Metcalf Nature Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Metcalf Nature Center clear sky chart from 2005-11-05 to 2017-12-20.

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
33%
16540
14%
48092
8%
16494
38%
16494
21%
32567

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
27%
900
11%
2506
6%
895
32%
895
17%
1848
January16th to endNight
21%
960
10%
2561
3%
960
26%
960
14%
1963
February1st to 15thNight
25%
880
13%
2288
4%
876
30%
876
19%
1643
February16th to endNight
27%
740
13%
2002
4%
740
33%
740
19%
1418
March1st to 15thNight
28%
597
13%
2037
9%
597
33%
597
17%
1371
March16th to endNight
27%
576
14%
2085
11%
576
34%
576
15%
1432
April1st to 15thNight
26%
539
15%
1797
10%
539
34%
539
18%
1197
April16th to endNight
25%
540
12%
1689
7%
540
32%
540
14%
1218
May1st to 15thNight
26%
540
13%
1479
7%
540
31%
540
20%
1032
May16th to endNight
38%
562
12%
1498
4%
561
42%
561
24%
1007
June1st to 15thNight
39%
540
9%
1440
3%
540
42%
540
26%
930
June16th to endNight
46%
540
13%
1440
6%
540
49%
540
32%
878
July1st to 15thNight
53%
510
13%
1360
6%
510
55%
510
39%
791
July16th to endNight
55%
564
17%
1417
10%
531
61%
531
41%
804
August1st to 15thNight
62%
539
20%
1610
18%
536
65%
536
33%
946
August16th to endNight
53%
573
20%
1806
19%
573
59%
573
31%
1048
September1st to 15thNight
55%
540
22%
1800
21%
540
61%
540
33%
990
September16th to endNight
42%
594
19%
1974
13%
594
50%
594
29%
1155
October1st to 15thNight
36%
720
22%
2160
14%
720
42%
720
28%
1314
October16th to endNight
33%
768
16%
2333
10%
768
38%
768
20%
1577
November1st to 15thNight
30%
884
18%
2595
11%
884
37%
884
22%
1732
November16th to endNight
25%
975
14%
2730
7%
975
31%
975
17%
1958
December1st to 15thNight
19%
975
9%
2730
3%
975
24%
975
13%
2097
December16th to endNight
18%
984
9%
2755
3%
984
23%
984
10%
2218

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%8%36%5%3445%7%36%
48758
Night
12%8%36%5%34446%39%
48260
Cloud CoverDay
25%7%25%5%23446%32%
48769
Night
24%7%25%423335%35%
48264
Cloud CoverDay
13%8%36%5%3445%7%36%
48767
Night
12%8%36%5%34446%40%
48264
TransparencyDay
46%6%14%22%9%
48445
Night
44%5%13%23%11%1
48092
SeeingDay
16%14%26%24%13%3
6415
Night
14%20%25%27%10%1
16541

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
9%12%7%9%7%46%446%27%
1432
16th to endDay
10%14%6%11%7%36%5%47%22%
1662
February1st to 15thDay
8%10%8%9%7%45%45%5%30%
1575
16th to endDay
11%10%5%7%6%35%5%47%30%
1470
March1st to 15thDay
14%10%47%5%34447%33%
1923
16th to endDay
18%10%36%5%24447%30%
2139
April1st to 15thDay
18%8%35%5%2335%6%36%
2151
16th to endDay
22%12%36%424445%28%
2269
May1st to 15thDay
19%8%36%5%3435%7%31%
2470
16th to endDay
14%7%25%6%35%45%7%38%
2617
June1st to 15thDay
16%5%2443445%8%39%
2520
16th to endDay
9%425%5%35%6%6%10%38%
2520
July1st to 15thDay
8%414425%5%6%8%48%
2520
16th to endDay
7%423425%6%6%9%46%
2655
August1st to 15thDay
9%425%6%35%6%6%8%40%
2340
16th to endDay
12%5%25%42445%7%47%
2396
September1st to 15thDay
11%4235%3445%8%46%
2160
16th to endDay
14%7%25%42445%7%41%
1971
October1st to 15thDay
16%7%24424345%44%
1800
16th to endDay
18%9%37%423345%37%
1890
November1st to 15thDay
11%11%48%5%23446%36%
1590
16th to endDay
15%8%46%7%24448%32%
1560
December1st to 15thDay
14%11%7%9%9%35%5%35%23%
1560
16th to endDay
18%16%7%10%7%3423420%
1568
January1st to 15thNight
10%9%5%7%7%45%5%46%31%
2506
16th to endNight
12%12%6%9%6%345%5%5%28%
2561
February1st to 15thNight
7%10%5%9%6%35%446%36%
2285
16th to endNight
9%9%36%7%45%5%46%36%
2002
March1st to 15thNight
11%9%46%5%4435%5%39%
2025
16th to endNight
17%9%47%424346%34%
2085
April1st to 15thNight
18%9%26%323446%38%
1797
16th to endNight
22%9%36%4245%45%31%
1689
May1st to 15thNight
19%6%25%424345%39%
1479
16th to endNight
10%5%26%5%4446%8%41%
1496
June1st to 15thNight
12%4245%2445%8%44%
1440
16th to endNight
6%4135%35%5%5%7%52%
1440
July1st to 15thNight
5%234345%5%10%55%
1440
16th to endNight
431432446%8%55%
1513
August1st to 15thNight
6%325%4345%6%8%50%
1619
16th to endNight
9%414424446%53%
1806
September1st to 15thNight
8%324423346%55%
1800
16th to endNight
12%324433446%49%
1974
October1st to 15thNight
15%5%23322346%49%
2160
16th to endNight
19%10%35%313336%39%
2333
November1st to 15thNight
14%9%35%423445%42%
2595
16th to endNight
12%11%46%6%25%347%34%
2730
December1st to 15thNight
13%13%5%10%7%34345%28%
2730
16th to endNight
16%15%7%10%8%24345%22%
2755

Percentage Cloud Cover SW (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
23%9%46%7%45%345%25%
1432
16th to endDay
24%13%49%7%34446%17%
1662
February1st to 15thDay
23%9%5%8%6%3433426%
1575
16th to endDay
25%8%46%434445%26%
1470
March1st to 15thDay
27%8%37%422336%29%
1934
16th to endDay
31%9%25%423346%25%
2139
April1st to 15thDay
31%8%25%422235%31%
2151
16th to endDay
36%10%25%42333422%
2269
May1st to 15thDay
33%7%25%5%23345%26%
2470
16th to endDay
29%6%145%23346%31%
2617
June1st to 15thDay
31%5%13323446%31%
2520
16th to endDay
25%415%5%2445%7%32%
2520
July1st to 15thDay
23%31432335%7%39%
2520
16th to endDay
23%3143245%5%7%38%
2655
August1st to 15thDay
17%5%145%35%5%6%7%37%
2340
16th to endDay
18%5%1432345%6%44%
2396
September1st to 15thDay
18%41342335%7%43%
2160
16th to endDay
20%5%2442345%6%39%
1971
October1st to 15thDay
23%6%24322345%41%
1800
16th to endDay
24%7%25%423235%36%
1890
November1st to 15thDay
22%9%36%423335%33%
1590
16th to endDay
29%6%35%5%12336%30%
1560
December1st to 15thDay
28%10%5%8%7%3343420%
1560
16th to endDay
30%13%5%9%7%3222318%
1568
January1st to 15thNight
24%7%46%6%35%34428%
2506
16th to endNight
26%10%48%5%24435%23%
2561
February1st to 15thNight
22%10%47%42333432%
2278
16th to endNight
23%7%26%6%44435%31%
2002
March1st to 15thNight
24%7%35%5%32335%34%
2037
16th to endNight
31%7%26%322335%30%
2085
April1st to 15thNight
30%7%25%32234433%
1797
16th to endNight
36%8%25%423435%25%
1689
May1st to 15thNight
34%5%24223235%33%
1478
16th to endNight
26%5%25%5%33445%35%
1496
June1st to 15thNight
27%313423446%37%
1440
16th to endNight
22%212423346%44%
1440
July1st to 15thNight
21%113423338%46%
1440
16th to endNight
20%21332335%6%47%
1513
August1st to 15thNight
15%32432445%7%46%
1619
16th to endNight
16%313323345%51%
1806
September1st to 15thNight
15%214333346%51%
1800
16th to endNight
18%314423345%47%
1974
October1st to 15thNight
23%5%13322335%45%
2160
16th to endNight
25%8%24313336%37%
2333
November1st to 15thNight
25%8%2441233438%
2595
16th to endNight
25%9%36%5%23245%31%
2730
December1st to 15thNight
27%11%49%6%23235%24%
2730
16th to endNight
28%12%5%9%7%2333419%
2755

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 15thDay
9%12%6%8%8%46%446%27%
1432
16th to endDay
9%15%5%11%8%45%5%47%22%
1662
February1st to 15thDay
8%10%8%10%7%45%445%30%
1575
16th to endDay
12%9%5%7%6%45%5%5%6%31%
1470
March1st to 15thDay
14%10%48%5%24447%32%
1934
16th to endDay
18%10%45%5%24447%30%
2137
April1st to 15thDay
17%9%35%5%23446%36%
2151
16th to endDay
22%11%46%42445%5%28%
2269
May1st to 15thDay
20%8%36%5%3445%6%31%
2470
16th to endDay
14%7%246%35%45%7%37%
2617
June1st to 15thDay
16%6%24335%46%8%38%
2520
16th to endDay
9%5%25%6%35%5%6%10%38%
2520
July1st to 15thDay
7%424425%5%6%9%47%
2520
16th to endDay
7%324425%6%6%9%47%
2655
August1st to 15thDay
9%5%25%5%35%6%7%8%40%
2340
16th to endDay
12%5%2442445%6%47%
2396
September1st to 15thDay
11%5%145%2446%8%45%
2160
16th to endDay
14%6%15%5%235%5%7%41%
1971
October1st to 15thDay
16%8%24423345%44%
1800
16th to endDay
18%9%35%433336%37%
1890
November1st to 15thDay
12%11%5%7%5%24446%36%
1590
16th to endDay
15%9%46%6%14448%33%
1560
December1st to 15thDay
14%11%7%10%9%335%45%23%
1560
16th to endDay
17%17%7%10%8%2423420%
1568
January1st to 15thNight
11%9%6%7%7%46%445%32%
2506
16th to endNight
12%12%6%10%6%35%5%45%28%
2561
February1st to 15thNight
7%11%5%9%5%34446%36%
2278
16th to endNight
9%9%36%6%45%446%36%
2002
March1st to 15thNight
11%8%46%5%34445%39%
2037
16th to endNight
17%9%47%423347%34%
2085
April1st to 15thNight
18%9%35%423446%38%
1797
16th to endNight
22%9%35%424446%31%
1689
May1st to 15thNight
20%6%26%333346%39%
1478
16th to endNight
9%6%35%6%35%45%8%41%
1496
June1st to 15thNight
13%4245%2446%7%44%
1440
16th to endNight
6%323435%5%5%7%52%
1440
July1st to 15thNight
5%11342445%10%55%
1440
16th to endNight
4313325%47%8%54%
1513
August1st to 15thNight
7%3244245%6%7%50%
1619
16th to endNight
9%424423446%53%
1806
September1st to 15thNight
8%314333446%55%
1800
16th to endNight
12%324433346%50%
1974
October1st to 15thNight
15%5%24322336%49%
2160
16th to endNight
19%10%25%313336%39%
2333
November1st to 15thNight
14%8%35%423445%42%
2595
16th to endNight
13%10%47%5%34346%34%
2730
December1st to 15thNight
13%12%5%10%7%34335%29%
2730
16th to endNight
16%15%7%10%8%24345%22%
2755

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
56%5%11%19%6%
1433
16th to endDay
60%7%13%14%4
1662
February1st to 15thDay
54%5%14%18%6%
1576
16th to endDay
52%7%11%23%5%
1470
March1st to 15thDay
51%5%15%19%7%
1934
16th to endDay
53%6%13%21%3
2139
April1st to 15thDay
48%412%21%10%1
2151
16th to endDay
56%6%12%15%9%
2269
May1st to 15thDay
52%5%13%20%6%
2470
16th to endDay
44%7%12%22%12%1
2621
June1st to 15thDay
41%7%14%25%9%
2520
16th to endDay
38%8%16%24%10%1
2520
July1st to 15thDay
31%7%16%28%14%1
2371
16th to endDay
31%9%17%24%15%2
2488
August1st to 15thDay
38%8%15%26%9%2
2326
16th to endDay
35%6%16%26%13%1
2396
September1st to 15thDay
35%6%15%30%11%
2160
16th to endDay
41%7%13%29%7%
1971
October1st to 15thDay
41%5%12%27%12%
1800
16th to endDay
48%5%14%23%8%
1890
November1st to 15thDay
48%5%12%19%12%1
1590
16th to endDay
49%6%20%14%7%
1560
December1st to 15thDay
62%6%14%12%4
1560
16th to endDay
68%49%12%4
1568
January1st to 15thNight
53%5%12%21%6%
2506
16th to endNight
56%5%15%16%5%
2561
February1st to 15thNight
48%5%14%23%8%
2288
16th to endNight
47%5%12%24%8%
2002
March1st to 15thNight
47%5%13%21%10%
2037
16th to endNight
50%5%12%22%7%
2085
April1st to 15thNight
46%48%24%14%1
1797
16th to endNight
52%6%9%17%11%2
1689
May1st to 15thNight
46%5%15%19%11%1
1479
16th to endNight
40%7%12%23%15%1
1498
June1st to 15thNight
36%6%16%25%13%1
1440
16th to endNight
29%7%13%29%17%2
1440
July1st to 15thNight
24%6%14%33%17%2
1360
16th to endNight
23%6%16%30%18%4
1417
August1st to 15thNight
30%7%13%28%16%3
1610
16th to endNight
31%6%14%28%15%3
1806
September1st to 15thNight
29%5%12%33%18%
1800
16th to endNight
35%5%14%29%14%
1974
October1st to 15thNight
37%411%29%15%2
2160
16th to endNight
46%5%13%21%12%
2333
November1st to 15thNight
44%5%11%23%14%
2595
16th to endNight
50%5%15%19%7%1
2730
December1st to 15thNight
57%5%13%17%5%
2730
16th to endNight
64%5%12%12%4
2755

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
21%8%36%25%6%1
90
16th to endDay
22%6%39%28%21
96
February1st to 15thDay
12%21%41%21%4
90
16th to endDay
22%11%37%27%11
81
March1st to 15thDay
17%12%44%20%5%
90
16th to endDay
28%10%30%21%6%1
123
April1st to 15thDay
22%19%22%25%8%
270
16th to endDay
30%20%23%18%6%
379
May1st to 15thDay
21%23%24%19%8%1
468
16th to endDay
17%19%26%19%11%3
517
June1st to 15thDay
15%18%25%24%13%2
495
16th to endDay
10%19%29%23%13%3
495
July1st to 15thDay
9%11%23%26%20%9%
475
16th to endDay
6%15%23%27%21%5%
515
August1st to 15thDay
12%9%19%33%20%4
493
16th to endDay
16%8%18%30%20%5%
436
September1st to 15thDay
11%8%24%31%19%5%
315
16th to endDay
16%12%28%25%13%3
195
October1st to 15thDay
14%14%32%23%9%4
135
16th to endDay
25%9%37%18%9%
144
November1st to 15thDay
14%10%34%30%9%1
135
16th to endDay
32%11%37%15%3
135
December1st to 15thDay
17%11%43%24%2
135
16th to endDay
39%15%34%9%
108
January1st to 15thNight
12%24%27%26%7%1
900
16th to endNight
16%23%30%25%3
960
February1st to 15thNight
13%24%30%23%7%1
880
16th to endNight
12%22%30%24%9%
740
March1st to 15thNight
12%23%29%26%7%
597
16th to endNight
19%25%23%20%10%1
576
April1st to 15thNight
18%23%27%25%5%
539
16th to endNight
22%21%26%22%5%
540
May1st to 15thNight
21%22%25%24%41
540
16th to endNight
12%21%22%28%12%1
563
June1st to 15thNight
12%19%24%32%10%
540
16th to endNight
8%18%23%38%11%
540
July1st to 15thNight
413%23%33%22%1
510
16th to endNight
6%17%17%38%18%1
564
August1st to 15thNight
7%11%13%42%23%2
539
16th to endNight
10%9%21%32%22%2
573
September1st to 15thNight
8%11%20%38%16%4
540
16th to endNight
12%13%26%28%16%1
594
October1st to 15thNight
19%14%27%24%12%1
720
16th to endNight
23%16%22%28%8%
768
November1st to 15thNight
17%20%26%25%8%
884
16th to endNight
16%26%28%22%6%
975
December1st to 15thNight
18%22%31%21%5%
975
16th to endNight
20%22%26%24%5%
984
Page generated at 2017-12-21 06:04:45. Version ac04

Copyright 2017 A. Danko


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