Fort Pickens
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Pickens clear sky chart from 2005-11-06 to 2024-04-10.

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	10% 6% 2 5% 5% 3 5% 5% 6% 9% 43%	83682
	Night	10% 6% 2 5% 5% 3 4 5% 6% 8% 46%	85096
Transparency	Day	34% 9% 15% 19% 16% 6%	83419
	Night	34% 8% 14% 18% 18% 7%	84878
Seeing	Day	11% 3 13% 25% 31% 17%	13726
	Night	11% 4 17% 26% 29% 12%	23773

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	14% 5% 2 5% 5% 3 5% 4 6% 7% 44%	2996
	11th to 20th	Day	11% 5% 2 5% 4 2 3 4 6% 8% 50%	3160
	21st to end	Day	26% 8% 3 4 3 2 3 4 5% 7% 35%	3476
February	1st to 10th	Day	15% 9% 3 5% 5% 3 4 4 4 7% 43%	1900
	11th to 20th	Day	14% 6% 2 4 4 2 5% 4 5% 8% 44%	1848
	21st to end	Day	14% 6% 3 6% 5% 3 4 5% 5% 8% 41%	1570
March	1st to 10th	Day	19% 11% 3 6% 5% 3 4 4 4 7% 35%	3120
	11th to 20th	Day	10% 5% 3 5% 5% 4 5% 5% 6% 9% 43%	3304
	21st to end	Day	14% 6% 2 5% 5% 3 4 5% 5% 7% 44%	4069
April	1st to 10th	Day	11% 6% 2 4 4 3 4 5% 5% 7% 48%	2269
	11th to 20th	Day	10% 5% 3 5% 4 3 4 4 6% 8% 47%	2134
	21st to end	Day	6% 3 1 4 4 3 4 4 6% 8% 57%	2160
May	1st to 10th	Day	7% 4 2 3 3 2 4 4 6% 8% 57%	2160
	11th to 20th	Day	5% 4 2 5% 6% 4 4 6% 7% 9% 48%	2273
	21st to end	Day	5% 4 2 4 5% 3 5% 6% 7% 11% 49%	2531
June	1st to 10th	Day	7% 5% 3 5% 6% 3 5% 7% 9% 12% 36%	2340
	11th to 20th	Day	5% 3 2 4 5% 4 6% 7% 10% 14% 39%	2340
	21st to end	Day	6% 5% 3 6% 5% 5% 6% 7% 9% 14% 35%	2340
July	1st to 10th	Day	8% 6% 3 7% 7% 5% 7% 8% 9% 13% 28%	2340
	11th to 20th	Day	7% 6% 2 6% 8% 5% 8% 9% 10% 13% 27%	2220
	21st to end	Day	5% 5% 2 6% 6% 4 8% 8% 9% 13% 34%	2350
August	1st to 10th	Day	7% 4 2 5% 6% 5% 7% 9% 9% 13% 34%	2148
	11th to 20th	Day	8% 5% 2 5% 7% 4 6% 8% 10% 14% 31%	2125
	21st to end	Day	10% 5% 3 6% 5% 4 5% 7% 7% 9% 37%	2376
September	1st to 10th	Day	8% 4 2 5% 5% 4 6% 7% 8% 11% 39%	2120
	11th to 20th	Day	10% 6% 3 6% 5% 4 5% 5% 7% 9% 41%	1980
	21st to end	Day	7% 4 2 4 5% 3 5% 6% 6% 7% 51%	1980
October	1st to 10th	Day	7% 4 2 3 4 2 4 5% 6% 9% 54%	1980
	11th to 20th	Day	7% 3 1 3 4 2 4 3 5% 9% 58%	1980
	21st to end	Day	10% 4 2 5% 5% 3 3 4 5% 6% 53%	2014
November	1st to 10th	Day	7% 5% 1 4 3 2 3 4 4 6% 58%	1672
	11th to 20th	Day	8% 5% 2 4 4 3 4 4 5% 7% 55%	1710
	21st to end	Day	10% 4 2 5% 5% 3 5% 5% 6% 8% 47%	1710
December	1st to 10th	Day	10% 6% 3 5% 5% 4 4 5% 5% 8% 45%	1710
	11th to 20th	Day	14% 7% 4 6% 5% 3 4 4 4 5% 43%	2153
	21st to end	Day	16% 10% 3 5% 5% 3 4 3 4 6% 41%	3124
January	1st to 10th	Night	15% 6% 2 5% 5% 4 5% 4 5% 6% 43%	3945
	11th to 20th	Night	12% 5% 3 5% 5% 2 4 3 5% 7% 49%	3800
	21st to end	Night	20% 9% 3 5% 4 2 4 3 4 6% 39%	4180
February	1st to 10th	Night	14% 7% 3 5% 4 3 3 3 5% 6% 46%	2280
	11th to 20th	Night	16% 6% 3 4 4 2 4 4 4 6% 46%	2218
	21st to end	Night	14% 7% 3 6% 5% 3 4 5% 5% 6% 43%	1884
March	1st to 10th	Night	20% 11% 3 7% 5% 3 4 4 5% 6% 34%	3733
	11th to 20th	Night	8% 6% 2 6% 5% 3 4 5% 7% 9% 43%	3654
	21st to end	Night	13% 6% 2 5% 5% 3 4 4 5% 7% 46%	3576
April	1st to 10th	Night	11% 7% 3 4 5% 3 5% 5% 4 8% 47%	1900
	11th to 20th	Night	12% 4 2 4 5% 3 5% 4 5% 7% 49%	1775
	21st to end	Night	5% 3 2 3 4 2 4 5% 4 7% 61%	1800
May	1st to 10th	Night	8% 3 2 3 3 2 4 4 5% 10% 57%	1800
	11th to 20th	Night	4 5% 3 5% 5% 3 6% 5% 6% 9% 51%	1615
	21st to end	Night	5% 3 2 4 4 3 5% 5% 7% 11% 49%	1744
June	1st to 10th	Night	7% 5% 3 6% 6% 3 4 5% 7% 13% 41%	1620
	11th to 20th	Night	3 2 2 4 4 3 5% 7% 9% 12% 49%	1620
	21st to end	Night	5% 5% 2 5% 4 3 6% 8% 9% 14% 40%	1620
July	1st to 10th	Night	5% 5% 2 5% 6% 3 6% 7% 11% 11% 39%	1620
	11th to 20th	Night	3 3 2 5% 6% 4 6% 7% 10% 16% 38%	1734
	21st to end	Night	2 3 2 4 6% 4 6% 7% 10% 14% 41%	1968
August	1st to 10th	Night	3 2 1 3 5% 4 5% 7% 10% 13% 46%	1790
	11th to 20th	Night	7% 4 2 5% 6% 3 6% 6% 10% 14% 37%	1776
	21st to end	Night	7% 5% 3 6% 7% 4 5% 7% 7% 11% 39%	1980
September	1st to 10th	Night	7% 4 2 6% 6% 4 5% 6% 8% 14% 38%	1819
	11th to 20th	Night	9% 6% 3 6% 6% 4 5% 4 6% 8% 42%	1980
	21st to end	Night	8% 4 2 5% 5% 3 5% 4 6% 9% 50%	1980
October	1st to 10th	Night	6% 5% 2 4 4 3 3 5% 6% 9% 54%	1980
	11th to 20th	Night	6% 3 2 3 3 3 4 5% 4 7% 60%	1980
	21st to end	Night	9% 5% 2 4 5% 3 4 4 5% 6% 53%	2335
November	1st to 10th	Night	8% 5% 2 4 4 2 3 4 5% 7% 57%	2406
	11th to 20th	Night	11% 5% 2 4 3 3 4 4 4 7% 53%	2470
	21st to end	Night	11% 5% 2 4 5% 3 4 5% 5% 7% 49%	2470
December	1st to 10th	Night	11% 6% 2 6% 5% 3 4 5% 5% 7% 46%	2470
	11th to 20th	Night	13% 6% 3 6% 4 3 4 5% 5% 7% 44%	3042
	21st to end	Night	14% 10% 4 6% 6% 3 4 3 4 6% 40%	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	36% 7% 9% 17% 21% 10%	2997
	11th to 20th	Day	30% 7% 9% 17% 28% 9%	3160
	21st to end	Day	48% 5% 5% 15% 18% 8%	3476
February	1st to 10th	Day	42% 5% 9% 16% 19% 10%	1900
	11th to 20th	Day	37% 7% 11% 17% 19% 9%	1858
	21st to end	Day	38% 10% 12% 17% 16% 8%	1570
March	1st to 10th	Day	47% 8% 10% 18% 13% 4	3120
	11th to 20th	Day	33% 10% 15% 18% 19% 4	3304
	21st to end	Day	37% 8% 13% 18% 16% 8%	4069
April	1st to 10th	Day	34% 8% 13% 18% 19% 8%	2269
	11th to 20th	Day	34% 6% 11% 22% 19% 7%	2134
	21st to end	Day	24% 7% 12% 26% 23% 8%	2160
May	1st to 10th	Day	24% 7% 14% 27% 21% 8%	2160
	11th to 20th	Day	27% 10% 21% 23% 17% 2	2277
	21st to end	Day	26% 10% 18% 25% 18% 2	2531
June	1st to 10th	Day	34% 11% 20% 27% 7% 1	2340
	11th to 20th	Day	28% 12% 23% 27% 9% 1	2340
	21st to end	Day	34% 14% 25% 18% 9% 1	2340
July	1st to 10th	Day	41% 17% 24% 15% 3	2275
	11th to 20th	Day	39% 18% 27% 13% 3	2153
	21st to end	Day	32% 17% 29% 19% 3	2219
August	1st to 10th	Day	33% 16% 27% 20% 3	2136
	11th to 20th	Day	35% 18% 28% 15% 5%	2125
	21st to end	Day	38% 13% 22% 17% 8% 2	2376
September	1st to 10th	Day	33% 13% 22% 18% 11% 4	2120
	11th to 20th	Day	37% 11% 17% 17% 13% 5%	1980
	21st to end	Day	29% 10% 13% 20% 21% 7%	1980
October	1st to 10th	Day	25% 8% 14% 21% 20% 12%	1980
	11th to 20th	Day	24% 6% 10% 23% 25% 12%	1980
	21st to end	Day	31% 5% 8% 15% 24% 16%	2014
November	1st to 10th	Day	27% 5% 11% 22% 24% 12%	1672
	11th to 20th	Day	29% 5% 9% 19% 26% 11%	1710
	21st to end	Day	33% 8% 11% 21% 18% 9%	1710
December	1st to 10th	Day	36% 8% 15% 17% 18% 6%	1710
	11th to 20th	Day	43% 6% 8% 15% 20% 8%	2150
	21st to end	Day	44% 6% 9% 17% 21% 3	3124
January	1st to 10th	Night	40% 7% 7% 11% 23% 12%	3945
	11th to 20th	Night	34% 6% 7% 15% 30% 7%	3800
	21st to end	Night	46% 5% 7% 14% 20% 7%	4180
February	1st to 10th	Night	39% 6% 8% 16% 22% 10%	2280
	11th to 20th	Night	39% 5% 9% 15% 20% 12%	2219
	21st to end	Night	40% 8% 11% 16% 14% 11%	1884
March	1st to 10th	Night	48% 9% 11% 15% 12% 5%	3733
	11th to 20th	Night	31% 9% 15% 18% 18% 8%	3654
	21st to end	Night	35% 7% 12% 19% 18% 9%	3576
April	1st to 10th	Night	35% 7% 14% 14% 19% 11%	1900
	11th to 20th	Night	34% 5% 11% 22% 20% 8%	1775
	21st to end	Night	21% 7% 9% 28% 26% 8%	1800
May	1st to 10th	Night	24% 7% 14% 22% 25% 8%	1800
	11th to 20th	Night	28% 9% 20% 21% 19% 3	1616
	21st to end	Night	27% 9% 18% 23% 21% 3	1745
June	1st to 10th	Night	33% 9% 24% 25% 9% 1	1620
	11th to 20th	Night	23% 13% 24% 27% 12% 1	1620
	21st to end	Night	29% 15% 27% 19% 9% 1	1620
July	1st to 10th	Night	33% 17% 25% 20% 5%	1575
	11th to 20th	Night	27% 19% 35% 15% 4	1678
	21st to end	Night	29% 15% 32% 21% 4	1858
August	1st to 10th	Night	24% 16% 32% 24% 3	1778
	11th to 20th	Night	34% 15% 31% 18% 3	1776
	21st to end	Night	37% 14% 21% 20% 6% 2	1980
September	1st to 10th	Night	33% 12% 25% 16% 11% 3	1819
	11th to 20th	Night	38% 9% 17% 17% 13% 5%	1980
	21st to end	Night	29% 9% 15% 22% 18% 7%	1980
October	1st to 10th	Night	27% 8% 12% 21% 20% 13%	1980
	11th to 20th	Night	24% 5% 9% 22% 27% 12%	1980
	21st to end	Night	32% 6% 7% 15% 26% 14%	2335
November	1st to 10th	Night	28% 4 9% 19% 26% 14%	2406
	11th to 20th	Night	33% 4 6% 20% 27% 10%	2470
	21st to end	Night	33% 6% 10% 19% 20% 11%	2470
December	1st to 10th	Night	35% 7% 12% 20% 20% 6%	2470
	11th to 20th	Night	39% 6% 9% 14% 21% 11%	3044
	21st to end	Night	45% 6% 8% 19% 19% 3	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	14% 8% 29% 31% 17% 1	270
	11th to 20th	Day	9% 7% 24% 40% 17% 3	270
	21st to end	Day	24% 8% 32% 28% 8% 1	297
February	1st to 10th	Day	17% 9% 25% 34% 13% 1	270
	11th to 20th	Day	17% 6% 24% 40% 12%	270
	21st to end	Day	9% 8% 28% 45% 9%	225
March	1st to 10th	Day	12% 6% 30% 35% 16%	270
	11th to 20th	Day	14% 4 24% 36% 20% 1	349
	21st to end	Day	13% 7% 23% 37% 19% 2	506
April	1st to 10th	Day	14% 7% 22% 37% 19% 2	457
	11th to 20th	Day	11% 7% 24% 31% 23% 5%	412
	21st to end	Day	7% 3 16% 35% 34% 4	420
May	1st to 10th	Day	8% 4 11% 35% 35% 7%	423
	11th to 20th	Day	6% 1 8% 30% 42% 13%	447
	21st to end	Day	7% 1 5% 23% 45% 19%	485
June	1st to 10th	Day	10% 2 5% 18% 45% 20%	450
	11th to 20th	Day	7% 1 5% 18% 42% 27%	450
	21st to end	Day	8% 1 4 17% 36% 33%	450
July	1st to 10th	Day	8% 3 3 9% 34% 43%	445
	11th to 20th	Day	6% 1 4 9% 32% 48%	444
	21st to end	Day	6% 4 10% 39% 41%	488
August	1st to 10th	Day	8% 1 2 9% 31% 50%	446
	11th to 20th	Day	9% 1 3 8% 33% 46%	439
	21st to end	Day	9% 2 4 14% 37% 33%	495
September	1st to 10th	Day	8% 1 5% 13% 34% 38%	450
	11th to 20th	Day	13% 3 4 16% 43% 20%	450
	21st to end	Day	10% 5% 22% 45% 18%	450
October	1st to 10th	Day	8% 1 12% 32% 40% 7%	450
	11th to 20th	Day	7% 2 11% 28% 37% 15%	450
	21st to end	Day	13% 5% 14% 28% 31% 8%	351
November	1st to 10th	Day	12% 1 10% 30% 41% 5%	270
	11th to 20th	Day	11% 4 18% 34% 28% 4	270
	21st to end	Day	11% 3 20% 35% 26% 5%	270
December	1st to 10th	Day	15% 4 26% 29% 24% 2	270
	11th to 20th	Day	19% 7% 23% 36% 16%	270
	21st to end	Day	22% 5% 20% 34% 18% 2	297
January	1st to 10th	Night	17% 10% 30% 29% 12% 2	760
	11th to 20th	Night	13% 11% 26% 33% 17% 2	760
	21st to end	Night	19% 9% 32% 31% 9%	836
February	1st to 10th	Night	16% 9% 27% 34% 13% 1	760
	11th to 20th	Night	17% 9% 28% 29% 17% 1	743
	21st to end	Night	16% 5% 29% 36% 14%	628
March	1st to 10th	Night	14% 5% 26% 37% 17% 1	760
	11th to 20th	Night	11% 5% 26% 32% 22% 4	760
	21st to end	Night	11% 5% 21% 36% 26% 2	698
April	1st to 10th	Night	13% 6% 20% 36% 23% 2	570
	11th to 20th	Night	13% 4 22% 31% 28% 3	533
	21st to end	Night	5% 3 17% 34% 34% 7%	540
May	1st to 10th	Night	8% 2 12% 34% 36% 7%	540
	11th to 20th	Night	6% 2 10% 30% 39% 13%	531
	21st to end	Night	6% 1 7% 18% 49% 18%	584
June	1st to 10th	Night	10% 1 3 18% 50% 17%	540
	11th to 20th	Night	3 1 3 17% 49% 27%	540
	21st to end	Night	8% 3 13% 46% 30%	540
July	1st to 10th	Night	6% 1 3 10% 42% 38%	525
	11th to 20th	Night	3 1 2 6% 37% 50%	522
	21st to end	Night	3 1 2 8% 46% 41%	591
August	1st to 10th	Night	4 1 8% 38% 49%	537
	11th to 20th	Night	7% 1 3 7% 42% 41%	534
	21st to end	Night	9% 2 6% 12% 42% 30%	594
September	1st to 10th	Night	9% 1 4 14% 41% 32%	559
	11th to 20th	Night	11% 3 8% 19% 43% 17%	720
	21st to end	Night	9% 1 8% 22% 45% 15%	720
October	1st to 10th	Night	9% 1 12% 33% 37% 8%	720
	11th to 20th	Night	8% 3 12% 29% 35% 12%	720
	21st to end	Night	11% 5% 18% 30% 33% 5%	792
November	1st to 10th	Night	11% 5% 19% 34% 25% 6%	740
	11th to 20th	Night	12% 8% 20% 35% 23% 3	760
	21st to end	Night	12% 4 26% 34% 20% 4	760
December	1st to 10th	Night	14% 7% 24% 29% 21% 5%	760
	11th to 20th	Night	16% 7% 26% 29% 19% 2	760
	21st to end	Night	20% 9% 23% 31% 16% 1	836

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