Sweet Run State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sweet Run State Park clear sky chart from 2005-11-06 to 2026-06-16.

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	14% 6% 2 6% 4 4 5% 4 6% 8% 41%	137738
	Night	14% 7% 2 6% 4 4 4 4 6% 7% 42%	134279
Transparency	Day	39% 6% 12% 24% 16% 3	141335
	Night	39% 6% 11% 24% 17% 3	138753
Seeing	Day	19% 14% 26% 22% 13% 5%	16977
	Night	18% 12% 29% 29% 12% 1	26564

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	14% 4 2 7% 4 5% 6% 4 6% 7% 42%	4881
	11th to 20th	Day	12% 9% 3 7% 4 4 4 3 4 5% 46%	5280
	21st to end	Day	13% 6% 2 7% 4 4 6% 5% 7% 7% 39%	5780
February	1st to 10th	Day	13% 8% 3 6% 4 4 5% 4 6% 6% 40%	1890
	11th to 20th	Day	17% 8% 3 8% 4 4 4 3 5% 6% 38%	1861
	21st to end	Day	16% 8% 3 7% 5% 4 4 3 4 6% 39%	1730
March	1st to 10th	Day	17% 6% 2 6% 4 5% 4 3 5% 6% 41%	5040
	11th to 20th	Day	11% 6% 2 6% 4 4 4 4 5% 7% 48%	5090
	21st to end	Day	15% 7% 2 6% 5% 5% 5% 4 5% 7% 39%	5624
April	1st to 10th	Day	14% 7% 3 6% 4 5% 4 3 6% 8% 39%	2520
	11th to 20th	Day	13% 7% 2 5% 4 4 4 4 5% 7% 45%	2494
	21st to end	Day	18% 6% 2 6% 4 4 4 4 5% 6% 41%	2530
May	1st to 10th	Day	16% 7% 3 7% 4 4 6% 5% 7% 9% 33%	7616
	11th to 20th	Day	18% 6% 2 5% 4 4 5% 4 7% 9% 35%	7919
	21st to end	Day	22% 6% 2 6% 4 4 4 4 5% 7% 37%	9045
June	1st to 10th	Day	12% 5% 2 5% 4 4 5% 4 7% 8% 44%	2940
	11th to 20th	Day	12% 5% 2 6% 4 5% 6% 5% 7% 9% 40%	2870
	21st to end	Day	9% 4 1 5% 4 4 5% 5% 7% 10% 45%	2800
July	1st to 10th	Day	6% 4 2 6% 5% 5% 6% 4 7% 10% 43%	6360
	11th to 20th	Day	8% 6% 3 7% 5% 6% 6% 6% 9% 11% 32%	6087
	21st to end	Day	8% 6% 2 7% 5% 5% 5% 4 7% 11% 40%	6424
August	1st to 10th	Day	16% 5% 2 7% 5% 5% 6% 4 6% 9% 35%	4234
	11th to 20th	Day	10% 5% 2 7% 5% 5% 6% 4 7% 10% 41%	4056
	21st to end	Day	10% 5% 2 6% 4 4 5% 4 6% 7% 49%	4312
September	1st to 10th	Day	15% 5% 2 5% 4 4 4 3 5% 6% 47%	2400
	11th to 20th	Day	13% 5% 2 5% 4 4 3 3 6% 8% 47%	2395
	21st to end	Day	22% 7% 2 5% 4 4 4 3 5% 7% 37%	2089
October	1st to 10th	Day	16% 5% 2 5% 3 4 3 3 5% 7% 47%	2000
	11th to 20th	Day	16% 4 2 6% 3 3 4 3 5% 6% 48%	2000
	21st to end	Day	13% 5% 2 5% 4 4 3 3 5% 6% 50%	2200
November	1st to 10th	Day	11% 6% 2 4 3 3 3 4 5% 7% 51%	1979
	11th to 20th	Day	15% 6% 2 4 3 4 4 3 5% 6% 47%	1814
	21st to end	Day	14% 6% 3 5% 4 4 5% 3 5% 7% 44%	1680
December	1st to 10th	Day	12% 6% 2 5% 3 5% 5% 4 6% 7% 45%	2680
	11th to 20th	Day	18% 9% 2 5% 4 4 4 3 5% 7% 39%	3070
	21st to end	Day	16% 8% 3 7% 5% 5% 5% 4 6% 9% 33%	4048
January	1st to 10th	Night	9% 8% 3 7% 5% 5% 5% 4 6% 8% 41%	7997
	11th to 20th	Night	13% 7% 2 5% 4 3 4 3 5% 5% 47%	7680
	21st to end	Night	12% 7% 2 5% 3 4 5% 4 6% 6% 46%	8401
February	1st to 10th	Night	14% 7% 3 5% 5% 4 4 4 5% 8% 40%	2730
	11th to 20th	Night	16% 8% 3 7% 4 3 5% 4 6% 5% 40%	2643
	21st to end	Night	16% 9% 3 6% 5% 4 4 4 5% 6% 39%	2076
March	1st to 10th	Night	16% 7% 2 6% 4 4 4 3 4 5% 46%	5030
	11th to 20th	Night	11% 5% 2 6% 4 4 4 3 5% 7% 48%	5090
	21st to end	Night	11% 8% 3 5% 4 6% 5% 4 5% 6% 44%	5549
April	1st to 10th	Night	15% 8% 2 7% 5% 5% 5% 4 6% 6% 39%	2100
	11th to 20th	Night	13% 5% 2 6% 5% 5% 4 3 6% 8% 42%	2075
	21st to end	Night	16% 4 2 5% 3 5% 4 4 5% 7% 44%	2100
May	1st to 10th	Night	18% 8% 3 8% 4 5% 5% 4 6% 8% 32%	5244
	11th to 20th	Night	20% 7% 2 6% 4 4 4 4 6% 10% 33%	4940
	21st to end	Night	23% 7% 3 7% 4 4 4 4 5% 6% 32%	5108
June	1st to 10th	Night	11% 5% 2 5% 4 5% 5% 4 6% 9% 45%	1680
	11th to 20th	Night	12% 5% 2 6% 5% 5% 5% 5% 8% 10% 39%	1640
	21st to end	Night	9% 5% 2 6% 4 5% 5% 4 6% 11% 44%	1600
July	1st to 10th	Night	6% 6% 3 8% 5% 6% 7% 5% 7% 9% 39%	3598
	11th to 20th	Night	7% 8% 3 9% 7% 6% 7% 6% 9% 10% 29%	3865
	21st to end	Night	8% 6% 2 6% 4 5% 6% 5% 7% 10% 42%	4427
August	1st to 10th	Night	15% 5% 3 8% 5% 5% 5% 5% 6% 10% 33%	2915
	11th to 20th	Night	10% 7% 3 7% 5% 5% 5% 4 7% 9% 39%	2959
	21st to end	Night	12% 5% 1 5% 3 4 4 4 6% 8% 47%	3586
September	1st to 10th	Night	14% 6% 1 6% 3 4 4 4 5% 7% 46%	2000
	11th to 20th	Night	11% 6% 2 5% 4 4 3 3 3 7% 51%	2001
	21st to end	Night	20% 7% 3 6% 5% 4 4 3 4 6% 39%	2310
October	1st to 10th	Night	19% 5% 2 5% 4 3 4 3 4 6% 47%	2400
	11th to 20th	Night	14% 5% 2 5% 3 3 3 3 4 6% 52%	2400
	21st to end	Night	15% 5% 1 5% 3 3 3 3 5% 6% 51%	2640
November	1st to 10th	Night	10% 5% 2 5% 3 3 3 3 5% 6% 54%	2536
	11th to 20th	Night	14% 6% 2 5% 4 3 3 3 6% 7% 47%	2804
	21st to end	Night	14% 4 2 6% 4 4 4 5% 6% 7% 45%	2940
December	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 6% 8% 48%	4720
	11th to 20th	Night	19% 7% 2 5% 4 4 5% 4 5% 7% 38%	5345
	21st to end	Night	16% 7% 2 7% 5% 5% 5% 5% 7% 8% 32%	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	38% 6% 10% 26% 16% 5%	4882
	11th to 20th	Day	40% 4 7% 21% 19% 8%	5280
	21st to end	Day	41% 5% 10% 28% 12% 3	5780
February	1st to 10th	Day	43% 6% 13% 23% 13% 2	1890
	11th to 20th	Day	47% 5% 8% 24% 14% 2	1870
	21st to end	Day	46% 5% 10% 21% 14% 3	1730
March	1st to 10th	Day	42% 5% 9% 21% 16% 7%	5040
	11th to 20th	Day	34% 5% 10% 27% 18% 6%	5090
	21st to end	Day	43% 5% 10% 19% 18% 5%	5624
April	1st to 10th	Day	41% 6% 13% 19% 17% 4	2520
	11th to 20th	Day	37% 7% 11% 22% 18% 5%	2494
	21st to end	Day	43% 5% 9% 23% 16% 3	2530
May	1st to 10th	Day	45% 7% 12% 22% 13% 1	7651
	11th to 20th	Day	42% 7% 11% 27% 11% 1	7923
	21st to end	Day	45% 6% 10% 18% 17% 2	9061
June	1st to 10th	Day	35% 8% 14% 24% 18% 1	2940
	11th to 20th	Day	37% 9% 16% 23% 14% 2	2870
	21st to end	Day	31% 8% 16% 26% 17% 2	2800
July	1st to 10th	Day	34% 9% 15% 23% 15% 4	6290
	11th to 20th	Day	41% 10% 17% 23% 9% 1	6013
	21st to end	Day	37% 7% 10% 23% 22% 1	6240
August	1st to 10th	Day	44% 8% 14% 25% 8% 1	4221
	11th to 20th	Day	37% 7% 13% 28% 15% 1	4095
	21st to end	Day	33% 7% 13% 27% 18% 2	4312
September	1st to 10th	Day	37% 6% 12% 20% 21% 4	2400
	11th to 20th	Day	35% 5% 9% 26% 22% 3	2395
	21st to end	Day	47% 5% 10% 18% 18% 2	2089
October	1st to 10th	Day	36% 5% 7% 20% 28% 5%	3260
	11th to 20th	Day	26% 5% 9% 29% 24% 8%	3240
	21st to end	Day	24% 3 11% 30% 28% 4	3538
November	1st to 10th	Day	32% 4 13% 26% 21% 4	1979
	11th to 20th	Day	36% 4 11% 23% 21% 4	1814
	21st to end	Day	39% 5% 12% 28% 14% 1	1680
December	1st to 10th	Day	38% 5% 13% 28% 11% 4	2680
	11th to 20th	Day	45% 5% 13% 26% 9% 2	3066
	21st to end	Day	45% 7% 16% 18% 13% 1	4048
January	1st to 10th	Night	39% 6% 10% 25% 18% 3	7998
	11th to 20th	Night	37% 3 8% 23% 22% 7%	7680
	21st to end	Night	37% 4 8% 31% 18% 2	8401
February	1st to 10th	Night	42% 5% 13% 24% 15% 2	2730
	11th to 20th	Night	44% 5% 10% 22% 15% 4	2645
	21st to end	Night	44% 5% 11% 21% 14% 5%	2076
March	1st to 10th	Night	40% 4 8% 26% 13% 8%	5030
	11th to 20th	Night	34% 5% 11% 29% 16% 5%	5090
	21st to end	Night	39% 4 10% 22% 20% 4	5549
April	1st to 10th	Night	43% 6% 10% 20% 17% 4	2100
	11th to 20th	Night	38% 6% 12% 21% 18% 5%	2075
	21st to end	Night	37% 6% 13% 26% 14% 4	2100
May	1st to 10th	Night	49% 5% 11% 20% 12% 3	5271
	11th to 20th	Night	45% 6% 12% 26% 10% 1	4941
	21st to end	Night	50% 7% 12% 19% 12% 2	5115
June	1st to 10th	Night	34% 7% 12% 25% 18% 3	1680
	11th to 20th	Night	38% 9% 14% 25% 13% 2	1640
	21st to end	Night	33% 8% 15% 24% 18% 2	1600
July	1st to 10th	Night	39% 9% 16% 18% 15% 4	3560
	11th to 20th	Night	46% 10% 18% 16% 10% 1	3819
	21st to end	Night	35% 8% 13% 23% 20% 1	4297
August	1st to 10th	Night	46% 7% 16% 22% 9% 1	2904
	11th to 20th	Night	40% 7% 12% 26% 14% 1	2986
	21st to end	Night	34% 6% 13% 30% 16% 2	3586
September	1st to 10th	Night	36% 7% 12% 22% 19% 5%	2000
	11th to 20th	Night	34% 5% 10% 27% 23% 2	2001
	21st to end	Night	47% 5% 9% 19% 17% 2	2310
October	1st to 10th	Night	40% 4 9% 22% 21% 3	3920
	11th to 20th	Night	25% 4 10% 23% 31% 7%	3899
	21st to end	Night	24% 4 10% 32% 26% 5%	4252
November	1st to 10th	Night	32% 4 11% 27% 23% 5%	2536
	11th to 20th	Night	36% 5% 9% 24% 21% 5%	2804
	21st to end	Night	37% 6% 12% 25% 18% 3	2940
December	1st to 10th	Night	33% 6% 14% 30% 16% 1	4720
	11th to 20th	Night	45% 5% 12% 20% 16% 3	5348
	21st to end	Night	44% 8% 15% 19% 13% 1	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	29% 30% 26% 12% 2 1	261
	11th to 20th	Day	32% 28% 27% 10% 2	330
	21st to end	Day	27% 30% 30% 9% 3 1	363
February	1st to 10th	Day	25% 29% 31% 13% 2	330
	11th to 20th	Day	37% 27% 29% 6% 1	348
	21st to end	Day	29% 20% 31% 17% 3	446
March	1st to 10th	Day	25% 23% 28% 20% 4	540
	11th to 20th	Day	28% 21% 29% 15% 5% 2	540
	21st to end	Day	23% 23% 31% 18% 4 1	594
April	1st to 10th	Day	24% 26% 24% 19% 6% 1	540
	11th to 20th	Day	20% 18% 30% 18% 11% 3	532
	21st to end	Day	27% 16% 28% 19% 9% 2	540
May	1st to 10th	Day	22% 20% 28% 18% 9% 3	543
	11th to 20th	Day	20% 15% 25% 23% 13% 4	567
	21st to end	Day	21% 8% 24% 24% 17% 5%	617
June	1st to 10th	Day	13% 12% 29% 22% 18% 6%	570
	11th to 20th	Day	14% 7% 28% 30% 17% 4	550
	21st to end	Day	10% 6% 26% 32% 20% 6%	530
July	1st to 10th	Day	10% 5% 19% 28% 26% 12%	525
	11th to 20th	Day	7% 2 21% 32% 29% 9%	524
	21st to end	Day	12% 5% 19% 32% 23% 9%	576
August	1st to 10th	Day	12% 5% 20% 28% 23% 13%	526
	11th to 20th	Day	14% 3 22% 30% 21% 10%	519
	21st to end	Day	10% 4 23% 30% 20% 14%	583
September	1st to 10th	Day	17% 8% 19% 23% 23% 10%	530
	11th to 20th	Day	14% 4 18% 31% 22% 10%	530
	21st to end	Day	28% 8% 23% 25% 13% 4	530
October	1st to 10th	Day	18% 8% 20% 27% 20% 8%	530
	11th to 20th	Day	17% 16% 26% 26% 13% 3	530
	21st to end	Day	16% 15% 33% 22% 12% 3	583
November	1st to 10th	Day	16% 14% 33% 24% 11% 3	494
	11th to 20th	Day	23% 18% 31% 18% 8% 1	354
	21st to end	Day	23% 22% 30% 20% 5%	220
December	1st to 10th	Day	22% 25% 36% 13% 4	220
	11th to 20th	Day	25% 22% 30% 17% 6%	220
	21st to end	Day	24% 22% 29% 18% 6%	242
January	1st to 10th	Night	19% 21% 39% 19% 3	840
	11th to 20th	Night	23% 18% 32% 24% 3	840
	21st to end	Night	18% 19% 39% 22% 2	924
February	1st to 10th	Night	17% 19% 35% 26% 3	840
	11th to 20th	Night	24% 23% 33% 18% 1	823
	21st to end	Night	23% 19% 37% 18% 3	692
March	1st to 10th	Night	22% 18% 36% 21% 3	840
	11th to 20th	Night	24% 18% 29% 23% 5% 1	840
	21st to end	Night	19% 19% 37% 21% 4 1	924
April	1st to 10th	Night	20% 19% 33% 23% 5%	840
	11th to 20th	Night	17% 14% 35% 26% 7%	831
	21st to end	Night	18% 13% 32% 30% 7%	840
May	1st to 10th	Night	21% 8% 30% 31% 9%	637
	11th to 20th	Night	20% 8% 27% 34% 11% 1	522
	21st to end	Night	17% 5% 25% 37% 16% 1	455
June	1st to 10th	Night	12% 4 25% 35% 23% 1	420
	11th to 20th	Night	12% 6% 20% 42% 19% 1	410
	21st to end	Night	10% 3 22% 45% 19% 2	400
July	1st to 10th	Night	10% 5% 16% 39% 27% 3	390
	11th to 20th	Night	8% 2 11% 43% 33% 3	499
	21st to end	Night	8% 2 17% 41% 29% 3	657
August	1st to 10th	Night	12% 2 11% 44% 29% 3	597
	11th to 20th	Night	11% 4 15% 38% 28% 3	639
	21st to end	Night	13% 3 16% 39% 25% 4	880
September	1st to 10th	Night	16% 2 20% 34% 25% 3	800
	11th to 20th	Night	14% 3 17% 37% 27% 3	800
	21st to end	Night	24% 4 20% 32% 20% 1	800
October	1st to 10th	Night	21% 7% 21% 28% 20% 3	800
	11th to 20th	Night	16% 12% 27% 31% 13% 1	800
	21st to end	Night	18% 10% 31% 29% 11%	880
November	1st to 10th	Night	13% 10% 34% 33% 10% 1	820
	11th to 20th	Night	18% 14% 33% 27% 7% 1	840
	21st to end	Night	17% 16% 32% 28% 7%	840
December	1st to 10th	Night	21% 14% 35% 24% 6%	840
	11th to 20th	Night	20% 13% 38% 26% 4	840
	21st to end	Night	20% 14% 34% 29% 3	924

Page generated at 2026-06-13 02:31:43. Version ac07

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