Fort Clinch State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Clinch State Park clear sky chart from 2005-11-06 to 2025-07-21.

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% 5% 4 7% 9% 42%	120277
	Night	10% 6% 2 6% 4 4 5% 4 6% 9% 43%	118840
Transparency	Day	21% 42% 12% 12% 9% 4	124017
	Night	23% 41% 9% 12% 11% 5%	123237
Seeing	Day	10% 3 13% 27% 30% 16%	16402
	Night	11% 4 16% 30% 30% 9%	26469

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% 5% 2 5% 3 4 3 3 4 6% 56%	4056
	11th to 20th	Day	17% 7% 3 7% 4 4 3 3 4 7% 41%	4060
	21st to end	Day	12% 7% 2 6% 4 3 3 3 5% 9% 46%	4466
February	1st to 10th	Day	15% 8% 3 5% 4 5% 3 3 5% 6% 43%	1963
	11th to 20th	Day	13% 6% 2 6% 4 3 5% 3 5% 5% 49%	1948
	21st to end	Day	13% 6% 2 5% 4 3 4 3 6% 6% 49%	1736
March	1st to 10th	Day	14% 9% 3 7% 4 4 3 4 5% 7% 40%	4935
	11th to 20th	Day	7% 3 2 4 3 3 4 3 6% 9% 58%	4980
	21st to end	Day	12% 5% 2 6% 4 4 4 4 5% 7% 48%	5465
April	1st to 10th	Day	7% 5% 2 4 4 5% 4 4 6% 9% 50%	2200
	11th to 20th	Day	8% 6% 2 7% 4 4 5% 5% 6% 6% 48%	2266
	21st to end	Day	5% 3 1 4 4 4 4 3 6% 8% 57%	2430
May	1st to 10th	Day	8% 4 2 5% 4 4 5% 4 7% 10% 47%	5862
	11th to 20th	Day	9% 6% 2 6% 4 5% 5% 4 6% 10% 43%	5861
	21st to end	Day	4 3 1 4 4 5% 6% 5% 8% 12% 48%	6433
June	1st to 10th	Day	10% 5% 2 7% 6% 6% 5% 5% 9% 12% 32%	2600
	11th to 20th	Day	4 5% 2 6% 7% 6% 7% 5% 9% 12% 37%	2600
	21st to end	Day	7% 5% 2 7% 7% 7% 7% 7% 10% 12% 31%	2600
July	1st to 10th	Day	6% 5% 2 7% 6% 7% 8% 6% 11% 13% 28%	4250
	11th to 20th	Day	4 3 2 5% 6% 6% 8% 6% 13% 15% 33%	4250
	21st to end	Day	4 4 2 6% 5% 6% 7% 8% 11% 16% 31%	4466
August	1st to 10th	Day	11% 6% 2 8% 6% 6% 7% 6% 9% 12% 27%	4104
	11th to 20th	Day	6% 4 2 6% 4 5% 6% 6% 10% 12% 40%	4015
	21st to end	Day	7% 5% 3 7% 6% 6% 6% 6% 8% 10% 35%	3906
September	1st to 10th	Day	11% 8% 2 9% 6% 6% 8% 5% 8% 10% 28%	2090
	11th to 20th	Day	14% 7% 3 7% 6% 6% 7% 4 8% 9% 28%	2090
	21st to end	Day	14% 6% 2 7% 5% 5% 5% 4 6% 9% 35%	2090
October	1st to 10th	Day	15% 5% 2 6% 4 4 5% 4 7% 9% 38%	2036
	11th to 20th	Day	7% 5% 2 5% 5% 4 4 3 5% 7% 54%	1900
	21st to end	Day	10% 4 2 4 4 4 5% 3 6% 8% 50%	2090
November	1st to 10th	Day	12% 6% 2 6% 3 4 4 3 5% 7% 47%	1957
	11th to 20th	Day	11% 7% 3 7% 4 4 5% 3 5% 6% 46%	2000
	21st to end	Day	11% 7% 3 7% 4 4 4 3 5% 6% 45%	1803
December	1st to 10th	Day	6% 3 2 5% 4 4 5% 4 6% 7% 55%	2930
	11th to 20th	Day	15% 8% 3 7% 5% 4 5% 3 5% 7% 39%	3373
	21st to end	Day	15% 8% 3 7% 5% 5% 4 3 5% 5% 41%	4466
January	1st to 10th	Night	10% 5% 2 4 3 2 3 3 4 6% 58%	5889
	11th to 20th	Night	14% 7% 3 7% 5% 4 5% 4 6% 7% 36%	5900
	21st to end	Night	13% 7% 3 6% 4 4 3 3 5% 8% 43%	6490
February	1st to 10th	Night	14% 7% 2 6% 4 4 5% 3 4 7% 44%	2435
	11th to 20th	Night	14% 7% 2 5% 5% 4 4 3 4 5% 46%	2338
	21st to end	Night	12% 5% 2 7% 4 4 5% 3 5% 6% 47%	1892
March	1st to 10th	Night	17% 8% 3 7% 4 3 3 3 5% 5% 42%	4918
	11th to 20th	Night	6% 4 2 4 3 3 3 3 6% 11% 54%	4980
	21st to end	Night	10% 6% 2 6% 4 4 4 3 5% 7% 50%	5467
April	1st to 10th	Night	9% 5% 2 5% 3 4 5% 5% 6% 9% 49%	2200
	11th to 20th	Night	8% 5% 2 6% 3 4 3 3 5% 7% 54%	2080
	21st to end	Night	5% 3 2 4 3 4 4 4 8% 9% 54%	1985
May	1st to 10th	Night	5% 4 2 6% 5% 4 5% 4 7% 10% 48%	4033
	11th to 20th	Night	10% 5% 2 5% 4 4 5% 5% 6% 10% 42%	4032
	21st to end	Night	4 3 2 6% 5% 5% 5% 5% 7% 12% 46%	4421
June	1st to 10th	Night	8% 5% 2 6% 5% 5% 6% 6% 9% 13% 36%	1800
	11th to 20th	Night	6% 6% 2 6% 5% 6% 6% 5% 10% 12% 37%	1800
	21st to end	Night	7% 5% 2 7% 5% 5% 7% 5% 10% 13% 35%	1800
July	1st to 10th	Night	6% 5% 3 9% 7% 7% 8% 6% 9% 12% 29%	2930
	11th to 20th	Night	4 4 2 8% 6% 6% 7% 6% 11% 16% 30%	2930
	21st to end	Night	5% 6% 3 7% 6% 7% 8% 7% 11% 14% 27%	3087
August	1st to 10th	Night	12% 6% 3 8% 6% 6% 7% 6% 9% 11% 28%	2825
	11th to 20th	Night	4 4 2 6% 5% 5% 6% 6% 9% 11% 42%	2785
	21st to end	Night	7% 5% 2 8% 5% 5% 6% 5% 8% 11% 38%	3727
September	1st to 10th	Night	11% 8% 3 8% 7% 7% 7% 5% 6% 10% 27%	2090
	11th to 20th	Night	13% 7% 2 9% 6% 6% 7% 6% 7% 10% 26%	2090
	21st to end	Night	11% 7% 3 7% 5% 5% 5% 4 7% 9% 38%	2090
October	1st to 10th	Night	14% 7% 3 6% 5% 5% 4 4 6% 8% 39%	2142
	11th to 20th	Night	7% 4 2 5% 4 4 5% 3 5% 8% 54%	2280
	21st to end	Night	8% 4 2 5% 4 4 5% 4 5% 7% 52%	2508
November	1st to 10th	Night	11% 6% 3 6% 4 4 4 4 6% 7% 45%	2341
	11th to 20th	Night	13% 6% 3 6% 4 4 4 3 5% 6% 46%	2400
	21st to end	Night	12% 6% 3 6% 5% 4 4 4 6% 7% 44%	2593
December	1st to 10th	Night	10% 5% 2 5% 3 3 4 3 5% 7% 54%	4250
	11th to 20th	Night	13% 8% 3 7% 4 4 4 3 4 5% 45%	4822
	21st to end	Night	14% 8% 3 7% 5% 4 4 3 5% 6% 40%	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	22% 28% 4 11% 28% 8%	4057
	11th to 20th	Day	36% 27% 4 8% 15% 10%	4060
	21st to end	Day	26% 31% 4 19% 11% 8%	4466
February	1st to 10th	Day	15% 63% 5% 7% 9% 3	1963
	11th to 20th	Day	14% 62% 4 8% 9% 3	1958
	21st to end	Day	14% 62% 4 6% 7% 6%	1736
March	1st to 10th	Day	35% 32% 8% 9% 12% 4	4935
	11th to 20th	Day	15% 31% 10% 11% 15% 18%	4980
	21st to end	Day	27% 30% 8% 14% 13% 9%	5465
April	1st to 10th	Day	11% 63% 6% 11% 5% 5%	2200
	11th to 20th	Day	13% 63% 3 9% 8% 5%	2266
	21st to end	Day	10% 62% 6% 12% 9% 2	2430
May	1st to 10th	Day	23% 33% 15% 20% 7% 1	5897
	11th to 20th	Day	25% 32% 13% 23% 6% 1	5865
	21st to end	Day	15% 32% 18% 22% 12% 1	6447
June	1st to 10th	Day	15% 66% 10% 6% 3	2600
	11th to 20th	Day	12% 66% 9% 9% 4	2600
	21st to end	Day	12% 65% 13% 8% 2	2600
July	1st to 10th	Day	24% 42% 24% 10%	4185
	11th to 20th	Day	14% 42% 37% 6% 1	4181
	21st to end	Day	20% 45% 29% 5% 1	4324
August	1st to 10th	Day	31% 41% 22% 5%	4091
	11th to 20th	Day	13% 41% 19% 17% 10%	4054
	21st to end	Day	18% 42% 17% 22% 1	3906
September	1st to 10th	Day	21% 64% 7% 3 4 1	2090
	11th to 20th	Day	17% 63% 9% 7% 4	2090
	21st to end	Day	15% 62% 8% 8% 6%	2090
October	1st to 10th	Day	34% 39% 7% 5% 9% 6%	3387
	11th to 20th	Day	13% 38% 4 12% 24% 10%	3140
	21st to end	Day	10% 39% 4 17% 25% 6%	3428
November	1st to 10th	Day	18% 58% 6% 9% 6% 3	1957
	11th to 20th	Day	20% 57% 3 7% 8% 4	2000
	21st to end	Day	16% 57% 5% 9% 8% 4	1803
December	1st to 10th	Day	17% 36% 8% 17% 16% 6%	2930
	11th to 20th	Day	28% 35% 8% 9% 16% 4	3370
	21st to end	Day	37% 28% 7% 15% 10% 3	4466
January	1st to 10th	Night	21% 26% 5% 9% 30% 9%	5889
	11th to 20th	Night	37% 28% 5% 9% 16% 5%	5900
	21st to end	Night	28% 30% 5% 16% 13% 7%	6490
February	1st to 10th	Night	14% 62% 5% 7% 10% 2	2435
	11th to 20th	Night	15% 60% 4 10% 8% 3	2339
	21st to end	Night	15% 62% 6% 5% 7% 5%	1892
March	1st to 10th	Night	34% 31% 7% 10% 9% 8%	4918
	11th to 20th	Night	17% 30% 8% 14% 15% 15%	4980
	21st to end	Night	27% 30% 6% 11% 15% 11%	5467
April	1st to 10th	Night	12% 62% 5% 10% 6% 5%	2200
	11th to 20th	Night	12% 63% 3 10% 7% 5%	2080
	21st to end	Night	11% 62% 7% 10% 8% 2	1985
May	1st to 10th	Night	23% 35% 17% 18% 7% 1	4060
	11th to 20th	Night	26% 32% 14% 21% 7%	4033
	21st to end	Night	20% 31% 15% 21% 12% 1	4429
June	1st to 10th	Night	14% 66% 10% 7% 3	1800
	11th to 20th	Night	14% 66% 9% 9% 3	1800
	21st to end	Night	13% 65% 11% 7% 3	1800
July	1st to 10th	Night	27% 40% 22% 11%	2885
	11th to 20th	Night	22% 45% 27% 5% 1	2876
	21st to end	Night	29% 45% 21% 5%	2988
August	1st to 10th	Night	35% 41% 20% 3	2814
	11th to 20th	Night	17% 42% 18% 15% 8%	2812
	21st to end	Night	19% 41% 17% 21% 1	3727
September	1st to 10th	Night	22% 62% 8% 4 3 1	2090
	11th to 20th	Night	18% 63% 8% 7% 3	2090
	21st to end	Night	16% 62% 7% 10% 6%	2090
October	1st to 10th	Night	37% 38% 5% 7% 8% 6%	3571
	11th to 20th	Night	13% 38% 4 11% 24% 11%	3779
	21st to end	Night	9% 38% 5% 14% 27% 8%	4120
November	1st to 10th	Night	18% 58% 6% 8% 6% 4	2341
	11th to 20th	Night	19% 58% 4 7% 8% 4	2400
	21st to end	Night	16% 57% 5% 9% 9% 4	2593
December	1st to 10th	Night	19% 35% 7% 15% 17% 8%	4250
	11th to 20th	Night	27% 33% 6% 16% 11% 6%	4824
	21st to end	Night	35% 29% 9% 12% 13% 1	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	12% 3 32% 40% 13%	300
	11th to 20th	Day	7% 7% 22% 43% 18% 3	300
	21st to end	Day	16% 6% 32% 38% 9%	330
February	1st to 10th	Day	16% 6% 20% 33% 23% 3	300
	11th to 20th	Day	15% 3 27% 39% 15% 1	300
	21st to end	Day	13% 3 24% 44% 15% 2	335
March	1st to 10th	Day	10% 6% 27% 37% 20% 1	500
	11th to 20th	Day	10% 5% 24% 36% 21% 4	500
	21st to end	Day	9% 6% 23% 39% 21% 2	550
April	1st to 10th	Day	9% 6% 22% 39% 22% 2	500
	11th to 20th	Day	7% 4 21% 35% 26% 7%	492
	21st to end	Day	5% 2 16% 33% 33% 11%	500
May	1st to 10th	Day	7% 2 15% 36% 31% 10%	503
	11th to 20th	Day	7% 2 11% 31% 35% 13%	527
	21st to end	Day	8% 1 6% 23% 39% 23%	573
June	1st to 10th	Day	11% 2 7% 24% 37% 18%	530
	11th to 20th	Day	5% 1 5% 19% 38% 32%	530
	21st to end	Day	6% 1 2 14% 44% 32%	530
July	1st to 10th	Day	5% 2 3 8% 39% 42%	525
	11th to 20th	Day	4 2 5% 41% 48%	524
	21st to end	Day	5% 1 4 11% 42% 37%	532
August	1st to 10th	Day	8% 1 3 14% 36% 38%	486
	11th to 20th	Day	4 1 2 7% 42% 44%	479
	21st to end	Day	12% 1 3 12% 38% 34%	539
September	1st to 10th	Day	11% 4 6% 13% 36% 31%	490
	11th to 20th	Day	15% 3 5% 19% 41% 17%	490
	21st to end	Day	12% 2 6% 21% 38% 21%	490
October	1st to 10th	Day	15% 4 9% 33% 29% 9%	490
	11th to 20th	Day	8% 2 16% 32% 33% 8%	490
	21st to end	Day	8% 2 14% 33% 38% 6%	539
November	1st to 10th	Day	15% 6% 16% 32% 25% 7%	495
	11th to 20th	Day	14% 7% 20% 35% 20% 4	500
	21st to end	Day	13% 5% 20% 38% 21% 3	303
December	1st to 10th	Day	9% 4 23% 38% 23% 3	300
	11th to 20th	Day	17% 6% 22% 35% 18% 2	300
	21st to end	Day	15% 6% 17% 36% 25% 2	330
January	1st to 10th	Night	13% 8% 33% 34% 12% 1	800
	11th to 20th	Night	13% 6% 25% 36% 18% 2	800
	21st to end	Night	16% 6% 31% 37% 9% 1	880
February	1st to 10th	Night	16% 6% 25% 36% 16% 2	800
	11th to 20th	Night	16% 6% 27% 38% 13%	783
	21st to end	Night	14% 4 24% 43% 14%	660
March	1st to 10th	Night	11% 5% 24% 41% 18% 1	800
	11th to 20th	Night	10% 7% 23% 39% 19% 2	800
	21st to end	Night	11% 4 23% 39% 21% 2	880
April	1st to 10th	Night	9% 5% 21% 40% 23% 2	800
	11th to 20th	Night	10% 5% 21% 35% 26% 4	791
	21st to end	Night	6% 3 13% 39% 33% 5%	785
May	1st to 10th	Night	6% 2 16% 39% 32% 7%	600
	11th to 20th	Night	8% 2 12% 31% 38% 9%	591
	21st to end	Night	8% 1 6% 24% 47% 14%	650
June	1st to 10th	Night	11% 1 5% 30% 42% 12%	600
	11th to 20th	Night	6% 3 6% 21% 43% 22%	600
	21st to end	Night	8% 1 4 19% 46% 22%	600
July	1st to 10th	Night	6% 2 4 14% 46% 28%	585
	11th to 20th	Night	7% 1 2 10% 49% 32%	582
	21st to end	Night	4 1 3 16% 55% 21%	624
August	1st to 10th	Night	8% 1 4 13% 51% 23%	567
	11th to 20th	Night	6% 1 2 11% 48% 32%	564
	21st to end	Night	11% 1 5% 16% 40% 27%	831
September	1st to 10th	Night	13% 2 6% 15% 46% 18%	760
	11th to 20th	Night	15% 1 8% 20% 44% 12%	760
	21st to end	Night	15% 2 5% 23% 43% 13%	760
October	1st to 10th	Night	18% 2 12% 27% 34% 8%	760
	11th to 20th	Night	9% 4 13% 33% 33% 8%	760
	21st to end	Night	10% 3 15% 30% 36% 7%	836
November	1st to 10th	Night	12% 4 19% 33% 28% 5%	780
	11th to 20th	Night	14% 6% 22% 33% 23% 3	800
	21st to end	Night	14% 6% 23% 32% 22% 4	800
December	1st to 10th	Night	12% 7% 24% 31% 24% 2	800
	11th to 20th	Night	14% 6% 23% 30% 22% 4	800
	21st to end	Night	14% 8% 18% 38% 21% 1	880

Page generated at 2025-07-18 01:09:58. Version ac07

Copyright © 2025 Attilla Danko.