Hurricane Ridge Visitor Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hurricane Ridge Visitor Center clear sky chart from 2005-11-06 to 2026-03-18.

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	9% 12% 4 9% 6% 5% 5% 4 5% 6% 35%	135013
	Night	6% 10% 4 10% 7% 6% 6% 5% 6% 7% 34%	135202
Transparency	Day	48% 8% 13% 17% 11% 3	134723
	Night	46% 10% 12% 16% 12% 4	135070
Seeing	Day	19% 18% 31% 21% 8% 2	17039
	Night	15% 12% 31% 26% 14% 3	25437

By Month

Percentage Cloud Cover NW (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% 21% 7% 16% 9% 7% 6% 4 5% 5% 12%	4125
	11th to 20th	Day	4 10% 4 7% 5% 6% 6% 5% 6% 8% 40%	4221
	21st to end	Day	6% 13% 5% 12% 8% 7% 7% 5% 6% 6% 27%	5484
February	1st to 10th	Day	10% 16% 5% 11% 8% 7% 6% 4 6% 8% 18%	1890
	11th to 20th	Day	8% 18% 7% 12% 7% 7% 6% 4 5% 5% 21%	1845
	21st to end	Day	8% 22% 7% 12% 8% 7% 6% 5% 6% 5% 15%	1568
March	1st to 10th	Day	5% 16% 6% 11% 9% 7% 8% 6% 7% 7% 19%	4860
	11th to 20th	Day	6% 21% 6% 13% 6% 6% 5% 4 5% 5% 24%	5078
	21st to end	Day	9% 24% 7% 13% 7% 5% 6% 4 5% 6% 14%	5568
April	1st to 10th	Day	11% 21% 6% 11% 7% 6% 6% 5% 7% 6% 15%	2400
	11th to 20th	Day	12% 19% 6% 10% 6% 5% 5% 4 5% 6% 23%	2470
	21st to end	Day	15% 19% 4 9% 6% 6% 5% 4 5% 6% 22%	2600
May	1st to 10th	Day	11% 13% 4 8% 5% 4 5% 4 5% 5% 38%	6317
	11th to 20th	Day	10% 11% 4 9% 6% 5% 5% 4 6% 9% 31%	6277
	21st to end	Day	15% 13% 3 8% 6% 5% 5% 4 6% 7% 27%	6903
June	1st to 10th	Day	18% 12% 3 8% 6% 5% 5% 4 5% 6% 28%	2995
	11th to 20th	Day	15% 11% 4 10% 7% 6% 5% 5% 5% 7% 25%	3000
	21st to end	Day	13% 8% 3 7% 5% 5% 5% 5% 6% 7% 37%	3000
July	1st to 10th	Day	7% 3 1 3 2 3 3 2 4 6% 66%	6780
	11th to 20th	Day	4 3 1 3 2 2 2 2 3 4 74%	6780
	21st to end	Day	5% 3 1 4 3 3 4 3 5% 6% 65%	6884
August	1st to 10th	Day	3 3 1 4 2 3 3 3 5% 7% 66%	4365
	11th to 20th	Day	9% 9% 3 7% 5% 6% 7% 4 6% 7% 38%	4156
	21st to end	Day	9% 6% 3 7% 5% 4 4 4 5% 6% 47%	4553
September	1st to 10th	Day	9% 6% 2 5% 4 3 4 3 5% 7% 53%	2400
	11th to 20th	Day	10% 8% 3 7% 6% 4 4 3 5% 7% 43%	2365
	21st to end	Day	9% 7% 3 8% 5% 5% 5% 4 5% 7% 41%	2125
October	1st to 10th	Day	10% 7% 3 8% 6% 5% 6% 5% 7% 9% 34%	3280
	11th to 20th	Day	10% 11% 3 12% 7% 5% 5% 4 6% 7% 28%	3261
	21st to end	Day	9% 10% 4 11% 8% 7% 6% 5% 6% 8% 26%	3382
November	1st to 10th	Day	13% 15% 6% 12% 10% 7% 6% 5% 6% 7% 15%	1648
	11th to 20th	Day	11% 16% 5% 10% 7% 7% 6% 4 7% 6% 21%	1680
	21st to end	Day	10% 16% 4 10% 7% 6% 7% 4 6% 7% 22%	1680
December	1st to 10th	Day	6% 11% 4 10% 7% 6% 5% 5% 6% 6% 34%	2700
	11th to 20th	Day	8% 15% 5% 13% 10% 8% 7% 5% 6% 6% 18%	2798
	21st to end	Day	7% 16% 5% 15% 9% 8% 7% 5% 7% 7% 14%	3575
January	1st to 10th	Night	6% 18% 6% 15% 9% 8% 8% 6% 6% 6% 12%	8770
	11th to 20th	Night	3 7% 3 9% 6% 5% 6% 4 7% 8% 41%	8661
	21st to end	Night	6% 10% 4 11% 7% 7% 7% 5% 7% 7% 28%	8711
February	1st to 10th	Night	9% 15% 5% 12% 8% 6% 6% 5% 6% 8% 21%	2730
	11th to 20th	Night	7% 15% 5% 12% 8% 7% 5% 4 6% 7% 24%	2662
	21st to end	Night	8% 19% 7% 13% 8% 6% 5% 4 6% 6% 18%	2236
March	1st to 10th	Night	3 10% 4 10% 7% 8% 7% 6% 9% 11% 23%	5237
	11th to 20th	Night	3 11% 4 10% 8% 8% 7% 5% 7% 7% 30%	5076
	21st to end	Night	6% 16% 6% 15% 9% 7% 8% 5% 7% 6% 15%	5407
April	1st to 10th	Night	7% 16% 4 12% 8% 7% 7% 4 7% 7% 21%	2000
	11th to 20th	Night	7% 12% 4 10% 7% 6% 6% 5% 7% 8% 28%	1876
	21st to end	Night	8% 13% 4 9% 7% 5% 7% 4 6% 7% 29%	1800
May	1st to 10th	Night	6% 8% 3 8% 5% 5% 5% 3 4 5% 48%	3641
	11th to 20th	Night	5% 9% 3 8% 4 5% 5% 4 6% 8% 43%	3616
	21st to end	Night	6% 8% 3 8% 6% 6% 7% 5% 7% 9% 33%	3972
June	1st to 10th	Night	9% 7% 3 8% 6% 4 5% 5% 5% 6% 41%	1402
	11th to 20th	Night	6% 8% 3 6% 7% 5% 5% 4 8% 8% 41%	1400
	21st to end	Night	5% 4 2 7% 4 4 5% 6% 6% 7% 51%	1400
July	1st to 10th	Night	3 3 1 3 3 2 2 2 3 4 73%	3180
	11th to 20th	Night	2 1 1 1 2 1 2 2 3 5% 80%	3180
	21st to end	Night	3 3 1 3 2 3 3 3 3 5% 70%	3959
August	1st to 10th	Night	2 3 1 2 2 2 2 3 4 5% 75%	2788
	11th to 20th	Night	7% 7% 2 6% 6% 5% 4 4 5% 7% 48%	2902
	21st to end	Night	9% 5% 2 4 3 3 5% 3 5% 8% 54%	3359
September	1st to 10th	Night	5% 3 1 5% 4 3 3 3 5% 7% 60%	2000
	11th to 20th	Night	8% 7% 2 6% 5% 5% 4 4 5% 7% 47%	2031
	21st to end	Night	8% 6% 2 7% 6% 5% 4 4 5% 7% 45%	2275
October	1st to 10th	Night	8% 6% 2 6% 5% 4 5% 5% 8% 8% 43%	3920
	11th to 20th	Night	10% 8% 3 10% 6% 6% 6% 4 7% 7% 31%	3897
	21st to end	Night	9% 9% 3 10% 7% 6% 6% 5% 7% 8% 30%	4418
November	1st to 10th	Night	12% 12% 5% 11% 8% 7% 7% 5% 6% 6% 21%	2870
	11th to 20th	Night	10% 15% 5% 10% 7% 7% 7% 5% 6% 7% 21%	2940
	21st to end	Night	8% 15% 3 12% 7% 7% 7% 6% 7% 7% 21%	2940
December	1st to 10th	Night	5% 11% 3 9% 6% 6% 7% 5% 7% 7% 34%	4700
	11th to 20th	Night	8% 15% 5% 14% 9% 7% 8% 5% 7% 6% 16%	5623
	21st to end	Night	5% 15% 5% 13% 10% 8% 8% 6% 7% 7% 15%	7623

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	69% 9% 8% 7% 6% 1	4125
	11th to 20th	Day	40% 7% 9% 16% 17% 11%	4242
	21st to end	Day	56% 9% 7% 10% 10% 8%	5485
February	1st to 10th	Day	62% 9% 13% 8% 6% 2	1890
	11th to 20th	Day	62% 9% 10% 10% 8% 2	1854
	21st to end	Day	65% 8% 13% 11% 4	1568
March	1st to 10th	Day	56% 10% 14% 11% 7% 1	4860
	11th to 20th	Day	60% 7% 9% 16% 8% 1	5078
	21st to end	Day	70% 8% 12% 8% 3	5568
April	1st to 10th	Day	67% 9% 12% 10% 2	2400
	11th to 20th	Day	63% 6% 9% 12% 8% 1	2470
	21st to end	Day	63% 7% 11% 14% 5% 1	2600
May	1st to 10th	Day	47% 5% 15% 20% 12% 2	6317
	11th to 20th	Day	48% 10% 22% 15% 5%	6280
	21st to end	Day	55% 9% 15% 16% 4	6904
June	1st to 10th	Day	57% 9% 16% 11% 7% 1	2995
	11th to 20th	Day	62% 9% 13% 11% 5% 1	3000
	21st to end	Day	47% 10% 17% 17% 8% 1	3000
July	1st to 10th	Day	22% 7% 16% 18% 24% 13%	6706
	11th to 20th	Day	17% 5% 13% 27% 31% 7%	6699
	21st to end	Day	20% 8% 20% 35% 15% 3	6690
August	1st to 10th	Day	19% 8% 12% 27% 29% 6%	4348
	11th to 20th	Day	38% 11% 18% 22% 10% 2	4195
	21st to end	Day	38% 7% 12% 26% 14% 2	4552
September	1st to 10th	Day	32% 7% 16% 24% 18% 4	2400
	11th to 20th	Day	41% 7% 12% 20% 17% 4	2365
	21st to end	Day	41% 7% 18% 19% 12% 3	2125
October	1st to 10th	Day	43% 9% 13% 24% 10% 1	3280
	11th to 20th	Day	53% 10% 11% 15% 10% 1	3261
	21st to end	Day	51% 11% 14% 15% 7% 2	3382
November	1st to 10th	Day	67% 7% 11% 10% 4 1	1648
	11th to 20th	Day	62% 11% 7% 11% 7% 2	1680
	21st to end	Day	60% 9% 8% 11% 11% 2	1680
December	1st to 10th	Day	51% 8% 7% 10% 17% 7%	2700
	11th to 20th	Day	64% 10% 10% 11% 4 1	2801
	21st to end	Day	62% 15% 9% 10% 4	3575
January	1st to 10th	Night	65% 12% 8% 8% 5% 2	8770
	11th to 20th	Night	37% 7% 10% 15% 17% 15%	8702
	21st to end	Night	50% 11% 7% 12% 11% 9%	8711
February	1st to 10th	Night	58% 9% 13% 9% 8% 3	2730
	11th to 20th	Night	57% 10% 10% 12% 9% 2	2664
	21st to end	Night	63% 9% 11% 12% 5% 1	2236
March	1st to 10th	Night	45% 13% 19% 11% 10% 2	5237
	11th to 20th	Night	45% 12% 13% 15% 13% 1	5077
	21st to end	Night	62% 13% 12% 10% 3	5407
April	1st to 10th	Night	60% 8% 15% 13% 4	2000
	11th to 20th	Night	52% 8% 14% 15% 10% 1	1876
	21st to end	Night	54% 8% 11% 17% 10% 1	1800
May	1st to 10th	Night	38% 5% 13% 25% 15% 4	3638
	11th to 20th	Night	39% 9% 20% 20% 10% 2	3616
	21st to end	Night	45% 13% 18% 19% 4 1	3972
June	1st to 10th	Night	46% 9% 17% 19% 8% 2	1402
	11th to 20th	Night	41% 10% 23% 19% 8%	1400
	21st to end	Night	30% 11% 24% 23% 9% 4	1400
July	1st to 10th	Night	18% 7% 16% 21% 22% 16%	3145
	11th to 20th	Night	10% 5% 11% 29% 32% 14%	3138
	21st to end	Night	19% 6% 16% 33% 20% 6%	3848
August	1st to 10th	Night	15% 5% 11% 26% 36% 6%	2780
	11th to 20th	Night	31% 11% 20% 22% 12% 4	2929
	21st to end	Night	28% 8% 15% 29% 18% 3	3359
September	1st to 10th	Night	25% 8% 16% 26% 21% 5%	2000
	11th to 20th	Night	37% 8% 12% 19% 18% 6%	2031
	21st to end	Night	40% 8% 12% 19% 16% 4	2275
October	1st to 10th	Night	37% 6% 12% 28% 15% 2	3920
	11th to 20th	Night	51% 7% 13% 17% 10% 2	3897
	21st to end	Night	47% 12% 11% 17% 11% 2	4418
November	1st to 10th	Night	61% 9% 11% 13% 5% 1	2870
	11th to 20th	Night	59% 12% 11% 8% 6% 3	2940
	21st to end	Night	59% 10% 10% 9% 9% 2	2940
December	1st to 10th	Night	48% 10% 9% 11% 16% 7%	4700
	11th to 20th	Night	63% 13% 8% 10% 5% 1	5619
	21st to end	Night	58% 16% 12% 10% 4 1	7623

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% 19% 28% 16% 8% 4	220
	11th to 20th	Day	15% 18% 31% 18% 16% 2	220
	21st to end	Day	22% 20% 29% 16% 9% 3	347
February	1st to 10th	Day	23% 23% 34% 15% 3 1	430
	11th to 20th	Day	23% 22% 36% 13% 6%	425
	21st to end	Day	31% 23% 30% 12% 3 1	362
March	1st to 10th	Day	24% 26% 32% 15% 3	540
	11th to 20th	Day	23% 27% 27% 19% 4	529
	21st to end	Day	25% 27% 34% 11% 3	550
April	1st to 10th	Day	27% 24% 30% 15% 4	500
	11th to 20th	Day	28% 22% 28% 16% 4 1	492
	21st to end	Day	29% 22% 29% 15% 5% 1	500
May	1st to 10th	Day	25% 18% 29% 20% 7% 1	503
	11th to 20th	Day	26% 16% 27% 21% 7% 2	528
	21st to end	Day	23% 14% 33% 18% 9% 2	573
June	1st to 10th	Day	24% 17% 29% 21% 7% 3	725
	11th to 20th	Day	20% 21% 32% 18% 7% 1	730
	21st to end	Day	14% 16% 34% 23% 9% 3	730
July	1st to 10th	Day	12% 10% 32% 32% 12% 2	721
	11th to 20th	Day	11% 12% 31% 30% 12% 4	718
	21st to end	Day	6% 11% 28% 36% 12% 7%	585
August	1st to 10th	Day	7% 10% 30% 33% 13% 6%	527
	11th to 20th	Day	9% 10% 28% 34% 13% 5%	517
	21st to end	Day	10% 17% 30% 28% 12% 3	583
September	1st to 10th	Day	12% 12% 37% 29% 8% 1	530
	11th to 20th	Day	13% 12% 38% 26% 9% 2	530
	21st to end	Day	15% 18% 35% 23% 7% 2	530
October	1st to 10th	Day	17% 19% 32% 20% 12% 1	530
	11th to 20th	Day	22% 22% 28% 15% 9% 2	530
	21st to end	Day	23% 25% 30% 13% 7% 2	492
November	1st to 10th	Day	24% 25% 28% 15% 7%	220
	11th to 20th	Day	22% 21% 25% 18% 8% 5%	220
	21st to end	Day	22% 17% 28% 19% 6% 7%	220
December	1st to 10th	Day	25% 15% 26% 16% 14% 5%	220
	11th to 20th	Day	24% 19% 34% 15% 9% 1	220
	21st to end	Day	24% 14% 34% 21% 5% 2	242
January	1st to 10th	Night	22% 20% 32% 16% 8% 2	950
	11th to 20th	Night	17% 16% 31% 23% 11% 2	928
	21st to end	Night	20% 12% 33% 22% 10% 2	924
February	1st to 10th	Night	20% 13% 40% 20% 8%	840
	11th to 20th	Night	16% 14% 32% 30% 7% 1	824
	21st to end	Night	22% 16% 35% 21% 5% 1	692
March	1st to 10th	Night	15% 18% 36% 21% 10% 1	840
	11th to 20th	Night	15% 18% 38% 20% 8% 1	828
	21st to end	Night	15% 16% 35% 26% 7% 1	880
April	1st to 10th	Night	17% 12% 36% 26% 9% 1	800
	11th to 20th	Night	14% 11% 42% 23% 9% 2	688
	21st to end	Night	13% 7% 41% 26% 11% 2	600
May	1st to 10th	Night	9% 7% 31% 35% 13% 4	401
	11th to 20th	Night	12% 5% 25% 34% 21% 3	394
	21st to end	Night	12% 6% 23% 36% 22% 1	433
June	1st to 10th	Night	12% 7% 25% 35% 20% 2	400
	11th to 20th	Night	9% 4 35% 36% 17% 1	400
	21st to end	Night	6% 3 25% 40% 22% 4	400
July	1st to 10th	Night	6% 2 15% 37% 37% 3	390
	11th to 20th	Night	4 4 17% 41% 29% 5%	388
	21st to end	Night	3 3 13% 41% 32% 8%	438
August	1st to 10th	Night	5% 3 14% 32% 36% 11%	499
	11th to 20th	Night	4 3 12% 36% 33% 12%	594
	21st to end	Night	8% 4 23% 34% 26% 5%	722
September	1st to 10th	Night	7% 2 23% 38% 25% 6%	800
	11th to 20th	Night	11% 4 23% 30% 24% 8%	800
	21st to end	Night	13% 10% 24% 33% 17% 4	800
October	1st to 10th	Night	13% 8% 29% 28% 20% 3	800
	11th to 20th	Night	16% 13% 30% 24% 13% 5%	800
	21st to end	Night	16% 15% 38% 20% 8% 3	880
November	1st to 10th	Night	20% 15% 40% 20% 5%	820
	11th to 20th	Night	21% 18% 36% 17% 7% 2	840
	21st to end	Night	19% 17% 38% 16% 7% 4	840
December	1st to 10th	Night	18% 13% 32% 24% 10% 2	840
	11th to 20th	Night	22% 16% 39% 16% 5% 1	919
	21st to end	Night	22% 19% 38% 16% 5%	1045

Page generated at 2026-03-14 23:23:57. Version ac07

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