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 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	13% 6% 2 5% 5% 3 5% 5% 5% 8% 43%	83772
	Night	13% 6% 2 5% 5% 3 4 4 5% 7% 46%	84968
Transparency	Day	39% 7% 11% 19% 19% 5%	83504
	Night	37% 6% 10% 19% 20% 7%	84755
Seeing	Day	15% 9% 21% 24% 21% 11%	13742
	Night	14% 7% 22% 30% 22% 5%	23699

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% 11% 3 5% 5% 2 4 5% 5% 6% 39%	2836
	11th to 20th	Day	15% 6% 3 5% 4 3 4 3 4 4 49%	3104
	21st to end	Day	23% 10% 2 4 3 2 2 3 3 6% 43%	3476
February	1st to 10th	Day	19% 9% 3 5% 5% 2 4 4 4 6% 40%	1900
	11th to 20th	Day	22% 7% 3 5% 5% 2 4 3 3 5% 41%	1848
	21st to end	Day	22% 6% 3 5% 4 3 3 4 4 5% 39%	1570
March	1st to 10th	Day	23% 7% 4 5% 5% 3 4 4 5% 6% 35%	3120
	11th to 20th	Day	14% 6% 3 5% 5% 3 4 4 6% 7% 42%	3256
	21st to end	Day	16% 7% 2 6% 5% 3 4 5% 5% 7% 40%	4150
April	1st to 10th	Day	12% 5% 3 4 4 3 5% 4 5% 8% 47%	2269
	11th to 20th	Day	12% 5% 2 5% 5% 3 4 3 5% 7% 48%	2134
	21st to end	Day	9% 4 2 4 5% 3 5% 5% 6% 8% 50%	2160
May	1st to 10th	Day	12% 5% 2 4 4 3 4 4 5% 7% 50%	2228
	11th to 20th	Day	10% 5% 2 6% 5% 3 5% 5% 6% 9% 44%	2301
	21st to end	Day	10% 4 2 5% 6% 3 6% 6% 5% 9% 45%	2531
June	1st to 10th	Day	9% 5% 3 6% 7% 3 6% 7% 8% 10% 36%	2340
	11th to 20th	Day	6% 3 1 3 5% 4 5% 6% 7% 11% 48%	2340
	21st to end	Day	6% 5% 3 6% 5% 3 6% 6% 7% 11% 42%	2412
July	1st to 10th	Day	9% 5% 3 6% 6% 4 7% 8% 8% 10% 33%	2404
	11th to 20th	Day	8% 4 2 6% 6% 5% 6% 8% 8% 11% 34%	2340
	21st to end	Day	7% 3 2 6% 8% 5% 8% 7% 6% 12% 36%	2387
August	1st to 10th	Day	6% 4 2 5% 6% 5% 6% 7% 9% 13% 38%	2148
	11th to 20th	Day	10% 6% 3 5% 7% 5% 6% 7% 8% 9% 36%	2125
	21st to end	Day	12% 6% 3 5% 6% 4 6% 6% 7% 9% 37%	2376
September	1st to 10th	Day	9% 5% 2 6% 6% 4 5% 5% 6% 9% 44%	2156
	11th to 20th	Day	12% 6% 2 5% 5% 3 4 5% 7% 8% 42%	1980
	21st to end	Day	8% 5% 2 4 5% 3 4 4 6% 6% 52%	1980
October	1st to 10th	Day	8% 5% 2 5% 5% 2 3 5% 4 6% 55%	1980
	11th to 20th	Day	10% 4 2 4 3 2 4 3 4 6% 57%	1936
	21st to end	Day	14% 4 2 4 4 2 4 4 4 5% 54%	1906
November	1st to 10th	Day	10% 6% 2 4 4 2 4 3 3 6% 57%	1672
	11th to 20th	Day	14% 4 2 4 5% 2 3 4 4 6% 53%	1710
	21st to end	Day	15% 6% 2 6% 4 2 4 3 5% 5% 48%	1710
December	1st to 10th	Day	19% 8% 2 5% 4 2 4 4 5% 7% 40%	1710
	11th to 20th	Day	17% 8% 3 4 5% 3 5% 4 3 5% 43%	2153
	21st to end	Day	17% 9% 3 7% 5% 3 4 4 4 6% 38%	3124
January	1st to 10th	Night	19% 11% 2 5% 4 3 3 3 4 5% 41%	4109
	11th to 20th	Night	16% 8% 4 5% 4 2 4 3 3 4 47%	3853
	21st to end	Night	22% 11% 3 5% 4 2 3 3 3 3 41%	4180
February	1st to 10th	Night	17% 7% 3 5% 5% 2 3 4 5% 6% 42%	2280
	11th to 20th	Night	21% 6% 3 5% 4 2 4 3 3 4 44%	2218
	21st to end	Night	20% 6% 3 6% 5% 3 4 4 4 7% 40%	1884
March	1st to 10th	Night	24% 10% 3 5% 4 2 3 4 4 6% 35%	3733
	11th to 20th	Night	13% 5% 2 4 5% 2 4 5% 6% 7% 47%	3690
	21st to end	Night	16% 8% 3 6% 5% 2 4 4 5% 6% 41%	3509
April	1st to 10th	Night	12% 5% 2 5% 4 3 4 5% 6% 7% 47%	1900
	11th to 20th	Night	13% 5% 2 4 3 3 4 4 4 7% 51%	1775
	21st to end	Night	9% 4 1 4 6% 3 5% 4 5% 7% 52%	1800
May	1st to 10th	Night	9% 5% 2 4 4 2 3 5% 3 8% 55%	1728
	11th to 20th	Night	11% 4 2 5% 5% 3 5% 5% 7% 9% 45%	1592
	21st to end	Night	7% 3 2 4 5% 3 5% 6% 7% 11% 47%	1744
June	1st to 10th	Night	6% 5% 2 5% 6% 5% 6% 6% 6% 10% 41%	1620
	11th to 20th	Night	4 3 1 3 4 3 5% 6% 7% 12% 52%	1620
	21st to end	Night	4 4 2 5% 5% 4 6% 7% 8% 12% 43%	1523
July	1st to 10th	Night	6% 5% 2 5% 7% 4 6% 7% 8% 10% 38%	1534
	11th to 20th	Night	5% 4 3 5% 5% 3 6% 7% 8% 10% 43%	1620
	21st to end	Night	5% 3 2 5% 7% 3 6% 8% 8% 12% 40%	1926
August	1st to 10th	Night	4 2 2 5% 6% 5% 6% 8% 10% 12% 40%	1790
	11th to 20th	Night	7% 4 3 6% 7% 4 6% 7% 7% 8% 42%	1776
	21st to end	Night	10% 6% 2 7% 6% 4 5% 5% 5% 10% 40%	1980
September	1st to 10th	Night	9% 6% 2 6% 6% 4 5% 4 6% 7% 46%	1800
	11th to 20th	Night	11% 5% 2 4 5% 3 4 5% 5% 9% 47%	1966
	21st to end	Night	7% 4 3 5% 4 2 4 5% 5% 6% 54%	1980
October	1st to 10th	Night	7% 4 2 4 4 1 4 4 5% 6% 60%	1980
	11th to 20th	Night	11% 5% 2 3 3 2 3 3 5% 7% 54%	2020
	21st to end	Night	15% 6% 2 4 3 2 3 3 3 4 56%	2448
November	1st to 10th	Night	10% 4 2 3 4 2 4 3 4 6% 58%	2406
	11th to 20th	Night	12% 5% 3 3 4 2 4 3 4 7% 54%	2470
	21st to end	Night	13% 5% 3 4 4 3 4 4 5% 6% 49%	2470
December	1st to 10th	Night	18% 6% 2 5% 5% 3 4 3 4 6% 43%	2470
	11th to 20th	Night	17% 6% 3 5% 3 2 3 3 3 5% 48%	3042
	21st to end	Night	18% 7% 3 6% 5% 2 4 5% 6% 8% 36%	4532

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	45% 5% 7% 17% 22% 4	2837
	11th to 20th	Day	39% 5% 6% 24% 22% 4	3104
	21st to end	Day	46% 3 7% 17% 19% 8%	3476
February	1st to 10th	Day	47% 4 7% 19% 18% 6%	1900
	11th to 20th	Day	48% 3 5% 16% 20% 8%	1858
	21st to end	Day	48% 5% 7% 14% 20% 8%	1570
March	1st to 10th	Day	50% 5% 9% 11% 17% 7%	3120
	11th to 20th	Day	40% 6% 8% 19% 19% 8%	3256
	21st to end	Day	43% 7% 9% 15% 20% 6%	4150
April	1st to 10th	Day	35% 7% 10% 20% 20% 8%	2269
	11th to 20th	Day	37% 5% 7% 20% 23% 8%	2134
	21st to end	Day	31% 6% 10% 23% 26% 3	2160
May	1st to 10th	Day	34% 6% 10% 23% 22% 5%	2228
	11th to 20th	Day	35% 8% 14% 24% 15% 3	2305
	21st to end	Day	35% 9% 12% 22% 19% 2	2531
June	1st to 10th	Day	39% 10% 14% 21% 14% 1	2340
	11th to 20th	Day	28% 10% 18% 26% 16% 2	2340
	21st to end	Day	34% 11% 17% 22% 13% 4	2412
July	1st to 10th	Day	40% 13% 18% 19% 8% 2	2339
	11th to 20th	Day	40% 13% 21% 16% 9% 1	2271
	21st to end	Day	38% 14% 19% 20% 8%	2253
August	1st to 10th	Day	32% 13% 22% 24% 9% 1	2136
	11th to 20th	Day	41% 12% 17% 18% 9% 3	2125
	21st to end	Day	42% 10% 16% 18% 10% 4	2376
September	1st to 10th	Day	36% 9% 14% 17% 20% 5%	2156
	11th to 20th	Day	39% 8% 12% 16% 21% 5%	1980
	21st to end	Day	33% 6% 11% 21% 22% 9%	1980
October	1st to 10th	Day	31% 5% 10% 18% 26% 10%	1980
	11th to 20th	Day	29% 5% 7% 23% 27% 9%	1936
	21st to end	Day	32% 4 6% 16% 31% 10%	1906
November	1st to 10th	Day	32% 3 6% 19% 28% 11%	1672
	11th to 20th	Day	34% 3 6% 18% 28% 11%	1710
	21st to end	Day	38% 4 7% 17% 25% 8%	1710
December	1st to 10th	Day	44% 6% 8% 16% 19% 6%	1710
	11th to 20th	Day	45% 4 7% 17% 23% 5%	2150
	21st to end	Day	45% 6% 8% 19% 20% 2	3124
January	1st to 10th	Night	46% 4 5% 15% 26% 4	4109
	11th to 20th	Night	41% 4 5% 22% 19% 8%	3853
	21st to end	Night	49% 4 3 17% 22% 5%	4180
February	1st to 10th	Night	43% 4 6% 18% 21% 8%	2280
	11th to 20th	Night	45% 4 5% 16% 20% 10%	2219
	21st to end	Night	44% 6% 7% 15% 18% 10%	1884
March	1st to 10th	Night	50% 5% 8% 14% 16% 8%	3733
	11th to 20th	Night	35% 6% 9% 19% 21% 11%	3690
	21st to end	Night	44% 5% 8% 19% 19% 5%	3509
April	1st to 10th	Night	35% 6% 11% 19% 20% 8%	1900
	11th to 20th	Night	33% 5% 7% 20% 23% 11%	1775
	21st to end	Night	29% 8% 10% 23% 24% 6%	1800
May	1st to 10th	Night	29% 7% 10% 23% 24% 7%	1728
	11th to 20th	Night	35% 8% 16% 20% 17% 4	1593
	21st to end	Night	29% 9% 15% 24% 20% 4	1745
June	1st to 10th	Night	37% 11% 14% 20% 17% 2	1620
	11th to 20th	Night	24% 8% 22% 26% 16% 4	1620
	21st to end	Night	30% 10% 18% 20% 17% 4	1523
July	1st to 10th	Night	36% 11% 21% 19% 11% 2	1489
	11th to 20th	Night	30% 14% 25% 20% 10% 2	1566
	21st to end	Night	31% 13% 27% 19% 8% 1	1819
August	1st to 10th	Night	28% 14% 22% 25% 10% 1	1778
	11th to 20th	Night	36% 12% 20% 15% 12% 5%	1776
	21st to end	Night	39% 10% 14% 20% 12% 5%	1980
September	1st to 10th	Night	37% 7% 16% 19% 17% 5%	1800
	11th to 20th	Night	32% 9% 14% 18% 20% 6%	1966
	21st to end	Night	29% 6% 11% 23% 22% 9%	1980
October	1st to 10th	Night	25% 5% 9% 21% 26% 14%	1980
	11th to 20th	Night	29% 5% 9% 18% 27% 12%	2020
	21st to end	Night	35% 3 5% 15% 28% 15%	2448
November	1st to 10th	Night	28% 5% 7% 16% 28% 15%	2406
	11th to 20th	Night	31% 4 6% 18% 27% 13%	2470
	21st to end	Night	36% 4 7% 20% 22% 10%	2470
December	1st to 10th	Night	42% 6% 9% 17% 21% 4	2470
	11th to 20th	Night	41% 4 6% 14% 28% 6%	3044
	21st to end	Night	42% 6% 10% 18% 21% 3	4532

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	23% 20% 34% 18% 5%	270
	11th to 20th	Day	23% 21% 31% 16% 7% 1	270
	21st to end	Day	23% 24% 33% 16% 2 1	297
February	1st to 10th	Day	24% 22% 32% 17% 6%	270
	11th to 20th	Day	36% 14% 32% 15% 2 1	270
	21st to end	Day	31% 23% 32% 14%	225
March	1st to 10th	Day	23% 21% 34% 16% 6% 1	270
	11th to 20th	Day	20% 17% 35% 19% 8%	327
	21st to end	Day	22% 16% 29% 22% 10% 1	506
April	1st to 10th	Day	18% 15% 31% 23% 12% 1	457
	11th to 20th	Day	15% 14% 29% 24% 14% 3	412
	21st to end	Day	11% 13% 28% 30% 15% 2	420
May	1st to 10th	Day	14% 7% 23% 32% 18% 6%	423
	11th to 20th	Day	10% 4 23% 27% 23% 13%	447
	21st to end	Day	11% 3 18% 30% 22% 15%	485
June	1st to 10th	Day	12% 4 13% 28% 26% 17%	450
	11th to 20th	Day	8% 1 12% 22% 33% 24%	450
	21st to end	Day	8% 2 11% 28% 32% 19%	522
July	1st to 10th	Day	8% 2 7% 23% 37% 23%	509
	11th to 20th	Day	7% 2 4 20% 32% 35%	444
	21st to end	Day	7% 1 7% 18% 37% 30%	488
August	1st to 10th	Day	9% 1 7% 20% 33% 29%	446
	11th to 20th	Day	10% 1 6% 24% 37% 23%	439
	21st to end	Day	16% 2 7% 22% 29% 24%	495
September	1st to 10th	Day	9% 2 8% 28% 38% 15%	450
	11th to 20th	Day	12% 2 13% 21% 37% 15%	450
	21st to end	Day	8% 4 14% 28% 33% 13%	450
October	1st to 10th	Day	10% 5% 19% 31% 25% 10%	450
	11th to 20th	Day	10% 6% 25% 35% 22% 2	406
	21st to end	Day	18% 13% 24% 27% 17% 2	297
November	1st to 10th	Day	19% 6% 30% 30% 10% 4	270
	11th to 20th	Day	17% 9% 40% 25% 7% 1	270
	21st to end	Day	14% 15% 34% 22% 12% 2	270
December	1st to 10th	Day	26% 16% 30% 22% 6% 1	270
	11th to 20th	Day	23% 14% 36% 17% 7% 1	270
	21st to end	Day	29% 14% 31% 20% 5% 1	297
January	1st to 10th	Night	23% 13% 32% 26% 6%	760
	11th to 20th	Night	21% 14% 29% 27% 9%	760
	21st to end	Night	20% 13% 36% 28% 3	836
February	1st to 10th	Night	21% 11% 31% 31% 5%	760
	11th to 20th	Night	25% 12% 30% 28% 4	743
	21st to end	Night	22% 15% 35% 25% 2	628
March	1st to 10th	Night	20% 11% 31% 30% 8%	760
	11th to 20th	Night	16% 10% 36% 27% 10% 1	760
	21st to end	Night	16% 12% 32% 28% 12%	657
April	1st to 10th	Night	13% 12% 32% 30% 13%	570
	11th to 20th	Night	15% 9% 31% 29% 14% 2	533
	21st to end	Night	10% 9% 28% 36% 15% 2	540
May	1st to 10th	Night	10% 4 26% 36% 21% 3	540
	11th to 20th	Night	11% 3 21% 33% 28% 4	531
	21st to end	Night	7% 2 11% 35% 38% 8%	584
June	1st to 10th	Night	8% 2 10% 38% 36% 6%	540
	11th to 20th	Night	5% 1 9% 29% 44% 12%	540
	21st to end	Night	6% 1 7% 30% 43% 13%	540
July	1st to 10th	Night	6% 1 5% 26% 46% 16%	525
	11th to 20th	Night	5% 1 7% 23% 43% 22%	522
	21st to end	Night	5% 1 7% 26% 45% 16%	591
August	1st to 10th	Night	5% 5% 21% 50% 19%	537
	11th to 20th	Night	9% 3 30% 45% 13%	534
	21st to end	Night	11% 1 8% 24% 41% 15%	594
September	1st to 10th	Night	11% 1 9% 29% 41% 10%	540
	11th to 20th	Night	12% 2 12% 28% 38% 7%	706
	21st to end	Night	9% 2 12% 36% 38% 4	720
October	1st to 10th	Night	8% 3 20% 33% 30% 5%	720
	11th to 20th	Night	13% 5% 22% 36% 23% 2	720
	21st to end	Night	18% 6% 17% 36% 21% 2	792
November	1st to 10th	Night	13% 6% 19% 36% 22% 4	740
	11th to 20th	Night	13% 7% 28% 36% 14% 2	760
	21st to end	Night	16% 9% 29% 34% 11% 2	760
December	1st to 10th	Night	21% 9% 27% 31% 11%	760
	11th to 20th	Night	24% 8% 29% 29% 11%	760
	21st to end	Night	24% 10% 30% 30% 6%	836

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