Woodland Altars Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Woodland Altars Campground clear sky chart from 2005-11-06 to 2024-01-15.

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	16% 9% 3 6% 5% 3 5% 5% 5% 7% 36%	74899
	Night	15% 9% 4 6% 5% 3 4 4 5% 7% 38%	74895
Transparency	Day	47% 7% 12% 20% 13% 2	74622
	Night	45% 7% 11% 21% 14% 2	74691
Seeing	Day	22% 14% 27% 21% 12% 5%	13693
	Night	20% 12% 25% 27% 15% 2	23835

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	17% 13% 6% 10% 8% 3 4 5% 4 5% 25%	1706
	11th to 20th	Day	21% 15% 7% 9% 6% 4 3 4 4 5% 22%	1656
	21st to end	Day	18% 16% 6% 7% 6% 3 4 4 5% 5% 25%	1782
February	1st to 10th	Day	21% 13% 5% 8% 5% 3 4 3 5% 5% 27%	1656
	11th to 20th	Day	19% 13% 5% 9% 6% 2 4 4 5% 5% 27%	1748
	21st to end	Day	21% 14% 5% 7% 5% 2 3 3 4 6% 30%	1480
March	1st to 10th	Day	18% 11% 3 6% 6% 3 4 4 4 6% 35%	1862
	11th to 20th	Day	20% 10% 5% 8% 6% 3 4 4 5% 5% 31%	1980
	21st to end	Day	22% 10% 5% 6% 6% 3 4 3 4 5% 31%	2178
April	1st to 10th	Day	13% 10% 4 6% 5% 3 4 4 6% 6% 38%	2041
	11th to 20th	Day	19% 8% 3 6% 5% 3 3 4 4 7% 39%	2231
	21st to end	Day	19% 7% 3 6% 7% 4 5% 4 5% 6% 34%	2340
May	1st to 10th	Day	21% 8% 3 6% 5% 3 5% 5% 5% 6% 34%	2340
	11th to 20th	Day	20% 8% 4 6% 6% 3 5% 5% 5% 6% 32%	2301
	21st to end	Day	10% 5% 3 6% 6% 4 6% 6% 7% 9% 37%	2531
June	1st to 10th	Day	13% 5% 2 5% 5% 4 6% 6% 6% 9% 40%	2340
	11th to 20th	Day	10% 6% 2 6% 6% 4 5% 6% 6% 8% 41%	2340
	21st to end	Day	11% 4 3 6% 5% 4 6% 6% 7% 10% 39%	2340
July	1st to 10th	Day	14% 5% 2 5% 6% 4 6% 5% 7% 8% 38%	2340
	11th to 20th	Day	11% 6% 2 5% 6% 4 6% 5% 6% 10% 38%	2340
	21st to end	Day	12% 5% 2 5% 5% 4 6% 6% 7% 9% 39%	2547
August	1st to 10th	Day	9% 5% 2 6% 6% 4 5% 6% 7% 10% 39%	2327
	11th to 20th	Day	9% 6% 2 6% 6% 4 6% 7% 7% 10% 37%	2303
	21st to end	Day	8% 4 2 5% 5% 3 5% 6% 6% 8% 47%	2475
September	1st to 10th	Day	15% 5% 2 4 4 3 5% 4 5% 6% 46%	1998
	11th to 20th	Day	10% 5% 2 5% 5% 3 5% 6% 5% 7% 49%	1980
	21st to end	Day	17% 6% 3 5% 4 2 3 4 4 6% 46%	1980
October	1st to 10th	Day	14% 5% 2 4 4 2 5% 5% 5% 8% 46%	1959
	11th to 20th	Day	15% 8% 3 5% 4 3 4 4 4 6% 45%	1800
	21st to end	Day	22% 9% 3 5% 5% 2 3 3 3 6% 39%	1919
November	1st to 10th	Day	11% 7% 2 4 4 2 3 4 4 6% 51%	1672
	11th to 20th	Day	15% 12% 4 5% 5% 2 4 4 5% 6% 38%	1710
	21st to end	Day	18% 10% 3 6% 5% 3 4 4 4 5% 37%	1710
December	1st to 10th	Day	22% 14% 5% 9% 5% 3 4 4 4 5% 24%	1710
	11th to 20th	Day	17% 15% 6% 9% 5% 3 5% 4 4 6% 26%	2153
	21st to end	Day	21% 20% 6% 9% 7% 3 4 3 4 6% 18%	3124
January	1st to 10th	Night	17% 14% 6% 10% 7% 3 5% 5% 4 5% 24%	2459
	11th to 20th	Night	20% 16% 6% 9% 7% 3 3 4 5% 4 24%	2399
	21st to end	Night	18% 13% 6% 8% 7% 3 4 3 4 5% 29%	2574
February	1st to 10th	Night	22% 14% 5% 7% 6% 3 4 4 4 6% 26%	2303
	11th to 20th	Night	20% 12% 4 8% 6% 3 4 4 4 6% 30%	2098
	21st to end	Night	23% 15% 4 6% 4 3 3 3 4 5% 29%	1776
March	1st to 10th	Night	16% 9% 4 6% 6% 3 4 4 5% 5% 37%	2098
	11th to 20th	Night	18% 10% 5% 7% 5% 3 4 4 5% 7% 33%	1980
	21st to end	Night	19% 8% 4 7% 5% 3 4 4 5% 7% 33%	2178
April	1st to 10th	Night	15% 7% 3 5% 6% 3 5% 5% 5% 8% 38%	1934
	11th to 20th	Night	14% 7% 3 6% 4 3 4 5% 6% 7% 40%	1676
	21st to end	Night	18% 6% 4 6% 5% 4 4 5% 5% 7% 38%	1620
May	1st to 10th	Night	19% 7% 3 6% 6% 3 4 4 5% 8% 36%	1620
	11th to 20th	Night	16% 7% 4 5% 5% 2 5% 4 6% 8% 37%	1592
	21st to end	Night	8% 4 2 4 5% 3 5% 5% 8% 13% 42%	1744
June	1st to 10th	Night	7% 4 2 5% 5% 3 6% 5% 5% 10% 48%	1620
	11th to 20th	Night	9% 3 2 4 4 3 5% 5% 6% 11% 48%	1620
	21st to end	Night	9% 4 2 4 4 2 6% 5% 9% 11% 46%	1620
July	1st to 10th	Night	11% 6% 2 4 6% 3 5% 5% 5% 8% 45%	1620
	11th to 20th	Night	6% 4 2 4 6% 2 4 5% 7% 10% 49%	1620
	21st to end	Night	8% 4 2 5% 4 3 5% 5% 6% 9% 48%	1771
August	1st to 10th	Night	6% 5% 2 5% 6% 3 5% 5% 7% 9% 47%	1611
	11th to 20th	Night	7% 5% 3 5% 6% 3 5% 6% 6% 10% 45%	1598
	21st to end	Night	7% 4 2 3 4 2 4 4 6% 9% 53%	1877
September	1st to 10th	Night	13% 5% 2 4 5% 2 3 4 4 7% 51%	1944
	11th to 20th	Night	10% 4 2 3 4 3 4 4 4 7% 54%	1980
	21st to end	Night	12% 4 2 5% 5% 3 4 4 5% 5% 49%	1980
October	1st to 10th	Night	9% 5% 2 5% 5% 2 3 4 5% 7% 52%	1999
	11th to 20th	Night	16% 7% 2 4 5% 2 4 4 5% 7% 44%	2160
	21st to end	Night	20% 8% 3 4 5% 3 4 4 4 5% 40%	2434
November	1st to 10th	Night	14% 7% 2 4 5% 2 4 3 4 6% 49%	2406
	11th to 20th	Night	16% 10% 4 5% 5% 3 4 4 3 7% 40%	2470
	21st to end	Night	20% 11% 3 6% 5% 3 4 4 4 6% 34%	2470
December	1st to 10th	Night	22% 14% 5% 7% 5% 3 4 4 4 6% 28%	2470
	11th to 20th	Night	18% 12% 7% 8% 5% 2 4 4 4 6% 30%	3042
	21st to end	Night	20% 19% 6% 8% 7% 4 4 4 4 5% 18%	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	60% 6% 9% 15% 10%	1707
	11th to 20th	Day	66% 5% 9% 14% 5%	1656
	21st to end	Day	61% 4 11% 16% 6% 1	1782
February	1st to 10th	Day	60% 5% 11% 16% 7% 1	1656
	11th to 20th	Day	58% 5% 10% 17% 9% 1	1758
	21st to end	Day	57% 5% 9% 19% 9% 2	1480
March	1st to 10th	Day	50% 5% 10% 25% 9% 1	1862
	11th to 20th	Day	54% 6% 9% 19% 11% 1	1980
	21st to end	Day	56% 5% 9% 19% 9% 2	2178
April	1st to 10th	Day	44% 7% 11% 24% 12% 2	2041
	11th to 20th	Day	45% 6% 10% 20% 15% 4	2231
	21st to end	Day	50% 7% 11% 20% 11% 3	2340
May	1st to 10th	Day	50% 6% 12% 21% 9% 2	2340
	11th to 20th	Day	52% 7% 12% 17% 11% 2	2305
	21st to end	Day	40% 11% 16% 19% 13% 1	2531
June	1st to 10th	Day	38% 9% 14% 23% 15% 2	2340
	11th to 20th	Day	37% 10% 15% 21% 16% 1	2340
	21st to end	Day	38% 10% 14% 22% 13% 3	2340
July	1st to 10th	Day	42% 9% 12% 19% 16% 2	2275
	11th to 20th	Day	39% 9% 14% 21% 16% 1	2271
	21st to end	Day	38% 9% 16% 22% 13% 2	2405
August	1st to 10th	Day	36% 11% 15% 26% 12% 1	2314
	11th to 20th	Day	38% 9% 15% 25% 12% 1	2303
	21st to end	Day	33% 9% 15% 22% 17% 5%	2475
September	1st to 10th	Day	37% 7% 12% 22% 17% 5%	1998
	11th to 20th	Day	33% 8% 12% 23% 22% 2	1980
	21st to end	Day	39% 5% 9% 23% 20% 2	1980
October	1st to 10th	Day	35% 8% 12% 23% 21% 2	1959
	11th to 20th	Day	40% 5% 9% 26% 17% 2	1800
	21st to end	Day	47% 5% 10% 22% 14% 2	1919
November	1st to 10th	Day	35% 5% 11% 26% 20% 3	1672
	11th to 20th	Day	47% 4 9% 21% 16% 3	1710
	21st to end	Day	49% 5% 10% 21% 14% 1	1710
December	1st to 10th	Day	62% 6% 10% 17% 5%	1710
	11th to 20th	Day	56% 8% 9% 16% 10%	2150
	21st to end	Day	67% 7% 9% 10% 6% 1	3124
January	1st to 10th	Night	62% 6% 8% 15% 9% 1	2459
	11th to 20th	Night	64% 5% 9% 15% 6% 1	2399
	21st to end	Night	57% 5% 10% 18% 7% 2	2574
February	1st to 10th	Night	60% 5% 10% 17% 6% 1	2303
	11th to 20th	Night	57% 4 9% 19% 11% 1	2099
	21st to end	Night	59% 4 10% 15% 9% 3	1776
March	1st to 10th	Night	49% 5% 8% 22% 14% 2	2098
	11th to 20th	Night	51% 6% 10% 20% 11% 1	1980
	21st to end	Night	50% 7% 10% 20% 10% 2	2178
April	1st to 10th	Night	42% 7% 11% 23% 14% 2	1934
	11th to 20th	Night	41% 7% 10% 17% 18% 6%	1676
	21st to end	Night	45% 7% 11% 20% 14% 3	1620
May	1st to 10th	Night	47% 7% 12% 20% 10% 3	1620
	11th to 20th	Night	44% 10% 13% 18% 13% 2	1593
	21st to end	Night	32% 11% 18% 22% 15% 3	1745
June	1st to 10th	Night	31% 9% 14% 24% 19% 2	1620
	11th to 20th	Night	30% 9% 16% 20% 21% 4	1620
	21st to end	Night	29% 10% 17% 24% 16% 4	1620
July	1st to 10th	Night	36% 8% 13% 23% 17% 4	1575
	11th to 20th	Night	27% 10% 17% 24% 19% 2	1566
	21st to end	Night	30% 10% 15% 28% 14% 2	1672
August	1st to 10th	Night	30% 10% 15% 28% 14% 2	1600
	11th to 20th	Night	33% 10% 14% 25% 17% 1	1598
	21st to end	Night	26% 9% 16% 24% 20% 5%	1877
September	1st to 10th	Night	32% 7% 13% 23% 17% 7%	1944
	11th to 20th	Night	29% 8% 12% 23% 26% 2	1980
	21st to end	Night	35% 6% 10% 21% 27% 1	1980
October	1st to 10th	Night	30% 7% 12% 26% 21% 4	1999
	11th to 20th	Night	39% 6% 9% 25% 18% 2	2160
	21st to end	Night	46% 5% 10% 21% 15% 3	2434
November	1st to 10th	Night	37% 3 11% 23% 22% 3	2406
	11th to 20th	Night	46% 4 8% 20% 18% 4	2470
	21st to end	Night	51% 5% 10% 21% 12% 2	2470
December	1st to 10th	Night	59% 5% 10% 19% 8% 1	2470
	11th to 20th	Night	54% 6% 10% 20% 9% 1	3044
	21st to end	Night	66% 7% 9% 13% 5%	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	31% 23% 30% 12% 3	270
	11th to 20th	Day	36% 23% 33% 8% 1	252
	21st to end	Day	36% 27% 25% 10% 3	264
February	1st to 10th	Day	36% 25% 28% 9% 2	240
	11th to 20th	Day	37% 31% 29% 3	240
	21st to end	Day	38% 25% 33% 4 1	198
March	1st to 10th	Day	32% 25% 27% 13% 3	302
	11th to 20th	Day	27% 23% 31% 13% 5%	420
	21st to end	Day	34% 20% 26% 16% 4	462
April	1st to 10th	Day	23% 20% 31% 17% 9% 1	420
	11th to 20th	Day	28% 19% 27% 14% 9% 3	412
	21st to end	Day	29% 16% 35% 11% 8% 2	420
May	1st to 10th	Day	28% 17% 30% 15% 8% 3	423
	11th to 20th	Day	22% 11% 34% 20% 9% 4	447
	21st to end	Day	13% 9% 26% 28% 18% 6%	485
June	1st to 10th	Day	16% 9% 24% 29% 16% 7%	450
	11th to 20th	Day	14% 9% 25% 29% 16% 6%	450
	21st to end	Day	12% 10% 31% 23% 16% 8%	450
July	1st to 10th	Day	16% 6% 16% 23% 18% 22%	445
	11th to 20th	Day	9% 7% 22% 30% 21% 11%	444
	21st to end	Day	13% 2 23% 30% 19% 14%	488
August	1st to 10th	Day	10% 5% 19% 29% 24% 14%	446
	11th to 20th	Day	13% 5% 20% 34% 19% 10%	439
	21st to end	Day	9% 5% 19% 32% 22% 12%	495
September	1st to 10th	Day	14% 4 19% 28% 23% 11%	450
	11th to 20th	Day	11% 3 20% 27% 28% 11%	450
	21st to end	Day	21% 9% 19% 24% 22% 4	450
October	1st to 10th	Day	14% 8% 27% 29% 15% 7%	450
	11th to 20th	Day	20% 14% 33% 19% 11% 3	450
	21st to end	Day	27% 17% 30% 21% 5%	434
November	1st to 10th	Day	17% 20% 33% 21% 7% 2	270
	11th to 20th	Day	29% 17% 29% 19% 4 2	270
	21st to end	Day	28% 22% 32% 14% 3	270
December	1st to 10th	Day	34% 19% 31% 11% 6%	270
	11th to 20th	Day	27% 23% 34% 12% 3	270
	21st to end	Day	34% 24% 28% 11% 3	297
January	1st to 10th	Night	29% 21% 28% 18% 5%	760
	11th to 20th	Night	31% 21% 29% 17% 2	739
	21st to end	Night	27% 21% 29% 21% 2	792
February	1st to 10th	Night	33% 16% 29% 20% 2	720
	11th to 20th	Night	31% 22% 29% 18% 1	703
	21st to end	Night	32% 18% 31% 18% 1	592
March	1st to 10th	Night	24% 20% 29% 23% 4	720
	11th to 20th	Night	25% 18% 30% 20% 7%	720
	21st to end	Night	25% 13% 30% 24% 7%	792
April	1st to 10th	Night	20% 15% 34% 23% 8%	674
	11th to 20th	Night	17% 14% 32% 23% 12% 1	533
	21st to end	Night	21% 11% 35% 27% 6% 1	540
May	1st to 10th	Night	22% 11% 30% 25% 11% 1	540
	11th to 20th	Night	19% 9% 26% 27% 18% 1	531
	21st to end	Night	8% 5% 22% 33% 28% 4	584
June	1st to 10th	Night	9% 3 25% 39% 23% 2	540
	11th to 20th	Night	9% 4 20% 38% 24% 4	540
	21st to end	Night	9% 4 24% 34% 26% 3	540
July	1st to 10th	Night	15% 1 13% 30% 30% 10%	525
	11th to 20th	Night	7% 2 16% 35% 35% 5%	522
	21st to end	Night	9% 3 14% 34% 36% 4	591
August	1st to 10th	Night	8% 2 10% 41% 34% 5%	537
	11th to 20th	Night	7% 4 13% 38% 31% 7%	534
	21st to end	Night	8% 1 16% 35% 32% 7%	594
September	1st to 10th	Night	13% 4 13% 32% 32% 6%	684
	11th to 20th	Night	10% 4 15% 31% 33% 7%	720
	21st to end	Night	13% 7% 19% 34% 24% 3	720
October	1st to 10th	Night	11% 7% 23% 32% 23% 4	720
	11th to 20th	Night	19% 11% 26% 30% 12% 1	720
	21st to end	Night	25% 13% 26% 26% 10% 1	792
November	1st to 10th	Night	19% 11% 24% 28% 17% 1	740
	11th to 20th	Night	24% 17% 26% 24% 10% 1	760
	21st to end	Night	27% 14% 25% 26% 7% 1	760
December	1st to 10th	Night	31% 17% 26% 20% 5%	760
	11th to 20th	Night	28% 15% 28% 22% 6% 1	760
	21st to end	Night	30% 18% 27% 22% 3	836

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