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 2024-11-03.

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	13% 9% 3 8% 5% 4 4 4 5% 7% 38%	101567
	Night	12% 9% 3 8% 5% 4 4 3 5% 6% 39%	97523
Transparency	Day	44% 7% 14% 24% 11% 1	101360
	Night	44% 6% 13% 23% 12% 1	97401
Seeing	Day	16% 12% 32% 26% 12% 3	16013
	Night	15% 10% 34% 30% 10% 1	25861

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	12% 16% 7% 18% 6% 5% 4 2 5% 4 22%	2527
	11th to 20th	Day	5% 13% 6% 13% 8% 8% 7% 7% 7% 5% 20%	2566
	21st to end	Day	8% 20% 7% 12% 6% 4 5% 3 4 6% 24%	3135
February	1st to 10th	Day	9% 12% 5% 9% 7% 6% 5% 5% 6% 6% 31%	1710
	11th to 20th	Day	9% 11% 5% 10% 6% 5% 4 5% 5% 6% 34%	1664
	21st to end	Day	12% 11% 4 11% 5% 5% 5% 4 6% 6% 31%	1473
March	1st to 10th	Day	12% 10% 4 7% 5% 4 4 3 5% 6% 40%	3368
	11th to 20th	Day	10% 10% 3 7% 5% 5% 5% 3 5% 7% 40%	3480
	21st to end	Day	25% 11% 5% 12% 5% 4 3 3 4 5% 23%	3860
April	1st to 10th	Day	17% 11% 3 6% 5% 3 4 3 5% 7% 34%	2280
	11th to 20th	Day	20% 11% 4 7% 5% 5% 4 3 4 5% 32%	2260
	21st to end	Day	21% 12% 3 6% 5% 4 5% 3 5% 6% 30%	2470
May	1st to 10th	Day	17% 6% 2 5% 4 4 5% 4 5% 8% 39%	4242
	11th to 20th	Day	13% 7% 2 6% 4 4 4 3 5% 7% 45%	4399
	21st to end	Day	17% 8% 3 7% 4 5% 5% 3 5% 8% 37%	4824
June	1st to 10th	Day	11% 5% 2 5% 4 4 5% 4 6% 9% 46%	2660
	11th to 20th	Day	13% 7% 2 7% 5% 5% 5% 4 6% 9% 37%	2660
	21st to end	Day	11% 4 2 6% 5% 6% 6% 5% 8% 8% 39%	2660
July	1st to 10th	Day	10% 5% 2 7% 5% 6% 6% 4 8% 10% 37%	4440
	11th to 20th	Day	5% 3 1 4 3 4 4 3 5% 8% 60%	4440
	21st to end	Day	6% 4 2 5% 5% 4 5% 5% 7% 8% 48%	4736
August	1st to 10th	Day	12% 7% 2 6% 4 5% 5% 4 7% 8% 41%	4104
	11th to 20th	Day	12% 5% 2 5% 4 4 4 4 6% 9% 44%	4041
	21st to end	Day	10% 5% 2 7% 5% 4 4 4 5% 8% 46%	4322
September	1st to 10th	Day	11% 5% 2 6% 4 4 4 4 5% 6% 48%	2280
	11th to 20th	Day	12% 5% 2 5% 3 3 5% 4 5% 7% 48%	2252
	21st to end	Day	14% 7% 2 6% 4 3 4 4 5% 7% 44%	2000
October	1st to 10th	Day	16% 7% 2 5% 4 4 3 3 5% 6% 45%	1900
	11th to 20th	Day	14% 9% 2 7% 5% 4 4 3 5% 7% 40%	1900
	21st to end	Day	18% 11% 3 7% 4 3 4 2 5% 6% 37%	2071
November	1st to 10th	Day	11% 11% 5% 8% 6% 4 4 3 6% 6% 38%	1582
	11th to 20th	Day	10% 14% 6% 11% 6% 4 5% 3 6% 5% 30%	1520
	21st to end	Day	14% 10% 3 8% 6% 4 3 4 5% 7% 36%	1520
December	1st to 10th	Day	12% 12% 4 12% 8% 6% 6% 3 5% 5% 27%	1520
	11th to 20th	Day	11% 14% 6% 11% 6% 4 5% 3 5% 6% 29%	1918
	21st to end	Day	21% 14% 7% 18% 5% 4 3 3 3 4 18%	2783
January	1st to 10th	Night	10% 15% 7% 16% 6% 4 3 3 4 5% 27%	4428
	11th to 20th	Night	7% 11% 6% 13% 8% 7% 8% 7% 7% 5% 22%	4402
	21st to end	Night	11% 21% 7% 11% 5% 4 4 3 3 4 27%	4532
February	1st to 10th	Night	7% 12% 5% 11% 6% 6% 5% 4 5% 6% 34%	2470
	11th to 20th	Night	7% 9% 4 8% 5% 6% 6% 4 5% 7% 39%	2403
	21st to end	Night	12% 9% 3 9% 5% 6% 4 3 5% 5% 38%	1980
March	1st to 10th	Night	9% 7% 3 6% 5% 4 4 3 5% 7% 47%	3515
	11th to 20th	Night	9% 7% 3 7% 5% 5% 6% 4 6% 8% 40%	3480
	21st to end	Night	26% 12% 3 10% 3 3 3 2 4 5% 29%	3770
April	1st to 10th	Night	16% 12% 3 6% 3 4 4 3 5% 6% 38%	1900
	11th to 20th	Night	21% 9% 4 6% 4 4 4 3 5% 6% 34%	1866
	21st to end	Night	18% 10% 2 6% 4 4 4 3 5% 7% 35%	1710
May	1st to 10th	Night	15% 7% 2 7% 5% 4 4 3 5% 7% 41%	2663
	11th to 20th	Night	14% 4 2 5% 3 3 4 3 5% 7% 51%	2506
	21st to end	Night	14% 7% 4 6% 4 4 4 4 4 7% 42%	2743
June	1st to 10th	Night	10% 5% 2 5% 4 3 4 4 6% 9% 49%	1520
	11th to 20th	Night	9% 5% 2 5% 5% 5% 5% 5% 6% 7% 46%	1520
	21st to end	Night	8% 3 2 5% 4 3 4 4 6% 9% 52%	1520
July	1st to 10th	Night	11% 3 2 5% 4 4 4 5% 7% 10% 45%	2530
	11th to 20th	Night	4 2 1 5% 3 4 4 4 6% 9% 58%	2530
	21st to end	Night	6% 3 2 5% 3 4 4 3 5% 7% 57%	2812
August	1st to 10th	Night	12% 6% 2 6% 4 4 4 4 5% 6% 47%	2836
	11th to 20th	Night	13% 5% 1 4 3 3 3 3 5% 8% 52%	2798
	21st to end	Night	9% 6% 3 7% 4 4 4 3 5% 7% 47%	3338
September	1st to 10th	Night	9% 4 2 4 4 3 3 3 5% 8% 54%	1900
	11th to 20th	Night	10% 5% 2 4 3 4 4 2 5% 8% 53%	1926
	21st to end	Night	13% 6% 2 6% 3 3 4 3 4 5% 52%	2161
October	1st to 10th	Night	14% 6% 3 6% 2 3 3 3 4 6% 50%	2280
	11th to 20th	Night	14% 9% 2 6% 4 4 4 3 5% 6% 42%	2280
	21st to end	Night	18% 10% 3 7% 4 3 4 2 5% 6% 37%	2525
November	1st to 10th	Night	12% 9% 3 6% 4 4 4 3 5% 6% 43%	2536
	11th to 20th	Night	12% 11% 4 11% 6% 5% 4 4 5% 5% 34%	2660
	21st to end	Night	14% 10% 4 9% 6% 4 5% 3 4 6% 38%	2660
December	1st to 10th	Night	10% 10% 4 11% 8% 5% 4 4 6% 6% 31%	2660
	11th to 20th	Night	11% 14% 5% 12% 7% 6% 5% 3 5% 6% 28%	3279
	21st to end	Night	23% 14% 5% 11% 5% 5% 4 3 4 4 21%	4884

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% 6% 11% 15% 3	2528
	11th to 20th	Day	62% 6% 10% 16% 5%	2566
	21st to end	Day	62% 6% 14% 14% 4	3135
February	1st to 10th	Day	52% 7% 15% 18% 8% 1	1710
	11th to 20th	Day	50% 5% 13% 24% 8% 1	1673
	21st to end	Day	51% 7% 13% 18% 11%	1473
March	1st to 10th	Day	43% 6% 14% 25% 11%	3368
	11th to 20th	Day	42% 6% 11% 31% 8% 2	3480
	21st to end	Day	64% 7% 8% 16% 5%	3860
April	1st to 10th	Day	48% 6% 13% 21% 11% 1	2280
	11th to 20th	Day	54% 5% 11% 18% 11% 2	2260
	21st to end	Day	54% 7% 12% 19% 8% 1	2470
May	1st to 10th	Day	40% 8% 13% 24% 13% 2	4280
	11th to 20th	Day	36% 8% 12% 28% 14% 2	4403
	21st to end	Day	45% 8% 12% 25% 10% 1	4837
June	1st to 10th	Day	33% 8% 15% 29% 13% 2	2660
	11th to 20th	Day	42% 8% 13% 22% 14% 1	2660
	21st to end	Day	37% 10% 17% 25% 10% 2	2660
July	1st to 10th	Day	38% 9% 20% 22% 10% 1	4371
	11th to 20th	Day	22% 6% 16% 35% 19% 2	4365
	21st to end	Day	29% 9% 15% 28% 18% 1	4587
August	1st to 10th	Day	39% 7% 12% 28% 12% 2	4090
	11th to 20th	Day	36% 7% 13% 33% 10%	4080
	21st to end	Day	35% 7% 16% 28% 14% 1	4321
September	1st to 10th	Day	35% 7% 13% 30% 14%	2280
	11th to 20th	Day	34% 7% 18% 32% 9%	2252
	21st to end	Day	39% 6% 13% 31% 11% 1	2000
October	1st to 10th	Day	40% 5% 12% 29% 13% 1	1900
	11th to 20th	Day	43% 5% 13% 26% 12% 1	1900
	21st to end	Day	48% 5% 14% 22% 10%	2071
November	1st to 10th	Day	46% 7% 14% 19% 13% 3	1582
	11th to 20th	Day	55% 6% 13% 17% 9% 1	1520
	21st to end	Day	47% 7% 18% 22% 7% 1	1520
December	1st to 10th	Day	58% 7% 16% 13% 6%	1520
	11th to 20th	Day	56% 7% 17% 15% 5%	1915
	21st to end	Day	69% 6% 10% 11% 4	2783
January	1st to 10th	Night	60% 5% 12% 17% 5%	4428
	11th to 20th	Night	60% 6% 13% 15% 5%	4402
	21st to end	Night	62% 4 9% 19% 6% 1	4532
February	1st to 10th	Night	51% 4 13% 21% 10% 1	2470
	11th to 20th	Night	45% 6% 14% 25% 9% 1	2404
	21st to end	Night	48% 5% 12% 22% 12% 1	1980
March	1st to 10th	Night	36% 7% 13% 27% 17% 1	3515
	11th to 20th	Night	39% 6% 11% 28% 15% 1	3480
	21st to end	Night	59% 4 8% 21% 7% 1	3770
April	1st to 10th	Night	47% 5% 10% 23% 14% 1	1900
	11th to 20th	Night	50% 5% 9% 19% 15% 2	1866
	21st to end	Night	47% 7% 10% 21% 14% 2	1710
May	1st to 10th	Night	40% 7% 12% 18% 21% 1	2690
	11th to 20th	Night	33% 6% 12% 26% 20% 4	2507
	21st to end	Night	41% 7% 12% 25% 15% 1	2751
June	1st to 10th	Night	30% 7% 14% 28% 18% 2	1520
	11th to 20th	Night	35% 7% 14% 22% 18% 3	1520
	21st to end	Night	27% 8% 16% 30% 16% 3	1520
July	1st to 10th	Night	32% 8% 21% 25% 13% 1	2490
	11th to 20th	Night	21% 6% 14% 39% 18% 2	2482
	21st to end	Night	25% 6% 16% 31% 19% 3	2722
August	1st to 10th	Night	37% 6% 11% 28% 14% 4	2826
	11th to 20th	Night	32% 5% 14% 31% 16% 1	2825
	21st to end	Night	35% 7% 16% 27% 13% 2	3338
September	1st to 10th	Night	28% 6% 13% 34% 18% 1	1900
	11th to 20th	Night	29% 6% 17% 31% 17% 1	1926
	21st to end	Night	34% 5% 12% 30% 17% 1	2161
October	1st to 10th	Night	35% 4 11% 31% 16% 3	2280
	11th to 20th	Night	41% 6% 13% 23% 15% 2	2280
	21st to end	Night	47% 5% 13% 22% 12% 1	2525
November	1st to 10th	Night	41% 7% 14% 23% 14% 2	2536
	11th to 20th	Night	53% 6% 12% 18% 11% 1	2660
	21st to end	Night	48% 5% 16% 22% 7% 1	2660
December	1st to 10th	Night	53% 7% 15% 19% 6%	2660
	11th to 20th	Night	56% 7% 14% 17% 5% 1	3281
	21st to end	Night	65% 6% 11% 14% 4	4884

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	11% 12% 36% 27% 11% 2	270
	11th to 20th	Day	14% 15% 41% 25% 4	270
	21st to end	Day	17% 11% 38% 23% 10% 2	297
February	1st to 10th	Day	14% 17% 43% 21% 4 1	270
	11th to 20th	Day	14% 18% 39% 23% 5% 1	270
	21st to end	Day	17% 15% 40% 26% 2	225
March	1st to 10th	Day	18% 15% 40% 20% 6%	270
	11th to 20th	Day	18% 14% 36% 24% 7% 1	270
	21st to end	Day	25% 19% 25% 21% 8% 2	318
April	1st to 10th	Day	23% 15% 36% 20% 5% 1	460
	11th to 20th	Day	28% 16% 24% 21% 9% 1	458
	21st to end	Day	26% 14% 30% 21% 8% 2	650
May	1st to 10th	Day	19% 16% 34% 22% 8% 1	653
	11th to 20th	Day	18% 14% 30% 22% 13% 3	675
	21st to end	Day	16% 12% 27% 29% 12% 3	734
June	1st to 10th	Day	9% 10% 28% 33% 17% 3	680
	11th to 20th	Day	14% 8% 39% 27% 9% 2	680
	21st to end	Day	12% 12% 31% 26% 16% 3	680
July	1st to 10th	Day	8% 6% 24% 31% 23% 7%	671
	11th to 20th	Day	9% 7% 28% 29% 21% 5%	668
	21st to end	Day	6% 5% 28% 37% 19% 5%	739
August	1st to 10th	Day	10% 6% 25% 34% 21% 4	676
	11th to 20th	Day	14% 5% 23% 31% 21% 5%	665
	21st to end	Day	11% 7% 28% 33% 16% 5%	629
September	1st to 10th	Day	14% 10% 29% 29% 13% 5%	490
	11th to 20th	Day	12% 8% 29% 31% 16% 3	462
	21st to end	Day	17% 14% 31% 21% 12% 4	300
October	1st to 10th	Day	18% 13% 27% 27% 11% 4	300
	11th to 20th	Day	16% 23% 36% 20% 4 1	300
	21st to end	Day	24% 17% 38% 14% 6% 1	330
November	1st to 10th	Day	17% 18% 38% 17% 8% 1	276
	11th to 20th	Day	16% 21% 43% 17% 3	270
	21st to end	Day	22% 14% 43% 16% 4	270
December	1st to 10th	Day	15% 13% 39% 27% 6% 1	270
	11th to 20th	Day	18% 18% 34% 24% 5%	270
	21st to end	Day	27% 15% 37% 16% 4	297
January	1st to 10th	Night	12% 12% 40% 29% 7% 1	950
	11th to 20th	Night	16% 13% 37% 28% 5% 1	950
	21st to end	Night	18% 11% 38% 28% 5% 1	1045
February	1st to 10th	Night	12% 12% 40% 29% 6% 1	950
	11th to 20th	Night	12% 12% 43% 26% 6% 1	929
	21st to end	Night	16% 13% 35% 28% 7% 1	724
March	1st to 10th	Night	15% 10% 40% 27% 8% 1	632
	11th to 20th	Night	17% 11% 38% 28% 6%	570
	21st to end	Night	22% 12% 29% 24% 11% 1	627
April	1st to 10th	Night	19% 14% 36% 26% 5%	570
	11th to 20th	Night	26% 12% 30% 27% 6%	563
	21st to end	Night	21% 10% 33% 25% 8% 1	570
May	1st to 10th	Night	18% 11% 35% 30% 6% 1	570
	11th to 20th	Night	16% 9% 33% 30% 11% 1	561
	21st to end	Night	15% 9% 27% 34% 13%	617
June	1st to 10th	Night	11% 5% 32% 40% 12%	570
	11th to 20th	Night	11% 4 37% 40% 8%	570
	21st to end	Night	10% 3 26% 46% 15% 1	570
July	1st to 10th	Night	6% 3 24% 39% 27% 1	555
	11th to 20th	Night	5% 5% 29% 43% 17% 2	552
	21st to end	Night	5% 2 24% 48% 18% 1	624
August	1st to 10th	Night	7% 5% 21% 46% 21% 1	567
	11th to 20th	Night	12% 2 21% 39% 22% 3	564
	21st to end	Night	7% 4 29% 35% 23% 2	627
September	1st to 10th	Night	10% 6% 25% 38% 17% 3	570
	11th to 20th	Night	10% 7% 35% 31% 15% 2	570
	21st to end	Night	13% 11% 33% 29% 14%	641
October	1st to 10th	Night	18% 11% 29% 28% 13% 1	760
	11th to 20th	Night	19% 12% 37% 25% 7% 1	760
	21st to end	Night	24% 11% 30% 27% 6%	836
November	1st to 10th	Night	17% 13% 36% 26% 7%	852
	11th to 20th	Night	17% 14% 37% 25% 6%	950
	21st to end	Night	17% 15% 37% 23% 7%	950
December	1st to 10th	Night	15% 11% 38% 28% 7%	950
	11th to 20th	Night	19% 11% 39% 25% 6% 1	950
	21st to end	Night	25% 13% 33% 25% 4	1045

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