Keivers Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Keivers Lake 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
42%
23471
14%
74660
10%
23441
47%
23441
22%
49164

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
36%
946
14%
2836
8%
946
41%
946
18%
2047
January11th to 20thNight
37%
930
17%
2790
10%
930
43%
930
20%
1948
January21st to endNight
36%
828
19%
2808
12%
828
46%
828
16%
1928
February1st to 10thNight
38%
720
14%
2520
13%
720
44%
720
16%
1754
February11th to 20thNight
34%
704
14%
2282
10%
700
41%
700
16%
1636
February21st to endNight
48%
592
17%
1843
15%
592
53%
592
23%
1220
March1st to 10thNight
41%
720
15%
2160
12%
720
46%
720
20%
1541
March11th to 20thNight
41%
720
17%
1994
10%
720
46%
720
23%
1394
March21st to endNight
37%
792
10%
2160
5%
792
40%
792
19%
1618
April1st to 10thNight
38%
649
14%
1729
5%
649
44%
649
20%
1245
April11th to 20thNight
39%
533
15%
1601
10%
533
43%
533
20%
1126
April21st to endNight
38%
540
12%
1620
10%
540
41%
540
21%
1106
May1st to 10thNight
38%
450
9%
1450
7%
450
43%
450
19%
994
May11th to 20thNight
47%
354
12%
1239
12%
354
51%
354
25%
761
May21st to endNight
45%
388
5%
1358
3%
388
46%
388
20%
899
June1st to 10thNight
43%
360
1%
1260
0%
360
43%
360
17%
872
June11th to 20thNight
35%
360
0%
1260
0%
360
35%
360
14%
906
June21st to endNight
55%
360
0%
1260
0%
360
55%
360
25%
770
July1st to 10thNight
60%
350
0%
1225
0%
350
60%
350
25%
740
July11th to 20thNight
58%
348
3%
1218
1%
348
59%
348
25%
757
July21st to endNight
68%
394
10%
1313
11%
372
68%
372
35%
692
August1st to 10thNight
60%
358
10%
1424
15%
356
63%
356
25%
798
August11th to 20thNight
58%
504
14%
1572
14%
504
60%
504
32%
909
August21st to endNight
60%
594
19%
1782
15%
594
62%
594
36%
1016
September1st to 10thNight
53%
602
19%
1704
13%
602
56%
602
35%
1021
September11th to 20thNight
52%
720
18%
1980
12%
720
56%
720
32%
1262
September21st to endNight
50%
720
22%
1980
14%
720
57%
720
35%
1221
October1st to 10thNight
46%
720
19%
2074
12%
720
53%
720
27%
1361
October11th to 20thNight
43%
720
17%
2286
11%
720
50%
720
25%
1456
October21st to endNight
37%
792
17%
2574
10%
792
46%
792
21%
1701
November1st to 10thNight
35%
876
18%
2541
11%
876
43%
876
21%
1774
November11th to 20thNight
32%
950
18%
2737
10%
950
40%
950
23%
1852
November21st to endNight
38%
950
13%
2850
8%
950
43%
950
23%
1922
December1st to 10thNight
38%
950
16%
2850
10%
950
43%
950
20%
1994
December11th to 20thNight
37%
949
14%
3475
8%
949
42%
949
16%
2339
December21st to endNight
36%
1028
12%
4905
9%
1026
43%
1026
16%
2584

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%8%47%6%45%5%6%8%36%
74656
Night
8%9%48%7%45%5%6%8%35%
75165
TransparencyDay
45%416%24%9%1
74338
Night
46%414%23%10%2
75001
SeeingDay
13%6%24%31%20%7%
14252
Night
12%5%28%36%16%2
23494

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
5%12%5%7%8%35%7%7%8%31%
1329
11th to 20thDay
7%11%5%8%8%46%6%6%7%32%
1298
21st to endDay
7%11%5%10%8%5%6%6%6%8%28%
1566
February1st to 10thDay
6%12%5%10%8%46%5%7%9%27%
1440
11th to 20thDay
8%13%5%9%8%5%6%7%7%8%25%
1566
21st to endDay
5%12%7%11%10%5%5%7%7%7%26%
1412
March1st to 10thDay
5%13%5%10%11%46%6%6%8%26%
1800
11th to 20thDay
7%10%49%7%5%6%5%6%9%32%
1965
21st to endDay
10%13%6%9%7%36%5%6%7%27%
2196
April1st to 10thDay
8%11%5%8%6%46%7%7%8%30%
2230
11th to 20thDay
12%13%5%8%6%35%5%7%8%29%
2310
21st to endDay
13%9%47%6%45%5%5%9%32%
2340
May1st to 10thDay
15%11%47%6%46%5%5%8%30%
2506
11th to 20thDay
11%6%25%6%46%6%6%9%40%
2654
21st to endDay
19%6%35%6%35%5%6%8%33%
2917
June1st to 10thDay
16%6%36%6%46%6%7%10%31%
2700
11th to 20thDay
18%7%47%6%46%6%7%7%26%
2700
21st to endDay
9%425%6%46%6%7%10%40%
2700
July1st to 10thDay
10%5%25%5%46%6%7%10%41%
2700
11th to 20thDay
11%5%24435%6%6%9%43%
2700
21st to endDay
7%4243345%6%10%52%
2925
August1st to 10thDay
11%5%244346%7%9%45%
2507
11th to 20thDay
9%5%2443447%10%47%
2327
21st to endDay
10%424435%6%6%9%47%
2574
September1st to 10thDay
12%5%35%5%345%5%8%46%
2252
11th to 20thDay
16%7%25%424447%45%
1980
21st to endDay
9%8%25%5%4446%9%43%
1980
October1st to 10thDay
12%10%36%5%3445%6%41%
1886
11th to 20thDay
9%9%47%6%5%45%6%7%38%
1674
21st to endDay
8%9%48%7%46%5%7%7%34%
1782
November1st to 10thDay
10%15%6%11%5%35%5%6%7%27%
1516
11th to 20thDay
8%12%410%6%36%5%5%7%34%
1440
21st to endDay
6%10%410%7%45%6%6%8%34%
1330
December1st to 10thDay
7%12%6%9%10%6%7%45%7%29%
1330
11th to 20thDay
5%10%6%10%9%47%5%6%8%30%
1682
21st to endDay
48%37%7%45%5%5%8%43%
2442
January1st to 10thNight
5%11%6%11%9%5%6%6%7%8%27%
2836
11th to 20thNight
6%11%6%9%8%45%6%6%9%31%
2790
21st to endNight
6%12%5%10%6%5%6%6%8%8%28%
2808
February1st to 10thNight
6%10%6%11%9%5%5%6%6%9%28%
2520
11th to 20thNight
6%12%6%10%9%5%7%6%7%6%27%
2281
21st to endNight
410%5%8%9%46%6%8%9%31%
1843
March1st to 10thNight
6%11%49%11%5%6%5%6%7%29%
2160
11th to 20thNight
6%10%5%9%8%46%6%7%8%31%
1994
21st to endNight
8%13%6%9%7%36%6%8%9%23%
2160
April1st to 10thNight
9%10%5%9%8%36%6%6%9%30%
1729
11th to 20thNight
9%11%410%8%46%6%6%7%29%
1601
21st to endNight
12%9%47%6%46%6%6%8%32%
1620
May1st to 10thNight
13%11%46%6%446%7%8%31%
1450
11th to 20thNight
9%7%36%7%45%5%5%9%39%
1239
21st to endNight
19%7%345%446%6%9%33%
1358
June1st to 10thNight
17%6%37%6%45%6%7%8%30%
1260
11th to 20thNight
18%7%48%8%48%5%6%7%26%
1260
21st to endNight
11%5%25%6%37%7%7%9%39%
1260
July1st to 10thNight
10%5%245%46%7%7%10%41%
1260
11th to 20thNight
8%436%7%46%7%8%9%38%
1260
21st to endNight
5%425%435%46%10%51%
1390
August1st to 10thNight
9%5%25%6%445%7%9%44%
1432
11th to 20thNight
9%6%25%5%346%6%10%45%
1572
21st to endNight
8%425%435%5%7%10%47%
1782
September1st to 10thNight
10%5%25%445%5%6%8%47%
1704
11th to 20thNight
14%7%25%4245%5%8%44%
1980
21st to endNight
10%6%25%43447%8%46%
1980
October1st to 10thNight
12%10%35%5%35%5%5%6%42%
2074
11th to 20thNight
9%7%37%6%45%5%6%8%38%
2286
21st to endNight
7%10%5%8%6%45%6%6%8%36%
2574
November1st to 10thNight
10%14%5%7%6%35%5%5%8%32%
2541
11th to 20thNight
5%9%5%9%8%5%6%6%6%9%33%
2737
21st to endNight
5%10%49%8%5%5%5%7%9%33%
2850
December1st to 10thNight
7%11%5%9%8%46%5%5%7%32%
2850
11th to 20thNight
39%5%11%9%5%7%6%6%8%31%
3510
21st to endNight
47%38%6%45%5%6%8%44%
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
49%5%13%22%9%2
1329
11th to 20thDay
52%412%22%8%3
1298
21st to endDay
53%413%17%11%1
1566
February1st to 10thDay
53%413%19%10%2
1440
11th to 20thDay
54%6%15%17%7%1
1575
21st to endDay
57%410%19%11%
1412
March1st to 10thDay
57%414%17%8%1
1800
11th to 20thDay
49%411%23%11%1
1966
21st to endDay
56%5%14%18%7%1
2196
April1st to 10thDay
49%6%15%20%9%1
2230
11th to 20thDay
53%49%23%10%1
2310
21st to endDay
50%314%23%8%1
2340
May1st to 10thDay
52%314%23%8%
2506
11th to 20thDay
40%416%29%11%
2658
21st to endDay
50%414%24%8%
2918
June1st to 10thDay
47%5%18%22%8%1
2700
11th to 20thDay
54%5%14%21%5%1
2700
21st to endDay
37%6%20%29%7%1
2700
July1st to 10thDay
37%6%23%26%8%1
2626
11th to 20thDay
36%6%23%29%6%
2619
21st to endDay
27%5%24%32%11%1
2762
August1st to 10thDay
34%6%22%29%7%1
2490
11th to 20thDay
32%5%24%28%9%1
2327
21st to endDay
33%420%29%12%1
2574
September1st to 10thDay
37%417%28%11%4
2252
11th to 20thDay
41%314%30%10%2
1980
21st to endDay
38%417%26%12%3
1980
October1st to 10thDay
44%315%26%10%2
1886
11th to 20thDay
44%415%25%10%1
1674
21st to endDay
47%5%12%23%12%1
1782
November1st to 10thDay
56%411%20%8%2
1516
11th to 20thDay
49%413%24%9%1
1440
21st to endDay
47%417%22%8%2
1330
December1st to 10thDay
58%311%16%10%2
1330
11th to 20thDay
52%315%23%5%1
1684
21st to endDay
40%210%25%18%5%
2442
January1st to 10thNight
53%5%12%17%9%3
2836
11th to 20thNight
51%413%22%7%3
2790
21st to endNight
52%412%19%11%2
2808
February1st to 10thNight
54%410%21%11%1
2520
11th to 20thNight
56%411%19%10%1
2282
21st to endNight
46%413%22%13%1
1843
March1st to 10thNight
52%5%13%22%7%1
2160
11th to 20thNight
48%5%14%22%10%1
1994
21st to endNight
56%414%18%7%1
2160
April1st to 10thNight
50%6%12%18%13%1
1729
11th to 20thNight
51%412%24%8%1
1601
21st to endNight
49%314%24%8%2
1620
May1st to 10thNight
50%413%21%10%1
1450
11th to 20thNight
42%412%25%16%
1239
21st to endNight
48%416%23%7%1
1358
June1st to 10thNight
50%6%14%20%9%
1260
11th to 20thNight
57%413%18%6%2
1260
21st to endNight
39%6%19%26%8%1
1260
July1st to 10thNight
37%8%21%26%7%1
1225
11th to 20thNight
39%8%21%23%8%1
1218
21st to endNight
28%6%22%31%13%1
1313
August1st to 10thNight
36%6%23%27%8%1
1424
11th to 20thNight
34%5%20%30%9%1
1572
21st to endNight
32%419%31%12%3
1782
September1st to 10thNight
35%416%28%13%5%
1704
11th to 20thNight
38%415%27%11%4
1980
21st to endNight
35%415%28%15%3
1980
October1st to 10thNight
44%313%26%12%1
2074
11th to 20thNight
43%5%15%24%11%2
2286
21st to endNight
46%5%15%24%10%1
2574
November1st to 10thNight
50%411%24%10%1
2541
11th to 20thNight
48%415%21%12%1
2737
21st to endNight
47%5%17%20%9%2
2850
December1st to 10thNight
52%312%22%10%2
2850
11th to 20thNight
51%417%21%6%1
3507
21st to endNight
39%210%28%15%5%
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%423%39%19%8%
180
11th to 20thDay
8%431%34%20%4
171
21st to endDay
9%9%28%25%23%7%
176
February1st to 10thDay
14%9%24%34%13%5%
160
11th to 20thDay
11%7%28%36%16%2
236
21st to endDay
8%5%22%36%23%5%
278
March1st to 10thDay
9%6%29%32%18%7%
420
11th to 20thDay
8%426%35%19%7%
420
21st to endDay
12%5%25%31%18%8%
462
April1st to 10thDay
11%8%29%32%15%6%
420
11th to 20thDay
16%9%26%26%17%6%
412
21st to endDay
16%8%27%29%18%3
420
May1st to 10thDay
18%9%21%27%19%6%
501
11th to 20thDay
13%5%21%33%21%6%
625
21st to endDay
18%419%29%22%8%
679
June1st to 10thDay
16%6%23%34%16%4
630
11th to 20thDay
20%8%22%32%16%3
630
21st to endDay
8%423%32%23%10%
630
July1st to 10thDay
11%419%33%25%9%
621
11th to 20thDay
13%320%34%23%7%
618
21st to endDay
6%321%31%29%10%
671
August1st to 10thDay
12%321%31%23%10%
447
11th to 20thDay
8%5%18%32%28%8%
437
21st to endDay
10%6%20%31%24%9%
495
September1st to 10thDay
14%6%29%28%17%5%
450
11th to 20thDay
18%6%23%27%19%6%
450
21st to endDay
14%11%27%27%14%5%
450
October1st to 10thDay
18%8%22%28%17%7%
356
11th to 20thDay
11%9%33%27%16%4
270
21st to endDay
15%12%30%29%11%2
297
November1st to 10thDay
16%6%27%36%11%4
270
11th to 20thDay
15%8%31%31%13%2
232
21st to endDay
6%5%33%29%18%9%
180
December1st to 10thDay
9%431%34%16%7%
180
11th to 20thDay
8%7%33%33%14%4
180
21st to endDay
10%322%34%24%7%
198
January1st to 10thNight
11%5%32%36%14%2
950
11th to 20thNight
11%6%32%36%14%2
930
21st to endNight
11%8%28%36%13%3
828
February1st to 10thNight
10%8%27%35%18%3
720
11th to 20thNight
11%5%34%37%12%1
704
21st to endNight
8%224%38%23%5%
592
March1st to 10thNight
10%428%39%16%3
720
11th to 20thNight
9%430%39%15%3
720
21st to endNight
13%6%26%36%17%3
792
April1st to 10thNight
13%5%28%35%16%3
649
11th to 20thNight
16%6%30%36%11%1
533
21st to endNight
16%7%28%35%13%1
540
May1st to 10thNight
16%8%26%33%16%1
450
11th to 20thNight
10%6%29%36%18%1
354
21st to endNight
21%322%32%19%2
389
June1st to 10thNight
18%7%25%35%12%4
360
11th to 20thNight
19%430%29%18%1
360
21st to endNight
12%321%40%22%2
360
July1st to 10thNight
12%115%44%25%2
350
11th to 20thNight
11%221%45%20%2
348
21st to endNight
6%318%42%29%3
394
August1st to 10thNight
12%315%39%27%4
358
11th to 20thNight
10%419%40%25%2
504
21st to endNight
10%421%41%24%
594
September1st to 10thNight
13%325%40%18%2
602
11th to 20thNight
16%322%37%20%2
720
21st to endNight
12%329%36%19%2
720
October1st to 10thNight
16%424%36%17%2
720
11th to 20thNight
11%5%30%36%16%2
720
21st to endNight
11%9%31%34%14%1
792
November1st to 10thNight
15%7%32%34%11%2
876
11th to 20thNight
9%7%39%31%11%3
950
21st to endNight
9%5%35%37%12%2
950
December1st to 10thNight
11%7%30%33%15%3
950
11th to 20thNight
9%6%34%37%13%2
950
21st to endNight
12%330%37%16%3
1045
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