White River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the White River clear sky chart from 2005-11-06 to 2026-07-01.

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	15% 13% 4 10% 5% 5% 5% 3 5% 6% 29%	138126
	Night	13% 14% 6% 12% 6% 5% 5% 4 5% 6% 25%	134524
Transparency	Day	56% 4 10% 20% 9% 1	141543
	Night	60% 4 10% 18% 8% 1	139195
Seeing	Day	24% 17% 33% 19% 7% 2	17826
	Night	22% 14% 32% 23% 8% 1	27172

By Month

Percentage Cloud Cover NE (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	6% 20% 8% 17% 10% 8% 6% 4 4 3 15%	4228
	11th to 20th	Day	6% 14% 7% 17% 9% 8% 9% 4 5% 6% 16%	4679
	21st to end	Day	6% 15% 9% 16% 7% 8% 7% 6% 7% 7% 13%	5156
February	1st to 10th	Day	7% 13% 5% 11% 8% 8% 8% 7% 7% 6% 21%	1680
	11th to 20th	Day	7% 17% 6% 14% 8% 7% 5% 3 5% 6% 20%	1937
	21st to end	Day	7% 16% 8% 14% 10% 5% 6% 4 6% 5% 20%	1730
March	1st to 10th	Day	12% 15% 4 10% 6% 5% 4 4 5% 6% 27%	4578
	11th to 20th	Day	12% 18% 7% 14% 7% 6% 5% 3 4 4 22%	4941
	21st to end	Day	17% 17% 5% 14% 5% 4 4 3 4 6% 22%	5833
April	1st to 10th	Day	14% 18% 6% 12% 7% 5% 3 3 3 5% 25%	2520
	11th to 20th	Day	16% 18% 5% 10% 4 4 4 3 4 6% 26%	2670
	21st to end	Day	17% 15% 3 8% 4 4 3 4 5% 5% 32%	2730
May	1st to 10th	Day	13% 15% 5% 8% 5% 4 4 3 4 6% 34%	7818
	11th to 20th	Day	18% 9% 3 8% 5% 4 4 3 5% 5% 36%	8341
	21st to end	Day	15% 11% 2 5% 4 3 4 3 5% 7% 40%	9716
June	1st to 10th	Day	20% 10% 3 7% 4 5% 4 4 6% 6% 31%	3150
	11th to 20th	Day	17% 9% 3 7% 4 4 5% 4 6% 7% 33%	3150
	21st to end	Day	21% 8% 3 7% 4 4 4 3 6% 7% 33%	3150
July	1st to 10th	Day	15% 7% 2 6% 5% 5% 5% 4 6% 8% 38%	6820
	11th to 20th	Day	16% 6% 2 5% 4 4 5% 4 6% 8% 40%	6595
	21st to end	Day	15% 6% 2 6% 4 4 4 4 6% 9% 40%	6926
August	1st to 10th	Day	16% 6% 2 6% 4 5% 6% 5% 7% 8% 34%	4563
	11th to 20th	Day	17% 7% 2 5% 3 3 3 3 5% 9% 42%	4187
	21st to end	Day	19% 8% 2 6% 3 4 4 3 5% 6% 41%	4643
September	1st to 10th	Day	19% 10% 3 7% 4 3 4 3 5% 5% 36%	2395
	11th to 20th	Day	21% 9% 2 6% 5% 4 4 3 5% 7% 34%	2200
	21st to end	Day	21% 13% 4 6% 4 4 4 2 5% 7% 30%	2200
October	1st to 10th	Day	18% 17% 5% 8% 4 4 3 3 4 5% 29%	2168
	11th to 20th	Day	20% 21% 5% 9% 5% 5% 4 3 4 7% 17%	1825
	21st to end	Day	20% 24% 6% 9% 5% 3 3 3 4 5% 16%	1980
November	1st to 10th	Day	18% 20% 7% 10% 5% 4 4 3 4 6% 17%	1852
	11th to 20th	Day	16% 23% 6% 15% 7% 5% 4 4 4 4 14%	1701
	21st to end	Day	15% 24% 9% 16% 8% 5% 4 3 4 3 9%	1470
December	1st to 10th	Day	10% 21% 9% 18% 13% 8% 4 2 3 3 8%	2350
	11th to 20th	Day	9% 20% 7% 16% 10% 5% 5% 3 4 5% 15%	2691
	21st to end	Day	19% 24% 7% 16% 6% 6% 3 2 3 4 11%	3553
January	1st to 10th	Night	7% 16% 9% 18% 9% 8% 7% 3 5% 5% 14%	8693
	11th to 20th	Night	5% 18% 9% 20% 9% 7% 6% 5% 6% 5% 12%	8236
	21st to end	Night	5% 12% 8% 18% 9% 8% 7% 5% 6% 5% 16%	9058
February	1st to 10th	Night	7% 15% 6% 12% 7% 7% 7% 5% 7% 7% 20%	2940
	11th to 20th	Night	7% 15% 6% 14% 9% 7% 6% 5% 5% 6% 19%	2565
	21st to end	Night	7% 16% 7% 12% 8% 7% 7% 4 6% 7% 19%	2076
March	1st to 10th	Night	10% 15% 6% 12% 8% 6% 5% 4 5% 6% 22%	5482
	11th to 20th	Night	12% 16% 6% 13% 7% 5% 4 3 4 5% 26%	5237
	21st to end	Night	15% 14% 4 10% 6% 7% 6% 3 5% 5% 25%	5383
April	1st to 10th	Night	15% 15% 5% 9% 5% 4 4 4 5% 7% 27%	2100
	11th to 20th	Night	16% 14% 4 9% 4 4 3 4 5% 5% 30%	1899
	21st to end	Night	18% 14% 3 7% 4 4 4 4 5% 5% 33%	1890
May	1st to 10th	Night	12% 13% 5% 8% 5% 4 4 3 5% 5% 35%	5087
	11th to 20th	Night	15% 9% 4 7% 4 4 4 4 6% 8% 35%	4535
	21st to end	Night	13% 11% 2 6% 3 4 4 4 5% 7% 41%	4492
June	1st to 10th	Night	17% 9% 2 6% 4 4 4 3 6% 6% 38%	1470
	11th to 20th	Night	16% 8% 3 6% 5% 4 5% 4 6% 7% 36%	1470
	21st to end	Night	17% 7% 2 7% 3 4 4 4 6% 8% 37%	1470
July	1st to 10th	Night	13% 4 2 5% 3 4 5% 3 6% 8% 46%	3160
	11th to 20th	Night	16% 7% 2 6% 4 4 5% 3 6% 6% 40%	3381
	21st to end	Night	16% 6% 2 5% 3 3 3 3 6% 7% 46%	3948
August	1st to 10th	Night	13% 8% 3 6% 4 3 4 4 6% 7% 42%	2597
	11th to 20th	Night	15% 7% 2 4 3 3 3 3 4 6% 49%	2861
	21st to end	Night	18% 7% 2 5% 2 3 3 3 4 6% 48%	3251
September	1st to 10th	Night	17% 9% 2 6% 5% 4 3 3 4 6% 41%	2000
	11th to 20th	Night	17% 10% 2 6% 4 5% 4 3 5% 7% 38%	2185
	21st to end	Night	23% 11% 3 6% 3 3 4 3 5% 7% 33%	2200
October	1st to 10th	Night	20% 15% 3 7% 4 3 3 3 4 7% 31%	2231
	11th to 20th	Night	20% 18% 5% 8% 5% 4 4 3 5% 6% 23%	2572
	21st to end	Night	20% 21% 5% 9% 5% 4 4 3 5% 5% 18%	2860
November	1st to 10th	Night	17% 18% 7% 12% 6% 5% 4 3 4 5% 19%	2666
	11th to 20th	Night	17% 21% 6% 16% 7% 5% 4 3 3 4 14%	2916
	21st to end	Night	15% 21% 9% 16% 9% 6% 4 3 3 4 11%	3150
December	1st to 10th	Night	8% 20% 10% 22% 10% 7% 4 3 3 4 10%	5060
	11th to 20th	Night	8% 20% 8% 14% 8% 7% 5% 4 5% 5% 16%	5736
	21st to end	Night	20% 24% 8% 12% 7% 5% 4 3 4 4 9%	7667

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	74% 4 5% 10% 3 4	4229
	11th to 20th	Day	71% 2 6% 16% 5%	4710
	21st to end	Day	69% 3 6% 15% 6% 1	5156
February	1st to 10th	Day	60% 7% 9% 15% 9% 1	1680
	11th to 20th	Day	64% 4 10% 14% 8% 1	1946
	21st to end	Day	65% 4 7% 13% 9% 2	1730
March	1st to 10th	Day	56% 4 8% 12% 14% 5%	4580
	11th to 20th	Day	66% 3 7% 14% 8% 2	4941
	21st to end	Day	64% 3 8% 13% 10% 2	5833
April	1st to 10th	Day	64% 4 6% 16% 10% 1	2520
	11th to 20th	Day	58% 5% 8% 19% 8% 1	2670
	21st to end	Day	54% 4 9% 17% 14% 3	2730
May	1st to 10th	Day	52% 3 8% 19% 15% 3	7827
	11th to 20th	Day	50% 4 8% 18% 17% 4	8345
	21st to end	Day	44% 4 8% 24% 16% 4	9717
June	1st to 10th	Day	51% 8% 8% 18% 13% 2	3150
	11th to 20th	Day	49% 6% 10% 22% 13% 1	3150
	21st to end	Day	50% 6% 10% 23% 10% 1	3150
July	1st to 10th	Day	45% 3 11% 31% 10%	6747
	11th to 20th	Day	43% 4 16% 29% 8% 1	6514
	21st to end	Day	42% 4 13% 33% 8%	6728
August	1st to 10th	Day	46% 5% 13% 28% 7%	4548
	11th to 20th	Day	41% 4 15% 33% 7%	4226
	21st to end	Day	45% 4 12% 29% 8%	4642
September	1st to 10th	Day	49% 6% 12% 24% 9% 1	2395
	11th to 20th	Day	50% 6% 20% 21% 3	2200
	21st to end	Day	54% 7% 12% 20% 8% 1	2200
October	1st to 10th	Day	52% 3 16% 19% 10%	3532
	11th to 20th	Day	62% 3 9% 22% 5%	2950
	21st to end	Day	70% 3 12% 11% 3	3180
November	1st to 10th	Day	69% 5% 10% 12% 4	1852
	11th to 20th	Day	74% 5% 9% 8% 3	1701
	21st to end	Day	80% 4 8% 6% 1 1	1470
December	1st to 10th	Day	82% 3 5% 6% 4	2350
	11th to 20th	Day	72% 4 8% 8% 8%	2691
	21st to end	Day	79% 2 6% 11% 2	3553
January	1st to 10th	Night	71% 3 6% 12% 4 3	8693
	11th to 20th	Night	73% 3 6% 14% 4	8280
	21st to end	Night	69% 3 6% 15% 7%	9058
February	1st to 10th	Night	60% 6% 10% 14% 9% 1	2940
	11th to 20th	Night	63% 5% 8% 16% 7%	2567
	21st to end	Night	63% 4 9% 14% 9% 1	2076
March	1st to 10th	Night	61% 5% 10% 11% 11% 3	5493
	11th to 20th	Night	62% 4 9% 17% 7% 1	5238
	21st to end	Night	60% 4 8% 14% 13% 1	5383
April	1st to 10th	Night	56% 6% 9% 17% 11% 2	2100
	11th to 20th	Night	55% 4 8% 21% 10% 1	1899
	21st to end	Night	52% 5% 10% 18% 13% 2	1890
May	1st to 10th	Night	51% 3 8% 21% 16% 1	5094
	11th to 20th	Night	47% 4 12% 25% 11% 1	4536
	21st to end	Night	43% 4 9% 24% 16% 3	4493
June	1st to 10th	Night	45% 7% 12% 21% 14% 2	1470
	11th to 20th	Night	45% 7% 10% 23% 14% 1	1470
	21st to end	Night	45% 7% 14% 25% 9% 1	1470
July	1st to 10th	Night	37% 4 16% 36% 8%	3125
	11th to 20th	Night	44% 4 16% 26% 8% 1	3339
	21st to end	Night	40% 3 14% 31% 12%	3832
August	1st to 10th	Night	40% 5% 16% 33% 5%	2588
	11th to 20th	Night	36% 5% 18% 32% 8%	2888
	21st to end	Night	39% 5% 10% 34% 12%	3251
September	1st to 10th	Night	45% 5% 13% 25% 10% 1	2000
	11th to 20th	Night	46% 8% 16% 26% 4	2185
	21st to end	Night	51% 6% 13% 22% 8% 1	2200
October	1st to 10th	Night	46% 4 14% 25% 12%	3647
	11th to 20th	Night	53% 4 16% 21% 5%	4186
	21st to end	Night	65% 4 17% 12% 2	4610
November	1st to 10th	Night	67% 6% 9% 12% 6%	2666
	11th to 20th	Night	75% 5% 7% 10% 3	2916
	21st to end	Night	78% 5% 7% 6% 3	3150
December	1st to 10th	Night	80% 3 7% 7% 3	5060
	11th to 20th	Night	70% 4 7% 13% 5% 1	5735
	21st to end	Night	80% 2 3 10% 4	7667

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	19% 18% 43% 14% 5% 1	243
	11th to 20th	Day	14% 14% 38% 25% 8% 1	330
	21st to end	Day	19% 15% 37% 23% 7% 1	363
February	1st to 10th	Day	20% 22% 35% 18% 3 1	330
	11th to 20th	Day	15% 25% 38% 17% 4 1	330
	21st to end	Day	20% 36% 32% 9% 2	273
March	1st to 10th	Day	23% 20% 38% 16% 3	330
	11th to 20th	Day	21% 25% 36% 13% 4 1	469
	21st to end	Day	26% 20% 31% 17% 5% 1	594
April	1st to 10th	Day	23% 18% 37% 17% 3 1	540
	11th to 20th	Day	28% 20% 29% 16% 6% 1	532
	21st to end	Day	27% 19% 28% 16% 8% 2	540
May	1st to 10th	Day	25% 15% 33% 17% 8% 2	603
	11th to 20th	Day	24% 18% 33% 17% 6% 2	775
	21st to end	Day	25% 16% 33% 19% 6% 1	844
June	1st to 10th	Day	25% 16% 34% 18% 6% 1	780
	11th to 20th	Day	24% 16% 33% 17% 8% 2	780
	21st to end	Day	24% 16% 28% 19% 9% 3	780
July	1st to 10th	Day	20% 11% 39% 21% 7% 3	722
	11th to 20th	Day	17% 14% 35% 24% 8% 3	718
	21st to end	Day	18% 12% 32% 26% 9% 3	794
August	1st to 10th	Day	20% 11% 33% 25% 9% 3	726
	11th to 20th	Day	20% 11% 25% 24% 13% 6%	532
	21st to end	Day	25% 12% 28% 21% 10% 5%	583
September	1st to 10th	Day	26% 12% 31% 18% 11% 3	530
	11th to 20th	Day	27% 12% 29% 22% 9% 3	530
	21st to end	Day	30% 12% 26% 22% 9% 1	530
October	1st to 10th	Day	28% 19% 27% 19% 6% 1	530
	11th to 20th	Day	30% 21% 30% 16% 3	355
	21st to end	Day	32% 21% 30% 12% 3 1	363
November	1st to 10th	Day	34% 16% 35% 13% 1	330
	11th to 20th	Day	30% 22% 33% 11% 3	245
	21st to end	Day	31% 21% 33% 11% 3	220
December	1st to 10th	Day	20% 20% 33% 19% 7% 1	220
	11th to 20th	Day	23% 18% 41% 14% 5%	220
	21st to end	Day	28% 18% 33% 13% 7% 1	242
January	1st to 10th	Night	20% 14% 41% 19% 5% 1	1050
	11th to 20th	Night	18% 16% 34% 23% 7% 1	1050
	21st to end	Night	16% 11% 39% 25% 8% 1	1155
February	1st to 10th	Night	16% 16% 36% 25% 6% 1	1050
	11th to 20th	Night	17% 15% 39% 20% 9% 1	823
	21st to end	Night	18% 18% 36% 23% 4 1	692
March	1st to 10th	Night	15% 18% 40% 20% 7% 1	840
	11th to 20th	Night	20% 19% 37% 18% 6%	840
	21st to end	Night	18% 16% 35% 22% 8% 1	835
April	1st to 10th	Night	24% 15% 30% 23% 6% 2	630
	11th to 20th	Night	25% 16% 29% 22% 8%	623
	21st to end	Night	24% 13% 28% 25% 8% 1	630
May	1st to 10th	Night	21% 13% 29% 31% 7%	630
	11th to 20th	Night	25% 13% 32% 21% 7% 1	577
	21st to end	Night	22% 11% 35% 28% 5%	455
June	1st to 10th	Night	23% 12% 30% 26% 9%	420
	11th to 20th	Night	21% 12% 33% 25% 10%	420
	21st to end	Night	19% 8% 32% 27% 13%	420
July	1st to 10th	Night	16% 7% 33% 31% 12% 1	390
	11th to 20th	Night	18% 9% 31% 31% 10% 1	479
	21st to end	Night	19% 6% 30% 30% 14%	657
August	1st to 10th	Night	15% 6% 28% 35% 16% 1	597
	11th to 20th	Night	16% 4 26% 34% 18% 2	594
	21st to end	Night	23% 6% 26% 28% 15% 1	660
September	1st to 10th	Night	22% 7% 30% 26% 13% 3	600
	11th to 20th	Night	24% 9% 31% 24% 10% 1	785
	21st to end	Night	29% 11% 26% 23% 11%	800
October	1st to 10th	Night	30% 14% 25% 22% 8%	800
	11th to 20th	Night	31% 13% 31% 20% 5% 1	800
	21st to end	Night	32% 14% 26% 22% 7%	880
November	1st to 10th	Night	27% 18% 32% 18% 4	820
	11th to 20th	Night	31% 16% 31% 17% 6%	865
	21st to end	Night	28% 19% 30% 19% 4	1050
December	1st to 10th	Night	19% 18% 34% 22% 7%	1050
	11th to 20th	Night	19% 18% 37% 17% 8% 1	1050
	21st to end	Night	28% 16% 30% 18% 7% 1	1155

Page generated at 2026-06-28 02:10:49. Version ac07

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