Grasslands National Park (West)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grasslands National Park (West) clear sky chart from 2005-11-06 to 2024-01-14.

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
41%
24153
16%
74474
10%
24112
47%
24112
25%
47058

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
34%
946
13%
2836
5%
946
41%
946
20%
1980
January11th to 20thNight
32%
920
16%
2750
8%
920
40%
920
20%
1899
January21st to endNight
28%
977
14%
2759
6%
977
36%
977
18%
1998
February1st to 10thNight
39%
720
14%
2340
11%
720
46%
720
20%
1580
February11th to 20thNight
34%
701
12%
2273
9%
700
39%
700
18%
1581
February21st to endNight
42%
592
16%
1899
11%
592
49%
592
20%
1305
March1st to 10thNight
35%
720
14%
2112
8%
720
41%
720
21%
1485
March11th to 20thNight
40%
720
16%
1980
9%
720
46%
720
26%
1341
March21st to endNight
37%
729
13%
2115
7%
729
43%
729
20%
1510
April1st to 10thNight
40%
540
17%
1800
12%
540
47%
540
22%
1156
April11th to 20thNight
35%
533
14%
1702
9%
533
40%
533
19%
1175
April21st to endNight
38%
540
15%
1558
11%
540
42%
540
23%
1072
May1st to 10thNight
47%
540
14%
1440
10%
540
50%
540
29%
953
May11th to 20thNight
50%
531
17%
1418
9%
531
53%
531
32%
913
May21st to endNight
43%
553
9%
1521
5%
551
46%
551
24%
1045
June1st to 10thNight
50%
360
9%
1260
8%
360
54%
360
23%
771
June11th to 20thNight
44%
360
8%
1260
6%
360
48%
360
27%
744
June21st to endNight
59%
360
10%
1260
10%
360
62%
360
35%
652
July1st to 10thNight
62%
350
11%
1225
11%
350
66%
350
40%
606
July11th to 20thNight
58%
348
16%
1218
12%
348
65%
348
42%
584
July21st to endNight
63%
557
22%
1456
15%
526
68%
526
55%
733
August1st to 10thNight
62%
537
22%
1427
16%
534
66%
534
49%
769
August11th to 20thNight
65%
534
25%
1602
20%
534
70%
534
46%
841
August21st to endNight
58%
594
26%
1848
21%
594
64%
594
40%
986
September1st to 10thNight
55%
540
23%
1800
22%
540
62%
540
37%
960
September11th to 20thNight
52%
540
25%
1800
23%
540
60%
540
33%
1006
September21st to endNight
50%
704
26%
2058
17%
704
59%
704
38%
1155
October1st to 10thNight
45%
720
21%
2160
13%
720
51%
720
27%
1343
October11th to 20thNight
42%
720
23%
2160
10%
720
51%
720
29%
1305
October21st to endNight
33%
913
18%
2515
7%
913
42%
913
24%
1704
November1st to 10thNight
31%
925
16%
2590
7%
925
38%
925
21%
1811
November11th to 20thNight
33%
950
19%
2660
9%
950
42%
950
25%
1765
November21st to endNight
30%
950
14%
2660
6%
950
36%
950
24%
1819
December1st to 10thNight
33%
950
12%
2660
6%
950
38%
950
19%
1944
December11th to 20thNight
31%
949
14%
3425
7%
949
39%
949
18%
2257
December21st to endNight
33%
1030
11%
4927
7%
1026
40%
1026
17%
2310

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
8%7%37%6%35%5%6%8%41%
74757
Night
7%7%47%6%35%5%6%8%42%
75001
TransparencyDay
40%7%15%24%12%2
74447
Night
39%7%15%24%13%2
74833
SeeingDay
12%9%29%30%16%4
14599
Night
11%8%32%36%13%1
24176

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 10thDay
6%8%49%7%46%7%6%7%34%
1329
11th to 20thDay
412%5%11%9%47%5%6%7%31%
1286
21st to endDay
410%5%9%9%6%7%8%6%9%27%
1611
February1st to 10thDay
8%11%6%10%10%5%7%5%7%6%27%
1620
11th to 20thDay
6%10%6%13%10%5%5%6%8%8%23%
1575
21st to endDay
5%11%5%10%11%5%7%8%6%7%26%
1356
March1st to 10thDay
6%9%5%12%8%5%6%7%6%9%28%
1844
11th to 20thDay
5%9%5%9%8%5%7%6%6%8%33%
1980
21st to endDay
7%11%5%10%8%46%6%5%9%28%
2240
April1st to 10thDay
8%8%38%7%46%6%5%9%34%
2160
11th to 20thDay
13%13%47%7%45%6%6%6%30%
2204
21st to endDay
14%9%36%6%35%5%5%8%36%
2402
May1st to 10thDay
14%11%36%6%345%5%8%35%
2520
11th to 20thDay
10%6%36%7%45%5%5%8%42%
2478
21st to endDay
19%7%36%6%345%6%7%33%
2751
June1st to 10thDay
14%5%35%6%36%6%6%9%37%
2700
11th to 20thDay
14%5%35%6%36%6%6%8%38%
2700
21st to endDay
6%3245%35%5%7%9%50%
2700
July1st to 10thDay
4324435%6%7%8%54%
2700
11th to 20thDay
4314435%47%9%57%
2700
21st to endDay
421332345%7%65%
2773
August1st to 10thDay
6%425%335%45%8%56%
2503
11th to 20thDay
6%41443345%9%57%
2299
21st to endDay
8%3144245%5%8%58%
2507
September1st to 10thDay
9%6%245%345%6%6%51%
2160
11th to 20thDay
11%6%25%42445%7%50%
2160
21st to endDay
12%6%2432345%7%51%
1900
October1st to 10thDay
12%9%36%42436%7%44%
1800
11th to 20thDay
7%7%47%6%35%5%5%8%43%
1800
21st to endDay
6%10%26%6%36%5%7%8%41%
1819
November1st to 10thDay
10%13%46%6%35%45%7%37%
1488
11th to 20thDay
5%7%5%7%7%36%7%6%7%40%
1520
21st to endDay
6%10%5%8%6%35%5%6%9%37%
1520
December1st to 10thDay
7%8%6%10%11%5%6%6%6%6%29%
1520
11th to 20thDay
49%6%11%8%46%5%6%7%34%
1690
21st to endDay
5%8%37%6%346%6%8%45%
2442
January1st to 10thNight
48%5%9%7%5%6%7%8%8%33%
2836
11th to 20thNight
5%8%49%8%5%6%6%6%9%34%
2750
21st to endNight
49%5%10%10%47%7%7%9%29%
2759
February1st to 10thNight
5%8%5%9%9%46%5%6%8%35%
2340
11th to 20thNight
410%5%10%8%5%6%6%6%9%31%
2272
21st to endNight
49%5%11%8%45%6%6%8%34%
1899
March1st to 10thNight
6%9%6%10%7%46%5%6%9%34%
2112
11th to 20thNight
6%7%48%6%35%6%6%10%38%
1980
21st to endNight
8%9%5%9%8%46%7%6%9%30%
2115
April1st to 10thNight
7%7%46%7%46%5%7%8%39%
1800
11th to 20thNight
13%10%47%6%35%6%6%8%34%
1702
21st to endNight
10%8%37%7%37%5%6%7%36%
1558
May1st to 10thNight
11%8%26%5%36%45%7%43%
1440
11th to 20thNight
10%5%246%36%5%6%9%44%
1417
21st to endNight
14%7%36%5%346%6%9%36%
1521
June1st to 10thNight
13%5%25%5%35%37%9%42%
1260
11th to 20thNight
14%334335%6%7%8%44%
1260
21st to endNight
5%3245%345%49%56%
1260
July1st to 10thNight
6%223325%5%5%8%59%
1260
11th to 20thNight
34134235%7%8%60%
1260
21st to endNight
421342346%9%63%
1542
August1st to 10thNight
5%31343435%8%60%
1435
11th to 20thNight
6%31332345%8%61%
1602
21st to endNight
9%32432345%7%59%
1848
September1st to 10thNight
10%42343345%7%56%
1800
11th to 20thNight
9%6%2442345%7%53%
1800
21st to endNight
9%5%1442345%10%52%
2058
October1st to 10thNight
10%7%35%5%3435%8%47%
2160
11th to 20thNight
8%7%36%5%345%6%8%47%
2160
21st to endNight
9%8%47%5%35%5%6%8%40%
2515
November1st to 10thNight
10%10%47%7%35%5%5%6%37%
2590
11th to 20thNight
47%5%7%8%35%6%6%8%41%
2660
21st to endNight
5%9%49%6%45%5%5%8%39%
2660
December1st to 10thNight
6%9%5%9%11%5%7%5%6%8%30%
2660
11th to 20thNight
5%9%5%10%6%45%6%6%8%36%
3496
21st to endNight
46%35%5%345%5%7%53%
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
45%9%16%21%8%
1329
11th to 20thDay
52%6%17%18%6%2
1286
21st to endDay
51%9%16%17%7%
1611
February1st to 10thDay
56%6%13%16%8%
1620
11th to 20thDay
56%6%16%13%8%1
1584
21st to endDay
55%7%16%12%9%1
1356
March1st to 10thDay
51%9%17%17%6%
1844
11th to 20thDay
48%7%18%21%5%1
1980
21st to endDay
51%9%18%16%6%
2240
April1st to 10thDay
46%8%15%21%9%
2160
11th to 20thDay
53%6%14%19%7%1
2207
21st to endDay
46%6%15%26%8%1
2402
May1st to 10thDay
47%6%12%22%12%1
2520
11th to 20thDay
40%7%15%27%11%
2482
21st to endDay
49%8%14%20%9%
2751
June1st to 10thDay
42%9%17%21%10%1
2700
11th to 20thDay
42%8%15%22%12%1
2700
21st to endDay
29%7%16%33%13%1
2700
July1st to 10thDay
25%8%16%31%15%5%
2626
11th to 20thDay
23%7%16%25%24%6%
2619
21st to endDay
19%5%11%33%27%6%
2619
August1st to 10thDay
27%7%13%31%19%5%
2487
11th to 20thDay
25%6%17%30%18%4
2299
21st to endDay
24%6%12%30%24%5%
2507
September1st to 10thDay
33%5%11%29%17%5%
2160
11th to 20thDay
33%6%15%29%14%3
2160
21st to endDay
34%413%31%16%2
1900
October1st to 10thDay
40%6%17%27%11%
1800
11th to 20thDay
39%6%15%28%11%1
1800
21st to endDay
39%7%19%26%9%
1819
November1st to 10thDay
47%6%16%22%8%1
1488
11th to 20thDay
42%8%18%24%8%1
1520
21st to endDay
44%8%20%21%7%1
1520
December1st to 10thDay
53%8%14%19%5%1
1520
11th to 20thDay
47%7%22%20%3
1689
21st to endDay
36%6%15%22%14%7%
2442
January1st to 10thNight
45%9%18%19%7%1
2836
11th to 20thNight
46%7%18%22%6%1
2750
21st to endNight
50%7%17%18%8%
2759
February1st to 10thNight
47%6%16%20%9%1
2340
11th to 20thNight
48%8%17%17%9%1
2273
21st to endNight
47%7%12%21%12%1
1899
March1st to 10thNight
47%8%17%18%10%
2112
11th to 20thNight
41%7%18%24%7%1
1980
21st to endNight
48%8%17%19%8%
2115
April1st to 10thNight
42%7%15%25%11%1
1800
11th to 20thNight
48%7%11%21%10%3
1702
21st to endNight
46%6%13%24%10%1
1558
May1st to 10thNight
39%7%11%28%14%1
1440
11th to 20thNight
35%8%13%27%17%1
1418
21st to endNight
43%8%15%24%8%1
1521
June1st to 10thNight
38%8%17%25%12%1
1260
11th to 20thNight
36%7%15%26%15%1
1260
21st to endNight
26%7%18%31%17%1
1260
July1st to 10thNight
23%6%13%32%20%6%
1225
11th to 20thNight
22%6%17%24%23%8%
1218
21st to endNight
18%414%30%29%6%
1456
August1st to 10thNight
22%414%31%21%7%
1427
11th to 20thNight
22%6%13%33%22%4
1602
21st to endNight
26%5%10%24%28%7%
1848
September1st to 10thNight
29%410%29%19%8%
1800
11th to 20thNight
32%5%11%28%19%5%
1800
21st to endNight
29%5%12%32%20%3
2058
October1st to 10thNight
37%7%13%25%17%1
2160
11th to 20thNight
35%6%14%29%15%1
2160
21st to endNight
41%8%15%24%11%1
2515
November1st to 10thNight
47%6%15%20%10%2
2590
11th to 20thNight
41%7%19%24%9%1
2660
21st to endNight
44%7%22%20%8%
2660
December1st to 10thNight
51%7%17%16%8%1
2660
11th to 20thNight
44%8%21%22%41
3497
21st to endNight
31%5%13%28%17%6%
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
9%9%31%29%14%7%
180
11th to 20thDay
8%11%30%26%22%4
169
21st to endDay
12%11%33%29%14%
264
February1st to 10thDay
13%10%40%28%7%1
240
11th to 20thDay
9%10%37%30%12%2
240
21st to endDay
12%434%36%9%6%
198
March1st to 10thDay
11%10%35%31%14%1
284
11th to 20thDay
9%9%37%28%13%4
420
21st to endDay
12%10%31%26%18%3
462
April1st to 10thDay
11%13%37%30%9%
420
11th to 20thDay
16%17%32%26%8%1
412
21st to endDay
20%11%29%28%10%1
482
May1st to 10thDay
18%8%22%29%19%4
603
11th to 20thDay
14%6%26%29%19%5%
625
21st to endDay
18%9%23%24%19%6%
679
June1st to 10thDay
14%11%24%28%20%3
630
11th to 20thDay
15%11%35%23%13%3
630
21st to endDay
10%7%24%31%22%5%
630
July1st to 10thDay
6%325%40%20%5%
621
11th to 20thDay
5%6%28%38%19%4
618
21st to endDay
4425%37%24%5%
684
August1st to 10thDay
8%5%22%38%21%7%
622
11th to 20thDay
9%6%22%32%22%10%
437
21st to endDay
8%6%23%36%21%6%
495
September1st to 10thDay
12%9%30%33%13%3
450
11th to 20thDay
14%7%25%30%21%3
450
21st to endDay
14%10%28%27%16%5%
356
October1st to 10thDay
24%10%19%22%21%4
270
11th to 20thDay
9%7%40%27%14%3
270
21st to endDay
13%14%37%24%9%2
297
November1st to 10thDay
19%13%32%27%10%
270
11th to 20thDay
10%16%35%28%10%1
270
21st to endDay
11%11%36%28%11%3
270
December1st to 10thDay
10%9%38%32%10%2
270
11th to 20thDay
10%15%34%32%7%2
183
21st to endDay
10%7%33%28%19%4
198
January1st to 10thNight
7%10%36%34%11%2
950
11th to 20thNight
10%11%35%33%9%2
920
21st to endNight
8%12%39%30%10%1
977
February1st to 10thNight
7%7%34%34%16%2
720
11th to 20thNight
10%6%38%36%9%1
704
21st to endNight
7%6%29%36%18%4
592
March1st to 10thNight
10%8%35%35%12%1
720
11th to 20thNight
10%7%35%34%11%2
720
21st to endNight
12%7%32%35%12%2
729
April1st to 10thNight
10%6%34%38%10%1
540
11th to 20thNight
20%7%33%31%9%
533
21st to endNight
14%9%31%38%9%
540
May1st to 10thNight
15%6%25%39%14%1
540
11th to 20thNight
12%428%38%16%2
531
21st to endNight
18%7%26%30%18%2
553
June1st to 10thNight
16%8%21%36%18%1
360
11th to 20thNight
16%6%29%38%11%
360
21st to endNight
7%6%23%44%19%1
360
July1st to 10thNight
6%423%48%18%1
350
11th to 20thNight
6%330%49%12%1
348
21st to endNight
4326%48%18%1
557
August1st to 10thNight
7%323%47%19%2
537
11th to 20thNight
7%322%45%22%1
534
21st to endNight
9%5%24%42%20%1
594
September1st to 10thNight
11%326%40%19%1
540
11th to 20thNight
11%427%38%18%1
540
21st to endNight
11%5%30%37%15%1
704
October1st to 10thNight
13%7%29%35%16%1
720
11th to 20thNight
12%9%31%34%14%1
720
21st to endNight
13%10%36%33%7%1
913
November1st to 10thNight
16%10%36%29%9%
925
11th to 20thNight
8%12%38%31%10%1
950
21st to endNight
9%11%40%31%9%
950
December1st to 10thNight
9%9%35%33%14%1
950
11th to 20thNight
9%9%37%34%10%1
950
21st to endNight
13%6%35%33%12%2
1045
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