Augusta
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Augusta clear sky chart from 2005-11-06 to 2025-08-05.

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	18% 8% 3 7% 4 4 4 3 5% 7% 37%	124973
	Night	18% 9% 3 7% 4 4 4 3 5% 6% 36%	123089
Transparency	Day	45% 7% 12% 21% 13% 2	128480
	Night	46% 6% 12% 21% 13% 2	127670
Seeing	Day	24% 17% 31% 19% 7% 2	16268
	Night	23% 13% 32% 24% 7%	24884

By Month

Percentage Cloud Cover NE (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% 8% 3 9% 5% 5% 5% 4 5% 6% 36%	3597
	11th to 20th	Day	14% 8% 3 7% 4 4 4 3 5% 5% 44%	3570
	21st to end	Day	11% 11% 3 7% 4 3 4 3 4 5% 44%	3960
February	1st to 10th	Day	16% 11% 3 6% 4 5% 4 3 5% 6% 36%	1774
	11th to 20th	Day	12% 10% 4 9% 5% 4 5% 4 5% 6% 36%	1923
	21st to end	Day	15% 11% 3 7% 4 5% 4 4 5% 4 36%	1650
March	1st to 10th	Day	23% 11% 3 8% 5% 4 4 3 4 4 31%	4476
	11th to 20th	Day	18% 11% 3 7% 5% 4 4 3 4 5% 36%	4924
	21st to end	Day	27% 8% 3 6% 4 3 3 3 5% 6% 32%	5556
April	1st to 10th	Day	20% 11% 3 7% 4 3 4 3 4 6% 35%	2400
	11th to 20th	Day	19% 7% 2 5% 5% 4 4 3 6% 6% 38%	2497
	21st to end	Day	23% 8% 3 7% 4 4 4 3 5% 5% 35%	2600
May	1st to 10th	Day	32% 11% 3 6% 4 4 4 3 4 5% 23%	5886
	11th to 20th	Day	19% 9% 3 8% 5% 5% 5% 4 5% 7% 31%	5942
	21st to end	Day	19% 7% 2 7% 4 5% 5% 4 7% 8% 33%	6949
June	1st to 10th	Day	23% 8% 3 5% 4 4 4 4 5% 8% 31%	2895
	11th to 20th	Day	18% 6% 2 6% 4 4 4 4 5% 8% 38%	3000
	21st to end	Day	23% 7% 2 6% 5% 5% 5% 4 6% 8% 31%	2878
July	1st to 10th	Day	16% 7% 2 7% 4 5% 6% 4 7% 9% 31%	6360
	11th to 20th	Day	14% 7% 2 6% 4 4 5% 5% 7% 9% 38%	6360
	21st to end	Day	15% 6% 2 5% 4 4 4 4 6% 8% 42%	6926
August	1st to 10th	Day	16% 6% 3 7% 5% 5% 5% 4 6% 8% 36%	4167
	11th to 20th	Day	16% 10% 3 8% 4 5% 5% 3 6% 7% 34%	4045
	21st to end	Day	10% 4 2 6% 4 4 4 4 6% 9% 46%	4387
September	1st to 10th	Day	12% 5% 2 5% 4 5% 4 3 6% 7% 48%	2223
	11th to 20th	Day	13% 5% 1 5% 2 3 3 3 5% 5% 54%	2090
	21st to end	Day	18% 5% 2 5% 4 3 3 3 5% 9% 44%	2090
October	1st to 10th	Day	18% 7% 2 6% 5% 4 4 3 4 6% 39%	2082
	11th to 20th	Day	19% 6% 2 6% 4 4 3 4 4 6% 41%	1834
	21st to end	Day	22% 8% 2 6% 4 4 4 3 4 6% 37%	1881
November	1st to 10th	Day	17% 6% 2 6% 3 3 5% 3 5% 6% 44%	1761
	11th to 20th	Day	19% 6% 1 5% 4 3 4 4 5% 7% 43%	1800
	21st to end	Day	22% 8% 2 5% 3 2 3 2 4 6% 42%	1699
December	1st to 10th	Day	16% 11% 2 5% 3 4 4 4 6% 8% 37%	2328
	11th to 20th	Day	20% 8% 2 4 3 3 3 3 4 5% 45%	2618
	21st to end	Day	21% 11% 3 6% 4 4 4 3 5% 5% 34%	3845
January	1st to 10th	Night	12% 9% 3 8% 5% 5% 4 3 5% 6% 40%	6349
	11th to 20th	Night	13% 11% 4 10% 5% 5% 5% 4 5% 6% 32%	6315
	21st to end	Night	13% 10% 3 7% 4 4 5% 4 5% 6% 40%	6996
February	1st to 10th	Night	16% 9% 3 8% 5% 5% 5% 4 5% 6% 34%	2625
	11th to 20th	Night	12% 10% 3 6% 6% 5% 4 4 5% 6% 39%	2361
	21st to end	Night	15% 9% 3 7% 5% 5% 4 3 5% 6% 39%	1980
March	1st to 10th	Night	27% 10% 2 8% 5% 4 4 3 3 5% 29%	5364
	11th to 20th	Night	16% 11% 3 7% 5% 4 5% 4 6% 6% 33%	5035
	21st to end	Night	24% 10% 2 6% 4 4 4 4 6% 6% 30%	5361
April	1st to 10th	Night	21% 12% 3 5% 4 4 3 3 4 6% 34%	2000
	11th to 20th	Night	20% 7% 2 7% 5% 4 4 4 5% 6% 36%	1852
	21st to end	Night	23% 8% 3 6% 5% 3 4 3 5% 5% 35%	1800
May	1st to 10th	Night	31% 10% 3 6% 4 4 4 3 5% 6% 24%	4054
	11th to 20th	Night	21% 9% 3 7% 4 5% 5% 4 6% 7% 29%	3994
	21st to end	Night	17% 8% 3 7% 5% 5% 5% 4 6% 8% 33%	3926
June	1st to 10th	Night	22% 7% 2 7% 5% 4 4 4 6% 6% 32%	1495
	11th to 20th	Night	16% 7% 2 6% 4 4 5% 4 5% 9% 38%	1400
	21st to end	Night	23% 9% 2 6% 4 2 4 4 7% 8% 31%	1512
July	1st to 10th	Night	13% 8% 3 6% 5% 5% 5% 5% 7% 9% 35%	3600
	11th to 20th	Night	16% 9% 2 7% 5% 5% 5% 4 6% 8% 36%	3600
	21st to end	Night	11% 5% 1 5% 4 4 5% 4 7% 9% 45%	3926
August	1st to 10th	Night	20% 7% 3 7% 5% 5% 5% 4 5% 6% 32%	2820
	11th to 20th	Night	16% 10% 3 7% 5% 4 5% 4 6% 9% 34%	2782
	21st to end	Night	10% 6% 2 6% 4 4 5% 4 6% 7% 45%	3252
September	1st to 10th	Night	13% 5% 2 5% 4 4 4 3 4 7% 49%	1956
	11th to 20th	Night	15% 6% 2 5% 2 2 3 3 4 6% 52%	2090
	21st to end	Night	16% 6% 2 5% 4 4 4 3 4 7% 45%	2090
October	1st to 10th	Night	18% 7% 3 5% 5% 3 4 4 5% 6% 40%	2097
	11th to 20th	Night	17% 6% 2 6% 4 5% 4 4 4 6% 42%	2343
	21st to end	Night	25% 8% 2 5% 3 4 4 3 4 6% 37%	2717
November	1st to 10th	Night	17% 6% 2 6% 3 4 4 3 5% 6% 44%	2537
	11th to 20th	Night	18% 6% 2 6% 4 4 4 3 4 6% 43%	2600
	21st to end	Night	18% 8% 2 5% 5% 4 4 4 5% 6% 40%	2696
December	1st to 10th	Night	17% 10% 2 6% 5% 4 4 3 6% 8% 35%	4862
	11th to 20th	Night	24% 7% 2 5% 4 3 4 2 4 5% 39%	5591
	21st to end	Night	22% 10% 3 6% 4 3 3 3 5% 5% 36%	7111

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	46% 6% 10% 26% 11%	3598
	11th to 20th	Day	41% 6% 12% 27% 11% 3	3600
	21st to end	Day	42% 5% 10% 19% 18% 6%	3960
February	1st to 10th	Day	47% 6% 10% 20% 14% 3	1774
	11th to 20th	Day	47% 6% 12% 20% 12% 3	1932
	21st to end	Day	48% 6% 11% 18% 12% 5%	1650
March	1st to 10th	Day	57% 5% 8% 10% 14% 7%	4479
	11th to 20th	Day	48% 7% 13% 19% 11% 2	4924
	21st to end	Day	52% 5% 6% 17% 16% 4	5556
April	1st to 10th	Day	51% 5% 8% 16% 15% 4	2400
	11th to 20th	Day	44% 7% 10% 22% 14% 3	2497
	21st to end	Day	51% 6% 8% 18% 13% 4	2600
May	1st to 10th	Day	61% 9% 9% 14% 6% 1	5897
	11th to 20th	Day	50% 9% 14% 17% 7% 3	5946
	21st to end	Day	44% 9% 13% 20% 11% 1	6949
June	1st to 10th	Day	49% 8% 13% 20% 10%	2895
	11th to 20th	Day	43% 8% 12% 20% 15% 3	3000
	21st to end	Day	51% 8% 11% 18% 10% 1	2878
July	1st to 10th	Day	47% 8% 14% 22% 9%	6290
	11th to 20th	Day	40% 8% 15% 22% 13% 1	6285
	21st to end	Day	38% 7% 13% 25% 16% 1	6728
August	1st to 10th	Day	45% 8% 14% 24% 8%	4153
	11th to 20th	Day	48% 7% 16% 22% 7%	4084
	21st to end	Day	32% 8% 14% 26% 18% 1	4387
September	1st to 10th	Day	34% 7% 14% 26% 19% 1	2223
	11th to 20th	Day	32% 5% 10% 30% 21% 2	2090
	21st to end	Day	37% 7% 12% 27% 16% 1	2090
October	1st to 10th	Day	48% 7% 11% 21% 12% 1	3459
	11th to 20th	Day	35% 4 11% 29% 20% 1	3024
	21st to end	Day	36% 4 13% 24% 19% 3	3081
November	1st to 10th	Day	41% 6% 14% 22% 16% 2	1761
	11th to 20th	Day	40% 6% 10% 21% 19% 4	1800
	21st to end	Day	43% 5% 16% 24% 11% 1	1699
December	1st to 10th	Day	44% 6% 16% 23% 12% 1	2328
	11th to 20th	Day	41% 5% 12% 19% 16% 8%	2618
	21st to end	Day	52% 4 9% 17% 14% 3	3845
January	1st to 10th	Night	44% 5% 11% 28% 11% 1	6349
	11th to 20th	Night	50% 7% 14% 19% 9% 2	6360
	21st to end	Night	45% 6% 8% 20% 16% 5%	6996
February	1st to 10th	Night	49% 6% 13% 16% 13% 3	2625
	11th to 20th	Night	46% 5% 11% 20% 15% 3	2363
	21st to end	Night	45% 6% 9% 21% 14% 4	1980
March	1st to 10th	Night	57% 4 7% 13% 13% 6%	5374
	11th to 20th	Night	47% 8% 18% 18% 7% 2	5036
	21st to end	Night	52% 6% 7% 15% 18% 3	5361
April	1st to 10th	Night	51% 5% 9% 17% 15% 4	2000
	11th to 20th	Night	46% 6% 11% 20% 15% 1	1852
	21st to end	Night	50% 6% 12% 16% 13% 3	1800
May	1st to 10th	Night	59% 7% 12% 14% 7% 1	4060
	11th to 20th	Night	50% 10% 12% 18% 7% 1	3995
	21st to end	Night	46% 9% 15% 19% 9% 1	3927
June	1st to 10th	Night	51% 7% 12% 20% 9% 1	1495
	11th to 20th	Night	42% 8% 16% 20% 13% 2	1400
	21st to end	Night	48% 10% 14% 17% 9% 2	1512
July	1st to 10th	Night	44% 8% 16% 23% 10%	3560
	11th to 20th	Night	47% 7% 13% 23% 10%	3552
	21st to end	Night	33% 8% 17% 30% 11% 1	3809
August	1st to 10th	Night	52% 8% 14% 19% 7%	2810
	11th to 20th	Night	46% 9% 16% 20% 10%	2809
	21st to end	Night	34% 9% 15% 25% 16% 2	3252
September	1st to 10th	Night	35% 6% 14% 28% 16%	1956
	11th to 20th	Night	34% 5% 12% 29% 18% 2	2090
	21st to end	Night	38% 6% 11% 29% 14% 2	2090
October	1st to 10th	Night	43% 8% 14% 21% 14% 1	3500
	11th to 20th	Night	35% 5% 10% 28% 21% 1	3892
	21st to end	Night	38% 4 12% 27% 17% 2	4467
November	1st to 10th	Night	41% 6% 12% 26% 14% 1	2537
	11th to 20th	Night	42% 5% 11% 23% 17% 3	2600
	21st to end	Night	44% 7% 14% 21% 13% 1	2696
December	1st to 10th	Night	46% 5% 10% 28% 10% 1	4862
	11th to 20th	Night	47% 5% 9% 18% 18% 2	5592
	21st to end	Night	49% 5% 10% 18% 16% 1	7111

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	32% 19% 29% 17% 4	200
	11th to 20th	Day	29% 23% 28% 17% 3 2	200
	21st to end	Day	21% 26% 35% 16% 2	220
February	1st to 10th	Day	29% 21% 28% 20% 2	374
	11th to 20th	Day	27% 26% 33% 12% 1	483
	21st to end	Day	25% 22% 33% 16% 3	414
March	1st to 10th	Day	28% 23% 33% 13% 3	500
	11th to 20th	Day	25% 28% 30% 13% 3 1	500
	21st to end	Day	29% 26% 26% 12% 6% 2	550
April	1st to 10th	Day	34% 21% 29% 10% 5% 1	500
	11th to 20th	Day	30% 26% 26% 13% 4 2	492
	21st to end	Day	30% 22% 31% 13% 4 1	500
May	1st to 10th	Day	35% 17% 29% 15% 4 1	503
	11th to 20th	Day	22% 20% 35% 16% 6% 2	527
	21st to end	Day	22% 18% 37% 18% 6%	573
June	1st to 10th	Day	22% 14% 35% 18% 9% 1	625
	11th to 20th	Day	21% 16% 30% 20% 11% 2	730
	21st to end	Day	24% 13% 32% 22% 8% 2	608
July	1st to 10th	Day	17% 13% 38% 22% 8% 2	525
	11th to 20th	Day	15% 10% 39% 23% 9% 3	524
	21st to end	Day	16% 10% 38% 24% 10% 3	576
August	1st to 10th	Day	13% 8% 33% 31% 12% 2	502
	11th to 20th	Day	18% 10% 29% 26% 13% 4	479
	21st to end	Day	13% 13% 32% 26% 13% 4	539
September	1st to 10th	Day	16% 10% 32% 26% 13% 3	490
	11th to 20th	Day	18% 12% 29% 19% 14% 8%	490
	21st to end	Day	19% 15% 29% 22% 11% 5%	490
October	1st to 10th	Day	21% 15% 26% 22% 12% 3	485
	11th to 20th	Day	25% 13% 33% 17% 11% 2	390
	21st to end	Day	33% 13% 29% 19% 6% 1	429
November	1st to 10th	Day	26% 15% 30% 20% 8% 2	395
	11th to 20th	Day	32% 16% 30% 18% 4 1	400
	21st to end	Day	31% 19% 26% 17% 7% 1	400
December	1st to 10th	Day	25% 19% 36% 15% 5%	235
	11th to 20th	Day	37% 24% 29% 10% 2	200
	21st to end	Day	34% 19% 28% 13% 6%	220
January	1st to 10th	Night	23% 16% 37% 21% 2	800
	11th to 20th	Night	27% 17% 33% 19% 4	800
	21st to end	Night	19% 18% 39% 21% 3	880
February	1st to 10th	Night	22% 19% 34% 22% 3	800
	11th to 20th	Night	21% 21% 39% 17% 2	783
	21st to end	Night	22% 16% 37% 22% 3	660
March	1st to 10th	Night	27% 16% 37% 18% 2	800
	11th to 20th	Night	22% 18% 34% 19% 6%	800
	21st to end	Night	25% 18% 33% 21% 3	880
April	1st to 10th	Night	29% 18% 32% 18% 4	800
	11th to 20th	Night	24% 16% 34% 22% 4	668
	21st to end	Night	28% 15% 33% 20% 3	600
May	1st to 10th	Night	25% 12% 33% 25% 5%	600
	11th to 20th	Night	23% 12% 35% 24% 5%	579
	21st to end	Night	22% 9% 31% 31% 6%	433
June	1st to 10th	Night	23% 10% 31% 29% 7%	400
	11th to 20th	Night	18% 6% 31% 34% 11%	400
	21st to end	Night	25% 6% 31% 33% 6%	400
July	1st to 10th	Night	19% 5% 28% 37% 12%	390
	11th to 20th	Night	18% 5% 28% 36% 13% 1	388
	21st to end	Night	15% 5% 25% 43% 12% 1	438
August	1st to 10th	Night	17% 4 28% 39% 12%	551
	11th to 20th	Night	15% 6% 29% 36% 14% 1	562
	21st to end	Night	15% 8% 26% 36% 15% 1	703
September	1st to 10th	Night	14% 6% 33% 32% 14% 1	760
	11th to 20th	Night	18% 8% 27% 25% 18% 3	760
	21st to end	Night	19% 9% 29% 27% 14% 1	760
October	1st to 10th	Night	22% 9% 25% 29% 14% 1	760
	11th to 20th	Night	21% 12% 31% 26% 9% 1	760
	21st to end	Night	30% 13% 30% 21% 6%	836
November	1st to 10th	Night	23% 12% 32% 26% 6% 1	780
	11th to 20th	Night	23% 13% 35% 21% 7% 1	800
	21st to end	Night	25% 19% 30% 22% 4	848
December	1st to 10th	Night	27% 13% 36% 18% 5%	900
	11th to 20th	Night	26% 19% 33% 19% 3	900
	21st to end	Night	28% 17% 33% 20% 3	905

Page generated at 2025-08-02 01:32:26. Version ac07

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