Berthoud Pass Trailhead
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Berthoud Pass Trailhead clear sky chart from 2005-11-05 to 2018-01-20.

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
33%
16509
21%
48500
10%
16462
44%
16462
26%
28323

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
19%
975
19%
2716
6%
970
32%
970
20%
1640
January16th to endNight
19%
801
24%
2574
10%
801
36%
801
22%
1468
February1st to 15thNight
13%
700
14%
2273
4%
696
26%
696
15%
1393
February16th to endNight
12%
632
21%
1894
3%
632
31%
632
16%
1168
March1st to 15thNight
22%
720
20%
2085
6%
720
35%
720
22%
1228
March16th to endNight
23%
699
20%
2043
7%
699
36%
699
21%
1246
April1st to 15thNight
21%
539
18%
1798
6%
539
35%
539
20%
1043
April16th to endNight
25%
540
18%
1800
10%
540
39%
540
19%
1109
May1st to 15thNight
30%
540
15%
1599
5%
540
41%
540
22%
1047
May16th to endNight
40%
563
16%
1498
8%
561
48%
561
30%
915
June1st to 15thNight
48%
540
22%
1440
11%
540
57%
540
45%
760
June16th to endNight
63%
540
26%
1440
18%
540
69%
540
51%
749
July1st to 15thNight
67%
510
17%
1360
13%
510
71%
510
34%
834
July16th to endNight
71%
564
18%
1475
16%
531
73%
531
35%
882
August1st to 15thNight
65%
539
16%
1641
14%
536
68%
536
33%
951
August16th to endNight
67%
573
25%
1910
24%
573
71%
573
32%
1087
September1st to 15thNight
57%
540
26%
1800
20%
540
67%
540
34%
977
September16th to endNight
54%
560
31%
1937
23%
560
66%
560
37%
980
October1st to 15thNight
35%
720
25%
2160
12%
720
46%
720
31%
1204
October16th to endNight
32%
774
31%
2310
11%
774
47%
774
30%
1248
November1st to 15thNight
24%
950
27%
2470
7%
950
38%
950
30%
1405
November16th to endNight
22%
975
27%
2635
8%
975
37%
975
27%
1497
December1st to 15thNight
15%
975
17%
2730
3%
975
27%
975
19%
1642
December16th to endNight
17%
1040
18%
2912
5%
1040
28%
1040
17%
1850

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
5%7%47%6%45%45%7%40%
49042
Night
2425%5%35%46%9%50%
48677
TransparencyDay
41%6%13%20%14%3
48721
Night
28%8%18%24%15%4
48500
SeeingDay
16%24%28%17%10%2
6223
Night
8%24%28%23%12%1
16513

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
239%7%47%36%11%41%
1552
16th to endDay
438%8%34449%47%
1763
February1st to 15thDay
35%11%10%46%46%8%38%
1589
16th to endDay
35%12%9%5%7%447%40%
1580
March1st to 15thDay
18%37%7%45%45%7%44%
1875
16th to endDay
29%6%8%8%35%46%7%36%
2181
April1st to 15thDay
212%5%9%6%45%46%6%36%
2150
16th to endDay
415%7%10%7%5%5%446%28%
2160
May1st to 15thDay
7%16%5%8%6%35%5%5%6%30%
2347
16th to endDay
7%11%47%7%35%6%6%7%30%
2616
June1st to 15thDay
6%6%26%6%36%45%8%43%
2520
16th to endDay
34245%35%5%5%8%50%
2520
July1st to 15thDay
9%8%37%7%36%5%5%7%36%
2520
16th to endDay
9%7%37%8%45%6%6%7%31%
2590
August1st to 15thDay
13%7%48%7%4446%6%31%
2308
16th to endDay
9%8%48%5%45%5%5%7%34%
2292
September1st to 15thDay
9%6%36%5%24445%47%
2160
16th to endDay
6%9%25%433346%50%
2021
October1st to 15thDay
5%8%35%5%5%4337%47%
1800
16th to endDay
46%26%434438%51%
1902
November1st to 15thDay
1437%5%3446%7%52%
1718
16th to endDay
435%5%3435%8%55%
1654
December1st to 15thDay
338%8%5%7%5%5%11%41%
1560
16th to endDay
348%8%6%5%47%9%41%
1664
January1st to 15thNight
115%6%48%5%7%13%45%
2716
16th to endNight
325%5%47%5%5%10%49%
2574
February1st to 15thNight
228%6%47%5%6%11%43%
2262
16th to endNight
238%6%46%46%11%44%
1894
March1st to 15thNight
335%436%46%10%50%
2085
16th to endNight
17%45%5%3445%8%50%
2043
April1st to 15thNight
6%36%5%35%5%6%9%48%
1798
16th to endNight
311%36%445%35%7%44%
1800
May1st to 15thNight
410%444346%6%9%41%
1598
16th to endNight
36%2443446%10%48%
1497
June1st to 15thNight
221232346%9%59%
1440
16th to endNight
111233346%7%62%
1440
July1st to 15thNight
4315%5%26%5%6%10%47%
1440
16th to endNight
43245%36%5%6%9%47%
1576
August1st to 15thNight
5%5%24425%5%6%8%48%
1650
16th to endNight
5%4245%25%5%5%9%49%
1910
September1st to 15thNight
5%31343445%8%53%
1800
16th to endNight
35%1332345%7%59%
1937
October1st to 15thNight
241343445%7%57%
2160
16th to endNight
25%24323347%58%
2310
November1st to 15thNight
3243345%6%8%58%
2470
16th to endNight
225%6%2445%9%57%
2635
December1st to 15thNight
4246%35%5%8%11%48%
2730
16th to endNight
237%6%46%5%8%12%43%
2912

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
35%9%22%19%9%2
1553
16th to endDay
35%6%21%20%12%3
1763
February1st to 15thDay
42%9%20%17%8%2
1589
16th to endDay
42%6%13%22%12%2
1580
March1st to 15thDay
38%8%13%25%13%1
1875
16th to endDay
46%6%13%22%8%2
2181
April1st to 15thDay
46%5%13%18%11%4
2150
16th to endDay
56%5%11%17%7%1
2160
May1st to 15thDay
53%6%11%18%9%
2347
16th to endDay
49%8%12%18%8%2
2620
June1st to 15thDay
37%6%12%16%19%7%
2520
16th to endDay
30%5%9%22%23%8%
2520
July1st to 15thDay
47%7%10%14%14%6%
2371
16th to endDay
48%8%12%16%9%3
2428
August1st to 15thDay
51%7%11%12%12%5%
2293
16th to endDay
46%6%9%19%14%3
2292
September1st to 15thDay
40%48%17%20%8%
2160
16th to endDay
34%412%24%21%2
2021
October1st to 15thDay
38%49%22%21%3
1800
16th to endDay
31%412%27%19%3
1902
November1st to 15thDay
28%5%15%20%23%5%
1718
16th to endDay
26%6%16%29%16%4
1654
December1st to 15thDay
36%10%19%23%9%1
1560
16th to endDay
39%9%15%21%11%2
1664
January1st to 15thNight
27%11%24%22%12%2
2716
16th to endNight
28%8%20%24%13%4
2574
February1st to 15thNight
33%9%23%21%10%1
2273
16th to endNight
33%7%19%22%13%3
1894
March1st to 15thNight
28%7%19%26%14%2
2085
16th to endNight
32%7%17%30%10%2
2043
April1st to 15thNight
31%8%16%25%13%4
1798
16th to endNight
38%6%17%24%12%
1800
May1st to 15thNight
38%9%16%23%11%
1599
16th to endNight
30%9%21%25%11%2
1498
June1st to 15thNight
19%6%19%24%22%7%
1440
16th to endNight
19%412%27%24%12%
1440
July1st to 15thNight
30%9%16%19%16%8%
1360
16th to endNight
29%9%21%22%12%5%
1475
August1st to 15thNight
30%7%21%19%15%6%
1641
16th to endNight
29%8%15%22%21%2
1910
September1st to 15thNight
28%6%15%20%19%9%
1800
16th to endNight
23%6%12%31%22%2
1937
October1st to 15thNight
25%7%14%25%21%5%
2160
16th to endNight
24%5%14%29%21%3
2310
November1st to 15thNight
23%7%14%26%22%5%
2470
16th to endNight
24%6%16%29%18%4
2635
December1st to 15thNight
26%11%24%23%12%2
2730
16th to endNight
33%9%22%20%11%2
2912

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
14%39%21%15%8%
135
16th to endDay
11%38%23%21%4
109
February1st to 15thDay
25%46%20%5%2
90
16th to endDay
20%34%25%14%3
81
March1st to 15thDay
23%41%22%10%1
165
16th to endDay
18%49%23%7%
288
April1st to 15thDay
23%37%26%9%2
269
16th to endDay
24%49%15%7%2
270
May1st to 15thDay
18%26%32%14%5%1
394
16th to endDay
17%23%28%17%10%2
517
June1st to 15thDay
11%17%32%21%13%2
495
16th to endDay
6%13%34%24%17%3
495
July1st to 15thDay
14%8%27%23%21%5%
475
16th to endDay
12%5%31%22%20%8%
449
August1st to 15thDay
21%10%36%22%8%
315
16th to endDay
17%10%31%28%9%2
332
September1st to 15thDay
15%21%34%17%8%1
315
16th to endDay
17%15%35%19%8%2
201
October1st to 15thDay
14%34%21%17%9%2
135
16th to endDay
24%29%20%18%6%
144
November1st to 15thDay
15%35%18%13%15%1
135
16th to endDay
26%37%28%6%
135
December1st to 15thDay
20%42%25%8%2
135
16th to endDay
15%51%19%9%2
144
January1st to 15thNight
14%33%28%15%6%1
975
16th to endNight
9%33%33%16%5%
801
February1st to 15thNight
10%36%33%13%5%
704
16th to endNight
11%38%31%15%3
632
March1st to 15thNight
6%36%30%18%7%
720
16th to endNight
7%33%32%22%4
699
April1st to 15thNight
8%28%38%19%4
539
16th to endNight
11%27%32%21%6%
540
May1st to 15thNight
9%16%38%24%9%1
540
16th to endNight
8%12%31%31%13%1
563
June1st to 15thNight
6%10%31%34%15%1
540
16th to endNight
35%23%41%24%1
540
July1st to 15thNight
7%113%37%36%2
510
16th to endNight
5%19%36%41%4
564
August1st to 15thNight
9%112%44%30%2
539
16th to endNight
6%314%37%31%6%
573
September1st to 15thNight
7%422%36%22%5%
540
16th to endNight
5%8%26%31%22%4
560
October1st to 15thNight
7%24%30%22%12%2
720
16th to endNight
8%27%27%22%11%2
774
November1st to 15thNight
8%32%32%17%8%1
950
16th to endNight
10%33%30%20%4
975
December1st to 15thNight
8%42%30%14%3
975
16th to endNight
12%36%28%17%4
1040
Page generated at 2018-01-21 10:19:25. Version ac04

Copyright 2018 A. Danko


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