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 2019-06-24.

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%
18303
10%
53836
6%
18263
39%
18263
18%
39597

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%
1048
10%
3324
7%
1045
32%
1045
12%
2584
January16th to endNight
26%
1120
9%
3223
5%
1120
30%
1120
12%
2582
February1st to 15thNight
35%
1025
11%
2884
5%
1025
40%
1025
18%
2132
February16th to endNight
40%
818
12%
2330
7%
818
43%
818
18%
1726
March1st to 15thNight
39%
840
17%
2520
13%
840
44%
840
19%
1786
March16th to endNight
43%
676
15%
2367
13%
676
50%
676
21%
1544
April1st to 15thNight
47%
629
18%
2011
17%
629
52%
629
25%
1288
April16th to endNight
44%
624
16%
1805
9%
624
47%
624
27%
1182
May1st to 15thNight
39%
630
8%
1558
4%
630
42%
630
26%
1126
May16th to endNight
45%
658
1%
1535
1%
657
46%
657
33%
1047
June1st to 15thNight
44%
437
0%
1277
0%
437
44%
437
24%
862
June16th to endNight
48%
406
0%
1218
0%
406
48%
406
21%
853
July1st to 15thNight
48%
370
0%
1110
0%
370
48%
370
30%
687
July16th to endNight
56%
580
1%
1329
2%
547
56%
547
32%
904
August1st to 15thNight
59%
575
9%
1528
5%
572
61%
572
37%
939
August16th to endNight
52%
621
14%
1805
9%
621
56%
621
31%
1133
September1st to 15thNight
46%
585
12%
1934
11%
585
51%
585
25%
1234
September16th to endNight
39%
582
15%
2145
13%
582
46%
582
18%
1430
October1st to 15thNight
31%
794
12%
2354
6%
794
37%
794
17%
1730
October16th to endNight
23%
1040
11%
2704
4%
1040
28%
1040
14%
2157
November1st to 15thNight
22%
1025
7%
2957
4%
1025
25%
1025
10%
2474
November16th to endNight
22%
1050
5%
3150
3%
1050
25%
1050
8%
2648
December1st to 15thNight
25%
1050
5%
3184
3%
1050
28%
1050
9%
2663
December16th to endNight
29%
1120
9%
3584
7%
1120
33%
1120
10%
2886

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
13%9%46%6%35%5%5%7%32%
55022
Night
12%10%48%7%35%5%5%6%30%
53969
Cloud CoverDay
13%9%36%6%35%5%5%7%32%
55030
Night
12%10%47%7%35%5%5%6%30%
53973
TransparencyDay
50%7%15%19%7%
54671
Night
53%6%13%18%7%
53836
SeeingDay
18%6%27%27%15%4
8636
Night
18%5%28%31%14%2
18311

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%9%9%35%7%9%6%18%
1271
16th to endDay
12%16%6%9%5%36%6%7%6%18%
1703
February1st to 15thDay
8%8%39%7%5%9%8%7%8%23%
1640
16th to endDay
6%9%5%9%9%5%7%7%6%7%23%
1725
March1st to 15thDay
12%9%48%7%45%446%30%
2090
16th to endDay
8%9%47%6%36%45%8%35%
2558
April1st to 15thDay
9%9%26%6%35%446%40%
2597
16th to endDay
10%6%35%5%3445%8%40%
2759
May1st to 15thDay
14%8%35%6%345%5%6%34%
3053
16th to endDay
17%6%2442445%8%39%
3283
June1st to 15thDay
18%8%35%4345%6%6%32%
3341
16th to endDay
16%7%36%5%46%5%6%7%31%
3250
July1st to 15thDay
14%5%145%35%5%6%7%40%
3120
16th to endDay
13%424425%6%6%9%40%
3104
August1st to 15thDay
12%4244345%6%8%42%
2677
16th to endDay
15%5%25%5%3445%8%39%
2749
September1st to 15thDay
15%5%35%5%345%47%36%
2355
16th to endDay
17%9%35%434448%34%
2145
October1st to 15thDay
18%16%38%6%335%45%24%
1923
16th to endDay
21%17%6%8%5%3335%5%19%
1872
November1st to 15thDay
17%16%6%10%10%3443318%
1558
16th to endDay
10%14%6%12%11%6%6%44417%
1470
December1st to 15thDay
8%12%8%12%11%5%6%6%5%5%17%
1435
16th to endDay
11%11%7%11%11%6%6%46%8%14%
1344
January1st to 15thNight
8%13%5%9%8%47%7%5%6%20%
3324
16th to endNight
12%14%6%9%6%46%6%6%5%20%
3223
February1st to 15thNight
7%9%48%9%5%8%6%5%7%27%
2880
16th to endNight
6%9%6%10%9%46%6%47%28%
2330
March1st to 15thNight
11%11%48%6%34345%35%
2507
16th to endNight
8%8%46%5%45%5%6%7%36%
2367
April1st to 15thNight
12%7%35%43345%6%41%
2011
16th to endNight
9%8%26%5%35%46%6%40%
1805
May1st to 15thNight
19%7%345%245%5%5%36%
1558
16th to endNight
15%5%25%32435%7%43%
1534
June1st to 15thNight
16%6%25%435%45%7%38%
1277
16th to endNight
14%6%36%4445%6%9%35%
1218
July1st to 15thNight
11%5%25%5%2345%7%45%
1170
16th to endNight
11%423425%5%7%9%43%
1412
August1st to 15thNight
10%41332335%9%50%
1536
16th to endNight
14%31332345%9%47%
1805
September1st to 15thNight
13%5%245%245%5%7%42%
1934
16th to endNight
16%6%35%5%35%45%6%37%
2145
October1st to 15thNight
18%13%36%5%24335%33%
2354
16th to endNight
19%15%5%7%5%3344425%
2704
November1st to 15thNight
16%16%7%10%9%3443418%
2957
16th to endNight
10%16%6%12%10%5%5%445%17%
3150
December1st to 15thNight
10%13%7%11%10%46%6%6%5%15%
3184
16th to endNight
11%15%6%11%11%45%45%6%16%
3584

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%7%10%8%45%7%9%6%18%
1271
16th to endDay
12%16%5%10%437%6%8%5%18%
1703
February1st to 15thDay
8%7%39%8%49%8%7%8%23%
1640
16th to endDay
6%10%5%10%9%5%7%7%6%7%24%
1725
March1st to 15thDay
13%9%5%8%8%46%346%30%
2100
16th to endDay
8%9%37%6%35%5%5%8%36%
2556
April1st to 15thDay
9%9%35%5%345%5%6%40%
2597
16th to endDay
10%6%25%5%35%5%5%7%41%
2759
May1st to 15thDay
14%8%36%5%35%5%5%6%35%
3053
16th to endDay
16%6%2443445%7%40%
3283
June1st to 15thDay
17%8%35%435%45%7%33%
3341
16th to endDay
15%7%36%5%36%6%6%7%31%
3250
July1st to 15thDay
14%5%145%35%5%5%7%41%
3120
16th to endDay
13%424425%5%6%9%41%
3104
August1st to 15thDay
12%4244345%6%8%43%
2677
16th to endDay
14%5%245%2446%8%40%
2749
September1st to 15thDay
15%6%25%5%445%5%8%36%
2355
16th to endDay
17%9%34434448%35%
2145
October1st to 15thDay
18%16%47%6%33446%23%
1923
16th to endDay
21%18%6%8%5%3334419%
1872
November1st to 15thDay
17%17%6%11%10%4343417%
1558
16th to endDay
10%13%8%11%12%6%5%5%4416%
1470
December1st to 15thDay
8%12%9%12%11%46%6%5%5%17%
1435
16th to endDay
11%12%6%12%11%5%6%45%8%15%
1344
January1st to 15thNight
8%13%6%9%9%46%7%6%6%20%
3324
16th to endNight
12%14%6%10%6%46%6%6%5%20%
3223
February1st to 15thNight
6%9%48%9%5%8%7%5%6%28%
2873
16th to endNight
6%9%5%10%9%5%5%6%5%6%29%
2330
March1st to 15thNight
11%11%5%8%7%33345%35%
2520
16th to endNight
9%8%46%6%35%5%6%7%36%
2365
April1st to 15thNight
11%8%25%5%2445%6%42%
2011
16th to endNight
9%8%35%5%35%45%6%40%
1805
May1st to 15thNight
19%7%25%5%2445%6%37%
1557
16th to endNight
15%5%1442345%7%44%
1535
June1st to 15thNight
16%7%245%34447%39%
1277
16th to endNight
15%5%35%5%45%5%6%9%35%
1218
July1st to 15thNight
11%425%5%3445%7%45%
1170
16th to endNight
12%423335%5%7%9%43%
1412
August1st to 15thNight
10%41431435%10%50%
1536
16th to endNight
14%41332345%8%47%
1805
September1st to 15thNight
13%6%245%3345%7%42%
1934
16th to endNight
17%6%25%5%3445%6%37%
2145
October1st to 15thNight
19%13%36%423345%32%
2354
16th to endNight
20%15%47%5%3334425%
2704
November1st to 15thNight
16%17%7%11%9%4434417%
2957
16th to endNight
10%16%6%12%11%5%5%445%17%
3150
December1st to 15thNight
10%13%7%11%10%5%6%6%6%5%15%
3184
16th to endNight
11%14%6%11%11%45%46%6%16%
3584

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
59%8%13%15%3
1271
16th to endDay
63%7%7%16%4
1703
February1st to 15thDay
54%7%16%16%5%
1640
16th to endDay
57%7%12%17%5%
1725
March1st to 15thDay
55%5%11%19%6%1
2100
16th to endDay
46%6%17%21%7%1
2558
April1st to 15thDay
43%5%15%20%14%1
2597
16th to endDay
40%6%13%24%14%
2759
May1st to 15thDay
48%6%11%21%10%1
3053
16th to endDay
42%5%11%25%13%
3287
June1st to 15thDay
48%7%12%18%12%
3341
16th to endDay
50%9%14%18%6%
3250
July1st to 15thDay
39%8%17%25%8%
2951
16th to endDay
39%10%21%23%5%
2924
August1st to 15thDay
36%10%25%23%3
2661
16th to endDay
40%10%25%21%2
2749
September1st to 15thDay
45%8%19%18%6%
2355
16th to endDay
48%8%18%21%3
2145
October1st to 15thDay
60%6%14%16%1
1923
16th to endDay
67%5%12%11%2
1872
November1st to 15thDay
71%5%10%8%3
1558
16th to endDay
69%7%12%9%
1470
December1st to 15thDay
67%7%13%7%4
1435
16th to endDay
67%5%10%13%2
1344
January1st to 15thNight
60%7%12%16%3
3324
16th to endNight
62%6%10%15%5%
3223
February1st to 15thNight
53%5%15%19%5%
2884
16th to endNight
53%6%14%18%6%
2330
March1st to 15thNight
50%5%11%22%8%1
2520
16th to endNight
44%6%15%22%10%1
2367
April1st to 15thNight
42%5%12%21%15%2
2011
16th to endNight
42%5%9%22%18%1
1805
May1st to 15thNight
46%6%12%21%11%2
1558
16th to endNight
38%5%11%24%17%2
1535
June1st to 15thNight
44%6%11%21%15%
1277
16th to endNight
43%11%17%19%7%
1218
July1st to 15thNight
36%6%17%26%12%
1110
16th to endNight
35%10%20%28%5%
1329
August1st to 15thNight
29%8%24%32%4
1528
16th to endNight
33%8%22%28%6%
1805
September1st to 15thNight
39%7%18%24%8%
1934
16th to endNight
45%8%14%23%8%
2145
October1st to 15thNight
53%6%14%20%4
2354
16th to endNight
61%5%13%15%3
2704
November1st to 15thNight
68%6%11%10%3
2957
16th to endNight
69%7%12%8%1
3150
December1st to 15thNight
66%8%12%9%3
3184
16th to endNight
67%410%14%3
3584

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
9%345%35%6%
125
16th to endDay
25%227%31%11%2
192
February1st to 15thDay
10%336%30%16%3
180
16th to endDay
8%6%23%34%22%4
159
March1st to 15thDay
12%431%38%13%
180
16th to endDay
14%10%27%24%20%3
290
April1st to 15thDay
15%6%31%31%14%1
476
16th to endDay
11%8%30%32%14%2
586
May1st to 15thDay
20%9%31%23%12%2
618
16th to endDay
18%5%25%28%16%4
677
June1st to 15thDay
22%9%28%22%14%3
645
16th to endDay
19%7%23%27%16%6%
611
July1st to 15thDay
18%7%24%26%17%5%
550
16th to endDay
14%6%24%26%18%8%
595
August1st to 15thDay
14%6%19%26%23%10%
549
16th to endDay
17%425%30%18%2
603
September1st to 15thDay
21%9%32%26%10%
390
16th to endDay
28%6%22%26%14%2
180
October1st to 15thDay
28%9%33%18%10%
180
16th to endDay
35%7%28%20%6%1
192
November1st to 15thDay
17%10%27%31%12%1
180
16th to endDay
25%5%33%27%6%1
180
December1st to 15thDay
17%330%34%8%5%
170
16th to endDay
8%326%42%15%3
128
January1st to 15thNight
14%6%33%31%11%2
1050
16th to endNight
19%6%35%29%9%
1120
February1st to 15thNight
11%432%34%14%2
1030
16th to endNight
10%5%26%34%20%2
818
March1st to 15thNight
15%7%25%32%17%1
840
16th to endNight
12%428%32%17%4
676
April1st to 15thNight
16%225%34%18%2
629
16th to endNight
12%430%33%16%2
624
May1st to 15thNight
21%427%30%13%1
630
16th to endNight
17%5%28%35%12%
659
June1st to 15thNight
21%323%33%17%
437
16th to endNight
20%420%35%17%2
406
July1st to 15thNight
13%427%32%20%1
370
16th to endNight
13%321%33%22%5%
580
August1st to 15thNight
10%421%33%24%6%
575
16th to endNight
16%224%34%21%
621
September1st to 15thNight
17%427%32%18%1
585
16th to endNight
21%427%34%10%1
582
October1st to 15thNight
26%6%23%31%10%
794
16th to endNight
29%8%28%23%8%
1040
November1st to 15thNight
23%6%29%27%11%1
1025
16th to endNight
20%8%32%29%7%1
1050
December1st to 15thNight
17%5%33%28%13%2
1050
16th to endNight
20%426%27%16%4
1120
Page generated at 2019-06-24 19:41:33. Version ac04

Copyright 2019 A. Danko


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