Churchill Chimes Equestrian Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Churchill Chimes Equestrian Center clear sky chart from 2005-11-06 to 2026-01-02.

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	15% 10% 3 9% 5% 5% 5% 4 6% 7% 32%	127521
	Night	14% 10% 3 9% 5% 5% 5% 4 6% 7% 32%	123822
Transparency	Day	47% 9% 13% 20% 11% 1	131111
	Night	46% 9% 13% 20% 11% 1	128317
Seeing	Day	21% 16% 30% 21% 9% 3	15823
	Night	20% 14% 31% 24% 9% 1	25263

By Month

Percentage Cloud Cover NE (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	13% 12% 4 10% 7% 6% 4 4 5% 6% 29%	3605
	11th to 20th	Day	9% 17% 7% 19% 9% 7% 5% 3 4 5% 15%	3843
	21st to end	Day	16% 18% 6% 16% 6% 5% 5% 3 4 5% 17%	4466
February	1st to 10th	Day	14% 18% 5% 11% 7% 6% 5% 3 5% 5% 20%	1800
	11th to 20th	Day	12% 15% 8% 12% 7% 5% 4 3 4 6% 24%	1753
	21st to end	Day	17% 15% 5% 10% 7% 5% 4 4 4 5% 25%	1534
March	1st to 10th	Day	18% 10% 5% 9% 6% 4 4 3 5% 5% 30%	4932
	11th to 20th	Day	11% 13% 4 9% 6% 6% 6% 4 5% 7% 29%	4980
	21st to end	Day	18% 12% 3 9% 4 4 4 3 5% 5% 33%	5465
April	1st to 10th	Day	18% 14% 3 8% 5% 4 4 4 5% 6% 28%	2375
	11th to 20th	Day	19% 11% 3 7% 4 4 4 4 5% 6% 34%	2437
	21st to end	Day	20% 9% 4 8% 5% 4 4 3 5% 6% 33%	2600
May	1st to 10th	Day	20% 9% 3 8% 4 4 4 4 5% 7% 31%	5924
	11th to 20th	Day	15% 10% 4 8% 5% 5% 5% 3 5% 7% 34%	6318
	21st to end	Day	18% 6% 2 6% 4 4 5% 4 5% 7% 37%	6949
June	1st to 10th	Day	15% 8% 3 6% 5% 4 5% 4 7% 8% 35%	2800
	11th to 20th	Day	12% 6% 3 6% 5% 5% 6% 4 6% 9% 38%	2800
	21st to end	Day	15% 5% 2 7% 5% 5% 5% 5% 6% 9% 36%	2800
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 6% 5% 7% 9% 38%	6360
	11th to 20th	Day	9% 5% 2 6% 4 5% 6% 5% 7% 10% 43%	6360
	21st to end	Day	7% 4 2 6% 5% 5% 6% 5% 7% 9% 45%	6566
August	1st to 10th	Day	15% 8% 2 6% 5% 5% 4 5% 6% 8% 36%	4234
	11th to 20th	Day	11% 7% 3 8% 5% 5% 5% 5% 7% 9% 35%	4174
	21st to end	Day	9% 6% 3 7% 4 5% 5% 4 6% 9% 43%	4482
September	1st to 10th	Day	12% 6% 2 8% 4 4 4 4 7% 7% 42%	2400
	11th to 20th	Day	11% 6% 2 6% 5% 4 4 4 6% 8% 45%	2303
	21st to end	Day	15% 7% 2 7% 5% 5% 5% 4 5% 7% 37%	2145
October	1st to 10th	Day	18% 9% 3 7% 5% 5% 4 4 4 8% 36%	2000
	11th to 20th	Day	19% 10% 3 9% 5% 4 6% 4 5% 6% 29%	2000
	21st to end	Day	23% 13% 3 9% 5% 5% 5% 4 5% 6% 23%	2200
November	1st to 10th	Day	15% 11% 3 9% 6% 5% 4 4 5% 7% 31%	1762
	11th to 20th	Day	15% 12% 4 10% 6% 6% 6% 4 6% 6% 24%	1680
	21st to end	Day	17% 15% 5% 11% 7% 5% 6% 3 4 6% 20%	1680
December	1st to 10th	Day	17% 18% 5% 13% 7% 6% 6% 4 6% 6% 11%	2680
	11th to 20th	Day	17% 19% 4 10% 6% 4 4 3 5% 6% 22%	3066
	21st to end	Day	23% 18% 5% 15% 6% 5% 4 3 4 5% 13%	4048
January	1st to 10th	Night	14% 12% 4 10% 7% 6% 6% 4 7% 8% 23%	6364
	11th to 20th	Night	12% 13% 5% 16% 9% 6% 6% 4 6% 7% 17%	6028
	21st to end	Night	14% 14% 6% 12% 6% 5% 5% 4 6% 7% 22%	6490
February	1st to 10th	Night	13% 16% 5% 10% 7% 5% 6% 5% 6% 6% 22%	2600
	11th to 20th	Night	14% 14% 5% 10% 6% 4 5% 4 5% 7% 25%	2533
	21st to end	Night	13% 12% 3 11% 5% 6% 4 5% 6% 6% 28%	2094
March	1st to 10th	Night	15% 11% 4 10% 5% 5% 5% 3 5% 6% 31%	4908
	11th to 20th	Night	9% 8% 3 8% 6% 5% 6% 5% 7% 8% 35%	4979
	21st to end	Night	20% 8% 3 7% 5% 4 5% 3 5% 6% 35%	5467
April	1st to 10th	Night	19% 12% 3 7% 5% 5% 5% 3 5% 6% 31%	2024
	11th to 20th	Night	16% 8% 3 7% 5% 5% 4 3 5% 6% 38%	1927
	21st to end	Night	15% 8% 3 8% 5% 5% 4 4 6% 8% 34%	1800
May	1st to 10th	Night	22% 9% 2 6% 4 4 4 4 5% 6% 34%	4015
	11th to 20th	Night	12% 9% 3 7% 5% 5% 4 4 6% 7% 39%	3575
	21st to end	Night	17% 6% 2 5% 4 4 4 4 5% 7% 42%	3926
June	1st to 10th	Night	12% 5% 2 7% 5% 4 5% 5% 6% 9% 41%	1600
	11th to 20th	Night	9% 6% 2 7% 6% 5% 6% 4 6% 8% 43%	1600
	21st to end	Night	12% 6% 2 7% 4 4 4 4 6% 8% 42%	1600
July	1st to 10th	Night	7% 6% 2 6% 5% 4 5% 5% 6% 9% 46%	3600
	11th to 20th	Night	9% 5% 2 5% 4 4 4 4 6% 9% 49%	3600
	21st to end	Night	8% 5% 1 5% 3 4 4 3 6% 9% 52%	4282
August	1st to 10th	Night	9% 6% 2 6% 5% 4 5% 4 5% 7% 48%	2915
	11th to 20th	Night	11% 5% 2 5% 4 3 4 3 5% 8% 50%	2875
	21st to end	Night	9% 5% 2 6% 4 4 5% 4 6% 7% 48%	3383
September	1st to 10th	Night	9% 5% 2 6% 3 6% 5% 4 6% 7% 47%	2000
	11th to 20th	Night	10% 4 2 4 4 4 3 3 5% 7% 55%	2094
	21st to end	Night	17% 7% 2 7% 4 3 4 3 5% 7% 41%	2253
October	1st to 10th	Night	14% 7% 2 8% 4 4 5% 4 6% 7% 40%	2400
	11th to 20th	Night	18% 9% 3 8% 5% 5% 5% 3 5% 6% 34%	2400
	21st to end	Night	20% 10% 3 7% 6% 5% 5% 4 6% 6% 30%	2640
November	1st to 10th	Night	17% 10% 3 7% 5% 4 4 4 6% 7% 34%	2752
	11th to 20th	Night	15% 12% 4 9% 7% 6% 5% 4 6% 7% 26%	2940
	21st to end	Night	18% 13% 3 9% 6% 6% 6% 4 6% 6% 22%	2940
December	1st to 10th	Night	16% 15% 4 11% 8% 5% 6% 5% 6% 7% 15%	4720
	11th to 20th	Night	15% 18% 5% 11% 6% 5% 5% 4 5% 5% 21%	5348
	21st to end	Night	23% 15% 5% 14% 6% 5% 5% 3 5% 5% 14%	7150

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	50% 10% 13% 15% 11%	3606
	11th to 20th	Day	69% 7% 10% 9% 4 1	3876
	21st to end	Day	66% 8% 10% 9% 6%	4466
February	1st to 10th	Day	63% 8% 10% 15% 3 1	1800
	11th to 20th	Day	58% 8% 11% 15% 6% 1	1762
	21st to end	Day	59% 8% 12% 14% 6% 1	1534
March	1st to 10th	Day	51% 7% 14% 14% 13% 1	4935
	11th to 20th	Day	49% 9% 16% 18% 7% 2	4980
	21st to end	Day	49% 7% 10% 18% 14% 1	5465
April	1st to 10th	Day	54% 6% 12% 17% 10% 1	2375
	11th to 20th	Day	48% 7% 10% 21% 13% 1	2437
	21st to end	Day	49% 8% 11% 17% 12% 3	2600
May	1st to 10th	Day	48% 8% 13% 16% 11% 4	5933
	11th to 20th	Day	47% 10% 11% 16% 16% 1	6322
	21st to end	Day	43% 7% 13% 22% 12% 3	6949
June	1st to 10th	Day	43% 9% 13% 19% 15% 1	2800
	11th to 20th	Day	39% 9% 13% 23% 15% 1	2800
	21st to end	Day	41% 9% 14% 22% 13% 1	2800
July	1st to 10th	Day	37% 9% 15% 23% 14% 2	6290
	11th to 20th	Day	31% 8% 15% 31% 14% 1	6285
	21st to end	Day	31% 10% 15% 29% 15%	6378
August	1st to 10th	Day	42% 9% 15% 22% 12% 1	4221
	11th to 20th	Day	39% 9% 15% 27% 9%	4213
	21st to end	Day	34% 8% 15% 33% 9% 1	4482
September	1st to 10th	Day	36% 10% 15% 27% 10% 1	2400
	11th to 20th	Day	33% 9% 15% 29% 14%	2303
	21st to end	Day	44% 8% 14% 25% 9%	2145
October	1st to 10th	Day	36% 7% 15% 27% 14% 1	3260
	11th to 20th	Day	39% 8% 17% 22% 14%	3240
	21st to end	Day	51% 9% 15% 20% 6%	3538
November	1st to 10th	Day	48% 9% 15% 19% 8% 1	1762
	11th to 20th	Day	54% 11% 14% 12% 7% 1	1680
	21st to end	Day	60% 10% 13% 14% 3	1680
December	1st to 10th	Day	67% 10% 13% 7% 3	2680
	11th to 20th	Day	60% 9% 12% 10% 8%	3066
	21st to end	Day	71% 9% 6% 8% 5% 1	4048
January	1st to 10th	Night	51% 10% 13% 19% 6%	6364
	11th to 20th	Night	62% 10% 12% 12% 4	6069
	21st to end	Night	57% 10% 12% 10% 10% 1	6490
February	1st to 10th	Night	58% 9% 11% 17% 5%	2600
	11th to 20th	Night	56% 8% 12% 17% 7%	2535
	21st to end	Night	52% 8% 14% 19% 7%	2094
March	1st to 10th	Night	50% 7% 11% 17% 11% 2	4918
	11th to 20th	Night	40% 9% 18% 22% 9% 2	4980
	21st to end	Night	45% 6% 11% 20% 15% 2	5467
April	1st to 10th	Night	51% 7% 11% 18% 12% 1	2024
	11th to 20th	Night	47% 7% 8% 20% 16% 2	1927
	21st to end	Night	45% 9% 12% 17% 16% 2	1800
May	1st to 10th	Night	48% 8% 11% 14% 14% 6%	4022
	11th to 20th	Night	41% 10% 13% 20% 14% 2	3576
	21st to end	Night	39% 8% 14% 23% 15% 2	3927
June	1st to 10th	Night	38% 8% 12% 24% 16% 2	1600
	11th to 20th	Night	36% 8% 13% 22% 20% 2	1600
	21st to end	Night	38% 8% 14% 23% 17% 1	1600
July	1st to 10th	Night	32% 8% 15% 25% 19% 2	3560
	11th to 20th	Night	29% 8% 13% 31% 17% 1	3552
	21st to end	Night	28% 8% 12% 30% 20% 1	4155
August	1st to 10th	Night	34% 6% 15% 28% 15% 2	2904
	11th to 20th	Night	32% 6% 17% 31% 13% 1	2902
	21st to end	Night	32% 8% 14% 32% 13% 1	3383
September	1st to 10th	Night	33% 8% 16% 27% 14% 1	2000
	11th to 20th	Night	28% 7% 13% 34% 18% 1	2094
	21st to end	Night	41% 8% 12% 26% 12% 1	2253
October	1st to 10th	Night	31% 7% 10% 28% 23% 1	3920
	11th to 20th	Night	39% 8% 16% 26% 11%	3899
	21st to end	Night	39% 8% 16% 26% 10%	4252
November	1st to 10th	Night	46% 7% 14% 21% 11% 1	2752
	11th to 20th	Night	52% 10% 14% 15% 9% 1	2940
	21st to end	Night	55% 12% 17% 13% 3	2940
December	1st to 10th	Night	61% 11% 14% 11% 3	4720
	11th to 20th	Night	59% 10% 10% 12% 9%	5348
	21st to end	Night	69% 10% 10% 7% 5%	7150

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	23% 26% 29% 17% 5%	202
	11th to 20th	Day	25% 30% 27% 14% 3 1	260
	21st to end	Day	25% 27% 33% 13% 2	330
February	1st to 10th	Day	30% 27% 29% 12% 2	300
	11th to 20th	Day	28% 28% 36% 7% 1	300
	21st to end	Day	35% 21% 36% 8%	279
March	1st to 10th	Day	26% 22% 35% 15% 3	500
	11th to 20th	Day	25% 23% 32% 16% 3 1	500
	21st to end	Day	32% 19% 30% 15% 4 1	550
April	1st to 10th	Day	29% 22% 32% 13% 5%	500
	11th to 20th	Day	31% 21% 25% 15% 6% 2	492
	21st to end	Day	27% 16% 35% 13% 7% 1	500
May	1st to 10th	Day	23% 16% 31% 18% 8% 4	503
	11th to 20th	Day	18% 16% 30% 24% 8% 3	527
	21st to end	Day	17% 13% 30% 26% 11% 3	573
June	1st to 10th	Day	17% 16% 31% 27% 8% 1	530
	11th to 20th	Day	15% 15% 31% 26% 11% 2	530
	21st to end	Day	22% 9% 32% 25% 10% 2	530
July	1st to 10th	Day	10% 9% 29% 33% 16% 3	525
	11th to 20th	Day	14% 8% 29% 30% 14% 6%	524
	21st to end	Day	8% 9% 36% 32% 10% 6%	576
August	1st to 10th	Day	12% 8% 27% 31% 15% 7%	526
	11th to 20th	Day	13% 10% 23% 29% 20% 6%	519
	21st to end	Day	13% 10% 30% 26% 15% 7%	583
September	1st to 10th	Day	14% 11% 26% 28% 15% 7%	530
	11th to 20th	Day	9% 7% 26% 25% 21% 12%	530
	21st to end	Day	17% 11% 30% 25% 11% 5%	530
October	1st to 10th	Day	20% 14% 29% 17% 17% 3	530
	11th to 20th	Day	22% 22% 32% 16% 6% 1	530
	21st to end	Day	28% 21% 29% 17% 4	583
November	1st to 10th	Day	27% 23% 29% 15% 6% 1	309
	11th to 20th	Day	25% 26% 30% 15% 4 1	220
	21st to end	Day	25% 26% 37% 10% 2	220
December	1st to 10th	Day	28% 20% 35% 12% 4	220
	11th to 20th	Day	33% 22% 32% 10% 3	220
	21st to end	Day	31% 21% 35% 12% 1	242
January	1st to 10th	Night	23% 24% 36% 12% 4	805
	11th to 20th	Night	28% 17% 33% 17% 4 1	800
	21st to end	Night	20% 17% 37% 21% 6%	880
February	1st to 10th	Night	22% 22% 38% 17% 2	800
	11th to 20th	Night	24% 20% 35% 18% 3	783
	21st to end	Night	22% 22% 37% 15% 4	660
March	1st to 10th	Night	21% 21% 37% 18% 3	800
	11th to 20th	Night	21% 20% 37% 17% 4 1	800
	21st to end	Night	21% 17% 32% 24% 6%	880
April	1st to 10th	Night	26% 17% 33% 21% 3	800
	11th to 20th	Night	19% 18% 35% 20% 8% 1	743
	21st to end	Night	20% 14% 35% 23% 9%	600
May	1st to 10th	Night	21% 9% 29% 29% 11% 2	588
	11th to 20th	Night	17% 9% 32% 29% 12% 1	394
	21st to end	Night	12% 9% 27% 35% 16% 1	433
June	1st to 10th	Night	13% 9% 32% 35% 11%	400
	11th to 20th	Night	12% 10% 30% 35% 14% 1	400
	21st to end	Night	14% 6% 31% 36% 12% 1	400
July	1st to 10th	Night	7% 6% 28% 39% 19% 1	390
	11th to 20th	Night	12% 4 28% 36% 20% 1	388
	21st to end	Night	10% 3 27% 40% 17% 2	589
August	1st to 10th	Night	10% 4 21% 37% 27% 2	597
	11th to 20th	Night	8% 4 20% 41% 24% 3	594
	21st to end	Night	11% 5% 28% 34% 18% 2	755
September	1st to 10th	Night	11% 8% 25% 33% 18% 4	800
	11th to 20th	Night	12% 7% 22% 31% 23% 5%	800
	21st to end	Night	19% 9% 23% 31% 15% 4	800
October	1st to 10th	Night	18% 8% 30% 26% 16% 2	800
	11th to 20th	Night	23% 16% 31% 21% 8% 1	800
	21st to end	Night	27% 14% 33% 22% 3	880
November	1st to 10th	Night	25% 14% 31% 23% 7%	820
	11th to 20th	Night	22% 21% 31% 19% 6% 1	840
	21st to end	Night	27% 19% 30% 20% 4	840
December	1st to 10th	Night	28% 19% 34% 16% 3	840
	11th to 20th	Night	22% 22% 36% 17% 3 1	840
	21st to end	Night	30% 18% 36% 14% 2	924

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