Al Meyers Airport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Al Meyers Airport clear sky chart from 2005-11-06 to 2024-03-23.

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% 9% 4 7% 6% 3 5% 5% 6% 7% 33%	78796
	Night	16% 10% 4 7% 6% 3 5% 4 5% 7% 34%	81128
Transparency	Day	49% 6% 12% 20% 12% 1	78506
	Night	50% 6% 11% 20% 12% 1	80939
Seeing	Day	17% 9% 28% 25% 15% 6%	14710
	Night	19% 8% 29% 30% 13% 1	24723

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	17% 15% 7% 9% 8% 3 5% 5% 5% 6% 20%	2527
	11th to 20th	Day	16% 15% 6% 12% 9% 4 7% 7% 5% 6% 13%	2530
	21st to end	Day	26% 18% 8% 10% 7% 3 4 3 3 4 14%	3036
February	1st to 10th	Day	14% 14% 5% 9% 10% 4 5% 5% 6% 7% 22%	1710
	11th to 20th	Day	16% 9% 4 9% 8% 5% 6% 5% 5% 7% 26%	1836
	21st to end	Day	16% 12% 5% 9% 6% 3 5% 6% 5% 6% 27%	1570
March	1st to 10th	Day	15% 10% 4 7% 7% 5% 6% 5% 5% 8% 28%	1920
	11th to 20th	Day	13% 11% 4 8% 7% 3 4 4 4 7% 34%	2090
	21st to end	Day	21% 12% 4 8% 5% 3 5% 4 5% 7% 27%	2200
April	1st to 10th	Day	16% 11% 5% 7% 6% 3 5% 5% 5% 7% 30%	2120
	11th to 20th	Day	17% 8% 3 7% 5% 4 6% 5% 5% 7% 33%	2248
	21st to end	Day	19% 8% 3 6% 6% 3 4 4 5% 7% 34%	2340
May	1st to 10th	Day	17% 8% 3 7% 5% 3 5% 5% 6% 8% 33%	2340
	11th to 20th	Day	19% 7% 3 6% 6% 3 4 4 5% 7% 34%	2301
	21st to end	Day	10% 6% 3 5% 5% 3 6% 5% 7% 9% 41%	2532
June	1st to 10th	Day	10% 5% 3 5% 6% 4 6% 5% 7% 8% 42%	2520
	11th to 20th	Day	11% 5% 2 5% 6% 3 5% 5% 6% 9% 42%	2520
	21st to end	Day	9% 5% 3 5% 5% 4 6% 6% 7% 10% 40%	2520
July	1st to 10th	Day	7% 4 2 5% 5% 3 5% 5% 6% 10% 46%	2520
	11th to 20th	Day	9% 4 3 5% 5% 3 5% 5% 7% 9% 46%	2520
	21st to end	Day	7% 5% 2 4 7% 4 6% 6% 7% 9% 43%	2604
August	1st to 10th	Day	9% 5% 2 5% 5% 3 5% 6% 7% 10% 44%	2327
	11th to 20th	Day	9% 6% 3 6% 6% 4 5% 6% 7% 9% 39%	2303
	21st to end	Day	9% 5% 3 5% 5% 3 5% 5% 6% 10% 43%	2503
September	1st to 10th	Day	12% 6% 3 6% 6% 3 5% 4 6% 7% 42%	2052
	11th to 20th	Day	10% 4 2 4 5% 3 5% 7% 7% 8% 46%	1980
	21st to end	Day	14% 5% 3 5% 5% 3 5% 5% 5% 8% 42%	1980
October	1st to 10th	Day	12% 5% 3 6% 5% 3 5% 3 6% 7% 43%	1958
	11th to 20th	Day	17% 8% 2 6% 6% 3 5% 5% 6% 7% 34%	1800
	21st to end	Day	20% 8% 3 6% 6% 4 5% 5% 5% 6% 31%	1814
November	1st to 10th	Day	12% 7% 4 7% 6% 3 5% 5% 6% 8% 40%	1672
	11th to 20th	Day	15% 12% 5% 7% 7% 4 5% 4 5% 5% 31%	1710
	21st to end	Day	19% 12% 4 7% 6% 3 5% 4 5% 6% 28%	1710
December	1st to 10th	Day	14% 15% 7% 11% 8% 4 5% 5% 4 4 23%	1710
	11th to 20th	Day	16% 13% 5% 10% 7% 3 5% 6% 6% 7% 22%	1990
	21st to end	Day	24% 19% 7% 10% 8% 4 4 4 4 5% 11%	2783
January	1st to 10th	Night	16% 16% 7% 9% 6% 3 4 3 4 6% 24%	4428
	11th to 20th	Night	15% 17% 7% 12% 7% 4 6% 6% 5% 7% 16%	4440
	21st to end	Night	25% 16% 7% 11% 6% 4 4 4 3 4 16%	4619
February	1st to 10th	Night	17% 12% 6% 9% 8% 4 5% 3 5% 7% 24%	2470
	11th to 20th	Night	14% 11% 6% 8% 7% 3 6% 4 5% 7% 28%	2228
	21st to end	Night	20% 10% 6% 8% 6% 3 4 3 4 7% 29%	1884
March	1st to 10th	Night	15% 9% 4 7% 7% 4 4 3 5% 6% 35%	2258
	11th to 20th	Night	14% 8% 3 5% 5% 3 5% 5% 6% 7% 40%	2090
	21st to end	Night	20% 8% 3 8% 6% 3 4 4 4 6% 34%	2201
April	1st to 10th	Night	16% 7% 4 7% 4 3 4 5% 5% 7% 38%	1854
	11th to 20th	Night	19% 7% 2 5% 6% 3 4 4 5% 7% 38%	1661
	21st to end	Night	17% 8% 3 5% 4 3 5% 5% 5% 7% 38%	1620
May	1st to 10th	Night	17% 7% 4 7% 6% 4 5% 4 7% 7% 32%	1620
	11th to 20th	Night	20% 6% 2 6% 4 3 4 5% 5% 7% 38%	1592
	21st to end	Night	10% 5% 2 6% 5% 3 4 5% 6% 10% 45%	1739
June	1st to 10th	Night	9% 4 2 4 5% 3 5% 4 6% 10% 47%	1440
	11th to 20th	Night	10% 6% 2 6% 5% 3 4 5% 5% 8% 44%	1440
	21st to end	Night	9% 4 2 5% 5% 2 5% 5% 7% 10% 46%	1440
July	1st to 10th	Night	7% 4 2 3 5% 3 4 5% 4 8% 55%	1440
	11th to 20th	Night	7% 5% 3 3 4 2 4 4 5% 8% 54%	1440
	21st to end	Night	6% 4 1 3 5% 3 5% 4 7% 11% 51%	1710
August	1st to 10th	Night	7% 5% 2 4 5% 3 5% 4 6% 8% 52%	1611
	11th to 20th	Night	8% 5% 1 4 4 3 5% 5% 7% 9% 48%	1598
	21st to end	Night	9% 4 2 5% 4 4 5% 5% 5% 7% 51%	1849
September	1st to 10th	Night	11% 5% 2 5% 5% 3 5% 4 5% 8% 48%	1890
	11th to 20th	Night	9% 5% 2 5% 4 3 4 4 5% 8% 52%	1980
	21st to end	Night	12% 6% 3 5% 5% 3 4 4 5% 6% 45%	1980
October	1st to 10th	Night	12% 7% 3 6% 5% 3 4 4 5% 7% 45%	2002
	11th to 20th	Night	17% 8% 3 7% 7% 3 4 5% 5% 5% 37%	2160
	21st to end	Night	21% 9% 3 5% 5% 3 4 5% 5% 6% 34%	2540
November	1st to 10th	Night	13% 8% 3 5% 4 3 5% 5% 4 7% 43%	2406
	11th to 20th	Night	16% 10% 3 6% 6% 3 4 5% 6% 8% 33%	2470
	21st to end	Night	19% 11% 5% 8% 6% 3 4 4 4 6% 29%	2470
December	1st to 10th	Night	17% 12% 6% 9% 7% 4 4 4 6% 7% 23%	2470
	11th to 20th	Night	16% 13% 5% 9% 7% 4 5% 5% 4 7% 25%	3204
	21st to end	Night	27% 18% 6% 10% 6% 3 4 4 4 6% 13%	4884

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	62% 8% 11% 13% 5%	2528
	11th to 20th	Day	69% 6% 12% 8% 4	2530
	21st to end	Day	76% 4 8% 8% 3	3036
February	1st to 10th	Day	61% 6% 10% 16% 7%	1710
	11th to 20th	Day	57% 6% 9% 18% 9% 1	1846
	21st to end	Day	56% 6% 12% 17% 6% 2	1570
March	1st to 10th	Day	54% 6% 13% 19% 8% 1	1920
	11th to 20th	Day	50% 5% 12% 19% 12% 2	2090
	21st to end	Day	58% 5% 10% 19% 7% 1	2200
April	1st to 10th	Day	53% 6% 11% 18% 13%	2120
	11th to 20th	Day	49% 6% 10% 20% 13% 2	2248
	21st to end	Day	49% 6% 12% 18% 14% 1	2340
May	1st to 10th	Day	49% 6% 12% 20% 11% 1	2340
	11th to 20th	Day	50% 6% 10% 18% 14% 2	2305
	21st to end	Day	39% 7% 15% 24% 13% 2	2532
June	1st to 10th	Day	38% 7% 12% 26% 15% 3	2520
	11th to 20th	Day	37% 7% 12% 22% 18% 2	2520
	21st to end	Day	37% 8% 14% 21% 17% 2	2520
July	1st to 10th	Day	33% 8% 12% 26% 18% 4	2451
	11th to 20th	Day	33% 6% 14% 27% 17% 2	2445
	21st to end	Day	33% 9% 13% 24% 19% 2	2459
August	1st to 10th	Day	32% 9% 13% 30% 14% 1	2314
	11th to 20th	Day	38% 10% 12% 24% 15% 2	2303
	21st to end	Day	35% 7% 11% 25% 18% 3	2503
September	1st to 10th	Day	40% 6% 16% 21% 15% 2	2052
	11th to 20th	Day	33% 8% 10% 33% 16% 1	1980
	21st to end	Day	40% 5% 13% 25% 16%	1980
October	1st to 10th	Day	40% 5% 11% 26% 16% 2	1958
	11th to 20th	Day	49% 6% 11% 21% 13% 1	1800
	21st to end	Day	53% 5% 12% 20% 9% 1	1814
November	1st to 10th	Day	42% 6% 12% 25% 14% 1	1672
	11th to 20th	Day	54% 4 12% 19% 9% 2	1710
	21st to end	Day	56% 5% 14% 17% 7% 1	1710
December	1st to 10th	Day	64% 6% 11% 14% 5%	1710
	11th to 20th	Day	59% 7% 14% 15% 4	1987
	21st to end	Day	76% 6% 8% 7% 3	2783
January	1st to 10th	Night	61% 6% 10% 16% 7% 1	4428
	11th to 20th	Night	68% 4 12% 11% 5%	4440
	21st to end	Night	71% 5% 9% 11% 4	4619
February	1st to 10th	Night	62% 5% 11% 14% 7% 1	2470
	11th to 20th	Night	55% 6% 9% 20% 9% 1	2229
	21st to end	Night	56% 5% 11% 17% 9% 2	1884
March	1st to 10th	Night	50% 5% 11% 23% 10% 1	2258
	11th to 20th	Night	42% 6% 12% 21% 16% 2	2090
	21st to end	Night	52% 5% 9% 23% 10% 2	2201
April	1st to 10th	Night	45% 6% 10% 22% 15% 2	1854
	11th to 20th	Night	46% 5% 10% 20% 18% 2	1661
	21st to end	Night	46% 6% 11% 19% 15% 3	1620
May	1st to 10th	Night	50% 6% 12% 19% 11% 2	1620
	11th to 20th	Night	45% 6% 9% 19% 18% 3	1593
	21st to end	Night	35% 7% 14% 26% 16% 2	1740
June	1st to 10th	Night	33% 6% 12% 29% 18% 3	1440
	11th to 20th	Night	37% 7% 11% 25% 17% 3	1440
	21st to end	Night	32% 7% 13% 26% 20% 1	1440
July	1st to 10th	Night	30% 6% 13% 27% 21% 4	1400
	11th to 20th	Night	29% 6% 14% 28% 20% 3	1392
	21st to end	Night	26% 7% 17% 24% 22% 4	1615
August	1st to 10th	Night	29% 8% 14% 30% 17% 2	1600
	11th to 20th	Night	30% 8% 16% 28% 15% 3	1598
	21st to end	Night	31% 6% 12% 26% 22% 3	1849
September	1st to 10th	Night	34% 6% 12% 27% 18% 3	1890
	11th to 20th	Night	31% 6% 10% 30% 22% 1	1980
	21st to end	Night	38% 6% 11% 28% 15% 1	1980
October	1st to 10th	Night	38% 5% 11% 25% 20% 1	2002
	11th to 20th	Night	48% 6% 10% 20% 16% 1	2160
	21st to end	Night	50% 5% 10% 24% 10% 1	2540
November	1st to 10th	Night	41% 6% 11% 25% 17% 1	2406
	11th to 20th	Night	48% 6% 13% 22% 10% 1	2470
	21st to end	Night	55% 5% 13% 20% 7%	2470
December	1st to 10th	Night	61% 6% 12% 15% 7%	2470
	11th to 20th	Night	59% 6% 12% 15% 7% 1	3206
	21st to end	Night	73% 7% 10% 8% 3	4884

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	26% 13% 34% 20% 6% 1	270
	11th to 20th	Day	23% 13% 41% 20% 3 1	270
	21st to end	Day	27% 11% 31% 24% 7%	297
February	1st to 10th	Day	22% 14% 38% 20% 4 1	270
	11th to 20th	Day	22% 14% 39% 22% 3	270
	21st to end	Day	24% 18% 39% 16% 2	225
March	1st to 10th	Day	21% 17% 37% 20% 4	290
	11th to 20th	Day	22% 10% 34% 26% 7% 1	460
	21st to end	Day	28% 13% 30% 21% 7% 1	470
April	1st to 10th	Day	20% 11% 33% 24% 11%	420
	11th to 20th	Day	22% 17% 30% 17% 9% 4	412
	21st to end	Day	23% 10% 33% 20% 11% 2	420
May	1st to 10th	Day	23% 11% 30% 18% 13% 4	423
	11th to 20th	Day	21% 9% 28% 22% 13% 7%	447
	21st to end	Day	13% 6% 24% 25% 21% 11%	486
June	1st to 10th	Day	10% 7% 28% 31% 20% 4	630
	11th to 20th	Day	13% 5% 28% 33% 16% 5%	630
	21st to end	Day	10% 6% 29% 33% 15% 7%	630
July	1st to 10th	Day	7% 3 18% 28% 28% 14%	621
	11th to 20th	Day	10% 5% 22% 30% 22% 12%	618
	21st to end	Day	8% 3 22% 31% 23% 13%	545
August	1st to 10th	Day	9% 3 13% 30% 26% 19%	446
	11th to 20th	Day	11% 5% 13% 31% 26% 13%	439
	21st to end	Day	10% 3 17% 28% 28% 14%	495
September	1st to 10th	Day	15% 4 17% 26% 24% 15%	450
	11th to 20th	Day	9% 4 17% 24% 32% 14%	450
	21st to end	Day	16% 9% 21% 23% 22% 10%	450
October	1st to 10th	Day	14% 6% 27% 26% 17% 10%	450
	11th to 20th	Day	20% 13% 30% 26% 9% 2	450
	21st to end	Day	25% 12% 40% 17% 5% 1	329
November	1st to 10th	Day	12% 15% 33% 25% 11% 3	270
	11th to 20th	Day	20% 19% 31% 22% 6% 2	270
	21st to end	Day	22% 13% 39% 21% 5%	270
December	1st to 10th	Day	23% 22% 30% 17% 7% 1	270
	11th to 20th	Day	19% 15% 43% 17% 5%	270
	21st to end	Day	28% 21% 30% 18% 3	297
January	1st to 10th	Night	23% 14% 35% 22% 6% 1	950
	11th to 20th	Night	25% 11% 35% 23% 5%	950
	21st to end	Night	21% 11% 36% 26% 6%	884
February	1st to 10th	Night	24% 11% 35% 26% 4	760
	11th to 20th	Night	22% 12% 35% 27% 4	743
	21st to end	Night	24% 13% 39% 22% 3	628
March	1st to 10th	Night	20% 11% 33% 28% 8%	760
	11th to 20th	Night	20% 12% 36% 26% 6% 1	760
	21st to end	Night	23% 8% 33% 28% 7%	801
April	1st to 10th	Night	19% 12% 35% 29% 5% 1	594
	11th to 20th	Night	20% 9% 35% 25% 10% 1	533
	21st to end	Night	22% 6% 32% 30% 9%	540
May	1st to 10th	Night	19% 7% 30% 33% 9% 1	540
	11th to 20th	Night	22% 3 26% 33% 14% 1	531
	21st to end	Night	13% 4 23% 35% 23% 2	584
June	1st to 10th	Night	11% 3 25% 43% 18%	540
	11th to 20th	Night	12% 4 21% 43% 19% 1	540
	21st to end	Night	10% 2 21% 41% 24% 2	540
July	1st to 10th	Night	9% 3 14% 40% 29% 6%	525
	11th to 20th	Night	9% 1 18% 41% 27% 4	522
	21st to end	Night	6% 2 16% 44% 30% 2	591
August	1st to 10th	Night	8% 3 13% 45% 27% 3	537
	11th to 20th	Night	9% 3 14% 38% 31% 5%	534
	21st to end	Night	11% 3 14% 34% 34% 5%	594
September	1st to 10th	Night	12% 3 18% 35% 28% 4	630
	11th to 20th	Night	10% 4 15% 35% 31% 5%	720
	21st to end	Night	14% 6% 19% 33% 23% 4	720
October	1st to 10th	Night	14% 7% 24% 34% 19% 3	720
	11th to 20th	Night	21% 10% 32% 26% 10% 1	720
	21st to end	Night	24% 10% 33% 26% 6%	792
November	1st to 10th	Night	19% 11% 31% 25% 13% 1	740
	11th to 20th	Night	21% 13% 35% 23% 7% 1	760
	21st to end	Night	24% 10% 33% 26% 7%	760
December	1st to 10th	Night	23% 13% 36% 21% 7%	760
	11th to 20th	Night	23% 12% 37% 22% 5% 1	875
	21st to end	Night	31% 11% 33% 23% 3	1045

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