Horseshoe Canyon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Horseshoe Canyon clear sky chart from 2005-11-06 to 2024-03-08.

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
42%
23709
13%
80854
9%
23655
47%
23655
20%
53514

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
38%
937
14%
4685
8%
926
42%
926
10%
3220
January11th to 20thNight
39%
940
18%
4615
10%
929
45%
929
12%
3061
January21st to endNight
36%
872
11%
4870
9%
867
44%
867
11%
2911
February1st to 10thNight
39%
760
14%
2634
12%
760
44%
760
16%
1868
February11th to 20thNight
37%
741
12%
2403
9%
740
42%
740
17%
1743
February21st to endNight
50%
628
14%
1977
14%
628
54%
628
21%
1351
March1st to 10thNight
39%
750
14%
2241
11%
750
43%
750
19%
1638
March11th to 20thNight
43%
720
17%
1980
10%
720
49%
720
23%
1392
March21st to endNight
38%
792
9%
2178
5%
792
41%
792
17%
1664
April1st to 10thNight
38%
630
12%
1723
5%
630
43%
630
20%
1248
April11th to 20thNight
38%
533
14%
1601
9%
533
42%
533
19%
1149
April21st to endNight
40%
540
12%
1620
10%
540
43%
540
21%
1111
May1st to 10thNight
39%
491
9%
1473
6%
491
43%
491
21%
1017
May11th to 20thNight
48%
354
13%
1239
11%
354
52%
354
24%
782
May21st to endNight
43%
388
5%
1358
3%
388
45%
388
16%
953
June1st to 10thNight
42%
360
1%
1260
0%
360
42%
360
17%
871
June11th to 20thNight
36%
360
0%
1260
0%
360
36%
360
13%
921
June21st to endNight
50%
360
0%
1260
0%
360
50%
360
25%
768
July1st to 10thNight
60%
350
1%
1225
0%
350
60%
350
25%
742
July11th to 20thNight
55%
348
4%
1218
2%
348
56%
348
24%
749
July21st to endNight
63%
394
12%
1302
11%
372
68%
372
35%
668
August1st to 10thNight
57%
362
10%
1419
14%
360
59%
360
24%
811
August11th to 20thNight
61%
534
14%
1602
13%
534
62%
534
35%
952
August21st to endNight
61%
594
20%
1782
17%
594
64%
594
35%
1041
September1st to 10thNight
55%
576
18%
1700
14%
576
57%
576
31%
1045
September11th to 20thNight
54%
720
18%
1980
12%
720
57%
720
32%
1268
September21st to endNight
49%
720
21%
1980
14%
720
55%
720
35%
1214
October1st to 10thNight
47%
720
19%
2092
12%
720
53%
720
27%
1366
October11th to 20thNight
42%
720
16%
2253
9%
720
50%
720
24%
1464
October21st to endNight
36%
792
15%
2574
9%
792
44%
792
20%
1728
November1st to 10thNight
34%
896
16%
2561
9%
896
40%
896
20%
1820
November11th to 20thNight
34%
950
16%
2696
9%
950
41%
950
21%
1877
November21st to endNight
38%
950
11%
2850
7%
950
42%
950
21%
1983
December1st to 10thNight
38%
950
13%
2850
8%
950
42%
950
18%
2067
December11th to 20thNight
35%
949
12%
3478
7%
949
40%
949
15%
2393
December21st to endNight
35%
1028
10%
4915
7%
1026
41%
1026
15%
2658

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%8%47%6%45%6%6%8%37%
77963
Night
7%9%48%7%46%6%6%8%35%
81554
TransparencyDay
43%9%16%22%9%1
77665
Night
44%8%15%21%10%2
81432
SeeingDay
12%7%26%31%19%5%
14427
Night
12%6%29%37%15%2
23771

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
410%6%13%8%46%5%7%9%28%
2219
11th to 20thDay
5%9%5%9%8%5%5%10%9%7%28%
2199
21st to endDay
5%9%49%7%45%6%7%8%36%
2730
February1st to 10thDay
8%12%5%10%9%5%7%5%5%7%26%
1545
11th to 20thDay
6%13%7%10%8%5%6%7%7%6%25%
1665
21st to endDay
412%8%12%9%47%7%5%7%25%
1475
March1st to 10thDay
6%12%6%12%11%5%6%6%6%6%24%
1879
11th to 20thDay
9%9%5%8%8%46%6%7%8%31%
1979
21st to endDay
9%14%6%9%6%46%6%6%7%28%
2178
April1st to 10thDay
9%12%46%7%46%6%7%7%31%
2235
11th to 20thDay
12%11%48%6%36%6%7%8%31%
2310
21st to endDay
14%9%37%6%46%5%6%8%32%
2340
May1st to 10thDay
15%9%47%6%46%5%6%8%31%
2482
11th to 20thDay
11%6%25%6%35%6%6%9%41%
2654
21st to endDay
20%6%36%6%35%5%6%6%34%
2917
June1st to 10thDay
15%6%36%5%46%6%7%8%34%
2700
11th to 20thDay
21%7%36%5%36%6%6%8%29%
2700
21st to endDay
10%425%5%35%6%8%10%43%
2700
July1st to 10thDay
8%425%5%45%6%7%10%44%
2700
11th to 20thDay
11%314436%5%7%10%46%
2700
21st to endDay
6%313435%5%6%9%55%
2938
August1st to 10thDay
9%5%245%345%6%9%47%
2509
11th to 20thDay
9%4244345%6%8%50%
2299
21st to endDay
10%425%4345%6%8%50%
2574
September1st to 10thDay
11%6%26%4245%5%7%48%
2256
11th to 20thDay
15%6%25%5%34447%46%
1980
21st to endDay
9%6%344345%6%9%46%
1980
October1st to 10thDay
13%9%36%5%3345%7%42%
1868
11th to 20thDay
10%7%35%6%45%5%6%8%41%
1706
21st to endDay
8%11%47%6%46%6%6%7%36%
1782
November1st to 10thDay
10%17%5%10%6%35%5%5%7%27%
1498
11th to 20thDay
8%13%5%9%7%35%46%7%34%
1482
21st to endDay
7%10%410%7%35%5%8%8%32%
1330
December1st to 10thDay
8%12%7%8%8%6%7%6%5%5%28%
1330
11th to 20thDay
310%5%14%9%46%6%6%8%29%
1682
21st to endDay
38%49%5%4446%7%46%
2442
January1st to 10thNight
313%6%11%8%5%7%7%6%10%25%
4726
11th to 20thNight
48%5%11%8%5%7%7%6%9%31%
4699
21st to endNight
5%10%5%10%7%35%6%7%9%34%
4954
February1st to 10thNight
6%11%6%11%8%5%5%5%6%8%29%
2634
11th to 20thNight
6%11%6%10%8%5%7%6%6%8%27%
2402
21st to endNight
5%9%6%9%7%47%7%7%7%33%
1977
March1st to 10thNight
5%10%5%11%9%5%6%6%6%8%29%
2241
11th to 20thNight
6%8%6%7%8%47%6%6%9%33%
1980
21st to endNight
9%13%5%9%8%5%7%7%6%8%25%
2178
April1st to 10thNight
10%10%5%8%6%5%6%5%6%8%31%
1723
11th to 20thNight
9%12%5%8%7%46%5%6%9%29%
1601
21st to endNight
10%9%48%6%46%47%8%34%
1620
May1st to 10thNight
13%9%47%5%35%5%7%9%32%
1473
11th to 20thNight
11%6%27%5%46%5%47%43%
1239
21st to endNight
19%7%26%5%46%6%6%7%32%
1358
June1st to 10thNight
15%8%36%5%45%6%6%9%31%
1260
11th to 20thNight
16%7%37%7%5%6%5%7%9%27%
1260
21st to endNight
9%6%27%6%35%5%6%9%43%
1260
July1st to 10thNight
8%435%6%5%6%5%7%8%44%
1260
11th to 20thNight
8%4246%47%7%7%8%43%
1260
21st to endNight
43245%346%6%9%54%
1379
August1st to 10thNight
8%426%6%35%5%7%9%45%
1426
11th to 20thNight
9%5%244345%6%11%47%
1602
21st to endNight
9%4244245%7%8%50%
1782
September1st to 10thNight
11%5%25%5%346%5%8%48%
1700
11th to 20thNight
13%7%25%43346%8%46%
1980
21st to endNight
9%6%3443447%9%47%
1980
October1st to 10thNight
12%8%35%5%35%5%6%8%41%
2092
11th to 20thNight
9%7%37%6%45%5%6%8%39%
2253
21st to endNight
7%9%49%7%35%6%6%9%35%
2574
November1st to 10thNight
10%14%46%6%45%46%7%33%
2561
11th to 20thNight
5%8%49%8%46%6%7%8%34%
2696
21st to endNight
6%9%49%8%46%6%6%9%32%
2850
December1st to 10thNight
7%12%5%11%8%45%5%5%8%30%
2850
11th to 20thNight
410%410%9%5%6%6%6%8%30%
3510
21st to endNight
47%46%7%45%5%5%8%44%
5214

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
49%9%13%20%8%1
2219
11th to 20thDay
47%8%15%13%15%2
2220
21st to endDay
42%9%15%28%6%
2730
February1st to 10thDay
55%6%14%15%9%1
1545
11th to 20thDay
55%8%14%15%7%1
1674
21st to endDay
56%6%11%17%10%
1475
March1st to 10thDay
57%9%14%14%5%
1879
11th to 20thDay
47%8%14%21%9%1
1980
21st to endDay
52%10%17%15%6%
2178
April1st to 10thDay
48%9%18%16%8%
2235
11th to 20thDay
49%9%13%21%8%1
2310
21st to endDay
48%8%15%20%8%1
2340
May1st to 10thDay
48%10%13%20%8%
2482
11th to 20thDay
38%9%15%26%11%
2658
21st to endDay
49%8%15%20%8%1
2918
June1st to 10thDay
45%9%16%21%8%1
2700
11th to 20thDay
51%10%16%17%6%1
2700
21st to endDay
33%11%21%26%7%2
2700
July1st to 10thDay
32%11%21%27%8%1
2626
11th to 20thDay
33%11%19%27%9%
2619
21st to endDay
25%9%21%31%13%1
2775
August1st to 10thDay
33%10%19%27%9%2
2491
11th to 20thDay
30%8%23%28%11%1
2299
21st to endDay
30%9%20%28%13%1
2574
September1st to 10thDay
33%8%17%26%12%4
2256
11th to 20thDay
39%6%14%29%10%2
1980
21st to endDay
34%9%17%26%11%3
1980
October1st to 10thDay
43%6%17%24%10%1
1868
11th to 20thDay
39%9%16%25%10%1
1706
21st to endDay
45%8%13%22%11%1
1782
November1st to 10thDay
56%7%12%16%6%2
1498
11th to 20thDay
49%7%13%22%8%1
1482
21st to endDay
46%9%16%20%8%1
1330
December1st to 10thDay
55%7%13%16%7%2
1330
11th to 20thDay
51%9%15%20%41
1684
21st to endDay
36%6%12%25%16%5%
2442
January1st to 10thNight
50%10%13%20%5%1
4726
11th to 20thNight
49%7%11%17%14%2
4740
21st to endNight
44%8%14%25%8%1
4954
February1st to 10thNight
52%7%12%19%10%1
2634
11th to 20thNight
51%8%13%15%11%1
2403
21st to endNight
46%7%14%21%10%1
1977
March1st to 10thNight
50%9%16%19%6%1
2241
11th to 20thNight
45%8%16%21%9%1
1980
21st to endNight
53%10%13%17%6%1
2178
April1st to 10thNight
49%8%15%16%11%1
1723
11th to 20thNight
50%8%13%22%7%1
1601
21st to endNight
44%9%14%23%8%2
1620
May1st to 10thNight
45%9%14%20%10%1
1473
11th to 20thNight
39%8%13%24%15%1
1239
21st to endNight
49%9%14%20%7%2
1358
June1st to 10thNight
48%9%14%21%9%
1260
11th to 20thNight
52%12%13%16%7%2
1260
21st to endNight
36%9%20%25%8%1
1260
July1st to 10thNight
35%11%21%24%8%1
1225
11th to 20thNight
34%13%21%22%9%1
1218
21st to endNight
25%8%22%30%15%1
1302
August1st to 10thNight
33%10%22%24%10%1
1419
11th to 20thNight
30%8%22%27%11%1
1602
21st to endNight
29%8%15%30%14%4
1782
September1st to 10thNight
33%8%16%24%13%6%
1700
11th to 20thNight
36%7%14%26%12%4
1980
21st to endNight
32%7%17%27%15%3
1980
October1st to 10thNight
40%7%15%24%12%1
2092
11th to 20thNight
41%8%16%22%10%3
2253
21st to endNight
43%10%15%24%7%1
2574
November1st to 10thNight
49%7%13%21%9%1
2561
11th to 20thNight
45%8%16%19%10%1
2696
21st to endNight
46%9%18%19%6%2
2850
December1st to 10thNight
52%7%12%20%8%1
2850
11th to 20thNight
47%10%20%18%5%
3507
21st to endNight
36%7%13%24%15%4
5214

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
6%6%28%30%19%11%
180
11th to 20thDay
7%7%33%29%19%4
180
21st to endDay
10%8%26%32%19%6%
198
February1st to 10thDay
12%9%26%34%13%5%
193
11th to 20thDay
9%6%30%34%17%4
270
21st to endDay
7%6%26%38%18%5%
287
March1st to 10thDay
12%6%32%32%14%4
449
11th to 20thDay
10%5%30%35%14%5%
420
21st to endDay
10%8%34%27%18%4
462
April1st to 10thDay
10%13%34%30%9%4
420
11th to 20thDay
13%10%29%27%17%3
412
21st to endDay
17%11%28%29%13%2
420
May1st to 10thDay
15%11%21%28%20%5%
519
11th to 20thDay
12%6%23%34%21%4
625
21st to endDay
19%5%22%27%22%6%
679
June1st to 10thDay
16%6%26%31%18%2
630
11th to 20thDay
21%8%27%29%13%2
630
21st to endDay
12%325%30%22%8%
630
July1st to 10thDay
9%420%35%24%8%
621
11th to 20thDay
12%5%22%31%24%6%
618
21st to endDay
5%419%34%29%8%
684
August1st to 10thDay
10%424%32%22%8%
453
11th to 20thDay
9%320%34%28%6%
437
21st to endDay
8%9%21%29%22%11%
495
September1st to 10thDay
14%7%28%30%18%4
450
11th to 20thDay
19%7%23%28%20%4
450
21st to endDay
12%11%30%28%16%3
450
October1st to 10thDay
17%6%24%30%18%5%
338
11th to 20thDay
12%8%33%30%12%6%
270
21st to endDay
14%11%34%28%11%1
297
November1st to 10thDay
20%9%26%31%11%3
270
11th to 20thDay
15%11%30%29%12%2
252
21st to endDay
8%7%31%32%11%11%
180
December1st to 10thDay
7%6%31%31%17%8%
180
11th to 20thDay
8%6%37%33%14%2
180
21st to endDay
8%5%22%36%23%7%
198
January1st to 10thNight
10%7%33%35%14%2
950
11th to 20thNight
11%6%32%37%13%2
950
21st to endNight
11%9%30%37%12%2
889
February1st to 10thNight
10%9%25%34%19%2
760
11th to 20thNight
10%433%38%14%1
744
21st to endNight
8%421%41%20%5%
628
March1st to 10thNight
10%332%36%15%4
750
11th to 20thNight
9%6%30%38%16%2
720
21st to endNight
13%6%27%36%16%2
792
April1st to 10thNight
14%6%29%35%15%2
630
11th to 20thNight
13%9%31%35%11%1
533
21st to endNight
16%6%28%37%13%1
540
May1st to 10thNight
15%8%26%34%15%1
491
11th to 20thNight
12%5%29%36%17%1
354
21st to endNight
22%5%22%32%18%1
389
June1st to 10thNight
18%8%24%38%11%2
360
11th to 20thNight
16%5%32%31%16%
360
21st to endNight
10%5%26%37%19%3
360
July1st to 10thNight
8%219%48%22%1
350
11th to 20thNight
10%322%46%18%1
348
21st to endNight
6%320%47%23%2
394
August1st to 10thNight
9%223%41%22%2
362
11th to 20thNight
10%219%46%21%1
534
21st to endNight
9%420%43%23%1
594
September1st to 10thNight
12%422%44%16%2
576
11th to 20thNight
16%5%19%41%18%1
720
21st to endNight
11%5%29%38%14%3
720
October1st to 10thNight
16%326%36%17%2
720
11th to 20thNight
12%432%36%13%2
720
21st to endNight
11%8%34%35%12%1
792
November1st to 10thNight
17%7%32%33%9%1
896
11th to 20thNight
9%9%37%31%11%2
950
21st to endNight
9%5%35%37%13%1
950
December1st to 10thNight
11%7%30%34%15%3
950
11th to 20thNight
10%6%33%37%11%2
950
21st to endNight
11%431%36%15%3
1045
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