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 2025-03-12.

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% 37%	109019
	Night	13% 10% 4 8% 5% 4 4 4 5% 6% 38%	110213
Transparency	Day	46% 3 11% 26% 13% 1	112563
	Night	47% 2 11% 24% 15% 1	114809
Seeing	Day	17% 11% 29% 25% 14% 4	16312
	Night	18% 9% 30% 31% 11% 1	26372

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	6% 12% 7% 17% 7% 6% 5% 3 4 5% 26%	3617
	11th to 20th	Day	7% 12% 6% 10% 6% 4 6% 6% 7% 7% 28%	3620
	21st to end	Day	11% 17% 6% 8% 4 3 3 3 4 6% 35%	4285
February	1st to 10th	Day	11% 13% 5% 9% 5% 4 5% 4 5% 7% 32%	1800
	11th to 20th	Day	12% 12% 4 7% 5% 3 5% 4 5% 7% 35%	1822
	21st to end	Day	12% 13% 4 9% 6% 6% 4 3 4 6% 34%	1650
March	1st to 10th	Day	15% 9% 3 5% 4 3 3 2 4 6% 46%	3220
	11th to 20th	Day	10% 7% 2 8% 5% 4 4 3 5% 7% 44%	3477
	21st to end	Day	24% 13% 3 9% 4 3 4 3 4 6% 28%	4053
April	1st to 10th	Day	20% 12% 3 7% 4 4 4 4 5% 6% 31%	2280
	11th to 20th	Day	17% 11% 3 8% 6% 4 4 3 5% 6% 34%	2254
	21st to end	Day	20% 9% 3 7% 5% 4 5% 3 5% 7% 32%	2299
May	1st to 10th	Day	17% 8% 2 7% 5% 4 4 4 6% 7% 36%	4354
	11th to 20th	Day	15% 7% 2 6% 3 4 4 3 6% 7% 42%	4399
	21st to end	Day	16% 7% 3 6% 4 5% 5% 4 6% 7% 37%	4824
June	1st to 10th	Day	12% 5% 2 6% 3 4 5% 4 6% 9% 45%	2660
	11th to 20th	Day	11% 6% 2 7% 5% 5% 5% 4 5% 9% 41%	2660
	21st to end	Day	12% 6% 2 7% 4 5% 5% 4 6% 8% 39%	2660
July	1st to 10th	Day	10% 6% 3 8% 6% 6% 6% 5% 7% 9% 36%	4440
	11th to 20th	Day	5% 4 2 5% 4 4 5% 4 8% 10% 49%	4440
	21st to end	Day	8% 6% 3 7% 5% 5% 5% 4 7% 9% 41%	4813
August	1st to 10th	Day	7% 6% 3 7% 6% 5% 6% 4 6% 9% 40%	4264
	11th to 20th	Day	12% 6% 2 5% 4 4 4 4 5% 7% 48%	3914
	21st to end	Day	9% 6% 2 6% 3 4 5% 4 7% 9% 44%	4180
September	1st to 10th	Day	13% 6% 2 6% 4 4 4 4 6% 7% 45%	2280
	11th to 20th	Day	13% 5% 2 5% 4 4 4 4 4 7% 47%	2261
	21st to end	Day	13% 6% 3 6% 5% 4 3 3 5% 7% 44%	2062
October	1st to 10th	Day	14% 6% 2 5% 4 4 5% 3 5% 7% 46%	1900
	11th to 20th	Day	18% 9% 3 6% 4 4 4 3 5% 6% 38%	1900
	21st to end	Day	16% 10% 3 7% 4 3 4 3 4 6% 40%	1957
November	1st to 10th	Day	13% 8% 3 6% 4 4 4 3 5% 7% 42%	1762
	11th to 20th	Day	15% 12% 4 9% 5% 4 4 4 5% 5% 33%	1712
	21st to end	Day	14% 12% 4 8% 4 4 4 3 4 6% 38%	1600
December	1st to 10th	Day	8% 9% 5% 11% 5% 5% 5% 4 6% 7% 36%	2610
	11th to 20th	Day	14% 14% 4 11% 6% 5% 6% 3 6% 7% 24%	3008
	21st to end	Day	20% 22% 8% 13% 5% 4 4 3 3 4 15%	3982
January	1st to 10th	Night	8% 11% 7% 14% 7% 5% 4 3 5% 5% 31%	6348
	11th to 20th	Night	10% 13% 6% 13% 6% 5% 5% 6% 8% 6% 22%	6360
	21st to end	Night	11% 15% 7% 10% 6% 4 3 3 5% 5% 30%	6692
February	1st to 10th	Night	9% 14% 5% 11% 5% 5% 4 4 5% 5% 32%	2600
	11th to 20th	Night	11% 10% 4 9% 5% 5% 5% 4 4 6% 39%	2463
	21st to end	Night	16% 11% 3 8% 4 4 5% 3 4 6% 35%	1980
March	1st to 10th	Night	16% 8% 4 7% 4 4 4 3 4 5% 42%	3853
	11th to 20th	Night	11% 6% 2 7% 4 4 4 4 6% 8% 44%	3540
	21st to end	Night	25% 12% 4 9% 5% 4 4 2 4 4 28%	3577
April	1st to 10th	Night	17% 10% 3 7% 5% 4 3 3 5% 5% 38%	1900
	11th to 20th	Night	19% 8% 2 6% 5% 4 4 3 5% 7% 37%	1875
	21st to end	Night	19% 7% 2 7% 4 4 4 3 7% 7% 36%	1881
May	1st to 10th	Night	18% 8% 3 6% 4 4 4 5% 5% 7% 36%	2547
	11th to 20th	Night	12% 7% 2 7% 4 4 4 3 6% 7% 45%	2506
	21st to end	Night	11% 6% 2 7% 4 4 4 4 6% 8% 45%	2743
June	1st to 10th	Night	9% 6% 2 5% 4 4 4 5% 8% 8% 45%	1520
	11th to 20th	Night	10% 7% 3 5% 3 4 4 3 7% 8% 47%	1520
	21st to end	Night	9% 6% 2 5% 4 3 4 3 5% 8% 48%	1520
July	1st to 10th	Night	12% 7% 2 7% 4 4 4 3 6% 8% 44%	2530
	11th to 20th	Night	4 3 1 5% 3 4 4 4 6% 9% 57%	2530
	21st to end	Night	6% 4 2 6% 5% 5% 5% 4 7% 9% 47%	2750
August	1st to 10th	Night	10% 5% 2 5% 4 4 5% 4 6% 8% 48%	2671
	11th to 20th	Night	10% 6% 1 6% 4 4 4 3 6% 7% 50%	2919
	21st to end	Night	10% 5% 2 6% 4 4 4 4 5% 8% 49%	3476
September	1st to 10th	Night	9% 5% 2 6% 4 4 4 3 5% 6% 53%	1900
	11th to 20th	Night	12% 5% 2 5% 4 3 3 3 4 7% 52%	1900
	21st to end	Night	10% 6% 2 5% 4 3 4 3 5% 7% 51%	2115
October	1st to 10th	Night	11% 6% 2 5% 3 4 3 3 4 6% 51%	2280
	11th to 20th	Night	16% 7% 2 6% 4 4 4 4 5% 5% 43%	2280
	21st to end	Night	18% 9% 3 6% 4 4 3 4 6% 7% 37%	2641
November	1st to 10th	Night	15% 8% 3 6% 4 3 4 3 5% 6% 44%	2536
	11th to 20th	Night	15% 11% 4 9% 6% 4 4 4 5% 5% 34%	2685
	21st to end	Night	16% 10% 3 8% 5% 3 3 3 5% 6% 37%	2800
December	1st to 10th	Night	8% 8% 3 10% 6% 6% 5% 4 6% 7% 38%	4580
	11th to 20th	Night	15% 17% 5% 10% 5% 5% 4 4 5% 5% 25%	5199
	21st to end	Night	22% 17% 6% 13% 6% 5% 4 3 4 4 17%	6996

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	62% 2 11% 18% 7%	3618
	11th to 20th	Day	55% 2 10% 14% 19% 1	3620
	21st to end	Day	53% 2 13% 20% 11%	4285
February	1st to 10th	Day	53% 2 12% 19% 12% 1	1800
	11th to 20th	Day	49% 2 12% 26% 9% 2	1831
	21st to end	Day	55% 2 9% 21% 11% 3	1650
March	1st to 10th	Day	42% 1 11% 29% 14% 3	3220
	11th to 20th	Day	41% 1 9% 33% 13% 1	3477
	21st to end	Day	61% 1 11% 17% 9% 2	4053
April	1st to 10th	Day	55% 2 10% 21% 11% 1	2280
	11th to 20th	Day	53% 2 8% 22% 13% 2	2254
	21st to end	Day	53% 2 11% 20% 13% 1	2299
May	1st to 10th	Day	49% 2 8% 26% 15% 1	4395
	11th to 20th	Day	43% 2 8% 35% 11%	4403
	21st to end	Day	46% 2 8% 26% 15% 2	4837
June	1st to 10th	Day	37% 3 13% 30% 16% 2	2660
	11th to 20th	Day	41% 3 12% 25% 18% 1	2660
	21st to end	Day	42% 4 13% 25% 15% 2	2660
July	1st to 10th	Day	44% 5% 14% 28% 8% 2	4371
	11th to 20th	Day	29% 5% 15% 33% 18% 1	4365
	21st to end	Day	39% 6% 13% 23% 18% 2	4662
August	1st to 10th	Day	39% 4 14% 28% 14% 1	4249
	11th to 20th	Day	36% 4 12% 33% 14% 1	3953
	21st to end	Day	35% 4 13% 32% 14% 1	4179
September	1st to 10th	Day	39% 3 13% 26% 18% 2	2280
	11th to 20th	Day	37% 2 12% 32% 15% 1	2261
	21st to end	Day	40% 2 11% 31% 15% 1	2062
October	1st to 10th	Day	25% 2 6% 42% 24% 1	3160
	11th to 20th	Day	38% 2 9% 28% 21% 2	3140
	21st to end	Day	42% 2 11% 30% 13% 2	3208
November	1st to 10th	Day	44% 2 12% 26% 14% 2	1762
	11th to 20th	Day	54% 2 11% 23% 10% 1	1712
	21st to end	Day	50% 2 15% 23% 8% 1	1600
December	1st to 10th	Day	48% 3 18% 23% 7% 1	2610
	11th to 20th	Day	60% 2 12% 18% 6% 2	3005
	21st to end	Day	75% 2 7% 11% 5%	3982
January	1st to 10th	Night	56% 2 10% 22% 9% 1	6348
	11th to 20th	Night	60% 3 9% 13% 15%	6360
	21st to end	Night	57% 2 11% 18% 12%	6692
February	1st to 10th	Night	55% 2 11% 20% 11% 2	2600
	11th to 20th	Night	49% 3 10% 24% 13% 1	2464
	21st to end	Night	52% 2 10% 22% 12% 2	1980
March	1st to 10th	Night	47% 2 9% 27% 11% 5%	3853
	11th to 20th	Night	39% 1 8% 30% 19% 2	3540
	21st to end	Night	62% 1 6% 20% 10% 1	3577
April	1st to 10th	Night	50% 2 9% 23% 15% 2	1900
	11th to 20th	Night	49% 2 7% 21% 19% 3	1875
	21st to end	Night	48% 2 10% 23% 14% 3	1881
May	1st to 10th	Night	49% 2 10% 18% 21% 1	2571
	11th to 20th	Night	41% 1 10% 27% 19% 2	2507
	21st to end	Night	39% 2 11% 25% 21% 2	2751
June	1st to 10th	Night	35% 2 13% 30% 18% 1	1520
	11th to 20th	Night	36% 2 11% 28% 21% 2	1520
	21st to end	Night	35% 3 13% 27% 18% 4	1520
July	1st to 10th	Night	39% 4 16% 27% 12% 3	2490
	11th to 20th	Night	25% 5% 16% 34% 18% 2	2482
	21st to end	Night	32% 7% 16% 23% 20% 3	2662
August	1st to 10th	Night	35% 4 13% 29% 19% 1	2662
	11th to 20th	Night	34% 5% 12% 32% 16% 1	2946
	21st to end	Night	35% 3 12% 27% 19% 3	3476
September	1st to 10th	Night	33% 3 10% 28% 24% 2	1900
	11th to 20th	Night	34% 2 10% 35% 17% 2	1900
	21st to end	Night	34% 2 9% 32% 22% 1	2115
October	1st to 10th	Night	27% 2 6% 36% 28% 1	3800
	11th to 20th	Night	33% 2 10% 30% 24% 1	3779
	21st to end	Night	45% 2 10% 28% 15% 1	4340
November	1st to 10th	Night	42% 2 12% 26% 16% 2	2536
	11th to 20th	Night	53% 2 12% 20% 11% 2	2685
	21st to end	Night	51% 1 13% 25% 8% 1	2800
December	1st to 10th	Night	45% 3 18% 26% 7% 1	4580
	11th to 20th	Night	61% 3 11% 17% 7% 1	5201
	21st to end	Night	72% 2 7% 13% 5%	6996

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% 24% 8% 2	300
	11th to 20th	Day	20% 16% 40% 17% 6% 1	300
	21st to end	Day	21% 18% 32% 25% 4 1	330
February	1st to 10th	Day	17% 20% 39% 17% 5% 1	300
	11th to 20th	Day	20% 23% 33% 18% 6%	300
	21st to end	Day	23% 18% 42% 14% 2	249
March	1st to 10th	Day	21% 19% 40% 15% 5%	300
	11th to 20th	Day	19% 20% 36% 16% 7% 2	273
	21st to end	Day	28% 12% 31% 19% 8% 1	433
April	1st to 10th	Day	29% 15% 31% 21% 4	460
	11th to 20th	Day	26% 18% 27% 17% 11% 2	452
	21st to end	Day	22% 15% 28% 24% 9% 2	460
May	1st to 10th	Day	19% 14% 32% 24% 10% 1	621
	11th to 20th	Day	21% 12% 26% 25% 13% 3	675
	21st to end	Day	18% 10% 25% 24% 15% 7%	734
June	1st to 10th	Day	12% 6% 26% 34% 18% 4	680
	11th to 20th	Day	14% 9% 32% 27% 14% 4	680
	21st to end	Day	14% 10% 27% 30% 15% 4	680
July	1st to 10th	Day	8% 4 19% 31% 25% 13%	671
	11th to 20th	Day	9% 5% 26% 32% 20% 8%	668
	21st to end	Day	7% 4 26% 35% 21% 7%	739
August	1st to 10th	Day	7% 4 21% 34% 24% 9%	676
	11th to 20th	Day	15% 5% 19% 27% 22% 12%	590
	21st to end	Day	11% 7% 20% 30% 23% 9%	539
September	1st to 10th	Day	16% 7% 21% 30% 20% 7%	490
	11th to 20th	Day	14% 4 20% 33% 22% 7%	490
	21st to end	Day	18% 9% 28% 23% 19% 3	462
October	1st to 10th	Day	18% 12% 26% 31% 11% 2	300
	11th to 20th	Day	25% 17% 32% 19% 6% 1	300
	21st to end	Day	23% 16% 35% 19% 7% 1	330
November	1st to 10th	Day	17% 13% 39% 21% 8% 2	300
	11th to 20th	Day	21% 18% 36% 16% 8% 1	300
	21st to end	Day	25% 13% 37% 21% 4	300
December	1st to 10th	Day	15% 17% 40% 20% 7% 1	300
	11th to 20th	Day	19% 16% 38% 19% 7% 1	300
	21st to end	Day	28% 17% 34% 17% 4 1	330
January	1st to 10th	Night	13% 15% 37% 26% 9% 1	1000
	11th to 20th	Night	19% 13% 35% 28% 5% 1	1000
	21st to end	Night	20% 10% 36% 28% 6% 1	1100
February	1st to 10th	Night	17% 12% 36% 28% 6% 1	1000
	11th to 20th	Night	17% 13% 38% 26% 5%	909
	21st to end	Night	21% 14% 35% 24% 4	660
March	1st to 10th	Night	22% 12% 34% 26% 6%	800
	11th to 20th	Night	18% 12% 33% 29% 8%	605
	21st to end	Night	26% 9% 29% 30% 7%	627
April	1st to 10th	Night	21% 11% 36% 26% 5%	570
	11th to 20th	Night	24% 9% 31% 30% 6%	563
	21st to end	Night	21% 10% 29% 29% 9% 1	570
May	1st to 10th	Night	19% 8% 33% 33% 6% 1	570
	11th to 20th	Night	21% 6% 27% 33% 12% 1	561
	21st to end	Night	15% 6% 27% 37% 15% 1	617
June	1st to 10th	Night	10% 6% 27% 44% 14%	570
	11th to 20th	Night	13% 4 31% 38% 14%	570
	21st to end	Night	12% 5% 22% 42% 18% 1	570
July	1st to 10th	Night	8% 2 14% 41% 32% 3	555
	11th to 20th	Night	8% 5% 19% 44% 23% 2	552
	21st to end	Night	7% 2 16% 47% 25% 3	624
August	1st to 10th	Night	6% 3 16% 45% 29% 1	567
	11th to 20th	Night	11% 3 13% 43% 25% 5%	564
	21st to end	Night	11% 3 17% 42% 24% 3	627
September	1st to 10th	Night	10% 5% 21% 41% 18% 6%	570
	11th to 20th	Night	14% 4 21% 32% 26% 4	570
	21st to end	Night	13% 8% 24% 37% 16% 1	760
October	1st to 10th	Night	15% 6% 28% 31% 18% 1	760
	11th to 20th	Night	20% 10% 31% 30% 9%	760
	21st to end	Night	24% 11% 28% 29% 9%	836
November	1st to 10th	Night	18% 10% 34% 27% 10% 1	780
	11th to 20th	Night	21% 13% 37% 22% 6% 1	885
	21st to end	Night	24% 12% 31% 27% 6%	1000
December	1st to 10th	Night	19% 12% 39% 24% 5% 1	1000
	11th to 20th	Night	24% 10% 35% 25% 5%	1000
	21st to end	Night	29% 11% 31% 25% 4	1100

Page generated at 2025-03-09 07:08:41. Version ac07

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