Tuscaloosa
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tuscaloosa clear sky chart from 2005-11-06 to 2025-10-19.

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% 2 6% 4 4 5% 4 6% 8% 43%	126396
	Night	13% 6% 2 6% 4 4 4 4 5% 7% 45%	123265
Transparency	Day	37% 7% 11% 21% 18% 6%	130173
	Night	36% 6% 10% 20% 20% 8%	127548
Seeing	Day	15% 9% 21% 24% 21% 11%	15833
	Night	14% 7% 22% 31% 22% 4	25597

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% 9% 3 6% 4 3 3 3 4 5% 45%	4056
	11th to 20th	Day	12% 6% 4 6% 3 3 4 2 4 5% 51%	4450
	21st to end	Day	22% 10% 3 6% 4 3 3 3 3 5% 40%	4972
February	1st to 10th	Day	19% 9% 3 6% 4 3 3 3 4 5% 40%	2000
	11th to 20th	Day	22% 7% 2 6% 4 4 4 2 3 5% 41%	1948
	21st to end	Day	21% 7% 3 6% 4 3 3 3 4 5% 40%	1650
March	1st to 10th	Day	20% 7% 3 7% 5% 4 4 3 5% 5% 36%	4480
	11th to 20th	Day	12% 6% 2 6% 4 3 4 3 6% 7% 46%	4658
	21st to end	Day	15% 8% 3 7% 4 4 4 3 5% 7% 40%	5938
April	1st to 10th	Day	12% 5% 2 5% 4 5% 4 4 5% 8% 46%	2400
	11th to 20th	Day	12% 6% 2 6% 4 4 4 3 5% 7% 48%	2374
	21st to end	Day	9% 5% 2 5% 5% 4 5% 4 6% 8% 48%	2400
May	1st to 10th	Day	14% 6% 2 7% 5% 5% 5% 4 6% 8% 38%	5585
	11th to 20th	Day	15% 6% 3 8% 5% 5% 5% 4 8% 10% 32%	5861
	21st to end	Day	10% 5% 2 6% 5% 4 5% 5% 6% 9% 42%	6433
June	1st to 10th	Day	9% 6% 3 6% 6% 5% 6% 5% 8% 10% 36%	2600
	11th to 20th	Day	6% 4 1 5% 5% 5% 5% 5% 8% 11% 46%	2600
	21st to end	Day	6% 5% 2 6% 5% 4 6% 6% 8% 11% 42%	2681
July	1st to 10th	Day	6% 4 2 7% 6% 6% 7% 6% 8% 11% 36%	6062
	11th to 20th	Day	6% 4 1 6% 5% 5% 6% 6% 9% 14% 37%	5900
	21st to end	Day	8% 6% 3 8% 6% 7% 7% 5% 9% 13% 29%	6015
August	1st to 10th	Day	4 2 1 4 3 4 4 4 7% 10% 57%	3905
	11th to 20th	Day	6% 4 2 6% 5% 5% 4 4 6% 9% 50%	3849
	21st to end	Day	7% 4 2 4 4 5% 6% 4 7% 9% 50%	4312
September	1st to 10th	Day	9% 5% 2 7% 5% 5% 4 4 6% 9% 45%	2395
	11th to 20th	Day	12% 6% 2 6% 4 5% 4 4 7% 7% 44%	2200
	21st to end	Day	8% 5% 2 6% 3 4 4 3 6% 7% 51%	2200
October	1st to 10th	Day	8% 5% 2 6% 5% 3 4 4 4 6% 55%	2200
	11th to 20th	Day	9% 4 1 5% 3 3 3 3 4 6% 60%	2130
	21st to end	Day	13% 4 1 4 3 3 3 2 4 5% 55%	2011
November	1st to 10th	Day	11% 6% 2 5% 3 3 3 3 3 6% 55%	1762
	11th to 20th	Day	14% 4 2 4 4 3 3 3 4 6% 54%	1800
	21st to end	Day	14% 6% 2 7% 3 3 4 3 5% 6% 49%	1800
December	1st to 10th	Day	19% 7% 2 5% 3 3 3 3 5% 6% 44%	2930
	11th to 20th	Day	16% 8% 3 6% 4 4 4 3 4 5% 43%	3373
	21st to end	Day	20% 8% 2 6% 3 3 3 2 4 6% 43%	4466
January	1st to 10th	Night	18% 9% 3 6% 3 3 3 2 4 4 46%	5889
	11th to 20th	Night	16% 8% 3 6% 3 3 3 3 4 5% 46%	5507
	21st to end	Night	20% 10% 2 6% 3 3 3 3 3 4 43%	5984
February	1st to 10th	Night	17% 8% 2 6% 4 3 3 3 5% 5% 43%	2400
	11th to 20th	Night	21% 6% 3 6% 3 4 3 3 3 4 43%	2338
	21st to end	Night	19% 6% 2 7% 4 4 4 3 5% 7% 41%	1980
March	1st to 10th	Night	21% 9% 3 6% 4 4 4 3 4 6% 36%	5373
	11th to 20th	Night	13% 6% 2 5% 4 3 4 3 5% 6% 51%	5288
	21st to end	Night	16% 7% 2 7% 4 3 4 3 4 5% 44%	5019
April	1st to 10th	Night	13% 6% 2 5% 4 4 3 4 6% 7% 47%	2000
	11th to 20th	Night	13% 5% 1 5% 3 4 3 3 4 7% 51%	1975
	21st to end	Night	9% 4 2 5% 5% 4 5% 3 6% 7% 50%	2000
May	1st to 10th	Night	13% 7% 3 7% 5% 5% 5% 4 5% 8% 39%	4306
	11th to 20th	Night	17% 8% 3 7% 4 4 5% 4 6% 7% 35%	4032
	21st to end	Night	10% 5% 2 6% 5% 4 5% 5% 7% 10% 41%	4421
June	1st to 10th	Night	7% 6% 2 6% 6% 6% 5% 5% 7% 10% 41%	1800
	11th to 20th	Night	5% 4 1 5% 5% 4 5% 5% 7% 11% 49%	1800
	21st to end	Night	4 5% 2 5% 4 5% 6% 5% 9% 11% 43%	1691
July	1st to 10th	Night	5% 6% 2 8% 5% 6% 6% 5% 8% 12% 37%	3855
	11th to 20th	Night	6% 5% 2 5% 4 4 7% 6% 10% 13% 38%	4057
	21st to end	Night	7% 6% 3 8% 7% 6% 7% 7% 9% 12% 29%	4831
August	1st to 10th	Night	3 2 1 4 4 5% 5% 4 7% 9% 56%	3244
	11th to 20th	Night	5% 3 2 5% 4 4 5% 4 7% 9% 53%	3200
	21st to end	Night	6% 4 2 6% 5% 4 4 5% 6% 9% 49%	3586
September	1st to 10th	Night	8% 6% 2 7% 5% 6% 5% 4 6% 7% 46%	2000
	11th to 20th	Night	11% 5% 2 5% 4 4 4 4 5% 9% 46%	2185
	21st to end	Night	7% 5% 2 6% 4 3 4 4 5% 6% 54%	2200
October	1st to 10th	Night	8% 4 2 5% 3 3 4 3 5% 5% 59%	2200
	11th to 20th	Night	10% 5% 2 4 2 3 3 2 5% 7% 58%	2222
	21st to end	Night	14% 6% 2 4 3 3 3 2 3 4 57%	2584
November	1st to 10th	Night	11% 5% 1 4 4 3 4 3 4 6% 56%	2536
	11th to 20th	Night	13% 5% 2 4 3 3 3 3 5% 7% 54%	2600
	21st to end	Night	13% 5% 2 5% 4 4 3 3 5% 6% 50%	2600
December	1st to 10th	Night	20% 5% 2 4 3 2 3 2 4 6% 49%	4250
	11th to 20th	Night	17% 8% 3 6% 3 3 3 2 3 4 47%	4822
	21st to end	Night	21% 7% 2 5% 4 3 3 3 5% 6% 42%	6490

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	41% 4 5% 28% 19% 3	4057
	11th to 20th	Day	35% 5% 5% 23% 28% 4	4450
	21st to end	Day	49% 2 6% 15% 18% 10%	4972
February	1st to 10th	Day	47% 4 7% 19% 18% 6%	2000
	11th to 20th	Day	48% 3 5% 17% 19% 7%	1958
	21st to end	Day	47% 5% 6% 14% 20% 8%	1650
March	1st to 10th	Day	49% 4 7% 13% 20% 6%	4480
	11th to 20th	Day	37% 5% 6% 17% 20% 15%	4658
	21st to end	Day	43% 5% 7% 18% 20% 5%	5940
April	1st to 10th	Day	36% 7% 10% 20% 20% 8%	2400
	11th to 20th	Day	37% 5% 7% 20% 22% 9%	2374
	21st to end	Day	32% 7% 11% 23% 25% 3	2400
May	1st to 10th	Day	41% 8% 12% 25% 12% 2	5620
	11th to 20th	Day	45% 8% 16% 21% 9% 1	5865
	21st to end	Day	36% 9% 14% 24% 16% 1	6447
June	1st to 10th	Day	38% 11% 15% 20% 14% 2	2600
	11th to 20th	Day	29% 10% 18% 25% 16% 2	2600
	21st to end	Day	33% 11% 17% 23% 13% 4	2681
July	1st to 10th	Day	36% 12% 18% 24% 9% 1	5997
	11th to 20th	Day	33% 14% 29% 20% 4	5831
	21st to end	Day	43% 13% 20% 21% 4	5842
August	1st to 10th	Day	21% 9% 13% 33% 23% 1	3893
	11th to 20th	Day	30% 8% 16% 28% 14% 2	3885
	21st to end	Day	30% 10% 16% 21% 19% 5%	4311
September	1st to 10th	Day	36% 8% 14% 17% 20% 5%	2395
	11th to 20th	Day	38% 8% 11% 18% 21% 4	2200
	21st to end	Day	32% 6% 11% 22% 21% 8%	2200
October	1st to 10th	Day	22% 4 6% 12% 30% 26%	3590
	11th to 20th	Day	17% 3 4 16% 30% 30%	3461
	21st to end	Day	22% 3 5% 18% 37% 14%	3288
November	1st to 10th	Day	34% 3 6% 19% 27% 11%	1762
	11th to 20th	Day	34% 3 6% 18% 29% 11%	1800
	21st to end	Day	38% 4 7% 17% 26% 9%	1800
December	1st to 10th	Day	42% 4 5% 19% 26% 4	2930
	11th to 20th	Day	44% 4 9% 18% 19% 5%	3370
	21st to end	Day	43% 4 6% 23% 23% 1	4466
January	1st to 10th	Night	43% 3 4 23% 24% 3	5889
	11th to 20th	Night	42% 4 4 19% 23% 8%	5507
	21st to end	Night	46% 3 4 16% 24% 7%	5984
February	1st to 10th	Night	42% 4 6% 18% 21% 9%	2400
	11th to 20th	Night	46% 3 5% 17% 19% 10%	2339
	21st to end	Night	43% 6% 7% 16% 18% 10%	1980
March	1st to 10th	Night	49% 4 6% 14% 18% 9%	5373
	11th to 20th	Night	34% 5% 7% 15% 21% 17%	5288
	21st to end	Night	43% 4 7% 21% 18% 8%	5019
April	1st to 10th	Night	35% 6% 11% 19% 20% 8%	2000
	11th to 20th	Night	33% 5% 7% 20% 24% 11%	1975
	21st to end	Night	31% 7% 11% 23% 23% 6%	2000
May	1st to 10th	Night	40% 10% 13% 19% 15% 3	4336
	11th to 20th	Night	46% 7% 14% 22% 9% 2	4033
	21st to end	Night	35% 9% 14% 22% 18% 2	4429
June	1st to 10th	Night	36% 10% 14% 19% 19% 2	1800
	11th to 20th	Night	27% 8% 21% 25% 16% 4	1800
	21st to end	Night	30% 10% 18% 21% 17% 4	1691
July	1st to 10th	Night	37% 10% 23% 21% 8% 1	3812
	11th to 20th	Night	32% 13% 31% 20% 4 1	4006
	21st to end	Night	43% 14% 22% 17% 4 1	4690
August	1st to 10th	Night	20% 9% 14% 35% 20% 2	3232
	11th to 20th	Night	26% 9% 18% 29% 15% 3	3230
	21st to end	Night	30% 7% 14% 20% 23% 5%	3586
September	1st to 10th	Night	37% 7% 16% 18% 16% 6%	2000
	11th to 20th	Night	33% 9% 13% 19% 20% 6%	2185
	21st to end	Night	30% 6% 10% 24% 23% 8%	2200
October	1st to 10th	Night	22% 4 5% 15% 26% 28%	3590
	11th to 20th	Night	17% 3 5% 16% 29% 31%	3630
	21st to end	Night	23% 2 4 20% 32% 19%	4244
November	1st to 10th	Night	29% 5% 8% 16% 27% 15%	2536
	11th to 20th	Night	31% 4 6% 17% 28% 13%	2600
	21st to end	Night	35% 4 7% 21% 22% 10%	2600
December	1st to 10th	Night	39% 3 6% 22% 25% 5%	4250
	11th to 20th	Night	42% 4 8% 17% 24% 5%	4824
	21st to end	Night	42% 5% 8% 21% 22% 2	6490

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	24% 20% 33% 18% 5%	300
	11th to 20th	Day	22% 22% 33% 16% 6% 1	300
	21st to end	Day	23% 23% 33% 17% 2 1	330
February	1st to 10th	Day	22% 22% 32% 18% 5%	300
	11th to 20th	Day	37% 14% 31% 15% 2 1	300
	21st to end	Day	29% 22% 33% 15% 1	249
March	1st to 10th	Day	23% 21% 35% 14% 5% 1	300
	11th to 20th	Day	22% 17% 36% 18% 7%	360
	21st to end	Day	22% 16% 30% 22% 9% 1	550
April	1st to 10th	Day	18% 17% 30% 22% 12% 2	500
	11th to 20th	Day	15% 15% 31% 24% 13% 3	492
	21st to end	Day	10% 12% 29% 32% 15% 2	500
May	1st to 10th	Day	15% 7% 26% 31% 16% 5%	503
	11th to 20th	Day	12% 5% 25% 26% 20% 11%	527
	21st to end	Day	11% 3 24% 29% 20% 13%	573
June	1st to 10th	Day	12% 4 15% 30% 24% 15%	530
	11th to 20th	Day	7% 2 14% 24% 32% 22%	530
	21st to end	Day	8% 2 10% 27% 32% 21%	611
July	1st to 10th	Day	7% 2 8% 24% 37% 22%	596
	11th to 20th	Day	6% 2 5% 19% 33% 34%	524
	21st to end	Day	7% 1 7% 19% 38% 27%	576
August	1st to 10th	Day	9% 2 7% 23% 33% 27%	526
	11th to 20th	Day	8% 1 7% 24% 37% 23%	519
	21st to end	Day	14% 2 9% 23% 28% 24%	583
September	1st to 10th	Day	9% 2 10% 30% 35% 13%	530
	11th to 20th	Day	12% 2 13% 23% 36% 14%	530
	21st to end	Day	9% 6% 15% 28% 30% 12%	530
October	1st to 10th	Day	10% 6% 20% 32% 23% 8%	530
	11th to 20th	Day	9% 6% 26% 36% 22% 2	474
	21st to end	Day	16% 12% 22% 28% 19% 2	330
November	1st to 10th	Day	19% 6% 32% 29% 10% 4	300
	11th to 20th	Day	17% 10% 39% 26% 7% 2	300
	21st to end	Day	14% 16% 33% 23% 11% 3	300
December	1st to 10th	Day	27% 15% 31% 22% 5% 1	300
	11th to 20th	Day	23% 15% 36% 19% 7% 1	300
	21st to end	Day	29% 15% 29% 19% 6% 1	330
January	1st to 10th	Night	22% 14% 33% 26% 6%	800
	11th to 20th	Night	21% 15% 29% 27% 9%	800
	21st to end	Night	20% 13% 36% 28% 3	880
February	1st to 10th	Night	21% 12% 31% 31% 5%	800
	11th to 20th	Night	26% 13% 29% 28% 4	783
	21st to end	Night	22% 14% 35% 26% 2	660
March	1st to 10th	Night	20% 12% 31% 30% 7%	800
	11th to 20th	Night	16% 11% 36% 27% 9% 1	800
	21st to end	Night	16% 12% 32% 28% 11%	691
April	1st to 10th	Night	14% 12% 32% 30% 13%	600
	11th to 20th	Night	15% 9% 32% 30% 13% 2	593
	21st to end	Night	11% 10% 27% 37% 15% 2	600
May	1st to 10th	Night	11% 4 26% 37% 20% 3	600
	11th to 20th	Night	12% 4 22% 32% 27% 3	591
	21st to end	Night	8% 2 12% 36% 34% 7%	650
June	1st to 10th	Night	8% 3 11% 37% 35% 6%	600
	11th to 20th	Night	6% 1 10% 31% 42% 11%	600
	21st to end	Night	6% 2 7% 30% 44% 13%	600
July	1st to 10th	Night	6% 1 5% 25% 47% 16%	585
	11th to 20th	Night	5% 1 6% 22% 44% 22%	582
	21st to end	Night	6% 1 7% 26% 44% 16%	657
August	1st to 10th	Night	5% 5% 23% 50% 18%	597
	11th to 20th	Night	8% 4 30% 45% 12%	594
	21st to end	Night	11% 1 9% 26% 40% 14%	660
September	1st to 10th	Night	10% 1 10% 31% 39% 9%	600
	11th to 20th	Night	13% 3 12% 29% 37% 6%	785
	21st to end	Night	9% 2 12% 36% 37% 4	800
October	1st to 10th	Night	9% 3 21% 34% 29% 5%	800
	11th to 20th	Night	12% 5% 21% 38% 23% 1	793
	21st to end	Night	17% 6% 17% 37% 21% 2	836
November	1st to 10th	Night	13% 7% 21% 35% 21% 4	780
	11th to 20th	Night	14% 7% 28% 35% 14% 2	800
	21st to end	Night	16% 9% 29% 34% 11% 2	800
December	1st to 10th	Night	21% 10% 27% 31% 11%	800
	11th to 20th	Night	24% 8% 28% 30% 10%	800
	21st to end	Night	24% 10% 30% 30% 6%	880

Page generated at 2025-10-16 00:50:29. Version ac07

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