Vicksburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vicksburg clear sky chart from 2005-11-06 to 2025-08-05.

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% 7% 2 6% 4 5% 5% 4 6% 8% 43%	124354
	Night	12% 6% 2 5% 4 4 4 3 5% 7% 46%	123816
Transparency	Day	37% 7% 11% 20% 18% 6%	127963
	Night	35% 6% 11% 20% 20% 9%	128284
Seeing	Day	14% 9% 22% 25% 21% 8%	16081
	Night	15% 8% 24% 30% 20% 3	25777

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% 11% 4 7% 3 3 3 3 4 5% 43%	4077
	11th to 20th	Day	13% 6% 2 5% 3 3 3 3 5% 7% 51%	4080
	21st to end	Day	20% 10% 3 6% 4 3 2 3 3 4 41%	4488
February	1st to 10th	Day	18% 9% 3 6% 4 3 4 3 4 5% 40%	1971
	11th to 20th	Day	20% 9% 3 6% 4 3 3 3 4 5% 39%	1948
	21st to end	Day	18% 10% 3 7% 5% 4 3 3 4 4 39%	1650
March	1st to 10th	Day	18% 10% 4 9% 5% 5% 4 3 5% 5% 32%	4819
	11th to 20th	Day	14% 6% 2 6% 4 4 4 4 6% 6% 46%	4980
	21st to end	Day	11% 10% 3 10% 6% 4 4 3 5% 5% 39%	5642
April	1st to 10th	Day	11% 7% 2 6% 5% 5% 5% 4 5% 6% 44%	2400
	11th to 20th	Day	14% 6% 2 7% 4 4 4 3 6% 7% 43%	2374
	21st to end	Day	9% 5% 2 6% 4 6% 4 4 6% 7% 46%	2400
May	1st to 10th	Day	13% 8% 3 7% 5% 5% 5% 4 6% 9% 36%	5405
	11th to 20th	Day	10% 6% 3 8% 5% 5% 5% 4 7% 9% 38%	5404
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 11% 41%	6062
June	1st to 10th	Day	8% 5% 2 7% 6% 6% 6% 5% 8% 10% 37%	2751
	11th to 20th	Day	4 5% 2 7% 6% 6% 6% 5% 8% 9% 41%	2790
	21st to end	Day	5% 5% 2 6% 6% 6% 7% 6% 8% 10% 40%	2600
July	1st to 10th	Day	4 5% 3 8% 6% 8% 7% 7% 9% 10% 32%	5900
	11th to 20th	Day	6% 4 2 5% 5% 6% 7% 6% 9% 11% 38%	5900
	21st to end	Day	9% 7% 3 7% 6% 6% 6% 5% 8% 11% 33%	6360
August	1st to 10th	Day	3 2 1 3 3 4 4 3 6% 8% 63%	3833
	11th to 20th	Day	4 4 2 5% 5% 5% 5% 5% 7% 11% 47%	3729
	21st to end	Day	9% 5% 2 5% 4 5% 6% 5% 6% 9% 45%	4180
September	1st to 10th	Day	8% 5% 2 6% 5% 6% 5% 5% 7% 8% 42%	2280
	11th to 20th	Day	11% 6% 2 7% 5% 4 5% 4 4 8% 45%	2268
	21st to end	Day	10% 5% 1 4 4 3 4 4 4 7% 54%	2090
October	1st to 10th	Day	5% 4 1 4 3 4 4 3 4 7% 59%	1900
	11th to 20th	Day	9% 4 2 4 3 3 3 3 5% 7% 56%	1900
	21st to end	Day	13% 5% 2 4 3 4 2 2 3 5% 56%	2090
November	1st to 10th	Day	10% 5% 2 5% 4 4 3 3 5% 5% 54%	1958
	11th to 20th	Day	11% 7% 2 5% 3 4 4 3 4 6% 53%	1885
	21st to end	Day	15% 6% 3 5% 3 4 4 3 5% 6% 46%	1800
December	1st to 10th	Day	18% 8% 2 6% 4 4 3 3 4 6% 42%	2930
	11th to 20th	Day	14% 9% 3 8% 5% 5% 4 3 5% 5% 40%	3114
	21st to end	Day	14% 7% 3 6% 3 3 3 3 4 5% 49%	4396
January	1st to 10th	Night	16% 8% 4 6% 3 3 3 2 3 4 48%	5888
	11th to 20th	Night	15% 7% 3 6% 3 3 3 3 5% 6% 47%	5900
	21st to end	Night	23% 9% 2 5% 4 4 3 2 4 4 39%	6490
February	1st to 10th	Night	16% 8% 3 6% 4 3 3 3 5% 6% 43%	2425
	11th to 20th	Night	19% 9% 3 5% 4 3 3 3 4 5% 43%	2338
	21st to end	Night	21% 9% 3 5% 5% 3 4 3 4 5% 40%	1980
March	1st to 10th	Night	17% 9% 2 7% 4 4 4 3 5% 6% 39%	5062
	11th to 20th	Night	11% 7% 2 5% 4 4 4 3 5% 8% 48%	4980
	21st to end	Night	15% 7% 3 6% 4 3 4 3 6% 6% 42%	5284
April	1st to 10th	Night	11% 7% 2 4 4 3 4 4 5% 8% 47%	2000
	11th to 20th	Night	12% 5% 2 5% 4 3 3 4 6% 7% 49%	1975
	21st to end	Night	7% 5% 2 6% 4 4 4 3 5% 7% 52%	2000
May	1st to 10th	Night	13% 6% 2 6% 4 5% 4 4 6% 9% 40%	4490
	11th to 20th	Night	15% 6% 2 7% 4 4 5% 4 6% 8% 37%	4489
	21st to end	Night	8% 5% 2 7% 5% 4 6% 4 7% 11% 41%	4791
June	1st to 10th	Night	6% 5% 2 6% 5% 5% 5% 4 6% 9% 47%	1635
	11th to 20th	Night	4 4 1 4 4 4 5% 3 7% 11% 53%	1600
	21st to end	Night	4 4 2 5% 7% 4 4 5% 7% 11% 48%	1794
July	1st to 10th	Night	4 5% 2 6% 5% 6% 5% 5% 9% 11% 42%	4078
	11th to 20th	Night	5% 4 1 5% 4 5% 6% 5% 10% 13% 41%	4077
	21st to end	Night	7% 6% 3 7% 5% 5% 5% 5% 7% 12% 38%	4492
August	1st to 10th	Night	2 2 1 3 3 3 4 4 6% 10% 63%	3184
	11th to 20th	Night	4 3 1 5% 4 4 5% 5% 8% 13% 47%	3100
	21st to end	Night	6% 5% 2 7% 5% 4 5% 4 7% 8% 48%	3476
September	1st to 10th	Night	7% 5% 2 5% 4 4 5% 4 7% 9% 48%	1900
	11th to 20th	Night	8% 5% 3 5% 4 5% 4 4 6% 8% 48%	1900
	21st to end	Night	8% 4 2 5% 3 3 3 3 5% 8% 55%	2080
October	1st to 10th	Night	5% 3 1 3 3 4 3 3 5% 6% 64%	2275
	11th to 20th	Night	11% 4 2 5% 3 3 3 3 5% 6% 55%	2280
	21st to end	Night	13% 5% 1 5% 3 3 3 2 3 5% 57%	2508
November	1st to 10th	Night	12% 5% 2 4 3 3 3 2 4 5% 56%	2340
	11th to 20th	Night	12% 6% 2 4 3 3 3 3 4 6% 56%	2510
	21st to end	Night	13% 6% 2 5% 4 4 4 3 5% 6% 49%	2600
December	1st to 10th	Night	22% 6% 2 5% 3 3 3 3 4 4 45%	4250
	11th to 20th	Night	14% 9% 3 7% 4 5% 4 3 4 5% 43%	5085
	21st to end	Night	16% 9% 3 6% 3 3 3 2 4 5% 47%	6560

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% 4 5% 23% 22% 3	4078
	11th to 20th	Day	33% 4 6% 22% 27% 8%	4080
	21st to end	Day	49% 3 5% 12% 20% 12%	4488
February	1st to 10th	Day	45% 4 7% 16% 17% 10%	1971
	11th to 20th	Day	48% 4 5% 17% 18% 8%	1958
	21st to end	Day	48% 5% 7% 13% 17% 10%	1650
March	1st to 10th	Day	53% 5% 6% 14% 16% 7%	4819
	11th to 20th	Day	37% 6% 6% 16% 20% 15%	4980
	21st to end	Day	47% 5% 7% 19% 16% 7%	5644
April	1st to 10th	Day	39% 5% 9% 22% 17% 8%	2400
	11th to 20th	Day	40% 5% 8% 17% 23% 7%	2374
	21st to end	Day	35% 7% 10% 24% 22% 3	2400
May	1st to 10th	Day	42% 9% 11% 23% 12% 2	5440
	11th to 20th	Day	40% 8% 15% 18% 17% 1	5408
	21st to end	Day	34% 10% 14% 26% 15% 1	6075
June	1st to 10th	Day	38% 9% 15% 24% 13% 1	2751
	11th to 20th	Day	35% 10% 16% 21% 15% 3	2790
	21st to end	Day	35% 11% 17% 22% 13% 2	2600
July	1st to 10th	Day	40% 12% 18% 19% 10% 1	5836
	11th to 20th	Day	34% 12% 27% 25% 3 1	5831
	21st to end	Day	41% 10% 17% 26% 6%	6179
August	1st to 10th	Day	19% 7% 12% 30% 28% 3	3821
	11th to 20th	Day	29% 9% 18% 29% 14% 2	3765
	21st to end	Day	35% 8% 15% 20% 20% 3	4179
September	1st to 10th	Day	36% 11% 15% 16% 15% 6%	2280
	11th to 20th	Day	39% 7% 10% 18% 19% 7%	2268
	21st to end	Day	29% 6% 11% 24% 19% 11%	2090
October	1st to 10th	Day	17% 4 6% 14% 26% 33%	3160
	11th to 20th	Day	17% 3 4 13% 34% 29%	3140
	21st to end	Day	23% 2 3 17% 38% 16%	3428
November	1st to 10th	Day	32% 5% 7% 17% 29% 10%	1958
	11th to 20th	Day	34% 4 6% 16% 27% 13%	1885
	21st to end	Day	38% 4 7% 20% 22% 9%	1800
December	1st to 10th	Day	43% 4 7% 18% 24% 5%	2930
	11th to 20th	Day	46% 5% 6% 16% 19% 9%	3111
	21st to end	Day	37% 4 6% 23% 29% 2	4396
January	1st to 10th	Night	41% 3 6% 21% 24% 6%	5888
	11th to 20th	Night	38% 4 5% 16% 26% 10%	5900
	21st to end	Night	50% 3 5% 14% 19% 10%	6490
February	1st to 10th	Night	42% 4 7% 18% 21% 9%	2425
	11th to 20th	Night	44% 4 6% 16% 20% 10%	2339
	21st to end	Night	47% 5% 5% 14% 16% 12%	1980
March	1st to 10th	Night	45% 5% 7% 13% 22% 9%	5062
	11th to 20th	Night	34% 6% 7% 16% 19% 17%	4980
	21st to end	Night	41% 6% 10% 17% 19% 6%	5284
April	1st to 10th	Night	35% 6% 11% 19% 19% 10%	2000
	11th to 20th	Night	34% 5% 10% 19% 23% 10%	1975
	21st to end	Night	30% 5% 11% 24% 25% 6%	2000
May	1st to 10th	Night	38% 9% 11% 23% 16% 3	4520
	11th to 20th	Night	41% 7% 15% 22% 13% 1	4490
	21st to end	Night	32% 9% 17% 25% 15% 2	4800
June	1st to 10th	Night	32% 9% 15% 24% 18% 2	1635
	11th to 20th	Night	24% 8% 19% 28% 16% 4	1600
	21st to end	Night	28% 11% 18% 25% 15% 3	1794
July	1st to 10th	Night	33% 12% 24% 22% 8% 1	4035
	11th to 20th	Night	28% 13% 32% 23% 4 1	4026
	21st to end	Night	37% 10% 18% 28% 7% 1	4362
August	1st to 10th	Night	15% 9% 17% 30% 28% 2	3172
	11th to 20th	Night	25% 9% 21% 32% 12% 2	3130
	21st to end	Night	34% 8% 12% 21% 20% 5%	3476
September	1st to 10th	Night	31% 10% 15% 21% 17% 8%	1900
	11th to 20th	Night	31% 9% 15% 16% 20% 9%	1900
	21st to end	Night	27% 5% 10% 24% 21% 12%	2080
October	1st to 10th	Night	15% 4 6% 16% 24% 36%	3795
	11th to 20th	Night	19% 3 4 15% 25% 33%	3779
	21st to end	Night	20% 3 6% 13% 37% 21%	4120
November	1st to 10th	Night	31% 4 7% 18% 26% 14%	2340
	11th to 20th	Night	30% 4 7% 15% 27% 16%	2510
	21st to end	Night	36% 4 7% 20% 20% 13%	2600
December	1st to 10th	Night	43% 4 6% 17% 26% 5%	4250
	11th to 20th	Night	44% 4 7% 16% 23% 6%	5087
	21st to end	Night	40% 4 6% 21% 26% 4	6560

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	21% 24% 39% 13% 2 1	300
	11th to 20th	Day	28% 19% 34% 12% 7%	300
	21st to end	Day	28% 21% 36% 13% 2	330
February	1st to 10th	Day	28% 18% 36% 13% 5% 1	300
	11th to 20th	Day	40% 13% 34% 11% 2	300
	21st to end	Day	28% 27% 33% 10% 2	249
March	1st to 10th	Day	26% 16% 38% 17% 2	300
	11th to 20th	Day	26% 21% 36% 14% 3	300
	21st to end	Day	20% 19% 37% 19% 5%	407
April	1st to 10th	Day	20% 17% 34% 21% 9%	500
	11th to 20th	Day	22% 15% 29% 23% 9% 2	492
	21st to end	Day	15% 10% 31% 29% 15% 1	500
May	1st to 10th	Day	14% 12% 30% 29% 12% 2	503
	11th to 20th	Day	13% 6% 29% 27% 18% 6%	527
	21st to end	Day	9% 5% 24% 31% 23% 9%	625
June	1st to 10th	Day	9% 5% 16% 34% 26% 10%	730
	11th to 20th	Day	5% 4 17% 36% 28% 9%	730
	21st to end	Day	8% 2 11% 31% 33% 16%	730
July	1st to 10th	Day	4 3 9% 32% 37% 14%	721
	11th to 20th	Day	7% 2 5% 25% 40% 21%	718
	21st to end	Day	7% 2 8% 27% 40% 16%	769
August	1st to 10th	Day	6% 1 9% 25% 38% 22%	502
	11th to 20th	Day	8% 1 5% 25% 40% 20%	479
	21st to end	Day	13% 2 6% 22% 34% 23%	539
September	1st to 10th	Day	8% 3 11% 28% 36% 14%	490
	11th to 20th	Day	11% 4 11% 24% 34% 16%	490
	21st to end	Day	11% 5% 13% 30% 31% 11%	490
October	1st to 10th	Day	7% 6% 25% 36% 19% 8%	300
	11th to 20th	Day	8% 9% 28% 32% 18% 4	300
	21st to end	Day	21% 10% 23% 27% 15% 5%	330
November	1st to 10th	Day	16% 7% 31% 31% 11% 3	300
	11th to 20th	Day	15% 14% 37% 22% 11%	300
	21st to end	Day	16% 16% 38% 17% 10% 3	300
December	1st to 10th	Day	22% 16% 36% 21% 4 1	300
	11th to 20th	Day	21% 14% 37% 23% 5% 1	300
	21st to end	Day	24% 18% 35% 18% 5% 1	330
January	1st to 10th	Night	23% 14% 33% 25% 5%	1000
	11th to 20th	Night	23% 16% 29% 25% 7%	1000
	21st to end	Night	22% 14% 35% 26% 3	1100
February	1st to 10th	Night	21% 13% 36% 26% 5%	825
	11th to 20th	Night	28% 15% 29% 24% 4	783
	21st to end	Night	26% 18% 33% 22% 1	660
March	1st to 10th	Night	19% 16% 32% 27% 5%	670
	11th to 20th	Night	17% 12% 39% 25% 6% 1	600
	21st to end	Night	17% 8% 39% 28% 7%	660
April	1st to 10th	Night	18% 11% 36% 26% 9%	600
	11th to 20th	Night	14% 12% 35% 29% 9% 1	593
	21st to end	Night	9% 11% 36% 32% 13%	600
May	1st to 10th	Night	10% 6% 27% 44% 12% 1	600
	11th to 20th	Night	12% 4 27% 34% 21% 2	591
	21st to end	Night	7% 3 21% 38% 26% 6%	650
June	1st to 10th	Night	8% 2 13% 39% 34% 4	600
	11th to 20th	Night	4 1 14% 34% 42% 6%	600
	21st to end	Night	4 1 12% 30% 43% 11%	600
July	1st to 10th	Night	5% 1 8% 30% 48% 9%	585
	11th to 20th	Night	5% 2 4 29% 45% 15%	582
	21st to end	Night	5% 2 4 33% 43% 12%	657
August	1st to 10th	Night	2 1 5% 28% 47% 17%	579
	11th to 20th	Night	6% 1 7% 28% 47% 11%	564
	21st to end	Night	10% 1 6% 26% 44% 13%	627
September	1st to 10th	Night	8% 2 10% 31% 42% 8%	570
	11th to 20th	Night	10% 2 12% 26% 42% 8%	570
	21st to end	Night	10% 3 12% 35% 36% 5%	750
October	1st to 10th	Night	7% 3 18% 38% 31% 5%	760
	11th to 20th	Night	13% 6% 23% 36% 21% 2	760
	21st to end	Night	16% 6% 22% 32% 21% 3	836
November	1st to 10th	Night	14% 6% 23% 37% 19% 2	780
	11th to 20th	Night	15% 9% 27% 34% 14% 1	800
	21st to end	Night	17% 10% 29% 30% 14% 1	800
December	1st to 10th	Night	22% 10% 28% 32% 8%	800
	11th to 20th	Night	21% 11% 31% 29% 7%	925
	21st to end	Night	25% 13% 30% 25% 6%	1100

Page generated at 2025-08-02 00:32:27. Version ac07

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