White River Canyon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the White River Canyon clear sky chart from 2005-11-06 to 2025-12-03.

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	7% 13% 4 9% 5% 5% 4 3 4 5% 40%	136237
	Night	9% 13% 4 9% 6% 5% 6% 4 5% 6% 34%	131798
Transparency	Day	39% 10% 11% 18% 16% 7%	130997
	Night	41% 13% 12% 15% 13% 6%	128036
Seeing	Day	19% 21% 29% 21% 8% 2	15913
	Night	16% 18% 24% 26% 13% 2	24914

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	14% 24% 7% 15% 9% 5% 4 3 3 4 10%	3639
	11th to 20th	Day	8% 16% 6% 10% 6% 4 6% 3 3 5% 33%	3640
	21st to end	Day	11% 21% 5% 9% 5% 4 4 3 3 4 30%	4257
February	1st to 10th	Day	12% 19% 6% 13% 8% 6% 6% 5% 4 5% 16%	1800
	11th to 20th	Day	9% 17% 6% 14% 8% 8% 5% 4 5% 4 19%	1755
	21st to end	Day	9% 23% 7% 14% 7% 6% 5% 3 4 4 18%	1616
March	1st to 10th	Day	7% 16% 8% 12% 7% 6% 6% 5% 6% 6% 19%	4598
	11th to 20th	Day	9% 25% 6% 12% 5% 4 3 3 3 3 27%	5000
	21st to end	Day	9% 26% 8% 16% 8% 6% 5% 3 3 4 11%	5700
April	1st to 10th	Day	12% 19% 6% 15% 8% 6% 6% 4 5% 4 16%	2400
	11th to 20th	Day	10% 18% 6% 12% 7% 5% 5% 4 4 4 26%	2369
	21st to end	Day	8% 15% 4 11% 7% 6% 7% 5% 6% 8% 25%	2531
May	1st to 10th	Day	8% 12% 3 9% 6% 4 4 4 4 4 42%	6320
	11th to 20th	Day	7% 12% 4 11% 7% 7% 5% 4 4 5% 34%	6277
	21st to end	Day	8% 11% 3 9% 6% 7% 7% 4 5% 7% 33%	6902
June	1st to 10th	Day	12% 12% 4 8% 5% 5% 5% 4 4 6% 35%	2800
	11th to 20th	Day	8% 11% 4 8% 6% 6% 7% 5% 6% 6% 33%	2800
	21st to end	Day	6% 5% 2 6% 4 4 4 3 5% 7% 54%	2800
July	1st to 10th	Day	2 2 1 2 1 1 2 2 3 5% 78%	6319
	11th to 20th	Day	2 2 1 2 2 1 2 2 2 3 82%	6320
	21st to end	Day	3 3 1 2 2 2 2 2 3 6% 75%	6880
August	1st to 10th	Day	2 3 1 4 3 3 3 3 4 6% 67%	5977
	11th to 20th	Day	3 3 1 4 3 3 3 4 5% 7% 64%	5796
	21st to end	Day	6% 5% 2 6% 4 4 4 3 5% 7% 54%	6037
September	1st to 10th	Day	3 3 2 5% 4 4 4 3 4 7% 61%	2400
	11th to 20th	Day	6% 6% 3 6% 5% 4 5% 3 5% 7% 49%	2400
	21st to end	Day	9% 8% 3 7% 5% 4 3 3 5% 5% 49%	2130
October	1st to 10th	Day	7% 8% 3 7% 4 3 4 3 4 5% 52%	3280
	11th to 20th	Day	8% 10% 4 11% 7% 6% 5% 4 6% 6% 34%	3261
	21st to end	Day	10% 19% 5% 12% 7% 5% 6% 3 5% 5% 22%	3396
November	1st to 10th	Day	14% 19% 5% 13% 7% 6% 5% 4 5% 5% 18%	1809
	11th to 20th	Day	11% 22% 6% 13% 8% 5% 6% 3 5% 5% 15%	1680
	21st to end	Day	11% 18% 5% 11% 8% 6% 5% 4 4 5% 23%	1680
December	1st to 10th	Day	8% 14% 4 9% 6% 6% 5% 3 4 4 37%	2636
	11th to 20th	Day	13% 26% 7% 12% 7% 6% 5% 4 5% 4 10%	3028
	21st to end	Day	11% 25% 8% 15% 8% 6% 5% 3 3 3 12%	4004
January	1st to 10th	Night	14% 24% 7% 13% 10% 6% 5% 4 4 4 11%	6306
	11th to 20th	Night	10% 15% 5% 9% 6% 5% 7% 3 5% 6% 29%	6320
	21st to end	Night	12% 17% 5% 9% 5% 5% 4 3 3 4 32%	6708
February	1st to 10th	Night	10% 17% 6% 14% 8% 7% 7% 4 5% 6% 16%	2600
	11th to 20th	Night	10% 16% 5% 12% 10% 7% 7% 5% 5% 4 21%	2532
	21st to end	Night	10% 18% 6% 14% 9% 8% 6% 3 4 5% 18%	2012
March	1st to 10th	Night	5% 12% 6% 14% 9% 8% 8% 5% 6% 6% 19%	5293
	11th to 20th	Night	8% 19% 8% 13% 7% 5% 4 2 3 3 29%	5000
	21st to end	Night	10% 21% 7% 15% 8% 7% 6% 4 5% 5% 11%	5275
April	1st to 10th	Night	11% 14% 6% 13% 9% 8% 7% 5% 4 5% 18%	2000
	11th to 20th	Night	7% 12% 5% 10% 9% 7% 7% 5% 4 6% 28%	1979
	21st to end	Night	8% 13% 4 9% 8% 7% 8% 5% 7% 7% 25%	1865
May	1st to 10th	Night	11% 10% 2 7% 5% 4 5% 5% 5% 7% 39%	3640
	11th to 20th	Night	5% 10% 3 9% 9% 8% 10% 5% 5% 6% 31%	3616
	21st to end	Night	7% 10% 3 9% 6% 6% 6% 5% 8% 9% 31%	3972
June	1st to 10th	Night	12% 12% 4 8% 5% 4 5% 4 6% 6% 35%	1600
	11th to 20th	Night	7% 8% 3 9% 6% 7% 7% 5% 7% 7% 35%	1600
	21st to end	Night	5% 7% 2 5% 3 4 4 3 5% 8% 54%	1600
July	1st to 10th	Night	2 2 1 3 2 3 4 4 4 6% 70%	3640
	11th to 20th	Night	2 2 1 3 1 2 2 1 3 4 79%	3640
	21st to end	Night	2 2 1 2 1 2 2 2 3 7% 76%	3970
August	1st to 10th	Night	3 4 2 5% 4 4 4 3 6% 8% 58%	3823
	11th to 20th	Night	6% 3 1 3 2 3 4 4 5% 10% 57%	4052
	21st to end	Night	5% 4 2 5% 3 4 4 4 5% 7% 57%	4959
September	1st to 10th	Night	3 3 1 3 3 4 4 4 6% 8% 61%	2000
	11th to 20th	Night	6% 6% 2 6% 5% 5% 5% 4 6% 7% 48%	2000
	21st to end	Night	7% 7% 2 6% 4 4 5% 4 6% 8% 47%	2267
October	1st to 10th	Night	6% 6% 3 6% 4 3 4 3 5% 6% 52%	3920
	11th to 20th	Night	8% 10% 4 9% 6% 5% 6% 4 5% 7% 35%	3897
	21st to end	Night	12% 14% 6% 12% 7% 6% 7% 4 4 4 25%	4409
November	1st to 10th	Night	15% 15% 4 12% 8% 7% 7% 4 4 4 19%	2707
	11th to 20th	Night	13% 17% 5% 13% 9% 6% 7% 5% 4 5% 16%	2940
	21st to end	Night	8% 15% 4 13% 8% 7% 8% 5% 6% 5% 22%	2940
December	1st to 10th	Night	7% 11% 4 8% 6% 6% 5% 4 4 6% 39%	4588
	11th to 20th	Night	14% 23% 7% 13% 8% 7% 6% 4 5% 4 9%	5176
	21st to end	Night	16% 19% 7% 14% 7% 6% 6% 4 3 4 14%	6952

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	64% 15% 10% 9% 2	3639
	11th to 20th	Day	45% 13% 9% 15% 16% 2	3640
	21st to end	Day	51% 11% 6% 11% 15% 7%	4257
February	1st to 10th	Day	60% 13% 13% 10% 3	1800
	11th to 20th	Day	58% 14% 11% 12% 6% 1	1764
	21st to end	Day	59% 13% 11% 9% 6% 1	1616
March	1st to 10th	Day	48% 12% 15% 13% 8% 2	4598
	11th to 20th	Day	54% 12% 7% 20% 8%	5000
	21st to end	Day	64% 15% 9% 9% 3	5700
April	1st to 10th	Day	58% 16% 12% 11% 4	2400
	11th to 20th	Day	53% 11% 13% 12% 9% 2	2372
	21st to end	Day	46% 16% 13% 15% 7% 2	2531
May	1st to 10th	Day	35% 10% 13% 24% 16% 2	6320
	11th to 20th	Day	38% 13% 17% 21% 12%	6280
	21st to end	Day	34% 18% 20% 23% 5% 1	6904
June	1st to 10th	Day	44% 9% 14% 21% 10% 1	2800
	11th to 20th	Day	38% 15% 15% 19% 9% 3	2800
	21st to end	Day	25% 9% 12% 29% 20% 5%	2800
July	1st to 10th	Day	9% 4 6% 18% 31% 31%	6251
	11th to 20th	Day	9% 3 4 11% 34% 39%	6245
	21st to end	Day	11% 3 9% 29% 32% 16%	6681
August	1st to 10th	Day	14% 5% 8% 18% 34% 21%	4348
	11th to 20th	Day	17% 5% 9% 37% 25% 6%	4195
	21st to end	Day	23% 7% 11% 23% 28% 8%	4352
September	1st to 10th	Day	18% 8% 10% 25% 27% 13%	2400
	11th to 20th	Day	28% 8% 12% 23% 21% 7%	2400
	21st to end	Day	33% 8% 12% 21% 20% 8%	2130
October	1st to 10th	Day	30% 7% 7% 20% 29% 6%	3280
	11th to 20th	Day	42% 9% 14% 21% 14% 1	3261
	21st to end	Day	51% 13% 8% 16% 10% 1	3396
November	1st to 10th	Day	58% 12% 12% 12% 5% 1	1809
	11th to 20th	Day	62% 15% 10% 8% 5% 1	1680
	21st to end	Day	55% 13% 9% 10% 12% 1	1680
December	1st to 10th	Day	43% 10% 8% 14% 21% 5%	2636
	11th to 20th	Day	69% 12% 9% 7% 3	3028
	21st to end	Day	67% 13% 9% 9% 2 1	4004
January	1st to 10th	Night	64% 16% 9% 8% 3	6306
	11th to 20th	Night	44% 13% 13% 15% 14% 2	6320
	21st to end	Night	49% 11% 7% 7% 18% 7%	6708
February	1st to 10th	Night	56% 18% 10% 10% 4	2600
	11th to 20th	Night	53% 15% 12% 10% 8% 1	2534
	21st to end	Night	55% 15% 11% 10% 8% 1	2012
March	1st to 10th	Night	44% 16% 16% 15% 6% 3	5293
	11th to 20th	Night	47% 15% 9% 22% 6%	5000
	21st to end	Night	56% 21% 13% 9% 1	5275
April	1st to 10th	Night	50% 20% 14% 12% 4	2000
	11th to 20th	Night	45% 16% 14% 13% 9% 3	1979
	21st to end	Night	42% 20% 14% 15% 8% 2	1865
May	1st to 10th	Night	31% 11% 15% 22% 20% 1	3637
	11th to 20th	Night	32% 18% 19% 21% 10% 1	3616
	21st to end	Night	30% 22% 20% 21% 5% 2	3972
June	1st to 10th	Night	42% 13% 12% 21% 10% 2	1600
	11th to 20th	Night	33% 18% 17% 20% 9% 3	1600
	21st to end	Night	24% 10% 14% 26% 21% 6%	1600
July	1st to 10th	Night	12% 6% 8% 14% 26% 34%	3600
	11th to 20th	Night	10% 3 6% 9% 29% 43%	3592
	21st to end	Night	9% 3 9% 29% 30% 20%	3857
August	1st to 10th	Night	14% 6% 9% 15% 35% 22%	2780
	11th to 20th	Night	14% 7% 14% 33% 24% 8%	2929
	21st to end	Night	18% 7% 13% 24% 28% 10%	3565
September	1st to 10th	Night	16% 7% 15% 24% 26% 13%	2000
	11th to 20th	Night	27% 11% 13% 19% 20% 11%	2000
	21st to end	Night	28% 11% 12% 21% 19% 9%	2267
October	1st to 10th	Night	28% 7% 9% 22% 31% 4	3920
	11th to 20th	Night	39% 11% 13% 21% 14% 3	3897
	21st to end	Night	49% 14% 10% 14% 12% 1	4409
November	1st to 10th	Night	56% 15% 10% 11% 7% 1	2707
	11th to 20th	Night	57% 17% 9% 10% 6%	2940
	21st to end	Night	50% 15% 11% 11% 12% 1	2940
December	1st to 10th	Night	37% 11% 10% 15% 22% 5%	4588
	11th to 20th	Night	69% 14% 8% 6% 3	5176
	21st to end	Night	61% 16% 13% 8% 2 1	6952

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	37% 25% 21% 12% 5% 1	200
	11th to 20th	Day	27% 26% 26% 14% 7% 1	200
	21st to end	Day	23% 27% 24% 18% 8%	330
February	1st to 10th	Day	28% 30% 23% 13% 6%	400
	11th to 20th	Day	28% 29% 29% 12% 2	395
	21st to end	Day	31% 24% 26% 16% 4	398
March	1st to 10th	Day	25% 26% 32% 12% 3 1	500
	11th to 20th	Day	25% 27% 26% 15% 6% 1	500
	21st to end	Day	31% 30% 23% 12% 3	550
April	1st to 10th	Day	28% 28% 23% 14% 6% 1	500
	11th to 20th	Day	27% 29% 25% 13% 4 2	492
	21st to end	Day	21% 27% 29% 18% 4 1	500
May	1st to 10th	Day	20% 24% 29% 18% 8% 1	503
	11th to 20th	Day	26% 20% 26% 17% 8% 3	528
	21st to end	Day	18% 21% 25% 26% 8% 3	573
June	1st to 10th	Day	17% 20% 28% 23% 9% 3	530
	11th to 20th	Day	20% 26% 30% 18% 5% 1	530
	21st to end	Day	9% 15% 36% 26% 11% 2	530
July	1st to 10th	Day	4 14% 38% 32% 9% 2	526
	11th to 20th	Day	3 14% 39% 28% 13% 3	524
	21st to end	Day	3 9% 35% 33% 15% 4	575
August	1st to 10th	Day	4 9% 36% 30% 15% 6%	527
	11th to 20th	Day	5% 10% 32% 33% 14% 6%	517
	21st to end	Day	8% 14% 34% 28% 11% 4	583
September	1st to 10th	Day	4 14% 35% 31% 14% 3	530
	11th to 20th	Day	13% 12% 33% 28% 12% 1	530
	21st to end	Day	14% 19% 30% 26% 10% 1	530
October	1st to 10th	Day	20% 17% 30% 24% 8% 1	530
	11th to 20th	Day	23% 21% 23% 21% 11% 1	530
	21st to end	Day	28% 27% 22% 14% 8% 1	483
November	1st to 10th	Day	29% 24% 24% 17% 6% 1	305
	11th to 20th	Day	33% 20% 22% 18% 5% 2	220
	21st to end	Day	26% 21% 26% 21% 5%	220
December	1st to 10th	Day	25% 18% 24% 20% 9% 4	204
	11th to 20th	Day	29% 30% 27% 11% 5%	200
	21st to end	Day	31% 26% 20% 15% 6% 1	220
January	1st to 10th	Night	28% 24% 21% 17% 9% 1	800
	11th to 20th	Night	22% 21% 24% 21% 10% 2	800
	21st to end	Night	20% 19% 24% 26% 10% 1	880
February	1st to 10th	Night	22% 22% 23% 24% 9% 1	800
	11th to 20th	Night	23% 23% 22% 23% 9% 1	784
	21st to end	Night	23% 23% 26% 21% 6% 1	660
March	1st to 10th	Night	17% 25% 25% 23% 9% 1	800
	11th to 20th	Night	16% 24% 24% 25% 10% 1	800
	21st to end	Night	22% 27% 24% 18% 8% 1	880
April	1st to 10th	Night	22% 20% 27% 20% 10% 1	800
	11th to 20th	Night	15% 26% 27% 17% 12% 3	791
	21st to end	Night	14% 26% 25% 22% 11% 1	665
May	1st to 10th	Night	14% 23% 24% 24% 15% 2	400
	11th to 20th	Night	15% 16% 20% 28% 18% 3	394
	21st to end	Night	11% 15% 24% 33% 14% 2	433
June	1st to 10th	Night	17% 16% 21% 29% 15% 1	400
	11th to 20th	Night	9% 24% 29% 26% 12% 1	400
	21st to end	Night	10% 11% 24% 39% 17% 1	400
July	1st to 10th	Night	5% 6% 28% 40% 20% 1	390
	11th to 20th	Night	3 5% 34% 40% 16% 2	388
	21st to end	Night	3 4 23% 47% 21% 2	438
August	1st to 10th	Night	3 4 22% 41% 24% 5%	499
	11th to 20th	Night	6% 3 19% 34% 30% 9%	594
	21st to end	Night	5% 8% 26% 36% 22% 4	850
September	1st to 10th	Night	5% 8% 23% 39% 23% 3	800
	11th to 20th	Night	9% 10% 22% 29% 26% 4	800
	21st to end	Night	13% 10% 20% 33% 22% 2	800
October	1st to 10th	Night	14% 13% 26% 28% 16% 4	800
	11th to 20th	Night	17% 16% 20% 27% 17% 4	800
	21st to end	Night	21% 22% 19% 24% 11% 3	880
November	1st to 10th	Night	24% 20% 25% 23% 8% 1	820
	11th to 20th	Night	24% 27% 22% 19% 7% 1	840
	21st to end	Night	17% 21% 25% 25% 11% 1	840
December	1st to 10th	Night	18% 20% 23% 25% 12% 1	808
	11th to 20th	Night	24% 22% 27% 19% 7% 1	800
	21st to end	Night	26% 27% 23% 18% 6% 1	880

Page generated at 2025-11-29 22:00:50. Version ac07

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