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 2026-10-29.

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% 9% 3 8% 5% 5% 5% 4 6% 8% 35%	149178
	Night	14% 10% 4 8% 5% 4 4 3 5% 7% 36%	143073
Transparency	Day	45% 6% 12% 22% 13% 1	152749
	Night	46% 6% 12% 21% 14% 1	147575
Seeing	Day	16% 10% 28% 25% 14% 6%	18387
	Night	18% 9% 29% 30% 13% 1	28137

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% 14% 7% 17% 6% 4 5% 4 5% 6% 18%	4691
	11th to 20th	Day	12% 13% 6% 15% 10% 7% 7% 5% 5% 6% 15%	4710
	21st to end	Day	18% 15% 5% 12% 8% 6% 6% 4 5% 5% 17%	5640
February	1st to 10th	Day	14% 15% 4 11% 9% 5% 5% 4 6% 6% 22%	1890
	11th to 20th	Day	15% 11% 4 11% 7% 6% 5% 4 5% 7% 25%	2036
	21st to end	Day	15% 13% 5% 11% 5% 4 5% 5% 6% 6% 26%	1730
March	1st to 10th	Day	16% 11% 5% 10% 6% 5% 5% 3 4 5% 29%	4641
	11th to 20th	Day	12% 11% 3 8% 5% 4 5% 4 5% 7% 36%	5090
	21st to end	Day	19% 14% 4 9% 5% 5% 4 4 5% 6% 25%	5586
April	1st to 10th	Day	17% 12% 4 7% 5% 4 5% 4 5% 7% 30%	2474
	11th to 20th	Day	16% 8% 2 8% 5% 5% 5% 4 5% 7% 34%	2628
	21st to end	Day	17% 9% 3 8% 5% 4 4 4 5% 8% 35%	2730
May	1st to 10th	Day	19% 8% 2 7% 4 4 5% 4 6% 7% 34%	7616
	11th to 20th	Day	15% 6% 3 7% 5% 4 5% 4 6% 9% 35%	7626
	21st to end	Day	15% 5% 2 6% 4 4 4 4 6% 7% 43%	8406
June	1st to 10th	Day	10% 6% 2 5% 5% 5% 5% 4 7% 8% 43%	2940
	11th to 20th	Day	10% 5% 2 6% 5% 5% 5% 5% 6% 9% 42%	2940
	21st to end	Day	9% 5% 2 6% 5% 5% 6% 5% 7% 10% 40%	2940
July	1st to 10th	Day	10% 5% 2 6% 5% 5% 5% 4 7% 10% 42%	8280
	11th to 20th	Day	6% 4 2 5% 5% 4 5% 4 7% 11% 49%	8280
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 5% 6% 9% 44%	8521
August	1st to 10th	Day	15% 6% 2 6% 4 4 4 4 5% 8% 44%	6014
	11th to 20th	Day	11% 7% 3 7% 5% 5% 5% 4 7% 9% 37%	5951
	21st to end	Day	7% 4 2 6% 5% 5% 5% 5% 7% 10% 44%	6407
September	1st to 10th	Day	11% 6% 2 6% 5% 4 4 3 6% 8% 45%	2394
	11th to 20th	Day	10% 4 2 5% 4 4 5% 4 6% 8% 48%	2310
	21st to end	Day	14% 6% 3 6% 4 4 4 4 5% 7% 41%	2310
October	1st to 10th	Day	11% 5% 3 6% 4 4 4 3 6% 7% 46%	2284
	11th to 20th	Day	17% 8% 2 7% 5% 4 5% 3 6% 6% 37%	2100
	21st to end	Day	18% 9% 2 7% 5% 5% 5% 4 6% 6% 33%	2089
November	1st to 10th	Day	12% 8% 3 8% 4 4 4 4 6% 7% 40%	1852
	11th to 20th	Day	15% 14% 4 8% 6% 5% 4 3 5% 6% 31%	1890
	21st to end	Day	18% 13% 4 9% 5% 5% 5% 3 5% 6% 27%	1890
December	1st to 10th	Day	12% 14% 7% 12% 6% 5% 5% 4 5% 6% 23%	3020
	11th to 20th	Day	20% 17% 5% 10% 7% 4 5% 4 5% 5% 18%	3202
	21st to end	Day	26% 20% 6% 11% 5% 5% 3 2 3 4 14%	4070
January	1st to 10th	Night	15% 15% 6% 14% 6% 5% 4 3 4 5% 23%	8232
	11th to 20th	Night	10% 15% 7% 14% 7% 6% 6% 4 6% 7% 19%	8280
	21st to end	Night	15% 14% 6% 11% 6% 5% 5% 4 5% 6% 25%	8544
February	1st to 10th	Night	16% 13% 5% 10% 7% 5% 4 2 5% 6% 25%	2730
	11th to 20th	Night	14% 12% 5% 10% 6% 4 5% 4 5% 6% 28%	2468
	21st to end	Night	19% 11% 5% 9% 4 4 4 3 4 7% 30%	2076
March	1st to 10th	Night	16% 11% 3 7% 4 4 4 3 5% 7% 37%	5430
	11th to 20th	Night	11% 7% 3 5% 4 4 5% 4 6% 7% 45%	5090
	21st to end	Night	17% 10% 3 8% 5% 4 4 3 5% 6% 36%	5588
April	1st to 10th	Night	17% 9% 4 7% 4 4 4 4 5% 6% 36%	2163
	11th to 20th	Night	18% 7% 2 7% 5% 4 4 3 5% 7% 37%	1940
	21st to end	Night	17% 8% 3 6% 4 4 5% 4 5% 7% 38%	1890
May	1st to 10th	Night	20% 8% 3 8% 5% 5% 5% 3 5% 6% 32%	5237
	11th to 20th	Night	16% 7% 2 6% 5% 4 4 3 5% 7% 41%	5234
	21st to end	Night	14% 5% 2 6% 4 4 4 4 5% 8% 45%	5730
June	1st to 10th	Night	10% 4 2 5% 5% 4 4 3 6% 9% 47%	1680
	11th to 20th	Night	10% 6% 2 6% 5% 3 5% 4 6% 9% 43%	1680
	21st to end	Night	9% 5% 1 6% 4 3 5% 5% 7% 9% 46%	1680
July	1st to 10th	Night	9% 4 2 5% 4 4 4 3 5% 9% 50%	4708
	11th to 20th	Night	6% 4 2 5% 4 4 5% 4 6% 9% 51%	4707
	21st to end	Night	9% 5% 1 5% 4 4 4 3 6% 9% 50%	5560
August	1st to 10th	Night	16% 6% 2 6% 4 3 4 3 5% 7% 45%	4135
	11th to 20th	Night	12% 6% 2 6% 4 4 5% 4 7% 9% 42%	4095
	21st to end	Night	8% 4 2 6% 4 4 4 4 6% 7% 50%	4715
September	1st to 10th	Night	9% 5% 2 6% 4 4 4 3 5% 8% 50%	2205
	11th to 20th	Night	9% 5% 2 5% 4 4 3 3 5% 8% 54%	2310
	21st to end	Night	13% 7% 3 7% 4 4 4 3 5% 6% 44%	2310
October	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 5% 7% 48%	2336
	11th to 20th	Night	16% 8% 3 7% 5% 3 4 3 5% 5% 39%	2520
	21st to end	Night	18% 8% 3 6% 4 4 4 4 5% 6% 37%	2926
November	1st to 10th	Night	13% 9% 3 6% 4 4 4 4 4 6% 43%	2666
	11th to 20th	Night	15% 10% 3 8% 5% 4 4 4 6% 8% 33%	2730
	21st to end	Night	18% 13% 4 9% 5% 4 4 4 5% 6% 28%	2730
December	1st to 10th	Night	13% 12% 6% 12% 6% 5% 4 3 6% 7% 26%	4380
	11th to 20th	Night	16% 17% 5% 11% 6% 5% 5% 4 4 6% 21%	5218
	21st to end	Night	27% 18% 6% 10% 5% 4 4 3 4 5% 15%	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	64% 8% 11% 13% 4	4692
	11th to 20th	Day	65% 7% 10% 9% 9%	4710
	21st to end	Day	66% 7% 10% 12% 6%	5640
February	1st to 10th	Day	61% 6% 10% 15% 7%	1890
	11th to 20th	Day	58% 6% 9% 18% 9% 1	2046
	21st to end	Day	56% 6% 12% 17% 7% 2	1730
March	1st to 10th	Day	56% 5% 12% 18% 9% 1	4641
	11th to 20th	Day	46% 5% 16% 22% 9% 2	5090
	21st to end	Day	58% 6% 11% 15% 10% 1	5586
April	1st to 10th	Day	53% 6% 11% 17% 13%	2474
	11th to 20th	Day	49% 5% 11% 21% 12% 2	2628
	21st to end	Day	48% 6% 12% 20% 14% 1	2730
May	1st to 10th	Day	47% 6% 11% 21% 13% 1	7651
	11th to 20th	Day	44% 7% 13% 21% 13% 1	7630
	21st to end	Day	39% 6% 9% 20% 21% 5%	8420
June	1st to 10th	Day	37% 7% 11% 25% 16% 3	2940
	11th to 20th	Day	37% 7% 12% 23% 18% 2	2940
	21st to end	Day	37% 8% 14% 22% 17% 2	2940
July	1st to 10th	Day	35% 7% 14% 26% 17% 2	8211
	11th to 20th	Day	27% 7% 14% 33% 18% 1	8205
	21st to end	Day	33% 8% 12% 24% 22% 1	8334
August	1st to 10th	Day	37% 7% 12% 23% 19% 2	6001
	11th to 20th	Day	40% 10% 13% 27% 10% 1	5990
	21st to end	Day	33% 8% 15% 33% 11% 1	6406
September	1st to 10th	Day	38% 6% 16% 24% 15% 2	2394
	11th to 20th	Day	32% 7% 10% 32% 18% 1	2310
	21st to end	Day	42% 5% 12% 24% 17% 1	2310
October	1st to 10th	Day	28% 5% 11% 32% 23% 1	3648
	11th to 20th	Day	38% 5% 10% 25% 21% 1	3340
	21st to end	Day	42% 5% 13% 24% 14% 1	3301
November	1st to 10th	Day	42% 6% 11% 26% 14% 1	1852
	11th to 20th	Day	54% 4 12% 19% 9% 2	1890
	21st to end	Day	58% 5% 13% 17% 7% 1	1890
December	1st to 10th	Day	60% 8% 16% 12% 5%	3020
	11th to 20th	Day	67% 6% 11% 13% 3	3199
	21st to end	Day	75% 5% 7% 8% 4	4070
January	1st to 10th	Night	61% 6% 9% 15% 7% 1	8233
	11th to 20th	Night	62% 6% 12% 12% 8%	8280
	21st to end	Night	58% 6% 12% 14% 9%	8544
February	1st to 10th	Night	60% 5% 11% 15% 7% 2	2730
	11th to 20th	Night	56% 6% 10% 19% 8% 1	2469
	21st to end	Night	55% 5% 12% 18% 9% 1	2076
March	1st to 10th	Night	46% 5% 13% 25% 10% 1	5430
	11th to 20th	Night	36% 6% 14% 27% 16% 1	5090
	21st to end	Night	48% 5% 11% 20% 14% 2	5588
April	1st to 10th	Night	48% 6% 9% 21% 14% 2	2163
	11th to 20th	Night	46% 5% 10% 19% 18% 1	1940
	21st to end	Night	45% 7% 11% 19% 15% 3	1890
May	1st to 10th	Night	50% 6% 10% 17% 13% 3	5264
	11th to 20th	Night	42% 7% 10% 27% 12% 2	5235
	21st to end	Night	37% 6% 12% 21% 21% 4	5740
June	1st to 10th	Night	33% 5% 11% 27% 21% 3	1680
	11th to 20th	Night	37% 7% 12% 25% 17% 2	1680
	21st to end	Night	32% 7% 15% 26% 19% 1	1680
July	1st to 10th	Night	31% 6% 12% 29% 18% 4	4670
	11th to 20th	Night	29% 7% 13% 28% 21% 2	4662
	21st to end	Night	30% 7% 13% 22% 27% 2	5434
August	1st to 10th	Night	39% 7% 11% 21% 21% 2	4124
	11th to 20th	Night	36% 8% 16% 27% 10% 1	4122
	21st to end	Night	31% 7% 14% 31% 14% 1	4715
September	1st to 10th	Night	32% 6% 11% 29% 19% 2	2205
	11th to 20th	Night	29% 5% 10% 30% 23% 2	2310
	21st to end	Night	40% 6% 11% 26% 16% 1	2310
October	1st to 10th	Night	25% 4 9% 32% 28% 1	3752
	11th to 20th	Night	38% 5% 10% 24% 22% 1	4019
	21st to end	Night	37% 4 9% 33% 16% 1	4664
November	1st to 10th	Night	41% 5% 11% 25% 17% 1	2666
	11th to 20th	Night	47% 6% 13% 22% 10% 2	2730
	21st to end	Night	57% 5% 12% 19% 7%	2730
December	1st to 10th	Night	56% 7% 15% 16% 5%	4380
	11th to 20th	Night	62% 6% 12% 13% 6% 1	5220
	21st to end	Night	71% 6% 9% 8% 6%	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	24% 12% 38% 20% 5% 1	330
	11th to 20th	Day	22% 16% 41% 18% 3 1	330
	21st to end	Day	25% 13% 33% 23% 6%	363
February	1st to 10th	Day	21% 14% 39% 20% 5% 2	330
	11th to 20th	Day	22% 15% 38% 21% 3	330
	21st to end	Day	22% 18% 42% 16% 2	273
March	1st to 10th	Day	23% 18% 38% 18% 4	352
	11th to 20th	Day	23% 13% 33% 24% 6% 1	540
	21st to end	Day	25% 15% 34% 20% 6% 1	594
April	1st to 10th	Day	22% 14% 34% 20% 9%	540
	11th to 20th	Day	21% 19% 32% 17% 8% 3	532
	21st to end	Day	22% 11% 33% 21% 11% 2	540
May	1st to 10th	Day	22% 13% 31% 19% 12% 3	543
	11th to 20th	Day	20% 11% 28% 21% 13% 6%	567
	21st to end	Day	13% 7% 26% 25% 19% 10%	619
June	1st to 10th	Day	10% 8% 28% 30% 19% 4	780
	11th to 20th	Day	12% 8% 30% 31% 14% 4	780
	21st to end	Day	10% 6% 29% 33% 15% 6%	780
July	1st to 10th	Day	9% 4 20% 29% 26% 13%	771
	11th to 20th	Day	8% 6% 22% 30% 22% 12%	768
	21st to end	Day	7% 4 22% 31% 24% 12%	686
August	1st to 10th	Day	9% 4 15% 30% 26% 17%	566
	11th to 20th	Day	11% 6% 14% 32% 25% 12%	559
	21st to end	Day	9% 2 19% 29% 28% 14%	627
September	1st to 10th	Day	14% 5% 18% 25% 23% 14%	570
	11th to 20th	Day	9% 4 16% 26% 29% 17%	570
	21st to end	Day	17% 8% 21% 24% 20% 9%	570
October	1st to 10th	Day	12% 7% 27% 27% 19% 9%	570
	11th to 20th	Day	18% 13% 28% 28% 11% 3	570
	21st to end	Day	22% 13% 37% 19% 8% 2	424
November	1st to 10th	Day	13% 16% 33% 25% 10% 3	330
	11th to 20th	Day	21% 22% 31% 21% 5% 2	330
	21st to end	Day	22% 16% 37% 20% 4	330
December	1st to 10th	Day	22% 20% 32% 18% 7% 1	330
	11th to 20th	Day	22% 16% 41% 16% 5%	330
	21st to end	Day	30% 20% 30% 17% 3	363
January	1st to 10th	Night	22% 14% 35% 23% 6% 1	1050
	11th to 20th	Night	24% 14% 36% 22% 5%	1050
	21st to end	Night	20% 13% 36% 26% 5%	976
February	1st to 10th	Night	23% 12% 35% 26% 4	840
	11th to 20th	Night	22% 13% 35% 26% 4	823
	21st to end	Night	23% 13% 40% 21% 2	692
March	1st to 10th	Night	20% 11% 35% 27% 7%	840
	11th to 20th	Night	21% 13% 35% 25% 6% 1	840
	21st to end	Night	23% 9% 34% 27% 6%	924
April	1st to 10th	Night	21% 13% 34% 27% 5%	693
	11th to 20th	Night	20% 11% 36% 23% 9% 1	623
	21st to end	Night	21% 7% 33% 30% 9%	630
May	1st to 10th	Night	19% 8% 31% 33% 9% 1	630
	11th to 20th	Night	22% 4 28% 32% 13% 1	621
	21st to end	Night	13% 4 24% 36% 20% 2	683
June	1st to 10th	Night	11% 3 26% 42% 18%	630
	11th to 20th	Night	12% 5% 22% 43% 18% 1	630
	21st to end	Night	10% 3 21% 41% 23% 2	630
July	1st to 10th	Night	9% 2 15% 41% 28% 5%	615
	11th to 20th	Night	8% 3 18% 40% 27% 4	612
	21st to end	Night	7% 3 16% 44% 30% 1	690
August	1st to 10th	Night	8% 2 15% 44% 28% 3	627
	11th to 20th	Night	10% 4 14% 39% 30% 4	624
	21st to end	Night	10% 2 15% 35% 33% 4	693
September	1st to 10th	Night	11% 3 19% 34% 28% 4	735
	11th to 20th	Night	9% 5% 15% 35% 33% 4	840
	21st to end	Night	15% 6% 20% 33% 22% 4	840
October	1st to 10th	Night	13% 7% 24% 35% 18% 3	840
	11th to 20th	Night	20% 10% 32% 26% 10% 1	840
	21st to end	Night	22% 10% 33% 28% 7%	913
November	1st to 10th	Night	18% 11% 33% 24% 12% 1	820
	11th to 20th	Night	20% 14% 35% 23% 7% 1	840
	21st to end	Night	24% 11% 34% 24% 6%	840
December	1st to 10th	Night	22% 13% 36% 22% 7%	840
	11th to 20th	Night	23% 12% 38% 22% 5% 1	968
	21st to end	Night	31% 11% 33% 23% 3	1155

Page generated at 2026-10-26 04:37:51. Version ac07

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