Clearwater Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Clearwater Lake clear sky chart from 2005-11-05 to 2017-09-23.

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%
15880
9%
46701
6%
15840
39%
15840
17%
34419

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
28%
898
9%
2847
6%
895
32%
895
12%
2234
January16th to endNight
24%
960
8%
2763
4%
960
29%
960
12%
2246
February1st to 15thNight
34%
875
11%
2464
4%
875
39%
875
18%
1827
February16th to endNight
38%
702
12%
2000
6%
702
42%
702
17%
1500
March1st to 15thNight
39%
720
15%
2160
11%
720
43%
720
19%
1547
March16th to endNight
42%
579
15%
2028
13%
579
48%
579
20%
1348
April1st to 15thNight
46%
539
17%
1723
15%
539
51%
539
25%
1106
April16th to endNight
44%
540
16%
1563
9%
540
47%
540
26%
1028
May1st to 15thNight
38%
540
6%
1335
3%
540
40%
540
24%
981
May16th to endNight
43%
562
1%
1311
1%
561
44%
561
30%
914
June1st to 15thNight
46%
375
0%
1095
0%
375
46%
375
24%
735
June16th to endNight
46%
360
0%
1080
0%
360
46%
360
20%
761
July1st to 15thNight
49%
340
0%
1020
0%
340
49%
340
30%
633
July16th to endNight
57%
535
1%
1219
2%
502
57%
502
33%
822
August1st to 15thNight
58%
539
9%
1432
5%
536
61%
536
37%
881
August16th to endNight
52%
573
14%
1666
9%
573
55%
573
31%
1047
September1st to 15thNight
47%
540
12%
1786
11%
540
52%
540
25%
1125
September16th to endNight
38%
516
15%
1903
13%
516
45%
516
18%
1272
October1st to 15thNight
32%
672
13%
1992
6%
672
39%
672
18%
1443
October16th to endNight
23%
880
11%
2288
4%
880
27%
880
14%
1838
November1st to 15thNight
22%
875
9%
2525
4%
875
25%
875
11%
2078
November16th to endNight
22%
900
5%
2700
2%
900
25%
900
8%
2279
December1st to 15thNight
25%
900
4%
2729
2%
900
27%
900
9%
2297
December16th to endNight
27%
960
9%
3072
7%
960
32%
960
10%
2477

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
14%9%46%6%35%5%5%7%31%
48244
Night
12%10%47%6%35%5%5%6%30%
46834
Cloud CoverDay
14%9%46%6%35%5%5%7%32%
48252
Night
13%10%47%7%35%5%5%6%30%
46838
TransparencyDay
50%7%15%19%6%
47893
Night
53%6%13%18%6%
46701
SeeingDay
18%7%26%27%15%4
6329
Night
18%5%28%30%14%2
15888

By Month

Percentage Cloud Cover NE (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%14%8%8%8%46%7%10%6%17%
1089
16th to endDay
12%16%6%10%6%37%6%7%5%18%
1459
February1st to 15thDay
9%8%49%7%5%9%8%7%8%22%
1400
16th to endDay
7%9%5%10%9%5%7%8%6%7%22%
1481
March1st to 15thDay
13%11%48%6%36%446%29%
1790
16th to endDay
9%9%47%6%36%45%7%34%
2193
April1st to 15thDay
9%10%36%6%3445%7%38%
2225
16th to endDay
11%6%36%5%3445%7%40%
2396
May1st to 15thDay
16%9%36%6%345%46%33%
2616
16th to endDay
18%6%3442445%7%37%
2803
June1st to 15thDay
18%8%35%435%5%6%6%33%
2864
16th to endDay
17%7%36%5%46%5%5%7%29%
2880
July1st to 15thDay
14%5%245%35%5%6%7%40%
2880
16th to endDay
13%424425%5%6%9%40%
2863
August1st to 15thDay
13%4244345%6%8%42%
2520
16th to endDay
14%5%25%5%2445%8%40%
2536
September1st to 15thDay
15%5%35%5%345%47%38%
2173
16th to endDay
17%8%35%43445%8%35%
1893
October1st to 15thDay
19%16%47%6%33445%24%
1627
16th to endDay
21%18%7%9%43334418%
1584
November1st to 15thDay
18%15%6%9%9%3333420%
1330
16th to endDay
10%14%6%13%11%6%6%35%417%
1260
December1st to 15thDay
9%12%9%11%12%5%6%5%4416%
1230
16th to endDay
11%13%7%11%11%5%6%45%7%14%
1152
January1st to 15thNight
8%13%6%10%9%47%7%6%6%19%
2847
16th to endNight
12%14%6%9%7%5%6%6%6%5%19%
2763
February1st to 15thNight
7%9%48%8%5%8%6%5%7%27%
2460
16th to endNight
7%9%6%11%8%46%6%46%28%
2000
March1st to 15thNight
12%11%5%8%6%34445%34%
2147
16th to endNight
9%8%46%6%35%5%6%7%35%
2028
April1st to 15thNight
13%7%35%4335%5%6%41%
1723
16th to endNight
9%8%36%5%35%45%5%41%
1563
May1st to 15thNight
20%7%345%2445%5%35%
1335
16th to endNight
16%5%25%42445%7%40%
1310
June1st to 15thNight
15%6%25%5%3445%8%38%
1095
16th to endNight
15%6%35%3445%6%9%34%
1080
July1st to 15thNight
11%6%25%5%2345%7%45%
1080
16th to endNight
10%423425%5%8%9%43%
1302
August1st to 15thNight
10%41432335%10%50%
1440
16th to endNight
14%31332345%8%47%
1666
September1st to 15thNight
13%5%244245%5%7%43%
1786
16th to endNight
16%6%25%6%35%45%7%36%
1903
October1st to 15thNight
18%13%36%423335%35%
1992
16th to endNight
20%15%5%8%5%3334325%
2288
November1st to 15thNight
17%17%7%9%8%3433420%
2525
16th to endNight
10%16%6%12%10%5%6%445%16%
2700
December1st to 15thNight
10%12%7%11%10%5%7%6%6%5%14%
2729
16th to endNight
12%16%6%12%10%45%45%6%16%
3072

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%14%8%9%7%45%7%10%7%17%
1089
16th to endDay
13%15%6%10%5%37%5%8%5%18%
1459
February1st to 15thDay
9%8%39%8%49%7%7%8%22%
1400
16th to endDay
7%10%410%9%5%7%7%7%7%22%
1481
March1st to 15thDay
14%10%5%8%6%36%346%29%
1800
16th to endDay
9%9%46%6%35%45%7%35%
2191
April1st to 15thDay
9%10%36%5%345%5%6%39%
2225
16th to endDay
12%6%25%5%35%45%7%41%
2396
May1st to 15thDay
15%8%36%5%35%5%46%33%
2616
16th to endDay
17%6%2443445%7%38%
2803
June1st to 15thDay
17%8%35%435%46%7%33%
2864
16th to endDay
16%7%46%5%36%5%6%7%30%
2880
July1st to 15thDay
13%5%145%35%5%5%7%41%
2880
16th to endDay
12%425%425%5%6%9%41%
2863
August1st to 15thDay
13%4244345%6%8%43%
2520
16th to endDay
14%5%245%2446%8%40%
2536
September1st to 15thDay
16%5%25%5%345%5%8%37%
2173
16th to endDay
17%8%34434448%35%
1893
October1st to 15thDay
20%16%46%6%33446%23%
1627
16th to endDay
21%19%7%9%5%3334418%
1584
November1st to 15thDay
18%16%5%10%8%3343420%
1330
16th to endDay
10%13%8%11%12%6%5%44417%
1260
December1st to 15thDay
9%12%9%11%12%46%6%5%5%17%
1230
16th to endDay
12%12%6%12%12%5%6%447%15%
1152
January1st to 15thNight
8%13%6%10%9%46%8%6%6%19%
2847
16th to endNight
12%14%6%10%7%46%6%6%5%19%
2763
February1st to 15thNight
7%9%48%8%48%7%5%6%28%
2453
16th to endNight
7%10%6%10%9%5%5%5%46%28%
2000
March1st to 15thNight
12%12%5%7%6%3435%5%34%
2160
16th to endNight
9%7%46%6%35%5%6%7%35%
2026
April1st to 15thNight
12%9%35%5%2445%6%41%
1723
16th to endNight
9%9%35%5%35%45%6%41%
1563
May1st to 15thNight
20%7%35%5%24446%35%
1334
16th to endNight
16%5%15%5%2345%7%41%
1311
June1st to 15thNight
15%7%25%6%34447%38%
1095
16th to endNight
16%5%35%445%5%7%9%34%
1080
July1st to 15thNight
12%425%5%2435%7%45%
1080
16th to endNight
10%413335%5%7%9%43%
1302
August1st to 15thNight
10%41431435%10%50%
1440
16th to endNight
14%41332345%8%47%
1666
September1st to 15thNight
13%6%235%3346%7%43%
1786
16th to endNight
17%6%25%6%35%46%6%36%
1903
October1st to 15thNight
19%13%35%423345%34%
1992
16th to endNight
22%15%5%7%6%3333424%
2288
November1st to 15thNight
18%17%7%10%8%3433419%
2525
16th to endNight
11%16%6%12%10%5%5%445%16%
2700
December1st to 15thNight
10%13%7%11%10%5%6%7%6%5%14%
2729
16th to endNight
12%15%6%12%10%35%45%5%17%
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
60%9%13%15%2
1089
16th to endDay
64%7%8%14%4
1459
February1st to 15thDay
55%7%16%15%5%
1400
16th to endDay
58%7%10%17%5%
1481
March1st to 15thDay
56%5%11%18%6%1
1800
16th to endDay
48%5%15%21%7%1
2193
April1st to 15thDay
44%6%16%19%12%1
2225
16th to endDay
41%6%13%24%14%
2396
May1st to 15thDay
50%6%11%20%9%1
2616
16th to endDay
44%5%11%23%12%1
2807
June1st to 15thDay
48%8%12%18%12%
2864
16th to endDay
52%9%14%19%4
2880
July1st to 15thDay
39%8%17%25%8%
2711
16th to endDay
38%10%21%23%5%
2683
August1st to 15thDay
37%10%24%23%3
2504
16th to endDay
40%10%24%21%2
2536
September1st to 15thDay
44%7%20%19%7%
2173
16th to endDay
47%8%18%21%4
1893
October1st to 15thDay
61%5%14%16%1
1627
16th to endDay
70%5%12%10%1
1584
November1st to 15thDay
68%5%11%10%4
1330
16th to endDay
70%6%12%9%1
1260
December1st to 15thDay
68%7%13%6%3
1230
16th to endDay
68%5%10%14%1
1152
January1st to 15thNight
61%7%12%15%3
2847
16th to endNight
64%6%10%13%4
2763
February1st to 15thNight
53%6%14%18%6%
2464
16th to endNight
55%6%13%18%7%
2000
March1st to 15thNight
51%6%11%21%8%1
2160
16th to endNight
45%7%15%20%9%1
2028
April1st to 15thNight
42%413%22%13%2
1723
16th to endNight
42%5%9%23%17%2
1563
May1st to 15thNight
48%6%11%19%11%2
1335
16th to endNight
41%5%10%23%16%2
1311
June1st to 15thNight
43%6%12%21%16%
1095
16th to endNight
44%11%18%19%5%
1080
July1st to 15thNight
36%5%18%25%12%
1020
16th to endNight
34%10%20%28%6%
1219
August1st to 15thNight
29%8%24%32%5%
1432
16th to endNight
33%8%21%28%6%
1666
September1st to 15thNight
38%7%19%24%9%
1786
16th to endNight
45%8%13%23%8%
1903
October1st to 15thNight
51%6%15%22%3
1992
16th to endNight
62%5%13%14%3
2288
November1st to 15thNight
67%5%11%11%3
2525
16th to endNight
69%7%12%8%2
2700
December1st to 15thNight
67%8%13%8%2
2729
16th to endNight
68%310%14%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
6%44%41%7%
63
16th to endDay
32%227%26%12%
96
February1st to 15thDay
10%147%28%8%3
90
16th to endDay
12%8%27%27%19%4
81
March1st to 15thDay
15%7%27%41%7%
90
16th to endDay
16%11%26%22%19%3
180
April1st to 15thDay
17%7%33%31%10%
344
16th to endDay
12%8%27%33%15%3
450
May1st to 15thDay
22%9%30%23%11%2
468
16th to endDay
21%7%22%26%17%4
517
June1st to 15thDay
21%9%28%20%16%4
495
16th to endDay
20%8%22%27%14%6%
495
July1st to 15thDay
17%7%25%25%18%6%
475
16th to endDay
13%6%27%27%17%7%
515
August1st to 15thDay
15%6%19%25%22%10%
493
16th to endDay
17%5%23%30%19%3
523
September1st to 15thDay
20%9%32%25%10%
328
16th to endDay
28%9%20%24%13%3
111
October1st to 15thDay
38%6%28%15%10%
90
16th to endDay
41%5%23%22%5%1
96
November1st to 15thDay
20%14%26%27%10%1
90
16th to endDay
28%323%33%7%3
90
December1st to 15thDay
18%321%31%15%9%
85
16th to endDay
6%328%48%14%
64
January1st to 15thNight
12%6%33%31%12%3
900
16th to endNight
20%6%36%27%9%
960
February1st to 15thNight
13%5%32%33%13%2
880
16th to endNight
10%5%27%32%20%2
702
March1st to 15thNight
16%8%24%31%17%1
720
16th to endNight
12%429%32%16%4
579
April1st to 15thNight
16%225%33%17%2
539
16th to endNight
12%5%28%33%17%2
540
May1st to 15thNight
22%428%30%12%1
540
16th to endNight
18%6%27%35%11%
563
June1st to 15thNight
20%322%33%18%1
375
16th to endNight
20%5%21%34%16%1
360
July1st to 15thNight
13%5%26%33%19%1
340
16th to endNight
11%221%35%22%4
535
August1st to 15thNight
10%421%33%23%6%
539
16th to endNight
16%224%34%20%
573
September1st to 15thNight
16%426%32%19%1
540
16th to endNight
20%428%35%10%1
516
October1st to 15thNight
26%7%24%29%10%
672
16th to endNight
30%7%28%22%9%1
880
November1st to 15thNight
25%7%30%23%11%1
875
16th to endNight
20%9%32%28%8%1
900
December1st to 15thNight
17%6%32%27%13%3
900
16th to endNight
21%5%27%24%16%4
960
Page generated at 2017-09-24 08:15:54. Version ac04

Copyright 2017 A. Danko


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