Mills Norrie State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mills Norrie State Park clear sky chart from 2005-11-06 to 2024-01-10.

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
34%
22971
18%
74626
10%
22931
43%
22931
21%
49275

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
23%
760
20%
2647
9%
757
39%
757
20%
1675
January11th to 20thNight
25%
720
16%
2520
7%
720
37%
720
15%
1722
January21st to endNight
23%
792
19%
2678
8%
792
37%
792
20%
1691
February1st to 10thNight
20%
720
15%
2340
5%
720
33%
720
17%
1605
February11th to 20thNight
18%
703
17%
2109
5%
700
33%
700
18%
1455
February21st to endNight
19%
592
22%
1776
8%
592
36%
592
19%
1214
March1st to 10thNight
24%
720
19%
2160
9%
720
37%
720
21%
1422
March11th to 20thNight
23%
720
19%
2073
7%
720
35%
720
20%
1421
March21st to endNight
23%
792
21%
1994
6%
792
34%
792
22%
1407
April1st to 10thNight
21%
720
17%
1800
4%
720
29%
720
19%
1319
April11th to 20thNight
27%
711
16%
1775
4%
711
33%
711
24%
1262
April21st to endNight
27%
666
18%
1746
6%
666
34%
666
22%
1242
May1st to 10thNight
26%
540
14%
1620
7%
540
32%
540
17%
1173
May11th to 20thNight
31%
354
20%
1416
13%
354
43%
354
18%
891
May21st to endNight
49%
388
15%
1551
16%
388
54%
388
20%
954
June1st to 10thNight
46%
360
17%
1440
18%
360
55%
360
20%
888
June11th to 20thNight
48%
360
13%
1440
16%
360
55%
360
20%
896
June21st to endNight
56%
360
15%
1440
18%
360
63%
360
25%
850
July1st to 10thNight
59%
350
15%
1400
21%
350
62%
350
23%
820
July11th to 20thNight
58%
348
14%
1392
18%
348
60%
348
22%
833
July21st to endNight
59%
394
18%
1486
21%
372
64%
372
24%
871
August1st to 10thNight
61%
401
19%
1465
18%
399
64%
399
26%
874
August11th to 20thNight
57%
710
15%
1774
10%
710
58%
710
28%
1263
August21st to endNight
54%
792
18%
1980
10%
792
57%
792
31%
1335
September1st to 10thNight
48%
720
20%
1800
9%
720
52%
720
31%
1218
September11th to 20thNight
50%
720
26%
1879
17%
720
55%
720
36%
1163
September21st to endNight
46%
720
25%
1980
17%
720
53%
720
30%
1275
October1st to 10thNight
38%
720
17%
2078
12%
720
44%
720
22%
1417
October11th to 20thNight
39%
720
21%
2160
13%
720
49%
720
25%
1401
October21st to endNight
28%
792
16%
2542
9%
792
38%
792
19%
1757
November1st to 10thNight
37%
740
23%
2407
13%
740
51%
740
25%
1488
November11th to 20thNight
29%
760
22%
2470
12%
760
43%
760
22%
1600
November21st to endNight
31%
760
20%
2584
11%
760
44%
760
22%
1615
December1st to 10thNight
23%
760
17%
2660
7%
760
36%
760
17%
1788
December11th to 20thNight
24%
760
13%
3218
5%
759
34%
759
13%
2150
December21st to endNight
20%
826
11%
4826
5%
817
36%
817
10%
3320

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
16%7%35%5%35%5%5%8%38%
74743
Night
17%7%36%5%3445%7%39%
74925
TransparencyDay
43%7%12%22%14%2
74448
Night
43%7%12%22%14%2
74754
SeeingDay
21%13%28%24%11%4
13769
Night
20%10%30%29%9%1
22982

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 10thDay
13%8%35%6%36%6%6%6%38%
1509
11th to 20thDay
16%8%36%6%36%6%7%8%30%
1440
21st to endDay
12%8%45%6%45%45%7%40%
1676
February1st to 10thDay
16%10%47%6%45%5%5%6%31%
1620
11th to 20thDay
13%8%47%6%35%45%7%38%
1737
21st to endDay
20%8%35%7%3445%7%35%
1480
March1st to 10thDay
14%7%47%6%3445%6%39%
1797
11th to 20thDay
15%9%46%5%345%5%7%38%
1885
21st to endDay
19%8%36%6%34445%38%
2362
April1st to 10thDay
17%9%46%5%2445%6%37%
2160
11th to 20thDay
16%7%25%6%35%446%41%
2134
21st to endDay
21%6%25%5%35%446%39%
2214
May1st to 10thDay
22%8%36%5%245%5%7%34%
2355
11th to 20thDay
17%6%35%435%5%5%9%39%
2478
21st to endDay
14%5%25%5%45%6%6%8%41%
2725
June1st to 10thDay
16%5%26%5%46%5%7%10%35%
2520
11th to 20thDay
15%5%36%5%35%5%7%10%36%
2520
21st to endDay
13%6%35%6%45%5%6%10%37%
2520
July1st to 10thDay
11%6%25%5%47%6%6%9%40%
2520
11th to 20thDay
10%5%25%5%46%5%7%11%40%
2520
21st to endDay
11%5%36%6%36%6%7%9%38%
2744
August1st to 10thDay
11%5%25%5%45%7%7%9%40%
2442
11th to 20thDay
11%6%26%5%35%6%9%10%37%
2126
21st to endDay
12%5%245%35%5%6%9%43%
2376
September1st to 10thDay
14%6%35%5%45%5%5%7%42%
2160
11th to 20thDay
13%5%2443446%6%49%
2080
21st to endDay
16%6%15%435%5%6%7%43%
1980
October1st to 10thDay
21%6%35%434446%41%
1879
11th to 20thDay
15%7%26%5%345%5%7%42%
1800
21st to endDay
23%7%25%435%45%7%33%
1813
November1st to 10thDay
14%7%35%5%34347%47%
1671
11th to 20thDay
18%7%35%5%3445%6%42%
1710
21st to endDay
18%8%35%42445%6%40%
1592
December1st to 10thDay
19%9%36%6%36%5%46%31%
1520
11th to 20thDay
24%6%2443445%6%39%
1906
21st to endDay
20%10%49%6%44446%28%
2772
January1st to 10thNight
15%8%36%5%3446%7%40%
2647
11th to 20thNight
18%8%46%5%35%5%6%6%33%
2520
21st to endNight
12%10%36%5%35%5%6%7%39%
2678
February1st to 10thNight
17%9%37%5%35%5%46%36%
2340
11th to 20thNight
15%8%46%6%36%5%6%5%37%
2107
21st to endNight
18%8%26%6%345%5%5%38%
1776
March1st to 10thNight
15%9%25%5%35%5%47%40%
2150
11th to 20thNight
16%8%46%5%35%5%5%6%38%
2072
21st to endNight
17%7%45%6%335%5%5%40%
1994
April1st to 10thNight
18%11%37%6%3445%8%33%
1800
11th to 20thNight
18%6%35%5%34448%38%
1775
21st to endNight
21%8%35%5%24346%39%
1746
May1st to 10thNight
22%9%36%5%34446%33%
1620
11th to 20thNight
17%6%36%6%26%45%7%39%
1415
21st to endNight
14%6%25%5%35%5%6%8%41%
1550
June1st to 10thNight
16%5%25%5%35%45%9%41%
1440
11th to 20thNight
15%7%25%43446%10%39%
1440
21st to endNight
12%4244445%8%10%43%
1440
July1st to 10thNight
13%435%4346%8%8%43%
1440
11th to 20thNight
12%5%16%5%35%6%8%9%39%
1440
21st to endNight
10%6%35%5%45%5%6%9%44%
1574
August1st to 10thNight
9%5%25%6%345%7%10%44%
1475
11th to 20thNight
11%6%36%6%45%6%7%10%36%
1774
21st to endNight
15%5%35%43445%8%44%
1980
September1st to 10thNight
14%6%26%43445%6%46%
1800
11th to 20thNight
13%5%2442335%7%53%
1879
21st to endNight
16%5%3443445%6%47%
1980
October1st to 10thNight
22%5%25%5%24445%41%
2078
11th to 20thNight
15%7%25%6%34446%43%
2160
21st to endNight
24%7%35%5%33445%36%
2542
November1st to 10thNight
14%6%35%4335%5%7%45%
2407
11th to 20thNight
20%7%35%424446%41%
2470
21st to endNight
15%7%25%5%3446%7%42%
2584
December1st to 10thNight
21%8%26%5%3445%8%35%
2660
11th to 20thNight
22%8%46%434446%34%
3288
21st to endNight
24%12%36%5%3445%6%30%
4884

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
42%7%13%24%12%2
1510
11th to 20thDay
49%8%14%17%9%2
1440
21st to endDay
42%6%12%23%14%2
1676
February1st to 10thDay
52%6%12%17%12%1
1620
11th to 20thDay
45%6%10%21%15%3
1746
21st to endDay
50%5%10%20%13%2
1480
March1st to 10thDay
45%5%12%21%13%3
1800
11th to 20thDay
46%6%11%22%14%2
1885
21st to endDay
49%5%8%17%17%5%
2362
April1st to 10thDay
47%6%9%21%13%4
2160
11th to 20thDay
43%5%11%22%16%3
2134
21st to endDay
46%6%9%20%15%4
2214
May1st to 10thDay
50%6%10%18%14%3
2355
11th to 20thDay
43%7%10%22%16%2
2482
21st to endDay
40%9%15%21%12%2
2725
June1st to 10thDay
43%9%14%20%13%1
2520
11th to 20thDay
42%8%14%24%10%2
2520
21st to endDay
41%9%12%25%12%1
2520
July1st to 10thDay
40%9%13%20%16%2
2450
11th to 20thDay
36%10%15%25%14%1
2445
21st to endDay
40%9%14%20%15%2
2591
August1st to 10thDay
36%12%14%25%12%1
2428
11th to 20thDay
38%10%17%24%11%
2126
21st to endDay
36%8%13%25%17%1
2376
September1st to 10thDay
40%7%12%23%16%2
2160
11th to 20thDay
35%6%10%24%23%2
2080
21st to endDay
38%7%12%22%18%3
1980
October1st to 10thDay
44%6%10%23%15%2
1879
11th to 20thDay
40%8%13%26%13%1
1800
21st to endDay
51%5%11%18%12%2
1813
November1st to 10thDay
37%6%13%26%16%2
1671
11th to 20thDay
42%6%11%21%17%2
1710
21st to endDay
44%5%14%26%9%2
1592
December1st to 10thDay
53%6%13%17%10%1
1520
11th to 20thDay
45%5%16%22%9%2
1906
21st to endDay
54%8%10%20%7%
2772
January1st to 10thNight
43%6%12%22%15%2
2647
11th to 20thNight
49%7%13%21%8%2
2520
21st to endNight
42%6%12%21%17%3
2678
February1st to 10thNight
48%6%13%19%11%2
2340
11th to 20thNight
46%7%11%17%16%3
2109
21st to endNight
46%6%8%22%14%4
1776
March1st to 10thNight
42%7%12%22%14%3
2160
11th to 20thNight
45%6%10%21%14%3
2073
21st to endNight
46%5%10%18%18%4
1994
April1st to 10thNight
49%6%9%20%14%2
1800
11th to 20thNight
45%7%10%18%19%1
1775
21st to endNight
46%7%8%21%15%4
1746
May1st to 10thNight
51%7%9%16%15%2
1620
11th to 20thNight
45%6%10%20%17%3
1416
21st to endNight
39%9%15%22%13%2
1551
June1st to 10thNight
42%7%11%23%15%2
1440
11th to 20thNight
39%10%14%26%10%1
1440
21st to endNight
33%11%13%27%14%1
1440
July1st to 10thNight
35%10%13%24%15%3
1400
11th to 20thNight
37%9%14%28%11%1
1392
21st to endNight
34%9%15%23%15%3
1486
August1st to 10thNight
34%10%14%26%15%1
1465
11th to 20thNight
41%10%15%23%11%
1774
21st to endNight
38%8%11%23%19%1
1980
September1st to 10thNight
39%7%12%26%16%1
1800
11th to 20thNight
33%6%10%25%25%2
1879
21st to endNight
37%7%9%23%23%1
1980
October1st to 10thNight
45%7%10%22%15%2
2078
11th to 20thNight
40%8%11%27%13%1
2160
21st to endNight
49%6%11%21%12%1
2542
November1st to 10thNight
38%7%10%22%20%3
2407
11th to 20thNight
45%410%22%16%4
2470
21st to endNight
41%6%15%28%10%1
2584
December1st to 10thNight
48%6%14%21%11%1
2660
11th to 20thNight
50%6%14%16%13%2
3288
21st to endNight
53%8%11%20%9%
4884

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
24%19%28%20%10%
178
11th to 20thDay
24%23%34%14%41
160
21st to endDay
20%19%41%13%5%2
218
February1st to 10thDay
32%20%32%14%3
240
11th to 20thDay
24%20%38%18%1
405
21st to endDay
27%20%33%17%3
346
March1st to 10thDay
23%19%32%22%4
420
11th to 20thDay
22%23%32%18%41
420
21st to endDay
29%18%29%18%43
462
April1st to 10thDay
28%18%28%17%7%3
420
11th to 20thDay
24%22%28%16%8%2
412
21st to endDay
30%15%28%18%5%3
420
May1st to 10thDay
31%15%27%17%8%2
423
11th to 20thDay
19%11%37%22%8%2
447
21st to endDay
19%10%22%30%14%5%
485
June1st to 10thDay
19%12%27%25%14%2
450
11th to 20thDay
14%12%30%26%14%2
450
21st to endDay
15%10%29%26%16%4
450
July1st to 10thDay
16%424%32%19%5%
445
11th to 20thDay
13%5%23%34%20%5%
444
21st to endDay
12%6%27%34%17%4
488
August1st to 10thDay
12%7%20%36%17%8%
446
11th to 20thDay
14%5%23%28%21%8%
439
21st to endDay
11%7%25%30%18%9%
495
September1st to 10thDay
18%11%19%25%19%8%
450
11th to 20thDay
15%8%30%19%17%11%
450
21st to endDay
17%10%27%27%13%6%
450
October1st to 10thDay
29%8%20%22%15%6%
450
11th to 20thDay
17%12%32%26%10%2
450
21st to endDay
27%13%28%22%8%1
411
November1st to 10thDay
18%14%25%30%10%2
365
11th to 20thDay
23%15%30%24%7%1
370
21st to endDay
21%15%30%26%7%1
252
December1st to 10thDay
23%22%33%14%8%
180
11th to 20thDay
27%21%33%17%2
180
21st to endDay
21%14%37%23%41
198
January1st to 10thNight
19%13%37%28%3
760
11th to 20thNight
23%11%35%27%4
720
21st to endNight
17%14%40%26%3
792
February1st to 10thNight
23%13%36%26%2
720
11th to 20thNight
20%15%42%22%1
703
21st to endNight
24%14%38%22%3
592
March1st to 10thNight
22%17%34%24%3
720
11th to 20thNight
22%14%38%21%5%
720
21st to endNight
22%16%36%20%6%1
792
April1st to 10thNight
26%14%34%22%4
720
11th to 20thNight
22%12%35%23%7%
711
21st to endNight
25%15%29%25%6%
666
May1st to 10thNight
24%13%32%24%7%
540
11th to 20thNight
18%6%36%34%5%
354
21st to endNight
17%6%21%41%15%1
389
June1st to 10thNight
17%426%38%15%1
360
11th to 20thNight
17%5%23%38%16%1
360
21st to endNight
14%124%44%17%
360
July1st to 10thNight
13%218%44%22%1
350
11th to 20thNight
13%5%17%45%18%1
348
21st to endNight
12%420%44%19%2
394
August1st to 10thNight
12%116%47%21%2
401
11th to 20thNight
12%416%41%24%3
710
21st to endNight
16%318%37%24%3
792
September1st to 10thNight
18%224%36%18%2
720
11th to 20thNight
16%424%30%21%5%
720
21st to endNight
17%6%25%35%15%2
720
October1st to 10thNight
25%6%24%30%13%2
720
11th to 20thNight
19%8%29%35%9%
720
21st to endNight
28%10%29%27%6%
792
November1st to 10thNight
16%9%33%31%10%1
740
11th to 20thNight
25%9%32%25%7%1
760
21st to endNight
20%11%33%29%6%1
760
December1st to 10thNight
25%12%34%23%5%
760
11th to 20thNight
25%10%34%27%4
760
21st to endNight
25%11%38%23%3
836
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