Nevada City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nevada City clear sky chart from 2005-11-05 to 2017-03-25.

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
66%
14658
27%
45302
25%
14620
70%
14620
39%
24785

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
59%
717
20%
2491
21%
716
62%
716
28%
1457
January16th to endNight
52%
768
25%
2496
23%
768
59%
768
27%
1532
February1st to 15thNight
53%
699
23%
2265
21%
696
60%
696
25%
1433
February16th to endNight
51%
632
24%
1895
22%
632
57%
632
26%
1213
March1st to 15thNight
49%
720
15%
2070
12%
720
53%
720
24%
1424
March16th to endNight
51%
744
19%
1990
14%
744
55%
744
28%
1333
April1st to 15thNight
54%
659
19%
1649
11%
659
56%
659
30%
1129
April16th to endNight
64%
660
23%
1650
12%
660
67%
660
43%
978
May1st to 15thNight
63%
499
29%
1489
22%
499
67%
499
48%
740
May16th to endNight
70%
343
22%
1368
27%
342
72%
342
36%
648
June1st to 15thNight
75%
330
27%
1320
35%
330
80%
330
42%
566
June16th to endNight
85%
330
33%
1320
45%
330
88%
330
61%
464
July1st to 15thNight
95%
310
36%
1240
49%
310
96%
310
73%
387
July16th to endNight
92%
437
38%
1385
40%
407
93%
407
76%
491
August1st to 15thNight
90%
522
40%
1505
33%
519
90%
519
72%
634
August16th to endNight
94%
700
43%
1750
28%
700
94%
700
83%
778
September1st to 15thNight
91%
660
44%
1650
32%
660
92%
660
81%
739
September16th to endNight
82%
656
43%
1778
37%
656
85%
656
68%
816
October1st to 15thNight
71%
660
31%
1980
32%
660
75%
660
48%
997
October16th to endNight
71%
704
34%
2112
34%
704
75%
704
45%
1097
November1st to 15thNight
66%
700
27%
2264
27%
700
71%
700
38%
1230
November16th to endNight
59%
720
23%
2427
24%
720
63%
720
30%
1385
December1st to 15thNight
52%
720
21%
2520
19%
720
59%
720
24%
1545
December16th to endNight
44%
768
22%
2688
18%
768
52%
768
20%
1769

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
11%312212335%61%
45654
Night
13%312213335%57%
45492
TransparencyDay
26%27%18%24%19%
45334
Night
29%37%18%22%18%
45312
SeeingDay
14%9%27%32%11%4
5138
Night
15%29%31%33%7%
14667

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%6%23322336%46%
1444
16th to endDay
23%8%12223336%43%
1728
February1st to 15thDay
22%6%23222335%45%
1590
16th to endDay
24%8%23322435%39%
1579
March1st to 15thDay
23%7%24423246%37%
1889
16th to endDay
22%6%2432235%7%39%
2100
April1st to 15thDay
20%5%234235%5%6%40%
1969
16th to endDay
12%422212346%57%
1980
May1st to 15thDay
7%312213347%63%
2130
16th to endDay
9%423323446%55%
2391
June1st to 15thDay
7%313213235%63%
2310
16th to endDay
2111122382%
2310
July1st to 15thDay
11111385%
2310
16th to endDay
1111112384%
2370
August1st to 15thDay
11111286%
2115
16th to endDay
1111287%
2100
September1st to 15thDay
11111122382%
1980
16th to endDay
41111112478%
1848
October1st to 15thDay
8%31221233465%
1650
16th to endDay
10%314313335%59%
1760
November1st to 15thDay
12%5%1332445%6%50%
1595
16th to endDay
18%42332424448%
1530
December1st to 15thDay
22%6%2431335%6%41%
1440
16th to endDay
26%7%23422345%38%
1536
January1st to 15thNight
18%42332335%7%45%
2491
16th to endNight
21%5%13313335%47%
2496
February1st to 15thNight
21%6%13324446%41%
2262
16th to endNight
23%6%13313445%42%
1895
March1st to 15thNight
23%6%24424346%36%
2070
16th to endNight
21%5%13333345%44%
1990
April1st to 15thNight
17%6%34424347%42%
1649
16th to endNight
12%322213345%58%
1650
May1st to 15thNight
7%212323346%63%
1489
16th to endNight
8%314323346%58%
1368
June1st to 15thNight
6%31213226%68%
1320
16th to endNight
211121221480%
1320
July1st to 15thNight
11221285%
1320
16th to endNight
1111111386%
1489
August1st to 15thNight
2111112380%
1514
16th to endNight
111113384%
1750
September1st to 15thNight
1111122384%
1650
16th to endNight
21121123477%
1778
October1st to 15thNight
8%21221323466%
1980
16th to endNight
10%212213346%61%
2112
November1st to 15thNight
12%413212346%55%
2264
16th to endNight
14%424413345%50%
2427
December1st to 15thNight
24%412223346%43%
2520
16th to endNight
27%5%2331334439%
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
39%38%20%19%8%
1444
16th to endDay
44%26%14%18%13%
1728
February1st to 15thDay
42%29%18%20%5%
1590
16th to endDay
46%39%25%12%2
1579
March1st to 15thDay
47%311%15%15%6%
1889
16th to endDay
44%5%14%17%15%3
2100
April1st to 15thDay
42%412%22%15%3
1969
16th to endDay
27%313%25%23%6%
1980
May1st to 15thDay
21%28%29%28%9%
2130
16th to endDay
27%313%28%19%7%
2395
June1st to 15thDay
22%210%20%21%22%
2310
16th to endDay
9%1315%40%29%
2310
July1st to 15thDay
7%139%29%49%
2161
16th to endDay
8%1210%24%51%
2211
August1st to 15thDay
7%1210%30%48%
2099
16th to endDay
5%1112%37%42%
2100
September1st to 15thDay
8%1310%34%43%
1980
16th to endDay
12%1422%34%25%
1848
October1st to 15thDay
21%36%25%27%16%
1650
16th to endDay
28%36%20%25%15%
1760
November1st to 15thDay
33%311%20%21%9%
1595
16th to endDay
38%38%20%21%7%
1530
December1st to 15thDay
43%37%18%21%4
1440
16th to endDay
48%29%13%17%7%
1536
January1st to 15thNight
37%39%19%17%10%
2491
16th to endNight
41%27%13%18%16%
2496
February1st to 15thNight
42%47%17%19%9%
2274
16th to endNight
41%48%24%16%4
1895
March1st to 15thNight
47%410%15%14%6%
2070
16th to endNight
41%5%9%20%16%6%
1990
April1st to 15thNight
42%413%19%14%5%
1649
16th to endNight
27%412%24%23%7%
1650
May1st to 15thNight
21%310%23%26%13%
1490
16th to endNight
25%414%29%17%8%
1368
June1st to 15thNight
19%410%20%22%21%
1320
16th to endNight
11%2414%34%33%
1320
July1st to 15thNight
6%129%29%50%
1240
16th to endNight
7%211%22%55%
1385
August1st to 15thNight
10%114%25%47%
1505
16th to endNight
6%1211%33%45%
1750
September1st to 15thNight
7%148%37%41%
1650
16th to endNight
11%15%18%35%26%
1778
October1st to 15thNight
22%26%23%25%19%
1980
16th to endNight
24%35%21%28%16%
2112
November1st to 15thNight
29%412%22%19%11%
2264
16th to endNight
34%47%20%21%10%
2427
December1st to 15thNight
41%48%17%20%7%
2520
16th to endNight
48%36%13%19%8%
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
50%419%15%8%2
72
16th to endDay
32%5%19%27%11%3
256
February1st to 15thDay
28%8%25%26%9%1
239
16th to endDay
32%14%22%21%8%
238
March1st to 15thDay
33%14%21%19%8%3
270
16th to endDay
24%16%29%20%7%1
264
April1st to 15thDay
27%21%27%15%7%1
209
16th to endDay
17%20%30%22%6%3
210
May1st to 15thDay
14%16%38%20%7%3
228
16th to endDay
10%15%22%33%10%7%
266
June1st to 15thDay
8%13%33%33%6%4
255
16th to endDay
36%37%38%7%6%
255
July1st to 15thDay
1230%49%8%7%
245
16th to endDay
227%53%9%5%
271
August1st to 15thDay
1331%44%12%6%
255
16th to endDay
228%49%12%6%
268
September1st to 15thDay
35%29%40%17%4
255
16th to endDay
6%6%30%34%18%3
255
October1st to 15thDay
7%12%31%29%13%5%
255
16th to endDay
16%7%25%34%16%
272
November1st to 15thDay
8%6%16%28%31%6%
101
16th to endDay
21%9%20%30%16%2
75
December1st to 15thDay
38%5%33%13%6%3
60
16th to endDay
28%318%21%25%3
64
January1st to 15thNight
21%210%35%24%5%
720
16th to endNight
24%212%31%24%4
768
February1st to 15thNight
24%111%36%23%2
704
16th to endNight
25%5%11%31%21%4
632
March1st to 15thNight
24%411%29%25%3
720
16th to endNight
23%413%30%24%3
744
April1st to 15thNight
18%5%14%35%22%3
659
16th to endNight
13%5%11%33%27%8%
660
May1st to 15thNight
9%417%33%30%5%
500
16th to endNight
9%28%31%40%7%
343
June1st to 15thNight
6%210%32%41%6%
330
16th to endNight
27%36%45%7%
330
July1st to 15thNight
124%62%10%
310
16th to endNight
1221%61%13%
437
August1st to 15thNight
2330%51%12%
522
16th to endNight
230%56%8%
700
September1st to 15thNight
1328%52%12%
660
16th to endNight
418%30%39%15%
656
October1st to 15thNight
9%210%31%35%9%
660
16th to endNight
12%210%28%35%10%
704
November1st to 15thNight
14%29%32%31%8%
700
16th to endNight
16%412%36%23%6%
720
December1st to 15thNight
26%410%32%20%5%
720
16th to endNight
30%313%30%18%2
768
Page generated at 2017-03-26 10:16:37. Version ac04

Copyright 2017 A. Danko


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