Blackwater Falls
Clear Sky Chart
History

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

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	14% 11% 4 9% 6% 5% 5% 4 5% 7% 30%	101058
	Night	13% 12% 5% 11% 6% 5% 5% 4 5% 6% 30%	98030
Transparency	Day	48% 8% 11% 20% 11% 2	104708
	Night	49% 9% 11% 19% 11% 2	102519
Seeing	Day	25% 20% 26% 17% 9% 3	14905
	Night	23% 20% 23% 22% 11% 1	24665

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% 11% 10% 14% 6% 5% 5% 3 4 6% 21%	2836
	11th to 20th	Day	10% 16% 8% 23% 6% 9% 3 2 2 3 17%	2840
	21st to end	Day	14% 15% 8% 14% 8% 6% 4 3 4 4 19%	3124
February	1st to 10th	Day	14% 14% 6% 13% 7% 6% 4 3 4 5% 23%	1710
	11th to 20th	Day	14% 12% 4 15% 7% 7% 6% 3 4 5% 22%	1663
	21st to end	Day	13% 15% 5% 14% 7% 5% 4 3 4 5% 26%	1612
March	1st to 10th	Day	15% 12% 6% 12% 5% 4 4 3 5% 7% 27%	3435
	11th to 20th	Day	11% 11% 4 11% 6% 4 4 3 4 8% 34%	3480
	21st to end	Day	15% 15% 5% 8% 6% 4 4 3 4 5% 30%	3815
April	1st to 10th	Day	14% 14% 5% 10% 5% 4 4 4 5% 6% 29%	2204
	11th to 20th	Day	15% 12% 4 7% 5% 5% 4 3 5% 5% 36%	2254
	21st to end	Day	18% 12% 4 8% 5% 4 4 3 5% 6% 30%	2421
May	1st to 10th	Day	21% 14% 4 9% 6% 5% 5% 4 5% 5% 24%	4082
	11th to 20th	Day	20% 11% 4 8% 5% 5% 5% 4 6% 6% 25%	4081
	21st to end	Day	10% 9% 4 8% 6% 6% 6% 5% 7% 9% 31%	4653
June	1st to 10th	Day	15% 8% 2 8% 5% 5% 5% 4 7% 9% 32%	2660
	11th to 20th	Day	14% 8% 3 7% 6% 6% 6% 5% 6% 9% 30%	2660
	21st to end	Day	12% 8% 2 7% 6% 6% 6% 5% 7% 8% 32%	2660
July	1st to 10th	Day	10% 8% 3 6% 6% 5% 5% 5% 7% 8% 37%	4186
	11th to 20th	Day	10% 9% 3 7% 6% 5% 5% 4 7% 9% 35%	4120
	21st to end	Day	17% 11% 3 8% 6% 5% 6% 4 6% 7% 27%	4466
August	1st to 10th	Day	14% 10% 3 9% 6% 6% 6% 5% 8% 8% 26%	4104
	11th to 20th	Day	13% 9% 2 8% 6% 6% 6% 6% 7% 8% 28%	4044
	21st to end	Day	8% 5% 2 7% 5% 5% 6% 5% 6% 9% 42%	4222
September	1st to 10th	Day	15% 7% 3 8% 4 5% 5% 3 5% 6% 39%	2280
	11th to 20th	Day	11% 9% 2 6% 5% 5% 6% 4 6% 8% 38%	2126
	21st to end	Day	18% 11% 3 7% 4 4 5% 4 5% 7% 33%	2067
October	1st to 10th	Day	14% 10% 2 6% 3 3 4 4 4 6% 42%	1900
	11th to 20th	Day	16% 13% 3 7% 4 4 3 3 4 5% 38%	1900
	21st to end	Day	14% 14% 4 8% 4 3 4 3 4 6% 36%	2090
November	1st to 10th	Day	12% 11% 3 8% 4 4 4 3 3 4 44%	1947
	11th to 20th	Day	11% 13% 5% 10% 5% 6% 4 3 5% 6% 30%	1621
	21st to end	Day	13% 14% 6% 11% 7% 4 5% 3 4 6% 28%	1520
December	1st to 10th	Day	16% 17% 8% 13% 7% 4 4 3 3 4 22%	1520
	11th to 20th	Day	14% 14% 8% 14% 6% 4 3 3 4 5% 25%	1910
	21st to end	Day	14% 14% 9% 12% 7% 6% 6% 4 6% 6% 17%	2845
January	1st to 10th	Night	9% 14% 9% 22% 6% 6% 6% 3 4 3 17%	4109
	11th to 20th	Night	11% 13% 6% 19% 10% 7% 5% 5% 4 3 18%	4120
	21st to end	Night	14% 17% 7% 13% 8% 9% 5% 3 3 3 18%	4532
February	1st to 10th	Night	11% 13% 6% 13% 8% 6% 5% 3 6% 5% 26%	2470
	11th to 20th	Night	13% 12% 5% 15% 9% 7% 5% 4 3 4 23%	2403
	21st to end	Night	14% 16% 4 12% 7% 5% 3 2 5% 5% 25%	1838
March	1st to 10th	Night	19% 12% 4 10% 6% 5% 5% 4 4 6% 26%	3418
	11th to 20th	Night	10% 10% 6% 15% 6% 4 4 3 6% 6% 30%	3480
	21st to end	Night	13% 12% 5% 9% 4 5% 4 3 4 5% 38%	3817
April	1st to 10th	Night	13% 14% 5% 10% 6% 3 4 3 5% 6% 31%	1975
	11th to 20th	Night	13% 10% 3 7% 5% 5% 5% 4 5% 8% 36%	1875
	21st to end	Night	14% 9% 4 8% 6% 5% 5% 4 6% 6% 33%	1775
May	1st to 10th	Night	24% 15% 4 9% 5% 3 3 3 4 5% 24%	2813
	11th to 20th	Night	20% 14% 3 8% 5% 5% 4 3 4 6% 28%	2812
	21st to end	Night	12% 10% 4 8% 5% 5% 5% 4 6% 8% 33%	2898
June	1st to 10th	Night	11% 9% 2 7% 5% 4 4 4 5% 8% 39%	1520
	11th to 20th	Night	11% 8% 4 9% 5% 4 4 5% 6% 9% 34%	1520
	21st to end	Night	11% 8% 3 6% 4 4 5% 4 8% 11% 37%	1520
July	1st to 10th	Night	11% 8% 2 7% 5% 6% 6% 4 7% 9% 35%	2767
	11th to 20th	Night	10% 8% 3 7% 5% 5% 4 4 7% 9% 38%	2840
	21st to end	Night	15% 10% 3 8% 6% 4 5% 4 6% 6% 33%	3087
August	1st to 10th	Night	13% 10% 3 8% 5% 5% 5% 4 7% 10% 30%	2825
	11th to 20th	Night	15% 11% 2 6% 4 5% 5% 4 6% 6% 36%	2785
	21st to end	Night	6% 6% 2 6% 4 4 5% 5% 7% 8% 46%	3400
September	1st to 10th	Night	13% 7% 2 7% 4 4 4 4 5% 6% 44%	1900
	11th to 20th	Night	10% 7% 2 5% 4 5% 5% 4 5% 6% 45%	2050
	21st to end	Night	15% 9% 4 8% 5% 5% 4 5% 5% 5% 35%	2112
October	1st to 10th	Night	14% 9% 2 7% 4 5% 4 3 5% 6% 41%	2280
	11th to 20th	Night	13% 12% 3 7% 4 4 4 4 5% 5% 39%	2280
	21st to end	Night	16% 14% 3 7% 4 5% 3 2 4 4 37%	2508
November	1st to 10th	Night	10% 12% 4 7% 5% 4 4 3 5% 4 43%	2336
	11th to 20th	Night	12% 12% 5% 13% 5% 6% 4 4 4 4 31%	2554
	21st to end	Night	12% 13% 6% 13% 8% 5% 4 3 4 5% 27%	2660
December	1st to 10th	Night	16% 15% 8% 15% 7% 4 4 3 4 4 19%	2660
	11th to 20th	Night	14% 11% 6% 16% 7% 5% 5% 4 4 5% 22%	3285
	21st to end	Night	13% 16% 8% 14% 6% 6% 6% 4 4 5% 19%	4806

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	55% 9% 11% 17% 7% 1	2837
	11th to 20th	Day	67% 6% 8% 11% 6% 1	2840
	21st to end	Day	61% 5% 9% 17% 7% 1	3124
February	1st to 10th	Day	60% 5% 10% 15% 9% 1	1710
	11th to 20th	Day	61% 5% 10% 14% 10% 1	1672
	21st to end	Day	58% 6% 10% 14% 10% 2	1612
March	1st to 10th	Day	52% 8% 10% 21% 8% 1	3435
	11th to 20th	Day	43% 9% 10% 26% 12% 1	3480
	21st to end	Day	51% 9% 8% 17% 13% 2	3815
April	1st to 10th	Day	53% 7% 11% 15% 12% 3	2204
	11th to 20th	Day	46% 7% 10% 18% 15% 3	2254
	21st to end	Day	52% 7% 10% 20% 10% 2	2421
May	1st to 10th	Day	58% 9% 8% 17% 7% 1	4120
	11th to 20th	Day	52% 11% 12% 20% 5% 1	4085
	21st to end	Day	40% 15% 15% 17% 10% 2	4667
June	1st to 10th	Day	44% 11% 13% 20% 12%	2660
	11th to 20th	Day	47% 10% 13% 20% 9% 1	2660
	21st to end	Day	44% 10% 15% 21% 9% 1	2660
July	1st to 10th	Day	41% 8% 15% 23% 10% 3	4121
	11th to 20th	Day	42% 9% 14% 27% 8% 1	4051
	21st to end	Day	52% 8% 10% 19% 10% 1	4324
August	1st to 10th	Day	50% 10% 15% 19% 6%	4091
	11th to 20th	Day	48% 9% 11% 24% 8%	4083
	21st to end	Day	34% 10% 16% 25% 13% 1	4222
September	1st to 10th	Day	44% 8% 9% 17% 18% 3	2280
	11th to 20th	Day	42% 7% 10% 22% 15% 3	2126
	21st to end	Day	48% 8% 11% 18% 14% 1	2067
October	1st to 10th	Day	32% 5% 8% 27% 22% 6%	3160
	11th to 20th	Day	40% 5% 10% 19% 15% 11%	3140
	21st to end	Day	33% 5% 9% 26% 22% 4	3428
November	1st to 10th	Day	42% 4 9% 20% 18% 5%	1947
	11th to 20th	Day	51% 6% 8% 15% 16% 4	1621
	21st to end	Day	55% 5% 11% 16% 11% 1	1520
December	1st to 10th	Day	66% 5% 9% 14% 5% 2	1520
	11th to 20th	Day	56% 7% 9% 19% 8% 2	1906
	21st to end	Day	55% 12% 12% 14% 7%	2845
January	1st to 10th	Night	62% 10% 8% 11% 8% 1	4109
	11th to 20th	Night	60% 8% 11% 17% 3	4120
	21st to end	Night	61% 9% 10% 10% 8% 1	4532
February	1st to 10th	Night	56% 6% 11% 16% 9% 1	2470
	11th to 20th	Night	62% 6% 9% 13% 9% 1	2405
	21st to end	Night	59% 6% 9% 14% 9% 3	1838
March	1st to 10th	Night	52% 11% 9% 18% 8% 1	3418
	11th to 20th	Night	46% 10% 13% 24% 7% 1	3480
	21st to end	Night	43% 9% 9% 22% 14% 3	3817
April	1st to 10th	Night	52% 7% 10% 17% 13% 2	1975
	11th to 20th	Night	43% 9% 12% 19% 13% 3	1875
	21st to end	Night	47% 8% 12% 21% 10% 2	1775
May	1st to 10th	Night	57% 10% 9% 15% 7% 1	2840
	11th to 20th	Night	49% 15% 11% 18% 6% 1	2813
	21st to end	Night	40% 16% 15% 19% 7% 3	2905
June	1st to 10th	Night	40% 9% 12% 26% 12% 1	1520
	11th to 20th	Night	43% 9% 16% 22% 10% 1	1520
	21st to end	Night	38% 10% 17% 21% 13% 1	1520
July	1st to 10th	Night	42% 9% 18% 18% 11% 1	2722
	11th to 20th	Night	39% 11% 16% 26% 8% 1	2786
	21st to end	Night	47% 9% 13% 19% 12%	2988
August	1st to 10th	Night	46% 11% 19% 17% 6%	2814
	11th to 20th	Night	45% 8% 11% 24% 12%	2812
	21st to end	Night	32% 9% 16% 32% 10% 1	3400
September	1st to 10th	Night	38% 8% 15% 18% 18% 3	1900
	11th to 20th	Night	35% 8% 11% 26% 17% 2	2050
	21st to end	Night	45% 9% 11% 19% 14% 1	2112
October	1st to 10th	Night	36% 7% 10% 25% 19% 3	3800
	11th to 20th	Night	40% 6% 9% 20% 14% 12%	3779
	21st to end	Night	35% 6% 6% 26% 19% 7%	4120
November	1st to 10th	Night	42% 8% 9% 18% 17% 6%	2336
	11th to 20th	Night	54% 5% 8% 14% 15% 3	2554
	21st to end	Night	57% 5% 10% 15% 11% 2	2660
December	1st to 10th	Night	65% 6% 8% 14% 4 2	2660
	11th to 20th	Night	59% 7% 8% 16% 9% 1	3288
	21st to end	Night	60% 11% 10% 13% 6%	4806

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	37% 31% 21% 7% 3	270
	11th to 20th	Day	44% 29% 21% 4 1	270
	21st to end	Day	38% 30% 23% 7% 2	297
February	1st to 10th	Day	42% 28% 22% 7% 1	270
	11th to 20th	Day	48% 29% 20% 3 1	270
	21st to end	Day	39% 32% 23% 6%	303
March	1st to 10th	Day	37% 27% 23% 10% 3	460
	11th to 20th	Day	38% 28% 21% 8% 4 1	460
	21st to end	Day	34% 25% 26% 11% 4	506
April	1st to 10th	Day	33% 25% 25% 13% 3 1	460
	11th to 20th	Day	26% 25% 29% 11% 7% 2	452
	21st to end	Day	30% 27% 25% 13% 4 1	460
May	1st to 10th	Day	30% 23% 25% 13% 6% 3	463
	11th to 20th	Day	26% 20% 31% 14% 6% 3	487
	21st to end	Day	18% 15% 29% 21% 12% 6%	529
June	1st to 10th	Day	17% 20% 29% 20% 10% 4	490
	11th to 20th	Day	18% 18% 28% 20% 12% 4	490
	21st to end	Day	13% 20% 31% 21% 12% 3	490
July	1st to 10th	Day	14% 13% 28% 20% 18% 7%	485
	11th to 20th	Day	10% 11% 32% 27% 14% 6%	484
	21st to end	Day	16% 10% 28% 25% 14% 6%	532
August	1st to 10th	Day	14% 13% 26% 23% 15% 8%	486
	11th to 20th	Day	15% 10% 29% 23% 15% 8%	479
	21st to end	Day	12% 9% 28% 25% 16% 10%	539
September	1st to 10th	Day	17% 11% 24% 25% 15% 8%	490
	11th to 20th	Day	11% 10% 27% 26% 19% 8%	490
	21st to end	Day	26% 16% 25% 20% 11% 3	490
October	1st to 10th	Day	19% 15% 26% 22% 15% 3	490
	11th to 20th	Day	24% 21% 25% 18% 10% 2	490
	21st to end	Day	27% 22% 27% 15% 8% 1	539
November	1st to 10th	Day	23% 20% 27% 20% 8% 1	491
	11th to 20th	Day	32% 26% 24% 12% 6%	233
	21st to end	Day	34% 24% 29% 9% 4 1	180
December	1st to 10th	Day	37% 29% 21% 9% 2 2	180
	11th to 20th	Day	43% 24% 21% 11% 2	180
	21st to end	Day	40% 25% 22% 9% 4	220
January	1st to 10th	Night	35% 31% 22% 10% 3	760
	11th to 20th	Night	35% 29% 25% 10% 1	760
	21st to end	Night	33% 33% 21% 12% 1	836
February	1st to 10th	Night	30% 29% 24% 16% 1	760
	11th to 20th	Night	36% 34% 22% 8% 1	743
	21st to end	Night	34% 30% 25% 10% 1	628
March	1st to 10th	Night	30% 25% 25% 17% 2	760
	11th to 20th	Night	33% 27% 21% 13% 5% 1	760
	21st to end	Night	27% 25% 27% 15% 5% 1	836
April	1st to 10th	Night	25% 28% 27% 16% 4	760
	11th to 20th	Night	23% 21% 26% 21% 9%	751
	21st to end	Night	23% 22% 23% 25% 6%	635
May	1st to 10th	Night	26% 16% 22% 26% 8% 1	570
	11th to 20th	Night	22% 16% 23% 27% 11% 1	561
	21st to end	Night	12% 10% 23% 28% 25% 2	513
June	1st to 10th	Night	11% 10% 26% 32% 19% 1	380
	11th to 20th	Night	14% 11% 24% 31% 19% 1	380
	21st to end	Night	12% 9% 26% 38% 14% 1	380
July	1st to 10th	Night	13% 6% 22% 33% 21% 5%	508
	11th to 20th	Night	8% 7% 21% 33% 27% 4	552
	21st to end	Night	11% 8% 19% 38% 22% 2	624
August	1st to 10th	Night	11% 6% 16% 38% 26% 2	567
	11th to 20th	Night	11% 7% 18% 37% 23% 4	564
	21st to end	Night	11% 8% 18% 35% 25% 3	786
September	1st to 10th	Night	14% 8% 23% 29% 21% 5%	760
	11th to 20th	Night	13% 8% 19% 31% 26% 3	760
	21st to end	Night	21% 13% 18% 29% 17% 2	760
October	1st to 10th	Night	18% 16% 20% 24% 19% 3	760
	11th to 20th	Night	22% 19% 24% 23% 12% 1	760
	21st to end	Night	26% 20% 22% 22% 9% 1	836
November	1st to 10th	Night	19% 18% 24% 27% 10% 1	779
	11th to 20th	Night	28% 19% 25% 19% 7% 1	760
	21st to end	Night	25% 27% 25% 17% 4 1	760
December	1st to 10th	Night	32% 29% 21% 14% 5%	760
	11th to 20th	Night	29% 30% 22% 16% 3	760
	21st to end	Night	28% 28% 25% 16% 2	836

Page generated at 2024-11-07 06:55:46. Version ac07

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