Wally's Corner
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wally's Corner clear sky chart from 2005-11-05 to 2017-03-13.

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
39%
15531
18%
45087
10%
15484
46%
15484
28%
28830

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 15thNight
33%
900
14%
2560
8%
895
39%
895
22%
1785
January16th to endNight
27%
960
16%
2502
5%
960
35%
960
20%
1828
February1st to 15thNight
29%
879
12%
2288
4%
875
34%
875
22%
1659
February16th to endNight
34%
699
18%
1961
7%
699
42%
699
26%
1299
March1st to 15thNight
32%
582
17%
2006
11%
582
41%
582
23%
1265
March16th to endNight
30%
528
14%
1936
11%
528
36%
528
18%
1280
April1st to 15thNight
32%
494
17%
1663
13%
494
42%
494
23%
1052
April16th to endNight
31%
495
16%
1485
11%
495
40%
495
20%
1032
May1st to 15thNight
34%
495
17%
1485
11%
495
41%
495
27%
945
May16th to endNight
41%
515
14%
1412
6%
513
46%
513
28%
918
June1st to 15thNight
46%
495
16%
1207
6%
495
49%
495
34%
789
June16th to endNight
59%
495
19%
1155
7%
495
61%
495
52%
675
July1st to 15thNight
64%
465
20%
1115
7%
465
66%
465
51%
644
July16th to endNight
71%
522
21%
1436
14%
489
72%
489
51%
712
August1st to 15thNight
67%
494
23%
1475
20%
491
70%
491
43%
793
August16th to endNight
62%
525
24%
1575
24%
525
67%
525
43%
837
September1st to 15thNight
58%
495
23%
1735
22%
495
67%
495
36%
925
September16th to endNight
47%
492
26%
1815
18%
492
60%
492
33%
934
October1st to 15thNight
36%
621
27%
1941
17%
621
45%
621
31%
1108
October16th to endNight
37%
745
20%
2153
11%
745
44%
745
29%
1363
November1st to 15thNight
39%
875
24%
2316
11%
875
47%
875
34%
1456
November16th to endNight
34%
900
20%
2520
11%
900
41%
900
28%
1621
December1st to 15thNight
29%
900
11%
2520
4%
900
35%
900
19%
1822
December16th to endNight
28%
960
13%
2826
6%
960
35%
960
16%
2088

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
12%7%35%5%3445%7%40%
45588
Night
10%6%35%42445%7%44%
45260
Cloud CoverDay
12%6%35%5%3445%7%40%
45598
Night
10%6%35%42445%7%45%
45263
Cloud CoverDay
12%7%35%5%3445%7%40%
45599
Night
10%6%35%42445%7%45%
45264
Cloud CoverDay
12%7%35%5%3445%7%40%
45597
Night
10%6%35%42445%7%44%
45264
TransparencyDay
42%6%15%23%11%1
45279
Night
38%6%15%24%13%1
45087
SeeingDay
15%8%30%29%14%2
5237
Night
13%7%33%33%10%
15532

By Month

Percentage Cloud Cover NE (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 15thDay
5%10%5%10%8%5%6%5%5%7%28%
1376
16th to endDay
9%12%7%10%6%45%5%47%25%
1719
February1st to 15thDay
11%11%49%8%35%35%6%29%
1575
16th to endDay
9%9%46%5%36%5%6%7%35%
1523
March1st to 15thDay
15%10%45%424448%35%
1889
16th to endDay
18%9%46%5%2445%6%31%
1936
April1st to 15thDay
16%6%3442445%7%39%
1951
16th to endDay
24%8%24424445%32%
2145
May1st to 15thDay
18%7%35%5%3446%6%34%
2136
16th to endDay
18%6%26%5%2445%8%34%
2351
June1st to 15thDay
17%6%34424448%37%
2420
16th to endDay
8%31342446%8%51%
2475
July1st to 15thDay
7%31342346%10%51%
2439
16th to endDay
5%2133245%6%8%55%
2315
August1st to 15thDay
9%4245%35%6%6%9%43%
2145
16th to endDay
8%425%42435%7%52%
2275
September1st to 15thDay
12%5%245%23446%49%
1893
16th to endDay
11%324313347%54%
1815
October1st to 15thDay
13%6%24423335%49%
1678
16th to endDay
15%7%24323336%46%
1716
November1st to 15thDay
8%7%26%42445%7%47%
1541
16th to endDay
13%9%36%435%45%8%36%
1440
December1st to 15thDay
11%12%410%6%45%45%6%29%
1440
16th to endDay
14%9%6%9%9%5%5%5%5%6%23%
1395
January1st to 15thNight
7%7%37%7%45%5%6%8%35%
2560
16th to endNight
8%10%5%8%5%345%5%8%33%
2502
February1st to 15thNight
10%10%48%6%34446%36%
2285
16th to endNight
7%7%36%6%3446%8%41%
1961
March1st to 15thNight
12%7%35%424447%42%
1994
16th to endNight
13%9%47%42345%6%37%
1936
April1st to 15thNight
15%6%24433446%44%
1663
16th to endNight
19%7%45%5%13345%37%
1485
May1st to 15thNight
15%6%24324346%46%
1485
16th to endNight
11%6%245%145%6%7%44%
1410
June1st to 15thNight
11%5%2342445%9%45%
1207
16th to endNight
5%233225%5%7%60%
1155
July1st to 15thNight
3312323348%62%
1188
16th to endNight
31121346%10%61%
1543
August1st to 15thNight
421233446%10%56%
1485
16th to endNight
6%223313347%60%
1575
September1st to 15thNight
9%31432335%5%57%
1735
16th to endNight
9%422223347%56%
1815
October1st to 15thNight
13%423313436%53%
1941
16th to endNight
15%7%24423346%47%
2153
November1st to 15thNight
8%5%25%433446%50%
2316
16th to endNight
10%6%25%434446%46%
2520
December1st to 15thNight
10%11%48%5%345%47%33%
2520
16th to endNight
15%10%48%6%3445%6%29%
2826

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 15thDay
5%10%6%10%8%46%5%48%29%
1377
16th to endDay
8%13%8%8%7%35%5%5%7%25%
1719
February1st to 15thDay
11%10%410%7%45%445%30%
1575
16th to endDay
9%10%36%5%26%46%8%35%
1523
March1st to 15thDay
14%10%5%5%423447%36%
1900
16th to endDay
18%9%46%6%25%45%6%31%
1934
April1st to 15thDay
16%6%345%2445%8%38%
1951
16th to endDay
24%8%24434346%33%
2145
May1st to 15thDay
18%6%26%5%35%46%6%34%
2136
16th to endDay
17%6%26%5%2446%7%34%
2351
June1st to 15thDay
18%6%245%34448%37%
2420
16th to endDay
8%31443446%7%51%
2475
July1st to 15thDay
7%3134245%6%10%51%
2439
16th to endDay
5%21332445%10%55%
2315
August1st to 15thDay
8%4245%25%6%7%8%43%
2145
16th to endDay
8%42442335%7%51%
2275
September1st to 15thDay
12%5%245%23346%49%
1893
16th to endDay
11%314323346%55%
1815
October1st to 15thDay
13%6%24323335%49%
1678
16th to endDay
15%7%24422345%47%
1716
November1st to 15thDay
8%6%35%5%2436%7%47%
1541
16th to endDay
12%9%45%435%45%8%36%
1440
December1st to 15thDay
11%11%410%6%3445%6%30%
1440
16th to endDay
14%9%6%10%8%5%5%446%24%
1395
January1st to 15thNight
6%7%47%8%35%5%6%8%35%
2560
16th to endNight
8%9%5%8%5%35%45%8%33%
2502
February1st to 15thNight
10%11%48%5%34346%36%
2278
16th to endNight
6%8%36%6%3446%7%41%
1961
March1st to 15thNight
12%7%36%424346%42%
2006
16th to endNight
13%9%36%42335%6%38%
1934
April1st to 15thNight
15%6%24424446%43%
1663
16th to endNight
19%7%36%5%23345%37%
1485
May1st to 15thNight
15%6%2342425%6%45%
1484
16th to endNight
11%6%2442446%8%44%
1411
June1st to 15thNight
10%5%24325%45%8%46%
1207
16th to endNight
5%21322246%7%61%
1155
July1st to 15thNight
5%21131335%7%62%
1188
16th to endNight
311212346%10%62%
1543
August1st to 15thNight
4113325%5%5%9%56%
1485
16th to endNight
6%314223447%60%
1575
September1st to 15thNight
9%313323445%57%
1735
16th to endNight
9%413223446%57%
1815
October1st to 15thNight
14%423312336%52%
1941
16th to endNight
15%6%24323346%47%
2153
November1st to 15thNight
8%5%25%424446%50%
2316
16th to endNight
9%6%25%5%34447%46%
2520
December1st to 15thNight
10%10%47%6%25%45%7%33%
2520
16th to endNight
15%10%47%6%4446%6%30%
2826

Percentage Cloud Cover SW (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 15thDay
5%11%5%10%8%46%5%5%7%28%
1376
16th to endDay
8%13%7%10%7%45%5%47%25%
1719
February1st to 15thDay
11%10%49%9%45%346%29%
1575
16th to endDay
9%9%46%5%27%5%6%7%34%
1523
March1st to 15thDay
15%10%45%424448%35%
1900
16th to endDay
17%9%36%5%2445%6%31%
1936
April1st to 15thDay
16%6%34425%45%7%38%
1951
16th to endDay
24%8%25%424346%32%
2145
May1st to 15thDay
18%6%35%5%3435%6%34%
2136
16th to endDay
18%6%26%5%245%5%8%34%
2351
June1st to 15thDay
17%6%34425%448%37%
2420
16th to endDay
8%3134345%6%8%51%
2475
July1st to 15thDay
7%31332446%10%51%
2439
16th to endDay
5%2133245%6%9%55%
2315
August1st to 15thDay
8%4245%35%6%6%9%42%
2145
16th to endDay
8%42442435%6%52%
2275
September1st to 15thDay
12%5%245%23445%49%
1893
16th to endDay
11%313313346%55%
1815
October1st to 15thDay
13%6%24433336%48%
1678
16th to endDay
15%7%24422346%46%
1716
November1st to 15thDay
8%7%26%5%1435%7%47%
1541
16th to endDay
12%9%36%435%45%8%36%
1440
December1st to 15thDay
11%11%5%9%7%35%45%6%29%
1440
16th to endDay
14%9%6%9%9%5%5%45%6%23%
1395
January1st to 15thNight
7%7%47%7%45%5%6%8%35%
2560
16th to endNight
8%10%5%8%5%345%5%8%33%
2502
February1st to 15thNight
11%10%48%6%33446%36%
2278
16th to endNight
7%7%36%6%3446%7%41%
1961
March1st to 15thNight
12%8%36%424447%42%
2006
16th to endNight
14%9%46%42345%6%37%
1936
April1st to 15thNight
15%6%24333446%44%
1663
16th to endNight
19%7%45%5%23345%37%
1485
May1st to 15thNight
15%6%2432435%7%45%
1484
16th to endNight
11%7%245%1446%7%44%
1410
June1st to 15thNight
11%5%24424449%45%
1207
16th to endNight
5%2123135%5%7%61%
1155
July1st to 15thNight
331232245%7%62%
1188
16th to endNight
31221346%10%62%
1543
August1st to 15thNight
421233446%10%56%
1485
16th to endNight
6%214313347%60%
1575
September1st to 15thNight
9%31432335%5%57%
1735
16th to endNight
9%413224347%56%
1815
October1st to 15thNight
13%5%33313436%52%
1941
16th to endNight
15%7%23423346%47%
2153
November1st to 15thNight
8%5%25%424446%50%
2316
16th to endNight
10%6%25%434446%46%
2520
December1st to 15thNight
10%11%48%5%25%5%47%33%
2520
16th to endNight
15%10%48%6%3445%6%29%
2826

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 15thDay
5%10%6%11%7%5%6%5%5%7%29%
1376
16th to endDay
8%13%7%10%7%36%5%47%26%
1719
February1st to 15thDay
11%10%49%8%35%5%46%29%
1575
16th to endDay
9%9%46%5%36%5%6%8%34%
1523
March1st to 15thDay
15%10%45%424448%35%
1900
16th to endDay
17%9%47%5%2445%6%31%
1934
April1st to 15thDay
15%7%3442445%7%39%
1951
16th to endDay
24%8%25%424345%32%
2145
May1st to 15thDay
18%7%25%5%3445%6%34%
2136
16th to endDay
18%5%26%5%2446%8%34%
2351
June1st to 15thDay
18%6%25%434448%37%
2420
16th to endDay
8%3144245%6%8%51%
2475
July1st to 15thDay
7%313325%46%10%51%
2439
16th to endDay
5%21333446%9%54%
2315
August1st to 15thDay
8%415%5%346%7%8%43%
2145
16th to endDay
8%42442335%7%51%
2275
September1st to 15thDay
13%5%24423346%48%
1893
16th to endDay
11%323323347%54%
1815
October1st to 15thDay
14%6%24423345%49%
1678
16th to endDay
15%7%24422336%46%
1716
November1st to 15thDay
8%6%26%5%23448%47%
1541
16th to endDay
13%8%36%435%45%8%36%
1440
December1st to 15thDay
11%11%5%9%6%45%45%6%29%
1440
16th to endDay
14%9%5%9%9%5%5%5%5%6%23%
1395
January1st to 15thNight
7%7%47%8%45%5%6%8%35%
2560
16th to endNight
8%10%5%8%5%345%5%9%33%
2502
February1st to 15thNight
10%10%47%6%33346%36%
2278
16th to endNight
7%7%36%6%345%6%8%40%
1961
March1st to 15thNight
12%7%45%423446%42%
2006
16th to endNight
14%9%46%42345%6%37%
1936
April1st to 15thNight
15%7%2443345%6%44%
1663
16th to endNight
20%8%36%423346%37%
1485
May1st to 15thNight
15%5%2431435%6%45%
1484
16th to endNight
12%6%2442446%7%44%
1410
June1st to 15thNight
11%5%23424449%45%
1207
16th to endNight
5%21231346%7%60%
1155
July1st to 15thNight
3312323448%62%
1188
16th to endNight
31121446%9%62%
1543
August1st to 15thNight
4212325%46%10%55%
1485
16th to endNight
6%31331335%7%60%
1575
September1st to 15thNight
8%314323445%57%
1735
16th to endNight
9%423223347%56%
1815
October1st to 15thNight
14%433313336%53%
1941
16th to endNight
15%7%24423336%47%
2153
November1st to 15thNight
8%5%25%434446%50%
2316
16th to endNight
10%6%25%434447%45%
2520
December1st to 15thNight
10%11%48%6%35%5%47%32%
2520
16th to endNight
15%10%48%7%3445%6%29%
2826

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 15thDay
53%5%14%18%8%
1377
16th to endDay
57%7%14%16%4
1719
February1st to 15thDay
55%5%14%18%6%
1576
16th to endDay
46%8%16%17%10%
1523
March1st to 15thDay
47%6%14%23%6%1
1900
16th to endDay
52%7%13%20%4
1936
April1st to 15thDay
43%6%14%26%8%1
1951
16th to endDay
52%5%12%19%8%
2145
May1st to 15thDay
49%7%14%19%9%
2136
16th to endDay
46%7%14%21%9%
2355
June1st to 15thDay
45%8%14%22%8%
2420
16th to endDay
29%8%17%28%13%3
2475
July1st to 15thDay
27%7%19%28%12%3
2283
16th to endDay
24%6%17%29%19%2
2159
August1st to 15thDay
35%8%17%24%11%1
2131
16th to endDay
31%5%15%29%14%3
2275
September1st to 15thDay
35%6%12%26%17%1
1893
16th to endDay
30%5%13%32%17%
1815
October1st to 15thDay
37%5%12%25%17%1
1678
16th to endDay
39%416%25%12%
1716
November1st to 15thDay
36%415%24%18%1
1541
16th to endDay
45%6%17%20%9%
1440
December1st to 15thDay
54%5%15%16%7%
1440
16th to endDay
60%5%12%14%6%1
1395
January1st to 15thNight
45%7%14%21%11%
2560
16th to endNight
47%8%16%19%7%
2502
February1st to 15thNight
49%5%13%21%9%
2288
16th to endNight
39%7%14%22%12%2
1961
March1st to 15thNight
41%5%16%25%8%1
2006
16th to endNight
46%6%13%24%8%
1936
April1st to 15thNight
40%6%13%25%12%
1663
16th to endNight
47%6%11%21%11%1
1485
May1st to 15thNight
39%5%14%23%14%2
1485
16th to endNight
37%8%15%23%14%
1412
June1st to 15thNight
35%6%18%26%12%
1207
16th to endNight
21%6%16%27%24%4
1155
July1st to 15thNight
21%6%18%30%18%5%
1115
16th to endNight
16%7%17%31%21%4
1436
August1st to 15thNight
23%7%16%31%18%2
1475
16th to endNight
24%5%16%28%19%5%
1575
September1st to 15thNight
27%6%14%27%20%2
1735
16th to endNight
27%6%12%33%19%1
1815
October1st to 15thNight
33%412%26%20%2
1941
16th to endNight
38%414%26%14%1
2153
November1st to 15thNight
34%413%23%20%2
2316
16th to endNight
38%5%17%25%12%
2520
December1st to 15thNight
49%6%16%19%7%
2520
16th to endNight
54%6%13%16%8%
2826

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 15thDay
12%12%45%23%6%
90
16th to endDay
26%5%35%25%8%
96
February1st to 15thDay
18%18%36%21%4
90
16th to endDay
13%16%35%23%9%1
81
March1st to 15thDay
25%16%28%28%1
81
16th to endDay
22%6%35%20%12%2
48
April1st to 15thDay
20%14%33%23%6%1
190
16th to endDay
29%13%29%16%7%2
375
May1st to 15thDay
23%11%33%20%9%1
393
16th to endDay
20%8%30%27%11%2
437
June1st to 15thDay
16%8%30%28%13%2
420
16th to endDay
6%5%33%35%16%2
420
July1st to 15thDay
8%426%36%19%5%
400
16th to endDay
5%226%42%20%2
445
August1st to 15thDay
8%223%38%22%3
418
16th to endDay
9%427%32%22%3
443
September1st to 15thDay
11%430%33%14%4
168
16th to endDay
16%5%30%26%16%4
90
October1st to 15thDay
14%7%35%31%6%4
90
16th to endDay
16%9%39%22%11%
96
November1st to 15thDay
38%24%44%15%3
90
16th to endDay
44%7%24%14%8%
90
December1st to 15thDay
21%15%41%12%10%
90
16th to endDay
22%22%33%19%1
96
January1st to 15thNight
10%10%38%31%7%1
900
16th to endNight
12%11%39%30%5%
960
February1st to 15thNight
16%9%36%28%7%1
880
16th to endNight
10%8%39%29%10%1
699
March1st to 15thNight
15%8%36%30%7%
582
16th to endNight
15%10%37%27%7%
528
April1st to 15thNight
19%10%32%31%5%
494
16th to endNight
22%12%31%23%8%2
495
May1st to 15thNight
19%7%35%27%8%
495
16th to endNight
15%5%31%36%11%
515
June1st to 15thNight
14%6%29%37%12%
495
16th to endNight
6%328%48%13%
495
July1st to 15thNight
6%23%45%22%1
465
16th to endNight
322%52%20%
522
August1st to 15thNight
5%121%47%24%
494
16th to endNight
7%322%40%24%1
525
September1st to 15thNight
9%226%40%17%3
495
16th to endNight
11%6%31%32%15%2
492
October1st to 15thNight
14%9%36%28%9%
621
16th to endNight
20%6%31%32%8%
745
November1st to 15thNight
12%9%34%33%9%
875
16th to endNight
13%10%38%28%9%
900
December1st to 15thNight
16%10%35%32%4
900
16th to endNight
20%8%33%28%8%
960
Page generated at 2017-03-14 03:34:48. Version ac04

Copyright 2017 A. Danko


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