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 2024-02-20.

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% 5% 3 5% 5% 5% 7% 41%	78500
	Night	14% 7% 3 5% 5% 3 4 4 5% 7% 43%	80697
Transparency	Day	42% 3 11% 25% 16% 3	78207
	Night	42% 3 9% 24% 18% 4	80511
Seeing	Day	16% 7% 22% 26% 20% 10%	14342
	Night	18% 7% 23% 31% 18% 3	24288

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% 12% 6% 8% 6% 4 4 5% 4 5% 33%	2527
	11th to 20th	Day	18% 9% 3 7% 6% 3 6% 3 4 5% 36%	2544
	21st to end	Day	24% 11% 5% 6% 5% 3 3 4 4 6% 29%	3242
February	1st to 10th	Day	17% 11% 3 5% 4 3 4 4 5% 6% 37%	1900
	11th to 20th	Day	19% 10% 4 6% 4 2 4 4 4 5% 37%	1838
	21st to end	Day	19% 10% 3 6% 6% 3 5% 4 4 6% 34%	1480
March	1st to 10th	Day	17% 9% 3 5% 6% 3 4 4 4 6% 40%	1800
	11th to 20th	Day	21% 10% 4 7% 5% 2 4 3 4 5% 35%	1849
	21st to end	Day	18% 10% 4 7% 6% 2 4 5% 6% 6% 33%	2376
April	1st to 10th	Day	12% 5% 2 6% 6% 3 5% 4 4 8% 45%	2160
	11th to 20th	Day	15% 7% 3 6% 5% 4 4 5% 5% 7% 40%	2134
	21st to end	Day	16% 7% 3 5% 5% 3 5% 3 5% 8% 40%	2160
May	1st to 10th	Day	16% 6% 3 5% 5% 3 5% 5% 6% 7% 39%	2326
	11th to 20th	Day	15% 6% 3 6% 6% 3 4 4 5% 7% 40%	2301
	21st to end	Day	8% 5% 3 6% 7% 4 6% 6% 7% 10% 38%	2548
June	1st to 10th	Day	10% 4 2 5% 4 3 4 5% 7% 9% 47%	2520
	11th to 20th	Day	4 3 2 4 6% 3 5% 6% 8% 10% 49%	2520
	21st to end	Day	5% 3 2 4 5% 4 6% 6% 7% 11% 47%	2520
July	1st to 10th	Day	8% 5% 2 6% 7% 4 6% 6% 8% 11% 37%	2520
	11th to 20th	Day	7% 5% 2 6% 5% 3 6% 5% 7% 10% 45%	2520
	21st to end	Day	7% 4 2 5% 6% 4 6% 6% 7% 11% 41%	2658
August	1st to 10th	Day	7% 5% 2 5% 5% 4 6% 6% 8% 10% 43%	2157
	11th to 20th	Day	9% 5% 2 5% 6% 4 6% 5% 7% 9% 41%	2125
	21st to end	Day	8% 4 2 5% 5% 3 5% 5% 6% 10% 46%	2376
September	1st to 10th	Day	10% 5% 2 6% 5% 3 5% 5% 6% 9% 45%	2160
	11th to 20th	Day	11% 4 3 5% 4 3 5% 4 5% 7% 49%	2010
	21st to end	Day	11% 5% 2 4 5% 2 4 4 5% 7% 51%	1980
October	1st to 10th	Day	10% 4 1 4 4 2 3 3 4 7% 56%	1980
	11th to 20th	Day	13% 5% 2 4 4 3 4 4 4 7% 51%	1845
	21st to end	Day	20% 7% 2 4 4 2 3 3 4 5% 46%	1845
November	1st to 10th	Day	11% 5% 2 5% 4 2 3 4 4 5% 56%	1672
	11th to 20th	Day	15% 7% 2 5% 3 2 3 4 5% 5% 50%	1710
	21st to end	Day	16% 9% 3 6% 5% 3 4 3 5% 5% 43%	1710
December	1st to 10th	Day	18% 9% 4 5% 4 3 4 5% 5% 6% 37%	1710
	11th to 20th	Day	15% 10% 4 6% 6% 4 4 5% 5% 6% 35%	1994
	21st to end	Day	16% 11% 5% 8% 6% 3 5% 4 5% 7% 30%	2783
January	1st to 10th	Night	19% 10% 3 5% 5% 2 3 4 5% 7% 37%	4428
	11th to 20th	Night	16% 11% 5% 9% 5% 3 4 3 4 5% 34%	4409
	21st to end	Night	24% 12% 4 5% 4 2 3 3 4 5% 33%	4405
February	1st to 10th	Night	21% 10% 4 7% 5% 3 4 4 3 5% 34%	2280
	11th to 20th	Night	19% 8% 3 6% 6% 3 4 3 4 6% 38%	2213
	21st to end	Night	21% 10% 3 6% 5% 3 4 4 5% 5% 34%	1776
March	1st to 10th	Night	16% 7% 3 5% 5% 3 4 4 4 6% 43%	2160
	11th to 20th	Night	18% 9% 3 6% 4 3 4 4 5% 6% 38%	2122
	21st to end	Night	17% 9% 3 7% 5% 3 4 4 6% 6% 35%	1983
April	1st to 10th	Night	11% 5% 2 4 4 3 5% 4 6% 8% 50%	1800
	11th to 20th	Night	15% 6% 3 4 4 3 3 4 5% 7% 46%	1775
	21st to end	Night	16% 5% 3 5% 5% 3 4 4 7% 8% 41%	1800
May	1st to 10th	Night	16% 7% 2 4 5% 3 3 4 6% 7% 43%	1631
	11th to 20th	Night	11% 5% 3 5% 6% 4 4 5% 7% 8% 41%	1592
	21st to end	Night	6% 3 2 5% 6% 3 6% 7% 6% 11% 45%	1722
June	1st to 10th	Night	11% 5% 3 5% 5% 2 3 4 5% 9% 47%	1440
	11th to 20th	Night	5% 2 1 3 4 3 5% 5% 7% 10% 56%	1440
	21st to end	Night	3 2 1 4 5% 3 6% 5% 7% 14% 50%	1440
July	1st to 10th	Night	7% 4 2 4 5% 3 6% 6% 7% 10% 46%	1440
	11th to 20th	Night	7% 4 1 4 5% 3 5% 5% 7% 9% 51%	1440
	21st to end	Night	7% 4 2 4 5% 3 6% 5% 7% 10% 48%	1657
August	1st to 10th	Night	6% 3 2 4 4 3 5% 6% 7% 10% 50%	1777
	11th to 20th	Night	7% 5% 2 5% 3 4 4 5% 6% 10% 49%	1776
	21st to end	Night	7% 4 2 4 4 3 4 5% 5% 9% 52%	1980
September	1st to 10th	Night	10% 5% 3 4 4 2 3 4 5% 8% 52%	1800
	11th to 20th	Night	10% 5% 2 5% 5% 3 4 4 5% 6% 52%	1930
	21st to end	Night	9% 5% 2 3 4 2 4 3 3 6% 57%	1980
October	1st to 10th	Night	9% 4 1 4 4 3 3 3 3 6% 60%	1980
	11th to 20th	Night	15% 5% 2 4 4 2 3 3 3 6% 52%	2113
	21st to end	Night	17% 7% 2 4 4 2 4 3 4 5% 46%	2510
November	1st to 10th	Night	12% 5% 2 4 4 2 3 3 4 6% 55%	2406
	11th to 20th	Night	13% 6% 2 5% 4 2 4 3 5% 7% 50%	2470
	21st to end	Night	17% 7% 3 4 3 2 3 4 4 5% 47%	2470
December	1st to 10th	Night	18% 11% 4 5% 4 3 4 5% 5% 5% 36%	2470
	11th to 20th	Night	16% 9% 3 5% 4 3 4 4 4 5% 43%	3198
	21st to end	Night	17% 12% 5% 8% 7% 4 5% 4 4 6% 29%	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	55% 2 6% 25% 10% 2	2528
	11th to 20th	Day	52% 3 7% 26% 12% 1	2544
	21st to end	Day	57% 3 8% 21% 10% 1	3242
February	1st to 10th	Day	50% 2 7% 26% 13% 2	1900
	11th to 20th	Day	51% 3 7% 22% 13% 4	1848
	21st to end	Day	52% 3 8% 18% 13% 5%	1480
March	1st to 10th	Day	48% 2 7% 21% 18% 4	1800
	11th to 20th	Day	53% 3 9% 21% 12% 2	1849
	21st to end	Day	52% 3 11% 21% 12% 1	2376
April	1st to 10th	Day	39% 3 10% 25% 20% 3	2160
	11th to 20th	Day	43% 3 9% 22% 19% 4	2134
	21st to end	Day	44% 3 9% 28% 14% 2	2160
May	1st to 10th	Day	45% 3 12% 26% 12% 1	2326
	11th to 20th	Day	44% 4 12% 24% 15% 1	2305
	21st to end	Day	40% 6% 16% 23% 13% 2	2548
June	1st to 10th	Day	34% 4 13% 25% 21% 3	2520
	11th to 20th	Day	29% 5% 15% 29% 19% 3	2520
	21st to end	Day	30% 5% 15% 27% 17% 5%	2520
July	1st to 10th	Day	39% 5% 15% 25% 13% 4	2451
	11th to 20th	Day	35% 4 17% 26% 15% 3	2445
	21st to end	Day	35% 6% 17% 29% 12% 2	2510
August	1st to 10th	Day	35% 6% 14% 30% 15% 1	2144
	11th to 20th	Day	39% 4 14% 25% 17% 2	2125
	21st to end	Day	33% 4 14% 28% 18% 4	2376
September	1st to 10th	Day	36% 5% 9% 28% 18% 3	2160
	11th to 20th	Day	36% 4 9% 25% 23% 3	2010
	21st to end	Day	33% 3 7% 27% 23% 6%	1980
October	1st to 10th	Day	30% 2 9% 26% 28% 5%	1980
	11th to 20th	Day	35% 3 6% 24% 24% 7%	1845
	21st to end	Day	43% 2 5% 25% 21% 4	1845
November	1st to 10th	Day	31% 3 9% 25% 26% 6%	1672
	11th to 20th	Day	38% 3 7% 24% 23% 6%	1710
	21st to end	Day	44% 2 6% 27% 16% 5%	1710
December	1st to 10th	Day	48% 2 10% 25% 13% 2	1710
	11th to 20th	Day	50% 3 9% 23% 13% 2	1991
	21st to end	Day	55% 2 12% 19% 11%	2783
January	1st to 10th	Night	49% 2 7% 29% 12% 1	4428
	11th to 20th	Night	54% 2 6% 23% 13% 2	4409
	21st to end	Night	56% 2 8% 23% 11% 1	4405
February	1st to 10th	Night	55% 2 8% 19% 14% 1	2280
	11th to 20th	Night	49% 3 5% 23% 16% 4	2214
	21st to end	Night	53% 3 9% 17% 15% 4	1776
March	1st to 10th	Night	45% 3 8% 17% 21% 7%	2160
	11th to 20th	Night	48% 3 10% 23% 14% 3	2122
	21st to end	Night	50% 3 11% 22% 13% 2	1983
April	1st to 10th	Night	34% 3 10% 29% 21% 3	1800
	11th to 20th	Night	38% 3 9% 22% 22% 7%	1775
	21st to end	Night	42% 3 8% 26% 19% 2	1800
May	1st to 10th	Night	41% 2 11% 24% 19% 3	1631
	11th to 20th	Night	39% 5% 14% 25% 15% 1	1593
	21st to end	Night	33% 6% 17% 25% 17% 2	1723
June	1st to 10th	Night	35% 4 12% 24% 22% 3	1440
	11th to 20th	Night	23% 4 16% 31% 22% 4	1440
	21st to end	Night	25% 6% 16% 29% 18% 6%	1440
July	1st to 10th	Night	31% 6% 16% 27% 16% 4	1400
	11th to 20th	Night	30% 4 18% 26% 17% 5%	1392
	21st to end	Night	30% 6% 15% 33% 15% 1	1565
August	1st to 10th	Night	28% 6% 17% 29% 19% 1	1766
	11th to 20th	Night	30% 5% 15% 27% 20% 2	1776
	21st to end	Night	29% 5% 14% 29% 19% 5%	1980
September	1st to 10th	Night	33% 3 9% 28% 21% 5%	1800
	11th to 20th	Night	33% 4 7% 27% 25% 5%	1930
	21st to end	Night	30% 2 7% 27% 26% 7%	1980
October	1st to 10th	Night	28% 3 8% 25% 29% 8%	1980
	11th to 20th	Night	36% 3 6% 22% 26% 7%	2113
	21st to end	Night	42% 2 5% 24% 22% 5%	2510
November	1st to 10th	Night	32% 2 6% 27% 27% 6%	2406
	11th to 20th	Night	36% 2 6% 25% 23% 9%	2470
	21st to end	Night	41% 3 7% 25% 21% 4	2470
December	1st to 10th	Night	50% 2 9% 22% 14% 2	2470
	11th to 20th	Night	45% 2 6% 25% 19% 3	3200
	21st to end	Night	57% 2 8% 18% 11% 3	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	25% 15% 32% 21% 5% 1	270
	11th to 20th	Day	27% 16% 37% 17% 3 1	270
	21st to end	Day	23% 16% 42% 16% 3	297
February	1st to 10th	Day	25% 17% 31% 22% 4 1	270
	11th to 20th	Day	30% 19% 38% 9% 3	267
	21st to end	Day	31% 13% 36% 13% 7%	198
March	1st to 10th	Day	23% 15% 43% 15% 3	240
	11th to 20th	Day	27% 16% 35% 16% 5% 1	277
	21st to end	Day	27% 13% 31% 20% 7% 1	462
April	1st to 10th	Day	19% 10% 34% 25% 11% 1	420
	11th to 20th	Day	22% 11% 28% 27% 10% 3	412
	21st to end	Day	23% 9% 30% 25% 9% 4	420
May	1st to 10th	Day	20% 12% 26% 29% 9% 4	423
	11th to 20th	Day	19% 6% 19% 30% 18% 8%	447
	21st to end	Day	10% 3 16% 30% 25% 15%	502
June	1st to 10th	Day	12% 3 17% 29% 24% 15%	630
	11th to 20th	Day	4 3 18% 31% 30% 15%	630
	21st to end	Day	7% 2 18% 34% 26% 13%	630
July	1st to 10th	Day	10% 1 9% 26% 31% 23%	621
	11th to 20th	Day	10% 1 9% 27% 33% 20%	618
	21st to end	Day	8% 1 11% 29% 32% 19%	599
August	1st to 10th	Day	11% 1 7% 29% 32% 20%	446
	11th to 20th	Day	14% 1 9% 31% 35% 11%	439
	21st to end	Day	10% 7% 23% 37% 22%	495
September	1st to 10th	Day	12% 1 10% 26% 33% 18%	450
	11th to 20th	Day	12% 1 8% 26% 34% 20%	450
	21st to end	Day	17% 4 15% 26% 26% 12%	450
October	1st to 10th	Day	10% 3 18% 33% 28% 8%	450
	11th to 20th	Day	13% 10% 30% 29% 14% 4	315
	21st to end	Day	28% 9% 28% 22% 10% 3	297
November	1st to 10th	Day	14% 5% 36% 29% 14% 3	270
	11th to 20th	Day	16% 16% 31% 26% 10% 2	270
	21st to end	Day	23% 9% 33% 21% 11% 2	270
December	1st to 10th	Day	21% 13% 34% 20% 11%	270
	11th to 20th	Day	23% 12% 34% 23% 7%	270
	21st to end	Day	24% 18% 37% 17% 3 1	297
January	1st to 10th	Night	25% 14% 29% 26% 4	950
	11th to 20th	Night	27% 15% 30% 23% 5%	950
	21st to end	Night	22% 13% 37% 25% 3	970
February	1st to 10th	Night	26% 13% 33% 26% 3	760
	11th to 20th	Night	25% 14% 36% 23% 3	742
	21st to end	Night	29% 11% 35% 23% 2	592
March	1st to 10th	Night	21% 13% 31% 29% 6%	720
	11th to 20th	Night	23% 8% 35% 28% 6% 1	720
	21st to end	Night	22% 10% 27% 32% 9% 1	597
April	1st to 10th	Night	14% 9% 34% 34% 9%	540
	11th to 20th	Night	20% 7% 27% 31% 14% 1	533
	21st to end	Night	20% 7% 27% 33% 12% 1	540
May	1st to 10th	Night	20% 6% 28% 29% 14% 2	540
	11th to 20th	Night	13% 3 18% 39% 23% 2	531
	21st to end	Night	9% 2 12% 43% 31% 4	584
June	1st to 10th	Night	14% 2 11% 39% 29% 5%	540
	11th to 20th	Night	6% 1 8% 44% 36% 4	540
	21st to end	Night	4 2 12% 40% 36% 6%	540
July	1st to 10th	Night	8% 1 7% 29% 44% 11%	525
	11th to 20th	Night	8% 2 7% 30% 45% 9%	522
	21st to end	Night	7% 1 7% 36% 41% 8%	591
August	1st to 10th	Night	7% 4 35% 44% 9%	537
	11th to 20th	Night	10% 1 7% 37% 40% 6%	534
	21st to end	Night	9% 1 6% 30% 45% 9%	594
September	1st to 10th	Night	13% 1 9% 31% 41% 6%	540
	11th to 20th	Night	13% 1 8% 32% 39% 7%	670
	21st to end	Night	12% 3 16% 32% 32% 4	720
October	1st to 10th	Night	13% 3 16% 32% 30% 6%	720
	11th to 20th	Night	18% 6% 21% 35% 17% 2	720
	21st to end	Night	22% 6% 26% 31% 14% 1	792
November	1st to 10th	Night	13% 7% 25% 37% 16% 2	740
	11th to 20th	Night	16% 10% 30% 33% 11% 1	760
	21st to end	Night	22% 10% 26% 30% 12% 1	760
December	1st to 10th	Night	25% 10% 28% 31% 6% 1	760
	11th to 20th	Night	23% 8% 30% 32% 7%	869
	21st to end	Night	27% 11% 29% 28% 5%	1045

Page generated at 2024-02-17 05:28:38. Version ac07

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