Ely Airport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ely Airport clear sky chart from 2005-11-06 to 2026-06-16.

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	3 6% 3 6% 4 4 4 3 5% 6% 57%	146218
	Night	2 6% 3 7% 4 4 4 3 5% 6% 57%	143296
Transparency	Day	23% 7% 9% 17% 24% 19%	141075
	Night	23% 7% 10% 19% 25% 16%	139433
Seeing	Day	9% 16% 30% 27% 14% 4	16986
	Night	7% 9% 25% 35% 20% 4	26666

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	1 10% 8% 14% 6% 3 4 3 5% 7% 38%	4722
	11th to 20th	Day	1 8% 3 5% 5% 3 3 2 3 5% 62%	4956
	21st to end	Day	2 9% 5% 6% 3 3 4 4 6% 8% 51%	5844
February	1st to 10th	Day	3 9% 5% 8% 5% 5% 4 4 5% 6% 45%	2006
	11th to 20th	Day	3 9% 3 10% 6% 4 4 4 6% 6% 44%	2050
	21st to end	Day	1 8% 4 9% 5% 4 4 3 5% 6% 51%	1730
March	1st to 10th	Day	1 12% 6% 9% 4 4 4 3 5% 8% 44%	4618
	11th to 20th	Day	1 7% 4 11% 5% 4 5% 3 6% 7% 47%	5105
	21st to end	Day	2 12% 6% 11% 5% 5% 5% 4 6% 8% 35%	5607
April	1st to 10th	Day	2 9% 3 7% 5% 4 4 4 6% 7% 50%	2493
	11th to 20th	Day	3 8% 2 7% 4 3 4 4 6% 7% 51%	2527
	21st to end	Day	5% 8% 2 5% 4 3 4 4 6% 7% 51%	2730
May	1st to 10th	Day	3 5% 3 5% 4 4 4 4 6% 7% 55%	7626
	11th to 20th	Day	3 8% 2 5% 3 3 3 3 4 5% 61%	7596
	21st to end	Day	3 4 2 5% 4 4 5% 4 6% 7% 54%	8370
June	1st to 10th	Day	4 3 2 5% 4 5% 4 4 6% 8% 57%	2794
	11th to 20th	Day	4 3 2 4 3 3 3 3 5% 5% 65%	2871
	21st to end	Day	3 3 1 3 3 4 4 3 4 5% 66%	2800
July	1st to 10th	Day	2 2 1 4 3 3 3 2 3 4 74%	6319
	11th to 20th	Day	3 4 2 5% 4 5% 5% 5% 7% 8% 53%	6232
	21st to end	Day	3 3 1 5% 4 4 4 3 5% 6% 64%	6401
August	1st to 10th	Day	2 2 1 3 2 3 3 3 4 6% 71%	5779
	11th to 20th	Day	1 2 1 3 2 3 2 2 3 4 77%	5761
	21st to end	Day	2 3 2 5% 4 4 5% 3 5% 6% 60%	5984
September	1st to 10th	Day	3 3 2 5% 4 4 4 3 4 5% 62%	2315
	11th to 20th	Day	3 3 1 4 3 3 3 3 4 5% 68%	2200
	21st to end	Day	3 3 1 3 4 2 3 2 4 5% 71%	2200
October	1st to 10th	Day	3 3 1 3 3 3 4 3 4 6% 66%	3600
	11th to 20th	Day	2 4 1 3 3 3 3 2 4 5% 70%	3359
	21st to end	Day	2 3 3 5% 3 2 2 2 4 6% 69%	3246
November	1st to 10th	Day	3 6% 2 6% 4 3 4 4 5% 7% 54%	1854
	11th to 20th	Day	3 7% 2 5% 4 4 3 3 6% 7% 57%	1890
	21st to end	Day	3 7% 3 8% 5% 5% 4 4 4 5% 53%	1890
December	1st to 10th	Day	2 5% 2 5% 3 2 3 2 4 6% 66%	3040
	11th to 20th	Day	3 9% 4 8% 4 4 5% 4 7% 9% 43%	3499
	21st to end	Day	2 10% 5% 11% 6% 5% 5% 4 6% 7% 40%	4204
January	1st to 10th	Night	1 10% 7% 14% 6% 4 4 3 5% 7% 40%	8172
	11th to 20th	Night	2 7% 3 5% 4 3 3 2 4 5% 62%	8009
	21st to end	Night	2 8% 4 9% 3 3 3 3 4 7% 55%	8370
February	1st to 10th	Night	2 9% 3 9% 5% 4 4 3 6% 7% 48%	2609
	11th to 20th	Night	3 9% 4 9% 4 4 5% 4 5% 7% 45%	2458
	21st to end	Night	1 7% 2 9% 5% 5% 5% 4 7% 6% 49%	2076
March	1st to 10th	Night	1 13% 5% 11% 5% 4 4 3 4 5% 45%	5496
	11th to 20th	Night	1 7% 4 11% 6% 5% 5% 4 6% 7% 44%	5115
	21st to end	Night	2 7% 4 9% 5% 4 5% 4 6% 8% 46%	5610
April	1st to 10th	Night	5% 9% 3 6% 4 3 4 3 6% 7% 51%	2124
	11th to 20th	Night	2 8% 2 6% 3 4 5% 4 6% 7% 53%	2039
	21st to end	Night	5% 7% 2 5% 4 4 4 3 6% 7% 53%	1890
May	1st to 10th	Night	3 6% 3 5% 3 3 3 3 4 6% 61%	5321
	11th to 20th	Night	4 4 2 4 3 3 4 3 5% 6% 62%	5296
	21st to end	Night	3 4 2 6% 4 4 4 3 6% 7% 57%	5837
June	1st to 10th	Night	4 4 1 4 4 4 4 3 6% 7% 59%	1820
	11th to 20th	Night	4 4 1 4 3 3 3 2 4 5% 67%	1640
	21st to end	Night	3 4 1 3 4 3 3 3 4 6% 67%	1600
July	1st to 10th	Night	2 1 1 3 3 3 3 2 4 4 76%	3640
	11th to 20th	Night	3 5% 2 7% 4 5% 6% 4 6% 8% 49%	3729
	21st to end	Night	2 3 1 6% 5% 5% 4 4 5% 6% 59%	4472
August	1st to 10th	Night	3 2 1 5% 3 3 3 2 4 5% 69%	4033
	11th to 20th	Night	2 2 1 2 2 2 2 2 3 4 78%	4087
	21st to end	Night	2 3 1 4 4 4 4 3 5% 5% 65%	5015
September	1st to 10th	Night	3 3 1 5% 3 4 4 4 5% 5% 64%	2085
	11th to 20th	Night	4 3 1 4 3 4 3 3 5% 5% 67%	2200
	21st to end	Night	3 3 1 3 2 2 2 3 3 4 74%	2200
October	1st to 10th	Night	3 3 1 3 2 3 3 2 4 5% 73%	3600
	11th to 20th	Night	3 5% 2 4 3 3 3 3 3 4 67%	3792
	21st to end	Night	2 4 2 5% 3 3 3 2 4 6% 68%	4537
November	1st to 10th	Night	3 6% 2 5% 3 3 3 3 5% 7% 59%	2665
	11th to 20th	Night	3 5% 1 6% 4 4 3 4 5% 7% 58%	2730
	21st to end	Night	3 6% 4 7% 4 3 4 3 5% 6% 54%	2730
December	1st to 10th	Night	1 5% 2 5% 3 3 4 3 5% 5% 65%	4370
	11th to 20th	Night	2 8% 3 8% 4 4 4 3 5% 9% 50%	4941
	21st to end	Night	3 9% 5% 11% 6% 5% 5% 4 6% 8% 38%	6988

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	34% 14% 19% 20% 11% 2	4723
	11th to 20th	Day	20% 8% 11% 15% 32% 14%	4956
	21st to end	Day	26% 7% 14% 19% 25% 8%	5844
February	1st to 10th	Day	36% 9% 12% 21% 15% 7%	2006
	11th to 20th	Day	34% 8% 13% 20% 19% 5%	2060
	21st to end	Day	30% 7% 13% 25% 19% 5%	1730
March	1st to 10th	Day	33% 9% 10% 21% 18% 10%	4618
	11th to 20th	Day	28% 10% 16% 27% 15% 3	5105
	21st to end	Day	35% 13% 15% 21% 13% 2	5607
April	1st to 10th	Day	30% 8% 13% 22% 20% 8%	2493
	11th to 20th	Day	27% 7% 12% 24% 24% 5%	2530
	21st to end	Day	28% 7% 12% 26% 24% 3	2730
May	1st to 10th	Day	20% 9% 10% 24% 28% 9%	7626
	11th to 20th	Day	22% 5% 6% 15% 39% 12%	7599
	21st to end	Day	20% 7% 8% 21% 35% 9%	8371
June	1st to 10th	Day	22% 6% 8% 17% 33% 13%	2794
	11th to 20th	Day	20% 4 5% 12% 30% 30%	2871
	21st to end	Day	17% 4 5% 11% 24% 39%	2800
July	1st to 10th	Day	14% 3 3 5% 12% 64%	6251
	11th to 20th	Day	21% 7% 5% 8% 18% 39%	6157
	21st to end	Day	18% 6% 6% 8% 14% 49%	6217
August	1st to 10th	Day	17% 4 6% 13% 26% 33%	4208
	11th to 20th	Day	13% 4 5% 8% 23% 47%	4172
	21st to end	Day	16% 3 5% 8% 22% 46%	4311
September	1st to 10th	Day	20% 6% 6% 10% 28% 30%	2315
	11th to 20th	Day	18% 4 7% 15% 28% 29%	2200
	21st to end	Day	16% 3 5% 14% 34% 28%	2200
October	1st to 10th	Day	17% 5% 6% 11% 30% 31%	3600
	11th to 20th	Day	16% 4 5% 17% 35% 23%	3359
	21st to end	Day	16% 5% 5% 25% 38% 11%	3246
November	1st to 10th	Day	24% 6% 11% 24% 23% 12%	1854
	11th to 20th	Day	24% 6% 10% 28% 27% 6%	1890
	21st to end	Day	31% 6% 9% 24% 21% 9%	1890
December	1st to 10th	Day	20% 4 8% 27% 30% 11%	3040
	11th to 20th	Day	31% 9% 13% 20% 21% 5%	3498
	21st to end	Day	34% 11% 12% 23% 17% 3	4204
January	1st to 10th	Night	30% 15% 17% 20% 16% 1	8172
	11th to 20th	Night	20% 7% 12% 18% 28% 14%	8009
	21st to end	Night	26% 6% 11% 19% 29% 8%	8370
February	1st to 10th	Night	32% 7% 13% 26% 16% 6%	2609
	11th to 20th	Night	32% 8% 12% 20% 22% 6%	2459
	21st to end	Night	29% 9% 14% 23% 19% 7%	2076
March	1st to 10th	Night	35% 8% 10% 18% 17% 11%	5496
	11th to 20th	Night	27% 13% 14% 26% 17% 3	5115
	21st to end	Night	27% 9% 17% 25% 20% 2	5610
April	1st to 10th	Night	31% 6% 13% 22% 22% 7%	2124
	11th to 20th	Night	24% 8% 10% 29% 22% 7%	2039
	21st to end	Night	26% 5% 11% 27% 26% 4	1890
May	1st to 10th	Night	20% 7% 10% 23% 33% 7%	5319
	11th to 20th	Night	17% 8% 8% 17% 37% 14%	5297
	21st to end	Night	20% 7% 8% 19% 37% 8%	5838
June	1st to 10th	Night	20% 6% 10% 17% 33% 13%	1820
	11th to 20th	Night	17% 4 6% 15% 26% 32%	1640
	21st to end	Night	17% 4 4 10% 27% 37%	1600
July	1st to 10th	Night	11% 3 4 5% 11% 67%	3600
	11th to 20th	Night	25% 7% 7% 10% 18% 33%	3681
	21st to end	Night	22% 6% 6% 9% 11% 45%	4344
August	1st to 10th	Night	24% 5% 5% 11% 23% 32%	2928
	11th to 20th	Night	12% 3 4 7% 21% 51%	2951
	21st to end	Night	15% 3 4 9% 26% 43%	3608
September	1st to 10th	Night	19% 5% 7% 11% 25% 33%	2085
	11th to 20th	Night	18% 5% 8% 14% 26% 30%	2200
	21st to end	Night	14% 3 5% 14% 33% 30%	2200
October	1st to 10th	Night	14% 4 6% 11% 36% 29%	3600
	11th to 20th	Night	17% 6% 4 16% 34% 22%	3792
	21st to end	Night	17% 5% 5% 24% 38% 11%	4537
November	1st to 10th	Night	22% 5% 13% 26% 25% 10%	2665
	11th to 20th	Night	22% 6% 12% 25% 29% 7%	2730
	21st to end	Night	27% 5% 9% 27% 25% 8%	2730
December	1st to 10th	Night	20% 5% 10% 25% 30% 11%	4370
	11th to 20th	Night	26% 8% 17% 19% 23% 6%	4941
	21st to end	Night	36% 10% 14% 21% 16% 3	6988

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	19% 22% 26% 21% 11% 1	220
	11th to 20th	Day	8% 19% 28% 26% 13% 6%	259
	21st to end	Day	6% 14% 29% 28% 17% 6%	363
February	1st to 10th	Day	13% 20% 31% 18% 14% 3	446
	11th to 20th	Day	12% 21% 33% 21% 11% 2	535
	21st to end	Day	7% 20% 40% 22% 10% 1	446
March	1st to 10th	Day	14% 19% 31% 24% 12% 1	540
	11th to 20th	Day	11% 18% 32% 26% 11% 3	540
	21st to end	Day	13% 22% 34% 21% 8% 1	594
April	1st to 10th	Day	8% 24% 28% 25% 13% 3	540
	11th to 20th	Day	13% 26% 33% 20% 7% 2	532
	21st to end	Day	13% 24% 31% 17% 12% 2	540
May	1st to 10th	Day	10% 24% 32% 23% 9% 2	543
	11th to 20th	Day	13% 18% 33% 21% 11% 3	568
	21st to end	Day	13% 17% 24% 29% 13% 4	617
June	1st to 10th	Day	6% 14% 34% 28% 13% 6%	570
	11th to 20th	Day	8% 20% 30% 26% 14% 2	551
	21st to end	Day	5% 12% 34% 32% 16% 2	530
July	1st to 10th	Day	5% 9% 40% 28% 16% 3	526
	11th to 20th	Day	5% 4 31% 37% 18% 5%	524
	21st to end	Day	5% 5% 30% 35% 19% 6%	575
August	1st to 10th	Day	5% 9% 31% 33% 17% 4	527
	11th to 20th	Day	6% 9% 30% 31% 18% 6%	517
	21st to end	Day	5% 8% 28% 33% 18% 8%	583
September	1st to 10th	Day	5% 11% 29% 30% 17% 8%	530
	11th to 20th	Day	5% 17% 26% 27% 17% 7%	530
	21st to end	Day	7% 13% 25% 31% 18% 7%	530
October	1st to 10th	Day	10% 18% 22% 26% 16% 7%	530
	11th to 20th	Day	9% 15% 25% 27% 18% 6%	400
	21st to end	Day	8% 16% 25% 31% 17% 3	363
November	1st to 10th	Day	9% 18% 27% 18% 20% 7%	330
	11th to 20th	Day	9% 19% 24% 29% 13% 6%	330
	21st to end	Day	11% 15% 21% 28% 20% 6%	330
December	1st to 10th	Day	7% 14% 25% 28% 19% 6%	330
	11th to 20th	Day	9% 13% 27% 32% 15% 4	330
	21st to end	Day	18% 18% 29% 23% 9% 3	267
January	1st to 10th	Night	7% 13% 27% 31% 16% 6%	840
	11th to 20th	Night	6% 8% 29% 33% 18% 5%	840
	21st to end	Night	9% 9% 26% 34% 16% 6%	924
February	1st to 10th	Night	9% 12% 31% 30% 15% 4	840
	11th to 20th	Night	8% 11% 29% 36% 13% 3	824
	21st to end	Night	5% 10% 37% 34% 11% 2	692
March	1st to 10th	Night	7% 12% 31% 34% 13% 3	840
	11th to 20th	Night	5% 11% 29% 36% 16% 3	840
	21st to end	Night	8% 15% 29% 35% 11% 2	924
April	1st to 10th	Night	10% 14% 25% 37% 13% 1	840
	11th to 20th	Night	7% 16% 32% 31% 12% 2	791
	21st to end	Night	9% 14% 29% 31% 16% 2	630
May	1st to 10th	Night	7% 14% 30% 34% 13% 1	630
	11th to 20th	Night	9% 10% 23% 35% 19% 4	621
	21st to end	Night	10% 10% 24% 33% 21% 2	683
June	1st to 10th	Night	6% 9% 22% 38% 23% 3	560
	11th to 20th	Night	7% 10% 23% 40% 20% 1	410
	21st to end	Night	4 3 25% 41% 25% 3	400
July	1st to 10th	Night	4 2 20% 44% 26% 4	390
	11th to 20th	Night	6% 3 17% 45% 26% 3	425
	21st to end	Night	5% 3 20% 37% 33% 2	657
August	1st to 10th	Night	6% 4 22% 43% 24% 1	597
	11th to 20th	Night	3 2 21% 42% 29% 3	604
	21st to end	Night	5% 4 15% 37% 34% 5%	880
September	1st to 10th	Night	4 5% 16% 36% 34% 6%	800
	11th to 20th	Night	5% 7% 17% 33% 31% 7%	800
	21st to end	Night	5% 5% 19% 33% 30% 9%	800
October	1st to 10th	Night	7% 7% 20% 36% 26% 5%	800
	11th to 20th	Night	7% 7% 18% 38% 24% 6%	800
	21st to end	Night	4 9% 23% 33% 24% 7%	880
November	1st to 10th	Night	6% 8% 25% 31% 22% 8%	820
	11th to 20th	Night	6% 7% 28% 36% 17% 5%	840
	21st to end	Night	6% 11% 24% 33% 21% 6%	840
December	1st to 10th	Night	6% 9% 28% 36% 16% 5%	840
	11th to 20th	Night	9% 9% 29% 35% 17% 2	840
	21st to end	Night	11% 13% 30% 32% 12% 2	924

Page generated at 2026-06-12 23:31:41. Version ac07

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