High Creek Fen Preserve
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the High Creek Fen Preserve clear sky chart from 2005-11-06 to 2026-10-14.

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	2 4 2 6% 4 5% 5% 4 6% 8% 52%	158111
	Night	2 4 2 4 3 3 4 3 5% 8% 62%	151238
Transparency	Day	25% 8% 11% 23% 23% 10%	153048
	Night	19% 6% 14% 26% 26% 9%	147310
Seeing	Day	7% 19% 29% 26% 15% 4	18170
	Night	4 14% 38% 30% 13% 1	28140

By Month

Percentage Cloud Cover SW (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	3 2 6% 4 3 3 3 5% 7% 64%	4720
	11th to 20th	Day	1 2 3 4 4 3 5% 7% 70%	5194
	21st to end	Day	2 2 5% 4 4 4 3 6% 7% 63%	5844
February	1st to 10th	Day	3 2 6% 3 3 5% 4 6% 8% 61%	1890
	11th to 20th	Day	2 1 4 3 4 5% 4 7% 7% 62%	1979
	21st to end	Day	2 2 6% 5% 4 4 3 6% 7% 61%	1730
March	1st to 10th	Day	4 3 6% 4 4 4 3 5% 6% 60%	4727
	11th to 20th	Day	1 7% 2 6% 5% 5% 6% 4 6% 10% 48%	5110
	21st to end	Day	1 4 2 6% 4 5% 5% 5% 7% 10% 51%	5831
April	1st to 10th	Day	1 5% 2 5% 4 5% 4 3 7% 8% 56%	2520
	11th to 20th	Day	3 7% 2 7% 5% 5% 5% 5% 6% 8% 47%	2491
	21st to end	Day	2 7% 2 6% 5% 5% 5% 5% 7% 9% 47%	2520
May	1st to 10th	Day	4 9% 3 8% 5% 5% 6% 4 7% 8% 41%	7279
	11th to 20th	Day	4 6% 2 6% 5% 6% 6% 5% 8% 8% 45%	8191
	21st to end	Day	2 3 2 5% 4 5% 7% 6% 8% 9% 48%	9026
June	1st to 10th	Day	3 4 1 5% 5% 6% 6% 5% 8% 9% 48%	2940
	11th to 20th	Day	4 4 2 5% 4 4 5% 4 5% 8% 56%	2940
	21st to end	Day	3 4 2 5% 5% 4 6% 4 8% 8% 51%	2940
July	1st to 10th	Day	3 3 1 5% 4 5% 6% 4 7% 7% 54%	8249
	11th to 20th	Day	3 4 2 7% 6% 7% 6% 5% 7% 9% 44%	8250
	21st to end	Day	5% 6% 2 9% 6% 7% 7% 6% 6% 8% 39%	8428
August	1st to 10th	Day	4 5% 2 7% 6% 6% 7% 5% 7% 10% 40%	7549
	11th to 20th	Day	3 4 2 6% 6% 6% 7% 5% 8% 10% 42%	7113
	21st to end	Day	4 5% 3 8% 6% 7% 8% 6% 7% 9% 37%	7751
September	1st to 10th	Day	6% 4 2 5% 5% 4 4 4 6% 7% 52%	2520
	11th to 20th	Day	4 3 2 6% 5% 4 5% 4 5% 7% 54%	2520
	21st to end	Day	4 4 2 5% 4 3 4 3 6% 6% 59%	2273
October	1st to 10th	Day	2 3 1 3 4 3 4 2 4 5% 69%	3370
	11th to 20th	Day	3 3 1 4 3 4 6% 4 6% 9% 57%	3280
	21st to end	Day	2 3 1 3 2 2 3 3 5% 6% 70%	3548
November	1st to 10th	Day	1 3 1 3 2 3 2 3 4 6% 73%	1857
	11th to 20th	Day	2 1 2 2 2 3 3 4 7% 75%	1890
	21st to end	Day	1 3 2 4 2 3 3 3 5% 8% 66%	1743
December	1st to 10th	Day	1 1 5% 3 2 2 2 4 6% 74%	2700
	11th to 20th	Day	2 1 2 2 2 3 3 4 9% 71%	3106
	21st to end	Day	2 2 5% 3 3 4 3 6% 10% 61%	4092
January	1st to 10th	Night	2 2 9% 4 3 3 3 5% 7% 63%	8201
	11th to 20th	Night	1 2 2 3 3 3 4 6% 76%	7853
	21st to end	Night	4 2 5% 2 3 3 3 4 6% 69%	8370
February	1st to 10th	Night	2 2 5% 2 3 3 2 4 7% 69%	2730
	11th to 20th	Night	2 2 6% 3 3 3 3 5% 6% 67%	2525
	21st to end	Night	3 2 4 3 2 3 2 5% 8% 67%	2076
March	1st to 10th	Night	5% 2 7% 3 3 3 3 4 7% 63%	5370
	11th to 20th	Night	1 9% 3 5% 3 2 3 2 4 7% 61%	5110
	21st to end	Night	1 4 2 4 3 3 4 3 6% 8% 62%	5361
April	1st to 10th	Night	1 3 1 3 2 3 4 3 5% 7% 67%	2100
	11th to 20th	Night	3 7% 3 4 3 3 4 3 6% 6% 57%	2077
	21st to end	Night	3 8% 1 6% 3 3 3 3 5% 6% 58%	2100
May	1st to 10th	Night	4 12% 3 6% 3 3 4 3 6% 8% 48%	5650
	11th to 20th	Night	4 8% 2 4 3 3 4 4 6% 8% 54%	4701
	21st to end	Night	5% 8% 2 5% 3 3 3 3 5% 6% 56%	5181
June	1st to 10th	Night	3 4 2 3 2 3 3 3 6% 9% 62%	1680
	11th to 20th	Night	4 2 1 3 2 2 3 4 5% 7% 67%	1680
	21st to end	Night	3 3 1 4 3 3 3 4 6% 9% 61%	1680
July	1st to 10th	Night	2 3 1 3 3 4 4 4 6% 8% 61%	4740
	11th to 20th	Night	1 2 1 4 4 4 5% 5% 8% 11% 55%	4740
	21st to end	Night	3 4 1 5% 5% 5% 6% 6% 9% 10% 46%	5664
August	1st to 10th	Night	2 3 2 5% 3 3 4 4 7% 10% 56%	5273
	11th to 20th	Night	2 3 1 4 4 4 5% 5% 9% 12% 51%	5741
	21st to end	Night	3 4 2 6% 5% 5% 6% 6% 9% 13% 41%	6465
September	1st to 10th	Night	5% 3 1 4 3 4 5% 5% 5% 8% 57%	2100
	11th to 20th	Night	5% 3 1 4 3 3 3 3 5% 8% 61%	2100
	21st to end	Night	5% 5% 1 4 3 4 3 3 5% 5% 62%	2343
October	1st to 10th	Night	3 3 1 2 2 2 2 2 3 5% 74%	4040
	11th to 20th	Night	3 4 2 3 2 3 3 3 5% 7% 67%	3934
	21st to end	Night	1 3 1 3 2 2 2 2 4 6% 75%	4252
November	1st to 10th	Night	1 3 1 3 2 1 2 3 4 6% 74%	2640
	11th to 20th	Night	1 1 2 2 2 2 3 4 7% 77%	2730
	21st to end	Night	1 4 2 3 2 2 2 3 6% 7% 67%	2872
December	1st to 10th	Night	1 1 3 2 2 2 2 3 5% 80%	4710
	11th to 20th	Night	2 1 2 2 2 3 2 5% 7% 74%	5321
	21st to end	Night	3 2 5% 4 4 4 3 6% 8% 62%	7128

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	19% 5% 11% 31% 26% 8%	4723
	11th to 20th	Day	11% 5% 15% 25% 32% 13%	5194
	21st to end	Day	17% 7% 8% 26% 27% 15%	5844
February	1st to 10th	Day	20% 8% 14% 27% 21% 10%	1890
	11th to 20th	Day	18% 8% 11% 27% 28% 9%	1988
	21st to end	Day	22% 8% 10% 20% 26% 15%	1730
March	1st to 10th	Day	21% 6% 7% 17% 33% 15%	4727
	11th to 20th	Day	28% 9% 8% 27% 23% 5%	5110
	21st to end	Day	21% 12% 10% 37% 17% 2	5831
April	1st to 10th	Day	23% 8% 13% 24% 22% 9%	2520
	11th to 20th	Day	32% 8% 11% 21% 23% 5%	2494
	21st to end	Day	30% 9% 11% 28% 19% 3	2520
May	1st to 10th	Day	33% 9% 10% 25% 19% 4	7279
	11th to 20th	Day	29% 11% 11% 22% 22% 6%	8195
	21st to end	Day	24% 9% 13% 21% 26% 7%	9027
June	1st to 10th	Day	28% 10% 13% 21% 21% 8%	2940
	11th to 20th	Day	25% 8% 8% 18% 24% 19%	2940
	21st to end	Day	26% 9% 8% 20% 21% 14%	2940
July	1st to 10th	Day	21% 9% 8% 13% 20% 29%	8181
	11th to 20th	Day	29% 11% 11% 21% 17% 11%	8175
	21st to end	Day	38% 11% 17% 13% 12% 9%	8241
August	1st to 10th	Day	36% 11% 14% 14% 15% 11%	5978
	11th to 20th	Day	33% 11% 19% 16% 15% 6%	5606
	21st to end	Day	34% 11% 17% 18% 16% 4	6078
September	1st to 10th	Day	29% 8% 9% 17% 24% 12%	2520
	11th to 20th	Day	26% 7% 11% 18% 27% 11%	2520
	21st to end	Day	24% 6% 7% 24% 30% 8%	2273
October	1st to 10th	Day	15% 6% 6% 20% 34% 18%	3370
	11th to 20th	Day	21% 6% 8% 31% 26% 7%	3280
	21st to end	Day	14% 5% 6% 28% 39% 8%	3548
November	1st to 10th	Day	13% 5% 11% 24% 37% 10%	1857
	11th to 20th	Day	11% 5% 10% 37% 28% 10%	1890
	21st to end	Day	17% 4 11% 29% 27% 12%	1743
December	1st to 10th	Day	13% 4 11% 32% 31% 9%	2700
	11th to 20th	Day	12% 5% 11% 36% 29% 6%	3104
	21st to end	Day	15% 7% 10% 28% 29% 11%	4092
January	1st to 10th	Night	21% 5% 9% 32% 28% 5%	8202
	11th to 20th	Night	8% 5% 13% 30% 27% 17%	7853
	21st to end	Night	16% 5% 10% 23% 30% 15%	8370
February	1st to 10th	Night	16% 4 14% 33% 25% 8%	2730
	11th to 20th	Night	17% 5% 13% 31% 28% 6%	2526
	21st to end	Night	17% 4 10% 28% 30% 11%	2076
March	1st to 10th	Night	20% 5% 8% 20% 37% 11%	5370
	11th to 20th	Night	24% 6% 9% 22% 31% 9%	5110
	21st to end	Night	18% 6% 17% 41% 16% 2	5361
April	1st to 10th	Night	16% 6% 15% 32% 26% 5%	2100
	11th to 20th	Night	26% 5% 10% 29% 24% 5%	2077
	21st to end	Night	27% 5% 14% 31% 20% 2	2100
May	1st to 10th	Night	30% 9% 13% 28% 15% 4	5648
	11th to 20th	Night	26% 7% 14% 26% 24% 3	4702
	21st to end	Night	25% 7% 14% 20% 27% 6%	5182
June	1st to 10th	Night	18% 7% 18% 29% 20% 9%	1680
	11th to 20th	Night	16% 6% 12% 21% 27% 18%	1680
	21st to end	Night	18% 6% 13% 23% 26% 14%	1680
July	1st to 10th	Night	19% 7% 9% 18% 25% 22%	4700
	11th to 20th	Night	19% 9% 20% 29% 18% 5%	4692
	21st to end	Night	27% 12% 26% 19% 8% 9%	5539
August	1st to 10th	Night	24% 10% 22% 24% 13% 7%	4168
	11th to 20th	Night	22% 11% 32% 15% 14% 5%	4524
	21st to end	Night	25% 12% 30% 16% 15% 2	5069
September	1st to 10th	Night	25% 7% 13% 24% 22% 9%	2100
	11th to 20th	Night	21% 6% 13% 24% 23% 12%	2100
	21st to end	Night	24% 5% 9% 27% 29% 6%	2343
October	1st to 10th	Night	14% 6% 8% 24% 34% 14%	4040
	11th to 20th	Night	16% 5% 10% 35% 27% 7%	3934
	21st to end	Night	12% 4 7% 27% 42% 9%	4252
November	1st to 10th	Night	12% 5% 11% 27% 35% 10%	2640
	11th to 20th	Night	9% 4 11% 37% 31% 9%	2730
	21st to end	Night	16% 4 11% 31% 28% 10%	2872
December	1st to 10th	Night	10% 3 11% 35% 34% 7%	4710
	11th to 20th	Night	11% 4 11% 30% 37% 6%	5322
	21st to end	Night	19% 6% 14% 25% 28% 10%	7128

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	5% 28% 31% 27% 8% 1	330
	11th to 20th	Day	7% 32% 33% 22% 6% 1	330
	21st to end	Day	1 25% 43% 24% 6% 1	363
February	1st to 10th	Day	4 42% 35% 15% 3 1	330
	11th to 20th	Day	3 40% 36% 17% 4	330
	21st to end	Day	7% 42% 32% 15% 4	273
March	1st to 10th	Day	3 30% 39% 21% 7%	379
	11th to 20th	Day	8% 30% 34% 22% 6%	540
	21st to end	Day	5% 37% 37% 16% 4 1	594
April	1st to 10th	Day	6% 31% 35% 22% 6% 1	540
	11th to 20th	Day	9% 39% 30% 15% 5% 1	532
	21st to end	Day	9% 28% 35% 21% 5% 1	540
May	1st to 10th	Day	8% 28% 34% 19% 9% 2	578
	11th to 20th	Day	10% 15% 30% 28% 13% 3	775
	21st to end	Day	8% 17% 28% 31% 15% 3	844
June	1st to 10th	Day	3 15% 26% 30% 21% 5%	780
	11th to 20th	Day	6% 14% 29% 32% 15% 4	780
	21st to end	Day	4 11% 29% 31% 19% 6%	780
July	1st to 10th	Day	5% 5% 20% 35% 27% 7%	771
	11th to 20th	Day	6% 3 18% 32% 32% 8%	768
	21st to end	Day	10% 5% 18% 31% 29% 7%	666
August	1st to 10th	Day	10% 6% 27% 31% 22% 5%	567
	11th to 20th	Day	7% 6% 24% 29% 25% 10%	557
	21st to end	Day	9% 7% 22% 31% 25% 7%	627
September	1st to 10th	Day	10% 7% 23% 32% 20% 8%	570
	11th to 20th	Day	5% 11% 32% 31% 18% 3	570
	21st to end	Day	7% 13% 22% 29% 22% 7%	381
October	1st to 10th	Day	5% 16% 22% 23% 27% 8%	360
	11th to 20th	Day	8% 25% 27% 25% 13% 3	339
	21st to end	Day	8% 24% 26% 28% 13% 1	363
November	1st to 10th	Day	6% 27% 33% 23% 10% 2	330
	11th to 20th	Day	5% 25% 32% 27% 11% 2	330
	21st to end	Day	5% 19% 43% 27% 6% 1	330
December	1st to 10th	Day	9% 27% 37% 17% 8% 2	330
	11th to 20th	Day	5% 32% 38% 17% 7% 1	330
	21st to end	Day	10% 26% 38% 20% 5% 1	363
January	1st to 10th	Night	2 23% 43% 24% 7% 1	1050
	11th to 20th	Night	3 26% 44% 21% 5% 1	913
	21st to end	Night	1 19% 51% 23% 5% 1	924
February	1st to 10th	Night	1 23% 54% 18% 5%	840
	11th to 20th	Night	2 24% 50% 20% 4	824
	21st to end	Night	1 21% 54% 21% 2	692
March	1st to 10th	Night	2 18% 48% 27% 4	840
	11th to 20th	Night	4 14% 48% 28% 7%	840
	21st to end	Night	3 16% 51% 26% 4	817
April	1st to 10th	Night	4 17% 48% 27% 4	630
	11th to 20th	Night	6% 18% 43% 27% 5% 1	623
	21st to end	Night	7% 16% 43% 27% 7%	630
May	1st to 10th	Night	7% 11% 42% 30% 9% 1	630
	11th to 20th	Night	11% 6% 29% 38% 14% 1	621
	21st to end	Night	9% 9% 31% 36% 14% 2	683
June	1st to 10th	Night	4 6% 29% 37% 23% 1	630
	11th to 20th	Night	5% 5% 33% 42% 13% 1	630
	21st to end	Night	3 3 27% 38% 27% 2	630
July	1st to 10th	Night	8% 2 12% 41% 34% 3	615
	11th to 20th	Night	3 1 11% 43% 38% 4	612
	21st to end	Night	8% 1 8% 36% 45% 3	690
August	1st to 10th	Night	7% 2 15% 39% 34% 2	627
	11th to 20th	Night	5% 2 14% 44% 31% 4	624
	21st to end	Night	6% 2 13% 42% 33% 3	693
September	1st to 10th	Night	7% 3 17% 45% 25% 4	630
	11th to 20th	Night	7% 2 25% 45% 19% 2	630
	21st to end	Night	6% 7% 27% 39% 19% 2	685
October	1st to 10th	Night	6% 6% 36% 35% 15% 3	840
	11th to 20th	Night	2 12% 42% 31% 11% 1	812
	21st to end	Night	5% 13% 41% 30% 9% 2	880
November	1st to 10th	Night	3 14% 46% 29% 8% 1	1000
	11th to 20th	Night	2 19% 48% 24% 6% 1	1050
	21st to end	Night	4 18% 42% 30% 5%	1050
December	1st to 10th	Night	2 21% 46% 25% 6%	1050
	11th to 20th	Night	3 24% 44% 22% 6%	1050
	21st to end	Night	4 24% 44% 23% 4	1155

Page generated at 2026-10-11 03:06:26. Version ac07

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