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 2024-09-29.

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 9% 6% 5% 4 3 5% 6% 29%	101409
	Night	14% 14% 5% 11% 6% 5% 5% 4 5% 6% 26%	96940
Transparency	Day	55% 5% 11% 19% 8% 1	101153
	Night	58% 6% 10% 18% 8% 1	96815
Seeing	Day	23% 16% 33% 19% 7% 2	15536
	Night	22% 14% 32% 23% 8% 1	24813

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	10% 19% 7% 15% 11% 8% 5% 4 5% 4 11%	2272
	11th to 20th	Day	6% 13% 6% 15% 10% 10% 6% 4 5% 6% 19%	2530
	21st to end	Day	10% 22% 13% 14% 6% 7% 5% 4 5% 5% 9%	2783
February	1st to 10th	Day	7% 13% 5% 11% 8% 7% 8% 7% 7% 5% 22%	1520
	11th to 20th	Day	7% 17% 6% 12% 8% 8% 5% 3 5% 7% 21%	1747
	21st to end	Day	8% 15% 8% 14% 10% 5% 6% 3 6% 5% 20%	1570
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 6% 7% 28%	2069
October	1st to 10th	Day	20% 18% 5% 8% 4 4 3 3 4 5% 28%	1952
	11th to 20th	Day	20% 22% 5% 9% 5% 4 4 3 4 7% 16%	1643
	21st to end	Day	20% 25% 6% 10% 5% 3 3 3 5% 5% 14%	1782
November	1st to 10th	Day	18% 21% 8% 10% 5% 4 4 3 4 6% 17%	1672
	11th to 20th	Day	15% 24% 6% 15% 7% 5% 4 3 4 3 14%	1540
	21st to end	Day	16% 24% 8% 16% 8% 5% 4 3 4 3 9%	1330
December	1st to 10th	Day	10% 17% 7% 17% 12% 8% 5% 3 5% 4 12%	1330
	11th to 20th	Day	10% 19% 5% 15% 11% 6% 5% 4 4 6% 15%	1671
	21st to end	Day	19% 22% 7% 14% 7% 7% 4 2 4 5% 9%	2431
January	1st to 10th	Night	8% 17% 10% 17% 9% 9% 7% 4 5% 5% 10%	4680
	11th to 20th	Night	6% 13% 7% 19% 9% 8% 6% 4 6% 5% 17%	4440
	21st to end	Night	9% 19% 11% 17% 8% 7% 5% 4 5% 4 10%	4884
February	1st to 10th	Night	7% 15% 6% 11% 7% 7% 7% 5% 7% 7% 21%	2660
	11th to 20th	Night	8% 15% 5% 13% 9% 7% 7% 6% 6% 6% 20%	2315
	21st to end	Night	7% 17% 7% 12% 8% 7% 7% 4 6% 7% 20%	1884
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% 32%	2079
October	1st to 10th	Night	21% 16% 4 7% 4 3 3 3 4 6% 29%	2007
	11th to 20th	Night	21% 19% 5% 8% 5% 3 4 3 5% 6% 21%	2314
	21st to end	Night	21% 21% 5% 9% 5% 4 4 3 4 5% 17%	2574
November	1st to 10th	Night	16% 18% 6% 12% 6% 4 4 3 5% 6% 19%	2406
	11th to 20th	Night	18% 20% 6% 15% 7% 5% 4 3 3 4 14%	2637
	21st to end	Night	16% 20% 8% 16% 9% 6% 4 3 3 4 12%	2850
December	1st to 10th	Night	8% 19% 8% 17% 10% 6% 5% 4 4 5% 13%	2850
	11th to 20th	Night	10% 19% 8% 13% 8% 6% 5% 4 5% 5% 17%	3526
	21st to end	Night	21% 23% 7% 12% 9% 5% 4 2 3 3 10%	5236

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	73% 7% 8% 9% 3	2273
	11th to 20th	Day	65% 4 9% 18% 4	2530
	21st to end	Day	75% 5% 7% 6% 6% 1	2783
February	1st to 10th	Day	58% 7% 9% 15% 9% 1	1520
	11th to 20th	Day	62% 5% 10% 14% 9% 1	1756
	21st to end	Day	64% 5% 7% 13% 9% 2	1570
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	55% 7% 12% 19% 7%	2069
October	1st to 10th	Day	60% 5% 15% 16% 4	1952
	11th to 20th	Day	69% 6% 10% 14% 1	1643
	21st to end	Day	71% 5% 10% 10% 3	1782
November	1st to 10th	Day	69% 5% 10% 12% 4	1672
	11th to 20th	Day	75% 5% 9% 7% 3	1540
	21st to end	Day	79% 5% 7% 7% 1 1	1330
December	1st to 10th	Day	75% 6% 7% 7% 5%	1330
	11th to 20th	Day	69% 6% 10% 10% 5%	1671
	21st to end	Day	78% 3 8% 8% 3	2431
January	1st to 10th	Night	73% 6% 9% 10% 3	4680
	11th to 20th	Night	66% 5% 9% 16% 4	4440
	21st to end	Night	75% 5% 6% 9% 4	4884
February	1st to 10th	Night	58% 7% 11% 14% 9% 1	2660
	11th to 20th	Night	62% 5% 9% 16% 7%	2317
	21st to end	Night	63% 5% 9% 13% 10% 1	1884
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%	2079
October	1st to 10th	Night	57% 6% 15% 17% 6% 1	2007
	11th to 20th	Night	62% 7% 14% 14% 2	2314
	21st to end	Night	69% 6% 10% 11% 4	2574
November	1st to 10th	Night	67% 6% 10% 12% 5%	2406
	11th to 20th	Night	75% 5% 7% 10% 3	2637
	21st to end	Night	77% 6% 8% 6% 3	2850
December	1st to 10th	Night	72% 6% 7% 10% 5%	2850
	11th to 20th	Night	67% 7% 8% 12% 6% 1	3525
	21st to end	Night	80% 3 4 9% 3	5236

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% 13% 5% 2	198
	11th to 20th	Day	13% 15% 38% 25% 9%	270
	21st to end	Day	22% 14% 36% 21% 6% 1	297
February	1st to 10th	Day	20% 20% 36% 19% 4 1	270
	11th to 20th	Day	16% 26% 37% 16% 4	270
	21st to end	Day	20% 39% 32% 8% 1	225
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	30% 12% 26% 21% 10% 1	483
October	1st to 10th	Day	28% 18% 26% 20% 7% 1	450
	11th to 20th	Day	30% 22% 29% 17% 3	293
	21st to end	Day	32% 24% 30% 10% 3	297
November	1st to 10th	Day	33% 16% 37% 13% 1	270
	11th to 20th	Day	28% 24% 35% 10% 2	201
	21st to end	Day	31% 22% 33% 11% 3 1	180
December	1st to 10th	Day	22% 19% 33% 17% 8% 1	180
	11th to 20th	Day	22% 19% 40% 13% 6%	180
	21st to end	Day	26% 20% 33% 14% 7% 1	198
January	1st to 10th	Night	20% 15% 40% 19% 5% 1	950
	11th to 20th	Night	18% 17% 34% 22% 7% 1	950
	21st to end	Night	18% 11% 38% 24% 8% 1	1045
February	1st to 10th	Night	16% 15% 37% 25% 6% 1	950
	11th to 20th	Night	17% 15% 38% 20% 10% 1	743
	21st to end	Night	18% 19% 36% 21% 4 1	628
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%	756
October	1st to 10th	Night	32% 13% 24% 23% 8%	720
	11th to 20th	Night	31% 13% 29% 20% 6% 1	720
	21st to end	Night	33% 14% 25% 21% 6%	792
November	1st to 10th	Night	26% 18% 33% 19% 4 1	740
	11th to 20th	Night	30% 16% 30% 17% 6%	782
	21st to end	Night	28% 19% 30% 19% 4	950
December	1st to 10th	Night	19% 18% 34% 21% 7% 1	950
	11th to 20th	Night	19% 19% 37% 17% 7% 1	950
	21st to end	Night	27% 16% 30% 18% 7% 1	1045

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