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 2024-11-06.

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% 5% 5% 5% 4 6% 8% 43%	100441
	Night	12% 6% 2 6% 4 4 4 4 6% 7% 46%	98614
Transparency	Day	38% 4 11% 22% 19% 6%	104145
	Night	36% 4 10% 21% 21% 9%	103037
Seeing	Day	13% 5% 19% 25% 24% 13%	15031
	Night	14% 6% 22% 30% 22% 5%	24743

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	15% 14% 3 5% 4 3 3 3 5% 6% 40%	2847
	11th to 20th	Day	15% 8% 3 5% 3 4 4 3 5% 5% 45%	2850
	21st to end	Day	20% 11% 3 6% 4 3 3 2 3 5% 40%	3235
February	1st to 10th	Day	15% 10% 4 7% 4 3 4 4 4 7% 39%	1900
	11th to 20th	Day	20% 9% 2 6% 4 3 3 3 5% 5% 40%	1848
	21st to end	Day	17% 7% 3 8% 4 4 4 3 4 6% 40%	1570
March	1st to 10th	Day	19% 10% 4 9% 6% 5% 4 3 4 7% 29%	3211
	11th to 20th	Day	14% 7% 3 6% 4 5% 6% 4 7% 9% 35%	3480
	21st to end	Day	13% 8% 2 8% 5% 5% 5% 4 5% 5% 40%	4026
April	1st to 10th	Day	11% 5% 2 7% 5% 4 5% 4 6% 7% 45%	2280
	11th to 20th	Day	15% 6% 2 6% 4 4 5% 3 4 7% 44%	2254
	21st to end	Day	8% 4 2 5% 5% 5% 4 4 6% 8% 48%	2280
May	1st to 10th	Day	9% 5% 2 6% 5% 5% 5% 5% 7% 10% 42%	3765
	11th to 20th	Day	10% 6% 3 7% 4 4 5% 3 5% 7% 45%	3764
	21st to end	Day	8% 4 2 6% 4 4 5% 6% 8% 11% 43%	4382
June	1st to 10th	Day	8% 5% 1 5% 5% 6% 7% 5% 8% 11% 39%	2611
	11th to 20th	Day	5% 5% 2 5% 5% 6% 6% 5% 7% 10% 45%	2660
	21st to end	Day	6% 4 2 6% 6% 6% 6% 5% 7% 10% 42%	2660
July	1st to 10th	Day	5% 5% 3 8% 7% 7% 8% 7% 8% 11% 32%	4137
	11th to 20th	Day	8% 5% 2 7% 5% 6% 7% 7% 9% 13% 32%	4120
	21st to end	Day	12% 8% 3 10% 7% 5% 6% 5% 7% 9% 27%	4284
August	1st to 10th	Day	3 2 1 3 3 4 4 3 6% 6% 64%	3785
	11th to 20th	Day	5% 3 2 5% 5% 5% 5% 5% 8% 11% 46%	3729
	21st to end	Day	8% 4 2 6% 5% 5% 5% 5% 7% 9% 45%	4180
September	1st to 10th	Day	8% 4 2 7% 5% 5% 6% 4 6% 8% 43%	2280
	11th to 20th	Day	12% 6% 3 6% 4 4 4 4 5% 6% 45%	2222
	21st to end	Day	9% 4 2 4 3 3 4 4 6% 8% 54%	2090
October	1st to 10th	Day	6% 3 1 5% 4 3 4 3 5% 6% 59%	1990
	11th to 20th	Day	8% 4 2 5% 4 4 4 3 5% 7% 55%	1900
	21st to end	Day	12% 5% 2 4 3 3 2 2 3 6% 57%	2090
November	1st to 10th	Day	10% 5% 2 5% 4 3 3 3 5% 5% 55%	1885
	11th to 20th	Day	11% 7% 2 6% 4 3 3 3 5% 5% 52%	1710
	21st to end	Day	15% 8% 2 4 4 3 4 3 4 6% 46%	1710
December	1st to 10th	Day	16% 9% 2 6% 4 4 5% 3 6% 6% 40%	1710
	11th to 20th	Day	14% 10% 3 6% 4 4 4 3 4 6% 41%	2113
	21st to end	Day	13% 7% 2 6% 4 5% 4 4 5% 6% 43%	2883
January	1st to 10th	Night	17% 10% 2 5% 3 3 4 3 4 5% 44%	4108
	11th to 20th	Night	13% 8% 3 6% 4 3 3 3 4 6% 47%	4120
	21st to end	Night	23% 10% 3 5% 3 3 2 2 3 5% 42%	4425
February	1st to 10th	Night	17% 9% 3 6% 4 3 3 3 5% 6% 41%	2280
	11th to 20th	Night	20% 8% 2 4 4 3 3 3 4 5% 45%	2218
	21st to end	Night	18% 9% 2 6% 4 4 3 3 4 5% 41%	1884
March	1st to 10th	Night	18% 11% 4 7% 4 3 4 3 4 6% 35%	3669
	11th to 20th	Night	11% 6% 2 6% 5% 4 5% 4 6% 8% 42%	3480
	21st to end	Night	15% 6% 3 6% 4 4 4 4 6% 6% 40%	3604
April	1st to 10th	Night	12% 6% 2 5% 5% 4 4 4 6% 6% 47%	1900
	11th to 20th	Night	12% 5% 2 5% 4 4 5% 3 5% 7% 48%	1875
	21st to end	Night	7% 4 2 6% 4 3 4 3 6% 8% 53%	1900
May	1st to 10th	Night	9% 5% 2 6% 4 4 5% 4 6% 10% 46%	3130
	11th to 20th	Night	15% 6% 2 5% 4 4 4 4 6% 8% 42%	3129
	21st to end	Night	7% 4 2 6% 5% 5% 6% 5% 7% 9% 43%	3155
June	1st to 10th	Night	6% 5% 1 7% 6% 6% 6% 4 6% 10% 42%	1564
	11th to 20th	Night	3 3 1 3 4 6% 5% 4 9% 11% 51%	1520
	21st to end	Night	4 4 1 5% 5% 4 5% 6% 8% 12% 46%	1520
July	1st to 10th	Night	5% 6% 3 7% 5% 6% 5% 5% 8% 11% 39%	2811
	11th to 20th	Night	7% 5% 2 6% 5% 6% 6% 6% 10% 13% 34%	2850
	21st to end	Night	9% 7% 3 9% 6% 5% 5% 5% 7% 10% 33%	3272
August	1st to 10th	Night	1 2 1 4 3 3 4 4 6% 9% 64%	3144
	11th to 20th	Night	3 3 2 5% 4 3 6% 4 8% 13% 49%	3100
	21st to end	Night	6% 4 2 6% 5% 5% 5% 5% 6% 9% 48%	3476
September	1st to 10th	Night	8% 5% 2 7% 4 4 4 5% 7% 9% 46%	1900
	11th to 20th	Night	9% 6% 2 6% 4 5% 6% 4 6% 8% 46%	1938
	21st to end	Night	8% 4 2 5% 4 3 4 3 6% 6% 55%	2090
October	1st to 10th	Night	6% 3 1 4 3 3 4 4 5% 6% 62%	2185
	11th to 20th	Night	11% 4 2 5% 3 3 3 3 4 6% 56%	2280
	21st to end	Night	13% 7% 2 4 3 3 3 2 3 4 57%	2508
November	1st to 10th	Night	12% 5% 1 4 3 2 3 4 4 6% 57%	2312
	11th to 20th	Night	12% 5% 2 4 3 4 3 3 4 6% 54%	2470
	21st to end	Night	13% 5% 2 5% 3 3 4 4 5% 6% 48%	2470
December	1st to 10th	Night	16% 7% 2 6% 4 3 4 3 5% 6% 43%	2470
	11th to 20th	Night	14% 8% 3 6% 5% 4 4 3 4 5% 45%	3078
	21st to end	Night	15% 11% 3 7% 4 3 3 3 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	46% 2 3 20% 25% 5%	2848
	11th to 20th	Day	41% 2 7% 22% 22% 5%	2850
	21st to end	Day	49% 2 6% 15% 22% 7%	3235
February	1st to 10th	Day	47% 2 7% 18% 16% 9%	1900
	11th to 20th	Day	48% 2 5% 17% 20% 8%	1858
	21st to end	Day	48% 3 6% 16% 19% 8%	1570
March	1st to 10th	Day	57% 2 7% 13% 16% 6%	3211
	11th to 20th	Day	46% 3 7% 23% 16% 6%	3480
	21st to end	Day	47% 2 6% 19% 20% 6%	4026
April	1st to 10th	Day	39% 3 9% 23% 19% 7%	2280
	11th to 20th	Day	41% 2 7% 19% 24% 7%	2254
	21st to end	Day	34% 3 9% 28% 23% 4	2280
May	1st to 10th	Day	38% 3 12% 30% 15% 3	3800
	11th to 20th	Day	40% 2 13% 24% 20% 1	3768
	21st to end	Day	36% 3 17% 31% 12% 1	4395
June	1st to 10th	Day	39% 4 15% 26% 14% 2	2611
	11th to 20th	Day	33% 4 17% 27% 15% 3	2660
	21st to end	Day	37% 6% 17% 24% 14% 3	2660
July	1st to 10th	Day	43% 10% 18% 20% 8% 1	4073
	11th to 20th	Day	39% 9% 26% 20% 4 1	4051
	21st to end	Day	53% 6% 13% 21% 6%	4148
August	1st to 10th	Day	20% 4 13% 31% 30% 2	3773
	11th to 20th	Day	30% 6% 18% 30% 14% 2	3765
	21st to end	Day	35% 6% 14% 22% 19% 4	4179
September	1st to 10th	Day	38% 5% 14% 19% 17% 6%	2280
	11th to 20th	Day	39% 5% 10% 18% 21% 7%	2222
	21st to end	Day	29% 3 10% 25% 22% 10%	2090
October	1st to 10th	Day	19% 2 6% 16% 27% 30%	3302
	11th to 20th	Day	19% 2 3 14% 33% 30%	3140
	21st to end	Day	23% 1 3 18% 37% 17%	3428
November	1st to 10th	Day	32% 2 6% 19% 30% 11%	1885
	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	44% 2 4 15% 27% 7%	4108
	11th to 20th	Night	41% 2 5% 22% 20% 10%	4120
	21st to end	Night	48% 2 3 18% 23% 6%	4425
February	1st to 10th	Night	45% 3 6% 17% 21% 8%	2280
	11th to 20th	Night	44% 3 5% 18% 20% 10%	2219
	21st to end	Night	48% 2 6% 15% 18% 11%	1884
March	1st to 10th	Night	52% 2 7% 17% 16% 7%	3669
	11th to 20th	Night	41% 3 9% 22% 18% 7%	3480
	21st to end	Night	45% 2 8% 19% 22% 4	3604
April	1st to 10th	Night	37% 4 11% 20% 19% 10%	1900
	11th to 20th	Night	37% 2 8% 22% 21% 9%	1875
	21st to end	Night	30% 3 9% 26% 26% 6%	1900
May	1st to 10th	Night	36% 3 12% 28% 19% 4	3160
	11th to 20th	Night	41% 3 10% 28% 17% 1	3130
	21st to end	Night	37% 4 14% 26% 17% 3	3163
June	1st to 10th	Night	37% 5% 16% 25% 16% 2	1564
	11th to 20th	Night	25% 6% 19% 29% 17% 5%	1520
	21st to end	Night	29% 6% 20% 25% 17% 3	1520
July	1st to 10th	Night	37% 10% 24% 20% 8% 2	2766
	11th to 20th	Night	36% 11% 27% 21% 5% 1	2796
	21st to end	Night	44% 8% 18% 22% 7% 1	3168
August	1st to 10th	Night	16% 5% 18% 32% 28% 1	3132
	11th to 20th	Night	24% 7% 22% 34% 11% 2	3130
	21st to end	Night	33% 6% 15% 21% 20% 5%	3476
September	1st to 10th	Night	33% 5% 14% 22% 18% 7%	1900
	11th to 20th	Night	36% 5% 13% 17% 20% 9%	1938
	21st to end	Night	30% 3 8% 28% 21% 10%	2090
October	1st to 10th	Night	17% 2 7% 16% 24% 35%	3640
	11th to 20th	Night	20% 2 4 15% 27% 33%	3779
	21st to end	Night	22% 2 5% 15% 35% 22%	4120
November	1st to 10th	Night	29% 3 7% 19% 30% 13%	2312
	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	25% 11% 35% 19% 7% 2	270
	21st to end	Day	24% 14% 36% 21% 5%	297
February	1st to 10th	Day	23% 10% 37% 20% 9% 1	270
	11th to 20th	Day	30% 11% 36% 16% 6%	270
	21st to end	Day	21% 16% 40% 19% 4	225
March	1st to 10th	Day	26% 9% 36% 22% 6% 1	270
	11th to 20th	Day	24% 10% 34% 23% 8% 1	270
	21st to end	Day	17% 12% 33% 29% 8% 1	419
April	1st to 10th	Day	17% 10% 34% 24% 12% 2	460
	11th to 20th	Day	21% 8% 27% 27% 13% 4	452
	21st to end	Day	12% 8% 26% 33% 18% 3	460
May	1st to 10th	Day	12% 7% 27% 31% 18% 5%	463
	11th to 20th	Day	11% 2 22% 30% 20% 14%	487
	21st to end	Day	8% 2 16% 33% 25% 16%	529
June	1st to 10th	Day	11% 2 10% 31% 30% 16%	631
	11th to 20th	Day	7% 2 10% 30% 37% 14%	680
	21st to end	Day	8% 2 9% 27% 35% 20%	680
July	1st to 10th	Day	7% 2 5% 23% 41% 22%	671
	11th to 20th	Day	9% 1 2 20% 39% 29%	668
	21st to end	Day	9% 1 5% 23% 36% 26%	633
August	1st to 10th	Day	6% 1 6% 19% 39% 30%	486
	11th to 20th	Day	6% 1 4 17% 43% 29%	479
	21st to end	Day	13% 1 5% 21% 30% 30%	539
September	1st to 10th	Day	9% 2 7% 20% 41% 21%	490
	11th to 20th	Day	12% 1 12% 14% 36% 25%	490
	21st to end	Day	11% 3 10% 29% 31% 17%	490
October	1st to 10th	Day	8% 3 14% 37% 25% 13%	390
	11th to 20th	Day	9% 4 21% 33% 24% 8%	300
	21st to end	Day	15% 7% 23% 25% 22% 8%	330
November	1st to 10th	Day	14% 3 22% 34% 21% 6%	285
	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% 14% 32% 26% 8%	950
	21st to end	Night	23% 11% 37% 25% 3	977
February	1st to 10th	Night	22% 11% 34% 28% 5%	760
	11th to 20th	Night	25% 14% 29% 27% 5%	743
	21st to end	Night	24% 15% 36% 23% 1	628
March	1st to 10th	Night	18% 12% 31% 31% 8%	722
	11th to 20th	Night	15% 8% 36% 33% 7% 1	570
	21st to end	Night	16% 10% 34% 30% 10% 1	627
April	1st to 10th	Night	16% 10% 35% 26% 12% 1	570
	11th to 20th	Night	15% 8% 34% 30% 11% 1	563
	21st to end	Night	8% 5% 32% 39% 15% 1	570
May	1st to 10th	Night	11% 4 26% 40% 17% 2	570
	11th to 20th	Night	11% 2 21% 39% 23% 4	561
	21st to end	Night	6% 2 15% 36% 34% 8%	617
June	1st to 10th	Night	7% 2 8% 36% 39% 7%	570
	11th to 20th	Night	4 1 7% 33% 44% 11%	570
	21st to end	Night	6% 1 7% 28% 45% 14%	570
July	1st to 10th	Night	7% 2 4 28% 46% 14%	555
	11th to 20th	Night	7% 2 24% 46% 20%	552
	21st to end	Night	4 1 3 27% 48% 17%	624
August	1st to 10th	Night	2 1 3 25% 46% 22%	567
	11th to 20th	Night	6% 1 3 22% 51% 18%	564
	21st to end	Night	9% 1 5% 25% 43% 18%	627
September	1st to 10th	Night	9% 1 7% 30% 43% 10%	570
	11th to 20th	Night	11% 1 7% 28% 42% 11%	608
	21st to end	Night	10% 2 10% 33% 39% 7%	760
October	1st to 10th	Night	7% 1 15% 39% 30% 8%	760
	11th to 20th	Night	13% 5% 20% 35% 24% 3	760
	21st to end	Night	16% 5% 20% 34% 22% 3	836
November	1st to 10th	Night	14% 4 21% 36% 22% 3	764
	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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