Brandy Creek Boat Ramp
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brandy Creek Boat Ramp clear sky chart from 2005-11-06 to 2026-01-02.

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% 4 1 3 2 2 2 2 4 5% 65%	136185
	Night	12% 4 1 3 2 2 3 2 4 5% 61%	132559
Transparency	Day	24% 2 7% 20% 25% 22%	131053
	Night	28% 2 8% 21% 24% 18%	128694
Seeing	Day	13% 10% 25% 30% 18% 5%	16522
	Night	14% 6% 22% 34% 21% 2	25734

By Month

Percentage Cloud Cover SW (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	21% 6% 2 5% 3 3 4 3 6% 7% 38%	3647
	11th to 20th	Day	21% 7% 2 4 2 2 2 1 2 3 55%	4027
	21st to end	Day	24% 5% 1 3 2 2 2 2 3 5% 50%	4510
February	1st to 10th	Day	21% 5% 2 4 3 4 4 4 5% 6% 43%	1800
	11th to 20th	Day	17% 7% 1 4 3 3 3 3 4 7% 48%	1759
	21st to end	Day	17% 6% 2 4 3 3 4 3 5% 7% 46%	1650
March	1st to 10th	Day	20% 11% 3 6% 4 3 3 2 3 5% 39%	4841
	11th to 20th	Day	19% 8% 2 4 3 3 3 2 4 6% 46%	5000
	21st to end	Day	21% 7% 3 6% 4 4 4 3 5% 8% 36%	5563
April	1st to 10th	Day	17% 6% 1 5% 3 4 3 3 6% 6% 46%	2400
	11th to 20th	Day	13% 5% 1 4 3 2 3 3 5% 7% 54%	2369
	21st to end	Day	6% 4 1 4 3 3 3 3 5% 7% 61%	2430
May	1st to 10th	Day	5% 3 1 3 2 2 2 2 4 6% 70%	5880
	11th to 20th	Day	3 2 1 2 2 2 2 2 4 6% 74%	6231
	21st to end	Day	3 1 1 2 1 1 2 2 4 6% 77%	6902
June	1st to 10th	Day	7% 3 1 3 3 3 3 3 5% 7% 62%	2800
	11th to 20th	Day	3 2 1 2 2 2 2 2 4 6% 76%	2800
	21st to end	Day	4 2 1 2 1 1 2 1 2 3 80%	2800
July	1st to 10th	Day	1 1 1 1 1 1 1 2 90%	6319
	11th to 20th	Day	1 1 1 1 1 1 1 2 2 89%	6286
	21st to end	Day	1 1 1 1 1 2 2 4 5% 82%	6402
August	1st to 10th	Day	1 1 1 1 1 2 2 4 4 82%	5777
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 87%	5721
	21st to end	Day	1 1 2 1 1 1 2 3 4 84%	5984
September	1st to 10th	Day	1 1 1 1 1 1 1 2 4 87%	2400
	11th to 20th	Day	4 2 2 2 2 3 3 4 6% 73%	2400
	21st to end	Day	4 2 1 2 1 2 2 1 3 5% 77%	2105
October	1st to 10th	Day	4 1 1 2 1 1 2 1 3 4 79%	3280
	11th to 20th	Day	5% 2 1 2 2 2 3 3 5% 7% 68%	3261
	21st to end	Day	10% 3 2 5% 3 3 4 4 5% 7% 54%	3558
November	1st to 10th	Day	13% 5% 2 3 4 4 4 3 4 7% 52%	1939
	11th to 20th	Day	17% 5% 1 5% 2 2 4 3 6% 7% 47%	1764
	21st to end	Day	13% 3 2 3 3 3 3 3 4 7% 56%	1680
December	1st to 10th	Day	12% 4 1 3 3 3 3 3 4 6% 57%	2700
	11th to 20th	Day	31% 7% 2 5% 3 4 4 3 5% 8% 28%	3108
	21st to end	Day	32% 6% 2 4 3 3 4 3 5% 5% 32%	4092
January	1st to 10th	Night	20% 6% 2 5% 4 4 4 4 6% 7% 39%	6320
	11th to 20th	Night	20% 7% 2 4 2 2 2 2 3 4 53%	5946
	21st to end	Night	20% 6% 2 4 3 3 3 3 4 4 47%	6468
February	1st to 10th	Night	21% 5% 1 4 3 3 3 4 5% 6% 46%	2600
	11th to 20th	Night	19% 6% 1 4 3 3 4 3 4 6% 46%	2527
	21st to end	Night	14% 6% 2 4 4 4 3 3 5% 6% 49%	1980
March	1st to 10th	Night	17% 7% 2 5% 3 4 4 3 5% 7% 42%	5036
	11th to 20th	Night	18% 6% 2 3 2 3 3 3 5% 7% 49%	5000
	21st to end	Night	16% 8% 2 7% 4 3 4 3 5% 7% 40%	5411
April	1st to 10th	Night	15% 6% 2 5% 4 4 4 3 5% 7% 47%	2000
	11th to 20th	Night	9% 5% 1 4 3 3 3 4 4 6% 57%	1979
	21st to end	Night	8% 4 1 4 2 2 2 3 4 7% 62%	1968
May	1st to 10th	Night	6% 3 1 3 1 2 1 1 3 6% 73%	4100
	11th to 20th	Night	4 2 1 3 1 2 2 3 4 6% 72%	3662
	21st to end	Night	3 2 1 2 2 1 1 2 3 5% 78%	3972
June	1st to 10th	Night	6% 4 1 3 3 2 3 4 6% 6% 61%	1600
	11th to 20th	Night	4 2 1 1 1 2 2 4 5% 78%	1600
	21st to end	Night	3 2 1 1 2 1 2 2 2 3 82%	1600
July	1st to 10th	Night	1 1 1 1 1 1 1 2 91%	3640
	11th to 20th	Night	1 1 1 1 1 2 1 1 2 88%	3658
	21st to end	Night	1 1 1 2 2 3 5% 84%	4472
August	1st to 10th	Night	2 1 1 1 1 2 2 3 3 83%	4035
	11th to 20th	Night	1 1 2 1 1 1 1 2 2 87%	4116
	21st to end	Night	3 1 2 1 1 1 1 2 3 84%	5015
September	1st to 10th	Night	1 1 1 1 1 1 1 2 3 87%	2000
	11th to 20th	Night	3 2 1 2 2 2 2 3 6% 76%	2000
	21st to end	Night	3 2 1 2 2 2 2 2 4 5% 77%	2291
October	1st to 10th	Night	4 1 2 2 2 3 2 3 3 80%	3920
	11th to 20th	Night	5% 2 1 2 1 2 2 2 3 6% 73%	3897
	21st to end	Night	8% 2 1 2 2 2 3 3 6% 8% 63%	4253
November	1st to 10th	Night	13% 4 1 3 3 3 4 3 6% 8% 52%	2580
	11th to 20th	Night	16% 4 2 4 3 3 4 4 6% 9% 47%	2851
	21st to end	Night	13% 4 1 4 3 3 4 3 5% 7% 54%	2940
December	1st to 10th	Night	13% 3 1 2 2 2 3 2 4 7% 60%	4700
	11th to 20th	Night	30% 7% 2 5% 3 3 4 4 6% 7% 30%	5316
	21st to end	Night	35% 6% 2 4 2 3 3 2 4 5% 35%	7106

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	45% 4 12% 23% 13% 3	3647
	11th to 20th	Day	39% 1 6% 22% 21% 10%	4027
	21st to end	Day	39% 1 10% 13% 20% 17%	4510
February	1st to 10th	Day	41% 3 10% 20% 17% 9%	1800
	11th to 20th	Day	38% 2 10% 22% 24% 5%	1768
	21st to end	Day	38% 3 10% 22% 20% 7%	1650
March	1st to 10th	Day	49% 2 8% 17% 20% 3	4841
	11th to 20th	Day	40% 3 12% 19% 21% 4	5000
	21st to end	Day	46% 4 13% 26% 10% 2	5563
April	1st to 10th	Day	38% 3 14% 22% 19% 5%	2400
	11th to 20th	Day	30% 2 12% 25% 20% 11%	2372
	21st to end	Day	23% 3 11% 27% 27% 8%	2430
May	1st to 10th	Day	17% 1 7% 26% 29% 19%	5880
	11th to 20th	Day	13% 1 5% 23% 32% 24%	6234
	21st to end	Day	10% 1 8% 32% 38% 10%	6904
June	1st to 10th	Day	22% 3 9% 24% 28% 14%	2800
	11th to 20th	Day	11% 1 8% 20% 34% 26%	2800
	21st to end	Day	12% 1 3 15% 33% 38%	2800
July	1st to 10th	Day	4 1 2 12% 22% 59%	6251
	11th to 20th	Day	6% 1 2 6% 22% 62%	6211
	21st to end	Day	7% 2 5% 21% 29% 36%	6217
August	1st to 10th	Day	10% 1 2 11% 26% 50%	4206
	11th to 20th	Day	6% 1 2 18% 37% 36%	4144
	21st to end	Day	7% 1 5% 16% 38% 33%	4311
September	1st to 10th	Day	5% 1 2 12% 24% 55%	2400
	11th to 20th	Day	14% 2 6% 22% 35% 22%	2400
	21st to end	Day	12% 2 5% 18% 32% 31%	2105
October	1st to 10th	Day	11% 2 5% 16% 21% 45%	3280
	11th to 20th	Day	15% 3 9% 26% 31% 16%	3261
	21st to end	Day	27% 4 8% 23% 25% 13%	3558
November	1st to 10th	Day	33% 2 9% 27% 17% 11%	1939
	11th to 20th	Day	36% 4 14% 22% 16% 8%	1764
	21st to end	Day	30% 2 10% 22% 24% 12%	1680
December	1st to 10th	Day	30% 2 7% 19% 32% 11%	2700
	11th to 20th	Day	56% 4 12% 16% 10% 3	3108
	21st to end	Day	54% 3 9% 18% 13% 2	4092
January	1st to 10th	Night	44% 4 15% 19% 15% 3	6320
	11th to 20th	Night	38% 2 7% 19% 24% 10%	5946
	21st to end	Night	42% 2 7% 11% 17% 21%	6468
February	1st to 10th	Night	40% 2 9% 21% 19% 9%	2600
	11th to 20th	Night	39% 3 9% 20% 22% 6%	2529
	21st to end	Night	36% 3 10% 21% 23% 7%	1980
March	1st to 10th	Night	44% 3 11% 22% 17% 5%	5036
	11th to 20th	Night	36% 3 11% 26% 19% 5%	5000
	21st to end	Night	45% 3 12% 28% 11% 2	5411
April	1st to 10th	Night	37% 3 15% 22% 18% 6%	2000
	11th to 20th	Night	28% 3 13% 25% 20% 10%	1979
	21st to end	Night	22% 3 12% 32% 25% 6%	1968
May	1st to 10th	Night	17% 1 6% 24% 36% 17%	4097
	11th to 20th	Night	13% 3 7% 26% 33% 19%	3662
	21st to end	Night	11% 2 8% 37% 36% 6%	3972
June	1st to 10th	Night	23% 3 11% 24% 29% 9%	1600
	11th to 20th	Night	10% 1 7% 23% 37% 22%	1600
	21st to end	Night	10% 1 5% 15% 38% 31%	1600
July	1st to 10th	Night	4 1 2 12% 28% 54%	3600
	11th to 20th	Night	6% 1 2 5% 23% 63%	3610
	21st to end	Night	5% 2 7% 20% 31% 35%	4345
August	1st to 10th	Night	11% 1 3 12% 29% 44%	2929
	11th to 20th	Night	5% 1 2 16% 42% 34%	2980
	21st to end	Night	9% 1 2 17% 38% 33%	3608
September	1st to 10th	Night	6% 1 2 11% 26% 54%	2000
	11th to 20th	Night	12% 3 5% 22% 37% 21%	2000
	21st to end	Night	13% 2 6% 20% 26% 33%	2291
October	1st to 10th	Night	13% 1 4 12% 22% 48%	3920
	11th to 20th	Night	16% 2 7% 32% 28% 15%	3897
	21st to end	Night	20% 3 8% 27% 28% 15%	4253
November	1st to 10th	Night	31% 3 12% 25% 18% 11%	2580
	11th to 20th	Night	34% 5% 13% 23% 17% 8%	2851
	21st to end	Night	31% 2 10% 23% 22% 12%	2940
December	1st to 10th	Night	26% 2 7% 19% 33% 13%	4700
	11th to 20th	Night	54% 4 8% 19% 13% 3	5316
	21st to end	Night	55% 2 11% 17% 13% 2	7106

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	39% 10% 23% 19% 7% 1	202
	11th to 20th	Day	28% 7% 25% 23% 11% 5%	366
	21st to end	Day	23% 10% 20% 28% 14% 4	440
February	1st to 10th	Day	25% 12% 23% 24% 15% 2	400
	11th to 20th	Day	24% 14% 30% 22% 7% 2	398
	21st to end	Day	20% 11% 30% 29% 9% 1	414
March	1st to 10th	Day	30% 17% 26% 19% 7% 1	500
	11th to 20th	Day	28% 12% 24% 22% 11% 2	500
	21st to end	Day	26% 15% 25% 23% 11% 1	550
April	1st to 10th	Day	22% 16% 24% 26% 10% 1	500
	11th to 20th	Day	19% 15% 28% 23% 12% 3	492
	21st to end	Day	10% 17% 29% 26% 14% 4	500
May	1st to 10th	Day	10% 19% 33% 23% 12% 3	503
	11th to 20th	Day	11% 13% 29% 28% 14% 5%	528
	21st to end	Day	8% 13% 26% 32% 17% 4	573
June	1st to 10th	Day	7% 12% 23% 33% 20% 4	530
	11th to 20th	Day	6% 18% 30% 29% 15% 3	530
	21st to end	Day	3 7% 26% 34% 24% 5%	530
July	1st to 10th	Day	2 5% 28% 40% 21% 6%	526
	11th to 20th	Day	3 19% 45% 25% 8%	524
	21st to end	Day	2 17% 44% 27% 10%	575
August	1st to 10th	Day	2 2 22% 39% 25% 10%	527
	11th to 20th	Day	1 5% 20% 36% 27% 11%	517
	21st to end	Day	2 4 19% 39% 27% 8%	583
September	1st to 10th	Day	2 4 22% 40% 27% 6%	530
	11th to 20th	Day	5% 6% 22% 39% 21% 7%	530
	21st to end	Day	5% 7% 27% 36% 22% 4	530
October	1st to 10th	Day	7% 10% 25% 30% 23% 5%	530
	11th to 20th	Day	8% 6% 28% 31% 22% 5%	530
	21st to end	Day	15% 9% 24% 28% 20% 4	583
November	1st to 10th	Day	17% 8% 23% 27% 20% 4	415
	11th to 20th	Day	20% 7% 25% 26% 17% 5%	264
	21st to end	Day	15% 7% 26% 31% 17% 3	220
December	1st to 10th	Day	21% 10% 22% 23% 18% 6%	220
	11th to 20th	Day	28% 5% 24% 25% 12% 6%	220
	21st to end	Day	26% 11% 24% 23% 14% 2	242
January	1st to 10th	Night	26% 6% 22% 27% 15% 3	804
	11th to 20th	Night	23% 8% 23% 31% 13% 3	800
	21st to end	Night	23% 6% 23% 29% 17% 2	880
February	1st to 10th	Night	23% 6% 24% 32% 14% 2	800
	11th to 20th	Night	22% 9% 26% 29% 12% 2	784
	21st to end	Night	18% 8% 29% 34% 9% 1	660
March	1st to 10th	Night	27% 8% 24% 27% 13% 2	800
	11th to 20th	Night	23% 7% 22% 30% 17% 1	800
	21st to end	Night	21% 10% 26% 31% 11% 1	880
April	1st to 10th	Night	17% 11% 28% 29% 14% 1	800
	11th to 20th	Night	13% 9% 30% 32% 14% 2	791
	21st to end	Night	9% 9% 30% 32% 18% 1	768
May	1st to 10th	Night	9% 12% 29% 32% 16% 1	600
	11th to 20th	Night	9% 7% 26% 35% 22% 1	414
	21st to end	Night	8% 9% 27% 35% 20%	433
June	1st to 10th	Night	7% 8% 27% 38% 20% 1	400
	11th to 20th	Night	5% 10% 30% 39% 16% 1	400
	21st to end	Night	4 3 21% 49% 23% 1	400
July	1st to 10th	Night	1 1 18% 46% 33% 2	390
	11th to 20th	Night	1 1 15% 43% 37% 3	393
	21st to end	Night	1 7% 41% 46% 4	657
August	1st to 10th	Night	3 2 10% 39% 42% 5%	597
	11th to 20th	Night	1 1 14% 40% 39% 4	619
	21st to end	Night	2 2 10% 41% 43% 3	880
September	1st to 10th	Night	1 2 16% 43% 35% 2	800
	11th to 20th	Night	4 4 14% 38% 38% 4	800
	21st to end	Night	4 6% 20% 36% 31% 4	800
October	1st to 10th	Night	7% 7% 21% 37% 26% 3	800
	11th to 20th	Night	8% 4 23% 35% 26% 4	800
	21st to end	Night	13% 5% 23% 34% 21% 4	880
November	1st to 10th	Night	14% 6% 19% 35% 23% 3	820
	11th to 20th	Night	18% 5% 23% 36% 17% 1	840
	21st to end	Night	15% 6% 24% 36% 17% 2	840
December	1st to 10th	Night	23% 4 22% 33% 14% 3	840
	11th to 20th	Night	28% 4 22% 30% 14% 2	840
	21st to end	Night	28% 6% 25% 29% 11% 1	924

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