Natchez Trace Milepost 108
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Natchez Trace Milepost 108 clear sky chart from 2005-11-06 to 2024-01-16.

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	11% 6% 2 5% 5% 3 5% 5% 6% 8% 43%	74760
	Night	11% 5% 2 5% 5% 3 4 5% 5% 8% 47%	75031
Transparency	Day	39% 4 11% 21% 19% 6%	74491
	Night	36% 4 11% 21% 21% 8%	74821
Seeing	Day	13% 5% 18% 25% 25% 14%	13899
	Night	14% 6% 22% 30% 22% 5%	23741

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	17% 8% 3 5% 4 3 3 4 4 6% 44%	1707
	11th to 20th	Day	19% 9% 3 5% 4 3 4 4 5% 5% 41%	1665
	21st to end	Day	18% 7% 3 5% 5% 3 3 4 4 5% 45%	1843
February	1st to 10th	Day	15% 9% 4 6% 5% 2 4 4 4 7% 40%	1800
	11th to 20th	Day	20% 9% 3 5% 5% 2 4 3 5% 5% 39%	1748
	21st to end	Day	18% 7% 4 7% 5% 3 4 4 4 6% 39%	1480
March	1st to 10th	Day	14% 7% 3 6% 5% 3 4 3 4 8% 42%	1849
	11th to 20th	Day	14% 7% 3 6% 4 4 6% 5% 5% 8% 37%	1980
	21st to end	Day	11% 7% 2 5% 6% 4 6% 5% 6% 7% 42%	2293
April	1st to 10th	Day	10% 5% 2 6% 5% 3 5% 5% 6% 8% 46%	2160
	11th to 20th	Day	14% 5% 3 5% 4 3 4 4 4 7% 44%	2134
	21st to end	Day	8% 4 2 4 6% 4 4 5% 5% 9% 49%	2160
May	1st to 10th	Day	9% 5% 2 5% 5% 4 5% 6% 6% 8% 45%	2160
	11th to 20th	Day	8% 6% 2 5% 5% 3 5% 5% 7% 8% 44%	2124
	21st to end	Day	7% 4 2 5% 5% 3 5% 7% 8% 11% 44%	2479
June	1st to 10th	Day	8% 4 2 4 6% 4 7% 7% 8% 11% 38%	2473
	11th to 20th	Day	5% 4 2 5% 5% 4 7% 6% 7% 10% 46%	2520
	21st to end	Day	6% 4 2 5% 7% 5% 7% 7% 7% 10% 42%	2520
July	1st to 10th	Day	6% 5% 3 6% 8% 5% 8% 9% 8% 11% 33%	2357
	11th to 20th	Day	8% 4 2 6% 6% 4 6% 9% 8% 12% 34%	2340
	21st to end	Day	7% 5% 2 6% 7% 4 7% 9% 9% 11% 33%	2446
August	1st to 10th	Day	5% 4 2 5% 6% 5% 7% 7% 9% 10% 42%	2148
	11th to 20th	Day	7% 5% 3 6% 7% 5% 7% 7% 8% 11% 35%	2125
	21st to end	Day	11% 4 2 5% 6% 3 6% 6% 7% 9% 39%	2376
September	1st to 10th	Day	8% 4 2 6% 6% 3 6% 6% 6% 8% 44%	2160
	11th to 20th	Day	11% 6% 3 5% 5% 3 4 5% 5% 6% 46%	2106
	21st to end	Day	9% 5% 2 4 3 3 3 5% 5% 8% 54%	1980
October	1st to 10th	Day	6% 3 1 4 5% 3 4 4 5% 7% 58%	1886
	11th to 20th	Day	8% 4 2 5% 5% 3 4 4 5% 7% 53%	1800
	21st to end	Day	13% 5% 2 4 4 2 3 3 4 6% 55%	1980
November	1st to 10th	Day	10% 5% 2 5% 4 2 4 3 4 5% 56%	1835
	11th to 20th	Day	11% 6% 2 5% 5% 2 3 4 4 5% 52%	1710
	21st to end	Day	15% 7% 2 4 5% 3 3 4 4 6% 47%	1710
December	1st to 10th	Day	16% 8% 3 5% 4 3 5% 4 6% 7% 40%	1710
	11th to 20th	Day	14% 10% 3 5% 5% 3 4 4 4 6% 42%	2113
	21st to end	Day	14% 7% 3 5% 5% 4 4 5% 5% 7% 43%	2883
January	1st to 10th	Night	17% 7% 3 4 4 2 3 4 3 6% 47%	2458
	11th to 20th	Night	16% 8% 4 5% 5% 3 4 3 4 6% 42%	2406
	21st to end	Night	17% 6% 3 5% 5% 3 3 3 4 6% 44%	2509
February	1st to 10th	Night	16% 9% 3 5% 5% 2 4 4 5% 6% 41%	2160
	11th to 20th	Night	20% 7% 2 4 4 3 3 3 4 5% 45%	2098
	21st to end	Night	20% 9% 3 6% 5% 2 4 4 4 5% 40%	1776
March	1st to 10th	Night	13% 7% 3 5% 4 2 4 4 4 7% 47%	2124
	11th to 20th	Night	14% 5% 3 6% 5% 3 5% 5% 6% 7% 41%	1980
	21st to end	Night	12% 5% 2 4 4 3 4 4 6% 8% 47%	2062
April	1st to 10th	Night	11% 5% 2 5% 5% 3 4 5% 6% 6% 48%	1800
	11th to 20th	Night	12% 5% 2 4 5% 3 5% 4 5% 7% 48%	1775
	21st to end	Night	7% 4 2 5% 5% 2 4 4 5% 8% 53%	1800
May	1st to 10th	Night	8% 3 2 3 4 3 5% 5% 5% 10% 52%	1800
	11th to 20th	Night	7% 5% 2 5% 5% 4 5% 5% 7% 10% 46%	1769
	21st to end	Night	5% 3 2 5% 4 3 5% 6% 7% 11% 48%	1792
June	1st to 10th	Night	6% 5% 2 6% 7% 5% 6% 5% 7% 10% 43%	1482
	11th to 20th	Night	3 2 1 3 5% 4 5% 5% 8% 12% 52%	1440
	21st to end	Night	4 3 1 5% 5% 3 5% 6% 8% 12% 47%	1440
July	1st to 10th	Night	5% 4 3 5% 5% 4 6% 6% 7% 13% 42%	1595
	11th to 20th	Night	5% 4 2 4 5% 3 6% 6% 8% 11% 45%	1620
	21st to end	Night	3 3 2 4 4 3 6% 7% 8% 13% 46%	1870
August	1st to 10th	Night	2 2 1 4 4 3 5% 6% 8% 13% 50%	1790
	11th to 20th	Night	5% 3 2 6% 6% 3 5% 5% 8% 13% 44%	1776
	21st to end	Night	9% 3 2 5% 6% 3 5% 6% 7% 11% 44%	1980
September	1st to 10th	Night	7% 4 2 6% 5% 4 5% 6% 7% 9% 46%	1800
	11th to 20th	Night	8% 5% 2 5% 5% 3 6% 6% 6% 8% 47%	1836
	21st to end	Night	8% 4 2 4 5% 3 4 4 6% 6% 55%	1980
October	1st to 10th	Night	6% 3 1 3 3 2 3 5% 5% 6% 62%	2070
	11th to 20th	Night	11% 4 2 5% 4 3 3 4 4 6% 54%	2160
	21st to end	Night	14% 7% 2 3 4 2 3 2 3 4 56%	2376
November	1st to 10th	Night	11% 4 1 3 4 1 3 4 4 6% 58%	2240
	11th to 20th	Night	13% 4 2 3 3 3 3 4 4 6% 54%	2470
	21st to end	Night	14% 5% 2 5% 4 2 4 5% 5% 7% 48%	2470
December	1st to 10th	Night	16% 7% 2 5% 4 2 4 4 5% 6% 43%	2470
	11th to 20th	Night	14% 7% 3 5% 6% 3 4 3 4 5% 45%	3078
	21st to end	Night	15% 10% 3 6% 5% 3 3 4 5% 6% 39%	4779

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	43% 2 4 22% 23% 6%	1708
	11th to 20th	Day	46% 3 5% 18% 22% 7%	1665
	21st to end	Day	44% 2 4 18% 25% 7%	1843
February	1st to 10th	Day	47% 2 7% 19% 16% 9%	1800
	11th to 20th	Day	48% 2 5% 18% 19% 7%	1758
	21st to end	Day	48% 3 6% 16% 19% 8%	1480
March	1st to 10th	Day	44% 2 9% 15% 21% 9%	1849
	11th to 20th	Day	46% 4 9% 17% 18% 6%	1980
	21st to end	Day	41% 4 9% 23% 20% 4	2293
April	1st to 10th	Day	37% 3 10% 24% 20% 6%	2160
	11th to 20th	Day	41% 3 7% 19% 25% 6%	2134
	21st to end	Day	33% 3 8% 28% 24% 3	2160
May	1st to 10th	Day	37% 5% 10% 22% 22% 4	2160
	11th to 20th	Day	38% 3 15% 28% 16% 1	2128
	21st to end	Day	34% 5% 17% 27% 16% 1	2479
June	1st to 10th	Day	40% 4 15% 26% 14% 2	2473
	11th to 20th	Day	33% 5% 18% 28% 14% 3	2520
	21st to end	Day	37% 6% 16% 24% 14% 2	2520
July	1st to 10th	Day	41% 8% 19% 22% 8% 2	2293
	11th to 20th	Day	38% 8% 24% 21% 7% 2	2271
	21st to end	Day	42% 6% 20% 22% 9% 1	2310
August	1st to 10th	Day	35% 7% 21% 28% 8%	2136
	11th to 20th	Day	43% 6% 18% 21% 10% 3	2125
	21st to end	Day	40% 5% 17% 22% 11% 5%	2376
September	1st to 10th	Day	37% 5% 14% 20% 18% 6%	2160
	11th to 20th	Day	39% 5% 10% 17% 21% 7%	2106
	21st to end	Day	30% 3 10% 24% 22% 10%	1980
October	1st to 10th	Day	27% 3 8% 23% 28% 11%	1886
	11th to 20th	Day	32% 3 5% 18% 30% 13%	1800
	21st to end	Day	33% 2 4 19% 30% 12%	1980
November	1st to 10th	Day	32% 2 6% 19% 30% 11%	1835
	11th to 20th	Day	35% 2 5% 16% 29% 13%	1710
	21st to end	Day	40% 3 6% 19% 23% 10%	1710
December	1st to 10th	Day	44% 3 9% 18% 17% 8%	1710
	11th to 20th	Day	45% 2 6% 16% 24% 6%	2110
	21st to end	Day	42% 2 6% 23% 25% 2	2883
January	1st to 10th	Night	41% 2 7% 17% 27% 6%	2458
	11th to 20th	Night	45% 3 4 19% 21% 7%	2406
	21st to end	Night	44% 2 4 16% 27% 7%	2509
February	1st to 10th	Night	44% 3 6% 17% 21% 9%	2160
	11th to 20th	Night	43% 3 5% 18% 20% 10%	2099
	21st to end	Night	49% 2 6% 14% 18% 11%	1776
March	1st to 10th	Night	39% 3 7% 17% 23% 12%	2124
	11th to 20th	Night	42% 5% 10% 18% 17% 8%	1980
	21st to end	Night	36% 3 10% 22% 23% 6%	2062
April	1st to 10th	Night	36% 4 11% 20% 20% 9%	1800
	11th to 20th	Night	37% 2 8% 22% 22% 9%	1775
	21st to end	Night	30% 3 9% 26% 27% 6%	1800
May	1st to 10th	Night	29% 4 12% 27% 23% 6%	1800
	11th to 20th	Night	34% 4 15% 27% 18% 2	1770
	21st to end	Night	29% 6% 16% 26% 20% 2	1793
June	1st to 10th	Night	36% 5% 16% 26% 16% 2	1482
	11th to 20th	Night	24% 6% 20% 29% 17% 4	1440
	21st to end	Night	28% 6% 20% 25% 18% 3	1440
July	1st to 10th	Night	32% 7% 24% 24% 9% 3	1550
	11th to 20th	Night	29% 9% 28% 25% 8% 2	1566
	21st to end	Night	26% 9% 27% 27% 10% 1	1766
August	1st to 10th	Night	22% 8% 28% 30% 11%	1778
	11th to 20th	Night	30% 8% 22% 24% 12% 4	1776
	21st to end	Night	34% 7% 22% 20% 13% 4	1980
September	1st to 10th	Night	33% 5% 14% 23% 19% 6%	1800
	11th to 20th	Night	34% 5% 13% 18% 20% 9%	1836
	21st to end	Night	30% 3 8% 27% 21% 11%	1980
October	1st to 10th	Night	24% 2 9% 23% 25% 16%	2070
	11th to 20th	Night	32% 3 5% 18% 28% 15%	2160
	21st to end	Night	35% 2 4 16% 26% 17%	2376
November	1st to 10th	Night	29% 2 6% 19% 31% 13%	2240
	11th to 20th	Night	33% 2 6% 17% 28% 15%	2470
	21st to end	Night	36% 3 6% 21% 21% 12%	2470
December	1st to 10th	Night	42% 2 10% 18% 20% 7%	2470
	11th to 20th	Night	43% 2 6% 14% 28% 7%	3080
	21st to end	Night	46% 3 6% 16% 25% 4	4779

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	22% 14% 40% 19% 4 1	270
	11th to 20th	Day	26% 9% 35% 20% 8% 2	255
	21st to end	Day	24% 14% 36% 20% 5%	264
February	1st to 10th	Day	21% 10% 38% 21% 8% 1	240
	11th to 20th	Day	31% 12% 37% 14% 5%	240
	21st to end	Day	21% 13% 41% 21% 4	198
March	1st to 10th	Day	25% 9% 37% 22% 7%	240
	11th to 20th	Day	24% 11% 34% 21% 8% 1	240
	21st to end	Day	16% 13% 32% 30% 9% 1	379
April	1st to 10th	Day	15% 9% 35% 25% 14% 2	420
	11th to 20th	Day	21% 8% 27% 27% 14% 4	412
	21st to end	Day	12% 8% 25% 34% 18% 2	420
May	1st to 10th	Day	12% 7% 27% 31% 18% 5%	423
	11th to 20th	Day	12% 2 20% 30% 20% 15%	447
	21st to end	Day	8% 1 14% 32% 26% 18%	485
June	1st to 10th	Day	11% 2 10% 29% 31% 17%	583
	11th to 20th	Day	6% 2 8% 31% 39% 15%	630
	21st to end	Day	8% 2 8% 26% 36% 21%	630
July	1st to 10th	Day	7% 2 4 24% 42% 22%	621
	11th to 20th	Day	9% 1 2 17% 40% 31%	618
	21st to end	Day	8% 1 4 21% 37% 28%	584
August	1st to 10th	Day	7% 1 5% 15% 41% 31%	446
	11th to 20th	Day	6% 1 3 17% 43% 30%	439
	21st to end	Day	14% 1 4 19% 30% 32%	495
September	1st to 10th	Day	8% 1 6% 20% 43% 22%	450
	11th to 20th	Day	11% 1 11% 14% 36% 27%	450
	21st to end	Day	11% 2 8% 29% 33% 18%	450
October	1st to 10th	Day	9% 1 12% 37% 27% 14%	356
	11th to 20th	Day	10% 4 20% 30% 26% 9%	270
	21st to end	Day	17% 7% 25% 25% 19% 7%	297
November	1st to 10th	Day	14% 2 20% 35% 22% 7%	270
	11th to 20th	Day	15% 10% 34% 24% 16% 1	270
	21st to end	Day	17% 10% 31% 23% 15% 4	270
December	1st to 10th	Day	23% 9% 34% 24% 9% 1	270
	11th to 20th	Day	19% 8% 37% 25% 10% 1	270
	21st to end	Day	22% 11% 32% 25% 8% 1	297
January	1st to 10th	Night	23% 11% 35% 26% 5%	950
	11th to 20th	Night	20% 13% 32% 26% 8%	926
	21st to end	Night	22% 12% 38% 25% 3	925
February	1st to 10th	Night	21% 11% 35% 28% 5%	720
	11th to 20th	Night	24% 14% 29% 27% 5%	703
	21st to end	Night	25% 13% 35% 24% 2	592
March	1st to 10th	Night	17% 12% 32% 31% 8%	684
	11th to 20th	Night	16% 8% 36% 33% 7% 1	540
	21st to end	Night	15% 10% 34% 31% 9% 1	594
April	1st to 10th	Night	15% 10% 34% 27% 13% 1	540
	11th to 20th	Night	15% 8% 33% 31% 12% 2	533
	21st to end	Night	8% 6% 32% 38% 16% 1	540
May	1st to 10th	Night	11% 4 26% 40% 16% 2	540
	11th to 20th	Night	10% 2 21% 39% 24% 5%	531
	21st to end	Night	5% 2 13% 36% 35% 8%	584
June	1st to 10th	Night	6% 2 8% 36% 40% 7%	540
	11th to 20th	Night	3 1 7% 33% 45% 11%	540
	21st to end	Night	6% 1 7% 27% 46% 14%	540
July	1st to 10th	Night	6% 2 3 28% 46% 15%	525
	11th to 20th	Night	6% 2 23% 47% 21%	522
	21st to end	Night	4 1 3 26% 49% 17%	591
August	1st to 10th	Night	2 1 3 24% 47% 23%	537
	11th to 20th	Night	7% 1 2 21% 51% 18%	534
	21st to end	Night	10% 1 4 23% 44% 18%	594
September	1st to 10th	Night	9% 1 5% 30% 44% 11%	540
	11th to 20th	Night	10% 1 7% 28% 43% 11%	576
	21st to end	Night	10% 1 9% 33% 39% 8%	720
October	1st to 10th	Night	7% 1 14% 38% 31% 9%	720
	11th to 20th	Night	13% 5% 19% 34% 25% 3	720
	21st to end	Night	17% 5% 21% 33% 21% 3	792
November	1st to 10th	Night	14% 4 20% 36% 23% 3	740
	11th to 20th	Night	14% 7% 29% 35% 14% 1	760
	21st to end	Night	16% 7% 29% 31% 14% 2	760
December	1st to 10th	Night	20% 8% 31% 30% 10%	760
	11th to 20th	Night	21% 7% 31% 33% 8%	783
	21st to end	Night	24% 11% 31% 29% 6%	1045

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