Garner State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Garner State Park clear sky chart from 2005-11-06 to 2024-01-27.

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	14% 5% 2 4 4 3 4 4 5% 7% 48%	74970
	Night	13% 5% 2 4 3 2 3 4 5% 7% 53%	75100
Transparency	Day	36% 3 9% 22% 19% 10%	74698
	Night	32% 3 11% 21% 20% 13%	74892
Seeing	Day	15% 6% 22% 31% 21% 4	13657
	Night	15% 6% 24% 38% 16% 1	23772

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	12% 6% 2 4 3 2 3 3 4 6% 56%	1707
	11th to 20th	Day	16% 5% 2 4 4 2 3 3 4 5% 51%	1795
	21st to end	Day	14% 7% 2 3 4 2 3 3 4 5% 53%	2040
February	1st to 10th	Day	15% 7% 2 4 3 3 3 4 4 5% 51%	1800
	11th to 20th	Day	18% 6% 2 4 4 2 3 4 5% 6% 46%	1749
	21st to end	Day	15% 5% 2 4 3 2 3 4 4 6% 54%	1480
March	1st to 10th	Day	19% 8% 2 4 3 2 3 4 3 5% 46%	1854
	11th to 20th	Day	18% 6% 2 5% 4 2 4 4 4 4 46%	1980
	21st to end	Day	19% 5% 3 3 3 2 3 3 4 6% 49%	2178
April	1st to 10th	Day	17% 7% 2 5% 3 2 3 4 5% 6% 46%	1980
	11th to 20th	Day	18% 5% 2 5% 4 2 3 4 5% 6% 47%	2124
	21st to end	Day	17% 5% 3 4 4 3 3 3 4 5% 49%	2163
May	1st to 10th	Day	18% 5% 2 5% 4 2 4 4 5% 7% 43%	2340
	11th to 20th	Day	17% 6% 3 5% 5% 3 5% 4 6% 8% 40%	2302
	21st to end	Day	19% 6% 2 5% 6% 3 5% 4 6% 7% 36%	2531
June	1st to 10th	Day	8% 4 2 4 5% 3 5% 5% 6% 10% 50%	2340
	11th to 20th	Day	10% 4 2 5% 4 3 6% 5% 6% 8% 47%	2340
	21st to end	Day	11% 5% 3 5% 5% 4 6% 6% 7% 9% 39%	2340
July	1st to 10th	Day	15% 6% 3 5% 5% 4 5% 6% 6% 7% 37%	2340
	11th to 20th	Day	7% 2 2 4 4 3 4 5% 6% 9% 54%	2340
	21st to end	Day	7% 3 1 4 4 2 4 5% 7% 11% 52%	2503
August	1st to 10th	Day	2 2 1 3 5% 2 4 5% 6% 10% 60%	2149
	11th to 20th	Day	7% 4 2 4 4 4 6% 6% 6% 8% 50%	2123
	21st to end	Day	8% 4 2 4 5% 4 6% 5% 6% 8% 47%	2374
September	1st to 10th	Day	12% 6% 2 7% 7% 4 5% 6% 5% 8% 39%	1980
	11th to 20th	Day	12% 6% 2 6% 5% 4 5% 5% 6% 7% 42%	1980
	21st to end	Day	11% 4 2 5% 6% 3 4 5% 6% 8% 46%	1980
October	1st to 10th	Day	9% 5% 2 4 4 2 5% 4 5% 7% 53%	1980
	11th to 20th	Day	16% 4 2 4 4 2 3 4 5% 6% 50%	1976
	21st to end	Day	16% 4 2 3 3 2 3 3 3 4 57%	1980
November	1st to 10th	Day	16% 7% 2 4 3 3 3 4 4 7% 46%	1796
	11th to 20th	Day	15% 6% 2 5% 4 3 3 4 5% 5% 50%	1710
	21st to end	Day	18% 6% 3 4 3 2 4 3 3 5% 49%	1710
December	1st to 10th	Day	17% 6% 2 4 4 2 3 3 4 7% 49%	1710
	11th to 20th	Day	17% 7% 3 5% 4 3 4 3 3 5% 46%	2161
	21st to end	Day	15% 6% 2 3 2 2 2 2 4 4 57%	3135
January	1st to 10th	Night	14% 5% 2 3 4 2 3 3 3 5% 57%	2458
	11th to 20th	Night	15% 6% 2 4 3 2 2 3 3 5% 54%	2399
	21st to end	Night	17% 6% 2 4 3 2 3 3 4 5% 51%	2460
February	1st to 10th	Night	14% 6% 2 3 3 2 3 3 5% 6% 55%	2160
	11th to 20th	Night	17% 5% 2 4 3 2 3 3 4 5% 53%	2098
	21st to end	Night	15% 5% 2 4 4 3 4 3 4 7% 50%	1776
March	1st to 10th	Night	16% 6% 2 4 4 2 3 3 5% 8% 46%	2103
	11th to 20th	Night	16% 6% 2 5% 4 3 3 4 4 4 49%	1980
	21st to end	Night	15% 5% 2 4 3 2 3 3 4 7% 53%	2178
April	1st to 10th	Night	12% 5% 2 4 5% 2 3 3 5% 7% 51%	1980
	11th to 20th	Night	17% 5% 2 4 3 3 4 3 4 5% 49%	1780
	21st to end	Night	17% 5% 2 4 4 2 3 3 4 5% 50%	1796
May	1st to 10th	Night	14% 4 3 4 4 2 3 5% 5% 7% 49%	1620
	11th to 20th	Night	15% 6% 3 4 4 2 3 3 5% 8% 47%	1593
	21st to end	Night	16% 5% 2 4 4 2 5% 4 4 9% 45%	1745
June	1st to 10th	Night	4 2 1 2 3 2 3 5% 6% 9% 62%	1620
	11th to 20th	Night	6% 4 1 3 3 2 4 5% 5% 8% 59%	1620
	21st to end	Night	9% 3 2 3 3 3 3 5% 5% 11% 52%	1620
July	1st to 10th	Night	10% 5% 2 5% 4 3 6% 6% 7% 10% 44%	1620
	11th to 20th	Night	4 3 1 3 3 2 3 4 5% 9% 63%	1620
	21st to end	Night	5% 3 1 2 2 2 4 5% 7% 11% 58%	1810
August	1st to 10th	Night	2 2 1 3 3 2 3 3 5% 8% 69%	1790
	11th to 20th	Night	5% 3 1 3 4 3 5% 4 6% 9% 56%	1778
	21st to end	Night	6% 4 2 5% 4 4 5% 5% 7% 9% 49%	1980
September	1st to 10th	Night	10% 5% 2 5% 4 4 4 5% 6% 10% 45%	1980
	11th to 20th	Night	12% 6% 2 4 5% 3 4 4 5% 8% 47%	1980
	21st to end	Night	9% 4 2 4 4 2 5% 5% 5% 8% 51%	1980
October	1st to 10th	Night	9% 4 1 4 3 2 3 3 4 7% 59%	1980
	11th to 20th	Night	14% 4 2 3 3 2 3 4 4 6% 55%	1980
	21st to end	Night	14% 4 1 3 2 2 1 2 2 4 64%	2359
November	1st to 10th	Night	14% 6% 2 3 4 1 3 3 3 5% 56%	2279
	11th to 20th	Night	11% 6% 2 4 4 2 3 3 5% 6% 56%	2470
	21st to end	Night	18% 5% 1 3 3 2 3 4 4 6% 49%	2470
December	1st to 10th	Night	14% 6% 1 3 3 2 3 4 4 6% 53%	2470
	11th to 20th	Night	16% 6% 3 4 4 2 3 3 3 5% 49%	3036
	21st to end	Night	18% 5% 1 2 2 1 2 3 4 7% 54%	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	33% 2 3 18% 23% 20%	1708
	11th to 20th	Day	37% 2 5% 16% 22% 18%	1795
	21st to end	Day	36% 2 5% 14% 24% 18%	2040
February	1st to 10th	Day	39% 2 5% 14% 21% 19%	1800
	11th to 20th	Day	41% 2 5% 17% 20% 14%	1759
	21st to end	Day	35% 2 7% 17% 21% 19%	1480
March	1st to 10th	Day	44% 2 6% 17% 18% 13%	1854
	11th to 20th	Day	42% 2 6% 16% 15% 19%	1980
	21st to end	Day	38% 3 8% 18% 18% 15%	2178
April	1st to 10th	Day	39% 3 8% 17% 19% 13%	1980
	11th to 20th	Day	39% 2 5% 22% 17% 16%	2124
	21st to end	Day	40% 3 6% 20% 18% 14%	2163
May	1st to 10th	Day	41% 3 9% 18% 20% 8%	2340
	11th to 20th	Day	42% 3 9% 21% 19% 4	2306
	21st to end	Day	47% 4 10% 21% 16% 2	2531
June	1st to 10th	Day	29% 4 14% 29% 19% 4	2340
	11th to 20th	Day	33% 5% 11% 27% 17% 6%	2340
	21st to end	Day	39% 6% 12% 23% 15% 4	2340
July	1st to 10th	Day	42% 4 16% 25% 12% 1	2276
	11th to 20th	Day	26% 4 17% 31% 20% 2	2271
	21st to end	Day	22% 5% 23% 36% 13% 1	2364
August	1st to 10th	Day	19% 3 17% 40% 19% 1	2136
	11th to 20th	Day	29% 4 17% 33% 13% 3	2123
	21st to end	Day	33% 5% 16% 29% 15% 3	2374
September	1st to 10th	Day	41% 6% 11% 20% 16% 5%	1980
	11th to 20th	Day	40% 5% 11% 22% 17% 5%	1980
	21st to end	Day	36% 5% 9% 22% 19% 9%	1980
October	1st to 10th	Day	31% 4 9% 24% 25% 7%	1980
	11th to 20th	Day	36% 3 8% 18% 20% 15%	1976
	21st to end	Day	32% 2 3 17% 26% 19%	1980
November	1st to 10th	Day	40% 3 8% 20% 19% 10%	1796
	11th to 20th	Day	38% 3 6% 18% 20% 15%	1710
	21st to end	Day	41% 1 4 18% 20% 15%	1710
December	1st to 10th	Day	39% 2 7% 18% 23% 11%	1710
	11th to 20th	Day	44% 1 5% 11% 21% 18%	2159
	21st to end	Day	34% 1 4 15% 30% 15%	3135
January	1st to 10th	Night	32% 2 5% 16% 23% 23%	2458
	11th to 20th	Night	35% 2 5% 16% 23% 19%	2399
	21st to end	Night	38% 2 4 15% 20% 21%	2460
February	1st to 10th	Night	32% 3 7% 15% 21% 22%	2160
	11th to 20th	Night	36% 2 6% 18% 20% 18%	2098
	21st to end	Night	36% 2 6% 15% 20% 20%	1776
March	1st to 10th	Night	39% 3 10% 16% 18% 14%	2103
	11th to 20th	Night	38% 3 8% 13% 17% 20%	1980
	21st to end	Night	33% 3 11% 19% 17% 17%	2178
April	1st to 10th	Night	34% 3 12% 18% 18% 16%	1980
	11th to 20th	Night	38% 3 8% 16% 16% 18%	1780
	21st to end	Night	37% 2 9% 19% 17% 15%	1796
May	1st to 10th	Night	35% 3 12% 21% 16% 12%	1620
	11th to 20th	Night	37% 3 11% 25% 18% 6%	1594
	21st to end	Night	37% 5% 15% 27% 14% 3	1746
June	1st to 10th	Night	20% 4 18% 33% 22% 3	1620
	11th to 20th	Night	24% 5% 13% 30% 22% 6%	1620
	21st to end	Night	26% 6% 20% 27% 17% 4	1620
July	1st to 10th	Night	34% 7% 22% 25% 11% 1	1575
	11th to 20th	Night	19% 5% 18% 32% 22% 2	1566
	21st to end	Night	18% 5% 28% 36% 13% 1	1709
August	1st to 10th	Night	13% 5% 21% 41% 19% 1	1779
	11th to 20th	Night	24% 5% 22% 30% 16% 3	1778
	21st to end	Night	30% 6% 20% 25% 15% 3	1980
September	1st to 10th	Night	35% 6% 14% 22% 17% 6%	1980
	11th to 20th	Night	35% 6% 17% 21% 16% 5%	1980
	21st to end	Night	31% 5% 12% 23% 19% 10%	1980
October	1st to 10th	Night	26% 3 12% 27% 21% 11%	1980
	11th to 20th	Night	32% 3 8% 20% 21% 15%	1980
	21st to end	Night	28% 2 5% 16% 26% 23%	2359
November	1st to 10th	Night	34% 2 6% 20% 24% 14%	2279
	11th to 20th	Night	31% 3 8% 20% 21% 17%	2470
	21st to end	Night	37% 2 7% 16% 21% 16%	2470
December	1st to 10th	Night	35% 1 9% 19% 22% 14%	2470
	11th to 20th	Night	39% 1 5% 16% 17% 21%	3037
	21st to end	Night	33% 2 5% 15% 27% 18%	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	20% 10% 34% 26% 9%	270
	11th to 20th	Day	23% 13% 29% 24% 10% 1	270
	21st to end	Day	21% 11% 35% 26% 7%	282
February	1st to 10th	Day	29% 10% 25% 25% 10% 1	240
	11th to 20th	Day	28% 8% 37% 20% 7% 1	240
	21st to end	Day	24% 13% 41% 18% 4	198
March	1st to 10th	Day	24% 13% 38% 23% 2	240
	11th to 20th	Day	21% 14% 42% 18% 5%	240
	21st to end	Day	23% 12% 42% 21% 3	264
April	1st to 10th	Day	23% 13% 38% 23% 3	240
	11th to 20th	Day	15% 17% 39% 24% 5%	402
	21st to end	Day	16% 13% 44% 21% 5%	423
May	1st to 10th	Day	20% 9% 35% 28% 7%	603
	11th to 20th	Day	23% 6% 31% 29% 9% 1	625
	21st to end	Day	21% 6% 29% 32% 11%	679
June	1st to 10th	Day	7% 3 18% 48% 21% 3	630
	11th to 20th	Day	11% 1 17% 50% 19% 2	630
	21st to end	Day	12% 3 13% 36% 30% 7%	630
July	1st to 10th	Day	15% 3 10% 31% 33% 8%	621
	11th to 20th	Day	7% 4 37% 46% 7%	618
	21st to end	Day	5% 1 5% 37% 45% 7%	641
August	1st to 10th	Day	2 4 40% 42% 11%	447
	11th to 20th	Day	8% 1 7% 31% 43% 11%	437
	21st to end	Day	8% 1 6% 30% 41% 14%	493
September	1st to 10th	Day	9% 1 8% 26% 41% 15%	270
	11th to 20th	Day	8% 1 6% 24% 43% 18%	270
	21st to end	Day	10% 3 6% 26% 44% 11%	270
October	1st to 10th	Day	10% 3 14% 36% 29% 7%	270
	11th to 20th	Day	13% 4 16% 44% 21% 2	270
	21st to end	Day	22% 12% 24% 25% 15% 2	297
November	1st to 10th	Day	21% 4 25% 32% 15% 3	270
	11th to 20th	Day	21% 9% 22% 31% 12% 5%	270
	21st to end	Day	25% 12% 31% 22% 8% 2	270
December	1st to 10th	Day	19% 9% 27% 29% 15% 2	270
	11th to 20th	Day	24% 14% 28% 23% 10%	270
	21st to end	Day	21% 7% 34% 25% 12% 1	297
January	1st to 10th	Night	17% 9% 26% 38% 9% 1	950
	11th to 20th	Night	20% 9% 26% 37% 8%	879
	21st to end	Night	23% 8% 27% 33% 8%	820
February	1st to 10th	Night	22% 9% 28% 33% 7% 1	720
	11th to 20th	Night	22% 11% 30% 31% 7%	704
	21st to end	Night	21% 10% 37% 30% 2	592
March	1st to 10th	Night	22% 10% 34% 28% 5% 1	663
	11th to 20th	Night	20% 9% 35% 31% 5%	540
	21st to end	Night	16% 9% 44% 26% 6%	594
April	1st to 10th	Night	13% 11% 43% 31% 2	540
	11th to 20th	Night	18% 12% 44% 23% 3	533
	21st to end	Night	18% 11% 42% 25% 4	540
May	1st to 10th	Night	15% 10% 41% 30% 4	540
	11th to 20th	Night	19% 7% 33% 35% 7%	531
	21st to end	Night	17% 6% 33% 35% 9%	584
June	1st to 10th	Night	5% 2 28% 49% 15%	540
	11th to 20th	Night	8% 1 30% 51% 11%	540
	21st to end	Night	9% 3 20% 48% 21% 1	540
July	1st to 10th	Night	11% 2 11% 52% 23% 1	525
	11th to 20th	Night	4 2 11% 51% 30% 2	522
	21st to end	Night	6% 1 7% 50% 35% 1	591
August	1st to 10th	Night	1 9% 48% 40% 1	537
	11th to 20th	Night	6% 1 5% 49% 37% 2	534
	21st to end	Night	6% 1 10% 42% 38% 3	594
September	1st to 10th	Night	8% 1 10% 41% 36% 3	540
	11th to 20th	Night	13% 1 7% 41% 36% 2	540
	21st to end	Night	11% 1 13% 36% 34% 4	540
October	1st to 10th	Night	9% 4 12% 47% 27% 2	540
	11th to 20th	Night	16% 3 20% 39% 21% 1	540
	21st to end	Night	15% 6% 23% 31% 21% 3	775
November	1st to 10th	Night	18% 4 16% 38% 21% 2	799
	11th to 20th	Night	14% 6% 20% 40% 17% 2	950
	21st to end	Night	22% 7% 23% 34% 13% 1	950
December	1st to 10th	Night	18% 5% 23% 38% 14% 2	950
	11th to 20th	Night	23% 9% 23% 35% 10%	950
	21st to end	Night	20% 8% 24% 39% 9% 1	1045

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