Dease Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dease Lake clear sky chart from 2005-11-05 to 2017-11-30.

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
40%
15001
5%
47622
4%
14970
41%
14970
11%
38164

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
30%
828
3%
2942
3%
823
31%
823
6%
2534
January16th to endNight
31%
800
8%
3026
7%
800
34%
800
8%
2458
February1st to 15thNight
36%
731
7%
2496
6%
729
38%
729
11%
1951
February16th to endNight
50%
644
10%
2110
9%
644
51%
644
15%
1572
March1st to 15thNight
35%
720
10%
2154
7%
720
38%
720
13%
1707
March16th to endNight
46%
692
8%
2036
7%
692
47%
692
14%
1584
April1st to 15thNight
44%
539
7%
1673
5%
539
46%
539
11%
1357
April16th to endNight
45%
498
2%
1461
2%
498
46%
498
12%
1182
May1st to 15thNight
49%
359
0%
1260
0%
359
49%
359
12%
969
May16th to endNight
59%
374
0%
1069
0%
374
59%
374
20%
774
June1st to 15thNight
46%
360
0%
900
0%
360
46%
360
17%
691
June16th to endNight
44%
360
0%
900
0%
360
44%
360
14%
723
July1st to 15thNight
51%
340
0%
882
0%
340
51%
340
19%
677
July16th to endNight
45%
376
0%
1074
0%
354
46%
354
12%
854
August1st to 15thNight
59%
402
1%
1295
1%
400
60%
400
20%
897
August16th to endNight
38%
573
3%
1622
2%
573
39%
573
10%
1368
September1st to 15thNight
39%
558
5%
1722
3%
558
40%
558
10%
1409
September16th to endNight
31%
716
7%
1980
4%
716
33%
716
11%
1623
October1st to 15thNight
36%
720
7%
2223
5%
720
39%
720
12%
1752
October16th to endNight
37%
768
6%
2551
5%
768
38%
768
10%
2029
November1st to 15thNight
33%
805
5%
2851
5%
805
35%
805
8%
2333
November16th to endNight
34%
916
6%
3071
7%
916
35%
916
8%
2527
December1st to 15thNight
37%
930
5%
3060
4%
930
38%
930
8%
2557
December16th to endNight
42%
992
6%
3264
6%
992
42%
992
10%
2636

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%12%6%10%8%46%6%6%6%20%
48852
Night
7%12%5%10%9%5%7%6%7%7%19%
47737
TransparencyDay
62%10%13%11%2
48472
Night
59%10%13%12%3
47622
SeeingDay
18%11%25%23%16%4
7643
Night
13%8%21%30%21%4
15006

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
6%14%9%15%11%5%8%7%7%6%7%
1006
16th to endDay
5%14%6%10%12%5%8%6%8%7%13%
1197
February1st to 15thDay
5%8%5%10%9%6%10%9%8%7%17%
1368
16th to endDay
111%9%11%8%48%8%8%6%22%
1361
March1st to 15thDay
211%6%11%11%7%8%6%7%6%18%
1806
16th to endDay
210%8%12%10%47%6%6%8%22%
2187
April1st to 15thDay
413%10%12%9%5%6%5%6%6%17%
2274
16th to endDay
5%16%8%12%10%47%6%6%6%15%
2499
May1st to 15thDay
9%18%7%10%7%36%5%4322%
2691
16th to endDay
15%10%5%7%6%35%5%6%7%26%
3044
June1st to 15thDay
15%10%48%7%36%5%6%7%22%
3060
16th to endDay
15%10%5%11%9%5%6%5%6%6%18%
3060
July1st to 15thDay
16%9%5%8%8%45%6%7%7%22%
3024
16th to endDay
20%8%48%8%46%5%5%7%20%
3022
August1st to 15thDay
13%6%36%7%46%5%6%7%30%
2655
16th to endDay
19%13%49%8%5%6%6%45%15%
2580
September1st to 15thDay
18%9%49%8%45%45%6%23%
2235
16th to endDay
16%13%5%9%8%5%6%6%5%5%18%
1980
October1st to 15thDay
8%12%48%8%45%6%6%7%26%
1737
16th to endDay
8%15%5%10%8%6%8%6%6%6%16%
1670
November1st to 15thDay
5%15%7%10%8%5%9%6%8%6%16%
1337
16th to endDay
214%9%13%9%5%9%6%6%6%15%
1199
December1st to 15thDay
6%13%7%13%12%6%8%7%7%8%10%
900
16th to endDay
212%6%13%11%7%10%7%6%7%12%
960
January1st to 15thNight
6%13%6%13%12%6%8%8%8%7%8%
2942
16th to endNight
5%13%8%12%10%5%8%6%7%7%15%
3026
February1st to 15thNight
5%11%6%10%10%5%9%7%7%7%18%
2484
16th to endNight
210%6%12%8%5%8%5%6%6%26%
2110
March1st to 15thNight
212%6%10%10%6%8%6%6%8%20%
2154
16th to endNight
210%6%12%8%5%8%7%6%7%23%
2032
April1st to 15thNight
412%8%9%9%5%7%6%7%7%22%
1673
16th to endNight
5%10%5%8%10%6%9%5%7%7%22%
1461
May1st to 15thNight
6%13%5%7%7%37%6%8%6%27%
1259
16th to endNight
8%8%36%5%35%7%8%10%31%
1069
June1st to 15thNight
10%8%48%6%37%7%8%10%26%
900
16th to endNight
15%6%39%9%47%8%5%8%21%
900
July1st to 15thNight
10%6%48%8%5%7%5%7%8%28%
934
16th to endNight
15%7%27%8%5%8%7%6%8%21%
1147
August1st to 15thNight
10%7%36%6%25%48%10%34%
1302
16th to endNight
18%9%48%9%5%5%5%6%6%20%
1622
September1st to 15thNight
17%11%49%7%46%5%5%6%21%
1722
16th to endNight
14%13%5%8%7%5%6%45%5%23%
1980
October1st to 15thNight
10%13%38%8%45%6%5%7%25%
2223
16th to endNight
7%13%5%9%9%5%7%7%5%7%20%
2551
November1st to 15thNight
414%7%13%9%6%7%7%6%7%15%
2851
16th to endNight
313%6%12%11%6%8%6%6%7%14%
3071
December1st to 15thNight
7%15%6%11%10%6%8%7%6%8%10%
3060
16th to endNight
210%6%12%11%6%9%8%8%8%14%
3264

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%11%8%5%1
1006
16th to endDay
61%9%14%9%31
1197
February1st to 15thDay
57%11%11%12%6%
1368
16th to endDay
57%7%14%12%7%
1361
March1st to 15thDay
62%8%10%13%41
1806
16th to endDay
58%10%15%11%4
2187
April1st to 15thDay
65%8%13%10%1
2274
16th to endDay
67%9%12%9%1
2499
May1st to 15thDay
64%8%10%12%4
2691
16th to endDay
56%9%14%16%3
3048
June1st to 15thDay
60%9%13%13%2
3060
16th to endDay
66%10%12%9%2
3060
July1st to 15thDay
59%12%15%12%
2848
16th to endDay
61%13%15%9%
2832
August1st to 15thDay
51%12%16%16%2
2637
16th to endDay
70%11%11%6%
2580
September1st to 15thDay
61%10%11%13%2
2235
16th to endDay
67%11%9%11%
1980
October1st to 15thDay
56%12%15%13%1
1737
16th to endDay
63%11%12%11%1
1670
November1st to 15thDay
63%11%13%9%2
1337
16th to endDay
66%9%10%8%4
1199
December1st to 15thDay
66%11%9%11%1
900
16th to endDay
63%11%11%8%21
960
January1st to 15thNight
68%11%10%6%2
2942
16th to endNight
64%9%9%11%21
3026
February1st to 15thNight
58%9%9%13%7%
2496
16th to endNight
55%7%17%11%7%
2110
March1st to 15thNight
61%6%12%11%6%1
2154
16th to endNight
55%10%13%14%5%
2036
April1st to 15thNight
59%11%9%15%2
1673
16th to endNight
58%11%16%12%1
1461
May1st to 15thNight
54%12%12%14%4
1260
16th to endNight
45%12%18%19%4
1069
June1st to 15thNight
50%12%15%17%3
900
16th to endNight
58%9%15%14%1
900
July1st to 15thNight
50%11%20%16%1
882
16th to endNight
56%13%18%11%
1074
August1st to 15thNight
44%11%22%20%2
1295
16th to endNight
64%11%15%8%1
1622
September1st to 15thNight
63%9%10%12%3
1722
16th to endNight
61%10%13%12%1
1980
October1st to 15thNight
56%11%14%14%2
2223
16th to endNight
59%10%15%12%1
2551
November1st to 15thNight
62%11%12%11%2
2851
16th to endNight
64%10%11%9%2
3071
December1st to 15thNight
65%10%11%9%2
3060
16th to endNight
60%11%13%10%31
3264

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%320%25%28%13%
60
16th to endDay
9%14%14%28%23%10%
64
February1st to 15thDay
10%11%28%28%14%6%
203
16th to endDay
7%6%27%34%16%7%
211
March1st to 15thDay
6%18%38%22%11%2
242
16th to endDay
6%12%27%28%21%2
288
April1st to 15thDay
14%13%27%27%13%4
269
16th to endDay
16%17%30%20%13%1
387
May1st to 15thDay
20%17%28%19%12%1
468
16th to endDay
18%11%20%25%15%7%
599
June1st to 15thDay
22%7%21%24%19%4
675
16th to endDay
17%9%23%22%20%5%
675
July1st to 15thDay
20%9%20%25%19%3
612
16th to endDay
25%8%25%21%16%2
515
August1st to 15thDay
16%10%21%22%20%8%
494
16th to endDay
27%16%25%19%8%2
429
September1st to 15thDay
26%12%27%16%13%4
315
16th to endDay
29%15%25%18%7%3
315
October1st to 15thDay
15%16%25%26%13%1
286
16th to endDay
16%12%27%21%15%6%
233
November1st to 15thDay
7%12%28%25%22%3
90
16th to endDay
8%5%21%24%35%3
89
December1st to 15thDay
3328%23%23%18%
60
16th to endDay
7%110%37%28%14%
64
January1st to 15thNight
13%9%23%33%17%2
828
16th to endNight
12%11%26%31%16%2
800
February1st to 15thNight
10%9%29%28%19%3
734
16th to endNight
7%419%36%25%6%
644
March1st to 15thNight
8%13%28%31%13%4
720
16th to endNight
5%6%21%33%25%7%
692
April1st to 15thNight
8%7%19%31%26%7%
539
16th to endNight
7%7%23%31%25%4
498
May1st to 15thNight
12%9%16%31%24%5%
360
16th to endNight
11%414%28%34%7%
375
June1st to 15thNight
14%6%19%26%28%5%
360
16th to endNight
16%5%17%29%28%2
360
July1st to 15thNight
14%5%16%30%29%4
340
16th to endNight
15%419%26%28%4
376
August1st to 15thNight
12%414%23%35%8%
402
16th to endNight
23%6%19%23%22%4
573
September1st to 15thNight
27%8%15%23%20%3
558
16th to endNight
24%12%22%21%17%2
716
October1st to 15thNight
18%13%21%27%16%2
720
16th to endNight
18%10%21%28%16%4
768
November1st to 15thNight
12%9%26%29%17%4
805
16th to endNight
11%7%22%38%18%1
916
December1st to 15thNight
13%8%20%36%17%3
930
16th to endNight
7%8%20%35%22%6%
992
Page generated at 2017-12-01 09:13:34. Version ac04

Copyright 2017 A. Danko


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