Aldergrove Lake Regional Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Aldergrove Lake Regional Park clear sky chart from 2005-11-05 to 2017-09-10.

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
35%
14451
10%
46636
8%
14423
38%
14423
14%
34328

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
25%
750
10%
2686
9%
746
29%
746
8%
2155
January16th to endNight
28%
773
9%
2715
8%
773
31%
773
9%
2112
February1st to 15thNight
21%
700
6%
2288
4%
700
25%
700
7%
1867
February16th to endNight
28%
632
13%
2029
9%
632
34%
632
12%
1512
March1st to 15thNight
22%
720
5%
2073
3%
720
24%
720
9%
1711
March16th to endNight
23%
768
6%
2064
3%
768
24%
768
9%
1743
April1st to 15thNight
31%
719
7%
1799
4%
719
32%
719
13%
1450
April16th to endNight
30%
512
8%
1592
5%
512
33%
512
11%
1253
May1st to 15thNight
46%
359
12%
1439
17%
359
49%
359
15%
920
May16th to endNight
46%
374
6%
1493
9%
374
48%
374
13%
994
June1st to 15thNight
43%
360
2%
1260
2%
360
43%
360
15%
890
June16th to endNight
46%
360
5%
1260
2%
360
48%
360
16%
835
July1st to 15thNight
62%
340
10%
1190
9%
340
64%
340
31%
641
July16th to endNight
66%
376
16%
1353
20%
354
74%
354
39%
610
August1st to 15thNight
70%
418
17%
1490
22%
416
71%
416
38%
703
August16th to endNight
65%
625
19%
1771
15%
625
67%
625
36%
1004
September1st to 15thNight
66%
700
20%
1750
10%
700
68%
700
39%
1048
September16th to endNight
44%
656
17%
1806
12%
656
48%
656
21%
1281
October1st to 15thNight
40%
660
12%
1980
11%
660
43%
660
19%
1380
October16th to endNight
31%
704
7%
2195
5%
704
35%
704
11%
1711
November1st to 15thNight
20%
700
6%
2450
4%
700
23%
700
6%
2063
November16th to endNight
22%
720
6%
2520
5%
720
25%
720
7%
2024
December1st to 15thNight
21%
725
9%
2553
5%
725
27%
725
8%
2037
December16th to endNight
16%
800
7%
2880
4%
800
19%
800
6%
2384

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
25%8%36%5%24345%30%
48015
Night
29%8%35%423345%29%
46792
Cloud CoverDay
26%8%36%5%23345%29%
48015
Night
29%8%35%424335%29%
46795
TransparencyDay
58%213%17%6%1
47674
Night
59%213%16%6%1
46637
SeeingDay
23%14%18%24%13%4
6033
Night
28%18%9%20%18%4
14457

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
41%9%36%42423318%
1253
16th to endDay
39%7%35%43434320%
1503
February1st to 15thDay
36%10%46%435%345%16%
1576
16th to endDay
28%11%35%6%43245%24%
1445
March1st to 15thDay
40%12%45%5%2433313%
1884
16th to endDay
33%11%39%6%45%33415%
2160
April1st to 15thDay
28%10%47%6%36%35%5%17%
2149
16th to endDay
26%9%38%7%3445%5%20%
2367
May1st to 15thDay
21%7%36%5%24446%32%
2511
16th to endDay
22%8%47%6%34446%27%
2615
June1st to 15thDay
24%7%37%6%34446%27%
2700
16th to endDay
19%9%46%5%35%45%6%30%
2700
July1st to 15thDay
10%414423345%53%
2700
16th to endDay
10%422323346%56%
2720
August1st to 15thDay
10%424323346%53%
2460
16th to endDay
13%41443345%6%48%
2430
September1st to 15thDay
14%5%24422235%50%
2097
16th to endDay
24%7%36%5%34345%31%
1821
October1st to 15thDay
26%8%27%5%2435%6%28%
1650
16th to endDay
36%8%35%5%24336%18%
1676
November1st to 15thDay
46%10%35%32333314%
1408
16th to endDay
38%11%35%42234318%
1440
December1st to 15thDay
36%13%36%41232221%
1406
16th to endDay
41%12%45%5%3233314%
1344
January1st to 15thNight
43%9%3431222421%
2686
16th to endNight
36%10%35%322335%22%
2715
February1st to 15thNight
37%10%37%5%2323419%
2276
16th to endNight
28%10%35%5%3433428%
2029
March1st to 15thNight
38%10%26%43433418%
2073
16th to endNight
35%10%37%5%3443417%
2060
April1st to 15thNight
28%9%46%6%3445%422%
1799
16th to endNight
29%9%36%6%34445%21%
1592
May1st to 15thNight
18%6%36%42445%6%36%
1439
16th to endNight
15%7%36%5%36%5%6%7%32%
1493
June1st to 15thNight
20%7%47%433446%32%
1260
16th to endNight
16%7%37%5%345%45%34%
1260
July1st to 15thNight
8%3245%2324458%
1260
16th to endNight
8%212212336%63%
1447
August1st to 15thNight
8%213312446%61%
1498
16th to endNight
8%32442346%8%50%
1771
September1st to 15thNight
9%2135%34435%58%
1750
16th to endNight
23%6%345%24346%35%
1806
October1st to 15thNight
24%6%25%425%43436%
1980
16th to endNight
35%6%25%433446%21%
2195
November1st to 15thNight
44%7%35%42433316%
2450
16th to endNight
37%9%46%5%2323319%
2520
December1st to 15thNight
36%11%3442434421%
2553
16th to endNight
42%12%36%41222218%
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
41%10%25%5%2332418%
1253
16th to endDay
37%10%36%423435%20%
1503
February1st to 15thDay
36%11%36%435%335%16%
1576
16th to endDay
28%11%36%5%3434424%
1445
March1st to 15thDay
40%12%46%5%2333314%
1884
16th to endDay
33%12%48%7%35%33414%
2160
April1st to 15thDay
30%9%47%7%35%345%16%
2149
16th to endDay
26%10%47%6%35%46%5%18%
2367
May1st to 15thDay
22%8%36%5%34445%32%
2511
16th to endDay
23%9%46%6%34446%25%
2615
June1st to 15thDay
26%8%36%6%34445%26%
2700
16th to endDay
20%8%37%5%45%445%29%
2700
July1st to 15thDay
12%424423345%52%
2700
16th to endDay
11%423312346%54%
2720
August1st to 15thDay
11%424323346%52%
2460
16th to endDay
13%5%2443345%7%48%
2430
September1st to 15thDay
13%7%2442223451%
2097
16th to endDay
24%8%37%5%33345%31%
1821
October1st to 15thDay
27%7%36%5%2345%5%29%
1650
16th to endDay
36%8%25%5%23346%19%
1676
November1st to 15thDay
46%10%35%33223314%
1408
16th to endDay
37%11%45%43233419%
1440
December1st to 15thDay
35%13%36%41323322%
1406
16th to endDay
40%13%46%5%2233314%
1344
January1st to 15thNight
43%9%3441222421%
2685
16th to endNight
36%11%35%313335%22%
2715
February1st to 15thNight
37%10%46%5%23235%18%
2276
16th to endNight
28%10%36%5%33335%27%
2029
March1st to 15thNight
36%10%35%425%435%17%
2073
16th to endNight
35%10%36%7%4334317%
2064
April1st to 15thNight
27%10%36%6%44445%21%
1799
16th to endNight
30%10%36%5%35%435%21%
1592
May1st to 15thNight
19%6%37%42435%6%36%
1439
16th to endNight
17%7%27%5%25%5%5%6%32%
1493
June1st to 15thNight
20%8%36%6%35%345%31%
1260
16th to endNight
16%7%36%5%35%5%6%6%33%
1260
July1st to 15thNight
7%5%3342423458%
1260
16th to endNight
9%112212346%62%
1447
August1st to 15thNight
9%21322245%6%60%
1498
16th to endNight
8%325%42446%8%50%
1771
September1st to 15thNight
9%21342444457%
1750
16th to endNight
22%6%25%5%24346%35%
1806
October1st to 15thNight
24%5%25%426%435%35%
1980
16th to endNight
34%8%25%423446%21%
2195
November1st to 15thNight
45%8%35%5%2333415%
2450
16th to endNight
38%9%36%43332419%
2520
December1st to 15thNight
37%10%35%42333421%
2553
16th to endNight
42%13%46%41222318%
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
72%26%10%6%1
1253
16th to endDay
67%210%13%31
1503
February1st to 15thDay
71%210%6%6%1
1576
16th to endDay
64%111%14%6%1
1445
March1st to 15thDay
76%28%10%2
1884
16th to endDay
75%28%12%1
2160
April1st to 15thDay
71%311%12%2
2149
16th to endDay
66%311%12%5%
2367
May1st to 15thDay
55%214%18%8%
2511
16th to endDay
60%318%14%2
2619
June1st to 15thDay
60%215%14%41
2700
16th to endDay
57%216%18%4
2700
July1st to 15thDay
35%216%28%12%2
2541
16th to endDay
30%220%32%12%1
2551
August1st to 15thDay
33%419%31%9%1
2443
16th to endDay
36%222%28%7%1
2430
September1st to 15thDay
38%216%23%17%2
2097
16th to endDay
57%212%17%9%1
1821
October1st to 15thDay
56%216%14%8%1
1650
16th to endDay
65%313%14%3
1676
November1st to 15thDay
77%17%9%21
1408
16th to endDay
70%27%10%7%1
1440
December1st to 15thDay
69%27%10%8%
1406
16th to endDay
75%17%10%41
1344
January1st to 15thNight
69%26%14%5%
2686
16th to endNight
66%210%13%5%2
2715
February1st to 15thNight
70%210%9%32
2288
16th to endNight
61%111%16%7%1
2029
March1st to 15thNight
70%311%11%3
2073
16th to endNight
71%311%11%1
2064
April1st to 15thNight
65%212%16%3
1799
16th to endNight
65%211%14%5%
1592
May1st to 15thNight
49%217%20%8%1
1440
16th to endNight
51%323%16%4
1493
June1st to 15thNight
55%219%15%5%1
1260
16th to endNight
50%219%21%41
1260
July1st to 15thNight
32%213%31%16%4
1190
16th to endNight
23%219%33%16%3
1353
August1st to 15thNight
24%221%34%12%3
1490
16th to endNight
31%221%29%11%2
1771
September1st to 15thNight
30%317%24%20%3
1750
16th to endNight
50%312%22%7%2
1806
October1st to 15thNight
51%215%19%9%1
1980
16th to endNight
64%215%13%4
2195
November1st to 15thNight
75%29%8%22
2450
16th to endNight
70%19%9%7%1
2520
December1st to 15thNight
68%39%11%6%
2553
16th to endNight
74%18%9%41
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
13%10%20%21%25%10%
60
16th to endDay
53%7%7%17%8%4
67
February1st to 15thDay
37%19%16%13%8%4
236
16th to endDay
32%18%20%16%10%1
215
March1st to 15thDay
46%18%15%15%2
270
16th to endDay
37%17%22%14%6%1
288
April1st to 15thDay
31%17%18%16%14%2
269
16th to endDay
22%19%24%22%7%2
270
May1st to 15thDay
22%17%22%22%12%2
288
16th to endDay
23%16%15%21%17%5%
330
June1st to 15thDay
19%16%18%28%12%3
495
16th to endDay
15%19%21%30%10%2
495
July1st to 15thDay
11%12%16%38%16%3
475
16th to endDay
7%14%17%32%22%5%
389
August1st to 15thDay
11%8%15%33%21%10%
315
16th to endDay
10%9%18%33%19%7%
332
September1st to 15thDay
15%10%21%23%21%6%
294
16th to endDay
21%9%19%27%15%6%
255
October1st to 15thDay
32%11%20%19%14%1
255
16th to endDay
38%12%16%19%9%3
191
November1st to 15thDay
65%6%16%10%1
60
16th to endDay
43%5%16%10%15%10%
60
December1st to 15thDay
50%10%21%11%33
60
16th to endDay
45%315%28%43
64
January1st to 15thNight
38%19%9%16%15%1
750
16th to endNight
33%20%8%20%13%3
773
February1st to 15thNight
38%21%11%17%9%2
704
16th to endNight
29%21%13%19%13%2
632
March1st to 15thNight
36%21%13%15%10%1
720
16th to endNight
34%21%11%20%9%3
768
April1st to 15thNight
27%20%9%22%15%3
719
16th to endNight
31%19%8%22%15%2
512
May1st to 15thNight
19%19%5%26%25%3
360
16th to endNight
17%20%419%32%6%
375
June1st to 15thNight
18%19%7%21%26%6%
360
16th to endNight
16%20%6%24%27%4
360
July1st to 15thNight
9%14%425%40%5%
340
16th to endNight
6%17%5%18%41%10%
376
August1st to 15thNight
10%10%216%42%18%
418
16th to endNight
10%10%421%41%11%
625
September1st to 15thNight
11%9%5%28%31%13%
700
16th to endNight
24%11%8%24%25%6%
656
October1st to 15thNight
25%12%11%25%19%4
660
16th to endNight
35%13%10%21%14%4
704
November1st to 15thNight
41%18%11%22%5%1
700
16th to endNight
37%22%8%16%11%2
720
December1st to 15thNight
36%21%13%19%8%
725
16th to endNight
42%21%14%16%5%
800
Page generated at 2017-09-11 16:35:33. Version ac04

Copyright 2017 A. Danko


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