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 2026-09-14.

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 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	2 4 2 6% 4 5% 5% 5% 7% 8% 52%	158199
	Night	2 4 2 6% 4 4 5% 5% 7% 9% 52%	150433
Transparency	Day	27% 8% 11% 23% 20% 11%	152935
	Night	27% 8% 13% 24% 19% 9%	146705
Seeing	Day	7% 14% 28% 29% 18% 5%	17961
	Night	5% 8% 24% 39% 22% 2	27782

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	6% 4 13% 7% 7% 8% 7% 10% 10% 28%	5318
	11th to 20th	Day	3 1 7% 5% 6% 7% 7% 9% 11% 45%	5340
	21st to end	Day	5% 4 9% 5% 5% 6% 5% 7% 9% 44%	5844
February	1st to 10th	Day	1 6% 4 8% 7% 7% 7% 6% 11% 11% 32%	1890
	11th to 20th	Day	1 9% 4 9% 6% 7% 8% 5% 8% 10% 32%	1856
	21st to end	Day	1 7% 3 10% 6% 6% 7% 5% 9% 9% 36%	1730
March	1st to 10th	Day	1 8% 4 10% 7% 6% 6% 6% 8% 8% 37%	4966
	11th to 20th	Day	1 5% 3 7% 5% 5% 7% 6% 7% 9% 45%	5110
	21st to end	Day	2 8% 4 10% 7% 6% 8% 6% 8% 9% 32%	5607
April	1st to 10th	Day	3 7% 3 7% 6% 5% 6% 4 8% 9% 42%	2369
	11th to 20th	Day	4 7% 2 6% 5% 6% 6% 6% 8% 9% 41%	2645
	21st to end	Day	4 5% 3 7% 5% 6% 5% 5% 7% 10% 44%	2730
May	1st to 10th	Day	4 5% 2 5% 4 5% 6% 4 6% 8% 52%	7626
	11th to 20th	Day	4 6% 2 5% 4 4 5% 4 7% 8% 51%	7596
	21st to end	Day	4 3 1 5% 4 4 5% 5% 7% 9% 53%	8729
June	1st to 10th	Day	3 4 1 4 4 4 5% 4 7% 9% 56%	2940
	11th to 20th	Day	4 3 1 4 3 3 4 4 6% 8% 60%	2944
	21st to end	Day	1 2 1 2 2 3 3 3 4 7% 70%	3150
July	1st to 10th	Day	2 2 1 3 3 3 3 3 5% 7% 69%	8148
	11th to 20th	Day	2 2 1 3 2 4 4 4 6% 8% 64%	7650
	21st to end	Day	2 2 1 3 3 3 4 3 5% 7% 66%	8304
August	1st to 10th	Day	1 1 1 2 2 3 3 3 4 6% 73%	7549
	11th to 20th	Day	2 2 1 3 3 4 4 4 6% 8% 63%	7565
	21st to end	Day	3 3 1 4 3 4 5% 4 6% 9% 59%	8300
September	1st to 10th	Day	2 2 1 2 2 3 3 3 6% 7% 68%	2432
	11th to 20th	Day	3 3 1 3 3 4 4 4 4 8% 64%	2234
	21st to end	Day	4 3 1 3 3 3 4 4 4 6% 66%	2200
October	1st to 10th	Day	3 4 2 4 3 3 3 3 5% 6% 65%	3381
	11th to 20th	Day	4 6% 1 4 3 3 4 5% 7% 8% 55%	3250
	21st to end	Day	2 6% 2 6% 4 5% 6% 4 6% 9% 51%	3522
November	1st to 10th	Day	3 6% 3 8% 4 5% 6% 5% 7% 9% 45%	1854
	11th to 20th	Day	1 7% 3 7% 5% 5% 7% 6% 6% 11% 43%	1795
	21st to end	Day	2 6% 4 7% 6% 6% 6% 5% 7% 8% 44%	1680
December	1st to 10th	Day	1 3 3 5% 4 6% 7% 6% 8% 9% 47%	2700
	11th to 20th	Day	5% 3 8% 6% 7% 8% 8% 11% 12% 31%	3106
	21st to end	Day	1 7% 4 11% 8% 9% 9% 7% 10% 9% 26%	4139
January	1st to 10th	Night	1 5% 3 10% 6% 6% 7% 7% 9% 11% 35%	7605
	11th to 20th	Night	3 2 6% 5% 5% 6% 5% 9% 11% 49%	7650
	21st to end	Night	1 6% 3 8% 6% 5% 5% 4 7% 9% 46%	8370
February	1st to 10th	Night	1 6% 2 8% 7% 7% 7% 6% 9% 11% 36%	2730
	11th to 20th	Night	1 7% 3 8% 5% 5% 7% 6% 9% 9% 41%	2646
	21st to end	Night	1 5% 3 7% 5% 5% 5% 6% 11% 11% 40%	2076
March	1st to 10th	Night	2 8% 3 7% 4 4 5% 6% 8% 10% 44%	5148
	11th to 20th	Night	1 6% 3 6% 4 5% 6% 4 7% 10% 49%	5110
	21st to end	Night	3 7% 3 6% 5% 5% 6% 5% 7% 8% 46%	5610
April	1st to 10th	Night	2 6% 3 5% 4 4 5% 6% 8% 8% 48%	2249
	11th to 20th	Night	3 6% 2 5% 6% 4 5% 4 7% 8% 50%	1919
	21st to end	Night	4 5% 2 5% 5% 4 6% 3 6% 9% 51%	1890
May	1st to 10th	Night	4 5% 2 5% 3 3 5% 4 6% 8% 56%	5321
	11th to 20th	Night	5% 4 2 4 2 3 3 3 4 7% 63%	5296
	21st to end	Night	4 4 1 5% 4 4 4 4 6% 9% 55%	5460
June	1st to 10th	Night	3 2 1 4 3 4 5% 4 6% 9% 58%	1680
	11th to 20th	Night	4 2 1 3 3 3 3 3 6% 8% 65%	1662
	21st to end	Night	2 2 1 2 2 3 4 2 5% 6% 70%	1470
July	1st to 10th	Night	1 2 1 4 3 3 4 3 5% 6% 68%	4771
	11th to 20th	Night	1 2 1 4 3 3 4 4 6% 9% 64%	5340
	21st to end	Night	1 2 1 4 3 4 4 4 6% 8% 63%	5805
August	1st to 10th	Night	1 1 1 2 2 2 3 3 5% 7% 72%	5273
	11th to 20th	Night	2 3 2 6% 4 3 5% 4 5% 7% 59%	5291
	21st to end	Night	3 3 1 5% 4 5% 5% 4 6% 8% 55%	5916
September	1st to 10th	Night	2 3 1 3 3 3 3 2 5% 6% 70%	2184
	11th to 20th	Night	4 3 1 4 3 4 4 3 5% 7% 64%	2233
	21st to end	Night	4 2 1 3 2 3 3 2 5% 5% 69%	2200
October	1st to 10th	Night	3 3 1 3 3 2 2 2 4 5% 72%	3811
	11th to 20th	Night	4 5% 2 7% 4 4 4 3 5% 7% 55%	3898
	21st to end	Night	3 6% 2 4 3 4 5% 4 7% 9% 53%	4273
November	1st to 10th	Night	3 5% 2 5% 4 4 6% 5% 8% 9% 49%	2665
	11th to 20th	Night	2 4 2 5% 5% 6% 7% 5% 9% 9% 46%	2800
	21st to end	Night	1 6% 2 5% 5% 6% 8% 5% 8% 9% 45%	2940
December	1st to 10th	Night	1 3 2 5% 5% 5% 7% 5% 8% 9% 51%	4710
	11th to 20th	Night	1 5% 3 7% 5% 6% 7% 7% 9% 10% 40%	5321
	21st to end	Night	1 5% 3 12% 9% 8% 9% 8% 9% 9% 26%	7110

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	44% 11% 23% 15% 7%	5321
	11th to 20th	Day	31% 13% 16% 25% 10% 5%	5340
	21st to end	Day	33% 11% 15% 26% 14% 2	5844
February	1st to 10th	Day	42% 14% 18% 18% 8% 1	1890
	11th to 20th	Day	45% 11% 16% 18% 8% 2	1865
	21st to end	Day	41% 13% 16% 18% 10% 2	1730
March	1st to 10th	Day	41% 12% 9% 23% 11% 3	4966
	11th to 20th	Day	29% 10% 15% 31% 13% 1	5110
	21st to end	Day	46% 10% 18% 21% 4	5607
April	1st to 10th	Day	37% 10% 14% 24% 12% 2	2369
	11th to 20th	Day	36% 10% 13% 25% 15%	2648
	21st to end	Day	35% 9% 15% 28% 13%	2730
May	1st to 10th	Day	27% 9% 10% 29% 21% 5%	7626
	11th to 20th	Day	29% 6% 7% 29% 24% 5%	7599
	21st to end	Day	25% 7% 9% 32% 25% 3	8730
June	1st to 10th	Day	23% 9% 13% 25% 26% 3	2940
	11th to 20th	Day	22% 6% 8% 20% 31% 13%	2944
	21st to end	Day	13% 5% 6% 19% 34% 23%	3150
July	1st to 10th	Day	14% 4 3 12% 23% 43%	8085
	11th to 20th	Day	15% 4 5% 16% 28% 31%	7581
	21st to end	Day	17% 4 5% 16% 29% 30%	8120
August	1st to 10th	Day	13% 4 4 16% 26% 38%	5978
	11th to 20th	Day	21% 4 9% 26% 26% 15%	5964
	21st to end	Day	17% 4 9% 24% 28% 17%	6507
September	1st to 10th	Day	14% 6% 7% 20% 33% 20%	2432
	11th to 20th	Day	20% 6% 8% 23% 31% 13%	2234
	21st to end	Day	18% 6% 8% 27% 34% 8%	2200
October	1st to 10th	Day	21% 4 6% 22% 31% 17%	3381
	11th to 20th	Day	26% 5% 10% 30% 23% 6%	3250
	21st to end	Day	28% 6% 13% 36% 16% 1	3522
November	1st to 10th	Day	34% 9% 16% 24% 14% 1	1854
	11th to 20th	Day	33% 11% 21% 23% 11% 1	1795
	21st to end	Day	34% 8% 17% 25% 14% 1	1680
December	1st to 10th	Day	30% 11% 21% 28% 8% 2	2700
	11th to 20th	Day	38% 10% 24% 22% 6%	3104
	21st to end	Day	44% 12% 15% 18% 10% 1	4139
January	1st to 10th	Night	37% 12% 18% 24% 8%	7605
	11th to 20th	Night	29% 13% 16% 29% 11% 1	7650
	21st to end	Night	31% 11% 14% 27% 16% 2	8370
February	1st to 10th	Night	38% 16% 17% 20% 8% 1	2730
	11th to 20th	Night	35% 12% 16% 22% 13% 2	2647
	21st to end	Night	33% 14% 15% 26% 10% 2	2076
March	1st to 10th	Night	33% 12% 13% 24% 14% 5%	5148
	11th to 20th	Night	27% 9% 17% 33% 13% 1	5110
	21st to end	Night	33% 11% 22% 26% 7% 1	5610
April	1st to 10th	Night	31% 11% 17% 24% 11% 5%	2249
	11th to 20th	Night	30% 9% 15% 27% 18% 1	1919
	21st to end	Night	29% 8% 15% 30% 18%	1890
May	1st to 10th	Night	23% 9% 11% 27% 27% 3	5319
	11th to 20th	Night	21% 5% 8% 26% 35% 5%	5297
	21st to end	Night	24% 6% 9% 35% 24% 2	5461
June	1st to 10th	Night	20% 9% 16% 25% 27% 3	1680
	11th to 20th	Night	16% 6% 10% 24% 29% 15%	1662
	21st to end	Night	15% 3 6% 20% 31% 25%	1470
July	1st to 10th	Night	17% 4 3 13% 22% 41%	4727
	11th to 20th	Night	18% 3 6% 14% 28% 31%	5286
	21st to end	Night	19% 4 5% 17% 30% 26%	5677
August	1st to 10th	Night	13% 4 4 14% 26% 39%	4168
	11th to 20th	Night	27% 3 8% 23% 23% 16%	4168
	21st to end	Night	23% 4 8% 19% 26% 21%	4640
September	1st to 10th	Night	17% 4 6% 20% 28% 26%	2184
	11th to 20th	Night	19% 5% 8% 22% 29% 16%	2233
	21st to end	Night	18% 4 8% 26% 35% 9%	2200
October	1st to 10th	Night	16% 4 6% 22% 39% 13%	3811
	11th to 20th	Night	30% 4 7% 29% 23% 7%	3898
	21st to end	Night	26% 5% 12% 36% 18% 3	4273
November	1st to 10th	Night	29% 9% 16% 25% 17% 3	2665
	11th to 20th	Night	30% 10% 20% 27% 12% 2	2800
	21st to end	Night	30% 9% 18% 28% 13% 3	2940
December	1st to 10th	Night	27% 11% 20% 29% 11% 2	4710
	11th to 20th	Night	33% 11% 24% 26% 6%	5322
	21st to end	Night	44% 10% 15% 21% 7% 2	7110

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	8% 18% 26% 27% 18% 2	330
	11th to 20th	Day	5% 15% 27% 33% 18% 2	330
	21st to end	Day	5% 13% 25% 40% 15% 3	363
February	1st to 10th	Day	8% 24% 34% 25% 8% 1	330
	11th to 20th	Day	9% 17% 35% 27% 10% 2	341
	21st to end	Day	7% 22% 37% 26% 7% 1	446
March	1st to 10th	Day	8% 24% 33% 26% 8% 2	540
	11th to 20th	Day	7% 20% 34% 27% 11% 1	540
	21st to end	Day	11% 25% 35% 22% 7% 1	594
April	1st to 10th	Day	10% 22% 27% 22% 16% 2	540
	11th to 20th	Day	11% 23% 38% 17% 8% 2	532
	21st to end	Day	11% 24% 28% 20% 13% 4	540
May	1st to 10th	Day	10% 20% 30% 21% 14% 6%	543
	11th to 20th	Day	11% 13% 33% 28% 13% 2	568
	21st to end	Day	10% 11% 25% 27% 22% 6%	742
June	1st to 10th	Day	4 11% 25% 30% 24% 6%	780
	11th to 20th	Day	6% 12% 29% 32% 19% 2	780
	21st to end	Day	2 7% 27% 38% 21% 5%	780
July	1st to 10th	Day	2 5% 23% 39% 24% 7%	657
	11th to 20th	Day	4 4 25% 34% 24% 9%	564
	21st to end	Day	4 3 21% 37% 28% 7%	619
August	1st to 10th	Day	4 4 29% 32% 23% 8%	567
	11th to 20th	Day	3 4 24% 35% 27% 7%	557
	21st to end	Day	4 6% 22% 36% 25% 8%	627
September	1st to 10th	Day	3 8% 23% 30% 23% 13%	570
	11th to 20th	Day	6% 12% 29% 24% 19% 10%	543
	21st to end	Day	5% 13% 21% 28% 24% 9%	530
October	1st to 10th	Day	5% 11% 22% 23% 29% 10%	402
	11th to 20th	Day	8% 13% 21% 28% 21% 8%	330
	21st to end	Day	7% 18% 26% 28% 18% 3	363
November	1st to 10th	Day	10% 15% 26% 27% 13% 8%	330
	11th to 20th	Day	8% 15% 27% 32% 14% 4	330
	21st to end	Day	6% 12% 24% 35% 18% 5%	330
December	1st to 10th	Day	5% 15% 26% 32% 16% 7%	330
	11th to 20th	Day	8% 16% 29% 33% 13% 1	330
	21st to end	Day	8% 17% 35% 24% 13% 3	363
January	1st to 10th	Night	4 9% 27% 39% 18% 2	840
	11th to 20th	Night	4 10% 27% 38% 19% 2	840
	21st to end	Night	2 7% 33% 42% 15% 2	924
February	1st to 10th	Night	4 14% 35% 35% 12% 1	840
	11th to 20th	Night	4 11% 30% 39% 14% 2	824
	21st to end	Night	5% 12% 33% 38% 11% 1	692
March	1st to 10th	Night	4 11% 30% 40% 13% 2	840
	11th to 20th	Night	3 9% 27% 44% 16% 1	840
	21st to end	Night	5% 10% 31% 38% 13% 1	924
April	1st to 10th	Night	6% 10% 28% 39% 16% 1	779
	11th to 20th	Night	8% 12% 30% 38% 12% 1	623
	21st to end	Night	7% 10% 26% 37% 18% 2	630
May	1st to 10th	Night	9% 10% 22% 37% 20% 1	630
	11th to 20th	Night	9% 5% 19% 37% 27% 2	621
	21st to end	Night	8% 6% 20% 37% 26% 3	683
June	1st to 10th	Night	3 6% 21% 38% 29% 3	630
	11th to 20th	Night	5% 7% 22% 43% 23%	612
	21st to end	Night	3 2 14% 43% 34% 4	420
July	1st to 10th	Night	1 1 12% 39% 45% 2	508
	11th to 20th	Night	2 2 11% 45% 39% 1	612
	21st to end	Night	3 1 7% 43% 42% 4	690
August	1st to 10th	Night	2 1 10% 48% 37% 2	627
	11th to 20th	Night	4 2 8% 45% 38% 3	624
	21st to end	Night	4 2 12% 39% 39% 4	693
September	1st to 10th	Night	4 4 14% 38% 36% 5%	714
	11th to 20th	Night	4 6% 13% 36% 35% 6%	812
	21st to end	Night	5% 5% 15% 34% 33% 8%	800
October	1st to 10th	Night	6% 6% 20% 36% 28% 4	800
	11th to 20th	Night	6% 10% 21% 36% 25% 4	800
	21st to end	Night	5% 8% 24% 39% 21% 3	880
November	1st to 10th	Night	5% 9% 25% 39% 19% 3	820
	11th to 20th	Night	4 12% 27% 40% 14% 2	910
	21st to end	Night	5% 11% 26% 38% 17% 3	1050
December	1st to 10th	Night	6% 10% 28% 40% 15% 1	1050
	11th to 20th	Night	4 11% 32% 40% 12% 1	1050
	21st to end	Night	4 15% 33% 35% 12% 1	1150

Page generated at 2026-09-11 02:11:56. Version ac07

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