Idyllwild
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Idyllwild clear sky chart from 2005-11-05 to 2017-09-19.

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
64%
16181
34%
46989
27%
16140
71%
16140
50%
23500

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
54%
717
30%
2327
25%
716
63%
716
39%
1194
January16th to endNight
50%
768
32%
2331
24%
768
61%
768
33%
1337
February1st to 15thNight
55%
698
32%
2109
26%
698
65%
698
39%
1150
February16th to endNight
48%
632
29%
1895
27%
632
55%
632
30%
1168
March1st to 15thNight
51%
720
30%
2151
25%
720
62%
720
38%
1172
March16th to endNight
56%
768
31%
2052
22%
768
64%
768
44%
1150
April1st to 15thNight
43%
719
30%
1799
13%
719
53%
719
43%
1051
April16th to endNight
50%
720
34%
1800
14%
720
59%
720
53%
964
May1st to 15thNight
59%
554
35%
1634
22%
554
65%
554
56%
759
May16th to endNight
54%
562
33%
1685
21%
561
61%
561
57%
748
June1st to 15thNight
65%
540
34%
1620
24%
540
71%
540
69%
663
June16th to endNight
76%
540
38%
1620
30%
540
80%
540
81%
610
July1st to 15thNight
85%
510
30%
1530
26%
510
86%
510
67%
649
July16th to endNight
83%
589
32%
1616
25%
554
83%
554
54%
782
August1st to 15thNight
86%
717
37%
1790
24%
713
86%
713
73%
846
August16th to endNight
88%
764
44%
1910
30%
764
88%
764
75%
894
September1st to 15thNight
86%
720
39%
1878
30%
720
88%
720
73%
849
September16th to endNight
81%
671
47%
1856
39%
671
87%
671
77%
781
October1st to 15thNight
65%
660
38%
1815
30%
660
74%
660
56%
892
October16th to endNight
72%
704
40%
2120
36%
704
79%
704
56%
985
November1st to 15thNight
70%
700
35%
2275
33%
700
78%
700
53%
1029
November16th to endNight
64%
720
36%
2340
35%
720
71%
720
43%
1164
December1st to 15thNight
54%
720
31%
2340
27%
720
62%
720
35%
1270
December16th to endNight
48%
768
32%
2496
27%
768
58%
768
33%
1393

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
2313323345%66%
47814
Night
2313423345%65%
47190
TransparencyDay
19%3413%27%30%
47512
Night
19%4413%26%31%
46993
SeeingDay
416%35%29%11%2
5875
Night
38%19%35%27%6%
16192

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
342442435%6%56%
1611
16th to endDay
7%5%25%5%24345%53%
1890
February1st to 15thDay
5%3245%34345%58%
1751
16th to endDay
5%7%37%6%23445%49%
1579
March1st to 15thDay
3323423447%60%
1807
16th to endDay
1424434347%57%
2169
April1st to 15thDay
34245%24345%58%
2149
16th to endDay
1212422248%67%
2160
May1st to 15thDay
2213412245%69%
2313
16th to endDay
122312336%72%
2429
June1st to 15thDay
111212236%77%
2340
16th to endDay
111111285%
2340
July1st to 15thDay
3212212345%71%
2340
16th to endDay
221342346%7%61%
2439
August1st to 15thDay
111222345%74%
2160
16th to endDay
122213345%72%
2292
September1st to 15thDay
2112213335%71%
2080
16th to endDay
21121112381%
1849
October1st to 15thDay
121442233469%
1815
16th to endDay
1113313346%69%
1749
November1st to 15thDay
222341223469%
1584
16th to endDay
3414422336%62%
1620
December1st to 15thDay
5%5%15%5%245%6%6%51%
1620
16th to endDay
5%6%35%5%23345%54%
1728
January1st to 15thNight
3326%5%3235%6%57%
2327
16th to endNight
5%5%35%6%23335%53%
2331
February1st to 15thNight
3425%5%23445%58%
2101
16th to endNight
45%37%7%35%45%6%47%
1895
March1st to 15thNight
23246%35%446%56%
2151
16th to endNight
13245%3445%8%56%
2052
April1st to 15thNight
25%245%3335%7%57%
1799
16th to endNight
2212433336%66%
1800
May1st to 15thNight
11342325%6%68%
1634
16th to endNight
111313346%71%
1684
June1st to 15thNight
1111245%79%
1620
16th to endNight
111111287%
1620
July1st to 15thNight
212212245%73%
1620
16th to endNight
2214423447%63%
1726
August1st to 15thNight
12211235%77%
1800
16th to endNight
1211112381%
1910
September1st to 15thNight
111111123479%
1878
16th to endNight
111122385%
1856
October1st to 15thNight
1113323345%68%
1815
16th to endNight
1212322345%69%
2120
November1st to 15thNight
12135%22335%68%
2275
16th to endNight
34125%33445%61%
2340
December1st to 15thNight
45%247%34347%52%
2340
16th to endNight
5%5%36%5%23235%54%
2496

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
25%35%14%27%23%
1612
16th to endDay
30%35%14%22%23%
1890
February1st to 15thDay
27%3415%25%23%
1751
16th to endDay
35%35%14%27%14%
1579
March1st to 15thDay
21%45%18%28%21%
1807
16th to endDay
25%36%20%28%15%
2169
April1st to 15thDay
26%4418%32%13%
2149
16th to endDay
15%36%18%33%21%
2160
May1st to 15thDay
15%35%16%32%26%
2313
16th to endDay
13%46%16%38%21%
2432
June1st to 15thDay
10%3211%27%44%
2340
16th to endDay
8%1317%67%
2340
July1st to 15thDay
14%2312%22%44%
2201
16th to endDay
20%47%19%22%26%
2286
August1st to 15thDay
12%2311%25%44%
2146
16th to endDay
13%349%30%37%
2292
September1st to 15thDay
15%25%8%27%39%
2080
16th to endDay
10%127%28%48%
1849
October1st to 15thDay
17%3312%30%32%
1815
16th to endDay
16%449%24%41%
1749
November1st to 15thDay
19%2413%30%28%
1584
16th to endDay
23%3410%28%29%
1620
December1st to 15thDay
28%46%17%21%21%
1620
16th to endDay
32%45%17%23%16%
1728
January1st to 15thNight
26%3414%24%26%
2327
16th to endNight
31%4412%20%25%
2331
February1st to 15thNight
26%5%313%24%26%
2112
16th to endNight
35%6%314%23%16%
1895
March1st to 15thNight
26%5%416%24%22%
2151
16th to endNight
23%5%6%19%27%17%
2052
April1st to 15thNight
24%6%6%19%28%15%
1799
16th to endNight
17%5%5%16%32%22%
1800
May1st to 15thNight
13%46%16%30%27%
1635
16th to endNight
11%5%9%16%38%20%
1685
June1st to 15thNight
9%2212%26%46%
1620
16th to endNight
6%2417%68%
1620
July1st to 15thNight
11%15%9%20%51%
1530
16th to endNight
18%37%18%23%28%
1616
August1st to 15thNight
10%2213%26%44%
1790
16th to endNight
9%1210%31%43%
1910
September1st to 15thNight
9%15%10%29%42%
1878
16th to endNight
6%328%30%49%
1856
October1st to 15thNight
15%4412%31%30%
1815
16th to endNight
15%448%22%44%
2120
November1st to 15thNight
17%2412%31%31%
2275
16th to endNight
23%4313%23%31%
2340
December1st to 15thNight
28%5%5%15%21%22%
2340
16th to endNight
32%36%14%24%18%
2496

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
11%24%35%25%3
90
16th to endDay
11%24%34%23%5%1
258
February1st to 15thDay
424%34%25%10%
266
16th to endDay
9%32%32%18%6%
238
March1st to 15thDay
8%24%31%22%9%2
270
16th to endDay
5%27%36%19%9%1
288
April1st to 15thDay
12%26%36%13%8%2
269
16th to endDay
334%39%14%7%
270
May1st to 15thDay
7%21%38%23%6%2
288
16th to endDay
222%39%23%9%2
330
June1st to 15thDay
212%45%27%8%3
315
16th to endDay
25%39%35%13%4
315
July1st to 15thDay
2332%42%14%4
305
16th to endDay
3122%48%15%7%
327
August1st to 15thDay
1335%40%15%3
315
16th to endDay
1130%43%15%6%
332
September1st to 15thDay
3345%34%11%
315
16th to endDay
211%33%38%11%1
268
October1st to 15thDay
119%44%25%7%
255
16th to endDay
112%34%31%19%1
195
November1st to 15thDay
318%16%30%23%7%
90
16th to endDay
6%17%34%24%16%
90
December1st to 15thDay
6%11%30%36%14%1
90
16th to endDay
7%21%37%29%4
96
January1st to 15thNight
410%22%35%18%7%
720
16th to endNight
7%12%22%32%21%4
768
February1st to 15thNight
311%23%33%23%4
704
16th to endNight
418%22%34%15%4
632
March1st to 15thNight
314%25%32%19%4
720
16th to endNight
114%22%33%21%5%
768
April1st to 15thNight
317%31%28%15%3
719
16th to endNight
213%31%29%17%5%
720
May1st to 15thNight
10%25%42%19%1
555
16th to endNight
111%30%32%21%2
563
June1st to 15thNight
5%27%44%19%2
540
16th to endNight
118%52%24%2
540
July1st to 15thNight
26%47%41%2
510
16th to endNight
31344%41%4
589
August1st to 15thNight
17%39%44%7%
717
16th to endNight
3328%50%13%
764
September1st to 15thNight
26%33%47%9%
720
16th to endNight
1213%34%38%9%
671
October1st to 15thNight
18%19%36%26%6%
660
16th to endNight
2416%33%31%12%
704
November1st to 15thNight
16%16%38%28%8%
700
16th to endNight
39%17%32%26%10%
720
December1st to 15thNight
410%23%33%22%5%
720
16th to endNight
7%13%23%32%16%5%
768
Page generated at 2017-09-20 01:49:45. Version ac04

Copyright 2017 A. Danko


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