Walnut Mountain Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Walnut Mountain Park clear sky chart from 2005-11-06 to 2025-10-19.

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	18% 8% 3 8% 5% 5% 5% 4 5% 7% 33%	126809
	Night	18% 9% 3 8% 5% 4 4 4 5% 7% 35%	122898
Transparency	Day	47% 7% 12% 20% 12% 2	130311
	Night	45% 7% 13% 20% 13% 2	127483
Seeing	Day	25% 18% 28% 18% 9% 3	16086
	Night	23% 16% 27% 24% 9% 1	25195

By Month

Percentage Cloud Cover NE (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% 6% 17% 7% 5% 5% 3 5% 6% 24%	3597
	11th to 20th	Day	15% 12% 6% 15% 8% 5% 5% 4 5% 5% 21%	3570
	21st to end	Day	17% 12% 6% 8% 6% 4 4 3 4 5% 32%	4325
February	1st to 10th	Day	15% 12% 5% 9% 6% 6% 5% 5% 5% 6% 27%	1800
	11th to 20th	Day	14% 9% 3 9% 7% 5% 4 4 5% 8% 31%	1889
	21st to end	Day	20% 10% 3 9% 6% 4 4 3 5% 6% 31%	1650
March	1st to 10th	Day	21% 10% 4 8% 5% 4 4 3 4 5% 33%	4476
	11th to 20th	Day	13% 9% 4 9% 5% 5% 4 4 4 6% 37%	4880
	21st to end	Day	20% 9% 3 6% 5% 5% 5% 4 5% 6% 34%	5865
April	1st to 10th	Day	19% 11% 3 7% 6% 4 4 3 5% 6% 32%	2400
	11th to 20th	Day	18% 10% 2 7% 4 5% 4 4 4 7% 35%	2374
	21st to end	Day	18% 9% 3 8% 5% 4 4 3 5% 6% 35%	2410
May	1st to 10th	Day	31% 8% 3 6% 4 4 4 3 5% 6% 26%	6068
	11th to 20th	Day	20% 10% 3 8% 6% 5% 4 3 5% 6% 29%	6318
	21st to end	Day	22% 6% 2 6% 4 5% 6% 5% 7% 8% 29%	6949
June	1st to 10th	Day	17% 6% 2 7% 6% 5% 5% 4 6% 10% 32%	2800
	11th to 20th	Day	18% 7% 2 7% 6% 4 4 5% 7% 9% 31%	2800
	21st to end	Day	16% 6% 3 7% 5% 5% 5% 4 6% 9% 34%	2800
July	1st to 10th	Day	11% 6% 3 8% 6% 5% 6% 5% 6% 8% 35%	6360
	11th to 20th	Day	12% 6% 3 7% 5% 5% 6% 5% 7% 11% 32%	6360
	21st to end	Day	15% 6% 2 6% 4 4 5% 4 7% 9% 38%	6926
August	1st to 10th	Day	21% 7% 3 7% 5% 5% 5% 4 6% 8% 31%	4352
	11th to 20th	Day	16% 6% 3 6% 4 4 5% 5% 7% 8% 36%	3886
	21st to end	Day	17% 5% 2 5% 3 4 4 4 7% 10% 40%	4312
September	1st to 10th	Day	16% 6% 3 6% 4 5% 4 3 6% 7% 40%	2400
	11th to 20th	Day	14% 5% 2 4 4 4 4 3 4 9% 46%	2350
	21st to end	Day	20% 7% 2 6% 4 4 4 4 5% 7% 36%	2200
October	1st to 10th	Day	19% 8% 3 7% 4 4 4 4 5% 7% 38%	2026
	11th to 20th	Day	17% 8% 2 6% 4 4 4 4 6% 7% 37%	1980
	21st to end	Day	23% 9% 3 7% 4 4 5% 4 5% 6% 31%	1957
November	1st to 10th	Day	15% 7% 2 6% 5% 3 4 2 6% 7% 43%	1761
	11th to 20th	Day	17% 10% 2 7% 5% 4 4 4 4 6% 36%	1800
	21st to end	Day	18% 11% 4 6% 5% 5% 5% 3 5% 7% 32%	1622
December	1st to 10th	Day	18% 10% 4 13% 7% 5% 5% 3 5% 6% 23%	2600
	11th to 20th	Day	23% 10% 4 7% 5% 4 3 3 4 5% 31%	2986
	21st to end	Day	18% 12% 6% 11% 5% 4 4 4 5% 6% 25%	3960
January	1st to 10th	Night	13% 9% 4 15% 7% 5% 4 4 5% 6% 28%	6349
	11th to 20th	Night	12% 10% 5% 16% 7% 6% 5% 4 5% 6% 24%	6315
	21st to end	Night	16% 11% 3 8% 6% 5% 5% 4 6% 6% 31%	6628
February	1st to 10th	Night	15% 11% 3 7% 6% 5% 5% 4 6% 6% 32%	2600
	11th to 20th	Night	15% 8% 3 9% 6% 5% 5% 5% 8% 7% 30%	2397
	21st to end	Night	18% 9% 3 6% 7% 4 5% 4 6% 6% 32%	1980
March	1st to 10th	Night	19% 10% 3 8% 4 4 3 3 5% 6% 34%	5364
	11th to 20th	Night	13% 8% 4 8% 5% 5% 4 3 5% 6% 38%	5076
	21st to end	Night	17% 10% 3 9% 5% 4 4 3 4 6% 35%	5066
April	1st to 10th	Night	19% 10% 3 8% 5% 5% 5% 4 6% 6% 30%	2000
	11th to 20th	Night	19% 9% 3 8% 4 4 4 3 5% 7% 35%	1975
	21st to end	Night	20% 7% 3 6% 4 3 3 3 5% 6% 39%	1990
May	1st to 10th	Night	34% 8% 2 5% 3 3 3 3 5% 7% 27%	3902
	11th to 20th	Night	22% 9% 3 8% 4 4 4 3 5% 6% 32%	3575
	21st to end	Night	22% 9% 3 7% 5% 4 5% 4 5% 7% 31%	3926
June	1st to 10th	Night	18% 6% 2 6% 4 4 4 4 5% 8% 40%	1600
	11th to 20th	Night	17% 6% 2 6% 4 3 3 4 5% 9% 41%	1600
	21st to end	Night	14% 4 2 4 3 4 5% 4 7% 9% 45%	1600
July	1st to 10th	Night	13% 7% 3 6% 4 5% 4 4 5% 9% 40%	3600
	11th to 20th	Night	18% 8% 3 7% 5% 5% 4 3 6% 8% 34%	3600
	21st to end	Night	14% 5% 2 5% 3 3 5% 4 5% 7% 46%	3926
August	1st to 10th	Night	24% 7% 2 6% 4 4 5% 4 5% 7% 32%	2780
	11th to 20th	Night	18% 6% 2 6% 4 4 3 4 5% 7% 41%	3129
	21st to end	Night	15% 4 1 4 3 4 4 3 5% 7% 49%	3586
September	1st to 10th	Night	16% 6% 2 5% 3 4 4 3 5% 8% 45%	2000
	11th to 20th	Night	13% 6% 2 5% 3 3 3 3 4 7% 52%	2050
	21st to end	Night	19% 8% 3 5% 3 3 3 3 5% 7% 41%	2200
October	1st to 10th	Night	22% 6% 2 5% 4 4 4 4 5% 5% 41%	2370
	11th to 20th	Night	18% 8% 2 5% 3 3 4 3 4 6% 43%	2377
	21st to end	Night	21% 10% 2 6% 4 4 4 3 5% 7% 34%	2641
November	1st to 10th	Night	14% 7% 3 6% 3 4 3 4 5% 6% 44%	2537
	11th to 20th	Night	20% 7% 2 6% 4 4 4 4 5% 7% 36%	2600
	21st to end	Night	15% 9% 3 6% 5% 4 4 4 6% 8% 35%	2775
December	1st to 10th	Night	15% 12% 5% 10% 5% 4 4 4 5% 7% 29%	4580
	11th to 20th	Night	26% 10% 3 7% 4 4 4 3 4 4 32%	5208
	21st to end	Night	20% 13% 5% 8% 5% 4 4 3 4 6% 28%	6996

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	52% 7% 12% 21% 6% 1	3598
	11th to 20th	Day	57% 8% 11% 15% 8% 2	3600
	21st to end	Day	51% 7% 9% 22% 11% 1	4325
February	1st to 10th	Day	54% 8% 12% 16% 11% 1	1800
	11th to 20th	Day	48% 7% 11% 20% 13% 2	1898
	21st to end	Day	52% 4 12% 20% 11% 1	1650
March	1st to 10th	Day	51% 5% 11% 17% 12% 5%	4479
	11th to 20th	Day	44% 7% 16% 23% 7% 4	4880
	21st to end	Day	47% 6% 10% 12% 20% 5%	5865
April	1st to 10th	Day	52% 6% 8% 20% 11% 3	2400
	11th to 20th	Day	48% 6% 10% 20% 14% 2	2374
	21st to end	Day	48% 6% 10% 19% 13% 4	2410
May	1st to 10th	Day	58% 7% 11% 14% 9% 1	6079
	11th to 20th	Day	52% 9% 9% 18% 11% 1	6322
	21st to end	Day	46% 9% 13% 20% 11% 1	6949
June	1st to 10th	Day	46% 8% 14% 19% 13%	2800
	11th to 20th	Day	47% 9% 13% 20% 10% 1	2800
	21st to end	Day	44% 8% 13% 24% 11% 1	2800
July	1st to 10th	Day	44% 10% 13% 21% 12% 1	6290
	11th to 20th	Day	40% 11% 16% 23% 10%	6285
	21st to end	Day	40% 8% 13% 23% 16% 1	6728
August	1st to 10th	Day	49% 8% 14% 19% 9% 1	4338
	11th to 20th	Day	41% 9% 16% 27% 7%	3923
	21st to end	Day	36% 7% 14% 31% 11% 1	4312
September	1st to 10th	Day	42% 7% 11% 23% 15% 1	2400
	11th to 20th	Day	35% 6% 11% 25% 22% 1	2350
	21st to end	Day	46% 6% 11% 19% 16% 2	2200
October	1st to 10th	Day	42% 7% 9% 22% 18% 2	3299
	11th to 20th	Day	38% 6% 10% 24% 15% 7%	3220
	21st to end	Day	34% 5% 17% 25% 14% 4	3208
November	1st to 10th	Day	40% 6% 13% 23% 17% 2	1761
	11th to 20th	Day	45% 6% 12% 19% 14% 3	1800
	21st to end	Day	49% 6% 15% 22% 6% 1	1622
December	1st to 10th	Day	54% 10% 13% 17% 6% 1	2600
	11th to 20th	Day	52% 7% 13% 17% 11% 1	2986
	21st to end	Day	56% 7% 9% 15% 12% 1	3960
January	1st to 10th	Night	51% 7% 11% 19% 10% 1	6349
	11th to 20th	Night	49% 11% 15% 14% 8% 2	6360
	21st to end	Night	48% 8% 11% 15% 16% 2	6628
February	1st to 10th	Night	48% 8% 14% 19% 9% 1	2600
	11th to 20th	Night	47% 7% 14% 18% 12% 2	2399
	21st to end	Night	47% 6% 12% 21% 12% 2	1980
March	1st to 10th	Night	46% 6% 14% 17% 14% 2	5374
	11th to 20th	Night	44% 6% 19% 20% 8% 4	5077
	21st to end	Night	47% 7% 8% 17% 18% 2	5066
April	1st to 10th	Night	52% 7% 10% 18% 12% 2	2000
	11th to 20th	Night	48% 6% 11% 18% 16%	1975
	21st to end	Night	44% 6% 11% 21% 16% 3	1990
May	1st to 10th	Night	56% 7% 12% 14% 9% 2	3908
	11th to 20th	Night	50% 8% 12% 17% 11% 1	3576
	21st to end	Night	48% 9% 13% 19% 9% 1	3927
June	1st to 10th	Night	42% 7% 11% 24% 16% 1	1600
	11th to 20th	Night	40% 7% 18% 25% 10% 1	1600
	21st to end	Night	33% 10% 17% 26% 13% 1	1600
July	1st to 10th	Night	40% 8% 15% 19% 15% 2	3560
	11th to 20th	Night	44% 9% 13% 22% 11% 1	3552
	21st to end	Night	35% 7% 14% 28% 16% 1	3809
August	1st to 10th	Night	48% 10% 15% 19% 7% 1	2770
	11th to 20th	Night	41% 7% 15% 28% 9%	3158
	21st to end	Night	33% 7% 13% 33% 13% 1	3586
September	1st to 10th	Night	37% 7% 14% 26% 15% 1	2000
	11th to 20th	Night	32% 6% 11% 25% 24% 1	2050
	21st to end	Night	42% 6% 11% 21% 18% 2	2200
October	1st to 10th	Night	43% 6% 10% 22% 18% 1	3877
	11th to 20th	Night	33% 6% 13% 23% 20% 6%	3876
	21st to end	Night	35% 6% 17% 26% 14% 1	4340
November	1st to 10th	Night	38% 7% 11% 23% 19% 2	2537
	11th to 20th	Night	43% 6% 15% 19% 15% 3	2600
	21st to end	Night	43% 7% 17% 24% 9%	2775
December	1st to 10th	Night	48% 8% 15% 24% 5%	4580
	11th to 20th	Night	52% 6% 13% 16% 12% 1	5208
	21st to end	Night	55% 6% 11% 14% 12% 2	6996

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	31% 28% 27% 12% 2 1	200
	11th to 20th	Day	42% 25% 24% 9% 1 1	200
	21st to end	Day	30% 27% 30% 10% 3	299
February	1st to 10th	Day	34% 32% 28% 4 1	300
	11th to 20th	Day	36% 31% 24% 7% 1	437
	21st to end	Day	35% 23% 29% 12% 2	414
March	1st to 10th	Day	32% 22% 29% 15% 2	500
	11th to 20th	Day	31% 25% 28% 12% 3 1	500
	21st to end	Day	32% 27% 27% 8% 5% 1	550
April	1st to 10th	Day	35% 25% 24% 11% 4 1	500
	11th to 20th	Day	33% 23% 24% 10% 7% 2	492
	21st to end	Day	30% 19% 34% 10% 4 2	500
May	1st to 10th	Day	35% 19% 26% 12% 6% 2	503
	11th to 20th	Day	23% 21% 31% 17% 7% 2	527
	21st to end	Day	21% 12% 28% 24% 12% 3	573
June	1st to 10th	Day	21% 15% 31% 21% 11% 2	530
	11th to 20th	Day	22% 15% 26% 25% 10% 2	530
	21st to end	Day	18% 14% 32% 25% 10% 2	530
July	1st to 10th	Day	13% 11% 27% 29% 16% 4	525
	11th to 20th	Day	12% 8% 31% 32% 15% 3	524
	21st to end	Day	16% 9% 35% 26% 10% 3	576
August	1st to 10th	Day	14% 10% 27% 27% 17% 5%	526
	11th to 20th	Day	16% 8% 25% 28% 16% 6%	519
	21st to end	Day	14% 11% 30% 23% 14% 7%	583
September	1st to 10th	Day	21% 12% 22% 23% 15% 7%	530
	11th to 20th	Day	14% 11% 24% 24% 16% 11%	530
	21st to end	Day	22% 12% 27% 21% 14% 4	530
October	1st to 10th	Day	26% 12% 24% 20% 14% 5%	530
	11th to 20th	Day	22% 20% 27% 20% 9% 1	522
	21st to end	Day	29% 17% 28% 18% 7% 1	469
November	1st to 10th	Day	22% 19% 26% 22% 9% 2	395
	11th to 20th	Day	28% 25% 25% 17% 4 1	400
	21st to end	Day	29% 24% 29% 15% 2	222
December	1st to 10th	Day	31% 28% 25% 12% 5% 1	200
	11th to 20th	Day	38% 23% 28% 10% 2	200
	21st to end	Day	30% 27% 26% 14% 3	220
January	1st to 10th	Night	26% 26% 32% 14% 3	800
	11th to 20th	Night	28% 22% 29% 20% 2	800
	21st to end	Night	21% 25% 35% 16% 3	880
February	1st to 10th	Night	27% 20% 36% 16% 1	800
	11th to 20th	Night	29% 26% 32% 12% 1	783
	21st to end	Night	30% 23% 29% 16% 3	660
March	1st to 10th	Night	28% 23% 32% 14% 3	800
	11th to 20th	Night	24% 25% 28% 19% 3	800
	21st to end	Night	24% 22% 32% 17% 5%	880
April	1st to 10th	Night	28% 22% 31% 17% 4	800
	11th to 20th	Night	25% 19% 30% 19% 6%	791
	21st to end	Night	25% 19% 26% 22% 7%	790
May	1st to 10th	Night	32% 14% 24% 23% 6% 1	539
	11th to 20th	Night	24% 10% 30% 28% 8%	394
	21st to end	Night	20% 8% 24% 34% 14%	433
June	1st to 10th	Night	18% 9% 27% 31% 16%	400
	11th to 20th	Night	18% 7% 25% 34% 15%	400
	21st to end	Night	13% 5% 28% 43% 12%	400
July	1st to 10th	Night	15% 5% 19% 40% 18% 2	390
	11th to 20th	Night	13% 2 23% 43% 17% 1	388
	21st to end	Night	14% 5% 21% 42% 17% 1	438
August	1st to 10th	Night	13% 4 21% 36% 24% 2	514
	11th to 20th	Night	17% 5% 15% 39% 21% 3	746
	21st to end	Night	17% 6% 18% 34% 23% 2	880
September	1st to 10th	Night	18% 7% 24% 29% 20% 2	800
	11th to 20th	Night	16% 8% 20% 29% 22% 6%	800
	21st to end	Night	21% 9% 21% 31% 15% 3	800
October	1st to 10th	Night	24% 11% 24% 23% 17% 2	800
	11th to 20th	Night	24% 13% 27% 28% 8% 1	793
	21st to end	Night	28% 16% 29% 22% 6%	836
November	1st to 10th	Night	18% 18% 29% 25% 8% 1	780
	11th to 20th	Night	26% 20% 24% 22% 6% 1	800
	21st to end	Night	22% 22% 30% 20% 6% 1	800
December	1st to 10th	Night	28% 25% 26% 17% 4	800
	11th to 20th	Night	29% 24% 27% 18% 3	800
	21st to end	Night	27% 23% 31% 16% 3	880

Page generated at 2025-10-16 01:50:28. Version ac07

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