10thNight
32%17%29%18%4
760
11th to 20thNight
28%18%32%19%4
760
21st to endNight
32%16%32%18%2
836
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