Whiskeytown National Recreation Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Whiskeytown National Recreation Area clear sky chart from 2005-11-05 to 2017-09-22.

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
57%
15098
27%
46940
21%
15056
65%
15056
40%
24895

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
51%
720
20%
2464
16%
716
60%
716
28%
1427
January16th to endNight
47%
768
25%
2496
20%
768
55%
768
27%
1516
February1st to 15thNight
45%
700
22%
2287
19%
698
53%
698
25%
1434
February16th to endNight
46%
632
22%
1951
17%
632
54%
632
27%
1202
March1st to 15thNight
44%
720
16%
2012
11%
720
51%
720
25%
1354
March16th to endNight
41%
768
20%
2092
11%
768
49%
768
31%
1318
April1st to 15thNight
39%
719
21%
1799
7%
719
48%
719
31%
1167
April16th to endNight
50%
702
27%
1782
12%
702
56%
702
48%
976
May1st to 15thNight
48%
491
27%
1571
15%
491
60%
491
49%
726
May16th to endNight
54%
374
24%
1496
22%
374
64%
374
37%
684
June1st to 15thNight
53%
360
23%
1440
20%
360
68%
360
38%
649
June16th to endNight
63%
360
33%
1440
37%
360
75%
360
62%
494
July1st to 15thNight
84%
340
32%
1360
41%
340
90%
340
72%
429
July16th to endNight
87%
508
39%
1537
38%
475
90%
475
78%
560
August1st to 15thNight
87%
538
39%
1611
31%
535
91%
535
77%
626
August16th to endNight
87%
723
45%
1869
29%
723
90%
723
85%
788
September1st to 15thNight
82%
720
44%
1800
26%
720
87%
720
85%
783
September16th to endNight
74%
683
40%
1878
32%
683
81%
683
65%
864
October1st to 15thNight
61%
660
32%
1980
25%
660
73%
660
50%
955
October16th to endNight
62%
704
33%
2112
30%
704
70%
704
44%
1098
November1st to 15thNight
59%
700
26%
2235
22%
700
67%
700
37%
1214
November16th to endNight
55%
720
20%
2520
19%
720
60%
720
30%
1414
December1st to 15thNight
45%
720
21%
2520
15%
720
55%
720
25%
1524
December16th to endNight
39%
768
21%
2688
15%
768
48%
768
21%
1693

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
10%312212346%61%
47947
Night
12%312312346%58%
47125
TransparencyDay
24%28%20%24%19%
47630
Night
27%39%21%23%15%
46942
SeeingDay
12%9%22%30%18%6%
5885
Night
13%5%18%34%25%3
15104

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 15thDay
19%31322445%8%44%
1471
16th to endDay
20%5%14322325%46%
1728
February1st to 15thDay
21%41242445%6%42%
1576
16th to endDay
18%5%145%2335%8%42%
1523
March1st to 15thDay
23%6%2432335%8%36%
1947
16th to endDay
21%423313249%42%
2131
April1st to 15thDay
18%5%2442346%7%41%
2149
16th to endDay
6%314413445%60%
2175
May1st to 15thDay
5%312213347%64%
2379
16th to endDay
8%31331335%7%57%
2615
June1st to 15thDay
7%312223346%62%
2520
16th to endDay
41111123478%
2520
July1st to 15thDay
111225%82%
2520
16th to endDay
111112386%
2522
August1st to 15thDay
111113384%
2340
16th to endDay
11111287%
2333
September1st to 15thDay
111125%84%
2160
16th to endDay
311112235%76%
1891
October1st to 15thDay
8%212212336%66%
1650
16th to endDay
14%313112346%58%
1760
November1st to 15thDay
10%413324348%51%
1621
16th to endDay
16%423324346%48%
1440
December1st to 15thDay
23%423223347%42%
1440
16th to endDay
27%413323246%40%
1536
January1st to 15thNight
17%41332345%6%46%
2464
16th to endNight
22%413312335%46%
2496
February1st to 15thNight
22%5%13424346%41%
2276
16th to endNight
20%42342345%7%42%
1951
March1st to 15thNight
22%6%2332435%8%36%
2012
16th to endNight
19%414423447%44%
2092
April1st to 15thNight
13%4345%2435%7%44%
1799
16th to endNight
8%313312346%61%
1782
May1st to 15thNight
6%311112348%64%
1571
16th to endNight
7%31232335%6%60%
1496
June1st to 15thNight
6%31321335%7%61%
1440
16th to endNight
3111213380%
1440
July1st to 15thNight
1111122482%
1440
16th to endNight
11111286%
1644
August1st to 15thNight
11122284%
1620
16th to endNight
1111387%
1869
September1st to 15thNight
1112487%
1800
16th to endNight
211211226%75%
1878
October1st to 15thNight
7%31212335%67%
1980
16th to endNight
10%212223336%60%
2112
November1st to 15thNight
11%3133135%5%8%52%
2235
16th to endNight
16%31332345%7%48%
2520
December1st to 15thNight
25%412312346%44%
2520
16th to endNight
26%413313346%40%
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
37%412%21%16%7%
1471
16th to endDay
40%28%16%18%12%
1728
February1st to 15thDay
40%312%18%21%3
1576
16th to endDay
39%310%27%15%2
1523
March1st to 15thDay
44%6%10%18%15%5%
1947
16th to endDay
38%414%20%16%4
2131
April1st to 15thDay
38%314%21%18%3
2149
16th to endDay
23%310%28%25%8%
2175
May1st to 15thDay
19%28%26%27%15%
2379
16th to endDay
24%310%25%27%9%
2619
June1st to 15thDay
21%39%19%24%21%
2520
16th to endDay
11%1316%34%32%
2520
July1st to 15thDay
6%1314%31%42%
2371
16th to endDay
6%1310%26%51%
2366
August1st to 15thDay
6%1317%33%38%
2324
16th to endDay
5%1115%32%42%
2333
September1st to 15thDay
6%1313%28%46%
2160
16th to endDay
11%26%22%34%24%
1891
October1st to 15thDay
20%38%21%29%17%
1650
16th to endDay
27%28%26%21%13%
1760
November1st to 15thDay
29%414%28%14%8%
1621
16th to endDay
36%410%21%18%8%
1440
December1st to 15thDay
42%38%19%20%6%
1440
16th to endDay
46%29%20%15%5%
1536
January1st to 15thNight
35%5%14%20%15%8%
2464
16th to endNight
40%28%16%19%12%
2496
February1st to 15thNight
43%29%18%19%5%
2288
16th to endNight
40%311%23%18%3
1951
March1st to 15thNight
43%5%11%18%15%5%
2012
16th to endNight
37%414%23%14%5%
2092
April1st to 15thNight
37%415%21%14%6%
1799
16th to endNight
22%211%32%23%6%
1782
May1st to 15thNight
18%311%25%30%10%
1572
16th to endNight
23%411%30%21%9%
1496
June1st to 15thNight
22%411%23%24%14%
1440
16th to endNight
11%1419%37%26%
1440
July1st to 15thNight
7%1315%33%39%
1360
16th to endNight
6%1312%25%50%
1537
August1st to 15thNight
6%2320%35%32%
1611
16th to endNight
4218%35%37%
1869
September1st to 15thNight
41314%32%44%
1800
16th to endNight
12%25%21%29%28%
1878
October1st to 15thNight
19%37%20%30%18%
1980
16th to endNight
25%28%25%21%16%
2112
November1st to 15thNight
28%5%16%28%13%7%
2235
16th to endNight
34%312%22%18%8%
2520
December1st to 15thNight
41%210%16%24%4
2520
16th to endNight
44%38%17%19%6%
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
31%8%26%20%10%4
99
16th to endDay
25%8%21%19%16%7%
256
February1st to 15thDay
27%6%21%24%16%2
236
16th to endDay
20%9%24%26%14%3
229
March1st to 15thDay
29%14%18%23%11%3
270
16th to endDay
24%14%23%22%13%1
288
April1st to 15thDay
23%17%21%23%11%2
269
16th to endDay
12%20%29%22%10%5%
270
May1st to 15thDay
9%17%34%22%14%3
288
16th to endDay
7%13%23%30%17%7%
330
June1st to 15thDay
10%13%24%29%19%3
315
16th to endDay
48%25%32%23%6%
315
July1st to 15thDay
1217%42%25%9%
305
16th to endDay
319%45%24%7%
327
August1st to 15thDay
1323%38%24%8%
315
16th to endDay
419%37%26%11%
332
September1st to 15thDay
1419%35%28%10%
315
16th to endDay
48%21%32%24%8%
280
October1st to 15thDay
10%9%20%32%18%9%
255
16th to endDay
17%5%24%30%17%5%
272
November1st to 15thDay
17%317%25%29%5%
135
16th to endDay
15%15%30%33%5%1
60
December1st to 15thDay
40%10%23%20%6%
60
16th to endDay
15%7%28%25%17%6%
64
January1st to 15thNight
18%5%17%35%19%4
720
16th to endNight
23%418%30%19%4
768
February1st to 15thNight
22%6%17%33%18%1
704
16th to endNight
19%8%16%37%14%3
632
March1st to 15thNight
23%7%16%31%18%2
720
16th to endNight
18%8%24%31%16%1
768
April1st to 15thNight
13%12%26%30%15%1
719
16th to endNight
9%7%27%35%16%2
702
May1st to 15thNight
9%7%31%33%17%1
492
16th to endNight
9%6%22%33%26%1
375
June1st to 15thNight
6%7%27%38%18%
360
16th to endNight
4326%45%20%
360
July1st to 15thNight
111%39%45%2
340
16th to endNight
18%35%48%5%
508
August1st to 15thNight
27%36%46%6%
538
16th to endNight
8%35%48%5%
723
September1st to 15thNight
1113%32%44%6%
720
16th to endNight
45%12%32%40%4
683
October1st to 15thNight
8%6%18%30%28%5%
660
16th to endNight
12%215%35%27%5%
704
November1st to 15thNight
11%317%37%26%3
700
16th to endNight
18%415%36%22%2
720
December1st to 15thNight
26%417%31%16%3
720
16th to endNight
27%421%30%15%1
768
Page generated at 2017-09-23 03:43:38. Version ac04

Copyright 2017 A. Danko


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