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 2005-11-05 to 2017-09-22.

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
45%
14675
12%
46929
11%
14649
48%
14649
18%
33529

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
29%
717
8%
2506
6%
716
33%
716
8%
2053
January16th to endNight
37%
768
11%
2583
10%
768
39%
768
12%
1975
February1st to 15thNight
36%
696
6%
2288
6%
696
38%
696
10%
1861
February16th to endNight
31%
632
10%
2008
6%
632
36%
632
11%
1574
March1st to 15thNight
31%
720
5%
2037
4%
720
32%
720
11%
1699
March16th to endNight
32%
768
6%
2084
4%
768
32%
768
11%
1760
April1st to 15thNight
34%
719
6%
1799
3%
719
35%
719
13%
1491
April16th to endNight
44%
600
10%
1680
7%
600
45%
600
18%
1257
May1st to 15thNight
47%
389
13%
1469
13%
389
53%
389
21%
920
May16th to endNight
51%
375
9%
1496
12%
374
53%
374
13%
1057
June1st to 15thNight
48%
360
8%
1440
9%
360
51%
360
15%
972
June16th to endNight
53%
360
12%
1440
16%
360
57%
360
22%
854
July1st to 15thNight
77%
340
18%
1360
26%
340
81%
340
45%
577
July16th to endNight
78%
376
27%
1416
37%
354
85%
354
54%
546
August1st to 15thNight
83%
526
24%
1600
23%
524
85%
524
55%
731
August16th to endNight
75%
654
32%
1800
22%
654
78%
654
53%
914
September1st to 15thNight
73%
720
27%
1800
16%
720
75%
720
56%
969
September16th to endNight
63%
683
23%
1881
19%
683
65%
683
34%
1165
October1st to 15thNight
51%
660
16%
1980
16%
660
53%
660
24%
1320
October16th to endNight
42%
704
11%
2134
12%
704
45%
704
17%
1585
November1st to 15thNight
34%
700
8%
2400
8%
700
36%
700
9%
1957
November16th to endNight
35%
720
6%
2520
6%
720
37%
720
11%
1966
December1st to 15thNight
31%
720
7%
2520
7%
720
33%
720
9%
2012
December16th to endNight
28%
768
5%
2688
5%
768
28%
768
6%
2314

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
21%8%36%5%24445%32%
47976
Night
21%7%35%424345%36%
47097
Cloud CoverDay
21%8%36%5%24445%31%
47976
Night
21%8%35%5%24345%35%
47101
TransparencyDay
53%7%11%15%9%2
47647
Night
51%7%12%16%10%2
46930
SeeingDay
24%8%20%25%16%4
5660
Night
25%5%16%30%20%1
14687

By Month

Percentage Cloud Cover NW (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
38%9%37%6%3333316%
1432
16th to endDay
30%8%48%435%335%22%
1640
February1st to 15thDay
33%10%38%6%235%45%14%
1576
16th to endDay
30%12%47%6%3432419%
1466
March1st to 15thDay
34%11%5%8%5%2344414%
1920
16th to endDay
32%11%48%7%45%445%13%
2139
April1st to 15thDay
26%11%5%7%6%35%45%6%17%
2149
16th to endDay
24%9%37%7%345%5%6%22%
2279
May1st to 15thDay
19%8%36%5%2335%6%35%
2480
16th to endDay
23%7%36%5%45%5%5%7%26%
2615
June1st to 15thDay
22%8%5%6%6%245%45%28%
2520
16th to endDay
15%6%35%5%35%5%46%38%
2520
July1st to 15thDay
6%314323346%60%
2520
16th to endDay
7%412212336%63%
2657
August1st to 15thDay
431332345%8%58%
2350
16th to endDay
7%41332335%7%57%
2402
September1st to 15thDay
7%313323346%60%
2160
16th to endDay
17%6%26%435%346%38%
1889
October1st to 15thDay
21%8%48%6%25%5%4429%
1650
16th to endDay
27%10%48%5%34345%22%
1738
November1st to 15thDay
34%10%48%6%25%35%413%
1458
16th to endDay
31%9%48%5%3433320%
1440
December1st to 15thDay
29%11%5%9%6%2334416%
1440
16th to endDay
36%13%49%6%3334312%
1536
January1st to 15thNight
33%10%36%6%2443420%
2506
16th to endNight
28%9%36%424345%27%
2583
February1st to 15thNight
26%10%46%6%34446%22%
2276
16th to endNight
25%10%36%5%34345%25%
2008
March1st to 15thNight
30%10%5%5%5%3434421%
2037
16th to endNight
28%8%36%6%35%5%5%6%19%
2080
April1st to 15thNight
24%11%46%5%3445%5%24%
1799
16th to endNight
21%8%25%5%2435%8%32%
1680
May1st to 15thNight
14%5%245%345%47%42%
1469
16th to endNight
18%6%35%425%5%6%8%32%
1496
June1st to 15thNight
16%5%36%5%35%436%39%
1440
16th to endNight
11%5%26%423445%49%
1440
July1st to 15thNight
421121234471%
1440
16th to endNight
22112225%77%
1512
August1st to 15thNight
221221246%72%
1608
16th to endNight
6%21221122470%
1800
September1st to 15thNight
5%21221232471%
1800
16th to endNight
12%41343335%6%51%
1881
October1st to 15thNight
18%6%25%424345%42%
1980
16th to endNight
24%7%25%5%2335%5%33%
2134
November1st to 15thNight
32%7%37%5%3435%5%20%
2400
16th to endNight
31%8%25%424445%26%
2520
December1st to 15thNight
29%10%5%6%5%24345%22%
2520
16th to endNight
34%10%47%5%3443317%
2688

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
38%10%48%7%3333314%
1432
16th to endDay
30%10%48%5%34335%22%
1640
February1st to 15thDay
31%13%5%8%5%245%35%14%
1576
16th to endDay
30%12%47%7%3423419%
1466
March1st to 15thDay
34%11%5%8%7%24345%12%
1920
16th to endDay
31%11%5%8%6%35%445%12%
2139
April1st to 15thDay
26%11%48%8%35%446%15%
2149
16th to endDay
22%10%38%7%35%45%6%22%
2279
May1st to 15thDay
17%10%37%6%24336%34%
2480
16th to endDay
23%7%36%6%35%5%5%6%25%
2615
June1st to 15thDay
21%9%47%6%25%446%26%
2520
16th to endDay
13%8%35%6%35%45%5%38%
2520
July1st to 15thDay
5%324423345%60%
2520
16th to endDay
7%313322336%62%
2657
August1st to 15thDay
441342345%7%58%
2350
16th to endDay
7%41342335%6%57%
2402
September1st to 15thDay
6%413333436%58%
2160
16th to endDay
16%7%27%6%33446%37%
1889
October1st to 15thDay
21%9%48%6%35%34428%
1650
16th to endDay
26%10%5%9%6%34346%20%
1738
November1st to 15thDay
33%12%5%8%6%34335%12%
1458
16th to endDay
29%11%49%7%2333419%
1440
December1st to 15thDay
29%14%5%10%6%23245%16%
1440
16th to endDay
36%14%48%7%2333312%
1536
January1st to 15thNight
33%10%47%5%3434420%
2506
16th to endNight
28%9%46%5%23345%26%
2583
February1st to 15thNight
27%11%47%5%3445%5%22%
2276
16th to endNight
27%10%37%5%2444424%
2008
March1st to 15thNight
29%11%47%435%34419%
2037
16th to endNight
27%10%47%7%25%5%5%5%18%
2084
April1st to 15thNight
24%12%48%5%34345%22%
1799
16th to endNight
21%8%35%5%24348%30%
1680
May1st to 15thNight
13%6%35%425%5%5%6%40%
1469
16th to endNight
18%7%36%5%35%5%5%8%30%
1496
June1st to 15thNight
16%7%37%6%34337%36%
1440
16th to endNight
10%6%35%5%24346%46%
1440
July1st to 15thNight
322221323470%
1440
16th to endNight
21211223476%
1512
August1st to 15thNight
1212312346%69%
1608
16th to endNight
5%22322135%70%
1800
September1st to 15thNight
5%21321223470%
1800
16th to endNight
12%414423446%49%
1881
October1st to 15thNight
18%7%24424335%42%
1980
16th to endNight
23%8%36%5%3335%6%31%
2134
November1st to 15thNight
32%9%37%7%3444420%
2400
16th to endNight
31%8%36%5%23345%25%
2520
December1st to 15thNight
30%10%47%5%24346%21%
2520
16th to endNight
35%11%5%7%5%2434416%
2688

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
75%45%8%41
1432
16th to endDay
67%5%7%10%6%2
1640
February1st to 15thDay
71%8%7%7%3
1576
16th to endDay
70%6%7%8%5%
1466
March1st to 15thDay
74%7%8%6%3
1920
16th to endDay
74%8%7%8%2
2139
April1st to 15thDay
68%8%11%9%2
2149
16th to endDay
63%8%11%10%5%1
2279
May1st to 15thDay
51%6%12%19%9%1
2480
16th to endDay
56%10%13%14%3
2619
June1st to 15thDay
57%8%14%12%5%
2520
16th to endDay
45%9%16%20%6%2
2520
July1st to 15thDay
24%6%14%25%22%5%
2371
16th to endDay
21%412%26%27%6%
2490
August1st to 15thDay
24%7%17%28%16%5%
2333
16th to endDay
25%7%13%28%20%4
2402
September1st to 15thDay
25%5%13%22%20%12%
2160
16th to endDay
47%7%13%16%12%3
1889
October1st to 15thDay
58%6%9%14%9%3
1650
16th to endDay
63%7%10%9%7%
1738
November1st to 15thDay
73%6%8%8%1
1458
16th to endDay
69%6%7%8%8%
1440
December1st to 15thDay
71%48%10%4
1440
16th to endDay
76%7%6%6%3
1536
January1st to 15thNight
67%6%8%9%6%1
2506
16th to endNight
60%6%9%10%10%3
2583
February1st to 15thNight
63%9%10%11%4
2288
16th to endNight
62%6%11%11%6%1
2008
March1st to 15thNight
66%7%9%11%4
2037
16th to endNight
65%9%11%10%2
2084
April1st to 15thNight
63%7%12%10%5%
1799
16th to endNight
52%8%15%15%5%1
1680
May1st to 15thNight
42%6%17%22%8%3
1470
16th to endNight
51%10%16%15%5%1
1496
June1st to 15thNight
48%8%17%19%6%
1440
16th to endNight
38%7%19%23%8%2
1440
July1st to 15thNight
16%6%14%31%24%7%
1360
16th to endNight
12%412%30%30%9%
1416
August1st to 15thNight
14%5%17%36%18%6%
1600
16th to endNight
19%414%37%18%6%
1800
September1st to 15thNight
17%5%14%26%21%13%
1800
16th to endNight
34%5%16%21%15%6%
1881
October1st to 15thNight
44%5%10%21%14%3
1980
16th to endNight
52%8%11%13%11%1
2134
November1st to 15thNight
66%7%9%12%4
2400
16th to endNight
61%8%9%9%10%1
2520
December1st to 15thNight
65%6%8%11%7%
2520
16th to endNight
71%8%8%7%3
2688

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
40%6%13%23%16%
60
16th to endDay
36%5%19%18%16%4
168
February1st to 15thDay
41%10%17%17%11%1
236
16th to endDay
38%11%23%17%7%
219
March1st to 15thDay
50%13%16%15%21
270
16th to endDay
38%12%25%15%6%1
288
April1st to 15thDay
28%16%22%20%5%6%
269
16th to endDay
32%10%27%18%9%2
270
May1st to 15thDay
25%15%22%22%12%1
288
16th to endDay
23%9%15%26%17%7%
330
June1st to 15thDay
20%11%21%24%17%4
315
16th to endDay
13%8%24%33%17%2
315
July1st to 15thDay
5%5%19%35%26%7%
305
16th to endDay
6%319%38%26%6%
327
August1st to 15thDay
6%313%37%28%11%
315
16th to endDay
7%217%29%31%11%
332
September1st to 15thDay
9%322%26%30%6%
315
16th to endDay
18%7%17%33%20%1
280
October1st to 15thDay
28%8%19%25%14%3
255
16th to endDay
34%6%24%21%9%4
250
November1st to 15thDay
30%10%23%26%8%1
69
16th to endDay
41%10%18%15%15%
60
December1st to 15thDay
48%15%26%10%
60
16th to endDay
42%9%12%18%15%1
64
January1st to 15thNight
38%6%16%23%13%1
720
16th to endNight
30%6%16%26%18%1
768
February1st to 15thNight
31%5%17%26%18%
704
16th to endNight
29%10%21%25%12%
632
March1st to 15thNight
34%8%18%26%12%
720
16th to endNight
30%8%18%28%12%
768
April1st to 15thNight
29%7%17%27%16%
719
16th to endNight
26%418%31%18%1
600
May1st to 15thNight
17%5%24%34%17%
390
16th to endNight
22%315%34%23%1
375
June1st to 15thNight
17%221%38%17%1
360
16th to endNight
13%323%40%19%
360
July1st to 15thNight
5%111%48%32%1
340
16th to endNight
3113%51%29%
376
August1st to 15thNight
36%38%44%6%
526
16th to endNight
7%111%39%38%2
654
September1st to 15thNight
7%113%36%36%4
720
16th to endNight
15%111%37%31%2
683
October1st to 15thNight
22%318%30%23%2
660
16th to endNight
27%5%16%26%21%2
704
November1st to 15thNight
34%6%15%30%12%
700
16th to endNight
34%6%16%25%15%
720
December1st to 15thNight
36%5%19%25%12%1
720
16th to endNight
39%6%18%21%13%1
768
Page generated at 2017-09-23 03:43:48. Version ac04

Copyright 2017 A. Danko


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