Treynor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Treynor clear sky chart from 2005-11-05 to 2017-08-12.

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
40%
15879
21%
46583
12%
15833
48%
15833
30%
28552

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
34%
900
20%
2327
9%
895
42%
895
30%
1519
January16th to endNight
28%
960
23%
2496
9%
960
38%
960
27%
1668
February1st to 15thNight
26%
880
12%
2288
5%
876
30%
876
22%
1638
February16th to endNight
29%
702
24%
1964
7%
702
41%
702
32%
1220
March1st to 15thNight
36%
543
22%
1983
16%
543
46%
543
26%
1142
March16th to endNight
26%
576
15%
2112
9%
576
36%
576
18%
1376
April1st to 15thNight
30%
539
20%
1865
12%
539
44%
539
24%
1131
April16th to endNight
31%
540
20%
1632
13%
540
43%
540
24%
1072
May1st to 15thNight
39%
540
18%
1620
12%
540
47%
540
26%
1044
May16th to endNight
42%
562
16%
1592
8%
561
49%
561
28%
1035
June1st to 15thNight
54%
540
18%
1440
7%
540
57%
540
38%
870
June16th to endNight
57%
540
22%
1440
9%
540
62%
540
50%
772
July1st to 15thNight
69%
510
17%
1459
11%
510
71%
510
46%
779
July16th to endNight
76%
564
24%
1594
21%
531
78%
531
51%
788
August1st to 15thNight
70%
527
21%
1575
23%
524
72%
524
39%
881
August16th to endNight
60%
525
23%
1613
22%
525
65%
525
36%
923
September1st to 15thNight
54%
495
25%
1721
23%
495
63%
495
32%
945
September16th to endNight
52%
492
28%
1815
23%
492
63%
492
37%
914
October1st to 15thNight
38%
638
27%
1958
17%
638
47%
638
33%
1144
October16th to endNight
40%
704
24%
2112
13%
704
48%
704
33%
1229
November1st to 15thNight
39%
842
27%
2252
12%
842
49%
842
39%
1303
November16th to endNight
32%
900
22%
2520
9%
900
42%
900
31%
1549
December1st to 15thNight
26%
900
15%
2520
6%
900
34%
900
23%
1720
December16th to endNight
28%
960
19%
2685
7%
960
38%
960
21%
1890

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
12%6%25%5%3445%7%43%
47371
Night
10%6%2442335%7%48%
46773
Cloud CoverDay
12%6%25%5%2445%7%43%
47382
Night
10%6%2442335%7%48%
46777
Cloud CoverDay
12%6%35%5%3445%7%42%
47380
Night
10%6%2442335%7%48%
46777
TransparencyDay
40%5%14%24%13%1
47079
Night
36%5%13%26%16%2
46583
SeeingDay
13%6%28%30%17%2
5848
Night
13%8%32%33%11%
15880

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%7%36%7%3445%7%41%
1611
16th to endDay
10%10%48%6%25%447%34%
1728
February1st to 15thDay
10%10%5%9%6%4445%6%33%
1575
16th to endDay
12%7%48%5%2345%6%38%
1518
March1st to 15thDay
11%8%5%6%425%446%40%
1965
16th to endDay
18%10%35%434347%34%
2112
April1st to 15thDay
16%8%26%5%24435%40%
2082
16th to endDay
22%7%25%433446%34%
2327
May1st to 15thDay
15%6%25%5%35%5%47%38%
2331
16th to endDay
15%5%36%5%3446%8%36%
2521
June1st to 15thDay
10%5%345%3446%8%42%
2520
16th to endDay
6%3145%25%46%8%51%
2520
July1st to 15thDay
8%3135%345%5%8%50%
2409
16th to endDay
42133345%5%9%54%
2466
August1st to 15thDay
7%3145%35%6%7%9%43%
2289
16th to endDay
10%425%435%5%5%7%45%
2235
September1st to 15thDay
12%5%2432345%5%49%
1908
16th to endDay
10%31332335%6%55%
1815
October1st to 15thDay
14%413312346%51%
1661
16th to endDay
14%6%245%2334447%
1760
November1st to 15thDay
9%424423345%55%
1602
16th to endDay
13%8%35%434447%40%
1440
December1st to 15thDay
12%11%48%6%3335%5%34%
1440
16th to endDay
13%10%49%7%25%445%30%
1536
January1st to 15thNight
8%6%35%6%3446%7%43%
2327
16th to endNight
10%8%45%5%24346%43%
2496
February1st to 15thNight
12%10%48%5%34346%35%
2285
16th to endNight
9%5%36%42335%6%48%
1964
March1st to 15thNight
10%7%34223347%49%
1971
16th to endNight
16%8%4442445%7%36%
2112
April1st to 15thNight
13%7%24423446%46%
1865
16th to endNight
16%7%26%323346%41%
1632
May1st to 15thNight
14%5%3442435%7%43%
1620
16th to endNight
12%6%245%33448%44%
1590
June1st to 15thNight
8%42441347%8%50%
1440
16th to endNight
311322447%9%58%
1440
July1st to 15thNight
422241445%10%58%
1548
16th to endNight
311231346%10%60%
1702
August1st to 15thNight
42144245%5%9%53%
1585
16th to endNight
10%424423345%55%
1613
September1st to 15thNight
11%423323347%53%
1721
16th to endNight
9%413312446%58%
1815
October1st to 15thNight
13%5%24313336%52%
1958
16th to endNight
13%423323345%53%
2112
November1st to 15thNight
8%5%23323346%56%
2252
16th to endNight
11%6%24423346%50%
2520
December1st to 15thNight
12%10%36%5%2425%6%39%
2520
16th to endNight
13%9%47%6%2345%6%36%
2685

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
9%7%35%7%345%47%41%
1611
16th to endDay
10%10%48%6%24447%34%
1728
February1st to 15thDay
10%10%5%8%6%4445%6%33%
1575
16th to endDay
12%8%47%5%2345%6%38%
1518
March1st to 15thDay
11%8%5%7%425%446%40%
1976
16th to endDay
18%10%35%424347%34%
2112
April1st to 15thDay
16%8%26%5%24335%40%
2082
16th to endDay
22%7%25%433446%34%
2327
May1st to 15thDay
15%6%25%5%35%45%7%38%
2331
16th to endDay
15%5%36%5%3446%8%36%
2521
June1st to 15thDay
10%5%345%3446%8%42%
2520
16th to endDay
6%3145%25%46%8%50%
2520
July1st to 15thDay
8%3135%345%6%8%49%
2409
16th to endDay
43134345%5%9%54%
2466
August1st to 15thDay
7%3145%45%6%7%9%43%
2289
16th to endDay
10%425%425%5%5%7%46%
2235
September1st to 15thDay
12%5%1432435%5%50%
1908
16th to endDay
10%413323346%55%
1815
October1st to 15thDay
14%423312446%51%
1661
16th to endDay
14%6%245%2334447%
1760
November1st to 15thDay
9%424423335%55%
1602
16th to endDay
13%8%36%424447%41%
1440
December1st to 15thDay
12%11%47%6%3335%6%34%
1440
16th to endDay
13%10%49%7%34445%30%
1536
January1st to 15thNight
8%6%35%6%3446%7%43%
2327
16th to endNight
10%8%45%5%24346%43%
2496
February1st to 15thNight
12%9%48%5%3435%6%36%
2278
16th to endNight
9%5%36%42335%6%48%
1964
March1st to 15thNight
11%7%34223337%49%
1983
16th to endNight
16%8%3442445%7%36%
2112
April1st to 15thNight
13%7%34423446%46%
1865
16th to endNight
16%7%26%333346%41%
1632
May1st to 15thNight
14%5%2442435%7%44%
1619
16th to endNight
12%6%245%33448%44%
1590
June1st to 15thNight
8%42442347%8%50%
1440
16th to endNight
311322447%9%58%
1440
July1st to 15thNight
421241445%10%58%
1548
16th to endNight
311231346%9%60%
1702
August1st to 15thNight
42144345%6%9%53%
1585
16th to endNight
10%424313346%55%
1613
September1st to 15thNight
11%423333346%53%
1721
16th to endNight
9%423213446%58%
1815
October1st to 15thNight
13%5%24313236%52%
1958
16th to endNight
13%423323335%53%
2112
November1st to 15thNight
8%5%23323346%56%
2252
16th to endNight
11%5%34423346%50%
2520
December1st to 15thNight
12%10%46%5%2425%6%39%
2520
16th to endNight
13%9%47%6%2345%6%36%
2685

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%7%36%6%345%47%41%
1611
16th to endDay
10%10%5%9%5%24437%35%
1728
February1st to 15thDay
10%10%5%9%5%4435%7%33%
1575
16th to endDay
12%7%47%5%2445%6%38%
1518
March1st to 15thDay
11%8%47%42445%6%39%
1976
16th to endDay
18%10%45%424347%34%
2110
April1st to 15thDay
16%8%26%5%24336%40%
2082
16th to endDay
22%7%35%423446%34%
2327
May1st to 15thDay
15%6%35%5%35%447%38%
2331
16th to endDay
15%5%36%5%3446%8%36%
2521
June1st to 15thDay
11%5%345%3446%8%42%
2520
16th to endDay
6%3145%2446%8%50%
2520
July1st to 15thDay
8%3235%345%5%8%49%
2409
16th to endDay
42133345%5%9%54%
2466
August1st to 15thDay
7%3145%45%6%7%9%43%
2289
16th to endDay
10%425%425%5%5%7%45%
2235
September1st to 15thDay
12%5%1433335%5%49%
1908
16th to endDay
10%323323346%55%
1815
October1st to 15thDay
14%41331235%6%52%
1661
16th to endDay
13%6%245%2334447%
1760
November1st to 15thDay
9%424423435%55%
1602
16th to endDay
13%7%36%424347%41%
1440
December1st to 15thDay
12%11%48%5%3335%6%34%
1440
16th to endDay
13%10%49%7%25%45%5%30%
1536
January1st to 15thNight
8%6%35%6%345%6%8%42%
2327
16th to endNight
10%9%45%5%23446%43%
2496
February1st to 15thNight
12%10%48%5%24346%36%
2278
16th to endNight
9%6%26%43335%7%47%
1964
March1st to 15thNight
11%8%34223337%49%
1983
16th to endNight
16%8%4442445%7%36%
2112
April1st to 15thNight
13%7%34423346%46%
1865
16th to endNight
16%7%26%333346%42%
1632
May1st to 15thNight
14%6%35%42445%7%44%
1619
16th to endNight
11%7%245%23447%44%
1590
June1st to 15thNight
8%42342347%8%49%
1440
16th to endNight
321332447%9%58%
1440
July1st to 15thNight
4212415%45%10%58%
1548
16th to endNight
311231346%9%60%
1702
August1st to 15thNight
42144345%6%9%53%
1585
16th to endNight
10%424323346%55%
1613
September1st to 15thNight
11%423323346%53%
1721
16th to endNight
9%423213346%58%
1815
October1st to 15thNight
13%5%24313236%52%
1958
16th to endNight
12%5%23322345%53%
2112
November1st to 15thNight
9%5%23323346%56%
2252
16th to endNight
11%5%34423346%50%
2520
December1st to 15thNight
12%10%46%5%2435%6%39%
2520
16th to endNight
13%9%47%5%2345%6%36%
2685

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
42%5%18%21%11%
1612
16th to endDay
50%416%19%8%
1728
February1st to 15thDay
50%416%20%7%
1576
16th to endDay
45%5%14%21%11%1
1518
March1st to 15thDay
44%6%14%22%11%1
1976
16th to endDay
50%5%15%19%6%1
2112
April1st to 15thDay
46%410%26%9%1
2082
16th to endDay
50%5%12%20%9%
2327
May1st to 15thDay
45%6%13%22%11%
2331
16th to endDay
44%7%15%21%9%
2525
June1st to 15thDay
38%7%15%23%13%2
2520
16th to endDay
29%7%17%29%13%2
2520
July1st to 15thDay
31%7%15%27%13%3
2269
16th to endDay
24%7%17%30%17%1
2311
August1st to 15thDay
33%8%17%24%14%
2275
16th to endDay
36%6%11%25%15%4
2235
September1st to 15thDay
35%412%25%18%3
1908
16th to endDay
29%412%32%20%
1815
October1st to 15thDay
32%312%28%20%1
1661
16th to endDay
39%411%24%18%2
1760
November1st to 15thDay
30%412%28%21%1
1602
16th to endDay
43%413%28%9%
1440
December1st to 15thDay
50%5%15%19%8%
1440
16th to endDay
54%5%13%17%8%
1536
January1st to 15thNight
37%5%16%24%14%
2327
16th to endNight
41%5%15%26%11%
2496
February1st to 15thNight
48%5%14%21%9%1
2288
16th to endNight
36%313%25%18%2
1964
March1st to 15thNight
36%412%27%15%2
1983
16th to endNight
45%6%13%24%8%1
2112
April1st to 15thNight
38%5%9%28%16%1
1865
16th to endNight
43%413%22%13%1
1632
May1st to 15thNight
40%6%12%23%15%1
1620
16th to endNight
38%7%16%22%13%2
1592
June1st to 15thNight
30%6%15%29%15%2
1440
16th to endNight
21%5%17%30%21%3
1440
July1st to 15thNight
21%6%19%30%16%4
1459
16th to endNight
18%5%16%37%19%2
1594
August1st to 15thNight
25%8%16%30%16%2
1575
16th to endNight
31%411%24%19%8%
1613
September1st to 15thNight
31%411%24%21%5%
1721
16th to endNight
27%310%34%21%2
1815
October1st to 15thNight
34%39%24%23%3
1958
16th to endNight
32%413%25%21%2
2112
November1st to 15thNight
28%414%25%23%3
2252
16th to endNight
36%314%28%15%1
2520
December1st to 15thNight
46%415%24%8%
2520
16th to endNight
47%6%13%21%10%1
2685

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%6%38%28%4
90
16th to endDay
23%6%37%28%4
96
February1st to 15thDay
16%16%42%21%3
90
16th to endDay
19%12%32%28%42
81
March1st to 15thDay
22%13%45%16%2
90
16th to endDay
26%13%37%18%4
96
April1st to 15thDay
19%9%36%25%7%
201
16th to endDay
26%13%30%20%8%
437
May1st to 15thDay
18%10%30%27%11%1
468
16th to endDay
18%6%31%28%13%1
517
June1st to 15thDay
9%429%32%20%3
495
16th to endDay
5%5%31%34%19%3
495
July1st to 15thDay
9%222%32%27%6%
475
16th to endDay
319%43%28%4
515
August1st to 15thDay
6%219%40%25%5%
474
16th to endDay
12%418%34%26%4
403
September1st to 15thDay
7%328%32%23%4
183
16th to endDay
6%437%27%21%2
90
October1st to 15thDay
7%7%28%35%12%7%
90
16th to endDay
10%10%40%28%10%
96
November1st to 15thDay
7%5%36%34%12%3
90
16th to endDay
42%11%34%10%2
90
December1st to 15thDay
15%23%38%14%6%1
90
16th to endDay
23%21%36%14%3
96
January1st to 15thNight
11%12%35%32%7%
900
16th to endNight
14%10%38%29%6%
960
February1st to 15thNight
16%12%36%29%4
880
16th to endNight
11%10%44%25%6%
702
March1st to 15thNight
15%11%32%31%8%
543
16th to endNight
19%10%40%22%6%
576
April1st to 15thNight
16%12%37%28%5%
539
16th to endNight
18%8%36%25%9%
540
May1st to 15thNight
15%9%30%32%12%
540
16th to endNight
14%5%30%36%12%
563
June1st to 15thNight
9%326%44%14%
540
16th to endNight
4230%45%16%
540
July1st to 15thNight
5%19%45%27%
510
16th to endNight
4113%53%26%1
564
August1st to 15thNight
416%49%25%2
527
16th to endNight
11%218%40%24%3
525
September1st to 15thNight
12%423%33%22%3
495
16th to endNight
11%429%35%18%1
492
October1st to 15thNight
16%6%34%29%11%2
638
16th to endNight
15%8%31%34%9%
704
November1st to 15thNight
12%10%34%32%10%
842
16th to endNight
15%12%37%26%7%
900
December1st to 15thNight
18%11%36%27%4
900
16th to endNight
17%10%33%31%6%
960
Page generated at 2017-08-13 13:16:58. Version ac04

Copyright 2017 A. Danko


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