Pine Valley Creek trailhead
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pine Valley Creek trailhead 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	3 4 1 3 2 2 3 3 4 5% 70%	157547
	Night	2 5% 1 3 2 2 3 3 4 5% 68%	152004
Transparency	Day	15% 4 5% 12% 27% 38%	152641
	Night	15% 5% 5% 11% 24% 40%	147888
Seeing	Day	9% 11% 30% 30% 13% 5%	18366
	Night	8% 6% 14% 33% 31% 8%	28687

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	7% 7% 2 5% 3 2 3 2 3 5% 60%	5318
	11th to 20th	Day	3 3 1 3 2 2 3 3 4 5% 72%	5579
	21st to end	Day	7% 9% 2 6% 4 4 4 4 4 8% 48%	6500
February	1st to 10th	Day	7% 8% 2 5% 4 4 3 2 4 5% 58%	2100
	11th to 20th	Day	5% 9% 2 6% 4 3 4 4 5% 7% 50%	2050
	21st to end	Day	6% 12% 2 6% 3 4 3 3 5% 6% 50%	1730
March	1st to 10th	Day	4 9% 2 6% 4 4 5% 4 7% 9% 46%	4618
	11th to 20th	Day	6% 9% 2 5% 3 3 4 4 5% 6% 54%	4947
	21st to end	Day	4 8% 1 4 3 3 3 3 5% 7% 58%	5775
April	1st to 10th	Day	4 7% 2 6% 3 3 3 3 5% 6% 57%	2520
	11th to 20th	Day	2 3 2 4 2 3 3 3 4 5% 68%	2489
	21st to end	Day	3 5% 1 3 3 3 3 2 4 8% 66%	2520
May	1st to 10th	Day	1 5% 2 4 2 2 2 2 2 4 74%	7507
	11th to 20th	Day	1 1 1 1 1 1 2 3 4 84%	7596
	21st to end	Day	1 1 1 1 1 2 2 3 4 84%	8370
June	1st to 10th	Day	1 2 1 2 2 2 2 2 3 4 79%	2730
	11th to 20th	Day	1 1 1 1 2 1 2 3 87%	2730
	21st to end	Day	2 2 2 1 2 1 1 2 3 84%	2730
July	1st to 10th	Day	1 1 1 1 1 1 1 1 1 2 88%	7649
	11th to 20th	Day	1 1 1 3 2 3 3 4 6% 8% 69%	7650
	21st to end	Day	1 1 1 1 2 2 3 4 6% 79%	8079
August	1st to 10th	Day	1 1 2 2 3 2 4 6% 79%	6986
	11th to 20th	Day	1 1 1 1 1 2 2 3 5% 81%	7001
	21st to end	Day	2 2 1 2 2 2 3 3 4 6% 74%	7750
September	1st to 10th	Day	3 2 1 3 2 2 4 3 4 6% 70%	2467
	11th to 20th	Day	2 1 1 1 1 1 1 2 3 87%	2310
	21st to end	Day	2 2 1 2 2 2 2 2 3 4 77%	2310
October	1st to 10th	Day	2 2 1 3 3 2 3 2 3 4 76%	3710
	11th to 20th	Day	1 1 1 2 2 2 2 1 2 3 83%	3613
	21st to end	Day	1 2 1 3 2 2 3 3 4 5% 74%	3431
November	1st to 10th	Day	3 5% 1 4 2 2 2 3 3 5% 71%	1854
	11th to 20th	Day	3 4 1 5% 3 3 2 3 4 5% 66%	1890
	21st to end	Day	6% 6% 2 5% 3 3 3 4 5% 5% 59%	1890
December	1st to 10th	Day	3 4 1 3 3 3 2 3 4 6% 69%	3040
	11th to 20th	Day	5% 5% 2 5% 5% 5% 5% 4 6% 6% 52%	3499
	21st to end	Day	4 6% 2 6% 6% 6% 5% 5% 7% 8% 44%	4609
January	1st to 10th	Night	6% 10% 2 5% 3 3 3 3 4 5% 56%	7605
	11th to 20th	Night	2 4 1 3 2 3 2 2 4 7% 69%	7408
	21st to end	Night	7% 12% 3 7% 4 3 3 3 4 6% 47%	7747
February	1st to 10th	Night	5% 9% 3 5% 3 3 4 3 4 5% 57%	2520
	11th to 20th	Night	5% 10% 3 7% 4 4 4 3 4 5% 51%	2458
	21st to end	Night	4 13% 2 6% 4 4 4 3 5% 6% 50%	2076
March	1st to 10th	Night	4 19% 3 5% 3 3 4 5% 6% 7% 41%	5496
	11th to 20th	Night	4 12% 4 6% 3 3 5% 4 5% 6% 48%	5259
	21st to end	Night	2 13% 2 4 3 4 5% 5% 6% 6% 50%	5436
April	1st to 10th	Night	4 8% 2 5% 4 3 3 3 5% 7% 56%	2100
	11th to 20th	Night	3 5% 1 5% 2 3 3 3 5% 6% 64%	2079
	21st to end	Night	1 5% 2 4 3 4 4 3 5% 6% 63%	2100
May	1st to 10th	Night	1 5% 1 4 2 2 3 2 4 4 71%	5444
	11th to 20th	Night	1 2 1 2 3 4 6% 6% 75%	5296
	21st to end	Night	1 1 2 1 2 3 4 6% 6% 74%	5837
June	1st to 10th	Night	1 2 1 3 2 1 2 2 3 6% 78%	1890
	11th to 20th	Night	1 1 1 1 2 1 2 4 86%	1890
	21st to end	Night	2 1 1 2 1 1 1 2 3 3 84%	1890
July	1st to 10th	Night	1 1 1 1 1 1 2 92%	5340
	11th to 20th	Night	1 1 1 1 2 2 4 7% 80%	5340
	21st to end	Night	1 1 1 1 2 1 2 5% 84%	6036
August	1st to 10th	Night	1 1 1 2 2 3 5% 86%	5866
	11th to 20th	Night	1 2 1 1 1 1 2 3 4 84%	5886
	21st to end	Night	2 1 1 1 1 1 1 2 4 84%	6499
September	1st to 10th	Night	2 2 1 3 2 2 2 1 3 4 80%	2152
	11th to 20th	Night	2 1 2 1 1 1 1 2 3 86%	2310
	21st to end	Night	2 1 2 2 2 2 2 3 4 81%	2310
October	1st to 10th	Night	2 2 1 3 1 2 2 1 2 3 80%	3710
	11th to 20th	Night	1 2 1 2 1 1 3 3 4 3 79%	3612
	21st to end	Night	1 2 1 4 3 2 3 3 4 5% 71%	4365
November	1st to 10th	Night	2 5% 1 4 3 2 2 2 4 5% 69%	2665
	11th to 20th	Night	4 5% 2 4 3 3 3 3 4 4 65%	2730
	21st to end	Night	5% 8% 2 5% 4 3 4 4 5% 5% 55%	2730
December	1st to 10th	Night	4 4 1 4 2 3 3 3 4 4 68%	4370
	11th to 20th	Night	4 7% 2 5% 4 4 5% 5% 6% 8% 50%	4941
	21st to end	Night	4 8% 2 6% 3 3 4 4 6% 10% 49%	6611

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	24% 5% 5% 11% 28% 27%	5321
	11th to 20th	Day	13% 4 4 12% 20% 47%	5579
	21st to end	Day	30% 6% 5% 9% 23% 27%	6500
February	1st to 10th	Day	26% 4 5% 10% 23% 32%	2100
	11th to 20th	Day	27% 6% 7% 14% 23% 23%	2060
	21st to end	Day	28% 6% 8% 12% 21% 25%	1730
March	1st to 10th	Day	20% 11% 7% 13% 25% 23%	4618
	11th to 20th	Day	25% 6% 9% 17% 27% 15%	4947
	21st to end	Day	19% 9% 7% 22% 30% 13%	5775
April	1st to 10th	Day	23% 3 8% 15% 31% 20%	2520
	11th to 20th	Day	15% 3 7% 14% 29% 32%	2492
	21st to end	Day	15% 4 6% 15% 35% 25%	2520
May	1st to 10th	Day	13% 4 3 10% 36% 34%	7507
	11th to 20th	Day	6% 1 2 8% 37% 44%	7599
	21st to end	Day	6% 1 3 8% 41% 41%	8371
June	1st to 10th	Day	10% 2 3 10% 31% 44%	2730
	11th to 20th	Day	5% 2 3 5% 19% 65%	2730
	21st to end	Day	8% 1 2 5% 13% 70%	2730
July	1st to 10th	Day	6% 1 2 5% 11% 74%	7586
	11th to 20th	Day	14% 5% 5% 15% 28% 33%	7581
	21st to end	Day	8% 3 5% 22% 20% 42%	7899
August	1st to 10th	Day	11% 3 7% 23% 29% 26%	5530
	11th to 20th	Day	11% 3 7% 18% 26% 35%	5517
	21st to end	Day	9% 2 3 12% 27% 47%	6077
September	1st to 10th	Day	16% 3 7% 8% 22% 45%	2467
	11th to 20th	Day	6% 1 3 6% 26% 58%	2310
	21st to end	Day	11% 2 5% 8% 26% 48%	2310
October	1st to 10th	Day	10% 3 4 6% 17% 59%	3710
	11th to 20th	Day	7% 2 3 6% 30% 51%	3613
	21st to end	Day	11% 3 3 5% 31% 47%	3431
November	1st to 10th	Day	15% 3 5% 11% 25% 42%	1854
	11th to 20th	Day	18% 3 6% 10% 24% 39%	1890
	21st to end	Day	24% 3 7% 11% 21% 33%	1890
December	1st to 10th	Day	17% 2 3 9% 28% 41%	3040
	11th to 20th	Day	25% 6% 7% 13% 28% 21%	3498
	21st to end	Day	27% 9% 9% 16% 22% 16%	4609
January	1st to 10th	Night	27% 6% 4 12% 23% 28%	7605
	11th to 20th	Night	11% 7% 5% 11% 18% 49%	7408
	21st to end	Night	33% 7% 4 8% 19% 29%	7747
February	1st to 10th	Night	25% 5% 6% 9% 21% 34%	2520
	11th to 20th	Night	32% 5% 6% 10% 21% 26%	2459
	21st to end	Night	28% 7% 6% 11% 21% 28%	2076
March	1st to 10th	Night	20% 19% 7% 10% 19% 24%	5496
	11th to 20th	Night	27% 8% 7% 15% 30% 13%	5259
	21st to end	Night	18% 13% 8% 15% 24% 22%	5436
April	1st to 10th	Night	22% 5% 8% 12% 28% 24%	2100
	11th to 20th	Night	16% 4 8% 11% 26% 35%	2079
	21st to end	Night	14% 5% 10% 11% 29% 31%	2100
May	1st to 10th	Night	13% 4 6% 5% 34% 38%	5442
	11th to 20th	Night	6% 2 4 7% 30% 51%	5297
	21st to end	Night	7% 2 5% 8% 30% 48%	5838
June	1st to 10th	Night	9% 2 5% 8% 26% 51%	1890
	11th to 20th	Night	4 2 3 7% 13% 72%	1890
	21st to end	Night	8% 1 2 5% 12% 72%	1890
July	1st to 10th	Night	3 1 2 5% 10% 80%	5295
	11th to 20th	Night	7% 2 6% 16% 25% 43%	5286
	21st to end	Night	6% 2 3 23% 20% 47%	5905
August	1st to 10th	Night	6% 1 5% 27% 28% 33%	4636
	11th to 20th	Night	9% 2 6% 17% 26% 39%	4636
	21st to end	Night	6% 1 1 8% 31% 52%	5092
September	1st to 10th	Night	10% 3 4 10% 24% 50%	2152
	11th to 20th	Night	6% 2 4 4 23% 62%	2310
	21st to end	Night	9% 1 5% 7% 28% 49%	2310
October	1st to 10th	Night	10% 2 3 6% 16% 63%	3710
	11th to 20th	Night	6% 3 4 6% 22% 60%	3612
	21st to end	Night	12% 3 4 6% 25% 50%	4365
November	1st to 10th	Night	16% 3 4 7% 25% 44%	2665
	11th to 20th	Night	19% 3 5% 9% 23% 40%	2730
	21st to end	Night	26% 4 7% 11% 20% 32%	2730
December	1st to 10th	Night	18% 3 4 8% 25% 42%	4370
	11th to 20th	Night	26% 6% 5% 11% 26% 25%	4941
	21st to end	Night	21% 9% 8% 20% 22% 20%	6611

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	26% 12% 25% 27% 8% 1	330
	11th to 20th	Day	19% 11% 27% 32% 10% 1	413
	21st to end	Day	18% 18% 32% 24% 6% 2	594
February	1st to 10th	Day	17% 16% 38% 20% 8% 2	540
	11th to 20th	Day	20% 19% 33% 21% 7%	535
	21st to end	Day	19% 21% 34% 19% 7%	446
March	1st to 10th	Day	21% 21% 34% 18% 5% 1	540
	11th to 20th	Day	18% 16% 35% 21% 8% 1	540
	21st to end	Day	17% 20% 35% 19% 8% 1	594
April	1st to 10th	Day	16% 18% 32% 20% 11% 3	540
	11th to 20th	Day	10% 21% 37% 18% 11% 3	532
	21st to end	Day	13% 18% 31% 22% 12% 5%	540
May	1st to 10th	Day	11% 18% 31% 24% 12% 4	543
	11th to 20th	Day	7% 13% 37% 27% 11% 5%	568
	21st to end	Day	7% 17% 33% 27% 9% 7%	617
June	1st to 10th	Day	3 10% 32% 31% 15% 9%	570
	11th to 20th	Day	1 8% 36% 30% 15% 9%	570
	21st to end	Day	2 5% 34% 33% 17% 9%	570
July	1st to 10th	Day	1 2 24% 43% 20% 11%	566
	11th to 20th	Day	1 1 19% 45% 20% 15%	564
	21st to end	Day	1 2 17% 45% 20% 15%	619
August	1st to 10th	Day	2 1 23% 41% 18% 14%	567
	11th to 20th	Day	2 2 21% 41% 19% 15%	557
	21st to end	Day	2 2 21% 47% 17% 11%	627
September	1st to 10th	Day	4 5% 29% 38% 17% 8%	570
	11th to 20th	Day	4 5% 36% 35% 15% 5%	570
	21st to end	Day	4 12% 27% 36% 15% 5%	570
October	1st to 10th	Day	6% 10% 33% 33% 15% 3	570
	11th to 20th	Day	6% 12% 36% 32% 13% 1	543
	21st to end	Day	7% 10% 27% 33% 17% 5%	448
November	1st to 10th	Day	12% 10% 26% 38% 12% 2	330
	11th to 20th	Day	9% 11% 32% 31% 15% 2	330
	21st to end	Day	13% 14% 31% 28% 11% 3	330
December	1st to 10th	Day	11% 11% 33% 32% 12% 2	330
	11th to 20th	Day	7% 9% 34% 32% 16% 2	330
	21st to end	Day	25% 16% 28% 20% 10% 2	363
January	1st to 10th	Night	14% 8% 22% 32% 18% 6%	840
	11th to 20th	Night	9% 10% 23% 35% 19% 5%	840
	21st to end	Night	17% 11% 20% 32% 17% 3	924
February	1st to 10th	Night	14% 9% 22% 31% 19% 5%	840
	11th to 20th	Night	14% 11% 22% 33% 15% 4	824
	21st to end	Night	15% 11% 22% 34% 15% 3	692
March	1st to 10th	Night	15% 12% 23% 35% 14% 2	840
	11th to 20th	Night	13% 6% 17% 35% 21% 7%	840
	21st to end	Night	10% 9% 18% 39% 21% 4	924
April	1st to 10th	Night	11% 10% 17% 37% 19% 5%	840
	11th to 20th	Night	8% 10% 18% 38% 21% 5%	831
	21st to end	Night	8% 8% 17% 33% 27% 7%	840
May	1st to 10th	Night	6% 7% 16% 37% 30% 4	675
	11th to 20th	Night	3 7% 13% 38% 33% 7%	621
	21st to end	Night	4 6% 15% 39% 31% 4	683
June	1st to 10th	Night	2 3 10% 42% 37% 7%	630
	11th to 20th	Night	1 1 10% 45% 39% 5%	630
	21st to end	Night	1 2 8% 36% 46% 7%	630
July	1st to 10th	Night	3 27% 59% 12%	615
	11th to 20th	Night	1 1 23% 64% 10%	612
	21st to end	Night	2 2 2 19% 60% 16%	768
August	1st to 10th	Night	1 1 25% 56% 16%	836
	11th to 20th	Night	1 1 2 16% 59% 21%	832
	21st to end	Night	3 1 20% 56% 20%	924
September	1st to 10th	Night	2 1 4 28% 51% 14%	840
	11th to 20th	Night	2 2 6% 36% 44% 11%	840
	21st to end	Night	2 2 10% 38% 36% 11%	840
October	1st to 10th	Night	5% 6% 10% 43% 31% 5%	840
	11th to 20th	Night	4 7% 15% 38% 27% 9%	812
	21st to end	Night	4 4 17% 36% 27% 12%	880
November	1st to 10th	Night	7% 6% 16% 42% 21% 8%	820
	11th to 20th	Night	8% 6% 20% 35% 22% 10%	840
	21st to end	Night	12% 8% 20% 33% 20% 6%	840
December	1st to 10th	Night	11% 9% 21% 33% 20% 6%	840
	11th to 20th	Night	14% 7% 23% 34% 19% 3	840
	21st to end	Night	16% 10% 21% 30% 18% 5%	924

Page generated at 2026-10-11 02:06:33. Version ac07

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