Agassiz
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Agassiz clear sky chart from 2005-11-05 to 2017-11-30.

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
28%
14747
8%
47636
5%
14718
31%
14718
12%
37032

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
16%
750
10%
2686
5%
746
23%
746
8%
2198
January16th to endNight
17%
769
8%
2694
4%
769
23%
769
9%
2164
February1st to 15thNight
14%
698
5%
2309
2%
697
18%
697
7%
1922
February16th to endNight
18%
632
11%
2014
4%
632
27%
632
10%
1598
March1st to 15thNight
17%
720
4%
2097
2%
720
19%
720
8%
1775
March16th to endNight
16%
768
4%
2046
1%
768
18%
768
8%
1795
April1st to 15thNight
24%
719
4%
1799
2%
719
25%
719
9%
1563
April16th to endNight
25%
507
6%
1587
4%
507
28%
507
10%
1315
May1st to 15thNight
38%
360
10%
1440
14%
360
42%
360
12%
1041
May16th to endNight
43%
374
5%
1496
7%
374
45%
374
10%
1152
June1st to 15thNight
37%
360
1%
1281
1%
360
37%
360
12%
1001
June16th to endNight
43%
360
4%
1260
2%
360
43%
360
15%
926
July1st to 15thNight
63%
340
6%
1190
6%
340
64%
340
29%
699
July16th to endNight
66%
376
13%
1375
20%
354
69%
354
31%
717
August1st to 15thNight
72%
390
14%
1462
19%
388
72%
388
31%
768
August16th to endNight
61%
639
17%
1785
13%
639
62%
639
32%
1111
September1st to 15thNight
55%
720
18%
1800
9%
720
57%
720
35%
1169
September16th to endNight
42%
716
16%
1962
12%
716
44%
716
20%
1447
October1st to 15thNight
31%
720
10%
2160
7%
720
35%
720
16%
1602
October16th to endNight
23%
768
8%
2412
5%
768
28%
768
10%
1936
November1st to 15thNight
8%
760
5%
2645
1%
760
13%
760
5%
2330
November16th to endNight
14%
780
5%
2730
3%
780
17%
780
6%
2280
December1st to 15thNight
12%
721
8%
2526
2%
721
19%
721
8%
2045
December16th to endNight
7%
800
5%
2880
1%
800
12%
800
5%
2478

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
24%11%36%5%24345%28%
48801
Night
25%11%35%5%24345%28%
47792
Cloud CoverDay
26%11%35%5%2434427%
48801
Night
26%12%35%5%24335%27%
47795
TransparencyDay
62%6%10%14%6%1
48461
Night
61%6%10%13%6%1
47636
SeeingDay
33%14%26%19%5%1
6208
Night
33%8%25%21%9%
14754

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 15thDay
35%12%35%43433420%
1253
16th to endDay
32%14%34423335%23%
1527
February1st to 15thDay
30%13%46%6%34335%18%
1555
16th to endDay
22%16%47%435%35%5%21%
1460
March1st to 15thDay
29%17%5%7%7%35%43313%
1863
16th to endDay
27%18%5%7%5%35%44413%
2178
April1st to 15thDay
27%18%48%434435%14%
2149
16th to endDay
26%15%47%5%35%5%45%16%
2371
May1st to 15thDay
23%10%46%5%3445%5%27%
2511
16th to endDay
27%10%46%5%34445%22%
2615
June1st to 15thDay
32%10%47%5%23335%21%
2677
16th to endDay
26%8%37%5%34345%26%
2700
July1st to 15thDay
14%5%24323345%50%
2700
16th to endDay
12%5%24323345%52%
2699
August1st to 15thDay
14%413423346%50%
2490
16th to endDay
15%4245%2335%7%45%
2417
September1st to 15thDay
12%5%1432344452%
2160
16th to endDay
24%7%25%5%24335%34%
1994
October1st to 15thDay
23%8%26%5%34446%31%
1800
16th to endDay
31%9%35%5%23446%23%
1812
November1st to 15thDay
41%13%46%5%2224312%
1540
16th to endDay
34%13%45%5%1334418%
1555
December1st to 15thDay
24%16%48%5%2433322%
1431
16th to endDay
30%19%47%43433215%
1344
January1st to 15thNight
36%12%3442333421%
2686
16th to endNight
29%14%45%5%24336%22%
2694
February1st to 15thNight
28%14%37%5%34445%19%
2297
16th to endNight
23%15%45%5%24335%28%
2014
March1st to 15thNight
29%14%46%6%2444418%
2097
16th to endNight
29%15%36%435%43417%
2042
April1st to 15thNight
24%16%48%5%35%445%18%
1799
16th to endNight
26%12%47%5%345%45%20%
1587
May1st to 15thNight
20%7%25%6%245%5%6%33%
1439
16th to endNight
22%9%26%5%35%45%6%29%
1496
June1st to 15thNight
23%10%46%5%245%45%27%
1281
16th to endNight
20%7%35%6%3435%6%32%
1260
July1st to 15thNight
10%5%23412446%55%
1260
16th to endNight
10%413313236%58%
1470
August1st to 15thNight
9%31221235%8%58%
1470
16th to endNight
9%4145%2345%8%49%
1785
September1st to 15thNight
10%413434446%53%
1800
16th to endNight
20%7%25%435%346%35%
1962
October1st to 15thNight
22%6%36%5%34435%33%
2160
16th to endNight
30%8%35%5%34446%23%
2412
November1st to 15thNight
39%12%36%43423414%
2645
16th to endNight
34%13%26%6%2332419%
2730
December1st to 15thNight
28%13%46%5%24435%22%
2526
16th to endNight
31%18%47%5%2333317%
2880

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
36%12%35%5%2333419%
1253
16th to endDay
33%14%3343333422%
1527
February1st to 15thDay
29%15%46%5%24335%18%
1555
16th to endDay
22%20%35%5%4445%420%
1460
March1st to 15thDay
29%19%5%6%6%3443312%
1863
16th to endDay
27%21%47%6%3444411%
2178
April1st to 15thDay
28%21%47%42444412%
2149
16th to endDay
28%17%37%5%35%44414%
2371
May1st to 15thDay
25%10%46%43435%5%25%
2511
16th to endDay
31%10%46%6%34345%20%
2615
June1st to 15thDay
36%10%45%5%23235%19%
2677
16th to endDay
29%8%36%6%34345%24%
2700
July1st to 15thDay
15%5%24313445%48%
2700
16th to endDay
14%6%23323345%50%
2699
August1st to 15thDay
15%41343445%5%48%
2490
16th to endDay
16%5%245%2345%7%43%
2417
September1st to 15thDay
14%425%42333451%
2160
16th to endDay
26%7%25%423335%33%
1994
October1st to 15thDay
24%9%25%5%24445%29%
1800
16th to endDay
33%9%35%5%2335%5%21%
1812
November1st to 15thDay
43%14%46%42333311%
1540
16th to endDay
35%13%35%5%2324318%
1555
December1st to 15thDay
25%17%46%6%2333421%
1431
16th to endDay
29%22%5%6%5%2322315%
1344
January1st to 15thNight
36%13%3432232420%
2685
16th to endNight
29%15%35%5%24336%20%
2694
February1st to 15thNight
28%14%47%5%23445%18%
2297
16th to endNight
23%17%45%423335%25%
2014
March1st to 15thNight
29%17%46%5%2434417%
2097
16th to endNight
29%17%46%5%3433416%
2046
April1st to 15thNight
26%18%47%5%34345%17%
1799
16th to endNight
28%13%46%7%23445%19%
1587
May1st to 15thNight
22%9%35%5%15%5%45%31%
1439
16th to endNight
25%9%35%5%35%5%46%27%
1496
June1st to 15thNight
26%10%36%5%35%435%25%
1281
16th to endNight
22%6%36%6%2445%6%31%
1260
July1st to 15thNight
11%5%24322436%53%
1260
16th to endNight
12%413313335%57%
1470
August1st to 15thNight
9%31322246%6%57%
1470
16th to endNight
10%425%424448%47%
1785
September1st to 15thNight
11%4145%24346%52%
1800
16th to endNight
22%7%35%434446%34%
1962
October1st to 15thNight
23%8%26%5%24435%33%
2160
16th to endNight
32%8%36%5%24346%21%
2412
November1st to 15thNight
41%12%45%5%2424413%
2645
16th to endNight
35%15%35%5%2323418%
2730
December1st to 15thNight
28%14%46%5%23435%21%
2526
16th to endNight
29%20%5%6%5%3333316%
2880

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
70%37%11%41
1253
16th to endDay
65%5%8%12%5%2
1527
February1st to 15thDay
71%5%7%8%5%1
1555
16th to endDay
69%5%6%13%3
1460
March1st to 15thDay
78%5%6%7%1
1863
16th to endDay
79%5%7%6%
2178
April1st to 15thDay
78%7%6%7%1
2149
16th to endDay
74%6%9%6%2
2371
May1st to 15thDay
62%6%10%13%5%
2511
16th to endDay
68%7%11%9%1
2619
June1st to 15thDay
70%5%11%9%21
2677
16th to endDay
65%5%11%14%3
2700
July1st to 15thDay
41%6%12%25%12%2
2541
16th to endDay
36%6%13%29%12%2
2531
August1st to 15thDay
38%6%16%25%9%2
2473
16th to endDay
41%7%17%24%8%1
2417
September1st to 15thDay
38%5%11%22%18%3
2160
16th to endDay
55%5%12%14%10%2
1994
October1st to 15thDay
57%6%11%14%8%
1800
16th to endDay
64%5%11%12%5%
1812
November1st to 15thDay
79%46%6%21
1540
16th to endDay
70%6%6%8%5%2
1555
December1st to 15thDay
69%5%6%10%7%
1431
16th to endDay
77%35%6%5%
1344
January1st to 15thNight
69%45%12%6%1
2686
16th to endNight
65%6%7%10%6%3
2694
February1st to 15thNight
69%6%8%9%41
2309
16th to endNight
64%5%8%15%41
2014
March1st to 15thNight
71%5%11%8%2
2097
16th to endNight
74%6%10%7%1
2046
April1st to 15thNight
72%5%10%8%2
1799
16th to endNight
67%6%11%11%3
1587
May1st to 15thNight
55%7%14%16%5%
1440
16th to endNight
59%9%15%12%2
1496
June1st to 15thNight
61%7%15%11%31
1281
16th to endNight
54%8%17%16%21
1260
July1st to 15thNight
33%7%18%24%14%2
1190
16th to endNight
30%5%14%31%15%2
1375
August1st to 15thNight
28%7%21%27%13%2
1462
16th to endNight
35%7%19%25%10%2
1785
September1st to 15thNight
35%6%13%20%21%3
1800
16th to endNight
52%5%11%18%8%2
1962
October1st to 15thNight
54%6%10%17%9%
2160
16th to endNight
64%6%9%12%6%
2412
November1st to 15thNight
76%6%6%6%11
2645
16th to endNight
71%46%8%7%1
2730
December1st to 15thNight
67%6%8%11%5%
2526
16th to endNight
74%5%6%6%5%1
2880

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
6%23%28%21%18%1
60
16th to endDay
48%7%21%17%4
64
February1st to 15thDay
44%16%17%16%4
215
16th to endDay
33%16%26%17%4
218
March1st to 15thDay
47%19%24%7%1
270
16th to endDay
43%21%21%11%2
288
April1st to 15thDay
46%17%17%14%21
269
16th to endDay
46%15%19%14%21
270
May1st to 15thDay
36%16%26%18%2
288
16th to endDay
42%12%17%16%8%2
330
June1st to 15thDay
39%14%22%18%5%
472
16th to endDay
32%16%27%17%5%
495
July1st to 15thDay
22%12%31%28%41
475
16th to endDay
17%13%37%25%33
368
August1st to 15thDay
17%8%30%30%10%3
315
16th to endDay
17%10%37%25%8%
332
September1st to 15thDay
21%14%28%25%7%1
315
16th to endDay
29%9%29%21%7%1
315
October1st to 15thDay
30%14%30%19%3
315
16th to endDay
41%7%24%21%6%
228
November1st to 15thDay
54%13%22%6%11
93
16th to endDay
56%7%16%8%7%2
89
December1st to 15thDay
46%15%30%6%1
60
16th to endDay
42%7%31%15%3
64
January1st to 15thNight
43%11%26%17%
750
16th to endNight
38%8%32%18%1
769
February1st to 15thNight
37%9%33%15%3
704
16th to endNight
35%11%31%18%3
632
March1st to 15thNight
40%11%27%16%4
720
16th to endNight
41%9%30%14%4
768
April1st to 15thNight
39%9%22%23%5%
719
16th to endNight
37%6%26%23%5%
507
May1st to 15thNight
27%5%22%30%13%
360
16th to endNight
29%418%30%16%
375
June1st to 15thNight
32%5%21%22%17%1
360
16th to endNight
25%6%20%32%15%
360
July1st to 15thNight
14%315%35%30%1
340
16th to endNight
12%215%36%30%2
376
August1st to 15thNight
11%110%33%40%2
390
16th to endNight
13%316%38%26%
639
September1st to 15thNight
13%423%28%28%1
720
16th to endNight
28%5%20%31%14%
716
October1st to 15thNight
29%7%28%26%8%
720
16th to endNight
39%8%26%21%4
768
November1st to 15thNight
50%8%30%9%1
760
16th to endNight
45%11%26%13%2
780
December1st to 15thNight
39%10%33%15%
721
16th to endNight
42%14%33%10%
800
Page generated at 2017-12-01 09:13:36. Version ac04

Copyright 2017 A. Danko


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