Burnaby
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Burnaby clear sky chart from 2005-11-05 to 2017-09-19.

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
36%
14484
9%
46736
8%
14456
39%
14456
13%
34589

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
26%
750
11%
2686
9%
746
29%
746
9%
2164
January16th to endNight
27%
779
9%
2743
8%
779
29%
779
9%
2146
February1st to 15thNight
25%
700
6%
2288
5%
700
28%
700
8%
1856
February16th to endNight
30%
632
13%
2043
9%
632
35%
632
12%
1532
March1st to 15thNight
21%
720
4%
2061
3%
720
22%
720
7%
1751
March16th to endNight
24%
768
6%
2073
3%
768
25%
768
9%
1750
April1st to 15thNight
32%
716
7%
1796
4%
716
33%
716
14%
1435
April16th to endNight
33%
503
8%
1583
5%
503
36%
503
11%
1215
May1st to 15thNight
46%
359
11%
1439
17%
359
50%
359
15%
912
May16th to endNight
47%
374
6%
1460
8%
374
49%
374
14%
970
June1st to 15thNight
46%
360
2%
1260
1%
360
46%
360
16%
866
June16th to endNight
44%
360
4%
1260
1%
360
45%
360
16%
863
July1st to 15thNight
65%
340
9%
1190
8%
340
66%
340
32%
628
July16th to endNight
69%
376
15%
1327
18%
354
77%
354
38%
618
August1st to 15thNight
71%
429
16%
1501
22%
427
72%
427
37%
723
August16th to endNight
63%
612
18%
1758
15%
612
65%
612
35%
1018
September1st to 15thNight
68%
720
21%
1800
13%
720
69%
720
42%
1051
September16th to endNight
43%
671
16%
1848
11%
671
45%
671
20%
1310
October1st to 15thNight
40%
660
11%
1980
10%
660
43%
660
18%
1389
October16th to endNight
32%
704
5%
2201
5%
704
34%
704
10%
1758
November1st to 15thNight
20%
700
5%
2450
5%
700
22%
700
6%
2081
November16th to endNight
22%
720
5%
2520
3%
720
26%
720
7%
2019
December1st to 15thNight
24%
731
8%
2589
6%
731
27%
731
8%
2111
December16th to endNight
19%
800
6%
2880
4%
800
23%
800
6%
2423

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
26%7%35%424345%30%
48101
Night
30%7%24423335%30%
46890
Cloud CoverDay
28%8%35%5%34345%28%
48101
Night
30%8%35%423345%29%
46893
TransparencyDay
57%5%13%16%6%1
47758
Night
57%413%15%6%1
46737
SeeingDay
25%12%15%25%16%4
6141
Night
29%16%8%21%19%4
14490

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
45%8%3442423316%
1253
16th to endDay
39%8%25%5%2445%418%
1478
February1st to 15thDay
38%9%35%5%34345%15%
1576
16th to endDay
27%10%46%5%35%336%23%
1430
March1st to 15thDay
43%11%35%5%2333413%
1898
16th to endDay
34%10%46%6%3433417%
2151
April1st to 15thDay
28%9%46%5%36%5%45%18%
2149
16th to endDay
27%9%46%43445%6%22%
2376
May1st to 15thDay
20%8%35%5%24446%33%
2511
16th to endDay
20%8%36%6%35%45%7%27%
2648
June1st to 15thDay
23%7%36%5%35%446%29%
2700
16th to endDay
20%8%46%5%25%46%6%30%
2700
July1st to 15thDay
11%423423346%52%
2700
16th to endDay
11%323323345%56%
2748
August1st to 15thDay
11%423413245%54%
2448
16th to endDay
12%423323447%48%
2444
September1st to 15thDay
14%5%24423345%50%
2160
16th to endDay
29%6%24423346%31%
1854
October1st to 15thDay
30%7%25%42445%6%27%
1650
16th to endDay
39%8%26%423345%18%
1667
November1st to 15thDay
50%7%35%32333313%
1408
16th to endDay
41%8%35%42433417%
1440
December1st to 15thDay
36%12%35%42242222%
1368
16th to endDay
46%11%2442342215%
1344
January1st to 15thNight
43%9%2421333422%
2686
16th to endNight
36%9%34413446%20%
2743
February1st to 15thNight
38%8%26%5%23346%18%
2276
16th to endNight
29%10%2442344428%
2043
March1st to 15thNight
42%9%3442433317%
2061
16th to endNight
36%9%35%5%34435%18%
2069
April1st to 15thNight
28%9%35%5%34445%24%
1796
16th to endNight
26%9%45%5%34435%26%
1583
May1st to 15thNight
18%435%5%335%5%6%38%
1439
16th to endNight
17%7%35%5%25%5%5%6%34%
1460
June1st to 15thNight
22%7%25%5%24336%37%
1260
16th to endNight
16%6%35%5%35%45%7%34%
1260
July1st to 15thNight
8%323313336%59%
1260
16th to endNight
8%113313346%63%
1419
August1st to 15thNight
7%312313345%63%
1509
16th to endNight
9%42342336%7%53%
1758
September1st to 15thNight
9%213323345%61%
1800
16th to endNight
25%6%25%422345%37%
1848
October1st to 15thNight
25%6%1432344438%
1980
16th to endNight
38%7%24323345%22%
2201
November1st to 15thNight
46%8%35%42433316%
2450
16th to endNight
38%8%35%5%2422421%
2520
December1st to 15thNight
37%10%35%42333421%
2589
16th to endNight
45%11%3431222318%
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
45%9%45%32233315%
1253
16th to endDay
38%10%345%2433418%
1478
February1st to 15thDay
38%11%37%433345%15%
1576
16th to endDay
27%12%47%5%43335%21%
1430
March1st to 15thDay
44%12%35%5%3422312%
1898
16th to endDay
36%11%38%6%4333214%
2151
April1st to 15thDay
30%12%47%6%45%43415%
2149
16th to endDay
29%9%46%6%45%445%18%
2376
May1st to 15thDay
22%8%36%6%34346%29%
2511
16th to endDay
23%8%37%6%35%45%5%24%
2648
June1st to 15thDay
26%9%36%5%24445%25%
2700
16th to endDay
23%9%46%5%45%446%26%
2700
July1st to 15thDay
12%4245%24345%50%
2700
16th to endDay
12%423323345%52%
2748
August1st to 15thDay
12%5%24423346%51%
2448
16th to endDay
13%425%42445%7%45%
2444
September1st to 15thDay
15%6%14423245%48%
2160
16th to endDay
31%6%35%43333429%
1854
October1st to 15thDay
31%7%25%43435%5%27%
1650
16th to endDay
41%8%35%423336%17%
1667
November1st to 15thDay
52%8%35%42322212%
1408
16th to endDay
42%8%35%42333417%
1440
December1st to 15thDay
36%13%45%32332222%
1368
16th to endDay
46%11%35%42322214%
1344
January1st to 15thNight
43%9%2431223421%
2685
16th to endNight
36%11%35%422336%20%
2743
February1st to 15thNight
38%9%35%423445%18%
2276
16th to endNight
30%11%26%42334426%
2043
March1st to 15thNight
43%10%3442332416%
2061
16th to endNight
37%10%36%6%25%33416%
2073
April1st to 15thNight
28%10%46%6%33446%22%
1796
16th to endNight
26%10%46%6%33436%24%
1583
May1st to 15thNight
19%5%26%43446%5%37%
1439
16th to endNight
17%8%35%6%35%45%7%32%
1460
June1st to 15thNight
23%7%245%25%345%34%
1260
16th to endNight
17%6%37%5%36%45%7%32%
1260
July1st to 15thNight
8%313423336%57%
1260
16th to endNight
8%223213346%60%
1419
August1st to 15thNight
8%31322325%461%
1509
16th to endNight
9%5%1341345%8%50%
1758
September1st to 15thNight
9%214323345%59%
1800
16th to endNight
26%7%25%423345%35%
1848
October1st to 15thNight
26%6%2442344435%
1980
16th to endNight
39%7%35%42335%420%
2201
November1st to 15thNight
48%7%26%42223315%
2450
16th to endNight
38%9%36%42432320%
2520
December1st to 15thNight
38%10%36%42332420%
2589
16th to endNight
45%13%25%32222316%
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
73%46%9%5%
1253
16th to endDay
68%5%9%12%21
1478
February1st to 15thDay
71%410%6%32
1576
16th to endDay
63%5%12%13%6%
1430
March1st to 15thDay
77%39%7%1
1898
16th to endDay
74%48%11%1
2151
April1st to 15thDay
69%6%11%11%1
2149
16th to endDay
64%6%12%12%4
2376
May1st to 15thDay
54%5%15%17%6%
2511
16th to endDay
58%6%17%15%2
2652
June1st to 15thDay
58%417%13%41
2700
16th to endDay
56%417%14%5%
2700
July1st to 15thDay
35%417%25%12%3
2541
16th to endDay
31%5%20%28%12%1
2577
August1st to 15thDay
33%6%18%29%10%1
2431
16th to endDay
36%5%21%27%7%1
2444
September1st to 15thDay
37%415%22%16%2
2160
16th to endDay
57%411%17%7%1
1854
October1st to 15thDay
58%414%14%7%
1650
16th to endDay
69%412%10%3
1667
November1st to 15thDay
78%36%7%11
1408
16th to endDay
70%47%9%7%
1440
December1st to 15thDay
69%46%11%7%1
1368
16th to endDay
76%36%8%21
1344
January1st to 15thNight
68%46%14%5%
2686
16th to endNight
65%410%13%32
2743
February1st to 15thNight
67%5%12%8%32
2288
16th to endNight
58%411%16%6%1
2043
March1st to 15thNight
72%410%10%2
2061
16th to endNight
70%412%10%2
2073
April1st to 15thNight
62%413%16%3
1796
16th to endNight
61%413%14%4
1583
May1st to 15thNight
45%5%18%19%9%1
1440
16th to endNight
50%423%17%4
1460
June1st to 15thNight
51%322%14%42
1260
16th to endNight
49%6%18%17%6%2
1260
July1st to 15thNight
28%5%18%29%15%3
1190
16th to endNight
21%5%21%33%14%3
1327
August1st to 15thNight
24%324%30%12%3
1501
16th to endNight
29%6%23%26%10%3
1758
September1st to 15thNight
26%418%25%20%4
1800
16th to endNight
50%413%22%7%2
1848
October1st to 15thNight
51%315%19%9%
1980
16th to endNight
65%5%13%11%3
2201
November1st to 15thNight
75%38%7%22
2450
16th to endNight
68%310%9%7%
2520
December1st to 15thNight
69%48%10%5%1
2589
16th to endNight
74%37%8%5%1
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
25%16%26%20%20%
60
16th to endDay
57%6%211%19%1
76
February1st to 15thDay
42%15%7%17%15%1
236
16th to endDay
30%17%15%18%14%3
213
March1st to 15thDay
48%15%18%13%4
270
16th to endDay
38%15%18%17%9%1
288
April1st to 15thDay
32%15%16%18%13%3
269
16th to endDay
27%17%17%24%11%1
270
May1st to 15thDay
23%13%19%28%13%2
288
16th to endDay
19%15%15%23%17%7%
363
June1st to 15thDay
19%16%17%29%12%3
495
16th to endDay
17%17%20%26%16%2
495
July1st to 15thDay
12%12%12%36%24%2
475
16th to endDay
8%13%13%34%25%4
417
August1st to 15thDay
14%7%10%32%25%9%
315
16th to endDay
13%6%17%32%23%7%
332
September1st to 15thDay
18%7%19%27%22%5%
315
16th to endDay
26%10%14%24%19%5%
268
October1st to 15thDay
37%8%15%20%14%2
255
16th to endDay
42%8%10%22%12%4
197
November1st to 15thDay
63%8%8%16%3
60
16th to endDay
50%5%18%8%18%
60
December1st to 15thDay
56%311%13%13%1
60
16th to endDay
43%49%25%10%6%
64
January1st to 15thNight
39%18%9%16%13%2
750
16th to endNight
35%18%8%21%12%3
779
February1st to 15thNight
36%18%10%20%12%1
704
16th to endNight
30%19%11%23%13%2
632
March1st to 15thNight
40%20%10%16%10%1
720
16th to endNight
36%19%9%19%11%3
768
April1st to 15thNight
27%20%10%22%17%3
716
16th to endNight
26%20%8%29%12%3
503
May1st to 15thNight
19%17%5%26%26%4
360
16th to endNight
16%18%324%32%3
375
June1st to 15thNight
18%18%6%24%26%5%
360
16th to endNight
16%18%8%25%27%3
360
July1st to 15thNight
8%12%426%40%6%
340
16th to endNight
6%17%122%41%10%
376
August1st to 15thNight
10%10%119%43%15%
429
16th to endNight
12%10%5%20%41%9%
612
September1st to 15thNight
10%9%327%35%13%
720
16th to endNight
26%11%6%23%24%6%
671
October1st to 15thNight
29%10%12%23%20%2
660
16th to endNight
39%11%7%23%14%2
704
November1st to 15thNight
44%17%10%21%6%
700
16th to endNight
36%21%10%17%11%2
720
December1st to 15thNight
39%19%9%21%10%
731
16th to endNight
44%19%10%17%7%
800
Page generated at 2017-09-20 01:49:53. Version ac04

Copyright 2017 A. Danko


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