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 2024-11-25.

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 8% 5% 5% 5% 4 6% 7% 32%	101658
	Night	15% 10% 3 8% 5% 5% 5% 4 5% 7% 34%	97825
Transparency	Day	46% 9% 14% 20% 10% 1	105260
	Night	46% 9% 13% 20% 11% 1	102311
Seeing	Day	20% 16% 30% 21% 9% 3	14474
	Night	20% 14% 32% 24% 9% 1	23859

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	17% 14% 5% 9% 6% 5% 4 3 4 5% 29%	2517
	11th to 20th	Day	11% 18% 7% 16% 9% 6% 5% 3 4 5% 17%	2712
	21st to end	Day	21% 20% 5% 13% 6% 4 5% 3 4 5% 16%	3124
February	1st to 10th	Day	14% 18% 5% 11% 7% 6% 5% 4 5% 5% 20%	1710
	11th to 20th	Day	12% 15% 8% 11% 6% 5% 4 3 4 6% 25%	1663
	21st to end	Day	17% 15% 5% 9% 6% 5% 4 4 4 5% 26%	1459
March	1st to 10th	Day	18% 12% 5% 9% 5% 4 4 3 5% 5% 31%	3432
	11th to 20th	Day	10% 15% 5% 9% 6% 6% 6% 4 5% 5% 28%	3480
	21st to end	Day	16% 10% 3 8% 5% 4 4 3 5% 5% 36%	3815
April	1st to 10th	Day	18% 15% 3 7% 5% 5% 4 4 5% 6% 27%	2256
	11th to 20th	Day	20% 10% 3 7% 4 4 4 4 5% 6% 35%	2314
	21st to end	Day	20% 9% 4 7% 5% 4 4 3 5% 6% 33%	2470
May	1st to 10th	Day	18% 9% 3 8% 5% 4 4 4 5% 8% 32%	4130
	11th to 20th	Day	15% 10% 3 8% 5% 5% 5% 4 6% 8% 32%	4398
	21st to end	Day	12% 5% 2 6% 4 4 5% 4 5% 7% 46%	4837
June	1st to 10th	Day	15% 8% 3 6% 5% 5% 5% 4 7% 8% 35%	2660
	11th to 20th	Day	12% 6% 3 5% 4 5% 6% 4 6% 9% 38%	2660
	21st to end	Day	15% 5% 2 7% 5% 5% 5% 4 6% 8% 36%	2660
July	1st to 10th	Day	11% 5% 2 6% 5% 5% 6% 5% 7% 10% 38%	4440
	11th to 20th	Day	10% 5% 2 6% 4 4 6% 5% 8% 10% 40%	4440
	21st to end	Day	7% 5% 2 7% 5% 5% 6% 5% 7% 9% 40%	4566
August	1st to 10th	Day	16% 8% 2 6% 5% 4 4 5% 6% 8% 35%	4104
	11th to 20th	Day	11% 7% 3 8% 5% 5% 5% 5% 8% 9% 35%	4044
	21st to end	Day	9% 6% 3 7% 4 5% 5% 4 6% 8% 43%	4345
September	1st to 10th	Day	12% 6% 2 8% 5% 4 4 4 7% 7% 42%	2280
	11th to 20th	Day	11% 6% 2 6% 5% 4 4 4 6% 8% 44%	2188
	21st to end	Day	15% 7% 2 7% 5% 5% 5% 4 5% 7% 37%	2038
October	1st to 10th	Day	18% 9% 3 7% 5% 5% 4 4 4 7% 34%	1900
	11th to 20th	Day	20% 10% 3 9% 5% 4 6% 3 5% 6% 29%	1900
	21st to end	Day	23% 13% 3 9% 5% 5% 5% 4 4 6% 23%	2090
November	1st to 10th	Day	15% 11% 4 9% 6% 5% 4 4 5% 7% 31%	1676
	11th to 20th	Day	16% 12% 4 10% 6% 6% 6% 5% 6% 6% 24%	1600
	21st to end	Day	19% 15% 5% 10% 6% 5% 6% 4 4 6% 20%	1552
December	1st to 10th	Day	16% 16% 5% 14% 7% 6% 6% 4 6% 6% 13%	1520
	11th to 20th	Day	17% 15% 4 9% 6% 5% 5% 4 5% 7% 22%	1906
	21st to end	Day	26% 18% 5% 13% 6% 5% 4 3 4 4 12%	2772
January	1st to 10th	Night	17% 14% 5% 10% 7% 5% 5% 4 5% 6% 22%	4429
	11th to 20th	Night	13% 13% 5% 15% 9% 6% 5% 4 5% 6% 18%	4247
	21st to end	Night	19% 13% 6% 10% 6% 5% 6% 3 6% 6% 20%	4532
February	1st to 10th	Night	13% 16% 5% 10% 7% 5% 6% 5% 5% 5% 22%	2470
	11th to 20th	Night	14% 14% 5% 10% 6% 4 5% 4 5% 7% 26%	2403
	21st to end	Night	14% 13% 3 11% 5% 6% 4 4 6% 5% 28%	1993
March	1st to 10th	Night	16% 10% 4 9% 6% 5% 5% 3 5% 5% 32%	3408
	11th to 20th	Night	12% 10% 3 9% 6% 4 5% 4 5% 6% 34%	3479
	21st to end	Night	15% 7% 3 7% 5% 5% 5% 4 5% 7% 39%	3817
April	1st to 10th	Night	19% 12% 3 6% 5% 5% 4 3 5% 6% 32%	1923
	11th to 20th	Night	16% 8% 3 7% 5% 5% 4 3 5% 6% 38%	1830
	21st to end	Night	16% 8% 3 8% 5% 5% 4 4 6% 8% 34%	1710
May	1st to 10th	Night	17% 9% 2 6% 4 4 4 4 5% 6% 39%	2809
	11th to 20th	Night	15% 8% 3 6% 4 5% 4 4 6% 8% 38%	2495
	21st to end	Night	10% 5% 2 5% 4 4 4 4 5% 8% 50%	2738
June	1st to 10th	Night	12% 5% 2 7% 6% 4 5% 5% 6% 9% 40%	1520
	11th to 20th	Night	9% 6% 2 7% 6% 4 6% 4 6% 8% 43%	1520
	21st to end	Night	13% 5% 2 7% 5% 4 4 4 6% 8% 42%	1520
July	1st to 10th	Night	6% 5% 2 5% 5% 4 4 5% 6% 9% 49%	2520
	11th to 20th	Night	11% 5% 2 4 3 3 4 4 6% 9% 49%	2520
	21st to end	Night	7% 5% 1 5% 4 4 4 3 7% 9% 51%	2983
August	1st to 10th	Night	9% 6% 2 6% 5% 4 4 4 5% 7% 47%	2825
	11th to 20th	Night	11% 5% 2 5% 4 3 4 3 5% 8% 50%	2785
	21st to end	Night	9% 5% 3 6% 4 4 4 4 5% 7% 48%	3279
September	1st to 10th	Night	9% 5% 2 6% 3 6% 5% 4 6% 7% 47%	1900
	11th to 20th	Night	10% 4 2 4 4 4 3 3 5% 7% 54%	1989
	21st to end	Night	16% 7% 2 7% 4 4 4 3 5% 7% 41%	2140
October	1st to 10th	Night	15% 7% 2 8% 5% 5% 5% 4 6% 7% 38%	2280
	11th to 20th	Night	18% 9% 3 8% 5% 5% 5% 3 5% 5% 33%	2280
	21st to end	Night	20% 10% 3 7% 6% 5% 5% 4 6% 6% 28%	2508
November	1st to 10th	Night	17% 9% 2 7% 5% 4 4 4 6% 7% 35%	2618
	11th to 20th	Night	16% 11% 4 9% 7% 6% 5% 4 6% 7% 27%	2800
	21st to end	Night	19% 13% 3 8% 5% 6% 6% 5% 7% 6% 23%	2723
December	1st to 10th	Night	18% 15% 5% 11% 7% 5% 5% 4 5% 7% 18%	2660
	11th to 20th	Night	15% 18% 5% 11% 6% 5% 5% 4 6% 5% 20%	3288
	21st to end	Night	27% 16% 4 11% 6% 5% 5% 3 4 5% 13%	4884

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	53% 12% 16% 11% 7% 1	2518
	11th to 20th	Day	68% 8% 11% 9% 4	2712
	21st to end	Day	68% 8% 11% 8% 4	3124
February	1st to 10th	Day	63% 8% 10% 15% 3 1	1710
	11th to 20th	Day	57% 8% 12% 16% 6% 1	1672
	21st to end	Day	58% 7% 13% 14% 7% 1	1459
March	1st to 10th	Day	52% 8% 13% 17% 9% 1	3435
	11th to 20th	Day	51% 10% 12% 18% 8% 1	3480
	21st to end	Day	45% 9% 12% 19% 14% 2	3815
April	1st to 10th	Day	54% 6% 12% 16% 9% 1	2256
	11th to 20th	Day	48% 7% 11% 21% 13% 1	2314
	21st to end	Day	50% 8% 11% 17% 12% 3	2470
May	1st to 10th	Day	46% 9% 13% 17% 13% 1	4142
	11th to 20th	Day	47% 11% 14% 19% 9% 1	4402
	21st to end	Day	35% 8% 14% 24% 16% 3	4837
June	1st to 10th	Day	43% 10% 13% 19% 14% 1	2660
	11th to 20th	Day	38% 9% 13% 22% 16% 1	2660
	21st to end	Day	41% 9% 14% 22% 13% 1	2660
July	1st to 10th	Day	36% 9% 16% 23% 14% 1	4370
	11th to 20th	Day	32% 9% 16% 33% 10% 1	4365
	21st to end	Day	35% 11% 15% 22% 17%	4420
August	1st to 10th	Day	43% 9% 14% 22% 12% 1	4091
	11th to 20th	Day	39% 9% 15% 27% 9%	4083
	21st to end	Day	34% 8% 15% 33% 9% 1	4345
September	1st to 10th	Day	37% 10% 15% 26% 10% 1	2280
	11th to 20th	Day	34% 9% 16% 28% 14%	2188
	21st to end	Day	44% 8% 14% 25% 8%	2038
October	1st to 10th	Day	37% 8% 15% 27% 14% 1	3160
	11th to 20th	Day	39% 8% 17% 23% 14%	3140
	21st to end	Day	51% 8% 15% 20% 5%	3428
November	1st to 10th	Day	48% 9% 15% 19% 8% 1	1676
	11th to 20th	Day	54% 11% 14% 12% 8% 1	1600
	21st to end	Day	60% 10% 14% 14% 3	1552
December	1st to 10th	Day	65% 11% 13% 9% 3	1520
	11th to 20th	Day	57% 12% 15% 11% 5%	1906
	21st to end	Day	73% 10% 8% 8% 2	2772
January	1st to 10th	Night	58% 10% 15% 12% 4	4429
	11th to 20th	Night	63% 11% 12% 10% 3 1	4247
	21st to end	Night	62% 10% 13% 10% 4 1	4532
February	1st to 10th	Night	58% 10% 11% 17% 4	2470
	11th to 20th	Night	55% 8% 13% 17% 7%	2405
	21st to end	Night	52% 8% 14% 18% 7%	1993
March	1st to 10th	Night	51% 7% 12% 22% 7% 1	3418
	11th to 20th	Night	45% 10% 14% 20% 9% 2	3480
	21st to end	Night	39% 7% 13% 24% 15% 2	3817
April	1st to 10th	Night	51% 7% 11% 18% 13% 1	1923
	11th to 20th	Night	46% 7% 9% 20% 16% 2	1830
	21st to end	Night	45% 9% 12% 17% 15% 2	1710
May	1st to 10th	Night	43% 9% 12% 17% 16% 3	2816
	11th to 20th	Night	42% 11% 14% 21% 11% 2	2496
	21st to end	Night	29% 9% 14% 25% 21% 2	2739
June	1st to 10th	Night	38% 8% 12% 24% 16% 2	1520
	11th to 20th	Night	35% 8% 13% 21% 20% 2	1520
	21st to end	Night	38% 8% 14% 23% 17% 1	1520
July	1st to 10th	Night	29% 8% 16% 26% 20% 3	2480
	11th to 20th	Night	30% 7% 14% 34% 15% 1	2472
	21st to end	Night	28% 9% 15% 30% 16% 1	2888
August	1st to 10th	Night	35% 6% 15% 28% 15% 2	2814
	11th to 20th	Night	32% 6% 18% 31% 12% 1	2812
	21st to end	Night	32% 8% 13% 32% 14% 1	3279
September	1st to 10th	Night	34% 8% 16% 26% 14% 1	1900
	11th to 20th	Night	29% 7% 12% 33% 18% 1	1989
	21st to end	Night	40% 9% 13% 26% 11%	2140
October	1st to 10th	Night	32% 7% 10% 27% 23% 1	3800
	11th to 20th	Night	39% 8% 16% 26% 11%	3779
	21st to end	Night	39% 9% 16% 26% 10%	4120
November	1st to 10th	Night	45% 7% 14% 21% 11% 1	2618
	11th to 20th	Night	51% 10% 14% 15% 9% 1	2800
	21st to end	Night	55% 12% 18% 12% 3	2723
December	1st to 10th	Night	62% 10% 14% 11% 3	2660
	11th to 20th	Night	61% 10% 13% 13% 4	3288
	21st to end	Night	70% 10% 11% 7% 2	4884

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% 24% 29% 18% 6%	180
	11th to 20th	Day	24% 31% 26% 15% 3 1	234
	21st to end	Day	24% 25% 36% 13% 2	297
February	1st to 10th	Day	27% 27% 31% 12% 3	270
	11th to 20th	Day	24% 27% 40% 8% 1	270
	21st to end	Day	35% 23% 34% 8%	253
March	1st to 10th	Day	24% 22% 36% 15% 3	460
	11th to 20th	Day	23% 23% 33% 17% 3 1	460
	21st to end	Day	31% 19% 30% 15% 4 1	506
April	1st to 10th	Day	27% 20% 34% 13% 6%	460
	11th to 20th	Day	31% 20% 25% 15% 7% 2	452
	21st to end	Day	27% 16% 35% 13% 7% 1	460
May	1st to 10th	Day	23% 14% 31% 19% 8% 4	463
	11th to 20th	Day	18% 16% 30% 25% 8% 3	487
	21st to end	Day	16% 12% 30% 27% 12% 4	529
June	1st to 10th	Day	16% 16% 30% 28% 9% 1	490
	11th to 20th	Day	14% 15% 30% 26% 12% 2	490
	21st to end	Day	22% 9% 32% 25% 10% 2	490
July	1st to 10th	Day	10% 9% 28% 33% 17% 4	485
	11th to 20th	Day	15% 7% 28% 30% 14% 6%	484
	21st to end	Day	8% 8% 34% 33% 11% 6%	532
August	1st to 10th	Day	13% 9% 27% 30% 15% 8%	486
	11th to 20th	Day	13% 9% 23% 28% 21% 6%	479
	21st to end	Day	13% 10% 29% 26% 15% 7%	539
September	1st to 10th	Day	13% 11% 27% 27% 15% 7%	490
	11th to 20th	Day	10% 8% 26% 25% 20% 12%	490
	21st to end	Day	17% 12% 29% 26% 12% 6%	490
October	1st to 10th	Day	21% 14% 30% 16% 16% 3	490
	11th to 20th	Day	22% 21% 32% 17% 7% 1	490
	21st to end	Day	28% 22% 28% 17% 5%	539
November	1st to 10th	Day	24% 24% 30% 16% 6% 1	283
	11th to 20th	Day	24% 27% 31% 15% 4 1	200
	21st to end	Day	24% 26% 38% 10% 2	188
December	1st to 10th	Day	24% 22% 36% 13% 4 1	180
	11th to 20th	Day	31% 21% 33% 12% 3 1	180
	21st to end	Day	30% 22% 36% 12% 1	198
January	1st to 10th	Night	23% 23% 36% 13% 5%	760
	11th to 20th	Night	28% 17% 33% 18% 4 1	760
	21st to end	Night	20% 16% 37% 21% 6%	836
February	1st to 10th	Night	21% 21% 38% 18% 2	760
	11th to 20th	Night	23% 19% 36% 19% 3	743
	21st to end	Night	22% 21% 37% 15% 4	628
March	1st to 10th	Night	20% 20% 37% 19% 3	760
	11th to 20th	Night	21% 21% 36% 17% 4 1	760
	21st to end	Night	20% 17% 33% 24% 6%	836
April	1st to 10th	Night	25% 17% 34% 21% 3	760
	11th to 20th	Night	19% 18% 35% 20% 8% 1	706
	21st to end	Night	20% 14% 34% 24% 9%	570
May	1st to 10th	Night	20% 9% 29% 30% 11% 2	559
	11th to 20th	Night	17% 7% 32% 30% 13% 1	374
	21st to end	Night	11% 8% 27% 36% 17% 1	411
June	1st to 10th	Night	14% 8% 31% 36% 12%	380
	11th to 20th	Night	11% 9% 30% 36% 13% 1	380
	21st to end	Night	15% 6% 30% 36% 12% 1	380
July	1st to 10th	Night	7% 6% 28% 39% 19% 1	370
	11th to 20th	Night	12% 4 29% 35% 21% 1	368
	21st to end	Night	10% 3 26% 41% 18% 2	559
August	1st to 10th	Night	10% 4 21% 36% 26% 2	567
	11th to 20th	Night	8% 4 19% 41% 24% 3	564
	21st to end	Night	12% 5% 28% 34% 19% 3	717
September	1st to 10th	Night	12% 8% 25% 33% 18% 4	760
	11th to 20th	Night	12% 8% 22% 29% 23% 5%	760
	21st to end	Night	18% 9% 23% 31% 15% 4	760
October	1st to 10th	Night	19% 8% 30% 25% 16% 2	760
	11th to 20th	Night	23% 16% 31% 22% 8% 1	760
	21st to end	Night	28% 14% 32% 22% 3	836
November	1st to 10th	Night	24% 14% 31% 22% 8% 1	780
	11th to 20th	Night	22% 20% 32% 19% 6% 1	800
	21st to end	Night	25% 19% 30% 21% 5%	779
December	1st to 10th	Night	28% 18% 35% 16% 3	760
	11th to 20th	Night	21% 20% 37% 18% 3 1	760
	21st to end	Night	30% 17% 36% 15% 2	836

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