Burr Oak State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Burr Oak State Park clear sky chart from 2005-11-06 to 2026-04-02.

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% 10% 3 8% 5% 4 5% 4 5% 7% 33%	131636
	Night	15% 10% 4 8% 5% 4 4 3 5% 6% 34%	130210
Transparency	Day	48% 5% 11% 22% 13% 2	135307
	Night	49% 5% 10% 21% 13% 2	134608
Seeing	Day	22% 14% 27% 20% 12% 5%	16767
	Night	21% 11% 25% 27% 14% 2	26935

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	17% 20% 6% 13% 6% 3 3 3 4 6% 19%	5258
	11th to 20th	Day	13% 18% 7% 15% 7% 4 4 3 3 4 23%	5280
	21st to end	Day	19% 15% 6% 10% 9% 6% 5% 3 5% 5% 19%	5780
February	1st to 10th	Day	22% 13% 5% 8% 5% 4 3 3 4 5% 27%	1890
	11th to 20th	Day	19% 14% 6% 11% 4 3 3 4 4 6% 26%	1977
	21st to end	Day	18% 14% 5% 9% 3 5% 3 2 4 5% 32%	1730
March	1st to 10th	Day	19% 15% 4 8% 4 4 4 2 4 5% 31%	4906
	11th to 20th	Day	12% 8% 3 6% 4 4 5% 4 5% 7% 41%	5090
	21st to end	Day	19% 8% 3 9% 5% 5% 5% 4 5% 6% 33%	5586
April	1st to 10th	Day	16% 13% 3 7% 5% 5% 4 3 5% 6% 32%	2211
	11th to 20th	Day	16% 9% 3 7% 5% 4 5% 3 5% 6% 38%	2532
	21st to end	Day	18% 8% 3 7% 4 4 4 4 6% 7% 35%	2600
May	1st to 10th	Day	20% 9% 3 8% 5% 5% 5% 4 7% 7% 27%	5862
	11th to 20th	Day	20% 10% 3 8% 5% 4 4 3 6% 8% 29%	5861
	21st to end	Day	17% 6% 2 6% 5% 5% 5% 4 7% 9% 34%	6433
June	1st to 10th	Day	12% 6% 2 5% 6% 5% 5% 5% 7% 9% 38%	2600
	11th to 20th	Day	11% 7% 2 7% 6% 6% 5% 5% 7% 9% 36%	2600
	21st to end	Day	11% 6% 3 6% 5% 5% 6% 5% 7% 10% 37%	2600
July	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 4 6% 8% 44%	5900
	11th to 20th	Day	12% 6% 2 7% 5% 5% 6% 5% 7% 10% 34%	5900
	21st to end	Day	12% 7% 3 7% 5% 5% 6% 5% 7% 9% 34%	6424
August	1st to 10th	Day	9% 6% 2 8% 5% 5% 6% 5% 7% 10% 37%	4234
	11th to 20th	Day	9% 6% 2 7% 5% 5% 6% 5% 7% 10% 39%	4174
	21st to end	Day	6% 3 2 6% 4 5% 6% 4 7% 9% 50%	4591
September	1st to 10th	Day	15% 5% 1 5% 3 4 4 4 5% 7% 48%	2220
	11th to 20th	Day	9% 6% 2 5% 4 4 5% 4 5% 8% 49%	2200
	21st to end	Day	19% 7% 3 6% 4 4 3 3 5% 6% 40%	2200
October	1st to 10th	Day	13% 5% 2 6% 4 4 4 3 6% 7% 46%	2102
	11th to 20th	Day	14% 7% 2 6% 5% 4 4 3 5% 7% 43%	2000
	21st to end	Day	21% 8% 3 7% 4 4 4 2 4 6% 38%	2200
November	1st to 10th	Day	12% 7% 2 6% 4 3 4 3 4 6% 49%	1867
	11th to 20th	Day	17% 14% 4 6% 4 4 3 3 5% 6% 35%	1890
	21st to end	Day	17% 13% 5% 8% 4 3 5% 3 4 6% 31%	1890
December	1st to 10th	Day	20% 13% 5% 13% 5% 5% 4 3 4 4 25%	3020
	11th to 20th	Day	24% 15% 6% 10% 4 4 3 3 4 5% 23%	3463
	21st to end	Day	21% 19% 5% 11% 5% 5% 5% 4 4 5% 17%	4565
January	1st to 10th	Night	15% 17% 7% 16% 6% 5% 5% 4 4 4 17%	7635
	11th to 20th	Night	14% 17% 7% 15% 8% 5% 5% 3 4 4 19%	7680
	21st to end	Night	19% 13% 5% 9% 6% 5% 4 3 4 5% 28%	8401
February	1st to 10th	Night	21% 12% 4 8% 5% 5% 4 3 4 5% 29%	2730
	11th to 20th	Night	20% 14% 4 9% 5% 5% 4 2 5% 5% 26%	2525
	21st to end	Night	20% 14% 6% 8% 5% 4 4 3 4 4 29%	2076
March	1st to 10th	Night	20% 13% 3 6% 4 3 3 3 4 6% 35%	5165
	11th to 20th	Night	12% 9% 3 6% 4 4 4 3 5% 7% 42%	5090
	21st to end	Night	18% 9% 3 7% 4 4 5% 4 5% 6% 34%	5588
April	1st to 10th	Night	17% 10% 3 6% 4 3 4 4 6% 7% 36%	2212
	11th to 20th	Night	14% 8% 2 5% 5% 5% 4 4 6% 8% 38%	1833
	21st to end	Night	15% 8% 3 7% 5% 4 4 3 7% 8% 37%	1800
May	1st to 10th	Night	25% 10% 3 7% 4 4 4 3 5% 7% 27%	4033
	11th to 20th	Night	17% 8% 3 6% 4 4 4 3 6% 9% 37%	4032
	21st to end	Night	16% 7% 2 7% 4 5% 4 4 6% 8% 37%	4421
June	1st to 10th	Night	11% 5% 2 5% 4 4 4 5% 7% 8% 44%	1800
	11th to 20th	Night	9% 5% 2 7% 4 4 4 5% 7% 9% 43%	1800
	21st to end	Night	10% 5% 2 5% 4 4 5% 4 7% 10% 44%	1800
July	1st to 10th	Night	10% 7% 3 6% 4 4 4 4 6% 7% 46%	4058
	11th to 20th	Night	11% 6% 3 7% 5% 5% 5% 5% 7% 9% 38%	4057
	21st to end	Night	8% 6% 3 8% 6% 5% 5% 5% 7% 7% 40%	4427
August	1st to 10th	Night	7% 7% 3 8% 4 5% 5% 4 7% 9% 40%	2915
	11th to 20th	Night	10% 7% 3 8% 4 5% 5% 3 5% 6% 44%	2875
	21st to end	Night	6% 3 2 7% 4 4 5% 4 7% 10% 49%	3273
September	1st to 10th	Night	11% 4 2 6% 3 3 4 3 4 7% 53%	2175
	11th to 20th	Night	9% 3 2 5% 4 3 4 4 5% 7% 54%	2200
	21st to end	Night	17% 8% 3 5% 4 3 5% 3 5% 5% 44%	2200
October	1st to 10th	Night	12% 5% 2 6% 3 3 4 3 5% 7% 51%	2296
	11th to 20th	Night	15% 7% 2 5% 4 3 4 4 5% 7% 45%	2400
	21st to end	Night	20% 7% 2 5% 3 4 4 3 5% 5% 41%	2640
November	1st to 10th	Night	14% 7% 2 4 4 3 3 3 4 6% 50%	2648
	11th to 20th	Night	17% 10% 3 6% 5% 5% 4 3 5% 6% 36%	2730
	21st to end	Night	19% 13% 4 7% 5% 4 4 3 4 6% 31%	2730
December	1st to 10th	Night	18% 14% 5% 12% 4 4 3 3 5% 6% 26%	4380
	11th to 20th	Night	19% 17% 7% 9% 4 4 4 3 4 5% 24%	4952
	21st to end	Night	21% 18% 5% 10% 5% 4 4 3 4 6% 18%	6633

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	68% 4 12% 13% 3	5259
	11th to 20th	Day	66% 3 8% 11% 11% 1	5280
	21st to end	Day	68% 3 9% 13% 6%	5780
February	1st to 10th	Day	59% 3 10% 18% 9% 1	1890
	11th to 20th	Day	60% 3 10% 17% 10%	1986
	21st to end	Day	56% 3 11% 19% 9% 1	1730
March	1st to 10th	Day	56% 3 7% 22% 9% 2	4906
	11th to 20th	Day	42% 4 9% 29% 13% 2	5090
	21st to end	Day	51% 4 9% 22% 12% 2	5586
April	1st to 10th	Day	53% 4 9% 19% 12% 3	2211
	11th to 20th	Day	47% 5% 11% 19% 15% 4	2532
	21st to end	Day	48% 5% 10% 22% 12% 2	2600
May	1st to 10th	Day	54% 7% 10% 18% 9% 2	5897
	11th to 20th	Day	52% 6% 9% 20% 12% 1	5865
	21st to end	Day	44% 8% 12% 21% 13% 3	6447
June	1st to 10th	Day	40% 8% 13% 23% 16% 2	2600
	11th to 20th	Day	42% 8% 13% 21% 15% 1	2600
	21st to end	Day	40% 8% 14% 22% 15% 2	2600
July	1st to 10th	Day	38% 6% 11% 27% 17% 2	5835
	11th to 20th	Day	42% 8% 12% 26% 11% 1	5831
	21st to end	Day	44% 7% 11% 20% 17% 2	6240
August	1st to 10th	Day	39% 7% 14% 28% 11% 1	4221
	11th to 20th	Day	37% 7% 11% 31% 14% 1	4213
	21st to end	Day	29% 7% 14% 31% 16% 3	4591
September	1st to 10th	Day	35% 5% 11% 22% 22% 4	2220
	11th to 20th	Day	33% 5% 12% 26% 22% 2	2200
	21st to end	Day	45% 4 9% 23% 19% 1	2200
October	1st to 10th	Day	25% 4 9% 31% 29% 2	3427
	11th to 20th	Day	34% 4 12% 27% 19% 4	3240
	21st to end	Day	36% 3 12% 28% 20% 2	3538
November	1st to 10th	Day	37% 4 10% 29% 18% 3	1867
	11th to 20th	Day	51% 4 8% 21% 14% 2	1890
	21st to end	Day	54% 3 10% 20% 11% 1	1890
December	1st to 10th	Day	64% 3 11% 18% 4	3020
	11th to 20th	Day	65% 3 9% 18% 5%	3460
	21st to end	Day	70% 4 10% 12% 4	4565
January	1st to 10th	Night	70% 3 10% 13% 4	7636
	11th to 20th	Night	69% 3 8% 12% 7% 1	7680
	21st to end	Night	60% 3 11% 18% 6% 1	8401
February	1st to 10th	Night	58% 4 10% 19% 9% 1	2730
	11th to 20th	Night	60% 3 9% 17% 10% 1	2526
	21st to end	Night	59% 3 10% 17% 8% 2	2076
March	1st to 10th	Night	51% 4 6% 25% 12% 2	5165
	11th to 20th	Night	40% 4 10% 30% 14% 1	5090
	21st to end	Night	50% 4 8% 23% 13% 2	5588
April	1st to 10th	Night	47% 5% 11% 20% 15% 3	2212
	11th to 20th	Night	43% 4 11% 20% 17% 4	1833
	21st to end	Night	44% 5% 11% 23% 16% 2	1800
May	1st to 10th	Night	57% 6% 10% 15% 8% 4	4060
	11th to 20th	Night	44% 7% 11% 23% 13% 1	4033
	21st to end	Night	43% 7% 12% 25% 9% 3	4429
June	1st to 10th	Night	35% 8% 11% 24% 20% 3	1800
	11th to 20th	Night	35% 7% 14% 23% 18% 2	1800
	21st to end	Night	34% 7% 14% 24% 19% 3	1800
July	1st to 10th	Night	37% 6% 9% 25% 19% 3	4015
	11th to 20th	Night	40% 8% 16% 24% 11% 1	4006
	21st to end	Night	39% 8% 12% 20% 17% 3	4297
August	1st to 10th	Night	39% 7% 14% 28% 11% 1	2904
	11th to 20th	Night	38% 6% 10% 23% 21% 1	2902
	21st to end	Night	28% 7% 13% 31% 18% 3	3273
September	1st to 10th	Night	32% 6% 12% 21% 23% 7%	2175
	11th to 20th	Night	29% 6% 11% 25% 27% 3	2200
	21st to end	Night	42% 5% 8% 21% 22% 2	2200
October	1st to 10th	Night	28% 4 7% 28% 29% 3	3751
	11th to 20th	Night	30% 4 11% 26% 22% 7%	3899
	21st to end	Night	32% 3 8% 28% 25% 4	4252
November	1st to 10th	Night	37% 4 11% 26% 20% 4	2648
	11th to 20th	Night	49% 3 9% 21% 15% 3	2730
	21st to end	Night	55% 3 12% 20% 10% 1	2730
December	1st to 10th	Night	60% 4 12% 20% 4	4380
	11th to 20th	Night	64% 4 11% 16% 5%	4954
	21st to end	Night	68% 3 10% 14% 5%	6633

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	32% 22% 32% 11% 3 1	330
	11th to 20th	Day	36% 28% 30% 5% 1	330
	21st to end	Day	36% 24% 29% 9% 2	363
February	1st to 10th	Day	36% 22% 28% 11% 2	330
	11th to 20th	Day	41% 25% 28% 4 2	330
	21st to end	Day	33% 21% 40% 6%	273
March	1st to 10th	Day	31% 22% 27% 17% 3	474
	11th to 20th	Day	32% 20% 31% 12% 5%	540
	21st to end	Day	30% 20% 33% 13% 4	594
April	1st to 10th	Day	29% 20% 28% 15% 7% 1	504
	11th to 20th	Day	28% 17% 29% 16% 7% 3	492
	21st to end	Day	25% 18% 32% 18% 7% 1	500
May	1st to 10th	Day	27% 20% 27% 16% 7% 3	503
	11th to 20th	Day	22% 13% 30% 20% 9% 5%	527
	21st to end	Day	15% 9% 29% 26% 14% 6%	573
June	1st to 10th	Day	14% 10% 28% 29% 14% 5%	530
	11th to 20th	Day	16% 10% 24% 31% 12% 7%	530
	21st to end	Day	12% 8% 28% 28% 16% 6%	530
July	1st to 10th	Day	13% 5% 20% 26% 21% 15%	525
	11th to 20th	Day	10% 6% 25% 28% 21% 10%	524
	21st to end	Day	15% 5% 22% 25% 23% 10%	576
August	1st to 10th	Day	11% 5% 20% 30% 22% 11%	526
	11th to 20th	Day	13% 5% 20% 32% 19% 12%	519
	21st to end	Day	9% 5% 21% 30% 23% 12%	583
September	1st to 10th	Day	15% 5% 18% 27% 22% 12%	530
	11th to 20th	Day	10% 3 16% 27% 30% 14%	530
	21st to end	Day	22% 11% 23% 23% 17% 4	530
October	1st to 10th	Day	12% 9% 28% 26% 19% 6%	530
	11th to 20th	Day	19% 12% 32% 22% 13% 3	530
	21st to end	Day	26% 15% 33% 17% 9%	583
November	1st to 10th	Day	19% 16% 34% 22% 6% 2	345
	11th to 20th	Day	32% 18% 30% 14% 5% 2	330
	21st to end	Day	31% 19% 32% 14% 3	330
December	1st to 10th	Day	28% 22% 35% 9% 4 1	330
	11th to 20th	Day	28% 24% 36% 8% 3 1	330
	21st to end	Day	34% 22% 28% 12% 4	363
January	1st to 10th	Night	30% 17% 31% 18% 3	840
	11th to 20th	Night	32% 21% 27% 18% 3	840
	21st to end	Night	27% 19% 32% 20% 2	924
February	1st to 10th	Night	28% 15% 29% 26% 1	840
	11th to 20th	Night	32% 19% 31% 17% 1	823
	21st to end	Night	31% 17% 32% 18% 2	692
March	1st to 10th	Night	28% 14% 30% 24% 5%	840
	11th to 20th	Night	27% 18% 26% 21% 7% 1	840
	21st to end	Night	26% 15% 30% 22% 6%	924
April	1st to 10th	Night	24% 16% 32% 21% 6%	805
	11th to 20th	Night	19% 15% 32% 25% 9% 1	643
	21st to end	Night	19% 12% 35% 27% 6% 1	600
May	1st to 10th	Night	19% 11% 28% 29% 11% 2	600
	11th to 20th	Night	20% 9% 24% 30% 15% 1	591
	21st to end	Night	12% 5% 23% 32% 25% 3	650
June	1st to 10th	Night	11% 5% 23% 40% 22% 1	600
	11th to 20th	Night	12% 4 20% 37% 26% 2	600
	21st to end	Night	13% 4 21% 36% 25% 3	600
July	1st to 10th	Night	12% 3 15% 35% 29% 6%	585
	11th to 20th	Night	7% 3 17% 36% 32% 5%	582
	21st to end	Night	11% 3 16% 33% 34% 3	657
August	1st to 10th	Night	8% 3 13% 39% 33% 4	597
	11th to 20th	Night	9% 3 16% 38% 30% 5%	594
	21st to end	Night	10% 2 16% 30% 36% 6%	684
September	1st to 10th	Night	13% 3 17% 34% 27% 6%	800
	11th to 20th	Night	11% 3 13% 35% 33% 5%	800
	21st to end	Night	20% 5% 21% 30% 21% 3	800
October	1st to 10th	Night	13% 6% 20% 33% 25% 3	800
	11th to 20th	Night	19% 10% 27% 29% 14% 1	800
	21st to end	Night	23% 11% 27% 28% 10% 1	880
November	1st to 10th	Night	20% 10% 28% 28% 14% 1	820
	11th to 20th	Night	24% 15% 27% 25% 8% 1	840
	21st to end	Night	27% 13% 25% 28% 6% 1	840
December	1st to 10th	Night	31% 14% 30% 20% 5%	840
	11th to 20th	Night	28% 17% 27% 23% 5%	840
	21st to end	Night	31% 16% 28% 23% 2	924

Page generated at 2026-03-30 02:18:46. Version ac07

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