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 2024-10-20.

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% 4 4 4 4 6% 7% 42%	100817
	Night	13% 7% 3 6% 4 4 4 3 5% 7% 44%	97862
Transparency	Day	42% 3 10% 26% 17% 3	100610
	Night	41% 3 9% 25% 18% 3	97740
Seeing	Day	16% 7% 22% 26% 20% 9%	15337
	Night	18% 7% 23% 31% 18% 3	25084

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	13% 12% 6% 9% 5% 5% 4 4 5% 5% 33%	2527
	11th to 20th	Day	18% 9% 3 8% 5% 4 5% 2 4 5% 36%	2544
	21st to end	Day	24% 11% 5% 7% 4 3 3 3 4 6% 29%	3242
February	1st to 10th	Day	17% 12% 3 6% 4 4 4 3 5% 6% 37%	1900
	11th to 20th	Day	18% 10% 4 7% 4 3 4 3 4 5% 37%	1848
	21st to end	Day	19% 10% 3 7% 6% 3 5% 3 4 6% 34%	1570
March	1st to 10th	Day	22% 14% 3 7% 4 3 3 2 4 5% 33%	3120
	11th to 20th	Day	14% 7% 2 5% 4 3 3 3 4 6% 49%	3265
	21st to end	Day	12% 8% 3 7% 4 4 4 4 5% 6% 42%	4165
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%	1937
	21st to end	Day	20% 7% 2 5% 3 3 3 2 4 5% 46%	1845
November	1st to 10th	Day	11% 5% 2 5% 3 3 3 3 5% 5% 56%	1672
	11th to 20th	Day	14% 8% 2 5% 3 3 3 4 5% 5% 49%	1710
	21st to end	Day	16% 9% 2 6% 4 3 4 2 5% 5% 43%	1710
December	1st to 10th	Day	18% 10% 4 5% 3 4 4 4 5% 6% 37%	1710
	11th to 20th	Day	15% 11% 3 7% 5% 5% 5% 4 5% 6% 34%	1994
	21st to end	Day	16% 11% 5% 9% 5% 5% 5% 3 6% 6% 30%	2783
January	1st to 10th	Night	19% 11% 3 5% 4 3 3 3 5% 7% 37%	4428
	11th to 20th	Night	16% 11% 5% 10% 4 4 4 2 4 5% 34%	4409
	21st to end	Night	24% 12% 4 5% 4 3 3 3 4 5% 33%	4405
February	1st to 10th	Night	21% 11% 4 8% 4 4 4 3 3 5% 33%	2280
	11th to 20th	Night	19% 9% 3 8% 5% 4 4 2 4 6% 38%	2218
	21st to end	Night	20% 10% 3 7% 5% 4 4 3 5% 5% 35%	1884
March	1st to 10th	Night	23% 10% 3 6% 4 3 4 2 4 4 35%	3733
	11th to 20th	Night	13% 8% 2 5% 4 3 3 3 5% 6% 48%	3720
	21st to end	Night	15% 8% 3 7% 5% 4 3 3 5% 7% 42%	3469
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%	2226
	21st to end	Night	17% 7% 2 5% 4 3 3 3 4 5% 46%	2510
November	1st to 10th	Night	11% 5% 2 5% 3 3 3 3 4 6% 55%	2406
	11th to 20th	Night	12% 7% 2 5% 3 3 3 3 5% 6% 50%	2470
	21st to end	Night	17% 7% 3 5% 3 3 3 3 4 5% 47%	2470
December	1st to 10th	Night	18% 12% 3 6% 3 4 4 4 5% 5% 36%	2470
	11th to 20th	Night	16% 10% 3 6% 4 4 3 3 4 5% 43%	3198
	21st to end	Night	17% 12% 4 9% 6% 5% 5% 3 5% 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	50% 3 7% 22% 14% 4	1858
	21st to end	Day	52% 2 8% 18% 14% 5%	1570
March	1st to 10th	Day	57% 2 5% 17% 13% 7%	3120
	11th to 20th	Day	39% 2 9% 28% 18% 4	3265
	21st to end	Day	43% 3 10% 24% 18% 1	4165
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	29% 2 8% 25% 30% 6%	2090
	11th to 20th	Day	34% 3 6% 25% 25% 7%	1937
	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	2219
	21st to end	Night	52% 3 8% 17% 16% 4	1884
March	1st to 10th	Night	54% 2 7% 14% 18% 6%	3733
	11th to 20th	Night	39% 2 11% 24% 15% 9%	3720
	21st to end	Night	45% 2 10% 25% 17% 1	3469
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	27% 3 7% 24% 31% 8%	2090
	11th to 20th	Night	34% 3 6% 22% 27% 7%	2226
	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	29% 19% 38% 10% 3	270
	21st to end	Day	32% 14% 36% 13% 6%	225
March	1st to 10th	Day	25% 15% 41% 14% 3 1	270
	11th to 20th	Day	25% 16% 37% 16% 5% 1	310
	21st to end	Day	26% 14% 33% 20% 7% 1	506
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% 14% 6%	344
	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% 2	743
	21st to end	Night	29% 12% 36% 22% 1	628
March	1st to 10th	Night	22% 13% 31% 28% 6%	760
	11th to 20th	Night	23% 9% 34% 28% 5% 1	760
	21st to end	Night	21% 11% 28% 31% 8% 1	630
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	759
	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 2024-10-17 12:09:41. Version ac07

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