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 2025-04-26.

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% 3 6% 5% 4 5% 4 6% 7% 38%	113351
	Night	16% 8% 3 6% 4 4 5% 4 5% 6% 38%	115249
Transparency	Day	44% 7% 12% 21% 14% 3	116893
	Night	44% 7% 12% 21% 14% 2	119871
Seeing	Day	22% 15% 29% 21% 9% 3	15414
	Night	20% 10% 28% 31% 10% 1	24409

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	13% 8% 4 9% 6% 6% 6% 4 5% 5% 35%	3597
	11th to 20th	Day	12% 8% 3 6% 4 5% 5% 4 5% 6% 43%	3570
	21st to end	Day	11% 9% 3 7% 4 3 3 3 6% 6% 44%	3960
February	1st to 10th	Day	13% 9% 3 7% 5% 5% 5% 4 5% 7% 37%	1758
	11th to 20th	Day	12% 7% 3 8% 5% 5% 4 5% 6% 7% 38%	1948
	21st to end	Day	14% 11% 3 7% 5% 5% 6% 4 5% 5% 35%	1650
March	1st to 10th	Day	19% 12% 3 9% 5% 4 4 4 4 5% 32%	4476
	11th to 20th	Day	16% 9% 3 6% 4 5% 5% 3 6% 6% 38%	4786
	21st to end	Day	24% 8% 3 6% 4 3 3 3 4 8% 34%	5758
April	1st to 10th	Day	18% 10% 3 6% 5% 3 4 3 4 6% 38%	2400
	11th to 20th	Day	17% 7% 2 5% 6% 4 5% 4 5% 7% 38%	2427
	21st to end	Day	21% 9% 3 7% 5% 5% 4 3 5% 6% 35%	2535
May	1st to 10th	Day	21% 12% 4 8% 5% 5% 5% 3 5% 6% 26%	4106
	11th to 20th	Day	18% 8% 2 8% 6% 5% 5% 4 5% 6% 32%	4261
	21st to end	Day	14% 5% 2 6% 4 5% 6% 5% 7% 9% 38%	4837
June	1st to 10th	Day	21% 7% 2 6% 5% 5% 5% 4 6% 7% 31%	2660
	11th to 20th	Day	16% 7% 2 6% 5% 4 4 4 7% 7% 38%	2660
	21st to end	Day	20% 7% 2 6% 5% 5% 5% 5% 6% 8% 31%	2660
July	1st to 10th	Day	13% 5% 3 6% 5% 4 5% 5% 7% 10% 37%	4440
	11th to 20th	Day	11% 5% 2 6% 4 5% 6% 5% 7% 11% 39%	4440
	21st to end	Day	18% 6% 2 7% 4 4 5% 4 6% 7% 37%	4814
August	1st to 10th	Day	14% 6% 2 7% 5% 6% 6% 4 6% 8% 36%	4233
	11th to 20th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 7% 33%	4045
	21st to end	Day	10% 4 2 5% 4 4 5% 4 6% 9% 46%	4225
September	1st to 10th	Day	12% 4 1 4 3 4 4 4 7% 9% 48%	2276
	11th to 20th	Day	13% 4 2 3 3 3 4 3 4 5% 54%	2090
	21st to end	Day	16% 4 2 5% 4 4 5% 3 5% 6% 46%	2090
October	1st to 10th	Day	20% 6% 2 6% 4 4 4 3 4 6% 40%	2090
	11th to 20th	Day	16% 7% 2 5% 4 4 4 3 5% 7% 43%	1812
	21st to end	Day	23% 9% 2 5% 4 4 4 4 4 5% 36%	1881
November	1st to 10th	Day	14% 6% 2 5% 4 4 4 4 5% 7% 46%	1761
	11th to 20th	Day	17% 5% 1 4 4 5% 4 3 7% 7% 42%	1800
	21st to end	Day	20% 7% 3 4 3 4 4 4 5% 6% 40%	1759
December	1st to 10th	Day	16% 8% 4 9% 5% 5% 5% 4 6% 7% 33%	2600
	11th to 20th	Day	18% 8% 2 4 3 4 4 4 6% 6% 41%	2986
	21st to end	Day	19% 9% 2 6% 5% 5% 5% 4 5% 5% 35%	3960
January	1st to 10th	Night	12% 8% 4 8% 5% 5% 4 4 5% 6% 39%	6349
	11th to 20th	Night	10% 9% 3 10% 7% 7% 6% 5% 6% 6% 30%	6315
	21st to end	Night	12% 7% 3 9% 5% 4 5% 4 6% 6% 38%	6996
February	1st to 10th	Night	12% 10% 3 7% 5% 5% 5% 4 6% 7% 36%	2635
	11th to 20th	Night	10% 9% 3 6% 5% 5% 5% 4 6% 6% 42%	2338
	21st to end	Night	12% 10% 3 5% 4 4 4 4 7% 8% 39%	1980
March	1st to 10th	Night	21% 10% 3 6% 4 4 5% 5% 5% 6% 32%	5364
	11th to 20th	Night	14% 9% 3 7% 5% 6% 5% 4 5% 6% 35%	5171
	21st to end	Night	23% 9% 3 6% 4 3 4 3 5% 6% 35%	5158
April	1st to 10th	Night	18% 10% 2 7% 4 4 4 3 4 6% 37%	2000
	11th to 20th	Night	17% 7% 2 6% 6% 4 4 4 6% 7% 37%	1922
	21st to end	Night	22% 6% 2 4 4 4 4 3 6% 6% 38%	1762
May	1st to 10th	Night	23% 12% 3 7% 4 5% 5% 3 5% 6% 27%	2834
	11th to 20th	Night	18% 9% 4 8% 5% 6% 5% 5% 6% 7% 28%	2660
	21st to end	Night	15% 6% 2 6% 4 4 4 4 6% 8% 41%	2738
June	1st to 10th	Night	21% 7% 2 5% 4 4 4 4 6% 7% 36%	1520
	11th to 20th	Night	19% 6% 2 3 4 4 5% 4 6% 7% 41%	1520
	21st to end	Night	19% 6% 2 5% 5% 4 4 4 6% 8% 37%	1520
July	1st to 10th	Night	13% 5% 1 5% 4 4 5% 5% 8% 9% 40%	2520
	11th to 20th	Night	15% 5% 1 6% 4 4 5% 3 5% 7% 45%	2520
	21st to end	Night	16% 5% 2 5% 5% 4 4 4 7% 7% 41%	2739
August	1st to 10th	Night	21% 7% 3 7% 5% 4 5% 4 6% 5% 34%	2664
	11th to 20th	Night	16% 7% 2 8% 5% 4 4 4 5% 7% 37%	2782
	21st to end	Night	10% 5% 2 4 4 3 4 4 6% 8% 49%	3429
September	1st to 10th	Night	12% 4 2 5% 3 3 3 4 5% 7% 53%	1903
	11th to 20th	Night	15% 5% 1 4 3 3 4 3 4 6% 53%	2090
	21st to end	Night	16% 5% 2 5% 3 3 3 3 5% 7% 47%	2090
October	1st to 10th	Night	19% 6% 2 6% 4 4 4 3 6% 6% 39%	2090
	11th to 20th	Night	16% 6% 2 5% 4 4 4 4 6% 7% 41%	2362
	21st to end	Night	23% 7% 2 5% 4 4 4 3 5% 5% 37%	2717
November	1st to 10th	Night	14% 5% 3 5% 4 4 5% 3 6% 6% 45%	2537
	11th to 20th	Night	15% 6% 2 6% 5% 4 5% 3 5% 6% 43%	2600
	21st to end	Night	15% 8% 2 6% 4 4 5% 4 4 7% 42%	2640
December	1st to 10th	Night	16% 10% 3 7% 5% 5% 5% 3 5% 6% 35%	4580
	11th to 20th	Night	23% 8% 2 5% 4 4 4 4 5% 4 37%	5208
	21st to end	Night	18% 9% 2 7% 4 4 4 3 5% 5% 37%	6996

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	47% 6% 10% 24% 13% 1	3598
	11th to 20th	Day	40% 6% 13% 25% 13% 3	3600
	21st to end	Day	39% 6% 11% 21% 18% 6%	3960
February	1st to 10th	Day	46% 6% 15% 19% 12% 3	1758
	11th to 20th	Day	45% 7% 11% 19% 13% 4	1957
	21st to end	Day	50% 6% 11% 17% 14% 3	1650
March	1st to 10th	Day	56% 5% 8% 12% 12% 8%	4479
	11th to 20th	Day	45% 7% 16% 17% 12% 4	4786
	21st to end	Day	50% 3 6% 17% 19% 4	5758
April	1st to 10th	Day	48% 5% 10% 19% 14% 4	2400
	11th to 20th	Day	44% 7% 12% 19% 15% 2	2427
	21st to end	Day	51% 6% 10% 17% 13% 3	2535
May	1st to 10th	Day	57% 8% 10% 16% 8% 1	4120
	11th to 20th	Day	51% 9% 14% 15% 9% 2	4265
	21st to end	Day	38% 8% 15% 22% 14% 1	4837
June	1st to 10th	Day	51% 7% 13% 20% 9% 1	2660
	11th to 20th	Day	43% 6% 14% 19% 15% 3	2660
	21st to end	Day	50% 9% 12% 18% 10% 1	2660
July	1st to 10th	Day	40% 7% 14% 24% 14%	4370
	11th to 20th	Day	37% 8% 17% 27% 10%	4365
	21st to end	Day	44% 7% 12% 22% 15% 1	4661
August	1st to 10th	Day	45% 7% 15% 23% 9%	4219
	11th to 20th	Day	49% 7% 14% 23% 7%	4084
	21st to end	Day	32% 8% 16% 26% 17% 2	4225
September	1st to 10th	Day	32% 8% 14% 29% 16% 1	2276
	11th to 20th	Day	32% 4 9% 33% 19% 2	2090
	21st to end	Day	38% 6% 12% 24% 19% 1	2090
October	1st to 10th	Day	46% 7% 10% 22% 15% 1	3480
	11th to 20th	Day	36% 4 12% 29% 16% 3	2976
	21st to end	Day	37% 4 11% 25% 19% 4	3081
November	1st to 10th	Day	36% 7% 15% 25% 14% 2	1761
	11th to 20th	Day	39% 6% 13% 19% 19% 4	1800
	21st to end	Day	45% 6% 16% 20% 11% 1	1759
December	1st to 10th	Day	49% 6% 14% 23% 7% 1	2600
	11th to 20th	Day	42% 6% 11% 18% 19% 5%	2986
	21st to end	Day	50% 6% 8% 17% 12% 6%	3960
January	1st to 10th	Night	45% 6% 11% 26% 11% 2	6349
	11th to 20th	Night	48% 9% 14% 17% 10% 2	6360
	21st to end	Night	43% 7% 10% 17% 17% 6%	6996
February	1st to 10th	Night	46% 6% 13% 18% 14% 3	2635
	11th to 20th	Night	41% 7% 12% 21% 15% 3	2340
	21st to end	Night	43% 6% 12% 21% 14% 4	1980
March	1st to 10th	Night	52% 5% 10% 13% 14% 6%	5374
	11th to 20th	Night	47% 8% 17% 16% 10% 2	5172
	21st to end	Night	50% 4 6% 15% 21% 4	5158
April	1st to 10th	Night	49% 5% 10% 19% 15% 3	2000
	11th to 20th	Night	45% 7% 10% 22% 15% 1	1922
	21st to end	Night	46% 5% 12% 18% 15% 3	1762
May	1st to 10th	Night	57% 9% 10% 17% 7% 1	2840
	11th to 20th	Night	52% 10% 13% 16% 8% 2	2661
	21st to end	Night	38% 9% 18% 20% 13% 2	2739
June	1st to 10th	Night	48% 8% 13% 19% 13%	1520
	11th to 20th	Night	43% 9% 15% 19% 13% 2	1520
	21st to end	Night	45% 9% 14% 21% 10% 1	1520
July	1st to 10th	Night	37% 9% 19% 21% 14%	2480
	11th to 20th	Night	39% 7% 15% 25% 14%	2472
	21st to end	Night	40% 7% 13% 28% 11% 1	2651
August	1st to 10th	Night	50% 7% 14% 20% 8%	2654
	11th to 20th	Night	45% 8% 16% 20% 11%	2809
	21st to end	Night	31% 7% 18% 28% 15% 1	3429
September	1st to 10th	Night	31% 7% 14% 31% 16%	1903
	11th to 20th	Night	33% 6% 11% 29% 19% 2	2090
	21st to end	Night	37% 7% 13% 28% 14% 2	2090
October	1st to 10th	Night	44% 8% 14% 20% 13% 1	3480
	11th to 20th	Night	33% 6% 11% 27% 20% 3	3937
	21st to end	Night	40% 4 10% 27% 16% 3	4467
November	1st to 10th	Night	39% 6% 12% 25% 15% 2	2537
	11th to 20th	Night	41% 6% 11% 23% 17% 3	2600
	21st to end	Night	43% 6% 15% 23% 12% 1	2640
December	1st to 10th	Night	48% 6% 11% 27% 8%	4580
	11th to 20th	Night	48% 6% 10% 15% 18% 3	5208
	21st to end	Night	49% 7% 9% 18% 16% 2	6996

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	27% 19% 28% 20% 6% 1	200
	11th to 20th	Day	25% 22% 24% 23% 6% 1	200
	21st to end	Day	17% 23% 33% 20% 7%	220
February	1st to 10th	Day	23% 23% 32% 18% 4	328
	11th to 20th	Day	24% 21% 34% 17% 3	496
	21st to end	Day	24% 20% 29% 22% 4	414
March	1st to 10th	Day	27% 19% 30% 21% 4	500
	11th to 20th	Day	26% 21% 31% 15% 6% 1	500
	21st to end	Day	26% 19% 31% 15% 7% 3	550
April	1st to 10th	Day	32% 20% 26% 15% 7% 2	500
	11th to 20th	Day	29% 22% 26% 14% 7% 2	492
	21st to end	Day	27% 21% 31% 13% 6% 2	480
May	1st to 10th	Day	32% 17% 29% 16% 4 2	463
	11th to 20th	Day	22% 17% 33% 19% 7% 2	487
	21st to end	Day	21% 16% 32% 21% 9% 2	529
June	1st to 10th	Day	21% 15% 35% 19% 9% 2	490
	11th to 20th	Day	17% 17% 31% 23% 8% 3	490
	21st to end	Day	22% 13% 36% 16% 12% 2	490
July	1st to 10th	Day	18% 9% 31% 24% 14% 3	485
	11th to 20th	Day	13% 7% 36% 30% 13% 3	484
	21st to end	Day	15% 9% 32% 28% 13% 3	532
August	1st to 10th	Day	11% 12% 27% 28% 17% 5%	486
	11th to 20th	Day	16% 10% 28% 26% 14% 7%	479
	21st to end	Day	12% 9% 26% 31% 15% 6%	539
September	1st to 10th	Day	16% 9% 24% 27% 18% 6%	490
	11th to 20th	Day	18% 10% 24% 21% 15% 11%	490
	21st to end	Day	17% 11% 27% 25% 13% 6%	490
October	1st to 10th	Day	25% 13% 21% 22% 14% 6%	490
	11th to 20th	Day	21% 14% 24% 25% 14% 3	417
	21st to end	Day	32% 10% 26% 24% 7% 1	429
November	1st to 10th	Day	21% 17% 26% 27% 7% 2	395
	11th to 20th	Day	27% 16% 26% 23% 7% 1	400
	21st to end	Day	28% 16% 30% 19% 6%	359
December	1st to 10th	Day	24% 26% 20% 22% 8% 1	200
	11th to 20th	Day	29% 21% 31% 16% 4	200
	21st to end	Day	29% 15% 30% 20% 6% 1	220
January	1st to 10th	Night	18% 13% 36% 30% 4	800
	11th to 20th	Night	22% 15% 29% 29% 5%	800
	21st to end	Night	16% 14% 37% 27% 5% 1	880
February	1st to 10th	Night	19% 14% 35% 30% 3	800
	11th to 20th	Night	18% 14% 42% 23% 3	783
	21st to end	Night	18% 14% 34% 29% 5%	660
March	1st to 10th	Night	22% 14% 32% 28% 3	800
	11th to 20th	Night	20% 15% 31% 27% 6%	800
	21st to end	Night	24% 11% 31% 25% 9% 1	880
April	1st to 10th	Night	24% 13% 31% 27% 5%	800
	11th to 20th	Night	21% 14% 32% 27% 6%	738
	21st to end	Night	26% 14% 27% 27% 6%	588
May	1st to 10th	Night	25% 10% 26% 29% 7% 1	570
	11th to 20th	Night	20% 10% 30% 30% 11%	474
	21st to end	Night	18% 7% 23% 39% 12% 1	411
June	1st to 10th	Night	21% 7% 26% 34% 11% 1	380
	11th to 20th	Night	21% 6% 22% 36% 15%	380
	21st to end	Night	20% 3 23% 40% 13% 1	380
July	1st to 10th	Night	17% 2 19% 43% 19% 1	370
	11th to 20th	Night	15% 2 19% 42% 21% 2	368
	21st to end	Night	14% 3 16% 48% 19% 1	416
August	1st to 10th	Night	17% 3 17% 42% 20% 1	471
	11th to 20th	Night	16% 5% 23% 37% 18% 2	562
	21st to end	Night	16% 3 18% 38% 21% 4	802
September	1st to 10th	Night	14% 4 22% 38% 20% 2	760
	11th to 20th	Night	17% 5% 21% 30% 22% 6%	760
	21st to end	Night	18% 6% 23% 31% 18% 3	760
October	1st to 10th	Night	23% 8% 21% 31% 17% 1	760
	11th to 20th	Night	20% 9% 29% 29% 13% 1	760
	21st to end	Night	28% 9% 26% 29% 7%	836
November	1st to 10th	Night	18% 11% 29% 31% 9% 1	780
	11th to 20th	Night	20% 13% 29% 28% 8% 1	800
	21st to end	Night	22% 16% 28% 29% 6% 1	800
December	1st to 10th	Night	24% 11% 35% 24% 6% 1	800
	11th to 20th	Night	24% 14% 28% 29% 4	800
	21st to end	Night	23% 13% 31% 29% 5%	880

Page generated at 2025-04-23 09:25:08. Version ac07

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