Burnsville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Burnsville clear sky chart from 2005-11-06 to 2026-10-29.

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	12% 8% 3 8% 5% 4 5% 4 6% 7% 39%	150375
	Night	11% 9% 4 8% 5% 4 5% 4 5% 6% 39%	142102
Transparency	Day	43% 6% 13% 26% 12% 1	153952
	Night	44% 5% 12% 24% 13% 1	146604
Seeing	Day	16% 13% 32% 25% 11% 2	18787
	Night	16% 11% 34% 30% 9% 1	28573

By Month

Percentage Cloud Cover SE (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	9% 14% 6% 20% 8% 6% 5% 2 5% 5% 21%	4691
	11th to 20th	Day	5% 12% 7% 13% 7% 7% 7% 7% 9% 5% 20%	4788
	21st to end	Day	5% 12% 6% 11% 5% 5% 7% 4 7% 6% 32%	5812
February	1st to 10th	Day	9% 12% 5% 10% 8% 6% 5% 4 6% 6% 30%	1890
	11th to 20th	Day	8% 11% 5% 11% 6% 5% 4 4 5% 6% 35%	1844
	21st to end	Day	11% 11% 4 10% 5% 5% 4 4 6% 7% 33%	1623
March	1st to 10th	Day	13% 8% 3 6% 4 3 4 3 5% 7% 45%	4948
	11th to 20th	Day	10% 10% 3 6% 4 5% 4 3 5% 7% 41%	5090
	21st to end	Day	22% 11% 4 10% 5% 4 4 3 4 6% 26%	5644
April	1st to 10th	Day	17% 11% 3 7% 5% 4 4 3 5% 7% 34%	2520
	11th to 20th	Day	19% 11% 4 8% 5% 5% 4 3 4 5% 31%	2501
	21st to end	Day	21% 11% 3 6% 5% 4 4 4 5% 6% 30%	2730
May	1st to 10th	Day	11% 5% 2 5% 4 4 5% 4 5% 7% 49%	7915
	11th to 20th	Day	15% 9% 2 5% 3 3 3 3 5% 7% 45%	8222
	21st to end	Day	15% 8% 3 7% 5% 4 5% 3 5% 7% 39%	9047
June	1st to 10th	Day	11% 5% 2 5% 4 4 5% 4 7% 9% 45%	2940
	11th to 20th	Day	13% 7% 2 7% 5% 5% 4 4 6% 9% 36%	2940
	21st to end	Day	11% 5% 2 6% 5% 6% 6% 5% 8% 8% 38%	2940
July	1st to 10th	Day	10% 6% 3 7% 5% 5% 5% 4 8% 11% 38%	8280
	11th to 20th	Day	7% 3 1 4 3 3 3 3 5% 9% 59%	8280
	21st to end	Day	7% 5% 2 5% 4 4 5% 4 7% 9% 48%	8857
August	1st to 10th	Day	11% 6% 2 5% 4 5% 5% 4 6% 7% 45%	6014
	11th to 20th	Day	12% 5% 2 6% 4 5% 5% 4 7% 10% 40%	5948
	21st to end	Day	9% 5% 2 6% 4 4 4 4 6% 8% 48%	6293
September	1st to 10th	Day	11% 6% 2 5% 4 5% 4 4 5% 7% 47%	2520
	11th to 20th	Day	13% 6% 2 6% 3 4 5% 4 5% 7% 45%	2488
	21st to end	Day	15% 7% 2 6% 4 3 4 4 5% 7% 43%	2210
October	1st to 10th	Day	15% 6% 2 5% 4 4 3 4 5% 6% 46%	2100
	11th to 20th	Day	15% 9% 2 6% 4 4 4 3 5% 7% 40%	2100
	21st to end	Day	17% 11% 3 7% 4 3 4 2 5% 6% 36%	2260
November	1st to 10th	Day	12% 10% 4 8% 6% 4 4 3 6% 6% 37%	1732
	11th to 20th	Day	10% 15% 6% 11% 6% 4 4 3 6% 5% 31%	1680
	21st to end	Day	13% 11% 4 9% 6% 4 3 3 5% 7% 34%	1680
December	1st to 10th	Day	8% 10% 4 14% 11% 8% 6% 4 5% 7% 24%	2690
	11th to 20th	Day	11% 16% 6% 11% 7% 5% 5% 3 5% 6% 26%	3088
	21st to end	Day	20% 18% 9% 19% 5% 3 3 2 3 4 14%	4070
January	1st to 10th	Night	9% 12% 5% 14% 8% 6% 4 4 5% 6% 27%	8232
	11th to 20th	Night	6% 11% 5% 13% 8% 7% 10% 8% 7% 4 20%	8186
	21st to end	Night	6% 13% 5% 9% 6% 5% 5% 4 5% 6% 35%	8402
February	1st to 10th	Night	7% 12% 5% 11% 7% 6% 5% 3 5% 6% 33%	2730
	11th to 20th	Night	7% 9% 5% 9% 5% 6% 6% 4 5% 7% 39%	2663
	21st to end	Night	11% 9% 3 9% 6% 6% 4 3 5% 6% 38%	2182
March	1st to 10th	Night	10% 6% 2 7% 4 4 4 3 5% 7% 47%	5170
	11th to 20th	Night	10% 6% 3 6% 5% 5% 6% 4 6% 10% 39%	5090
	21st to end	Night	24% 12% 4 9% 4 3 3 3 4 5% 28%	5526
April	1st to 10th	Night	16% 12% 3 7% 3 4 4 3 5% 6% 37%	2100
	11th to 20th	Night	20% 9% 4 6% 4 4 4 3 5% 6% 35%	2065
	21st to end	Night	19% 10% 2 7% 4 4 4 4 5% 7% 35%	1890
May	1st to 10th	Night	10% 6% 2 6% 4 4 4 3 5% 6% 51%	4968
	11th to 20th	Night	15% 5% 2 5% 3 3 4 3 4 6% 49%	4670
	21st to end	Night	15% 9% 4 6% 5% 4 4 4 5% 6% 38%	5139
June	1st to 10th	Night	11% 5% 2 5% 4 3 4 4 6% 9% 48%	1680
	11th to 20th	Night	10% 6% 2 6% 5% 5% 5% 5% 6% 7% 45%	1680
	21st to end	Night	9% 3 2 5% 4 3 4 4 6% 9% 51%	1680
July	1st to 10th	Night	10% 4 2 5% 4 4 5% 5% 8% 10% 44%	4708
	11th to 20th	Night	5% 3 1 4 3 3 4 4 6% 9% 57%	4707
	21st to end	Night	9% 5% 2 5% 4 4 4 3 6% 7% 50%	5235
August	1st to 10th	Night	10% 5% 2 6% 4 4 3 3 5% 6% 52%	4156
	11th to 20th	Night	13% 5% 2 5% 3 3 4 4 5% 9% 46%	4118
	21st to end	Night	8% 5% 2 6% 4 4 4 4 6% 9% 50%	4842
September	1st to 10th	Night	9% 4 2 5% 4 3 3 4 5% 8% 53%	2100
	11th to 20th	Night	11% 5% 2 4 3 4 4 2 6% 7% 52%	2129
	21st to end	Night	13% 6% 2 6% 3 3 4 3 4 5% 51%	2389
October	1st to 10th	Night	13% 6% 2 6% 2 3 3 3 4 6% 51%	2520
	11th to 20th	Night	15% 9% 3 7% 4 4 4 3 5% 6% 42%	2520
	21st to end	Night	18% 11% 3 7% 4 3 4 2 5% 6% 37%	2755
November	1st to 10th	Night	13% 9% 3 6% 4 4 4 3 5% 6% 42%	2781
	11th to 20th	Night	12% 11% 4 10% 5% 5% 4 4 5% 5% 35%	2940
	21st to end	Night	14% 11% 4 10% 5% 4 4 3 4 6% 36%	2940
December	1st to 10th	Night	6% 8% 4 14% 8% 8% 6% 4 6% 6% 30%	4720
	11th to 20th	Night	10% 16% 6% 14% 7% 5% 4 4 5% 5% 24%	5339
	21st to end	Night	22% 15% 8% 14% 5% 4 4 3 3 4 17%	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	65% 4 11% 14% 5%	4692
	11th to 20th	Day	60% 4 9% 17% 10%	4788
	21st to end	Day	50% 6% 13% 22% 9%	5812
February	1st to 10th	Day	52% 6% 14% 18% 8% 1	1890
	11th to 20th	Day	49% 5% 12% 26% 7%	1853
	21st to end	Day	49% 6% 14% 19% 10%	1623
March	1st to 10th	Day	38% 5% 17% 27% 11% 2	4948
	11th to 20th	Day	42% 4 15% 28% 9% 1	5090
	21st to end	Day	59% 6% 10% 18% 7%	5646
April	1st to 10th	Day	49% 5% 12% 21% 11% 1	2520
	11th to 20th	Day	54% 5% 12% 17% 11% 1	2501
	21st to end	Day	53% 6% 11% 20% 9% 1	2730
May	1st to 10th	Day	33% 5% 10% 30% 20% 2	7953
	11th to 20th	Day	39% 5% 8% 25% 19% 4	8226
	21st to end	Day	44% 6% 9% 29% 10% 1	9061
June	1st to 10th	Day	34% 8% 15% 29% 13% 1	2940
	11th to 20th	Day	43% 8% 13% 22% 13% 1	2940
	21st to end	Day	38% 9% 17% 25% 10% 2	2940
July	1st to 10th	Day	38% 8% 17% 30% 7%	8211
	11th to 20th	Day	23% 5% 13% 40% 19% 1	8205
	21st to end	Day	31% 7% 13% 32% 16% 1	8663
August	1st to 10th	Day	37% 6% 13% 32% 12% 1	6000
	11th to 20th	Day	38% 7% 18% 29% 8%	5987
	21st to end	Day	33% 6% 17% 29% 13% 1	6292
September	1st to 10th	Day	36% 7% 14% 30% 14%	2520
	11th to 20th	Day	36% 7% 18% 30% 9%	2488
	21st to end	Day	40% 5% 12% 31% 11% 1	2210
October	1st to 10th	Day	30% 3 8% 36% 22%	3360
	11th to 20th	Day	39% 4 10% 27% 18% 1	3340
	21st to end	Day	44% 4 14% 29% 9%	3586
November	1st to 10th	Day	46% 6% 14% 19% 13% 2	1732
	11th to 20th	Day	54% 5% 13% 18% 9% 1	1680
	21st to end	Day	49% 6% 16% 21% 6% 1	1680
December	1st to 10th	Day	59% 7% 16% 13% 6%	2690
	11th to 20th	Day	60% 5% 14% 16% 5%	3085
	21st to end	Day	75% 5% 8% 9% 3	4070
January	1st to 10th	Night	58% 4 15% 17% 6%	8233
	11th to 20th	Night	63% 5% 10% 14% 8%	8186
	21st to end	Night	49% 4 10% 26% 10%	8402
February	1st to 10th	Night	51% 4 13% 20% 10% 1	2730
	11th to 20th	Night	45% 5% 13% 26% 9% 1	2664
	21st to end	Night	47% 5% 13% 22% 12% 1	2182
March	1st to 10th	Night	37% 5% 13% 27% 16% 2	5170
	11th to 20th	Night	39% 5% 15% 27% 14% 1	5090
	21st to end	Night	59% 4 9% 18% 9% 1	5526
April	1st to 10th	Night	48% 5% 10% 23% 14% 1	2100
	11th to 20th	Night	49% 5% 10% 20% 15% 2	2065
	21st to end	Night	48% 6% 9% 21% 14% 2	1890
May	1st to 10th	Night	32% 6% 9% 31% 21% 2	4995
	11th to 20th	Night	36% 5% 9% 21% 23% 6%	4671
	21st to end	Night	46% 5% 9% 27% 12% 2	5149
June	1st to 10th	Night	31% 7% 14% 28% 18% 2	1680
	11th to 20th	Night	37% 7% 14% 22% 18% 3	1680
	21st to end	Night	28% 7% 17% 30% 16% 3	1680
July	1st to 10th	Night	33% 8% 19% 29% 11% 1	4670
	11th to 20th	Night	22% 5% 12% 39% 20% 1	4662
	21st to end	Night	32% 6% 14% 30% 17% 2	5118
August	1st to 10th	Night	34% 5% 12% 30% 16% 3	4146
	11th to 20th	Night	36% 6% 18% 27% 12% 1	4145
	21st to end	Night	31% 7% 18% 29% 14% 1	4842
September	1st to 10th	Night	30% 6% 13% 34% 17% 1	2100
	11th to 20th	Night	31% 6% 17% 31% 15%	2129
	21st to end	Night	35% 5% 12% 30% 17% 1	2389
October	1st to 10th	Night	24% 3 7% 35% 27% 4	4040
	11th to 20th	Night	33% 5% 12% 25% 22% 4	4019
	21st to end	Night	44% 4 11% 28% 13%	4379
November	1st to 10th	Night	42% 6% 13% 24% 13% 1	2781
	11th to 20th	Night	51% 6% 11% 19% 11% 1	2940
	21st to end	Night	50% 4 16% 22% 7% 1	2940
December	1st to 10th	Night	53% 6% 17% 18% 5%	4720
	11th to 20th	Night	62% 5% 11% 17% 5% 1	5341
	21st to end	Night	71% 5% 9% 12% 3	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	12% 13% 38% 25% 10% 2	330
	11th to 20th	Day	14% 16% 42% 23% 4	330
	21st to end	Day	17% 13% 39% 21% 8% 1	363
February	1st to 10th	Day	18% 15% 44% 18% 4 1	330
	11th to 20th	Day	13% 18% 40% 22% 5% 1	330
	21st to end	Day	18% 16% 40% 24% 2	273
March	1st to 10th	Day	19% 16% 41% 19% 5%	330
	11th to 20th	Day	22% 14% 36% 22% 5% 1	330
	21st to end	Day	26% 21% 27% 19% 7% 1	386
April	1st to 10th	Day	25% 16% 36% 19% 4 1	540
	11th to 20th	Day	28% 18% 25% 20% 8% 1	539
	21st to end	Day	26% 14% 32% 19% 7% 1	750
May	1st to 10th	Day	18% 16% 33% 23% 8% 1	753
	11th to 20th	Day	20% 14% 29% 22% 12% 3	775
	21st to end	Day	18% 12% 28% 29% 11% 2	844
June	1st to 10th	Day	9% 11% 28% 33% 17% 2	780
	11th to 20th	Day	16% 10% 37% 26% 9% 2	780
	21st to end	Day	13% 12% 32% 25% 14% 3	780
July	1st to 10th	Day	9% 6% 24% 31% 22% 7%	771
	11th to 20th	Day	10% 7% 28% 30% 20% 5%	768
	21st to end	Day	6% 6% 30% 36% 17% 4	849
August	1st to 10th	Day	10% 7% 25% 35% 19% 4	776
	11th to 20th	Day	14% 5% 25% 32% 20% 5%	765
	21st to end	Day	10% 8% 29% 33% 16% 4	727
September	1st to 10th	Day	14% 11% 29% 27% 13% 5%	570
	11th to 20th	Day	14% 10% 30% 30% 14% 2	538
	21st to end	Day	19% 12% 29% 21% 15% 4	360
October	1st to 10th	Day	16% 13% 31% 26% 10% 3	360
	11th to 20th	Day	19% 22% 36% 18% 4 1	360
	21st to end	Day	25% 17% 37% 15% 6% 1	387
November	1st to 10th	Day	20% 18% 37% 16% 7% 1	330
	11th to 20th	Day	18% 22% 41% 17% 2	330
	21st to end	Day	24% 15% 42% 16% 3	330
December	1st to 10th	Day	15% 15% 40% 25% 5% 1	330
	11th to 20th	Day	21% 18% 36% 21% 4	330
	21st to end	Day	26% 16% 39% 15% 4	363
January	1st to 10th	Night	12% 13% 40% 28% 7% 1	1050
	11th to 20th	Night	16% 14% 38% 27% 5% 1	1050
	21st to end	Night	17% 12% 38% 28% 5% 1	1155
February	1st to 10th	Night	13% 13% 41% 27% 6%	1050
	11th to 20th	Night	12% 13% 44% 25% 5% 1	1029
	21st to end	Night	15% 15% 37% 26% 6% 1	798
March	1st to 10th	Night	15% 11% 39% 27% 7% 1	698
	11th to 20th	Night	18% 12% 38% 26% 6%	630
	21st to end	Night	22% 13% 31% 23% 10% 1	693
April	1st to 10th	Night	20% 14% 35% 26% 5%	630
	11th to 20th	Night	25% 12% 30% 27% 6%	623
	21st to end	Night	23% 10% 33% 25% 8% 1	630
May	1st to 10th	Night	18% 11% 34% 30% 7%	630
	11th to 20th	Night	17% 10% 33% 30% 10%	621
	21st to end	Night	16% 9% 27% 35% 12%	683
June	1st to 10th	Night	11% 6% 32% 40% 11%	630
	11th to 20th	Night	11% 6% 36% 39% 7%	630
	21st to end	Night	11% 3 27% 44% 14% 1	630
July	1st to 10th	Night	6% 3 24% 40% 26% 1	615
	11th to 20th	Night	6% 4 29% 43% 17% 2	612
	21st to end	Night	6% 4 25% 47% 17% 1	690
August	1st to 10th	Night	7% 5% 21% 45% 21% 1	627
	11th to 20th	Night	13% 3 21% 39% 21% 3	624
	21st to end	Night	7% 4 30% 36% 22% 1	693
September	1st to 10th	Night	10% 7% 26% 37% 17% 3	630
	11th to 20th	Night	11% 7% 35% 30% 14% 2	630
	21st to end	Night	14% 10% 32% 29% 15%	709
October	1st to 10th	Night	17% 10% 31% 28% 12% 1	840
	11th to 20th	Night	20% 12% 38% 24% 6% 1	840
	21st to end	Night	25% 12% 30% 27% 6%	913
November	1st to 10th	Night	18% 13% 37% 25% 6%	935
	11th to 20th	Night	18% 15% 37% 24% 6%	1050
	21st to end	Night	18% 16% 37% 22% 7%	1050
December	1st to 10th	Night	15% 12% 39% 28% 6%	1050
	11th to 20th	Night	20% 14% 37% 24% 5%	1050
	21st to end	Night	25% 13% 33% 25% 4 1	1155

Page generated at 2026-10-26 03:37:46. Version ac07

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