Suwannee Skies Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Suwannee Skies Observatory clear sky chart from 2005-11-06 to 2026-07-31.

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	9% 5% 2 6% 5% 5% 6% 5% 7% 10% 40%	138214
	Night	9% 6% 2 6% 4 4 5% 4 6% 9% 44%	134791
Transparency	Day	35% 9% 16% 18% 15% 6%	141987
	Night	35% 8% 15% 19% 16% 8%	139090
Seeing	Day	10% 7% 22% 26% 22% 13%	17590
	Night	11% 6% 21% 32% 24% 6%	27587

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	10% 6% 2 5% 3 2 4 3 5% 8% 53%	5258
	11th to 20th	Day	18% 9% 3 7% 4 3 4 3 5% 6% 37%	5280
	21st to end	Day	8% 5% 2 6% 4 3 4 3 7% 9% 48%	6232
February	1st to 10th	Day	15% 6% 2 5% 4 4 3 3 5% 7% 46%	2100
	11th to 20th	Day	14% 5% 2 5% 4 3 3 3 5% 5% 51%	2048
	21st to end	Day	12% 6% 2 5% 4 4 4 3 5% 6% 50%	1730
March	1st to 10th	Day	15% 6% 2 5% 3 3 4 4 6% 9% 41%	5014
	11th to 20th	Day	8% 4 1 4 3 3 3 3 6% 8% 56%	5090
	21st to end	Day	11% 4 2 5% 3 4 4 4 5% 8% 50%	5586
April	1st to 10th	Day	8% 5% 2 5% 4 5% 4 3 6% 9% 49%	2310
	11th to 20th	Day	10% 5% 2 6% 4 3 4 4 5% 7% 49%	2286
	21st to end	Day	5% 3 1 5% 4 4 4 5% 7% 8% 54%	2662
May	1st to 10th	Day	7% 5% 2 6% 5% 5% 6% 5% 7% 11% 43%	7616
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 6% 9% 45%	7626
	21st to end	Day	4 4 2 5% 5% 6% 6% 6% 9% 13% 42%	8391
June	1st to 10th	Day	9% 6% 3 7% 6% 7% 7% 6% 8% 11% 29%	2730
	11th to 20th	Day	5% 5% 3 7% 7% 7% 8% 7% 10% 12% 29%	2730
	21st to end	Day	7% 5% 2 7% 7% 7% 8% 7% 9% 11% 30%	2730
July	1st to 10th	Day	5% 6% 3 10% 7% 8% 9% 9% 11% 14% 18%	6030
	11th to 20th	Day	4 3 2 7% 6% 7% 9% 7% 12% 15% 27%	6030
	21st to end	Day	4 5% 2 7% 7% 7% 9% 8% 10% 15% 26%	6554
August	1st to 10th	Day	11% 4 2 7% 6% 7% 7% 6% 10% 13% 27%	4211
	11th to 20th	Day	6% 5% 2 8% 6% 7% 7% 6% 10% 12% 31%	3849
	21st to end	Day	9% 6% 3 9% 7% 7% 8% 6% 8% 10% 27%	4066
September	1st to 10th	Day	10% 8% 3 10% 8% 8% 8% 6% 8% 9% 22%	2200
	11th to 20th	Day	9% 7% 3 10% 7% 7% 7% 5% 7% 9% 28%	2200
	21st to end	Day	9% 6% 3 9% 5% 5% 5% 5% 7% 7% 38%	2200
October	1st to 10th	Day	13% 6% 2 7% 5% 5% 6% 4 7% 8% 38%	2200
	11th to 20th	Day	5% 4 2 5% 4 3 3 4 5% 8% 58%	2065
	21st to end	Day	7% 4 2 6% 4 5% 5% 3 6% 7% 51%	2200
November	1st to 10th	Day	8% 5% 2 5% 4 4 5% 3 6% 8% 51%	2057
	11th to 20th	Day	9% 6% 2 5% 4 4 5% 3 5% 7% 51%	1995
	21st to end	Day	10% 6% 2 5% 4 4 4 3 5% 8% 49%	1890
December	1st to 10th	Day	6% 4 1 5% 4 4 5% 3 5% 6% 56%	3020
	11th to 20th	Day	10% 6% 2 6% 4 4 4 3 6% 8% 48%	3463
	21st to end	Day	15% 8% 3 6% 4 4 4 3 5% 6% 42%	4565
January	1st to 10th	Night	9% 7% 3 4 3 3 3 3 4 8% 55%	7635
	11th to 20th	Night	16% 8% 3 7% 5% 4 5% 4 6% 7% 36%	7680
	21st to end	Night	15% 7% 3 6% 4 3 4 4 5% 7% 42%	7945
February	1st to 10th	Night	12% 6% 2 7% 5% 3 3 4 5% 6% 48%	2520
	11th to 20th	Night	12% 8% 2 5% 4 3 4 3 5% 6% 48%	2458
	21st to end	Night	11% 7% 2 6% 3 3 3 3 5% 6% 50%	2076
March	1st to 10th	Night	15% 8% 3 7% 4 4 4 4 4 6% 42%	5057
	11th to 20th	Night	7% 6% 2 4 3 4 3 3 5% 9% 55%	5090
	21st to end	Night	10% 5% 2 5% 4 3 4 3 6% 7% 50%	5588
April	1st to 10th	Night	10% 6% 3 5% 5% 3 4 3 5% 7% 49%	2310
	11th to 20th	Night	7% 5% 2 5% 4 3 4 4 6% 7% 53%	2283
	21st to end	Night	5% 3 2 4 3 4 4 3 6% 8% 57%	1970
May	1st to 10th	Night	7% 5% 2 6% 5% 5% 4 4 6% 9% 47%	5237
	11th to 20th	Night	9% 6% 3 6% 4 4 4 3 6% 9% 47%	5234
	21st to end	Night	3 3 2 5% 4 4 5% 4 7% 12% 52%	5761
June	1st to 10th	Night	9% 6% 2 7% 6% 6% 5% 5% 7% 11% 37%	1890
	11th to 20th	Night	4 5% 2 6% 5% 5% 6% 5% 10% 15% 37%	1890
	21st to end	Night	6% 5% 3 5% 5% 5% 6% 5% 9% 13% 39%	1890
July	1st to 10th	Night	5% 6% 3 9% 8% 7% 8% 7% 11% 14% 21%	4148
	11th to 20th	Night	3 3 2 6% 5% 5% 6% 6% 10% 15% 40%	4147
	21st to end	Night	4 5% 3 8% 6% 6% 8% 7% 10% 14% 29%	4517
August	1st to 10th	Night	8% 5% 2 7% 6% 6% 7% 6% 10% 13% 31%	2932
	11th to 20th	Night	3 3 1 5% 4 4 5% 5% 9% 16% 45%	3200
	21st to end	Night	7% 7% 3 9% 7% 6% 6% 6% 9% 12% 28%	3784
September	1st to 10th	Night	8% 7% 3 10% 7% 6% 6% 6% 8% 11% 28%	2200
	11th to 20th	Night	11% 7% 4 8% 5% 6% 7% 5% 8% 10% 31%	2200
	21st to end	Night	10% 6% 3 6% 5% 4 5% 4 7% 9% 42%	2200
October	1st to 10th	Night	11% 7% 3 7% 4 5% 5% 3 6% 7% 43%	2200
	11th to 20th	Night	7% 4 2 5% 4 3 4 3 5% 6% 58%	2333
	21st to end	Night	7% 4 2 5% 5% 3 4 3 6% 7% 53%	2640
November	1st to 10th	Night	8% 4 2 5% 4 4 4 4 6% 8% 51%	2461
	11th to 20th	Night	9% 5% 2 6% 3 3 4 3 5% 6% 53%	2620
	21st to end	Night	9% 7% 3 5% 4 3 5% 3 5% 6% 49%	2730
December	1st to 10th	Night	10% 5% 2 5% 3 3 4 3 5% 6% 53%	4380
	11th to 20th	Night	12% 8% 2 6% 3 3 3 3 5% 6% 48%	4952
	21st to end	Night	14% 8% 3 6% 4 4 4 3 5% 6% 41%	6633

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	31% 4 11% 16% 26% 12%	5259
	11th to 20th	Day	47% 4 5% 12% 17% 14%	5280
	21st to end	Day	31% 5% 13% 21% 18% 13%	6232
February	1st to 10th	Day	39% 4 9% 14% 21% 13%	2100
	11th to 20th	Day	35% 4 8% 18% 23% 11%	2058
	21st to end	Day	34% 5% 9% 17% 22% 13%	1730
March	1st to 10th	Day	38% 6% 11% 16% 20% 10%	5014
	11th to 20th	Day	26% 6% 11% 17% 23% 17%	5090
	21st to end	Day	30% 6% 10% 25% 20% 10%	5586
April	1st to 10th	Day	31% 6% 15% 19% 18% 11%	2310
	11th to 20th	Day	33% 5% 9% 20% 23% 10%	2286
	21st to end	Day	25% 7% 14% 25% 22% 9%	2662
May	1st to 10th	Day	33% 9% 18% 23% 14% 4	7651
	11th to 20th	Day	32% 7% 16% 28% 14% 2	7630
	21st to end	Day	28% 12% 22% 24% 13% 1	8405
June	1st to 10th	Day	43% 12% 19% 18% 8% 1	2730
	11th to 20th	Day	40% 15% 22% 18% 5%	2730
	21st to end	Day	41% 15% 21% 16% 6% 1	2730
July	1st to 10th	Day	46% 18% 28% 7%	5965
	11th to 20th	Day	37% 17% 35% 11% 1	5961
	21st to end	Day	39% 16% 26% 18% 1	6370
August	1st to 10th	Day	42% 13% 26% 15% 4	4198
	11th to 20th	Day	37% 15% 25% 15% 7%	3885
	21st to end	Day	45% 12% 22% 17% 3	4066
September	1st to 10th	Day	53% 13% 16% 11% 6% 1	2200
	11th to 20th	Day	49% 11% 17% 14% 8% 1	2200
	21st to end	Day	40% 8% 13% 19% 14% 5%	2200
October	1st to 10th	Day	50% 8% 9% 14% 13% 7%	3590
	11th to 20th	Day	17% 4 5% 17% 39% 17%	3344
	21st to end	Day	21% 5% 7% 22% 34% 11%	3538
November	1st to 10th	Day	29% 5% 12% 19% 20% 15%	2057
	11th to 20th	Day	32% 5% 8% 18% 25% 12%	1995
	21st to end	Day	34% 4 9% 22% 22% 8%	1890
December	1st to 10th	Day	29% 5% 12% 19% 25% 12%	3020
	11th to 20th	Day	34% 6% 10% 21% 21% 8%	3460
	21st to end	Day	42% 5% 7% 18% 22% 5%	4565
January	1st to 10th	Night	29% 4 10% 18% 27% 12%	7636
	11th to 20th	Night	47% 4 6% 15% 17% 11%	7680
	21st to end	Night	40% 5% 10% 17% 17% 10%	7945
February	1st to 10th	Night	37% 5% 8% 16% 21% 13%	2520
	11th to 20th	Night	37% 5% 9% 19% 19% 11%	2459
	21st to end	Night	35% 5% 11% 17% 21% 11%	2076
March	1st to 10th	Night	42% 6% 9% 16% 17% 10%	5057
	11th to 20th	Night	26% 5% 11% 18% 21% 17%	5090
	21st to end	Night	32% 6% 10% 22% 20% 11%	5588
April	1st to 10th	Night	35% 5% 13% 18% 18% 10%	2310
	11th to 20th	Night	28% 7% 9% 23% 23% 10%	2283
	21st to end	Night	23% 6% 13% 29% 21% 8%	1970
May	1st to 10th	Night	31% 9% 18% 26% 12% 4	5264
	11th to 20th	Night	33% 8% 17% 25% 15% 3	5235
	21st to end	Night	24% 10% 23% 28% 14% 1	5771
June	1st to 10th	Night	38% 9% 21% 24% 7%	1890
	11th to 20th	Night	30% 15% 29% 21% 5%	1890
	21st to end	Night	34% 12% 26% 21% 6% 1	1890
July	1st to 10th	Night	47% 18% 28% 6% 1	4105
	11th to 20th	Night	30% 14% 42% 13% 1	4096
	21st to end	Night	39% 14% 29% 17% 1	4387
August	1st to 10th	Night	39% 13% 32% 12% 3	2921
	11th to 20th	Night	24% 13% 34% 23% 6%	3230
	21st to end	Night	44% 14% 24% 14% 3	3784
September	1st to 10th	Night	45% 14% 21% 13% 6% 1	2200
	11th to 20th	Night	44% 13% 20% 16% 7% 1	2200
	21st to end	Night	36% 10% 17% 19% 14% 4	2200
October	1st to 10th	Night	51% 9% 10% 12% 11% 7%	3590
	11th to 20th	Night	20% 4 7% 20% 33% 16%	3793
	21st to end	Night	21% 5% 8% 21% 34% 11%	4252
November	1st to 10th	Night	30% 5% 11% 21% 19% 14%	2461
	11th to 20th	Night	32% 4 8% 19% 23% 14%	2620
	21st to end	Night	35% 5% 11% 19% 20% 11%	2730
December	1st to 10th	Night	32% 4 10% 19% 19% 16%	4380
	11th to 20th	Night	37% 5% 10% 19% 19% 10%	4954
	21st to end	Night	41% 5% 9% 19% 19% 6%	6633

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	12% 15% 50% 18% 5% 1	330
	11th to 20th	Day	12% 20% 40% 18% 8% 1	330
	21st to end	Day	18% 20% 42% 15% 4	363
February	1st to 10th	Day	15% 14% 38% 24% 8% 2	330
	11th to 20th	Day	19% 16% 37% 21% 6% 1	330
	21st to end	Day	14% 15% 45% 18% 7% 1	273
March	1st to 10th	Day	11% 17% 31% 27% 13% 1	522
	11th to 20th	Day	14% 14% 33% 25% 12% 2	540
	21st to end	Day	10% 13% 33% 28% 14% 2	594
April	1st to 10th	Day	12% 13% 31% 26% 17% 1	540
	11th to 20th	Day	12% 10% 28% 29% 19% 2	532
	21st to end	Day	6% 5% 26% 35% 20% 7%	540
May	1st to 10th	Day	7% 9% 24% 31% 19% 10%	543
	11th to 20th	Day	7% 5% 18% 34% 23% 13%	567
	21st to end	Day	8% 3 12% 28% 31% 18%	617
June	1st to 10th	Day	11% 2 13% 27% 29% 18%	570
	11th to 20th	Day	6% 4 14% 23% 30% 23%	570
	21st to end	Day	6% 2 6% 26% 31% 29%	570
July	1st to 10th	Day	6% 2 7% 17% 31% 37%	565
	11th to 20th	Day	6% 1 3 17% 34% 39%	564
	21st to end	Day	6% 3 6% 20% 37% 28%	616
August	1st to 10th	Day	12% 2 6% 18% 32% 30%	526
	11th to 20th	Day	10% 2 3 15% 35% 36%	519
	21st to end	Day	10% 3 5% 23% 34% 26%	583
September	1st to 10th	Day	11% 3 9% 24% 28% 24%	530
	11th to 20th	Day	11% 4 10% 31% 28% 17%	530
	21st to end	Day	10% 3 10% 27% 32% 17%	530
October	1st to 10th	Day	13% 5% 25% 31% 19% 7%	530
	11th to 20th	Day	6% 5% 22% 33% 28% 6%	530
	21st to end	Day	9% 6% 25% 38% 18% 5%	583
November	1st to 10th	Day	12% 5% 23% 36% 20% 4	535
	11th to 20th	Day	13% 8% 31% 30% 15% 3	435
	21st to end	Day	10% 10% 41% 28% 12% 1	330
December	1st to 10th	Day	11% 15% 38% 21% 13% 2	330
	11th to 20th	Day	14% 14% 36% 26% 9% 1	330
	21st to end	Day	15% 12% 32% 28% 11% 2	363
January	1st to 10th	Night	16% 13% 31% 31% 9% 1	840
	11th to 20th	Night	13% 10% 29% 35% 13%	840
	21st to end	Night	18% 11% 35% 30% 6%	924
February	1st to 10th	Night	16% 8% 31% 34% 12%	840
	11th to 20th	Night	15% 10% 34% 32% 8% 1	823
	21st to end	Night	15% 10% 32% 39% 5%	692
March	1st to 10th	Night	12% 9% 34% 36% 9%	840
	11th to 20th	Night	13% 8% 31% 34% 14%	840
	21st to end	Night	11% 8% 31% 36% 13% 1	924
April	1st to 10th	Night	12% 8% 29% 34% 16% 1	840
	11th to 20th	Night	9% 8% 31% 36% 15%	831
	21st to end	Night	5% 4 26% 40% 23% 2	660
May	1st to 10th	Night	6% 2 20% 47% 22% 3	630
	11th to 20th	Night	7% 3 18% 41% 28% 4	621
	21st to end	Night	6% 2 10% 36% 39% 8%	683
June	1st to 10th	Night	10% 2 10% 35% 35% 8%	630
	11th to 20th	Night	6% 2 9% 27% 40% 17%	630
	21st to end	Night	8% 2 5% 20% 47% 18%	630
July	1st to 10th	Night	6% 2 4 16% 45% 27%	615
	11th to 20th	Night	5% 2 13% 53% 27%	612
	21st to end	Night	4 1 4 16% 54% 21%	687
August	1st to 10th	Night	8% 2 4 17% 49% 20%	597
	11th to 20th	Night	7% 1 3 13% 52% 25%	594
	21st to end	Night	8% 2 6% 25% 42% 18%	780
September	1st to 10th	Night	9% 3 9% 24% 40% 15%	800
	11th to 20th	Night	12% 4 9% 33% 33% 9%	800
	21st to end	Night	13% 3 12% 30% 36% 7%	800
October	1st to 10th	Night	13% 4 21% 37% 23% 3	800
	11th to 20th	Night	7% 4 21% 39% 27% 2	800
	21st to end	Night	9% 4 25% 38% 22% 1	880
November	1st to 10th	Night	9% 4 27% 40% 19% 1	820
	11th to 20th	Night	12% 6% 26% 39% 15% 2	840
	21st to end	Night	12% 8% 28% 38% 13% 1	840
December	1st to 10th	Night	14% 7% 28% 33% 17% 1	840
	11th to 20th	Night	13% 11% 27% 35% 15%	840
	21st to end	Night	14% 7% 30% 35% 14% 1	924

Page generated at 2026-07-28 03:25:24. Version ac07

Copyright © 2026 Attilla Danko.