Bayfield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bayfield clear sky chart from 2005-11-06 to 2025-12-18.

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	15% 12% 4 10% 5% 4 4 3 5% 7% 32%	127073
	Night	16% 14% 5% 11% 5% 4 4 3 4 5% 27%	124012
Transparency	Day	51% 6% 12% 19% 10% 1	130640
	Night	57% 5% 11% 16% 9% 1	128520
Seeing	Day	19% 10% 27% 26% 14% 5%	16595
	Night	22% 10% 27% 28% 11% 1	25934

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	14% 20% 12% 30% 5% 3 2 1 2 3 8%	3452
	11th to 20th	Day	11% 24% 11% 26% 12% 5% 2 1 2 2 4	3780
	21st to end	Day	18% 19% 8% 21% 7% 6% 4 2 3 3 9%	4466
February	1st to 10th	Day	15% 19% 5% 16% 9% 5% 4 3 4 5% 15%	1800
	11th to 20th	Day	14% 15% 9% 17% 9% 6% 4 3 4 5% 17%	1766
	21st to end	Day	15% 18% 6% 12% 6% 3 5% 4 4 5% 23%	1650
March	1st to 10th	Day	16% 12% 7% 13% 6% 4 3 3 4 5% 28%	4748
	11th to 20th	Day	13% 14% 5% 10% 5% 3 4 3 6% 8% 29%	4980
	21st to end	Day	19% 12% 5% 12% 5% 4 4 3 4 4 28%	5465
April	1st to 10th	Day	17% 14% 5% 8% 4 4 3 4 5% 6% 31%	2284
	11th to 20th	Day	18% 10% 2 5% 4 3 4 4 6% 7% 37%	2572
	21st to end	Day	17% 10% 3 6% 4 4 4 3 6% 7% 36%	2600
May	1st to 10th	Day	17% 8% 3 7% 4 4 4 4 6% 7% 36%	5888
	11th to 20th	Day	15% 9% 3 7% 4 4 4 3 5% 8% 38%	5861
	21st to end	Day	18% 8% 2 5% 3 3 4 3 5% 6% 42%	6945
June	1st to 10th	Day	11% 6% 2 7% 5% 5% 5% 4 5% 8% 41%	2898
	11th to 20th	Day	10% 6% 1 6% 4 5% 5% 5% 7% 9% 42%	3000
	21st to end	Day	14% 6% 2 5% 4 4 4 5% 7% 7% 43%	3000
July	1st to 10th	Day	11% 7% 2 6% 4 4 5% 4 6% 10% 42%	6819
	11th to 20th	Day	10% 6% 2 5% 4 4 3 3 5% 8% 50%	6278
	21st to end	Day	8% 5% 2 5% 3 4 4 4 6% 9% 49%	6424
August	1st to 10th	Day	12% 6% 2 6% 4 5% 5% 4 7% 9% 41%	4234
	11th to 20th	Day	10% 5% 2 7% 4 5% 5% 4 8% 11% 39%	4174
	21st to end	Day	9% 5% 2 7% 4 4 4 3 6% 9% 46%	4657
September	1st to 10th	Day	12% 5% 2 7% 4 4 4 4 7% 8% 43%	2320
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 5% 8% 48%	2200
	21st to end	Day	18% 7% 2 6% 5% 4 5% 5% 6% 8% 35%	2200
October	1st to 10th	Day	18% 7% 2 5% 5% 5% 4 4 5% 7% 37%	2059
	11th to 20th	Day	24% 13% 3 7% 5% 4 5% 3 5% 6% 23%	2000
	21st to end	Day	27% 15% 4 8% 5% 3 5% 4 4 5% 19%	2120
November	1st to 10th	Day	20% 16% 3 8% 5% 4 4 4 5% 6% 26%	1852
	11th to 20th	Day	19% 21% 4 10% 6% 4 4 4 5% 5% 19%	1730
	21st to end	Day	19% 29% 7% 11% 6% 4 3 3 3 4 11%	1680
December	1st to 10th	Day	18% 37% 12% 11% 5% 3 3 2 3 2 5%	2680
	11th to 20th	Day	23% 23% 9% 17% 5% 3 3 2 3 3 8%	3015
	21st to end	Day	28% 23% 6% 13% 4 4 3 3 3 4 9%	3476
January	1st to 10th	Night	14% 21% 11% 29% 5% 4 2 1 2 2 7%	6511
	11th to 20th	Night	14% 22% 10% 24% 13% 5% 2 2 2 2 5%	6112
	21st to end	Night	17% 18% 9% 18% 6% 8% 4 3 3 3 10%	6490
February	1st to 10th	Night	17% 18% 5% 17% 10% 5% 4 3 3 3 15%	2600
	11th to 20th	Night	16% 16% 8% 14% 8% 6% 5% 3 4 5% 16%	2518
	21st to end	Night	16% 15% 6% 13% 6% 5% 5% 4 5% 4 22%	1980
March	1st to 10th	Night	15% 13% 4 9% 6% 4 4 3 5% 6% 31%	5091
	11th to 20th	Night	11% 11% 5% 9% 5% 4 4 4 6% 9% 32%	4979
	21st to end	Night	20% 10% 4 10% 5% 4 4 3 4 4 32%	5467
April	1st to 10th	Night	20% 14% 3 7% 4 4 4 4 6% 5% 30%	2132
	11th to 20th	Night	19% 8% 3 7% 4 4 4 3 5% 6% 36%	1777
	21st to end	Night	18% 11% 4 7% 5% 4 4 3 5% 7% 34%	1800
May	1st to 10th	Night	19% 8% 3 7% 4 4 4 3 4 7% 37%	4053
	11th to 20th	Night	15% 9% 3 8% 5% 4 5% 3 4 6% 37%	4032
	21st to end	Night	19% 6% 2 5% 3 3 3 3 5% 7% 44%	3927
June	1st to 10th	Night	13% 6% 2 7% 5% 5% 4 4 5% 7% 42%	1497
	11th to 20th	Night	11% 6% 2 7% 4 4 4 5% 8% 9% 40%	1400
	21st to end	Night	12% 5% 2 6% 4 4 5% 3 5% 9% 45%	1400
July	1st to 10th	Night	8% 6% 2 7% 5% 5% 4 4 7% 8% 44%	3160
	11th to 20th	Night	11% 5% 2 5% 3 4 4 4 5% 7% 50%	3678
	21st to end	Night	9% 5% 2 6% 4 4 4 4 5% 8% 48%	4428
August	1st to 10th	Night	11% 5% 2 6% 4 4 4 4 5% 8% 45%	2915
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 6% 9% 44%	2875
	21st to end	Night	11% 5% 3 6% 4 4 4 4 5% 7% 47%	3223
September	1st to 10th	Night	12% 5% 2 6% 5% 4 5% 4 6% 6% 45%	2062
	11th to 20th	Night	12% 4 2 5% 4 3 4 3 4 7% 53%	2200
	21st to end	Night	18% 8% 3 6% 5% 5% 5% 3 5% 6% 38%	2200
October	1st to 10th	Night	17% 9% 3 7% 4 4 4 2 5% 6% 40%	2340
	11th to 20th	Night	26% 10% 3 8% 5% 4 4 2 6% 5% 26%	2400
	21st to end	Night	28% 13% 3 8% 5% 4 4 3 4 5% 22%	2719
November	1st to 10th	Night	19% 16% 4 7% 5% 4 4 3 4 5% 29%	2666
	11th to 20th	Night	19% 22% 5% 11% 5% 5% 4 3 4 5% 18%	2888
	21st to end	Night	24% 26% 7% 9% 4 4 3 2 3 4 13%	2940
December	1st to 10th	Night	15% 33% 15% 11% 4 4 3 2 2 3 6%	4720
	11th to 20th	Night	17% 28% 9% 17% 5% 3 3 2 3 3 10%	5330
	21st to end	Night	24% 23% 7% 13% 5% 3 3 3 4 4 10%	7502

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	83% 5% 7% 5% 1	3453
	11th to 20th	Day	91% 2 4 2 1	3813
	21st to end	Day	81% 6% 8% 4 2	4466
February	1st to 10th	Day	73% 7% 8% 11% 2	1800
	11th to 20th	Day	71% 6% 8% 11% 4	1775
	21st to end	Day	63% 7% 11% 14% 5% 1	1650
March	1st to 10th	Day	60% 5% 15% 15% 5%	4751
	11th to 20th	Day	52% 7% 15% 19% 7% 2	4980
	21st to end	Day	58% 6% 11% 16% 8% 1	5465
April	1st to 10th	Day	55% 6% 11% 19% 9%	2284
	11th to 20th	Day	46% 6% 12% 21% 13% 1	2572
	21st to end	Day	48% 7% 12% 19% 12% 2	2600
May	1st to 10th	Day	45% 7% 12% 18% 12% 6%	5897
	11th to 20th	Day	45% 9% 11% 19% 13% 2	5865
	21st to end	Day	42% 6% 10% 20% 17% 5%	6945
June	1st to 10th	Day	40% 8% 12% 25% 13% 2	2898
	11th to 20th	Day	36% 8% 12% 27% 16% 1	3000
	21st to end	Day	39% 8% 13% 26% 15% 1	3000
July	1st to 10th	Day	37% 6% 14% 24% 18% 1	6746
	11th to 20th	Day	32% 6% 11% 33% 16% 2	6202
	21st to end	Day	31% 6% 16% 27% 19% 1	6240
August	1st to 10th	Day	38% 9% 13% 25% 15% 1	4221
	11th to 20th	Day	38% 10% 16% 27% 9%	4213
	21st to end	Day	35% 7% 14% 31% 13% 1	4657
September	1st to 10th	Day	38% 8% 16% 26% 11% 2	2320
	11th to 20th	Day	34% 6% 14% 31% 14% 1	2200
	21st to end	Day	45% 8% 13% 23% 10%	2200
October	1st to 10th	Day	42% 7% 12% 25% 13% 1	3345
	11th to 20th	Day	46% 6% 12% 23% 12%	3240
	21st to end	Day	57% 6% 15% 16% 6%	3409
November	1st to 10th	Day	58% 6% 11% 18% 7% 1	1852
	11th to 20th	Day	66% 6% 11% 11% 6% 1	1730
	21st to end	Day	78% 6% 8% 8% 1	1680
December	1st to 10th	Day	85% 5% 5% 4	2680
	11th to 20th	Day	82% 4 7% 6% 1	3015
	21st to end	Day	81% 4 9% 5% 1	3476
January	1st to 10th	Night	82% 6% 6% 5% 1	6511
	11th to 20th	Night	88% 3 5% 2 1	6154
	21st to end	Night	78% 5% 9% 5% 2	6490
February	1st to 10th	Night	75% 5% 7% 11% 2	2600
	11th to 20th	Night	70% 6% 10% 12% 3	2520
	21st to end	Night	62% 7% 12% 13% 6%	1980
March	1st to 10th	Night	54% 6% 13% 18% 8% 1	5101
	11th to 20th	Night	47% 7% 18% 20% 8% 1	4980
	21st to end	Night	54% 5% 12% 17% 11% 1	5467
April	1st to 10th	Night	55% 5% 9% 19% 11% 1	2132
	11th to 20th	Night	49% 5% 9% 18% 17% 2	1777
	21st to end	Night	50% 5% 9% 18% 15% 3	1800
May	1st to 10th	Night	47% 6% 11% 15% 14% 8%	4060
	11th to 20th	Night	46% 8% 10% 20% 14% 2	4033
	21st to end	Night	40% 6% 11% 24% 16% 4	3928
June	1st to 10th	Night	41% 5% 10% 24% 17% 3	1497
	11th to 20th	Night	37% 7% 12% 25% 16% 4	1400
	21st to end	Night	37% 5% 13% 25% 18% 2	1400
July	1st to 10th	Night	35% 6% 14% 23% 17% 4	3125
	11th to 20th	Night	33% 5% 11% 28% 21% 2	3631
	21st to end	Night	34% 6% 10% 25% 22% 2	4297
August	1st to 10th	Night	37% 6% 12% 27% 17% 1	2904
	11th to 20th	Night	38% 7% 14% 25% 15% 1	2902
	21st to end	Night	35% 6% 11% 33% 14% 1	3223
September	1st to 10th	Night	37% 7% 13% 26% 15% 2	2062
	11th to 20th	Night	32% 5% 14% 29% 20% 1	2200
	21st to end	Night	45% 7% 13% 22% 12% 1	2200
October	1st to 10th	Night	36% 5% 11% 25% 22% 1	3821
	11th to 20th	Night	49% 6% 15% 19% 12%	3899
	21st to end	Night	53% 5% 15% 19% 8%	4380
November	1st to 10th	Night	56% 6% 12% 19% 8%	2666
	11th to 20th	Night	67% 5% 10% 12% 4 1	2888
	21st to end	Night	75% 5% 10% 8% 2	2940
December	1st to 10th	Night	86% 4 6% 3 1	4720
	11th to 20th	Night	81% 4 8% 6% 1	5330
	21st to end	Night	77% 4 9% 7% 2	7502

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	22% 19% 33% 16% 9% 1	263
	11th to 20th	Day	23% 17% 41% 13% 5%	300
	21st to end	Day	26% 15% 35% 20% 3 1	330
February	1st to 10th	Day	23% 23% 35% 15% 4	300
	11th to 20th	Day	22% 18% 44% 15% 2	300
	21st to end	Day	20% 27% 34% 17% 2	249
March	1st to 10th	Day	21% 16% 37% 20% 5%	415
	11th to 20th	Day	21% 16% 27% 28% 8%	500
	21st to end	Day	27% 13% 30% 23% 6% 1	550
April	1st to 10th	Day	21% 15% 36% 20% 7% 1	500
	11th to 20th	Day	26% 13% 26% 21% 11% 4	492
	21st to end	Day	22% 11% 33% 24% 9% 1	500
May	1st to 10th	Day	18% 10% 29% 29% 11% 2	503
	11th to 20th	Day	17% 8% 23% 30% 18% 5%	527
	21st to end	Day	16% 6% 22% 28% 21% 8%	573
June	1st to 10th	Day	11% 6% 33% 30% 15% 4	628
	11th to 20th	Day	14% 6% 26% 35% 15% 4	730
	21st to end	Day	17% 4 22% 37% 16% 3	730
July	1st to 10th	Day	9% 5% 22% 31% 25% 8%	721
	11th to 20th	Day	12% 5% 23% 32% 22% 7%	678
	21st to end	Day	8% 2 21% 39% 22% 7%	576
August	1st to 10th	Day	9% 3 18% 33% 25% 12%	526
	11th to 20th	Day	13% 2 15% 34% 24% 12%	519
	21st to end	Day	15% 4 18% 30% 25% 8%	583
September	1st to 10th	Day	14% 4 25% 24% 21% 12%	530
	11th to 20th	Day	8% 5% 17% 25% 28% 17%	530
	21st to end	Day	18% 9% 23% 25% 17% 8%	530
October	1st to 10th	Day	18% 8% 24% 26% 18% 5%	530
	11th to 20th	Day	27% 15% 26% 25% 6% 1	530
	21st to end	Day	31% 15% 31% 17% 5% 1	503
November	1st to 10th	Day	26% 16% 30% 19% 8% 1	330
	11th to 20th	Day	27% 23% 28% 17% 4 1	245
	21st to end	Day	32% 18% 36% 12% 2	220
December	1st to 10th	Day	30% 21% 30% 14% 5%	220
	11th to 20th	Day	28% 25% 29% 14% 4	214
	21st to end	Day	34% 17% 35% 11% 2	220
January	1st to 10th	Night	25% 17% 35% 17% 5% 1	1000
	11th to 20th	Night	27% 17% 32% 19% 4	911
	21st to end	Night	21% 14% 36% 24% 5%	880
February	1st to 10th	Night	25% 14% 36% 23% 3	800
	11th to 20th	Night	24% 14% 33% 24% 5%	783
	21st to end	Night	23% 14% 37% 22% 4	660
March	1st to 10th	Night	20% 13% 35% 26% 7%	800
	11th to 20th	Night	19% 13% 37% 24% 7% 1	800
	21st to end	Night	23% 9% 30% 28% 9% 1	880
April	1st to 10th	Night	26% 13% 27% 28% 5%	792
	11th to 20th	Night	22% 10% 29% 27% 11% 1	593
	21st to end	Night	20% 10% 29% 30% 9% 1	600
May	1st to 10th	Night	21% 5% 28% 33% 13% 1	600
	11th to 20th	Night	18% 4 26% 36% 15% 1	591
	21st to end	Night	14% 3 23% 39% 20% 2	434
June	1st to 10th	Night	15% 4 23% 42% 14% 2	400
	11th to 20th	Night	12% 4 24% 44% 17%	400
	21st to end	Night	11% 4 19% 43% 21% 1	400
July	1st to 10th	Night	7% 2 14% 52% 23% 3	390
	11th to 20th	Night	12% 2 18% 39% 26% 4	568
	21st to end	Night	9% 2 16% 47% 24% 2	657
August	1st to 10th	Night	9% 3 12% 40% 33% 3	597
	11th to 20th	Night	11% 3 15% 38% 29% 5%	594
	21st to end	Night	13% 3 16% 36% 29% 3	660
September	1st to 10th	Night	13% 5% 19% 36% 22% 5%	785
	11th to 20th	Night	11% 4 16% 34% 31% 5%	800
	21st to end	Night	20% 7% 21% 32% 16% 5%	800
October	1st to 10th	Night	20% 7% 25% 29% 17% 2	800
	11th to 20th	Night	29% 12% 25% 26% 8% 1	800
	21st to end	Night	33% 10% 30% 24% 3	880
November	1st to 10th	Night	27% 13% 27% 25% 8%	820
	11th to 20th	Night	29% 18% 31% 17% 5% 1	840
	21st to end	Night	34% 14% 29% 20% 3	840
December	1st to 10th	Night	32% 19% 29% 17% 3	840
	11th to 20th	Night	25% 22% 34% 16% 3	839
	21st to end	Night	33% 14% 35% 16% 2	1100

Page generated at 2025-12-15 01:13:56. Version ac07

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