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 2025-11-03.

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 6% 4 4 5% 4 6% 8% 43%	125606
	Night	12% 6% 2 6% 4 4 4 4 6% 8% 45%	124560
Transparency	Day	38% 4 11% 22% 19% 6%	129273
	Night	37% 4 10% 20% 20% 8%	128955
Seeing	Day	13% 6% 20% 25% 24% 12%	16365
	Night	14% 6% 22% 30% 21% 5%	26034

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% 11% 4 9% 4 3 3 3 5% 5% 42%	4077
	11th to 20th	Day	12% 6% 3 5% 3 4 4 3 5% 7% 48%	4080
	21st to end	Day	20% 12% 3 6% 4 3 3 2 3 5% 40%	4640
February	1st to 10th	Day	15% 10% 4 7% 4 3 4 4 4 7% 39%	2000
	11th to 20th	Day	20% 10% 3 6% 4 3 3 3 5% 5% 39%	1948
	21st to end	Day	17% 7% 3 8% 4 4 4 3 4 6% 40%	1650
March	1st to 10th	Day	17% 9% 3 9% 6% 5% 4 4 5% 7% 32%	4613
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 5% 7% 44%	4980
	21st to end	Day	13% 8% 3 8% 5% 5% 4 3 5% 5% 40%	5772
April	1st to 10th	Day	11% 5% 2 6% 5% 4 5% 4 6% 7% 45%	2400
	11th to 20th	Day	14% 6% 2 6% 4 4 5% 3 4 7% 45%	2374
	21st to end	Day	8% 4 2 5% 5% 5% 4 4 6% 8% 47%	2400
May	1st to 10th	Day	13% 6% 2 6% 4 5% 5% 5% 6% 9% 38%	5405
	11th to 20th	Day	10% 6% 3 7% 5% 5% 6% 4 6% 9% 39%	5404
	21st to end	Day	8% 4 2 6% 4 4 5% 5% 7% 10% 44%	6297
June	1st to 10th	Day	8% 5% 1 5% 5% 6% 7% 5% 8% 11% 39%	2749
	11th to 20th	Day	5% 5% 2 5% 5% 6% 6% 5% 7% 10% 45%	2800
	21st to end	Day	6% 4 2 5% 6% 6% 6% 6% 7% 10% 42%	2800
July	1st to 10th	Day	5% 5% 3 8% 6% 7% 7% 7% 8% 11% 34%	5931
	11th to 20th	Day	6% 4 2 5% 4 5% 6% 6% 8% 13% 40%	5900
	21st to end	Day	9% 6% 3 8% 6% 5% 6% 5% 7% 11% 34%	6158
August	1st to 10th	Day	3 2 1 3 3 4 4 3 6% 7% 64%	3905
	11th to 20th	Day	5% 3 2 5% 4 5% 5% 5% 8% 11% 46%	3849
	21st to end	Day	8% 4 2 6% 5% 5% 5% 5% 7% 9% 45%	4312
September	1st to 10th	Day	8% 4 2 7% 5% 5% 6% 4 6% 8% 44%	2400
	11th to 20th	Day	11% 6% 2 6% 4 4 4 4 5% 7% 46%	2339
	21st to end	Day	8% 4 2 4 3 3 4 4 6% 9% 53%	2200
October	1st to 10th	Day	6% 3 1 5% 4 3 4 3 5% 6% 60%	2095
	11th to 20th	Day	7% 4 2 5% 4 4 4 3 5% 7% 57%	2000
	21st to end	Day	13% 5% 2 4 3 3 3 2 4 6% 56%	2200
November	1st to 10th	Day	10% 5% 2 5% 4 4 3 3 5% 6% 54%	1953
	11th to 20th	Day	11% 7% 2 6% 4 3 3 3 5% 5% 53%	1800
	21st to end	Day	14% 8% 2 5% 4 3 4 3 4 6% 47%	1800
December	1st to 10th	Day	17% 8% 2 5% 3 3 4 3 5% 6% 43%	2930
	11th to 20th	Day	14% 9% 3 8% 5% 5% 4 3 4 6% 41%	3307
	21st to end	Day	14% 7% 2 6% 4 4 3 3 4 5% 48%	4138
January	1st to 10th	Night	17% 8% 4 6% 3 2 3 2 3 5% 46%	5888
	11th to 20th	Night	13% 8% 4 5% 3 3 3 3 5% 6% 46%	5900
	21st to end	Night	23% 9% 3 6% 3 4 3 2 4 5% 39%	6327
February	1st to 10th	Night	16% 9% 3 6% 4 3 3 3 5% 6% 42%	2400
	11th to 20th	Night	20% 8% 2 5% 4 3 3 3 4 5% 43%	2338
	21st to end	Night	18% 9% 2 6% 4 4 3 3 4 5% 42%	1980
March	1st to 10th	Night	17% 9% 3 7% 4 4 4 4 4 6% 39%	5281
	11th to 20th	Night	9% 5% 2 5% 4 4 5% 3 5% 8% 50%	4980
	21st to end	Night	15% 6% 3 6% 4 4 4 4 5% 6% 43%	5156
April	1st to 10th	Night	12% 6% 2 5% 5% 4 4 4 6% 6% 47%	2000
	11th to 20th	Night	12% 5% 2 5% 4 4 5% 3 5% 7% 49%	1975
	21st to end	Night	8% 4 2 6% 4 3 4 3 6% 8% 51%	2000
May	1st to 10th	Night	13% 5% 2 6% 4 4 5% 4 6% 9% 40%	4490
	11th to 20th	Night	15% 6% 2 7% 4 5% 5% 4 6% 8% 36%	4489
	21st to end	Night	8% 4 2 6% 5% 5% 6% 5% 8% 10% 41%	4539
June	1st to 10th	Night	6% 5% 1 7% 6% 6% 6% 4 6% 10% 43%	1646
	11th to 20th	Night	3 3 2 4 5% 6% 4 4 9% 12% 50%	1600
	21st to end	Night	4 4 1 5% 5% 4 5% 6% 9% 12% 45%	1600
July	1st to 10th	Night	5% 5% 2 7% 5% 6% 6% 5% 8% 12% 38%	4025
	11th to 20th	Night	5% 4 1 5% 5% 5% 5% 6% 10% 15% 38%	4077
	21st to end	Night	7% 6% 2 7% 6% 5% 6% 6% 8% 12% 35%	4701
August	1st to 10th	Night	1 2 1 4 3 3 4 3 6% 9% 64%	3244
	11th to 20th	Night	3 3 2 5% 4 3 5% 4 8% 13% 50%	3200
	21st to end	Night	6% 4 2 6% 5% 5% 5% 5% 6% 9% 48%	3586
September	1st to 10th	Night	8% 5% 2 7% 4 4 5% 5% 7% 9% 45%	2000
	11th to 20th	Night	8% 6% 2 6% 4 4 6% 4 6% 8% 47%	2040
	21st to end	Night	8% 4 2 5% 4 3 4 3 6% 6% 55%	2200
October	1st to 10th	Night	6% 3 1 4 3 3 4 4 5% 6% 62%	2300
	11th to 20th	Night	10% 4 1 5% 3 3 2 3 4 6% 58%	2400
	21st to end	Night	14% 7% 1 4 3 3 3 2 3 4 56%	2640
November	1st to 10th	Night	11% 5% 1 4 3 3 3 4 4 6% 56%	2387
	11th to 20th	Night	13% 5% 2 4 3 3 3 3 4 7% 54%	2600
	21st to end	Night	13% 5% 2 6% 3 3 4 4 5% 6% 49%	2600
December	1st to 10th	Night	19% 6% 2 5% 4 3 4 3 4 5% 45%	4250
	11th to 20th	Night	14% 9% 2 6% 5% 4 4 3 4 5% 44%	4886
	21st to end	Night	16% 9% 3 6% 3 3 3 2 4 6% 45%	6835

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	46% 2 3 24% 22% 3	4078
	11th to 20th	Day	37% 2 6% 22% 27% 6%	4080
	21st to end	Day	50% 2 5% 13% 19% 11%	4640
February	1st to 10th	Day	47% 2 7% 18% 17% 9%	2000
	11th to 20th	Day	49% 2 5% 18% 19% 7%	1958
	21st to end	Day	47% 3 6% 16% 19% 8%	1650
March	1st to 10th	Day	53% 2 6% 14% 18% 6%	4613
	11th to 20th	Day	40% 2 6% 17% 20% 15%	4980
	21st to end	Day	47% 3 7% 19% 17% 7%	5774
April	1st to 10th	Day	38% 3 10% 23% 19% 7%	2400
	11th to 20th	Day	40% 3 7% 19% 25% 7%	2374
	21st to end	Day	34% 3 9% 28% 22% 3	2400
May	1st to 10th	Day	43% 4 12% 27% 13% 2	5440
	11th to 20th	Day	42% 4 16% 21% 16% 1	5408
	21st to end	Day	35% 4 17% 28% 15% 1	6311
June	1st to 10th	Day	38% 4 15% 27% 14% 2	2749
	11th to 20th	Day	33% 5% 19% 26% 14% 3	2800
	21st to end	Day	36% 6% 17% 25% 13% 3	2800
July	1st to 10th	Day	41% 10% 18% 20% 10% 1	5867
	11th to 20th	Day	32% 10% 30% 24% 3 1	5831
	21st to end	Day	42% 8% 17% 28% 4	5982
August	1st to 10th	Day	20% 4 13% 31% 29% 2	3893
	11th to 20th	Day	30% 6% 19% 29% 14% 2	3885
	21st to end	Day	36% 6% 14% 22% 19% 4	4311
September	1st to 10th	Day	37% 5% 15% 20% 17% 6%	2400
	11th to 20th	Day	38% 5% 10% 20% 20% 7%	2339
	21st to end	Day	29% 3 10% 26% 22% 10%	2200
October	1st to 10th	Day	19% 2 6% 16% 27% 30%	3407
	11th to 20th	Day	18% 2 3 14% 33% 30%	3240
	21st to end	Day	23% 1 4 18% 37% 17%	3538
November	1st to 10th	Day	33% 2 7% 18% 29% 10%	1953
	11th to 20th	Day	35% 2 5% 16% 29% 13%	1800
	21st to end	Day	39% 3 6% 19% 24% 9%	1800
December	1st to 10th	Day	42% 3 6% 19% 25% 5%	2930
	11th to 20th	Day	46% 3 7% 16% 19% 8%	3304
	21st to end	Day	40% 2 5% 24% 27% 2	4138
January	1st to 10th	Night	43% 2 4 22% 24% 5%	5888
	11th to 20th	Night	40% 1 4 18% 26% 10%	5900
	21st to end	Night	50% 1 3 15% 21% 9%	6327
February	1st to 10th	Night	43% 3 6% 17% 22% 9%	2400
	11th to 20th	Night	45% 3 5% 18% 19% 10%	2339
	21st to end	Night	47% 2 6% 16% 18% 12%	1980
March	1st to 10th	Night	48% 1 6% 14% 20% 10%	5281
	11th to 20th	Night	35% 2 7% 19% 20% 17%	4980
	21st to end	Night	43% 2 9% 20% 19% 7%	5156
April	1st to 10th	Night	37% 4 10% 20% 19% 10%	2000
	11th to 20th	Night	36% 2 8% 22% 22% 10%	1975
	21st to end	Night	31% 3 9% 26% 25% 6%	2000
May	1st to 10th	Night	41% 4 13% 24% 16% 2	4520
	11th to 20th	Night	45% 4 14% 24% 13% 1	4490
	21st to end	Night	37% 4 16% 25% 17% 2	4547
June	1st to 10th	Night	36% 5% 15% 25% 17% 2	1646
	11th to 20th	Night	26% 7% 19% 28% 16% 4	1600
	21st to end	Night	29% 7% 20% 25% 17% 3	1600
July	1st to 10th	Night	36% 11% 22% 21% 8% 1	3982
	11th to 20th	Night	30% 13% 33% 20% 3 1	4026
	21st to end	Night	39% 10% 19% 26% 5% 1	4564
August	1st to 10th	Night	16% 5% 17% 33% 27% 1	3232
	11th to 20th	Night	24% 7% 23% 34% 11% 2	3230
	21st to end	Night	33% 6% 15% 20% 20% 5%	3586
September	1st to 10th	Night	34% 5% 14% 22% 18% 6%	2000
	11th to 20th	Night	35% 5% 13% 18% 21% 8%	2040
	21st to end	Night	30% 3 8% 27% 21% 10%	2200
October	1st to 10th	Night	18% 2 7% 16% 24% 34%	3755
	11th to 20th	Night	19% 2 4 15% 27% 33%	3899
	21st to end	Night	23% 2 5% 15% 34% 22%	4252
November	1st to 10th	Night	30% 3 7% 19% 29% 13%	2387
	11th to 20th	Night	33% 2 6% 16% 28% 15%	2600
	21st to end	Night	36% 3 6% 22% 21% 13%	2600
December	1st to 10th	Night	43% 2 6% 18% 26% 5%	4250
	11th to 20th	Night	44% 2 7% 17% 24% 6%	4888
	21st to end	Night	43% 3 5% 20% 27% 3	6835

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	23% 16% 40% 17% 4 1	300
	11th to 20th	Day	24% 13% 36% 18% 7% 2	300
	21st to end	Day	26% 14% 36% 20% 4	330
February	1st to 10th	Day	22% 10% 38% 21% 8% 1	300
	11th to 20th	Day	31% 13% 35% 15% 5%	300
	21st to end	Day	20% 16% 40% 20% 3	249
March	1st to 10th	Day	27% 11% 36% 20% 6% 1	300
	11th to 20th	Day	25% 11% 34% 21% 7% 1	300
	21st to end	Day	17% 13% 34% 28% 8% 1	459
April	1st to 10th	Day	16% 13% 34% 24% 12% 2	500
	11th to 20th	Day	20% 10% 29% 26% 12% 3	492
	21st to end	Day	12% 8% 25% 32% 19% 2	500
May	1st to 10th	Day	14% 7% 27% 30% 17% 4	503
	11th to 20th	Day	11% 5% 24% 29% 18% 13%	527
	21st to end	Day	8% 2 18% 33% 24% 15%	573
June	1st to 10th	Day	11% 2 11% 31% 29% 15%	679
	11th to 20th	Day	7% 2 10% 32% 37% 13%	730
	21st to end	Day	7% 2 8% 26% 37% 20%	730
July	1st to 10th	Day	7% 2 5% 24% 42% 21%	721
	11th to 20th	Day	8% 1 2 20% 41% 28%	718
	21st to end	Day	9% 2 5% 23% 38% 25%	682
August	1st to 10th	Day	6% 1 5% 21% 39% 28%	526
	11th to 20th	Day	5% 1 4 17% 44% 29%	519
	21st to end	Day	13% 2 6% 21% 30% 28%	583
September	1st to 10th	Day	9% 2 8% 23% 40% 19%	530
	11th to 20th	Day	11% 1 12% 15% 37% 25%	530
	21st to end	Day	11% 3 10% 30% 30% 16%	530
October	1st to 10th	Day	8% 2 16% 37% 24% 12%	425
	11th to 20th	Day	8% 5% 22% 32% 24% 8%	330
	21st to end	Day	16% 8% 23% 26% 20% 7%	363
November	1st to 10th	Day	14% 4 23% 33% 19% 6%	306
	11th to 20th	Day	15% 10% 35% 23% 16% 1	300
	21st to end	Day	16% 12% 32% 21% 14% 4	300
December	1st to 10th	Day	22% 11% 35% 23% 8% 1	300
	11th to 20th	Day	17% 11% 37% 24% 10% 1	300
	21st to end	Day	22% 12% 31% 25% 8% 1	330
January	1st to 10th	Night	23% 12% 35% 25% 4	1000
	11th to 20th	Night	20% 15% 31% 26% 8%	1000
	21st to end	Night	24% 11% 36% 25% 3	1028
February	1st to 10th	Night	21% 11% 35% 28% 5%	800
	11th to 20th	Night	26% 14% 29% 26% 5%	783
	21st to end	Night	24% 14% 37% 24% 2	660
March	1st to 10th	Night	18% 13% 32% 30% 7%	760
	11th to 20th	Night	16% 8% 37% 32% 7% 1	600
	21st to end	Night	16% 10% 34% 30% 9% 1	660
April	1st to 10th	Night	17% 11% 34% 26% 12% 1	600
	11th to 20th	Night	15% 8% 34% 30% 11% 1	593
	21st to end	Night	8% 6% 32% 39% 15% 1	600
May	1st to 10th	Night	12% 4 26% 40% 16% 2	600
	11th to 20th	Night	12% 3 23% 37% 21% 4	591
	21st to end	Night	6% 2 14% 38% 32% 8%	650
June	1st to 10th	Night	7% 2 9% 37% 38% 7%	600
	11th to 20th	Night	4 1 7% 34% 44% 11%	600
	21st to end	Night	6% 1 7% 27% 46% 13%	600
July	1st to 10th	Night	6% 2 4 28% 46% 14%	585
	11th to 20th	Night	7% 3 24% 46% 20%	582
	21st to end	Night	4 1 3 27% 48% 17%	657
August	1st to 10th	Night	2 1 4 26% 46% 21%	597
	11th to 20th	Night	6% 1 3 22% 51% 18%	594
	21st to end	Night	9% 1 6% 25% 42% 17%	660
September	1st to 10th	Night	9% 1 8% 31% 42% 10%	600
	11th to 20th	Night	10% 1 7% 28% 44% 10%	640
	21st to end	Night	10% 2 10% 33% 38% 7%	800
October	1st to 10th	Night	7% 1 16% 39% 29% 8%	800
	11th to 20th	Night	13% 5% 20% 35% 25% 3	800
	21st to end	Night	16% 5% 21% 34% 21% 3	880
November	1st to 10th	Night	14% 4 21% 36% 22% 3	789
	11th to 20th	Night	15% 7% 29% 35% 14% 1	800
	21st to end	Night	16% 8% 30% 31% 14% 2	800
December	1st to 10th	Night	20% 9% 32% 30% 10%	800
	11th to 20th	Night	21% 7% 31% 33% 8%	825
	21st to end	Night	23% 11% 31% 28% 6%	1100

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