Sarasota
Clear Sky Chart
History

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

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	7% 5% 2 6% 5% 5% 6% 5% 8% 10% 42%	114223
	Night	7% 5% 2 6% 5% 5% 5% 4 7% 9% 43%	114718
Transparency	Day	33% 11% 17% 20% 14% 4	118040
	Night	34% 9% 16% 20% 15% 5%	119040
Seeing	Day	7% 4 17% 26% 27% 18%	16144
	Night	8% 3 17% 33% 29% 10%	26263

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	8% 6% 3 6% 3 4 4 4 6% 8% 48%	4056
	11th to 20th	Day	19% 9% 3 8% 4 4 5% 3 6% 8% 32%	4060
	21st to end	Day	14% 5% 2 5% 4 3 4 3 6% 9% 45%	4942
February	1st to 10th	Day	10% 5% 2 6% 4 4 4 4 7% 7% 47%	2000
	11th to 20th	Day	6% 4 2 4 4 3 4 4 5% 8% 56%	1948
	21st to end	Day	7% 4 2 5% 4 4 3 3 5% 8% 55%	1705
March	1st to 10th	Day	7% 4 2 7% 4 4 5% 4 6% 8% 49%	4935
	11th to 20th	Day	4 3 1 4 3 3 3 3 6% 9% 61%	4980
	21st to end	Day	6% 4 2 5% 4 4 4 4 6% 9% 53%	5465
April	1st to 10th	Day	5% 3 2 5% 4 3 4 5% 8% 9% 53%	2200
	11th to 20th	Day	7% 4 2 5% 3 5% 5% 4 6% 8% 51%	2176
	21st to end	Day	4 2 1 4 3 4 4 5% 6% 10% 56%	2351
May	1st to 10th	Day	3 2 1 3 3 2 3 3 7% 10% 63%	4212
	11th to 20th	Day	8% 4 2 5% 4 5% 6% 4 8% 12% 43%	4081
	21st to end	Day	3 3 1 4 3 3 5% 4 6% 9% 59%	4476
June	1st to 10th	Day	9% 6% 3 8% 6% 6% 6% 5% 9% 12% 29%	2470
	11th to 20th	Day	6% 5% 2 7% 6% 7% 8% 7% 10% 11% 30%	2470
	21st to end	Day	7% 6% 2 7% 6% 6% 8% 8% 10% 11% 27%	2470
July	1st to 10th	Day	6% 4 2 7% 6% 8% 9% 7% 10% 15% 26%	4120
	11th to 20th	Day	3 5% 2 8% 7% 9% 10% 8% 12% 14% 23%	4120
	21st to end	Day	4 4 2 8% 7% 8% 9% 7% 11% 15% 24%	4466
August	1st to 10th	Day	6% 5% 3 9% 7% 8% 8% 7% 10% 13% 26%	3992
	11th to 20th	Day	3 3 2 6% 6% 6% 8% 7% 10% 13% 35%	3707
	21st to end	Day	7% 4 2 8% 7% 8% 9% 8% 11% 13% 23%	3828
September	1st to 10th	Day	7% 6% 2 7% 6% 7% 10% 7% 10% 12% 25%	2090
	11th to 20th	Day	9% 6% 2 7% 7% 7% 8% 7% 10% 11% 25%	2090
	21st to end	Day	6% 5% 3 7% 7% 7% 6% 6% 9% 13% 32%	2090
October	1st to 10th	Day	9% 6% 3 9% 5% 6% 6% 5% 7% 10% 36%	2090
	11th to 20th	Day	5% 4 2 5% 5% 5% 5% 4 7% 9% 48%	1957
	21st to end	Day	7% 5% 2 6% 4 4 4 4 6% 8% 50%	2090
November	1st to 10th	Day	6% 4 2 5% 4 6% 5% 4 6% 8% 50%	1957
	11th to 20th	Day	7% 6% 2 6% 5% 4 5% 4 6% 8% 48%	2000
	21st to end	Day	7% 5% 1 5% 4 5% 5% 4 6% 9% 50%	1860
December	1st to 10th	Day	3 3 1 3 3 4 4 3 5% 9% 62%	2930
	11th to 20th	Day	8% 6% 2 7% 5% 4 5% 4 6% 8% 47%	3373
	21st to end	Day	10% 7% 3 9% 6% 5% 5% 4 5% 8% 38%	4466
January	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 6% 9% 46%	5889
	11th to 20th	Night	17% 11% 4 9% 5% 4 4 4 6% 7% 28%	5900
	21st to end	Night	13% 6% 2 6% 4 4 5% 4 7% 8% 41%	6011
February	1st to 10th	Night	9% 6% 2 6% 4 4 4 3 6% 7% 47%	2400
	11th to 20th	Night	9% 6% 2 5% 4 4 4 3 5% 7% 52%	2338
	21st to end	Night	5% 5% 2 4 4 4 5% 4 7% 9% 51%	1923
March	1st to 10th	Night	7% 6% 2 6% 4 4 4 4 5% 8% 50%	4918
	11th to 20th	Night	4 3 1 4 4 3 4 4 6% 10% 57%	4980
	21st to end	Night	8% 5% 2 6% 3 3 4 4 5% 7% 51%	5467
April	1st to 10th	Night	5% 4 2 4 4 4 4 4 7% 9% 54%	2200
	11th to 20th	Night	5% 4 1 5% 3 4 5% 4 7% 9% 52%	2173
	21st to end	Night	4 3 1 4 4 4 4 4 6% 9% 57%	2062
May	1st to 10th	Night	2 3 1 4 4 4 5% 4 6% 10% 57%	2903
	11th to 20th	Night	7% 5% 2 6% 4 4 5% 4 7% 8% 49%	2818
	21st to end	Night	3 3 1 4 3 3 4 4 5% 7% 64%	3079
June	1st to 10th	Night	10% 6% 2 6% 5% 6% 5% 4 7% 11% 39%	1710
	11th to 20th	Night	6% 4 2 6% 4 7% 6% 5% 11% 12% 39%	1710
	21st to end	Night	6% 6% 2 6% 6% 5% 5% 7% 10% 14% 34%	1710
July	1st to 10th	Night	7% 6% 3 9% 6% 6% 8% 6% 10% 13% 27%	2840
	11th to 20th	Night	3 4 3 8% 6% 7% 8% 7% 11% 14% 29%	2840
	21st to end	Night	5% 8% 4 12% 8% 8% 9% 6% 9% 10% 19%	3087
August	1st to 10th	Night	5% 5% 2 8% 5% 6% 7% 6% 10% 13% 34%	2917
	11th to 20th	Night	3 4 2 6% 5% 5% 7% 7% 11% 16% 34%	3100
	21st to end	Night	7% 5% 3 9% 6% 7% 7% 7% 10% 13% 26%	3815
September	1st to 10th	Night	6% 5% 2 7% 6% 7% 8% 6% 11% 13% 29%	2090
	11th to 20th	Night	8% 6% 2 8% 7% 6% 7% 5% 8% 11% 30%	2090
	21st to end	Night	7% 7% 3 9% 6% 6% 6% 6% 9% 10% 31%	2090
October	1st to 10th	Night	9% 5% 3 7% 5% 5% 6% 4 7% 9% 39%	2090
	11th to 20th	Night	6% 6% 2 6% 4 4 4 4 6% 8% 50%	2221
	21st to end	Night	8% 5% 2 6% 4 4 4 4 6% 9% 48%	2508
November	1st to 10th	Night	6% 4 2 6% 6% 4 5% 3 6% 7% 51%	2341
	11th to 20th	Night	8% 6% 2 6% 5% 4 4 4 6% 8% 48%	2400
	21st to end	Night	8% 5% 2 6% 5% 4 4 4 6% 9% 48%	2536
December	1st to 10th	Night	4 3 1 4 3 3 3 3 6% 8% 62%	4250
	11th to 20th	Night	10% 7% 2 5% 4 4 4 4 5% 7% 49%	4822
	21st to end	Night	11% 8% 3 8% 5% 5% 5% 4 6% 8% 35%	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	31% 7% 9% 20% 25% 8%	4057
	11th to 20th	Day	50% 5% 7% 19% 15% 4	4060
	21st to end	Day	35% 6% 8% 28% 19% 4	4942
February	1st to 10th	Day	34% 7% 10% 20% 19% 10%	2000
	11th to 20th	Day	25% 6% 12% 23% 24% 10%	1958
	21st to end	Day	28% 4 13% 19% 27% 9%	1705
March	1st to 10th	Day	31% 8% 12% 21% 21% 6%	4935
	11th to 20th	Day	20% 7% 13% 23% 20% 17%	4980
	21st to end	Day	27% 5% 11% 29% 22% 6%	5465
April	1st to 10th	Day	24% 8% 18% 26% 18% 6%	2200
	11th to 20th	Day	29% 8% 15% 18% 22% 8%	2176
	21st to end	Day	22% 8% 15% 24% 26% 5%	2351
May	1st to 10th	Day	14% 7% 20% 34% 20% 4	4250
	11th to 20th	Day	30% 12% 22% 22% 13% 1	4085
	21st to end	Day	21% 8% 16% 36% 18% 1	4489
June	1st to 10th	Day	43% 13% 21% 18% 4	2470
	11th to 20th	Day	40% 14% 25% 18% 3	2470
	21st to end	Day	42% 17% 25% 13% 2	2470
July	1st to 10th	Day	40% 20% 30% 9% 1	4055
	11th to 20th	Day	43% 20% 31% 6%	4051
	21st to end	Day	41% 22% 26% 9%	4324
August	1st to 10th	Day	42% 17% 30% 8% 3	3979
	11th to 20th	Day	32% 18% 28% 17% 5%	3743
	21st to end	Day	42% 20% 28% 9% 1	3828
September	1st to 10th	Day	45% 19% 24% 11% 1	2090
	11th to 20th	Day	44% 17% 22% 13% 3	2090
	21st to end	Day	40% 15% 18% 17% 9% 2	2090
October	1st to 10th	Day	51% 13% 15% 10% 8% 4	3480
	11th to 20th	Day	25% 8% 11% 23% 30% 3	3236
	21st to end	Day	27% 6% 8% 26% 25% 8%	3428
November	1st to 10th	Day	29% 7% 12% 22% 19% 11%	1957
	11th to 20th	Day	34% 6% 11% 22% 20% 8%	2000
	21st to end	Day	30% 6% 14% 20% 20% 10%	1860
December	1st to 10th	Day	21% 6% 14% 29% 21% 9%	2930
	11th to 20th	Day	34% 6% 10% 20% 20% 10%	3370
	21st to end	Day	42% 8% 12% 20% 15% 3	4466
January	1st to 10th	Night	33% 5% 9% 21% 25% 7%	5889
	11th to 20th	Night	54% 6% 10% 15% 13% 3	5900
	21st to end	Night	39% 6% 10% 23% 18% 5%	6011
February	1st to 10th	Night	34% 6% 11% 20% 20% 8%	2400
	11th to 20th	Night	31% 4 11% 21% 22% 10%	2339
	21st to end	Night	27% 7% 13% 20% 26% 7%	1923
March	1st to 10th	Night	31% 7% 13% 23% 18% 8%	4918
	11th to 20th	Night	21% 7% 16% 21% 19% 16%	4980
	21st to end	Night	31% 6% 10% 27% 22% 4	5467
April	1st to 10th	Night	24% 7% 19% 27% 16% 7%	2200
	11th to 20th	Night	26% 8% 16% 22% 23% 6%	2173
	21st to end	Night	22% 7% 14% 26% 27% 4	2062
May	1st to 10th	Night	20% 10% 17% 30% 18% 5%	2930
	11th to 20th	Night	28% 10% 19% 32% 10% 1	2819
	21st to end	Night	18% 8% 14% 38% 21% 1	3087
June	1st to 10th	Night	38% 10% 22% 24% 6%	1710
	11th to 20th	Night	32% 14% 29% 21% 4	1710
	21st to end	Night	35% 18% 28% 14% 5%	1710
July	1st to 10th	Night	44% 16% 31% 8% 1	2795
	11th to 20th	Night	39% 20% 34% 7%	2786
	21st to end	Night	54% 17% 21% 7%	2988
August	1st to 10th	Night	37% 16% 29% 11% 6%	2906
	11th to 20th	Night	30% 17% 35% 16% 2	3130
	21st to end	Night	43% 19% 30% 8% 1	3815
September	1st to 10th	Night	40% 19% 26% 13% 1	2090
	11th to 20th	Night	45% 15% 22% 15% 3	2090
	21st to end	Night	42% 14% 18% 17% 8% 1	2090
October	1st to 10th	Night	54% 11% 14% 10% 8% 4	3480
	11th to 20th	Night	25% 8% 11% 27% 24% 4	3681
	21st to end	Night	30% 6% 9% 26% 24% 6%	4120
November	1st to 10th	Night	31% 6% 11% 21% 20% 11%	2341
	11th to 20th	Night	33% 6% 11% 22% 19% 8%	2400
	21st to end	Night	31% 7% 12% 21% 20% 8%	2536
December	1st to 10th	Night	20% 5% 16% 31% 16% 12%	4250
	11th to 20th	Night	33% 6% 12% 20% 21% 8%	4824
	21st to end	Night	43% 8% 15% 16% 14% 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	10% 9% 39% 31% 11% 1	300
	11th to 20th	Day	10% 14% 32% 26% 14% 3	300
	21st to end	Day	12% 14% 42% 26% 5%	330
February	1st to 10th	Day	8% 9% 29% 35% 17% 2	300
	11th to 20th	Day	6% 7% 31% 37% 15% 3	300
	21st to end	Day	7% 5% 27% 41% 17% 2	304
March	1st to 10th	Day	6% 6% 38% 34% 14% 1	500
	11th to 20th	Day	8% 9% 28% 32% 23% 2	500
	21st to end	Day	5% 5% 32% 34% 19% 4	550
April	1st to 10th	Day	5% 6% 33% 37% 17% 2	500
	11th to 20th	Day	6% 8% 23% 40% 20% 3	492
	21st to end	Day	4 2 22% 37% 31% 4	500
May	1st to 10th	Day	4 3 19% 36% 30% 8%	503
	11th to 20th	Day	9% 3 15% 29% 30% 14%	487
	21st to end	Day	6% 2 8% 23% 38% 23%	529
June	1st to 10th	Day	12% 2 9% 25% 32% 21%	490
	11th to 20th	Day	9% 3 6% 22% 30% 31%	490
	21st to end	Day	6% 4 12% 32% 45%	490
July	1st to 10th	Day	5% 1 3 10% 31% 50%	485
	11th to 20th	Day	5% 1 2 7% 36% 49%	484
	21st to end	Day	9% 1 5% 12% 29% 44%	532
August	1st to 10th	Day	7% 1 5% 11% 33% 43%	486
	11th to 20th	Day	5% 1 3 10% 31% 51%	479
	21st to end	Day	9% 1 6% 16% 32% 36%	539
September	1st to 10th	Day	8% 1 4 13% 33% 40%	490
	11th to 20th	Day	8% 2 7% 20% 35% 28%	490
	21st to end	Day	5% 3 6% 20% 37% 30%	490
October	1st to 10th	Day	11% 2 12% 31% 33% 10%	490
	11th to 20th	Day	6% 3 17% 31% 31% 13%	490
	21st to end	Day	8% 4 17% 34% 31% 6%	539
November	1st to 10th	Day	7% 3 18% 36% 30% 6%	495
	11th to 20th	Day	10% 4 21% 37% 23% 5%	500
	21st to end	Day	8% 6% 24% 34% 23% 5%	360
December	1st to 10th	Day	4 9% 32% 33% 16% 7%	300
	11th to 20th	Day	8% 7% 31% 31% 20% 3	300
	21st to end	Day	6% 8% 31% 33% 19% 3	330
January	1st to 10th	Night	11% 5% 27% 38% 17% 1	800
	11th to 20th	Night	12% 6% 24% 42% 15% 1	800
	21st to end	Night	12% 8% 29% 38% 12%	880
February	1st to 10th	Night	11% 6% 28% 38% 18% 1	800
	11th to 20th	Night	10% 5% 25% 41% 18% 1	783
	21st to end	Night	7% 4 23% 45% 21%	660
March	1st to 10th	Night	5% 5% 31% 45% 14% 1	800
	11th to 20th	Night	6% 4 24% 44% 21% 1	800
	21st to end	Night	6% 4 26% 44% 18% 1	880
April	1st to 10th	Night	5% 4 24% 46% 21% 1	800
	11th to 20th	Night	6% 4 25% 46% 18% 1	791
	21st to end	Night	5% 2 23% 46% 23% 1	798
May	1st to 10th	Night	3 1 12% 46% 36% 3	600
	11th to 20th	Night	8% 2 12% 38% 36% 5%	563
	21st to end	Night	6% 1 7% 34% 44% 8%	617
June	1st to 10th	Night	10% 5% 24% 48% 13%	570
	11th to 20th	Night	5% 2 4 14% 50% 25%	570
	21st to end	Night	6% 2 3 12% 46% 32%	570
July	1st to 10th	Night	8% 1 3 6% 43% 40%	555
	11th to 20th	Night	4 1 3 8% 39% 45%	552
	21st to end	Night	5% 1 3 7% 45% 39%	624
August	1st to 10th	Night	5% 3 11% 44% 37%	567
	11th to 20th	Night	6% 1 2 8% 38% 46%	564
	21st to end	Night	11% 1 6% 15% 39% 27%	823
September	1st to 10th	Night	7% 2 4 16% 46% 25%	760
	11th to 20th	Night	9% 2 5% 21% 42% 20%	760
	21st to end	Night	10% 2 7% 25% 42% 15%	760
October	1st to 10th	Night	10% 2 13% 37% 33% 6%	760
	11th to 20th	Night	8% 2 14% 37% 35% 4	760
	21st to end	Night	9% 3 18% 39% 28% 3	836
November	1st to 10th	Night	7% 3 23% 44% 21% 3	780
	11th to 20th	Night	8% 4 22% 42% 23% 2	800
	21st to end	Night	9% 3 23% 44% 21% 1	800
December	1st to 10th	Night	8% 4 22% 38% 27% 1	800
	11th to 20th	Night	9% 4 23% 39% 22% 2	800
	21st to end	Night	9% 4 25% 39% 22% 1	880

Page generated at 2025-05-08 09:34:00. Version ac07

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