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 2024-11-01.

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	14% 6% 2 6% 4 4 4 4 6% 8% 42%	100990
	Night	15% 6% 2 6% 4 4 4 4 5% 7% 43%	97905
Transparency	Day	39% 7% 13% 22% 16% 3	100800
	Night	39% 6% 11% 22% 17% 4	97766
Seeing	Day	18% 11% 27% 25% 14% 5%	15084
	Night	17% 9% 28% 31% 13% 1	24776

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	18% 5% 2 4 3 3 3 2 4 5% 51%	2836
	11th to 20th	Day	15% 8% 3 7% 4 3 4 3 5% 5% 44%	2840
	21st to end	Day	18% 10% 2 7% 4 4 4 3 4 6% 38%	3124
February	1st to 10th	Day	12% 8% 3 7% 4 4 5% 4 6% 6% 41%	1710
	11th to 20th	Day	20% 7% 2 5% 3 3 3 3 5% 6% 43%	1696
	21st to end	Day	18% 8% 2 7% 5% 4 4 4 5% 6% 37%	1608
March	1st to 10th	Day	20% 8% 2 6% 4 5% 4 3 4 7% 37%	3435
	11th to 20th	Day	10% 4 2 5% 4 4 4 4 5% 7% 52%	3480
	21st to end	Day	21% 7% 2 5% 5% 4 4 3 5% 6% 38%	3815
April	1st to 10th	Day	11% 5% 2 4 4 4 4 4 5% 7% 51%	2270
	11th to 20th	Day	12% 6% 3 5% 4 3 4 4 5% 6% 49%	2254
	21st to end	Day	16% 5% 2 6% 5% 4 4 4 5% 7% 41%	2280
May	1st to 10th	Day	17% 8% 3 7% 5% 5% 6% 4 5% 8% 32%	4037
	11th to 20th	Day	21% 7% 3 6% 4 5% 5% 4 6% 9% 31%	4081
	21st to end	Day	9% 4 2 5% 4 4 5% 4 6% 10% 47%	4779
June	1st to 10th	Day	10% 5% 2 6% 4 5% 4 4 7% 10% 44%	2660
	11th to 20th	Day	10% 5% 2 5% 5% 5% 5% 5% 8% 10% 41%	2660
	21st to end	Day	7% 5% 2 5% 5% 5% 6% 5% 7% 10% 43%	2660
July	1st to 10th	Day	6% 4 2 5% 4 5% 6% 5% 8% 12% 42%	4296
	11th to 20th	Day	11% 5% 2 6% 5% 5% 5% 5% 9% 12% 37%	4120
	21st to end	Day	11% 6% 3 7% 6% 6% 6% 5% 7% 9% 34%	4466
August	1st to 10th	Day	16% 7% 2 6% 5% 5% 5% 4 8% 10% 31%	4104
	11th to 20th	Day	9% 5% 2 7% 5% 6% 6% 5% 7% 9% 39%	3894
	21st to end	Day	8% 4 2 5% 4 4 4 3 6% 10% 49%	4180
September	1st to 10th	Day	13% 5% 2 6% 4 4 4 4 6% 7% 46%	2280
	11th to 20th	Day	12% 6% 2 6% 4 4 4 4 5% 8% 44%	2251
	21st to end	Day	21% 6% 3 6% 4 4 4 3 5% 7% 39%	1997
October	1st to 10th	Day	16% 6% 2 5% 4 3 4 3 4 6% 48%	1900
	11th to 20th	Day	16% 3 2 4 4 3 3 3 5% 5% 53%	1900
	21st to end	Day	14% 4 2 6% 3 3 3 3 4 5% 53%	2090
November	1st to 10th	Day	13% 5% 1 3 4 4 3 3 3 6% 54%	1857
	11th to 20th	Day	15% 6% 2 3 3 4 4 2 5% 5% 50%	1708
	21st to end	Day	15% 4 2 4 3 3 3 4 5% 6% 51%	1520
December	1st to 10th	Day	17% 7% 2 5% 4 5% 4 4 6% 7% 41%	1520
	11th to 20th	Day	17% 6% 1 5% 2 4 3 2 3 5% 51%	1910
	21st to end	Day	17% 7% 3 7% 4 4 5% 3 5% 6% 39%	2772
January	1st to 10th	Night	14% 8% 2 5% 4 4 3 3 5% 5% 47%	4109
	11th to 20th	Night	18% 7% 2 5% 3 3 3 3 3 5% 47%	4120
	21st to end	Night	21% 8% 2 6% 3 3 3 3 4 4 43%	4532
February	1st to 10th	Night	14% 7% 2 5% 4 4 4 4 5% 6% 44%	2470
	11th to 20th	Night	19% 7% 2 6% 4 4 3 2 4 6% 43%	2369
	21st to end	Night	17% 6% 3 6% 5% 3 3 3 4 6% 45%	1843
March	1st to 10th	Night	20% 7% 2 6% 3 4 4 3 6% 6% 39%	3418
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 5% 7% 51%	3480
	21st to end	Night	15% 7% 2 5% 3 3 4 3 4 6% 48%	3817
April	1st to 10th	Night	14% 6% 2 5% 4 4 4 3 5% 6% 47%	1910
	11th to 20th	Night	11% 5% 3 5% 4 3 4 3 5% 8% 50%	1875
	21st to end	Night	14% 5% 2 6% 4 3 4 4 6% 7% 45%	1900
May	1st to 10th	Night	17% 8% 3 7% 5% 4 4 4 5% 9% 34%	2886
	11th to 20th	Night	23% 7% 3 7% 5% 4 4 3 6% 6% 33%	2812
	21st to end	Night	10% 5% 2 5% 5% 5% 4 4 7% 10% 44%	2772
June	1st to 10th	Night	10% 5% 2 7% 5% 4 5% 4 6% 9% 44%	1520
	11th to 20th	Night	9% 5% 2 6% 5% 5% 5% 5% 7% 10% 40%	1520
	21st to end	Night	9% 4 3 5% 5% 3 4 4 8% 11% 45%	1520
July	1st to 10th	Night	7% 5% 2 7% 5% 6% 6% 5% 8% 11% 38%	2645
	11th to 20th	Night	9% 5% 2 8% 5% 6% 6% 5% 8% 10% 36%	2840
	21st to end	Night	11% 8% 3 9% 6% 6% 7% 5% 6% 7% 31%	3087
August	1st to 10th	Night	16% 6% 3 7% 5% 5% 6% 4 8% 9% 32%	2825
	11th to 20th	Night	10% 6% 3 7% 6% 5% 6% 4 7% 9% 38%	2903
	21st to end	Night	9% 6% 2 6% 5% 4 5% 4 6% 9% 44%	3476
September	1st to 10th	Night	13% 6% 2 6% 4 4 5% 3 6% 6% 45%	1900
	11th to 20th	Night	12% 6% 2 5% 4 4 4 4 7% 6% 46%	1926
	21st to end	Night	22% 8% 3 6% 3 3 4 3 5% 5% 38%	2181
October	1st to 10th	Night	17% 6% 2 4 4 3 3 4 4 6% 47%	2280
	11th to 20th	Night	16% 5% 2 5% 4 3 3 4 5% 6% 48%	2280
	21st to end	Night	13% 4 2 5% 3 3 4 3 4 6% 53%	2508
November	1st to 10th	Night	12% 7% 2 6% 3 3 3 3 4 5% 52%	2228
	11th to 20th	Night	14% 5% 2 5% 3 3 4 3 4 6% 51%	2467
	21st to end	Night	13% 4 2 4 3 4 4 4 5% 6% 50%	2660
December	1st to 10th	Night	17% 8% 2 6% 4 4 3 4 5% 5% 42%	2660
	11th to 20th	Night	18% 7% 2 5% 3 3 3 3 5% 6% 46%	3285
	21st to end	Night	17% 7% 3 6% 4 4 4 4 6% 6% 40%	4881

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	36% 4 7% 32% 17% 5%	2837
	11th to 20th	Day	40% 5% 8% 20% 22% 5%	2840
	21st to end	Day	47% 5% 9% 21% 15% 3	3124
February	1st to 10th	Day	41% 6% 10% 26% 14% 2	1710
	11th to 20th	Day	41% 5% 8% 21% 20% 5%	1705
	21st to end	Day	46% 7% 11% 14% 16% 5%	1608
March	1st to 10th	Day	46% 7% 10% 18% 14% 6%	3435
	11th to 20th	Day	29% 6% 9% 23% 23% 9%	3480
	21st to end	Day	46% 6% 10% 18% 17% 3	3815
April	1st to 10th	Day	31% 6% 11% 24% 19% 8%	2270
	11th to 20th	Day	35% 5% 11% 21% 21% 6%	2254
	21st to end	Day	42% 5% 12% 21% 15% 5%	2280
May	1st to 10th	Day	47% 9% 13% 18% 11% 2	4074
	11th to 20th	Day	47% 8% 14% 21% 10% 1	4085
	21st to end	Day	30% 9% 17% 22% 20% 2	4793
June	1st to 10th	Day	33% 9% 17% 25% 15% 1	2660
	11th to 20th	Day	35% 9% 16% 22% 15% 2	2660
	21st to end	Day	32% 10% 16% 24% 16% 2	2660
July	1st to 10th	Day	33% 9% 24% 18% 12% 5%	4230
	11th to 20th	Day	38% 7% 24% 24% 8% 1	4051
	21st to end	Day	44% 8% 14% 19% 14% 1	4324
August	1st to 10th	Day	47% 6% 18% 22% 7% 1	4091
	11th to 20th	Day	38% 8% 16% 25% 12%	3933
	21st to end	Day	30% 5% 17% 29% 17% 2	4180
September	1st to 10th	Day	37% 7% 13% 17% 21% 4	2280
	11th to 20th	Day	37% 7% 9% 25% 19% 4	2251
	21st to end	Day	47% 4 9% 20% 16% 4	1997
October	1st to 10th	Day	38% 4 11% 23% 21% 4	1900
	11th to 20th	Day	33% 5% 8% 24% 24% 5%	1900
	21st to end	Day	33% 5% 7% 26% 23% 7%	2090
November	1st to 10th	Day	33% 4 9% 24% 26% 5%	1857
	11th to 20th	Day	35% 4 10% 21% 22% 7%	1708
	21st to end	Day	34% 5% 9% 23% 24% 5%	1520
December	1st to 10th	Day	41% 5% 11% 24% 14% 5%	1520
	11th to 20th	Day	36% 4 8% 29% 16% 7%	1906
	21st to end	Day	42% 7% 11% 25% 13% 1	2772
January	1st to 10th	Night	37% 4 9% 23% 21% 5%	4109
	11th to 20th	Night	40% 4 7% 21% 22% 5%	4120
	21st to end	Night	45% 4 7% 22% 16% 6%	4532
February	1st to 10th	Night	40% 5% 11% 24% 17% 3	2470
	11th to 20th	Night	44% 3 8% 20% 19% 7%	2371
	21st to end	Night	42% 4 9% 22% 17% 7%	1843
March	1st to 10th	Night	45% 5% 10% 22% 16% 3	3418
	11th to 20th	Night	31% 5% 8% 21% 26% 9%	3480
	21st to end	Night	38% 5% 9% 22% 21% 5%	3817
April	1st to 10th	Night	38% 7% 10% 16% 23% 7%	1910
	11th to 20th	Night	32% 6% 12% 22% 22% 6%	1875
	21st to end	Night	37% 7% 12% 23% 16% 5%	1900
May	1st to 10th	Night	46% 8% 15% 18% 12% 2	2914
	11th to 20th	Night	48% 9% 12% 21% 8% 1	2813
	21st to end	Night	32% 9% 17% 25% 15% 2	2779
June	1st to 10th	Night	35% 9% 14% 25% 15% 1	1520
	11th to 20th	Night	35% 11% 18% 19% 15% 2	1520
	21st to end	Night	32% 9% 16% 22% 18% 4	1520
July	1st to 10th	Night	38% 10% 21% 16% 12% 3	2602
	11th to 20th	Night	41% 8% 22% 21% 6% 1	2786
	21st to end	Night	50% 8% 13% 16% 11%	2988
August	1st to 10th	Night	48% 7% 17% 22% 6%	2814
	11th to 20th	Night	41% 6% 17% 24% 12%	2930
	21st to end	Night	35% 7% 12% 29% 16% 1	3476
September	1st to 10th	Night	39% 8% 14% 18% 15% 6%	1900
	11th to 20th	Night	36% 7% 11% 22% 21% 2	1926
	21st to end	Night	47% 6% 10% 18% 15% 4	2181
October	1st to 10th	Night	38% 5% 11% 22% 20% 4	2280
	11th to 20th	Night	36% 5% 9% 22% 23% 6%	2280
	21st to end	Night	33% 4 9% 24% 23% 7%	2508
November	1st to 10th	Night	35% 5% 9% 22% 23% 6%	2228
	11th to 20th	Night	36% 5% 9% 19% 23% 9%	2467
	21st to end	Night	33% 5% 9% 25% 22% 5%	2660
December	1st to 10th	Night	43% 5% 9% 22% 16% 4	2660
	11th to 20th	Night	39% 5% 9% 22% 20% 6%	3288
	21st to end	Night	40% 7% 11% 24% 16% 2	4881

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% 23% 30% 16% 5%	270
	11th to 20th	Day	27% 27% 32% 12% 3	270
	21st to end	Day	24% 23% 40% 10% 3	297
February	1st to 10th	Day	21% 24% 40% 11% 3	270
	11th to 20th	Day	38% 22% 29% 10% 2	303
	21st to end	Day	31% 16% 30% 20% 2	382
March	1st to 10th	Day	23% 19% 34% 18% 5%	460
	11th to 20th	Day	22% 22% 34% 16% 5% 1	460
	21st to end	Day	25% 17% 35% 18% 5% 1	506
April	1st to 10th	Day	23% 17% 33% 19% 6% 1	460
	11th to 20th	Day	19% 14% 31% 24% 8% 4	452
	21st to end	Day	25% 10% 36% 21% 7% 1	460
May	1st to 10th	Day	21% 16% 30% 23% 7% 3	463
	11th to 20th	Day	21% 8% 30% 26% 13% 3	487
	21st to end	Day	17% 4 26% 29% 20% 4	529
June	1st to 10th	Day	11% 6% 27% 30% 23% 4	490
	11th to 20th	Day	12% 6% 23% 32% 17% 10%	490
	21st to end	Day	9% 5% 25% 33% 22% 6%	490
July	1st to 10th	Day	10% 5% 16% 33% 27% 10%	485
	11th to 20th	Day	7% 1 17% 36% 29% 10%	484
	21st to end	Day	11% 3 21% 31% 23% 10%	532
August	1st to 10th	Day	12% 4 19% 30% 26% 9%	486
	11th to 20th	Day	9% 5% 18% 31% 28% 10%	479
	21st to end	Day	10% 3 17% 29% 26% 15%	539
September	1st to 10th	Day	15% 5% 17% 26% 21% 15%	490
	11th to 20th	Day	16% 3 17% 31% 23% 10%	490
	21st to end	Day	28% 6% 23% 27% 11% 5%	490
October	1st to 10th	Day	22% 6% 24% 23% 18% 7%	490
	11th to 20th	Day	16% 12% 23% 29% 18% 2	490
	21st to end	Day	16% 12% 32% 27% 10% 3	539
November	1st to 10th	Day	18% 10% 27% 28% 12% 4	455
	11th to 20th	Day	20% 13% 28% 26% 11% 2	358
	21st to end	Day	21% 15% 31% 23% 8% 2	180
December	1st to 10th	Day	23% 16% 37% 18% 5% 1	180
	11th to 20th	Day	23% 16% 34% 17% 8% 2	180
	21st to end	Day	29% 15% 28% 18% 11% 1	198
January	1st to 10th	Night	21% 17% 38% 21% 3	760
	11th to 20th	Night	22% 16% 33% 25% 3	760
	21st to end	Night	20% 16% 38% 24% 2	836
February	1st to 10th	Night	20% 13% 40% 24% 4	760
	11th to 20th	Night	26% 18% 36% 19% 1	743
	21st to end	Night	23% 16% 37% 21% 3	628
March	1st to 10th	Night	19% 16% 36% 25% 4	760
	11th to 20th	Night	22% 18% 34% 20% 6%	760
	21st to end	Night	18% 14% 37% 25% 6%	836
April	1st to 10th	Night	16% 18% 38% 22% 5%	760
	11th to 20th	Night	14% 14% 36% 28% 7% 1	751
	21st to end	Night	16% 10% 36% 29% 8%	760
May	1st to 10th	Night	16% 11% 33% 29% 11%	618
	11th to 20th	Night	18% 5% 29% 32% 15% 1	561
	21st to end	Night	14% 1 20% 41% 22% 3	439
June	1st to 10th	Night	10% 3 19% 45% 24%	380
	11th to 20th	Night	10% 4 18% 45% 21% 2	380
	21st to end	Night	8% 4 22% 44% 22% 1	380
July	1st to 10th	Night	10% 3 13% 44% 25% 4	440
	11th to 20th	Night	6% 1 12% 41% 34% 6%	552
	21st to end	Night	8% 2 17% 43% 27% 4	624
August	1st to 10th	Night	13% 1 12% 41% 30% 3	567
	11th to 20th	Night	14% 3 11% 42% 27% 4	630
	21st to end	Night	12% 2 14% 35% 32% 5%	836
September	1st to 10th	Night	15% 3 12% 36% 29% 5%	760
	11th to 20th	Night	14% 4 15% 33% 30% 4	760
	21st to end	Night	25% 5% 18% 32% 19% 1	760
October	1st to 10th	Night	20% 4 19% 31% 21% 4	760
	11th to 20th	Night	18% 7% 26% 32% 15% 1	760
	21st to end	Night	15% 8% 28% 33% 14% 1	836
November	1st to 10th	Night	17% 8% 29% 32% 13% 2	743
	11th to 20th	Night	17% 11% 33% 29% 10%	760
	21st to end	Night	14% 12% 32% 32% 9% 1	760
December	1st to 10th	Night	23% 11% 33% 27% 6% 1	760
	11th to 20th	Night	19% 9% 35% 31% 5%	760
	21st to end	Night	20% 13% 28% 34% 4	836

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