Smithers
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Smithers 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
36%
14415
6%
46110
4%
14387
39%
14387
12%
35913

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
20%
750
5%
2686
3%
746
24%
746
6%
2331
January16th to endNight
23%
800
7%
2880
5%
800
28%
800
7%
2414
February1st to 15thNight
30%
724
7%
2437
4%
724
34%
724
10%
1974
February16th to endNight
43%
632
11%
2053
10%
632
45%
632
15%
1521
March1st to 15thNight
31%
720
9%
2103
5%
720
35%
720
13%
1649
March16th to endNight
39%
768
7%
2112
4%
768
41%
768
14%
1674
April1st to 15thNight
39%
545
7%
1650
5%
545
41%
545
14%
1276
April16th to endNight
38%
510
7%
1590
5%
510
41%
510
13%
1234
May1st to 15thNight
43%
359
3%
1283
2%
359
44%
359
14%
927
May16th to endNight
44%
374
0%
1309
0%
374
44%
374
14%
952
June1st to 15thNight
53%
360
0%
1103
0%
360
53%
360
21%
774
June16th to endNight
47%
360
0%
919
0%
360
47%
360
21%
690
July1st to 15thNight
51%
340
0%
1111
0%
340
51%
340
21%
739
July16th to endNight
56%
376
1%
1239
0%
354
57%
354
23%
778
August1st to 15thNight
64%
411
8%
1298
7%
409
66%
409
34%
737
August16th to endNight
47%
525
8%
1575
7%
525
49%
525
19%
1138
September1st to 15thNight
52%
575
10%
1603
7%
575
53%
575
23%
1124
September16th to endNight
38%
656
9%
1815
5%
656
41%
656
14%
1435
October1st to 15thNight
41%
660
7%
1981
6%
660
43%
660
13%
1548
October16th to endNight
28%
704
4%
2337
3%
704
30%
704
8%
1954
November1st to 15thNight
29%
706
7%
2486
5%
706
33%
706
9%
1986
November16th to endNight
26%
750
6%
2700
5%
750
29%
750
8%
2232
December1st to 15thNight
29%
893
7%
2843
4%
893
31%
893
10%
2329
December16th to endNight
25%
917
7%
2997
4%
917
28%
917
8%
2497

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
11%11%5%9%8%46%5%5%6%22%
47904
Night
9%12%5%9%8%46%6%6%7%22%
46252
TransparencyDay
59%9%13%14%3
47550
Night
57%9%14%14%3
46110
SeeingDay
18%14%27%25%11%2
6787
Night
16%8%24%31%16%2
14421

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
7%18%8%13%11%48%6%5%411%
1253
16th to endDay
9%15%7%12%8%5%7%6%8%6%11%
1344
February1st to 15thDay
10%14%7%11%8%47%6%5%6%17%
1427
16th to endDay
412%7%9%9%48%5%6%6%25%
1421
March1st to 15thDay
7%15%7%12%11%46%5%5%6%17%
1857
16th to endDay
6%13%6%11%9%5%7%6%7%6%17%
2112
April1st to 15thDay
9%17%7%11%9%45%5%45%18%
2297
16th to endDay
12%16%6%9%10%5%7%5%5%5%15%
2370
May1st to 15thDay
13%13%5%10%8%45%45%5%21%
2667
16th to endDay
16%11%5%9%9%45%5%46%21%
2804
June1st to 15thDay
12%9%410%7%46%5%5%6%27%
2853
16th to endDay
16%9%5%8%7%45%5%5%6%24%
3038
July1st to 15thDay
10%7%49%8%46%5%5%6%31%
2778
16th to endDay
9%6%37%8%36%5%6%8%32%
2846
August1st to 15thDay
8%426%6%45%6%6%7%41%
2567
16th to endDay
14%9%49%9%35%5%5%6%25%
2275
September1st to 15thDay
11%8%48%8%45%5%7%8%26%
2025
16th to endDay
17%11%49%7%47%6%5%6%20%
1815
October1st to 15thDay
16%14%38%8%36%45%7%20%
1648
16th to endDay
17%14%5%8%6%48%5%5%6%16%
1535
November1st to 15thDay
11%13%5%10%9%5%6%6%7%6%17%
1372
16th to endDay
8%15%6%11%10%5%8%7%5%6%14%
1260
December1st to 15thDay
7%12%6%14%12%46%7%45%18%
1104
16th to endDay
6%16%9%11%9%6%6%5%5%7%13%
1236
January1st to 15thNight
8%19%9%14%10%46%435%12%
2686
16th to endNight
11%16%5%11%9%5%6%6%6%7%12%
2880
February1st to 15thNight
11%16%6%11%8%4446%6%19%
2425
16th to endNight
5%12%6%9%8%47%6%6%7%25%
2053
March1st to 15thNight
6%12%8%9%7%6%7%6%6%7%21%
2103
16th to endNight
6%13%6%9%8%5%7%8%6%8%20%
2108
April1st to 15thNight
9%13%410%8%46%6%6%7%23%
1650
16th to endNight
7%14%6%9%7%47%5%5%8%22%
1590
May1st to 15thNight
11%9%5%9%6%45%5%5%7%28%
1282
16th to endNight
15%10%36%5%36%5%7%8%27%
1309
June1st to 15thNight
6%7%46%7%46%7%7%9%32%
1103
16th to endNight
12%7%46%5%36%7%6%8%31%
919
July1st to 15thNight
9%5%25%7%36%6%6%9%38%
1179
16th to endNight
5%4246%46%6%7%9%41%
1323
August1st to 15thNight
6%2135%245%5%7%53%
1305
16th to endNight
10%6%38%8%35%46%8%32%
1575
September1st to 15thNight
9%6%37%7%35%5%5%7%37%
1603
16th to endNight
12%9%49%7%46%8%6%5%25%
1815
October1st to 15thNight
16%11%48%6%35%5%5%6%26%
1981
16th to endNight
16%16%5%9%7%36%5%6%6%15%
2337
November1st to 15thNight
12%13%48%8%5%6%7%7%8%17%
2486
16th to endNight
7%16%7%12%9%6%6%5%5%7%15%
2700
December1st to 15thNight
9%13%7%10%11%46%5%6%6%17%
2843
16th to endNight
6%15%9%14%10%5%6%6%6%6%13%
2997

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%10%9%7%
1253
16th to endDay
66%8%10%9%31
1344
February1st to 15thDay
62%10%9%10%6%
1427
16th to endDay
55%9%13%14%6%
1421
March1st to 15thDay
64%8%10%12%2
1857
16th to endDay
61%9%14%11%2
2112
April1st to 15thDay
66%8%9%13%1
2297
16th to endDay
68%7%10%9%3
2370
May1st to 15thDay
63%6%10%14%4
2667
16th to endDay
62%7%14%13%1
2808
June1st to 15thDay
56%7%15%14%5%
2853
16th to endDay
57%9%14%15%2
3038
July1st to 15thDay
50%9%15%20%4
2617
16th to endDay
45%10%22%20%1
2667
August1st to 15thDay
38%9%19%26%5%
2549
16th to endDay
56%11%16%13%2
2275
September1st to 15thDay
51%11%19%15%2
2025
16th to endDay
61%9%12%13%2
1815
October1st to 15thDay
61%10%15%10%1
1648
16th to endDay
65%10%11%10%1
1535
November1st to 15thDay
64%7%12%12%2
1372
16th to endDay
64%11%11%9%3
1260
December1st to 15thDay
65%9%8%13%3
1104
16th to endDay
65%11%8%12%2
1236
January1st to 15thNight
73%7%9%8%1
2686
16th to endNight
67%9%9%8%5%
2880
February1st to 15thNight
64%7%9%11%7%
2437
16th to endNight
54%8%14%16%6%
2053
March1st to 15thNight
58%9%13%15%21
2103
16th to endNight
58%9%14%15%2
2112
April1st to 15thNight
56%9%14%16%3
1650
16th to endNight
58%8%14%15%3
1590
May1st to 15thNight
53%8%17%15%4
1283
16th to endNight
53%8%19%16%2
1309
June1st to 15thNight
44%10%19%20%4
1103
16th to endNight
48%10%17%20%3
919
July1st to 15thNight
40%11%19%23%4
1111
16th to endNight
34%12%28%21%2
1239
August1st to 15thNight
27%9%27%29%6%
1298
16th to endNight
46%11%20%20%1
1575
September1st to 15thNight
42%11%24%18%3
1603
16th to endNight
55%11%13%16%2
1815
October1st to 15thNight
55%11%15%14%2
1981
16th to endNight
64%11%13%10%
2337
November1st to 15thNight
59%11%13%12%2
2486
16th to endNight
65%9%9%11%3
2700
December1st to 15thNight
63%9%11%11%3
2843
16th to endNight
67%8%10%10%3
2997

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
8%126%28%28%6%
60
16th to endDay
23%14%18%23%14%6%
64
February1st to 15thDay
23%7%26%27%11%1
230
16th to endDay
13%11%30%30%10%3
211
March1st to 15thDay
20%23%34%15%6%
252
16th to endDay
17%16%29%26%9%1
288
April1st to 15thDay
21%14%33%17%9%2
269
16th to endDay
25%24%22%18%7%1
270
May1st to 15thDay
24%17%24%24%8%1
444
16th to endDay
19%16%24%28%8%2
518
June1st to 15thDay
15%12%32%25%13%
612
16th to endDay
18%10%26%27%14%3
653
July1st to 15thDay
15%16%30%25%10%1
475
16th to endDay
12%12%33%27%12%2
515
August1st to 15thDay
8%9%23%34%17%5%
461
16th to endDay
23%13%32%23%5%1
268
September1st to 15thDay
19%17%27%21%12%1
255
16th to endDay
26%12%28%20%11%1
255
October1st to 15thDay
30%14%25%15%11%2
252
16th to endDay
28%13%20%25%9%2
191
November1st to 15thDay
18%11%18%31%11%8%
60
16th to endDay
11%5%13%33%25%11%
60
December1st to 15thDay
13%323%28%25%6%
60
16th to endDay
7%6%17%32%26%9%
64
January1st to 15thNight
17%10%27%30%12%1
750
16th to endNight
21%9%28%29%10%1
800
February1st to 15thNight
18%9%26%28%15%1
728
16th to endNight
11%7%21%38%17%3
632
March1st to 15thNight
13%14%30%27%12%1
720
16th to endNight
12%10%23%29%20%4
768
April1st to 15thNight
15%8%21%27%22%3
545
16th to endNight
14%9%27%26%20%1
510
May1st to 15thNight
15%7%21%34%19%1
360
16th to endNight
19%7%20%30%20%1
375
June1st to 15thNight
8%5%21%43%20%1
360
16th to endNight
15%6%22%37%17%1
360
July1st to 15thNight
12%5%22%40%17%1
340
16th to endNight
7%423%43%18%2
376
August1st to 15thNight
9%314%32%37%2
411
16th to endNight
14%422%39%18%
525
September1st to 15thNight
12%9%18%34%21%3
575
16th to endNight
17%8%24%30%16%2
656
October1st to 15thNight
24%9%16%31%15%3
660
16th to endNight
26%8%20%29%12%2
704
November1st to 15thNight
19%10%30%26%11%1
706
16th to endNight
17%9%30%28%12%1
750
December1st to 15thNight
15%9%28%30%12%2
893
16th to endNight
14%8%28%31%14%2
917
Page generated at 2017-08-13 11:16:35. Version ac04

Copyright 2017 A. Danko


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