Writing-on-Stone Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Writing-on-Stone Provincial Park clear sky chart from 2005-11-05 to 2018-01-12.

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
35%
15899
15%
48359
9%
15871
42%
15871
21%
31301

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
29%
954
12%
2852
6%
951
34%
951
17%
1999
January16th to endNight
27%
834
16%
2754
9%
834
35%
834
16%
1824
February1st to 15thNight
33%
700
12%
2303
9%
700
38%
700
16%
1553
February16th to endNight
30%
632
11%
2022
7%
632
36%
632
15%
1445
March1st to 15thNight
29%
720
10%
2055
5%
720
34%
720
19%
1415
March16th to endNight
26%
768
10%
2112
3%
768
31%
768
15%
1557
April1st to 15thNight
28%
585
14%
1728
6%
585
35%
585
19%
1163
April16th to endNight
31%
540
15%
1620
8%
540
38%
540
16%
1106
May1st to 15thNight
39%
539
14%
1512
10%
539
44%
539
24%
962
May16th to endNight
38%
391
10%
1326
8%
390
43%
390
15%
899
June1st to 15thNight
37%
360
6%
1260
4%
360
40%
360
23%
745
June16th to endNight
45%
360
8%
1260
5%
360
49%
360
25%
683
July1st to 15thNight
54%
340
10%
1190
6%
340
58%
340
34%
588
July16th to endNight
58%
376
21%
1261
19%
354
72%
354
41%
563
August1st to 15thNight
56%
510
18%
1583
15%
508
62%
508
34%
862
August16th to endNight
54%
573
26%
1719
17%
573
61%
573
37%
919
September1st to 15thNight
50%
600
21%
1814
15%
600
56%
600
33%
1018
September16th to endNight
50%
716
24%
1980
16%
716
56%
716
36%
1171
October1st to 15thNight
35%
720
18%
2136
9%
720
44%
720
22%
1396
October16th to endNight
38%
768
20%
2433
11%
768
48%
768
24%
1492
November1st to 15thNight
29%
923
16%
2633
7%
923
36%
923
21%
1769
November16th to endNight
26%
975
14%
2761
5%
975
33%
975
21%
1873
December1st to 15thNight
28%
975
12%
2925
7%
975
33%
975
16%
2069
December16th to endNight
26%
1040
14%
3120
5%
1040
34%
1040
15%
2230

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%7%35%5%3445%8%41%
49015
Night
8%8%36%5%3445%7%40%
48507
Cloud CoverDay
10%7%35%5%35%45%8%40%
49016
Night
8%8%36%5%3445%8%40%
48509
TransparencyDay
40%5%15%23%11%2
48668
Night
41%6%16%22%11%2
48359
SeeingDay
13%17%24%24%15%3
6336
Night
10%21%25%27%13%1
15906

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%13%5%7%6%3445%7%33%
1330
16th to endDay
5%12%5%9%6%45%5%7%8%30%
1482
February1st to 15thDay
8%11%47%7%46%46%7%31%
1559
16th to endDay
6%13%6%9%6%44447%30%
1450
March1st to 15thDay
5%9%48%6%35%45%9%36%
1904
16th to endDay
10%14%48%5%25%46%8%28%
2111
April1st to 15thDay
10%11%5%5%6%36%46%8%31%
2216
16th to endDay
15%9%36%5%24348%36%
2340
May1st to 15thDay
11%7%26%5%345%5%7%40%
2439
16th to endDay
23%8%35%434447%29%
2784
June1st to 15thDay
16%5%25%5%35%5%5%8%35%
2700
16th to endDay
11%414435%5%6%8%44%
2700
July1st to 15thDay
6%31333445%9%54%
2700
16th to endDay
5%21222446%8%60%
2822
August1st to 15thDay
8%31232345%10%53%
2367
16th to endDay
8%313324446%57%
2483
September1st to 15thDay
13%5%13322245%54%
2142
16th to endDay
12%414323337%52%
1980
October1st to 15thDay
12%9%37%5%24446%38%
1824
16th to endDay
8%8%36%5%25%5%6%7%40%
1791
November1st to 15thDay
9%10%36%6%35%5%47%37%
1543
16th to endDay
5%11%5%6%5%3446%8%39%
1527
December1st to 15thDay
5%11%5%9%7%37%46%8%30%
1365
16th to endDay
6%12%49%6%5%5%5%5%8%29%
1456
January1st to 15thNight
7%12%5%7%445%5%5%10%32%
2852
16th to endNight
6%11%49%43445%7%37%
2754
February1st to 15thNight
7%11%46%6%35%5%5%7%35%
2292
16th to endNight
7%13%5%9%7%46%5%47%28%
2022
March1st to 15thNight
48%47%7%35%6%7%10%33%
2055
16th to endNight
9%13%47%6%35%5%6%8%29%
2109
April1st to 15thNight
11%9%36%4335%5%8%36%
1728
16th to endNight
14%10%345%35%5%5%5%37%
1620
May1st to 15thNight
9%6%25%5%25%5%6%7%43%
1511
16th to endNight
19%6%25%425%45%5%35%
1326
June1st to 15thNight
14%42343446%8%44%
1260
16th to endNight
11%31332445%8%50%
1260
July1st to 15thNight
7%313222347%61%
1260
16th to endNight
5%2232346%6%63%
1346
August1st to 15thNight
8%31432345%9%54%
1591
16th to endNight
8%413324347%56%
1719
September1st to 15thNight
11%5%13222346%55%
1814
16th to endNight
9%424323447%52%
1980
October1st to 15thNight
12%7%35%5%24347%41%
2136
16th to endNight
9%6%245%35%46%8%43%
2433
November1st to 15thNight
8%9%36%5%3446%6%39%
2633
16th to endNight
6%11%47%5%3446%9%36%
2761
December1st to 15thNight
5%10%48%8%45%5%6%8%31%
2925
16th to endNight
6%13%5%9%6%3446%7%31%
3120

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
7%13%5%6%7%3446%6%33%
1330
16th to endDay
411%6%8%6%45%5%6%9%31%
1482
February1st to 15thDay
7%12%37%6%46%5%5%8%31%
1559
16th to endDay
6%12%6%9%7%45%447%30%
1450
March1st to 15thDay
49%48%6%45%5%5%9%36%
1904
16th to endDay
9%13%6%7%6%35%5%6%8%27%
2112
April1st to 15thDay
11%9%37%6%36%5%6%7%31%
2216
16th to endDay
15%8%27%5%24448%35%
2340
May1st to 15thDay
11%7%35%5%35%46%7%39%
2439
16th to endDay
23%7%35%5%25%45%7%29%
2784
June1st to 15thDay
15%6%25%5%35%5%6%7%35%
2700
16th to endDay
11%3235%25%5%7%8%44%
2700
July1st to 15thDay
6%31342445%9%54%
2700
16th to endDay
421232446%9%59%
2822
August1st to 15thDay
7%31232445%10%53%
2367
16th to endDay
8%21242435%6%57%
2483
September1st to 15thDay
13%423313346%53%
2142
16th to endDay
12%413324347%52%
1980
October1st to 15thDay
12%9%47%5%23447%38%
1824
16th to endDay
8%7%26%5%345%5%9%40%
1791
November1st to 15thDay
9%9%36%5%35%5%5%7%37%
1543
16th to endDay
5%11%47%6%245%5%7%39%
1527
December1st to 15thDay
5%11%5%9%7%37%45%8%30%
1365
16th to endDay
7%11%410%6%45%6%5%8%29%
1456
January1st to 15thNight
7%11%5%6%5%45%5%6%9%32%
2852
16th to endNight
5%11%5%9%435%45%7%37%
2754
February1st to 15thNight
7%10%47%5%35%5%6%7%35%
2292
16th to endNight
7%13%5%9%6%46%5%5%6%28%
2022
March1st to 15thNight
47%48%6%45%5%7%10%34%
2055
16th to endNight
9%12%47%6%35%6%6%8%29%
2112
April1st to 15thNight
11%9%46%435%45%7%36%
1728
16th to endNight
12%10%35%5%26%5%46%37%
1620
May1st to 15thNight
9%6%35%5%25%5%5%7%44%
1511
16th to endNight
19%6%26%436%445%36%
1325
June1st to 15thNight
13%422425%45%9%44%
1260
16th to endNight
10%31442346%9%50%
1260
July1st to 15thNight
7%21232335%8%60%
1260
16th to endNight
42132345%8%63%
1346
August1st to 15thNight
7%31342445%9%53%
1591
16th to endNight
7%413423448%56%
1719
September1st to 15thNight
12%41332235%6%55%
1814
16th to endNight
8%4234245%5%6%52%
1980
October1st to 15thNight
12%6%36%5%34347%41%
2136
16th to endNight
9%5%25%435%5%6%8%43%
2433
November1st to 15thNight
7%9%37%6%35%46%6%39%
2633
16th to endNight
5%12%47%5%2445%10%36%
2761
December1st to 15thNight
5%10%49%7%46%5%6%8%31%
2925
16th to endNight
6%12%5%10%6%35%46%8%31%
3120

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
50%7%15%21%21
1330
16th to endDay
47%7%16%19%5%1
1482
February1st to 15thDay
49%6%17%18%6%
1559
16th to endDay
53%5%16%19%4
1450
March1st to 15thDay
42%7%22%21%4
1904
16th to endDay
52%7%14%18%5%
2112
April1st to 15thDay
50%5%14%19%7%
2216
16th to endDay
47%5%13%23%7%1
2340
May1st to 15thDay
41%418%24%10%
2439
16th to endDay
53%6%14%17%8%
2789
June1st to 15thDay
45%6%16%18%11%1
2700
16th to endDay
34%5%17%29%12%
2700
July1st to 15thDay
26%6%15%28%19%3
2541
16th to endDay
20%5%12%28%25%6%
2645
August1st to 15thDay
26%415%31%18%3
2350
16th to endDay
26%410%30%23%4
2483
September1st to 15thDay
32%312%26%18%7%
2142
16th to endDay
31%413%28%16%4
1980
October1st to 15thDay
46%5%16%22%8%
1824
16th to endDay
40%6%17%25%8%
1791
November1st to 15thDay
44%7%17%19%7%2
1543
16th to endDay
42%7%21%20%7%1
1527
December1st to 15thDay
51%5%16%22%4
1365
16th to endDay
51%7%16%18%5%
1456
January1st to 15thNight
47%7%19%18%6%1
2852
16th to endNight
45%5%17%20%8%1
2754
February1st to 15thNight
47%6%17%19%9%1
2303
16th to endNight
53%415%18%7%
2022
March1st to 15thNight
43%7%23%19%4
2055
16th to endNight
51%6%16%20%5%
2112
April1st to 15thNight
44%6%16%23%8%
1728
16th to endNight
47%6%13%22%9%1
1620
May1st to 15thNight
37%5%14%27%12%1
1512
16th to endNight
48%5%15%21%7%1
1326
June1st to 15thNight
36%5%18%27%11%
1260
16th to endNight
30%6%16%28%16%1
1260
July1st to 15thNight
23%5%9%30%23%6%
1190
16th to endNight
18%5%10%30%25%10%
1261
August1st to 15thNight
26%6%13%29%20%3
1583
16th to endNight
26%39%25%26%7%
1719
September1st to 15thNight
30%38%28%19%8%
1814
16th to endNight
31%314%28%17%3
1980
October1st to 15thNight
42%5%17%21%11%2
2136
16th to endNight
37%5%18%26%11%
2433
November1st to 15thNight
43%6%17%19%11%1
2633
16th to endNight
42%6%23%16%8%1
2761
December1st to 15thNight
48%7%15%21%6%
2925
16th to endNight
50%6%17%19%5%
3120

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
12%7%21%25%17%15%
82
16th to endDay
14%15%29%21%9%9%
64
February1st to 15thDay
16%16%34%24%6%2
87
16th to endDay
19%14%28%22%14%
109
March1st to 15thDay
9%31%37%17%4
270
16th to endDay
14%30%29%18%6%
288
April1st to 15thDay
15%26%29%21%6%
269
16th to endDay
20%18%23%23%12%1
270
May1st to 15thDay
15%20%20%23%15%3
396
16th to endDay
22%17%15%23%16%5%
517
June1st to 15thDay
14%21%24%23%14%2
495
16th to endDay
9%21%25%22%17%3
495
July1st to 15thDay
8%11%20%33%23%3
475
16th to endDay
6%16%23%31%19%4
491
August1st to 15thDay
8%11%21%32%20%5%
315
16th to endDay
8%11%19%34%20%5%
332
September1st to 15thDay
17%15%22%25%15%3
315
16th to endDay
10%17%24%23%16%6%
315
October1st to 15thDay
22%12%29%20%13%1
159
16th to endDay
12%11%34%21%18%2
144
November1st to 15thDay
19%6%31%26%15%
135
16th to endDay
9%14%44%17%10%3
127
December1st to 15thDay
13%15%37%12%20%1
90
16th to endDay
21%12%29%23%9%3
96
January1st to 15thNight
10%25%28%23%11%1
956
16th to endNight
11%26%26%22%10%2
834
February1st to 15thNight
9%27%23%23%13%3
704
16th to endNight
9%22%26%26%12%2
632
March1st to 15thNight
6%26%31%23%10%1
720
16th to endNight
11%27%27%22%9%
768
April1st to 15thNight
11%25%28%22%9%1
585
16th to endNight
15%23%23%23%13%1
540
May1st to 15thNight
11%21%21%24%18%1
540
16th to endNight
19%22%13%25%17%2
391
June1st to 15thNight
13%21%25%24%14%1
360
16th to endNight
9%22%20%30%16%
360
July1st to 15thNight
9%14%18%37%20%
340
16th to endNight
5%18%15%41%18%1
376
August1st to 15thNight
8%10%18%36%24%1
510
16th to endNight
9%12%20%36%20%1
573
September1st to 15thNight
12%11%22%28%21%3
600
16th to endNight
8%13%23%31%19%4
716
October1st to 15thNight
15%16%25%26%14%2
720
16th to endNight
10%17%27%31%11%1
768
November1st to 15thNight
11%24%28%25%9%1
923
16th to endNight
10%24%33%25%6%
975
December1st to 15thNight
8%24%28%27%9%2
975
16th to endNight
13%24%26%25%7%2
1040
Page generated at 2018-01-12 20:01:30. Version ac04

Copyright 2018 A. Danko


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