Laurel Bank
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Laurel Bank clear sky chart from 2005-11-06 to 2026-04-02.

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	13% 6% 2 6% 5% 5% 5% 4 6% 8% 39%	130987
	Night	13% 6% 2 6% 4 4 4 4 6% 7% 43%	130830
Transparency	Day	39% 9% 13% 21% 15% 4	134593
	Night	37% 8% 13% 22% 17% 4	135294
Seeing	Day	21% 15% 24% 22% 14% 5%	16897
	Night	18% 12% 22% 30% 16% 2	27302

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	13% 8% 2 6% 4 4 4 3 4 6% 46%	5258
	11th to 20th	Day	9% 8% 3 7% 4 4 4 3 5% 6% 47%	5280
	21st to end	Day	14% 7% 2 8% 5% 4 3 2 3 5% 47%	5780
February	1st to 10th	Day	12% 8% 2 8% 5% 5% 5% 4 5% 6% 39%	1890
	11th to 20th	Day	17% 7% 2 7% 5% 5% 5% 4 5% 7% 38%	1880
	21st to end	Day	15% 8% 2 6% 4 4 5% 4 6% 7% 38%	1809
March	1st to 10th	Day	17% 7% 3 7% 5% 5% 5% 4 6% 7% 35%	5045
	11th to 20th	Day	11% 5% 2 4 4 3 4 3 5% 8% 50%	5090
	21st to end	Day	13% 7% 3 7% 5% 5% 5% 3 6% 6% 40%	5586
April	1st to 10th	Day	11% 7% 2 6% 4 5% 4 4 5% 7% 45%	2288
	11th to 20th	Day	13% 5% 2 6% 5% 4 5% 4 6% 7% 44%	2374
	21st to end	Day	15% 6% 2 7% 5% 4 5% 4 5% 7% 41%	2542
May	1st to 10th	Day	13% 6% 2 7% 6% 7% 6% 6% 8% 9% 30%	5862
	11th to 20th	Day	21% 7% 2 7% 5% 5% 5% 5% 7% 7% 29%	5861
	21st to end	Day	14% 5% 2 6% 5% 4 6% 5% 7% 10% 37%	6433
June	1st to 10th	Day	11% 4 2 6% 6% 5% 6% 5% 7% 10% 40%	2600
	11th to 20th	Day	10% 5% 2 6% 5% 6% 6% 5% 7% 11% 37%	2600
	21st to end	Day	8% 5% 2 7% 5% 6% 5% 5% 8% 12% 39%	2600
July	1st to 10th	Day	6% 4 2 6% 6% 5% 6% 5% 8% 11% 40%	5900
	11th to 20th	Day	7% 6% 2 7% 6% 7% 8% 6% 9% 12% 30%	5900
	21st to end	Day	10% 7% 3 8% 6% 6% 7% 6% 9% 11% 28%	6424
August	1st to 10th	Day	14% 6% 2 7% 6% 6% 6% 5% 7% 11% 30%	4234
	11th to 20th	Day	9% 4 2 7% 5% 5% 7% 5% 8% 11% 36%	4174
	21st to end	Day	8% 4 2 5% 4 4 5% 5% 7% 10% 47%	4355
September	1st to 10th	Day	13% 5% 2 6% 3 4 5% 4 5% 7% 45%	2370
	11th to 20th	Day	16% 6% 3 7% 4 4 3 4 5% 8% 40%	2200
	21st to end	Day	24% 6% 3 6% 5% 4 3 3 5% 6% 35%	2200
October	1st to 10th	Day	17% 5% 1 4 3 4 4 3 4 6% 48%	2010
	11th to 20th	Day	13% 5% 2 5% 4 3 4 3 5% 6% 49%	2000
	21st to end	Day	15% 6% 2 5% 5% 4 3 3 4 5% 49%	2200
November	1st to 10th	Day	11% 5% 2 5% 4 3 4 3 5% 7% 53%	2057
	11th to 20th	Day	13% 6% 2 3 4 3 4 3 6% 7% 49%	1921
	21st to end	Day	12% 6% 3 6% 4 4 4 3 5% 6% 47%	1785
December	1st to 10th	Day	10% 7% 2 7% 5% 4 4 4 5% 6% 46%	2680
	11th to 20th	Day	17% 7% 2 6% 4 4 4 3 5% 7% 40%	3234
	21st to end	Day	19% 7% 3 9% 5% 5% 6% 4 6% 6% 31%	4565
January	1st to 10th	Night	11% 7% 2 6% 4 5% 5% 4 6% 6% 45%	7635
	11th to 20th	Night	10% 7% 3 7% 5% 3 3 3 4 5% 49%	7680
	21st to end	Night	15% 8% 3 6% 4 3 3 3 4 5% 47%	8401
February	1st to 10th	Night	13% 8% 3 6% 4 4 5% 3 6% 7% 42%	2730
	11th to 20th	Night	18% 7% 3 7% 5% 4 4 3 5% 6% 38%	2621
	21st to end	Night	14% 7% 2 7% 5% 4 5% 4 6% 7% 40%	1996
March	1st to 10th	Night	18% 7% 2 5% 4 4 4 3 6% 6% 42%	5028
	11th to 20th	Night	11% 4 2 5% 3 3 4 3 5% 8% 52%	5090
	21st to end	Night	12% 7% 3 6% 5% 4 4 3 5% 6% 43%	5588
April	1st to 10th	Night	14% 7% 2 5% 4 4 4 4 6% 8% 42%	2133
	11th to 20th	Night	13% 5% 2 5% 4 4 4 5% 5% 8% 47%	1975
	21st to end	Night	14% 6% 2 5% 4 4 4 3 6% 6% 46%	1874
May	1st to 10th	Night	15% 7% 3 8% 5% 4 4 4 6% 9% 37%	4033
	11th to 20th	Night	24% 7% 3 8% 4 4 5% 3 5% 6% 31%	4032
	21st to end	Night	16% 6% 2 6% 4 4 5% 4 7% 9% 37%	4421
June	1st to 10th	Night	9% 5% 1 5% 4 4 5% 4 9% 10% 44%	1800
	11th to 20th	Night	9% 5% 2 6% 4 4 4 4 7% 10% 46%	1800
	21st to end	Night	8% 3 1 5% 4 5% 5% 4 6% 10% 49%	1800
July	1st to 10th	Night	8% 4 2 6% 4 5% 6% 4 7% 11% 41%	4058
	11th to 20th	Night	8% 7% 3 8% 5% 5% 6% 5% 7% 11% 34%	4057
	21st to end	Night	9% 7% 3 8% 6% 6% 6% 5% 7% 10% 32%	4427
August	1st to 10th	Night	17% 5% 2 7% 5% 4 4 4 6% 10% 36%	2915
	11th to 20th	Night	9% 5% 2 7% 4 6% 6% 5% 7% 9% 40%	2875
	21st to end	Night	8% 4 2 6% 4 4 4 3 7% 9% 48%	3509
September	1st to 10th	Night	11% 5% 2 6% 4 4 4 4 7% 7% 47%	2025
	11th to 20th	Night	16% 6% 2 6% 4 3 3 4 5% 7% 44%	2200
	21st to end	Night	23% 7% 2 5% 4 5% 3 3 5% 5% 38%	2200
October	1st to 10th	Night	16% 5% 2 4 3 4 4 3 5% 6% 48%	2390
	11th to 20th	Night	14% 6% 2 4 3 4 4 3 5% 6% 50%	2400
	21st to end	Night	15% 4 2 4 3 3 3 3 5% 6% 52%	2640
November	1st to 10th	Night	13% 6% 2 5% 4 3 3 3 4 5% 52%	2461
	11th to 20th	Night	13% 5% 2 5% 4 3 4 4 5% 7% 50%	2693
	21st to end	Night	12% 5% 2 6% 4 4 4 4 5% 6% 48%	2828
December	1st to 10th	Night	11% 6% 2 5% 4 4 4 4 5% 7% 49%	4720
	11th to 20th	Night	16% 9% 3 6% 5% 5% 4 4 5% 6% 37%	5162
	21st to end	Night	17% 6% 2 6% 5% 5% 5% 4 7% 7% 37%	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	37% 6% 12% 20% 22% 3	5259
	11th to 20th	Day	35% 7% 7% 17% 24% 10%	5280
	21st to end	Day	41% 4 7% 26% 18% 4	5780
February	1st to 10th	Day	44% 7% 11% 20% 16% 2	1890
	11th to 20th	Day	46% 5% 9% 21% 15% 3	1889
	21st to end	Day	44% 8% 10% 18% 16% 5%	1809
March	1st to 10th	Day	44% 7% 11% 18% 13% 7%	5045
	11th to 20th	Day	31% 7% 9% 23% 21% 9%	5090
	21st to end	Day	42% 7% 10% 19% 16% 5%	5586
April	1st to 10th	Day	37% 8% 12% 21% 16% 6%	2288
	11th to 20th	Day	36% 8% 12% 23% 16% 4	2374
	21st to end	Day	42% 8% 12% 23% 12% 3	2542
May	1st to 10th	Day	44% 11% 14% 20% 9% 2	5897
	11th to 20th	Day	50% 10% 12% 18% 9% 1	5865
	21st to end	Day	38% 11% 15% 18% 14% 4	6447
June	1st to 10th	Day	36% 11% 16% 23% 14% 1	2600
	11th to 20th	Day	38% 12% 16% 18% 14% 1	2600
	21st to end	Day	35% 13% 15% 24% 12% 2	2600
July	1st to 10th	Day	34% 12% 19% 20% 11% 4	5835
	11th to 20th	Day	40% 14% 19% 20% 7%	5831
	21st to end	Day	46% 11% 16% 19% 8%	6240
August	1st to 10th	Day	44% 10% 18% 22% 6%	4221
	11th to 20th	Day	37% 11% 15% 25% 11% 1	4213
	21st to end	Day	31% 9% 19% 28% 13% 1	4355
September	1st to 10th	Day	37% 8% 12% 19% 19% 4	2370
	11th to 20th	Day	42% 7% 11% 22% 17% 2	2200
	21st to end	Day	50% 7% 10% 17% 14% 1	2200
October	1st to 10th	Day	31% 5% 9% 21% 27% 7%	3270
	11th to 20th	Day	25% 5% 9% 24% 23% 14%	3240
	21st to end	Day	25% 4 12% 26% 20% 12%	3538
November	1st to 10th	Day	31% 6% 11% 22% 26% 5%	2057
	11th to 20th	Day	33% 6% 10% 23% 22% 5%	1921
	21st to end	Day	37% 5% 12% 24% 19% 3	1785
December	1st to 10th	Day	38% 7% 10% 19% 21% 5%	2680
	11th to 20th	Day	41% 7% 11% 20% 17% 4	3231
	21st to end	Day	47% 10% 11% 19% 12% 1	4565
January	1st to 10th	Night	34% 8% 12% 22% 18% 5%	7636
	11th to 20th	Night	34% 6% 8% 21% 23% 8%	7680
	21st to end	Night	39% 5% 8% 26% 18% 4	8401
February	1st to 10th	Night	41% 6% 13% 21% 18% 2	2730
	11th to 20th	Night	46% 6% 9% 19% 16% 4	2623
	21st to end	Night	41% 8% 12% 22% 12% 5%	1996
March	1st to 10th	Night	39% 7% 10% 20% 17% 7%	5028
	11th to 20th	Night	28% 6% 10% 23% 27% 6%	5090
	21st to end	Night	40% 6% 11% 21% 18% 4	5588
April	1st to 10th	Night	38% 8% 14% 20% 16% 4	2133
	11th to 20th	Night	34% 8% 13% 21% 20% 5%	1975
	21st to end	Night	36% 8% 13% 25% 16% 2	1874
May	1st to 10th	Night	42% 10% 17% 20% 10% 1	4060
	11th to 20th	Night	52% 9% 13% 18% 9%	4033
	21st to end	Night	39% 11% 17% 23% 7% 3	4429
June	1st to 10th	Night	31% 13% 17% 23% 15% 1	1800
	11th to 20th	Night	32% 11% 18% 24% 14% 1	1800
	21st to end	Night	29% 12% 18% 24% 15% 2	1800
July	1st to 10th	Night	35% 13% 18% 20% 12% 2	4015
	11th to 20th	Night	41% 12% 20% 20% 6% 1	4006
	21st to end	Night	44% 12% 16% 19% 9%	4297
August	1st to 10th	Night	43% 9% 19% 23% 5%	2904
	11th to 20th	Night	36% 9% 18% 25% 11% 1	2902
	21st to end	Night	31% 8% 17% 31% 12% 1	3509
September	1st to 10th	Night	35% 9% 15% 20% 17% 5%	2025
	11th to 20th	Night	39% 7% 13% 23% 18% 2	2200
	21st to end	Night	47% 7% 10% 18% 15% 2	2200
October	1st to 10th	Night	34% 5% 9% 21% 26% 5%	3910
	11th to 20th	Night	23% 4 11% 23% 28% 10%	3899
	21st to end	Night	20% 4 10% 30% 26% 10%	4252
November	1st to 10th	Night	34% 5% 9% 22% 24% 5%	2461
	11th to 20th	Night	33% 6% 10% 23% 23% 6%	2693
	21st to end	Night	35% 7% 11% 25% 19% 4	2828
December	1st to 10th	Night	34% 6% 10% 27% 21% 2	4720
	11th to 20th	Night	45% 6% 13% 19% 14% 3	5164
	21st to end	Night	40% 9% 17% 21% 13% 1	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	36% 26% 25% 11% 2	330
	11th to 20th	Day	38% 25% 27% 10%	330
	21st to end	Day	32% 32% 24% 10% 2	363
February	1st to 10th	Day	27% 27% 31% 13% 2	330
	11th to 20th	Day	47% 24% 22% 6% 1	330
	21st to end	Day	32% 26% 29% 12% 2	352
March	1st to 10th	Day	27% 23% 25% 20% 5%	540
	11th to 20th	Day	30% 24% 24% 17% 4 1	540
	21st to end	Day	25% 23% 29% 17% 5%	594
April	1st to 10th	Day	25% 26% 24% 17% 8%	504
	11th to 20th	Day	21% 19% 30% 19% 9% 3	492
	21st to end	Day	23% 17% 29% 19% 10% 2	500
May	1st to 10th	Day	22% 19% 31% 17% 9% 3	503
	11th to 20th	Day	23% 11% 30% 19% 12% 5%	527
	21st to end	Day	20% 11% 23% 22% 18% 7%	573
June	1st to 10th	Day	13% 8% 30% 25% 17% 7%	530
	11th to 20th	Day	11% 9% 24% 29% 19% 8%	530
	21st to end	Day	9% 7% 27% 32% 17% 8%	530
July	1st to 10th	Day	11% 5% 19% 30% 25% 11%	525
	11th to 20th	Day	4 4 19% 35% 25% 12%	524
	21st to end	Day	12% 5% 22% 27% 24% 11%	576
August	1st to 10th	Day	17% 4 21% 23% 25% 10%	526
	11th to 20th	Day	13% 5% 19% 28% 24% 12%	519
	21st to end	Day	11% 4 14% 30% 24% 17%	583
September	1st to 10th	Day	16% 5% 16% 26% 26% 11%	530
	11th to 20th	Day	18% 4 13% 28% 28% 9%	530
	21st to end	Day	31% 9% 18% 26% 15% 3	530
October	1st to 10th	Day	22% 8% 17% 30% 19% 5%	530
	11th to 20th	Day	16% 17% 22% 26% 16% 3	530
	21st to end	Day	22% 16% 26% 23% 12% 2	583
November	1st to 10th	Day	18% 13% 30% 27% 11% 2	535
	11th to 20th	Day	24% 21% 25% 21% 8%	361
	21st to end	Day	25% 22% 26% 20% 6% 1	275
December	1st to 10th	Day	26% 29% 29% 12% 4	220
	11th to 20th	Day	27% 22% 27% 18% 5% 1	259
	21st to end	Day	29% 21% 28% 15% 6%	363
January	1st to 10th	Night	23% 23% 30% 20% 3	840
	11th to 20th	Night	23% 21% 30% 24% 3	840
	21st to end	Night	21% 22% 35% 21% 1	924
February	1st to 10th	Night	20% 20% 29% 29% 2	840
	11th to 20th	Night	29% 24% 28% 18% 1	823
	21st to end	Night	22% 23% 33% 20% 2	692
March	1st to 10th	Night	20% 18% 32% 27% 3	840
	11th to 20th	Night	26% 17% 26% 24% 6%	840
	21st to end	Night	18% 17% 32% 26% 7%	924
April	1st to 10th	Night	22% 19% 28% 26% 6%	805
	11th to 20th	Night	17% 16% 28% 27% 11% 1	791
	21st to end	Night	16% 12% 25% 36% 10%	674
May	1st to 10th	Night	18% 9% 28% 31% 14% 1	600
	11th to 20th	Night	19% 9% 18% 37% 16% 1	591
	21st to end	Night	17% 4 13% 34% 28% 4	650
June	1st to 10th	Night	9% 3 16% 44% 28% 1	600
	11th to 20th	Night	10% 3 14% 37% 34% 3	600
	21st to end	Night	8% 3 12% 42% 32% 4	600
July	1st to 10th	Night	11% 2 10% 38% 35% 5%	585
	11th to 20th	Night	6% 1 9% 34% 44% 5%	582
	21st to end	Night	9% 2 11% 38% 37% 4	657
August	1st to 10th	Night	15% 2 10% 35% 35% 3	597
	11th to 20th	Night	13% 2 6% 37% 38% 3	594
	21st to end	Night	12% 2 9% 35% 36% 6%	829
September	1st to 10th	Night	12% 3 12% 34% 34% 6%	800
	11th to 20th	Night	18% 3 11% 30% 34% 5%	800
	21st to end	Night	25% 6% 17% 29% 22% 2	800
October	1st to 10th	Night	18% 9% 15% 28% 28% 4	800
	11th to 20th	Night	18% 10% 25% 29% 17% 1	800
	21st to end	Night	18% 11% 22% 36% 12% 1	880
November	1st to 10th	Night	18% 9% 23% 35% 14% 1	820
	11th to 20th	Night	19% 15% 22% 33% 10% 1	840
	21st to end	Night	16% 17% 26% 32% 9% 1	840
December	1st to 10th	Night	22% 18% 29% 25% 5%	840
	11th to 20th	Night	19% 18% 28% 31% 5%	840
	21st to end	Night	22% 16% 27% 31% 3	924

Page generated at 2026-03-30 02:18:46. Version ac07

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