West Grand High School
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the West Grand High School clear sky chart from 2005-11-05 to 2018-08-29.

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
53%
17227
21%
50625
16%
17187
57%
17187
32%
30632

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
41%
966
14%
2709
11%
963
43%
963
23%
1863
January16th to endNight
42%
832
21%
2704
18%
832
48%
832
25%
1706
February1st to 15thNight
35%
759
12%
2483
9%
759
40%
759
19%
1729
February16th to endNight
35%
684
19%
2059
10%
684
44%
684
24%
1386
March1st to 15thNight
47%
780
22%
2230
14%
780
53%
780
34%
1342
March16th to endNight
46%
776
20%
2232
12%
776
53%
776
31%
1400
April1st to 15thNight
42%
584
17%
1948
13%
584
49%
584
27%
1169
April16th to endNight
45%
579
20%
1929
17%
579
53%
579
27%
1186
May1st to 15thNight
51%
585
19%
1716
15%
585
56%
585
26%
1123
May16th to endNight
60%
610
19%
1626
14%
609
65%
609
37%
969
June1st to 15thNight
68%
585
26%
1560
19%
585
72%
585
57%
780
June16th to endNight
74%
585
28%
1560
24%
585
76%
585
59%
763
July1st to 15thNight
82%
555
19%
1480
17%
555
82%
555
46%
820
July16th to endNight
82%
612
19%
1632
18%
579
83%
579
44%
887
August1st to 15thNight
77%
575
20%
1724
20%
572
78%
572
40%
924
August16th to endNight
78%
615
26%
2050
30%
615
79%
615
35%
1132
September1st to 15thNight
76%
540
28%
1800
30%
540
80%
540
40%
925
September16th to endNight
72%
591
33%
1950
33%
591
76%
591
46%
956
October1st to 15thNight
56%
720
25%
2160
19%
720
60%
720
37%
1243
October16th to endNight
57%
768
32%
2304
22%
768
64%
768
40%
1256
November1st to 15thNight
47%
936
25%
2456
14%
936
52%
936
39%
1474
November16th to endNight
48%
975
25%
2671
16%
975
53%
975
39%
1565
December1st to 15thNight
37%
975
12%
2730
7%
975
40%
975
23%
1897
December16th to endNight
33%
1040
15%
2912
10%
1040
37%
1040
19%
2137

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
36%36%5%35%5%6%8%45%
51639
Night
26%36%5%2445%7%51%
50804
TransparencyDay
35%8%13%22%15%4
51320
Night
32%7%14%24%15%4
50625
SeeingDay
8%14%28%27%16%3
7107
Night
5%7%25%39%19%1
17235

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
8%5%9%7%46%6%6%9%34%
1569
16th to endDay
19%6%10%5%35%448%40%
1872
February1st to 15thDay
110%6%10%7%35%7%6%6%34%
1710
16th to endDay
7%5%8%7%47%6%7%7%37%
1701
March1st to 15thDay
17%5%6%6%35%45%6%47%
2057
16th to endDay
29%47%5%345%6%8%40%
2343
April1st to 15thDay
310%36%5%35%46%8%41%
2330
16th to endDay
39%36%6%45%6%7%8%36%
2306
May1st to 15thDay
6%8%25%7%36%5%7%8%37%
2562
16th to endDay
5%5%26%6%46%6%6%9%41%
2840
June1st to 15thDay
32133245%6%9%56%
2730
16th to endDay
211232345%7%64%
2730
July1st to 15thDay
4314436%6%6%10%48%
2730
16th to endDay
4315%5%47%5%7%9%44%
2782
August1st to 15thDay
6%425%6%35%6%6%9%41%
2479
16th to endDay
34146%36%6%7%9%46%
2449
September1st to 15thDay
5%324425%45%7%54%
2160
16th to endDay
5%41442345%7%57%
2009
October1st to 15thDay
5%7%245%24445%53%
1800
16th to endDay
46%25%423446%54%
1920
November1st to 15thDay
26%3442345%7%53%
1718
16th to endDay
26%36%424346%56%
1618
December1st to 15thDay
110%5%10%7%45%6%6%7%34%
1560
16th to endDay
18%411%10%47%6%6%6%32%
1664
January1st to 15thNight
110%6%8%7%34447%42%
2709
16th to endNight
110%6%9%6%23445%45%
2704
February1st to 15thNight
19%6%9%7%245%5%7%38%
2472
16th to endNight
18%6%10%6%3445%6%41%
2059
March1st to 15thNight
17%37%423446%55%
2230
16th to endNight
28%35%42445%6%50%
2232
April1st to 15thNight
46%35%5%245%6%9%48%
1948
16th to endNight
5%9%34434447%48%
1929
May1st to 15thNight
5%6%25%6%35%46%8%44%
1715
16th to endNight
43134245%6%10%51%
1625
June1st to 15thNight
11223348%69%
1560
16th to endNight
211231245%8%68%
1560
July1st to 15thNight
21343446%12%55%
1560
16th to endNight
2312426%6%7%8%55%
1735
August1st to 15thNight
22145%3446%10%54%
1733
16th to endNight
33235%246%5%8%54%
2050
September1st to 15thNight
431342345%7%58%
1800
16th to endNight
3313322347%66%
1950
October1st to 15thNight
5%5%14324447%56%
2160
16th to endNight
5%6%23323336%60%
2304
November1st to 15thNight
36%3441335%6%56%
2456
16th to endNight
17%35%322347%57%
2671
December1st to 15thNight
29%48%7%44446%42%
2730
16th to endNight
17%6%12%8%35%5%5%7%36%
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
44%10%18%19%5%1
1570
16th to endDay
42%8%18%20%9%
1872
February1st to 15thDay
48%11%16%15%7%
1710
16th to endDay
44%9%15%20%9%1
1701
March1st to 15thDay
37%6%15%24%14%
2057
16th to endDay
40%8%13%25%9%2
2343
April1st to 15thDay
41%7%14%20%12%3
2330
16th to endDay
44%8%12%21%10%1
2306
May1st to 15thDay
42%11%11%21%12%
2562
16th to endDay
38%9%12%21%15%2
2844
June1st to 15thDay
23%7%11%18%27%11%
2730
16th to endDay
17%47%22%30%17%
2730
July1st to 15thDay
30%9%11%16%18%13%
2581
16th to endDay
32%9%14%21%14%6%
2622
August1st to 15thDay
36%9%13%16%15%7%
2464
16th to endDay
30%9%12%22%18%5%
2449
September1st to 15thDay
28%7%10%19%23%11%
2160
16th to endDay
26%6%9%30%23%3
2009
October1st to 15thDay
33%5%9%26%21%3
1800
16th to endDay
29%6%13%31%16%2
1920
November1st to 15thDay
32%5%14%25%19%2
1718
16th to endDay
28%7%18%33%10%1
1618
December1st to 15thDay
46%10%16%20%6%
1560
16th to endDay
52%9%10%20%6%1
1664
January1st to 15thNight
42%8%17%21%8%1
2709
16th to endNight
40%6%15%24%10%1
2704
February1st to 15thNight
43%11%16%19%7%
2483
16th to endNight
42%7%12%23%11%1
2059
March1st to 15thNight
32%6%15%30%14%
2230
16th to endNight
34%7%15%32%9%1
2232
April1st to 15thNight
33%9%16%23%15%2
1948
16th to endNight
37%6%12%24%18%
1929
May1st to 15thNight
37%9%12%27%11%
1716
16th to endNight
26%9%16%28%15%3
1626
June1st to 15thNight
14%5%13%25%26%13%
1560
16th to endNight
15%48%22%29%20%
1560
July1st to 15thNight
20%9%20%17%17%14%
1480
16th to endNight
22%7%24%19%16%9%
1632
August1st to 15thNight
23%8%19%20%17%10%
1724
16th to endNight
26%9%12%20%24%7%
2050
September1st to 15thNight
24%5%13%19%22%14%
1800
16th to endNight
20%5%10%32%26%4
1950
October1st to 15thNight
28%6%10%27%20%4
2160
16th to endNight
26%411%33%19%3
2304
November1st to 15thNight
29%5%12%28%19%3
2456
16th to endNight
27%6%16%32%15%1
2671
December1st to 15thNight
43%9%17%20%9%
2730
16th to endNight
49%9%13%20%6%
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
8%13%23%37%12%3
135
16th to endDay
6%10%32%31%17%2
144
February1st to 15thDay
14%22%33%23%5%
135
16th to endDay
6%23%34%24%10%
120
March1st to 15thDay
11%22%33%24%7%
242
16th to endDay
11%36%35%13%3
352
April1st to 15thDay
13%33%30%14%6%1
329
16th to endDay
14%32%31%14%5%2
318
May1st to 15thDay
13%17%28%26%12%1
442
16th to endDay
9%13%29%25%18%3
597
June1st to 15thDay
5%11%28%31%20%3
570
16th to endDay
310%26%32%24%2
570
July1st to 15thDay
8%417%31%34%4
550
16th to endDay
6%322%33%28%6%
497
August1st to 15thDay
10%6%30%32%15%3
359
16th to endDay
5%7%25%37%17%5%
385
September1st to 15thDay
8%15%29%25%14%6%
315
16th to endDay
8%10%31%26%17%5%
219
October1st to 15thDay
11%11%25%25%20%5%
135
16th to endDay
10%11%30%27%18%
144
November1st to 15thDay
313%31%23%20%7%
135
16th to endDay
10%19%36%27%6%
135
December1st to 15thDay
5%18%35%32%7%
135
16th to endDay
219%39%32%5%
144
January1st to 15thNight
6%15%26%36%13%
968
16th to endNight
5%10%31%39%11%
832
February1st to 15thNight
6%9%36%39%7%
764
16th to endNight
410%38%39%6%
684
March1st to 15thNight
49%32%40%12%
780
16th to endNight
5%7%35%43%8%
776
April1st to 15thNight
6%12%33%38%8%
584
16th to endNight
9%9%30%35%13%
579
May1st to 15thNight
9%6%24%42%15%1
585
16th to endNight
7%421%39%25%1
611
June1st to 15thNight
2421%46%23%1
585
16th to endNight
3117%49%27%
585
July1st to 15thNight
215%37%50%2
555
16th to endNight
2437%51%3
612
August1st to 15thNight
47%41%44%1
575
16th to endNight
5%6%40%42%4
615
September1st to 15thNight
5%10%49%30%3
540
16th to endNight
4314%40%34%2
591
October1st to 15thNight
8%5%25%40%18%2
720
16th to endNight
9%6%22%41%19%2
768
November1st to 15thNight
7%10%30%36%13%
936
16th to endNight
5%9%33%38%11%1
975
December1st to 15thNight
7%12%36%35%8%
975
16th to endNight
415%34%34%10%
1040
Page generated at 2018-08-30 03:34:17. Version ac04

Copyright 2018 A. Danko


West Grand High School Clear Sky Chart |Charts Home