Brevard
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brevard 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	13% 6% 2 6% 5% 5% 5% 4 6% 7% 41%	120298
	Night	14% 6% 2 5% 4 4 4 4 5% 7% 45%	118807
Transparency	Day	40% 7% 11% 18% 17% 7%	124064
	Night	38% 6% 11% 18% 19% 8%	123178
Seeing	Day	18% 14% 25% 23% 14% 7%	15958
	Night	18% 10% 24% 27% 18% 4	26015

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	11% 5% 2 4 2 3 2 2 4 6% 58%	4056
	11th to 20th	Day	9% 5% 2 5% 2 3 4 3 3 3 62%	4060
	21st to end	Day	17% 4 2 6% 4 4 3 3 4 5% 49%	4466
February	1st to 10th	Day	14% 5% 2 5% 4 4 4 3 6% 6% 46%	1911
	11th to 20th	Day	18% 7% 2 5% 4 4 4 3 4 6% 43%	1948
	21st to end	Day	15% 7% 2 5% 5% 5% 4 4 5% 5% 42%	1650
March	1st to 10th	Day	18% 7% 2 5% 4 3 4 4 4 5% 42%	4802
	11th to 20th	Day	11% 6% 2 6% 3 3 3 3 4 6% 54%	4980
	21st to end	Day	17% 6% 2 5% 4 3 4 3 5% 5% 45%	5465
April	1st to 10th	Day	12% 5% 2 6% 5% 4 4 5% 7% 7% 45%	2200
	11th to 20th	Day	13% 5% 2 5% 5% 4 4 4 6% 7% 44%	2385
	21st to end	Day	12% 5% 2 5% 4 4 5% 4 5% 7% 47%	2600
May	1st to 10th	Day	11% 7% 3 8% 6% 5% 5% 5% 7% 8% 35%	5862
	11th to 20th	Day	18% 7% 2 7% 5% 6% 6% 5% 7% 8% 28%	5861
	21st to end	Day	13% 5% 2 7% 5% 5% 5% 5% 7% 9% 38%	6433
June	1st to 10th	Day	11% 7% 3 7% 5% 6% 7% 5% 8% 9% 30%	2600
	11th to 20th	Day	8% 6% 2 6% 6% 6% 8% 7% 9% 10% 33%	2600
	21st to end	Day	8% 6% 2 6% 7% 6% 7% 6% 8% 10% 34%	2600
July	1st to 10th	Day	9% 6% 2 7% 7% 7% 6% 6% 9% 11% 31%	4250
	11th to 20th	Day	11% 6% 3 9% 7% 7% 7% 6% 7% 9% 28%	4250
	21st to end	Day	11% 9% 4 12% 9% 9% 9% 6% 8% 8% 16%	4466
August	1st to 10th	Day	13% 7% 3 9% 7% 7% 7% 6% 7% 10% 24%	4104
	11th to 20th	Day	12% 6% 2 8% 6% 6% 6% 5% 7% 11% 30%	4044
	21st to end	Day	8% 4 2 6% 5% 6% 5% 5% 7% 8% 44%	4143
September	1st to 10th	Day	12% 6% 3 7% 6% 6% 6% 5% 7% 8% 35%	2090
	11th to 20th	Day	18% 8% 2 7% 5% 5% 6% 5% 6% 7% 32%	2090
	21st to end	Day	19% 5% 2 6% 4 4 5% 4 5% 7% 39%	2090
October	1st to 10th	Day	16% 5% 1 5% 3 3 3 3 4 6% 50%	2071
	11th to 20th	Day	12% 6% 2 4 2 2 3 2 4 6% 58%	1900
	21st to end	Day	15% 4 2 5% 3 2 3 3 4 5% 57%	2090
November	1st to 10th	Day	13% 6% 1 4 4 2 2 2 4 5% 55%	1862
	11th to 20th	Day	12% 5% 2 4 3 2 4 3 4 6% 55%	1800
	21st to end	Day	14% 4 2 5% 3 3 4 3 4 7% 52%	1800
December	1st to 10th	Day	12% 6% 2 6% 3 4 3 3 4 5% 53%	2930
	11th to 20th	Day	15% 6% 1 5% 3 4 5% 4 5% 6% 45%	3373
	21st to end	Day	20% 5% 1 4 2 3 3 3 4 6% 48%	4466
January	1st to 10th	Night	13% 4 2 4 2 3 3 2 3 4 60%	5889
	11th to 20th	Night	8% 5% 2 5% 4 3 4 3 5% 5% 57%	5900
	21st to end	Night	17% 4 2 4 3 3 4 3 5% 6% 50%	6490
February	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 6% 6% 48%	2485
	11th to 20th	Night	17% 7% 2 5% 4 3 4 4 4 5% 45%	2338
	21st to end	Night	15% 7% 2 5% 4 4 3 4 6% 6% 44%	1980
March	1st to 10th	Night	17% 7% 2 6% 4 4 4 3 5% 5% 42%	5037
	11th to 20th	Night	10% 4 1 4 3 3 4 4 6% 7% 55%	4980
	21st to end	Night	17% 5% 2 5% 4 4 4 3 5% 7% 45%	5467
April	1st to 10th	Night	14% 6% 3 4 3 3 4 3 5% 7% 49%	2200
	11th to 20th	Night	14% 6% 2 4 3 3 3 3 4 6% 52%	1978
	21st to end	Night	12% 5% 1 5% 4 3 3 3 5% 7% 50%	1800
May	1st to 10th	Night	12% 7% 2 7% 5% 6% 5% 5% 6% 9% 37%	4033
	11th to 20th	Night	22% 7% 3 7% 4 4 5% 4 6% 8% 31%	4032
	21st to end	Night	14% 5% 2 5% 4 4 4 3 6% 9% 42%	4421
June	1st to 10th	Night	10% 6% 2 8% 5% 5% 5% 6% 9% 10% 34%	1800
	11th to 20th	Night	9% 5% 2 8% 5% 3 5% 5% 8% 11% 39%	1800
	21st to end	Night	7% 5% 2 6% 5% 5% 5% 4 7% 12% 41%	1800
July	1st to 10th	Night	9% 6% 2 8% 7% 6% 7% 6% 8% 11% 31%	2930
	11th to 20th	Night	8% 6% 3 7% 5% 5% 6% 6% 10% 12% 32%	2930
	21st to end	Night	12% 9% 4 10% 7% 7% 6% 6% 8% 10% 22%	3087
August	1st to 10th	Night	13% 7% 3 7% 5% 6% 6% 5% 8% 9% 30%	2825
	11th to 20th	Night	13% 9% 3 9% 6% 5% 5% 5% 6% 8% 31%	2785
	21st to end	Night	8% 5% 2 6% 4 4 4 4 7% 9% 45%	3460
September	1st to 10th	Night	13% 6% 2 7% 5% 4 6% 5% 6% 8% 38%	2090
	11th to 20th	Night	20% 8% 2 6% 5% 5% 4 3 5% 7% 35%	2090
	21st to end	Night	19% 6% 2 6% 4 3 4 3 5% 7% 42%	2090
October	1st to 10th	Night	16% 5% 2 5% 3 3 3 3 4 6% 49%	2109
	11th to 20th	Night	15% 6% 1 4 3 3 3 3 4 5% 53%	2280
	21st to end	Night	14% 4 1 3 2 3 3 3 3 5% 57%	2508
November	1st to 10th	Night	14% 5% 2 4 3 3 3 3 4 5% 54%	2431
	11th to 20th	Night	14% 6% 2 5% 3 3 3 2 3 6% 53%	2600
	21st to end	Night	14% 4 2 4 3 4 4 4 5% 6% 50%	2600
December	1st to 10th	Night	12% 6% 2 5% 4 3 4 3 4 4 53%	4250
	11th to 20th	Night	16% 7% 2 6% 4 4 3 3 4 5% 46%	4822
	21st to end	Night	21% 6% 2 4 3 3 3 2 5% 5% 46%	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% 2 5% 17% 35% 11%	4057
	11th to 20th	Day	29% 3 4 12% 40% 13%	4060
	21st to end	Day	40% 3 5% 16% 24% 13%	4466
February	1st to 10th	Day	39% 5% 10% 20% 20% 7%	1911
	11th to 20th	Day	42% 6% 8% 16% 21% 7%	1958
	21st to end	Day	44% 6% 7% 13% 21% 9%	1650
March	1st to 10th	Day	43% 4 6% 15% 18% 14%	4802
	11th to 20th	Day	33% 3 6% 14% 24% 21%	4980
	21st to end	Day	41% 3 8% 25% 17% 6%	5465
April	1st to 10th	Day	37% 6% 12% 20% 20% 5%	2200
	11th to 20th	Day	38% 7% 10% 18% 20% 8%	2385
	21st to end	Day	36% 8% 12% 24% 16% 3	2600
May	1st to 10th	Day	46% 9% 14% 17% 12% 2	5897
	11th to 20th	Day	52% 9% 14% 16% 9% 1	5865
	21st to end	Day	41% 8% 14% 18% 16% 3	6447
June	1st to 10th	Day	46% 12% 15% 19% 7% 1	2600
	11th to 20th	Day	40% 14% 19% 17% 9% 2	2600
	21st to end	Day	41% 12% 17% 17% 11% 2	2600
July	1st to 10th	Day	43% 12% 20% 17% 7% 1	4185
	11th to 20th	Day	50% 10% 22% 14% 4 1	4181
	21st to end	Day	61% 12% 14% 8% 4 1	4324
August	1st to 10th	Day	52% 8% 16% 20% 4	4091
	11th to 20th	Day	44% 8% 23% 14% 9% 2	4083
	21st to end	Day	37% 8% 13% 27% 14% 1	4143
September	1st to 10th	Day	43% 11% 12% 17% 13% 3	2090
	11th to 20th	Day	49% 9% 12% 14% 15% 2	2090
	21st to end	Day	44% 6% 12% 17% 15% 6%	2090
October	1st to 10th	Day	30% 4 6% 20% 30% 11%	3448
	11th to 20th	Day	20% 3 6% 17% 24% 30%	3140
	21st to end	Day	30% 3 6% 23% 23% 16%	3428
November	1st to 10th	Day	32% 4 7% 18% 28% 11%	1862
	11th to 20th	Day	32% 4 6% 22% 26% 10%	1800
	21st to end	Day	34% 6% 7% 20% 27% 7%	1800
December	1st to 10th	Day	36% 4 5% 17% 25% 14%	2930
	11th to 20th	Day	40% 4 10% 16% 20% 10%	3370
	21st to end	Day	37% 3 11% 26% 20% 3	4466
January	1st to 10th	Night	30% 2 7% 17% 31% 13%	5889
	11th to 20th	Night	31% 4 6% 13% 35% 12%	5900
	21st to end	Night	36% 3 7% 16% 25% 13%	6490
February	1st to 10th	Night	38% 3 11% 21% 21% 7%	2485
	11th to 20th	Night	42% 5% 7% 18% 21% 7%	2339
	21st to end	Night	41% 6% 9% 15% 21% 8%	1980
March	1st to 10th	Night	43% 4 6% 13% 24% 9%	5037
	11th to 20th	Night	28% 4 7% 18% 24% 19%	4980
	21st to end	Night	40% 3 10% 22% 18% 8%	5467
April	1st to 10th	Night	35% 5% 11% 20% 24% 4	2200
	11th to 20th	Night	33% 5% 10% 22% 23% 7%	1978
	21st to end	Night	34% 8% 13% 24% 19% 2	1800
May	1st to 10th	Night	44% 8% 13% 23% 10% 1	4060
	11th to 20th	Night	50% 8% 16% 17% 9%	4033
	21st to end	Night	37% 9% 15% 23% 13% 2	4429
June	1st to 10th	Night	40% 14% 17% 20% 8% 1	1800
	11th to 20th	Night	37% 11% 21% 22% 9% 1	1800
	21st to end	Night	34% 14% 18% 18% 13% 3	1800
July	1st to 10th	Night	46% 11% 20% 16% 6% 1	2885
	11th to 20th	Night	40% 13% 26% 16% 3 1	2876
	21st to end	Night	54% 13% 16% 12% 4 1	2988
August	1st to 10th	Night	48% 9% 22% 16% 5%	2814
	11th to 20th	Night	50% 8% 18% 13% 10% 1	2812
	21st to end	Night	35% 7% 16% 31% 10% 1	3460
September	1st to 10th	Night	41% 11% 13% 18% 13% 3	2090
	11th to 20th	Night	48% 9% 12% 16% 15% 1	2090
	21st to end	Night	43% 5% 10% 20% 17% 5%	2090
October	1st to 10th	Night	32% 5% 8% 18% 28% 10%	3512
	11th to 20th	Night	22% 3 5% 18% 28% 24%	3779
	21st to end	Night	33% 2 4 21% 25% 15%	4120
November	1st to 10th	Night	33% 5% 9% 18% 25% 11%	2431
	11th to 20th	Night	34% 4 6% 17% 28% 11%	2600
	21st to end	Night	34% 5% 7% 20% 26% 8%	2600
December	1st to 10th	Night	35% 4 6% 19% 25% 10%	4250
	11th to 20th	Night	42% 4 7% 17% 19% 11%	4824
	21st to end	Night	41% 3 12% 20% 20% 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	24% 27% 38% 9% 1	300
	11th to 20th	Day	28% 26% 31% 14% 2	300
	21st to end	Day	26% 31% 34% 6% 2	330
February	1st to 10th	Day	23% 28% 37% 10% 2	300
	11th to 20th	Day	36% 32% 25% 6%	300
	21st to end	Day	32% 35% 27% 6% 1	249
March	1st to 10th	Day	26% 25% 28% 16% 5%	440
	11th to 20th	Day	26% 23% 32% 15% 4 1	500
	21st to end	Day	26% 25% 29% 16% 4 1	550
April	1st to 10th	Day	24% 20% 29% 19% 7% 1	500
	11th to 20th	Day	18% 21% 30% 20% 10% 1	492
	21st to end	Day	20% 15% 28% 22% 11% 4	500
May	1st to 10th	Day	17% 19% 32% 19% 9% 5%	503
	11th to 20th	Day	20% 12% 24% 26% 12% 6%	527
	21st to end	Day	18% 10% 20% 27% 14% 10%	573
June	1st to 10th	Day	13% 9% 22% 31% 16% 9%	530
	11th to 20th	Day	12% 5% 22% 26% 22% 13%	530
	21st to end	Day	9% 5% 21% 34% 18% 13%	530
July	1st to 10th	Day	8% 3 17% 26% 29% 16%	525
	11th to 20th	Day	10% 1 12% 29% 27% 20%	524
	21st to end	Day	10% 2 14% 31% 24% 20%	532
August	1st to 10th	Day	18% 4 19% 25% 18% 17%	486
	11th to 20th	Day	11% 3 15% 34% 23% 14%	479
	21st to end	Day	14% 3 12% 29% 27% 16%	539
September	1st to 10th	Day	9% 4 16% 32% 27% 12%	490
	11th to 20th	Day	19% 4 16% 28% 25% 8%	490
	21st to end	Day	21% 8% 18% 30% 20% 4	490
October	1st to 10th	Day	20% 7% 23% 26% 17% 7%	490
	11th to 20th	Day	13% 13% 28% 28% 14% 3	490
	21st to end	Day	20% 10% 24% 31% 12% 3	539
November	1st to 10th	Day	23% 13% 28% 24% 11% 2	400
	11th to 20th	Day	17% 21% 38% 21% 3	300
	21st to end	Day	13% 19% 44% 17% 6% 1	300
December	1st to 10th	Day	26% 25% 35% 12% 2	300
	11th to 20th	Day	21% 19% 41% 15% 4	300
	21st to end	Day	28% 18% 38% 11% 5% 1	330
January	1st to 10th	Night	21% 18% 34% 22% 5%	800
	11th to 20th	Night	19% 16% 38% 22% 5%	800
	21st to end	Night	20% 16% 38% 23% 3	880
February	1st to 10th	Night	18% 15% 35% 28% 4	800
	11th to 20th	Night	23% 17% 38% 19% 2	783
	21st to end	Night	22% 20% 33% 21% 3	660
March	1st to 10th	Night	19% 19% 33% 24% 5%	800
	11th to 20th	Night	21% 16% 31% 24% 7% 1	800
	21st to end	Night	22% 15% 34% 20% 8%	880
April	1st to 10th	Night	19% 17% 31% 24% 8%	800
	11th to 20th	Night	20% 15% 26% 27% 12% 1	682
	21st to end	Night	15% 10% 26% 32% 18% 1	600
May	1st to 10th	Night	15% 10% 29% 27% 18% 1	600
	11th to 20th	Night	18% 6% 23% 29% 22% 2	591
	21st to end	Night	16% 4 15% 28% 30% 7%	650
June	1st to 10th	Night	12% 5% 15% 33% 30% 5%	600
	11th to 20th	Night	11% 2 16% 28% 32% 11%	600
	21st to end	Night	8% 2 12% 31% 39% 8%	600
July	1st to 10th	Night	11% 2 10% 22% 46% 9%	585
	11th to 20th	Night	11% 2 7% 22% 45% 13%	582
	21st to end	Night	8% 2 9% 26% 43% 12%	624
August	1st to 10th	Night	16% 3 10% 25% 37% 11%	567
	11th to 20th	Night	16% 3 7% 29% 36% 9%	564
	21st to end	Night	14% 2 9% 25% 41% 10%	671
September	1st to 10th	Night	14% 3 13% 28% 34% 8%	760
	11th to 20th	Night	23% 4 13% 23% 30% 7%	760
	21st to end	Night	21% 3 17% 32% 23% 3	760
October	1st to 10th	Night	18% 7% 18% 25% 24% 8%	760
	11th to 20th	Night	18% 8% 24% 29% 19% 3	760
	21st to end	Night	18% 9% 21% 34% 16% 3	836
November	1st to 10th	Night	17% 6% 23% 33% 18% 3	780
	11th to 20th	Night	17% 13% 25% 32% 12% 1	800
	21st to end	Night	17% 12% 27% 31% 12% 2	800
December	1st to 10th	Night	21% 14% 28% 29% 8%	800
	11th to 20th	Night	19% 11% 32% 30% 7% 1	800
	21st to end	Night	26% 13% 28% 27% 6%	880

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