Charlie Elliott WLC
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Charlie Elliott WLC clear sky chart from 2005-11-06 to 2026-03-03.

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%	131140
	Night	13% 6% 2 6% 4 4 4 4 6% 8% 44%	130026
Transparency	Day	38% 6% 11% 20% 18% 6%	134916
	Night	37% 5% 10% 20% 20% 8%	134320
Seeing	Day	17% 10% 22% 24% 19% 9%	16674
	Night	15% 9% 22% 29% 21% 4	26782

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	16% 8% 3 6% 4 4 4 3 4 5% 44%	5258
	11th to 20th	Day	10% 7% 2 4 3 2 2 2 4 5% 58%	5280
	21st to end	Day	22% 9% 3 6% 4 4 3 3 3 5% 38%	5942
February	1st to 10th	Day	14% 8% 3 6% 4 4 4 4 5% 7% 40%	2100
	11th to 20th	Day	22% 6% 2 5% 4 3 4 3 4 5% 42%	2048
	21st to end	Day	18% 6% 2 7% 4 4 4 3 5% 5% 41%	1730
March	1st to 10th	Day	21% 8% 3 7% 5% 4 4 3 4 5% 37%	4725
	11th to 20th	Day	9% 5% 2 5% 4 4 4 3 5% 7% 53%	4980
	21st to end	Day	16% 6% 3 7% 4 4 4 3 4 5% 46%	5465
April	1st to 10th	Day	12% 5% 2 6% 4 3 4 4 5% 6% 48%	2200
	11th to 20th	Day	11% 5% 2 6% 4 4 4 3 5% 8% 49%	2360
	21st to end	Day	9% 5% 2 5% 4 4 5% 3 6% 6% 51%	2585
May	1st to 10th	Day	11% 7% 2 6% 5% 5% 5% 4 6% 8% 40%	5862
	11th to 20th	Day	17% 7% 3 7% 5% 5% 6% 5% 7% 8% 31%	5861
	21st to end	Day	11% 6% 2 7% 4 5% 5% 4 6% 9% 42%	6433
June	1st to 10th	Day	9% 6% 3 7% 6% 7% 6% 5% 8% 10% 33%	2600
	11th to 20th	Day	6% 4 2 5% 5% 5% 7% 5% 9% 11% 41%	2600
	21st to end	Day	6% 4 2 5% 5% 6% 7% 6% 8% 10% 40%	2600
July	1st to 10th	Day	7% 6% 3 9% 7% 7% 8% 6% 9% 11% 28%	5900
	11th to 20th	Day	5% 3 2 6% 6% 6% 7% 7% 10% 13% 35%	5900
	21st to end	Day	7% 7% 3 9% 7% 8% 8% 7% 9% 11% 25%	6424
August	1st to 10th	Day	12% 6% 2 6% 6% 6% 6% 6% 9% 11% 31%	4234
	11th to 20th	Day	6% 5% 2 6% 5% 5% 5% 5% 8% 9% 46%	3977
	21st to end	Day	7% 5% 2 6% 4 4 5% 4 6% 9% 48%	4252
September	1st to 10th	Day	11% 6% 2 7% 5% 5% 5% 5% 7% 8% 39%	2200
	11th to 20th	Day	14% 7% 2 5% 4 5% 5% 4 6% 7% 41%	2200
	21st to end	Day	14% 6% 2 5% 5% 4 4 4 5% 6% 46%	2200
October	1st to 10th	Day	12% 5% 2 5% 3 3 3 4 5% 7% 53%	2200
	11th to 20th	Day	12% 5% 1 3 3 2 3 3 4 7% 58%	2061
	21st to end	Day	12% 5% 2 4 3 4 3 2 4 5% 56%	2200
November	1st to 10th	Day	13% 5% 1 4 4 3 3 3 4 4 55%	1935
	11th to 20th	Day	13% 5% 1 4 3 3 3 3 4 6% 53%	1890
	21st to end	Day	13% 6% 2 5% 4 4 4 4 4 6% 49%	1890
December	1st to 10th	Day	15% 8% 2 6% 3 3 3 2 5% 6% 47%	3020
	11th to 20th	Day	17% 8% 2 5% 4 4 4 2 4 5% 46%	3463
	21st to end	Day	22% 6% 2 5% 3 3 3 3 4 6% 43%	4565
January	1st to 10th	Night	13% 6% 3 5% 4 4 4 3 5% 6% 48%	7635
	11th to 20th	Night	12% 7% 2 6% 3 4 4 3 5% 5% 50%	7680
	21st to end	Night	19% 10% 2 7% 3 3 3 3 4 5% 40%	8221
February	1st to 10th	Night	14% 6% 2 6% 5% 4 4 3 5% 6% 45%	2520
	11th to 20th	Night	20% 7% 3 5% 4 3 3 3 4 5% 43%	2458
	21st to end	Night	16% 6% 2 6% 5% 4 3 4 5% 5% 44%	2076
March	1st to 10th	Night	20% 8% 3 6% 4 3 4 3 5% 6% 38%	5172
	11th to 20th	Night	10% 4 2 4 3 3 4 4 6% 8% 53%	4980
	21st to end	Night	15% 6% 2 5% 3 4 4 3 5% 6% 47%	5467
April	1st to 10th	Night	11% 4 2 5% 3 4 5% 4 6% 8% 49%	2200
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 5% 8% 51%	2005
	21st to end	Night	7% 5% 2 6% 4 4 5% 3 6% 7% 52%	1812
May	1st to 10th	Night	10% 6% 2 7% 5% 5% 5% 4 7% 11% 38%	4033
	11th to 20th	Night	18% 6% 2 6% 5% 5% 5% 4 6% 8% 33%	4032
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 6% 10% 45%	4421
June	1st to 10th	Night	7% 6% 2 8% 5% 5% 7% 5% 8% 11% 38%	1800
	11th to 20th	Night	6% 4 2 5% 5% 4 5% 5% 8% 13% 44%	1800
	21st to end	Night	5% 4 2 6% 6% 5% 6% 6% 9% 12% 40%	1800
July	1st to 10th	Night	8% 8% 3 9% 7% 5% 6% 5% 8% 12% 30%	4058
	11th to 20th	Night	5% 4 2 7% 5% 6% 7% 6% 11% 15% 32%	4057
	21st to end	Night	8% 9% 3 9% 6% 6% 7% 6% 8% 10% 28%	4427
August	1st to 10th	Night	10% 6% 3 7% 6% 6% 7% 6% 8% 14% 28%	2915
	11th to 20th	Night	7% 4 2 6% 5% 6% 5% 4 6% 11% 44%	3067
	21st to end	Night	8% 4 1 5% 4 4 5% 4 6% 8% 50%	3610
September	1st to 10th	Night	7% 6% 3 7% 5% 5% 6% 4 8% 11% 38%	2200
	11th to 20th	Night	12% 5% 2 7% 5% 4 4 4 6% 7% 44%	2200
	21st to end	Night	11% 6% 2 7% 4 4 4 5% 5% 8% 45%	2200
October	1st to 10th	Night	11% 5% 2 6% 4 3 4 4 5% 6% 51%	2200
	11th to 20th	Night	11% 4 2 5% 2 3 3 2 4 5% 59%	2336
	21st to end	Night	12% 4 1 4 4 4 4 3 4 5% 57%	2640
November	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 4 6% 54%	2579
	11th to 20th	Night	13% 5% 2 5% 3 2 3 2 4 5% 56%	2730
	21st to end	Night	13% 5% 2 5% 4 4 3 3 4 7% 49%	2730
December	1st to 10th	Night	14% 7% 2 5% 3 3 3 3 4 5% 53%	4380
	11th to 20th	Night	16% 6% 2 5% 3 3 3 3 5% 7% 48%	4952
	21st to end	Night	20% 7% 2 6% 4 4 3 3 4 6% 42%	6633

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	42% 4 5% 21% 20% 7%	5259
	11th to 20th	Day	30% 2 3 19% 31% 15%	5280
	21st to end	Day	50% 2 4 15% 20% 9%	5942
February	1st to 10th	Day	43% 4 8% 19% 19% 7%	2100
	11th to 20th	Day	44% 4 5% 20% 22% 6%	2058
	21st to end	Day	45% 4 7% 16% 20% 9%	1730
March	1st to 10th	Day	49% 3 7% 12% 22% 7%	4725
	11th to 20th	Day	31% 4 7% 16% 22% 20%	4980
	21st to end	Day	43% 3 5% 21% 20% 8%	5465
April	1st to 10th	Day	36% 4 10% 22% 21% 8%	2200
	11th to 20th	Day	34% 3 8% 21% 24% 9%	2360
	21st to end	Day	32% 4 10% 27% 24% 3	2585
May	1st to 10th	Day	40% 7% 14% 22% 15% 2	5897
	11th to 20th	Day	48% 8% 15% 19% 10% 1	5865
	21st to end	Day	38% 6% 12% 22% 20% 2	6447
June	1st to 10th	Day	43% 7% 15% 22% 11% 2	2600
	11th to 20th	Day	32% 8% 18% 25% 15% 1	2600
	21st to end	Day	34% 9% 19% 21% 14% 3	2600
July	1st to 10th	Day	43% 12% 18% 21% 5% 1	5835
	11th to 20th	Day	33% 14% 27% 21% 4 1	5831
	21st to end	Day	47% 14% 16% 19% 4	6240
August	1st to 10th	Day	42% 9% 17% 28% 4	4221
	11th to 20th	Day	31% 8% 17% 28% 14% 2	4016
	21st to end	Day	31% 7% 15% 26% 17% 4	4252
September	1st to 10th	Day	39% 8% 15% 16% 18% 4	2200
	11th to 20th	Day	40% 7% 10% 20% 21% 2	2200
	21st to end	Day	38% 4 10% 22% 20% 6%	2200
October	1st to 10th	Day	27% 3 7% 16% 35% 13%	3590
	11th to 20th	Day	18% 2 4 17% 29% 30%	3340
	21st to end	Day	24% 2 5% 21% 35% 13%	3538
November	1st to 10th	Day	34% 3 8% 15% 29% 12%	1935
	11th to 20th	Day	32% 3 6% 20% 27% 12%	1890
	21st to end	Day	36% 4 7% 21% 26% 7%	1890
December	1st to 10th	Day	40% 3 5% 18% 25% 9%	3020
	11th to 20th	Day	42% 3 8% 19% 20% 7%	3460
	21st to end	Day	42% 4 7% 23% 22% 2	4565
January	1st to 10th	Night	37% 4 7% 23% 23% 6%	7636
	11th to 20th	Night	35% 3 4 20% 27% 10%	7680
	21st to end	Night	48% 2 3 15% 24% 8%	8221
February	1st to 10th	Night	40% 3 7% 20% 22% 9%	2520
	11th to 20th	Night	45% 3 5% 19% 20% 8%	2459
	21st to end	Night	41% 4 7% 17% 18% 13%	2076
March	1st to 10th	Night	47% 3 8% 15% 17% 10%	5172
	11th to 20th	Night	29% 4 8% 14% 26% 19%	4980
	21st to end	Night	38% 4 6% 20% 21% 12%	5467
April	1st to 10th	Night	33% 3 11% 21% 22% 10%	2200
	11th to 20th	Night	32% 4 6% 23% 24% 11%	2005
	21st to end	Night	30% 5% 11% 24% 24% 6%	1812
May	1st to 10th	Night	38% 7% 16% 22% 13% 3	4060
	11th to 20th	Night	47% 6% 15% 20% 11% 1	4033
	21st to end	Night	33% 7% 15% 23% 20% 3	4429
June	1st to 10th	Night	38% 8% 18% 21% 14% 1	1800
	11th to 20th	Night	30% 7% 21% 28% 12% 3	1800
	21st to end	Night	31% 9% 22% 20% 14% 3	1800
July	1st to 10th	Night	44% 12% 21% 18% 4 1	4015
	11th to 20th	Night	34% 15% 29% 18% 4 1	4006
	21st to end	Night	47% 13% 20% 16% 4 1	4297
August	1st to 10th	Night	43% 10% 18% 24% 5%	2904
	11th to 20th	Night	33% 8% 18% 25% 14% 2	3094
	21st to end	Night	31% 7% 14% 26% 20% 2	3610
September	1st to 10th	Night	37% 8% 16% 18% 16% 4	2200
	11th to 20th	Night	38% 7% 13% 20% 19% 4	2200
	21st to end	Night	37% 6% 11% 18% 21% 7%	2200
October	1st to 10th	Night	30% 4 8% 14% 31% 12%	3590
	11th to 20th	Night	18% 2 3 16% 29% 31%	3796
	21st to end	Night	23% 3 4 21% 31% 19%	4252
November	1st to 10th	Night	32% 3 8% 16% 28% 13%	2579
	11th to 20th	Night	33% 2 6% 18% 28% 13%	2730
	21st to end	Night	36% 3 7% 19% 26% 9%	2730
December	1st to 10th	Night	35% 3 5% 19% 30% 8%	4380
	11th to 20th	Night	37% 3 11% 18% 23% 7%	4954
	21st to end	Night	45% 4 5% 25% 19% 2	6633

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	25% 23% 40% 10% 2	330
	11th to 20th	Day	26% 22% 32% 12% 6% 1	330
	21st to end	Day	25% 26% 35% 11% 3	363
February	1st to 10th	Day	22% 20% 39% 15% 4	330
	11th to 20th	Day	38% 16% 31% 13% 1	330
	21st to end	Day	26% 21% 36% 15% 3	273
March	1st to 10th	Day	24% 18% 32% 18% 7%	401
	11th to 20th	Day	22% 15% 34% 22% 6% 1	500
	21st to end	Day	20% 17% 33% 23% 6% 1	550
April	1st to 10th	Day	20% 16% 29% 24% 10% 1	500
	11th to 20th	Day	13% 15% 33% 23% 13% 2	492
	21st to end	Day	14% 11% 26% 29% 17% 3	500
May	1st to 10th	Day	14% 14% 28% 25% 14% 5%	503
	11th to 20th	Day	16% 7% 23% 27% 18% 10%	527
	21st to end	Day	16% 6% 17% 29% 22% 11%	573
June	1st to 10th	Day	10% 6% 19% 26% 28% 12%	530
	11th to 20th	Day	7% 4 16% 28% 25% 20%	530
	21st to end	Day	9% 2 13% 32% 27% 17%	530
July	1st to 10th	Day	9% 3 8% 24% 34% 23%	525
	11th to 20th	Day	8% 1 5% 24% 37% 26%	524
	21st to end	Day	6% 3 8% 23% 38% 22%	576
August	1st to 10th	Day	16% 3 12% 23% 27% 18%	526
	11th to 20th	Day	10% 2 8% 24% 36% 20%	519
	21st to end	Day	14% 2 10% 28% 29% 17%	583
September	1st to 10th	Day	10% 5% 12% 30% 28% 15%	530
	11th to 20th	Day	17% 2 11% 27% 31% 12%	530
	21st to end	Day	16% 3 16% 26% 31% 7%	530
October	1st to 10th	Day	15% 5% 22% 32% 16% 8%	530
	11th to 20th	Day	15% 8% 23% 27% 22% 5%	530
	21st to end	Day	16% 9% 25% 28% 18% 4	583
November	1st to 10th	Day	21% 7% 26% 30% 14% 2	413
	11th to 20th	Day	17% 15% 38% 24% 5% 2	330
	21st to end	Day	17% 17% 30% 23% 11% 2	330
December	1st to 10th	Day	31% 18% 30% 15% 5% 1	330
	11th to 20th	Day	25% 17% 30% 20% 7%	330
	21st to end	Day	30% 14% 30% 20% 5% 1	363
January	1st to 10th	Night	24% 18% 30% 22% 6% 1	840
	11th to 20th	Night	22% 16% 29% 25% 8%	840
	21st to end	Night	23% 15% 34% 24% 3	924
February	1st to 10th	Night	19% 14% 32% 30% 5%	840
	11th to 20th	Night	24% 18% 30% 26% 2	823
	21st to end	Night	20% 17% 35% 25% 3	692
March	1st to 10th	Night	18% 14% 31% 30% 7%	809
	11th to 20th	Night	18% 12% 35% 26% 9%	800
	21st to end	Night	17% 14% 30% 28% 10%	880
April	1st to 10th	Night	15% 13% 32% 27% 13%	800
	11th to 20th	Night	15% 11% 27% 30% 16% 1	623
	21st to end	Night	9% 9% 22% 40% 19% 1	600
May	1st to 10th	Night	10% 7% 26% 37% 19% 2	600
	11th to 20th	Night	14% 4 21% 33% 23% 5%	591
	21st to end	Night	11% 3 14% 34% 30% 8%	650
June	1st to 10th	Night	9% 3 11% 40% 33% 5%	600
	11th to 20th	Night	7% 1 13% 30% 36% 13%	600
	21st to end	Night	7% 2 8% 34% 40% 9%	600
July	1st to 10th	Night	10% 2 6% 27% 42% 14%	585
	11th to 20th	Night	7% 2 4 25% 48% 15%	582
	21st to end	Night	7% 2 5% 27% 48% 10%	657
August	1st to 10th	Night	10% 3 7% 29% 38% 13%	597
	11th to 20th	Night	10% 3 8% 24% 46% 9%	594
	21st to end	Night	14% 3 8% 27% 37% 10%	671
September	1st to 10th	Night	8% 3 12% 29% 38% 9%	800
	11th to 20th	Night	14% 2 12% 27% 41% 6%	800
	21st to end	Night	13% 4 13% 32% 34% 4	800
October	1st to 10th	Night	14% 4 18% 33% 25% 6%	800
	11th to 20th	Night	12% 6% 25% 31% 23% 3	800
	21st to end	Night	15% 9% 20% 33% 21% 3	880
November	1st to 10th	Night	14% 8% 23% 33% 20% 1	820
	11th to 20th	Night	14% 12% 28% 31% 14% 1	840
	21st to end	Night	16% 14% 26% 31% 13% 1	840
December	1st to 10th	Night	22% 12% 28% 28% 9% 1	840
	11th to 20th	Night	20% 12% 28% 28% 10% 1	840
	21st to end	Night	27% 13% 24% 28% 7%	924

Page generated at 2026-02-28 01:40:21. Version ac07

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