Trigg County Schools
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Trigg County Schools clear sky chart from 2005-11-06 to 2025-03-27.

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% 7% 3 6% 4 4 4 4 5% 7% 42%	108914
	Night	14% 8% 3 6% 4 4 4 3 5% 6% 44%	110521
Transparency	Day	41% 3 10% 26% 18% 3	112601
	Night	40% 3 9% 25% 19% 4	114974
Seeing	Day	16% 7% 23% 25% 19% 9%	15819
	Night	18% 7% 23% 31% 18% 3	25753

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% 10% 7% 9% 4 5% 4 4 5% 6% 32%	3617
	11th to 20th	Day	14% 8% 3 9% 4 3 4 2 4 6% 43%	3648
	21st to end	Day	19% 9% 4 6% 4 4 4 3 4 6% 38%	4647
February	1st to 10th	Day	17% 12% 3 6% 4 4 4 3 5% 6% 36%	2000
	11th to 20th	Day	19% 10% 4 7% 4 3 4 2 4 5% 36%	1948
	21st to end	Day	18% 10% 3 6% 5% 3 5% 3 4 6% 36%	1650
March	1st to 10th	Day	21% 14% 3 7% 4 3 3 3 4 5% 34%	3220
	11th to 20th	Day	14% 7% 2 5% 4 3 3 3 4 6% 49%	3368
	21st to end	Day	12% 8% 3 7% 4 4 4 4 5% 6% 42%	4237
April	1st to 10th	Day	12% 6% 2 7% 5% 4 4 3 4 8% 44%	2280
	11th to 20th	Day	14% 7% 3 7% 4 5% 4 4 6% 6% 40%	2254
	21st to end	Day	15% 7% 3 6% 4 4 4 3 5% 8% 41%	2280
May	1st to 10th	Day	17% 8% 3 7% 5% 5% 5% 4 7% 9% 32%	4068
	11th to 20th	Day	17% 7% 3 7% 4 4 4 4 5% 8% 38%	4081
	21st to end	Day	11% 6% 3 8% 5% 5% 6% 4 6% 8% 40%	4507
June	1st to 10th	Day	10% 5% 2 6% 4 4 4 4 7% 8% 46%	2660
	11th to 20th	Day	4 4 2 5% 5% 5% 5% 5% 8% 10% 48%	2660
	21st to end	Day	5% 3 2 5% 5% 6% 5% 5% 7% 10% 47%	2660
July	1st to 10th	Day	8% 5% 2 7% 5% 5% 5% 5% 7% 11% 39%	4440
	11th to 20th	Day	7% 4 2 5% 4 4 5% 5% 7% 10% 47%	4440
	21st to end	Day	12% 9% 3 9% 7% 5% 6% 4 6% 8% 29%	4661
August	1st to 10th	Day	5% 4 2 4 3 4 4 4 6% 9% 55%	3794
	11th to 20th	Day	8% 5% 2 7% 5% 5% 5% 4 8% 9% 41%	3729
	21st to end	Day	5% 3 1 4 3 3 4 3 6% 8% 58%	4180
September	1st to 10th	Day	9% 6% 2 6% 4 4 5% 4 5% 8% 46%	2280
	11th to 20th	Day	12% 4 2 6% 4 4 5% 4 5% 7% 48%	2121
	21st to end	Day	11% 5% 2 5% 5% 3 4 3 5% 7% 49%	2090
October	1st to 10th	Day	10% 4 1 4 4 3 3 2 4 7% 57%	2090
	11th to 20th	Day	12% 5% 2 5% 3 4 4 2 4 7% 52%	1947
	21st to end	Day	19% 7% 2 5% 3 3 3 2 4 5% 47%	1947
November	1st to 10th	Day	11% 6% 2 5% 3 3 3 3 5% 5% 54%	1762
	11th to 20th	Day	14% 8% 2 5% 3 3 3 4 4 5% 49%	1800
	21st to end	Day	15% 10% 2 7% 4 3 3 2 5% 5% 43%	1800
December	1st to 10th	Day	15% 9% 3 5% 4 3 3 3 5% 5% 44%	2930
	11th to 20th	Day	16% 11% 3 7% 5% 4 4 3 5% 6% 34%	3136
	21st to end	Day	17% 11% 4 10% 6% 5% 5% 3 6% 6% 27%	3982
January	1st to 10th	Night	17% 12% 4 9% 4 3 3 3 5% 6% 34%	6348
	11th to 20th	Night	16% 10% 4 9% 4 4 3 2 4 4 39%	6315
	21st to end	Night	20% 10% 4 6% 4 3 3 3 4 5% 40%	6307
February	1st to 10th	Night	21% 11% 4 8% 4 4 4 3 3 5% 33%	2400
	11th to 20th	Night	20% 9% 3 8% 5% 4 4 2 3 6% 37%	2338
	21st to end	Night	19% 10% 3 7% 4 4 4 3 5% 5% 36%	1980
March	1st to 10th	Night	23% 10% 3 6% 4 3 4 3 4 4 36%	3853
	11th to 20th	Night	13% 8% 2 5% 4 3 3 3 5% 6% 48%	3838
	21st to end	Night	15% 8% 3 7% 5% 4 3 3 5% 7% 42%	3535
April	1st to 10th	Night	11% 5% 2 5% 4 4 4 3 6% 7% 48%	1900
	11th to 20th	Night	15% 6% 3 4 3 4 4 3 5% 7% 46%	1875
	21st to end	Night	15% 6% 2 6% 5% 4 4 3 6% 8% 40%	1900
May	1st to 10th	Night	18% 7% 2 6% 4 4 4 3 6% 8% 38%	2824
	11th to 20th	Night	12% 7% 2 7% 5% 4 4 4 6% 7% 42%	2812
	21st to end	Night	9% 5% 2 6% 5% 4 5% 5% 6% 9% 44%	3031
June	1st to 10th	Night	12% 6% 2 6% 4 3 3 4 5% 9% 47%	1520
	11th to 20th	Night	5% 3 1 4 3 4 5% 4 7% 9% 55%	1520
	21st to end	Night	3 3 1 4 5% 5% 5% 4 7% 14% 50%	1520
July	1st to 10th	Night	6% 5% 2 5% 5% 4 5% 5% 7% 10% 45%	2530
	11th to 20th	Night	5% 4 1 5% 4 4 4 3 6% 8% 56%	2530
	21st to end	Night	9% 7% 3 10% 7% 5% 6% 5% 7% 8% 32%	2895
August	1st to 10th	Night	4 3 1 4 3 3 4 3 6% 8% 61%	3131
	11th to 20th	Night	4 4 2 6% 4 5% 5% 4 7% 10% 51%	3100
	21st to end	Night	4 3 1 3 3 3 3 4 5% 9% 61%	3476
September	1st to 10th	Night	10% 5% 3 5% 3 3 3 3 5% 7% 53%	1900
	11th to 20th	Night	10% 5% 2 5% 4 4 4 3 5% 6% 51%	2038
	21st to end	Night	10% 5% 2 4 3 4 3 3 3 7% 55%	2090
October	1st to 10th	Night	9% 4 1 4 3 3 3 2 4 6% 61%	2090
	11th to 20th	Night	15% 5% 2 5% 3 3 3 2 3 5% 54%	2231
	21st to end	Night	17% 7% 2 5% 3 3 3 3 4 5% 47%	2650
November	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 4 6% 53%	2536
	11th to 20th	Night	12% 7% 2 5% 3 3 3 3 5% 6% 49%	2600
	21st to end	Night	17% 7% 3 4 4 3 3 3 4 5% 47%	2600
December	1st to 10th	Night	16% 10% 3 7% 3 4 4 3 4 4 43%	4250
	11th to 20th	Night	19% 9% 2 6% 3 4 3 3 4 5% 42%	5062
	21st to end	Night	20% 12% 5% 8% 5% 5% 4 3 4 5% 28%	6996

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	54% 2 10% 22% 10% 2	3618
	11th to 20th	Day	45% 2 5% 28% 19% 2	3648
	21st to end	Day	49% 2 7% 20% 17% 5%	4647
February	1st to 10th	Day	50% 2 8% 26% 12% 2	2000
	11th to 20th	Day	52% 3 7% 21% 14% 4	1958
	21st to end	Day	50% 2 8% 19% 15% 5%	1650
March	1st to 10th	Day	56% 2 4 18% 13% 7%	3220
	11th to 20th	Day	39% 2 8% 28% 18% 5%	3368
	21st to end	Day	43% 3 10% 25% 18% 1	4237
April	1st to 10th	Day	40% 3 10% 25% 20% 3	2280
	11th to 20th	Day	43% 3 8% 23% 19% 4	2254
	21st to end	Day	44% 3 9% 28% 14% 2	2280
May	1st to 10th	Day	49% 3 13% 22% 11% 1	4106
	11th to 20th	Day	46% 3 11% 26% 13% 1	4085
	21st to end	Day	42% 5% 10% 21% 22% 1	4520
June	1st to 10th	Day	35% 4 13% 24% 21% 3	2660
	11th to 20th	Day	29% 5% 14% 29% 20% 3	2660
	21st to end	Day	31% 5% 15% 27% 17% 5%	2660
July	1st to 10th	Day	39% 3 16% 29% 11% 3	4371
	11th to 20th	Day	32% 3 13% 38% 12% 2	4365
	21st to end	Day	52% 4 13% 22% 8% 1	4513
August	1st to 10th	Day	26% 4 13% 33% 23% 1	3781
	11th to 20th	Day	38% 3 13% 26% 18% 2	3765
	21st to end	Day	24% 3 11% 37% 22% 2	4179
September	1st to 10th	Day	36% 5% 8% 27% 19% 5%	2280
	11th to 20th	Day	37% 4 9% 25% 23% 3	2121
	21st to end	Day	35% 3 7% 26% 23% 6%	2090
October	1st to 10th	Day	19% 1 5% 18% 48% 9%	3480
	11th to 20th	Day	24% 2 6% 27% 30% 11%	3213
	21st to end	Day	31% 1 4 28% 30% 6%	3185
November	1st to 10th	Day	33% 3 9% 24% 26% 5%	1762
	11th to 20th	Day	38% 3 7% 24% 23% 6%	1800
	21st to end	Day	44% 2 6% 27% 16% 4	1800
December	1st to 10th	Day	43% 2 7% 30% 18% 1	2930
	11th to 20th	Day	52% 2 8% 22% 14% 2	3133
	21st to end	Day	58% 2 11% 21% 8%	3982
January	1st to 10th	Night	53% 1 8% 25% 12% 1	6348
	11th to 20th	Night	50% 2 4 24% 18% 2	6315
	21st to end	Night	50% 2 6% 23% 15% 4	6307
February	1st to 10th	Night	56% 2 9% 18% 14% 1	2400
	11th to 20th	Night	51% 2 5% 22% 16% 4	2339
	21st to end	Night	50% 3 8% 19% 17% 3	1980
March	1st to 10th	Night	54% 2 6% 14% 18% 6%	3853
	11th to 20th	Night	39% 2 10% 24% 15% 10%	3838
	21st to end	Night	45% 2 10% 25% 17% 1	3535
April	1st to 10th	Night	36% 3 9% 28% 21% 3	1900
	11th to 20th	Night	39% 3 9% 21% 21% 7%	1875
	21st to end	Night	42% 3 8% 26% 19% 2	1900
May	1st to 10th	Night	46% 3 14% 23% 12% 2	2851
	11th to 20th	Night	41% 4 14% 25% 15% 1	2813
	21st to end	Night	37% 4 14% 26% 18% 1	3039
June	1st to 10th	Night	35% 4 12% 24% 22% 3	1520
	11th to 20th	Night	23% 4 15% 30% 23% 4	1520
	21st to end	Night	24% 6% 17% 28% 19% 6%	1520
July	1st to 10th	Night	33% 4 15% 31% 14% 3	2490
	11th to 20th	Night	28% 3 13% 37% 17% 3	2482
	21st to end	Night	48% 5% 14% 23% 9% 1	2803
August	1st to 10th	Night	23% 4 13% 39% 21% 1	3120
	11th to 20th	Night	28% 4 16% 31% 19% 2	3130
	21st to end	Night	21% 3 10% 38% 24% 3	3476
September	1st to 10th	Night	33% 3 9% 27% 23% 6%	1900
	11th to 20th	Night	34% 3 7% 27% 25% 4	2038
	21st to end	Night	32% 2 8% 26% 25% 7%	2090
October	1st to 10th	Night	19% 2 5% 16% 46% 12%	3480
	11th to 20th	Night	21% 2 4 22% 40% 11%	3704
	21st to end	Night	29% 2 6% 25% 28% 10%	4362
November	1st to 10th	Night	34% 2 6% 26% 27% 6%	2536
	11th to 20th	Night	36% 2 5% 25% 23% 9%	2600
	21st to end	Night	41% 2 7% 26% 20% 4	2600
December	1st to 10th	Night	46% 1 8% 24% 20% 1	4250
	11th to 20th	Night	46% 2 8% 25% 18% 2	5064
	21st to end	Night	60% 2 8% 20% 9% 2	6996

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	25% 16% 32% 21% 4 1	300
	11th to 20th	Day	24% 18% 37% 17% 3 1	300
	21st to end	Day	22% 15% 44% 16% 3	330
February	1st to 10th	Day	25% 16% 33% 21% 4 1	300
	11th to 20th	Day	30% 21% 37% 9% 3	300
	21st to end	Day	29% 14% 39% 14% 5%	249
March	1st to 10th	Day	25% 16% 40% 14% 4 1	300
	11th to 20th	Day	26% 16% 38% 16% 4 1	342
	21st to end	Day	25% 15% 34% 19% 6% 1	530
April	1st to 10th	Day	20% 12% 33% 23% 10% 1	460
	11th to 20th	Day	23% 12% 27% 26% 9% 3	452
	21st to end	Day	21% 9% 32% 24% 9% 4	460
May	1st to 10th	Day	20% 11% 27% 28% 10% 4	463
	11th to 20th	Day	19% 6% 19% 30% 18% 8%	487
	21st to end	Day	10% 3 20% 30% 23% 14%	547
June	1st to 10th	Day	13% 3 18% 29% 23% 14%	680
	11th to 20th	Day	4 2 17% 31% 30% 14%	680
	21st to end	Day	7% 2 19% 34% 25% 13%	680
July	1st to 10th	Day	10% 1 10% 26% 31% 21%	671
	11th to 20th	Day	10% 1 10% 28% 32% 19%	668
	21st to end	Day	9% 1 11% 31% 30% 18%	649
August	1st to 10th	Day	11% 1 7% 29% 32% 19%	486
	11th to 20th	Day	13% 1 11% 32% 34% 10%	479
	21st to end	Day	9% 1 7% 22% 36% 24%	539
September	1st to 10th	Day	12% 1 11% 26% 32% 17%	490
	11th to 20th	Day	12% 1 8% 26% 33% 19%	490
	21st to end	Day	18% 5% 15% 26% 24% 11%	490
October	1st to 10th	Day	10% 2 18% 33% 29% 9%	490
	11th to 20th	Day	12% 9% 31% 27% 15% 6%	347
	21st to end	Day	26% 9% 30% 22% 10% 2	330
November	1st to 10th	Day	15% 6% 36% 28% 12% 2	300
	11th to 20th	Day	15% 15% 32% 26% 9% 2	300
	21st to end	Day	23% 9% 35% 21% 11% 2	300
December	1st to 10th	Day	22% 13% 35% 19% 11%	300
	11th to 20th	Day	25% 12% 34% 22% 6%	300
	21st to end	Day	25% 16% 38% 18% 3 1	330
January	1st to 10th	Night	25% 14% 30% 26% 4	1000
	11th to 20th	Night	27% 15% 31% 23% 5%	1000
	21st to end	Night	22% 13% 37% 25% 3	1021
February	1st to 10th	Night	27% 12% 34% 25% 3	800
	11th to 20th	Night	26% 14% 35% 22% 2	783
	21st to end	Night	27% 11% 37% 23% 1	660
March	1st to 10th	Night	22% 13% 32% 28% 6%	800
	11th to 20th	Night	23% 9% 35% 28% 5% 1	800
	21st to end	Night	21% 11% 29% 30% 8% 1	650
April	1st to 10th	Night	15% 10% 34% 32% 9%	570
	11th to 20th	Night	20% 7% 29% 30% 13% 1	563
	21st to end	Night	20% 7% 28% 32% 11% 1	570
May	1st to 10th	Night	20% 6% 28% 29% 15% 2	570
	11th to 20th	Night	13% 3 18% 40% 24% 2	561
	21st to end	Night	9% 2 13% 43% 29% 4	617
June	1st to 10th	Night	14% 2 12% 39% 29% 5%	570
	11th to 20th	Night	6% 1 9% 44% 36% 4	570
	21st to end	Night	4 2 12% 40% 36% 6%	570
July	1st to 10th	Night	8% 1 7% 30% 43% 11%	555
	11th to 20th	Night	8% 2 6% 31% 44% 9%	552
	21st to end	Night	8% 1 7% 36% 40% 8%	624
August	1st to 10th	Night	7% 5% 35% 43% 9%	567
	11th to 20th	Night	9% 1 8% 37% 39% 6%	564
	21st to end	Night	8% 1 6% 30% 45% 10%	627
September	1st to 10th	Night	13% 1 9% 31% 40% 6%	570
	11th to 20th	Night	14% 1 8% 32% 38% 7%	708
	21st to end	Night	13% 3 16% 33% 31% 4	760
October	1st to 10th	Night	13% 3 16% 32% 31% 6%	760
	11th to 20th	Night	17% 6% 21% 35% 19% 2	760
	21st to end	Night	21% 6% 26% 31% 15% 1	836
November	1st to 10th	Night	15% 7% 25% 37% 15% 2	780
	11th to 20th	Night	16% 10% 29% 34% 11% 1	800
	21st to end	Night	22% 11% 26% 30% 11% 1	800
December	1st to 10th	Night	25% 10% 28% 31% 6% 1	800
	11th to 20th	Night	23% 8% 31% 31% 7%	915
	21st to end	Night	28% 11% 28% 28% 5%	1100

Page generated at 2025-03-24 08:04:30. Version ac07

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