Eugene
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Eugene clear sky chart from 2005-11-06 to 2024-03-18.

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
49%
22998
13%
80852
14%
22904
51%
22904
17%
57653

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
28%
753
3%
4405
6%
736
30%
736
4%
3842
January11th to 20thNight
31%
757
5%
4371
10%
740
34%
740
5%
3786
January21st to endNight
38%
835
7%
4484
13%
814
40%
814
7%
3719
February1st to 10thNight
37%
760
7%
2470
8%
760
37%
760
10%
2025
February11th to 20thNight
39%
740
9%
2404
9%
740
41%
740
12%
1863
February21st to endNight
35%
628
11%
1960
10%
628
38%
628
13%
1528
March1st to 10thNight
37%
760
9%
2152
8%
760
38%
760
14%
1699
March11th to 20thNight
42%
752
11%
2067
10%
752
44%
752
18%
1591
March21st to endNight
34%
792
5%
2152
4%
792
35%
792
11%
1804
April1st to 10thNight
35%
720
9%
1800
5%
720
36%
720
13%
1474
April11th to 20thNight
42%
711
11%
1779
6%
711
43%
711
19%
1371
April21st to endNight
46%
558
11%
1638
7%
558
47%
558
17%
1226
May1st to 10thNight
49%
462
13%
1542
12%
462
51%
462
22%
1001
May11th to 20thNight
54%
354
13%
1416
18%
354
55%
354
16%
954
May21st to endNight
51%
389
10%
1552
12%
388
55%
388
16%
1047
June1st to 10thNight
55%
360
10%
1440
15%
360
58%
360
18%
931
June11th to 20thNight
52%
360
13%
1440
17%
360
57%
360
24%
833
June21st to endNight
70%
360
19%
1440
29%
360
76%
360
39%
661
July1st to 10thNight
74%
350
22%
1400
32%
350
80%
350
47%
578
July11th to 20thNight
67%
348
29%
1392
34%
348
80%
348
48%
567
July21st to endNight
78%
452
36%
1543
39%
427
88%
427
70%
538
August1st to 10thNight
81%
537
29%
1602
26%
534
83%
534
58%
730
August11th to 20thNight
85%
534
35%
1602
29%
534
87%
534
61%
714
August21st to endNight
74%
728
36%
1916
22%
728
78%
728
59%
960
September1st to 10thNight
74%
720
34%
1800
20%
720
76%
720
60%
943
September11th to 20thNight
70%
720
29%
1817
20%
720
72%
720
44%
1085
September21st to endNight
66%
720
24%
2056
23%
720
67%
720
35%
1239
October1st to 10thNight
60%
720
16%
2160
17%
720
63%
720
31%
1353
October11th to 20thNight
60%
720
18%
2160
21%
720
61%
720
26%
1420
October21st to endNight
46%
792
17%
2376
16%
792
49%
792
19%
1686
November1st to 10thNight
40%
740
11%
2469
11%
740
41%
740
12%
1872
November11th to 20thNight
37%
760
9%
2660
10%
760
37%
760
10%
2093
November21st to endNight
44%
760
9%
2660
10%
760
45%
760
14%
1944
December1st to 10thNight
42%
760
11%
2660
11%
760
43%
760
14%
1957
December11th to 20thNight
34%
759
6%
3241
9%
759
34%
759
7%
2666
December21st to endNight
26%
827
3%
4826
6%
817
27%
817
4%
3953

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
20%8%36%5%3445%6%35%
78662
Night
22%9%36%5%34445%33%
81156
TransparencyDay
50%5%12%18%12%3
78369
Night
53%5%11%17%10%3
80970
SeeingDay
21%9%21%27%16%4
13866
Night
24%5%13%31%24%3
23023

By Month

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 10thDay
34%14%46%7%46%5%5%5%9%
2539
11th to 20thDay
41%13%48%6%3433411%
2579
21st to endDay
31%11%47%7%46%5%5%6%13%
3146
February1st to 10thDay
28%11%47%7%36%6%6%6%16%
1710
11th to 20thDay
28%12%47%7%345%5%5%20%
1665
21st to endDay
30%12%6%7%6%35%445%18%
1494
March1st to 10thDay
25%12%5%9%7%35%45%6%19%
2025
11th to 20thDay
27%10%46%6%35%45%6%24%
2059
21st to endDay
29%11%5%8%8%35%445%16%
2202
April1st to 10thDay
26%13%5%9%7%45%44419%
2160
11th to 20thDay
25%11%47%6%35%445%25%
2129
21st to endDay
22%8%47%5%345%6%6%29%
2317
May1st to 10thDay
16%9%36%6%34446%38%
2416
11th to 20thDay
19%9%37%5%35%5%6%7%31%
2477
21st to endDay
23%8%36%6%445%5%7%31%
2723
June1st to 10thDay
21%8%37%6%3345%6%34%
2520
11th to 20thDay
17%7%37%5%35%45%8%36%
2520
21st to endDay
10%423323346%59%
2520
July1st to 10thDay
5%323323335%68%
2520
11th to 20thDay
7%412212235%70%
2520
21st to endDay
421121333477%
2680
August1st to 10thDay
3312223347%70%
2328
11th to 20thDay
4312322346%71%
2298
21st to endDay
5%313423347%66%
2440
September1st to 10thDay
6%31322224471%
2160
11th to 20thDay
10%7%25%5%2445%6%50%
2141
21st to endDay
14%6%35%5%34446%47%
1904
October1st to 10thDay
16%7%26%435%45%7%42%
1800
11th to 20thDay
20%6%27%6%45%5%5%8%33%
1800
21st to endDay
23%8%36%6%35%45%7%29%
1980
November1st to 10thDay
31%9%48%6%445%5%6%19%
1608
11th to 20thDay
28%10%48%6%35%5%6%7%19%
1520
21st to endDay
28%9%47%6%35%5%7%7%20%
1520
December1st to 10thDay
26%9%37%6%5%5%45%8%23%
1520
11th to 20thDay
26%13%5%9%9%46%5%6%6%11%
1928
21st to endDay
32%14%5%10%8%5%6%5%5%5%7%
2794
January1st to 10thNight
33%17%6%9%7%35%43410%
4406
11th to 20thNight
39%16%47%6%3343312%
4380
21st to endNight
37%13%47%5%3443415%
4521
February1st to 10thNight
28%13%48%6%45%446%18%
2470
11th to 20thNight
27%11%46%6%3445%6%24%
2402
21st to endNight
27%11%5%7%6%35%45%6%22%
1960
March1st to 10thNight
26%12%47%5%3446%6%22%
2152
11th to 20thNight
22%9%48%6%345%5%7%27%
2067
21st to endNight
28%13%48%6%45%445%20%
2152
April1st to 10thNight
28%13%47%5%35%44424%
1800
11th to 20thNight
22%10%46%5%3445%6%30%
1779
21st to endNight
22%8%36%5%36%5%5%7%31%
1638
May1st to 10thNight
16%8%46%6%33446%41%
1542
11th to 20thNight
15%8%46%6%45%45%6%35%
1416
21st to endNight
18%6%47%5%35%47%6%36%
1552
June1st to 10thNight
19%7%345%345%5%6%39%
1440
11th to 20thNight
14%8%24433449%45%
1440
21st to endNight
9%323222345%65%
1440
July1st to 10thNight
5%21321323473%
1440
11th to 20thNight
422231333472%
1440
21st to endNight
221111112484%
1634
August1st to 10thNight
2312212346%72%
1611
11th to 20thNight
321221223476%
1602
21st to endNight
4312313235%73%
1916
September1st to 10thNight
6%21221233472%
1800
11th to 20thNight
10%32342435%6%57%
1817
21st to endNight
12%5%24425%45%7%51%
2056
October1st to 10thNight
15%6%25%43345%6%48%
2160
11th to 20thNight
17%5%25%5%345%46%42%
2160
21st to endNight
23%10%25%434446%36%
2376
November1st to 10thNight
28%8%37%6%45%6%5%5%24%
2469
11th to 20thNight
30%9%47%5%345%45%21%
2660
21st to endNight
23%10%46%6%45%5%5%6%28%
2660
December1st to 10thNight
28%8%47%5%3445%6%26%
2660
11th to 20thNight
28%11%5%9%7%5%6%5%5%5%16%
3276
21st to endNight
29%13%5%12%9%45%5%45%11%
4862

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
75%413%5%21
2539
11th to 20thDay
77%46%6%42
2579
21st to endDay
69%5%11%9%5%1
3146
February1st to 10thDay
66%6%12%10%6%
1710
11th to 20thDay
66%6%12%10%42
1674
21st to endDay
69%410%10%6%2
1494
March1st to 10thDay
66%5%12%13%4
2025
11th to 20thDay
62%5%11%17%5%1
2059
21st to endDay
71%7%10%11%2
2202
April1st to 10thDay
69%5%10%11%4
2160
11th to 20thDay
62%6%11%12%6%3
2132
21st to endDay
55%8%15%14%8%1
2317
May1st to 10thDay
48%6%17%21%8%1
2416
11th to 20thDay
52%7%14%20%6%1
2480
21st to endDay
55%6%16%19%3
2724
June1st to 10thDay
52%6%15%22%5%
2520
11th to 20thDay
47%5%20%21%6%
2520
21st to endDay
28%416%33%16%3
2520
July1st to 10thDay
20%413%29%26%8%
2451
11th to 20thDay
19%38%24%34%12%
2445
21st to endDay
13%35%29%40%10%
2531
August1st to 10thDay
16%413%35%24%7%
2312
11th to 20thDay
17%311%35%27%7%
2298
21st to endDay
20%311%32%29%5%
2440
September1st to 10thDay
19%38%31%25%13%
2160
11th to 20thDay
35%5%11%25%17%8%
2141
21st to endDay
38%6%12%21%18%6%
1904
October1st to 10thDay
42%7%10%18%18%5%
1800
11th to 20thDay
49%6%13%17%13%3
1800
21st to endDay
53%6%11%14%13%2
1980
November1st to 10thDay
65%412%13%6%
1608
11th to 20thDay
63%5%12%11%6%2
1520
21st to endDay
62%5%11%7%13%2
1520
December1st to 10thDay
60%411%12%11%1
1520
11th to 20thDay
70%5%11%10%2
1928
21st to endDay
76%413%5%21
2794
January1st to 10thNight
79%48%431
4406
11th to 20thNight
76%6%5%7%42
4380
21st to endNight
73%47%10%5%1
4521
February1st to 10thNight
68%5%9%12%41
2470
11th to 20thNight
62%5%13%12%5%2
2404
21st to endNight
62%5%12%12%6%2
1960
March1st to 10thNight
61%6%13%14%5%1
2152
11th to 20thNight
57%6%14%16%6%1
2067
21st to endNight
68%6%12%12%2
2152
April1st to 10thNight
66%5%11%13%5%
1800
11th to 20thNight
55%6%16%14%5%3
1779
21st to endNight
54%8%15%16%5%3
1638
May1st to 10thNight
45%5%17%22%9%1
1542
11th to 20thNight
50%6%15%20%6%3
1416
21st to endNight
48%9%18%21%4
1552
June1st to 10thNight
44%8%15%28%4
1440
11th to 20thNight
38%5%22%26%7%1
1440
21st to endNight
23%5%18%36%15%4
1440
July1st to 10thNight
18%413%30%25%11%
1400
11th to 20thNight
18%38%24%34%13%
1392
21st to endNight
8%26%31%43%10%
1543
August1st to 10thNight
14%5%13%40%23%6%
1602
11th to 20thNight
14%310%37%29%7%
1602
21st to endNight
17%310%36%28%7%
1916
September1st to 10thNight
17%410%31%26%13%
1800
11th to 20thNight
29%413%30%16%9%
1817
21st to endNight
34%5%13%23%18%8%
2056
October1st to 10thNight
38%5%11%22%18%6%
2160
11th to 20thNight
42%6%14%20%15%3
2160
21st to endNight
50%6%10%14%16%4
2376
November1st to 10thNight
60%5%11%14%8%
2469
11th to 20thNight
65%6%10%11%7%2
2660
21st to endNight
57%5%10%12%11%5%
2660
December1st to 10thNight
58%412%14%10%1
2660
11th to 20thNight
70%5%10%10%4
3276
21st to endNight
73%5%12%8%21
4862

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
48%11%14%13%12%2
180
11th to 20thDay
36%11%14%21%15%3
206
21st to endDay
30%10%20%20%16%4
407
February1st to 10thDay
33%9%19%24%12%3
370
11th to 20thDay
35%9%26%18%10%2
365
21st to endDay
35%15%17%23%9%2
346
March1st to 10thDay
34%13%24%19%9%1
460
11th to 20thDay
29%10%25%24%11%2
449
21st to endDay
31%15%24%18%10%2
462
April1st to 10thDay
32%16%18%20%11%3
420
11th to 20thDay
33%14%23%17%9%4
412
21st to endDay
29%12%22%23%11%3
420
May1st to 10thDay
20%13%24%26%13%4
423
11th to 20thDay
28%9%15%29%15%4
448
21st to endDay
19%12%21%27%17%5%
485
June1st to 10thDay
21%10%20%27%17%4
450
11th to 20thDay
18%14%28%27%11%2
450
21st to endDay
9%424%40%19%5%
450
July1st to 10thDay
7%423%40%22%4
446
11th to 20thDay
45%28%40%17%6%
444
21st to endDay
2323%42%25%5%
487
August1st to 10thDay
4221%41%26%7%
447
11th to 20thDay
3317%42%28%8%
437
21st to endDay
5%5%26%35%23%6%
495
September1st to 10thDay
7%425%33%23%6%
450
11th to 20thDay
15%6%20%31%23%5%
450
21st to endDay
17%8%25%28%17%6%
450
October1st to 10thDay
18%8%23%24%19%7%
450
11th to 20thDay
22%8%15%27%20%9%
450
21st to endDay
26%12%20%21%15%5%
495
November1st to 10thDay
27%12%20%23%14%4
244
11th to 20thDay
28%11%19%19%14%8%
180
21st to endDay
33%9%14%20%19%4
180
December1st to 10thDay
32%11%17%19%13%8%
180
11th to 20thDay
37%11%16%20%13%3
180
21st to endDay
37%11%17%19%16%1
198
January1st to 10thNight
39%7%16%22%13%3
760
11th to 20thNight
35%7%13%23%17%4
760
21st to endNight
32%5%13%29%19%3
836
February1st to 10thNight
34%6%11%29%18%1
760
11th to 20thNight
32%6%13%30%18%1
744
21st to endNight
31%12%14%28%15%
628
March1st to 10thNight
32%9%13%31%15%1
760
11th to 20thNight
25%7%16%32%19%1
752
21st to endNight
33%9%14%27%16%1
792
April1st to 10thNight
33%8%15%24%19%1
720
11th to 20thNight
27%7%17%28%20%2
711
21st to endNight
26%416%30%22%2
558
May1st to 10thNight
18%6%19%31%23%3
462
11th to 20thNight
21%110%35%30%3
354
21st to endNight
20%214%34%28%2
389
June1st to 10thNight
20%312%38%25%2
360
11th to 20thNight
18%223%33%23%2
360
21st to endNight
11%211%45%31%1
360
July1st to 10thNight
6%212%45%35%1
350
11th to 20thNight
5%320%46%26%1
348
21st to endNight
3116%39%39%2
452
August1st to 10thNight
4110%35%43%7%
537
11th to 20thNight
416%39%44%6%
534
21st to endNight
6%314%41%33%4
728
September1st to 10thNight
7%214%37%37%4
720
11th to 20thNight
11%210%30%40%7%
720
21st to endNight
13%412%34%33%4
720
October1st to 10thNight
16%313%34%29%5%
720
11th to 20thNight
20%47%32%30%7%
720
21st to endNight
29%7%10%28%21%5%
792
November1st to 10thNight
30%6%14%30%18%2
740
11th to 20thNight
34%7%13%26%17%2
760
21st to endNight
28%6%12%31%19%4
760
December1st to 10thNight
28%7%13%27%21%3
760
11th to 20thNight
39%7%10%26%17%1
760
21st to endNight
42%8%13%27%10%1
836
Page generated at 2024-03-15 11:01:41. Version ac07

Copyright © 2024 Attilla Danko.


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