100 Mile House
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the 100 Mile House 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
37%
15079
10%
47668
7%
15051
40%
15051
16%
34180

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
23%
749
6%
2686
4%
746
26%
746
7%
2184
January16th to endNight
33%
784
9%
2784
8%
784
37%
784
12%
2039
February1st to 15thNight
29%
698
8%
2369
6%
697
33%
697
12%
1799
February16th to endNight
40%
632
14%
2023
12%
632
45%
632
20%
1369
March1st to 15thNight
27%
720
11%
2121
5%
720
33%
720
14%
1577
March16th to endNight
33%
768
12%
2031
6%
768
37%
768
18%
1505
April1st to 15thNight
38%
719
10%
1799
4%
719
41%
719
19%
1358
April16th to endNight
38%
441
12%
1521
11%
441
42%
441
15%
1100
May1st to 15thNight
37%
359
10%
1440
12%
359
41%
359
14%
979
May16th to endNight
42%
374
4%
1391
2%
374
43%
374
15%
999
June1st to 15thNight
41%
360
0%
1080
0%
360
41%
360
16%
805
June16th to endNight
43%
360
0%
1080
0%
360
43%
360
18%
789
July1st to 15thNight
52%
340
1%
1130
0%
340
52%
340
25%
705
July16th to endNight
57%
376
8%
1302
8%
354
60%
354
25%
754
August1st to 15thNight
68%
360
15%
1432
23%
358
70%
358
28%
752
August16th to endNight
58%
589
18%
1735
16%
589
60%
589
31%
1030
September1st to 15thNight
58%
720
18%
1800
10%
720
59%
720
37%
1127
September16th to endNight
46%
716
19%
1961
11%
716
51%
716
26%
1302
October1st to 15thNight
42%
720
13%
2160
10%
720
45%
720
23%
1428
October16th to endNight
31%
768
12%
2467
7%
768
38%
768
16%
1737
November1st to 15thNight
26%
760
9%
2660
6%
760
31%
760
11%
1993
November16th to endNight
28%
854
8%
2804
5%
854
33%
854
11%
2159
December1st to 15thNight
30%
920
8%
2820
5%
920
34%
920
11%
2226
December16th to endNight
22%
992
7%
3072
3%
992
25%
992
10%
2464

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
10%10%48%7%46%5%6%7%29%
48767
Night
9%11%49%7%46%5%6%7%27%
47818
TransparencyDay
52%315%19%7%
48421
Night
53%414%19%6%
47668
SeeingDay
16%12%24%25%16%4
6720
Night
17%10%23%28%17%3
15088

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
9%15%7%11%8%5%6%6%7%7%15%
1253
16th to endDay
7%13%6%11%9%45%5%5%5%23%
1439
February1st to 15thDay
8%17%7%9%7%45%436%24%
1492
16th to endDay
5%12%6%10%7%36%5%7%6%26%
1451
March1st to 15thDay
5%13%7%10%9%5%7%5%6%6%20%
1839
16th to endDay
5%12%6%10%9%5%5%7%7%7%23%
2193
April1st to 15thDay
8%15%5%9%8%5%6%6%5%7%20%
2149
16th to endDay
9%12%5%10%9%5%7%6%6%5%20%
2437
May1st to 15thDay
10%10%49%7%35%45%6%28%
2511
16th to endDay
15%10%48%8%45%6%5%7%23%
2719
June1st to 15thDay
17%9%48%7%46%5%5%6%24%
2880
16th to endDay
12%8%48%8%46%5%6%7%26%
2880
July1st to 15thDay
8%5%36%6%445%6%7%40%
2758
16th to endDay
8%4245%35%5%6%7%46%
2776
August1st to 15thDay
5%425%5%35%6%5%8%46%
2520
16th to endDay
9%426%5%46%46%8%40%
2463
September1st to 15thDay
9%5%25%42435%6%48%
2160
16th to endDay
15%7%35%5%45%45%7%34%
1997
October1st to 15thDay
12%10%26%6%2445%6%36%
1800
16th to endDay
15%12%47%6%35%45%6%29%
1756
November1st to 15thDay
12%15%5%9%7%46%6%5%6%21%
1528
16th to endDay
8%13%7%10%8%5%6%5%5%7%19%
1468
December1st to 15thDay
9%14%6%10%6%5%7%6%5%7%20%
1137
16th to endDay
7%16%7%9%9%47%5%5%6%20%
1161
January1st to 15thNight
10%16%6%13%10%46%5%5%5%14%
2686
16th to endNight
9%11%6%10%8%45%5%7%9%21%
2784
February1st to 15thNight
9%16%7%11%7%45%45%5%23%
2357
16th to endNight
6%11%48%8%45%5%5%7%33%
2023
March1st to 15thNight
6%13%6%9%7%45%5%6%6%24%
2121
16th to endNight
410%49%9%47%7%7%7%25%
2027
April1st to 15thNight
412%5%10%8%46%5%6%7%27%
1799
16th to endNight
7%13%47%8%6%7%5%7%7%24%
1521
May1st to 15thNight
9%11%5%9%8%35%5%5%7%28%
1439
16th to endNight
14%10%37%7%5%8%6%7%9%20%
1391
June1st to 15thNight
17%9%45%7%6%6%6%6%6%23%
1080
16th to endNight
12%7%38%8%5%6%5%5%6%28%
1080
July1st to 15thNight
7%6%36%5%36%5%8%9%38%
1200
16th to endNight
7%426%5%46%7%7%9%37%
1391
August1st to 15thNight
45%35%5%345%7%7%46%
1440
16th to endNight
7%425%5%36%5%7%8%41%
1735
September1st to 15thNight
8%5%26%42445%6%49%
1800
16th to endNight
12%7%35%5%35%5%5%7%39%
1961
October1st to 15thNight
11%8%37%6%3445%7%36%
2160
16th to endNight
13%11%37%6%35%6%5%6%29%
2467
November1st to 15thNight
12%13%410%7%36%6%5%7%23%
2660
16th to endNight
8%14%6%10%8%5%5%5%5%6%22%
2804
December1st to 15thNight
10%15%6%10%7%46%5%5%6%21%
2820
16th to endNight
7%16%7%12%9%5%6%45%7%19%
3072

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
65%6%17%8%3
1253
16th to endDay
60%416%13%4
1439
February1st to 15thDay
61%416%12%5%
1492
16th to endDay
54%416%15%8%
1451
March1st to 15thDay
60%414%13%6%
1839
16th to endDay
56%415%18%4
2193
April1st to 15thDay
61%410%16%6%
2149
16th to endDay
62%311%15%6%
2437
May1st to 15thDay
54%211%18%12%
2511
16th to endDay
59%214%18%4
2723
June1st to 15thDay
58%310%17%8%1
2880
16th to endDay
54%314%18%7%
2880
July1st to 15thDay
41%314%24%14%2
2599
16th to endDay
34%317%31%11%
2602
August1st to 15thDay
34%318%31%10%
2503
16th to endDay
40%319%26%9%1
2463
September1st to 15thDay
35%317%30%11%1
2160
16th to endDay
49%314%22%9%1
1997
October1st to 15thDay
47%320%23%4
1800
16th to endDay
55%419%18%3
1756
November1st to 15thDay
61%413%15%5%
1528
16th to endDay
63%5%12%14%4
1468
December1st to 15thDay
62%7%15%13%2
1137
16th to endDay
63%5%14%12%3
1161
January1st to 15thNight
69%412%9%3
2686
16th to endNight
57%5%17%14%31
2784
February1st to 15thNight
61%413%14%5%
2369
16th to endNight
48%318%20%9%
2023
March1st to 15thNight
56%414%17%6%
2121
16th to endNight
53%417%20%3
2031
April1st to 15thNight
54%412%21%6%
1799
16th to endNight
56%411%19%7%
1521
May1st to 15thNight
55%210%20%11%
1440
16th to endNight
56%318%15%5%
1391
June1st to 15thNight
56%5%10%20%6%
1080
16th to endNight
53%5%15%17%7%1
1080
July1st to 15thNight
40%6%13%22%15%3
1130
16th to endNight
38%416%28%11%
1302
August1st to 15thNight
32%417%31%12%1
1432
16th to endNight
36%419%28%9%2
1735
September1st to 15thNight
34%313%31%14%2
1800
16th to endNight
42%414%23%11%2
1961
October1st to 15thNight
46%316%26%7%
2160
16th to endNight
53%418%20%2
2467
November1st to 15thNight
59%5%14%14%5%
2660
16th to endNight
61%5%14%14%4
2804
December1st to 15thNight
62%5%14%14%2
2820
16th to endNight
65%6%12%13%2
3072

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%6%23%23%20%13%
60
16th to endDay
20%21%26%15%12%3
64
February1st to 15thDay
15%19%30%26%7%1
152
16th to endDay
14%14%24%27%15%4
217
March1st to 15thDay
20%26%28%15%7%1
270
16th to endDay
20%21%35%18%31
288
April1st to 15thDay
18%17%26%23%11%2
269
16th to endDay
21%19%27%21%8%1
270
May1st to 15thDay
17%15%27%22%13%4
288
16th to endDay
20%10%17%26%21%4
434
June1st to 15thDay
20%8%23%27%17%3
675
16th to endDay
17%9%20%29%18%4
675
July1st to 15thDay
12%6%24%30%21%4
533
16th to endDay
11%7%21%33%19%5%
445
August1st to 15thDay
7%5%17%33%25%9%
315
16th to endDay
9%9%26%28%19%5%
332
September1st to 15thDay
13%10%25%28%16%6%
315
16th to endDay
19%12%22%23%18%4
315
October1st to 15thDay
22%14%23%21%13%5%
315
16th to endDay
24%12%22%19%17%3
185
November1st to 15thDay
22%28%24%12%8%3
90
16th to endDay
19%16%22%17%15%7%
89
December1st to 15thDay
18%5%28%21%8%18%
60
16th to endDay
18%9%23%23%15%9%
64
January1st to 15thNight
23%11%22%26%13%2
750
16th to endNight
17%11%26%28%13%2
784
February1st to 15thNight
19%10%24%29%13%2
704
16th to endNight
13%8%25%34%16%2
632
March1st to 15thNight
18%15%28%24%10%2
720
16th to endNight
10%19%25%26%15%1
768
April1st to 15thNight
13%10%23%28%20%3
719
16th to endNight
14%9%29%29%14%2
441
May1st to 15thNight
16%9%25%29%18%2
360
16th to endNight
20%7%15%29%23%4
375
June1st to 15thNight
21%5%19%32%19%1
360
16th to endNight
15%7%21%32%20%2
360
July1st to 15thNight
10%421%31%28%2
340
16th to endNight
10%316%33%30%5%
376
August1st to 15thNight
6%310%32%37%8%
360
16th to endNight
11%317%33%30%4
589
September1st to 15thNight
10%416%31%28%7%
720
16th to endNight
17%8%20%28%21%4
716
October1st to 15thNight
17%9%20%30%18%3
720
16th to endNight
21%13%25%23%13%2
768
November1st to 15thNight
23%18%23%23%8%2
760
16th to endNight
22%12%25%26%10%2
854
December1st to 15thNight
19%11%23%30%13%1
920
16th to endNight
19%14%29%25%9%
992
Page generated at 2017-12-01 09:13:33. Version ac04

Copyright 2017 A. Danko


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