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Chain Lake Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chain Lake Provincial Park clear sky chart from 2005-11-06 to 2024-01-16.

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
33%
23444
15%
74722
8%
23399
41%
23399
21%
46941

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 10thNight
20%
950
15%
2836
4%
946
31%
946
16%
1907
January11th to 20thNight
22%
864
18%
2714
6%
864
35%
864
18%
1792
January21st to endNight
25%
792
21%
2772
9%
792
42%
792
19%
1656
February1st to 10thNight
29%
720
14%
2516
8%
720
39%
720
14%
1634
February11th to 20thNight
23%
703
14%
2273
6%
700
34%
700
16%
1522
February21st to endNight
32%
592
18%
1790
11%
592
43%
592
17%
1231
March1st to 10thNight
26%
720
14%
2160
7%
720
35%
720
17%
1455
March11th to 20thNight
31%
720
20%
2008
8%
720
41%
720
22%
1310
March21st to endNight
32%
792
12%
2142
3%
792
38%
792
19%
1509
April1st to 10thNight
29%
688
15%
1768
4%
688
36%
688
20%
1242
April11th to 20thNight
29%
533
14%
1601
7%
533
35%
533
17%
1132
April21st to endNight
30%
540
11%
1620
7%
540
35%
540
17%
1134
May1st to 10thNight
37%
478
10%
1558
9%
478
41%
478
18%
1046
May11th to 20thNight
48%
354
14%
1244
16%
354
51%
354
23%
761
May21st to endNight
42%
388
7%
1358
5%
388
45%
388
16%
944
June1st to 10thNight
39%
360
5%
1260
1%
360
41%
360
19%
835
June11th to 20thNight
33%
360
3%
1260
0%
360
34%
360
17%
853
June21st to endNight
53%
360
4%
1260
1%
360
54%
360
28%
700
July1st to 10thNight
62%
350
5%
1225
1%
350
63%
350
32%
670
July11th to 20thNight
52%
348
11%
1218
9%
348
56%
348
33%
654
July21st to endNight
64%
394
18%
1413
22%
372
72%
372
39%
650
August1st to 10thNight
62%
358
18%
1424
22%
356
70%
356
30%
724
August11th to 20thNight
59%
521
20%
1589
17%
521
64%
521
39%
865
August21st to endNight
50%
594
24%
1782
17%
594
56%
594
37%
975
September1st to 10thNight
49%
653
20%
1746
11%
653
53%
653
35%
1047
September11th to 20thNight
49%
720
21%
1980
13%
720
54%
720
34%
1194
September21st to endNight
37%
720
22%
1980
11%
720
46%
720
30%
1201
October1st to 10thNight
42%
720
20%
2042
10%
720
51%
720
26%
1322
October11th to 20thNight
35%
720
20%
2290
9%
720
49%
720
25%
1361
October21st to endNight
27%
792
18%
2574
7%
792
40%
792
18%
1620
November1st to 10thNight
21%
801
16%
2466
6%
801
32%
801
15%
1661
November11th to 20thNight
17%
950
21%
2702
4%
950
33%
950
19%
1685
November21st to endNight
22%
950
15%
2850
4%
950
32%
950
19%
1813
December1st to 10thNight
24%
950
17%
2850
8%
950
33%
950
19%
1843
December11th to 20thNight
23%
949
14%
3481
5%
949
32%
949
15%
2285
December21st to endNight
21%
1040
11%
4970
5%
1026
31%
1026
12%
2708

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
8%8%36%6%35%5%6%8%40%
74641
Night
5%7%47%6%35%5%6%8%43%
75162
TransparencyDay
41%9%15%21%11%2
74329
Night
37%9%17%22%12%3
74992
SeeingDay
15%19%31%23%10%2
14167
Night
11%17%32%27%11%2
23452

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 10thDay
16%5%9%7%46%6%6%9%41%
1329
11th to 20thDay
25%37%5%46%5%8%13%42%
1371
21st to endDay
210%48%8%35%5%8%8%38%
1584
February1st to 10thDay
36%48%9%46%7%8%9%37%
1444
11th to 20thDay
28%5%8%8%47%7%6%10%34%
1575
21st to endDay
29%6%10%8%46%5%6%9%34%
1466
March1st to 10thDay
27%5%10%7%35%5%7%10%39%
1800
11th to 20thDay
39%47%6%35%6%6%8%42%
1951
21st to endDay
5%12%6%10%7%5%5%6%6%8%30%
2212
April1st to 10thDay
7%12%5%9%6%45%6%7%8%30%
2191
11th to 20thDay
8%15%5%9%6%45%6%6%7%30%
2310
21st to endDay
10%13%46%7%35%5%6%7%33%
2340
May1st to 10thDay
13%12%47%7%45%5%6%8%28%
2401
11th to 20thDay
14%10%36%6%35%6%6%8%34%
2647
21st to endDay
22%9%37%7%35%5%6%6%26%
2917
June1st to 10thDay
17%9%46%6%46%6%7%7%29%
2700
11th to 20thDay
21%8%36%7%45%5%6%7%27%
2700
21st to endDay
9%5%246%46%7%7%8%41%
2700
July1st to 10thDay
8%6%25%6%36%6%7%8%44%
2700
11th to 20thDay
9%424435%6%6%9%48%
2700
21st to endDay
5%314435%5%5%7%57%
2817
August1st to 10thDay
9%5%24445%6%7%8%47%
2507
11th to 20thDay
9%4134245%5%10%51%
2311
21st to endDay
10%4244345%6%7%51%
2574
September1st to 10thDay
11%7%245%24447%50%
2211
11th to 20thDay
12%5%245%345%47%48%
1980
21st to endDay
9%8%24425%5%5%8%48%
1980
October1st to 10thDay
10%9%35%4345%6%8%42%
1918
11th to 20thDay
6%9%36%6%35%46%9%43%
1668
21st to endDay
411%47%7%35%5%7%10%38%
1782
November1st to 10thDay
5%12%5%7%6%35%5%6%7%39%
1594
11th to 20thDay
38%47%5%3446%9%47%
1477
21st to endDay
310%5%9%5%445%5%8%41%
1330
December1st to 10thDay
26%49%8%45%6%5%10%42%
1330
11th to 20thDay
39%49%7%45%6%8%10%36%
1682
21st to endDay
27%36%6%45%5%6%9%47%
2442
January1st to 10thNight
27%5%7%8%5%5%7%7%11%38%
2836
11th to 20thNight
36%48%8%45%6%6%10%40%
2714
21st to endNight
27%47%6%46%6%8%11%41%
2772
February1st to 10thNight
26%410%7%46%6%7%9%39%
2516
11th to 20thNight
210%6%9%8%45%6%6%8%36%
2272
21st to endNight
37%6%10%8%5%7%46%6%40%
1790
March1st to 10thNight
18%5%9%8%5%6%5%7%9%38%
2160
11th to 20thNight
38%5%6%6%35%5%6%11%43%
2008
21st to endNight
410%5%8%6%35%6%7%10%37%
2142
April1st to 10thNight
6%11%5%8%7%345%5%6%40%
1768
11th to 20thNight
8%13%48%5%35%6%6%7%34%
1601
21st to endNight
8%11%49%6%35%5%5%7%37%
1620
May1st to 10thNight
10%12%47%6%345%5%9%36%
1558
11th to 20thNight
11%7%25%6%45%45%8%44%
1244
21st to endNight
22%7%27%42445%7%35%
1358
June1st to 10thNight
14%6%36%5%36%46%5%41%
1260
11th to 20thNight
20%7%25%5%35%45%8%35%
1260
21st to endNight
6%434436%7%6%8%50%
1260
July1st to 10thNight
7%425%5%345%5%8%52%
1260
11th to 20thNight
7%4335%3346%8%54%
1260
21st to endNight
6%31232346%7%62%
1496
August1st to 10thNight
8%5%2443445%7%55%
1432
11th to 20thNight
8%32343446%7%56%
1589
21st to endNight
9%32442445%8%56%
1782
September1st to 10thNight
11%41343445%7%54%
1746
11th to 20thNight
11%8%2332236%7%52%
1980
21st to endNight
9%7%2443345%8%51%
1980
October1st to 10thNight
10%9%25%5%3445%8%47%
2042
11th to 20thNight
6%8%25%425%5%7%9%47%
2290
21st to endNight
5%9%47%6%45%6%6%7%42%
2574
November1st to 10thNight
5%11%5%7%6%35%5%7%8%39%
2466
11th to 20thNight
27%35%6%35%5%6%9%47%
2702
21st to endNight
28%48%6%5%446%10%43%
2850
December1st to 10thNight
28%5%8%6%36%6%5%10%42%
2850
11th to 20thNight
27%410%8%46%6%8%10%37%
3510
21st to endNight
28%48%6%35%5%6%7%46%
5214

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 10thDay
40%10%15%22%8%4
1329
11th to 20thDay
35%11%18%23%9%4
1371
21st to endDay
41%9%17%19%12%2
1584
February1st to 10thDay
41%12%15%20%9%2
1444
11th to 20thDay
43%10%17%19%8%2
1584
21st to endDay
47%8%14%17%12%2
1466
March1st to 10thDay
39%11%18%20%11%1
1800
11th to 20thDay
40%9%16%21%13%1
1952
21st to endDay
51%11%15%16%6%1
2212
April1st to 10thDay
50%9%16%16%7%1
2191
11th to 20thDay
52%8%13%16%9%1
2310
21st to endDay
49%9%15%18%8%1
2340
May1st to 10thDay
54%8%14%17%7%
2401
11th to 20thDay
46%10%15%20%8%1
2651
21st to endDay
55%10%14%14%7%
2918
June1st to 10thDay
50%10%15%16%9%1
2700
11th to 20thDay
55%9%12%14%9%1
2700
21st to endDay
35%11%17%23%12%2
2700
July1st to 10thDay
34%10%17%23%12%3
2626
11th to 20thDay
32%9%14%24%18%4
2619
21st to endDay
25%7%12%28%22%5%
2660
August1st to 10thDay
31%10%16%24%15%4
2490
11th to 20thDay
28%9%18%31%11%3
2311
21st to endDay
31%7%14%27%17%4
2574
September1st to 10thDay
35%6%12%24%17%5%
2211
11th to 20thDay
34%8%14%26%16%2
1980
21st to endDay
34%8%14%29%13%2
1980
October1st to 10thDay
40%10%16%22%11%2
1918
11th to 20thDay
38%7%18%23%11%2
1668
21st to endDay
40%10%17%20%10%2
1782
November1st to 10thDay
44%9%14%19%12%
1594
11th to 20thDay
34%10%20%22%12%1
1477
21st to endDay
40%8%20%19%9%4
1330
December1st to 10thDay
39%9%18%19%11%4
1330
11th to 20thDay
41%11%19%21%7%1
1684
21st to endDay
31%9%13%23%17%6%
2442
January1st to 10thNight
39%12%16%19%11%4
2836
11th to 20thNight
39%11%16%20%10%4
2714
21st to endNight
34%10%17%22%15%2
2772
February1st to 10thNight
42%9%15%19%12%3
2516
11th to 20thNight
43%9%17%19%10%1
2273
21st to endNight
47%6%12%20%11%3
1790
March1st to 10thNight
42%9%19%20%9%1
2160
11th to 20thNight
35%10%18%23%13%1
2008
21st to endNight
42%11%19%19%9%1
2142
April1st to 10thNight
43%8%15%21%11%1
1768
11th to 20thNight
48%8%13%21%8%1
1601
21st to endNight
47%9%13%22%8%2
1620
May1st to 10thNight
45%8%16%23%8%
1558
11th to 20thNight
38%8%16%29%8%2
1244
21st to endNight
50%7%15%19%8%1
1358
June1st to 10thNight
44%8%16%22%9%1
1260
11th to 20thNight
46%8%15%20%10%1
1260
21st to endNight
28%10%19%27%14%2
1260
July1st to 10thNight
27%9%21%27%14%2
1225
11th to 20thNight
27%8%16%26%20%4
1218
21st to endNight
20%7%15%29%24%5%
1413
August1st to 10thNight
28%7%16%29%16%4
1424
11th to 20thNight
25%7%19%31%15%3
1589
21st to endNight
25%7%14%30%22%3
1782
September1st to 10thNight
30%6%15%28%16%4
1746
11th to 20thNight
30%7%14%28%16%4
1980
21st to endNight
31%8%18%26%14%4
1980
October1st to 10thNight
36%9%14%23%16%2
2042
11th to 20thNight
32%9%18%24%14%4
2290
21st to endNight
38%9%17%23%12%1
2574
November1st to 10thNight
42%10%16%20%11%2
2466
11th to 20thNight
31%11%19%21%16%1
2702
21st to endNight
36%9%20%20%11%4
2850
December1st to 10thNight
38%9%18%19%12%4
2850
11th to 20thNight
38%14%21%20%7%1
3507
21st to endNight
34%8%15%23%13%7%
5214

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 10thDay
7%24%31%21%11%6%
180
11th to 20thDay
8%18%38%27%8%2
170
21st to endDay
9%29%36%16%6%4
176
February1st to 10thDay
15%26%35%19%42
162
11th to 20thDay
12%23%38%19%8%1
240
21st to endDay
11%22%36%25%6%1
332
March1st to 10thDay
11%26%38%15%7%2
420
11th to 20thDay
13%25%30%22%8%2
420
21st to endDay
15%26%34%17%6%3
462
April1st to 10thDay
14%26%35%20%4
420
11th to 20thDay
19%24%30%18%8%1
412
21st to endDay
20%25%25%19%9%2
420
May1st to 10thDay
19%16%30%22%11%2
423
11th to 20thDay
21%13%22%25%16%3
618
21st to endDay
23%11%22%28%15%2
679
June1st to 10thDay
19%18%28%23%9%3
630
11th to 20thDay
23%18%29%20%9%2
630
21st to endDay
11%13%30%26%15%4
630
July1st to 10thDay
11%11%29%28%19%3
621
11th to 20thDay
12%13%31%27%14%3
618
21st to endDay
7%14%33%29%15%2
563
August1st to 10thDay
11%14%32%29%13%2
447
11th to 20thDay
7%13%32%30%15%3
437
21st to endDay
12%15%33%25%12%3
495
September1st to 10thDay
16%19%31%24%7%2
450
11th to 20thDay
14%17%31%24%12%2
450
21st to endDay
19%25%30%18%6%2
450
October1st to 10thDay
16%17%30%24%11%2
388
11th to 20thDay
15%23%30%18%11%4
270
21st to endDay
18%23%34%19%43
297
November1st to 10thDay
20%23%32%20%5%
270
11th to 20thDay
21%24%37%14%4
249
21st to endDay
17%24%27%19%6%7%
180
December1st to 10thDay
11%21%38%21%8%2
180
11th to 20thDay
9%24%38%21%6%2
180
21st to endDay
11%16%36%24%9%5%
198
January1st to 10thNight
10%24%39%20%6%1
950
11th to 20thNight
9%21%43%20%6%1
864
21st to endNight
8%23%38%23%7%1
792
February1st to 10thNight
8%21%35%24%9%3
720
11th to 20thNight
8%19%38%27%7%1
704
21st to endNight
8%14%36%28%13%2
592
March1st to 10thNight
7%20%38%24%9%2
720
11th to 20thNight
9%23%31%28%8%1
720
21st to endNight
9%16%33%29%10%3
792
April1st to 10thNight
11%19%31%26%11%2
688
11th to 20thNight
16%17%29%27%11%1
533
21st to endNight
13%16%33%28%10%
540
May1st to 10thNight
16%13%27%29%15%1
478
11th to 20thNight
14%9%21%33%20%2
354
21st to endNight
26%6%19%30%19%1
389
June1st to 10thNight
15%11%28%29%14%2
360
11th to 20thNight
22%11%28%26%13%1
360
21st to endNight
9%9%23%35%23%1
360
July1st to 10thNight
9%7%17%44%23%
350
11th to 20thNight
8%8%26%39%18%2
348
21st to endNight
7%7%18%46%21%2
394
August1st to 10thNight
10%316%40%28%2
358
11th to 20thNight
8%423%40%23%2
521
21st to endNight
8%11%25%39%15%2
594
September1st to 10thNight
14%9%23%32%17%4
653
11th to 20thNight
15%7%25%31%18%4
720
21st to endNight
13%17%29%25%12%4
720
October1st to 10thNight
15%13%25%32%13%2
720
11th to 20thNight
12%16%31%28%10%2
720
21st to endNight
13%20%33%26%7%1
792
November1st to 10thNight
15%24%35%18%7%
801
11th to 20thNight
11%28%40%17%31
950
21st to endNight
8%26%38%20%6%2
950
December1st to 10thNight
8%24%37%22%8%2
950
11th to 20thNight
7%25%38%24%5%1
950
21st to endNight
9%21%39%21%9%1
1045
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