Aberdeen Regional Airport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Aberdeen Regional Airport clear sky chart from 2005-11-06 to 2026-10-14.

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	10% 7% 3 7% 5% 5% 5% 4 6% 7% 43%	158291
	Night	9% 7% 3 7% 5% 5% 5% 4 6% 7% 43%	150913
Transparency	Day	40% 5% 14% 26% 13% 2	152952
	Night	39% 6% 15% 25% 13% 2	147263
Seeing	Day	13% 9% 31% 31% 13% 3	18760
	Night	12% 7% 33% 37% 10% 1	28560

By Month

Percentage Cloud Cover SW (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	5% 13% 5% 15% 11% 9% 7% 5% 6% 5% 19%	4519
	11th to 20th	Day	4 7% 4 12% 8% 9% 9% 6% 8% 8% 25%	4740
	21st to end	Day	3 7% 6% 15% 8% 7% 7% 4 5% 6% 32%	5245
February	1st to 10th	Day	8% 13% 5% 12% 6% 7% 4 3 7% 6% 29%	1890
	11th to 20th	Day	6% 10% 5% 11% 6% 6% 5% 4 6% 7% 33%	1918
	21st to end	Day	8% 12% 4 9% 5% 8% 5% 4 7% 7% 30%	1730
March	1st to 10th	Day	8% 8% 3 7% 4 4 4 3 5% 7% 46%	4662
	11th to 20th	Day	9% 8% 2 8% 4 4 4 3 6% 9% 42%	5090
	21st to end	Day	18% 13% 4 12% 6% 4 5% 3 4 6% 24%	5585
April	1st to 10th	Day	16% 8% 3 6% 3 4 4 3 6% 6% 41%	2468
	11th to 20th	Day	17% 8% 3 7% 5% 5% 4 3 5% 6% 36%	2699
	21st to end	Day	19% 9% 2 6% 4 4 4 4 5% 6% 35%	2730
May	1st to 10th	Day	10% 5% 2 5% 4 4 3 3 5% 7% 53%	7655
	11th to 20th	Day	18% 7% 2 4 3 3 3 3 4 5% 47%	7627
	21st to end	Day	15% 7% 3 6% 4 4 4 4 5% 8% 40%	9560
June	1st to 10th	Day	10% 6% 2 6% 4 4 4 4 7% 9% 43%	3150
	11th to 20th	Day	11% 5% 2 6% 5% 4 4 4 7% 8% 44%	3150
	21st to end	Day	10% 4 2 4 4 4 5% 3 6% 8% 50%	3150
July	1st to 10th	Day	9% 5% 2 5% 4 4 5% 4 7% 10% 45%	8849
	11th to 20th	Day	6% 4 2 4 3 3 3 3 5% 7% 60%	8254
	21st to end	Day	8% 4 2 6% 4 4 5% 5% 6% 9% 46%	8924
August	1st to 10th	Day	9% 5% 2 5% 4 4 4 3 6% 8% 50%	7581
	11th to 20th	Day	10% 6% 2 7% 5% 5% 5% 4 7% 9% 41%	7598
	21st to end	Day	6% 4 2 5% 3 4 4 3 5% 8% 57%	8408
September	1st to 10th	Day	9% 4 1 4 3 3 3 4 5% 8% 55%	2459
	11th to 20th	Day	11% 5% 2 5% 4 4 4 3 6% 8% 49%	2310
	21st to end	Day	15% 6% 2 4 3 3 3 2 4 6% 53%	2310
October	1st to 10th	Day	11% 4 2 4 3 3 3 2 3 6% 59%	3564
	11th to 20th	Day	11% 5% 2 5% 3 4 3 3 4 6% 54%	3246
	21st to end	Day	13% 7% 3 7% 4 4 4 3 5% 7% 45%	3190
November	1st to 10th	Day	11% 10% 3 8% 3 4 3 4 5% 7% 41%	1853
	11th to 20th	Day	7% 11% 3 8% 5% 5% 5% 3 6% 6% 40%	1764
	21st to end	Day	8% 11% 3 8% 5% 4 5% 5% 6% 8% 37%	1680
December	1st to 10th	Day	7% 10% 4 12% 8% 7% 6% 3 5% 6% 31%	2445
	11th to 20th	Day	7% 14% 6% 13% 7% 7% 6% 4 5% 7% 23%	2713
	21st to end	Day	15% 12% 4 12% 6% 5% 5% 4 5% 5% 28%	3575
January	1st to 10th	Night	4 10% 5% 13% 9% 9% 8% 5% 7% 7% 22%	8400
	11th to 20th	Night	3 9% 4 10% 7% 8% 9% 6% 8% 8% 28%	8250
	21st to end	Night	3 7% 5% 11% 6% 6% 6% 5% 7% 6% 37%	8956
February	1st to 10th	Night	7% 11% 4 11% 6% 7% 4 4 5% 7% 33%	2730
	11th to 20th	Night	6% 10% 3 9% 6% 4 5% 4 6% 7% 40%	2606
	21st to end	Night	8% 9% 3 8% 5% 5% 5% 5% 6% 7% 38%	2076
March	1st to 10th	Night	8% 7% 2 7% 5% 5% 5% 4 6% 7% 44%	5429
	11th to 20th	Night	9% 6% 2 7% 4 4 5% 4 7% 8% 43%	5090
	21st to end	Night	18% 10% 3 8% 5% 4 5% 4 6% 7% 30%	5588
April	1st to 10th	Night	13% 9% 3 6% 4 3 4 4 5% 8% 42%	2148
	11th to 20th	Night	15% 8% 3 7% 5% 3 4 3 4 7% 42%	1869
	21st to end	Night	17% 10% 3 7% 4 4 4 4 5% 7% 35%	1890
May	1st to 10th	Night	10% 4 2 5% 3 4 4 3 6% 7% 54%	5292
	11th to 20th	Night	13% 7% 2 4 3 3 3 3 4 6% 51%	5265
	21st to end	Night	13% 6% 2 6% 4 4 4 3 6% 8% 44%	4641
June	1st to 10th	Night	10% 4 1 4 3 3 3 4 7% 8% 52%	1470
	11th to 20th	Night	8% 4 2 7% 4 4 4 3 6% 9% 49%	1470
	21st to end	Night	6% 3 1 4 3 3 3 4 5% 9% 58%	1470
July	1st to 10th	Night	7% 4 2 6% 5% 4 4 4 7% 9% 49%	4140
	11th to 20th	Night	5% 2 1 3 3 2 3 2 4 6% 68%	4731
	21st to end	Night	6% 4 2 6% 4 3 4 4 7% 9% 49%	5182
August	1st to 10th	Night	8% 4 2 5% 4 4 4 4 5% 7% 53%	5241
	11th to 20th	Night	10% 6% 2 6% 4 3 4 4 6% 9% 47%	5258
	21st to end	Night	6% 4 2 5% 4 4 4 4 5% 7% 56%	5808
September	1st to 10th	Night	8% 4 1 4 2 3 4 3 4 6% 60%	2155
	11th to 20th	Night	10% 4 2 5% 4 3 4 3 4 6% 55%	2310
	21st to end	Night	12% 4 2 5% 3 3 3 3 4 6% 57%	2310
October	1st to 10th	Night	9% 4 1 3 2 2 3 2 4 5% 65%	3802
	11th to 20th	Night	11% 5% 2 5% 4 3 4 3 6% 7% 51%	3958
	21st to end	Night	11% 6% 2 6% 4 5% 4 3 5% 7% 47%	4610
November	1st to 10th	Night	9% 7% 2 6% 4 4 4 3 6% 8% 47%	2665
	11th to 20th	Night	7% 9% 3 9% 6% 5% 5% 4 5% 6% 41%	2853
	21st to end	Night	8% 7% 3 7% 4 4 4 3 5% 8% 45%	2940
December	1st to 10th	Night	5% 8% 5% 11% 7% 6% 5% 4 5% 7% 38%	4951
	11th to 20th	Night	6% 11% 5% 10% 7% 6% 5% 4 6% 7% 32%	5714
	21st to end	Night	14% 12% 4 12% 7% 4 4 3 5% 5% 29%	7645

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% 7% 12% 11% 5% 1	4521
	11th to 20th	Day	53% 6% 15% 17% 8%	4740
	21st to end	Day	52% 5% 16% 20% 7%	5245
February	1st to 10th	Day	54% 7% 13% 18% 7% 1	1890
	11th to 20th	Day	48% 7% 13% 22% 9% 1	1927
	21st to end	Day	50% 7% 16% 18% 8% 1	1730
March	1st to 10th	Day	38% 6% 11% 34% 10% 1	4662
	11th to 20th	Day	38% 5% 16% 27% 13% 1	5090
	21st to end	Day	61% 6% 13% 15% 5%	5585
April	1st to 10th	Day	42% 5% 15% 25% 12% 1	2468
	11th to 20th	Day	48% 6% 11% 21% 12% 1	2702
	21st to end	Day	49% 6% 13% 23% 8%	2730
May	1st to 10th	Day	32% 3 8% 32% 23% 1	7655
	11th to 20th	Day	39% 5% 7% 24% 20% 5%	7631
	21st to end	Day	42% 6% 11% 28% 13%	9561
June	1st to 10th	Day	35% 8% 16% 28% 12% 2	3150
	11th to 20th	Day	35% 8% 15% 25% 14% 2	3150
	21st to end	Day	30% 8% 16% 29% 15% 2	3150
July	1st to 10th	Day	34% 5% 19% 28% 12% 1	8776
	11th to 20th	Day	25% 3 11% 33% 22% 6%	8178
	21st to end	Day	33% 5% 19% 29% 12% 1	8726
August	1st to 10th	Day	29% 5% 13% 35% 17% 2	6000
	11th to 20th	Day	40% 6% 22% 25% 6% 1	5987
	21st to end	Day	27% 5% 18% 31% 16% 2	6592
September	1st to 10th	Day	28% 6% 13% 34% 18% 1	2459
	11th to 20th	Day	33% 6% 17% 30% 14% 1	2310
	21st to end	Day	33% 6% 12% 29% 18% 2	2310
October	1st to 10th	Day	28% 4 9% 29% 27% 3	3564
	11th to 20th	Day	34% 4 9% 34% 17% 2	3246
	21st to end	Day	40% 4 15% 23% 17% 1	3190
November	1st to 10th	Day	40% 6% 15% 24% 12% 2	1853
	11th to 20th	Day	43% 6% 16% 25% 10% 1	1764
	21st to end	Day	44% 7% 17% 24% 7% 2	1680
December	1st to 10th	Day	54% 6% 17% 19% 4	2445
	11th to 20th	Day	59% 7% 15% 15% 3	2710
	21st to end	Day	58% 5% 14% 17% 5%	3575
January	1st to 10th	Night	58% 8% 15% 14% 6%	8401
	11th to 20th	Night	49% 6% 15% 18% 11%	8250
	21st to end	Night	44% 7% 17% 22% 11%	8956
February	1st to 10th	Night	50% 7% 14% 18% 11% 1	2730
	11th to 20th	Night	43% 6% 13% 24% 12% 1	2607
	21st to end	Night	43% 7% 14% 23% 12% 2	2076
March	1st to 10th	Night	37% 5% 14% 31% 10% 2	5429
	11th to 20th	Night	37% 5% 15% 30% 12% 1	5090
	21st to end	Night	51% 6% 15% 21% 6%	5588
April	1st to 10th	Night	41% 5% 13% 28% 12% 1	2148
	11th to 20th	Night	43% 5% 10% 24% 15% 3	1869
	21st to end	Night	48% 7% 10% 23% 12% 1	1890
May	1st to 10th	Night	29% 5% 11% 32% 21% 3	5293
	11th to 20th	Night	34% 5% 8% 24% 23% 6%	5266
	21st to end	Night	37% 6% 13% 32% 12% 1	4642
June	1st to 10th	Night	28% 6% 17% 29% 15% 4	1470
	11th to 20th	Night	31% 6% 17% 25% 17% 4	1470
	21st to end	Night	23% 6% 20% 29% 19% 3	1470
July	1st to 10th	Night	31% 5% 19% 31% 13% 1	4105
	11th to 20th	Night	19% 3 11% 39% 21% 6%	4684
	21st to end	Night	30% 5% 24% 28% 11% 1	5068
August	1st to 10th	Night	25% 5% 14% 31% 22% 3	4146
	11th to 20th	Night	36% 5% 24% 25% 8% 1	4145
	21st to end	Night	29% 6% 14% 30% 18% 2	4555
September	1st to 10th	Night	24% 5% 14% 33% 21% 3	2155
	11th to 20th	Night	31% 5% 16% 29% 17% 2	2310
	21st to end	Night	30% 4 11% 31% 21% 3	2310
October	1st to 10th	Night	23% 3 7% 27% 37% 3	3802
	11th to 20th	Night	32% 3 10% 32% 20% 2	3958
	21st to end	Night	38% 5% 13% 26% 17% 1	4610
November	1st to 10th	Night	35% 6% 15% 24% 17% 3	2665
	11th to 20th	Night	42% 7% 16% 22% 13% 2	2853
	21st to end	Night	37% 6% 20% 27% 10% 1	2940
December	1st to 10th	Night	47% 5% 17% 23% 8%	4951
	11th to 20th	Night	50% 6% 19% 19% 5%	5716
	21st to end	Night	57% 4 14% 18% 6%	7645

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	11% 8% 29% 42% 8% 2	330
	11th to 20th	Day	12% 10% 37% 29% 10% 1	330
	21st to end	Day	13% 10% 37% 25% 14% 1	363
February	1st to 10th	Day	12% 13% 40% 31% 4	330
	11th to 20th	Day	12% 10% 39% 25% 11% 3	330
	21st to end	Day	14% 10% 40% 33% 4	273
March	1st to 10th	Day	15% 12% 36% 29% 6% 2	330
	11th to 20th	Day	14% 13% 34% 25% 13% 2	330
	21st to end	Day	17% 12% 31% 24% 12% 4	363
April	1st to 10th	Day	23% 14% 31% 27% 6%	488
	11th to 20th	Day	21% 15% 29% 26% 8% 1	740
	21st to end	Day	23% 11% 28% 27% 9% 1	750
May	1st to 10th	Day	16% 12% 29% 29% 14% 1	753
	11th to 20th	Day	18% 12% 26% 27% 15% 1	775
	21st to end	Day	18% 8% 26% 29% 16% 4	844
June	1st to 10th	Day	9% 8% 28% 32% 17% 6%	780
	11th to 20th	Day	11% 9% 37% 28% 13% 2	780
	21st to end	Day	12% 8% 31% 32% 15% 2	780
July	1st to 10th	Day	7% 5% 24% 38% 21% 6%	771
	11th to 20th	Day	6% 5% 30% 41% 17% 2	768
	21st to end	Day	6% 5% 26% 41% 18% 4	849
August	1st to 10th	Day	10% 4 23% 40% 20% 4	776
	11th to 20th	Day	10% 5% 25% 38% 18% 4	765
	21st to end	Day	7% 3 26% 37% 22% 4	858
September	1st to 10th	Day	11% 7% 28% 35% 14% 5%	509
	11th to 20th	Day	14% 4 35% 31% 14% 2	360
	21st to end	Day	18% 11% 29% 23% 14% 6%	360
October	1st to 10th	Day	16% 8% 30% 31% 12% 4	360
	11th to 20th	Day	16% 15% 35% 28% 6%	339
	21st to end	Day	16% 14% 39% 21% 8% 2	363
November	1st to 10th	Day	20% 10% 31% 31% 8% 1	330
	11th to 20th	Day	13% 9% 41% 25% 10% 1	330
	21st to end	Day	16% 12% 38% 26% 8% 1	330
December	1st to 10th	Day	14% 7% 34% 33% 11% 1	330
	11th to 20th	Day	14% 9% 44% 28% 4	330
	21st to end	Day	18% 10% 33% 28% 10%	363
January	1st to 10th	Night	11% 6% 38% 36% 8% 1	1050
	11th to 20th	Night	12% 9% 35% 38% 7%	1050
	21st to end	Night	12% 8% 35% 38% 7% 1	1155
February	1st to 10th	Night	11% 9% 36% 35% 8% 1	1050
	11th to 20th	Night	10% 6% 40% 33% 9% 1	972
	21st to end	Night	13% 7% 34% 32% 11% 2	692
March	1st to 10th	Night	13% 10% 34% 35% 8%	814
	11th to 20th	Night	18% 8% 33% 33% 9%	630
	21st to end	Night	16% 8% 34% 32% 9% 1	693
April	1st to 10th	Night	16% 10% 38% 30% 6%	630
	11th to 20th	Night	18% 13% 30% 29% 10%	623
	21st to end	Night	19% 8% 34% 30% 9%	630
May	1st to 10th	Night	11% 7% 35% 35% 11%	630
	11th to 20th	Night	13% 6% 33% 39% 9%	621
	21st to end	Night	13% 7% 32% 36% 12%	683
June	1st to 10th	Night	10% 5% 25% 44% 14%	630
	11th to 20th	Night	10% 6% 36% 40% 8%	630
	21st to end	Night	8% 4 29% 47% 11%	630
July	1st to 10th	Night	5% 3 26% 47% 18% 1	615
	11th to 20th	Night	5% 2 28% 50% 14%	612
	21st to end	Night	5% 2 25% 54% 12% 1	690
August	1st to 10th	Night	8% 3 22% 51% 16%	627
	11th to 20th	Night	10% 2 23% 45% 19% 1	624
	21st to end	Night	5% 4 25% 47% 17%	693
September	1st to 10th	Night	10% 3 30% 42% 14% 2	630
	11th to 20th	Night	10% 6% 28% 43% 12% 1	630
	21st to end	Night	12% 5% 32% 35% 15% 1	630
October	1st to 10th	Night	15% 8% 32% 32% 11%	693
	11th to 20th	Night	17% 8% 34% 33% 8%	823
	21st to end	Night	16% 9% 35% 31% 9%	1100
November	1st to 10th	Night	12% 8% 35% 35% 10%	1025
	11th to 20th	Night	10% 9% 37% 33% 9% 1	1050
	21st to end	Night	11% 9% 34% 38% 9%	1050
December	1st to 10th	Night	11% 7% 37% 35% 9% 1	1050
	11th to 20th	Night	15% 9% 34% 34% 8%	1050
	21st to end	Night	19% 7% 36% 30% 7% 1	1155

Page generated at 2026-10-11 04:06:31. Version ac07

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