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 2024-11-03.

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	14% 9% 3 8% 5% 5% 5% 4 6% 7% 35%	101204
	Night	15% 10% 4 8% 5% 4 4 4 5% 7% 36%	97804
Transparency	Day	47% 7% 12% 21% 12% 1	101003
	Night	47% 6% 12% 21% 13% 1	97676
Seeing	Day	16% 9% 28% 25% 15% 6%	15652
	Night	18% 8% 29% 30% 13% 1	25468

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% 16% 6% 10% 6% 5% 5% 4 5% 6% 20%	2527
	11th to 20th	Day	16% 16% 6% 13% 7% 6% 7% 5% 5% 6% 13%	2530
	21st to end	Day	26% 19% 7% 12% 6% 4 3 2 3 3 14%	3036
February	1st to 10th	Day	14% 15% 4 11% 8% 5% 5% 4 6% 6% 22%	1710
	11th to 20th	Day	15% 10% 3 11% 7% 6% 6% 4 5% 7% 26%	1836
	21st to end	Day	16% 13% 4 10% 5% 4 5% 5% 5% 6% 27%	1570
March	1st to 10th	Day	18% 14% 4 9% 6% 5% 4 3 4 6% 26%	3166
	11th to 20th	Day	12% 12% 4 9% 5% 5% 5% 4 5% 6% 34%	3480
	21st to end	Day	20% 13% 4 9% 5% 4 5% 4 5% 6% 26%	3815
April	1st to 10th	Day	15% 12% 4 7% 5% 4 5% 4 5% 7% 30%	2238
	11th to 20th	Day	17% 8% 2 8% 4 5% 5% 4 5% 7% 34%	2375
	21st to end	Day	18% 9% 3 7% 5% 4 4 4 5% 8% 34%	2470
May	1st to 10th	Day	18% 7% 2 7% 4 5% 5% 4 6% 7% 35%	4082
	11th to 20th	Day	16% 7% 3 7% 6% 4 4 4 6% 9% 34%	4081
	21st to end	Day	9% 6% 2 6% 5% 4 5% 4 6% 8% 45%	4491
June	1st to 10th	Day	10% 6% 2 5% 5% 5% 5% 4 7% 8% 42%	2660
	11th to 20th	Day	10% 5% 2 6% 5% 5% 5% 5% 6% 8% 43%	2660
	21st to end	Day	9% 6% 2 6% 5% 5% 6% 5% 7% 10% 39%	2660
July	1st to 10th	Day	11% 5% 2 7% 5% 5% 5% 4 7% 10% 39%	4440
	11th to 20th	Day	7% 4 2 5% 4 4 5% 4 7% 9% 49%	4440
	21st to end	Day	7% 5% 2 7% 5% 5% 6% 5% 7% 9% 42%	4565
August	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 6% 9% 45%	4104
	11th to 20th	Day	9% 6% 2 6% 5% 4 5% 4 7% 9% 42%	4044
	21st to end	Day	8% 4 2 7% 5% 5% 5% 5% 6% 10% 42%	4405
September	1st to 10th	Day	11% 6% 2 6% 5% 4 4 4 6% 8% 44%	2166
	11th to 20th	Day	9% 4 2 5% 4 4 5% 5% 7% 8% 47%	2090
	21st to end	Day	14% 6% 3 6% 5% 4 5% 4 5% 8% 40%	2090
October	1st to 10th	Day	12% 6% 3 7% 4 4 4 3 6% 8% 44%	2066
	11th to 20th	Day	17% 8% 2 7% 5% 4 5% 3 6% 7% 35%	1900
	21st to end	Day	19% 9% 3 7% 5% 5% 5% 4 6% 6% 32%	1914
November	1st to 10th	Day	12% 8% 3 8% 5% 4 4 4 6% 7% 40%	1690
	11th to 20th	Day	14% 14% 4 8% 6% 5% 4 3 5% 6% 31%	1710
	21st to end	Day	19% 12% 4 8% 5% 5% 5% 3 5% 6% 28%	1710
December	1st to 10th	Day	14% 16% 6% 12% 8% 5% 4 4 4 4 22%	1710
	11th to 20th	Day	16% 14% 5% 11% 6% 4 5% 5% 6% 7% 22%	1990
	21st to end	Day	24% 20% 7% 12% 6% 5% 4 3 4 5% 11%	2783
January	1st to 10th	Night	16% 17% 6% 10% 5% 4 4 3 4 6% 24%	4428
	11th to 20th	Night	14% 18% 7% 13% 6% 5% 5% 4 5% 7% 16%	4440
	21st to end	Night	24% 18% 6% 12% 5% 4 4 3 3 4 16%	4619
February	1st to 10th	Night	17% 14% 5% 10% 8% 6% 4 2 5% 6% 24%	2470
	11th to 20th	Night	14% 12% 5% 9% 6% 4 6% 4 5% 6% 28%	2228
	21st to end	Night	19% 11% 5% 9% 5% 4 4 3 4 7% 29%	1884
March	1st to 10th	Night	16% 12% 4 8% 5% 4 4 3 4 5% 36%	3685
	11th to 20th	Night	10% 7% 2 5% 5% 4 5% 4 6% 7% 46%	3480
	21st to end	Night	18% 9% 3 9% 5% 4 4 3 5% 6% 34%	3817
April	1st to 10th	Night	16% 8% 4 7% 4 4 4 4 5% 6% 37%	1957
	11th to 20th	Night	19% 7% 2 6% 5% 4 4 3 5% 7% 38%	1754
	21st to end	Night	17% 8% 3 6% 4 4 5% 4 5% 6% 38%	1710
May	1st to 10th	Night	17% 8% 3 7% 5% 5% 5% 4 6% 7% 33%	2813
	11th to 20th	Night	17% 7% 2 7% 4 4 4 4 5% 7% 39%	2812
	21st to end	Night	11% 5% 2 6% 4 4 4 4 5% 9% 47%	3061
June	1st to 10th	Night	10% 4 2 5% 5% 4 4 3 6% 10% 47%	1520
	11th to 20th	Night	10% 6% 2 6% 5% 4 5% 4 6% 8% 43%	1520
	21st to end	Night	9% 5% 1 6% 4 3 5% 5% 7% 9% 46%	1520
July	1st to 10th	Night	9% 4 2 4 4 4 4 4 6% 10% 50%	2530
	11th to 20th	Night	8% 4 2 4 4 3 4 4 6% 8% 54%	2530
	21st to end	Night	6% 4 1 5% 4 4 5% 4 7% 10% 48%	2987
August	1st to 10th	Night	12% 5% 2 6% 4 3 4 3 5% 8% 46%	2825
	11th to 20th	Night	8% 5% 1 5% 3 4 5% 4 6% 8% 49%	2785
	21st to end	Night	9% 4 2 6% 4 5% 5% 4 6% 7% 48%	3247
September	1st to 10th	Night	10% 5% 2 6% 4 4 4 3 5% 8% 50%	1995
	11th to 20th	Night	9% 5% 1 5% 4 4 3 2 5% 8% 54%	2090
	21st to end	Night	13% 7% 3 7% 4 4 4 3 5% 6% 44%	2090
October	1st to 10th	Night	11% 7% 2 6% 4 4 4 3 5% 7% 47%	2114
	11th to 20th	Night	16% 8% 3 7% 6% 4 5% 3 5% 5% 38%	2280
	21st to end	Night	20% 9% 3 6% 4 4 4 4 5% 6% 36%	2682
November	1st to 10th	Night	13% 9% 3 6% 4 4 4 4 4 7% 43%	2433
	11th to 20th	Night	16% 10% 2 8% 5% 4 4 4 6% 8% 32%	2470
	21st to end	Night	18% 13% 4 9% 5% 4 4 3 5% 6% 29%	2470
December	1st to 10th	Night	17% 14% 5% 10% 6% 5% 4 3 6% 7% 23%	2470
	11th to 20th	Night	16% 14% 5% 10% 6% 5% 5% 4 4 7% 25%	3204
	21st to end	Night	27% 18% 6% 11% 5% 4 4 3 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	59% 5% 11% 19% 6% 1	3166
	11th to 20th	Day	48% 5% 16% 20% 8% 2	3480
	21st to end	Day	58% 6% 11% 15% 9% 1	3815
April	1st to 10th	Day	52% 6% 11% 18% 13%	2238
	11th to 20th	Day	49% 5% 10% 21% 13% 2	2375
	21st to end	Day	49% 6% 12% 18% 14% 1	2470
May	1st to 10th	Day	47% 6% 11% 23% 12% 1	4120
	11th to 20th	Day	45% 8% 13% 23% 10% 1	4085
	21st to end	Day	36% 6% 11% 20% 22% 5%	4504
June	1st to 10th	Day	38% 7% 11% 26% 14% 3	2660
	11th to 20th	Day	37% 7% 12% 23% 19% 3	2660
	21st to end	Day	37% 8% 14% 21% 17% 2	2660
July	1st to 10th	Day	39% 7% 14% 22% 16% 3	4371
	11th to 20th	Day	29% 7% 13% 33% 17% 1	4365
	21st to end	Day	35% 9% 14% 20% 21% 2	4420
August	1st to 10th	Day	34% 8% 13% 28% 16% 1	4091
	11th to 20th	Day	35% 9% 11% 30% 14% 1	4083
	21st to end	Day	35% 7% 13% 31% 12% 2	4404
September	1st to 10th	Day	38% 6% 16% 22% 16% 2	2166
	11th to 20th	Day	32% 7% 9% 32% 18% 1	2090
	21st to end	Day	42% 5% 13% 24% 16%	2090
October	1st to 10th	Day	38% 5% 11% 27% 17% 2	2066
	11th to 20th	Day	48% 5% 12% 22% 13% 1	1900
	21st to end	Day	52% 5% 12% 20% 10% 1	1914
November	1st to 10th	Day	41% 6% 12% 26% 14% 1	1690
	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% 12% 25% 8% 1	3685
	11th to 20th	Night	35% 7% 14% 22% 20% 2	3480
	21st to end	Night	50% 6% 12% 22% 9% 1	3817
April	1st to 10th	Night	46% 6% 10% 22% 15% 2	1957
	11th to 20th	Night	46% 5% 10% 20% 18% 1	1754
	21st to end	Night	46% 7% 11% 18% 16% 3	1710
May	1st to 10th	Night	48% 7% 11% 21% 13% 2	2840
	11th to 20th	Night	43% 7% 9% 26% 12% 1	2813
	21st to end	Night	33% 7% 13% 23% 21% 3	3069
June	1st to 10th	Night	33% 5% 12% 29% 19% 3	1520
	11th to 20th	Night	37% 7% 11% 25% 17% 3	1520
	21st to end	Night	32% 7% 14% 25% 20% 1	1520
July	1st to 10th	Night	30% 6% 13% 29% 16% 6%	2490
	11th to 20th	Night	27% 6% 15% 28% 21% 2	2482
	21st to end	Night	28% 9% 18% 19% 23% 2	2892
August	1st to 10th	Night	35% 8% 13% 27% 16% 1	2814
	11th to 20th	Night	30% 8% 13% 33% 14% 2	2812
	21st to end	Night	34% 7% 11% 29% 17% 2	3247
September	1st to 10th	Night	32% 6% 12% 27% 20% 3	1995
	11th to 20th	Night	29% 5% 10% 30% 24% 2	2090
	21st to end	Night	40% 6% 10% 27% 15% 1	2090
October	1st to 10th	Night	37% 5% 11% 26% 21% 1	2114
	11th to 20th	Night	47% 6% 10% 20% 17% 1	2280
	21st to end	Night	48% 5% 10% 25% 11% 1	2682
November	1st to 10th	Night	40% 6% 11% 25% 17% 1	2433
	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% 31% 21% 7% 1	506
April	1st to 10th	Day	19% 12% 35% 23% 11%	460
	11th to 20th	Day	22% 17% 31% 17% 9% 4	452
	21st to end	Day	22% 10% 34% 20% 11% 2	460
May	1st to 10th	Day	23% 11% 31% 18% 13% 3	463
	11th to 20th	Day	20% 9% 27% 22% 14% 7%	487
	21st to end	Day	12% 6% 24% 26% 21% 11%	531
June	1st to 10th	Day	10% 8% 28% 31% 20% 4	680
	11th to 20th	Day	13% 6% 29% 33% 15% 5%	680
	21st to end	Day	11% 6% 30% 32% 14% 7%	680
July	1st to 10th	Day	8% 4 20% 28% 27% 13%	671
	11th to 20th	Day	9% 6% 22% 30% 21% 13%	668
	21st to end	Day	8% 3 21% 31% 23% 13%	592
August	1st to 10th	Day	9% 4 15% 29% 25% 17%	486
	11th to 20th	Day	11% 6% 14% 31% 25% 13%	479
	21st to end	Day	10% 2 17% 28% 29% 14%	539
September	1st to 10th	Day	14% 5% 18% 26% 23% 15%	490
	11th to 20th	Day	8% 4 16% 25% 31% 16%	490
	21st to end	Day	17% 9% 21% 23% 20% 9%	490
October	1st to 10th	Day	13% 7% 27% 27% 18% 10%	490
	11th to 20th	Day	19% 13% 28% 27% 10% 3	490
	21st to end	Day	24% 12% 40% 17% 6% 1	363
November	1st to 10th	Day	12% 15% 33% 26% 11% 3	276
	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%	836
April	1st to 10th	Night	19% 12% 34% 29% 5%	627
	11th to 20th	Night	21% 10% 35% 24% 9% 1	563
	21st to end	Night	22% 6% 33% 30% 9%	570
May	1st to 10th	Night	19% 7% 30% 34% 9% 1	570
	11th to 20th	Night	22% 3 27% 33% 14% 1	561
	21st to end	Night	12% 4 24% 35% 22% 2	617
June	1st to 10th	Night	11% 2 26% 42% 18%	570
	11th to 20th	Night	11% 4 22% 44% 19% 1	570
	21st to end	Night	11% 2 21% 40% 24% 2	570
July	1st to 10th	Night	9% 3 15% 41% 27% 5%	555
	11th to 20th	Night	9% 2 18% 40% 27% 4	552
	21st to end	Night	6% 2 16% 44% 31% 2	624
August	1st to 10th	Night	8% 2 14% 45% 27% 3	567
	11th to 20th	Night	9% 3 15% 38% 30% 4	564
	21st to end	Night	11% 3 14% 34% 34% 5%	627
September	1st to 10th	Night	12% 3 18% 34% 28% 4	665
	11th to 20th	Night	9% 4 14% 36% 32% 5%	760
	21st to end	Night	16% 6% 19% 33% 22% 4	760
October	1st to 10th	Night	13% 7% 25% 34% 18% 3	760
	11th to 20th	Night	21% 10% 32% 26% 10% 1	760
	21st to end	Night	23% 11% 33% 27% 6%	836
November	1st to 10th	Night	18% 11% 31% 25% 13% 1	749
	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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