Slidell
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Slidell clear sky chart from 2005-11-06 to 2024-02-15.

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% 5% 3 5% 5% 3 5% 6% 6% 9% 41%	79195
	Night	11% 5% 2 5% 5% 3 4 5% 6% 8% 46%	79834
Transparency	Day	25% 37% 9% 13% 12% 4	78934
	Night	24% 36% 8% 13% 13% 6%	79615
Seeing	Day	12% 4 13% 25% 30% 16%	13551
	Night	12% 4 16% 29% 29% 10%	23153

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% 5% 3 4 5% 3 5% 5% 6% 6% 41%	3156
	11th to 20th	Day	13% 5% 2 4 4 2 3 4 4 5% 54%	3160
	21st to end	Day	24% 7% 3 5% 4 3 4 4 4 5% 37%	3476
February	1st to 10th	Day	16% 8% 3 6% 6% 2 4 4 5% 6% 40%	1900
	11th to 20th	Day	15% 7% 3 4 4 3 4 3 5% 7% 45%	1788
	21st to end	Day	16% 7% 4 7% 5% 3 4 4 6% 6% 37%	1480
March	1st to 10th	Day	14% 5% 2 5% 4 4 4 4 5% 8% 44%	1841
	11th to 20th	Day	12% 7% 3 6% 5% 3 6% 4 5% 8% 40%	1980
	21st to end	Day	11% 4 3 5% 5% 2 4 5% 5% 8% 48%	2305
April	1st to 10th	Day	10% 5% 3 5% 6% 3 5% 6% 7% 9% 41%	2160
	11th to 20th	Day	14% 6% 2 6% 4 3 5% 5% 6% 8% 40%	2134
	21st to end	Day	9% 4 2 4 5% 2 5% 5% 6% 8% 49%	2160
May	1st to 10th	Day	10% 4 1 5% 4 3 5% 5% 6% 9% 48%	2160
	11th to 20th	Day	9% 5% 2 5% 5% 3 5% 5% 6% 10% 44%	2124
	21st to end	Day	7% 4 2 5% 6% 4 6% 6% 8% 11% 40%	2337
June	1st to 10th	Day	9% 5% 3 5% 6% 4 8% 8% 8% 12% 32%	2262
	11th to 20th	Day	4 4 2 5% 7% 4 8% 9% 9% 14% 35%	2291
	21st to end	Day	6% 6% 3 7% 8% 5% 8% 8% 10% 12% 28%	2340
July	1st to 10th	Day	9% 6% 4 7% 6% 5% 8% 8% 9% 10% 27%	2340
	11th to 20th	Day	8% 5% 3 8% 7% 6% 8% 9% 9% 12% 25%	2205
	21st to end	Day	7% 6% 3 7% 7% 5% 7% 8% 9% 12% 30%	2350
August	1st to 10th	Day	5% 4 2 6% 6% 5% 8% 8% 10% 13% 32%	2148
	11th to 20th	Day	10% 5% 4 6% 8% 6% 8% 8% 9% 11% 27%	2125
	21st to end	Day	10% 5% 3 7% 7% 4 6% 8% 9% 11% 31%	2376
September	1st to 10th	Day	8% 6% 3 6% 7% 4 7% 8% 8% 10% 35%	2160
	11th to 20th	Day	9% 6% 2 5% 6% 4 6% 5% 7% 10% 39%	2081
	21st to end	Day	9% 4 3 4 5% 3 5% 6% 7% 9% 46%	1980
October	1st to 10th	Day	5% 3 1 5% 4 3 4 5% 6% 7% 57%	1954
	11th to 20th	Day	5% 3 2 4 4 2 4 4 5% 9% 57%	1800
	21st to end	Day	10% 3 1 4 4 3 4 3 4 7% 57%	1980
November	1st to 10th	Day	9% 4 2 3 3 2 4 4 5% 6% 58%	1858
	11th to 20th	Day	10% 4 1 4 5% 2 4 3 4 6% 56%	1767
	21st to end	Day	12% 5% 2 5% 5% 3 4 5% 6% 7% 46%	1710
December	1st to 10th	Day	14% 6% 2 5% 4 3 4 4 6% 7% 44%	1710
	11th to 20th	Day	13% 8% 3 6% 6% 3 4 4 6% 6% 40%	2153
	21st to end	Day	17% 8% 3 5% 6% 3 4 5% 5% 7% 39%	3444
January	1st to 10th	Night	15% 7% 2 4 5% 3 3 4 4 7% 46%	3789
	11th to 20th	Night	15% 5% 2 4 3 2 3 3 4 6% 52%	3800
	21st to end	Night	26% 7% 2 4 3 2 3 3 4 6% 40%	4180
February	1st to 10th	Night	17% 6% 2 6% 5% 3 4 4 4 6% 43%	2280
	11th to 20th	Night	17% 7% 2 5% 4 3 3 4 5% 7% 42%	2153
	21st to end	Night	19% 8% 3 4 4 3 4 4 5% 7% 38%	1776
March	1st to 10th	Night	14% 5% 2 5% 4 2 4 5% 6% 7% 45%	2132
	11th to 20th	Night	13% 6% 3 5% 5% 3 5% 6% 5% 8% 42%	1980
	21st to end	Night	12% 4 2 4 3 3 4 4 5% 7% 53%	2048
April	1st to 10th	Night	13% 6% 3 5% 4 3 4 5% 5% 6% 47%	1800
	11th to 20th	Night	13% 5% 2 5% 5% 3 4 5% 6% 6% 45%	1775
	21st to end	Night	6% 3 1 4 3 3 3 5% 7% 8% 56%	1800
May	1st to 10th	Night	10% 3 2 3 4 2 4 4 5% 11% 53%	1800
	11th to 20th	Night	5% 5% 2 5% 4 4 5% 6% 6% 10% 48%	1769
	21st to end	Night	6% 4 2 4 5% 4 6% 5% 7% 11% 47%	1938
June	1st to 10th	Night	8% 5% 2 4 5% 4 6% 5% 7% 11% 44%	1680
	11th to 20th	Night	3 3 2 4 4 3 6% 7% 8% 13% 46%	1638
	21st to end	Night	7% 5% 3 5% 6% 4 6% 6% 8% 10% 42%	1620
July	1st to 10th	Night	5% 5% 2 6% 6% 3 5% 7% 7% 12% 42%	1620
	11th to 20th	Night	5% 3 2 5% 6% 4 7% 7% 9% 15% 38%	1750
	21st to end	Night	4 4 2 5% 7% 4 6% 7% 8% 15% 39%	1968
August	1st to 10th	Night	2 4 2 4 4 3 4 6% 7% 13% 50%	1790
	11th to 20th	Night	5% 4 2 4 6% 3 5% 8% 10% 16% 36%	1776
	21st to end	Night	8% 4 1 5% 6% 4 5% 6% 9% 12% 39%	1980
September	1st to 10th	Night	7% 5% 2 5% 6% 3 6% 6% 7% 11% 41%	1800
	11th to 20th	Night	9% 4 2 5% 6% 4 5% 5% 6% 11% 44%	1858
	21st to end	Night	8% 5% 2 4 5% 3 4 5% 6% 8% 51%	1980
October	1st to 10th	Night	6% 4 2 4 4 2 3 4 4 7% 60%	2002
	11th to 20th	Night	6% 3 1 4 3 3 3 3 5% 7% 61%	2160
	21st to end	Night	11% 4 2 4 5% 2 4 4 4 6% 55%	2376
November	1st to 10th	Night	9% 5% 2 4 4 2 3 3 4 6% 58%	2220
	11th to 20th	Night	10% 5% 2 3 4 2 4 4 4 6% 56%	2409
	21st to end	Night	11% 5% 3 5% 5% 3 4 5% 5% 6% 49%	2470
December	1st to 10th	Night	14% 6% 3 5% 5% 3 3 4 4 7% 46%	2470
	11th to 20th	Night	15% 6% 2 5% 5% 3 4 5% 5% 6% 43%	3042
	21st to end	Night	18% 9% 4 6% 5% 2 4 4 4 5% 40%	4205

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	29% 27% 5% 12% 18% 9%	3157
	11th to 20th	Day	22% 26% 5% 13% 26% 8%	3160
	21st to end	Day	41% 24% 3 13% 13% 5%	3476
February	1st to 10th	Day	30% 35% 6% 9% 13% 6%	1900
	11th to 20th	Day	26% 37% 5% 10% 12% 9%	1798
	21st to end	Day	30% 38% 6% 12% 9% 5%	1480
March	1st to 10th	Day	23% 37% 6% 15% 14% 4	1841
	11th to 20th	Day	24% 39% 8% 10% 13% 6%	1980
	21st to end	Day	21% 39% 10% 13% 13% 4	2305
April	1st to 10th	Day	22% 40% 11% 13% 9% 6%	2160
	11th to 20th	Day	24% 37% 7% 14% 13% 5%	2134
	21st to end	Day	18% 37% 10% 16% 15% 3	2160
May	1st to 10th	Day	22% 39% 9% 19% 10% 2	2160
	11th to 20th	Day	21% 40% 13% 14% 12% 1	2128
	21st to end	Day	21% 39% 12% 17% 10% 1	2337
June	1st to 10th	Day	25% 41% 13% 15% 6% 1	2262
	11th to 20th	Day	19% 41% 13% 19% 7% 1	2291
	21st to end	Day	26% 41% 13% 13% 7%	2340
July	1st to 10th	Day	35% 44% 11% 8% 2	2276
	11th to 20th	Day	28% 45% 14% 10% 2 1	2139
	21st to end	Day	26% 45% 17% 9% 2	2219
August	1st to 10th	Day	22% 43% 16% 13% 5%	2136
	11th to 20th	Day	30% 42% 13% 12% 3 1	2125
	21st to end	Day	27% 43% 12% 12% 5% 1	2376
September	1st to 10th	Day	26% 41% 12% 12% 7% 2	2160
	11th to 20th	Day	26% 40% 9% 12% 8% 4	2081
	21st to end	Day	21% 39% 9% 12% 12% 7%	1980
October	1st to 10th	Day	17% 37% 6% 14% 14% 12%	1954
	11th to 20th	Day	17% 37% 6% 14% 17% 9%	1800
	21st to end	Day	16% 37% 5% 14% 19% 9%	1980
November	1st to 10th	Day	12% 41% 5% 12% 21% 9%	1858
	11th to 20th	Day	18% 40% 3 12% 20% 7%	1767
	21st to end	Day	23% 40% 5% 13% 13% 6%	1710
December	1st to 10th	Day	23% 42% 6% 13% 12% 5%	1710
	11th to 20th	Day	30% 32% 7% 9% 18% 4	2150
	21st to end	Day	30% 28% 7% 13% 20% 2	3444
January	1st to 10th	Night	29% 26% 5% 11% 20% 9%	3789
	11th to 20th	Night	25% 25% 4 14% 25% 7%	3800
	21st to end	Night	38% 22% 5% 12% 16% 7%	4180
February	1st to 10th	Night	29% 34% 5% 11% 14% 6%	2280
	11th to 20th	Night	29% 37% 4 8% 12% 9%	2154
	21st to end	Night	30% 37% 6% 11% 8% 8%	1776
March	1st to 10th	Night	22% 37% 7% 11% 16% 8%	2132
	11th to 20th	Night	23% 38% 10% 10% 13% 6%	1980
	21st to end	Night	22% 36% 8% 14% 15% 5%	2048
April	1st to 10th	Night	24% 38% 9% 13% 10% 6%	1800
	11th to 20th	Night	25% 36% 6% 16% 11% 6%	1775
	21st to end	Night	15% 37% 9% 18% 17% 5%	1800
May	1st to 10th	Night	20% 38% 9% 19% 12% 2	1800
	11th to 20th	Night	20% 42% 11% 15% 11% 2	1770
	21st to end	Night	19% 40% 10% 20% 10% 1	1939
June	1st to 10th	Night	22% 39% 16% 17% 6%	1680
	11th to 20th	Night	15% 40% 16% 19% 9%	1638
	21st to end	Night	21% 42% 15% 16% 6%	1620
July	1st to 10th	Night	27% 44% 18% 8% 2	1575
	11th to 20th	Night	20% 44% 21% 12% 2	1693
	21st to end	Night	23% 45% 18% 11% 2 1	1858
August	1st to 10th	Night	14% 41% 21% 17% 7%	1778
	11th to 20th	Night	20% 44% 19% 13% 3 1	1776
	21st to end	Night	25% 42% 14% 12% 5% 2	1980
September	1st to 10th	Night	25% 41% 12% 11% 9% 3	1800
	11th to 20th	Night	25% 40% 10% 12% 9% 5%	1858
	21st to end	Night	18% 39% 8% 15% 12% 8%	1980
October	1st to 10th	Night	18% 36% 4 13% 15% 14%	2002
	11th to 20th	Night	18% 36% 6% 13% 17% 10%	2160
	21st to end	Night	16% 38% 4 12% 19% 11%	2376
November	1st to 10th	Night	14% 40% 3 12% 20% 11%	2220
	11th to 20th	Night	17% 40% 5% 11% 18% 9%	2409
	21st to end	Night	24% 40% 4 12% 13% 7%	2470
December	1st to 10th	Night	24% 41% 5% 12% 15% 4	2470
	11th to 20th	Night	28% 34% 6% 10% 13% 9%	3044
	21st to end	Night	33% 26% 5% 14% 16% 6%	4205

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	19% 9% 26% 35% 10%	270
	11th to 20th	Day	16% 10% 24% 36% 12% 1	270
	21st to end	Day	21% 9% 34% 29% 6%	297
February	1st to 10th	Day	24% 8% 27% 31% 9% 1	270
	11th to 20th	Day	22% 8% 25% 34% 10% 1	252
	21st to end	Day	14% 11% 39% 32% 5%	198
March	1st to 10th	Day	13% 3 33% 41% 9%	240
	11th to 20th	Day	18% 11% 27% 31% 12% 1	240
	21st to end	Day	11% 7% 30% 33% 17% 1	391
April	1st to 10th	Day	12% 5% 26% 40% 15% 1	420
	11th to 20th	Day	14% 9% 24% 35% 15% 2	412
	21st to end	Day	9% 5% 18% 39% 25% 4	420
May	1st to 10th	Day	10% 3 17% 36% 28% 5%	423
	11th to 20th	Day	11% 2 11% 30% 35% 11%	447
	21st to end	Day	5% 2 6% 28% 43% 16%	485
June	1st to 10th	Day	12% 2 3 23% 38% 22%	450
	11th to 20th	Day	8% 2 3 20% 45% 23%	473
	21st to end	Day	9% 3 3 18% 39% 27%	630
July	1st to 10th	Day	9% 4 2 12% 39% 34%	621
	11th to 20th	Day	8% 2 2 7% 38% 43%	486
	21st to end	Day	9% 1 3 9% 41% 37%	488
August	1st to 10th	Day	5% 1 3 11% 36% 44%	446
	11th to 20th	Day	8% 2 6% 38% 45%	439
	21st to end	Day	10% 1 5% 12% 37% 34%	495
September	1st to 10th	Day	8% 1 2 16% 40% 33%	450
	11th to 20th	Day	11% 3 6% 18% 41% 22%	450
	21st to end	Day	9% 2 5% 22% 44% 18%	450
October	1st to 10th	Day	6% 2 6% 36% 42% 8%	424
	11th to 20th	Day	6% 9% 36% 40% 9%	270
	21st to end	Day	14% 7% 14% 28% 30% 7%	297
November	1st to 10th	Day	11% 2 12% 31% 37% 7%	270
	11th to 20th	Day	16% 5% 19% 32% 26% 3	270
	21st to end	Day	15% 5% 20% 40% 16% 4	270
December	1st to 10th	Day	16% 4 23% 34% 19% 3	270
	11th to 20th	Day	21% 3 26% 37% 12%	270
	21st to end	Day	25% 5% 26% 28% 14% 1	297
January	1st to 10th	Night	18% 8% 28% 36% 10% 1	760
	11th to 20th	Night	17% 5% 25% 39% 12% 1	760
	21st to end	Night	22% 6% 29% 34% 10%	836
February	1st to 10th	Night	19% 5% 27% 38% 10%	760
	11th to 20th	Night	19% 8% 27% 32% 13% 1	722
	21st to end	Night	20% 6% 28% 38% 8%	592
March	1st to 10th	Night	14% 5% 29% 38% 14%	692
	11th to 20th	Night	14% 5% 23% 35% 22% 1	540
	21st to end	Night	13% 5% 21% 38% 20% 2	594
April	1st to 10th	Night	15% 6% 21% 37% 20% 1	540
	11th to 20th	Night	14% 5% 26% 30% 23% 2	533
	21st to end	Night	8% 4 17% 41% 29% 2	540
May	1st to 10th	Night	9% 2 14% 41% 32% 3	540
	11th to 20th	Night	5% 3 8% 39% 37% 7%	531
	21st to end	Night	7% 2 5% 27% 47% 13%	584
June	1st to 10th	Night	10% 1 5% 24% 46% 14%	540
	11th to 20th	Night	4 1 2 19% 58% 16%	540
	21st to end	Night	8% 3 4 15% 46% 24%	540
July	1st to 10th	Night	7% 2 2 9% 50% 30%	525
	11th to 20th	Night	3 1 1 5% 47% 43%	522
	21st to end	Night	5% 1 2 10% 48% 34%	591
August	1st to 10th	Night	3 1 1 8% 48% 39%	537
	11th to 20th	Night	7% 2 7% 45% 39%	534
	21st to end	Night	9% 2 3 13% 40% 33%	594
September	1st to 10th	Night	8% 1 4 13% 45% 30%	540
	11th to 20th	Night	10% 4 6% 19% 47% 15%	598
	21st to end	Night	10% 1 4 28% 44% 12%	720
October	1st to 10th	Night	7% 2 7% 33% 41% 11%	720
	11th to 20th	Night	7% 4 14% 30% 37% 8%	720
	21st to end	Night	11% 4 17% 32% 31% 4	792
November	1st to 10th	Night	11% 3 12% 38% 30% 5%	740
	11th to 20th	Night	12% 4 21% 39% 21% 3	760
	21st to end	Night	12% 4 24% 37% 21% 2	760
December	1st to 10th	Night	16% 6% 21% 33% 21% 3	760
	11th to 20th	Night	18% 5% 22% 38% 15% 2	760
	21st to end	Night	22% 7% 23% 34% 13% 1	836

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