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 2026-07-31.

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	12% 7% 3 7% 4 4 4 4 6% 8% 41%	137797
	Night	14% 8% 3 7% 4 4 4 3 5% 7% 43%	135378
Transparency	Day	42% 3 10% 25% 17% 3	141440
	Night	42% 2 10% 24% 18% 4	139810
Seeing	Day	16% 7% 24% 25% 19% 9%	17740
	Night	18% 7% 23% 31% 18% 3	27457

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	14% 11% 6% 10% 4 4 4 4 5% 6% 33%	4691
	11th to 20th	Day	11% 8% 3 8% 4 3 3 2 4 6% 49%	4752
	21st to end	Day	19% 9% 4 6% 4 4 4 3 4 6% 37%	6023
February	1st to 10th	Day	17% 11% 3 6% 4 4 4 3 5% 6% 37%	2100
	11th to 20th	Day	19% 10% 4 7% 4 3 4 2 4 5% 37%	2048
	21st to end	Day	17% 10% 3 7% 6% 3 5% 3 4 6% 36%	1730
March	1st to 10th	Day	17% 13% 3 7% 4 3 3 3 4 5% 38%	4580
	11th to 20th	Day	13% 8% 3 6% 4 3 3 2 4 6% 48%	4770
	21st to end	Day	11% 8% 3 8% 4 4 4 4 5% 6% 43%	6099
April	1st to 10th	Day	13% 6% 2 7% 5% 4 4 3 4 8% 43%	2520
	11th to 20th	Day	14% 7% 3 7% 4 5% 4 4 6% 6% 40%	2494
	21st to end	Day	14% 7% 3 6% 4 5% 4 3 5% 8% 41%	2520
May	1st to 10th	Day	16% 8% 3 8% 5% 5% 5% 4 6% 8% 32%	7588
	11th to 20th	Day	15% 6% 3 7% 5% 5% 5% 4 6% 8% 37%	7626
	21st to end	Day	18% 9% 3 8% 5% 5% 5% 4 5% 7% 31%	8450
June	1st to 10th	Day	10% 5% 2 6% 4 4 4 4 7% 9% 46%	2940
	11th to 20th	Day	5% 5% 2 5% 5% 5% 5% 4 8% 10% 47%	2940
	21st to end	Day	5% 3 2 5% 5% 5% 5% 4 7% 11% 47%	2940
July	1st to 10th	Day	8% 5% 2 7% 5% 5% 4 4 7% 11% 41%	6500
	11th to 20th	Day	6% 4 2 6% 5% 5% 6% 5% 8% 12% 41%	6500
	21st to end	Day	9% 7% 2 8% 6% 5% 6% 5% 8% 11% 34%	6839
August	1st to 10th	Day	5% 4 2 4 3 4 4 4 6% 10% 54%	3914
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 4 8% 9% 42%	3849
	21st to end	Day	5% 3 1 4 3 4 4 4 6% 8% 58%	4312
September	1st to 10th	Day	9% 6% 2 6% 4 4 5% 4 5% 8% 46%	2400
	11th to 20th	Day	11% 4 2 6% 3 4 5% 4 5% 7% 49%	2232
	21st to end	Day	12% 5% 2 5% 5% 3 4 3 5% 7% 49%	2200
October	1st to 10th	Day	10% 4 1 4 3 3 3 2 4 7% 58%	2200
	11th to 20th	Day	12% 5% 2 5% 3 4 4 2 4 7% 54%	2049
	21st to end	Day	19% 7% 2 4 3 3 3 2 4 5% 47%	2049
November	1st to 10th	Day	11% 6% 3 5% 3 3 3 3 5% 5% 53%	1852
	11th to 20th	Day	14% 8% 2 5% 3 3 4 4 5% 6% 48%	1890
	21st to end	Day	15% 10% 3 7% 4 3 3 2 5% 5% 43%	1890
December	1st to 10th	Day	15% 9% 3 6% 4 3 3 3 5% 5% 44%	3020
	11th to 20th	Day	15% 11% 3 7% 5% 4 4 3 5% 6% 35%	3220
	21st to end	Day	17% 11% 4 10% 6% 5% 5% 3 6% 6% 27%	4070
January	1st to 10th	Night	17% 10% 4 8% 4 3 3 3 5% 5% 38%	8232
	11th to 20th	Night	14% 9% 4 9% 4 4 3 2 4 4 42%	8221
	21st to end	Night	19% 10% 4 7% 4 4 3 3 4 4 37%	8163
February	1st to 10th	Night	20% 11% 4 8% 4 4 4 3 3 5% 33%	2520
	11th to 20th	Night	20% 9% 3 8% 5% 4 4 2 3 6% 36%	2458
	21st to end	Night	19% 10% 3 7% 4 4 4 3 5% 5% 37%	2076
March	1st to 10th	Night	18% 11% 4 7% 4 4 4 3 4 5% 36%	5493
	11th to 20th	Night	11% 7% 2 5% 4 3 3 3 5% 6% 49%	5450
	21st to end	Night	14% 7% 3 8% 5% 4 4 3 5% 7% 40%	5075
April	1st to 10th	Night	13% 5% 2 5% 3 4 4 3 6% 7% 47%	2100
	11th to 20th	Night	14% 6% 3 5% 3 4 4 3 5% 7% 47%	2075
	21st to end	Night	15% 6% 2 6% 5% 4 4 3 6% 8% 40%	2100
May	1st to 10th	Night	16% 7% 2 7% 5% 5% 5% 4 7% 7% 35%	5262
	11th to 20th	Night	12% 8% 2 8% 5% 5% 4 4 6% 8% 37%	5234
	21st to end	Night	17% 8% 3 8% 5% 5% 5% 4 6% 7% 32%	5687
June	1st to 10th	Night	12% 6% 2 5% 4 3 4 4 5% 9% 47%	1680
	11th to 20th	Night	5% 4 2 5% 3 3 5% 4 7% 9% 53%	1680
	21st to end	Night	3 3 1 4 5% 5% 5% 5% 7% 13% 50%	1680
July	1st to 10th	Night	6% 5% 2 6% 5% 5% 5% 5% 7% 9% 46%	3698
	11th to 20th	Night	5% 4 2 6% 4 5% 5% 4 7% 10% 48%	3697
	21st to end	Night	6% 6% 3 8% 5% 5% 6% 5% 9% 13% 34%	4241
August	1st to 10th	Night	4 3 1 4 3 3 4 3 6% 8% 60%	3231
	11th to 20th	Night	4 4 2 5% 4 5% 5% 4 7% 10% 51%	3200
	21st to end	Night	4 3 1 4 3 3 3 4 5% 9% 61%	3586
September	1st to 10th	Night	10% 5% 3 4 3 3 3 3 5% 7% 53%	2000
	11th to 20th	Night	10% 5% 2 5% 4 4 3 3 5% 6% 52%	2146
	21st to end	Night	11% 5% 2 4 4 4 3 3 3 6% 54%	2200
October	1st to 10th	Night	9% 4 1 4 3 3 3 2 4 6% 61%	2200
	11th to 20th	Night	14% 5% 2 4 3 3 3 2 3 5% 56%	2349
	21st to end	Night	17% 7% 2 5% 3 3 3 3 4 5% 47%	2790
November	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 4 6% 53%	2666
	11th to 20th	Night	12% 7% 2 5% 3 3 3 3 5% 6% 49%	2730
	21st to end	Night	17% 7% 3 4 4 3 3 3 4 5% 46%	2730
December	1st to 10th	Night	16% 10% 3 7% 3 4 4 3 4 4 43%	4380
	11th to 20th	Night	18% 9% 2 6% 3 4 3 3 4 5% 42%	5198
	21st to end	Night	21% 12% 4 8% 5% 5% 4 3 4 5% 28%	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	54% 2 12% 24% 8% 1	4692
	11th to 20th	Day	40% 2 4 32% 21% 2	4752
	21st to end	Day	51% 2 8% 21% 14% 5%	6023
February	1st to 10th	Day	50% 2 9% 26% 12% 2	2100
	11th to 20th	Day	51% 3 7% 21% 13% 4	2058
	21st to end	Day	51% 2 7% 20% 15% 5%	1730
March	1st to 10th	Day	52% 2 4 20% 17% 6%	4580
	11th to 20th	Day	39% 2 7% 26% 21% 4	4770
	21st to end	Day	43% 2 9% 28% 17% 1	6101
April	1st to 10th	Day	40% 3 11% 24% 19% 2	2520
	11th to 20th	Day	43% 2 9% 23% 18% 4	2494
	21st to end	Day	43% 2 10% 28% 14% 2	2520
May	1st to 10th	Day	51% 2 12% 23% 10% 1	7623
	11th to 20th	Day	47% 2 13% 22% 15% 2	7630
	21st to end	Day	53% 3 9% 18% 14% 2	8464
June	1st to 10th	Day	36% 4 13% 24% 21% 3	2940
	11th to 20th	Day	31% 4 14% 29% 19% 3	2940
	21st to end	Day	31% 5% 15% 28% 17% 5%	2940
July	1st to 10th	Day	37% 3 13% 31% 13% 2	6431
	11th to 20th	Day	36% 4 18% 33% 8% 1	6425
	21st to end	Day	43% 3 21% 25% 7% 1	6647
August	1st to 10th	Day	26% 4 14% 34% 23% 1	3901
	11th to 20th	Day	38% 3 13% 27% 18% 2	3885
	21st to end	Day	24% 3 11% 37% 22% 3	4311
September	1st to 10th	Day	36% 4 9% 27% 20% 5%	2400
	11th to 20th	Day	36% 4 9% 25% 24% 3	2232
	21st to end	Day	36% 3 7% 25% 23% 6%	2200
October	1st to 10th	Day	19% 1 5% 18% 47% 9%	3590
	11th to 20th	Day	23% 2 6% 27% 30% 11%	3315
	21st to end	Day	31% 1 5% 28% 29% 6%	3287
November	1st to 10th	Day	34% 3 9% 25% 25% 5%	1852
	11th to 20th	Day	38% 2 8% 24% 22% 5%	1890
	21st to end	Day	45% 2 6% 27% 16% 4	1890
December	1st to 10th	Day	44% 2 7% 29% 17% 1	3020
	11th to 20th	Day	51% 2 8% 22% 14% 2	3217
	21st to end	Day	58% 2 11% 21% 8%	4070
January	1st to 10th	Night	50% 1 12% 26% 10% 1	8233
	11th to 20th	Night	46% 2 4 24% 21% 3	8221
	21st to end	Night	52% 1 7% 22% 14% 3	8163
February	1st to 10th	Night	56% 2 9% 18% 14% 1	2520
	11th to 20th	Night	51% 2 5% 23% 15% 3	2459
	21st to end	Night	50% 3 8% 19% 17% 3	2076
March	1st to 10th	Night	52% 2 5% 16% 19% 6%	5493
	11th to 20th	Night	38% 1 8% 23% 19% 11%	5450
	21st to end	Night	45% 1 10% 27% 15% 2	5075
April	1st to 10th	Night	37% 3 11% 28% 20% 3	2100
	11th to 20th	Night	38% 3 10% 22% 21% 6%	2075
	21st to end	Night	42% 3 8% 26% 19% 2	2100
May	1st to 10th	Night	49% 2 13% 24% 11% 1	5289
	11th to 20th	Night	46% 3 14% 21% 15% 1	5235
	21st to end	Night	52% 3 13% 20% 11% 1	5697
June	1st to 10th	Night	35% 4 12% 24% 22% 3	1680
	11th to 20th	Night	26% 4 15% 29% 23% 4	1680
	21st to end	Night	25% 6% 17% 29% 18% 5%	1680
July	1st to 10th	Night	34% 4 13% 28% 18% 2	3660
	11th to 20th	Night	32% 6% 20% 30% 12% 2	3652
	21st to end	Night	40% 4 22% 26% 7% 1	4120
August	1st to 10th	Night	23% 3 13% 39% 21% 1	3220
	11th to 20th	Night	28% 4 16% 32% 18% 2	3230
	21st to end	Night	21% 3 10% 37% 25% 3	3586
September	1st to 10th	Night	32% 3 9% 27% 23% 6%	2000
	11th to 20th	Night	32% 3 8% 27% 26% 4	2146
	21st to end	Night	33% 2 8% 25% 26% 7%	2200
October	1st to 10th	Night	19% 2 5% 16% 45% 13%	3590
	11th to 20th	Night	21% 2 4 22% 40% 11%	3822
	21st to end	Night	30% 2 6% 25% 28% 10%	4502
November	1st to 10th	Night	33% 2 6% 26% 26% 5%	2666
	11th to 20th	Night	36% 2 6% 25% 22% 9%	2730
	21st to end	Night	42% 2 7% 26% 19% 4	2730
December	1st to 10th	Night	46% 1 8% 24% 19% 1	4380
	11th to 20th	Night	46% 2 8% 25% 19% 2	5200
	21st to end	Night	60% 2 8% 20% 9% 2	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	25% 16% 32% 21% 5% 1	330
	11th to 20th	Day	23% 20% 38% 16% 3 1	330
	21st to end	Day	22% 16% 44% 15% 2	363
February	1st to 10th	Day	24% 16% 35% 20% 5% 1	330
	11th to 20th	Day	30% 21% 37% 10% 2	330
	21st to end	Day	28% 14% 39% 14% 5%	273
March	1st to 10th	Day	25% 16% 42% 13% 4 1	330
	11th to 20th	Day	25% 16% 39% 15% 4 1	374
	21st to end	Day	25% 14% 36% 19% 6% 1	594
April	1st to 10th	Day	21% 11% 35% 23% 9% 1	540
	11th to 20th	Day	22% 14% 28% 25% 9% 2	532
	21st to end	Day	20% 9% 33% 25% 9% 4	540
May	1st to 10th	Day	21% 12% 27% 28% 9% 3	543
	11th to 20th	Day	18% 7% 22% 29% 17% 7%	567
	21st to end	Day	14% 4 20% 29% 21% 12%	637
June	1st to 10th	Day	13% 3 19% 30% 23% 13%	780
	11th to 20th	Day	6% 3 18% 31% 29% 13%	780
	21st to end	Day	7% 2 18% 34% 26% 14%	780
July	1st to 10th	Day	11% 1 9% 26% 31% 22%	771
	11th to 20th	Day	9% 2 9% 28% 33% 18%	768
	21st to end	Day	8% 2 12% 30% 30% 18%	745
August	1st to 10th	Day	11% 1 7% 29% 32% 19%	526
	11th to 20th	Day	12% 1 11% 32% 34% 11%	519
	21st to end	Day	9% 1 8% 24% 36% 23%	583
September	1st to 10th	Day	12% 1 11% 27% 32% 16%	530
	11th to 20th	Day	12% 1 8% 26% 34% 19%	530
	21st to end	Day	19% 5% 15% 27% 24% 11%	530
October	1st to 10th	Day	10% 2 17% 33% 29% 9%	530
	11th to 20th	Day	11% 9% 30% 28% 17% 6%	379
	21st to end	Day	27% 9% 31% 21% 9% 2	363
November	1st to 10th	Day	16% 6% 37% 27% 12% 2	330
	11th to 20th	Day	15% 16% 33% 25% 9% 2	330
	21st to end	Day	23% 10% 35% 21% 10% 2	330
December	1st to 10th	Day	22% 13% 36% 19% 10%	330
	11th to 20th	Day	23% 13% 35% 22% 6%	330
	21st to end	Day	25% 16% 39% 17% 3 1	363
January	1st to 10th	Night	25% 14% 30% 27% 4	1050
	11th to 20th	Night	26% 15% 32% 23% 4	1050
	21st to end	Night	22% 14% 37% 25% 3	1072
February	1st to 10th	Night	26% 12% 35% 25% 2	840
	11th to 20th	Night	27% 14% 35% 22% 2	823
	21st to end	Night	27% 12% 36% 24% 1	692
March	1st to 10th	Night	22% 13% 32% 28% 6%	840
	11th to 20th	Night	23% 9% 35% 28% 5% 1	840
	21st to end	Night	21% 11% 31% 29% 8% 1	696
April	1st to 10th	Night	16% 10% 34% 32% 9%	630
	11th to 20th	Night	19% 8% 30% 31% 12%	623
	21st to end	Night	19% 8% 28% 33% 12% 1	630
May	1st to 10th	Night	20% 6% 28% 31% 13% 2	630
	11th to 20th	Night	13% 4 19% 39% 23% 2	621
	21st to end	Night	11% 2 14% 43% 27% 3	683
June	1st to 10th	Night	14% 2 12% 41% 28% 4	630
	11th to 20th	Night	7% 1 10% 43% 34% 4	630
	21st to end	Night	4 2 11% 39% 38% 5%	630
July	1st to 10th	Night	8% 1 7% 28% 45% 10%	615
	11th to 20th	Night	8% 1 6% 31% 45% 8%	612
	21st to end	Night	8% 1 7% 35% 41% 8%	687
August	1st to 10th	Night	7% 6% 35% 43% 9%	597
	11th to 20th	Night	9% 1 7% 37% 40% 6%	594
	21st to end	Night	8% 1 7% 31% 44% 9%	660
September	1st to 10th	Night	12% 1 10% 32% 39% 6%	600
	11th to 20th	Night	13% 1 8% 32% 39% 7%	746
	21st to end	Night	13% 3 15% 34% 30% 4	800
October	1st to 10th	Night	12% 3 16% 33% 31% 5%	800
	11th to 20th	Night	16% 6% 21% 37% 19% 2	800
	21st to end	Night	22% 6% 26% 31% 14% 1	880
November	1st to 10th	Night	14% 7% 26% 37% 15% 2	820
	11th to 20th	Night	16% 10% 30% 34% 10% 1	840
	21st to end	Night	23% 10% 26% 30% 11% 1	840
December	1st to 10th	Night	25% 10% 28% 31% 6%	840
	11th to 20th	Night	23% 8% 31% 31% 7%	961
	21st to end	Night	28% 11% 29% 27% 5%	1155

Page generated at 2026-07-28 02:25:21. Version ac07

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