Tualatin River National Wildlife Refuge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tualatin River National Wildlife Refuge clear sky chart from 2005-11-06 to 2024-01-13.

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
44%
22585
12%
74766
12%
22547
47%
22547
17%
53441

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
25%
757
6%
2646
5%
756
28%
756
7%
2252
January11th to 20thNight
31%
732
8%
2562
8%
732
33%
732
9%
2053
January21st to endNight
34%
792
11%
2614
11%
792
36%
792
12%
2046
February1st to 10thNight
34%
720
6%
2340
6%
720
35%
720
9%
1934
February11th to 20thNight
32%
700
8%
2274
6%
700
36%
700
11%
1790
February21st to endNight
31%
592
9%
1857
7%
592
34%
592
11%
1495
March1st to 10thNight
33%
720
9%
2066
7%
720
35%
720
13%
1658
March11th to 20thNight
36%
720
10%
1980
8%
720
38%
720
15%
1553
March21st to endNight
31%
792
5%
2138
3%
792
31%
792
10%
1821
April1st to 10thNight
33%
720
7%
1800
4%
720
34%
720
13%
1496
April11th to 20thNight
40%
711
10%
1779
5%
711
41%
711
19%
1372
April21st to endNight
38%
540
10%
1620
7%
540
40%
540
16%
1206
May1st to 10thNight
46%
406
13%
1486
12%
406
51%
406
21%
954
May11th to 20thNight
50%
354
13%
1416
14%
354
55%
354
17%
924
May21st to endNight
48%
389
9%
1552
10%
388
52%
388
14%
1058
June1st to 10thNight
46%
360
8%
1440
10%
360
49%
360
17%
935
June11th to 20thNight
46%
360
8%
1440
11%
360
49%
360
16%
960
June21st to endNight
59%
360
16%
1440
21%
360
66%
360
32%
721
July1st to 10thNight
72%
350
17%
1400
24%
350
76%
350
39%
644
July11th to 20thNight
65%
348
25%
1392
31%
348
75%
348
45%
598
July21st to endNight
78%
394
31%
1488
40%
372
86%
372
65%
512
August1st to 10thNight
79%
519
26%
1585
24%
517
82%
517
58%
709
August11th to 20thNight
82%
534
31%
1602
26%
534
84%
534
54%
752
August21st to endNight
69%
715
31%
1903
20%
715
72%
715
51%
1011
September1st to 10thNight
68%
720
27%
1800
16%
720
70%
720
52%
1008
September11th to 20thNight
61%
720
23%
1800
15%
720
63%
720
34%
1176
September21st to endNight
63%
720
21%
2065
19%
720
65%
720
34%
1246
October1st to 10thNight
52%
720
14%
2160
14%
720
55%
720
27%
1408
October11th to 20thNight
53%
720
18%
2160
20%
720
55%
720
24%
1446
October21st to endNight
40%
792
16%
2412
14%
792
45%
792
19%
1713
November1st to 10thNight
36%
740
10%
2508
11%
740
38%
740
11%
1986
November11th to 20thNight
31%
760
7%
2660
6%
760
34%
760
9%
2149
November21st to endNight
37%
760
7%
2660
7%
760
39%
760
12%
2034
December1st to 10thNight
34%
760
9%
2660
9%
760
36%
760
11%
2073
December11th to 20thNight
26%
759
6%
3214
6%
759
27%
759
6%
2671
December21st to endNight
24%
829
3%
4847
5%
817
25%
817
3%
4077

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
19%9%37%6%3445%6%33%
74742
Night
20%9%36%5%34446%35%
75025
TransparencyDay
51%9%12%16%10%3
74445
Night
50%9%13%16%10%3
74843
SeeingDay
21%9%20%26%18%5%
13525
Night
24%6%18%31%19%2
22600

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
39%12%410%8%35%33311%
1519
11th to 20thDay
34%12%46%8%3343418%
1459
21st to endDay
25%12%410%7%4444422%
1741
February1st to 10thDay
30%11%49%6%45%5%5%6%15%
1620
11th to 20thDay
28%14%5%9%8%35%34418%
1575
21st to endDay
29%13%5%7%7%44345%19%
1399
March1st to 10thDay
27%12%5%9%8%35%45%6%16%
1890
11th to 20thDay
28%11%5%8%6%34446%20%
1980
21st to endDay
27%12%6%9%8%46%5%5%6%13%
2218
April1st to 10thDay
27%11%5%9%8%35%45%6%17%
2160
11th to 20thDay
23%11%48%7%45%5%46%24%
2129
21st to endDay
19%10%38%7%45%6%6%7%25%
2338
May1st to 10thDay
14%10%48%6%45%5%46%35%
2471
11th to 20thDay
19%8%37%7%35%5%5%7%31%
2477
21st to endDay
22%8%36%7%46%5%6%6%28%
2723
June1st to 10thDay
20%8%47%6%35%45%6%32%
2520
11th to 20thDay
18%10%36%7%47%6%6%7%27%
2520
21st to endDay
8%5%25%5%3445%6%51%
2520
July1st to 10thDay
6%425%5%3445%6%57%
2520
11th to 20thDay
6%323423446%62%
2520
21st to endDay
5%312322335%72%
2741
August1st to 10thDay
4412434447%62%
2344
11th to 20thDay
5%31342345%6%64%
2298
21st to endDay
6%5%15%42446%7%55%
2453
September1st to 10thDay
7%313433447%61%
2160
11th to 20thDay
11%7%37%5%35%5%47%43%
2159
21st to endDay
15%6%36%6%345%46%44%
1894
October1st to 10thDay
19%8%37%6%35%445%36%
1800
11th to 20thDay
18%9%5%8%7%35%45%8%29%
1800
21st to endDay
27%10%48%5%24345%27%
1944
November1st to 10thDay
29%13%5%9%7%45%45%5%14%
1568
11th to 20thDay
29%12%5%9%6%34446%19%
1520
21st to endDay
27%11%410%7%345%4421%
1520
December1st to 10thDay
27%13%5%9%6%34246%22%
1520
11th to 20thDay
29%13%5%9%6%345%6%6%15%
1928
21st to endDay
31%15%5%11%11%45%4337%
2794
January1st to 10thNight
35%12%48%5%4434416%
2646
11th to 20thNight
32%11%47%6%35%346%20%
2562
21st to endNight
26%12%48%6%33445%25%
2614
February1st to 10thNight
25%13%5%8%7%445%5%6%20%
2340
11th to 20thNight
27%11%47%6%35%45%425%
2272
21st to endNight
27%13%48%5%345%45%22%
1857
March1st to 10thNight
24%12%49%6%35%45%5%24%
2066
11th to 20thNight
24%11%36%7%35%5%6%7%25%
1980
21st to endNight
25%10%49%8%36%6%5%5%20%
2138
April1st to 10thNight
25%13%5%8%6%45%345%23%
1800
11th to 20thNight
19%10%47%5%4445%8%31%
1779
21st to endNight
23%9%46%6%2445%7%30%
1620
May1st to 10thNight
12%8%46%6%35%45%7%41%
1486
11th to 20thNight
16%7%36%5%45%5%5%9%35%
1416
21st to endNight
15%7%37%5%37%6%6%8%33%
1552
June1st to 10thNight
15%7%37%6%35%448%37%
1440
11th to 20thNight
13%8%5%7%6%35%45%6%37%
1440
21st to endNight
7%423433345%60%
1440
July1st to 10thNight
5%42333333467%
1440
11th to 20thNight
5%32331433471%
1440
21st to endNight
211221223381%
1576
August1st to 10thNight
3312313246%72%
1593
11th to 20thNight
3212323245%72%
1602
21st to endNight
6%313422246%66%
1903
September1st to 10thNight
6%324313345%67%
1800
11th to 20thNight
10%5%35%5%345%5%5%49%
1800
21st to endNight
11%425%5%2445%7%51%
2065
October1st to 10thNight
15%7%35%435%345%46%
2160
11th to 20thNight
17%7%36%5%3445%7%40%
2160
21st to endNight
22%9%36%5%23345%38%
2412
November1st to 10thNight
28%10%38%7%3445%5%24%
2508
11th to 20thNight
32%10%47%6%34445%21%
2660
21st to endNight
25%9%37%8%3445%5%27%
2660
December1st to 10thNight
28%10%5%7%5%3345%6%24%
2660
11th to 20thNight
29%12%48%6%35%346%19%
3276
21st to endNight
29%13%6%9%8%45%44414%
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
78%7%5%5%31
1519
11th to 20thDay
72%5%8%8%43
1459
21st to endDay
66%7%8%11%8%
1741
February1st to 10thDay
69%10%10%8%4
1620
11th to 20thDay
68%10%7%9%42
1584
21st to endDay
68%7%10%8%6%2
1399
March1st to 10thDay
65%11%11%9%5%
1890
11th to 20thDay
65%8%9%12%6%1
1980
21st to endDay
70%11%10%9%1
2218
April1st to 10thDay
65%10%12%11%3
2160
11th to 20thDay
61%9%9%12%6%3
2132
21st to endDay
57%11%12%11%8%1
2338
May1st to 10thDay
49%9%15%18%9%1
2471
11th to 20thDay
50%11%14%17%7%1
2480
21st to endDay
52%12%16%16%3
2724
June1st to 10thDay
51%10%17%17%5%1
2520
11th to 20thDay
52%12%18%13%5%
2520
21st to endDay
33%7%19%27%10%4
2520
July1st to 10thDay
26%9%15%24%21%5%
2451
11th to 20thDay
22%7%11%26%28%6%
2445
21st to endDay
14%411%31%34%6%
2589
August1st to 10thDay
21%7%17%31%20%5%
2327
11th to 20thDay
20%6%15%30%21%7%
2298
21st to endDay
25%8%13%29%21%4
2453
September1st to 10thDay
23%7%14%26%19%12%
2160
11th to 20thDay
38%9%15%17%14%7%
2159
21st to endDay
39%10%14%18%15%5%
1894
October1st to 10thDay
48%8%8%18%14%3
1800
11th to 20thDay
54%9%13%12%12%2
1800
21st to endDay
59%7%8%11%13%1
1944
November1st to 10thDay
70%8%9%10%3
1568
11th to 20thDay
67%7%11%8%6%1
1520
21st to endDay
65%8%6%9%11%1
1520
December1st to 10thDay
65%6%9%10%8%1
1520
11th to 20thDay
66%12%11%9%2
1928
21st to endDay
77%11%6%32
2794
January1st to 10thNight
72%7%8%7%42
2646
11th to 20thNight
66%6%9%10%7%2
2562
21st to endNight
61%7%10%11%9%1
2614
February1st to 10thNight
64%11%11%10%41
2340
11th to 20thNight
61%8%13%10%6%2
2274
21st to endNight
63%9%11%10%5%2
1857
March1st to 10thNight
60%9%11%14%6%
2066
11th to 20thNight
56%9%14%13%6%1
1980
21st to endNight
64%12%12%11%1
2138
April1st to 10thNight
63%9%12%11%5%
1800
11th to 20thNight
50%11%16%13%6%3
1779
21st to endNight
52%10%15%14%7%2
1620
May1st to 10thNight
40%10%17%22%8%2
1486
11th to 20thNight
45%9%19%18%5%4
1416
21st to endNight
46%12%19%17%5%
1552
June1st to 10thNight
46%8%18%23%5%1
1440
11th to 20thNight
46%10%20%20%5%
1440
21st to endNight
26%8%19%31%12%5%
1440
July1st to 10thNight
20%8%14%29%22%7%
1400
11th to 20thNight
18%6%13%26%31%7%
1392
21st to endNight
8%412%35%31%10%
1488
August1st to 10thNight
14%5%17%37%22%6%
1585
11th to 20thNight
15%6%16%36%19%8%
1602
21st to endNight
20%5%14%36%20%5%
1903
September1st to 10thNight
19%7%14%28%20%12%
1800
11th to 20thNight
33%9%13%23%13%9%
1800
21st to endNight
32%7%18%19%18%7%
2065
October1st to 10thNight
40%7%11%22%16%3
2160
11th to 20thNight
41%9%13%18%15%3
2160
21st to endNight
48%8%11%14%16%2
2412
November1st to 10thNight
60%10%9%14%6%
2508
11th to 20thNight
64%8%10%8%7%2
2660
21st to endNight
57%10%9%10%12%2
2660
December1st to 10thNight
60%9%9%11%10%1
2660
11th to 20thNight
66%11%9%11%4
3276
21st to endNight
67%14%11%6%2
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
46%11%16%14%11%1
180
11th to 20thDay
41%10%18%19%9%2
165
21st to endDay
32%10%19%22%14%4
333
February1st to 10thDay
36%12%18%19%13%2
340
11th to 20thDay
33%13%26%18%9%2
335
21st to endDay
35%15%23%17%9%1
310
March1st to 10thDay
33%13%23%22%7%2
420
11th to 20thDay
29%13%23%22%12%2
420
21st to endDay
32%15%22%19%11%1
462
April1st to 10thDay
32%14%21%22%7%5%
420
11th to 20thDay
30%14%25%19%8%4
412
21st to endDay
23%13%27%22%14%1
420
May1st to 10thDay
20%14%21%26%16%4
423
11th to 20thDay
28%10%15%27%15%4
448
21st to endDay
19%9%17%29%19%6%
485
June1st to 10thDay
21%9%21%25%20%4
450
11th to 20thDay
18%11%26%27%15%3
450
21st to endDay
8%6%20%36%25%6%
450
July1st to 10thDay
7%5%17%35%28%7%
446
11th to 20thDay
45%21%40%25%6%
444
21st to endDay
4316%38%32%8%
487
August1st to 10thDay
6%311%38%32%11%
447
11th to 20thDay
3213%36%35%11%
437
21st to endDay
7%421%34%26%8%
495
September1st to 10thDay
8%425%30%27%6%
450
11th to 20thDay
14%6%17%28%28%7%
450
21st to endDay
15%8%20%34%19%3
450
October1st to 10thDay
21%8%21%25%19%7%
450
11th to 20thDay
22%8%16%29%18%7%
450
21st to endDay
31%11%22%19%11%5%
459
November1st to 10thDay
30%11%24%19%13%2
219
11th to 20thDay
26%20%21%17%13%4
180
21st to endDay
28%13%20%19%19%2
180
December1st to 10thDay
36%11%18%21%11%4
180
11th to 20thDay
39%12%24%17%6%1
180
21st to endDay
40%15%16%16%12%1
198
January1st to 10thNight
41%9%17%20%11%1
760
11th to 20thNight
35%10%16%23%15%1
732
21st to endNight
33%6%16%31%13%2
792
February1st to 10thNight
33%8%16%28%14%1
720
11th to 20thNight
31%9%20%23%16%
704
21st to endNight
31%12%19%30%8%
592
March1st to 10thNight
29%9%21%27%13%1
720
11th to 20thNight
26%10%18%32%13%1
720
21st to endNight
29%8%22%28%13%1
792
April1st to 10thNight
31%8%17%27%16%1
720
11th to 20thNight
23%9%22%30%15%1
711
21st to endNight
27%5%21%30%15%1
540
May1st to 10thNight
16%7%24%34%17%1
406
11th to 20thNight
18%5%18%36%22%2
354
21st to endNight
17%5%22%33%21%1
389
June1st to 10thNight
17%325%33%21%1
360
11th to 20thNight
15%6%25%41%13%1
360
21st to endNight
10%223%45%20%
360
July1st to 10thNight
6%314%50%27%1
350
11th to 20thNight
6%123%45%24%1
348
21st to endNight
2216%52%29%1
394
August1st to 10thNight
5%110%40%39%5%
519
11th to 20thNight
5%18%37%45%4
534
21st to endNight
8%316%43%30%2
715
September1st to 10thNight
7%318%41%29%2
720
11th to 20thNight
12%313%32%36%4
720
21st to endNight
13%315%39%26%3
720
October1st to 10thNight
18%319%31%25%3
720
11th to 20thNight
19%6%14%31%27%3
720
21st to endNight
25%9%18%28%16%3
792
November1st to 10thNight
30%8%16%31%14%
740
11th to 20thNight
35%9%18%25%12%1
760
21st to endNight
29%6%20%29%16%1
760
December1st to 10thNight
31%8%18%28%13%1
760
11th to 20thNight
38%7%20%23%12%1
760
21st to endNight
38%9%20%22%9%1
836
Page generated at 2024-01-10 16:35:24. Version ac07

Copyright 2024 Attilla Danko


Tualatin River National Wildlife Refuge Clear Sky Chart |Charts Home