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 2025-02-25.

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% 6% 5% 5% 3 5% 6% 28%	108378
	Night	13% 15% 6% 12% 6% 5% 5% 3 5% 5% 25%	110467
Transparency	Day	57% 5% 10% 19% 8% 1	111842
	Night	60% 5% 10% 18% 7% 1	115166
Seeing	Day	23% 16% 33% 19% 7% 2	15939
	Night	22% 14% 32% 23% 8% 1	25492

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	7% 16% 7% 17% 11% 10% 7% 4 4 4 13%	3264
	11th to 20th	Day	6% 14% 6% 18% 10% 8% 7% 3 5% 6% 17%	3589
	21st to end	Day	8% 20% 11% 17% 6% 7% 6% 4 5% 6% 11%	3982
February	1st to 10th	Day	7% 13% 5% 11% 9% 8% 8% 7% 7% 6% 21%	1600
	11th to 20th	Day	7% 16% 6% 14% 8% 8% 5% 3 6% 7% 21%	1842
	21st to end	Day	7% 16% 7% 14% 10% 5% 5% 3 7% 5% 20%	1610
March	1st to 10th	Day	10% 13% 4 10% 6% 6% 5% 5% 5% 7% 31%	3118
	11th to 20th	Day	8% 16% 6% 15% 8% 5% 5% 2 4 4 26%	3376
	21st to end	Day	15% 16% 6% 16% 6% 4 4 3 4 5% 22%	3987
April	1st to 10th	Day	14% 18% 5% 12% 6% 5% 3 3 4 5% 25%	2280
	11th to 20th	Day	16% 18% 4 9% 4 4 4 3 4 6% 26%	2413
	21st to end	Day	16% 15% 3 8% 4 4 3 4 5% 5% 33%	2470
May	1st to 10th	Day	16% 14% 4 8% 5% 4 4 3 5% 7% 31%	4201
	11th to 20th	Day	15% 10% 3 8% 5% 5% 5% 4 5% 6% 35%	4462
	21st to end	Day	20% 11% 3 7% 4 4 4 3 5% 7% 33%	5185
June	1st to 10th	Day	21% 10% 3 7% 4 5% 4 4 6% 6% 30%	2850
	11th to 20th	Day	18% 9% 3 7% 4 4 5% 4 6% 7% 34%	2850
	21st to end	Day	20% 8% 3 7% 4 4 4 3 6% 7% 33%	2850
July	1st to 10th	Day	17% 8% 3 6% 5% 5% 5% 4 6% 8% 34%	4760
	11th to 20th	Day	12% 5% 2 6% 5% 4 5% 4 6% 8% 43%	4605
	21st to end	Day	15% 6% 3 6% 4 4 4 3 6% 8% 40%	4814
August	1st to 10th	Day	16% 6% 2 6% 4 5% 6% 5% 7% 8% 34%	4423
	11th to 20th	Day	17% 7% 2 5% 3 3 3 3 5% 9% 42%	4057
	21st to end	Day	19% 8% 2 6% 3 4 3 3 5% 6% 41%	4501
September	1st to 10th	Day	19% 9% 3 7% 4 3 3 3 5% 6% 37%	2275
	11th to 20th	Day	22% 9% 2 6% 5% 4 4 3 5% 7% 32%	2090
	21st to end	Day	22% 13% 4 6% 4 4 4 2 5% 7% 29%	2090
October	1st to 10th	Day	19% 18% 5% 8% 4 4 3 3 4 5% 28%	2060
	11th to 20th	Day	20% 22% 5% 9% 5% 5% 4 3 4 7% 16%	1734
	21st to end	Day	21% 25% 6% 9% 5% 3 3 3 5% 5% 14%	1881
November	1st to 10th	Day	18% 20% 7% 10% 5% 4 4 3 4 6% 17%	1762
	11th to 20th	Day	15% 23% 6% 15% 7% 5% 4 3 4 4 14%	1620
	21st to end	Day	15% 25% 9% 16% 7% 5% 4 3 3 3 9%	1400
December	1st to 10th	Day	11% 21% 9% 18% 13% 8% 4 2 3 3 8%	2280
	11th to 20th	Day	9% 20% 7% 16% 10% 5% 5% 4 4 5% 15%	2621
	21st to end	Day	19% 24% 7% 16% 6% 6% 3 2 3 4 11%	3476
January	1st to 10th	Night	6% 15% 8% 19% 10% 10% 7% 3 5% 5% 12%	6698
	11th to 20th	Night	5% 16% 8% 19% 9% 7% 5% 5% 6% 5% 15%	6316
	21st to end	Night	7% 16% 10% 18% 9% 8% 6% 4 5% 4 14%	6996
February	1st to 10th	Night	7% 15% 6% 12% 7% 7% 7% 6% 7% 7% 21%	2800
	11th to 20th	Night	7% 15% 6% 14% 9% 7% 6% 5% 5% 6% 20%	2440
	21st to end	Night	7% 16% 7% 12% 8% 7% 7% 4 6% 7% 20%	1939
March	1st to 10th	Night	11% 15% 5% 11% 6% 6% 5% 4 6% 7% 24%	3722
	11th to 20th	Night	7% 14% 7% 14% 7% 4 4 3 4 5% 30%	3582
	21st to end	Night	13% 12% 4 10% 6% 7% 6% 3 5% 5% 29%	3672
April	1st to 10th	Night	15% 15% 5% 9% 4 4 4 4 5% 7% 27%	1900
	11th to 20th	Night	16% 14% 4 9% 4 4 3 4 5% 6% 31%	1716
	21st to end	Night	17% 14% 3 7% 4 4 4 4 5% 5% 34%	1710
May	1st to 10th	Night	16% 16% 4 7% 4 3 3 2 4 4 36%	2740
	11th to 20th	Night	15% 9% 4 8% 4 4 4 4 8% 8% 33%	2427
	21st to end	Night	17% 13% 3 6% 4 4 4 4 4 7% 36%	2402
June	1st to 10th	Night	18% 9% 2 6% 5% 4 4 3 6% 6% 37%	1330
	11th to 20th	Night	16% 8% 3 6% 5% 4 5% 4 6% 7% 37%	1330
	21st to end	Night	17% 7% 2 8% 3 4 4 4 6% 8% 37%	1330
July	1st to 10th	Night	13% 5% 2 6% 4 4 5% 3 6% 8% 44%	2210
	11th to 20th	Night	12% 7% 2 6% 4 4 5% 3 6% 7% 44%	2361
	21st to end	Night	15% 6% 2 5% 3 3 3 2 5% 7% 49%	2750
August	1st to 10th	Night	13% 8% 3 6% 4 3 4 4 6% 8% 42%	2517
	11th to 20th	Night	15% 6% 2 4 3 3 3 3 4 6% 49%	2772
	21st to end	Night	18% 6% 2 5% 2 3 3 3 3 6% 48%	3151
September	1st to 10th	Night	16% 9% 2 6% 5% 4 3 3 4 6% 42%	1900
	11th to 20th	Night	18% 10% 2 6% 4 5% 4 3 5% 7% 36%	2076
	21st to end	Night	23% 11% 3 6% 3 3 4 3 5% 7% 33%	2090
October	1st to 10th	Night	20% 15% 3 7% 4 3 3 3 4 6% 31%	2119
	11th to 20th	Night	20% 18% 5% 8% 5% 4 4 3 5% 6% 22%	2443
	21st to end	Night	21% 21% 5% 9% 5% 4 4 3 5% 5% 17%	2717
November	1st to 10th	Night	17% 18% 6% 12% 6% 5% 4 3 4 5% 19%	2536
	11th to 20th	Night	18% 20% 6% 15% 7% 5% 4 3 3 4 14%	2777
	21st to end	Night	15% 21% 9% 16% 8% 6% 4 3 3 4 11%	3000
December	1st to 10th	Night	8% 21% 10% 22% 11% 7% 4 3 3 4 9%	4910
	11th to 20th	Night	8% 20% 9% 14% 8% 7% 5% 4 5% 5% 16%	5586
	21st to end	Night	20% 25% 8% 12% 7% 5% 4 3 4 4 9%	7502

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	75% 5% 6% 9% 3 3	3265
	11th to 20th	Day	69% 3 6% 16% 5%	3620
	21st to end	Day	74% 4 5% 9% 7% 1	3982
February	1st to 10th	Day	59% 7% 9% 15% 9% 1	1600
	11th to 20th	Day	63% 4 10% 13% 9% 1	1851
	21st to end	Day	64% 4 7% 13% 9% 2	1610
March	1st to 10th	Day	52% 6% 11% 15% 14% 2	3120
	11th to 20th	Day	61% 4 8% 18% 7% 1	3376
	21st to end	Day	63% 4 9% 11% 12% 1	3987
April	1st to 10th	Day	63% 4 7% 15% 10% 1	2280
	11th to 20th	Day	58% 5% 8% 19% 9% 2	2413
	21st to end	Day	52% 5% 9% 17% 14% 3	2470
May	1st to 10th	Day	51% 5% 11% 20% 12% 2	4213
	11th to 20th	Day	48% 6% 10% 21% 13% 1	4466
	21st to end	Day	49% 6% 12% 20% 11% 2	5185
June	1st to 10th	Day	51% 9% 9% 17% 12% 2	2850
	11th to 20th	Day	48% 7% 10% 20% 13% 1	2850
	21st to end	Day	50% 7% 10% 23% 10% 1	2850
July	1st to 10th	Day	48% 5% 13% 25% 10%	4686
	11th to 20th	Day	39% 5% 17% 28% 9% 2	4524
	21st to end	Day	43% 5% 10% 34% 9%	4662
August	1st to 10th	Day	46% 5% 13% 27% 8%	4408
	11th to 20th	Day	41% 4 15% 33% 7%	4096
	21st to end	Day	45% 4 12% 30% 8%	4500
September	1st to 10th	Day	48% 7% 12% 24% 10% 1	2275
	11th to 20th	Day	51% 7% 20% 19% 3	2090
	21st to end	Day	54% 7% 12% 18% 8% 1	2090
October	1st to 10th	Day	53% 3 15% 19% 10%	3424
	11th to 20th	Day	62% 3 9% 22% 5%	2859
	21st to end	Day	71% 4 12% 10% 4	3081
November	1st to 10th	Day	69% 5% 10% 12% 4	1762
	11th to 20th	Day	74% 5% 9% 8% 3	1620
	21st to end	Day	80% 5% 7% 7% 1 1	1400
December	1st to 10th	Day	83% 3 5% 6% 3	2280
	11th to 20th	Day	71% 4 9% 8% 8%	2621
	21st to end	Day	79% 2 6% 11% 3	3476
January	1st to 10th	Night	72% 4 6% 10% 3 4	6698
	11th to 20th	Night	69% 4 7% 15% 5%	6360
	21st to end	Night	72% 4 5% 13% 6%	6996
February	1st to 10th	Night	59% 7% 10% 14% 9% 1	2800
	11th to 20th	Night	63% 5% 9% 16% 7%	2442
	21st to end	Night	63% 4 9% 13% 9% 1	1939
March	1st to 10th	Night	57% 6% 12% 14% 9% 1	3733
	11th to 20th	Night	56% 5% 8% 22% 8% 1	3583
	21st to end	Night	54% 6% 11% 14% 14% 1	3672
April	1st to 10th	Night	55% 6% 9% 17% 11% 1	1900
	11th to 20th	Night	54% 4 9% 21% 10% 2	1716
	21st to end	Night	50% 5% 9% 19% 14% 2	1710
May	1st to 10th	Night	51% 5% 7% 22% 14% 1	2747
	11th to 20th	Night	45% 7% 13% 27% 7% 1	2428
	21st to end	Night	48% 6% 11% 20% 13% 3	2403
June	1st to 10th	Night	45% 7% 12% 21% 12% 1	1330
	11th to 20th	Night	45% 7% 11% 22% 15% 1	1330
	21st to end	Night	44% 8% 14% 24% 9% 1	1330
July	1st to 10th	Night	39% 5% 16% 32% 8%	2175
	11th to 20th	Night	38% 5% 18% 26% 11% 2	2319
	21st to end	Night	36% 4 15% 30% 15%	2662
August	1st to 10th	Night	40% 5% 16% 33% 5%	2508
	11th to 20th	Night	36% 5% 18% 32% 8%	2799
	21st to end	Night	38% 5% 10% 35% 12%	3151
September	1st to 10th	Night	44% 5% 13% 26% 11% 1	1900
	11th to 20th	Night	47% 8% 16% 24% 5%	2076
	21st to end	Night	52% 6% 13% 21% 8% 1	2090
October	1st to 10th	Night	46% 4 13% 25% 12%	3535
	11th to 20th	Night	53% 4 16% 21% 5%	4057
	21st to end	Night	65% 5% 17% 10% 2	4467
November	1st to 10th	Night	67% 6% 9% 13% 5%	2536
	11th to 20th	Night	75% 5% 7% 11% 3	2777
	21st to end	Night	78% 5% 8% 6% 3	3000
December	1st to 10th	Night	80% 3 7% 6% 3	4910
	11th to 20th	Night	70% 5% 7% 13% 5% 1	5585
	21st to end	Night	80% 2 3 10% 4	7502

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% 17% 43% 15% 5% 1	221
	11th to 20th	Day	14% 15% 36% 26% 8%	300
	21st to end	Day	21% 15% 36% 22% 6% 1	330
February	1st to 10th	Day	20% 21% 36% 19% 3 1	300
	11th to 20th	Day	15% 26% 38% 17% 4	300
	21st to end	Day	19% 38% 32% 8% 2	237
March	1st to 10th	Day	19% 19% 41% 18% 4	270
	11th to 20th	Day	19% 23% 38% 14% 4 2	395
	21st to end	Day	23% 18% 33% 19% 5% 1	506
April	1st to 10th	Day	22% 17% 38% 19% 3 1	460
	11th to 20th	Day	28% 20% 27% 17% 6% 2	452
	21st to end	Day	25% 20% 27% 16% 8% 2	460
May	1st to 10th	Day	26% 15% 33% 15% 8% 2	517
	11th to 20th	Day	22% 18% 33% 18% 7% 2	675
	21st to end	Day	26% 16% 33% 19% 6% 1	734
June	1st to 10th	Day	27% 15% 33% 18% 6% 2	680
	11th to 20th	Day	23% 16% 33% 18% 9% 2	680
	21st to end	Day	23% 15% 29% 21% 10% 3	680
July	1st to 10th	Day	20% 10% 39% 21% 8% 3	671
	11th to 20th	Day	16% 13% 35% 25% 9% 3	668
	21st to end	Day	19% 11% 32% 25% 9% 4	739
August	1st to 10th	Day	20% 11% 32% 25% 9% 3	676
	11th to 20th	Day	20% 10% 25% 25% 14% 7%	492
	21st to end	Day	24% 12% 28% 20% 11% 5%	539
September	1st to 10th	Day	25% 12% 32% 18% 11% 3	490
	11th to 20th	Day	28% 12% 30% 21% 7% 2	490
	21st to end	Day	29% 12% 26% 22% 10% 1	490
October	1st to 10th	Day	28% 19% 26% 19% 7% 1	490
	11th to 20th	Day	30% 21% 30% 16% 3	324
	21st to end	Day	34% 23% 30% 10% 3	330
November	1st to 10th	Day	34% 17% 35% 13% 1	300
	11th to 20th	Day	29% 22% 34% 11% 4	223
	21st to end	Day	31% 21% 34% 11% 3 1	200
December	1st to 10th	Day	23% 19% 33% 18% 7% 1	200
	11th to 20th	Day	22% 18% 42% 14% 5%	200
	21st to end	Day	27% 18% 33% 14% 7% 1	220
January	1st to 10th	Night	20% 14% 40% 20% 5% 1	1000
	11th to 20th	Night	18% 16% 34% 23% 7% 1	1000
	21st to end	Night	17% 12% 38% 24% 8% 1	1100
February	1st to 10th	Night	16% 16% 37% 25% 6% 1	1000
	11th to 20th	Night	16% 15% 39% 20% 9% 1	783
	21st to end	Night	18% 19% 36% 22% 4 1	647
March	1st to 10th	Night	14% 18% 39% 20% 7% 1	760
	11th to 20th	Night	19% 19% 37% 18% 7%	760
	21st to end	Night	17% 15% 37% 22% 8% 1	755
April	1st to 10th	Night	24% 15% 31% 23% 6% 2	570
	11th to 20th	Night	24% 16% 29% 23% 8% 1	563
	21st to end	Night	23% 13% 29% 25% 9% 2	570
May	1st to 10th	Night	22% 13% 29% 30% 7%	570
	11th to 20th	Night	25% 12% 32% 22% 8% 1	521
	21st to end	Night	22% 10% 35% 27% 5%	411
June	1st to 10th	Night	23% 12% 30% 26% 9%	380
	11th to 20th	Night	22% 11% 33% 24% 10%	380
	21st to end	Night	19% 8% 32% 28% 12% 1	380
July	1st to 10th	Night	16% 8% 33% 31% 12% 1	370
	11th to 20th	Night	17% 9% 31% 32% 11% 1	454
	21st to end	Night	19% 6% 30% 29% 15%	624
August	1st to 10th	Night	15% 6% 28% 35% 16% 1	567
	11th to 20th	Night	16% 4 26% 34% 18% 2	564
	21st to end	Night	23% 6% 27% 28% 14% 1	627
September	1st to 10th	Night	22% 6% 30% 26% 13% 3	570
	11th to 20th	Night	25% 9% 32% 23% 9% 1	746
	21st to end	Night	29% 11% 26% 23% 11%	760
October	1st to 10th	Night	31% 14% 25% 22% 8%	760
	11th to 20th	Night	30% 13% 31% 19% 6% 1	760
	21st to end	Night	33% 14% 26% 21% 6%	836
November	1st to 10th	Night	27% 18% 32% 18% 4 1	780
	11th to 20th	Night	31% 16% 30% 17% 5%	824
	21st to end	Night	28% 19% 30% 19% 4	1000
December	1st to 10th	Night	19% 18% 34% 22% 7% 1	1000
	11th to 20th	Night	18% 18% 37% 18% 8% 1	1000
	21st to end	Night	28% 16% 30% 18% 7% 1	1100

Page generated at 2025-02-22 06:51:34. Version ac07

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