Snoqualmie Point Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Snoqualmie Point Park clear sky chart from 2005-11-06 to 2024-01-16.

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%
22361
9%
74272
9%
22317
38%
22317
13%
57060

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
18%
760
6%
2646
5%
756
21%
756
6%
2262
January11th to 20thNight
28%
744
9%
2602
8%
744
31%
744
9%
2080
January21st to endNight
29%
792
9%
2740
8%
792
32%
792
11%
2156
February1st to 10thNight
21%
720
6%
2340
5%
720
24%
720
7%
1982
February11th to 20thNight
28%
700
7%
2274
6%
700
30%
700
9%
1864
February21st to endNight
23%
592
9%
1844
6%
592
28%
592
9%
1548
March1st to 10thNight
29%
720
8%
2138
7%
720
31%
720
12%
1721
March11th to 20thNight
28%
720
9%
1980
6%
720
30%
720
12%
1624
March21st to endNight
24%
792
4%
2089
2%
792
25%
792
8%
1830
April1st to 10thNight
27%
720
4%
1800
2%
720
28%
720
9%
1574
April11th to 20thNight
31%
711
9%
1779
4%
711
33%
711
14%
1448
April21st to endNight
30%
483
7%
1563
5%
483
31%
483
8%
1304
May1st to 10thNight
43%
360
9%
1440
12%
360
44%
360
12%
1052
May11th to 20thNight
45%
354
8%
1416
12%
354
47%
354
12%
1035
May21st to endNight
37%
388
4%
1552
6%
388
38%
388
8%
1227
June1st to 10thNight
41%
360
3%
1440
5%
360
41%
360
10%
1098
June11th to 20thNight
36%
360
2%
1279
3%
360
36%
360
9%
1044
June21st to endNight
57%
360
8%
1260
10%
360
58%
360
20%
833
July1st to 10thNight
61%
350
8%
1225
11%
350
61%
350
22%
780
July11th to 20thNight
63%
348
15%
1385
26%
348
63%
348
26%
759
July21st to endNight
73%
394
21%
1488
35%
372
75%
372
35%
719
August1st to 10thNight
72%
375
19%
1441
27%
373
73%
373
32%
742
August11th to 20thNight
73%
534
23%
1602
22%
534
73%
534
38%
900
August21st to endNight
63%
720
21%
1908
15%
720
63%
720
32%
1222
September1st to 10thNight
64%
720
19%
1800
12%
720
64%
720
36%
1160
September11th to 20thNight
53%
720
16%
1800
12%
720
53%
720
24%
1322
September21st to endNight
51%
720
15%
2045
14%
720
51%
720
21%
1458
October1st to 10thNight
48%
720
10%
2160
10%
720
49%
720
20%
1540
October11th to 20thNight
38%
720
13%
2160
12%
720
41%
720
15%
1638
October21st to endNight
33%
792
11%
2502
10%
792
36%
792
14%
1908
November1st to 10thNight
23%
740
6%
2522
5%
740
25%
740
8%
2086
November11th to 20thNight
23%
760
8%
2660
6%
760
26%
760
8%
2175
November21st to endNight
25%
760
6%
2660
5%
760
27%
760
8%
2162
December1st to 10thNight
29%
760
9%
2660
8%
760
31%
760
10%
2122
December11th to 20thNight
17%
760
7%
3229
4%
759
20%
759
6%
2661
December21st to endNight
15%
832
3%
4843
4%
817
18%
817
3%
4024

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
27%11%46%5%34445%28%
75297
Night
29%11%36%5%34345%27%
74517
TransparencyDay
59%6%11%15%7%1
74994
Night
60%6%11%14%7%1
74338
SeeingDay
30%9%21%25%12%2
13824
Night
34%7%16%26%16%2
22370

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
41%14%37%43332416%
1519
11th to 20thDay
33%10%47%5%34446%21%
1480
21st to endDay
35%14%45%424346%20%
1612
February1st to 10thDay
36%12%5%7%5%33445%16%
1620
11th to 20thDay
34%18%37%5%22345%18%
1575
21st to endDay
32%17%5%7%5%3323319%
1411
March1st to 10thDay
31%15%5%7%5%4443417%
1818
11th to 20thDay
35%15%5%6%5%2443417%
1980
21st to endDay
34%17%47%6%345%4411%
2266
April1st to 10thDay
30%17%5%7%7%3445%413%
2160
11th to 20thDay
28%14%5%7%6%35%45%419%
2132
21st to endDay
29%15%5%9%6%34445%17%
2393
May1st to 10thDay
26%13%36%6%44445%26%
2520
11th to 20thDay
26%10%46%5%35%46%7%23%
2477
21st to endDay
33%11%47%5%34445%20%
2723
June1st to 10thDay
31%10%37%5%3445%6%22%
2520
11th to 20thDay
32%12%48%6%35%45%5%16%
2675
21st to endDay
17%9%37%435%5%5%7%35%
2700
July1st to 10thDay
15%7%35%5%34445%45%
2700
11th to 20thDay
14%7%35%43445%6%45%
2525
21st to endDay
11%5%23323345%58%
2741
August1st to 10thDay
14%6%2443435%6%49%
2488
11th to 20thDay
11%5%25%323447%53%
2298
21st to endDay
16%8%35%4335%46%42%
2448
September1st to 10thDay
14%7%25%42345%6%48%
2160
11th to 20thDay
20%8%35%5%345%45%38%
2160
21st to endDay
23%9%36%434345%37%
1911
October1st to 10thDay
24%10%26%5%34445%32%
1800
11th to 20thDay
29%10%25%5%2335%6%28%
1800
21st to endDay
36%9%36%433345%25%
1854
November1st to 10thDay
41%11%36%4245%35%16%
1552
11th to 20thDay
39%12%46%5%2333320%
1520
21st to endDay
37%13%46%43332420%
1520
December1st to 10thDay
32%12%5%5%5%34345%23%
1520
11th to 20thDay
35%13%47%5%2335%319%
1925
21st to endDay
29%15%49%7%44445%16%
2794
January1st to 10thNight
44%12%25%5%2333415%
2646
11th to 20thNight
36%12%37%5%23345%21%
2602
21st to endNight
33%12%36%5%33346%22%
2740
February1st to 10thNight
35%15%47%6%24345%16%
2340
11th to 20thNight
34%14%36%43334421%
2272
21st to endNight
32%18%35%5%34345%18%
1844
March1st to 10thNight
31%13%35%5%34446%22%
2138
11th to 20thNight
32%11%47%5%34345%22%
1979
21st to endNight
33%15%48%6%3445%5%15%
2089
April1st to 10thNight
30%15%5%7%5%3446%6%16%
1800
11th to 20thNight
27%14%47%5%34345%24%
1779
21st to endNight
33%11%46%6%35%45%5%19%
1563
May1st to 10thNight
27%11%36%5%24445%30%
1440
11th to 20thNight
24%11%36%5%245%5%7%28%
1416
21st to endNight
29%10%38%5%24446%25%
1552
June1st to 10thNight
28%9%47%7%4433427%
1440
11th to 20thNight
30%11%5%7%6%34445%21%
1279
21st to endNight
17%7%26%5%43337%42%
1260
July1st to 10thNight
16%7%25%434346%47%
1260
11th to 20thNight
11%7%25%423335%54%
1432
21st to endNight
10%423312345%62%
1576
August1st to 10thNight
12%5%2331235%8%56%
1449
11th to 20thNight
9%5%23323336%60%
1602
21st to endNight
16%7%25%313346%50%
1908
September1st to 10thNight
14%5%25%423345%52%
1800
11th to 20thNight
21%8%36%42444440%
1800
21st to endNight
22%8%26%5%33345%39%
2045
October1st to 10thNight
23%9%35%5%34346%35%
2160
11th to 20thNight
29%9%35%5%3444430%
2160
21st to endNight
33%10%35%423345%27%
2502
November1st to 10thNight
38%12%36%5%3444418%
2522
11th to 20thNight
39%10%45%5%3323321%
2660
21st to endNight
37%12%46%43333421%
2660
December1st to 10thNight
32%11%46%5%34435%23%
2660
11th to 20thNight
34%16%47%5%2433418%
3280
21st to endNight
30%16%48%7%35%5%4414%
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
73%7%5%9%5%1
1519
11th to 20thDay
65%6%11%8%7%3
1480
21st to endDay
67%49%11%7%1
1612
February1st to 10thDay
73%5%10%8%31
1620
11th to 20thDay
72%5%7%9%6%1
1584
21st to endDay
72%5%8%10%5%
1411
March1st to 10thDay
70%7%9%11%3
1818
11th to 20thDay
72%6%8%10%31
1980
21st to endDay
77%7%9%7%1
2266
April1st to 10thDay
74%7%12%8%1
2160
11th to 20thDay
68%6%9%11%5%1
2132
21st to endDay
73%5%9%9%41
2393
May1st to 10thDay
61%6%15%14%4
2520
11th to 20thDay
60%8%16%12%4
2480
21st to endDay
67%8%12%12%
2724
June1st to 10thDay
64%7%15%10%4
2520
11th to 20thDay
70%7%12%9%2
2675
21st to endDay
49%7%17%17%8%2
2700
July1st to 10thDay
43%8%13%23%12%2
2626
11th to 20thDay
39%7%11%27%15%1
2449
21st to endDay
27%5%13%34%18%4
2589
August1st to 10thDay
36%6%15%26%14%2
2471
11th to 20thDay
30%6%19%28%15%2
2298
21st to endDay
43%6%13%28%9%1
2448
September1st to 10thDay
37%6%15%24%13%5%
2160
11th to 20thDay
49%6%11%16%15%3
2160
21st to endDay
50%6%14%16%11%3
1911
October1st to 10thDay
54%7%10%20%8%1
1800
11th to 20thDay
56%6%12%17%7%1
1800
21st to endDay
63%5%9%13%10%
1854
November1st to 10thDay
72%5%9%10%4
1552
11th to 20thDay
71%5%7%8%6%2
1520
21st to endDay
71%449%9%3
1520
December1st to 10thDay
65%6%9%11%8%1
1520
11th to 20thDay
70%5%10%11%41
1928
21st to endDay
71%6%10%9%3
2794
January1st to 10thNight
74%5%7%8%42
2646
11th to 20thNight
66%6%9%9%7%3
2602
21st to endNight
65%49%10%9%2
2740
February1st to 10thNight
73%5%8%9%41
2340
11th to 20thNight
68%6%9%8%6%2
2274
21st to endNight
70%6%8%11%5%
1844
March1st to 10thNight
64%6%12%13%4
2138
11th to 20thNight
66%6%10%13%41
1980
21st to endNight
72%8%11%7%1
2089
April1st to 10thNight
69%10%11%9%1
1800
11th to 20thNight
63%7%11%13%6%1
1779
21st to endNight
69%7%8%10%6%1
1563
May1st to 10thNight
56%8%15%13%7%1
1440
11th to 20thNight
56%8%17%12%5%1
1416
21st to endNight
62%10%15%11%1
1552
June1st to 10thNight
62%6%15%12%5%
1440
11th to 20thNight
66%8%15%8%3
1279
21st to endNight
44%8%20%18%7%2
1260
July1st to 10thNight
40%9%15%20%12%3
1225
11th to 20thNight
36%414%30%15%1
1385
21st to endNight
25%6%12%33%20%5%
1488
August1st to 10thNight
29%6%14%30%18%3
1441
11th to 20thNight
28%7%17%30%15%4
1602
21st to endNight
37%6%15%29%12%1
1908
September1st to 10thNight
35%6%15%24%15%4
1800
11th to 20thNight
49%6%8%18%13%5%
1800
21st to endNight
49%7%12%17%12%4
2045
October1st to 10thNight
51%5%13%20%9%1
2160
11th to 20thNight
58%6%8%17%9%1
2160
21st to endNight
60%5%10%14%11%1
2502
November1st to 10thNight
70%5%10%10%4
2522
11th to 20thNight
70%5%8%9%5%3
2660
21st to endNight
69%5%6%8%10%1
2660
December1st to 10thNight
66%5%8%11%8%2
2660
11th to 20thNight
70%6%10%9%5%
3276
21st to endNight
73%7%10%7%3
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
44%9%19%15%8%4
180
11th to 20thDay
35%16%16%19%11%2
170
21st to endDay
47%9%17%18%8%1
204
February1st to 10thDay
46%10%19%16%8%
340
11th to 20thDay
48%9%22%15%6%
335
21st to endDay
40%15%19%22%4
316
March1st to 10thDay
39%15%20%19%6%1
420
11th to 20thDay
35%13%21%21%7%2
420
21st to endDay
44%11%23%14%8%
462
April1st to 10thDay
41%11%22%16%8%2
420
11th to 20thDay
33%18%25%14%9%2
412
21st to endDay
34%12%26%20%7%1
420
May1st to 10thDay
26%9%28%28%7%1
423
11th to 20thDay
33%9%22%23%10%3
448
21st to endDay
33%8%22%25%9%3
485
June1st to 10thDay
29%9%23%25%12%2
450
11th to 20thDay
32%13%25%20%9%1
605
21st to endDay
18%6%25%34%15%3
630
July1st to 10thDay
17%6%21%38%16%2
621
11th to 20thDay
15%7%23%36%17%3
448
21st to endDay
10%321%41%20%5%
487
August1st to 10thDay
15%5%17%37%20%6%
447
11th to 20thDay
9%319%40%23%7%
437
21st to endDay
18%8%22%35%13%5%
495
September1st to 10thDay
16%9%26%36%12%2
450
11th to 20thDay
23%6%19%32%18%2
450
21st to endDay
25%7%22%26%17%3
450
October1st to 10thDay
28%9%22%20%20%2
450
11th to 20thDay
35%8%18%22%13%4
450
21st to endDay
38%11%19%20%9%3
369
November1st to 10thDay
42%12%17%21%8%
212
11th to 20thDay
44%12%11%15%15%3
180
21st to endDay
43%6%17%18%11%6%
180
December1st to 10thDay
47%9%14%13%12%5%
180
11th to 20thDay
43%11%22%18%7%
180
21st to endDay
40%10%20%20%10%1
198
January1st to 10thNight
51%9%17%16%7%
760
11th to 20thNight
42%10%15%25%8%1
744
21st to endNight
40%8%16%27%9%
792
February1st to 10thNight
43%7%21%23%6%
720
11th to 20thNight
40%8%16%28%8%
704
21st to endNight
42%8%21%21%6%1
592
March1st to 10thNight
38%9%18%22%12%1
720
11th to 20thNight
37%8%21%24%9%1
720
21st to endNight
41%9%18%24%7%1
792
April1st to 10thNight
36%8%18%25%10%2
720
11th to 20thNight
32%9%19%27%11%2
711
21st to endNight
36%7%17%28%11%
483
May1st to 10thNight
29%6%13%33%17%1
360
11th to 20thNight
30%5%12%29%21%3
354
21st to endNight
32%415%22%24%3
389
June1st to 10thNight
32%411%30%21%2
360
11th to 20thNight
36%6%13%27%18%1
360
21st to endNight
19%413%33%29%3
360
July1st to 10thNight
17%411%30%36%4
350
11th to 20thNight
16%39%33%35%4
348
21st to endNight
11%47%29%44%5%
394
August1st to 10thNight
14%27%25%45%7%
375
11th to 20thNight
11%27%26%42%12%
534
21st to endNight
19%48%30%36%4
720
September1st to 10thNight
17%210%39%28%4
720
11th to 20thNight
23%5%11%25%31%5%
720
21st to endNight
26%5%12%31%24%2
720
October1st to 10thNight
27%5%14%29%23%2
720
11th to 20thNight
33%6%16%24%18%3
720
21st to endNight
39%8%17%25%9%2
792
November1st to 10thNight
42%8%21%23%5%
740
11th to 20thNight
44%7%20%22%6%1
760
21st to endNight
42%9%18%23%9%
760
December1st to 10thNight
37%8%19%25%10%1
760
11th to 20thNight
47%9%21%18%5%1
760
21st to endNight
51%10%17%18%3
836
Page generated at 2024-01-13 06:37:58. Version ac07

Copyright 2024 Attilla Danko


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