Fort Lauderdale
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Lauderdale clear sky chart from 2005-11-06 to 2025-09-04.

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	6% 5% 2 7% 6% 6% 7% 6% 9% 11% 35%	125373
	Night	6% 5% 2 7% 5% 5% 6% 5% 8% 10% 41%	123350
Transparency	Day	38% 11% 19% 20% 10% 2	129026
	Night	35% 10% 21% 21% 11% 2	127766
Seeing	Day	7% 4 16% 29% 27% 17%	17187
	Night	7% 3 15% 32% 31% 12%	27295

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	7% 6% 2 5% 3 4 4 4 7% 10% 47%	4056
	11th to 20th	Day	16% 8% 4 9% 5% 6% 5% 4 7% 9% 27%	4060
	21st to end	Day	10% 8% 3 8% 5% 5% 5% 5% 7% 8% 38%	4490
February	1st to 10th	Day	9% 6% 3 6% 5% 5% 6% 4 7% 10% 39%	2000
	11th to 20th	Day	7% 5% 2 4 4 5% 5% 4 8% 10% 47%	2086
	21st to end	Day	6% 5% 2 6% 5% 6% 5% 6% 7% 10% 42%	1815
March	1st to 10th	Day	5% 4 2 7% 5% 6% 7% 5% 9% 9% 39%	4935
	11th to 20th	Day	4 2 1 3 3 3 4 4 7% 9% 59%	4980
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 5% 8% 10% 41%	5465
April	1st to 10th	Day	3 4 1 5% 5% 4 6% 6% 9% 13% 43%	2200
	11th to 20th	Day	6% 5% 3 6% 5% 5% 6% 5% 8% 10% 40%	2284
	21st to end	Day	6% 3 2 5% 4 6% 6% 6% 9% 11% 42%	2400
May	1st to 10th	Day	2 2 1 3 3 4 5% 5% 9% 12% 54%	5405
	11th to 20th	Day	5% 5% 2 6% 5% 5% 5% 5% 8% 10% 43%	5404
	21st to end	Day	4 4 2 6% 5% 6% 8% 7% 11% 13% 35%	6429
June	1st to 10th	Day	12% 8% 4 12% 8% 8% 8% 6% 9% 8% 16%	2600
	11th to 20th	Day	7% 6% 4 10% 9% 9% 9% 7% 9% 11% 20%	2600
	21st to end	Day	5% 8% 3 10% 7% 8% 8% 8% 10% 12% 21%	2600
July	1st to 10th	Day	6% 7% 3 8% 7% 6% 7% 6% 10% 14% 26%	5900
	11th to 20th	Day	5% 5% 3 8% 6% 7% 8% 7% 10% 13% 28%	5900
	21st to end	Day	2 3 1 5% 5% 5% 6% 6% 11% 17% 38%	6424
August	1st to 10th	Day	4 5% 2 11% 8% 8% 9% 8% 12% 13% 21%	4116
	11th to 20th	Day	4 4 2 7% 5% 7% 9% 8% 12% 16% 27%	3850
	21st to end	Day	5% 4 2 8% 6% 8% 10% 8% 13% 18% 20%	4062
September	1st to 10th	Day	7% 5% 3 10% 8% 8% 11% 8% 9% 11% 19%	2123
	11th to 20th	Day	6% 6% 3 11% 9% 9% 9% 8% 10% 11% 20%	2090
	21st to end	Day	10% 9% 3 11% 7% 8% 10% 6% 8% 9% 18%	2090
October	1st to 10th	Day	9% 6% 4 11% 9% 7% 7% 7% 11% 10% 20%	1986
	11th to 20th	Day	9% 7% 3 8% 7% 7% 8% 6% 10% 11% 24%	1900
	21st to end	Day	11% 7% 3 8% 6% 5% 6% 4 7% 10% 33%	2090
November	1st to 10th	Day	7% 7% 2 7% 5% 6% 5% 6% 9% 10% 36%	1957
	11th to 20th	Day	9% 7% 3 9% 7% 7% 6% 5% 8% 9% 30%	2000
	21st to end	Day	8% 5% 2 8% 6% 5% 6% 6% 8% 8% 38%	2000
December	1st to 10th	Day	6% 4 2 5% 4 4 5% 5% 7% 9% 50%	3237
	11th to 20th	Day	9% 6% 2 7% 6% 5% 6% 5% 8% 11% 35%	3373
	21st to end	Day	11% 7% 3 9% 6% 6% 7% 6% 8% 9% 27%	4466
January	1st to 10th	Night	6% 6% 2 6% 5% 5% 6% 5% 7% 10% 42%	5889
	11th to 20th	Night	15% 9% 3 9% 5% 6% 5% 4 5% 7% 31%	5900
	21st to end	Night	10% 9% 3 7% 5% 5% 5% 4 5% 7% 41%	6462
February	1st to 10th	Night	8% 6% 2 5% 4 4 4 4 7% 10% 45%	2400
	11th to 20th	Night	6% 4 2 4 4 4 4 4 6% 8% 54%	2197
	21st to end	Night	6% 2 2 5% 4 4 5% 4 6% 8% 53%	1815
March	1st to 10th	Night	4 4 2 7% 4 5% 5% 4 6% 9% 50%	4918
	11th to 20th	Night	4 3 1 4 4 4 3 3 5% 10% 60%	4980
	21st to end	Night	6% 4 1 6% 5% 5% 5% 5% 7% 9% 48%	5467
April	1st to 10th	Night	4 3 1 4 3 4 4 4 8% 10% 55%	2200
	11th to 20th	Night	5% 3 2 5% 5% 5% 5% 5% 7% 9% 49%	2061
	21st to end	Night	5% 5% 2 4 4 3 5% 4 7% 11% 50%	2000
May	1st to 10th	Night	2 2 1 3 3 3 4 4 8% 11% 60%	4490
	11th to 20th	Night	5% 5% 2 5% 4 4 4 4 8% 9% 50%	4490
	21st to end	Night	4 4 2 6% 4 5% 6% 7% 9% 12% 40%	4451
June	1st to 10th	Night	11% 8% 3 9% 6% 8% 7% 5% 9% 9% 25%	1800
	11th to 20th	Night	6% 6% 3 6% 6% 5% 6% 6% 8% 14% 33%	1800
	21st to end	Night	4 5% 3 7% 7% 6% 7% 7% 10% 14% 31%	1800
July	1st to 10th	Night	5% 6% 3 8% 7% 6% 6% 5% 8% 11% 35%	4058
	11th to 20th	Night	4 4 2 7% 5% 6% 6% 5% 9% 13% 38%	4057
	21st to end	Night	2 3 2 5% 4 4 5% 5% 8% 13% 50%	4427
August	1st to 10th	Night	4 4 2 7% 6% 6% 8% 7% 10% 13% 33%	2999
	11th to 20th	Night	2 3 2 6% 6% 5% 7% 6% 9% 14% 39%	3197
	21st to end	Night	5% 4 2 7% 5% 7% 8% 8% 13% 18% 24%	3815
September	1st to 10th	Night	5% 6% 3 8% 7% 8% 8% 7% 10% 11% 27%	2124
	11th to 20th	Night	7% 6% 3 9% 7% 7% 7% 7% 9% 12% 27%	2090
	21st to end	Night	8% 8% 3 10% 7% 8% 8% 6% 8% 9% 24%	2090
October	1st to 10th	Night	8% 6% 4 9% 7% 8% 8% 7% 8% 11% 24%	2194
	11th to 20th	Night	8% 7% 3 7% 5% 6% 6% 5% 8% 12% 33%	2280
	21st to end	Night	10% 6% 3 7% 5% 5% 5% 5% 7% 8% 38%	2508
November	1st to 10th	Night	9% 5% 2 6% 5% 5% 6% 4 6% 11% 41%	2341
	11th to 20th	Night	8% 7% 2 8% 7% 6% 6% 5% 6% 9% 36%	2400
	21st to end	Night	7% 6% 2 7% 5% 4 6% 4 7% 8% 42%	2400
December	1st to 10th	Night	6% 5% 2 5% 4 4 4 4 6% 8% 52%	3938
	11th to 20th	Night	11% 8% 3 8% 5% 5% 5% 4 7% 9% 35%	4822
	21st to end	Night	9% 8% 4 10% 7% 6% 6% 5% 8% 9% 28%	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	30% 6% 11% 27% 20% 6%	4057
	11th to 20th	Day	51% 8% 14% 18% 7% 2	4060
	21st to end	Day	42% 6% 8% 28% 12% 4	4490
February	1st to 10th	Day	36% 9% 13% 23% 15% 5%	2000
	11th to 20th	Day	28% 7% 13% 27% 20% 6%	2096
	21st to end	Day	32% 9% 13% 17% 22% 7%	1815
March	1st to 10th	Day	33% 12% 13% 18% 20% 4	4935
	11th to 20th	Day	18% 8% 14% 29% 20% 11%	4980
	21st to end	Day	34% 7% 13% 27% 15% 5%	5465
April	1st to 10th	Day	26% 9% 21% 25% 17% 3	2200
	11th to 20th	Day	34% 9% 17% 19% 16% 5%	2284
	21st to end	Day	31% 9% 13% 24% 19% 3	2400
May	1st to 10th	Day	18% 7% 20% 34% 18% 3	5437
	11th to 20th	Day	30% 10% 21% 32% 7% 1	5408
	21st to end	Day	32% 10% 23% 28% 8%	6443
June	1st to 10th	Day	59% 14% 15% 10% 2	2600
	11th to 20th	Day	50% 18% 17% 14% 2	2600
	21st to end	Day	49% 18% 23% 9%	2600
July	1st to 10th	Day	43% 13% 31% 12%	5835
	11th to 20th	Day	43% 12% 31% 13% 1	5831
	21st to end	Day	30% 12% 34% 23% 1	6240
August	1st to 10th	Day	47% 17% 27% 9% 1	4103
	11th to 20th	Day	38% 14% 31% 17% 1	3886
	21st to end	Day	42% 15% 36% 6% 1	4062
September	1st to 10th	Day	48% 22% 19% 10%	2123
	11th to 20th	Day	51% 19% 20% 8% 2	2090
	21st to end	Day	55% 16% 14% 9% 5% 1	2090
October	1st to 10th	Day	50% 12% 19% 13% 5% 1	3298
	11th to 20th	Day	49% 10% 15% 16% 9% 1	3140
	21st to end	Day	39% 6% 11% 27% 15% 3	3428
November	1st to 10th	Day	35% 11% 15% 17% 16% 6%	1957
	11th to 20th	Day	46% 9% 11% 16% 13% 5%	2000
	21st to end	Day	38% 9% 14% 16% 19% 4	2000
December	1st to 10th	Day	29% 6% 13% 28% 19% 4	3237
	11th to 20th	Day	39% 6% 13% 20% 18% 4	3370
	21st to end	Day	47% 8% 16% 15% 13% 1	4466
January	1st to 10th	Night	34% 8% 13% 25% 17% 4	5889
	11th to 20th	Night	51% 6% 17% 16% 8% 2	5900
	21st to end	Night	40% 7% 10% 28% 12% 4	6462
February	1st to 10th	Night	31% 8% 15% 26% 17% 3	2400
	11th to 20th	Night	25% 7% 13% 28% 21% 6%	2198
	21st to end	Night	25% 8% 13% 23% 24% 6%	1815
March	1st to 10th	Night	28% 9% 14% 21% 24% 4	4918
	11th to 20th	Night	19% 9% 19% 26% 17% 10%	4980
	21st to end	Night	29% 7% 15% 27% 19% 3	5467
April	1st to 10th	Night	20% 9% 20% 32% 16% 4	2200
	11th to 20th	Night	26% 10% 19% 21% 20% 5%	2061
	21st to end	Night	25% 9% 17% 27% 19% 4	2000
May	1st to 10th	Night	16% 6% 25% 37% 13% 2	4520
	11th to 20th	Night	26% 10% 19% 33% 11% 1	4491
	21st to end	Night	29% 11% 28% 27% 5%	4459
June	1st to 10th	Night	49% 14% 23% 12% 2	1800
	11th to 20th	Night	38% 16% 26% 18% 3	1800
	21st to end	Night	37% 20% 31% 11% 1	1800
July	1st to 10th	Night	40% 11% 36% 12%	4015
	11th to 20th	Night	35% 12% 40% 12%	4006
	21st to end	Night	25% 11% 40% 21% 3	4297
August	1st to 10th	Night	37% 16% 28% 16% 2	2988
	11th to 20th	Night	31% 14% 34% 21%	3227
	21st to end	Night	39% 17% 37% 6% 1	3815
September	1st to 10th	Night	42% 22% 25% 11% 1	2124
	11th to 20th	Night	44% 20% 23% 11% 2	2090
	21st to end	Night	50% 18% 15% 12% 5%	2090
October	1st to 10th	Night	50% 13% 19% 14% 4 1	3662
	11th to 20th	Night	47% 7% 18% 16% 11% 1	3779
	21st to end	Night	39% 6% 12% 27% 14% 3	4120
November	1st to 10th	Night	34% 7% 18% 19% 16% 6%	2341
	11th to 20th	Night	39% 9% 14% 21% 12% 5%	2400
	21st to end	Night	34% 9% 17% 18% 17% 5%	2400
December	1st to 10th	Night	28% 7% 15% 29% 18% 3	3938
	11th to 20th	Night	43% 5% 12% 20% 14% 5%	4824
	21st to end	Night	46% 9% 16% 15% 12% 2	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	7% 10% 32% 39% 11% 1	300
	11th to 20th	Day	15% 10% 29% 31% 14% 2	300
	21st to end	Day	11% 8% 40% 34% 7% 1	330
February	1st to 10th	Day	6% 9% 26% 40% 17% 2	300
	11th to 20th	Day	6% 6% 27% 38% 19% 4	439
	21st to end	Day	5% 5% 23% 38% 28% 1	414
March	1st to 10th	Day	4 7% 32% 38% 16% 3	500
	11th to 20th	Day	6% 7% 26% 38% 21% 2	500
	21st to end	Day	5% 4 28% 37% 23% 4	550
April	1st to 10th	Day	3 3 31% 40% 18% 5%	500
	11th to 20th	Day	5% 4 28% 37% 21% 5%	492
	21st to end	Day	5% 3 18% 43% 25% 6%	500
May	1st to 10th	Day	4 2 16% 39% 30% 9%	503
	11th to 20th	Day	8% 3 15% 34% 28% 11%	527
	21st to end	Day	8% 3 11% 22% 35% 22%	573
June	1st to 10th	Day	10% 3 9% 26% 32% 19%	530
	11th to 20th	Day	8% 2 8% 22% 31% 29%	530
	21st to end	Day	4 2 5% 17% 31% 42%	530
July	1st to 10th	Day	4 1 3 13% 36% 42%	525
	11th to 20th	Day	6% 4 15% 38% 37%	524
	21st to end	Day	3 1 4 18% 30% 43%	576
August	1st to 10th	Day	5% 1 6% 16% 34% 39%	526
	11th to 20th	Day	4 1 3 16% 36% 40%	519
	21st to end	Day	8% 1 5% 20% 34% 32%	583
September	1st to 10th	Day	7% 1 4 16% 34% 38%	502
	11th to 20th	Day	5% 2 6% 16% 32% 39%	490
	21st to end	Day	9% 3 7% 22% 32% 27%	490
October	1st to 10th	Day	12% 2 10% 30% 34% 11%	490
	11th to 20th	Day	10% 3 14% 32% 28% 11%	490
	21st to end	Day	9% 5% 19% 32% 28% 7%	539
November	1st to 10th	Day	8% 5% 19% 37% 25% 6%	495
	11th to 20th	Day	10% 5% 23% 34% 24% 4	500
	21st to end	Day	6% 4 24% 40% 24% 2	500
December	1st to 10th	Day	9% 5% 20% 39% 24% 3	490
	11th to 20th	Day	8% 5% 26% 35% 22% 4	300
	21st to end	Day	10% 9% 25% 34% 18% 5%	330
January	1st to 10th	Night	8% 7% 23% 38% 23% 2	800
	11th to 20th	Night	10% 6% 27% 37% 20% 1	800
	21st to end	Night	8% 7% 28% 43% 14%	880
February	1st to 10th	Night	9% 5% 23% 40% 21% 2	800
	11th to 20th	Night	6% 5% 26% 40% 22% 1	783
	21st to end	Night	6% 3 23% 47% 20% 1	660
March	1st to 10th	Night	5% 4 31% 40% 19% 1	800
	11th to 20th	Night	7% 4 22% 45% 22% 2	800
	21st to end	Night	5% 5% 24% 44% 20% 1	880
April	1st to 10th	Night	4 3 18% 50% 25% 2	800
	11th to 20th	Night	6% 4 22% 44% 24% 1	791
	21st to end	Night	7% 2 17% 47% 25% 2	800
May	1st to 10th	Night	4 1 13% 46% 34% 3	800
	11th to 20th	Night	8% 2 16% 41% 32% 2	789
	21st to end	Night	7% 2 7% 27% 46% 11%	667
June	1st to 10th	Night	11% 2 5% 24% 43% 16%	600
	11th to 20th	Night	7% 1 3 16% 46% 27%	600
	21st to end	Night	4 1 3 13% 41% 38%	600
July	1st to 10th	Night	5% 1 2 11% 41% 41%	585
	11th to 20th	Night	4 1 3 12% 40% 41%	582
	21st to end	Night	3 1 10% 42% 44%	657
August	1st to 10th	Night	7% 2 11% 45% 34%	642
	11th to 20th	Night	3 1 3 11% 45% 37%	790
	21st to end	Night	9% 1 5% 17% 39% 29%	880
September	1st to 10th	Night	7% 1 5% 14% 40% 33%	773
	11th to 20th	Night	9% 2 5% 16% 39% 29%	760
	21st to end	Night	10% 2 8% 18% 39% 24%	760
October	1st to 10th	Night	10% 1 10% 33% 36% 10%	760
	11th to 20th	Night	11% 3 11% 28% 40% 9%	760
	21st to end	Night	13% 2 16% 35% 28% 6%	836
November	1st to 10th	Night	9% 3 24% 32% 28% 4	780
	11th to 20th	Night	10% 3 19% 33% 31% 4	800
	21st to end	Night	8% 3 20% 43% 24% 2	800
December	1st to 10th	Night	7% 3 19% 38% 30% 3	800
	11th to 20th	Night	9% 6% 21% 33% 28% 4	800
	21st to end	Night	8% 5% 22% 37% 27% 2	880

Page generated at 2025-09-01 01:51:04. Version ac07

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