Garden City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Garden City clear sky chart from 2005-11-05 to 2017-10-31.

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
45%
16020
28%
47272
16%
15976
56%
15976
41%
25582

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
45%
900
30%
2506
17%
895
55%
895
44%
1360
January16th to endNight
44%
942
35%
2514
17%
942
55%
942
49%
1335
February1st to 15thNight
39%
702
24%
2112
12%
700
48%
700
34%
1197
February16th to endNight
32%
632
33%
1894
13%
632
49%
632
40%
1012
March1st to 15thNight
38%
693
27%
2133
13%
693
51%
693
38%
1138
March16th to endNight
31%
576
25%
2082
14%
576
47%
576
30%
1096
April1st to 15thNight
25%
539
24%
1798
10%
539
45%
539
31%
970
April16th to endNight
29%
540
23%
1710
13%
540
47%
540
29%
991
May1st to 15thNight
37%
540
23%
1620
15%
540
51%
540
33%
943
May16th to endNight
35%
562
19%
1684
9%
561
47%
561
34%
972
June1st to 15thNight
37%
540
21%
1515
8%
540
49%
540
43%
828
June16th to endNight
48%
540
26%
1440
13%
540
57%
540
49%
771
July1st to 15thNight
62%
510
22%
1360
13%
510
68%
510
47%
764
July16th to endNight
69%
564
24%
1544
21%
531
72%
531
42%
856
August1st to 15thNight
61%
539
20%
1640
19%
536
65%
536
36%
945
August16th to endNight
64%
573
27%
1910
27%
573
71%
573
42%
966
September1st to 15thNight
54%
540
25%
1885
20%
540
67%
540
38%
987
September16th to endNight
51%
537
34%
1980
27%
537
65%
537
42%
911
October1st to 15thNight
43%
540
33%
1980
23%
540
57%
540
34%
1018
October16th to endNight
52%
876
36%
2412
19%
876
61%
876
52%
1220
November1st to 15thNight
50%
875
35%
2275
15%
875
61%
875
55%
1157
November16th to endNight
50%
900
36%
2340
17%
900
60%
900
51%
1250
December1st to 15thNight
43%
900
28%
2340
13%
900
52%
900
42%
1367
December16th to endNight
43%
960
31%
2598
17%
960
53%
960
38%
1528

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
6%413323347%57%
48473
Night
6%41332345%7%57%
47457
Cloud CoverDay
7%413323347%58%
48471
Night
6%41332345%7%58%
47457
TransparencyDay
26%411%26%23%7%
48160
Night
25%5%11%25%23%9%
47273
SeeingDay
9%6%28%34%17%3
5963
Night
8%7%34%37%11%
16023

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
5%413313335%62%
1432
16th to endDay
45%1332325%5%61%
1718
February1st to 15thDay
6%6%35%323246%53%
1750
16th to endDay
45%13323446%59%
1580
March1st to 15thDay
6%413333346%58%
1827
16th to endDay
11%423322347%55%
2140
April1st to 15thDay
11%413323346%54%
2150
16th to endDay
12%42342335%6%50%
2248
May1st to 15thDay
8%31332445%7%54%
2331
16th to endDay
7%3133345%5%7%53%
2430
June1st to 15thDay
431232445%8%59%
2441
16th to endDay
221232335%8%65%
2520
July1st to 15thDay
4313325%5%6%9%53%
2520
16th to endDay
421232346%11%56%
2514
August1st to 15thDay
6%324435%5%6%9%50%
2307
16th to endDay
6%313324448%56%
2292
September1st to 15thDay
9%4234235%5%6%52%
2073
16th to endDay
5%213223336%63%
1980
October1st to 15thDay
11%31331223461%
1980
16th to endDay
6%312211245%68%
1797
November1st to 15thDay
5%212222336%65%
1583
16th to endDay
5%41321233467%
1620
December1st to 15thDay
7%6%25%412345%56%
1620
16th to endDay
8%6%24312337%56%
1620
January1st to 15thNight
35%24323245%62%
2506
16th to endNight
35%23213235%65%
2514
February1st to 15thNight
5%7%34322346%54%
2102
16th to endNight
6%424223445%60%
1894
March1st to 15thNight
5%5%23324347%56%
2133
16th to endNight
9%412323447%54%
2082
April1st to 15thNight
9%4133145%6%9%50%
1798
16th to endNight
11%5%2342345%6%50%
1710
May1st to 15thNight
7%424425%45%7%52%
1619
16th to endNight
7%31343445%8%52%
1683
June1st to 15thNight
422225%5%6%11%54%
1515
16th to endNight
3134235%5%11%58%
1440
July1st to 15thNight
32143245%7%10%53%
1440
16th to endNight
5%31332346%11%54%
1651
August1st to 15thNight
6%3244346%7%13%44%
1650
16th to endNight
5%31241246%8%58%
1910
September1st to 15thNight
7%21333445%10%54%
1885
16th to endNight
6%21322235%6%63%
1980
October1st to 15thNight
11%322222335%59%
1980
16th to endNight
5%2221333469%
2412
November1st to 15thNight
3212212337%68%
2275
16th to endNight
5%313212246%65%
2340
December1st to 15thNight
6%5%14412446%56%
2340
16th to endNight
8%6%24412346%54%
2598

Percentage Cloud Cover SE (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
5%413212345%63%
1432
16th to endDay
45%1331325%5%61%
1718
February1st to 15thDay
6%6%35%314346%54%
1750
16th to endDay
45%14323436%59%
1580
March1st to 15thDay
6%41333335%6%58%
1827
16th to endDay
11%423312346%55%
2138
April1st to 15thDay
11%413313346%54%
2150
16th to endDay
12%41342335%7%50%
2248
May1st to 15thDay
8%313414447%54%
2331
16th to endDay
7%3134245%5%7%53%
2430
June1st to 15thDay
431222435%8%59%
2441
16th to endDay
321232335%8%64%
2520
July1st to 15thDay
4313325%5%6%9%53%
2520
16th to endDay
421232336%11%57%
2514
August1st to 15thDay
6%314435%5%6%9%50%
2307
16th to endDay
7%312324448%56%
2292
September1st to 15thDay
9%41342345%7%52%
2073
16th to endDay
5%213223336%64%
1980
October1st to 15thDay
12%313212235%61%
1980
16th to endDay
6%312111236%68%
1797
November1st to 15thDay
5%212222336%65%
1583
16th to endDay
5%41321223467%
1620
December1st to 15thDay
7%6%25%412346%56%
1620
16th to endDay
8%6%15%312246%56%
1620
January1st to 15thNight
3425%323245%62%
2506
16th to endNight
3423212245%65%
2514
February1st to 15thNight
6%7%34323346%54%
2102
16th to endNight
6%424223345%60%
1894
March1st to 15thNight
5%5%1332435%7%56%
2133
16th to endNight
9%422323447%55%
2082
April1st to 15thNight
9%4134145%5%9%51%
1798
16th to endNight
11%5%2342335%6%51%
1710
May1st to 15thNight
7%424425%447%52%
1619
16th to endNight
7%313425%45%8%52%
1683
June1st to 15thNight
423225%5%6%11%55%
1515
16th to endNight
3134235%6%11%58%
1440
July1st to 15thNight
3213325%5%7%10%53%
1440
16th to endNight
5%31332436%11%54%
1651
August1st to 15thNight
6%3244346%7%12%45%
1650
16th to endNight
5%31231246%8%58%
1910
September1st to 15thNight
7%21322446%9%54%
1885
16th to endNight
6%2322235%7%63%
1980
October1st to 15thNight
11%413212335%59%
1980
16th to endNight
5%3221333469%
2412
November1st to 15thNight
3212213346%68%
2275
16th to endNight
5%313222246%65%
2340
December1st to 15thNight
6%5%1441245%6%56%
2340
16th to endNight
8%6%24412346%54%
2598

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
23%314%31%22%4
1433
16th to endDay
24%211%33%21%5%
1718
February1st to 15thDay
31%313%30%14%6%
1751
16th to endDay
25%411%27%21%10%
1580
March1st to 15thDay
26%310%26%24%9%
1827
16th to endDay
30%413%24%20%6%
2140
April1st to 15thDay
29%5%10%25%21%7%
2150
16th to endDay
32%5%10%25%20%4
2248
May1st to 15thDay
28%5%11%26%23%4
2331
16th to endDay
28%7%14%25%17%6%
2434
June1st to 15thDay
21%6%16%26%19%8%
2441
16th to endDay
17%5%11%27%27%10%
2520
July1st to 15thDay
25%6%11%23%27%4
2371
16th to endDay
22%6%15%28%22%5%
2358
August1st to 15thDay
28%8%16%25%13%7%
2293
16th to endDay
25%6%9%27%23%6%
2292
September1st to 15thDay
29%6%9%24%19%9%
2073
16th to endDay
22%49%28%27%8%
1980
October1st to 15thDay
28%310%22%26%9%
1980
16th to endDay
18%29%24%34%9%
1797
November1st to 15thDay
21%29%23%30%13%
1583
16th to endDay
21%27%23%32%12%
1620
December1st to 15thDay
30%312%29%20%3
1620
16th to endDay
29%311%27%23%4
1620
January1st to 15thNight
25%39%29%26%5%
2506
16th to endNight
21%39%29%27%7%
2514
February1st to 15thNight
31%412%25%19%6%
2112
16th to endNight
26%310%24%25%10%
1894
March1st to 15thNight
27%39%22%24%11%
2133
16th to endNight
29%5%11%22%21%9%
2082
April1st to 15thNight
28%5%12%25%19%8%
1798
16th to endNight
32%5%12%24%19%4
1710
May1st to 15thNight
29%7%12%22%22%6%
1620
16th to endNight
28%7%18%20%18%6%
1685
June1st to 15thNight
21%8%17%28%17%6%
1515
16th to endNight
18%6%13%26%24%9%
1440
July1st to 15thNight
22%6%13%26%23%7%
1360
16th to endNight
23%7%14%25%21%6%
1544
August1st to 15thNight
29%6%18%26%13%5%
1640
16th to endNight
22%6%12%29%21%8%
1910
September1st to 15thNight
25%6%12%25%21%8%
1885
16th to endNight
21%49%23%30%10%
1980
October1st to 15thNight
27%49%18%28%11%
1980
16th to endNight
19%37%23%29%17%
2412
November1st to 15thNight
17%39%21%30%17%
2275
16th to endNight
21%27%25%28%15%
2340
December1st to 15thNight
27%411%30%20%5%
2340
16th to endNight
31%311%24%23%5%
2598

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%331%34%14%2
90
16th to endDay
9%9%43%29%7%1
96
February1st to 15thDay
12%6%46%27%5%1
90
16th to endDay
314%44%24%12%
81
March1st to 15thDay
5%10%33%40%11%
90
16th to endDay
13%14%32%25%11%3
124
April1st to 15thDay
13%18%40%23%21
269
16th to endDay
18%13%37%22%7%
358
May1st to 15thDay
11%9%35%27%13%2
468
16th to endDay
11%9%31%32%14%1
517
June1st to 15thDay
5%5%32%37%13%5%
495
16th to endDay
2428%36%24%3
495
July1st to 15thDay
6%118%41%25%6%
475
16th to endDay
6%13%40%31%6%
515
August1st to 15thDay
7%115%44%26%3
460
16th to endDay
6%324%39%21%4
332
September1st to 15thDay
6%224%41%19%6%
228
16th to endDay
10%5%28%31%20%3
135
October1st to 15thDay
12%5%25%38%16%2
135
16th to endDay
6%11%31%28%18%2
144
November1st to 15thDay
5%332%31%23%4
90
16th to endDay
21%13%28%24%11%1
90
December1st to 15thDay
11%5%43%27%10%2
90
16th to endDay
15%8%35%32%8%
96
January1st to 15thNight
6%7%35%40%9%1
900
16th to endNight
6%8%37%37%9%
942
February1st to 15thNight
9%7%38%37%6%
704
16th to endNight
9%10%46%28%5%
632
March1st to 15thNight
7%10%38%34%8%
693
16th to endNight
13%12%40%27%6%
576
April1st to 15thNight
10%17%43%25%3
539
16th to endNight
15%12%40%23%7%
540
May1st to 15thNight
10%9%38%31%9%
540
16th to endNight
8%10%41%29%10%
563
June1st to 15thNight
5%7%47%30%9%
540
16th to endNight
36%38%41%10%
540
July1st to 15thNight
3127%45%21%
510
16th to endNight
6%18%50%22%1
564
August1st to 15thNight
8%20%47%20%
539
16th to endNight
5%223%45%20%1
573
September1st to 15thNight
8%32%40%17%
540
16th to endNight
8%433%36%16%
537
October1st to 15thNight
14%8%30%35%10%
540
16th to endNight
8%6%31%35%17%
876
November1st to 15thNight
5%8%33%41%11%
875
16th to endNight
8%8%31%38%11%1
900
December1st to 15thNight
9%8%34%40%6%
900
16th to endNight
10%10%31%37%10%
960
Page generated at 2017-11-01 16:23:37. Version ac04

Copyright 2017 A. Danko


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