Garden City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Garden City clear sky chart from 2005-11-06 to 2026-05-02.

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 Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(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

By Month

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 Forecast	Data Points
Cloud Cover	Day	7% 5% 2 4 3 3 3 3 5% 7% 59%	140450
	Night	7% 5% 2 5% 3 3 3 3 5% 7% 57%	139440
Transparency	Day	25% 4 10% 25% 26% 9%	135380
	Night	27% 4 10% 24% 25% 10%	135520
Seeing	Day	9% 8% 30% 33% 16% 3	17491
	Night	9% 9% 37% 35% 10%	27540

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	8% 9% 3 6% 4 3 3 2 4 6% 52%	4720
	11th to 20th	Day	4 5% 2 6% 3 3 5% 3 3 5% 62%	4837
	21st to end	Day	6% 6% 2 6% 3 3 4 3 5% 5% 58%	5968
February	1st to 10th	Day	5% 8% 2 7% 4 3 3 2 4 7% 53%	2100
	11th to 20th	Day	4 5% 2 7% 4 4 5% 3 5% 7% 54%	2049
	21st to end	Day	4 4 2 5% 3 3 3 3 5% 6% 62%	1730
March	1st to 10th	Day	5% 7% 2 4 3 3 3 2 4 5% 62%	4600
	11th to 20th	Day	6% 4 1 4 3 2 3 3 5% 7% 62%	4972
	21st to end	Day	5% 5% 1 4 3 3 4 4 6% 7% 58%	5710
April	1st to 10th	Day	9% 5% 2 3 2 2 3 3 5% 5% 61%	2520
	11th to 20th	Day	10% 5% 2 4 3 3 3 3 5% 6% 55%	2491
	21st to end	Day	12% 5% 1 5% 4 3 3 4 5% 6% 51%	2674
May	1st to 10th	Day	13% 5% 2 4 3 3 4 3 5% 6% 52%	5914
	11th to 20th	Day	5% 4 1 4 2 3 4 4 5% 6% 63%	5862
	21st to end	Day	15% 5% 2 4 3 3 3 3 5% 6% 52%	6446
June	1st to 10th	Day	4 4 1 3 3 3 3 3 6% 10% 59%	2668
	11th to 20th	Day	5% 4 1 3 3 3 3 3 5% 8% 62%	2800
	21st to end	Day	4 3 1 4 4 4 3 3 5% 8% 61%	2800
July	1st to 10th	Day	6% 3 1 4 4 4 4 4 6% 8% 57%	6339
	11th to 20th	Day	5% 3 1 3 2 3 3 3 5% 8% 65%	6296
	21st to end	Day	4 3 1 4 3 4 4 4 6% 10% 57%	6424
August	1st to 10th	Day	10% 5% 2 5% 3 3 4 3 5% 8% 51%	5801
	11th to 20th	Day	4 3 1 3 3 3 3 4 6% 9% 61%	5460
	21st to end	Day	12% 5% 2 5% 3 3 4 3 5% 7% 51%	5984
September	1st to 10th	Day	8% 4 1 4 3 2 4 4 5% 6% 60%	2356
	11th to 20th	Day	7% 3 1 4 2 3 4 3 5% 6% 63%	2200
	21st to end	Day	6% 3 1 4 3 3 2 3 4 6% 65%	2200
October	1st to 10th	Day	7% 3 1 3 2 2 1 1 3 4 74%	3590
	11th to 20th	Day	5% 3 1 4 3 3 3 2 4 5% 66%	3423
	21st to end	Day	6% 4 1 3 2 2 2 2 3 5% 71%	3190
November	1st to 10th	Day	7% 4 1 4 2 2 3 2 4 5% 66%	1853
	11th to 20th	Day	4 4 1 4 3 3 3 2 3 6% 67%	1890
	21st to end	Day	7% 6% 2 4 3 3 3 3 4 5% 62%	1890
December	1st to 10th	Day	3 4 1 4 2 2 2 2 4 5% 71%	3030
	11th to 20th	Day	4 4 1 4 2 2 2 3 3 6% 68%	3481
	21st to end	Day	7% 13% 4 7% 3 3 3 2 4 6% 48%	4182
January	1st to 10th	Night	7% 8% 3 7% 4 4 4 3 4 6% 50%	8201
	11th to 20th	Night	3 4 2 5% 3 3 3 3 4 6% 64%	8123
	21st to end	Night	6% 8% 3 7% 4 3 3 3 4 4 56%	8304
February	1st to 10th	Night	6% 8% 3 5% 4 4 2 3 4 6% 55%	2520
	11th to 20th	Night	6% 7% 3 6% 4 4 5% 3 5% 6% 51%	2458
	21st to end	Night	6% 5% 2 5% 2 2 3 3 4 6% 64%	2076
March	1st to 10th	Night	5% 6% 2 3 2 2 3 3 4 6% 65%	5494
	11th to 20th	Night	6% 4 2 4 3 3 3 3 5% 7% 61%	5212
	21st to end	Night	7% 6% 2 5% 4 3 4 4 6% 8% 52%	5465
April	1st to 10th	Night	7% 5% 1 5% 3 3 4 3 6% 9% 55%	2100
	11th to 20th	Night	9% 5% 2 4 3 3 4 4 6% 7% 53%	2077
	21st to end	Night	10% 6% 2 4 4 3 3 3 5% 7% 51%	1943
May	1st to 10th	Night	12% 6% 2 5% 3 3 4 3 6% 7% 49%	4089
	11th to 20th	Night	6% 4 2 5% 3 3 3 3 4 6% 60%	4053
	21st to end	Night	15% 6% 1 5% 3 3 4 3 5% 7% 48%	4451
June	1st to 10th	Night	5% 3 1 4 3 3 5% 5% 7% 12% 53%	1726
	11th to 20th	Night	4 3 1 4 4 4 3 3 6% 9% 58%	1600
	21st to end	Night	5% 3 1 5% 5% 4 5% 4 6% 9% 53%	1600
July	1st to 10th	Night	5% 4 1 5% 4 4 4 4 6% 10% 52%	3640
	11th to 20th	Night	5% 4 2 6% 4 4 5% 5% 8% 11% 47%	3679
	21st to end	Night	5% 3 1 5% 4 4 5% 4 8% 12% 50%	4449
August	1st to 10th	Night	9% 6% 2 6% 4 3 5% 4 7% 10% 45%	4011
	11th to 20th	Night	6% 4 1 5% 4 4 5% 5% 7% 11% 48%	4385
	21st to end	Night	12% 6% 2 6% 5% 4 5% 5% 8% 9% 40%	4993
September	1st to 10th	Night	6% 3 1 4 2 4 4 3 5% 8% 60%	2042
	11th to 20th	Night	7% 3 1 4 3 3 3 3 6% 8% 61%	2200
	21st to end	Night	7% 3 1 4 3 3 2 3 5% 6% 63%	2200
October	1st to 10th	Night	6% 3 1 2 1 2 2 2 3 4 74%	3590
	11th to 20th	Night	6% 3 1 3 2 3 3 2 4 6% 69%	3680
	21st to end	Night	7% 3 1 3 3 3 2 3 3 3 69%	4610
November	1st to 10th	Night	5% 3 1 3 2 2 2 3 4 6% 67%	2665
	11th to 20th	Night	4 3 1 3 2 3 3 2 4 5% 70%	2730
	21st to end	Night	6% 4 1 3 3 3 3 3 5% 7% 61%	2730
December	1st to 10th	Night	3 4 2 4 3 2 2 2 4 6% 68%	4380
	11th to 20th	Night	4 4 1 4 3 3 3 3 4 6% 66%	4946
	21st to end	Night	8% 10% 3 6% 4 3 4 3 4 6% 50%	7018

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	34% 2 8% 27% 23% 6%	4723
	11th to 20th	Day	27% 3 8% 21% 28% 12%	4837
	21st to end	Day	29% 3 9% 22% 31% 7%	5968
February	1st to 10th	Day	32% 3 10% 27% 20% 8%	2100
	11th to 20th	Day	30% 4 12% 27% 20% 8%	2059
	21st to end	Day	24% 3 8% 24% 28% 15%	1730
March	1st to 10th	Day	26% 2 7% 14% 31% 21%	4600
	11th to 20th	Day	23% 3 8% 18% 34% 15%	4972
	21st to end	Day	24% 4 11% 37% 20% 4	5710
April	1st to 10th	Day	25% 4 9% 24% 27% 12%	2520
	11th to 20th	Day	30% 4 10% 24% 22% 10%	2494
	21st to end	Day	32% 5% 9% 25% 23% 5%	2674
May	1st to 10th	Day	33% 6% 11% 22% 19% 9%	5914
	11th to 20th	Day	21% 6% 10% 22% 25% 16%	5866
	21st to end	Day	34% 5% 11% 19% 24% 7%	6447
June	1st to 10th	Day	20% 6% 19% 31% 18% 6%	2668
	11th to 20th	Day	21% 6% 12% 25% 26% 11%	2800
	21st to end	Day	21% 5% 11% 27% 26% 10%	2800
July	1st to 10th	Day	24% 5% 13% 21% 31% 6%	6271
	11th to 20th	Day	18% 4 16% 32% 25% 5%	6221
	21st to end	Day	22% 6% 13% 32% 20% 6%	6240
August	1st to 10th	Day	29% 6% 14% 30% 17% 3	4220
	11th to 20th	Day	22% 6% 14% 27% 26% 6%	3952
	21st to end	Day	21% 5% 12% 29% 25% 7%	4311
September	1st to 10th	Day	25% 6% 8% 24% 24% 13%	2356
	11th to 20th	Day	23% 4 8% 26% 29% 10%	2200
	21st to end	Day	22% 3 9% 26% 27% 13%	2200
October	1st to 10th	Day	17% 2 6% 18% 42% 15%	3590
	11th to 20th	Day	21% 3 8% 25% 31% 12%	3423
	21st to end	Day	18% 2 6% 22% 38% 14%	3190
November	1st to 10th	Day	21% 3 8% 24% 32% 12%	1853
	11th to 20th	Day	20% 2 8% 29% 31% 11%	1890
	21st to end	Day	26% 3 9% 21% 30% 13%	1890
December	1st to 10th	Day	17% 3 8% 35% 29% 9%	3030
	11th to 20th	Day	19% 2 6% 34% 34% 5%	3479
	21st to end	Day	39% 3 7% 21% 23% 7%	4182
January	1st to 10th	Night	36% 3 9% 27% 20% 5%	8202
	11th to 20th	Night	22% 3 9% 24% 29% 12%	8123
	21st to end	Night	33% 3 8% 21% 26% 10%	8304
February	1st to 10th	Night	32% 3 10% 23% 23% 9%	2520
	11th to 20th	Night	33% 4 12% 22% 22% 7%	2458
	21st to end	Night	24% 2 6% 21% 30% 17%	2076
March	1st to 10th	Night	21% 3 5% 18% 30% 23%	5494
	11th to 20th	Night	23% 4 8% 18% 29% 19%	5212
	21st to end	Night	29% 5% 12% 33% 17% 4	5465
April	1st to 10th	Night	26% 4 12% 23% 23% 12%	2100
	11th to 20th	Night	29% 5% 11% 24% 21% 11%	2077
	21st to end	Night	32% 5% 11% 25% 23% 4	1943
May	1st to 10th	Night	33% 7% 15% 19% 18% 7%	4089
	11th to 20th	Night	25% 6% 10% 18% 24% 17%	4054
	21st to end	Night	36% 6% 13% 21% 16% 9%	4452
June	1st to 10th	Night	23% 8% 18% 30% 15% 5%	1726
	11th to 20th	Night	22% 7% 15% 27% 22% 8%	1600
	21st to end	Night	26% 7% 13% 24% 22% 9%	1600
July	1st to 10th	Night	27% 7% 17% 23% 23% 3	3600
	11th to 20th	Night	29% 7% 15% 23% 22% 5%	3631
	21st to end	Night	25% 6% 14% 31% 17% 6%	4320
August	1st to 10th	Night	33% 5% 13% 27% 19% 3	2916
	11th to 20th	Night	29% 7% 13% 27% 19% 4	3169
	21st to end	Night	27% 6% 15% 23% 23% 6%	3597
September	1st to 10th	Night	23% 6% 11% 24% 24% 12%	2042
	11th to 20th	Night	22% 5% 10% 23% 29% 11%	2200
	21st to end	Night	22% 4 7% 22% 30% 14%	2200
October	1st to 10th	Night	16% 3 6% 18% 43% 15%	3590
	11th to 20th	Night	18% 3 11% 23% 31% 13%	3680
	21st to end	Night	22% 3 5% 21% 37% 13%	4610
November	1st to 10th	Night	19% 4 9% 26% 27% 16%	2665
	11th to 20th	Night	18% 3 7% 26% 34% 13%	2730
	21st to end	Night	24% 3 10% 24% 26% 13%	2730
December	1st to 10th	Night	19% 3 8% 36% 27% 7%	4380
	11th to 20th	Night	20% 2 5% 30% 34% 8%	4947
	21st to end	Night	36% 3 8% 25% 22% 5%	7018

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	10% 8% 37% 30% 13% 2	330
	11th to 20th	Day	13% 9% 38% 29% 9% 2	330
	21st to end	Day	6% 9% 39% 34% 10% 2	363
February	1st to 10th	Day	7% 10% 49% 26% 7%	330
	11th to 20th	Day	8% 13% 44% 23% 11% 1	330
	21st to end	Day	5% 15% 48% 27% 4	273
March	1st to 10th	Day	10% 12% 38% 31% 9%	330
	11th to 20th	Day	14% 14% 33% 28% 9% 2	330
	21st to end	Day	12% 18% 39% 23% 7% 1	411
April	1st to 10th	Day	13% 16% 39% 25% 6% 1	540
	11th to 20th	Day	14% 20% 38% 22% 5% 1	532
	21st to end	Day	17% 14% 37% 25% 7% 1	694
May	1st to 10th	Day	12% 12% 36% 28% 11% 1	709
	11th to 20th	Day	14% 9% 29% 32% 14% 3	725
	21st to end	Day	13% 10% 36% 28% 12% 1	789
June	1st to 10th	Day	5% 5% 28% 37% 18% 6%	730
	11th to 20th	Day	6% 7% 33% 38% 15% 2	730
	21st to end	Day	5% 5% 30% 39% 19% 2	730
July	1st to 10th	Day	7% 2 19% 41% 25% 5%	721
	11th to 20th	Day	3 1 15% 43% 30% 8%	718
	21st to end	Day	6% 1 14% 38% 33% 7%	794
August	1st to 10th	Day	6% 2 17% 41% 30% 5%	726
	11th to 20th	Day	5% 1 20% 46% 25% 4	561
	21st to end	Day	7% 3 20% 40% 24% 6%	583
September	1st to 10th	Day	9% 2 20% 41% 23% 4	486
	11th to 20th	Day	3 4 26% 38% 22% 7%	330
	21st to end	Day	8% 7% 25% 34% 21% 5%	330
October	1st to 10th	Day	16% 6% 21% 32% 19% 6%	330
	11th to 20th	Day	5% 6% 42% 27% 16% 3	330
	21st to end	Day	16% 11% 30% 26% 14% 2	363
November	1st to 10th	Day	11% 9% 33% 29% 15% 3	330
	11th to 20th	Day	9% 11% 35% 29% 15% 2	330
	21st to end	Day	15% 12% 29% 27% 15% 3	330
December	1st to 10th	Day	7% 6% 38% 31% 15% 4	330
	11th to 20th	Day	9% 10% 38% 31% 11% 1	330
	21st to end	Day	15% 11% 34% 33% 7% 1	363
January	1st to 10th	Night	7% 8% 38% 38% 8% 1	1050
	11th to 20th	Night	8% 9% 38% 35% 9% 1	1050
	21st to end	Night	6% 9% 41% 36% 7%	1122
February	1st to 10th	Night	10% 10% 39% 35% 5%	840
	11th to 20th	Night	9% 11% 48% 27% 5%	824
	21st to end	Night	8% 12% 48% 29% 3	692
March	1st to 10th	Night	9% 14% 41% 30% 6%	840
	11th to 20th	Night	12% 11% 37% 31% 8% 1	687
	21st to end	Night	13% 15% 45% 23% 4	693
April	1st to 10th	Night	10% 16% 44% 27% 4	630
	11th to 20th	Night	13% 18% 43% 23% 3	623
	21st to end	Night	14% 16% 40% 23% 7%	630
May	1st to 10th	Night	12% 12% 42% 27% 7%	603
	11th to 20th	Night	11% 10% 36% 31% 10% 1	591
	21st to end	Night	10% 15% 42% 25% 7%	650
June	1st to 10th	Night	5% 7% 42% 34% 12% 1	600
	11th to 20th	Night	5% 11% 46% 32% 6% 1	600
	21st to end	Night	6% 6% 39% 40% 9%	600
July	1st to 10th	Night	5% 3 30% 45% 17%	585
	11th to 20th	Night	5% 2 27% 46% 19% 1	582
	21st to end	Night	7% 2 18% 51% 20% 1	657
August	1st to 10th	Night	8% 3 22% 46% 21% 1	597
	11th to 20th	Night	8% 3 28% 47% 14%	594
	21st to end	Night	6% 3 28% 44% 18% 1	660
September	1st to 10th	Night	6% 1 31% 47% 14%	600
	11th to 20th	Night	8% 3 40% 37% 12% 1	600
	21st to end	Night	8% 7% 30% 40% 15%	600
October	1st to 10th	Night	13% 8% 31% 37% 11%	600
	11th to 20th	Night	8% 9% 40% 33% 10% 1	660
	21st to end	Night	12% 9% 32% 32% 15% 1	1100
November	1st to 10th	Night	8% 8% 34% 41% 9%	1025
	11th to 20th	Night	6% 9% 40% 36% 10%	1050
	21st to end	Night	9% 10% 29% 39% 11% 2	1050
December	1st to 10th	Night	8% 8% 36% 40% 8% 1	1050
	11th to 20th	Night	8% 10% 37% 36% 8%	1050
	21st to end	Night	11% 11% 35% 35% 8%	1155

Page generated at 2026-04-29 01:21:41. Version ac07

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