Falling Waters
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Falling Waters clear sky chart from 2005-11-06 to 2026-02-16.

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% 6% 2 6% 4 4 5% 4 6% 8% 40%	130996
	Night	14% 7% 2 6% 5% 4 5% 4 6% 7% 41%	129840
Transparency	Day	40% 6% 12% 23% 15% 3	134592
	Night	40% 6% 12% 24% 16% 3	134314
Seeing	Day	20% 13% 24% 22% 15% 6%	16462
	Night	18% 11% 26% 31% 13% 1	26123

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% 6% 3 8% 5% 5% 5% 4 6% 7% 38%	4878
	11th to 20th	Day	11% 9% 3 7% 4 5% 5% 4 6% 7% 40%	5280
	21st to end	Day	13% 6% 2 7% 5% 5% 5% 5% 7% 7% 37%	5780
February	1st to 10th	Day	13% 9% 3 8% 6% 3 5% 4 5% 6% 38%	1890
	11th to 20th	Day	15% 9% 3 7% 5% 5% 5% 2 5% 6% 39%	1801
	21st to end	Day	16% 9% 3 7% 4 4 5% 3 4 5% 39%	1652
March	1st to 10th	Day	17% 8% 2 6% 4 4 4 3 5% 6% 40%	4935
	11th to 20th	Day	11% 6% 2 6% 4 4 4 3 6% 8% 46%	4980
	21st to end	Day	15% 8% 2 7% 5% 4 5% 4 6% 6% 39%	5482
April	1st to 10th	Day	14% 7% 3 7% 5% 4 5% 4 7% 7% 37%	2400
	11th to 20th	Day	14% 6% 2 6% 4 5% 5% 4 5% 8% 43%	2374
	21st to end	Day	17% 7% 2 5% 4 4 5% 4 5% 6% 41%	2433
May	1st to 10th	Day	20% 7% 3 6% 4 5% 5% 5% 7% 9% 30%	5862
	11th to 20th	Day	23% 6% 3 6% 4 4 4 4 6% 10% 31%	6084
	21st to end	Day	16% 5% 2 7% 4 4 5% 4 7% 9% 36%	6934
June	1st to 10th	Day	12% 5% 2 4 4 4 5% 5% 7% 10% 43%	2800
	11th to 20th	Day	11% 5% 2 6% 5% 5% 6% 5% 7% 10% 38%	2800
	21st to end	Day	10% 4 1 6% 4 4 5% 4 6% 10% 46%	2800
July	1st to 10th	Day	6% 4 2 6% 5% 5% 5% 5% 7% 10% 46%	6360
	11th to 20th	Day	8% 6% 2 7% 6% 6% 6% 5% 8% 12% 35%	6090
	21st to end	Day	9% 6% 3 7% 4 5% 5% 4 7% 10% 41%	6424
August	1st to 10th	Day	16% 6% 2 6% 5% 5% 6% 4 7% 9% 34%	4234
	11th to 20th	Day	9% 5% 2 6% 5% 5% 6% 4 7% 9% 42%	4085
	21st to end	Day	11% 4 2 5% 4 4 4 4 5% 8% 48%	4312
September	1st to 10th	Day	15% 5% 2 5% 4 4 4 4 5% 7% 46%	2400
	11th to 20th	Day	11% 5% 2 6% 3 4 3 4 6% 8% 48%	2381
	21st to end	Day	21% 8% 2 7% 3 4 4 3 5% 6% 37%	2095
October	1st to 10th	Day	16% 5% 2 6% 3 4 3 3 4 7% 47%	2000
	11th to 20th	Day	15% 5% 2 5% 4 3 4 4 6% 7% 46%	2000
	21st to end	Day	14% 5% 2 6% 4 4 4 3 6% 6% 47%	2200
November	1st to 10th	Day	11% 6% 1 4 4 3 3 3 6% 7% 51%	1982
	11th to 20th	Day	15% 6% 2 5% 4 3 4 4 6% 6% 45%	1790
	21st to end	Day	15% 7% 2 6% 4 5% 4 3 5% 7% 42%	1680
December	1st to 10th	Day	13% 8% 2 7% 5% 4 4 4 7% 6% 40%	2680
	11th to 20th	Day	20% 8% 3 5% 4 4 4 2 5% 6% 37%	3070
	21st to end	Day	16% 9% 3 7% 6% 5% 6% 5% 6% 8% 29%	4048
January	1st to 10th	Night	10% 8% 2 8% 5% 5% 5% 4 6% 8% 38%	8011
	11th to 20th	Night	12% 8% 2 6% 5% 4 4 3 5% 6% 44%	7680
	21st to end	Night	13% 7% 2 6% 4 3 4 4 6% 7% 43%	8401
February	1st to 10th	Night	14% 8% 3 6% 4 4 4 4 7% 7% 39%	2730
	11th to 20th	Night	16% 9% 3 7% 5% 4 4 3 5% 6% 38%	2594
	21st to end	Night	16% 9% 3 7% 5% 4 4 3 5% 7% 36%	1975
March	1st to 10th	Night	17% 6% 2 6% 4 4 4 3 4 6% 44%	4918
	11th to 20th	Night	10% 6% 2 5% 4 4 5% 3 5% 8% 47%	4980
	21st to end	Night	11% 6% 2 6% 4 5% 5% 4 6% 6% 45%	5435
April	1st to 10th	Night	16% 9% 3 7% 5% 4 4 4 5% 5% 37%	2000
	11th to 20th	Night	13% 6% 2 6% 5% 4 4 3 6% 7% 43%	1975
	21st to end	Night	17% 5% 2 5% 4 4 4 4 6% 7% 43%	1984
May	1st to 10th	Night	23% 8% 3 7% 5% 5% 5% 4 6% 7% 28%	4033
	11th to 20th	Night	24% 7% 3 6% 4 3 4 4 6% 9% 30%	3809
	21st to end	Night	18% 6% 2 7% 4 5% 5% 4 6% 8% 34%	3920
June	1st to 10th	Night	11% 5% 2 5% 4 4 4 4 7% 8% 47%	1600
	11th to 20th	Night	12% 5% 1 7% 5% 5% 4 4 8% 9% 41%	1600
	21st to end	Night	9% 5% 2 5% 5% 4 5% 4 7% 10% 45%	1600
July	1st to 10th	Night	8% 5% 2 8% 5% 5% 6% 4 7% 10% 41%	3598
	11th to 20th	Night	8% 7% 3 10% 7% 6% 7% 5% 7% 10% 29%	3863
	21st to end	Night	8% 5% 2 7% 5% 5% 5% 4 8% 10% 41%	4427
August	1st to 10th	Night	16% 5% 3 8% 6% 5% 6% 4 7% 8% 34%	2915
	11th to 20th	Night	10% 5% 3 7% 5% 5% 5% 4 6% 8% 42%	2931
	21st to end	Night	12% 5% 2 5% 4 4 4 3 6% 8% 46%	3586
September	1st to 10th	Night	13% 5% 2 5% 4 4 4 4 6% 6% 47%	2000
	11th to 20th	Night	10% 8% 3 6% 3 4 4 2 5% 7% 50%	2015
	21st to end	Night	20% 8% 2 5% 4 4 4 3 5% 6% 40%	2304
October	1st to 10th	Night	18% 6% 2 5% 3 3 4 4 4 6% 46%	2400
	11th to 20th	Night	14% 5% 2 5% 3 3 3 2 6% 6% 51%	2400
	21st to end	Night	15% 6% 2 4 3 3 3 3 5% 6% 49%	2640
November	1st to 10th	Night	10% 6% 1 5% 4 3 4 3 5% 6% 53%	2535
	11th to 20th	Night	14% 7% 2 5% 4 4 4 3 6% 6% 45%	2826
	21st to end	Night	13% 6% 2 6% 5% 4 5% 4 6% 7% 42%	2940
December	1st to 10th	Night	10% 6% 2 6% 6% 4 4 4 5% 7% 46%	4720
	11th to 20th	Night	19% 8% 2 6% 4 5% 4 4 5% 7% 36%	5345
	21st to end	Night	16% 9% 3 7% 5% 5% 6% 5% 7% 8% 29%	7150

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	44% 5% 10% 24% 13% 4	4879
	11th to 20th	Day	42% 5% 9% 20% 18% 7%	5280
	21st to end	Day	43% 5% 11% 26% 12% 3	5780
February	1st to 10th	Day	45% 6% 12% 23% 12% 2	1890
	11th to 20th	Day	47% 4 10% 23% 13% 2	1810
	21st to end	Day	48% 4 11% 20% 14% 3	1652
March	1st to 10th	Day	44% 5% 9% 22% 14% 7%	4935
	11th to 20th	Day	35% 5% 11% 27% 17% 5%	4980
	21st to end	Day	45% 5% 9% 19% 18% 4	5482
April	1st to 10th	Day	44% 7% 11% 18% 17% 4	2400
	11th to 20th	Day	39% 5% 11% 22% 18% 5%	2374
	21st to end	Day	43% 5% 10% 22% 17% 3	2433
May	1st to 10th	Day	48% 7% 13% 19% 10% 2	5897
	11th to 20th	Day	49% 7% 10% 24% 9% 1	6088
	21st to end	Day	41% 8% 13% 21% 16% 1	6949
June	1st to 10th	Day	35% 8% 15% 24% 17% 1	2800
	11th to 20th	Day	38% 10% 14% 22% 14% 2	2800
	21st to end	Day	33% 8% 15% 26% 16% 2	2800
July	1st to 10th	Day	33% 9% 14% 25% 16% 4	6290
	11th to 20th	Day	41% 8% 17% 24% 10% 1	6016
	21st to end	Day	38% 7% 10% 23% 22% 1	6240
August	1st to 10th	Day	45% 7% 14% 25% 9%	4221
	11th to 20th	Day	37% 7% 12% 28% 15% 1	4124
	21st to end	Day	34% 6% 14% 27% 17% 2	4312
September	1st to 10th	Day	38% 6% 11% 20% 21% 4	2400
	11th to 20th	Day	33% 6% 10% 27% 21% 2	2381
	21st to end	Day	48% 5% 9% 18% 18% 2	2095
October	1st to 10th	Day	36% 4 8% 22% 25% 5%	3260
	11th to 20th	Day	27% 6% 10% 30% 22% 5%	3240
	21st to end	Day	26% 5% 12% 29% 25% 3	3538
November	1st to 10th	Day	32% 5% 13% 25% 21% 4	1982
	11th to 20th	Day	38% 5% 11% 21% 21% 3	1790
	21st to end	Day	41% 6% 12% 27% 12% 1	1680
December	1st to 10th	Day	41% 7% 14% 26% 8% 4	2680
	11th to 20th	Day	48% 4 14% 24% 8% 2	3066
	21st to end	Day	49% 7% 17% 14% 13% 1	4048
January	1st to 10th	Night	42% 5% 11% 25% 15% 2	8012
	11th to 20th	Night	40% 4 9% 22% 19% 6%	7680
	21st to end	Night	38% 4 10% 29% 16% 2	8401
February	1st to 10th	Night	42% 6% 13% 24% 13% 2	2730
	11th to 20th	Night	46% 4 11% 21% 15% 3	2596
	21st to end	Night	47% 5% 11% 19% 13% 5%	1975
March	1st to 10th	Night	40% 5% 9% 26% 12% 8%	4918
	11th to 20th	Night	35% 5% 12% 30% 14% 5%	4980
	21st to end	Night	38% 5% 11% 22% 20% 4	5435
April	1st to 10th	Night	46% 6% 9% 19% 16% 3	2000
	11th to 20th	Night	39% 7% 11% 21% 18% 5%	1975
	21st to end	Night	39% 6% 11% 25% 15% 4	1984
May	1st to 10th	Night	54% 6% 10% 16% 10% 4	4060
	11th to 20th	Night	49% 7% 10% 22% 11% 1	3810
	21st to end	Night	45% 8% 13% 25% 8% 2	3927
June	1st to 10th	Night	34% 9% 10% 26% 18% 3	1600
	11th to 20th	Night	38% 9% 12% 26% 14% 2	1600
	21st to end	Night	33% 10% 13% 24% 18% 2	1600
July	1st to 10th	Night	39% 9% 16% 18% 14% 4	3560
	11th to 20th	Night	47% 9% 16% 16% 11% 1	3817
	21st to end	Night	35% 7% 13% 23% 20% 1	4297
August	1st to 10th	Night	46% 8% 15% 21% 9% 1	2904
	11th to 20th	Night	38% 7% 12% 26% 15% 1	2958
	21st to end	Night	35% 7% 13% 29% 15% 2	3586
September	1st to 10th	Night	37% 7% 11% 20% 21% 4	2000
	11th to 20th	Night	35% 5% 8% 27% 23% 2	2015
	21st to end	Night	45% 7% 11% 19% 17% 2	2304
October	1st to 10th	Night	38% 5% 10% 22% 21% 3	3920
	11th to 20th	Night	25% 5% 12% 23% 29% 5%	3899
	21st to end	Night	25% 4 11% 32% 25% 4	4252
November	1st to 10th	Night	32% 5% 11% 26% 22% 4	2535
	11th to 20th	Night	38% 5% 9% 24% 20% 5%	2826
	21st to end	Night	40% 6% 12% 24% 16% 2	2940
December	1st to 10th	Night	37% 6% 13% 31% 13% 1	4720
	11th to 20th	Night	47% 5% 13% 20% 13% 2	5348
	21st to end	Night	48% 8% 14% 18% 12% 1	7150

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	31% 25% 25% 15% 4	259
	11th to 20th	Day	33% 26% 26% 12% 3	330
	21st to end	Day	26% 29% 28% 13% 3 1	363
February	1st to 10th	Day	27% 24% 31% 14% 3 1	330
	11th to 20th	Day	40% 24% 28% 7% 1	318
	21st to end	Day	30% 19% 28% 20% 3	414
March	1st to 10th	Day	27% 20% 25% 24% 3	500
	11th to 20th	Day	27% 21% 29% 15% 8% 1	500
	21st to end	Day	25% 18% 33% 18% 6% 1	550
April	1st to 10th	Day	26% 21% 26% 19% 7% 2	500
	11th to 20th	Day	20% 17% 32% 15% 12% 5%	492
	21st to end	Day	27% 16% 27% 18% 11% 2	500
May	1st to 10th	Day	24% 16% 27% 17% 12% 4	503
	11th to 20th	Day	23% 14% 25% 19% 15% 4	527
	21st to end	Day	18% 9% 22% 23% 19% 8%	573
June	1st to 10th	Day	15% 9% 27% 22% 19% 8%	530
	11th to 20th	Day	14% 9% 24% 26% 19% 7%	530
	21st to end	Day	11% 7% 25% 29% 20% 8%	530
July	1st to 10th	Day	11% 3 19% 26% 27% 14%	525
	11th to 20th	Day	7% 5% 19% 26% 31% 12%	524
	21st to end	Day	12% 4 19% 29% 26% 10%	576
August	1st to 10th	Day	14% 4 19% 24% 26% 14%	526
	11th to 20th	Day	14% 4 18% 28% 25% 12%	519
	21st to end	Day	10% 3 19% 28% 25% 14%	583
September	1st to 10th	Day	16% 6% 19% 23% 23% 13%	530
	11th to 20th	Day	15% 4 17% 28% 24% 13%	530
	21st to end	Day	27% 9% 20% 23% 18% 4	530
October	1st to 10th	Day	20% 6% 19% 25% 23% 7%	530
	11th to 20th	Day	17% 14% 25% 26% 15% 3	530
	21st to end	Day	17% 15% 28% 25% 12% 3	583
November	1st to 10th	Day	15% 15% 29% 24% 14% 3	495
	11th to 20th	Day	26% 12% 27% 23% 9% 2	330
	21st to end	Day	22% 20% 28% 23% 6% 1	220
December	1st to 10th	Day	27% 16% 31% 21% 5%	220
	11th to 20th	Day	25% 22% 26% 19% 7%	220
	21st to end	Day	22% 18% 30% 21% 8%	242
January	1st to 10th	Night	18% 22% 34% 23% 3	840
	11th to 20th	Night	23% 16% 31% 26% 3	840
	21st to end	Night	19% 19% 36% 24% 2	924
February	1st to 10th	Night	19% 19% 30% 30% 2	840
	11th to 20th	Night	24% 23% 33% 20% 1	804
	21st to end	Night	25% 19% 33% 20% 3	660
March	1st to 10th	Night	21% 16% 36% 23% 4	800
	11th to 20th	Night	23% 19% 29% 23% 6%	800
	21st to end	Night	18% 16% 38% 23% 4 1	880
April	1st to 10th	Night	22% 18% 32% 22% 5%	800
	11th to 20th	Night	18% 14% 31% 28% 8%	791
	21st to end	Night	20% 12% 27% 33% 7%	784
May	1st to 10th	Night	21% 7% 26% 34% 12% 1	600
	11th to 20th	Night	21% 6% 26% 35% 12% 1	498
	21st to end	Night	16% 4 23% 37% 19% 1	433
June	1st to 10th	Night	12% 3 25% 37% 24% 1	400
	11th to 20th	Night	12% 6% 21% 40% 21% 2	400
	21st to end	Night	10% 3 20% 46% 20% 2	400
July	1st to 10th	Night	12% 2 16% 36% 31% 3	390
	11th to 20th	Night	7% 2 13% 39% 35% 4	497
	21st to end	Night	8% 3 13% 38% 35% 3	657
August	1st to 10th	Night	11% 3 11% 43% 30% 2	597
	11th to 20th	Night	11% 4 11% 39% 31% 3	624
	21st to end	Night	12% 2 15% 39% 28% 4	880
September	1st to 10th	Night	16% 3 16% 34% 28% 4	800
	11th to 20th	Night	14% 4 16% 34% 29% 3	800
	21st to end	Night	23% 5% 19% 32% 19% 2	800
October	1st to 10th	Night	22% 6% 18% 30% 21% 3	800
	11th to 20th	Night	17% 9% 27% 33% 13% 2	800
	21st to end	Night	18% 10% 29% 31% 11% 1	880
November	1st to 10th	Night	13% 10% 29% 37% 10% 1	820
	11th to 20th	Night	19% 15% 26% 30% 9%	840
	21st to end	Night	18% 13% 32% 30% 7%	840
December	1st to 10th	Night	19% 16% 34% 25% 6%	840
	11th to 20th	Night	20% 13% 34% 28% 4	840
	21st to end	Night	20% 13% 30% 34% 3	924

Page generated at 2026-02-13 01:42:15. Version ac07

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