Leakes Mill Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Leakes Mill Park 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	13% 6% 2 6% 4 4 4 4 6% 8% 43%	148553
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 44%	142526
Transparency	Day	38% 5% 13% 22% 17% 4	152157
	Night	39% 5% 11% 22% 18% 5%	146993
Seeing	Day	18% 11% 27% 25% 14% 5%	17529
	Night	17% 10% 28% 31% 13% 1	27199

By Month

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	15% 6% 2 5% 3 3 4 3 5% 6% 49%	5258
	11th to 20th	Day	13% 6% 3 5% 3 3 3 2 4 4 55%	5280
	21st to end	Day	14% 7% 2 7% 4 4 4 3 5% 6% 45%	5780
February	1st to 10th	Day	12% 8% 3 6% 4 4 5% 4 6% 7% 42%	1890
	11th to 20th	Day	22% 7% 2 5% 3 3 3 3 5% 6% 42%	1880
	21st to end	Day	18% 7% 2 7% 5% 4 4 3 5% 6% 38%	1772
March	1st to 10th	Day	17% 6% 2 6% 4 5% 5% 4 5% 7% 39%	5045
	11th to 20th	Day	11% 5% 2 5% 4 3 4 4 5% 7% 51%	5090
	21st to end	Day	17% 6% 2 6% 5% 4 4 3 5% 6% 42%	5586
April	1st to 10th	Day	11% 5% 2 4 4 4 4 4 5% 7% 50%	2509
	11th to 20th	Day	12% 6% 2 5% 4 3 4 4 5% 6% 49%	2494
	21st to end	Day	16% 5% 2 6% 5% 4 4 4 4 7% 42%	2520
May	1st to 10th	Day	14% 6% 2 6% 5% 5% 5% 4 6% 9% 38%	7529
	11th to 20th	Day	17% 6% 2 6% 4 4 5% 4 6% 9% 39%	7626
	21st to end	Day	20% 6% 2 5% 4 4 4 3 5% 8% 39%	8946
June	1st to 10th	Day	9% 5% 2 6% 4 5% 4 4 7% 9% 44%	2940
	11th to 20th	Day	10% 4 2 5% 5% 5% 5% 5% 8% 10% 41%	2940
	21st to end	Day	7% 5% 2 5% 5% 4 6% 5% 7% 10% 44%	2940
July	1st to 10th	Day	8% 5% 2 5% 4 4 5% 4 7% 11% 44%	8024
	11th to 20th	Day	11% 6% 2 6% 5% 5% 6% 5% 9% 13% 31%	7680
	21st to end	Day	10% 5% 2 6% 5% 5% 6% 5% 7% 10% 38%	8340
August	1st to 10th	Day	15% 7% 2 7% 5% 5% 6% 4 8% 12% 29%	6014
	11th to 20th	Day	8% 5% 2 7% 5% 6% 7% 6% 8% 11% 35%	5741
	21st to end	Day	8% 4 2 5% 4 4 4 4 7% 10% 49%	6080
September	1st to 10th	Day	12% 5% 2 6% 4 4 4 4 5% 7% 47%	2520
	11th to 20th	Day	13% 6% 2 6% 4 4 4 4 6% 8% 44%	2405
	21st to end	Day	21% 6% 3 6% 4 4 4 3 5% 7% 37%	2102
October	1st to 10th	Day	15% 5% 2 5% 4 3 4 3 5% 6% 49%	2000
	11th to 20th	Day	16% 4 2 4 4 3 3 3 4 5% 53%	2000
	21st to end	Day	14% 4 2 6% 3 3 3 3 4 5% 54%	2200
November	1st to 10th	Day	12% 5% 1 4 3 4 4 3 4 6% 54%	2057
	11th to 20th	Day	15% 6% 2 3 3 4 3 2 5% 5% 51%	1887
	21st to end	Day	14% 5% 1 4 3 3 4 4 4 5% 51%	1680
December	1st to 10th	Day	13% 6% 2 5% 3 4 3 3 6% 6% 50%	2680
	11th to 20th	Day	19% 6% 2 5% 2 3 3 2 4 6% 47%	3070
	21st to end	Day	16% 6% 3 7% 4 4 5% 3 5% 6% 41%	4048
January	1st to 10th	Night	12% 6% 2 5% 3 4 3 3 5% 6% 50%	7635
	11th to 20th	Night	14% 6% 2 5% 3 2 3 2 3 4 55%	7680
	21st to end	Night	15% 6% 2 6% 3 3 3 3 4 5% 50%	8401
February	1st to 10th	Night	14% 7% 2 5% 4 4 4 4 5% 6% 44%	2730
	11th to 20th	Night	20% 7% 2 5% 4 4 3 3 4 6% 42%	2625
	21st to end	Night	16% 6% 3 6% 5% 3 3 3 4 6% 46%	2031
March	1st to 10th	Night	15% 5% 2 6% 3 4 3 3 6% 6% 47%	5028
	11th to 20th	Night	12% 4 2 5% 3 3 3 3 5% 8% 53%	5090
	21st to end	Night	13% 6% 2 6% 3 4 4 3 4 7% 47%	5588
April	1st to 10th	Night	14% 6% 2 5% 4 4 5% 4 5% 6% 47%	2111
	11th to 20th	Night	11% 5% 3 5% 4 4 4 3 5% 9% 48%	2075
	21st to end	Night	13% 5% 2 6% 4 3 4 4 6% 7% 45%	2100
May	1st to 10th	Night	14% 7% 3 7% 5% 4 5% 4 6% 9% 36%	5380
	11th to 20th	Night	18% 6% 2 6% 4 4 4 3 6% 7% 40%	5234
	21st to end	Night	22% 7% 2 6% 4 4 4 3 5% 7% 35%	5190
June	1st to 10th	Night	10% 5% 2 6% 5% 4 5% 4 6% 9% 44%	1680
	11th to 20th	Night	10% 5% 2 6% 5% 5% 5% 5% 7% 10% 40%	1680
	21st to end	Night	9% 4 2 5% 5% 3 4 4 7% 11% 45%	1680
July	1st to 10th	Night	11% 5% 2 8% 5% 6% 5% 4 7% 9% 37%	4915
	11th to 20th	Night	14% 7% 3 8% 6% 5% 6% 5% 8% 9% 28%	5277
	21st to end	Night	11% 7% 3 9% 6% 6% 7% 5% 7% 8% 33%	5736
August	1st to 10th	Night	16% 7% 3 7% 5% 5% 6% 4 7% 10% 29%	4135
	11th to 20th	Night	10% 7% 3 8% 6% 5% 6% 5% 7% 9% 35%	4259
	21st to end	Night	9% 6% 2 7% 5% 5% 6% 4 6% 9% 42%	5045
September	1st to 10th	Night	12% 5% 2 6% 4 4 5% 3 6% 7% 47%	2100
	11th to 20th	Night	12% 6% 2 6% 4 4 4 4 7% 6% 46%	2059
	21st to end	Night	22% 8% 3 6% 3 3 4 3 5% 6% 37%	2296
October	1st to 10th	Night	17% 6% 2 4 4 3 3 4 4 6% 48%	2400
	11th to 20th	Night	16% 5% 2 5% 4 3 3 4 5% 6% 49%	2400
	21st to end	Night	13% 5% 2 5% 3 3 4 3 4 6% 53%	2640
November	1st to 10th	Night	12% 7% 2 5% 4 3 3 3 4 5% 53%	2461
	11th to 20th	Night	14% 6% 2 5% 3 3 4 3 4 6% 50%	2727
	21st to end	Night	13% 4 2 5% 3 4 4 4 5% 6% 51%	2940
December	1st to 10th	Night	10% 5% 2 5% 4 3 3 3 6% 6% 53%	4720
	11th to 20th	Night	20% 6% 2 6% 3 3 4 3 5% 5% 41%	5345
	21st to end	Night	16% 6% 2 5% 3 4 4 3 6% 6% 44%	7133

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	37% 2 9% 24% 20% 8%	5259
	11th to 20th	Day	34% 3 5% 18% 28% 13%	5280
	21st to end	Day	42% 3 7% 27% 18% 4	5780
February	1st to 10th	Day	40% 6% 11% 25% 15% 3	1890
	11th to 20th	Day	43% 4 8% 21% 19% 5%	1889
	21st to end	Day	46% 6% 10% 17% 16% 5%	1772
March	1st to 10th	Day	44% 6% 9% 17% 17% 8%	5045
	11th to 20th	Day	32% 5% 9% 23% 22% 10%	5090
	21st to end	Day	43% 4 10% 18% 18% 6%	5586
April	1st to 10th	Day	32% 6% 12% 23% 20% 8%	2509
	11th to 20th	Day	34% 5% 11% 23% 21% 6%	2494
	21st to end	Day	41% 5% 12% 23% 15% 5%	2520
May	1st to 10th	Day	42% 6% 13% 22% 15% 1	7563
	11th to 20th	Day	42% 5% 13% 23% 16% 1	7630
	21st to end	Day	43% 6% 12% 19% 17% 3	8961
June	1st to 10th	Day	33% 8% 17% 24% 16% 2	2940
	11th to 20th	Day	35% 9% 17% 23% 15% 1	2940
	21st to end	Day	32% 9% 16% 25% 15% 1	2940
July	1st to 10th	Day	34% 6% 21% 23% 12% 3	7958
	11th to 20th	Day	43% 7% 22% 21% 7% 1	7611
	21st to end	Day	40% 5% 14% 21% 18%	8156
August	1st to 10th	Day	47% 7% 22% 19% 5%	6001
	11th to 20th	Day	40% 7% 21% 22% 9%	5780
	21st to end	Day	32% 4 19% 28% 16% 1	6080
September	1st to 10th	Day	36% 7% 14% 19% 21% 4	2520
	11th to 20th	Day	38% 6% 9% 24% 19% 3	2405
	21st to end	Day	47% 4 10% 19% 15% 4	2102
October	1st to 10th	Day	36% 3 8% 19% 29% 5%	3260
	11th to 20th	Day	25% 3 5% 22% 32% 13%	3240
	21st to end	Day	21% 3 10% 28% 25% 13%	3538
November	1st to 10th	Day	32% 4 9% 25% 26% 4	2057
	11th to 20th	Day	35% 3 10% 22% 22% 7%	1887
	21st to end	Day	34% 4 9% 24% 24% 5%	1680
December	1st to 10th	Day	35% 4 9% 27% 18% 8%	2680
	11th to 20th	Day	40% 3 12% 24% 16% 5%	3066
	21st to end	Day	41% 5% 13% 25% 15% 1	4048
January	1st to 10th	Night	34% 3 10% 22% 22% 8%	7636
	11th to 20th	Night	34% 3 4 21% 28% 10%	7680
	21st to end	Night	38% 3 6% 27% 20% 6%	8401
February	1st to 10th	Night	40% 5% 11% 23% 18% 3	2730
	11th to 20th	Night	45% 3 8% 19% 19% 6%	2627
	21st to end	Night	41% 3 8% 22% 17% 8%	2031
March	1st to 10th	Night	37% 4 8% 21% 21% 8%	5028
	11th to 20th	Night	31% 4 8% 21% 26% 10%	5090
	21st to end	Night	38% 4 9% 22% 21% 6%	5588
April	1st to 10th	Night	38% 6% 11% 17% 22% 6%	2111
	11th to 20th	Night	33% 6% 12% 23% 21% 6%	2075
	21st to end	Night	37% 7% 11% 24% 16% 5%	2100
May	1st to 10th	Night	45% 5% 15% 22% 12% 1	5408
	11th to 20th	Night	43% 6% 13% 25% 13% 1	5235
	21st to end	Night	48% 6% 12% 19% 14% 2	5197
June	1st to 10th	Night	35% 9% 14% 24% 17% 1	1680
	11th to 20th	Night	36% 10% 18% 20% 15% 1	1680
	21st to end	Night	32% 8% 16% 23% 18% 3	1680
July	1st to 10th	Night	44% 8% 16% 19% 11% 2	4874
	11th to 20th	Night	50% 8% 17% 17% 6% 1	5226
	21st to end	Night	48% 6% 13% 17% 15%	5606
August	1st to 10th	Night	49% 8% 19% 19% 5%	4124
	11th to 20th	Night	44% 6% 20% 22% 8%	4286
	21st to end	Night	39% 6% 13% 27% 14% 1	5045
September	1st to 10th	Night	37% 7% 14% 21% 15% 6%	2100
	11th to 20th	Night	37% 7% 11% 23% 20% 2	2059
	21st to end	Night	48% 6% 11% 17% 14% 3	2296
October	1st to 10th	Night	40% 4 10% 18% 23% 5%	3920
	11th to 20th	Night	26% 3 8% 21% 31% 11%	3899
	21st to end	Night	22% 2 6% 31% 26% 13%	4252
November	1st to 10th	Night	34% 5% 9% 22% 25% 5%	2461
	11th to 20th	Night	36% 5% 8% 19% 23% 9%	2727
	21st to end	Night	33% 5% 9% 25% 23% 6%	2940
December	1st to 10th	Night	31% 4 8% 28% 24% 5%	4720
	11th to 20th	Night	45% 3 10% 20% 15% 6%	5348
	21st to end	Night	38% 5% 12% 27% 16% 2	7133

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	27% 24% 29% 15% 5%	330
	11th to 20th	Day	27% 28% 32% 11% 2	330
	21st to end	Day	24% 27% 36% 10% 3	363
February	1st to 10th	Day	21% 24% 40% 12% 3	330
	11th to 20th	Day	40% 22% 28% 9% 2	367
	21st to end	Day	30% 16% 32% 19% 3	446
March	1st to 10th	Day	23% 19% 35% 19% 4	540
	11th to 20th	Day	23% 21% 34% 16% 5% 1	540
	21st to end	Day	25% 18% 36% 17% 4 1	594
April	1st to 10th	Day	22% 17% 33% 20% 6% 1	540
	11th to 20th	Day	19% 14% 33% 24% 8% 3	532
	21st to end	Day	24% 11% 34% 22% 8% 1	540
May	1st to 10th	Day	21% 16% 33% 21% 6% 3	543
	11th to 20th	Day	20% 9% 30% 26% 13% 2	567
	21st to end	Day	20% 7% 25% 27% 18% 3	617
June	1st to 10th	Day	10% 6% 30% 28% 21% 5%	570
	11th to 20th	Day	13% 6% 25% 31% 17% 8%	570
	21st to end	Day	9% 5% 24% 34% 22% 6%	570
July	1st to 10th	Day	10% 4 16% 31% 28% 11%	565
	11th to 20th	Day	6% 2 16% 36% 28% 11%	564
	21st to end	Day	10% 3 21% 31% 24% 11%	620
August	1st to 10th	Day	14% 4 19% 30% 25% 8%	566
	11th to 20th	Day	9% 4 18% 32% 27% 9%	559
	21st to end	Day	9% 3 19% 30% 25% 13%	627
September	1st to 10th	Day	14% 5% 18% 28% 21% 13%	570
	11th to 20th	Day	16% 3 17% 29% 24% 10%	542
	21st to end	Day	28% 6% 23% 26% 11% 5%	530
October	1st to 10th	Day	21% 5% 24% 24% 18% 8%	530
	11th to 20th	Day	17% 13% 23% 28% 17% 2	530
	21st to end	Day	18% 13% 31% 26% 9% 3	583
November	1st to 10th	Day	16% 11% 30% 29% 11% 4	535
	11th to 20th	Day	21% 13% 29% 26% 10% 1	417
	21st to end	Day	23% 18% 29% 20% 9% 2	220
December	1st to 10th	Day	24% 15% 38% 17% 5% 1	220
	11th to 20th	Day	23% 15% 35% 19% 7% 1	220
	21st to end	Day	27% 17% 28% 17% 10%	242
January	1st to 10th	Night	20% 18% 38% 21% 3	840
	11th to 20th	Night	21% 18% 35% 23% 3	840
	21st to end	Night	20% 16% 40% 23% 2	924
February	1st to 10th	Night	20% 13% 40% 24% 3	840
	11th to 20th	Night	27% 17% 36% 18% 1	823
	21st to end	Night	22% 18% 36% 21% 3	692
March	1st to 10th	Night	18% 16% 37% 25% 3	840
	11th to 20th	Night	21% 17% 35% 21% 6%	840
	21st to end	Night	17% 15% 39% 24% 5%	924
April	1st to 10th	Night	17% 18% 38% 22% 5%	840
	11th to 20th	Night	13% 14% 38% 27% 7%	831
	21st to end	Night	15% 10% 37% 30% 8%	840
May	1st to 10th	Night	16% 11% 34% 29% 10%	683
	11th to 20th	Night	17% 5% 30% 31% 15% 1	621
	21st to end	Night	17% 2 21% 39% 20% 2	486
June	1st to 10th	Night	10% 3 21% 43% 23%	420
	11th to 20th	Night	11% 4 19% 44% 19% 2	420
	21st to end	Night	8% 3 21% 44% 23% 1	420
July	1st to 10th	Night	12% 3 12% 44% 26% 4	488
	11th to 20th	Night	7% 1 11% 41% 34% 6%	612
	21st to end	Night	8% 2 16% 43% 27% 4	690
August	1st to 10th	Night	13% 2 12% 42% 29% 3	627
	11th to 20th	Night	13% 3 11% 42% 27% 4	697
	21st to end	Night	12% 2 15% 36% 31% 4	924
September	1st to 10th	Night	14% 3 13% 37% 28% 5%	840
	11th to 20th	Night	14% 5% 15% 33% 30% 4	813
	21st to end	Night	25% 5% 18% 33% 18% 1	800
October	1st to 10th	Night	20% 4 19% 31% 22% 4	800
	11th to 20th	Night	19% 7% 26% 32% 15% 1	800
	21st to end	Night	16% 8% 28% 33% 13% 1	880
November	1st to 10th	Night	16% 9% 29% 32% 13% 2	820
	11th to 20th	Night	18% 11% 33% 29% 9%	840
	21st to end	Night	14% 12% 34% 31% 9% 1	840
December	1st to 10th	Night	21% 11% 35% 27% 5% 1	840
	11th to 20th	Night	20% 10% 35% 31% 5%	840
	21st to end	Night	20% 13% 29% 33% 4	924

Page generated at 2026-09-11 04:11:58. Version ac07

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