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 2024-04-10.

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	12% 6% 3 6% 5% 3 5% 5% 6% 8% 42%	83305
	Night	12% 6% 2 5% 4 3 4 4 5% 7% 47%	85487
Transparency	Day	39% 7% 11% 19% 18% 6%	83032
	Night	36% 6% 11% 19% 20% 8%	85281
Seeing	Day	14% 9% 22% 25% 22% 9%	14207
	Night	15% 8% 24% 30% 20% 4	24120

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	16% 12% 3 5% 3 2 2 4 4 6% 41%	2847
	11th to 20th	Day	18% 7% 3 5% 3 2 2 3 4 6% 47%	2850
	21st to end	Day	21% 9% 3 5% 5% 2 3 3 4 5% 41%	3135
February	1st to 10th	Day	18% 8% 3 5% 5% 2 4 4 4 5% 40%	1872
	11th to 20th	Day	20% 9% 3 6% 4 2 3 4 4 5% 40%	1848
	21st to end	Day	18% 9% 4 6% 5% 3 3 4 4 4 39%	1570
March	1st to 10th	Day	20% 9% 4 7% 7% 3 5% 4 5% 6% 30%	3361
	11th to 20th	Day	15% 7% 3 5% 6% 3 5% 6% 7% 7% 35%	3480
	21st to end	Day	11% 9% 3 8% 7% 3 5% 4 5% 5% 40%	3938
April	1st to 10th	Day	11% 6% 3 6% 5% 3 5% 5% 5% 7% 45%	2269
	11th to 20th	Day	14% 6% 3 6% 5% 3 5% 4 5% 7% 42%	2134
	21st to end	Day	9% 5% 3 5% 4 4 4 5% 6% 7% 47%	2160
May	1st to 10th	Day	10% 5% 3 6% 6% 4 6% 6% 5% 8% 42%	2160
	11th to 20th	Day	9% 5% 2 6% 6% 3 6% 5% 7% 9% 43%	2124
	21st to end	Day	6% 4 3 6% 7% 4 6% 7% 7% 9% 40%	2383
June	1st to 10th	Day	9% 4 3 6% 7% 5% 7% 6% 8% 10% 36%	2475
	11th to 20th	Day	4 4 3 7% 6% 5% 6% 7% 7% 10% 42%	2512
	21st to end	Day	6% 4 3 5% 6% 4 7% 7% 7% 10% 40%	2340
July	1st to 10th	Day	6% 5% 3 7% 7% 5% 7% 8% 9% 11% 32%	2340
	11th to 20th	Day	8% 4 3 5% 7% 5% 8% 9% 8% 11% 31%	2340
	21st to end	Day	7% 5% 2 6% 7% 4 8% 8% 9% 11% 33%	2524
August	1st to 10th	Day	5% 4 2 5% 7% 5% 7% 7% 9% 12% 38%	2148
	11th to 20th	Day	7% 6% 3 6% 7% 5% 7% 6% 7% 10% 36%	2125
	21st to end	Day	12% 5% 2 4 4 4 6% 7% 6% 11% 39%	2376
September	1st to 10th	Day	8% 5% 2 5% 5% 4 6% 6% 7% 8% 42%	2160
	11th to 20th	Day	10% 5% 2 6% 6% 3 5% 5% 4 7% 46%	2149
	21st to end	Day	10% 5% 1 4 4 2 4 4 4 7% 54%	1980
October	1st to 10th	Day	6% 4 2 4 4 3 5% 4 4 7% 58%	1800
	11th to 20th	Day	9% 5% 2 4 4 2 4 4 5% 7% 54%	1800
	21st to end	Day	14% 5% 2 4 3 3 3 3 3 5% 55%	1980
November	1st to 10th	Day	10% 4 2 4 4 3 3 4 4 5% 57%	1858
	11th to 20th	Day	11% 7% 2 5% 3 3 4 4 3 6% 52%	1791
	21st to end	Day	16% 6% 3 4 4 3 4 4 5% 6% 46%	1710
December	1st to 10th	Day	17% 8% 2 6% 5% 3 3 4 4 7% 40%	1710
	11th to 20th	Day	15% 10% 3 6% 5% 3 4 4 5% 6% 41%	1985
	21st to end	Day	16% 7% 3 5% 4 2 4 5% 5% 6% 44%	3071
January	1st to 10th	Night	17% 10% 3 4 4 3 3 4 3 5% 46%	4108
	11th to 20th	Night	15% 6% 2 5% 4 2 3 3 4 5% 48%	4120
	21st to end	Night	23% 9% 2 4 4 3 2 3 3 4 43%	4532
February	1st to 10th	Night	16% 8% 3 6% 4 2 3 4 5% 6% 42%	2304
	11th to 20th	Night	19% 8% 3 4 4 2 3 4 3 6% 45%	2218
	21st to end	Night	21% 8% 3 5% 6% 2 4 4 3 5% 40%	1884
March	1st to 10th	Night	19% 10% 3 6% 5% 3 4 4 5% 7% 35%	3520
	11th to 20th	Night	12% 7% 3 5% 6% 3 5% 5% 5% 9% 39%	3480
	21st to end	Night	15% 8% 3 6% 5% 3 4 5% 6% 6% 41%	3690
April	1st to 10th	Night	10% 6% 3 4 5% 3 4 5% 5% 9% 47%	1900
	11th to 20th	Night	13% 5% 3 4 4 2 3 4 6% 7% 48%	1775
	21st to end	Night	7% 5% 2 5% 5% 2 5% 4 5% 8% 54%	1800
May	1st to 10th	Night	7% 4 2 4 3 3 4 5% 6% 10% 52%	1800
	11th to 20th	Night	8% 5% 2 4 5% 3 5% 5% 7% 10% 46%	1769
	21st to end	Night	5% 4 2 5% 6% 3 5% 5% 7% 12% 48%	1885
June	1st to 10th	Night	6% 5% 3 5% 5% 3 6% 5% 6% 9% 47%	1472
	11th to 20th	Night	3 3 2 3 3 3 4 5% 8% 11% 54%	1440
	21st to end	Night	4 3 2 4 7% 3 4 6% 7% 11% 49%	1614
July	1st to 10th	Night	5% 4 2 4 6% 4 4 4 8% 12% 46%	1620
	11th to 20th	Night	6% 3 1 4 5% 3 6% 6% 8% 9% 49%	1620
	21st to end	Night	4 3 2 4 5% 3 5% 6% 7% 14% 48%	1790
August	1st to 10th	Night	2 2 1 3 4 3 5% 6% 8% 14% 49%	1790
	11th to 20th	Night	6% 4 2 5% 4 3 6% 6% 8% 13% 43%	1776
	21st to end	Night	10% 4 2 4 5% 2 6% 5% 7% 10% 46%	1980
September	1st to 10th	Night	7% 5% 2 5% 4 3 5% 6% 7% 9% 49%	1800
	11th to 20th	Night	7% 5% 3 4 4 4 5% 5% 6% 8% 49%	1800
	21st to end	Night	9% 4 2 4 4 2 3 4 5% 8% 55%	1970
October	1st to 10th	Night	6% 3 1 3 3 2 4 4 4 6% 63%	2155
	11th to 20th	Night	12% 4 2 4 4 3 3 4 4 6% 54%	2160
	21st to end	Night	14% 5% 2 4 4 2 3 2 3 5% 56%	2376
November	1st to 10th	Night	11% 4 2 4 3 2 4 3 3 6% 58%	2220
	11th to 20th	Night	12% 6% 2 3 3 2 3 4 4 6% 56%	2384
	21st to end	Night	13% 6% 2 5% 4 2 4 4 5% 6% 48%	2470
December	1st to 10th	Night	17% 6% 3 4 5% 3 4 4 5% 6% 45%	2470
	11th to 20th	Night	14% 8% 3 5% 5% 4 4 4 4 5% 45%	3207
	21st to end	Night	16% 9% 3 6% 4 2 3 3 5% 6% 43%	4588

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% 17% 26% 5%	2848
	11th to 20th	Day	39% 4 9% 21% 22% 5%	2850
	21st to end	Day	49% 2 5% 14% 22% 7%	3135
February	1st to 10th	Day	45% 5% 8% 17% 17% 10%	1872
	11th to 20th	Day	47% 4 5% 17% 19% 8%	1858
	21st to end	Day	48% 5% 7% 13% 17% 9%	1570
March	1st to 10th	Day	54% 6% 9% 11% 15% 5%	3361
	11th to 20th	Day	44% 8% 9% 19% 15% 5%	3480
	21st to end	Day	45% 6% 7% 18% 19% 6%	3938
April	1st to 10th	Day	39% 6% 9% 22% 17% 8%	2269
	11th to 20th	Day	41% 5% 8% 17% 23% 6%	2134
	21st to end	Day	35% 6% 9% 24% 23% 2	2160
May	1st to 10th	Day	38% 8% 11% 18% 19% 5%	2160
	11th to 20th	Day	36% 9% 14% 25% 15% 1	2128
	21st to end	Day	37% 9% 15% 24% 15% 1	2383
June	1st to 10th	Day	39% 9% 15% 23% 12% 1	2475
	11th to 20th	Day	35% 10% 16% 22% 14% 3	2512
	21st to end	Day	36% 10% 16% 21% 14% 2	2340
July	1st to 10th	Day	40% 13% 19% 19% 7% 2	2276
	11th to 20th	Day	39% 14% 22% 17% 7% 1	2271
	21st to end	Day	39% 13% 19% 19% 9% 1	2384
August	1st to 10th	Day	34% 13% 21% 25% 8%	2136
	11th to 20th	Day	39% 13% 16% 19% 10% 3	2125
	21st to end	Day	37% 10% 19% 18% 12% 3	2376
September	1st to 10th	Day	35% 10% 15% 17% 16% 6%	2160
	11th to 20th	Day	39% 7% 10% 17% 20% 8%	2149
	21st to end	Day	29% 6% 11% 24% 19% 11%	1980
October	1st to 10th	Day	27% 6% 9% 21% 24% 13%	1800
	11th to 20th	Day	30% 5% 7% 16% 30% 13%	1800
	21st to end	Day	33% 3 5% 17% 31% 12%	1980
November	1st to 10th	Day	30% 5% 7% 17% 31% 10%	1858
	11th to 20th	Day	34% 4 6% 16% 27% 13%	1791
	21st to end	Day	39% 4 7% 20% 22% 9%	1710
December	1st to 10th	Day	43% 5% 10% 17% 16% 9%	1710
	11th to 20th	Day	45% 5% 6% 14% 24% 6%	1982
	21st to end	Day	39% 5% 8% 18% 28% 2	3071
January	1st to 10th	Night	42% 4 6% 15% 25% 8%	4108
	11th to 20th	Night	38% 5% 7% 20% 20% 10%	4120
	21st to end	Night	46% 3 6% 16% 21% 6%	4532
February	1st to 10th	Night	43% 5% 7% 17% 20% 8%	2304
	11th to 20th	Night	42% 4 6% 16% 21% 10%	2219
	21st to end	Night	48% 5% 5% 14% 17% 11%	1884
March	1st to 10th	Night	48% 7% 9% 15% 16% 6%	3520
	11th to 20th	Night	40% 8% 10% 18% 18% 6%	3480
	21st to end	Night	42% 7% 10% 17% 21% 4	3690
April	1st to 10th	Night	35% 6% 11% 19% 19% 10%	1900
	11th to 20th	Night	35% 5% 10% 19% 22% 10%	1775
	21st to end	Night	28% 5% 11% 24% 27% 5%	1800
May	1st to 10th	Night	27% 8% 12% 24% 22% 7%	1800
	11th to 20th	Night	31% 8% 17% 25% 18% 2	1770
	21st to end	Night	27% 9% 17% 28% 18% 1	1886
June	1st to 10th	Night	32% 9% 16% 25% 16% 2	1472
	11th to 20th	Night	22% 8% 19% 29% 17% 4	1440
	21st to end	Night	28% 10% 18% 25% 16% 3	1614
July	1st to 10th	Night	29% 12% 23% 25% 8% 4	1575
	11th to 20th	Night	27% 14% 24% 24% 9% 2	1566
	21st to end	Night	25% 11% 25% 27% 11% 1	1690
August	1st to 10th	Night	20% 13% 29% 26% 11%	1778
	11th to 20th	Night	30% 12% 22% 19% 14% 3	1776
	21st to end	Night	32% 11% 18% 19% 15% 5%	1980
September	1st to 10th	Night	31% 10% 14% 22% 17% 7%	1800
	11th to 20th	Night	30% 9% 15% 16% 20% 10%	1800
	21st to end	Night	28% 6% 10% 23% 21% 12%	1970
October	1st to 10th	Night	22% 5% 10% 21% 25% 16%	2155
	11th to 20th	Night	31% 4 6% 15% 28% 15%	2160
	21st to end	Night	32% 4 6% 15% 27% 15%	2376
November	1st to 10th	Night	29% 3 7% 18% 28% 15%	2220
	11th to 20th	Night	30% 4 8% 16% 27% 15%	2384
	21st to end	Night	37% 4 7% 20% 20% 12%	2470
December	1st to 10th	Night	40% 6% 10% 17% 20% 7%	2470
	11th to 20th	Night	41% 4 7% 13% 26% 8%	3209
	21st to end	Night	43% 5% 6% 17% 24% 5%	4588

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% 23% 39% 14% 2 1	270
	11th to 20th	Day	29% 18% 33% 12% 8%	270
	21st to end	Day	28% 23% 34% 14% 2	297
February	1st to 10th	Day	29% 18% 36% 13% 5% 1	270
	11th to 20th	Day	40% 12% 35% 11% 2	270
	21st to end	Day	29% 28% 34% 8% 1	225
March	1st to 10th	Day	26% 16% 38% 18% 2	270
	11th to 20th	Day	24% 21% 36% 16% 3	270
	21st to end	Day	20% 19% 36% 19% 6%	370
April	1st to 10th	Day	18% 17% 34% 22% 9%	457
	11th to 20th	Day	23% 14% 28% 24% 10% 2	412
	21st to end	Day	16% 9% 31% 30% 14% 1	420
May	1st to 10th	Day	14% 10% 30% 31% 14% 2	423
	11th to 20th	Day	13% 5% 26% 29% 21% 7%	447
	21st to end	Day	9% 4 21% 31% 25% 10%	531
June	1st to 10th	Day	10% 4 14% 33% 27% 11%	630
	11th to 20th	Day	4 4 16% 36% 30% 9%	630
	21st to end	Day	8% 2 11% 32% 32% 15%	630
July	1st to 10th	Day	4 2 9% 33% 37% 14%	621
	11th to 20th	Day	6% 2 5% 24% 41% 22%	618
	21st to end	Day	6% 2 8% 27% 40% 17%	662
August	1st to 10th	Day	6% 1 9% 22% 39% 23%	446
	11th to 20th	Day	9% 1 5% 25% 41% 19%	439
	21st to end	Day	14% 3 6% 20% 35% 24%	495
September	1st to 10th	Day	6% 3 10% 28% 37% 16%	450
	11th to 20th	Day	10% 4 10% 24% 35% 16%	450
	21st to end	Day	11% 4 10% 31% 32% 11%	450
October	1st to 10th	Day	8% 6% 22% 36% 20% 9%	270
	11th to 20th	Day	9% 9% 29% 30% 19% 5%	270
	21st to end	Day	23% 11% 24% 27% 12% 4	297
November	1st to 10th	Day	16% 7% 30% 32% 12% 4	270
	11th to 20th	Day	16% 13% 37% 22% 11%	270
	21st to end	Day	17% 15% 38% 17% 11% 2	270
December	1st to 10th	Day	23% 16% 34% 21% 5% 1	270
	11th to 20th	Day	22% 13% 36% 24% 5% 1	270
	21st to end	Day	25% 16% 36% 16% 5% 1	297
January	1st to 10th	Night	23% 14% 32% 25% 5%	950
	11th to 20th	Night	23% 16% 28% 25% 8%	950
	21st to end	Night	22% 14% 36% 25% 3	1045
February	1st to 10th	Night	22% 13% 36% 25% 5%	784
	11th to 20th	Night	27% 15% 29% 25% 5%	743
	21st to end	Night	26% 19% 33% 21% 1	628
March	1st to 10th	Night	19% 16% 31% 28% 6%	637
	11th to 20th	Night	17% 11% 39% 26% 7% 1	570
	21st to end	Night	17% 8% 39% 28% 8%	627
April	1st to 10th	Night	16% 11% 36% 26% 10%	570
	11th to 20th	Night	15% 12% 33% 30% 10% 1	533
	21st to end	Night	9% 10% 36% 32% 13%	540
May	1st to 10th	Night	9% 5% 27% 45% 12% 1	540
	11th to 20th	Night	10% 3 26% 36% 23% 2	531
	21st to end	Night	6% 1 19% 38% 29% 6%	584
June	1st to 10th	Night	8% 2 12% 39% 35% 4	540
	11th to 20th	Night	3 1 12% 34% 43% 6%	540
	21st to end	Night	4 1 12% 30% 41% 11%	540
July	1st to 10th	Night	4 1 8% 30% 47% 10%	525
	11th to 20th	Night	4 1 5% 29% 46% 15%	522
	21st to end	Night	5% 1 4 34% 43% 13%	591
August	1st to 10th	Night	2 1 5% 28% 47% 17%	537
	11th to 20th	Night	7% 1 6% 28% 47% 11%	534
	21st to end	Night	10% 1 6% 24% 44% 13%	594
September	1st to 10th	Night	8% 2 8% 31% 43% 8%	540
	11th to 20th	Night	9% 2 12% 27% 42% 8%	540
	21st to end	Night	11% 2 11% 35% 36% 5%	710
October	1st to 10th	Night	7% 3 17% 37% 31% 5%	720
	11th to 20th	Night	14% 6% 22% 35% 22% 2	720
	21st to end	Night	17% 7% 22% 31% 20% 3	792
November	1st to 10th	Night	13% 6% 22% 38% 20% 2	740
	11th to 20th	Night	15% 9% 27% 34% 13% 1	760
	21st to end	Night	17% 9% 29% 30% 14% 1	760
December	1st to 10th	Night	21% 10% 28% 32% 8%	760
	11th to 20th	Night	20% 12% 31% 29% 8%	878
	21st to end	Night	25% 13% 30% 25% 6%	1045

Page generated at 2024-04-07 08:28:16. Version ac07

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