Meadowlark Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Meadowlark Ridge Observatory 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	12% 9% 3 8% 5% 4 4 4 6% 7% 38%	127571
	Night	12% 9% 4 8% 5% 4 4 3 5% 6% 39%	124046
Transparency	Day	44% 5% 12% 25% 13% 1	131053
	Night	45% 4 11% 23% 15% 2	128637
Seeing	Day	16% 11% 29% 25% 14% 5%	17454
	Night	17% 10% 30% 31% 12% 1	27361

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	8% 9% 8% 16% 7% 6% 5% 3 5% 5% 27%	3625
	11th to 20th	Day	8% 10% 6% 12% 5% 4 4 7% 6% 7% 31%	3620
	21st to end	Day	12% 15% 7% 9% 4 3 3 2 5% 6% 36%	4240
February	1st to 10th	Day	11% 13% 5% 10% 5% 5% 4 4 5% 6% 31%	1800
	11th to 20th	Day	13% 12% 4 7% 5% 4 5% 4 5% 6% 36%	1871
	21st to end	Day	11% 14% 4 10% 6% 5% 4 3 5% 6% 33%	1650
March	1st to 10th	Day	15% 8% 3 6% 3 3 3 3 4 7% 45%	4480
	11th to 20th	Day	11% 6% 2 8% 4 4 4 4 6% 8% 44%	4859
	21st to end	Day	21% 13% 4 9% 5% 4 4 3 4 5% 28%	5867
April	1st to 10th	Day	18% 12% 4 7% 5% 5% 4 3 5% 6% 31%	2400
	11th to 20th	Day	17% 10% 3 8% 5% 4 4 4 5% 6% 33%	2374
	21st to end	Day	18% 10% 3 9% 5% 4 4 3 5% 6% 33%	2442
May	1st to 10th	Day	14% 8% 3 6% 5% 4 4 4 7% 7% 39%	6087
	11th to 20th	Day	13% 5% 2 7% 5% 5% 5% 4 6% 8% 41%	6319
	21st to end	Day	14% 7% 2 6% 4 4 5% 4 7% 9% 38%	6935
June	1st to 10th	Day	11% 5% 1 6% 5% 4 5% 5% 6% 9% 43%	2800
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 5% 7% 9% 42%	2800
	21st to end	Day	11% 6% 3 7% 4 5% 5% 5% 6% 8% 39%	2800
July	1st to 10th	Day	8% 6% 2 8% 4 5% 6% 4 8% 10% 38%	6360
	11th to 20th	Day	7% 6% 2 6% 4 5% 5% 4 6% 9% 46%	6360
	21st to end	Day	9% 7% 3 7% 5% 5% 5% 5% 6% 10% 38%	6924
August	1st to 10th	Day	9% 5% 2 7% 5% 5% 6% 5% 7% 9% 41%	4440
	11th to 20th	Day	11% 5% 2 6% 4 5% 5% 4 6% 8% 46%	3952
	21st to end	Day	9% 6% 3 6% 4 4 4 4 6% 9% 46%	4312
September	1st to 10th	Day	11% 5% 2 6% 5% 4 5% 3 6% 7% 44%	2400
	11th to 20th	Day	11% 5% 2 5% 3 3 3 4 6% 7% 51%	2348
	21st to end	Day	11% 7% 3 7% 4 4 4 3 6% 7% 45%	2200
October	1st to 10th	Day	12% 7% 2 6% 4 3 4 3 4 6% 49%	2022
	11th to 20th	Day	18% 9% 3 8% 4 3 4 3 5% 6% 37%	2000
	21st to end	Day	16% 11% 3 6% 4 4 4 2 5% 5% 40%	2035
November	1st to 10th	Day	12% 7% 3 7% 5% 4 4 4 5% 6% 43%	1852
	11th to 20th	Day	13% 13% 3 8% 5% 4 5% 3 5% 6% 34%	1869
	21st to end	Day	13% 13% 4 10% 4 4 3 3 4 6% 35%	1680
December	1st to 10th	Day	8% 9% 4 8% 6% 4 5% 4 5% 7% 40%	2690
	11th to 20th	Day	13% 14% 5% 11% 7% 5% 5% 4 6% 7% 25%	3088
	21st to end	Day	19% 23% 9% 11% 5% 4 4 4 5% 5% 13%	4070
January	1st to 10th	Night	9% 11% 6% 15% 7% 4 4 3 5% 5% 32%	6363
	11th to 20th	Night	10% 13% 6% 13% 7% 5% 5% 5% 7% 6% 24%	6360
	21st to end	Night	12% 15% 6% 10% 4 5% 4 3 4 5% 31%	6724
February	1st to 10th	Night	11% 14% 4 10% 5% 6% 4 3 5% 5% 33%	2600
	11th to 20th	Night	11% 11% 3 8% 6% 4 4 3 5% 5% 39%	2416
	21st to end	Night	16% 11% 4 8% 4 3 4 3 5% 6% 36%	1980
March	1st to 10th	Night	16% 9% 3 7% 4 4 3 3 4 4 42%	5373
	11th to 20th	Night	9% 7% 2 6% 4 4 4 3 5% 7% 49%	5131
	21st to end	Night	21% 13% 5% 11% 5% 4 4 3 4 5% 26%	5060
April	1st to 10th	Night	17% 9% 3 7% 5% 3 4 3 6% 6% 38%	2000
	11th to 20th	Night	18% 9% 3 7% 4 4 4 3 5% 6% 37%	1975
	21st to end	Night	17% 7% 3 7% 4 5% 3 4 5% 8% 37%	1956
May	1st to 10th	Night	17% 7% 3 7% 4 3 4 3 6% 7% 39%	3813
	11th to 20th	Night	10% 5% 2 5% 4 5% 4 4 6% 8% 46%	3596
	21st to end	Night	14% 7% 2 6% 4 5% 4 4 5% 8% 41%	3942
June	1st to 10th	Night	9% 4 2 5% 5% 4 5% 4 7% 10% 46%	1600
	11th to 20th	Night	12% 6% 2 5% 4 4 4 3 6% 11% 43%	1600
	21st to end	Night	9% 6% 3 6% 4 4 4 4 5% 7% 49%	1600
July	1st to 10th	Night	12% 6% 3 6% 4 4 5% 4 6% 8% 42%	3618
	11th to 20th	Night	5% 5% 2 5% 5% 4 5% 4 6% 8% 52%	3617
	21st to end	Night	7% 6% 2 6% 4 4 5% 4 6% 8% 48%	3947
August	1st to 10th	Night	8% 5% 2 5% 4 4 5% 4 6% 8% 51%	2717
	11th to 20th	Night	9% 5% 3 6% 3 4 4 3 5% 9% 50%	3100
	21st to end	Night	9% 5% 2 6% 4 4 4 3 5% 7% 51%	3586
September	1st to 10th	Night	8% 4 2 5% 4 3 4 3 5% 8% 55%	2000
	11th to 20th	Night	10% 5% 1 4 3 4 3 4 5% 8% 52%	2030
	21st to end	Night	9% 6% 2 5% 3 4 4 4 5% 7% 51%	2200
October	1st to 10th	Night	11% 6% 3 5% 4 3 4 3 5% 6% 50%	2375
	11th to 20th	Night	15% 9% 2 6% 3 3 3 3 3 6% 45%	2400
	21st to end	Night	18% 8% 4 6% 5% 4 5% 3 5% 7% 37%	2805
November	1st to 10th	Night	11% 8% 3 6% 4 4 3 3 4 6% 47%	2666
	11th to 20th	Night	14% 10% 4 9% 5% 4 4 3 4 6% 36%	2747
	21st to end	Night	16% 11% 4 7% 4 4 3 2 5% 6% 37%	2940
December	1st to 10th	Night	8% 8% 3 7% 5% 5% 5% 4 5% 6% 42%	4720
	11th to 20th	Night	15% 16% 4 10% 6% 5% 4 3 4 5% 27%	5339
	21st to end	Night	20% 19% 6% 13% 5% 5% 4 3 4 5% 17%	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	60% 3 11% 18% 7%	3626
	11th to 20th	Day	50% 4 13% 11% 19% 3	3620
	21st to end	Day	51% 3 13% 20% 12%	4240
February	1st to 10th	Day	54% 4 12% 18% 12% 1	1800
	11th to 20th	Day	49% 4 12% 23% 10% 2	1880
	21st to end	Day	53% 4 9% 20% 11% 2	1650
March	1st to 10th	Day	40% 4 11% 29% 11% 4	4480
	11th to 20th	Day	38% 4 13% 30% 13% 2	4859
	21st to end	Day	59% 4 11% 15% 10% 2	5869
April	1st to 10th	Day	53% 5% 10% 20% 11% 1	2400
	11th to 20th	Day	50% 6% 10% 21% 12% 2	2374
	21st to end	Day	51% 6% 11% 18% 12% 2	2442
May	1st to 10th	Day	43% 5% 10% 24% 18% 1	6122
	11th to 20th	Day	40% 7% 10% 29% 14% 1	6323
	21st to end	Day	41% 6% 11% 28% 12% 2	6949
June	1st to 10th	Day	35% 7% 14% 26% 15% 1	2800
	11th to 20th	Day	37% 7% 14% 24% 17% 2	2800
	21st to end	Day	41% 7% 13% 24% 13% 2	2800
July	1st to 10th	Day	39% 6% 15% 29% 10% 1	6291
	11th to 20th	Day	34% 6% 14% 31% 14% 1	6285
	21st to end	Day	41% 6% 15% 22% 15% 2	6728
August	1st to 10th	Day	38% 6% 15% 28% 13% 1	4425
	11th to 20th	Day	36% 5% 14% 31% 14% 1	3990
	21st to end	Day	34% 5% 14% 31% 16% 1	4311
September	1st to 10th	Day	37% 7% 10% 27% 18% 1	2400
	11th to 20th	Day	31% 5% 13% 32% 17% 2	2348
	21st to end	Day	39% 5% 9% 29% 18% 1	2200
October	1st to 10th	Day	24% 4 6% 39% 26% 1	3295
	11th to 20th	Day	36% 3 8% 27% 24% 2	3240
	21st to end	Day	42% 3 10% 28% 14% 3	3260
November	1st to 10th	Day	41% 5% 13% 25% 14% 2	1852
	11th to 20th	Day	51% 5% 13% 20% 10% 1	1869
	21st to end	Day	52% 4 15% 21% 7% 1	1680
December	1st to 10th	Day	44% 4 19% 25% 7% 1	2690
	11th to 20th	Day	59% 3 13% 17% 7% 2	3085
	21st to end	Day	73% 4 8% 9% 6%	4070
January	1st to 10th	Night	54% 4 10% 21% 11% 1	6363
	11th to 20th	Night	58% 3 10% 11% 16% 1	6360
	21st to end	Night	56% 3 12% 18% 11%	6724
February	1st to 10th	Night	54% 4 10% 18% 12% 2	2600
	11th to 20th	Night	47% 4 11% 22% 14% 1	2417
	21st to end	Night	50% 4 12% 20% 11% 3	1980
March	1st to 10th	Night	46% 4 11% 22% 10% 7%	5373
	11th to 20th	Night	34% 4 11% 34% 14% 3	5131
	21st to end	Night	61% 4 9% 16% 10% 1	5060
April	1st to 10th	Night	46% 6% 10% 23% 14% 2	2000
	11th to 20th	Night	48% 4 6% 21% 17% 3	1975
	21st to end	Night	45% 6% 12% 23% 12% 2	1956
May	1st to 10th	Night	44% 6% 11% 18% 21% 1	3840
	11th to 20th	Night	36% 7% 15% 22% 18% 2	3597
	21st to end	Night	39% 7% 12% 25% 15% 2	3950
June	1st to 10th	Night	32% 7% 14% 27% 20% 1	1600
	11th to 20th	Night	35% 6% 10% 25% 22% 2	1600
	21st to end	Night	34% 6% 16% 22% 19% 3	1600
July	1st to 10th	Night	39% 6% 14% 26% 14% 2	3580
	11th to 20th	Night	29% 6% 13% 31% 18% 2	3572
	21st to end	Night	32% 6% 17% 23% 19% 3	3832
August	1st to 10th	Night	31% 5% 14% 29% 20% 1	2708
	11th to 20th	Night	32% 5% 13% 32% 18% 1	3128
	21st to end	Night	33% 5% 12% 29% 18% 3	3586
September	1st to 10th	Night	28% 5% 13% 28% 24% 2	2000
	11th to 20th	Night	30% 5% 12% 33% 18% 2	2030
	21st to end	Night	34% 4 10% 30% 21% 1	2200
October	1st to 10th	Night	25% 3 6% 37% 28% 1	3882
	11th to 20th	Night	33% 3 10% 27% 24% 3	3899
	21st to end	Night	44% 4 8% 27% 15% 2	4530
November	1st to 10th	Night	40% 4 10% 26% 17% 2	2666
	11th to 20th	Night	49% 5% 12% 22% 11% 2	2747
	21st to end	Night	50% 3 13% 23% 10% 1	2940
December	1st to 10th	Night	43% 4 15% 28% 10% 1	4720
	11th to 20th	Night	60% 4 11% 15% 10% 1	5341
	21st to end	Night	70% 4 8% 13% 5%	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	17% 16% 30% 27% 9% 2	303
	11th to 20th	Day	18% 17% 40% 18% 5% 1	300
	21st to end	Day	21% 16% 35% 22% 6%	330
February	1st to 10th	Day	16% 21% 40% 17% 5% 1	300
	11th to 20th	Day	22% 20% 35% 20% 3	300
	21st to end	Day	24% 19% 38% 17% 2	249
March	1st to 10th	Day	18% 19% 42% 17% 4	300
	11th to 20th	Day	21% 20% 36% 15% 6% 2	300
	21st to end	Day	28% 14% 32% 19% 6% 2	502
April	1st to 10th	Day	25% 15% 33% 22% 5%	500
	11th to 20th	Day	26% 17% 26% 18% 11% 2	492
	21st to end	Day	24% 11% 31% 23% 9% 2	500
May	1st to 10th	Day	21% 9% 31% 28% 9% 3	598
	11th to 20th	Day	21% 10% 27% 25% 12% 5%	725
	21st to end	Day	17% 9% 26% 25% 16% 7%	789
June	1st to 10th	Day	9% 7% 30% 29% 20% 5%	730
	11th to 20th	Day	12% 6% 30% 30% 14% 6%	730
	21st to end	Day	13% 8% 27% 31% 16% 4	730
July	1st to 10th	Day	8% 3 19% 30% 26% 13%	721
	11th to 20th	Day	10% 6% 24% 27% 23% 10%	718
	21st to end	Day	9% 4 25% 32% 22% 8%	794
August	1st to 10th	Day	8% 3 19% 34% 26% 10%	726
	11th to 20th	Day	13% 4 20% 26% 23% 13%	586
	21st to end	Day	12% 6% 19% 30% 25% 9%	583
September	1st to 10th	Day	12% 7% 23% 29% 20% 9%	530
	11th to 20th	Day	11% 3 19% 31% 24% 11%	530
	21st to end	Day	13% 10% 26% 27% 19% 6%	530
October	1st to 10th	Day	14% 10% 27% 30% 15% 4	352
	11th to 20th	Day	22% 16% 32% 19% 9% 1	330
	21st to end	Day	25% 17% 28% 23% 6% 1	363
November	1st to 10th	Day	17% 18% 37% 20% 8% 2	330
	11th to 20th	Day	20% 19% 35% 18% 7% 1	330
	21st to end	Day	22% 14% 42% 18% 5%	330
December	1st to 10th	Day	16% 18% 39% 18% 7% 2	330
	11th to 20th	Day	20% 15% 38% 19% 8%	330
	21st to end	Day	27% 15% 38% 17% 3	363
January	1st to 10th	Night	16% 15% 37% 25% 7% 1	1006
	11th to 20th	Night	19% 13% 37% 25% 5% 1	1000
	21st to end	Night	20% 12% 36% 27% 5%	1100
February	1st to 10th	Night	19% 12% 39% 24% 6%	1000
	11th to 20th	Night	17% 16% 38% 25% 4	861
	21st to end	Night	22% 13% 39% 22% 4	660
March	1st to 10th	Night	22% 13% 36% 24% 5% 1	800
	11th to 20th	Night	17% 11% 35% 29% 8%	673
	21st to end	Night	24% 10% 32% 27% 6% 1	660
April	1st to 10th	Night	20% 15% 36% 24% 5%	600
	11th to 20th	Night	24% 12% 29% 27% 7%	593
	21st to end	Night	20% 10% 32% 29% 9% 1	600
May	1st to 10th	Night	18% 8% 34% 31% 9% 1	600
	11th to 20th	Night	19% 6% 29% 34% 11% 1	591
	21st to end	Night	13% 6% 27% 39% 15% 1	650
June	1st to 10th	Night	10% 5% 24% 45% 15% 1	600
	11th to 20th	Night	15% 3 29% 39% 14%	600
	21st to end	Night	10% 6% 25% 43% 16% 1	600
July	1st to 10th	Night	9% 3 12% 39% 32% 4	585
	11th to 20th	Night	8% 3 20% 42% 24% 3	582
	21st to end	Night	7% 2 19% 46% 25% 2	657
August	1st to 10th	Night	5% 3 15% 46% 28% 3	597
	11th to 20th	Night	10% 4 13% 38% 30% 5%	594
	21st to end	Night	11% 1 15% 44% 27% 2	660
September	1st to 10th	Night	9% 3 22% 37% 24% 6%	600
	11th to 20th	Night	12% 3 20% 34% 27% 4	630
	21st to end	Night	12% 8% 22% 37% 20% 2	800
October	1st to 10th	Night	15% 7% 26% 34% 18% 1	800
	11th to 20th	Night	20% 12% 28% 31% 9%	800
	21st to end	Night	21% 12% 32% 28% 7% 1	880
November	1st to 10th	Night	16% 10% 38% 26% 10% 1	820
	11th to 20th	Night	19% 14% 37% 24% 5% 1	857
	21st to end	Night	21% 15% 32% 25% 7%	1050
December	1st to 10th	Night	20% 13% 36% 25% 6%	1050
	11th to 20th	Night	23% 13% 34% 24% 5% 1	1050
	21st to end	Night	28% 14% 31% 24% 3	1155

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