Richland Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Richland Center clear sky chart from 2005-11-06 to 2026-07-16.

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	12% 9% 3 8% 5% 4 5% 4 6% 7% 38%	138622
	Night	12% 9% 4 8% 5% 4 4 4 5% 6% 38%	134402
Transparency	Day	45% 3 11% 26% 13% 1	142121
	Night	47% 3 11% 24% 15% 2	138979
Seeing	Day	17% 12% 29% 25% 13% 4	18268
	Night	18% 9% 30% 31% 11% 1	28108

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	8% 13% 7% 16% 7% 6% 5% 3 4 6% 24%	4691
	11th to 20th	Day	6% 13% 6% 10% 6% 4 6% 7% 7% 7% 29%	4710
	21st to end	Day	9% 14% 5% 8% 6% 4 4 3 4 6% 38%	5554
February	1st to 10th	Day	10% 13% 6% 10% 5% 4 5% 4 5% 7% 32%	1890
	11th to 20th	Day	12% 12% 4 7% 5% 3 5% 4 5% 7% 36%	1916
	21st to end	Day	12% 13% 4 10% 6% 5% 4 3 4 6% 33%	1730
March	1st to 10th	Day	15% 8% 2 5% 4 3 3 2 4 6% 47%	4580
	11th to 20th	Day	12% 6% 2 7% 4 4 4 3 6% 8% 44%	5062
	21st to end	Day	24% 11% 3 8% 4 3 4 3 4 5% 30%	5927
April	1st to 10th	Day	19% 13% 3 7% 4 4 4 4 5% 6% 31%	2520
	11th to 20th	Day	17% 11% 3 8% 5% 4 4 3 5% 6% 32%	2494
	21st to end	Day	19% 9% 3 7% 5% 4 5% 3 6% 6% 32%	2541
May	1st to 10th	Day	12% 7% 2 7% 5% 5% 4 4 7% 8% 41%	8125
	11th to 20th	Day	14% 6% 3 7% 4 4 4 3 6% 8% 42%	8222
	21st to end	Day	15% 7% 3 7% 4 4 5% 4 5% 8% 38%	9047
June	1st to 10th	Day	12% 5% 2 6% 3 4 5% 4 6% 9% 44%	2940
	11th to 20th	Day	12% 6% 2 7% 5% 5% 5% 4 6% 9% 41%	2940
	21st to end	Day	13% 6% 2 7% 5% 5% 5% 4 6% 9% 39%	2940
July	1st to 10th	Day	8% 5% 2 7% 5% 5% 6% 4 7% 10% 39%	6500
	11th to 20th	Day	7% 6% 2 6% 4 4 5% 4 7% 8% 47%	6431
	21st to end	Day	9% 6% 3 8% 5% 5% 5% 4 7% 9% 39%	6924
August	1st to 10th	Day	7% 6% 3 7% 6% 5% 6% 4 6% 9% 41%	4399
	11th to 20th	Day	12% 6% 2 5% 4 4 4 4 5% 7% 47%	4040
	21st to end	Day	9% 6% 2 6% 3 4 5% 4 7% 9% 45%	4312
September	1st to 10th	Day	13% 5% 2 5% 4 4 4 4 6% 7% 45%	2400
	11th to 20th	Day	13% 5% 2 5% 4 4 4 4 4 7% 47%	2380
	21st to end	Day	13% 6% 2 7% 4 4 4 3 5% 7% 45%	2170
October	1st to 10th	Day	14% 6% 2 5% 4 4 4 3 5% 7% 47%	2000
	11th to 20th	Day	18% 9% 3 7% 4 4 4 3 5% 6% 38%	2000
	21st to end	Day	16% 11% 3 7% 4 4 4 3 4 6% 40%	2060
November	1st to 10th	Day	13% 8% 3 7% 4 4 4 3 5% 7% 42%	1852
	11th to 20th	Day	15% 12% 4 9% 5% 4 4 4 5% 5% 34%	1797
	21st to end	Day	14% 12% 4 9% 4 4 4 3 4 6% 37%	1680
December	1st to 10th	Day	8% 9% 5% 11% 5% 5% 5% 4 6% 7% 35%	2690
	11th to 20th	Day	14% 14% 4 11% 6% 5% 6% 3 6% 7% 24%	3088
	21st to end	Day	20% 22% 8% 13% 5% 4 4 3 3 4 15%	4070
January	1st to 10th	Night	9% 12% 6% 13% 6% 5% 4 3 4 5% 31%	8232
	11th to 20th	Night	8% 14% 7% 14% 6% 5% 6% 5% 7% 5% 22%	8280
	21st to end	Night	9% 13% 6% 9% 7% 5% 4 4 5% 6% 33%	8659
February	1st to 10th	Night	9% 13% 5% 11% 5% 5% 4 4 5% 6% 32%	2730
	11th to 20th	Night	11% 10% 4 9% 5% 4 5% 4 4 6% 39%	2589
	21st to end	Night	15% 11% 3 9% 4 4 5% 3 4 6% 35%	2076
March	1st to 10th	Night	15% 8% 4 7% 4 4 4 3 4 5% 43%	5493
	11th to 20th	Night	11% 7% 2 6% 4 4 4 4 5% 8% 45%	5148
	21st to end	Night	23% 13% 4 9% 4 4 4 3 4 5% 28%	5243
April	1st to 10th	Night	18% 9% 4 7% 5% 4 3 3 4 5% 38%	2100
	11th to 20th	Night	20% 8% 2 6% 5% 4 4 3 4 7% 37%	2075
	21st to end	Night	19% 8% 2 7% 4 4 4 3 6% 7% 36%	2079
May	1st to 10th	Night	13% 6% 2 6% 4 3 4 4 5% 8% 45%	4751
	11th to 20th	Night	13% 6% 2 6% 4 4 4 3 6% 8% 46%	4670
	21st to end	Night	14% 7% 3 8% 5% 4 4 4 5% 7% 38%	5139
June	1st to 10th	Night	9% 6% 2 6% 4 4 4 5% 7% 8% 45%	1680
	11th to 20th	Night	10% 7% 2 5% 3 4 4 3 7% 8% 46%	1680
	21st to end	Night	10% 6% 2 5% 4 4 4 3 5% 8% 48%	1680
July	1st to 10th	Night	11% 7% 2 7% 4 4 4 4 6% 8% 43%	3698
	11th to 20th	Night	6% 5% 2 6% 3 4 4 4 5% 8% 54%	3657
	21st to end	Night	7% 5% 2 6% 5% 5% 5% 4 7% 8% 47%	3947
August	1st to 10th	Night	10% 5% 2 5% 4 4 5% 4 6% 8% 49%	2756
	11th to 20th	Night	10% 6% 2 6% 4 4 4 3 6% 7% 49%	3013
	21st to end	Night	10% 5% 2 6% 4 4 4 4 5% 8% 49%	3586
September	1st to 10th	Night	9% 5% 2 6% 4 4 4 3 5% 7% 53%	2000
	11th to 20th	Night	12% 5% 2 5% 4 4 3 3 4 7% 52%	2000
	21st to end	Night	10% 6% 2 5% 4 3 4 3 5% 7% 52%	2227
October	1st to 10th	Night	11% 7% 2 5% 4 5% 3 3 4 5% 51%	2400
	11th to 20th	Night	16% 8% 2 6% 4 4 4 3 5% 5% 42%	2400
	21st to end	Night	17% 9% 3 6% 4 4 3 4 6% 7% 38%	2780
November	1st to 10th	Night	14% 8% 3 6% 4 3 4 3 5% 6% 44%	2666
	11th to 20th	Night	14% 11% 4 9% 5% 4 4 4 5% 5% 34%	2819
	21st to end	Night	16% 11% 3 8% 5% 3 3 3 5% 6% 36%	2940
December	1st to 10th	Night	8% 8% 3 10% 6% 5% 5% 4 6% 7% 38%	4720
	11th to 20th	Night	14% 17% 5% 10% 5% 5% 5% 4 5% 5% 25%	5339
	21st to end	Night	22% 17% 6% 13% 6% 4 4 3 4 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	63% 2 13% 15% 7%	4692
	11th to 20th	Day	53% 2 9% 19% 17% 1	4710
	21st to end	Day	50% 2 12% 26% 11%	5554
February	1st to 10th	Day	54% 2 13% 19% 12% 1	1890
	11th to 20th	Day	48% 2 11% 27% 9% 3	1925
	21st to end	Day	54% 2 9% 21% 10% 3	1730
March	1st to 10th	Day	41% 1 12% 29% 13% 4	4580
	11th to 20th	Day	39% 2 12% 31% 13% 2	5062
	21st to end	Day	58% 2 10% 17% 11% 2	5929
April	1st to 10th	Day	55% 3 10% 21% 11% 1	2520
	11th to 20th	Day	54% 2 9% 22% 12% 2	2494
	21st to end	Day	53% 2 11% 21% 12% 1	2541
May	1st to 10th	Day	41% 3 7% 30% 17% 2	8163
	11th to 20th	Day	42% 4 8% 30% 16% 1	8226
	21st to end	Day	45% 3 9% 26% 14% 3	9061
June	1st to 10th	Day	37% 3 12% 30% 16% 2	2940
	11th to 20th	Day	41% 3 13% 26% 17% 1	2940
	21st to end	Day	42% 4 14% 24% 14% 1	2940
July	1st to 10th	Day	39% 6% 15% 32% 8% 1	6431
	11th to 20th	Day	33% 5% 13% 33% 16% 1	6356
	21st to end	Day	40% 6% 13% 23% 16% 1	6728
August	1st to 10th	Day	39% 4 14% 28% 14% 1	4384
	11th to 20th	Day	36% 4 12% 33% 14% 1	4079
	21st to end	Day	35% 4 13% 32% 14% 1	4311
September	1st to 10th	Day	38% 3 13% 27% 18% 2	2400
	11th to 20th	Day	37% 3 12% 32% 14% 1	2380
	21st to end	Day	40% 2 10% 31% 16% 1	2170
October	1st to 10th	Day	25% 2 6% 42% 24% 1	3260
	11th to 20th	Day	38% 2 9% 28% 21% 3	3240
	21st to end	Day	42% 2 11% 30% 13% 2	3311
November	1st to 10th	Day	43% 2 12% 26% 15% 2	1852
	11th to 20th	Day	53% 2 11% 24% 10% 1	1797
	21st to end	Day	51% 2 15% 23% 8% 1	1680
December	1st to 10th	Day	49% 3 18% 23% 7% 1	2690
	11th to 20th	Day	60% 2 12% 18% 6% 2	3085
	21st to end	Day	75% 2 7% 11% 5%	4070
January	1st to 10th	Night	56% 2 13% 20% 7%	8233
	11th to 20th	Night	62% 2 9% 12% 14%	8280
	21st to end	Night	53% 2 11% 21% 12%	8659
February	1st to 10th	Night	54% 2 11% 20% 11% 1	2730
	11th to 20th	Night	48% 3 10% 25% 13% 1	2590
	21st to end	Night	52% 2 10% 23% 12% 2	2076
March	1st to 10th	Night	47% 2 10% 24% 11% 6%	5493
	11th to 20th	Night	39% 2 10% 31% 15% 3	5148
	21st to end	Night	61% 2 8% 17% 11% 1	5243
April	1st to 10th	Night	50% 2 9% 23% 15% 2	2100
	11th to 20th	Night	49% 2 7% 21% 18% 3	2075
	21st to end	Night	48% 2 10% 24% 14% 3	2079
May	1st to 10th	Night	39% 3 8% 25% 25% 1	4775
	11th to 20th	Night	38% 3 12% 24% 20% 2	4671
	21st to end	Night	45% 3 8% 24% 17% 3	5149
June	1st to 10th	Night	36% 3 12% 30% 18% 1	1680
	11th to 20th	Night	37% 3 11% 27% 20% 2	1680
	21st to end	Night	36% 3 13% 26% 17% 4	1680
July	1st to 10th	Night	38% 5% 13% 29% 13% 2	3660
	11th to 20th	Night	29% 5% 14% 32% 19% 1	3612
	21st to end	Night	32% 7% 17% 23% 19% 2	3832
August	1st to 10th	Night	34% 4 13% 29% 19% 1	2747
	11th to 20th	Night	34% 5% 12% 32% 16% 1	3040
	21st to end	Night	35% 4 12% 27% 19% 3	3586
September	1st to 10th	Night	33% 3 10% 29% 24% 1	2000
	11th to 20th	Night	34% 2 10% 35% 16% 2	2000
	21st to end	Night	34% 2 9% 32% 23% 1	2227
October	1st to 10th	Night	27% 2 6% 35% 28% 2	3920
	11th to 20th	Night	34% 2 9% 29% 24% 1	3899
	21st to end	Night	45% 2 9% 28% 15% 1	4479
November	1st to 10th	Night	42% 3 12% 26% 16% 2	2666
	11th to 20th	Night	52% 2 12% 21% 11% 2	2819
	21st to end	Night	51% 2 13% 25% 8% 1	2940
December	1st to 10th	Night	46% 3 18% 26% 7% 1	4720
	11th to 20th	Night	61% 3 12% 17% 7% 1	5341
	21st to end	Night	72% 2 7% 13% 6%	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	16% 15% 35% 23% 8% 2	330
	11th to 20th	Day	20% 16% 40% 17% 5% 1	330
	21st to end	Day	20% 19% 32% 25% 4 1	363
February	1st to 10th	Day	17% 20% 39% 17% 6% 1	330
	11th to 20th	Day	19% 24% 33% 18% 6%	330
	21st to end	Day	23% 17% 43% 14% 2	273
March	1st to 10th	Day	21% 19% 39% 15% 5%	330
	11th to 20th	Day	22% 19% 37% 15% 6% 2	330
	21st to end	Day	28% 14% 32% 18% 7% 1	513
April	1st to 10th	Day	29% 16% 31% 21% 3	540
	11th to 20th	Day	26% 20% 26% 17% 10% 1	532
	21st to end	Day	22% 15% 29% 23% 9% 1	540
May	1st to 10th	Day	18% 14% 31% 25% 10% 1	718
	11th to 20th	Day	21% 13% 26% 24% 13% 3	775
	21st to end	Day	18% 11% 25% 25% 15% 7%	844
June	1st to 10th	Day	12% 7% 25% 34% 18% 4	780
	11th to 20th	Day	15% 10% 32% 26% 13% 4	780
	21st to end	Day	15% 10% 28% 29% 15% 4	780
July	1st to 10th	Day	8% 4 19% 31% 25% 12%	771
	11th to 20th	Day	9% 6% 25% 32% 20% 8%	744
	21st to end	Day	8% 4 26% 34% 20% 7%	794
August	1st to 10th	Day	7% 3 22% 34% 24% 10%	726
	11th to 20th	Day	15% 5% 19% 27% 22% 12%	636
	21st to end	Day	11% 7% 20% 30% 23% 8%	583
September	1st to 10th	Day	16% 8% 20% 30% 19% 7%	530
	11th to 20th	Day	13% 4 20% 33% 23% 7%	530
	21st to end	Day	17% 9% 27% 23% 19% 5%	500
October	1st to 10th	Day	17% 11% 27% 30% 12% 2	330
	11th to 20th	Day	25% 17% 34% 18% 5% 1	330
	21st to end	Day	22% 16% 34% 19% 8% 1	363
November	1st to 10th	Day	16% 15% 39% 20% 7% 2	330
	11th to 20th	Day	21% 20% 35% 16% 8% 1	330
	21st to end	Day	24% 14% 37% 21% 4	330
December	1st to 10th	Day	15% 19% 39% 20% 6% 1	330
	11th to 20th	Day	19% 16% 38% 19% 7% 1	330
	21st to end	Day	28% 17% 35% 16% 3 1	363
January	1st to 10th	Night	14% 15% 37% 26% 8% 1	1050
	11th to 20th	Night	19% 14% 35% 27% 5% 1	1050
	21st to end	Night	19% 10% 36% 28% 5% 1	1155
February	1st to 10th	Night	16% 12% 37% 28% 6% 1	1050
	11th to 20th	Night	17% 13% 37% 27% 5%	955
	21st to end	Night	21% 14% 36% 24% 4	692
March	1st to 10th	Night	21% 12% 34% 26% 6%	840
	11th to 20th	Night	20% 12% 32% 28% 7%	662
	21st to end	Night	25% 10% 30% 29% 6%	693
April	1st to 10th	Night	22% 12% 36% 25% 5%	630
	11th to 20th	Night	24% 10% 30% 30% 6%	623
	21st to end	Night	22% 10% 29% 30% 9% 1	630
May	1st to 10th	Night	18% 8% 32% 34% 7%	630
	11th to 20th	Night	21% 6% 28% 33% 12% 1	621
	21st to end	Night	15% 5% 26% 38% 14% 1	683
June	1st to 10th	Night	10% 6% 26% 43% 14%	630
	11th to 20th	Night	13% 4 32% 37% 13%	630
	21st to end	Night	12% 6% 22% 42% 17% 1	630
July	1st to 10th	Night	9% 3 13% 40% 32% 3	615
	11th to 20th	Night	8% 5% 18% 43% 24% 2	597
	21st to end	Night	8% 2 16% 47% 25% 2	657
August	1st to 10th	Night	6% 3 16% 45% 29% 1	597
	11th to 20th	Night	11% 3 13% 42% 26% 5%	594
	21st to end	Night	11% 3 17% 42% 24% 3	660
September	1st to 10th	Night	10% 5% 20% 41% 18% 6%	600
	11th to 20th	Night	13% 4 20% 32% 27% 4	600
	21st to end	Night	13% 8% 24% 38% 18% 1	800
October	1st to 10th	Night	15% 6% 29% 31% 18% 1	800
	11th to 20th	Night	21% 10% 31% 30% 9%	800
	21st to end	Night	24% 10% 27% 30% 8%	880
November	1st to 10th	Night	18% 11% 33% 27% 10% 1	820
	11th to 20th	Night	21% 13% 37% 23% 6% 1	929
	21st to end	Night	24% 12% 31% 27% 6%	1050
December	1st to 10th	Night	20% 12% 38% 24% 6% 1	1050
	11th to 20th	Night	23% 12% 35% 25% 5%	1050
	21st to end	Night	29% 11% 31% 24% 4	1155

Page generated at 2026-07-13 02:14:48. Version ac07

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