Dauphin Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dauphin Island clear sky chart from 2005-11-06 to 2026-08-15.

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	9% 5% 2 6% 4 4 5% 4 7% 10% 45%	142453
	Night	10% 5% 2 6% 4 4 4 4 6% 9% 46%	139407
Transparency	Day	34% 8% 17% 20% 15% 6%	146316
	Night	34% 7% 16% 20% 17% 7%	143620
Seeing	Day	11% 2 10% 24% 32% 21%	16719
	Night	12% 3 14% 28% 30% 14%	26572

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	11% 5% 3 6% 4 4 4 3 6% 9% 45%	5833
	11th to 20th	Day	11% 6% 2 5% 3 4 3 4 6% 8% 48%	5880
	21st to end	Day	19% 8% 3 7% 4 4 4 3 4 6% 38%	6436
February	1st to 10th	Day	14% 7% 2 7% 5% 4 3 2 5% 6% 45%	2100
	11th to 20th	Day	14% 6% 2 6% 4 4 4 3 6% 7% 44%	2048
	21st to end	Day	14% 8% 2 6% 4 4 4 4 6% 8% 40%	1730
March	1st to 10th	Day	14% 8% 3 7% 4 4 4 4 5% 6% 41%	4580
	11th to 20th	Day	9% 5% 2 5% 4 3 4 3 5% 7% 54%	4815
	21st to end	Day	15% 6% 2 7% 4 4 4 3 5% 6% 45%	6099
April	1st to 10th	Day	12% 7% 2 5% 4 5% 4 3 5% 7% 46%	2520
	11th to 20th	Day	9% 6% 2 5% 4 4 4 4 6% 8% 48%	2494
	21st to end	Day	7% 4 1 5% 3 4 4 4 5% 7% 56%	2520
May	1st to 10th	Day	17% 6% 3 6% 4 4 4 4 6% 10% 37%	7021
	11th to 20th	Day	8% 4 2 5% 4 4 5% 4 7% 10% 46%	7226
	21st to end	Day	6% 4 2 6% 5% 5% 5% 4 7% 12% 43%	8391
June	1st to 10th	Day	7% 5% 2 6% 4 4 5% 5% 9% 13% 39%	2730
	11th to 20th	Day	5% 3 2 5% 4 4 5% 6% 10% 11% 44%	2730
	21st to end	Day	7% 5% 2 6% 4 4 5% 5% 9% 14% 37%	2730
July	1st to 10th	Day	3 3 2 5% 5% 6% 6% 6% 10% 17% 38%	7450
	11th to 20th	Day	3 4 2 7% 5% 6% 6% 6% 9% 12% 40%	7080
	21st to end	Day	4 3 2 5% 5% 5% 7% 6% 11% 16% 38%	7687
August	1st to 10th	Day	4 3 1 4 3 5% 5% 5% 8% 12% 51%	4025
	11th to 20th	Day	6% 2 1 5% 3 4 6% 5% 9% 12% 48%	3897
	21st to end	Day	6% 5% 2 8% 6% 6% 6% 5% 7% 10% 38%	4312
September	1st to 10th	Day	9% 5% 1 6% 4 5% 5% 5% 8% 11% 42%	2400
	11th to 20th	Day	10% 4 2 6% 4 4 4 4 7% 8% 46%	2209
	21st to end	Day	7% 4 2 5% 4 3 4 3 5% 8% 55%	2200
October	1st to 10th	Day	8% 3 2 3 3 2 3 4 6% 8% 57%	2200
	11th to 20th	Day	6% 3 1 3 3 3 4 3 4 7% 63%	2170
	21st to end	Day	9% 4 2 6% 4 3 4 3 4 6% 56%	2200
November	1st to 10th	Day	9% 4 2 4 3 3 3 4 4 5% 59%	1912
	11th to 20th	Day	10% 4 1 4 3 3 4 3 5% 8% 56%	1890
	21st to end	Day	10% 5% 2 6% 5% 4 5% 3 6% 7% 48%	1890
December	1st to 10th	Day	13% 6% 3 7% 4 3 4 3 5% 7% 45%	3020
	11th to 20th	Day	9% 6% 2 5% 4 3 4 3 5% 7% 52%	3463
	21st to end	Day	16% 8% 4 7% 4 3 3 2 4 5% 45%	4565
January	1st to 10th	Night	11% 5% 3 7% 4 5% 5% 4 6% 8% 44%	7041
	11th to 20th	Night	15% 8% 3 6% 3 3 3 3 4 7% 44%	7080
	21st to end	Night	15% 9% 3 7% 5% 4 4 3 5% 7% 38%	7745
February	1st to 10th	Night	13% 7% 3 6% 4 4 3 3 4 7% 47%	2520
	11th to 20th	Night	16% 8% 2 5% 4 3 4 3 5% 6% 43%	2458
	21st to end	Night	14% 8% 2 6% 4 4 5% 4 5% 6% 44%	2076
March	1st to 10th	Night	19% 9% 3 7% 4 4 3 3 5% 7% 38%	5493
	11th to 20th	Night	10% 6% 2 5% 4 4 4 3 5% 7% 50%	5394
	21st to end	Night	11% 6% 2 5% 4 4 4 3 5% 7% 50%	5072
April	1st to 10th	Night	11% 6% 2 5% 4 4 5% 4 5% 7% 47%	2100
	11th to 20th	Night	10% 5% 2 5% 3 4 4 4 6% 8% 50%	2075
	21st to end	Night	5% 4 2 4 3 3 4 4 5% 7% 60%	2100
May	1st to 10th	Night	15% 7% 2 7% 5% 4 4 4 6% 8% 38%	5832
	11th to 20th	Night	8% 5% 2 5% 4 4 5% 4 6% 10% 49%	5617
	21st to end	Night	5% 4 2 6% 5% 5% 5% 5% 8% 13% 43%	5761
June	1st to 10th	Night	6% 5% 2 6% 4 5% 5% 5% 7% 13% 42%	1890
	11th to 20th	Night	3 4 1 5% 4 5% 5% 5% 8% 12% 48%	1890
	21st to end	Night	5% 4 2 6% 6% 5% 5% 5% 9% 14% 39%	1890
July	1st to 10th	Night	2 3 1 4 4 5% 6% 6% 9% 16% 42%	5474
	11th to 20th	Night	2 3 1 5% 4 5% 6% 5% 10% 12% 46%	5877
	21st to end	Night	3 3 1 5% 5% 6% 7% 7% 12% 16% 34%	6389
August	1st to 10th	Night	2 2 1 3 4 5% 5% 5% 8% 14% 52%	3344
	11th to 20th	Night	4 2 1 4 3 4 4 6% 7% 13% 52%	3240
	21st to end	Night	5% 4 2 6% 5% 5% 6% 5% 8% 12% 43%	3586
September	1st to 10th	Night	8% 5% 2 6% 4 4 6% 5% 7% 12% 40%	2000
	11th to 20th	Night	8% 5% 2 6% 5% 4 4 4 7% 9% 45%	2170
	21st to end	Night	8% 5% 2 5% 3 4 4 4 6% 8% 52%	2200
October	1st to 10th	Night	7% 4 2 5% 4 4 4 4 6% 8% 52%	2200
	11th to 20th	Night	7% 4 2 4 3 3 2 3 4 6% 63%	2225
	21st to end	Night	10% 5% 2 4 4 3 3 3 4 6% 56%	2640
November	1st to 10th	Night	9% 4 2 5% 3 4 3 3 4 7% 55%	2603
	11th to 20th	Night	11% 5% 2 5% 4 3 3 3 4 6% 54%	2730
	21st to end	Night	9% 5% 2 5% 4 4 4 4 6% 7% 50%	2730
December	1st to 10th	Night	12% 5% 2 7% 4 4 4 4 5% 6% 46%	4380
	11th to 20th	Night	12% 5% 2 4 4 4 4 3 5% 6% 52%	4952
	21st to end	Night	15% 8% 3 7% 4 4 4 2 4 5% 44%	6633

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	37% 5% 12% 17% 22% 6%	5834
	11th to 20th	Day	34% 4 5% 21% 27% 9%	5880
	21st to end	Day	48% 5% 7% 14% 16% 11%	6436
February	1st to 10th	Day	41% 5% 9% 15% 20% 10%	2100
	11th to 20th	Day	39% 6% 11% 18% 19% 8%	2058
	21st to end	Day	39% 7% 12% 18% 16% 8%	1730
March	1st to 10th	Day	42% 6% 9% 21% 14% 8%	4580
	11th to 20th	Day	28% 7% 11% 17% 24% 13%	4815
	21st to end	Day	40% 6% 12% 20% 14% 8%	6101
April	1st to 10th	Day	37% 6% 13% 20% 17% 8%	2520
	11th to 20th	Day	32% 7% 10% 22% 22% 7%	2494
	21st to end	Day	27% 6% 14% 25% 21% 7%	2520
May	1st to 10th	Day	41% 8% 17% 18% 12% 3	7056
	11th to 20th	Day	32% 6% 20% 26% 14% 2	7230
	21st to end	Day	32% 9% 23% 26% 9% 1	8405
June	1st to 10th	Day	33% 10% 21% 25% 10% 1	2730
	11th to 20th	Day	28% 11% 24% 26% 10% 1	2730
	21st to end	Day	34% 11% 27% 19% 9% 1	2730
July	1st to 10th	Day	31% 11% 36% 19% 2	7388
	11th to 20th	Day	33% 12% 40% 13% 1	7017
	21st to end	Day	31% 12% 33% 24% 1	7517
August	1st to 10th	Day	24% 9% 21% 31% 15% 1	4013
	11th to 20th	Day	26% 10% 24% 29% 10%	3933
	21st to end	Day	39% 12% 20% 18% 10% 2	4311
September	1st to 10th	Day	34% 12% 22% 18% 11% 4	2400
	11th to 20th	Day	33% 11% 15% 18% 16% 5%	2209
	21st to end	Day	28% 7% 13% 26% 19% 7%	2200
October	1st to 10th	Day	28% 4 9% 14% 18% 26%	3590
	11th to 20th	Day	14% 3 7% 23% 24% 29%	3514
	21st to end	Day	22% 4 6% 13% 37% 18%	3538
November	1st to 10th	Day	26% 5% 10% 23% 24% 12%	1912
	11th to 20th	Day	27% 6% 9% 20% 26% 12%	1890
	21st to end	Day	33% 7% 12% 19% 19% 9%	1890
December	1st to 10th	Day	39% 5% 11% 17% 23% 5%	3020
	11th to 20th	Day	33% 5% 9% 23% 21% 9%	3460
	21st to end	Day	42% 5% 8% 16% 25% 3	4565
January	1st to 10th	Night	39% 4 13% 15% 21% 7%	7042
	11th to 20th	Night	41% 4 4 18% 25% 9%	7080
	21st to end	Night	47% 3 9% 15% 18% 8%	7745
February	1st to 10th	Night	38% 6% 7% 18% 22% 10%	2520
	11th to 20th	Night	41% 6% 9% 15% 19% 10%	2459
	21st to end	Night	40% 8% 10% 17% 15% 11%	2076
March	1st to 10th	Night	45% 6% 9% 15% 17% 7%	5493
	11th to 20th	Night	32% 7% 11% 16% 20% 14%	5394
	21st to end	Night	33% 6% 13% 21% 17% 9%	5072
April	1st to 10th	Night	36% 8% 12% 16% 18% 10%	2100
	11th to 20th	Night	32% 6% 10% 21% 23% 8%	2075
	21st to end	Night	23% 6% 13% 29% 22% 7%	2100
May	1st to 10th	Night	41% 8% 16% 17% 14% 4	5862
	11th to 20th	Night	30% 6% 17% 28% 17% 2	5618
	21st to end	Night	30% 11% 21% 27% 10% 1	5771
June	1st to 10th	Night	31% 11% 22% 26% 9% 1	1890
	11th to 20th	Night	26% 11% 26% 25% 11% 1	1890
	21st to end	Night	31% 12% 29% 19% 9% 1	1890
July	1st to 10th	Night	27% 10% 39% 21% 2	5428
	11th to 20th	Night	27% 13% 47% 13% 1	5820
	21st to end	Night	32% 15% 29% 23% 1	6245
August	1st to 10th	Night	20% 10% 27% 28% 14% 1	3332
	11th to 20th	Night	22% 10% 27% 34% 6%	3270
	21st to end	Night	33% 13% 22% 19% 11% 2	3586
September	1st to 10th	Night	33% 11% 23% 17% 12% 3	2000
	11th to 20th	Night	33% 10% 18% 19% 15% 5%	2170
	21st to end	Night	28% 8% 15% 24% 18% 8%	2200
October	1st to 10th	Night	34% 6% 7% 14% 19% 20%	3590
	11th to 20th	Night	15% 3 5% 21% 27% 28%	3620
	21st to end	Night	21% 3 5% 11% 46% 15%	4252
November	1st to 10th	Night	29% 4 8% 19% 27% 12%	2603
	11th to 20th	Night	31% 4 6% 21% 26% 11%	2730
	21st to end	Night	32% 6% 12% 20% 21% 11%	2730
December	1st to 10th	Night	38% 4 9% 18% 22% 8%	4380
	11th to 20th	Night	33% 4 8% 26% 19% 10%	4954
	21st to end	Night	42% 5% 7% 18% 24% 5%	6633

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	15% 5% 25% 37% 16% 2	330
	11th to 20th	Day	11% 6% 24% 38% 17% 4	330
	21st to end	Day	24% 5% 20% 38% 12% 1	363
February	1st to 10th	Day	18% 4 17% 40% 19% 2	330
	11th to 20th	Day	20% 4 26% 33% 16% 1	330
	21st to end	Day	15% 3 23% 42% 16% 1	273
March	1st to 10th	Day	14% 3 21% 37% 22% 2	330
	11th to 20th	Day	14% 3 26% 34% 19% 4	361
	21st to end	Day	14% 2 20% 36% 24% 4	594
April	1st to 10th	Day	17% 3 20% 36% 22% 4	540
	11th to 20th	Day	13% 3 19% 34% 26% 5%	532
	21st to end	Day	7% 1 14% 34% 36% 8%	540
May	1st to 10th	Day	11% 2 11% 35% 32% 9%	543
	11th to 20th	Day	7% 1 7% 31% 41% 13%	567
	21st to end	Day	7% 2 4 23% 45% 19%	617
June	1st to 10th	Day	9% 1 2 18% 48% 22%	570
	11th to 20th	Day	8% 2 4 16% 42% 29%	570
	21st to end	Day	8% 1 1 15% 40% 35%	570
July	1st to 10th	Day	8% 1 6% 34% 50%	565
	11th to 20th	Day	7% 1 1 4 33% 54%	564
	21st to end	Day	7% 1 7% 37% 46%	620
August	1st to 10th	Day	5% 1 7% 36% 51%	566
	11th to 20th	Day	7% 1 4 32% 55%	535
	21st to end	Day	9% 2 2 11% 37% 39%	583
September	1st to 10th	Day	11% 1 3 9% 34% 42%	530
	11th to 20th	Day	13% 1 5% 12% 40% 29%	530
	21st to end	Day	9% 1 3 21% 41% 26%	530
October	1st to 10th	Day	11% 2 8% 31% 36% 12%	530
	11th to 20th	Day	7% 1 10% 23% 37% 22%	500
	21st to end	Day	13% 2 9% 27% 32% 16%	363
November	1st to 10th	Day	13% 2 7% 28% 38% 12%	330
	11th to 20th	Day	15% 1 15% 28% 30% 10%	330
	21st to end	Day	12% 3 19% 34% 24% 8%	330
December	1st to 10th	Day	18% 3 18% 33% 23% 6%	330
	11th to 20th	Day	15% 2 21% 37% 21% 4	330
	21st to end	Day	20% 2 15% 32% 25% 7%	363
January	1st to 10th	Night	16% 6% 28% 35% 14% 1	840
	11th to 20th	Night	15% 6% 24% 36% 16% 2	840
	21st to end	Night	20% 7% 27% 37% 9% 1	924
February	1st to 10th	Night	16% 6% 23% 39% 16% 1	840
	11th to 20th	Night	20% 6% 25% 31% 17% 1	823
	21st to end	Night	17% 5% 24% 39% 15%	692
March	1st to 10th	Night	16% 5% 20% 39% 19% 1	840
	11th to 20th	Night	13% 3 23% 34% 22% 5%	809
	21st to end	Night	11% 4 17% 40% 27% 3	693
April	1st to 10th	Night	15% 3 21% 36% 23% 3	630
	11th to 20th	Night	13% 2 19% 36% 27% 4	623
	21st to end	Night	7% 2 14% 34% 36% 6%	630
May	1st to 10th	Night	11% 3 11% 34% 34% 7%	630
	11th to 20th	Night	7% 1 8% 33% 42% 9%	621
	21st to end	Night	7% 1 3 23% 48% 17%	683
June	1st to 10th	Night	8% 1 2 23% 46% 20%	630
	11th to 20th	Night	5% 2 13% 49% 30%	630
	21st to end	Night	7% 1 12% 47% 32%	630
July	1st to 10th	Night	6% 1 7% 44% 42%	615
	11th to 20th	Night	4 1 4 35% 56%	612
	21st to end	Night	4 1 1 6% 46% 42%	690
August	1st to 10th	Night	3 1 7% 38% 52%	627
	11th to 20th	Night	7% 1 5% 39% 47%	606
	21st to end	Night	10% 1 2 11% 40% 35%	660
September	1st to 10th	Night	10% 1 3 13% 39% 34%	600
	11th to 20th	Night	10% 1 4 17% 47% 21%	770
	21st to end	Night	10% 1 5% 22% 48% 14%	800
October	1st to 10th	Night	9% 2 10% 32% 38% 10%	800
	11th to 20th	Night	9% 3 12% 29% 36% 13%	800
	21st to end	Night	12% 4 14% 32% 31% 7%	880
November	1st to 10th	Night	10% 4 13% 33% 31% 8%	820
	11th to 20th	Night	12% 5% 19% 32% 28% 3	840
	21st to end	Night	11% 3 24% 34% 23% 5%	840
December	1st to 10th	Night	14% 4 23% 33% 19% 6%	840
	11th to 20th	Night	17% 4 23% 32% 21% 3	840
	21st to end	Night	20% 5% 19% 37% 16% 3	924

Page generated at 2026-08-12 02:37:19. Version ac07

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