Lynnwood
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lynnwood clear sky chart from 2005-11-05 to 2018-04-23.

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
36%
15405
9%
49397
8%
15376
38%
15376
12%
37513

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%
811
8%
2849
9%
807
31%
807
8%
2330
January16th to endNight
26%
832
7%
2883
7%
832
28%
832
8%
2326
February1st to 15thNight
25%
761
7%
2483
6%
760
27%
760
8%
2022
February16th to endNight
29%
684
9%
2180
8%
684
32%
684
10%
1728
March1st to 15thNight
25%
780
6%
2245
5%
780
26%
780
10%
1853
March16th to endNight
26%
832
6%
2236
3%
832
27%
832
8%
1889
April1st to 15thNight
31%
779
5%
1949
3%
779
31%
779
10%
1682
April16th to endNight
33%
569
7%
1685
5%
569
35%
569
11%
1346
May1st to 15thNight
40%
359
11%
1439
15%
359
44%
359
14%
952
May16th to endNight
38%
374
5%
1496
7%
374
39%
374
8%
1122
June1st to 15thNight
40%
360
3%
1335
3%
360
40%
360
12%
982
June16th to endNight
38%
360
6%
1260
5%
360
41%
360
12%
914
July1st to 15thNight
61%
340
12%
1193
14%
340
63%
340
28%
664
July16th to endNight
62%
376
17%
1416
23%
354
70%
354
29%
721
August1st to 15thNight
70%
440
18%
1513
22%
438
71%
438
33%
786
August16th to endNight
61%
642
20%
1788
15%
642
64%
642
33%
1065
September1st to 15thNight
65%
720
20%
1800
12%
720
66%
720
37%
1109
September16th to endNight
46%
716
18%
1970
12%
716
49%
716
20%
1407
October1st to 15thNight
42%
720
10%
2160
10%
720
43%
720
18%
1541
October16th to endNight
33%
768
9%
2379
8%
768
36%
768
12%
1854
November1st to 15thNight
27%
760
5%
2636
5%
760
28%
760
7%
2205
November16th to endNight
24%
780
5%
2730
4%
780
26%
780
7%
2235
December1st to 15thNight
31%
780
8%
2730
9%
780
32%
780
9%
2160
December16th to endNight
19%
862
5%
3042
4%
862
21%
862
5%
2620

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%36%5%3445%6%30%
50142
Night
23%9%36%5%34445%29%
49555
Cloud CoverDay
23%8%36%5%34445%30%
50142
Night
25%8%36%5%24445%29%
49558
TransparencyDay
56%7%13%15%6%
49803
Night
57%7%12%15%6%1
49398
SeeingDay
25%13%16%22%16%4
6605
Night
27%18%10%21%18%3
15410

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
33%11%46%6%2443319%
1417
16th to endDay
29%12%48%5%35%5%45%15%
1693
February1st to 15thDay
26%13%49%7%35%346%16%
1711
16th to endDay
24%12%5%6%6%34445%22%
1579
March1st to 15thDay
29%12%5%7%6%3444417%
2044
16th to endDay
26%11%5%10%7%35%445%15%
2340
April1st to 15thDay
26%11%37%6%35%5%6%6%17%
2329
16th to endDay
20%9%47%6%36%5%6%7%21%
2385
May1st to 15thDay
16%8%36%435%45%8%32%
2511
16th to endDay
20%8%37%6%345%5%7%27%
2615
June1st to 15thDay
20%7%37%6%25%5%5%7%29%
2622
16th to endDay
15%8%46%6%35%5%5%7%31%
2700
July1st to 15thDay
9%423323346%55%
2694
16th to endDay
9%42331235%6%56%
2657
August1st to 15thDay
8%42432335%7%54%
2436
16th to endDay
9%5%25%435%35%7%49%
2414
September1st to 15thDay
9%5%24423347%52%
2160
16th to endDay
16%7%36%7%3445%6%33%
1989
October1st to 15thDay
19%10%36%5%2445%7%29%
1800
16th to endDay
28%11%47%6%2445%6%18%
1845
November1st to 15thDay
36%10%45%5%2344416%
1550
16th to endDay
35%12%35%5%23445%15%
1560
December1st to 15thDay
23%13%6%8%5%25%46%419%
1560
16th to endDay
32%12%5%8%5%3444315%
1531
January1st to 15thNight
33%9%35%5%23345%21%
2849
16th to endNight
29%10%47%5%35%446%18%
2883
February1st to 15thNight
28%11%36%6%35%445%20%
2471
16th to endNight
25%12%46%5%24445%24%
2180
March1st to 15thNight
28%10%45%5%345%5%5%22%
2245
16th to endNight
25%11%47%6%35%5%5%6%18%
2232
April1st to 15thNight
21%10%47%6%46%6%5%5%20%
1949
16th to endNight
22%9%36%5%35%5%46%26%
1685
May1st to 15thNight
17%7%35%5%2345%5%38%
1439
16th to endNight
19%7%47%6%36%5%5%7%28%
1496
June1st to 15thNight
22%8%45%5%2445%7%28%
1335
16th to endNight
15%7%5%7%7%4446%5%31%
1260
July1st to 15thNight
7%5%23423447%54%
1263
16th to endNight
8%422323435%59%
1512
August1st to 15thNight
7%31322225%7%59%
1521
16th to endNight
7%424423346%55%
1788
September1st to 15thNight
7%42443235%457%
1800
16th to endNight
17%6%36%5%34446%37%
1970
October1st to 15thNight
17%8%36%5%34345%36%
2160
16th to endNight
26%9%36%5%24447%25%
2379
November1st to 15thNight
34%10%26%5%3344420%
2636
16th to endNight
30%10%47%5%34436%19%
2730
December1st to 15thNight
26%10%5%7%5%23445%23%
2730
16th to endNight
32%13%5%7%5%2433416%
3042

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
37%9%46%5%2333419%
1417
16th to endDay
33%10%5%7%5%34345%16%
1693
February1st to 15thDay
29%12%38%6%25%346%16%
1711
16th to endDay
27%13%46%5%3433422%
1579
March1st to 15thDay
32%12%46%6%3434417%
2044
16th to endDay
30%11%5%8%6%45%43415%
2340
April1st to 15thDay
28%10%37%6%45%45%6%16%
2329
16th to endDay
23%9%47%6%45%6%5%6%20%
2385
May1st to 15thDay
19%8%35%5%35%46%6%32%
2511
16th to endDay
23%9%37%5%3445%7%26%
2615
June1st to 15thDay
23%8%36%5%34446%29%
2622
16th to endDay
17%8%47%5%345%5%6%31%
2700
July1st to 15thDay
10%424324345%55%
2694
16th to endDay
11%423313246%56%
2657
August1st to 15thDay
9%414323447%54%
2436
16th to endDay
10%5%2443445%6%48%
2414
September1st to 15thDay
10%5%25%423346%52%
2160
16th to endDay
19%8%26%5%23347%34%
1989
October1st to 15thDay
21%10%26%425%45%7%28%
1800
16th to endDay
31%10%37%43445%5%19%
1845
November1st to 15thDay
40%10%35%42443416%
1550
16th to endDay
38%11%36%423335%17%
1560
December1st to 15thDay
28%11%5%7%5%3434420%
1560
16th to endDay
34%12%5%7%43433316%
1531
January1st to 15thNight
36%9%25%42344421%
2848
16th to endNight
32%10%37%5%24446%19%
2883
February1st to 15thNight
30%11%46%5%34445%20%
2471
16th to endNight
28%12%36%5%23445%24%
2180
March1st to 15thNight
30%10%45%425%5%45%21%
2245
16th to endNight
29%10%36%6%35%5%45%18%
2236
April1st to 15thNight
24%9%47%7%46%5%5%5%19%
1949
16th to endNight
24%9%36%6%345%5%5%25%
1685
May1st to 15thNight
18%7%36%424445%38%
1439
16th to endNight
21%7%36%5%45%45%6%27%
1496
June1st to 15thNight
23%8%46%5%2445%6%28%
1335
16th to endNight
16%8%47%6%435%5%5%32%
1260
July1st to 15thNight
7%5%14423446%55%
1263
16th to endNight
8%423312436%58%
1512
August1st to 15thNight
8%413313247%60%
1521
16th to endNight
8%414423345%55%
1788
September1st to 15thNight
8%42442334457%
1800
16th to endNight
18%7%25%5%24346%37%
1970
October1st to 15thNight
19%8%36%433346%36%
2160
16th to endNight
29%8%26%5%33347%25%
2379
November1st to 15thNight
37%8%35%424435%18%
2636
16th to endNight
33%10%46%5%34335%20%
2730
December1st to 15thNight
28%10%45%5%2344424%
2730
16th to endNight
36%12%47%42333416%
3042

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
70%5%8%10%5%
1417
16th to endDay
69%6%11%9%21
1693
February1st to 15thDay
69%7%9%8%41
1711
16th to endDay
66%6%9%12%5%
1579
March1st to 15thDay
71%6%10%9%1
2044
16th to endDay
73%7%8%9%
2340
April1st to 15thDay
69%9%11%8%1
2329
16th to endDay
64%8%12%10%2
2385
May1st to 15thDay
52%8%14%17%6%
2511
16th to endDay
58%9%16%12%2
2619
June1st to 15thDay
57%8%16%11%4
2622
16th to endDay
54%8%16%15%4
2700
July1st to 15thDay
33%7%13%27%15%2
2535
16th to endDay
30%6%14%31%15%1
2490
August1st to 15thDay
30%8%18%28%11%2
2419
16th to endDay
35%7%16%29%9%2
2414
September1st to 15thDay
33%5%14%24%19%2
2160
16th to endDay
49%7%16%15%8%1
1989
October1st to 15thDay
52%8%14%16%6%
1800
16th to endDay
65%7%12%10%4
1845
November1st to 15thDay
72%7%8%6%21
1550
16th to endDay
70%6%8%8%5%
1560
December1st to 15thDay
67%5%9%11%5%
1560
16th to endDay
74%6%7%7%4
1531
January1st to 15thNight
66%7%8%11%4
2849
16th to endNight
65%6%10%10%5%1
2883
February1st to 15thNight
65%7%10%9%41
2483
16th to endNight
63%5%11%14%5%
2180
March1st to 15thNight
65%7%11%13%2
2245
16th to endNight
66%9%11%11%
2236
April1st to 15thNight
65%10%10%12%1
1949
16th to endNight
59%9%13%13%3
1685
May1st to 15thNight
47%7%16%18%9%1
1440
16th to endNight
56%10%16%12%3
1496
June1st to 15thNight
57%6%17%13%4
1335
16th to endNight
52%8%16%17%31
1260
July1st to 15thNight
31%7%14%30%13%4
1193
16th to endNight
26%7%13%30%18%3
1416
August1st to 15thNight
25%7%17%30%15%3
1513
16th to endNight
30%6%19%30%10%2
1788
September1st to 15thNight
29%6%13%26%19%4
1800
16th to endNight
47%7%11%21%10%1
1970
October1st to 15thNight
50%6%14%19%7%
2160
16th to endNight
60%6%13%13%5%
2379
November1st to 15thNight
67%8%10%8%12
2636
16th to endNight
67%6%9%8%7%
2730
December1st to 15thNight
63%6%12%11%5%
2730
16th to endNight
74%6%8%7%3
3042

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
34%5%18%25%15%
90
16th to endDay
55%15%12%6%8%2
125
February1st to 15thDay
43%16%12%15%9%2
281
16th to endDay
34%18%20%15%9%1
260
March1st to 15thDay
40%21%18%13%6%1
330
16th to endDay
38%20%17%11%10%2
352
April1st to 15thDay
32%17%23%13%9%2
329
16th to endDay
27%18%22%19%10%2
288
May1st to 15thDay
23%17%17%26%13%1
288
16th to endDay
22%16%13%22%15%9%
330
June1st to 15thDay
20%14%18%26%17%3
417
16th to endDay
17%16%17%28%16%2
495
July1st to 15thDay
10%10%14%33%26%4
469
16th to endDay
9%11%12%30%28%7%
327
August1st to 15thDay
10%6%11%30%28%11%
315
16th to endDay
11%7%12%34%25%7%
332
September1st to 15thDay
15%7%19%28%23%5%
315
16th to endDay
20%12%16%27%17%4
315
October1st to 15thDay
29%11%20%18%17%2
315
16th to endDay
35%11%16%18%15%3
261
November1st to 15thDay
55%14%13%10%32
95
16th to endDay
46%7%14%15%312%
90
December1st to 15thDay
38%5%14%13%17%10%
90
16th to endDay
41%11%15%19%7%4
96
January1st to 15thNight
34%20%8%15%18%3
811
16th to endNight
34%19%10%16%14%2
832
February1st to 15thNight
33%21%10%20%11%2
764
16th to endNight
30%19%11%21%13%2
684
March1st to 15thNight
33%22%14%15%12%1
780
16th to endNight
29%22%16%20%9%1
832
April1st to 15thNight
27%21%12%22%13%1
779
16th to endNight
25%20%13%24%15%1
569
May1st to 15thNight
18%22%10%24%22%1
360
16th to endNight
22%20%9%19%22%5%
375
June1st to 15thNight
22%19%10%23%21%2
360
16th to endNight
19%19%12%28%17%3
360
July1st to 15thNight
10%13%8%29%32%5%
340
16th to endNight
7%18%6%25%37%5%
376
August1st to 15thNight
11%9%223%41%11%
440
16th to endNight
11%10%8%25%37%7%
642
September1st to 15thNight
10%10%6%27%33%10%
720
16th to endNight
22%12%9%24%26%4
716
October1st to 15thNight
22%13%11%28%20%3
720
16th to endNight
33%13%12%19%16%4
768
November1st to 15thNight
36%17%13%22%9%1
760
16th to endNight
35%20%13%15%11%3
780
December1st to 15thNight
32%21%7%20%14%2
780
16th to endNight
38%20%13%16%9%1
862
Page generated at 2018-04-24 07:03:02. Version ac04

Copyright 2018 A. Danko


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