Yankton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Yankton clear sky chart from 2005-11-06 to 2025-03-27.

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	11% 7% 3 7% 4 4 4 3 5% 7% 44%	108877
	Night	9% 7% 3 7% 4 4 4 3 5% 7% 46%	110631
Transparency	Day	23% 44% 8% 15% 9% 1	112500
	Night	23% 42% 8% 16% 11% 1	115141
Seeing	Day	14% 9% 31% 30% 13% 3	16328
	Night	13% 9% 34% 34% 10% 1	26423

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	11% 11% 5% 15% 8% 6% 6% 3 5% 5% 25%	3638
	11th to 20th	Day	5% 11% 4 10% 8% 5% 6% 4 7% 7% 33%	3769
	21st to end	Day	4 10% 4 11% 5% 4 5% 4 5% 6% 41%	4488
February	1st to 10th	Day	10% 11% 4 10% 8% 6% 6% 4 6% 6% 30%	1800
	11th to 20th	Day	9% 11% 4 9% 5% 4 5% 3 4 7% 38%	1825
	21st to end	Day	10% 10% 4 9% 7% 4 5% 3 5% 8% 37%	1650
March	1st to 10th	Day	10% 8% 3 8% 4 3 4 3 3 6% 46%	3380
	11th to 20th	Day	10% 8% 2 6% 4 4 4 3 4 6% 49%	3590
	21st to end	Day	24% 11% 4 11% 4 5% 4 3 4 5% 24%	3880
April	1st to 10th	Day	15% 8% 3 7% 4 4 4 4 5% 6% 41%	2148
	11th to 20th	Day	18% 9% 2 6% 4 4 4 4 4 6% 40%	2442
	21st to end	Day	21% 6% 3 6% 4 4 4 2 5% 6% 39%	2470
May	1st to 10th	Day	16% 6% 2 6% 5% 4 5% 4 7% 7% 37%	4082
	11th to 20th	Day	11% 6% 2 6% 4 4 4 3 5% 6% 50%	4082
	21st to end	Day	17% 6% 2 6% 4 4 3 3 5% 8% 41%	4625
June	1st to 10th	Day	10% 4 2 5% 4 3 5% 4 6% 7% 50%	2769
	11th to 20th	Day	12% 6% 2 5% 4 4 4 4 6% 8% 47%	2850
	21st to end	Day	8% 4 2 5% 3 4 4 4 7% 8% 51%	2850
July	1st to 10th	Day	10% 4 2 6% 5% 4 4 4 7% 9% 45%	4528
	11th to 20th	Day	6% 4 2 5% 3 4 3 3 5% 7% 57%	4386
	21st to end	Day	4 3 1 5% 4 3 4 4 6% 9% 57%	4465
August	1st to 10th	Day	8% 5% 2 6% 4 4 5% 4 6% 8% 49%	4104
	11th to 20th	Day	16% 7% 3 6% 4 4 4 4 6% 7% 39%	4041
	21st to end	Day	7% 5% 2 5% 4 4 3 3 5% 7% 55%	4532
September	1st to 10th	Day	14% 6% 2 4 3 3 3 3 5% 5% 54%	2177
	11th to 20th	Day	7% 5% 2 4 3 4 4 3 5% 8% 56%	2090
	21st to end	Day	10% 4 1 4 3 3 3 3 5% 7% 57%	2090
October	1st to 10th	Day	14% 5% 2 5% 3 3 3 3 4 5% 52%	1990
	11th to 20th	Day	11% 7% 2 4 3 2 3 3 5% 6% 55%	1900
	21st to end	Day	15% 6% 3 6% 3 3 4 3 4 5% 48%	1986
November	1st to 10th	Day	9% 7% 2 5% 4 3 5% 4 5% 7% 48%	1763
	11th to 20th	Day	9% 7% 2 7% 5% 5% 4 3 4 7% 46%	1747
	21st to end	Day	10% 9% 3 7% 4 4 4 4 5% 8% 44%	1600
December	1st to 10th	Day	5% 7% 3 8% 7% 6% 5% 3 5% 8% 44%	2610
	11th to 20th	Day	8% 10% 4 9% 5% 5% 5% 4 5% 7% 37%	2940
	21st to end	Day	13% 9% 4 16% 5% 4 4 3 5% 7% 30%	3590
January	1st to 10th	Night	9% 10% 5% 13% 9% 8% 6% 4 6% 6% 24%	6327
	11th to 20th	Night	3 9% 4 10% 6% 6% 6% 4 8% 6% 38%	6194
	21st to end	Night	4 8% 5% 10% 4 4 5% 4 6% 7% 43%	6490
February	1st to 10th	Night	10% 10% 4 9% 6% 4 4 4 4 6% 39%	2600
	11th to 20th	Night	8% 11% 4 8% 4 3 4 3 5% 7% 42%	2478
	21st to end	Night	9% 9% 3 6% 4 4 5% 4 5% 6% 46%	1980
March	1st to 10th	Night	10% 6% 2 5% 3 3 3 3 5% 6% 53%	3699
	11th to 20th	Night	10% 6% 2 5% 3 3 4 3 4 8% 52%	3590
	21st to end	Night	20% 10% 3 8% 5% 5% 4 4 5% 6% 30%	3889
April	1st to 10th	Night	13% 9% 2 6% 4 3 4 4 5% 7% 42%	2028
	11th to 20th	Night	16% 7% 2 6% 4 4 3 3 6% 5% 44%	1689
	21st to end	Night	17% 7% 2 5% 5% 3 4 3 5% 5% 43%	1710
May	1st to 10th	Night	17% 5% 2 5% 4 3 3 3 5% 6% 47%	2823
	11th to 20th	Night	10% 5% 2 5% 3 3 4 4 6% 7% 51%	2823
	21st to end	Night	16% 6% 2 5% 4 3 3 4 5% 8% 44%	2941
June	1st to 10th	Night	7% 6% 2 3 3 4 3 3 6% 10% 54%	1406
	11th to 20th	Night	7% 5% 1 4 3 4 3 4 7% 10% 52%	1330
	21st to end	Night	7% 3 1 4 3 2 4 3 6% 8% 58%	1330
July	1st to 10th	Night	7% 5% 2 6% 4 4 3 3 6% 8% 53%	2436
	11th to 20th	Night	5% 3 1 3 2 3 3 3 5% 7% 64%	2571
	21st to end	Night	2 2 1 4 3 3 4 4 6% 11% 61%	3098
August	1st to 10th	Night	5% 5% 2 6% 5% 4 4 3 7% 9% 50%	2836
	11th to 20th	Night	10% 5% 2 5% 3 4 4 4 6% 9% 49%	2798
	21st to end	Night	7% 3 2 6% 3 3 4 3 6% 9% 55%	3135
September	1st to 10th	Night	8% 4 1 5% 2 3 4 3 5% 6% 59%	1996
	11th to 20th	Night	8% 3 2 4 3 2 3 3 5% 7% 59%	2090
	21st to end	Night	8% 4 1 3 3 3 4 3 4 7% 61%	2090
October	1st to 10th	Night	16% 4 2 5% 3 3 3 3 4 5% 53%	2171
	11th to 20th	Night	10% 5% 2 4 3 3 4 3 5% 5% 56%	2280
	21st to end	Night	13% 6% 2 4 3 3 3 3 4 6% 52%	2608
November	1st to 10th	Night	8% 5% 2 5% 4 3 4 3 4 8% 54%	2535
	11th to 20th	Night	8% 6% 2 7% 4 4 4 3 6% 6% 50%	2650
	21st to end	Night	9% 7% 2 5% 4 4 4 4 7% 7% 49%	2800
December	1st to 10th	Night	5% 7% 3 8% 5% 5% 5% 3 5% 6% 48%	4580
	11th to 20th	Night	8% 8% 4 9% 6% 6% 6% 4 5% 8% 37%	5260
	21st to end	Night	15% 11% 4 11% 5% 4 3 3 5% 5% 32%	7370

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	49% 27% 10% 11% 3	3639
	11th to 20th	Day	37% 26% 11% 13% 13% 1	3769
	21st to end	Day	28% 28% 14% 18% 9% 2	4488
February	1st to 10th	Day	22% 64% 5% 5% 4	1800
	11th to 20th	Day	19% 61% 4 9% 5% 1	1834
	21st to end	Day	17% 61% 5% 7% 9% 1	1650
March	1st to 10th	Day	22% 39% 6% 20% 12% 1	3380
	11th to 20th	Day	20% 38% 5% 21% 12% 3	3590
	21st to end	Day	42% 39% 8% 9% 1	3880
April	1st to 10th	Day	18% 65% 5% 8% 4	2148
	11th to 20th	Day	15% 66% 5% 9% 4 1	2442
	21st to end	Day	18% 65% 4 8% 5%	2470
May	1st to 10th	Day	27% 41% 7% 13% 10%	4120
	11th to 20th	Day	20% 40% 7% 18% 13% 2	4086
	21st to end	Day	26% 40% 7% 17% 10%	4638
June	1st to 10th	Day	9% 65% 6% 13% 6% 1	2769
	11th to 20th	Day	14% 66% 6% 10% 4 1	2850
	21st to end	Day	12% 65% 6% 12% 4 1	2850
July	1st to 10th	Day	25% 38% 13% 15% 8%	4459
	11th to 20th	Day	19% 37% 9% 23% 11% 1	4311
	21st to end	Day	15% 38% 12% 18% 14% 2	4325
August	1st to 10th	Day	22% 39% 9% 21% 9% 2	4090
	11th to 20th	Day	33% 40% 8% 15% 5%	4080
	21st to end	Day	21% 39% 12% 17% 10% 1	4531
September	1st to 10th	Day	14% 60% 5% 14% 6%	2177
	11th to 20th	Day	9% 61% 6% 16% 8% 1	2090
	21st to end	Day	14% 61% 3 12% 8% 1	2090
October	1st to 10th	Day	12% 36% 3 15% 30% 4	3302
	11th to 20th	Day	13% 38% 11% 19% 15% 5%	3140
	21st to end	Day	22% 37% 8% 18% 13% 2	3255
November	1st to 10th	Day	19% 56% 8% 11% 6%	1763
	11th to 20th	Day	16% 57% 5% 14% 7% 1	1747
	21st to end	Day	21% 58% 5% 10% 6% 1	1600
December	1st to 10th	Day	25% 36% 11% 20% 7% 1	2610
	11th to 20th	Day	32% 32% 13% 16% 7%	2937
	21st to end	Day	41% 26% 9% 19% 4 1	3590
January	1st to 10th	Night	49% 27% 9% 10% 6%	6327
	11th to 20th	Night	32% 27% 12% 15% 14% 2	6194
	21st to end	Night	26% 28% 11% 22% 13%	6490
February	1st to 10th	Night	18% 63% 7% 7% 5% 1	2600
	11th to 20th	Night	19% 61% 6% 8% 5% 2	2479
	21st to end	Night	13% 62% 4 10% 8% 3	1980
March	1st to 10th	Night	16% 40% 6% 15% 21% 1	3699
	11th to 20th	Night	18% 39% 6% 20% 14% 3	3590
	21st to end	Night	36% 40% 11% 10% 2	3889
April	1st to 10th	Night	15% 66% 6% 8% 4 1	2028
	11th to 20th	Night	14% 67% 4 9% 6% 1	1689
	21st to end	Night	16% 65% 5% 7% 6% 1	1710
May	1st to 10th	Night	24% 40% 8% 11% 14% 2	2850
	11th to 20th	Night	18% 40% 8% 16% 16% 2	2824
	21st to end	Night	22% 40% 7% 19% 11% 1	2949
June	1st to 10th	Night	7% 66% 6% 10% 8% 2	1406
	11th to 20th	Night	12% 66% 5% 10% 7%	1330
	21st to end	Night	9% 63% 8% 13% 6% 1	1330
July	1st to 10th	Night	21% 37% 16% 18% 7% 2	2396
	11th to 20th	Night	14% 36% 9% 28% 11% 1	2523
	21st to end	Night	11% 38% 13% 21% 14% 3	2999
August	1st to 10th	Night	20% 38% 9% 21% 10% 1	2826
	11th to 20th	Night	25% 40% 11% 17% 7% 1	2825
	21st to end	Night	19% 40% 12% 15% 13% 1	3135
September	1st to 10th	Night	11% 61% 5% 12% 10% 1	1996
	11th to 20th	Night	10% 60% 5% 16% 9% 1	2090
	21st to end	Night	12% 61% 4 11% 11% 1	2090
October	1st to 10th	Night	9% 36% 3 11% 37% 4	3626
	11th to 20th	Night	10% 36% 7% 23% 20% 4	3779
	21st to end	Night	23% 38% 7% 21% 11%	4295
November	1st to 10th	Night	15% 56% 7% 12% 8% 1	2535
	11th to 20th	Night	13% 57% 6% 14% 9% 2	2650
	21st to end	Night	16% 57% 7% 13% 6% 1	2800
December	1st to 10th	Night	23% 36% 9% 24% 8%	4580
	11th to 20th	Night	31% 33% 10% 20% 6%	5262
	21st to end	Night	43% 27% 8% 16% 5%	7370

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	17% 12% 29% 29% 10% 3	300
	11th to 20th	Day	15% 14% 33% 30% 7% 1	300
	21st to end	Day	12% 11% 41% 26% 9% 2	330
February	1st to 10th	Day	11% 18% 41% 28% 3	300
	11th to 20th	Day	15% 13% 39% 25% 8% 1	300
	21st to end	Day	17% 12% 39% 26% 6%	249
March	1st to 10th	Day	15% 11% 43% 27% 3 1	300
	11th to 20th	Day	17% 13% 38% 21% 10% 1	300
	21st to end	Day	29% 10% 37% 18% 4 2	315
April	1st to 10th	Day	20% 19% 38% 18% 4	328
	11th to 20th	Day	24% 15% 31% 25% 6%	640
	21st to end	Day	25% 11% 31% 22% 9% 2	650
May	1st to 10th	Day	19% 13% 34% 24% 9% 1	653
	11th to 20th	Day	19% 9% 30% 24% 15% 3	675
	21st to end	Day	19% 8% 30% 28% 12% 3	734
June	1st to 10th	Day	8% 8% 23% 34% 22% 5%	680
	11th to 20th	Day	12% 7% 35% 30% 14% 2	680
	21st to end	Day	10% 8% 27% 36% 17% 2	680
July	1st to 10th	Day	6% 3 22% 36% 27% 6%	671
	11th to 20th	Day	7% 5% 24% 42% 19% 3	668
	21st to end	Day	5% 4 24% 45% 19% 4	739
August	1st to 10th	Day	9% 3 20% 42% 23% 3	676
	11th to 20th	Day	11% 4 24% 36% 21% 5%	665
	21st to end	Day	7% 4 27% 36% 23% 3	748
September	1st to 10th	Day	17% 5% 28% 30% 17% 4	387
	11th to 20th	Day	7% 5% 35% 32% 18% 3	300
	21st to end	Day	16% 10% 31% 26% 12% 5%	300
October	1st to 10th	Day	18% 9% 27% 27% 15% 4	300
	11th to 20th	Day	16% 15% 35% 23% 9% 1	300
	21st to end	Day	18% 15% 34% 24% 8% 1	330
November	1st to 10th	Day	20% 10% 33% 25% 8% 4	300
	11th to 20th	Day	14% 18% 38% 24% 6%	300
	21st to end	Day	18% 17% 30% 23% 11% 1	300
December	1st to 10th	Day	12% 11% 36% 31% 8% 2	300
	11th to 20th	Day	15% 13% 39% 25% 8%	300
	21st to end	Day	22% 10% 36% 25% 7%	330
January	1st to 10th	Night	12% 11% 35% 32% 9% 1	1000
	11th to 20th	Night	12% 15% 35% 31% 7% 1	1000
	21st to end	Night	12% 8% 41% 30% 8%	1100
February	1st to 10th	Night	15% 11% 39% 29% 5%	1000
	11th to 20th	Night	13% 11% 39% 31% 6%	924
	21st to end	Night	14% 9% 36% 32% 8% 1	660
March	1st to 10th	Night	13% 10% 42% 30% 5% 1	710
	11th to 20th	Night	15% 11% 39% 29% 6%	600
	21st to end	Night	18% 9% 40% 25% 7%	647
April	1st to 10th	Night	17% 14% 38% 28% 3	570
	11th to 20th	Night	18% 13% 35% 26% 7%	563
	21st to end	Night	18% 10% 38% 27% 7% 1	570
May	1st to 10th	Night	15% 9% 36% 31% 8%	570
	11th to 20th	Night	16% 8% 30% 36% 11%	561
	21st to end	Night	18% 6% 31% 35% 10%	617
June	1st to 10th	Night	9% 5% 27% 41% 18% 1	570
	11th to 20th	Night	10% 4 33% 41% 12% 1	570
	21st to end	Night	7% 4 26% 47% 16%	570
July	1st to 10th	Night	6% 3 18% 45% 27% 1	555
	11th to 20th	Night	5% 2 20% 56% 17% 1	552
	21st to end	Night	5% 1 21% 56% 17% 1	624
August	1st to 10th	Night	7% 4 22% 47% 20% 1	567
	11th to 20th	Night	8% 4 23% 42% 21% 1	564
	21st to end	Night	7% 3 25% 46% 18% 1	627
September	1st to 10th	Night	9% 4 26% 43% 17% 1	570
	11th to 20th	Night	8% 5% 31% 39% 15% 2	570
	21st to end	Night	10% 6% 37% 33% 14% 1	570
October	1st to 10th	Night	18% 8% 31% 32% 10% 1	651
	11th to 20th	Night	15% 11% 37% 29% 8% 1	760
	21st to end	Night	16% 13% 32% 30% 9%	936
November	1st to 10th	Night	11% 10% 35% 34% 9% 1	975
	11th to 20th	Night	12% 12% 38% 32% 6% 1	1000
	21st to end	Night	11% 11% 35% 34% 9%	1000
December	1st to 10th	Night	12% 10% 39% 31% 7% 1	1000
	11th to 20th	Night	14% 9% 35% 35% 8% 1	1000
	21st to end	Night	20% 10% 35% 28% 6%	1100

Page generated at 2025-03-24 08:04:29. Version ac07

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