This page made possible by the sponsorship of: Rob & Theresa Britschgi.

Bend
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bend clear sky chart from 2005-11-06 to 2024-02-20.

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
52%
22851
17%
80472
17%
22771
55%
22771
24%
50224

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
32%
749
7%
4383
7%
736
36%
736
8%
3086
January11th to 20thNight
39%
754
11%
4406
12%
740
44%
740
10%
3126
January21st to endNight
41%
832
11%
4623
16%
814
47%
814
10%
3348
February1st to 10thNight
34%
760
12%
2470
9%
760
39%
760
16%
1724
February11th to 20thNight
39%
739
13%
2389
11%
738
43%
738
20%
1587
February21st to endNight
38%
592
14%
1776
12%
592
42%
592
16%
1300
March1st to 10thNight
37%
720
11%
2138
8%
720
41%
720
18%
1518
March11th to 20thNight
41%
720
14%
1980
11%
720
44%
720
23%
1381
March21st to endNight
37%
792
10%
2084
5%
792
40%
792
18%
1552
April1st to 10thNight
41%
720
12%
1800
6%
720
42%
720
22%
1310
April11th to 20thNight
42%
711
15%
1779
8%
711
44%
711
26%
1252
April21st to endNight
47%
666
13%
1746
8%
666
49%
666
26%
1189
May1st to 10thNight
56%
369
19%
1449
18%
369
62%
369
27%
798
May11th to 20thNight
61%
354
18%
1416
22%
354
65%
354
23%
833
May21st to endNight
56%
388
12%
1552
16%
388
60%
388
20%
965
June1st to 10thNight
58%
360
12%
1440
18%
360
61%
360
22%
862
June11th to 20thNight
62%
360
18%
1440
26%
360
69%
360
35%
707
June21st to endNight
77%
360
23%
1440
39%
360
80%
360
45%
615
July1st to 10thNight
86%
350
24%
1400
37%
350
90%
350
59%
506
July11th to 20thNight
83%
348
33%
1392
47%
348
88%
348
64%
479
July21st to endNight
86%
394
38%
1488
52%
372
90%
372
67%
498
August1st to 10thNight
86%
476
33%
1542
33%
474
88%
474
64%
625
August11th to 20thNight
88%
547
36%
1615
29%
547
90%
547
66%
705
August21st to endNight
77%
792
39%
1980
25%
792
78%
792
71%
940
September1st to 10thNight
78%
720
39%
1800
23%
720
81%
720
72%
859
September11th to 20thNight
73%
720
33%
1800
22%
720
75%
720
51%
1008
September21st to endNight
66%
720
29%
2029
26%
720
68%
720
44%
1107
October1st to 10thNight
58%
720
21%
2160
19%
720
64%
720
37%
1239
October11th to 20thNight
59%
720
24%
2160
23%
720
64%
720
36%
1248
October21st to endNight
48%
792
19%
2455
18%
792
53%
792
25%
1561
November1st to 10thNight
43%
740
16%
2405
16%
740
46%
740
20%
1633
November11th to 20thNight
38%
760
13%
2633
11%
760
43%
760
17%
1807
November21st to endNight
45%
760
14%
2660
11%
760
50%
760
21%
1704
December1st to 10thNight
45%
760
14%
2660
12%
760
49%
760
19%
1757
December11th to 20thNight
39%
759
12%
3209
11%
759
42%
759
12%
2288
December21st to endNight
29%
827
8%
4773
8%
817
33%
817
8%
3107

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%6%35%5%35%5%6%7%49%
78344
Night
5%7%36%5%35%5%6%8%47%
80865
TransparencyDay
32%11%13%20%17%7%
78047
Night
33%13%15%20%15%5%
80683
SeeingDay
9%16%27%27%17%5%
13654
Night
7%12%24%36%19%2
22886

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
7%11%48%8%47%7%7%9%28%
2539
11th to 20thDay
10%11%49%7%5%7%6%8%7%26%
2540
21st to endDay
8%10%47%6%46%5%6%9%33%
3018
February1st to 10thDay
410%37%7%5%6%6%6%10%36%
1710
11th to 20thDay
5%9%5%6%5%45%5%7%10%40%
1662
21st to endDay
310%6%8%7%47%8%7%9%32%
1480
March1st to 10thDay
5%8%5%8%7%5%6%6%8%9%32%
1818
11th to 20thDay
39%37%7%46%7%9%9%37%
1980
21st to endDay
5%9%47%8%6%7%7%7%8%31%
2272
April1st to 10thDay
7%11%49%7%45%6%6%8%33%
2160
11th to 20thDay
7%10%47%7%45%5%5%8%39%
2129
21st to endDay
6%7%26%5%3446%8%47%
2212
May1st to 10thDay
6%7%25%5%35%46%8%48%
2510
11th to 20thDay
9%6%36%5%45%5%5%7%43%
2477
21st to endDay
11%7%35%6%35%5%6%8%41%
2723
June1st to 10thDay
9%6%35%5%45%5%5%7%43%
2520
11th to 20thDay
7%5%25%5%2445%7%54%
2520
21st to endDay
3323324346%66%
2520
July1st to 10thDay
211232344475%
2520
11th to 20thDay
3112222345%75%
2520
21st to endDay
22121223480%
2741
August1st to 10thDay
121232446%7%69%
2386
11th to 20thDay
2212323345%75%
2285
21st to endDay
2211223235%77%
2376
September1st to 10thDay
2212213346%75%
2160
11th to 20thDay
342443445%7%61%
2160
21st to endDay
7%5%24423347%59%
1926
October1st to 10thDay
7%7%25%434445%53%
1800
11th to 20thDay
5%5%246%35%6%6%8%51%
1800
21st to endDay
7%7%26%5%45%5%5%6%48%
1900
November1st to 10thDay
5%8%37%6%45%6%7%8%40%
1674
11th to 20thDay
5%6%36%8%46%7%9%9%37%
1544
21st to endDay
5%7%46%5%35%7%9%10%39%
1520
December1st to 10thDay
48%45%5%435%8%8%44%
1520
11th to 20thDay
5%9%48%7%5%5%8%8%9%33%
1928
21st to endDay
411%5%9%8%5%5%6%7%9%31%
2794
January1st to 10thNight
410%48%8%6%8%8%8%9%28%
4406
11th to 20thNight
6%10%5%9%8%46%7%7%9%28%
4420
21st to endNight
8%14%5%9%7%45%5%6%7%30%
4641
February1st to 10thNight
410%48%7%35%6%7%8%39%
2470
11th to 20thNight
410%37%6%35%6%7%9%40%
2387
21st to endNight
49%48%6%46%6%6%10%37%
1776
March1st to 10thNight
5%8%35%7%46%7%7%9%37%
2138
11th to 20thNight
37%37%6%46%6%8%10%39%
1980
21st to endNight
48%48%6%47%8%8%10%33%
2084
April1st to 10thNight
7%11%37%6%36%5%6%8%39%
1800
11th to 20thNight
6%9%46%5%35%6%8%8%41%
1779
21st to endNight
7%8%345%36%5%7%9%44%
1746
May1st to 10thNight
5%7%35%44445%9%51%
1449
11th to 20thNight
6%5%25%5%35%6%6%8%49%
1416
21st to endNight
9%7%346%36%5%7%8%43%
1552
June1st to 10thNight
11%5%35%5%335%48%48%
1440
11th to 20thNight
7%5%2442335%7%61%
1440
21st to endNight
3312323446%69%
1440
July1st to 10thNight
2112223345%77%
1440
11th to 20thNight
21121223483%
1440
21st to endNight
111121223483%
1576
August1st to 10thNight
2212312246%75%
1550
11th to 20thNight
1111222345%78%
1615
21st to endNight
121221223481%
1980
September1st to 10thNight
2111113335%80%
1800
11th to 20thNight
321432435%6%66%
1800
21st to endNight
6%41342335%6%63%
2029
October1st to 10thNight
6%6%2442335%5%59%
2160
11th to 20thNight
5%425%5%2446%7%57%
2160
21st to endNight
6%7%26%6%346%5%7%48%
2455
November1st to 10thNight
6%8%36%6%35%6%7%7%41%
2405
11th to 20thNight
6%7%37%7%45%6%8%9%38%
2633
21st to endNight
38%36%5%35%7%7%8%45%
2660
December1st to 10thNight
5%8%46%5%35%5%7%8%44%
2660
11th to 20thNight
49%48%7%5%6%6%8%9%33%
3276
21st to endNight
49%47%7%5%6%6%6%7%37%
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
41%22%20%13%5%
2539
11th to 20thDay
48%18%13%13%5%3
2540
21st to endDay
42%20%14%16%6%1
3018
February1st to 10thDay
43%15%15%18%8%1
1710
11th to 20thDay
37%14%17%19%10%2
1671
21st to endDay
44%18%15%13%9%1
1480
March1st to 10thDay
44%12%19%15%8%1
1818
11th to 20thDay
38%18%15%21%8%
1980
21st to endDay
46%17%16%16%6%
2272
April1st to 10thDay
47%13%13%17%9%2
2160
11th to 20thDay
43%9%15%18%11%3
2132
21st to endDay
35%10%17%23%12%2
2212
May1st to 10thDay
33%10%14%26%16%1
2510
11th to 20thDay
39%10%13%25%11%2
2480
21st to endDay
42%10%16%20%11%1
2724
June1st to 10thDay
38%9%13%28%11%1
2520
11th to 20thDay
30%7%12%31%16%3
2520
21st to endDay
20%6%11%28%26%9%
2520
July1st to 10thDay
14%5%10%21%27%24%
2451
11th to 20thDay
13%39%14%31%31%
2445
21st to endDay
10%2414%39%30%
2589
August1st to 10thDay
14%49%25%30%17%
2369
11th to 20thDay
13%47%22%33%21%
2285
21st to endDay
12%47%23%38%16%
2376
September1st to 10thDay
11%46%25%33%21%
2160
11th to 20thDay
23%7%10%22%26%12%
2160
21st to endDay
24%8%12%24%22%10%
1926
October1st to 10thDay
34%7%10%18%23%8%
1800
11th to 20thDay
29%10%14%22%20%5%
1800
21st to endDay
33%13%12%19%20%3
1900
November1st to 10thDay
39%12%14%20%14%1
1674
11th to 20thDay
38%19%19%15%9%1
1544
21st to endDay
37%16%15%15%15%2
1520
December1st to 10thDay
33%17%16%22%11%1
1520
11th to 20thDay
43%17%17%15%7%1
1928
21st to endDay
44%17%15%18%41
2794
January1st to 10thNight
41%22%19%12%5%
4406
11th to 20thNight
45%18%15%14%5%4
4420
21st to endNight
49%15%15%13%7%1
4641
February1st to 10thNight
40%17%18%16%9%1
2470
11th to 20thNight
38%14%19%19%8%3
2389
21st to endNight
41%19%15%16%8%2
1776
March1st to 10thNight
39%17%17%17%9%1
2138
11th to 20thNight
35%17%19%21%7%
1980
21st to endNight
41%18%19%17%5%
2084
April1st to 10thNight
41%14%19%17%9%1
1800
11th to 20thNight
37%14%17%19%11%2
1779
21st to endNight
36%13%18%22%10%1
1746
May1st to 10thNight
29%10%18%28%14%1
1449
11th to 20thNight
32%13%15%28%10%2
1416
21st to endNight
38%12%17%25%8%
1552
June1st to 10thNight
36%10%13%30%10%1
1440
11th to 20thNight
24%8%16%35%15%2
1440
21st to endNight
17%6%12%33%25%7%
1440
July1st to 10thNight
11%412%27%27%19%
1400
11th to 20thNight
9%37%21%32%28%
1392
21st to endNight
8%3417%43%25%
1488
August1st to 10thNight
11%39%29%35%12%
1542
11th to 20thNight
9%6%7%29%35%15%
1615
21st to endNight
9%47%27%40%14%
1980
September1st to 10thNight
9%37%27%36%17%
1800
11th to 20thNight
19%8%11%23%28%11%
1800
21st to endNight
22%7%11%23%24%13%
2029
October1st to 10thNight
28%8%11%21%25%7%
2160
11th to 20thNight
25%10%16%22%20%6%
2160
21st to endNight
32%14%15%16%19%4
2455
November1st to 10thNight
39%14%14%16%13%3
2405
11th to 20thNight
38%17%16%19%9%1
2633
21st to endNight
33%17%15%16%16%3
2660
December1st to 10thNight
36%16%15%20%11%2
2660
11th to 20thNight
41%19%15%16%9%
3276
21st to endNight
40%18%15%20%7%1
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
16%24%32%19%8%2
180
11th to 20thDay
19%13%30%24%11%2
180
21st to endDay
10%24%26%27%11%2
331
February1st to 10thDay
14%23%27%27%8%1
370
11th to 20thDay
12%28%30%20%8%1
366
21st to endDay
12%26%30%23%9%1
346
March1st to 10thDay
11%25%32%26%5%
420
11th to 20thDay
10%26%26%26%11%1
420
21st to endDay
13%28%27%24%7%
462
April1st to 10thDay
14%24%30%19%11%3
420
11th to 20thDay
16%24%29%19%8%4
412
21st to endDay
10%25%29%21%12%3
420
May1st to 10thDay
9%20%28%27%13%3
423
11th to 20thDay
18%15%28%19%16%5%
448
21st to endDay
12%13%24%27%18%5%
485
June1st to 10thDay
9%15%26%25%19%6%
450
11th to 20thDay
8%18%31%24%16%3
450
21st to endDay
47%26%32%23%8%
450
July1st to 10thDay
27%27%37%22%6%
446
11th to 20thDay
25%32%30%24%8%
444
21st to endDay
16%27%36%21%9%
487
August1st to 10thDay
1426%33%24%11%
447
11th to 20thDay
25%21%33%26%13%
437
21st to endDay
48%22%33%24%9%
495
September1st to 10thDay
35%24%34%27%7%
450
11th to 20thDay
410%22%34%24%6%
450
21st to endDay
8%14%21%33%21%3
450
October1st to 10thDay
9%16%24%26%22%4
450
11th to 20thDay
10%17%21%24%24%4
450
21st to endDay
10%17%31%20%17%5%
415
November1st to 10thDay
10%17%30%29%12%2
270
11th to 20thDay
8%24%26%25%15%3
192
21st to endDay
13%23%20%29%13%2
180
December1st to 10thDay
10%19%24%26%14%6%
180
11th to 20thDay
12%25%34%23%6%1
180
21st to endDay
14%20%30%25%9%2
198
January1st to 10thNight
9%20%31%26%12%2
760
11th to 20thNight
8%20%29%25%17%2
760
21st to endNight
11%15%25%33%14%2
836
February1st to 10thNight
7%18%31%32%11%1
760
11th to 20thNight
8%14%32%33%12%1
742
21st to endNight
8%18%32%34%8%1
592
March1st to 10thNight
9%20%27%33%10%2
720
11th to 20thNight
6%16%27%35%14%1
720
21st to endNight
7%18%31%30%13%1
792
April1st to 10thNight
11%14%27%31%15%1
720
11th to 20thNight
9%13%31%28%16%3
711
21st to endNight
10%12%27%35%15%1
666
May1st to 10thNight
9%8%23%39%20%1
369
11th to 20thNight
8%7%19%43%22%1
354
21st to endNight
10%7%22%34%24%2
389
June1st to 10thNight
9%7%21%42%20%1
360
11th to 20thNight
7%6%22%45%20%1
360
21st to endNight
4114%58%23%
360
July1st to 10thNight
219%59%28%1
350
11th to 20thNight
212%63%22%1
348
21st to endNight
110%58%30%1
394
August1st to 10thNight
316%49%38%4
476
11th to 20thNight
116%42%43%6%
547
21st to endNight
1217%46%31%2
792
September1st to 10thNight
2216%46%32%3
720
11th to 20thNight
3314%41%33%6%
720
21st to endNight
8%5%17%38%26%5%
720
October1st to 10thNight
8%5%23%37%24%3
720
11th to 20thNight
7%10%21%34%24%4
720
21st to endNight
9%13%25%32%16%6%
792
November1st to 10thNight
9%13%30%33%13%2
740
11th to 20thNight
9%19%28%27%15%2
760
21st to endNight
7%17%24%33%15%3
760
December1st to 10thNight
9%14%26%33%17%2
760
11th to 20thNight
8%19%30%30%13%1
760
21st to endNight
8%24%32%25%10%
836
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