Hemlock Crossings Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hemlock Crossings Park clear sky chart from 2005-11-06 to 2024-03-08.

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%
24852
12%
80909
10%
24756
40%
24756
15%
60823

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
15%
943
4%
4416
2%
926
18%
926
4%
3873
January11th to 20thNight
14%
947
2%
4437
2%
930
16%
930
3%
4127
January21st to endNight
16%
1037
1%
4881
1%
1023
17%
1023
3%
4452
February1st to 10thNight
19%
819
7%
2434
4%
819
22%
819
9%
2051
February11th to 20thNight
21%
740
10%
2219
6%
740
25%
740
10%
1808
February21st to endNight
19%
628
9%
1884
3%
628
25%
628
12%
1489
March1st to 10thNight
32%
751
14%
2251
9%
751
36%
751
18%
1617
March11th to 20thNight
37%
720
20%
2057
11%
720
44%
720
24%
1410
March21st to endNight
35%
698
17%
2084
12%
698
40%
698
20%
1475
April1st to 10thNight
34%
540
13%
1800
10%
540
40%
540
18%
1250
April11th to 20thNight
38%
533
19%
1745
15%
533
44%
533
19%
1179
April21st to endNight
41%
540
18%
1620
10%
540
48%
540
23%
1095
May1st to 10thNight
42%
540
14%
1620
9%
540
46%
540
20%
1133
May11th to 20thNight
47%
531
18%
1558
13%
531
52%
531
25%
1033
May21st to endNight
55%
583
15%
1552
11%
582
58%
582
28%
1054
June1st to 10thNight
59%
540
16%
1440
12%
540
62%
540
34%
917
June11th to 20thNight
58%
540
18%
1440
13%
540
60%
540
33%
912
June21st to endNight
61%
540
16%
1440
12%
540
63%
540
32%
932
July1st to 10thNight
70%
525
17%
1400
14%
525
71%
525
40%
833
July11th to 20thNight
69%
522
20%
1392
17%
522
70%
522
40%
836
July21st to endNight
68%
591
21%
1487
18%
558
69%
558
38%
901
August1st to 10thNight
70%
537
22%
1547
18%
534
72%
534
37%
902
August11th to 20thNight
67%
534
22%
1598
20%
534
70%
534
34%
944
August21st to endNight
65%
594
22%
1978
21%
594
68%
594
31%
1132
September1st to 10thNight
61%
540
21%
1800
21%
540
64%
540
29%
1066
September11th to 20thNight
63%
710
28%
1970
24%
710
66%
710
38%
1169
September21st to endNight
49%
720
20%
1980
15%
720
52%
720
27%
1326
October1st to 10thNight
50%
720
22%
1980
18%
720
53%
720
28%
1313
October11th to 20thNight
31%
720
13%
2209
8%
720
38%
720
16%
1600
October21st to endNight
24%
792
12%
2574
8%
792
31%
792
14%
1933
November1st to 10thNight
32%
740
17%
2406
15%
740
38%
740
16%
1709
November11th to 20thNight
19%
760
11%
2470
7%
760
25%
760
10%
1976
November21st to endNight
22%
760
9%
2470
6%
760
26%
760
10%
1992
December1st to 10thNight
13%
931
3%
2641
2%
931
14%
931
6%
2332
December11th to 20thNight
15%
949
4%
3269
2%
949
17%
949
6%
2857
December21st to endNight
10%
1037
3%
4860
1%
1026
14%
1026
3%
4195

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%10%48%6%3445%7%34%
78466
Night
16%13%6%9%6%34446%29%
81143
TransparencyDay
50%7%12%20%11%1
78167
Night
56%6%10%17%9%1
80963
SeeingDay
17%8%24%29%17%5%
14821
Night
20%8%26%29%15%2
24883

By Month

Percentage Cloud Cover SE (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
15%24%10%14%10%45%3339%
2527
11th to 20thDay
13%16%10%16%19%7%44336%
2530
21st to endDay
20%22%9%17%9%342228%
2783
February1st to 10thDay
12%14%7%15%13%45%44417%
1739
11th to 20thDay
13%12%7%13%11%5%4445%21%
1848
21st to endDay
15%14%7%11%7%5%5%5%5%6%22%
1570
March1st to 10thDay
13%11%47%8%45%5%6%7%30%
1870
11th to 20thDay
13%9%47%6%345%6%9%36%
1902
21st to endDay
18%11%47%5%35%5%5%7%31%
2286
April1st to 10thDay
19%10%5%6%5%35%45%6%32%
2160
11th to 20thDay
17%9%35%5%345%5%7%37%
2164
21st to endDay
16%9%37%5%345%5%7%36%
2340
May1st to 10thDay
16%6%26%5%35%5%5%8%37%
2340
11th to 20thDay
17%6%35%5%3435%8%41%
2333
21st to endDay
11%5%26%4345%5%8%47%
2725
June1st to 10thDay
10%4245%45%46%9%48%
2520
11th to 20thDay
10%425%43445%9%51%
2520
21st to endDay
10%5%25%435%5%6%9%47%
2520
July1st to 10thDay
6%4233345%6%9%56%
2520
11th to 20thDay
9%423335%5%6%9%51%
2520
21st to endDay
8%4235%345%6%9%50%
2743
August1st to 10thDay
10%4244345%6%11%48%
2381
11th to 20thDay
10%4244245%6%8%49%
2302
21st to endDay
10%426%42446%8%49%
2376
September1st to 10thDay
11%6%345%3445%8%46%
2152
11th to 20thDay
12%5%24435%5%6%8%48%
1980
21st to endDay
11%6%36%5%45%45%8%42%
1980
October1st to 10thDay
16%8%35%6%34445%42%
1980
11th to 20thDay
23%11%36%6%46%5%5%6%24%
1745
21st to endDay
24%12%48%7%4435%6%23%
1782
November1st to 10thDay
15%12%37%6%3445%6%34%
1672
11th to 20thDay
17%19%7%10%6%3445%421%
1710
21st to endDay
22%19%6%9%6%24435%21%
1710
December1st to 10thDay
15%24%13%13%6%33335%12%
1535
11th to 20thDay
15%20%12%13%8%45%44311%
1918
21st to endDay
20%25%9%11%9%243449%
2783
January1st to 10thNight
15%23%12%13%9%3333312%
4428
11th to 20thNight
14%19%12%17%13%6%33228%
4440
21st to endNight
22%20%10%13%9%443339%
4884
February1st to 10thNight
13%18%7%14%11%5%433418%
2434
11th to 20thNight
14%15%8%12%9%4443422%
2218
21st to endNight
17%15%6%10%7%35%5%45%23%
1884
March1st to 10thNight
16%10%5%7%6%45%46%6%32%
2251
11th to 20thNight
13%9%37%6%34446%41%
2057
21st to endNight
19%9%47%5%34446%35%
2084
April1st to 10thNight
15%9%5%6%6%35%5%6%6%35%
1800
11th to 20thNight
20%9%26%425%5%5%6%36%
1745
21st to endNight
17%7%36%5%345%5%7%37%
1620
May1st to 10thNight
15%9%38%6%45%5%5%6%35%
1620
11th to 20thNight
18%6%25%4246%5%8%39%
1557
21st to endNight
11%6%46%5%36%45%8%41%
1551
June1st to 10thNight
10%5%245%35%6%5%9%45%
1440
11th to 20thNight
9%6%25%5%35%45%9%45%
1440
21st to endNight
9%5%35%5%35%5%6%9%44%
1440
July1st to 10thNight
6%5%145%35%46%9%53%
1440
11th to 20thNight
6%3245%35%5%6%9%52%
1440
21st to endNight
7%415%5%2446%9%51%
1575
August1st to 10thNight
7%3345%345%6%9%51%
1556
11th to 20thNight
9%4245%35%5%6%9%49%
1598
21st to endNight
10%5%25%5%3345%7%51%
1978
September1st to 10thNight
11%5%35%5%3445%7%49%
1800
11th to 20thNight
11%4245%2345%6%54%
1970
21st to endNight
12%7%26%5%4445%7%43%
1980
October1st to 10thNight
19%6%24424447%44%
1980
11th to 20thNight
25%11%37%433345%33%
2209
21st to endNight
27%10%46%433345%30%
2574
November1st to 10thNight
16%12%46%5%34446%35%
2406
11th to 20thNight
19%18%6%9%5%3345%5%21%
2470
21st to endNight
19%20%7%10%5%23336%22%
2470
December1st to 10thNight
18%24%10%12%6%3434413%
2641
11th to 20thNight
16%21%10%13%7%3434414%
3279
21st to endNight
26%22%8%10%5%3434412%
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
79%8%6%6%1
2528
11th to 20thDay
84%6%6%31
2530
21st to endDay
83%6%6%42
2783
February1st to 10thDay
71%7%7%13%3
1739
11th to 20thDay
66%5%10%13%6%1
1858
21st to endDay
62%7%13%13%5%
1570
March1st to 10thDay
54%6%14%19%8%1
1870
11th to 20thDay
46%6%14%20%11%2
1902
21st to endDay
52%6%14%20%7%1
2286
April1st to 10thDay
53%6%11%19%11%
2160
11th to 20thDay
46%6%11%20%14%3
2164
21st to endDay
46%6%13%18%14%2
2340
May1st to 10thDay
43%7%13%25%11%1
2340
11th to 20thDay
43%6%13%21%15%2
2337
21st to endDay
36%8%14%27%14%2
2725
June1st to 10thDay
34%7%13%28%17%2
2520
11th to 20thDay
32%8%14%24%21%1
2520
21st to endDay
33%8%16%24%18%2
2520
July1st to 10thDay
24%8%13%33%17%4
2451
11th to 20thDay
29%7%14%29%19%3
2445
21st to endDay
29%7%15%27%19%3
2591
August1st to 10thDay
31%7%16%32%13%2
2366
11th to 20thDay
30%8%16%29%15%2
2302
21st to endDay
31%6%14%27%18%3
2376
September1st to 10thDay
36%7%15%26%14%2
2152
11th to 20thDay
33%7%14%31%13%2
1980
21st to endDay
41%6%13%25%15%
1980
October1st to 10thDay
45%6%9%26%13%1
1980
11th to 20thDay
59%8%13%14%7%
1745
21st to endDay
63%6%12%13%6%1
1782
November1st to 10thDay
50%7%11%19%11%1
1672
11th to 20thDay
67%6%9%13%41
1710
21st to endDay
67%5%12%11%4
1710
December1st to 10thDay
78%5%7%7%2
1535
11th to 20thDay
76%8%9%6%1
1915
21st to endDay
80%5%6%7%1
2783
January1st to 10thNight
77%6%8%6%2
4428
11th to 20thNight
84%5%5%42
4440
21st to endNight
81%7%7%31
4884
February1st to 10thNight
71%5%9%10%5%
2434
11th to 20thNight
66%6%7%15%6%
2219
21st to endNight
63%6%11%13%6%1
1884
March1st to 10thNight
51%6%13%21%8%1
2251
11th to 20thNight
45%7%11%22%12%3
2057
21st to endNight
51%5%10%22%10%2
2084
April1st to 10thNight
49%8%11%19%13%1
1800
11th to 20thNight
49%5%8%17%19%3
1745
21st to endNight
44%7%11%19%15%4
1620
May1st to 10thNight
49%6%10%20%13%2
1620
11th to 20thNight
43%6%11%19%17%4
1558
21st to endNight
41%8%11%23%15%2
1552
June1st to 10thNight
35%7%10%28%18%3
1440
11th to 20thNight
36%6%11%25%20%2
1440
21st to endNight
35%8%14%25%15%3
1440
July1st to 10thNight
28%7%12%28%20%5%
1400
11th to 20thNight
28%8%14%27%21%3
1392
21st to endNight
30%7%13%25%20%4
1487
August1st to 10thNight
29%7%14%30%17%2
1547
11th to 20thNight
30%9%12%31%16%2
1598
21st to endNight
33%6%11%26%21%3
1978
September1st to 10thNight
35%7%13%25%18%3
1800
11th to 20thNight
31%6%11%34%17%2
1970
21st to endNight
41%8%12%26%13%1
1980
October1st to 10thNight
41%6%8%28%16%2
1980
11th to 20thNight
55%5%12%19%9%1
2209
21st to endNight
57%6%12%16%8%
2574
November1st to 10thNight
51%7%9%20%12%1
2406
11th to 20thNight
65%6%10%13%5%1
2470
21st to endNight
66%6%13%14%2
2470
December1st to 10thNight
76%6%7%8%3
2641
11th to 20thNight
73%8%10%6%2
3281
21st to endNight
77%6%10%6%2
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
22%11%33%26%5%3
270
11th to 20thDay
22%15%30%24%7%1
270
21st to endDay
27%8%31%28%6%1
297
February1st to 10thDay
17%16%37%21%7%2
270
11th to 20thDay
19%16%36%22%7%1
270
21st to endDay
21%12%40%20%5%
225
March1st to 10thDay
18%13%39%22%7%
261
11th to 20thDay
18%10%29%30%13%1
342
21st to endDay
27%9%25%28%9%2
462
April1st to 10thDay
23%8%30%30%9%
420
11th to 20thDay
20%13%30%25%9%4
412
21st to endDay
22%7%29%25%14%2
420
May1st to 10thDay
21%8%29%27%12%2
423
11th to 20thDay
18%6%21%32%19%4
479
21st to endDay
14%322%30%23%7%
679
June1st to 10thDay
11%323%37%21%5%
630
11th to 20thDay
12%418%38%21%6%
630
21st to endDay
11%422%39%18%5%
630
July1st to 10thDay
6%218%35%28%12%
621
11th to 20thDay
8%319%37%25%8%
618
21st to endDay
9%117%43%24%7%
684
August1st to 10thDay
10%213%30%33%12%
500
11th to 20thDay
11%411%31%31%13%
439
21st to endDay
11%414%31%30%11%
495
September1st to 10thDay
15%414%33%25%9%
450
11th to 20thDay
8%5%14%28%28%17%
450
21st to endDay
15%7%22%22%24%11%
450
October1st to 10thDay
19%6%25%24%19%7%
450
11th to 20thDay
26%16%22%28%8%1
330
21st to endDay
32%9%31%20%6%2
297
November1st to 10thDay
20%16%26%25%10%3
270
11th to 20thDay
24%20%31%19%4
270
21st to endDay
27%12%38%17%5%
270
December1st to 10thDay
24%21%29%18%7%1
270
11th to 20thDay
21%20%31%22%5%1
270
21st to endDay
27%18%34%16%31
297
January1st to 10thNight
23%15%31%23%7%
950
11th to 20thNight
25%13%32%24%6%1
950
21st to endNight
23%10%33%28%6%
1045
February1st to 10thNight
21%11%35%27%6%1
819
11th to 20thNight
22%10%34%27%7%
743
21st to endNight
25%12%36%24%4
628
March1st to 10thNight
20%8%30%33%8%1
751
11th to 20thNight
16%9%31%33%10%1
720
21st to endNight
21%7%28%30%13%1
698
April1st to 10thNight
17%8%32%33%9%1
540
11th to 20thNight
24%8%25%33%10%1
533
21st to endNight
20%428%35%11%2
540
May1st to 10thNight
18%5%24%38%14%2
540
11th to 20thNight
21%222%33%21%1
531
21st to endNight
15%317%35%26%4
584
June1st to 10thNight
12%219%41%24%3
540
11th to 20thNight
11%319%38%25%2
540
21st to endNight
11%316%39%29%3
540
July1st to 10thNight
8%211%35%38%6%
525
11th to 20thNight
7%214%39%32%5%
522
21st to endNight
9%113%40%34%3
591
August1st to 10thNight
8%112%40%33%6%
537
11th to 20thNight
11%210%37%33%7%
534
21st to endNight
11%213%36%32%5%
594
September1st to 10thNight
12%315%38%27%5%
540
11th to 20thNight
13%413%33%30%7%
710
21st to endNight
15%7%22%25%25%6%
720
October1st to 10thNight
23%419%31%21%3
720
11th to 20thNight
30%10%23%25%10%1
720
21st to endNight
32%10%29%21%7%1
792
November1st to 10thNight
24%9%29%26%11%1
740
11th to 20thNight
28%15%31%21%5%
760
21st to endNight
28%13%29%24%5%
760
December1st to 10thNight
28%15%32%19%5%
931
11th to 20thNight
27%14%34%20%5%
950
21st to endNight
32%11%35%19%2
1045
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