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 2024-01-16.

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	16% 9% 4 7% 6% 3 5% 5% 5% 7% 34%	74927
	Night	16% 9% 4 6% 5% 3 4 4 5% 7% 36%	74894
Transparency	Day	49% 5% 11% 21% 12% 2	74649
	Night	48% 5% 11% 21% 13% 2	74690
Seeing	Day	22% 13% 27% 21% 12% 5%	13834
	Night	21% 11% 25% 27% 14% 2	23989

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	19% 14% 6% 10% 7% 3 5% 4 5% 4 23%	1706
	11th to 20th	Day	18% 18% 8% 10% 6% 3 4 3 4 5% 21%	1671
	21st to end	Day	19% 17% 6% 10% 6% 3 5% 4 3 5% 22%	1782
February	1st to 10th	Day	24% 13% 5% 8% 6% 3 4 3 4 5% 25%	1620
	11th to 20th	Day	19% 13% 7% 10% 5% 3 3 5% 5% 6% 25%	1687
	21st to end	Day	20% 13% 6% 8% 4 3 3 3 4 5% 31%	1480
March	1st to 10th	Day	19% 10% 4 5% 5% 3 4 3 5% 7% 34%	1923
	11th to 20th	Day	18% 12% 4 7% 6% 3 5% 4 5% 6% 31%	1980
	21st to end	Day	21% 9% 4 7% 6% 3 5% 4 4 6% 31%	2178
April	1st to 10th	Day	15% 12% 3 6% 6% 4 4 4 4 7% 34%	1980
	11th to 20th	Day	17% 9% 3 6% 5% 3 5% 4 5% 6% 37%	2274
	21st to end	Day	19% 8% 3 6% 5% 3 4 5% 5% 7% 34%	2340
May	1st to 10th	Day	19% 8% 3 7% 7% 3 5% 4 5% 7% 30%	2340
	11th to 20th	Day	20% 8% 3 7% 6% 3 4 4 6% 8% 31%	2301
	21st to end	Day	10% 5% 2 5% 6% 3 6% 7% 7% 10% 39%	2531
June	1st to 10th	Day	13% 5% 3 4 6% 3 5% 6% 6% 9% 38%	2340
	11th to 20th	Day	11% 6% 2 5% 7% 5% 5% 6% 6% 10% 36%	2340
	21st to end	Day	12% 5% 3 5% 6% 4 6% 6% 7% 10% 36%	2340
July	1st to 10th	Day	12% 6% 2 6% 5% 4 6% 6% 6% 9% 36%	2340
	11th to 20th	Day	11% 6% 3 5% 6% 4 7% 5% 7% 10% 37%	2340
	21st to end	Day	12% 5% 3 5% 5% 4 6% 6% 7% 10% 36%	2547
August	1st to 10th	Day	9% 5% 3 6% 6% 4 7% 6% 8% 10% 36%	2327
	11th to 20th	Day	10% 6% 3 6% 6% 3 7% 7% 8% 11% 34%	2303
	21st to end	Day	9% 5% 3 6% 5% 4 6% 5% 5% 9% 43%	2534
September	1st to 10th	Day	16% 5% 2 5% 4 3 4 5% 5% 7% 46%	1998
	11th to 20th	Day	10% 6% 2 5% 5% 3 5% 4 5% 8% 48%	1980
	21st to end	Day	17% 6% 2 5% 5% 2 4 3 5% 6% 43%	1980
October	1st to 10th	Day	13% 6% 2 5% 5% 3 4 5% 5% 8% 43%	1892
	11th to 20th	Day	15% 7% 2 6% 6% 3 4 4 5% 7% 41%	1800
	21st to end	Day	22% 8% 3 6% 4 2 4 3 4 6% 37%	1980
November	1st to 10th	Day	12% 7% 2 5% 4 2 4 3 3 7% 50%	1686
	11th to 20th	Day	17% 12% 5% 6% 4 3 3 4 5% 6% 35%	1710
	21st to end	Day	17% 11% 5% 7% 5% 2 5% 5% 4 6% 34%	1710
December	1st to 10th	Day	23% 13% 7% 9% 6% 3 5% 3 4 4 22%	1710
	11th to 20th	Day	19% 15% 6% 10% 5% 3 4 3 5% 6% 24%	2153
	21st to end	Day	21% 21% 5% 9% 6% 3 5% 4 4 6% 15%	3124
January	1st to 10th	Night	18% 14% 7% 10% 7% 3 5% 4 4 5% 23%	2459
	11th to 20th	Night	21% 15% 6% 9% 7% 3 4 4 4 5% 23%	2417
	21st to end	Night	18% 14% 6% 9% 7% 3 4 4 5% 5% 25%	2574
February	1st to 10th	Night	23% 11% 4 7% 6% 3 5% 4 4 6% 27%	2340
	11th to 20th	Night	21% 13% 4 8% 6% 3 5% 3 5% 5% 26%	2155
	21st to end	Night	21% 14% 6% 6% 6% 2 5% 4 4 4 29%	1776
March	1st to 10th	Night	17% 10% 4 6% 5% 4 4 4 5% 5% 37%	2035
	11th to 20th	Night	19% 10% 4 6% 5% 2 4 4 5% 6% 35%	1980
	21st to end	Night	21% 10% 4 6% 4 2 4 4 5% 6% 35%	2178
April	1st to 10th	Night	15% 9% 2 6% 4 3 5% 5% 6% 7% 38%	1980
	11th to 20th	Night	15% 8% 2 4 6% 3 5% 4 6% 8% 39%	1649
	21st to end	Night	15% 8% 3 6% 6% 3 4 4 6% 8% 37%	1620
May	1st to 10th	Night	17% 7% 4 6% 5% 4 5% 6% 5% 8% 34%	1620
	11th to 20th	Night	16% 8% 4 6% 6% 3 5% 5% 3 7% 37%	1592
	21st to end	Night	9% 5% 2 5% 6% 3 5% 5% 8% 10% 42%	1744
June	1st to 10th	Night	10% 4 2 5% 4 3 5% 6% 7% 9% 44%	1620
	11th to 20th	Night	9% 4 2 6% 5% 3 4 5% 8% 10% 43%	1620
	21st to end	Night	11% 4 2 4 5% 3 5% 5% 6% 10% 45%	1620
July	1st to 10th	Night	10% 6% 2 5% 5% 4 5% 5% 7% 8% 45%	1620
	11th to 20th	Night	7% 4 2 5% 5% 3 5% 6% 7% 9% 47%	1620
	21st to end	Night	9% 5% 2 5% 7% 4 6% 6% 6% 7% 43%	1771
August	1st to 10th	Night	6% 5% 2 6% 5% 4 4 5% 8% 9% 46%	1611
	11th to 20th	Night	8% 6% 2 6% 5% 3 6% 5% 6% 8% 44%	1598
	21st to end	Night	9% 3 2 6% 4 3 3 4 6% 8% 51%	1803
September	1st to 10th	Night	11% 5% 2 5% 5% 3 3 4 4 7% 52%	1957
	11th to 20th	Night	10% 3 2 4 4 3 4 5% 5% 7% 53%	1980
	21st to end	Night	15% 7% 3 4 4 2 4 4 4 6% 46%	1980
October	1st to 10th	Night	11% 5% 3 5% 5% 3 4 4 5% 7% 49%	2066
	11th to 20th	Night	16% 7% 2 4 5% 3 4 5% 5% 8% 42%	2160
	21st to end	Night	22% 7% 3 5% 4 3 4 4 5% 5% 40%	2376
November	1st to 10th	Night	14% 6% 3 4 5% 2 3 3 4 6% 50%	2389
	11th to 20th	Night	17% 9% 4 6% 6% 3 5% 3 5% 6% 36%	2470
	21st to end	Night	18% 11% 4 6% 5% 3 5% 3 5% 6% 33%	2470
December	1st to 10th	Night	22% 14% 6% 8% 5% 3 4 4 4 5% 25%	2470
	11th to 20th	Night	18% 15% 6% 7% 5% 3 4 4 5% 6% 27%	3042
	21st to end	Night	21% 19% 6% 9% 6% 3 5% 4 4 5% 18%	4532

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% 5% 9% 14% 7%	1707
	11th to 20th	Day	67% 4 10% 14% 4	1671
	21st to end	Day	66% 3 10% 14% 6% 1	1782
February	1st to 10th	Day	63% 3 11% 16% 8% 1	1620
	11th to 20th	Day	60% 3 11% 17% 9%	1696
	21st to end	Day	57% 3 10% 19% 9% 1	1480
March	1st to 10th	Day	50% 3 10% 26% 10% 1	1923
	11th to 20th	Day	55% 4 9% 20% 10% 2	1980
	21st to end	Day	56% 5% 9% 19% 11% 1	2178
April	1st to 10th	Day	51% 4 10% 20% 12% 3	1980
	11th to 20th	Day	47% 5% 11% 17% 16% 4	2274
	21st to end	Day	50% 5% 10% 21% 11% 2	2340
May	1st to 10th	Day	52% 6% 12% 19% 9% 2	2340
	11th to 20th	Day	52% 6% 11% 17% 12% 2	2305
	21st to end	Day	38% 10% 16% 23% 13% 1	2531
June	1st to 10th	Day	40% 7% 13% 23% 15% 2	2340
	11th to 20th	Day	42% 8% 13% 21% 15% 1	2340
	21st to end	Day	41% 8% 14% 21% 14% 2	2340
July	1st to 10th	Day	43% 8% 13% 20% 15% 1	2275
	11th to 20th	Day	40% 8% 12% 24% 14% 2	2271
	21st to end	Day	40% 8% 13% 25% 13% 2	2405
August	1st to 10th	Day	39% 8% 13% 25% 13% 1	2314
	11th to 20th	Day	40% 8% 14% 27% 10% 1	2303
	21st to end	Day	36% 7% 13% 24% 15% 5%	2534
September	1st to 10th	Day	37% 6% 11% 22% 20% 5%	1998
	11th to 20th	Day	34% 6% 12% 26% 20% 2	1980
	21st to end	Day	43% 4 9% 24% 19% 1	1980
October	1st to 10th	Day	39% 6% 11% 24% 19% 1	1892
	11th to 20th	Day	43% 4 11% 25% 16% 1	1800
	21st to end	Day	50% 3 11% 22% 13% 1	1980
November	1st to 10th	Day	36% 4 10% 29% 17% 3	1686
	11th to 20th	Day	51% 3 8% 21% 14% 3	1710
	21st to end	Day	52% 4 11% 21% 12% 1	1710
December	1st to 10th	Day	66% 4 10% 16% 4	1710
	11th to 20th	Day	62% 3 10% 18% 7%	2150
	21st to end	Day	71% 4 11% 10% 4	3124
January	1st to 10th	Night	64% 4 8% 15% 8% 1	2459
	11th to 20th	Night	65% 4 12% 15% 4 1	2417
	21st to end	Night	61% 3 10% 18% 6% 2	2574
February	1st to 10th	Night	60% 4 10% 18% 7% 1	2340
	11th to 20th	Night	60% 4 9% 18% 9% 1	2156
	21st to end	Night	61% 3 9% 17% 8% 2	1776
March	1st to 10th	Night	50% 4 8% 23% 14% 1	2035
	11th to 20th	Night	50% 4 11% 23% 11% 2	1980
	21st to end	Night	51% 4 8% 21% 13% 3	2178
April	1st to 10th	Night	45% 5% 11% 21% 16% 3	1980
	11th to 20th	Night	43% 4 11% 19% 18% 5%	1649
	21st to end	Night	45% 6% 11% 22% 15% 2	1620
May	1st to 10th	Night	48% 7% 13% 18% 11% 3	1620
	11th to 20th	Night	48% 6% 10% 20% 13% 3	1593
	21st to end	Night	35% 8% 16% 26% 13% 2	1745
June	1st to 10th	Night	34% 8% 12% 25% 18% 3	1620
	11th to 20th	Night	35% 8% 15% 24% 17% 2	1620
	21st to end	Night	34% 6% 15% 25% 18% 3	1620
July	1st to 10th	Night	36% 8% 11% 22% 20% 3	1575
	11th to 20th	Night	32% 8% 14% 25% 19% 3	1566
	21st to end	Night	36% 9% 13% 24% 16% 1	1672
August	1st to 10th	Night	32% 8% 15% 29% 15% 1	1600
	11th to 20th	Night	35% 8% 15% 23% 18% 1	1598
	21st to end	Night	30% 6% 13% 28% 17% 6%	1803
September	1st to 10th	Night	33% 6% 12% 22% 20% 7%	1957
	11th to 20th	Night	30% 6% 11% 25% 25% 3	1980
	21st to end	Night	39% 5% 9% 22% 23% 2	1980
October	1st to 10th	Night	34% 6% 11% 25% 21% 3	2066
	11th to 20th	Night	40% 5% 10% 25% 18% 2	2160
	21st to end	Night	46% 4 9% 24% 14% 2	2376
November	1st to 10th	Night	37% 3 11% 24% 20% 4	2389
	11th to 20th	Night	49% 3 9% 20% 16% 3	2470
	21st to end	Night	53% 3 12% 21% 10% 1	2470
December	1st to 10th	Night	62% 5% 9% 18% 5% 1	2470
	11th to 20th	Night	58% 4 11% 20% 7%	3044
	21st to end	Night	69% 3 10% 14% 4	4532

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% 23% 33% 11% 3 1	270
	11th to 20th	Day	33% 25% 34% 7% 1	257
	21st to end	Day	35% 25% 28% 9% 3	264
February	1st to 10th	Day	43% 22% 25% 10% 1	240
	11th to 20th	Day	41% 27% 29% 3	240
	21st to end	Day	36% 21% 36% 6%	198
March	1st to 10th	Day	29% 21% 29% 18% 3	363
	11th to 20th	Day	30% 20% 31% 13% 6%	420
	21st to end	Day	32% 18% 33% 13% 4	462
April	1st to 10th	Day	25% 19% 30% 17% 9% 1	420
	11th to 20th	Day	29% 15% 29% 16% 8% 4	412
	21st to end	Day	27% 18% 30% 17% 6% 1	420
May	1st to 10th	Day	28% 20% 26% 15% 8% 3	423
	11th to 20th	Day	23% 12% 31% 20% 9% 4	447
	21st to end	Day	13% 8% 28% 28% 16% 7%	485
June	1st to 10th	Day	15% 8% 28% 28% 16% 5%	450
	11th to 20th	Day	16% 10% 23% 30% 12% 8%	450
	21st to end	Day	13% 9% 28% 29% 16% 6%	450
July	1st to 10th	Day	14% 4 18% 25% 21% 17%	445
	11th to 20th	Day	9% 5% 25% 29% 21% 11%	444
	21st to end	Day	15% 4 22% 27% 21% 11%	488
August	1st to 10th	Day	12% 5% 20% 30% 22% 11%	446
	11th to 20th	Day	14% 4 19% 32% 18% 12%	439
	21st to end	Day	10% 5% 22% 29% 22% 12%	495
September	1st to 10th	Day	16% 4 19% 26% 23% 12%	450
	11th to 20th	Day	12% 4 18% 26% 28% 13%	450
	21st to end	Day	21% 10% 23% 24% 18% 4	450
October	1st to 10th	Day	13% 10% 30% 25% 17% 6%	450
	11th to 20th	Day	20% 12% 32% 22% 12% 2	450
	21st to end	Day	28% 15% 31% 17% 9%	495
November	1st to 10th	Day	18% 16% 32% 24% 7% 2	284
	11th to 20th	Day	30% 17% 29% 16% 6% 2	270
	21st to end	Day	26% 19% 34% 17% 4	270
December	1st to 10th	Day	30% 19% 34% 10% 5% 1	270
	11th to 20th	Day	26% 24% 37% 9% 3 1	270
	21st to end	Day	35% 21% 27% 13% 5%	297
January	1st to 10th	Night	29% 18% 32% 18% 3	760
	11th to 20th	Night	31% 19% 27% 19% 3	744
	21st to end	Night	27% 18% 32% 21% 2	792
February	1st to 10th	Night	30% 15% 29% 24% 1	720
	11th to 20th	Night	32% 18% 32% 17% 1	703
	21st to end	Night	32% 18% 31% 18% 2	592
March	1st to 10th	Night	26% 14% 31% 24% 5%	720
	11th to 20th	Night	27% 18% 27% 21% 7% 1	720
	21st to end	Night	26% 15% 30% 23% 7%	792
April	1st to 10th	Night	23% 16% 32% 22% 7%	720
	11th to 20th	Night	19% 14% 32% 25% 10% 1	579
	21st to end	Night	20% 12% 35% 27% 6% 1	540
May	1st to 10th	Night	19% 11% 29% 27% 11% 2	540
	11th to 20th	Night	20% 9% 25% 31% 14% 1	531
	21st to end	Night	12% 4 21% 33% 27% 3	584
June	1st to 10th	Night	10% 4 23% 40% 21% 1	540
	11th to 20th	Night	11% 4 20% 36% 26% 2	540
	21st to end	Night	13% 3 21% 36% 24% 2	540
July	1st to 10th	Night	12% 3 15% 33% 30% 6%	525
	11th to 20th	Night	7% 2 17% 36% 32% 6%	522
	21st to end	Night	11% 3 16% 32% 36% 3	591
August	1st to 10th	Night	8% 3 12% 39% 34% 4	537
	11th to 20th	Night	9% 2 16% 37% 31% 5%	534
	21st to end	Night	11% 2 16% 30% 35% 6%	615
September	1st to 10th	Night	13% 3 17% 33% 28% 7%	720
	11th to 20th	Night	12% 3 14% 33% 33% 6%	720
	21st to end	Night	17% 6% 21% 31% 22% 3	720
October	1st to 10th	Night	13% 7% 21% 33% 24% 3	720
	11th to 20th	Night	20% 10% 27% 28% 14% 1	720
	21st to end	Night	25% 11% 26% 28% 10%	792
November	1st to 10th	Night	20% 10% 26% 28% 16% 1	740
	11th to 20th	Night	23% 15% 27% 26% 8% 1	760
	21st to end	Night	26% 12% 26% 29% 6% 1	760
December	1st to 10th	Night	32% 14% 29% 19% 5%	760
	11th to 20th	Night	27% 17% 27% 23% 6%	760
	21st to end	Night	31% 15% 28% 24% 2	836

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