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 2024-11-04.

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% 5% 7% 9% 41%	101005
	Night	10% 6% 2 6% 5% 5% 5% 4 7% 9% 42%	97949
Transparency	Day	19% 49% 11% 11% 8% 3	104747
	Night	21% 49% 9% 10% 8% 3	102346
Seeing	Day	10% 3 13% 27% 30% 16%	15461
	Night	11% 4 16% 29% 30% 9%	25518

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	12% 8% 2 6% 4 4 3 4 5% 7% 46%	2836
	11th to 20th	Day	14% 6% 3 7% 5% 4 4 4 5% 7% 42%	2840
	21st to end	Day	12% 7% 2 6% 5% 4 4 3 5% 8% 44%	3124
February	1st to 10th	Day	16% 8% 3 5% 4 5% 3 3 5% 6% 42%	1864
	11th to 20th	Day	13% 6% 2 6% 4 3 5% 3 5% 5% 49%	1848
	21st to end	Day	12% 6% 2 5% 4 3 4 3 6% 7% 48%	1651
March	1st to 10th	Day	13% 10% 3 8% 4 4 4 4 6% 7% 37%	3435
	11th to 20th	Day	7% 4 2 4 3 4 4 4 6% 9% 53%	3480
	21st to end	Day	15% 6% 2 6% 4 4 4 4 6% 7% 43%	3815
April	1st to 10th	Day	7% 5% 2 4 5% 5% 4 4 5% 9% 50%	2090
	11th to 20th	Day	8% 6% 2 7% 4 4 5% 5% 6% 7% 46%	2151
	21st to end	Day	6% 3 1 4 4 4 4 3 6% 8% 57%	2308
May	1st to 10th	Day	6% 3 1 4 4 3 4 4 7% 9% 55%	4082
	11th to 20th	Day	8% 7% 3 6% 5% 5% 6% 5% 7% 9% 39%	4081
	21st to end	Day	6% 3 1 4 4 4 5% 5% 8% 11% 50%	4476
June	1st to 10th	Day	10% 5% 2 7% 6% 5% 6% 5% 9% 12% 33%	2470
	11th to 20th	Day	5% 5% 2 7% 7% 6% 6% 5% 8% 12% 37%	2470
	21st to end	Day	7% 5% 2 7% 7% 7% 7% 7% 9% 11% 30%	2470
July	1st to 10th	Day	6% 5% 2 7% 6% 7% 8% 6% 11% 13% 28%	4120
	11th to 20th	Day	4 3 2 5% 6% 6% 8% 6% 13% 15% 32%	4120
	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% 6% 48%	1887
	11th to 20th	Day	12% 7% 3 7% 4 4 5% 3 4 5% 46%	1900
	21st to end	Day	12% 7% 3 7% 5% 4 4 3 5% 6% 44%	1713
December	1st to 10th	Day	11% 5% 3 6% 4 5% 5% 4 6% 8% 45%	1710
	11th to 20th	Day	15% 7% 2 6% 4 3 4 3 5% 7% 43%	2153
	21st to end	Day	15% 8% 3 7% 5% 4 4 3 5% 5% 42%	3124
January	1st to 10th	Night	14% 8% 3 6% 4 3 3 4 5% 7% 43%	4109
	11th to 20th	Night	10% 8% 3 7% 5% 4 5% 5% 7% 8% 38%	4120
	21st to end	Night	12% 8% 3 8% 5% 5% 4 3 5% 7% 40%	4532
February	1st to 10th	Night	14% 7% 3 6% 4 4 5% 3 4 7% 43%	2314
	11th to 20th	Night	14% 7% 2 5% 5% 4 4 3 4 5% 47%	2218
	21st to end	Night	12% 5% 2 7% 5% 5% 5% 3 5% 6% 46%	1801
March	1st to 10th	Night	18% 10% 3 8% 4 3 3 3 5% 5% 37%	3418
	11th to 20th	Night	7% 4 2 5% 4 4 4 4 7% 10% 50%	3480
	21st to end	Night	13% 6% 3 6% 4 4 3 3 4 6% 47%	3817
April	1st to 10th	Night	9% 5% 1 5% 3 4 5% 4 6% 8% 49%	2090
	11th to 20th	Night	9% 5% 2 6% 3 3 3 4 6% 7% 52%	1975
	21st to end	Night	6% 3 2 4 3 4 3 4 8% 9% 55%	1886
May	1st to 10th	Night	4 2 1 4 4 4 5% 4 7% 9% 55%	2813
	11th to 20th	Night	10% 5% 2 5% 5% 5% 5% 4 6% 10% 43%	2812
	21st to end	Night	5% 3 1 4 4 4 4 5% 7% 10% 54%	3079
June	1st to 10th	Night	8% 5% 2 6% 4 5% 6% 6% 9% 13% 37%	1710
	11th to 20th	Night	6% 5% 2 5% 5% 6% 6% 5% 10% 12% 38%	1710
	21st to end	Night	7% 5% 2 7% 5% 5% 7% 5% 10% 13% 34%	1710
July	1st to 10th	Night	6% 5% 3 8% 7% 7% 8% 5% 9% 12% 30%	2840
	11th to 20th	Night	4 4 2 8% 6% 6% 7% 6% 12% 16% 29%	2840
	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% 2 5% 5% 4 4 4 6% 7% 47%	2264
	11th to 20th	Night	13% 6% 3 6% 4 4 4 3 5% 6% 46%	2280
	21st to end	Night	13% 6% 3 5% 5% 4 4 4 6% 7% 42%	2463
December	1st to 10th	Night	12% 6% 2 6% 3 4 4 4 5% 9% 44%	2470
	11th to 20th	Night	14% 7% 3 6% 4 4 4 3 4 6% 45%	3042
	21st to end	Night	14% 8% 3 7% 5% 4 4 4 5% 7% 38%	4532

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	25% 39% 4 10% 16% 6%	2837
	11th to 20th	Day	31% 39% 4 7% 11% 7%	2840
	21st to end	Day	23% 44% 4 12% 9% 8%	3124
February	1st to 10th	Day	14% 66% 5% 6% 7% 3	1864
	11th to 20th	Day	12% 65% 3 8% 9% 3	1858
	21st to end	Day	13% 66% 5% 4 7% 5%	1651
March	1st to 10th	Day	33% 45% 7% 10% 4 2	3435
	11th to 20th	Day	14% 44% 11% 9% 13% 9%	3480
	21st to end	Day	26% 42% 6% 12% 8% 6%	3815
April	1st to 10th	Day	11% 66% 6% 8% 4 5%	2090
	11th to 20th	Day	13% 66% 3 8% 5% 4	2151
	21st to end	Day	8% 65% 5% 11% 8% 2	2308
May	1st to 10th	Day	12% 44% 12% 21% 9% 2	4120
	11th to 20th	Day	25% 44% 8% 15% 7% 1	4085
	21st to end	Day	9% 43% 13% 23% 11% 1	4489
June	1st to 10th	Day	13% 68% 10% 6% 3	2470
	11th to 20th	Day	11% 68% 8% 9% 4	2470
	21st to end	Day	12% 68% 12% 6% 2	2470
July	1st to 10th	Day	24% 42% 24% 10%	4055
	11th to 20th	Day	15% 43% 37% 5% 1	4051
	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	16% 60% 6% 9% 6% 3	1887
	11th to 20th	Day	20% 60% 3 6% 8% 4	1900
	21st to end	Day	16% 60% 5% 9% 8% 2	1713
December	1st to 10th	Day	16% 61% 7% 8% 6% 1	1710
	11th to 20th	Day	18% 50% 6% 6% 16% 4	2150
	21st to end	Day	32% 39% 5% 10% 9% 5%	3124
January	1st to 10th	Night	29% 37% 4 7% 12% 10%	4109
	11th to 20th	Night	30% 39% 6% 8% 12% 6%	4120
	21st to end	Night	26% 42% 5% 10% 9% 7%	4532
February	1st to 10th	Night	14% 65% 4 6% 8% 3	2314
	11th to 20th	Night	13% 63% 4 9% 7% 3	2219
	21st to end	Night	15% 65% 6% 4 6% 5%	1801
March	1st to 10th	Night	35% 44% 8% 7% 4 2	3418
	11th to 20th	Night	16% 43% 9% 14% 12% 6%	3480
	21st to end	Night	26% 42% 5% 8% 12% 8%	3817
April	1st to 10th	Night	12% 66% 5% 8% 5% 5%	2090
	11th to 20th	Night	12% 66% 3 10% 5% 4	1975
	21st to end	Night	10% 65% 6% 10% 7% 2	1886
May	1st to 10th	Night	12% 47% 15% 17% 8% 2	2840
	11th to 20th	Night	23% 44% 10% 16% 6% 1	2813
	21st to end	Night	10% 43% 12% 22% 13% 1	3087
June	1st to 10th	Night	12% 68% 9% 7% 3	1710
	11th to 20th	Night	11% 68% 8% 9% 3	1710
	21st to end	Night	13% 68% 10% 6% 2	1710
July	1st to 10th	Night	26% 41% 22% 11%	2795
	11th to 20th	Night	22% 46% 27% 4 1	2786
	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	17% 60% 6% 8% 5% 4	2264
	11th to 20th	Night	18% 61% 5% 6% 7% 3	2280
	21st to end	Night	15% 60% 4 9% 8% 2	2463
December	1st to 10th	Night	15% 60% 9% 10% 5% 1	2470
	11th to 20th	Night	18% 49% 4 9% 14% 5%	3044
	21st to end	Night	33% 40% 8% 8% 9% 1	4532

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	13% 4 31% 39% 14%	270
	11th to 20th	Day	4 8% 23% 43% 19% 3	270
	21st to end	Day	16% 6% 32% 37% 9%	297
February	1st to 10th	Day	18% 6% 21% 33% 20% 1	270
	11th to 20th	Day	16% 3 25% 39% 16% 1	270
	21st to end	Day	12% 3 24% 44% 15% 2	306
March	1st to 10th	Day	9% 6% 26% 37% 21% 1	460
	11th to 20th	Day	10% 5% 23% 36% 21% 4	460
	21st to end	Day	9% 6% 24% 38% 20% 2	506
April	1st to 10th	Day	10% 7% 22% 38% 21% 2	460
	11th to 20th	Day	7% 5% 22% 34% 25% 7%	452
	21st to end	Day	5% 3 17% 35% 30% 10%	460
May	1st to 10th	Day	6% 2 15% 36% 32% 10%	463
	11th to 20th	Day	7% 2 10% 31% 36% 14%	487
	21st to end	Day	8% 1 5% 22% 39% 24%	529
June	1st to 10th	Day	11% 2 7% 22% 37% 20%	490
	11th to 20th	Day	5% 1 6% 20% 37% 31%	490
	21st to end	Day	7% 1 3 15% 43% 32%	490
July	1st to 10th	Day	6% 2 4 8% 39% 43%	485
	11th to 20th	Day	5% 2 5% 40% 48%	484
	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	14% 6% 16% 31% 25% 7%	467
	11th to 20th	Day	15% 8% 20% 34% 20% 3	460
	21st to end	Day	14% 5% 17% 40% 21% 2	273
December	1st to 10th	Day	10% 4 20% 39% 23% 3	270
	11th to 20th	Day	17% 6% 21% 35% 18% 2	270
	21st to end	Day	14% 6% 17% 35% 27% 2	297
January	1st to 10th	Night	13% 8% 32% 33% 13% 1	760
	11th to 20th	Night	12% 6% 24% 37% 18% 2	760
	21st to end	Night	17% 7% 31% 36% 9% 1	836
February	1st to 10th	Night	16% 6% 26% 36% 14% 1	760
	11th to 20th	Night	16% 6% 27% 38% 13%	743
	21st to end	Night	14% 4 24% 44% 14%	628
March	1st to 10th	Night	11% 5% 23% 41% 19% 1	760
	11th to 20th	Night	10% 7% 22% 39% 19% 2	760
	21st to end	Night	12% 4 24% 37% 21% 2	836
April	1st to 10th	Night	9% 5% 22% 40% 23% 2	760
	11th to 20th	Night	10% 5% 21% 34% 26% 4	751
	21st to end	Night	7% 3 14% 40% 33% 4	746
May	1st to 10th	Night	6% 2 15% 38% 32% 7%	570
	11th to 20th	Night	8% 2 12% 29% 39% 10%	561
	21st to end	Night	8% 1 6% 23% 48% 14%	617
June	1st to 10th	Night	11% 1 5% 28% 43% 13%	570
	11th to 20th	Night	6% 2 5% 22% 42% 22%	570
	21st to end	Night	9% 1 4 19% 45% 21%	570
July	1st to 10th	Night	6% 2 4 14% 46% 28%	555
	11th to 20th	Night	7% 1 2 11% 47% 33%	552
	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%	755
	11th to 20th	Night	14% 6% 22% 33% 23% 3	760
	21st to end	Night	14% 5% 23% 33% 21% 4	760
December	1st to 10th	Night	13% 7% 22% 31% 25% 2	760
	11th to 20th	Night	14% 6% 24% 31% 21% 4	760
	21st to end	Night	14% 8% 18% 37% 22% 1	836

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