Victoria
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Victoria clear sky chart from 2005-11-05 to 2017-08-12.

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
46%
14388
10%
46364
8%
14362
48%
14362
17%
33321

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
32%
747
8%
2686
6%
746
35%
746
9%
2182
January16th to endNight
37%
777
7%
2695
7%
777
39%
777
10%
2133
February1st to 15thNight
36%
696
6%
2288
4%
696
39%
696
11%
1823
February16th to endNight
38%
632
10%
2047
9%
632
41%
632
14%
1567
March1st to 15thNight
34%
720
5%
2043
4%
720
36%
720
11%
1663
March16th to endNight
36%
768
7%
2085
5%
768
37%
768
13%
1688
April1st to 15thNight
42%
716
9%
1796
4%
716
44%
716
20%
1382
April16th to endNight
42%
528
12%
1608
7%
528
46%
528
18%
1144
May1st to 15thNight
53%
359
12%
1439
17%
359
57%
359
22%
860
May16th to endNight
57%
375
7%
1481
11%
374
60%
374
18%
969
June1st to 15thNight
53%
360
6%
1260
5%
360
53%
360
21%
814
June16th to endNight
55%
360
8%
1260
6%
360
57%
360
25%
786
July1st to 15thNight
70%
340
12%
1190
11%
340
73%
340
40%
591
July16th to endNight
77%
376
17%
1342
24%
354
82%
354
49%
571
August1st to 15thNight
82%
449
18%
1499
22%
447
83%
447
46%
705
August16th to endNight
72%
558
22%
1608
18%
558
75%
558
44%
866
September1st to 15thNight
77%
660
23%
1650
15%
660
78%
660
51%
920
September16th to endNight
57%
656
18%
1815
15%
656
59%
656
27%
1225
October1st to 15thNight
53%
660
12%
1980
12%
660
55%
660
22%
1372
October16th to endNight
43%
704
9%
2177
7%
704
46%
704
14%
1666
November1st to 15thNight
32%
700
7%
2450
6%
700
35%
700
9%
1980
November16th to endNight
33%
720
7%
2520
4%
720
36%
720
9%
1989
December1st to 15thNight
34%
727
6%
2565
4%
727
37%
727
9%
2068
December16th to endNight
25%
800
6%
2880
2%
800
29%
800
8%
2357

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%7%36%5%3445%6%36%
47635
Night
18%7%35%5%3445%6%34%
46519
Cloud CoverDay
16%7%36%5%34447%36%
47635
Night
19%8%35%5%34446%34%
46522
TransparencyDay
48%7%17%19%6%
47293
Night
51%7%15%17%6%1
46365
SeeingDay
17%313%26%25%13%
6006
Night
22%416%26%22%7%
14400

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 15thDay
27%11%5%7%7%35%34417%
1253
16th to endDay
26%12%7%10%7%235%5%413%
1524
February1st to 15thDay
27%13%36%6%45%445%16%
1576
16th to endDay
18%11%5%7%6%46%45%7%22%
1427
March1st to 15thDay
22%12%5%8%7%45%5%6%5%17%
1915
16th to endDay
19%12%49%6%35%5%5%6%21%
2139
April1st to 15thDay
17%8%35%5%37%6%6%9%25%
2152
16th to endDay
15%8%36%5%36%5%7%8%29%
2352
May1st to 15thDay
12%5%26%5%35%5%47%40%
2511
16th to endDay
14%7%35%5%36%46%7%34%
2627
June1st to 15thDay
11%5%25%6%3446%7%42%
2700
16th to endDay
11%5%25%435%5%6%7%42%
2700
July1st to 15thDay
5%313313345%62%
2700
16th to endDay
5%112213336%67%
2734
August1st to 15thDay
6%312313246%63%
2366
16th to endDay
7%41442345%8%53%
2242
September1st to 15thDay
7%5%24333347%55%
1980
16th to endDay
15%7%26%5%34347%39%
1812
October1st to 15thDay
19%10%36%5%346%5%6%29%
1650
16th to endDay
22%10%48%6%35%45%7%20%
1691
November1st to 15thDay
31%10%48%5%33445%19%
1408
16th to endDay
25%12%5%9%6%35%445%16%
1440
December1st to 15thDay
25%11%6%6%6%25%5%4421%
1392
16th to endDay
25%13%48%5%345%46%17%
1344
January1st to 15thNight
27%10%46%5%35%44422%
2686
16th to endNight
24%10%46%6%345%5%5%22%
2695
February1st to 15thNight
22%11%37%6%36%446%23%
2276
16th to endNight
20%9%37%5%35%45%6%27%
2047
March1st to 15thNight
23%10%47%6%35%5%5%5%20%
2043
16th to endNight
19%9%47%7%345%6%6%23%
2081
April1st to 15thNight
18%8%35%5%345%5%8%31%
1796
16th to endNight
18%6%35%5%345%5%8%33%
1608
May1st to 15thNight
11%5%25%4346%5%6%44%
1439
16th to endNight
10%5%25%6%36%5%5%10%38%
1481
June1st to 15thNight
12%5%45%5%3445%6%41%
1260
16th to endNight
10%4344245%7%9%43%
1260
July1st to 15thNight
5%213323236%64%
1260
16th to endNight
4212112235%72%
1435
August1st to 15thNight
2212213437%67%
1507
16th to endNight
7%212313348%61%
1608
September1st to 15thNight
7%12212346%65%
1650
16th to endNight
15%6%24424447%42%
1815
October1st to 15thNight
17%7%27%43344440%
1980
16th to endNight
26%7%36%5%3445%6%26%
2177
November1st to 15thNight
29%8%36%5%35%5%45%21%
2450
16th to endNight
21%11%5%7%6%35%5%46%23%
2520
December1st to 15thNight
23%11%36%6%36%446%22%
2565
16th to endNight
25%11%46%5%35%45%5%20%
2880

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
28%12%48%5%35%44418%
1253
16th to endDay
27%12%8%9%7%34445%13%
1524
February1st to 15thDay
27%13%47%5%35%446%16%
1576
16th to endDay
19%12%47%7%44447%23%
1427
March1st to 15thDay
23%10%5%9%7%36%45%6%17%
1915
16th to endDay
19%12%48%6%46%446%21%
2139
April1st to 15thDay
18%8%35%437%6%6%10%25%
2152
16th to endDay
16%8%36%5%35%6%7%8%29%
2352
May1st to 15thDay
13%5%25%5%35%5%48%39%
2511
16th to endDay
15%7%35%6%345%5%7%35%
2627
June1st to 15thDay
12%6%245%3445%8%42%
2700
16th to endDay
11%5%25%5%35%5%5%6%43%
2700
July1st to 15thDay
6%223323336%62%
2700
16th to endDay
6%112212346%67%
2734
August1st to 15thDay
6%313223337%62%
2366
16th to endDay
8%31442345%8%52%
2242
September1st to 15thDay
7%414423446%55%
1980
16th to endDay
16%7%35%5%3445%6%38%
1812
October1st to 15thDay
20%9%37%4335%5%7%28%
1650
16th to endDay
24%13%36%6%3435%8%20%
1691
November1st to 15thDay
32%9%36%5%335%35%19%
1408
16th to endDay
25%12%6%7%7%345%35%17%
1440
December1st to 15thDay
27%11%5%7%5%3444421%
1392
16th to endDay
26%12%5%7%6%35%5%45%17%
1344
January1st to 15thNight
27%10%46%434445%22%
2685
16th to endNight
24%11%46%6%35%45%6%22%
2695
February1st to 15thNight
23%11%47%6%35%5%46%23%
2276
16th to endNight
20%9%36%5%345%5%6%27%
2047
March1st to 15thNight
25%9%46%6%36%45%5%20%
2043
16th to endNight
21%10%37%6%345%5%6%23%
2085
April1st to 15thNight
19%8%25%5%35%6%5%7%30%
1796
16th to endNight
19%6%25%5%345%5%8%32%
1608
May1st to 15thNight
10%6%25%435%5%6%5%45%
1439
16th to endNight
11%436%6%26%5%6%9%37%
1481
June1st to 15thNight
12%7%26%5%24447%41%
1260
16th to endNight
11%5%135%25%5%6%9%42%
1260
July1st to 15thNight
5%413213346%63%
1260
16th to endNight
5%21211223472%
1435
August1st to 15thNight
221232335%5%67%
1507
16th to endNight
7%23313438%61%
1608
September1st to 15thNight
7%22212346%65%
1650
16th to endNight
16%425%435%447%42%
1815
October1st to 15thNight
18%7%25%424435%40%
1980
16th to endNight
27%7%35%5%3445%6%26%
2177
November1st to 15thNight
31%8%36%5%345%45%21%
2450
16th to endNight
22%11%5%7%5%35%446%23%
2520
December1st to 15thNight
23%12%46%446%446%22%
2565
16th to endNight
25%12%47%5%3445%5%20%
2880

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
70%8%8%8%4
1253
16th to endDay
73%7%10%6%1
1524
February1st to 15thDay
69%9%9%7%31
1576
16th to endDay
61%7%13%13%4
1427
March1st to 15thDay
65%8%13%11%1
1915
16th to endDay
63%6%14%13%1
2139
April1st to 15thDay
52%9%19%16%2
2152
16th to endDay
49%10%14%19%5%
2352
May1st to 15thDay
42%7%19%21%7%
2511
16th to endDay
47%9%22%17%3
2631
June1st to 15thDay
42%7%23%19%6%
2700
16th to endDay
40%7%23%22%5%
2700
July1st to 15thDay
24%6%20%32%13%2
2541
16th to endDay
18%6%24%35%12%1
2564
August1st to 15thDay
23%7%21%34%10%2
2349
16th to endDay
29%6%22%31%8%1
2242
September1st to 15thDay
30%7%18%26%15%1
1980
16th to endDay
48%8%13%20%8%
1812
October1st to 15thDay
54%8%15%15%5%
1650
16th to endDay
63%8%15%9%3
1691
November1st to 15thDay
67%6%11%9%21
1408
16th to endDay
69%7%10%10%2
1440
December1st to 15thDay
67%6%9%11%3
1392
16th to endDay
68%7%11%8%3
1344
January1st to 15thNight
65%8%11%9%5%
2686
16th to endNight
63%7%13%12%21
2695
February1st to 15thNight
62%7%13%11%3
2288
16th to endNight
57%6%14%15%5%
2047
March1st to 15thNight
64%7%12%13%2
2043
16th to endNight
60%9%12%15%2
2085
April1st to 15thNight
52%9%15%18%4
1796
16th to endNight
49%7%15%21%5%
1608
May1st to 15thNight
39%6%19%22%10%1
1440
16th to endNight
43%9%22%17%5%
1481
June1st to 15thNight
43%6%20%23%41
1260
16th to endNight
38%8%20%25%5%1
1260
July1st to 15thNight
22%6%17%31%16%3
1190
16th to endNight
16%422%33%18%3
1342
August1st to 15thNight
17%7%23%32%14%4
1499
16th to endNight
22%7%20%34%11%3
1608
September1st to 15thNight
21%5%20%27%20%5%
1650
16th to endNight
42%6%15%22%10%1
1815
October1st to 15thNight
48%5%15%20%9%
1980
16th to endNight
58%6%15%14%4
2177
November1st to 15thNight
65%7%11%11%22
2450
16th to endNight
63%7%12%11%5%
2520
December1st to 15thNight
65%7%13%9%5%
2565
16th to endNight
65%8%12%8%3
2880

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
10%328%28%25%5%
60
16th to endDay
39%123%16%12%5%
106
February1st to 15thDay
31%319%29%13%2
236
16th to endDay
22%9%16%26%17%7%
213
March1st to 15thDay
35%7%21%20%10%4
270
16th to endDay
27%7%17%29%13%4
288
April1st to 15thDay
20%317%24%24%10%
269
16th to endDay
17%317%33%20%8%
270
May1st to 15thDay
19%411%23%31%10%
288
16th to endDay
14%211%25%28%18%
342
June1st to 15thDay
11%215%30%29%10%
495
16th to endDay
10%312%36%25%10%
495
July1st to 15thDay
5%9%28%36%18%
475
16th to endDay
37%25%33%29%
403
August1st to 15thDay
6%2122%29%38%
300
16th to endDay
8%17%18%39%25%
268
September1st to 15thDay
11%8%23%30%25%
255
16th to endDay
16%110%27%30%14%
255
October1st to 15thDay
26%210%26%25%8%
255
16th to endDay
29%415%24%21%5%
219
November1st to 15thDay
43%128%16%10%
60
16th to endDay
25%315%30%13%13%
60
December1st to 15thDay
31%8%36%13%10%
60
16th to endDay
43%6%26%15%7%
64
January1st to 15thNight
30%6%19%22%18%2
750
16th to endNight
30%315%23%21%4
777
February1st to 15thNight
28%5%17%27%18%3
704
16th to endNight
24%6%19%24%17%7%
632
March1st to 15thNight
31%7%18%22%14%5%
720
16th to endNight
22%8%19%27%17%4
768
April1st to 15thNight
21%322%23%23%5%
716
16th to endNight
20%322%32%16%4
528
May1st to 15thNight
13%221%29%24%7%
360
16th to endNight
10%414%31%31%7%
375
June1st to 15thNight
15%218%34%25%4
360
16th to endNight
11%221%33%22%8%
360
July1st to 15thNight
7%14%34%35%7%
340
16th to endNight
6%110%36%35%10%
376
August1st to 15thNight
46%28%46%14%
449
16th to endNight
9%11%27%39%11%
558
September1st to 15thNight
8%16%25%33%23%
660
16th to endNight
18%110%25%30%14%
656
October1st to 15thNight
22%111%27%23%12%
660
16th to endNight
30%312%25%20%7%
704
November1st to 15thNight
34%5%18%25%14%2
700
16th to endNight
25%8%21%22%15%6%
720
December1st to 15thNight
29%5%19%26%16%2
727
16th to endNight
29%6%26%25%10%1
800
Page generated at 2017-08-13 11:16:54. Version ac04

Copyright 2017 A. Danko


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