Conway
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Conway clear sky chart from 2005-11-06 to 2026-08-30.

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	16% 7% 2 6% 4 4 5% 4 6% 7% 38%	143796
	Night	16% 8% 3 6% 4 4 5% 4 6% 6% 38%	138435
Transparency	Day	44% 6% 12% 22% 13% 2	147292
	Night	44% 6% 12% 21% 14% 2	143028
Seeing	Day	22% 16% 29% 21% 9% 3	17192
	Night	20% 10% 28% 31% 10% 1	25961

By Month

Percentage Cloud Cover NE (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	11% 8% 3 10% 6% 6% 6% 4 6% 6% 35%	4661
	11th to 20th	Day	12% 10% 3 7% 4 4 4 4 5% 6% 41%	4650
	21st to end	Day	9% 9% 2 7% 5% 4 4 3 5% 6% 44%	5124
February	1st to 10th	Day	12% 9% 3 7% 5% 5% 5% 4 5% 7% 38%	1846
	11th to 20th	Day	11% 7% 3 8% 5% 5% 4 5% 6% 7% 39%	2048
	21st to end	Day	13% 11% 3 7% 5% 5% 6% 4 5% 5% 36%	1730
March	1st to 10th	Day	19% 12% 3 9% 5% 4 4 4 4 5% 32%	4576
	11th to 20th	Day	16% 9% 3 6% 4 5% 5% 3 6% 6% 38%	4892
	21st to end	Day	24% 8% 3 6% 4 3 3 3 4 8% 34%	5885
April	1st to 10th	Day	18% 10% 3 6% 5% 3 4 3 4 7% 37%	2520
	11th to 20th	Day	17% 7% 2 5% 6% 4 5% 4 5% 7% 38%	2550
	21st to end	Day	21% 9% 3 7% 4 4 3 3 5% 6% 36%	2730
May	1st to 10th	Day	28% 9% 3 7% 4 4 5% 3 5% 6% 25%	7639
	11th to 20th	Day	18% 7% 2 7% 5% 5% 5% 4 6% 7% 32%	7973
	21st to end	Day	19% 7% 3 6% 4 4 5% 4 7% 8% 32%	9060
June	1st to 10th	Day	21% 7% 2 6% 5% 5% 5% 4 6% 8% 31%	2940
	11th to 20th	Day	15% 7% 2 6% 5% 4 4 4 7% 8% 37%	2940
	21st to end	Day	19% 7% 2 6% 5% 6% 6% 4 6% 8% 32%	2940
July	1st to 10th	Day	15% 5% 2 6% 4 5% 5% 5% 7% 10% 36%	8280
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 4 6% 9% 45%	8280
	21st to end	Day	15% 5% 2 6% 4 4 4 4 6% 7% 43%	8993
August	1st to 10th	Day	14% 6% 2 7% 6% 6% 6% 4 6% 8% 36%	4501
	11th to 20th	Day	17% 7% 3 7% 5% 5% 5% 4 6% 7% 34%	4305
	21st to end	Day	10% 4 2 6% 4 4 5% 4 6% 9% 47%	4468
September	1st to 10th	Day	12% 4 1 4 3 4 4 4 7% 9% 49%	2396
	11th to 20th	Day	13% 4 2 4 3 3 4 3 4 6% 54%	2200
	21st to end	Day	16% 4 2 4 4 4 5% 3 5% 7% 47%	2200
October	1st to 10th	Day	19% 6% 2 5% 4 3 4 3 4 6% 42%	2200
	11th to 20th	Day	16% 7% 2 5% 4 4 4 3 5% 7% 43%	1907
	21st to end	Day	22% 8% 2 6% 4 4 4 4 5% 5% 36%	1980
November	1st to 10th	Day	14% 6% 2 5% 4 4 4 4 5% 6% 46%	1851
	11th to 20th	Day	17% 5% 1 5% 4 4 4 3 6% 7% 43%	1890
	21st to end	Day	19% 8% 3 5% 4 4 4 4 5% 6% 39%	1847
December	1st to 10th	Day	15% 8% 4 9% 5% 5% 5% 4 6% 7% 33%	2680
	11th to 20th	Day	18% 8% 2 5% 3 4 4 4 6% 6% 41%	3066
	21st to end	Day	19% 9% 2 7% 5% 4 5% 4 5% 5% 35%	4048
January	1st to 10th	Night	11% 8% 4 8% 5% 5% 4 4 5% 6% 39%	8234
	11th to 20th	Night	11% 11% 4 10% 6% 6% 6% 5% 6% 6% 28%	8235
	21st to end	Night	11% 6% 3 8% 5% 5% 6% 4 6% 7% 39%	9057
February	1st to 10th	Night	12% 9% 3 7% 5% 5% 5% 4 6% 7% 37%	2767
	11th to 20th	Night	10% 9% 3 6% 5% 5% 6% 4 6% 6% 42%	2458
	21st to end	Night	12% 10% 3 5% 4 4 4 4 6% 8% 40%	2076
March	1st to 10th	Night	21% 10% 3 6% 4 4 5% 4 5% 6% 32%	5484
	11th to 20th	Night	14% 9% 3 7% 5% 6% 5% 4 5% 6% 35%	5285
	21st to end	Night	23% 9% 3 6% 3 4 4 3 5% 6% 35%	5273
April	1st to 10th	Night	18% 10% 2 7% 4 4 4 3 4 6% 37%	2100
	11th to 20th	Night	17% 7% 2 6% 6% 4 5% 4 6% 6% 37%	2019
	21st to end	Night	22% 6% 2 4 4 4 4 3 6% 6% 39%	1890
May	1st to 10th	Night	30% 9% 2 6% 4 4 4 3 5% 6% 27%	5259
	11th to 20th	Night	16% 7% 3 8% 5% 5% 5% 4 6% 8% 33%	4942
	21st to end	Night	20% 6% 2 6% 4 4 4 4 6% 8% 36%	5114
June	1st to 10th	Night	20% 7% 2 5% 4 3 4 4 6% 7% 38%	1680
	11th to 20th	Night	18% 6% 2 4 4 4 5% 4 6% 7% 40%	1680
	21st to end	Night	18% 6% 2 5% 5% 4 4 4 6% 8% 38%	1680
July	1st to 10th	Night	13% 6% 2 6% 4 4 5% 5% 7% 9% 39%	4680
	11th to 20th	Night	12% 5% 2 6% 4 4 5% 3 6% 7% 46%	4680
	21st to end	Night	15% 4 1 4 3 3 4 4 6% 7% 49%	5084
August	1st to 10th	Night	20% 7% 3 7% 5% 4 4 4 6% 6% 35%	2834
	11th to 20th	Night	16% 7% 2 7% 4 4 4 4 5% 7% 38%	2962
	21st to end	Night	10% 5% 2 4 4 4 4 4 6% 8% 49%	3626
September	1st to 10th	Night	11% 5% 2 4 3 3 3 4 5% 7% 53%	2003
	11th to 20th	Night	14% 5% 1 4 3 3 4 3 4 6% 54%	2200
	21st to end	Night	16% 5% 2 5% 3 3 3 3 5% 7% 47%	2200
October	1st to 10th	Night	19% 6% 2 5% 4 4 4 3 5% 6% 41%	2200
	11th to 20th	Night	16% 6% 2 5% 4 4 4 4 6% 7% 41%	2486
	21st to end	Night	23% 7% 2 5% 4 4 4 3 5% 6% 37%	2860
November	1st to 10th	Night	14% 6% 3 6% 4 4 5% 3 6% 6% 45%	2667
	11th to 20th	Night	15% 6% 2 6% 5% 4 5% 4 5% 6% 43%	2730
	21st to end	Night	15% 8% 3 6% 4 4 5% 4 4 7% 41%	2772
December	1st to 10th	Night	16% 9% 3 7% 5% 5% 4 4 5% 6% 35%	4720
	11th to 20th	Night	23% 8% 2 5% 4 4 4 4 5% 5% 37%	5348
	21st to end	Night	18% 9% 2 7% 5% 4 4 3 5% 5% 37%	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	46% 6% 12% 22% 14% 1	4662
	11th to 20th	Day	43% 5% 12% 23% 15% 3	4680
	21st to end	Day	39% 6% 10% 22% 18% 5%	5124
February	1st to 10th	Day	45% 6% 14% 20% 12% 3	1846
	11th to 20th	Day	45% 6% 11% 20% 14% 4	2057
	21st to end	Day	49% 5% 11% 17% 14% 3	1730
March	1st to 10th	Day	55% 5% 8% 12% 12% 8%	4579
	11th to 20th	Day	45% 7% 15% 17% 12% 4	4892
	21st to end	Day	50% 3 6% 17% 19% 4	5885
April	1st to 10th	Day	48% 5% 10% 19% 14% 4	2520
	11th to 20th	Day	44% 7% 12% 19% 15% 2	2550
	21st to end	Day	50% 6% 9% 18% 14% 3	2730
May	1st to 10th	Day	58% 6% 11% 15% 8% 1	7651
	11th to 20th	Day	49% 8% 15% 17% 10% 2	7977
	21st to end	Day	47% 7% 13% 22% 11% 1	9061
June	1st to 10th	Day	50% 6% 13% 21% 10%	2940
	11th to 20th	Day	43% 6% 14% 19% 15% 2	2940
	21st to end	Day	49% 9% 12% 19% 10% 1	2940
July	1st to 10th	Day	42% 7% 16% 24% 12%	8210
	11th to 20th	Day	34% 7% 14% 29% 14% 1	8205
	21st to end	Day	38% 6% 12% 28% 15%	8795
August	1st to 10th	Day	44% 7% 15% 24% 10%	4487
	11th to 20th	Day	47% 7% 14% 24% 8%	4344
	21st to end	Day	32% 8% 16% 26% 17% 2	4468
September	1st to 10th	Day	31% 8% 14% 29% 17% 1	2396
	11th to 20th	Day	32% 5% 9% 33% 20% 2	2200
	21st to end	Day	38% 5% 12% 24% 19% 2	2200
October	1st to 10th	Day	44% 6% 10% 22% 16% 2	3590
	11th to 20th	Day	36% 4 12% 29% 16% 3	3071
	21st to end	Day	37% 4 11% 25% 19% 4	3180
November	1st to 10th	Day	37% 7% 14% 25% 15% 2	1851
	11th to 20th	Day	39% 6% 13% 19% 19% 3	1890
	21st to end	Day	45% 6% 16% 20% 11% 1	1847
December	1st to 10th	Day	49% 6% 14% 23% 8% 1	2680
	11th to 20th	Day	42% 6% 11% 18% 18% 5%	3066
	21st to end	Day	50% 6% 8% 18% 12% 6%	4048
January	1st to 10th	Night	44% 6% 11% 25% 12% 2	8234
	11th to 20th	Night	51% 8% 12% 15% 11% 3	8280
	21st to end	Night	41% 6% 9% 20% 18% 6%	9057
February	1st to 10th	Night	46% 6% 12% 19% 15% 2	2767
	11th to 20th	Night	41% 7% 12% 22% 15% 3	2460
	21st to end	Night	43% 6% 11% 21% 14% 4	2076
March	1st to 10th	Night	52% 5% 10% 14% 14% 5%	5494
	11th to 20th	Night	47% 7% 17% 16% 10% 2	5286
	21st to end	Night	50% 4 6% 14% 21% 4	5273
April	1st to 10th	Night	48% 5% 10% 18% 15% 2	2100
	11th to 20th	Night	46% 6% 10% 22% 15% 1	2019
	21st to end	Night	46% 5% 11% 18% 16% 3	1890
May	1st to 10th	Night	58% 6% 10% 15% 10% 1	5265
	11th to 20th	Night	48% 8% 11% 23% 8% 1	4943
	21st to end	Night	45% 7% 14% 23% 11% 1	5115
June	1st to 10th	Night	46% 8% 12% 21% 13%	1680
	11th to 20th	Night	42% 9% 15% 20% 13% 2	1680
	21st to end	Night	44% 8% 14% 22% 10% 1	1680
July	1st to 10th	Night	40% 7% 19% 22% 12%	4640
	11th to 20th	Night	36% 7% 13% 27% 17%	4632
	21st to end	Night	34% 5% 15% 33% 12%	4967
August	1st to 10th	Night	49% 8% 14% 21% 8% 1	2824
	11th to 20th	Night	44% 8% 16% 21% 11%	2989
	21st to end	Night	31% 7% 17% 29% 15% 1	3626
September	1st to 10th	Night	31% 7% 14% 31% 17%	2003
	11th to 20th	Night	32% 5% 11% 30% 20% 2	2200
	21st to end	Night	37% 7% 12% 28% 15% 2	2200
October	1st to 10th	Night	43% 7% 14% 21% 14% 1	3590
	11th to 20th	Night	33% 6% 11% 27% 19% 3	4061
	21st to end	Night	40% 4 10% 27% 15% 3	4610
November	1st to 10th	Night	40% 6% 12% 24% 16% 2	2667
	11th to 20th	Night	41% 6% 11% 22% 17% 3	2730
	21st to end	Night	43% 6% 16% 22% 12% 1	2772
December	1st to 10th	Night	48% 6% 11% 27% 8% 1	4720
	11th to 20th	Night	48% 6% 10% 15% 18% 3	5348
	21st to end	Night	49% 6% 9% 18% 16% 2	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	25% 20% 27% 21% 6%	220
	11th to 20th	Day	26% 22% 25% 21% 5% 1	220
	21st to end	Day	18% 24% 32% 19% 7%	242
February	1st to 10th	Day	21% 23% 33% 19% 4	356
	11th to 20th	Day	23% 20% 36% 17% 4	536
	21st to end	Day	24% 20% 30% 22% 4	446
March	1st to 10th	Day	27% 19% 29% 21% 4	540
	11th to 20th	Day	28% 21% 30% 15% 6% 1	540
	21st to end	Day	27% 21% 29% 14% 6% 2	594
April	1st to 10th	Day	32% 19% 26% 15% 6% 1	540
	11th to 20th	Day	29% 22% 27% 14% 7% 2	532
	21st to end	Day	28% 20% 29% 14% 6% 2	540
May	1st to 10th	Day	33% 18% 29% 15% 3 2	543
	11th to 20th	Day	23% 18% 32% 19% 7% 2	567
	21st to end	Day	21% 17% 32% 20% 8% 1	617
June	1st to 10th	Day	21% 14% 35% 19% 10% 2	570
	11th to 20th	Day	19% 17% 32% 22% 8% 3	570
	21st to end	Day	21% 13% 36% 18% 11% 2	570
July	1st to 10th	Day	18% 10% 32% 24% 13% 3	565
	11th to 20th	Day	13% 8% 35% 29% 12% 3	564
	21st to end	Day	15% 10% 31% 26% 14% 4	620
August	1st to 10th	Day	11% 11% 28% 27% 18% 6%	566
	11th to 20th	Day	15% 10% 27% 26% 15% 7%	559
	21st to end	Day	12% 10% 27% 30% 15% 6%	619
September	1st to 10th	Day	16% 9% 24% 28% 18% 6%	530
	11th to 20th	Day	17% 10% 24% 21% 17% 11%	530
	21st to end	Day	17% 11% 28% 25% 13% 6%	530
October	1st to 10th	Day	23% 14% 21% 22% 14% 6%	530
	11th to 20th	Day	22% 14% 24% 25% 14% 2	450
	21st to end	Day	31% 11% 27% 23% 7% 1	462
November	1st to 10th	Day	22% 17% 27% 26% 7% 1	425
	11th to 20th	Day	25% 16% 27% 23% 8% 1	430
	21st to end	Day	28% 17% 30% 19% 6%	387
December	1st to 10th	Day	24% 26% 20% 21% 8% 1	220
	11th to 20th	Day	29% 22% 31% 15% 4	220
	21st to end	Day	28% 17% 29% 19% 5% 1	242
January	1st to 10th	Night	18% 13% 35% 31% 4	840
	11th to 20th	Night	23% 15% 29% 29% 5%	840
	21st to end	Night	16% 14% 37% 27% 6% 1	924
February	1st to 10th	Night	18% 14% 34% 31% 4	840
	11th to 20th	Night	17% 13% 42% 25% 4	823
	21st to end	Night	18% 14% 34% 29% 4	692
March	1st to 10th	Night	22% 14% 33% 28% 3	840
	11th to 20th	Night	21% 15% 31% 27% 6%	840
	21st to end	Night	24% 11% 31% 25% 8% 1	924
April	1st to 10th	Night	25% 13% 31% 27% 4	840
	11th to 20th	Night	21% 14% 32% 27% 6%	775
	21st to end	Night	26% 13% 27% 27% 7%	630
May	1st to 10th	Night	27% 10% 27% 29% 7% 1	630
	11th to 20th	Night	19% 9% 31% 30% 10%	524
	21st to end	Night	19% 7% 24% 38% 11% 1	455
June	1st to 10th	Night	21% 6% 25% 35% 12% 1	420
	11th to 20th	Night	21% 6% 23% 36% 14%	420
	21st to end	Night	20% 3 22% 42% 13%	420
July	1st to 10th	Night	17% 3 19% 44% 18%	410
	11th to 20th	Night	14% 2 19% 42% 20% 2	408
	21st to end	Night	14% 3 16% 46% 20% 2	460
August	1st to 10th	Night	16% 3 17% 41% 21% 1	521
	11th to 20th	Night	15% 5% 23% 37% 18% 2	622
	21st to end	Night	15% 4 19% 38% 21% 3	879
September	1st to 10th	Night	14% 4 22% 37% 20% 2	800
	11th to 20th	Night	16% 5% 20% 30% 23% 6%	800
	21st to end	Night	18% 6% 23% 33% 18% 3	800
October	1st to 10th	Night	22% 7% 21% 31% 18% 2	800
	11th to 20th	Night	20% 9% 28% 30% 13% 1	800
	21st to end	Night	28% 9% 26% 30% 7%	880
November	1st to 10th	Night	19% 11% 29% 31% 8% 1	820
	11th to 20th	Night	20% 13% 29% 28% 9% 1	840
	21st to end	Night	22% 15% 29% 28% 6%	840
December	1st to 10th	Night	23% 11% 35% 25% 5% 1	840
	11th to 20th	Night	24% 14% 29% 29% 4	840
	21st to end	Night	23% 13% 31% 29% 4	924

Page generated at 2026-08-27 04:07:09. Version ac07

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