Phenix City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Phenix City clear sky chart from 2005-11-06 to 2025-04-11.

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%	113797
	Night	12% 6% 2 6% 4 4 4 4 6% 8% 45%	114512
Transparency	Day	36% 7% 11% 19% 19% 7%	117678
	Night	36% 7% 10% 18% 20% 9%	118769
Seeing	Day	14% 8% 22% 25% 21% 11%	15340
	Night	14% 6% 22% 31% 23% 4	25438

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	15% 7% 2 6% 4 3 2 3 4 5% 50%	4056
	11th to 20th	Day	12% 7% 2 5% 3 3 3 3 5% 7% 51%	4060
	21st to end	Day	21% 7% 3 7% 4 3 3 2 4 6% 40%	4940
February	1st to 10th	Day	14% 8% 2 7% 5% 5% 4 4 5% 6% 39%	2000
	11th to 20th	Day	20% 8% 2 5% 3 3 4 3 5% 5% 42%	1948
	21st to end	Day	14% 7% 3 6% 4 5% 4 4 5% 6% 41%	1650
March	1st to 10th	Day	18% 8% 3 6% 4 4 4 4 5% 6% 37%	4542
	11th to 20th	Day	9% 6% 2 5% 4 4 4 4 5% 6% 52%	4980
	21st to end	Day	15% 6% 2 6% 4 4 4 3 5% 7% 44%	5465
April	1st to 10th	Day	11% 5% 3 5% 5% 4 5% 3 5% 8% 46%	2307
	11th to 20th	Day	12% 6% 1 5% 4 4 5% 4 6% 8% 47%	2254
	21st to end	Day	7% 4 2 5% 4 4 4 4 5% 7% 54%	2343
May	1st to 10th	Day	8% 5% 2 6% 4 4 5% 4 6% 9% 47%	4082
	11th to 20th	Day	15% 7% 2 6% 4 4 5% 4 5% 8% 39%	4081
	21st to end	Day	6% 4 2 6% 4 5% 5% 4 8% 10% 46%	4476
June	1st to 10th	Day	10% 6% 2 7% 6% 5% 7% 6% 9% 11% 32%	2470
	11th to 20th	Day	6% 4 1 6% 5% 5% 6% 5% 9% 11% 41%	2470
	21st to end	Day	6% 6% 2 6% 6% 6% 7% 6% 8% 12% 35%	2470
July	1st to 10th	Day	10% 6% 2 8% 6% 6% 7% 7% 9% 12% 26%	4120
	11th to 20th	Day	6% 6% 2 7% 6% 5% 7% 6% 8% 11% 36%	4120
	21st to end	Day	8% 7% 3 9% 6% 6% 8% 7% 11% 14% 21%	4466
August	1st to 10th	Day	6% 3 2 5% 4 6% 6% 6% 10% 13% 38%	3918
	11th to 20th	Day	7% 4 2 5% 4 5% 5% 4 6% 9% 49%	3729
	21st to end	Day	7% 4 2 5% 4 4 5% 5% 7% 11% 46%	4180
September	1st to 10th	Day	9% 6% 2 8% 6% 5% 6% 5% 6% 8% 38%	2121
	11th to 20th	Day	15% 6% 2 6% 4 4 5% 4 6% 8% 39%	2090
	21st to end	Day	11% 5% 2 7% 5% 4 4 3 5% 6% 48%	2090
October	1st to 10th	Day	11% 5% 2 6% 3 3 3 3 5% 7% 53%	2090
	11th to 20th	Day	10% 4 1 4 3 3 3 3 5% 8% 57%	2055
	21st to end	Day	10% 6% 2 5% 3 3 4 2 4 5% 57%	2090
November	1st to 10th	Day	12% 6% 2 5% 4 3 3 4 4 5% 52%	1765
	11th to 20th	Day	13% 5% 2 4 2 3 3 3 4 6% 56%	1800
	21st to end	Day	13% 5% 2 5% 4 4 5% 3 4 7% 47%	1800
December	1st to 10th	Day	16% 5% 2 4 3 3 3 2 5% 5% 50%	2930
	11th to 20th	Day	14% 8% 2 6% 4 3 3 3 4 6% 47%	3373
	21st to end	Day	20% 7% 2 6% 3 3 3 2 4 5% 43%	4466
January	1st to 10th	Night	15% 6% 3 5% 3 4 3 3 4 5% 48%	5889
	11th to 20th	Night	13% 6% 3 7% 5% 4 4 3 5% 6% 44%	5900
	21st to end	Night	18% 9% 2 5% 3 3 4 3 4 6% 42%	6012
February	1st to 10th	Night	14% 7% 2 7% 5% 4 3 3 5% 6% 45%	2400
	11th to 20th	Night	20% 7% 2 5% 3 3 3 3 4 4 45%	2338
	21st to end	Night	15% 7% 2 6% 4 4 4 3 5% 5% 44%	1980
March	1st to 10th	Night	20% 8% 2 7% 5% 4 4 3 5% 6% 37%	5310
	11th to 20th	Night	11% 5% 2 5% 4 4 4 4 5% 6% 50%	4980
	21st to end	Night	12% 5% 2 6% 5% 4 4 3 5% 6% 47%	5467
April	1st to 10th	Night	11% 6% 2 5% 4 4 5% 4 6% 6% 47%	2109
	11th to 20th	Night	12% 4 3 5% 3 3 3 3 5% 9% 49%	1881
	21st to end	Night	7% 4 1 5% 4 4 4 3 5% 7% 56%	1834
May	1st to 10th	Night	6% 5% 2 6% 4 4 5% 4 7% 11% 46%	2813
	11th to 20th	Night	15% 8% 2 6% 4 4 4 4 5% 7% 41%	2812
	21st to end	Night	6% 3 1 5% 4 3 4 4 7% 11% 51%	3079
June	1st to 10th	Night	8% 7% 2 7% 6% 6% 8% 6% 9% 9% 34%	1710
	11th to 20th	Night	3 3 2 4 4 6% 5% 6% 10% 12% 46%	1710
	21st to end	Night	5% 5% 2 6% 6% 5% 5% 7% 10% 13% 36%	1710
July	1st to 10th	Night	9% 8% 3 8% 7% 7% 7% 6% 10% 13% 23%	2840
	11th to 20th	Night	5% 5% 2 7% 6% 6% 8% 6% 9% 12% 33%	2840
	21st to end	Night	10% 7% 3 9% 6% 6% 6% 6% 9% 13% 24%	3087
August	1st to 10th	Night	6% 5% 2 8% 6% 5% 7% 6% 8% 14% 34%	3006
	11th to 20th	Night	5% 4 2 5% 5% 4 5% 5% 8% 12% 46%	3100
	21st to end	Night	6% 5% 2 5% 3 5% 4 4 6% 9% 49%	3476
September	1st to 10th	Night	10% 5% 3 6% 5% 5% 5% 4 6% 11% 39%	2038
	11th to 20th	Night	12% 8% 3 6% 4 5% 5% 4 6% 7% 42%	2090
	21st to end	Night	9% 5% 2 7% 4 5% 4 3 5% 7% 48%	2090
October	1st to 10th	Night	9% 4 2 5% 3 3 4 3 5% 6% 56%	2090
	11th to 20th	Night	10% 5% 2 4 3 3 3 3 4 6% 59%	2123
	21st to end	Night	10% 5% 1 4 4 2 3 3 4 5% 59%	2508
November	1st to 10th	Night	11% 5% 2 6% 3 3 3 3 4 5% 56%	2528
	11th to 20th	Night	14% 5% 2 4 4 3 3 2 4 5% 56%	2600
	21st to end	Night	14% 6% 2 5% 4 4 3 3 4 6% 50%	2600
December	1st to 10th	Night	13% 7% 2 5% 3 3 3 2 4 5% 53%	4250
	11th to 20th	Night	16% 5% 2 5% 4 3 3 2 5% 6% 48%	4822
	21st to end	Night	20% 7% 2 6% 3 4 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	37% 4 4 19% 29% 6%	4057
	11th to 20th	Day	34% 4 5% 17% 33% 8%	4060
	21st to end	Day	47% 4 8% 11% 19% 11%	4940
February	1st to 10th	Day	45% 5% 7% 16% 19% 8%	2000
	11th to 20th	Day	44% 4 5% 16% 22% 8%	1958
	21st to end	Day	42% 6% 7% 15% 20% 10%	1650
March	1st to 10th	Day	46% 6% 7% 13% 20% 7%	4542
	11th to 20th	Day	32% 6% 7% 13% 22% 20%	4980
	21st to end	Day	40% 5% 9% 17% 18% 10%	5465
April	1st to 10th	Day	36% 6% 10% 22% 15% 10%	2307
	11th to 20th	Day	34% 5% 10% 18% 23% 9%	2254
	21st to end	Day	28% 7% 10% 23% 26% 6%	2343
May	1st to 10th	Day	31% 10% 13% 23% 21% 3	4120
	11th to 20th	Day	40% 9% 13% 24% 13% 2	4085
	21st to end	Day	29% 10% 15% 26% 18% 2	4489
June	1st to 10th	Day	41% 13% 16% 18% 10% 2	2470
	11th to 20th	Day	31% 11% 18% 23% 15% 2	2470
	21st to end	Day	37% 13% 18% 19% 10% 3	2470
July	1st to 10th	Day	45% 13% 26% 12% 3 1	4055
	11th to 20th	Day	39% 13% 21% 22% 5% 1	4051
	21st to end	Day	50% 16% 19% 12% 4	4324
August	1st to 10th	Day	31% 11% 17% 30% 11%	3905
	11th to 20th	Day	31% 9% 14% 29% 16% 1	3765
	21st to end	Day	29% 10% 18% 25% 15% 2	4179
September	1st to 10th	Day	42% 10% 14% 15% 15% 4	2121
	11th to 20th	Day	41% 9% 12% 16% 17% 5%	2090
	21st to end	Day	36% 6% 8% 22% 21% 7%	2090
October	1st to 10th	Day	29% 4 7% 13% 26% 21%	3480
	11th to 20th	Day	16% 3 5% 16% 26% 34%	3399
	21st to end	Day	20% 3 5% 18% 42% 13%	3428
November	1st to 10th	Day	35% 5% 6% 14% 27% 14%	1765
	11th to 20th	Day	31% 3 7% 16% 26% 16%	1800
	21st to end	Day	37% 6% 7% 16% 24% 10%	1800
December	1st to 10th	Day	37% 4 6% 18% 26% 8%	2930
	11th to 20th	Day	40% 4 9% 19% 21% 7%	3370
	21st to end	Day	44% 4 6% 21% 22% 3	4466
January	1st to 10th	Night	36% 5% 5% 19% 29% 6%	5889
	11th to 20th	Night	39% 4 6% 18% 24% 10%	5900
	21st to end	Night	43% 3 6% 15% 25% 8%	6012
February	1st to 10th	Night	41% 4 7% 18% 19% 11%	2400
	11th to 20th	Night	43% 5% 6% 14% 22% 11%	2339
	21st to end	Night	40% 7% 8% 15% 16% 14%	1980
March	1st to 10th	Night	47% 6% 7% 14% 17% 10%	5310
	11th to 20th	Night	33% 6% 8% 12% 22% 19%	4980
	21st to end	Night	37% 5% 7% 18% 22% 11%	5467
April	1st to 10th	Night	35% 6% 11% 16% 19% 12%	2109
	11th to 20th	Night	32% 5% 8% 21% 23% 11%	1881
	21st to end	Night	27% 6% 11% 23% 25% 9%	1834
May	1st to 10th	Night	28% 12% 15% 23% 19% 4	2840
	11th to 20th	Night	40% 8% 13% 23% 13% 3	2813
	21st to end	Night	23% 10% 17% 29% 19% 3	3087
June	1st to 10th	Night	40% 12% 17% 16% 13% 1	1710
	11th to 20th	Night	25% 11% 20% 26% 14% 3	1710
	21st to end	Night	33% 14% 18% 19% 12% 4	1710
July	1st to 10th	Night	48% 15% 22% 10% 4 1	2795
	11th to 20th	Night	38% 14% 23% 19% 6% 1	2786
	21st to end	Night	48% 14% 19% 14% 4 1	2988
August	1st to 10th	Night	36% 11% 16% 26% 11% 1	2995
	11th to 20th	Night	27% 10% 18% 29% 14% 2	3130
	21st to end	Night	29% 8% 18% 25% 18% 2	3476
September	1st to 10th	Night	38% 10% 16% 17% 14% 5%	2038
	11th to 20th	Night	38% 10% 12% 18% 17% 5%	2090
	21st to end	Night	35% 8% 9% 20% 21% 8%	2090
October	1st to 10th	Night	32% 5% 8% 14% 24% 17%	3480
	11th to 20th	Night	16% 3 4 13% 30% 33%	3518
	21st to end	Night	20% 3 4 19% 35% 20%	4120
November	1st to 10th	Night	31% 4 9% 15% 25% 15%	2528
	11th to 20th	Night	32% 3 6% 16% 27% 16%	2600
	21st to end	Night	36% 5% 8% 17% 24% 11%	2600
December	1st to 10th	Night	35% 3 6% 20% 27% 9%	4250
	11th to 20th	Night	37% 4 10% 19% 23% 7%	4824
	21st to end	Night	42% 5% 6% 20% 23% 3	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	21% 20% 38% 16% 4	300
	11th to 20th	Day	17% 25% 32% 17% 7% 2	300
	21st to end	Day	21% 23% 39% 12% 4 1	330
February	1st to 10th	Day	21% 20% 36% 17% 7%	300
	11th to 20th	Day	31% 17% 33% 15% 3	300
	21st to end	Day	17% 24% 39% 18% 2	249
March	1st to 10th	Day	22% 18% 35% 20% 5% 1	323
	11th to 20th	Day	18% 15% 35% 23% 8% 1	500
	21st to end	Day	18% 13% 36% 25% 7% 1	550
April	1st to 10th	Day	16% 17% 29% 26% 11% 1	500
	11th to 20th	Day	14% 13% 31% 24% 16% 2	452
	21st to end	Day	10% 10% 24% 35% 18% 3	460
May	1st to 10th	Day	10% 8% 26% 30% 21% 5%	463
	11th to 20th	Day	11% 2 22% 30% 25% 10%	487
	21st to end	Day	12% 3 15% 29% 28% 13%	529
June	1st to 10th	Day	11% 3 13% 31% 28% 14%	490
	11th to 20th	Day	7% 2 14% 23% 27% 27%	490
	21st to end	Day	6% 3 14% 26% 27% 23%	490
July	1st to 10th	Day	8% 2 5% 22% 35% 28%	485
	11th to 20th	Day	5% 1 5% 20% 33% 36%	484
	21st to end	Day	6% 1 6% 18% 40% 28%	532
August	1st to 10th	Day	10% 1 8% 23% 31% 27%	486
	11th to 20th	Day	8% 2 7% 19% 38% 26%	479
	21st to end	Day	13% 2 6% 27% 32% 21%	539
September	1st to 10th	Day	10% 3 11% 24% 36% 16%	490
	11th to 20th	Day	18% 3 10% 27% 31% 12%	490
	21st to end	Day	12% 2 12% 28% 33% 12%	490
October	1st to 10th	Day	14% 4 25% 31% 19% 8%	490
	11th to 20th	Day	9% 7% 20% 34% 22% 6%	490
	21st to end	Day	15% 7% 23% 28% 22% 5%	539
November	1st to 10th	Day	20% 8% 24% 28% 15% 4	303
	11th to 20th	Day	16% 11% 36% 26% 10% 2	300
	21st to end	Day	13% 15% 33% 27% 11% 1	300
December	1st to 10th	Day	21% 14% 37% 20% 6% 1	300
	11th to 20th	Day	27% 15% 32% 21% 5% 1	300
	21st to end	Day	26% 12% 28% 26% 7% 1	330
January	1st to 10th	Night	19% 14% 34% 26% 6%	800
	11th to 20th	Night	19% 11% 32% 31% 9%	800
	21st to end	Night	20% 10% 38% 28% 4	880
February	1st to 10th	Night	17% 9% 32% 35% 7%	800
	11th to 20th	Night	23% 9% 34% 29% 4	783
	21st to end	Night	17% 12% 38% 28% 5%	660
March	1st to 10th	Night	14% 13% 33% 35% 6%	800
	11th to 20th	Night	16% 9% 33% 30% 11% 1	800
	21st to end	Night	13% 12% 31% 33% 11%	880
April	1st to 10th	Night	13% 7% 31% 33% 15%	709
	11th to 20th	Night	14% 8% 25% 33% 18% 1	565
	21st to end	Night	9% 5% 25% 36% 25% 1	570
May	1st to 10th	Night	8% 5% 23% 36% 25% 3	570
	11th to 20th	Night	12% 2 20% 34% 27% 5%	561
	21st to end	Night	10% 1 11% 32% 39% 6%	617
June	1st to 10th	Night	9% 2 10% 38% 36% 6%	570
	11th to 20th	Night	4 2 9% 29% 42% 14%	570
	21st to end	Night	6% 2 6% 29% 48% 10%	570
July	1st to 10th	Night	8% 1 4 26% 45% 15%	555
	11th to 20th	Night	6% 1 2 19% 51% 20%	552
	21st to end	Night	7% 1 4 23% 50% 14%	624
August	1st to 10th	Night	7% 2 6% 25% 43% 18%	567
	11th to 20th	Night	9% 1 6% 23% 50% 11%	564
	21st to end	Night	12% 2 9% 26% 37% 14%	627
September	1st to 10th	Night	12% 3 8% 24% 42% 11%	708
	11th to 20th	Night	14% 2 13% 33% 34% 5%	760
	21st to end	Night	11% 1 14% 31% 39% 3	760
October	1st to 10th	Night	10% 3 21% 36% 26% 5%	760
	11th to 20th	Night	12% 4 21% 35% 25% 3	760
	21st to end	Night	13% 4 23% 35% 23% 2	836
November	1st to 10th	Night	13% 5% 21% 37% 21% 2	780
	11th to 20th	Night	14% 8% 29% 34% 14% 1	800
	21st to end	Night	16% 7% 29% 34% 13% 2	800
December	1st to 10th	Night	20% 9% 28% 33% 11% 1	800
	11th to 20th	Night	21% 7% 31% 31% 10% 1	800
	21st to end	Night	27% 9% 25% 31% 8%	880

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