Redcliffe Plantation State Historic Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Redcliffe Plantation State Historic Site clear sky chart from 2005-11-06 to 2025-12-18.

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	12% 6% 2 6% 4 4 5% 4 6% 8% 42%	127091
	Night	13% 6% 2 6% 4 4 4 4 6% 8% 44%	123939
Transparency	Day	24% 40% 8% 12% 12% 4	130789
	Night	23% 39% 7% 11% 13% 5%	128310
Seeing	Day	14% 8% 21% 24% 21% 12%	16741
	Night	14% 6% 22% 32% 22% 3	26800

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	15% 5% 1 4 3 3 3 2 5% 6% 53%	4056
	11th to 20th	Day	13% 5% 2 4 3 3 3 2 4 6% 56%	4060
	21st to end	Day	15% 7% 2 6% 4 4 3 2 5% 6% 45%	4466
February	1st to 10th	Day	14% 7% 3 6% 4 4 5% 4 6% 7% 41%	1903
	11th to 20th	Day	20% 7% 2 6% 3 2 3 3 4 6% 44%	1948
	21st to end	Day	17% 6% 2 5% 4 4 4 4 4 5% 45%	1666
March	1st to 10th	Day	20% 8% 3 7% 4 3 4 3 4 5% 39%	4935
	11th to 20th	Day	8% 4 1 5% 3 3 4 3 5% 7% 56%	4980
	21st to end	Day	15% 7% 3 6% 4 4 3 3 3 5% 46%	5465
April	1st to 10th	Day	9% 6% 2 5% 4 4 4 3 5% 7% 50%	2200
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 6% 7% 49%	2284
	21st to end	Day	7% 4 1 5% 4 4 5% 4 6% 9% 52%	2584
May	1st to 10th	Day	11% 6% 2 6% 4 5% 5% 4 6% 10% 41%	5862
	11th to 20th	Day	17% 7% 3 7% 4 5% 5% 4 7% 9% 32%	5861
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 4 7% 8% 43%	6433
June	1st to 10th	Day	10% 6% 2 7% 5% 6% 5% 5% 7% 10% 36%	2600
	11th to 20th	Day	6% 4 2 5% 4 5% 7% 6% 7% 10% 43%	2600
	21st to end	Day	6% 4 2 6% 6% 6% 6% 6% 9% 12% 38%	2600
July	1st to 10th	Day	11% 6% 3 8% 6% 6% 7% 6% 9% 10% 26%	5900
	11th to 20th	Day	4 3 2 6% 5% 6% 7% 6% 10% 15% 36%	5900
	21st to end	Day	7% 6% 3 8% 6% 6% 7% 6% 10% 12% 28%	6424
August	1st to 10th	Day	18% 7% 3 7% 5% 6% 6% 6% 8% 10% 24%	4234
	11th to 20th	Day	8% 5% 2 6% 5% 6% 6% 5% 8% 11% 37%	4174
	21st to end	Day	8% 5% 2 5% 5% 4 5% 4 7% 11% 45%	4203
September	1st to 10th	Day	7% 5% 2 7% 5% 5% 6% 5% 7% 9% 41%	2200
	11th to 20th	Day	14% 5% 3 6% 5% 4 5% 4 6% 8% 42%	2200
	21st to end	Day	15% 7% 2 7% 4 4 4 4 4 6% 42%	2200
October	1st to 10th	Day	11% 6% 3 7% 4 4 4 3 4 5% 50%	2145
	11th to 20th	Day	11% 4 1 4 3 3 2 2 4 6% 59%	2000
	21st to end	Day	12% 4 2 5% 3 4 3 3 4 4 57%	2200
November	1st to 10th	Day	12% 6% 2 5% 3 3 3 3 4 5% 53%	2057
	11th to 20th	Day	14% 6% 2 3 3 2 2 2 3 5% 56%	1939
	21st to end	Day	13% 5% 1 5% 5% 4 3 3 5% 6% 49%	1890
December	1st to 10th	Day	12% 5% 2 6% 4 4 4 4 5% 6% 49%	3020
	11th to 20th	Day	14% 7% 2 5% 4 4 4 3 4 6% 47%	3436
	21st to end	Day	21% 7% 2 5% 3 3 3 3 5% 5% 45%	4466
January	1st to 10th	Night	12% 5% 2 4 3 3 3 3 4 5% 56%	5889
	11th to 20th	Night	12% 6% 2 5% 4 4 4 4 6% 7% 47%	5900
	21st to end	Night	16% 8% 3 6% 4 3 4 3 4 5% 45%	6490
February	1st to 10th	Night	15% 6% 2 5% 4 4 4 3 5% 6% 45%	2495
	11th to 20th	Night	18% 7% 2 6% 4 4 3 2 4 5% 45%	2338
	21st to end	Night	13% 7% 3 5% 4 4 5% 3 5% 7% 46%	1962
March	1st to 10th	Night	20% 7% 2 6% 4 4 4 3 5% 6% 39%	4918
	11th to 20th	Night	10% 3 2 4 3 3 4 4 6% 7% 55%	4980
	21st to end	Night	15% 5% 2 5% 4 4 4 3 5% 6% 48%	5467
April	1st to 10th	Night	11% 4 2 5% 4 5% 5% 3 5% 7% 49%	2200
	11th to 20th	Night	12% 4 2 5% 3 4 4 3 5% 8% 51%	2063
	21st to end	Night	8% 4 1 4 5% 4 4 4 5% 8% 53%	1831
May	1st to 10th	Night	9% 6% 3 7% 5% 5% 5% 4 7% 10% 39%	4033
	11th to 20th	Night	17% 6% 2 5% 4 4 5% 4 6% 10% 36%	4032
	21st to end	Night	10% 5% 2 6% 4 4 5% 3 7% 8% 47%	4421
June	1st to 10th	Night	10% 7% 3 6% 5% 6% 6% 6% 8% 10% 34%	1800
	11th to 20th	Night	7% 5% 2 6% 6% 5% 6% 4 8% 11% 41%	1800
	21st to end	Night	7% 4 2 6% 6% 6% 6% 6% 10% 14% 34%	1800
July	1st to 10th	Night	13% 8% 3 9% 6% 7% 6% 6% 7% 10% 25%	4058
	11th to 20th	Night	5% 5% 3 7% 6% 6% 7% 6% 10% 15% 31%	4057
	21st to end	Night	10% 7% 3 9% 7% 6% 7% 6% 8% 12% 25%	4427
August	1st to 10th	Night	19% 6% 3 8% 6% 6% 6% 6% 9% 11% 21%	2915
	11th to 20th	Night	10% 5% 2 7% 5% 5% 6% 5% 8% 10% 35%	2875
	21st to end	Night	6% 5% 2 5% 4 5% 4 4 6% 11% 48%	3640
September	1st to 10th	Night	9% 5% 2 7% 5% 5% 5% 5% 8% 9% 40%	2200
	11th to 20th	Night	10% 8% 3 7% 6% 5% 5% 4 5% 6% 42%	2200
	21st to end	Night	14% 6% 2 6% 5% 5% 5% 4 6% 7% 42%	2200
October	1st to 10th	Night	12% 5% 2 6% 4 4 4 3 4 6% 51%	2255
	11th to 20th	Night	12% 4 2 4 3 2 3 2 4 4 60%	2400
	21st to end	Night	11% 5% 1 5% 3 3 3 3 4 5% 57%	2640
November	1st to 10th	Night	11% 5% 2 4 3 4 3 3 5% 4 56%	2461
	11th to 20th	Night	15% 6% 2 4 3 3 3 2 4 5% 53%	2678
	21st to end	Night	13% 5% 2 5% 3 3 4 4 5% 7% 50%	2730
December	1st to 10th	Night	13% 6% 2 5% 3 3 3 2 4 5% 55%	4380
	11th to 20th	Night	17% 7% 2 5% 4 3 3 2 4 5% 47%	4914
	21st to end	Night	20% 7% 2 5% 3 3 4 3 4 5% 43%	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	23% 27% 4 15% 24% 6%	4057
	11th to 20th	Day	21% 26% 3 13% 27% 9%	4060
	21st to end	Day	29% 29% 4 14% 16% 9%	4466
February	1st to 10th	Day	16% 62% 4 10% 6% 3	1903
	11th to 20th	Day	18% 61% 3 7% 9% 2	1958
	21st to end	Day	17% 61% 3 5% 8% 5%	1666
March	1st to 10th	Day	38% 30% 5% 5% 16% 5%	4935
	11th to 20th	Day	18% 29% 5% 11% 20% 17%	4980
	21st to end	Day	31% 28% 3 12% 17% 8%	5465
April	1st to 10th	Day	14% 62% 4 9% 8% 4	2200
	11th to 20th	Day	15% 63% 5% 8% 6% 4	2284
	21st to end	Day	12% 63% 5% 10% 8% 2	2584
May	1st to 10th	Day	28% 33% 12% 19% 7% 1	5897
	11th to 20th	Day	37% 32% 12% 13% 6%	5865
	21st to end	Day	26% 32% 10% 12% 18% 1	6447
June	1st to 10th	Day	16% 64% 8% 7% 4 1	2600
	11th to 20th	Day	10% 65% 10% 9% 6%	2600
	21st to end	Day	13% 64% 10% 9% 4	2600
July	1st to 10th	Day	35% 33% 16% 15% 2	5835
	11th to 20th	Day	21% 37% 27% 14% 1	5831
	21st to end	Day	32% 35% 16% 13% 4	6240
August	1st to 10th	Day	38% 40% 13% 8%	4221
	11th to 20th	Day	20% 41% 12% 17% 10% 1	4213
	21st to end	Day	12% 38% 10% 28% 11% 1	4203
September	1st to 10th	Day	13% 61% 8% 9% 8% 2	2200
	11th to 20th	Day	17% 59% 6% 9% 7% 2	2200
	21st to end	Day	19% 58% 8% 8% 6% 1	2200
October	1st to 10th	Day	21% 36% 5% 9% 23% 7%	3496
	11th to 20th	Day	7% 35% 3 8% 21% 27%	3240
	21st to end	Day	13% 36% 3 15% 25% 9%	3538
November	1st to 10th	Day	19% 54% 4 6% 12% 5%	2057
	11th to 20th	Day	17% 54% 4 10% 11% 5%	1939
	21st to end	Day	15% 55% 4 11% 11% 4	1890
December	1st to 10th	Day	23% 35% 4 11% 21% 5%	3020
	11th to 20th	Day	25% 31% 6% 16% 17% 5%	3433
	21st to end	Day	32% 27% 5% 18% 17% 1	4466
January	1st to 10th	Night	21% 27% 4 12% 28% 7%	5889
	11th to 20th	Night	25% 28% 4 13% 25% 6%	5900
	21st to end	Night	30% 29% 3 9% 22% 7%	6490
February	1st to 10th	Night	14% 62% 4 9% 9% 3	2495
	11th to 20th	Night	20% 61% 2 7% 8% 2	2339
	21st to end	Night	17% 62% 3 5% 6% 7%	1962
March	1st to 10th	Night	36% 30% 7% 8% 14% 5%	4918
	11th to 20th	Night	18% 29% 4 8% 22% 18%	4980
	21st to end	Night	26% 29% 5% 12% 16% 12%	5467
April	1st to 10th	Night	15% 63% 4 7% 7% 5%	2200
	11th to 20th	Night	14% 63% 4 9% 7% 4	2063
	21st to end	Night	12% 63% 5% 11% 7% 2	1831
May	1st to 10th	Night	29% 34% 12% 18% 8% 1	4060
	11th to 20th	Night	32% 31% 16% 14% 7%	4033
	21st to end	Night	24% 32% 11% 16% 16% 2	4429
June	1st to 10th	Night	18% 64% 7% 6% 4 1	1800
	11th to 20th	Night	14% 63% 9% 8% 5% 1	1800
	21st to end	Night	12% 66% 10% 8% 4	1800
July	1st to 10th	Night	40% 33% 15% 10% 1	4015
	11th to 20th	Night	28% 35% 26% 11% 1	4006
	21st to end	Night	40% 33% 13% 11% 3	4297
August	1st to 10th	Night	40% 42% 12% 6% 1	2904
	11th to 20th	Night	22% 42% 15% 15% 6% 1	2902
	21st to end	Night	11% 38% 12% 28% 11% 1	3640
September	1st to 10th	Night	14% 60% 7% 10% 6% 2	2200
	11th to 20th	Night	19% 58% 5% 9% 7% 1	2200
	21st to end	Night	17% 59% 9% 10% 5% 1	2200
October	1st to 10th	Night	22% 37% 7% 10% 19% 6%	3684
	11th to 20th	Night	7% 35% 2 8% 15% 32%	3899
	21st to end	Night	12% 35% 3 12% 24% 14%	4252
November	1st to 10th	Night	18% 54% 4 7% 12% 4	2461
	11th to 20th	Night	17% 54% 3 7% 12% 6%	2678
	21st to end	Night	14% 55% 4 9% 12% 5%	2730
December	1st to 10th	Night	22% 34% 3 9% 25% 6%	4380
	11th to 20th	Night	27% 31% 8% 13% 14% 6%	4916
	21st to end	Night	33% 28% 3 17% 18% 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	19% 18% 43% 17% 3	300
	11th to 20th	Day	20% 17% 35% 22% 6%	300
	21st to end	Day	21% 23% 37% 15% 4 1	330
February	1st to 10th	Day	18% 15% 41% 20% 6%	300
	11th to 20th	Day	30% 18% 35% 15% 2	300
	21st to end	Day	22% 20% 34% 18% 6%	265
March	1st to 10th	Day	20% 13% 30% 26% 11% 1	500
	11th to 20th	Day	14% 14% 38% 26% 8% 1	500
	21st to end	Day	18% 13% 37% 22% 9% 1	550
April	1st to 10th	Day	13% 16% 31% 26% 13% 1	500
	11th to 20th	Day	13% 11% 25% 27% 19% 6%	492
	21st to end	Day	9% 11% 22% 28% 21% 9%	500
May	1st to 10th	Day	9% 11% 24% 30% 19% 7%	503
	11th to 20th	Day	14% 3 19% 29% 23% 13%	527
	21st to end	Day	15% 5% 14% 25% 23% 18%	573
June	1st to 10th	Day	12% 3 14% 25% 30% 16%	530
	11th to 20th	Day	8% 3 14% 24% 25% 26%	530
	21st to end	Day	7% 2 8% 29% 28% 25%	530
July	1st to 10th	Day	8% 2 7% 19% 32% 33%	525
	11th to 20th	Day	8% 2 3 16% 40% 31%	524
	21st to end	Day	7% 1 7% 22% 36% 27%	576
August	1st to 10th	Day	13% 2 11% 19% 33% 21%	526
	11th to 20th	Day	12% 3 5% 18% 37% 26%	519
	21st to end	Day	13% 2 8% 23% 28% 24%	583
September	1st to 10th	Day	9% 4 9% 29% 29% 20%	530
	11th to 20th	Day	17% 2 12% 25% 31% 13%	530
	21st to end	Day	18% 2 15% 23% 27% 15%	530
October	1st to 10th	Day	15% 4 20% 30% 23% 9%	530
	11th to 20th	Day	11% 5% 20% 31% 23% 10%	530
	21st to end	Day	15% 6% 23% 28% 22% 5%	583
November	1st to 10th	Day	18% 6% 26% 27% 18% 5%	535
	11th to 20th	Day	16% 11% 35% 24% 11% 2	379
	21st to end	Day	11% 14% 33% 27% 13% 2	330
December	1st to 10th	Day	22% 13% 36% 22% 7% 1	330
	11th to 20th	Day	19% 13% 37% 19% 11% 1	321
	21st to end	Day	28% 13% 31% 17% 8% 2	330
January	1st to 10th	Night	19% 13% 33% 29% 6%	800
	11th to 20th	Night	18% 10% 34% 32% 8%	800
	21st to end	Night	20% 9% 39% 29% 3	880
February	1st to 10th	Night	17% 11% 31% 34% 8%	800
	11th to 20th	Night	21% 11% 34% 30% 3	783
	21st to end	Night	17% 13% 36% 30% 4	660
March	1st to 10th	Night	15% 10% 32% 36% 7%	800
	11th to 20th	Night	15% 10% 35% 33% 8% 1	800
	21st to end	Night	14% 11% 35% 30% 9%	880
April	1st to 10th	Night	12% 11% 31% 33% 12%	800
	11th to 20th	Night	14% 9% 26% 35% 15%	791
	21st to end	Night	9% 4 23% 44% 18% 1	631
May	1st to 10th	Night	10% 5% 26% 41% 17% 1	600
	11th to 20th	Night	10% 3 23% 39% 21% 4	591
	21st to end	Night	12% 2 11% 37% 34% 4	650
June	1st to 10th	Night	13% 2 12% 36% 32% 4	600
	11th to 20th	Night	7% 4 11% 32% 36% 11%	600
	21st to end	Night	7% 2 7% 31% 46% 6%	600
July	1st to 10th	Night	10% 3 6% 26% 47% 7%	585
	11th to 20th	Night	8% 1 3 25% 52% 10%	582
	21st to end	Night	8% 2 8% 28% 48% 7%	657
August	1st to 10th	Night	12% 2 6% 27% 45% 9%	597
	11th to 20th	Night	14% 2 3 29% 43% 9%	594
	21st to end	Night	13% 1 10% 27% 41% 8%	790
September	1st to 10th	Night	10% 2 10% 31% 40% 6%	800
	11th to 20th	Night	14% 2 10% 31% 38% 4	800
	21st to end	Night	17% 2 13% 31% 33% 5%	800
October	1st to 10th	Night	14% 3 16% 36% 26% 5%	800
	11th to 20th	Night	14% 4 19% 36% 25% 3	800
	21st to end	Night	12% 5% 23% 33% 24% 2	880
November	1st to 10th	Night	13% 6% 22% 35% 20% 4	820
	11th to 20th	Night	17% 8% 26% 34% 15% 1	840
	21st to end	Night	14% 7% 29% 33% 15% 1	840
December	1st to 10th	Night	19% 7% 30% 34% 10% 1	840
	11th to 20th	Night	18% 6% 28% 34% 13% 1	829
	21st to end	Night	24% 10% 26% 30% 9%	880

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