Canton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canton clear sky chart from 2005-11-06 to 2025-09-19.

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	17% 7% 2 6% 4 4 4 4 6% 7% 38%	126135
	Night	18% 7% 2 6% 4 4 4 3 5% 6% 41%	122903
Transparency	Day	43% 6% 11% 22% 15% 3	129653
	Night	43% 5% 12% 22% 16% 3	127460
Seeing	Day	24% 14% 31% 20% 9% 3	16097
	Night	22% 12% 32% 27% 8% 1	25072

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 9% 4 5% 5% 3 5% 5% 42%	3597
	11th to 20th	Day	13% 9% 2 9% 4 4 4 4 5% 5% 41%	3570
	21st to end	Day	18% 9% 3 6% 4 4 4 4 4 5% 40%	4052
February	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 4 6% 6% 36%	1855
	11th to 20th	Day	13% 7% 3 7% 5% 5% 5% 4 6% 7% 39%	1948
	21st to end	Day	19% 10% 3 5% 4 4 4 3 4 5% 39%	1650
March	1st to 10th	Day	21% 9% 2 6% 4 3 3 3 5% 5% 38%	4476
	11th to 20th	Day	14% 7% 2 6% 4 4 5% 4 6% 7% 40%	4653
	21st to end	Day	20% 8% 2 6% 4 4 4 3 6% 6% 37%	5970
April	1st to 10th	Day	19% 9% 2 6% 5% 4 3 4 5% 6% 37%	2400
	11th to 20th	Day	17% 6% 2 6% 5% 3 4 4 6% 6% 40%	2374
	21st to end	Day	21% 6% 2 5% 4 4 4 4 5% 6% 40%	2517
May	1st to 10th	Day	31% 7% 2 6% 4 3 4 3 6% 8% 25%	5886
	11th to 20th	Day	20% 8% 3 8% 5% 4 4 3 5% 6% 34%	6175
	21st to end	Day	20% 7% 2 6% 4 4 4 4 6% 8% 34%	6949
June	1st to 10th	Day	17% 6% 2 6% 5% 5% 5% 5% 7% 8% 35%	2800
	11th to 20th	Day	16% 6% 2 6% 4 5% 5% 3 7% 10% 36%	2800
	21st to end	Day	14% 7% 3 6% 4 4 5% 4 6% 8% 38%	2800
July	1st to 10th	Day	12% 7% 2 7% 5% 5% 6% 4 7% 10% 34%	6360
	11th to 20th	Day	10% 6% 2 7% 5% 6% 5% 5% 8% 11% 35%	6360
	21st to end	Day	15% 7% 2 6% 4 4 4 4 5% 7% 41%	6926
August	1st to 10th	Day	18% 6% 2 8% 6% 5% 5% 4 6% 8% 32%	4412
	11th to 20th	Day	12% 6% 2 7% 5% 5% 4 4 6% 8% 41%	3889
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 4 7% 9% 43%	4312
September	1st to 10th	Day	12% 6% 2 7% 4 4 5% 4 5% 6% 44%	2400
	11th to 20th	Day	13% 5% 2 5% 3 3 4 3 5% 6% 50%	2242
	21st to end	Day	18% 6% 2 5% 4 4 4 3 5% 7% 42%	2090
October	1st to 10th	Day	22% 6% 2 5% 3 3 5% 3 4 5% 40%	2055
	11th to 20th	Day	14% 6% 2 5% 4 4 4 3 6% 8% 45%	1879
	21st to end	Day	22% 6% 2 4 4 4 4 4 4 7% 40%	1881
November	1st to 10th	Day	13% 6% 2 5% 5% 3 4 3 4 5% 49%	1761
	11th to 20th	Day	19% 5% 2 4 2 3 4 3 5% 7% 47%	1800
	21st to end	Day	18% 8% 2 6% 4 3 3 3 4 6% 42%	1750
December	1st to 10th	Day	16% 6% 3 6% 4 4 4 3 4 6% 45%	2600
	11th to 20th	Day	21% 6% 2 4 2 2 3 4 5% 6% 45%	2986
	21st to end	Day	18% 12% 3 7% 4 4 3 3 4 6% 36%	3960
January	1st to 10th	Night	14% 6% 2 8% 4 3 4 3 6% 6% 44%	6349
	11th to 20th	Night	13% 8% 3 8% 4 4 4 3 5% 5% 42%	6315
	21st to end	Night	16% 9% 3 7% 5% 4 4 3 5% 6% 38%	6889
February	1st to 10th	Night	16% 9% 3 5% 4 4 3 4 5% 6% 40%	2543
	11th to 20th	Night	14% 8% 3 7% 5% 4 5% 4 5% 7% 40%	2338
	21st to end	Night	18% 7% 2 7% 6% 4 4 3 4 6% 41%	1980
March	1st to 10th	Night	21% 9% 2 5% 3 3 3 3 5% 6% 40%	5364
	11th to 20th	Night	17% 8% 3 6% 4 4 4 3 4 7% 41%	5288
	21st to end	Night	22% 9% 2 6% 3 3 4 3 5% 6% 38%	4962
April	1st to 10th	Night	18% 8% 3 5% 5% 5% 4 4 5% 5% 37%	2000
	11th to 20th	Night	19% 6% 2 6% 5% 4 5% 3 4 6% 40%	1975
	21st to end	Night	20% 8% 2 6% 4 3 3 2 5% 5% 42%	1881
May	1st to 10th	Night	31% 10% 3 6% 4 4 3 2 4 7% 27%	4054
	11th to 20th	Night	20% 9% 3 8% 4 4 4 4 5% 7% 31%	3760
	21st to end	Night	22% 7% 3 6% 4 4 4 4 6% 7% 34%	3926
June	1st to 10th	Night	17% 6% 2 6% 4 4 4 3 5% 7% 41%	1600
	11th to 20th	Night	17% 7% 2 5% 4 4 4 5% 5% 9% 38%	1600
	21st to end	Night	15% 6% 2 6% 4 4 4 3 6% 9% 43%	1600
July	1st to 10th	Night	13% 6% 2 7% 4 4 4 4 6% 9% 39%	3600
	11th to 20th	Night	15% 7% 3 7% 4 4 5% 3 6% 9% 36%	3600
	21st to end	Night	12% 7% 2 6% 4 4 4 3 5% 7% 45%	3926
August	1st to 10th	Night	20% 6% 2 8% 4 5% 5% 4 6% 7% 32%	2703
	11th to 20th	Night	15% 7% 3 7% 4 4 4 3 6% 6% 42%	3156
	21st to end	Night	10% 5% 1 5% 3 3 4 3 5% 8% 53%	3586
September	1st to 10th	Night	14% 5% 2 7% 4 4 4 3 5% 6% 46%	2000
	11th to 20th	Night	14% 5% 2 5% 3 2 3 3 4 6% 53%	2114
	21st to end	Night	17% 6% 1 6% 4 3 4 4 5% 6% 45%	2090
October	1st to 10th	Night	20% 6% 2 6% 4 4 3 3 5% 6% 42%	2122
	11th to 20th	Night	15% 5% 2 5% 3 4 4 3 5% 6% 48%	2299
	21st to end	Night	24% 5% 2 4 4 4 4 3 4 6% 40%	2717
November	1st to 10th	Night	13% 5% 3 6% 4 4 4 4 5% 6% 48%	2537
	11th to 20th	Night	18% 7% 2 5% 3 3 4 3 5% 5% 46%	2600
	21st to end	Night	16% 7% 2 5% 3 4 5% 3 5% 6% 45%	2645
December	1st to 10th	Night	17% 7% 2 6% 4 3 3 3 5% 5% 45%	4580
	11th to 20th	Night	24% 7% 2 4 3 3 3 3 4 4 41%	5208
	21st to end	Night	19% 10% 3 7% 3 3 3 3 4 4 40%	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	43% 4 9% 28% 13% 3	3598
	11th to 20th	Day	44% 5% 9% 22% 13% 8%	3600
	21st to end	Day	46% 5% 9% 23% 16% 1	4052
February	1st to 10th	Day	47% 6% 12% 19% 14% 2	1855
	11th to 20th	Day	44% 6% 9% 22% 16% 3	1957
	21st to end	Day	47% 4 10% 21% 15% 3	1650
March	1st to 10th	Day	47% 4 10% 17% 12% 10%	4479
	11th to 20th	Day	39% 7% 12% 28% 10% 2	4653
	21st to end	Day	47% 4 7% 16% 20% 6%	5970
April	1st to 10th	Day	47% 5% 10% 20% 15% 4	2400
	11th to 20th	Day	43% 4 11% 21% 18% 3	2374
	21st to end	Day	44% 5% 9% 20% 17% 4	2517
May	1st to 10th	Day	56% 7% 13% 14% 9% 1	5897
	11th to 20th	Day	50% 7% 11% 19% 13% 1	6179
	21st to end	Day	46% 7% 11% 22% 13% 2	6949
June	1st to 10th	Day	44% 7% 11% 23% 13% 1	2800
	11th to 20th	Day	43% 6% 13% 23% 13% 2	2800
	21st to end	Day	41% 7% 12% 23% 15% 1	2800
July	1st to 10th	Day	44% 8% 12% 20% 15% 1	6290
	11th to 20th	Day	38% 9% 17% 23% 12% 1	6285
	21st to end	Day	41% 6% 11% 24% 18% 1	6728
August	1st to 10th	Day	48% 7% 14% 20% 9% 1	4398
	11th to 20th	Day	39% 7% 14% 28% 11% 1	3926
	21st to end	Day	34% 7% 13% 27% 17% 2	4312
September	1st to 10th	Day	40% 5% 10% 24% 19% 2	2400
	11th to 20th	Day	34% 5% 9% 25% 24% 3	2242
	21st to end	Day	43% 4 9% 23% 19% 3	2090
October	1st to 10th	Day	38% 6% 9% 19% 25% 4	3419
	11th to 20th	Day	28% 4 9% 27% 28% 4	3095
	21st to end	Day	32% 5% 13% 25% 21% 4	3081
November	1st to 10th	Day	38% 4 12% 24% 20% 3	1761
	11th to 20th	Day	38% 4 10% 23% 21% 4	1800
	21st to end	Day	43% 4 11% 27% 11% 3	1750
December	1st to 10th	Day	41% 4 15% 28% 11% 1	2600
	11th to 20th	Day	40% 4 16% 20% 17% 3	2986
	21st to end	Day	49% 5% 8% 19% 14% 5%	3960
January	1st to 10th	Night	40% 4 11% 27% 16% 3	6349
	11th to 20th	Night	43% 5% 13% 21% 13% 6%	6360
	21st to end	Night	47% 5% 10% 17% 17% 4	6889
February	1st to 10th	Night	46% 5% 12% 23% 12% 2	2543
	11th to 20th	Night	44% 5% 9% 19% 18% 4	2340
	21st to end	Night	46% 4 9% 23% 14% 5%	1980
March	1st to 10th	Night	46% 5% 10% 18% 16% 5%	5374
	11th to 20th	Night	43% 6% 15% 22% 11% 3	5289
	21st to end	Night	47% 5% 6% 13% 24% 5%	4962
April	1st to 10th	Night	47% 5% 9% 21% 15% 3	2000
	11th to 20th	Night	45% 6% 9% 19% 20% 2	1975
	21st to end	Night	44% 4 9% 22% 16% 4	1881
May	1st to 10th	Night	59% 6% 12% 12% 10% 1	4060
	11th to 20th	Night	51% 7% 13% 16% 11% 3	3761
	21st to end	Night	48% 7% 14% 20% 10% 1	3927
June	1st to 10th	Night	43% 6% 10% 23% 16% 1	1600
	11th to 20th	Night	42% 6% 15% 25% 11% 1	1600
	21st to end	Night	37% 6% 15% 26% 15% 1	1600
July	1st to 10th	Night	41% 8% 15% 21% 15% 1	3560
	11th to 20th	Night	43% 7% 17% 21% 11% 1	3552
	21st to end	Night	38% 6% 11% 26% 17% 1	3809
August	1st to 10th	Night	50% 9% 13% 18% 10% 1	2693
	11th to 20th	Night	41% 6% 14% 29% 9% 1	3185
	21st to end	Night	28% 6% 14% 34% 17% 1	3586
September	1st to 10th	Night	40% 5% 10% 26% 19% 1	2000
	11th to 20th	Night	34% 5% 10% 24% 25% 2	2114
	21st to end	Night	40% 5% 9% 24% 20% 2	2090
October	1st to 10th	Night	38% 6% 13% 21% 19% 2	3538
	11th to 20th	Night	27% 4 10% 27% 29% 3	3810
	21st to end	Night	33% 4 13% 30% 19% 2	4467
November	1st to 10th	Night	37% 5% 11% 22% 21% 4	2537
	11th to 20th	Night	41% 4 10% 21% 20% 4	2600
	21st to end	Night	41% 4 14% 28% 12% 1	2645
December	1st to 10th	Night	41% 4 13% 31% 11% 1	4580
	11th to 20th	Night	46% 4 13% 16% 18% 2	5208
	21st to end	Night	48% 4 8% 21% 16% 4	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	29% 18% 33% 16% 5%	200
	11th to 20th	Day	30% 24% 33% 10% 3	200
	21st to end	Day	24% 23% 33% 13% 5% 1	240
February	1st to 10th	Day	33% 19% 33% 13% 2	355
	11th to 20th	Day	31% 21% 34% 12% 2	496
	21st to end	Day	30% 16% 36% 14% 4	414
March	1st to 10th	Day	27% 20% 35% 16% 3	500
	11th to 20th	Day	27% 21% 33% 15% 3 1	500
	21st to end	Day	32% 19% 33% 10% 5% 2	550
April	1st to 10th	Day	33% 19% 30% 11% 6% 1	500
	11th to 20th	Day	32% 18% 30% 13% 6% 1	492
	21st to end	Day	33% 15% 32% 12% 5% 1	500
May	1st to 10th	Day	36% 17% 25% 13% 8% 1	503
	11th to 20th	Day	23% 17% 34% 19% 6% 1	527
	21st to end	Day	22% 14% 30% 22% 9% 3	573
June	1st to 10th	Day	20% 13% 31% 24% 10% 3	530
	11th to 20th	Day	20% 13% 33% 25% 8% 2	530
	21st to end	Day	19% 11% 30% 27% 9% 3	530
July	1st to 10th	Day	15% 8% 30% 28% 15% 4	525
	11th to 20th	Day	13% 6% 32% 31% 15% 4	524
	21st to end	Day	15% 10% 33% 29% 11% 3	576
August	1st to 10th	Day	13% 8% 32% 30% 12% 6%	526
	11th to 20th	Day	15% 6% 31% 27% 15% 7%	519
	21st to end	Day	13% 9% 31% 26% 15% 7%	583
September	1st to 10th	Day	17% 11% 24% 25% 15% 7%	530
	11th to 20th	Day	15% 9% 27% 25% 13% 11%	522
	21st to end	Day	21% 11% 31% 22% 10% 6%	490
October	1st to 10th	Day	28% 9% 25% 19% 13% 6%	490
	11th to 20th	Day	19% 15% 30% 24% 9% 3	478
	21st to end	Day	30% 13% 25% 23% 8% 1	429
November	1st to 10th	Day	21% 13% 30% 24% 10% 2	395
	11th to 20th	Day	29% 17% 28% 18% 7% 1	400
	21st to end	Day	29% 14% 29% 19% 8% 1	350
December	1st to 10th	Day	23% 21% 34% 15% 7% 1	200
	11th to 20th	Day	32% 21% 32% 11% 4	200
	21st to end	Day	28% 13% 39% 13% 7%	220
January	1st to 10th	Night	23% 16% 38% 21% 3	800
	11th to 20th	Night	27% 15% 33% 22% 3	800
	21st to end	Night	21% 16% 37% 23% 3	880
February	1st to 10th	Night	24% 15% 34% 25% 2	800
	11th to 20th	Night	24% 17% 39% 18% 1	783
	21st to end	Night	25% 14% 37% 21% 3	660
March	1st to 10th	Night	25% 18% 35% 20% 2	800
	11th to 20th	Night	23% 17% 36% 20% 4	800
	21st to end	Night	25% 16% 35% 19% 4	880
April	1st to 10th	Night	26% 16% 35% 19% 4	800
	11th to 20th	Night	26% 15% 35% 19% 6%	791
	21st to end	Night	25% 18% 32% 20% 4	681
May	1st to 10th	Night	30% 15% 30% 22% 4	600
	11th to 20th	Night	23% 12% 39% 22% 4	475
	21st to end	Night	21% 8% 29% 34% 7% 1	433
June	1st to 10th	Night	21% 7% 32% 32% 10%	400
	11th to 20th	Night	20% 7% 30% 35% 9%	400
	21st to end	Night	18% 4 31% 35% 11%	400
July	1st to 10th	Night	13% 5% 26% 39% 16% 1	390
	11th to 20th	Night	17% 3 22% 40% 16% 1	388
	21st to end	Night	13% 4 25% 43% 14%	438
August	1st to 10th	Night	13% 3 26% 42% 14% 1	463
	11th to 20th	Night	14% 5% 22% 39% 19% 1	761
	21st to end	Night	15% 4 25% 35% 19% 2	880
September	1st to 10th	Night	17% 5% 28% 33% 15% 2	800
	11th to 20th	Night	16% 4 25% 34% 18% 3	793
	21st to end	Night	21% 6% 27% 29% 15% 2	760
October	1st to 10th	Night	24% 7% 25% 30% 12% 3	760
	11th to 20th	Night	19% 10% 31% 30% 9% 1	760
	21st to end	Night	28% 10% 30% 24% 7%	836
November	1st to 10th	Night	18% 12% 32% 27% 10% 1	780
	11th to 20th	Night	23% 13% 33% 24% 6% 1	800
	21st to end	Night	24% 14% 31% 26% 5% 1	800
December	1st to 10th	Night	26% 13% 32% 23% 5% 1	800
	11th to 20th	Night	24% 14% 34% 25% 4	800
	21st to end	Night	27% 13% 32% 25% 3	880

Page generated at 2025-09-16 01:49:15. Version ac07

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