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 2024-01-16.

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	11% 12% 4 8% 7% 4 6% 5% 5% 7% 31%	74779
	Night	8% 10% 4 8% 8% 4 6% 6% 6% 7% 32%	75023
Transparency	Day	53% 8% 13% 16% 8% 1	74470
	Night	50% 9% 14% 15% 9% 2	74850
Seeing	Day	19% 17% 31% 22% 8% 3	14249
	Night	15% 11% 31% 26% 15% 3	22656

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	10% 15% 6% 11% 10% 4 8% 6% 7% 6% 16%	1329
	11th to 20th	Day	7% 14% 6% 8% 9% 6% 6% 7% 6% 8% 23%	1327
	21st to end	Day	9% 17% 6% 8% 8% 5% 6% 6% 5% 8% 20%	1674
February	1st to 10th	Day	12% 16% 5% 9% 9% 5% 8% 5% 6% 8% 19%	1620
	11th to 20th	Day	9% 17% 8% 10% 8% 5% 7% 5% 5% 5% 21%	1575
	21st to end	Day	9% 20% 9% 10% 10% 5% 6% 6% 6% 4 15%	1340
March	1st to 10th	Day	6% 18% 7% 9% 10% 4 7% 7% 6% 6% 20%	1894
	11th to 20th	Day	8% 22% 7% 9% 8% 5% 6% 5% 5% 6% 18%	1980
	21st to end	Day	12% 23% 7% 11% 9% 4 5% 5% 4 6% 13%	2209
April	1st to 10th	Day	12% 19% 6% 9% 8% 4 6% 7% 7% 6% 14%	2160
	11th to 20th	Day	14% 19% 7% 10% 7% 4 6% 5% 4 5% 19%	2219
	21st to end	Day	15% 18% 5% 9% 7% 5% 6% 5% 4 6% 21%	2340
May	1st to 10th	Day	14% 14% 4 8% 7% 3 6% 4 6% 6% 29%	2517
	11th to 20th	Day	15% 10% 4 8% 6% 4 6% 6% 6% 8% 26%	2477
	21st to end	Day	20% 12% 4 7% 7% 4 4 4 5% 6% 28%	2723
June	1st to 10th	Day	20% 12% 4 8% 7% 3 5% 5% 5% 7% 25%	2695
	11th to 20th	Day	17% 10% 4 9% 8% 4 5% 6% 5% 7% 24%	2700
	21st to end	Day	13% 7% 3 6% 6% 3 5% 6% 5% 7% 39%	2700
July	1st to 10th	Day	10% 6% 3 5% 5% 3 5% 4 4 7% 48%	2700
	11th to 20th	Day	10% 5% 2 5% 4 2 4 3 5% 7% 53%	2700
	21st to end	Day	4 3 1 4 3 3 3 3 4 7% 64%	2751
August	1st to 10th	Day	6% 4 2 5% 3 2 3 3 6% 8% 57%	2414
	11th to 20th	Day	7% 5% 2 3 4 3 4 4 6% 7% 55%	2298
	21st to end	Day	7% 5% 3 6% 5% 3 4 6% 6% 9% 46%	2518
September	1st to 10th	Day	9% 6% 2 5% 4 2 3 4 5% 7% 52%	2160
	11th to 20th	Day	10% 8% 3 7% 7% 4 4 4 5% 6% 41%	2129
	21st to end	Day	10% 8% 3 7% 6% 3 5% 5% 5% 7% 42%	1913
October	1st to 10th	Day	13% 9% 3 7% 7% 3 6% 4 5% 7% 34%	1800
	11th to 20th	Day	11% 11% 4 7% 8% 4 5% 6% 6% 8% 30%	1800
	21st to end	Day	14% 9% 4 8% 7% 4 7% 7% 6% 7% 28%	1889
November	1st to 10th	Day	14% 14% 7% 10% 11% 5% 7% 6% 5% 6% 15%	1488
	11th to 20th	Day	11% 15% 6% 9% 8% 5% 7% 5% 6% 6% 22%	1520
	21st to end	Day	12% 14% 5% 9% 8% 4 8% 5% 6% 6% 23%	1520
December	1st to 10th	Day	8% 12% 5% 9% 9% 5% 6% 6% 6% 7% 26%	1520
	11th to 20th	Day	7% 15% 7% 11% 10% 6% 8% 7% 5% 5% 20%	1738
	21st to end	Day	8% 15% 5% 12% 9% 6% 9% 7% 8% 7% 15%	2442
January	1st to 10th	Night	8% 14% 6% 10% 10% 5% 8% 7% 6% 6% 18%	2836
	11th to 20th	Night	6% 10% 6% 11% 10% 6% 8% 7% 7% 8% 22%	2741
	21st to end	Night	11% 11% 4 9% 8% 4 7% 7% 8% 8% 23%	2682
February	1st to 10th	Night	10% 15% 6% 10% 9% 4 6% 6% 6% 8% 21%	2340
	11th to 20th	Night	7% 15% 6% 11% 9% 6% 6% 5% 6% 7% 24%	2272
	21st to end	Night	9% 18% 8% 12% 9% 4 6% 5% 6% 6% 17%	1914
March	1st to 10th	Night	5% 13% 5% 8% 9% 6% 8% 7% 7% 9% 24%	2062
	11th to 20th	Night	5% 13% 5% 8% 10% 6% 8% 8% 7% 9% 21%	1979
	21st to end	Night	8% 14% 7% 10% 11% 4 10% 6% 7% 6% 18%	2147
April	1st to 10th	Night	8% 15% 5% 11% 8% 5% 8% 6% 6% 7% 21%	1800
	11th to 20th	Night	8% 12% 5% 9% 8% 4 7% 6% 7% 9% 25%	1687
	21st to end	Night	9% 11% 5% 8% 9% 4 6% 6% 6% 8% 28%	1620
May	1st to 10th	Night	6% 8% 4 7% 7% 4 5% 5% 5% 8% 41%	1441
	11th to 20th	Night	7% 8% 4 8% 5% 5% 6% 7% 8% 9% 34%	1416
	21st to end	Night	10% 8% 4 6% 7% 4 5% 5% 5% 9% 37%	1552
June	1st to 10th	Night	10% 6% 3 8% 6% 4 5% 6% 5% 6% 40%	1262
	11th to 20th	Night	7% 8% 3 6% 7% 4 6% 5% 7% 8% 40%	1260
	21st to end	Night	5% 3 2 5% 5% 3 4 7% 6% 7% 53%	1260
July	1st to 10th	Night	5% 3 1 4 5% 3 3 4 5% 6% 60%	1260
	11th to 20th	Night	4 3 1 3 4 2 5% 4 4 7% 65%	1260
	21st to end	Night	2 2 1 2 2 2 3 4 3 5% 74%	1566
August	1st to 10th	Night	3 4 1 4 3 2 3 3 4 6% 67%	1522
	11th to 20th	Night	3 2 1 2 3 2 2 4 6% 7% 68%	1602
	21st to end	Night	5% 5% 2 5% 4 3 4 5% 5% 8% 56%	1837
September	1st to 10th	Night	5% 3 1 4 5% 2 4 4 5% 7% 60%	1800
	11th to 20th	Night	8% 7% 3 5% 6% 4 5% 5% 5% 7% 46%	1827
	21st to end	Night	8% 6% 2 6% 7% 4 4 5% 5% 7% 44%	2047
October	1st to 10th	Night	10% 9% 3 6% 7% 4 4 6% 6% 5% 39%	2160
	11th to 20th	Night	11% 9% 3 8% 7% 4 6% 6% 7% 7% 32%	2160
	21st to end	Night	11% 10% 3 9% 8% 5% 5% 5% 6% 7% 31%	2463
November	1st to 10th	Night	12% 11% 5% 10% 9% 5% 7% 7% 6% 6% 21%	2590
	11th to 20th	Night	11% 14% 6% 8% 8% 5% 7% 7% 6% 7% 22%	2660
	21st to end	Night	9% 13% 5% 10% 9% 5% 7% 7% 6% 6% 22%	2660
December	1st to 10th	Night	7% 12% 6% 10% 9% 4 8% 6% 6% 7% 26%	2660
	11th to 20th	Night	7% 14% 5% 11% 11% 6% 8% 7% 6% 6% 20%	3464
	21st to end	Night	6% 14% 5% 10% 11% 6% 9% 9% 7% 7% 16%	5214

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	65% 10% 10% 9% 5% 2	1329
	11th to 20th	Day	54% 13% 13% 10% 8% 3	1327
	21st to end	Day	61% 8% 11% 11% 8% 1	1674
February	1st to 10th	Day	62% 9% 13% 8% 6% 1	1620
	11th to 20th	Day	62% 9% 10% 11% 6% 1	1584
	21st to end	Day	67% 7% 12% 10% 4	1340
March	1st to 10th	Day	61% 9% 13% 10% 5% 1	1894
	11th to 20th	Day	68% 7% 10% 11% 4 1	1980
	21st to end	Day	74% 6% 10% 9% 2	2209
April	1st to 10th	Day	68% 8% 12% 10% 2	2160
	11th to 20th	Day	69% 5% 9% 10% 7%	2219
	21st to end	Day	65% 7% 10% 12% 6% 1	2340
May	1st to 10th	Day	56% 8% 15% 14% 6%	2517
	11th to 20th	Day	57% 9% 15% 13% 6%	2480
	21st to end	Day	61% 7% 15% 14% 3	2724
June	1st to 10th	Day	61% 9% 15% 9% 5% 1	2695
	11th to 20th	Day	63% 9% 14% 11% 4	2700
	21st to end	Day	46% 9% 18% 16% 8% 2	2700
July	1st to 10th	Day	38% 9% 14% 23% 13% 3	2626
	11th to 20th	Day	32% 9% 15% 27% 15% 2	2619
	21st to end	Day	22% 7% 15% 34% 18% 4	2598
August	1st to 10th	Day	27% 9% 19% 26% 17% 2	2397
	11th to 20th	Day	29% 7% 17% 29% 15% 2	2298
	21st to end	Day	35% 9% 16% 29% 10% 1	2518
September	1st to 10th	Day	33% 6% 16% 23% 18% 4	2160
	11th to 20th	Day	43% 7% 12% 19% 16% 3	2129
	21st to end	Day	42% 7% 17% 18% 13% 3	1913
October	1st to 10th	Day	49% 8% 13% 20% 9% 1	1800
	11th to 20th	Day	51% 9% 14% 16% 9% 1	1800
	21st to end	Day	52% 8% 12% 17% 9% 2	1889
November	1st to 10th	Day	69% 6% 11% 9% 5% 1	1488
	11th to 20th	Day	61% 10% 7% 12% 7% 2	1520
	21st to end	Day	61% 9% 7% 11% 11% 2	1520
December	1st to 10th	Day	57% 9% 11% 13% 8% 1	1520
	11th to 20th	Day	63% 8% 13% 11% 4 1	1741
	21st to end	Day	62% 13% 11% 9% 4	2442
January	1st to 10th	Night	62% 12% 10% 9% 5% 2	2836
	11th to 20th	Night	57% 11% 12% 10% 7% 4	2741
	21st to end	Night	55% 10% 13% 11% 9% 3	2682
February	1st to 10th	Night	59% 9% 13% 10% 7% 2	2340
	11th to 20th	Night	58% 10% 10% 12% 7% 2	2274
	21st to end	Night	65% 8% 11% 11% 4	1914
March	1st to 10th	Night	54% 11% 14% 14% 7%	2062
	11th to 20th	Night	57% 10% 14% 12% 5% 2	1980
	21st to end	Night	65% 10% 12% 11% 2	2147
April	1st to 10th	Night	61% 8% 15% 12% 4	1800
	11th to 20th	Night	55% 8% 15% 14% 8% 1	1687
	21st to end	Night	55% 8% 11% 15% 11% 1	1620
May	1st to 10th	Night	41% 9% 18% 22% 8% 1	1441
	11th to 20th	Night	47% 11% 17% 16% 8% 1	1416
	21st to end	Night	48% 9% 17% 20% 5%	1552
June	1st to 10th	Night	48% 9% 17% 19% 6% 2	1262
	11th to 20th	Night	42% 10% 25% 17% 6%	1260
	21st to end	Night	28% 11% 24% 23% 9% 4	1260
July	1st to 10th	Night	26% 9% 19% 27% 14% 5%	1225
	11th to 20th	Night	21% 8% 20% 29% 17% 5%	1218
	21st to end	Night	15% 5% 17% 33% 23% 6%	1479
August	1st to 10th	Night	22% 8% 17% 29% 21% 4	1514
	11th to 20th	Night	17% 7% 21% 30% 19% 7%	1602
	21st to end	Night	27% 7% 17% 31% 16% 2	1837
September	1st to 10th	Night	25% 8% 17% 25% 20% 5%	1800
	11th to 20th	Night	38% 8% 12% 18% 18% 6%	1827
	21st to end	Night	40% 8% 12% 18% 17% 4	2047
October	1st to 10th	Night	45% 6% 12% 20% 15% 1	2160
	11th to 20th	Night	48% 7% 16% 16% 12% 1	2160
	21st to end	Night	50% 8% 12% 15% 13% 1	2463
November	1st to 10th	Night	61% 8% 12% 13% 5% 1	2590
	11th to 20th	Night	59% 12% 12% 8% 6% 3	2660
	21st to end	Night	58% 10% 11% 9% 10% 2	2660
December	1st to 10th	Night	56% 12% 11% 11% 8% 2	2660
	11th to 20th	Night	61% 10% 12% 11% 5% 1	3460
	21st to end	Night	59% 11% 15% 10% 5% 1	5214

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	24% 21% 24% 17% 9% 4	180
	11th to 20th	Day	16% 20% 31% 15% 16% 2	170
	21st to end	Day	23% 19% 28% 18% 9% 3	266
February	1st to 10th	Day	24% 21% 36% 15% 3 1	340
	11th to 20th	Day	24% 23% 35% 13% 5%	335
	21st to end	Day	27% 23% 32% 14% 3	284
March	1st to 10th	Day	23% 26% 32% 16% 4	420
	11th to 20th	Day	21% 25% 31% 20% 3	420
	21st to end	Day	24% 27% 34% 12% 3	462
April	1st to 10th	Day	26% 24% 29% 15% 5%	420
	11th to 20th	Day	29% 22% 26% 17% 5% 1	412
	21st to end	Day	29% 22% 30% 14% 4 1	420
May	1st to 10th	Day	24% 17% 31% 21% 7% 1	423
	11th to 20th	Day	25% 16% 27% 22% 8% 2	448
	21st to end	Day	21% 14% 34% 19% 9% 3	485
June	1st to 10th	Day	25% 17% 29% 21% 7% 3	625
	11th to 20th	Day	20% 20% 33% 18% 7% 1	630
	21st to end	Day	14% 14% 35% 25% 9% 3	630
July	1st to 10th	Day	13% 9% 32% 31% 12% 3	621
	11th to 20th	Day	13% 12% 31% 29% 10% 5%	618
	21st to end	Day	5% 10% 28% 36% 13% 7%	497
August	1st to 10th	Day	8% 10% 28% 34% 14% 7%	447
	11th to 20th	Day	6% 8% 29% 36% 14% 6%	437
	21st to end	Day	9% 18% 32% 26% 11% 4	495
September	1st to 10th	Day	14% 12% 38% 28% 8% 1	450
	11th to 20th	Day	14% 12% 37% 25% 10% 2	450
	21st to end	Day	14% 18% 32% 25% 8% 2	450
October	1st to 10th	Day	18% 17% 31% 21% 13% 1	450
	11th to 20th	Day	21% 20% 29% 16% 11% 3	450
	21st to end	Day	22% 21% 32% 14% 8% 3	416
November	1st to 10th	Day	24% 23% 29% 16% 8% 1	180
	11th to 20th	Day	21% 19% 26% 19% 9% 6%	180
	21st to end	Day	23% 16% 26% 21% 6% 9%	180
December	1st to 10th	Day	22% 15% 27% 18% 12% 6%	180
	11th to 20th	Day	17% 18% 36% 17% 11% 1	180
	21st to end	Day	20% 12% 38% 23% 6% 2	198
January	1st to 10th	Night	22% 19% 31% 16% 9% 3	850
	11th to 20th	Night	18% 16% 31% 22% 12% 3	809
	21st to end	Night	20% 12% 32% 23% 11% 2	792
February	1st to 10th	Night	21% 11% 40% 20% 7%	720
	11th to 20th	Night	16% 14% 32% 30% 7% 1	704
	21st to end	Night	19% 16% 34% 23% 6% 1	592
March	1st to 10th	Night	15% 16% 36% 21% 10% 1	720
	11th to 20th	Night	14% 16% 39% 20% 8% 2	720
	21st to end	Night	15% 15% 35% 26% 8% 1	792
April	1st to 10th	Night	17% 11% 35% 26% 10% 1	720
	11th to 20th	Night	14% 10% 41% 23% 9% 2	619
	21st to end	Night	13% 7% 42% 25% 10% 2	540
May	1st to 10th	Night	10% 7% 27% 37% 15% 4	361
	11th to 20th	Night	11% 4 24% 34% 23% 3	354
	21st to end	Night	13% 5% 20% 36% 24% 1	389
June	1st to 10th	Night	13% 6% 24% 34% 21% 3	360
	11th to 20th	Night	9% 3 35% 35% 17% 1	360
	21st to end	Night	6% 3 24% 39% 25% 4	360
July	1st to 10th	Night	7% 2 12% 36% 40% 3	350
	11th to 20th	Night	5% 4 16% 39% 31% 5%	348
	21st to end	Night	3 2 12% 41% 33% 9%	394
August	1st to 10th	Night	5% 3 13% 30% 37% 13%	448
	11th to 20th	Night	3 1 10% 37% 35% 13%	534
	21st to end	Night	7% 3 24% 33% 28% 6%	649
September	1st to 10th	Night	7% 2 23% 36% 26% 6%	720
	11th to 20th	Night	12% 3 22% 29% 26% 9%	720
	21st to end	Night	13% 8% 23% 33% 18% 4	720
October	1st to 10th	Night	13% 7% 28% 28% 22% 3	720
	11th to 20th	Night	16% 11% 28% 25% 15% 5%	720
	21st to end	Night	16% 13% 38% 21% 8% 4	792
November	1st to 10th	Night	19% 14% 40% 21% 6%	740
	11th to 20th	Night	20% 16% 36% 18% 8% 2	760
	21st to end	Night	20% 16% 37% 16% 8% 4	760
December	1st to 10th	Night	16% 14% 33% 24% 11% 3	760
	11th to 20th	Night	19% 16% 41% 18% 6% 1	824
	21st to end	Night	22% 18% 38% 16% 5% 1	935

Page generated at 2024-01-12 22:38:12. Version ac07

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