Rock Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rock Lake clear sky chart from 2005-11-06 to 2024-01-13.

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%
25080
14%
74727
8%
25031
41%
25031
21%
51235

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
24%
948
11%
2837
5%
946
30%
946
14%
2114
January11th to 20thNight
22%
915
9%
2614
5%
915
27%
915
13%
2059
January21st to endNight
23%
990
12%
2772
5%
990
29%
990
13%
2211
February1st to 10thNight
27%
900
11%
2492
4%
900
33%
900
17%
1855
February11th to 20thNight
33%
866
14%
2265
6%
865
38%
865
21%
1645
February21st to endNight
38%
592
18%
1776
9%
592
46%
592
22%
1238
March1st to 10thNight
29%
720
10%
2160
5%
720
34%
720
16%
1632
March11th to 20thNight
35%
568
21%
2008
13%
568
47%
568
21%
1287
March21st to endNight
37%
594
13%
2147
12%
594
42%
594
17%
1472
April1st to 10thNight
38%
540
19%
1782
14%
540
49%
540
25%
1093
April11th to 20thNight
36%
533
15%
1599
11%
533
43%
533
21%
1117
April21st to endNight
37%
540
13%
1620
10%
540
41%
540
23%
1089
May1st to 10thNight
40%
540
14%
1594
6%
540
43%
540
28%
1028
May11th to 20thNight
43%
531
16%
1293
7%
531
45%
531
30%
903
May21st to endNight
41%
584
11%
1358
5%
582
43%
582
31%
953
June1st to 10thNight
43%
540
7%
1260
3%
540
46%
540
35%
846
June11th to 20thNight
40%
540
7%
1260
4%
540
44%
540
30%
875
June21st to endNight
53%
540
9%
1260
5%
540
56%
540
37%
817
July1st to 10thNight
59%
525
10%
1225
6%
525
62%
525
49%
736
July11th to 20thNight
54%
522
13%
1218
5%
522
58%
522
44%
759
July21st to endNight
64%
591
17%
1468
10%
558
65%
558
49%
812
August1st to 10thNight
60%
537
18%
1436
8%
534
64%
534
41%
844
August11th to 20thNight
58%
534
21%
1600
12%
534
65%
534
39%
875
August21st to endNight
52%
594
24%
1782
21%
594
60%
594
38%
990
September1st to 10thNight
48%
540
20%
1769
17%
540
58%
540
34%
966
September11th to 20thNight
45%
540
20%
1980
17%
540
54%
540
29%
1103
September21st to endNight
38%
540
21%
1980
17%
540
49%
540
23%
1200
October1st to 10thNight
33%
592
18%
2032
12%
592
41%
592
20%
1349
October11th to 20thNight
33%
836
19%
2276
9%
836
40%
836
24%
1545
October21st to endNight
28%
990
15%
2574
5%
990
34%
990
21%
1869
November1st to 10thNight
26%
925
16%
2444
4%
925
34%
925
19%
1772
November11th to 20thNight
24%
950
13%
2660
5%
950
30%
950
15%
2025
November21st to endNight
20%
950
11%
2850
4%
950
28%
950
15%
2115
December1st to 10thNight
26%
950
9%
2850
4%
950
32%
950
14%
2163
December11th to 20thNight
20%
950
8%
3498
3%
949
27%
949
9%
2666
December21st to endNight
22%
1033
8%
4988
6%
1026
29%
1026
8%
3212

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
11%9%47%6%35%5%6%7%36%
74614
Night
9%9%48%7%45%5%6%7%36%
75154
TransparencyDay
46%7%15%23%9%1
74306
Night
46%6%14%23%10%1
74982
SeeingDay
14%9%31%29%14%4
15016
Night
14%8%33%32%12%1
25098

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
6%10%5%14%10%46%5%7%7%25%
1329
11th to 20thDay
6%13%7%12%11%5%8%6%7%7%18%
1406
21st to endDay
7%15%7%12%10%5%7%7%6%7%16%
1584
February1st to 10thDay
9%12%5%11%8%5%7%5%7%8%22%
1467
11th to 20thDay
6%9%5%10%11%5%8%9%8%8%23%
1598
21st to endDay
7%11%5%10%8%5%7%7%6%7%27%
1480
March1st to 10thDay
10%12%8%13%10%35%6%6%6%22%
1800
11th to 20thDay
7%11%49%9%46%5%5%8%32%
1950
21st to endDay
13%11%6%10%6%45%46%8%27%
2206
April1st to 10thDay
10%11%5%7%6%35%5%6%8%35%
2178
11th to 20thDay
13%11%5%8%7%35%5%6%7%31%
2312
21st to endDay
15%9%5%8%6%35%5%6%5%33%
2340
May1st to 10thDay
15%9%46%5%3445%7%39%
2364
11th to 20thDay
16%8%36%5%3445%8%38%
2601
21st to endDay
18%7%35%5%345%5%8%36%
2918
June1st to 10thDay
13%6%35%6%347%7%8%39%
2700
11th to 20thDay
15%5%36%6%46%5%6%8%37%
2700
21st to endDay
12%6%35%6%36%7%7%9%38%
2700
July1st to 10thDay
8%4245%345%6%9%48%
2700
11th to 20thDay
9%435%5%35%5%7%8%46%
2700
21st to endDay
6%31443447%9%55%
2760
August1st to 10thDay
9%5%25%5%345%6%8%48%
2495
11th to 20thDay
10%425%42446%10%49%
2301
21st to endDay
12%5%2443345%6%51%
2574
September1st to 10thDay
12%5%245%3345%7%50%
2188
11th to 20thDay
15%6%25%4335%5%7%46%
1980
21st to endDay
14%6%25%5%3446%9%42%
1980
October1st to 10thDay
17%12%35%6%24446%36%
1909
11th to 20thDay
12%11%47%5%3445%8%37%
1681
21st to endDay
14%13%49%6%445%6%7%28%
1782
November1st to 10thDay
16%14%6%9%5%35%5%4430%
1632
11th to 20thDay
8%14%7%14%9%45%5%45%26%
1518
21st to endDay
10%13%5%10%8%5%6%45%5%29%
1330
December1st to 10thDay
7%12%6%13%12%5%6%7%6%5%21%
1330
11th to 20thDay
9%13%6%14%10%5%6%5%6%6%19%
1679
21st to endDay
8%8%411%7%45%6%6%6%35%
2442
January1st to 10thNight
6%11%6%11%9%5%7%5%6%7%27%
2837
11th to 20thNight
9%13%7%11%8%46%6%5%6%22%
2614
21st to endNight
6%12%7%13%11%47%7%6%6%19%
2772
February1st to 10thNight
8%9%5%10%9%48%8%7%7%25%
2492
11th to 20thNight
6%9%39%8%47%7%7%7%31%
2264
21st to endNight
7%9%48%8%5%6%6%7%7%33%
1776
March1st to 10thNight
10%12%6%10%7%5%6%6%6%7%26%
2160
11th to 20thNight
7%9%48%8%445%6%7%39%
2008
21st to endNight
10%10%48%7%45%5%6%7%34%
2147
April1st to 10thNight
8%7%36%6%36%5%6%8%41%
1782
11th to 20thNight
13%11%46%5%35%5%5%7%35%
1599
21st to endNight
14%7%36%5%36%6%6%7%36%
1620
May1st to 10thNight
13%7%35%6%35%46%7%42%
1594
11th to 20thNight
15%8%245%345%6%8%41%
1293
21st to endNight
16%8%36%42446%7%41%
1358
June1st to 10thNight
11%5%245%35%6%6%10%45%
1260
11th to 20thNight
11%6%35%6%36%6%6%6%42%
1260
21st to endNight
8%425%3347%7%11%46%
1260
July1st to 10thNight
6%2145%2445%9%58%
1260
11th to 20thNight
6%314425%5%7%8%55%
1260
21st to endNight
5%413325%46%9%59%
1554
August1st to 10thNight
6%425%435%45%7%55%
1444
11th to 20thNight
6%4144345%6%11%54%
1600
21st to endNight
9%5%23423446%58%
1782
September1st to 10thNight
9%5%135%34447%55%
1769
11th to 20thNight
12%425%42347%7%50%
1980
21st to endNight
14%7%35%5%2445%7%44%
1980
October1st to 10thNight
14%10%36%6%3445%6%40%
2032
11th to 20thNight
15%10%35%5%35%45%7%38%
2276
21st to endNight
11%11%48%6%445%6%6%35%
2574
November1st to 10thNight
11%11%5%8%6%35%6%6%8%32%
2444
11th to 20thNight
8%12%6%13%8%45%5%5%6%28%
2660
21st to endNight
10%13%5%10%8%345%46%31%
2850
December1st to 10thNight
7%10%6%12%9%5%7%6%6%6%26%
2850
11th to 20thNight
9%15%6%13%9%46%45%7%22%
3518
21st to endNight
8%10%5%10%7%5%6%5%5%5%34%
5225

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
56%7%12%19%6%1
1329
11th to 20thDay
63%6%10%15%7%
1406
21st to endDay
66%5%9%13%7%
1584
February1st to 10thDay
59%5%11%18%7%
1467
11th to 20thDay
54%7%11%18%10%1
1607
21st to endDay
55%6%12%18%8%
1480
March1st to 10thDay
61%7%13%13%6%
1800
11th to 20thDay
49%8%13%21%9%
1952
21st to endDay
54%7%14%19%6%
2206
April1st to 10thDay
47%5%16%23%9%1
2178
11th to 20thDay
52%5%12%19%11%1
2312
21st to endDay
51%5%16%18%8%1
2340
May1st to 10thDay
44%6%11%26%11%1
2364
11th to 20thDay
45%6%12%26%10%1
2605
21st to endDay
46%7%14%24%8%1
2918
June1st to 10thDay
42%8%18%22%9%1
2700
11th to 20thDay
45%8%15%22%9%1
2700
21st to endDay
39%9%20%25%6%1
2700
July1st to 10thDay
31%8%19%32%10%1
2626
11th to 20thDay
34%9%17%29%11%
2619
21st to endDay
25%8%19%35%12%1
2607
August1st to 10thDay
33%8%18%30%10%1
2479
11th to 20thDay
30%8%19%33%9%
2301
21st to endDay
34%6%14%33%13%1
2574
September1st to 10thDay
33%6%17%29%13%1
2188
11th to 20thDay
39%6%18%25%11%1
1980
21st to endDay
39%6%16%31%8%
1980
October1st to 10thDay
49%6%12%24%9%
1909
11th to 20thDay
46%414%26%9%
1681
21st to endDay
54%6%14%19%6%
1782
November1st to 10thDay
57%5%11%18%9%1
1632
11th to 20thDay
59%5%15%14%6%
1518
21st to endDay
57%7%11%18%7%
1330
December1st to 10thDay
62%8%11%15%4
1330
11th to 20thDay
64%7%10%14%5%
1680
21st to endDay
47%6%12%20%14%1
2442
January1st to 10thNight
55%7%10%20%7%
2837
11th to 20thNight
60%7%11%13%8%
2614
21st to endNight
62%6%11%13%8%
2772
February1st to 10thNight
54%6%13%17%10%1
2492
11th to 20thNight
50%6%14%18%12%1
2265
21st to endNight
48%6%12%22%11%1
1776
March1st to 10thNight
56%6%13%17%6%
2160
11th to 20thNight
45%5%12%27%11%1
2008
21st to endNight
48%8%15%20%8%
2147
April1st to 10thNight
40%5%12%25%16%2
1782
11th to 20thNight
49%5%11%20%14%1
1599
21st to endNight
44%7%15%21%11%2
1620
May1st to 10thNight
41%5%13%27%13%1
1594
11th to 20thNight
41%6%11%25%14%3
1293
21st to endNight
42%5%14%26%12%1
1358
June1st to 10thNight
34%8%19%28%8%2
1260
11th to 20thNight
39%8%15%24%12%2
1260
21st to endNight
31%9%21%33%6%1
1260
July1st to 10thNight
23%7%18%35%15%2
1225
11th to 20thNight
25%9%18%31%16%1
1218
21st to endNight
22%6%17%37%17%2
1468
August1st to 10thNight
27%7%17%34%12%2
1436
11th to 20thNight
25%8%20%34%12%1
1600
21st to endNight
28%6%14%35%17%2
1782
September1st to 10thNight
30%5%13%34%16%2
1769
11th to 20thNight
32%6%17%30%13%1
1980
21st to endNight
41%5%12%31%10%1
1980
October1st to 10thNight
46%6%13%25%10%
2032
11th to 20thNight
46%412%27%11%
2276
21st to endNight
49%7%14%24%7%1
2574
November1st to 10thNight
49%7%13%20%9%2
2444
11th to 20thNight
57%6%13%16%7%1
2660
21st to endNight
55%7%15%17%6%
2850
December1st to 10thNight
57%7%14%16%6%
2850
11th to 20thNight
62%6%14%13%5%1
3516
21st to endNight
50%5%11%20%13%1
5225

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
10%10%35%29%12%4
270
11th to 20thDay
11%8%37%31%12%2
248
21st to endDay
17%7%39%27%8%3
264
February1st to 10thDay
13%10%45%26%5%2
240
11th to 20thDay
11%9%35%34%10%1
240
21st to endDay
6%7%39%34%13%2
198
March1st to 10thDay
13%12%33%29%10%3
240
11th to 20thDay
11%8%35%29%15%3
240
21st to endDay
16%8%31%27%13%5%
292
April1st to 10thDay
14%12%35%29%7%2
438
11th to 20thDay
19%9%32%25%13%2
590
21st to endDay
19%10%31%25%13%3
600
May1st to 10thDay
16%10%26%31%15%2
603
11th to 20thDay
19%8%31%25%14%3
625
21st to endDay
20%8%23%30%16%3
679
June1st to 10thDay
14%9%29%29%12%7%
630
11th to 20thDay
14%8%34%28%11%5%
630
21st to endDay
12%8%28%31%16%5%
630
July1st to 10thDay
9%5%29%32%20%6%
621
11th to 20thDay
10%8%28%30%19%4
618
21st to endDay
7%425%37%19%8%
684
August1st to 10thDay
9%5%23%35%22%6%
626
11th to 20thDay
12%7%24%30%21%7%
615
21st to endDay
12%7%25%31%20%4
693
September1st to 10thDay
14%8%36%28%11%3
478
11th to 20thDay
17%8%27%35%11%2
270
21st to endDay
20%12%30%26%11%1
270
October1st to 10thDay
24%13%26%24%10%3
270
11th to 20thDay
19%8%37%24%8%3
270
21st to endDay
25%9%37%22%5%2
297
November1st to 10thDay
27%10%30%22%9%2
270
11th to 20thDay
14%14%36%28%8%
270
21st to endDay
16%15%39%24%5%1
270
December1st to 10thDay
14%9%36%27%11%3
270
11th to 20thDay
13%14%38%28%6%1
270
21st to endDay
13%8%40%27%10%3
297
January1st to 10thNight
11%10%37%29%10%1
950
11th to 20thNight
15%10%38%28%8%1
915
21st to endNight
13%12%37%30%7%1
990
February1st to 10thNight
12%9%38%31%10%1
900
11th to 20thNight
11%9%36%32%10%2
870
21st to endNight
12%6%33%35%12%2
592
March1st to 10thNight
13%8%35%28%12%3
720
11th to 20thNight
12%7%36%32%12%1
568
21st to endNight
15%6%31%32%14%2
594
April1st to 10thNight
10%6%39%32%11%1
540
11th to 20thNight
19%8%29%34%10%1
533
21st to endNight
16%6%34%30%13%1
540
May1st to 10thNight
16%6%30%32%13%1
540
11th to 20thNight
18%7%26%34%13%
531
21st to endNight
21%7%26%33%14%1
584
June1st to 10thNight
12%6%33%33%14%1
540
11th to 20thNight
13%6%35%30%17%1
540
21st to endNight
12%325%41%19%
540
July1st to 10thNight
6%325%43%22%1
525
11th to 20thNight
8%5%27%42%17%1
522
21st to endNight
6%223%48%19%2
591
August1st to 10thNight
8%321%49%18%1
537
11th to 20thNight
7%326%40%21%3
534
21st to endNight
11%427%41%16%1
594
September1st to 10thNight
11%5%31%33%17%3
540
11th to 20thNight
15%5%31%38%11%1
540
21st to endNight
18%6%32%30%12%1
540
October1st to 10thNight
19%7%32%31%10%
592
11th to 20thNight
21%9%29%31%9%
836
21st to endNight
16%11%36%29%7%1
990
November1st to 10thNight
17%11%37%28%7%1
925
11th to 20thNight
14%11%38%26%8%2
950
21st to endNight
18%13%38%24%6%1
950
December1st to 10thNight
11%10%37%31%10%2
950
11th to 20thNight
17%10%33%28%9%2
950
21st to endNight
18%6%34%30%9%2
1045
Page generated at 2024-01-10 18:35:19. Version ac07

Copyright 2024 Attilla Danko


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