Savannah
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Savannah clear sky chart from 2005-11-06 to 2025-11-03.

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% 7% 2 6% 4 4 4 4 6% 8% 42%	126332
	Night	14% 7% 2 6% 4 4 4 3 5% 7% 44%	123838
Transparency	Day	39% 6% 11% 22% 18% 4	130029
	Night	38% 5% 10% 22% 19% 5%	128217
Seeing	Day	16% 7% 20% 24% 22% 12%	16570
	Night	16% 6% 22% 32% 21% 3	26262

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	14% 12% 4 10% 3 3 3 2 3 4 42%	3617
	11th to 20th	Day	16% 6% 2 8% 3 3 3 3 3 4 48%	3914
	21st to end	Day	19% 8% 2 5% 3 4 4 3 5% 6% 41%	4774
February	1st to 10th	Day	21% 10% 4 7% 4 3 2 2 4 6% 38%	2000
	11th to 20th	Day	21% 10% 4 6% 4 3 3 3 4 5% 38%	1948
	21st to end	Day	21% 7% 3 7% 4 4 3 3 4 6% 37%	1650
March	1st to 10th	Day	16% 13% 3 9% 5% 5% 4 3 4 4 35%	4480
	11th to 20th	Day	13% 8% 3 7% 4 4 4 2 4 5% 47%	4698
	21st to end	Day	12% 8% 3 7% 4 4 4 3 5% 7% 43%	5967
April	1st to 10th	Day	15% 7% 2 5% 4 4 4 3 6% 5% 45%	2400
	11th to 20th	Day	15% 7% 3 6% 4 4 3 3 4 6% 46%	2374
	21st to end	Day	12% 6% 2 6% 5% 4 5% 4 6% 8% 43%	2400
May	1st to 10th	Day	18% 7% 3 7% 5% 5% 6% 5% 7% 8% 30%	5631
	11th to 20th	Day	14% 9% 3 9% 5% 5% 5% 5% 6% 8% 30%	5861
	21st to end	Day	17% 7% 3 7% 4 4 5% 4 6% 8% 36%	6433
June	1st to 10th	Day	9% 6% 2 6% 5% 5% 5% 4 8% 10% 40%	2736
	11th to 20th	Day	5% 4 2 6% 4 5% 6% 5% 7% 10% 46%	2800
	21st to end	Day	5% 3 2 6% 4 6% 5% 6% 8% 11% 44%	2800
July	1st to 10th	Day	6% 6% 2 7% 5% 5% 6% 6% 8% 11% 38%	6360
	11th to 20th	Day	7% 5% 2 6% 5% 6% 6% 6% 10% 13% 35%	6360
	21st to end	Day	11% 7% 3 7% 5% 5% 5% 5% 8% 12% 31%	6262
August	1st to 10th	Day	3 3 1 4 4 4 4 4 7% 10% 55%	3905
	11th to 20th	Day	8% 4 2 6% 4 5% 5% 4 7% 10% 47%	3849
	21st to end	Day	6% 4 2 6% 4 4 5% 3 6% 8% 53%	4312
September	1st to 10th	Day	10% 5% 2 6% 6% 4 4 4 7% 8% 45%	2400
	11th to 20th	Day	12% 6% 2 6% 4 5% 5% 4 5% 7% 45%	2246
	21st to end	Day	11% 4 2 5% 4 5% 4 3 5% 7% 50%	2200
October	1st to 10th	Day	10% 4 2 5% 3 2 3 3 4 6% 58%	2200
	11th to 20th	Day	9% 5% 2 5% 3 3 3 3 4 6% 57%	2040
	21st to end	Day	16% 6% 2 4 3 3 3 3 4 4 51%	2116
November	1st to 10th	Day	13% 6% 1 5% 2 2 2 3 4 6% 54%	1780
	11th to 20th	Day	14% 7% 2 5% 3 3 3 3 4 6% 50%	1800
	21st to end	Day	16% 9% 2 5% 3 4 3 3 5% 6% 44%	1800
December	1st to 10th	Day	17% 8% 2 6% 4 3 3 2 4 5% 46%	2930
	11th to 20th	Day	22% 9% 3 7% 4 3 3 2 3 5% 39%	3307
	21st to end	Day	17% 11% 3 7% 4 4 4 4 6% 6% 35%	3982
January	1st to 10th	Night	17% 12% 3 9% 3 3 3 3 4 5% 38%	6348
	11th to 20th	Night	16% 9% 4 8% 4 3 3 2 3 4 45%	6061
	21st to end	Night	21% 9% 2 6% 3 3 3 3 4 4 42%	6187
February	1st to 10th	Night	20% 10% 3 6% 4 4 4 3 4 4 37%	2400
	11th to 20th	Night	20% 11% 3 7% 4 3 3 2 3 5% 38%	2338
	21st to end	Night	21% 7% 3 7% 4 4 4 3 4 5% 39%	1980
March	1st to 10th	Night	19% 10% 3 7% 5% 4 4 3 4 6% 37%	5373
	11th to 20th	Night	12% 7% 2 5% 3 3 3 3 4 7% 50%	5304
	21st to end	Night	15% 7% 3 6% 4 4 4 3 4 5% 43%	4962
April	1st to 10th	Night	14% 6% 2 7% 4 3 4 4 4 7% 45%	2000
	11th to 20th	Night	15% 6% 2 4 3 3 4 3 5% 7% 49%	1975
	21st to end	Night	12% 6% 3 6% 4 4 5% 3 6% 8% 45%	2000
May	1st to 10th	Night	17% 9% 3 7% 5% 4 5% 3 5% 7% 35%	4260
	11th to 20th	Night	15% 9% 3 9% 6% 5% 5% 3 5% 7% 33%	4032
	21st to end	Night	13% 7% 3 7% 5% 5% 5% 4 6% 9% 37%	4421
June	1st to 10th	Night	9% 5% 2 5% 4 5% 5% 3 6% 11% 44%	1658
	11th to 20th	Night	3 4 1 5% 3 3 4 4 7% 11% 54%	1600
	21st to end	Night	3 4 1 4 4 4 4 4 7% 10% 55%	1600
July	1st to 10th	Night	6% 5% 2 7% 5% 5% 5% 5% 8% 12% 40%	3618
	11th to 20th	Night	5% 4 2 5% 4 5% 5% 4 8% 14% 44%	3617
	21st to end	Night	7% 6% 3 8% 5% 5% 5% 5% 8% 13% 34%	4575
August	1st to 10th	Night	3 2 1 3 3 4 4 4 6% 9% 62%	3244
	11th to 20th	Night	4 3 1 4 4 4 5% 5% 6% 11% 54%	3200
	21st to end	Night	5% 3 2 4 4 3 4 4 7% 9% 55%	3586
September	1st to 10th	Night	7% 5% 2 5% 3 5% 4 4 7% 9% 50%	2000
	11th to 20th	Night	10% 5% 2 5% 5% 4 4 4 5% 8% 49%	2132
	21st to end	Night	9% 5% 2 4 3 4 4 3 5% 5% 56%	2200
October	1st to 10th	Night	8% 4 1 4 2 3 2 3 4 6% 63%	2200
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 4 6% 56%	2355
	21st to end	Night	16% 8% 2 4 3 3 3 3 3 5% 50%	2721
November	1st to 10th	Night	12% 5% 2 5% 4 3 3 3 5% 6% 53%	2563
	11th to 20th	Night	12% 5% 2 4 3 3 4 3 6% 7% 51%	2600
	21st to end	Night	17% 6% 2 3 4 4 4 3 4 5% 48%	2600
December	1st to 10th	Night	19% 8% 2 6% 3 3 3 2 3 5% 45%	4250
	11th to 20th	Night	22% 9% 2 5% 3 3 2 2 4 4 44%	4882
	21st to end	Night	19% 10% 3 6% 4 5% 5% 4 5% 6% 33%	6996

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	48% 2 10% 22% 16% 2	3618
	11th to 20th	Day	40% 3 6% 26% 24% 1	3914
	21st to end	Day	44% 4 7% 19% 21% 4	4774
February	1st to 10th	Day	49% 3 8% 20% 17% 3	2000
	11th to 20th	Day	50% 4 6% 19% 16% 5%	1958
	21st to end	Day	48% 3 8% 15% 18% 7%	1650
March	1st to 10th	Day	52% 4 5% 14% 15% 9%	4480
	11th to 20th	Day	40% 4 6% 21% 20% 10%	4698
	21st to end	Day	41% 5% 9% 24% 20% 1	5969
April	1st to 10th	Day	39% 6% 9% 22% 20% 4	2400
	11th to 20th	Day	40% 5% 7% 21% 21% 6%	2374
	21st to end	Day	38% 7% 10% 26% 17% 2	2400
May	1st to 10th	Day	48% 9% 12% 20% 11% 1	5666
	11th to 20th	Day	49% 8% 14% 18% 9% 1	5865
	21st to end	Day	45% 7% 10% 22% 14% 2	6447
June	1st to 10th	Day	37% 9% 13% 22% 18% 2	2736
	11th to 20th	Day	31% 8% 15% 26% 18% 2	2800
	21st to end	Day	31% 10% 15% 23% 17% 3	2800
July	1st to 10th	Day	35% 9% 17% 27% 11% 1	6291
	11th to 20th	Day	35% 10% 21% 28% 5% 1	6285
	21st to end	Day	42% 10% 22% 21% 5%	6084
August	1st to 10th	Day	22% 7% 16% 33% 20% 2	3893
	11th to 20th	Day	32% 7% 16% 26% 17% 3	3885
	21st to end	Day	28% 7% 11% 26% 25% 3	4311
September	1st to 10th	Day	35% 9% 11% 24% 17% 4	2400
	11th to 20th	Day	37% 7% 10% 21% 21% 4	2246
	21st to end	Day	33% 6% 10% 22% 23% 7%	2200
October	1st to 10th	Day	20% 3 6% 15% 40% 16%	3590
	11th to 20th	Day	19% 2 5% 23% 34% 16%	3306
	21st to end	Day	28% 3 5% 24% 33% 8%	3393
November	1st to 10th	Day	33% 3 8% 20% 28% 7%	1780
	11th to 20th	Day	35% 4 9% 18% 27% 8%	1800
	21st to end	Day	41% 4 8% 21% 23% 4	1800
December	1st to 10th	Day	43% 3 4 27% 21% 2	2930
	11th to 20th	Day	50% 3 6% 21% 16% 4	3304
	21st to end	Day	49% 5% 10% 24% 11% 1	3982
January	1st to 10th	Night	51% 3 9% 17% 18% 3	6348
	11th to 20th	Night	44% 3 6% 19% 23% 5%	6061
	21st to end	Night	47% 2 6% 21% 19% 6%	6187
February	1st to 10th	Night	51% 4 9% 16% 18% 3	2400
	11th to 20th	Night	52% 3 6% 17% 17% 5%	2339
	21st to end	Night	49% 4 6% 17% 18% 6%	1980
March	1st to 10th	Night	49% 4 8% 15% 17% 7%	5373
	11th to 20th	Night	35% 4 6% 20% 18% 15%	5304
	21st to end	Night	43% 4 8% 20% 21% 3	4962
April	1st to 10th	Night	38% 5% 12% 21% 20% 4	2000
	11th to 20th	Night	36% 4 8% 21% 24% 8%	1975
	21st to end	Night	37% 5% 12% 25% 17% 3	2000
May	1st to 10th	Night	49% 6% 11% 20% 13% 2	4290
	11th to 20th	Night	49% 7% 14% 19% 10% 1	4033
	21st to end	Night	42% 9% 11% 23% 13% 1	4429
June	1st to 10th	Night	33% 8% 13% 23% 20% 2	1658
	11th to 20th	Night	23% 8% 15% 31% 21% 3	1600
	21st to end	Night	23% 9% 17% 28% 18% 4	1600
July	1st to 10th	Night	34% 10% 19% 26% 10% 1	3580
	11th to 20th	Night	27% 9% 25% 32% 5% 2	3572
	21st to end	Night	39% 10% 25% 21% 6%	4441
August	1st to 10th	Night	17% 7% 12% 38% 24% 1	3232
	11th to 20th	Night	22% 9% 22% 28% 17% 2	3230
	21st to end	Night	24% 7% 13% 25% 27% 4	3586
September	1st to 10th	Night	30% 8% 12% 25% 20% 6%	2000
	11th to 20th	Night	33% 7% 11% 20% 26% 4	2132
	21st to end	Night	29% 5% 8% 25% 24% 8%	2200
October	1st to 10th	Night	17% 3 7% 17% 38% 18%	3590
	11th to 20th	Night	20% 3 4 17% 35% 21%	3828
	21st to end	Night	27% 3 6% 26% 24% 14%	4394
November	1st to 10th	Night	33% 4 7% 21% 25% 9%	2563
	11th to 20th	Night	32% 4 8% 20% 26% 10%	2600
	21st to end	Night	38% 4 7% 21% 23% 6%	2600
December	1st to 10th	Night	44% 3 6% 22% 23% 2	4250
	11th to 20th	Night	46% 3 4 22% 22% 3	4884
	21st to end	Night	50% 4 10% 23% 10% 3	6996

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	25% 13% 36% 18% 7% 1	300
	11th to 20th	Day	27% 15% 38% 14% 3 2	300
	21st to end	Day	22% 15% 38% 20% 5%	330
February	1st to 10th	Day	25% 15% 33% 18% 7% 1	300
	11th to 20th	Day	34% 17% 30% 14% 4 1	300
	21st to end	Day	33% 13% 37% 11% 5%	249
March	1st to 10th	Day	28% 13% 31% 21% 7% 1	300
	11th to 20th	Day	22% 14% 37% 22% 5%	320
	21st to end	Day	22% 13% 33% 23% 9% 1	550
April	1st to 10th	Day	23% 14% 24% 25% 14%	500
	11th to 20th	Day	20% 12% 30% 24% 12% 2	492
	21st to end	Day	19% 9% 26% 28% 14% 4	500
May	1st to 10th	Day	19% 9% 24% 27% 15% 6%	503
	11th to 20th	Day	16% 4 24% 25% 18% 13%	527
	21st to end	Day	11% 5% 20% 27% 21% 16%	573
June	1st to 10th	Day	11% 3 15% 25% 27% 18%	666
	11th to 20th	Day	7% 2 13% 29% 29% 20%	730
	21st to end	Day	7% 2 12% 28% 33% 18%	730
July	1st to 10th	Day	8% 2 7% 27% 31% 25%	721
	11th to 20th	Day	9% 3 7% 23% 33% 25%	718
	21st to end	Day	8% 2 8% 20% 38% 25%	644
August	1st to 10th	Day	6% 3 7% 24% 38% 22%	526
	11th to 20th	Day	12% 3 6% 25% 35% 19%	519
	21st to end	Day	11% 1 6% 22% 32% 27%	583
September	1st to 10th	Day	9% 2 10% 24% 37% 18%	530
	11th to 20th	Day	13% 2 6% 22% 35% 20%	530
	21st to end	Day	13% 4 12% 28% 29% 13%	530
October	1st to 10th	Day	11% 2 14% 31% 30% 12%	530
	11th to 20th	Day	9% 7% 28% 34% 18% 5%	370
	21st to end	Day	21% 8% 29% 26% 12% 2	363
November	1st to 10th	Day	21% 7% 23% 26% 19% 4	306
	11th to 20th	Day	15% 9% 34% 28% 13% 2	300
	21st to end	Day	22% 10% 30% 18% 17% 3	300
December	1st to 10th	Day	27% 13% 29% 25% 5% 1	300
	11th to 20th	Day	24% 11% 31% 22% 11% 1	300
	21st to end	Day	24% 12% 34% 23% 6%	330
January	1st to 10th	Night	23% 12% 31% 29% 6%	1000
	11th to 20th	Night	24% 12% 32% 26% 5%	1000
	21st to end	Night	22% 8% 37% 30% 3	966
February	1st to 10th	Night	23% 11% 33% 28% 5%	800
	11th to 20th	Night	27% 15% 29% 26% 3	783
	21st to end	Night	25% 13% 34% 26% 2	660
March	1st to 10th	Night	22% 10% 33% 32% 4	800
	11th to 20th	Night	21% 9% 33% 31% 6% 1	762
	21st to end	Night	18% 7% 34% 30% 10%	660
April	1st to 10th	Night	16% 8% 35% 30% 11%	600
	11th to 20th	Night	18% 5% 32% 31% 13% 1	593
	21st to end	Night	15% 6% 29% 35% 15% 1	600
May	1st to 10th	Night	17% 5% 24% 36% 17% 2	600
	11th to 20th	Night	12% 5% 23% 34% 23% 4	591
	21st to end	Night	9% 3 14% 39% 29% 7%	650
June	1st to 10th	Night	10% 3 9% 41% 31% 7%	600
	11th to 20th	Night	4 1 10% 39% 42% 5%	600
	21st to end	Night	4 1 8% 33% 45% 10%	600
July	1st to 10th	Night	9% 2 6% 26% 47% 11%	585
	11th to 20th	Night	7% 1 6% 27% 45% 14%	582
	21st to end	Night	6% 2 5% 29% 46% 12%	657
August	1st to 10th	Night	4 1 3 28% 53% 10%	597
	11th to 20th	Night	6% 2 4 36% 44% 7%	594
	21st to end	Night	9% 1 4 27% 49% 10%	660
September	1st to 10th	Night	8% 3 6% 35% 42% 7%	600
	11th to 20th	Night	11% 3 8% 31% 40% 8%	732
	21st to end	Night	11% 3 11% 33% 37% 5%	800
October	1st to 10th	Night	10% 3 12% 35% 35% 5%	800
	11th to 20th	Night	15% 3 20% 38% 23% 2	800
	21st to end	Night	19% 5% 22% 35% 17% 2	880
November	1st to 10th	Night	13% 6% 19% 42% 18% 2	789
	11th to 20th	Night	15% 7% 28% 37% 13% 1	800
	21st to end	Night	20% 9% 25% 33% 13% 1	800
December	1st to 10th	Night	25% 8% 29% 31% 7% 1	800
	11th to 20th	Night	22% 7% 28% 35% 8%	821
	21st to end	Night	27% 9% 28% 30% 6%	1100

Page generated at 2025-10-31 01:02:38. Version ac07

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