Sunriver
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sunriver clear sky chart from 2005-11-05 to 2018-03-21.

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
47%
15498
18%
49249
15%
15474
51%
15474
25%
31314

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%
776
11%
2716
10%
776
36%
776
14%
1961
January16th to endNight
39%
832
16%
2809
14%
832
44%
832
18%
1915
February1st to 15thNight
35%
756
9%
2483
8%
756
37%
756
14%
1804
February16th to endNight
33%
684
13%
2112
12%
684
37%
684
16%
1532
March1st to 15thNight
34%
780
10%
2252
7%
780
38%
780
16%
1664
March16th to endNight
29%
792
10%
2118
6%
792
31%
792
17%
1606
April1st to 15thNight
34%
719
10%
1799
5%
719
35%
719
18%
1389
April16th to endNight
46%
681
14%
1761
9%
681
48%
681
27%
1210
May1st to 15thNight
51%
371
18%
1451
17%
371
59%
371
28%
786
May16th to endNight
55%
374
13%
1496
16%
374
59%
374
19%
946
June1st to 15thNight
53%
360
13%
1440
18%
360
59%
360
24%
826
June16th to endNight
63%
360
21%
1440
32%
360
70%
360
40%
654
July1st to 15thNight
81%
340
24%
1360
34%
340
86%
340
59%
490
July16th to endNight
76%
376
34%
1416
42%
354
85%
354
59%
506
August1st to 15thNight
84%
508
34%
1582
29%
506
88%
506
66%
655
August16th to endNight
76%
713
40%
1859
26%
713
79%
713
70%
864
September1st to 15thNight
75%
720
38%
1800
23%
720
78%
720
68%
874
September16th to endNight
63%
716
31%
1956
25%
716
66%
716
45%
1078
October1st to 15thNight
52%
720
20%
2160
17%
720
58%
720
33%
1259
October16th to endNight
45%
768
20%
2350
18%
768
49%
768
23%
1526
November1st to 15thNight
32%
760
13%
2517
10%
760
37%
760
16%
1794
November16th to endNight
35%
780
11%
2730
9%
780
40%
780
16%
1904
December1st to 15thNight
41%
780
13%
2730
13%
780
44%
780
17%
1883
December16th to endNight
29%
832
12%
2912
10%
832
33%
832
12%
2188

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
5%8%46%5%34446%44%
49616
Night
48%47%6%35%45%7%42%
49417
Cloud CoverDay
47%37%6%35%45%6%43%
49616
Night
36%36%7%46%6%6%7%42%
49421
TransparencyDay
40%410%20%17%6%
49287
Night
41%5%12%20%15%4
49250
SeeingDay
13%20%28%23%11%2
6184
Night
8%15%23%31%18%2
15512

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
6%13%5%9%8%36%6%6%7%25%
1552
16th to endDay
6%11%6%8%7%345%5%8%31%
1765
February1st to 15thDay
6%12%6%9%7%35%6%6%10%25%
1711
16th to endDay
414%7%9%8%47%6%5%7%23%
1648
March1st to 15thDay
6%14%7%10%7%5%6%5%5%6%23%
2034
16th to endDay
7%15%7%11%7%45%5%46%23%
2233
April1st to 15thDay
6%15%7%11%7%35%45%6%25%
2149
16th to endDay
5%11%5%7%5%2445%8%38%
2196
May1st to 15thDay
6%9%46%5%3446%7%43%
2499
16th to endDay
10%10%48%6%34447%34%
2615
June1st to 15thDay
9%9%25%5%2445%7%42%
2520
16th to endDay
5%415%423446%57%
2520
July1st to 15thDay
112313335%72%
2520
16th to endDay
21221333474%
2657
August1st to 15thDay
112213346%71%
2367
16th to endDay
221111222476%
2342
September1st to 15thDay
1112212335%73%
2160
16th to endDay
6%5%24424447%52%
2002
October1st to 15thDay
8%8%37%6%3445%5%42%
1800
16th to endDay
8%8%37%6%25%447%40%
1872
November1st to 15thDay
8%12%48%7%345%6%7%30%
1670
16th to endDay
6%8%6%10%8%5%6%6%5%7%25%
1560
December1st to 15thDay
7%10%5%9%7%35%5%6%9%29%
1560
16th to endDay
5%15%6%11%7%5%6%6%5%7%23%
1664
January1st to 15thNight
5%12%5%9%8%5%6%5%6%7%27%
2716
16th to endNight
311%5%9%8%35%46%9%31%
2809
February1st to 15thNight
6%12%5%8%8%46%5%6%7%26%
2471
16th to endNight
411%6%11%8%45%5%5%6%30%
2112
March1st to 15thNight
48%6%10%8%46%6%6%9%27%
2252
16th to endNight
311%6%10%10%47%5%6%8%24%
2114
April1st to 15thNight
5%12%5%11%8%5%5%5%46%28%
1799
16th to endNight
49%47%6%35%45%8%39%
1761
May1st to 15thNight
5%6%35%5%2436%8%49%
1451
16th to endNight
5%8%37%6%36%45%7%40%
1496
June1st to 15thNight
8%7%35%423447%47%
1440
16th to endNight
4413223346%63%
1440
July1st to 15thNight
11113335%75%
1440
16th to endNight
21111112479%
1512
August1st to 15thNight
122111246%75%
1590
16th to endNight
11211223379%
1859
September1st to 15thNight
1221222478%
1800
16th to endNight
441342345%7%58%
1956
October1st to 15thNight
5%6%3442445%7%50%
2160
16th to endNight
8%9%27%6%35%45%6%40%
2350
November1st to 15thNight
7%10%48%7%46%6%6%8%27%
2517
16th to endNight
5%9%49%8%47%6%6%7%30%
2730
December1st to 15thNight
6%11%5%9%7%345%5%8%31%
2730
16th to endNight
312%6%11%9%46%5%6%7%25%
2912

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
5%8%39%7%5%9%6%6%6%29%
1552
16th to endDay
5%9%48%7%47%5%6%8%33%
1765
February1st to 15thDay
410%6%9%7%47%6%7%9%26%
1711
16th to endDay
210%6%10%11%5%7%7%7%6%23%
1648
March1st to 15thDay
310%5%11%10%6%8%7%6%7%23%
2034
16th to endDay
412%6%11%10%5%8%5%5%7%22%
2233
April1st to 15thDay
6%14%7%11%8%45%446%26%
2149
16th to endDay
5%10%47%5%35%45%8%38%
2196
May1st to 15thDay
6%8%37%5%345%5%6%41%
2499
16th to endDay
10%11%49%6%35%436%33%
2615
June1st to 15thDay
9%8%46%5%2445%6%41%
2520
16th to endDay
45%24433445%56%
2520
July1st to 15thDay
1112323345%69%
2520
16th to endDay
211221323473%
2657
August1st to 15thDay
1112323436%68%
2367
16th to endDay
12221223476%
2342
September1st to 15thDay
1112212337%72%
2160
16th to endDay
5%6%25%424446%52%
2002
October1st to 15thDay
6%9%36%7%445%46%41%
1800
16th to endDay
6%6%38%7%45%45%7%41%
1872
November1st to 15thDay
5%10%5%8%8%47%6%7%7%29%
1670
16th to endDay
37%310%10%5%8%7%7%8%26%
1560
December1st to 15thDay
47%5%9%9%45%5%7%9%31%
1560
16th to endDay
310%6%10%9%5%8%6%6%7%24%
1664
January1st to 15thNight
39%47%9%6%9%6%7%8%26%
2716
16th to endNight
28%37%8%5%8%7%7%7%32%
2809
February1st to 15thNight
29%5%10%9%47%7%7%6%27%
2471
16th to endNight
28%5%10%8%5%9%6%6%6%30%
2112
March1st to 15thNight
25%5%8%8%5%10%9%7%9%27%
2252
16th to endNight
26%5%9%10%5%10%8%8%8%23%
2118
April1st to 15thNight
5%11%5%8%9%48%7%5%5%27%
1799
16th to endNight
47%47%6%35%5%5%7%40%
1761
May1st to 15thNight
46%36%6%245%48%48%
1451
16th to endNight
7%8%46%6%36%5%6%6%39%
1496
June1st to 15thNight
8%7%35%422447%47%
1440
16th to endNight
4414214336%63%
1440
July1st to 15thNight
11213345%75%
1440
16th to endNight
21221113379%
1512
August1st to 15thNight
112112237%74%
1590
16th to endNight
1221123479%
1859
September1st to 15thNight
11221232477%
1800
16th to endNight
332442345%6%58%
1956
October1st to 15thNight
36%36%5%245%5%6%49%
2160
16th to endNight
6%7%38%6%46%5%5%6%41%
2350
November1st to 15thNight
49%48%8%48%7%7%8%27%
2517
16th to endNight
25%38%9%6%7%7%8%8%30%
2730
December1st to 15thNight
28%48%8%47%7%5%8%33%
2730
16th to endNight
18%5%9%11%6%10%7%6%6%25%
2912

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
52%7%14%14%8%1
1552
16th to endDay
48%6%12%17%9%4
1765
February1st to 15thDay
52%6%16%15%8%
1711
16th to endDay
58%6%12%15%6%
1648
March1st to 15thDay
59%6%11%15%7%
2034
16th to endDay
61%5%14%14%4
2233
April1st to 15thDay
59%310%19%5%
2149
16th to endDay
44%5%15%21%11%1
2196
May1st to 15thDay
40%412%26%14%1
2499
16th to endDay
53%39%23%8%
2619
June1st to 15thDay
43%39%26%14%2
2520
16th to endDay
29%29%31%21%4
2520
July1st to 15thDay
17%28%22%30%18%
2371
16th to endDay
16%1314%36%27%
2490
August1st to 15thDay
16%37%26%27%18%
2350
16th to endDay
14%2424%39%15%
2342
September1st to 15thDay
14%2424%36%17%
2160
16th to endDay
32%49%25%21%7%
2002
October1st to 15thDay
43%5%9%18%18%5%
1800
16th to endDay
42%5%12%19%18%1
1872
November1st to 15thDay
50%5%14%17%10%
1670
16th to endDay
53%6%14%14%10%1
1560
December1st to 15thDay
48%8%12%20%9%1
1560
16th to endDay
58%5%12%15%7%1
1664
January1st to 15thNight
53%7%14%13%9%1
2716
16th to endNight
48%6%11%17%9%6%
2809
February1st to 15thNight
53%7%16%12%9%
2483
16th to endNight
54%5%12%18%7%1
2112
March1st to 15thNight
50%8%13%16%9%
2252
16th to endNight
54%6%17%17%3
2118
April1st to 15thNight
57%5%14%15%7%
1799
16th to endNight
42%6%16%23%10%
1761
May1st to 15thNight
34%316%31%11%2
1452
16th to endNight
44%6%15%24%8%
1496
June1st to 15thNight
38%5%12%28%12%2
1440
16th to endNight
23%311%37%19%4
1440
July1st to 15thNight
12%110%30%28%15%
1360
16th to endNight
12%1418%38%24%
1416
August1st to 15thNight
12%17%30%33%14%
1582
16th to endNight
11%26%27%38%14%
1859
September1st to 15thNight
11%2328%40%13%
1800
16th to endNight
25%411%24%23%10%
1956
October1st to 15thNight
33%412%23%19%6%
2160
16th to endNight
43%413%17%18%2
2350
November1st to 15thNight
51%6%12%18%9%2
2517
16th to endNight
48%8%12%15%11%2
2730
December1st to 15thNight
48%7%11%20%10%1
2730
16th to endNight
59%5%11%15%7%
2912

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
14%18%26%26%12%1
90
16th to endDay
15%26%27%21%7%1
197
February1st to 15thDay
14%29%28%21%5%
281
16th to endDay
14%33%32%13%5%1
276
March1st to 15thDay
16%38%23%17%3
330
16th to endDay
18%34%30%11%3
311
April1st to 15thDay
19%23%29%14%9%3
269
16th to endDay
22%28%24%15%5%2
270
May1st to 15thDay
21%21%31%17%7%
288
16th to endDay
23%16%19%22%13%4
330
June1st to 15thDay
14%19%28%21%13%2
315
16th to endDay
7%16%31%27%12%3
315
July1st to 15thDay
5%10%33%29%15%4
305
16th to endDay
110%37%31%16%2
327
August1st to 15thDay
39%28%35%16%6%
315
16th to endDay
310%23%32%19%9%
332
September1st to 15thDay
310%28%32%20%5%
315
16th to endDay
11%13%24%32%15%2
315
October1st to 15thDay
16%21%28%20%10%1
315
16th to endDay
17%19%25%20%14%3
288
November1st to 15thDay
9%26%40%16%6%
124
16th to endDay
14%37%25%20%2
90
December1st to 15thDay
11%27%37%8%11%3
90
16th to endDay
14%18%38%21%6%
96
January1st to 15thNight
12%19%28%23%15%1
780
16th to endNight
10%18%24%29%14%1
832
February1st to 15thNight
9%19%26%29%12%1
764
16th to endNight
9%22%28%29%9%
684
March1st to 15thNight
9%28%25%25%11%1
780
16th to endNight
7%24%32%21%12%
792
April1st to 15thNight
9%22%26%25%13%2
719
16th to endNight
9%15%24%28%19%2
681
May1st to 15thNight
9%9%24%36%19%1
372
16th to endNight
10%8%16%35%26%2
375
June1st to 15thNight
12%5%20%41%19%1
360
16th to endNight
6%420%48%20%
360
July1st to 15thNight
114%55%27%1
340
16th to endNight
2115%51%27%1
376
August1st to 15thNight
37%44%38%4
508
16th to endNight
1215%43%33%3
713
September1st to 15thNight
2315%38%35%5%
720
16th to endNight
7%6%19%32%30%4
716
October1st to 15thNight
6%10%25%32%21%3
720
16th to endNight
10%13%23%26%20%5%
768
November1st to 15thNight
12%18%31%26%8%1
760
16th to endNight
8%28%24%23%12%2
780
December1st to 15thNight
11%18%22%31%14%1
780
16th to endNight
10%28%26%24%8%
832
Page generated at 2018-03-22 08:34:23. Version ac04

Copyright 2018 A. Danko


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