Whiteside Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Whiteside Mountain clear sky chart from 2005-11-06 to 2026-08-30.

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% 7% 3 7% 5% 5% 5% 4 6% 7% 38%	143530
	Night	16% 7% 2 6% 4 4 4 4 5% 7% 41%	138697
Transparency	Day	40% 9% 12% 17% 15% 6%	147267
	Night	37% 8% 13% 18% 16% 7%	143032
Seeing	Day	21% 14% 24% 21% 13% 6%	17406
	Night	20% 11% 21% 27% 18% 4	27398

By Month

Percentage Cloud Cover SE (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	17% 6% 2 4 2 2 2 2 5% 5% 52%	5258
	11th to 20th	Day	10% 6% 2 5% 3 2 2 1 3 3 64%	5280
	21st to end	Day	21% 8% 3 6% 3 3 4 3 4 5% 41%	5780
February	1st to 10th	Day	16% 8% 3 6% 4 3 3 3 5% 5% 43%	2048
	11th to 20th	Day	20% 7% 2 6% 4 4 3 3 4 6% 40%	2048
	21st to end	Day	20% 7% 2 5% 4 4 3 3 4 6% 40%	1730
March	1st to 10th	Day	20% 6% 2 6% 4 4 3 3 4 6% 40%	4859
	11th to 20th	Day	13% 6% 2 5% 3 3 3 2 5% 6% 52%	5090
	21st to end	Day	19% 7% 2 6% 4 4 4 3 4 5% 44%	5586
April	1st to 10th	Day	14% 6% 2 6% 4 5% 4 5% 7% 7% 40%	2310
	11th to 20th	Day	15% 5% 2 5% 5% 4 5% 4 5% 6% 43%	2515
	21st to end	Day	15% 5% 2 5% 4 4 5% 4 5% 6% 45%	2730
May	1st to 10th	Day	15% 9% 3 8% 5% 5% 5% 4 6% 7% 34%	7616
	11th to 20th	Day	17% 7% 3 8% 5% 5% 6% 5% 6% 7% 32%	7626
	21st to end	Day	19% 8% 3 8% 5% 5% 5% 4 6% 7% 28%	8391
June	1st to 10th	Day	13% 7% 3 8% 6% 6% 6% 5% 7% 9% 29%	2730
	11th to 20th	Day	8% 6% 2 7% 6% 6% 7% 6% 9% 10% 32%	2730
	21st to end	Day	9% 6% 2 7% 7% 6% 8% 6% 7% 9% 32%	2730
July	1st to 10th	Day	6% 4 3 9% 7% 8% 7% 7% 9% 10% 30%	7680
	11th to 20th	Day	11% 7% 3 9% 7% 8% 8% 6% 9% 10% 22%	7680
	21st to end	Day	14% 8% 3 11% 7% 6% 8% 5% 8% 9% 23%	8340
August	1st to 10th	Day	13% 7% 3 8% 6% 7% 7% 6% 8% 10% 24%	4364
	11th to 20th	Day	11% 5% 2 8% 5% 6% 7% 6% 8% 10% 32%	4304
	21st to end	Day	8% 6% 2 7% 4 5% 6% 5% 7% 8% 41%	4345
September	1st to 10th	Day	13% 8% 3 6% 6% 6% 5% 6% 7% 7% 33%	2200
	11th to 20th	Day	17% 7% 3 8% 6% 5% 6% 4 6% 8% 31%	2200
	21st to end	Day	17% 6% 2 8% 6% 5% 5% 4 5% 6% 36%	2200
October	1st to 10th	Day	15% 6% 2 4 4 3 4 3 4 7% 49%	2200
	11th to 20th	Day	13% 5% 1 4 3 3 4 3 4 6% 55%	2005
	21st to end	Day	15% 5% 1 5% 3 3 4 3 4 4 54%	2200
November	1st to 10th	Day	13% 6% 2 4 3 3 2 3 4 6% 55%	1927
	11th to 20th	Day	15% 5% 1 3 3 2 3 3 5% 6% 53%	1890
	21st to end	Day	17% 4 2 5% 3 3 3 4 5% 7% 47%	1890
December	1st to 10th	Day	17% 5% 2 4 3 3 4 3 4 4 48%	3020
	11th to 20th	Day	17% 7% 2 6% 3 4 4 3 5% 5% 43%	3463
	21st to end	Day	22% 5% 1 4 2 3 3 3 5% 7% 45%	4565
January	1st to 10th	Night	17% 5% 2 4 3 3 3 3 5% 5% 52%	7635
	11th to 20th	Night	11% 7% 2 5% 3 3 3 2 3 5% 55%	7680
	21st to end	Night	18% 7% 2 5% 3 4 4 3 5% 6% 44%	8401
February	1st to 10th	Night	15% 7% 2 6% 4 3 4 3 5% 7% 44%	2569
	11th to 20th	Night	20% 8% 2 5% 4 4 4 3 5% 4 41%	2458
	21st to end	Night	20% 7% 2 7% 4 4 5% 3 5% 6% 38%	2076
March	1st to 10th	Night	20% 8% 2 5% 4 5% 4 4 6% 5% 35%	5212
	11th to 20th	Night	12% 4 2 4 3 3 4 3 6% 8% 51%	5090
	21st to end	Night	18% 6% 2 5% 4 5% 4 3 4 6% 43%	5588
April	1st to 10th	Night	15% 6% 2 6% 3 3 4 4 5% 6% 46%	2310
	11th to 20th	Night	14% 7% 2 4 3 3 3 3 5% 7% 50%	2068
	21st to end	Night	13% 7% 1 6% 4 3 4 3 4 8% 47%	1890
May	1st to 10th	Night	15% 8% 3 7% 5% 5% 5% 5% 7% 7% 32%	5237
	11th to 20th	Night	20% 8% 3 7% 4 4 4 4 5% 8% 34%	5234
	21st to end	Night	22% 8% 2 6% 5% 4 5% 4 7% 8% 29%	5761
June	1st to 10th	Night	12% 6% 3 7% 6% 6% 5% 5% 8% 10% 33%	1890
	11th to 20th	Night	10% 5% 2 6% 6% 4 6% 4 7% 10% 40%	1890
	21st to end	Night	8% 4 2 6% 4 5% 5% 5% 9% 11% 40%	1890
July	1st to 10th	Night	7% 6% 2 8% 5% 5% 6% 6% 9% 12% 35%	5278
	11th to 20th	Night	13% 6% 3 7% 6% 5% 6% 6% 8% 11% 29%	5277
	21st to end	Night	17% 9% 3 8% 5% 5% 5% 4 6% 9% 28%	5736
August	1st to 10th	Night	14% 8% 2 8% 5% 6% 5% 6% 7% 10% 29%	3005
	11th to 20th	Night	15% 9% 3 7% 5% 4 5% 4 6% 7% 34%	2965
	21st to end	Night	8% 6% 2 6% 4 4 5% 4 7% 10% 44%	3712
September	1st to 10th	Night	13% 7% 2 7% 5% 4 6% 5% 6% 8% 37%	2200
	11th to 20th	Night	18% 8% 3 7% 5% 4 5% 4 5% 6% 34%	2200
	21st to end	Night	18% 7% 2 6% 4 4 3 3 4 7% 42%	2200
October	1st to 10th	Night	16% 6% 2 5% 3 3 3 3 4 6% 50%	2200
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 4 5% 52%	2394
	21st to end	Night	15% 5% 1 4 3 3 4 3 4 4 54%	2640
November	1st to 10th	Night	14% 6% 2 4 3 3 3 2 4 7% 52%	2586
	11th to 20th	Night	15% 6% 2 4 3 3 4 4 4 5% 51%	2730
	21st to end	Night	16% 5% 2 6% 4 3 3 4 5% 6% 46%	2730
December	1st to 10th	Night	17% 6% 2 5% 3 3 4 3 4 4 49%	4380
	11th to 20th	Night	18% 8% 3 6% 3 4 4 3 5% 5% 42%	4952
	21st to end	Night	21% 7% 2 5% 4 3 3 3 4 6% 41%	6633

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	34% 3 9% 22% 24% 8%	5259
	11th to 20th	Day	26% 4 4 11% 34% 21%	5280
	21st to end	Day	43% 5% 6% 16% 17% 13%	5780
February	1st to 10th	Day	41% 6% 8% 21% 19% 6%	2048
	11th to 20th	Day	45% 5% 8% 17% 19% 7%	2058
	21st to end	Day	44% 5% 9% 15% 18% 9%	1730
March	1st to 10th	Day	42% 6% 8% 15% 18% 12%	4859
	11th to 20th	Day	32% 5% 6% 13% 23% 20%	5090
	21st to end	Day	42% 5% 8% 23% 16% 6%	5586
April	1st to 10th	Day	38% 6% 13% 19% 19% 5%	2310
	11th to 20th	Day	38% 5% 10% 19% 21% 7%	2515
	21st to end	Day	37% 7% 12% 25% 16% 2	2730
May	1st to 10th	Day	44% 10% 13% 21% 11% 2	7651
	11th to 20th	Day	45% 11% 15% 18% 9% 2	7630
	21st to end	Day	51% 10% 11% 14% 12% 2	8405
June	1st to 10th	Day	46% 11% 15% 19% 7% 2	2730
	11th to 20th	Day	40% 14% 17% 18% 9% 1	2730
	21st to end	Day	42% 12% 17% 17% 10% 2	2730
July	1st to 10th	Day	39% 17% 21% 17% 5%	7615
	11th to 20th	Day	49% 19% 21% 9% 2 1	7611
	21st to end	Day	52% 14% 16% 12% 6% 1	8156
August	1st to 10th	Day	46% 15% 17% 19% 3	4351
	11th to 20th	Day	38% 16% 21% 13% 9% 3	4343
	21st to end	Day	36% 11% 16% 27% 10% 1	4345
September	1st to 10th	Day	44% 11% 12% 17% 14% 3	2200
	11th to 20th	Day	48% 9% 11% 17% 13% 2	2200
	21st to end	Day	45% 8% 11% 16% 15% 5%	2200
October	1st to 10th	Day	27% 5% 9% 16% 32% 11%	3590
	11th to 20th	Day	20% 4 7% 17% 24% 29%	3245
	21st to end	Day	27% 6% 7% 22% 22% 16%	3538
November	1st to 10th	Day	31% 5% 8% 18% 27% 11%	1927
	11th to 20th	Day	31% 3 7% 23% 26% 10%	1890
	21st to end	Day	36% 4 8% 20% 26% 6%	1890
December	1st to 10th	Day	36% 5% 7% 16% 22% 13%	3020
	11th to 20th	Day	40% 5% 9% 17% 19% 10%	3460
	21st to end	Day	37% 4 10% 27% 19% 3	4565
January	1st to 10th	Night	32% 4 13% 21% 20% 11%	7636
	11th to 20th	Night	30% 4 7% 11% 29% 18%	7680
	21st to end	Night	38% 4 8% 15% 22% 13%	8401
February	1st to 10th	Night	37% 5% 12% 21% 19% 6%	2569
	11th to 20th	Night	45% 4 8% 18% 19% 6%	2459
	21st to end	Night	44% 5% 9% 18% 18% 7%	2076
March	1st to 10th	Night	41% 7% 11% 17% 19% 6%	5212
	11th to 20th	Night	29% 5% 9% 18% 21% 18%	5090
	21st to end	Night	40% 6% 12% 21% 15% 7%	5588
April	1st to 10th	Night	36% 6% 12% 21% 22% 4	2310
	11th to 20th	Night	33% 4 11% 25% 22% 6%	2068
	21st to end	Night	35% 7% 14% 25% 18% 2	1890
May	1st to 10th	Night	43% 11% 13% 21% 11% 2	5264
	11th to 20th	Night	43% 11% 18% 18% 9% 2	5235
	21st to end	Night	46% 11% 15% 18% 8% 1	5771
June	1st to 10th	Night	41% 13% 16% 19% 8% 1	1890
	11th to 20th	Night	35% 11% 22% 23% 9% 1	1890
	21st to end	Night	31% 15% 20% 19% 12% 3	1890
July	1st to 10th	Night	34% 17% 28% 17% 4	5235
	11th to 20th	Night	41% 19% 26% 12% 1 1	5226
	21st to end	Night	48% 13% 20% 13% 4 2	5606
August	1st to 10th	Night	44% 15% 22% 16% 4	2994
	11th to 20th	Night	44% 14% 18% 13% 9% 2	2992
	21st to end	Night	31% 12% 19% 28% 9% 1	3712
September	1st to 10th	Night	40% 11% 15% 18% 12% 3	2200
	11th to 20th	Night	46% 10% 13% 17% 13% 1	2200
	21st to end	Night	42% 6% 12% 21% 16% 4	2200
October	1st to 10th	Night	26% 8% 12% 18% 29% 7%	3590
	11th to 20th	Night	21% 4 7% 18% 25% 26%	3893
	21st to end	Night	31% 5% 5% 20% 23% 16%	4252
November	1st to 10th	Night	33% 4 10% 19% 23% 10%	2586
	11th to 20th	Night	33% 5% 8% 17% 26% 11%	2730
	21st to end	Night	37% 4 7% 21% 24% 7%	2730
December	1st to 10th	Night	35% 4 9% 17% 23% 12%	4380
	11th to 20th	Night	40% 6% 9% 18% 20% 7%	4954
	21st to end	Night	40% 4 12% 22% 18% 3	6633

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	36% 23% 30% 9% 2	330
	11th to 20th	Day	41% 20% 26% 11% 2	330
	21st to end	Day	36% 28% 27% 7% 2	363
February	1st to 10th	Day	27% 28% 36% 8% 1	330
	11th to 20th	Day	46% 23% 26% 4	330
	21st to end	Day	41% 27% 26% 5% 1	273
March	1st to 10th	Day	32% 18% 30% 14% 6%	453
	11th to 20th	Day	32% 21% 29% 14% 3 1	540
	21st to end	Day	28% 23% 29% 15% 4 1	594
April	1st to 10th	Day	27% 16% 30% 19% 8% 1	540
	11th to 20th	Day	20% 22% 28% 20% 9% 1	532
	21st to end	Day	21% 17% 26% 21% 11% 4	540
May	1st to 10th	Day	19% 24% 26% 19% 8% 4	543
	11th to 20th	Day	22% 12% 23% 24% 12% 7%	567
	21st to end	Day	22% 12% 20% 24% 12% 10%	617
June	1st to 10th	Day	16% 9% 22% 28% 15% 10%	570
	11th to 20th	Day	10% 9% 22% 24% 21% 13%	570
	21st to end	Day	9% 7% 26% 29% 16% 12%	570
July	1st to 10th	Day	8% 4 16% 30% 26% 16%	565
	11th to 20th	Day	9% 4 17% 26% 26% 18%	564
	21st to end	Day	10% 5% 17% 28% 24% 17%	620
August	1st to 10th	Day	18% 6% 20% 24% 18% 14%	566
	11th to 20th	Day	10% 6% 16% 29% 26% 13%	559
	21st to end	Day	15% 5% 16% 24% 27% 13%	619
September	1st to 10th	Day	12% 5% 19% 27% 28% 9%	530
	11th to 20th	Day	17% 5% 17% 25% 26% 10%	530
	21st to end	Day	20% 7% 18% 29% 22% 5%	530
October	1st to 10th	Day	19% 8% 22% 28% 17% 7%	530
	11th to 20th	Day	15% 12% 28% 27% 14% 4	530
	21st to end	Day	23% 12% 25% 28% 10% 3	583
November	1st to 10th	Day	21% 13% 30% 23% 10% 2	405
	11th to 20th	Day	22% 23% 32% 19% 3	330
	21st to end	Day	23% 17% 36% 17% 5% 1	330
December	1st to 10th	Day	35% 22% 29% 11% 2 1	330
	11th to 20th	Day	29% 17% 32% 17% 4	330
	21st to end	Day	32% 20% 32% 11% 4 1	363
January	1st to 10th	Night	29% 15% 29% 21% 5%	840
	11th to 20th	Night	25% 20% 27% 22% 6%	840
	21st to end	Night	25% 17% 34% 21% 3	924
February	1st to 10th	Night	22% 16% 28% 30% 4	840
	11th to 20th	Night	29% 18% 31% 19% 2	823
	21st to end	Night	29% 20% 29% 19% 3	692
March	1st to 10th	Night	24% 15% 28% 28% 4	840
	11th to 20th	Night	24% 14% 31% 22% 7% 1	840
	21st to end	Night	23% 15% 31% 22% 8%	924
April	1st to 10th	Night	23% 17% 27% 25% 9%	840
	11th to 20th	Night	22% 12% 26% 27% 13% 1	677
	21st to end	Night	15% 11% 22% 32% 18% 2	630
May	1st to 10th	Night	16% 12% 24% 27% 19% 1	630
	11th to 20th	Night	20% 8% 18% 29% 21% 4	621
	21st to end	Night	20% 4 14% 26% 28% 8%	683
June	1st to 10th	Night	14% 4 16% 31% 29% 7%	630
	11th to 20th	Night	9% 4 17% 28% 30% 12%	630
	21st to end	Night	7% 3 14% 29% 41% 7%	630
July	1st to 10th	Night	10% 3 8% 25% 46% 9%	615
	11th to 20th	Night	12% 3 11% 23% 39% 12%	612
	21st to end	Night	9% 4 10% 26% 40% 11%	690
August	1st to 10th	Night	19% 4 10% 24% 34% 10%	627
	11th to 20th	Night	16% 5% 10% 25% 35% 10%	624
	21st to end	Night	13% 4 10% 26% 37% 10%	712
September	1st to 10th	Night	13% 4 12% 28% 33% 9%	800
	11th to 20th	Night	21% 3 12% 26% 32% 6%	800
	21st to end	Night	21% 6% 10% 33% 26% 4	800
October	1st to 10th	Night	18% 7% 18% 25% 25% 7%	800
	11th to 20th	Night	18% 11% 18% 31% 19% 3	800
	21st to end	Night	21% 9% 18% 34% 15% 3	880
November	1st to 10th	Night	18% 9% 21% 31% 18% 3	820
	11th to 20th	Night	20% 15% 22% 30% 11% 2	840
	21st to end	Night	21% 13% 21% 32% 13% 1	840
December	1st to 10th	Night	28% 15% 23% 28% 7%	840
	11th to 20th	Night	22% 14% 25% 30% 8% 1	840
	21st to end	Night	30% 13% 23% 28% 5%	924

Page generated at 2026-08-27 04:07:15. Version ac07

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