Lynnwood
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lynnwood clear sky chart from 2005-11-06 to 2024-01-11.

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
41%
22495
9%
74593
9%
22442
42%
22442
14%
56356

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
24%
850
6%
2836
6%
846
25%
846
6%
2427
January11th to 20thNight
32%
725
7%
2535
8%
725
32%
725
8%
2078
January21st to endNight
32%
792
7%
2731
8%
792
32%
792
9%
2188
February1st to 10thNight
28%
720
7%
2340
6%
720
30%
720
9%
1932
February11th to 20thNight
31%
701
7%
2274
7%
700
33%
700
10%
1848
February21st to endNight
32%
592
9%
1866
8%
592
35%
592
11%
1489
March1st to 10thNight
35%
720
8%
2118
8%
720
36%
720
13%
1677
March11th to 20thNight
33%
720
10%
1980
7%
720
35%
720
12%
1604
March21st to endNight
29%
792
5%
2106
2%
792
30%
792
9%
1786
April1st to 10thNight
35%
720
6%
1800
3%
720
36%
720
12%
1522
April11th to 20thNight
37%
682
10%
1750
6%
682
39%
682
16%
1404
April21st to endNight
37%
496
7%
1576
6%
496
38%
496
11%
1250
May1st to 10thNight
48%
360
11%
1440
15%
360
50%
360
15%
976
May11th to 20thNight
51%
354
9%
1416
15%
354
51%
354
14%
968
May21st to endNight
45%
388
5%
1552
9%
388
46%
388
11%
1146
June1st to 10thNight
46%
360
4%
1374
5%
360
47%
360
13%
978
June11th to 20thNight
39%
360
3%
1260
4%
360
39%
360
10%
996
June21st to endNight
56%
360
9%
1260
8%
360
58%
360
23%
795
July1st to 10thNight
64%
350
10%
1225
14%
350
64%
350
26%
725
July11th to 20thNight
68%
348
16%
1311
24%
348
70%
348
32%
703
July21st to endNight
74%
394
20%
1488
32%
372
77%
372
38%
689
August1st to 10thNight
76%
388
19%
1454
27%
386
77%
386
34%
742
August11th to 20thNight
77%
534
24%
1602
23%
534
78%
534
41%
868
August21st to endNight
63%
697
20%
1885
16%
697
64%
697
33%
1178
September1st to 10thNight
67%
720
19%
1800
12%
720
68%
720
37%
1136
September11th to 20thNight
56%
720
18%
1800
12%
720
56%
720
27%
1273
September21st to endNight
52%
720
17%
2054
14%
720
54%
720
23%
1445
October1st to 10thNight
50%
720
10%
2160
10%
720
51%
720
20%
1542
October11th to 20thNight
42%
720
11%
2160
11%
720
43%
720
17%
1587
October21st to endNight
37%
792
11%
2488
10%
792
39%
792
14%
1903
November1st to 10thNight
30%
740
6%
2554
7%
740
31%
740
9%
2081
November11th to 20thNight
29%
760
8%
2660
8%
760
30%
760
9%
2127
November21st to endNight
30%
760
6%
2660
5%
760
32%
760
9%
2144
December1st to 10thNight
35%
760
9%
2660
10%
760
36%
760
10%
2096
December11th to 20thNight
23%
759
4%
3254
4%
759
23%
759
5%
2692
December21st to endNight
20%
921
3%
5164
4%
897
23%
897
3%
4361

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
20%9%47%6%35%5%5%7%31%
74899
Night
23%10%46%6%3445%6%29%
74808
TransparencyDay
54%8%14%16%7%1
74592
Night
56%8%13%15%6%1
74633
SeeingDay
24%9%19%26%18%5%
13977
Night
29%8%14%25%20%4
22505

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 10thDay
36%12%49%7%3433316%
1329
11th to 20thDay
27%11%6%9%7%35%6%5%6%16%
1433
21st to endDay
29%13%49%6%46%45%6%15%
1624
February1st to 10thDay
29%13%49%7%35%45%7%14%
1620
11th to 20thDay
23%16%5%9%7%45%445%19%
1575
21st to endDay
24%14%5%7%6%35%45%5%21%
1389
March1st to 10thDay
24%13%5%8%7%45%5%5%7%18%
1840
11th to 20thDay
25%12%5%7%7%45%45%5%21%
1980
21st to endDay
24%11%5%10%6%46%5%5%6%17%
2250
April1st to 10thDay
23%13%47%6%45%5%7%7%19%
2160
11th to 20thDay
22%10%47%7%46%6%5%7%24%
2157
21st to endDay
18%9%48%7%46%5%6%7%25%
2384
May1st to 10thDay
15%8%37%6%45%5%6%8%32%
2520
11th to 20thDay
16%8%36%6%46%6%5%9%31%
2477
21st to endDay
22%9%38%7%34447%28%
2723
June1st to 10thDay
21%8%36%6%35%6%5%8%30%
2582
11th to 20thDay
21%8%48%7%36%5%5%7%25%
2700
21st to endDay
11%7%36%5%35%5%6%8%41%
2700
July1st to 10thDay
10%5%3443445%7%50%
2700
11th to 20thDay
9%5%2443345%7%53%
2604
21st to endDay
8%323422346%63%
2741
August1st to 10thDay
8%5%2432345%7%56%
2473
11th to 20thDay
8%425%32336%8%57%
2298
21st to endDay
11%6%36%5%35%45%8%45%
2471
September1st to 10thDay
11%6%25%43445%7%50%
2160
11th to 20thDay
14%7%36%6%44448%39%
2160
21st to endDay
18%7%36%6%3445%6%37%
1904
October1st to 10thDay
18%10%46%6%345%6%7%30%
1800
11th to 20thDay
24%11%38%6%25%45%7%26%
1800
21st to endDay
27%11%47%6%3445%7%21%
1868
November1st to 10thDay
32%13%47%5%445%45%17%
1523
11th to 20thDay
32%12%46%5%24445%22%
1520
21st to endDay
33%11%36%5%345%5%6%18%
1520
December1st to 10thDay
25%13%6%7%6%4445%422%
1520
11th to 20thDay
30%14%5%9%6%46%44414%
1925
21st to endDay
25%13%6%11%8%45%6%5%413%
2469
January1st to 10thNight
36%12%47%5%4444416%
2836
11th to 20thNight
30%11%47%6%35%45%5%19%
2535
21st to endNight
27%11%5%7%6%35%45%6%19%
2731
February1st to 10thNight
30%12%47%7%35%45%5%19%
2340
11th to 20thNight
25%14%5%7%6%25%445%22%
2272
21st to endNight
26%13%46%5%35%5%5%5%23%
1866
March1st to 10thNight
24%11%45%6%36%6%6%7%23%
2118
11th to 20thNight
25%11%46%5%35%45%6%25%
1979
21st to endNight
24%12%48%7%45%6%5%6%19%
2106
April1st to 10thNight
23%10%47%6%46%7%6%6%20%
1800
11th to 20thNight
20%9%47%6%5%5%6%5%5%29%
1750
21st to endNight
23%11%37%6%45%5%5%6%26%
1576
May1st to 10thNight
17%8%47%5%3445%5%38%
1440
11th to 20thNight
18%7%27%6%35%5%5%7%35%
1416
21st to endNight
21%7%47%6%35%5%5%6%30%
1552
June1st to 10thNight
21%7%45%5%36%5%5%7%31%
1374
11th to 20thNight
23%10%6%8%6%3445%5%25%
1260
21st to endNight
12%5%35%5%4446%7%43%
1260
July1st to 10thNight
11%5%35%5%2335%6%52%
1260
11th to 20thNight
8%5%23333448%57%
1354
21st to endNight
8%32332343464%
1576
August1st to 10thNight
9%42432335%7%59%
1462
11th to 20thNight
6%324323347%62%
1602
21st to endNight
12%5%3443445%6%51%
1885
September1st to 10thNight
10%5%2443345%5%55%
1800
11th to 20thNight
16%7%36%5%44445%42%
1800
21st to endNight
17%7%36%5%3445%6%39%
2054
October1st to 10thNight
17%8%37%6%45%446%36%
2160
11th to 20thNight
24%8%35%5%245%46%34%
2160
21st to endNight
25%9%36%5%2445%7%29%
2488
November1st to 10thNight
32%10%36%5%4444423%
2554
11th to 20thNight
30%12%37%5%35%44422%
2660
21st to endNight
30%10%47%6%45%5%46%20%
2660
December1st to 10thNight
27%12%5%7%6%3345%5%24%
2660
11th to 20thNight
27%14%6%8%7%45%44417%
3280
21st to endNight
27%15%5%10%7%45%445%14%
5182

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
74%5%6%10%41
1329
11th to 20thDay
67%9%11%8%5%1
1433
21st to endDay
68%7%12%10%3
1624
February1st to 10thDay
70%8%9%8%41
1620
11th to 20thDay
68%7%9%9%7%
1584
21st to endDay
67%8%10%10%5%
1389
March1st to 10thDay
66%8%12%11%4
1840
11th to 20thDay
67%8%10%12%31
1980
21st to endDay
70%9%11%10%1
2250
April1st to 10thDay
65%10%15%10%1
2160
11th to 20thDay
62%8%11%12%6%1
2157
21st to endDay
61%10%12%12%5%1
2384
May1st to 10thDay
52%9%16%16%6%
2520
11th to 20thDay
50%13%17%15%5%
2480
21st to endDay
58%9%16%14%2
2724
June1st to 10thDay
56%9%18%13%5%1
2582
11th to 20thDay
60%11%15%12%3
2700
21st to endDay
44%9%20%19%7%1
2700
July1st to 10thDay
35%10%14%26%13%2
2626
11th to 20thDay
32%8%15%30%14%1
2524
21st to endDay
24%6%14%37%17%2
2589
August1st to 10thDay
30%9%17%29%14%2
2456
11th to 20thDay
26%8%21%29%12%3
2298
21st to endDay
38%8%15%28%9%1
2471
September1st to 10thDay
36%7%15%26%12%4
2160
11th to 20thDay
45%7%14%18%15%2
2160
21st to endDay
48%8%16%17%9%2
1904
October1st to 10thDay
51%10%14%18%6%
1800
11th to 20thDay
58%8%14%15%5%1
1800
21st to endDay
62%9%10%12%7%
1868
November1st to 10thDay
68%8%12%9%3
1523
11th to 20thDay
66%8%9%9%6%2
1520
21st to endDay
66%8%8%10%7%1
1520
December1st to 10thDay
66%6%8%11%8%1
1520
11th to 20thDay
69%9%12%7%21
1928
21st to endDay
71%9%12%6%2
2469
January1st to 10thNight
72%7%8%8%31
2836
11th to 20thNight
67%8%10%10%5%1
2535
21st to endNight
65%7%11%12%41
2731
February1st to 10thNight
67%8%10%10%5%1
2340
11th to 20thNight
66%7%10%10%6%1
2274
21st to endNight
62%8%11%14%41
1866
March1st to 10thNight
61%7%13%14%5%
2118
11th to 20thNight
61%10%10%15%41
1980
21st to endNight
66%10%13%10%1
2106
April1st to 10thNight
62%12%12%12%2
1800
11th to 20thNight
57%9%13%13%7%1
1750
21st to endNight
59%11%11%12%6%1
1576
May1st to 10thNight
48%9%17%18%8%1
1440
11th to 20thNight
49%9%20%15%6%1
1416
21st to endNight
55%10%17%16%2
1552
June1st to 10thNight
53%8%17%16%5%
1374
11th to 20thNight
61%9%15%12%3
1260
21st to endNight
40%8%23%20%6%3
1260
July1st to 10thNight
35%8%15%26%12%4
1225
11th to 20thNight
29%7%16%31%15%1
1311
21st to endNight
22%7%13%34%20%4
1488
August1st to 10thNight
27%7%15%30%18%3
1454
11th to 20thNight
23%8%18%31%16%3
1602
21st to endNight
34%7%17%31%11%1
1885
September1st to 10thNight
31%8%15%28%13%4
1800
11th to 20thNight
45%6%12%20%14%4
1800
21st to endNight
46%8%12%22%11%1
2054
October1st to 10thNight
49%8%14%22%7%1
2160
11th to 20thNight
53%7%16%17%6%1
2160
21st to endNight
57%8%11%16%8%
2488
November1st to 10thNight
64%9%12%11%31
2554
11th to 20thNight
65%7%10%11%42
2660
21st to endNight
65%8%9%10%8%
2660
December1st to 10thNight
63%7%11%11%7%
2660
11th to 20thNight
69%9%13%6%3
3276
21st to endNight
70%11%9%7%2
5182

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
37%11%15%16%14%7%
180
11th to 20thDay
36%9%18%19%12%6%
160
21st to endDay
42%12%14%15%12%5%
216
February1st to 10thDay
45%10%17%17%9%2
340
11th to 20thDay
39%14%22%15%9%2
335
21st to endDay
31%16%20%21%11%2
306
March1st to 10thDay
32%15%24%16%12%2
420
11th to 20thDay
30%14%20%18%13%5%
420
21st to endDay
36%13%20%19%10%2
462
April1st to 10thDay
30%13%24%18%12%3
420
11th to 20thDay
27%15%26%17%9%7%
412
21st to endDay
23%13%25%25%12%2
420
May1st to 10thDay
17%11%21%33%16%3
423
11th to 20thDay
25%7%17%25%18%8%
448
21st to endDay
24%8%15%28%16%8%
485
June1st to 10thDay
24%6%23%27%16%4
512
11th to 20thDay
23%7%22%30%15%3
630
21st to endDay
14%420%34%23%5%
630
July1st to 10thDay
13%417%34%28%5%
621
11th to 20thDay
9%5%20%31%29%7%
523
21st to endDay
7%314%36%32%8%
487
August1st to 10thDay
12%312%33%28%13%
447
11th to 20thDay
8%212%35%32%11%
437
21st to endDay
14%6%17%34%20%9%
495
September1st to 10thDay
15%6%21%35%17%6%
450
11th to 20thDay
18%8%16%28%25%5%
450
21st to endDay
22%8%19%29%16%6%
450
October1st to 10thDay
24%9%19%21%20%8%
450
11th to 20thDay
30%8%16%22%18%6%
450
21st to endDay
32%11%18%20%14%5%
383
November1st to 10thDay
42%14%14%19%10%2
197
11th to 20thDay
39%11%13%14%13%9%
180
21st to endDay
32%13%18%17%9%11%
180
December1st to 10thDay
40%9%13%11%16%11%
180
11th to 20thDay
39%12%22%16%11%1
180
21st to endDay
36%10%19%21%12%3
198
January1st to 10thNight
43%11%14%16%14%3
850
11th to 20thNight
38%10%12%19%18%3
725
21st to endNight
36%9%13%24%16%3
792
February1st to 10thNight
37%10%15%25%10%2
720
11th to 20thNight
35%10%13%24%16%2
704
21st to endNight
32%10%17%26%13%2
592
March1st to 10thNight
32%10%16%24%15%2
720
11th to 20thNight
33%12%15%24%14%2
720
21st to endNight
31%11%20%26%11%2
792
April1st to 10thNight
31%8%17%26%16%2
720
11th to 20thNight
26%9%17%28%17%3
682
21st to endNight
28%7%18%30%14%3
496
May1st to 10thNight
21%9%13%35%21%2
360
11th to 20thNight
21%5%13%29%28%4
354
21st to endNight
24%5%13%26%26%6%
389
June1st to 10thNight
23%6%18%31%19%4
360
11th to 20thNight
28%8%15%28%19%2
360
21st to endNight
13%416%34%28%5%
360
July1st to 10thNight
14%5%9%32%36%5%
350
11th to 20thNight
10%212%35%37%4
348
21st to endNight
7%48%32%43%5%
394
August1st to 10thNight
12%1430%45%9%
388
11th to 20thNight
9%16%25%46%12%
534
21st to endNight
15%310%31%34%7%
697
September1st to 10thNight
13%39%35%34%5%
720
11th to 20thNight
20%48%23%35%10%
720
21st to endNight
21%7%11%28%26%6%
720
October1st to 10thNight
22%6%11%29%26%7%
720
11th to 20thNight
29%6%16%23%21%5%
720
21st to endNight
32%9%16%24%16%4
792
November1st to 10thNight
38%10%15%24%12%1
740
11th to 20thNight
36%10%17%19%14%3
760
21st to endNight
38%8%15%20%14%5%
760
December1st to 10thNight
33%9%12%26%17%3
760
11th to 20thNight
40%11%16%20%11%1
760
21st to endNight
43%11%16%19%10%1
926
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