Walnut Point State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Walnut Point State Park clear sky chart from 2005-11-06 to 2026-05-02.

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% 8% 3 7% 5% 4 4 4 5% 8% 38%	131551
	Night	14% 9% 3 7% 4 4 4 3 5% 6% 39%	131203
Transparency	Day	44% 5% 12% 23% 14% 2	135123
	Night	44% 5% 10% 23% 15% 2	135706
Seeing	Day	16% 10% 27% 25% 17% 6%	17606
	Night	17% 9% 29% 30% 13% 1	27535

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% 11% 6% 13% 6% 5% 4 3 4 7% 27%	4691
	11th to 20th	Day	9% 11% 6% 14% 8% 7% 6% 5% 5% 5% 24%	4710
	21st to end	Day	17% 16% 5% 12% 7% 4 4 3 3 4 24%	5550
February	1st to 10th	Day	15% 12% 5% 11% 6% 4 4 3 5% 6% 30%	2019
	11th to 20th	Day	16% 11% 4 9% 7% 5% 4 4 5% 6% 30%	2048
	21st to end	Day	15% 13% 4 9% 4 4 4 3 4 6% 34%	1730
March	1st to 10th	Day	19% 14% 3 8% 3 3 3 2 3 3 39%	4580
	11th to 20th	Day	10% 10% 3 5% 3 4 4 3 5% 7% 44%	4787
	21st to end	Day	17% 10% 4 8% 5% 5% 5% 4 5% 7% 31%	6099
April	1st to 10th	Day	16% 9% 3 7% 5% 4 4 4 6% 8% 35%	2520
	11th to 20th	Day	16% 9% 3 6% 5% 4 4 4 5% 6% 40%	2494
	21st to end	Day	20% 8% 2 7% 4 4 4 4 5% 6% 36%	2578
May	1st to 10th	Day	19% 8% 3 7% 5% 4 5% 4 6% 9% 30%	5875
	11th to 20th	Day	17% 7% 3 7% 4 4 4 4 5% 8% 37%	5897
	21st to end	Day	12% 6% 3 7% 5% 5% 5% 5% 7% 9% 37%	6935
June	1st to 10th	Day	10% 6% 2 5% 5% 4 5% 4 6% 9% 45%	2800
	11th to 20th	Day	9% 4 1 5% 5% 5% 5% 4 6% 8% 47%	2800
	21st to end	Day	8% 5% 2 6% 6% 5% 5% 4 7% 9% 44%	2800
July	1st to 10th	Day	11% 4 2 6% 4 4 5% 4 7% 11% 43%	6360
	11th to 20th	Day	9% 5% 2 7% 5% 5% 5% 5% 8% 11% 36%	6360
	21st to end	Day	11% 6% 3 6% 4 4 6% 5% 8% 10% 38%	6924
August	1st to 10th	Day	8% 4 1 4 3 3 4 4 6% 9% 53%	4208
	11th to 20th	Day	9% 5% 2 6% 5% 5% 5% 5% 7% 10% 42%	3849
	21st to end	Day	6% 3 2 5% 4 4 4 4 6% 10% 51%	4312
September	1st to 10th	Day	12% 5% 2 6% 4 5% 4 3 4 7% 47%	2400
	11th to 20th	Day	9% 4 2 4 4 5% 5% 4 6% 7% 50%	2259
	21st to end	Day	11% 4 2 5% 4 5% 4 3 6% 6% 50%	2200
October	1st to 10th	Day	11% 5% 1 5% 4 4 4 3 4 7% 52%	2183
	11th to 20th	Day	15% 7% 2 6% 4 3 4 3 5% 5% 46%	2000
	21st to end	Day	19% 9% 3 6% 3 4 3 2 4 6% 40%	2004
November	1st to 10th	Day	11% 7% 3 5% 3 3 3 2 5% 6% 51%	1852
	11th to 20th	Day	17% 10% 3 5% 5% 4 3 3 5% 5% 40%	1890
	21st to end	Day	16% 11% 4 7% 5% 4 4 3 4 5% 37%	1890
December	1st to 10th	Day	11% 10% 4 8% 5% 4 4 3 4 6% 42%	2789
	11th to 20th	Day	13% 15% 5% 11% 5% 5% 4 3 5% 7% 27%	3088
	21st to end	Day	28% 16% 6% 11% 5% 3 4 2 4 4 16%	4070
January	1st to 10th	Night	14% 13% 7% 11% 4 3 4 3 4 5% 31%	8232
	11th to 20th	Night	11% 15% 5% 12% 5% 6% 6% 4 4 4 28%	8280
	21st to end	Night	18% 11% 5% 8% 5% 4 5% 3 4 6% 30%	8660
February	1st to 10th	Night	17% 12% 5% 9% 5% 5% 3 4 5% 6% 31%	2599
	11th to 20th	Night	15% 10% 3 9% 5% 4 4 3 4 6% 36%	2458
	21st to end	Night	18% 10% 3 7% 5% 4 4 3 4 5% 37%	2076
March	1st to 10th	Night	18% 14% 3 7% 4 3 3 2 3 5% 37%	5493
	11th to 20th	Night	13% 7% 2 5% 3 4 3 3 5% 7% 48%	5435
	21st to end	Night	18% 9% 3 8% 5% 5% 4 4 5% 6% 32%	5072
April	1st to 10th	Night	14% 8% 2 6% 5% 4 4 4 5% 6% 41%	2100
	11th to 20th	Night	17% 7% 2 6% 5% 3 3 4 4 6% 43%	2075
	21st to end	Night	17% 8% 2 6% 4 5% 5% 5% 5% 5% 37%	2041
May	1st to 10th	Night	19% 9% 3 7% 4 4 4 4 5% 7% 35%	4042
	11th to 20th	Night	16% 6% 2 5% 4 4 4 4 6% 9% 39%	3993
	21st to end	Night	15% 6% 3 7% 4 5% 5% 4 5% 8% 39%	3942
June	1st to 10th	Night	9% 5% 2 7% 4 4 4 4 5% 7% 50%	1600
	11th to 20th	Night	9% 5% 2 5% 4 4 5% 3 6% 7% 51%	1600
	21st to end	Night	7% 4 2 5% 5% 4 4 4 7% 12% 46%	1600
July	1st to 10th	Night	10% 4 2 6% 5% 4 5% 3 6% 9% 47%	3618
	11th to 20th	Night	6% 5% 2 6% 4 4 5% 4 7% 10% 48%	3617
	21st to end	Night	9% 5% 3 8% 5% 5% 4 4 8% 10% 40%	3947
August	1st to 10th	Night	7% 3 2 5% 3 3 4 4 6% 9% 54%	2940
	11th to 20th	Night	7% 4 2 6% 4 5% 4 4 6% 8% 50%	3200
	21st to end	Night	5% 3 1 4 3 3 3 4 5% 9% 57%	3586
September	1st to 10th	Night	12% 4 2 4 3 4 3 3 4 7% 54%	2000
	11th to 20th	Night	6% 5% 2 5% 4 3 3 3 6% 8% 56%	2120
	21st to end	Night	12% 6% 2 4 4 3 4 4 5% 6% 51%	2200
October	1st to 10th	Night	9% 4 2 4 4 3 3 3 5% 6% 57%	2214
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 4 6% 51%	2400
	21st to end	Night	18% 8% 2 5% 3 4 5% 3 5% 6% 41%	2835
November	1st to 10th	Night	10% 6% 2 5% 4 4 3 3 4 6% 52%	2666
	11th to 20th	Night	13% 8% 3 6% 4 4 4 3 5% 6% 44%	2730
	21st to end	Night	19% 10% 4 7% 4 4 4 2 4 6% 37%	2730
December	1st to 10th	Night	14% 9% 4 8% 4 4 3 3 4 5% 44%	4613
	11th to 20th	Night	16% 10% 5% 9% 5% 4 4 3 4 6% 33%	5339
	21st to end	Night	29% 17% 5% 9% 5% 4 3 3 3 4 18%	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	57% 3 11% 20% 7% 1	4692
	11th to 20th	Day	62% 3 9% 13% 11% 2	4710
	21st to end	Day	64% 3 7% 17% 6% 2	5550
February	1st to 10th	Day	55% 4 12% 18% 9% 1	2019
	11th to 20th	Day	55% 4 10% 20% 10% 1	2058
	21st to end	Day	52% 4 9% 23% 9% 3	1730
March	1st to 10th	Day	52% 3 6% 19% 17% 3	4580
	11th to 20th	Day	38% 4 10% 31% 15% 1	4787
	21st to end	Day	52% 6% 11% 22% 7% 1	6101
April	1st to 10th	Day	47% 7% 12% 21% 14% 1	2520
	11th to 20th	Day	45% 5% 11% 25% 11% 3	2494
	21st to end	Day	48% 5% 12% 22% 11% 2	2578
May	1st to 10th	Day	49% 7% 13% 20% 10% 1	5910
	11th to 20th	Day	45% 7% 11% 25% 11% 1	5901
	21st to end	Day	42% 7% 13% 21% 16% 2	6949
June	1st to 10th	Day	35% 7% 13% 26% 16% 3	2800
	11th to 20th	Day	34% 7% 11% 23% 21% 4	2800
	21st to end	Day	35% 8% 16% 21% 17% 4	2800
July	1st to 10th	Day	35% 5% 11% 30% 17% 2	6291
	11th to 20th	Day	39% 8% 15% 24% 13% 1	6285
	21st to end	Day	39% 7% 18% 23% 11% 1	6728
August	1st to 10th	Day	28% 6% 15% 35% 15% 1	4193
	11th to 20th	Day	35% 7% 15% 26% 15% 1	3885
	21st to end	Day	28% 6% 16% 31% 15% 4	4311
September	1st to 10th	Day	36% 5% 11% 24% 19% 4	2400
	11th to 20th	Day	32% 6% 11% 23% 25% 3	2259
	21st to end	Day	34% 5% 10% 24% 24% 3	2200
October	1st to 10th	Day	23% 4 8% 25% 37% 3	3560
	11th to 20th	Day	29% 3 8% 24% 34% 2	3240
	21st to end	Day	39% 3 8% 23% 25% 1	3216
November	1st to 10th	Day	35% 4 13% 26% 18% 4	1852
	11th to 20th	Day	45% 4 10% 23% 15% 4	1890
	21st to end	Day	50% 5% 8% 22% 14% 1	1890
December	1st to 10th	Day	44% 3 12% 28% 11%	2789
	11th to 20th	Day	58% 3 9% 23% 6% 1	3085
	21st to end	Day	73% 3 10% 10% 4	4070
January	1st to 10th	Night	56% 4 11% 22% 7%	8233
	11th to 20th	Night	60% 3 7% 14% 13% 3	8280
	21st to end	Night	56% 3 9% 22% 9% 1	8660
February	1st to 10th	Night	55% 4 11% 19% 9% 2	2599
	11th to 20th	Night	49% 4 10% 22% 12% 2	2459
	21st to end	Night	50% 4 9% 22% 12% 2	2076
March	1st to 10th	Night	52% 3 7% 21% 13% 4	5493
	11th to 20th	Night	36% 4 10% 29% 19% 2	5435
	21st to end	Night	52% 5% 9% 25% 8% 1	5072
April	1st to 10th	Night	43% 6% 10% 23% 16% 2	2100
	11th to 20th	Night	42% 5% 10% 22% 17% 4	2075
	21st to end	Night	47% 6% 10% 22% 12% 3	2041
May	1st to 10th	Night	48% 8% 12% 20% 10% 1	4069
	11th to 20th	Night	41% 7% 11% 26% 14% 1	3994
	21st to end	Night	43% 6% 13% 20% 14% 3	3950
June	1st to 10th	Night	33% 6% 10% 27% 19% 5%	1600
	11th to 20th	Night	32% 6% 10% 25% 23% 4	1600
	21st to end	Night	31% 7% 16% 23% 19% 5%	1600
July	1st to 10th	Night	34% 5% 10% 28% 19% 3	3580
	11th to 20th	Night	31% 6% 16% 28% 18% 1	3572
	21st to end	Night	38% 6% 17% 24% 13% 2	3832
August	1st to 10th	Night	26% 6% 15% 36% 16% 1	2931
	11th to 20th	Night	32% 6% 14% 28% 19% 1	3230
	21st to end	Night	24% 6% 14% 32% 20% 4	3586
September	1st to 10th	Night	30% 5% 9% 28% 20% 7%	2000
	11th to 20th	Night	27% 4 10% 26% 28% 5%	2120
	21st to end	Night	32% 7% 9% 23% 25% 4	2200
October	1st to 10th	Night	20% 3 6% 24% 43% 3	3617
	11th to 20th	Night	24% 3 7% 27% 35% 3	3899
	21st to end	Night	36% 4 7% 24% 24% 5%	4573
November	1st to 10th	Night	33% 5% 9% 26% 22% 5%	2666
	11th to 20th	Night	41% 4 10% 25% 19% 2	2730
	21st to end	Night	50% 4 9% 22% 14% 1	2730
December	1st to 10th	Night	44% 3 11% 27% 14%	4613
	11th to 20th	Night	53% 4 11% 20% 11%	5341
	21st to end	Night	71% 4 9% 11% 5% 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	20% 19% 34% 20% 7%	330
	11th to 20th	Day	21% 21% 37% 17% 3	330
	21st to end	Day	20% 17% 38% 20% 4	363
February	1st to 10th	Day	24% 15% 35% 22% 5%	330
	11th to 20th	Day	25% 21% 36% 14% 2 2	330
	21st to end	Day	24% 15% 40% 18% 2	273
March	1st to 10th	Day	22% 19% 38% 17% 3	330
	11th to 20th	Day	25% 19% 36% 15% 4	361
	21st to end	Day	27% 15% 37% 15% 5% 1	594
April	1st to 10th	Day	21% 16% 31% 24% 7% 1	540
	11th to 20th	Day	20% 19% 27% 20% 12% 2	532
	21st to end	Day	24% 14% 34% 19% 8% 2	540
May	1st to 10th	Day	20% 12% 31% 24% 11% 2	507
	11th to 20th	Day	19% 8% 27% 27% 14% 5%	537
	21st to end	Day	11% 6% 32% 27% 16% 8%	789
June	1st to 10th	Day	11% 6% 24% 31% 21% 7%	730
	11th to 20th	Day	11% 3 24% 34% 21% 7%	730
	21st to end	Day	9% 6% 29% 28% 22% 6%	730
July	1st to 10th	Day	10% 3 14% 27% 27% 18%	721
	11th to 20th	Day	7% 3 18% 33% 26% 12%	718
	21st to end	Day	10% 2 14% 32% 31% 10%	794
August	1st to 10th	Day	8% 2 15% 29% 34% 12%	586
	11th to 20th	Day	11% 3 17% 29% 28% 12%	519
	21st to end	Day	5% 2 13% 32% 34% 14%	583
September	1st to 10th	Day	10% 5% 16% 28% 31% 10%	530
	11th to 20th	Day	8% 2 12% 29% 32% 16%	530
	21st to end	Day	13% 7% 22% 24% 20% 14%	530
October	1st to 10th	Day	12% 4 24% 30% 24% 8%	513
	11th to 20th	Day	14% 14% 33% 23% 14% 2	330
	21st to end	Day	27% 16% 33% 19% 5% 1	363
November	1st to 10th	Day	11% 15% 31% 27% 12% 3	330
	11th to 20th	Day	20% 18% 32% 21% 9% 1	330
	21st to end	Day	25% 12% 34% 23% 6% 1	330
December	1st to 10th	Day	14% 18% 41% 19% 6% 2	330
	11th to 20th	Day	20% 15% 38% 20% 6% 1	330
	21st to end	Day	27% 18% 34% 16% 5%	363
January	1st to 10th	Night	20% 14% 38% 24% 3	1050
	11th to 20th	Night	22% 18% 36% 20% 4	1050
	21st to end	Night	21% 14% 38% 24% 2	1155
February	1st to 10th	Night	24% 12% 38% 23% 2	919
	11th to 20th	Night	19% 17% 37% 24% 3	823
	21st to end	Night	25% 12% 39% 23% 2	692
March	1st to 10th	Night	24% 14% 33% 25% 4	840
	11th to 20th	Night	21% 12% 38% 23% 6%	824
	21st to end	Night	23% 12% 32% 27% 5%	693
April	1st to 10th	Night	19% 13% 35% 27% 5%	630
	11th to 20th	Night	21% 12% 33% 24% 10%	623
	21st to end	Night	21% 8% 38% 26% 7% 1	630
May	1st to 10th	Night	18% 7% 33% 33% 8%	603
	11th to 20th	Night	17% 6% 28% 33% 15% 1	591
	21st to end	Night	11% 5% 25% 34% 22% 2	650
June	1st to 10th	Night	11% 3 24% 40% 22%	600
	11th to 20th	Night	9% 2 23% 45% 21% 1	600
	21st to end	Night	8% 3 24% 41% 25% 1	600
July	1st to 10th	Night	10% 1 12% 34% 37% 6%	585
	11th to 20th	Night	5% 3 15% 43% 30% 4	582
	21st to end	Night	7% 1 13% 45% 31% 3	657
August	1st to 10th	Night	7% 3 11% 42% 33% 4	597
	11th to 20th	Night	7% 1 13% 40% 34% 4	594
	21st to end	Night	7% 1 13% 36% 39% 4	660
September	1st to 10th	Night	13% 3 15% 35% 30% 4	600
	11th to 20th	Night	7% 3 13% 40% 33% 4	720
	21st to end	Night	14% 5% 20% 31% 26% 4	800
October	1st to 10th	Night	10% 4 24% 38% 21% 4	800
	11th to 20th	Night	18% 11% 27% 30% 13% 1	800
	21st to end	Night	21% 12% 34% 26% 6%	880
November	1st to 10th	Night	12% 10% 39% 28% 11%	820
	11th to 20th	Night	18% 13% 33% 28% 7% 1	840
	21st to end	Night	25% 13% 30% 26% 6%	840
December	1st to 10th	Night	23% 10% 39% 24% 4 1	982
	11th to 20th	Night	23% 10% 35% 26% 6%	1050
	21st to end	Night	29% 16% 32% 20% 3	1155

Page generated at 2026-04-29 01:21:47. Version ac07

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