Lake Wenatchee
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Wenatchee clear sky chart from 2005-11-05 to 2017-08-12.

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
33%
14339
11%
46289
7%
14310
39%
14310
20%
30376

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
25%
720
8%
2506
5%
716
29%
716
8%
1981
January16th to endNight
32%
768
9%
2688
8%
768
34%
768
12%
1985
February1st to 15thNight
28%
696
6%
2306
4%
696
31%
696
13%
1732
February16th to endNight
33%
632
11%
1975
8%
632
38%
632
17%
1388
March1st to 15thNight
25%
720
5%
2121
3%
720
29%
720
14%
1592
March16th to endNight
23%
768
8%
2028
2%
768
26%
768
17%
1474
April1st to 15thNight
29%
719
8%
1799
3%
719
31%
719
20%
1304
April16th to endNight
29%
558
12%
1638
5%
558
36%
558
25%
1027
May1st to 15thNight
42%
360
13%
1439
16%
359
47%
359
26%
766
May16th to endNight
40%
374
7%
1496
9%
374
45%
374
18%
927
June1st to 15thNight
33%
360
6%
1440
4%
360
38%
360
22%
800
June16th to endNight
32%
360
10%
1284
5%
360
39%
360
27%
697
July1st to 15thNight
50%
340
13%
1306
10%
340
59%
340
45%
540
July16th to endNight
47%
376
20%
1416
19%
354
65%
354
50%
520
August1st to 15thNight
59%
376
26%
1424
22%
374
73%
374
55%
538
August16th to endNight
48%
624
24%
1674
12%
624
55%
624
49%
872
September1st to 15thNight
55%
660
26%
1650
12%
660
60%
660
55%
864
September16th to endNight
46%
656
24%
1789
15%
656
52%
656
37%
1022
October1st to 15thNight
40%
660
15%
1980
12%
660
45%
660
27%
1224
October16th to endNight
36%
704
11%
2219
8%
704
41%
704
19%
1510
November1st to 15thNight
23%
700
8%
2383
4%
700
29%
700
12%
1756
November16th to endNight
25%
720
7%
2520
3%
720
30%
720
12%
1855
December1st to 15thNight
25%
720
8%
2520
4%
720
30%
720
11%
1931
December16th to endNight
16%
768
7%
2688
2%
768
22%
768
10%
2071

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
7%7%36%6%45%5%6%8%36%
47695
Night
7%8%36%6%35%6%7%9%35%
46457
Cloud CoverDay
6%7%36%6%35%5%6%8%39%
47695
Night
6%7%36%6%35%5%6%8%38%
46461
TransparencyDay
42%5%19%19%9%2
47366
Night
42%7%21%19%7%1
46290
SeeingDay
15%21%34%20%7%1
5492
Night
14%11%34%26%11%1
14348

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
11%12%5%11%7%46%6%6%6%21%
1432
16th to endDay
8%14%5%8%7%45%46%9%25%
1536
February1st to 15thDay
8%14%6%8%7%46%6%7%9%20%
1555
16th to endDay
7%12%6%10%8%47%5%7%7%22%
1499
March1st to 15thDay
11%13%6%9%9%5%7%5%6%6%16%
1836
16th to endDay
8%14%5%9%9%6%7%7%6%7%17%
2196
April1st to 15thDay
8%10%49%10%47%6%7%7%22%
2149
16th to endDay
5%7%47%8%47%6%8%9%27%
2320
May1st to 15thDay
6%6%36%6%47%7%8%8%35%
2511
16th to endDay
9%6%47%7%5%7%5%7%9%28%
2615
June1st to 15thDay
9%5%36%6%446%7%10%34%
2520
16th to endDay
5%5%36%6%36%7%7%8%38%
2670
July1st to 15thDay
2313325%45%7%60%
2568
16th to endDay
321231335%6%67%
2657
August1st to 15thDay
11332345%9%63%
2442
16th to endDay
3215%5%3445%8%55%
2176
September1st to 15thDay
321342245%6%62%
1980
16th to endDay
6%5%246%45%46%8%44%
1840
October1st to 15thDay
10%5%27%6%35%5%7%8%36%
1650
16th to endDay
14%9%36%5%46%5%7%7%29%
1653
November1st to 15thDay
14%9%49%8%45%6%8%8%20%
1474
16th to endDay
11%14%7%8%7%46%6%6%7%19%
1440
December1st to 15thDay
9%10%5%8%7%6%5%6%6%9%24%
1440
16th to endDay
12%14%6%9%5%35%45%8%22%
1536
January1st to 15thNight
13%11%5%10%8%46%6%6%8%17%
2506
16th to endNight
8%12%5%6%8%46%6%7%9%22%
2688
February1st to 15thNight
9%11%5%9%8%346%7%9%23%
2294
16th to endNight
6%10%27%7%46%8%6%9%30%
1975
March1st to 15thNight
9%11%47%7%5%7%5%7%9%23%
2121
16th to endNight
5%10%48%7%47%8%8%8%25%
2024
April1st to 15thNight
5%7%5%7%8%37%6%7%10%29%
1799
16th to endNight
45%36%5%36%7%8%10%38%
1638
May1st to 15thNight
3426%5%36%6%7%10%42%
1439
16th to endNight
5%426%7%46%8%10%12%32%
1496
June1st to 15thNight
43247%5%7%5%8%9%40%
1440
16th to endNight
3325%5%46%8%7%9%45%
1284
July1st to 15thNight
122235%5%8%66%
1386
16th to endNight
2213348%72%
1512
August1st to 15thNight
121335%9%72%
1432
16th to endNight
221232345%8%62%
1674
September1st to 15thNight
221223335%7%66%
1650
16th to endNight
5%314425%5%7%9%50%
1789
October1st to 15thNight
8%5%35%5%35%5%7%8%41%
1980
16th to endNight
13%7%35%6%35%6%8%9%28%
2219
November1st to 15thNight
13%10%47%6%46%7%9%10%21%
2383
16th to endNight
11%12%5%10%7%35%6%6%8%22%
2520
December1st to 15thNight
8%13%5%7%8%46%6%6%8%22%
2520
16th to endNight
13%14%7%8%7%35%45%9%19%
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
10%12%5%9%8%47%5%7%7%21%
1432
16th to endDay
6%13%6%7%8%445%7%9%26%
1536
February1st to 15thDay
7%13%6%8%7%46%5%8%9%23%
1555
16th to endDay
5%12%5%8%9%5%5%7%6%7%25%
1499
March1st to 15thDay
9%13%6%9%8%48%6%6%7%19%
1836
16th to endDay
7%11%48%9%46%7%7%8%21%
2196
April1st to 15thDay
7%8%49%9%46%7%6%8%25%
2149
16th to endDay
46%37%8%47%6%7%9%33%
2320
May1st to 15thDay
6%435%6%37%5%7%8%40%
2511
16th to endDay
8%5%37%7%47%6%7%9%31%
2615
June1st to 15thDay
8%5%26%6%36%5%6%9%40%
2520
16th to endDay
5%5%26%6%35%5%6%8%44%
2670
July1st to 15thDay
1213324445%63%
2568
16th to endDay
2112222345%70%
2657
August1st to 15thDay
11232345%7%65%
2442
16th to endDay
22145%25%5%47%57%
2176
September1st to 15thDay
3312323346%65%
1980
16th to endDay
6%325%5%35%6%6%8%47%
1840
October1st to 15thDay
10%5%26%5%45%5%6%8%40%
1650
16th to endDay
12%8%37%5%46%5%6%7%32%
1653
November1st to 15thDay
12%9%37%8%46%5%8%8%24%
1474
16th to endDay
9%12%6%9%7%46%5%7%8%21%
1440
December1st to 15thDay
9%8%5%9%8%5%7%6%6%7%27%
1440
16th to endDay
10%15%5%7%6%445%5%8%25%
1536
January1st to 15thNight
12%11%49%8%47%6%7%8%20%
2506
16th to endNight
8%11%36%8%47%7%7%8%24%
2688
February1st to 15thNight
9%11%48%7%36%6%6%8%27%
2294
16th to endNight
5%9%36%6%46%8%6%9%32%
1975
March1st to 15thNight
8%10%48%7%37%7%7%7%26%
2121
16th to endNight
5%9%37%7%46%7%8%8%30%
2028
April1st to 15thNight
47%46%8%5%7%6%5%10%33%
1799
16th to endNight
45%15%5%35%7%7%9%43%
1638
May1st to 15thNight
3425%5%36%5%6%9%48%
1439
16th to endNight
4425%7%37%7%8%12%36%
1496
June1st to 15thNight
43145%46%47%10%44%
1440
16th to endNight
23146%45%6%6%7%51%
1284
July1st to 15thNight
11122345%8%68%
1386
16th to endNight
1113335%76%
1512
August1st to 15thNight
1122347%74%
1432
16th to endNight
121331335%8%63%
1674
September1st to 15thNight
2112214346%68%
1650
16th to endNight
42144235%7%9%54%
1789
October1st to 15thNight
7%5%24435%5%6%8%44%
1980
16th to endNight
10%7%25%7%45%5%7%10%32%
2219
November1st to 15thNight
11%10%37%6%46%6%7%8%27%
2383
16th to endNight
10%11%5%8%8%35%5%6%8%24%
2520
December1st to 15thNight
9%12%5%7%7%47%5%6%8%25%
2520
16th to endNight
11%15%6%9%6%35%45%7%23%
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
58%10%14%11%3
1432
16th to endDay
53%8%18%12%5%1
1536
February1st to 15thDay
56%9%18%12%2
1555
16th to endDay
56%6%19%13%4
1499
March1st to 15thDay
62%6%18%9%3
1836
16th to endDay
59%6%20%12%1
2196
April1st to 15thDay
55%5%22%13%2
2149
16th to endDay
46%8%23%17%3
2320
May1st to 15thDay
39%5%25%22%7%
2511
16th to endDay
47%6%26%17%2
2619
June1st to 15thDay
41%5%23%21%7%1
2520
16th to endDay
36%324%23%11%
2670
July1st to 15thDay
21%417%27%21%7%
2419
16th to endDay
16%312%29%28%9%
2490
August1st to 15thDay
17%316%33%22%6%
2425
16th to endDay
25%415%30%19%4
2176
September1st to 15thDay
21%215%30%23%6%
1980
16th to endDay
35%417%23%13%5%
1840
October1st to 15thDay
43%318%24%8%1
1650
16th to endDay
50%318%18%8%
1653
November1st to 15thDay
55%8%18%13%21
1474
16th to endDay
58%8%17%10%4
1440
December1st to 15thDay
54%10%17%13%3
1440
16th to endDay
57%7%19%10%4
1536
January1st to 15thNight
59%10%13%10%4
2506
16th to endNight
53%9%16%13%42
2688
February1st to 15thNight
52%11%20%11%3
2306
16th to endNight
46%9%22%17%3
1975
March1st to 15thNight
52%8%22%12%2
2121
16th to endNight
48%8%25%16%
2028
April1st to 15thNight
45%8%24%18%3
1799
16th to endNight
34%8%29%23%4
1638
May1st to 15thNight
31%5%27%26%7%1
1440
16th to endNight
37%11%29%18%2
1496
June1st to 15thNight
34%6%30%20%8%
1440
16th to endNight
30%6%25%26%10%1
1284
July1st to 15thNight
14%6%20%34%19%4
1306
16th to endNight
11%318%31%26%7%
1416
August1st to 15thNight
10%420%34%24%4
1424
16th to endNight
19%420%35%16%2
1674
September1st to 15thNight
16%320%30%23%4
1650
16th to endNight
26%7%21%27%13%5%
1789
October1st to 15thNight
37%5%22%23%11%
1980
16th to endNight
47%5%20%20%5%
2219
November1st to 15thNight
51%10%18%14%21
2383
16th to endNight
56%6%19%12%5%
2520
December1st to 15thNight
57%9%15%14%3
2520
16th to endNight
60%7%18%10%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
16%18%28%35%1
60
16th to endDay
26%434%18%12%3
64
February1st to 15thDay
23%17%34%19%5%
215
16th to endDay
21%18%35%15%8%1
225
March1st to 15thDay
28%26%32%12%
270
16th to endDay
26%33%26%10%3
288
April1st to 15thDay
22%25%32%14%12
269
16th to endDay
18%33%29%11%41
270
May1st to 15thDay
18%25%30%21%4
288
16th to endDay
13%19%32%22%9%2
330
June1st to 15thDay
14%23%35%19%6%
315
16th to endDay
10%27%36%18%6%
465
July1st to 15thDay
418%44%25%7%
353
16th to endDay
318%40%25%8%2
327
August1st to 15thDay
6%12%38%28%12%3
300
16th to endDay
7%16%35%29%8%2
268
September1st to 15thDay
9%23%33%23%7%1
255
16th to endDay
10%22%36%22%7%1
255
October1st to 15thDay
21%21%27%22%5%1
255
16th to endDay
25%12%30%21%9%
165
November1st to 15thDay
23%15%36%23%
71
16th to endDay
8%13%23%28%18%8%
60
December1st to 15thDay
18%11%43%18%8%
60
16th to endDay
12%137%32%15%
64
January1st to 15thNight
27%10%26%23%11%
720
16th to endNight
19%7%32%26%12%1
768
February1st to 15thNight
18%9%33%28%8%
704
16th to endNight
18%10%31%28%11%
632
March1st to 15thNight
17%13%36%23%8%
720
16th to endNight
14%14%43%20%5%
768
April1st to 15thNight
11%15%36%25%8%1
719
16th to endNight
9%18%37%22%9%1
558
May1st to 15thNight
7%15%33%29%13%1
360
16th to endNight
7%9%36%32%13%
375
June1st to 15thNight
7%16%40%26%9%
360
16th to endNight
5%16%41%25%10%
360
July1st to 15thNight
110%37%40%9%
340
16th to endNight
112%38%34%12%
376
August1st to 15thNight
18%30%36%21%1
376
16th to endNight
410%35%30%17%2
624
September1st to 15thNight
49%27%29%23%5%
660
16th to endNight
9%9%31%29%17%3
656
October1st to 15thNight
14%9%29%27%17%1
660
16th to endNight
20%9%28%26%12%1
704
November1st to 15thNight
23%10%38%24%4
700
16th to endNight
22%8%33%20%12%2
720
December1st to 15thNight
20%7%35%28%7%
720
16th to endNight
23%8%39%23%4
768
Page generated at 2017-08-13 11:16:23. Version ac04

Copyright 2017 A. Danko


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