Scenic
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Scenic clear sky chart from 2005-11-06 to 2026-07-16.

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	8% 6% 2 6% 4 4 4 3 6% 8% 51%	146782
	Night	7% 6% 2 6% 4 4 4 4 6% 7% 49%	143338
Transparency	Day	31% 6% 14% 27% 19% 4	141543
	Night	33% 6% 14% 26% 18% 3	139589
Seeing	Day	11% 8% 27% 33% 18% 3	18262
	Night	10% 7% 32% 40% 11%	28198

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	3 8% 4 11% 6% 5% 4 4 5% 8% 42%	4720
	11th to 20th	Day	3 8% 5% 12% 5% 4 4 3 5% 7% 43%	4740
	21st to end	Day	3 7% 3 8% 6% 4 5% 4 5% 7% 49%	5188
February	1st to 10th	Day	6% 11% 4 8% 7% 4 5% 4 5% 6% 40%	1857
	11th to 20th	Day	6% 9% 4 7% 4 4 4 4 6% 7% 45%	2049
	21st to end	Day	5% 8% 3 7% 5% 4 5% 4 7% 7% 46%	1730
March	1st to 10th	Day	7% 8% 3 5% 4 3 3 3 4 7% 54%	4600
	11th to 20th	Day	7% 5% 2 4 3 2 3 3 5% 8% 57%	4764
	21st to end	Day	14% 9% 3 9% 5% 4 4 3 5% 7% 36%	6054
April	1st to 10th	Day	12% 8% 3 4 5% 3 4 4 5% 8% 44%	2520
	11th to 20th	Day	12% 7% 3 7% 4 4 4 4 6% 8% 41%	2491
	21st to end	Day	15% 7% 2 6% 4 4 4 3 5% 8% 42%	2711
May	1st to 10th	Day	10% 6% 2 5% 4 4 4 4 5% 7% 49%	7655
	11th to 20th	Day	12% 6% 2 5% 4 4 4 3 5% 7% 48%	8166
	21st to end	Day	14% 5% 2 5% 3 4 4 4 6% 8% 44%	9026
June	1st to 10th	Day	9% 4 1 4 3 4 4 4 6% 9% 51%	2940
	11th to 20th	Day	9% 3 2 4 4 3 5% 4 7% 10% 50%	2940
	21st to end	Day	5% 3 1 4 3 3 4 3 6% 8% 60%	2940
July	1st to 10th	Day	5% 4 2 5% 4 4 4 4 7% 10% 53%	6479
	11th to 20th	Day	7% 3 1 4 3 3 4 4 6% 9% 55%	6411
	21st to end	Day	6% 3 1 4 3 3 4 4 6% 8% 56%	6903
August	1st to 10th	Day	5% 5% 2 5% 4 3 4 4 7% 10% 52%	6174
	11th to 20th	Day	4 3 2 4 3 3 4 4 7% 9% 57%	5641
	21st to end	Day	8% 4 2 4 4 4 4 3 6% 8% 53%	5984
September	1st to 10th	Day	6% 4 1 3 3 3 3 2 4 7% 65%	2400
	11th to 20th	Day	8% 3 1 3 3 3 3 3 5% 6% 61%	2275
	21st to end	Day	9% 3 1 4 2 2 3 3 5% 7% 63%	2200
October	1st to 10th	Day	7% 3 1 3 2 2 2 2 3 5% 70%	3513
	11th to 20th	Day	9% 5% 1 4 3 3 3 3 4 7% 61%	3127
	21st to end	Day	9% 6% 2 6% 4 4 4 3 5% 6% 50%	3190
November	1st to 10th	Day	6% 6% 2 6% 3 4 3 4 6% 9% 52%	1853
	11th to 20th	Day	5% 5% 2 5% 4 4 4 4 6% 7% 54%	1890
	21st to end	Day	5% 8% 3 6% 4 4 3 4 5% 7% 52%	1753
December	1st to 10th	Day	3 8% 3 9% 5% 3 4 3 6% 7% 49%	2700
	11th to 20th	Day	3 7% 2 7% 4 4 5% 4 6% 8% 51%	3106
	21st to end	Day	8% 11% 3 7% 4 4 4 3 4 6% 47%	4092
January	1st to 10th	Night	6% 11% 4 11% 6% 4 4 4 5% 6% 41%	8201
	11th to 20th	Night	3 7% 3 11% 6% 5% 5% 4 5% 7% 44%	8250
	21st to end	Night	2 5% 3 9% 5% 4 4 3 5% 6% 52%	9026
February	1st to 10th	Night	8% 11% 4 8% 5% 4 5% 4 6% 7% 40%	2777
	11th to 20th	Night	4 10% 3 8% 6% 5% 4 4 6% 6% 43%	2458
	21st to end	Night	5% 8% 3 6% 5% 3 4 4 6% 8% 48%	2076
March	1st to 10th	Night	8% 9% 3 6% 4 3 3 3 5% 6% 49%	5494
	11th to 20th	Night	6% 6% 2 5% 4 4 4 4 6% 9% 52%	5430
	21st to end	Night	12% 10% 4 8% 4 4 4 4 6% 9% 35%	5124
April	1st to 10th	Night	14% 7% 3 5% 3 4 4 4 6% 8% 43%	2100
	11th to 20th	Night	13% 7% 3 7% 4 4 3 4 6% 7% 43%	2077
	21st to end	Night	14% 8% 2 5% 4 4 4 3 6% 7% 42%	1907
May	1st to 10th	Night	8% 5% 2 6% 4 5% 5% 5% 7% 8% 46%	5292
	11th to 20th	Night	11% 5% 2 5% 3 4 4 4 7% 7% 49%	4711
	21st to end	Night	16% 6% 2 6% 4 3 4 4 5% 8% 43%	5181
June	1st to 10th	Night	9% 4 2 4 3 4 4 3 7% 9% 50%	1680
	11th to 20th	Night	10% 4 1 6% 5% 4 4 4 7% 8% 48%	1680
	21st to end	Night	7% 4 1 4 3 4 4 5% 6% 6% 55%	1680
July	1st to 10th	Night	5% 3 1 5% 4 3 4 3 6% 9% 57%	3720
	11th to 20th	Night	5% 4 1 5% 3 4 5% 4 6% 8% 56%	3680
	21st to end	Night	6% 4 1 4 4 4 5% 5% 6% 8% 52%	3970
August	1st to 10th	Night	5% 4 2 6% 4 4 5% 5% 7% 9% 50%	3635
	11th to 20th	Night	4 4 2 5% 4 4 4 4 6% 9% 54%	4205
	21st to end	Night	7% 6% 2 7% 4 5% 4 4 6% 7% 47%	4993
September	1st to 10th	Night	6% 3 1 3 3 3 4 2 5% 5% 65%	2000
	11th to 20th	Night	8% 3 1 3 4 3 4 4 5% 7% 59%	2123
	21st to end	Night	9% 4 1 4 3 3 3 3 4 5% 63%	2200
October	1st to 10th	Night	8% 3 1 2 2 2 2 2 3 4 70%	3655
	11th to 20th	Night	8% 5% 1 4 3 3 4 3 5% 7% 57%	3988
	21st to end	Night	10% 6% 1 5% 3 4 4 3 5% 8% 51%	4610
November	1st to 10th	Night	8% 6% 2 5% 4 3 4 3 6% 8% 49%	2665
	11th to 20th	Night	6% 7% 3 7% 4 3 4 4 5% 6% 51%	2730
	21st to end	Night	6% 7% 2 5% 3 4 4 4 6% 8% 52%	2861
December	1st to 10th	Night	3 7% 2 6% 4 5% 4 4 6% 8% 50%	4710
	11th to 20th	Night	4 8% 2 6% 5% 5% 5% 4 6% 8% 47%	5321
	21st to end	Night	8% 11% 3 7% 4 4 4 3 6% 7% 43%	7128

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	40% 6% 15% 28% 11% 1	4723
	11th to 20th	Day	40% 5% 14% 24% 15% 2	4740
	21st to end	Day	32% 6% 14% 30% 16% 3	5188
February	1st to 10th	Day	43% 8% 13% 21% 13% 2	1857
	11th to 20th	Day	38% 6% 16% 19% 16% 4	2059
	21st to end	Day	34% 7% 15% 28% 13% 3	1730
March	1st to 10th	Day	31% 4 10% 28% 24% 4	4600
	11th to 20th	Day	25% 5% 14% 35% 20% 1	4764
	21st to end	Day	45% 7% 17% 20% 10%	6054
April	1st to 10th	Day	37% 7% 16% 28% 10% 3	2520
	11th to 20th	Day	39% 7% 14% 22% 16% 2	2494
	21st to end	Day	39% 7% 16% 26% 10% 1	2711
May	1st to 10th	Day	33% 6% 11% 31% 18% 1	7655
	11th to 20th	Day	34% 6% 12% 23% 21% 4	8170
	21st to end	Day	36% 7% 13% 25% 18% 2	9027
June	1st to 10th	Day	27% 8% 21% 28% 14% 2	2940
	11th to 20th	Day	27% 7% 19% 26% 18% 4	2940
	21st to end	Day	20% 7% 13% 31% 22% 6%	2940
July	1st to 10th	Day	25% 5% 12% 32% 23% 2	6411
	11th to 20th	Day	24% 5% 12% 29% 23% 7%	6336
	21st to end	Day	24% 5% 12% 24% 25% 9%	6705
August	1st to 10th	Day	26% 6% 18% 23% 21% 6%	4489
	11th to 20th	Day	26% 7% 15% 29% 17% 5%	4082
	21st to end	Day	21% 4 11% 25% 25% 13%	4311
September	1st to 10th	Day	20% 4 10% 29% 27% 10%	2400
	11th to 20th	Day	24% 5% 11% 28% 24% 8%	2275
	21st to end	Day	22% 4 9% 33% 27% 4	2200
October	1st to 10th	Day	19% 3 9% 20% 31% 17%	3513
	11th to 20th	Day	25% 4 11% 37% 20% 3	3127
	21st to end	Day	34% 5% 12% 30% 16% 4	3190
November	1st to 10th	Day	29% 5% 14% 26% 19% 5%	1853
	11th to 20th	Day	28% 6% 13% 28% 21% 4	1890
	21st to end	Day	31% 5% 15% 32% 14% 4	1753
December	1st to 10th	Day	33% 4 18% 28% 16% 1	2700
	11th to 20th	Day	29% 6% 21% 30% 13% 1	3104
	21st to end	Day	38% 4 9% 35% 13% 1	4092
January	1st to 10th	Night	43% 5% 12% 29% 9% 1	8202
	11th to 20th	Night	38% 5% 16% 24% 16% 1	8250
	21st to end	Night	32% 5% 14% 27% 20% 2	9026
February	1st to 10th	Night	42% 7% 14% 22% 13% 1	2777
	11th to 20th	Night	40% 6% 13% 24% 14% 3	2458
	21st to end	Night	33% 5% 15% 28% 14% 4	2076
March	1st to 10th	Night	34% 5% 9% 26% 22% 3	5494
	11th to 20th	Night	27% 6% 16% 28% 22% 1	5430
	21st to end	Night	45% 7% 18% 20% 10%	5124
April	1st to 10th	Night	39% 7% 14% 25% 12% 2	2100
	11th to 20th	Night	39% 6% 12% 23% 17% 2	2077
	21st to end	Night	39% 7% 14% 25% 13% 1	1907
May	1st to 10th	Night	33% 8% 11% 26% 21% 2	5293
	11th to 20th	Night	32% 6% 14% 29% 17% 3	4712
	21st to end	Night	39% 6% 12% 25% 16% 1	5182
June	1st to 10th	Night	29% 8% 19% 26% 16% 2	1680
	11th to 20th	Night	31% 9% 19% 22% 16% 3	1680
	21st to end	Night	25% 7% 16% 28% 19% 6%	1680
July	1st to 10th	Night	24% 5% 16% 29% 23% 3	3680
	11th to 20th	Night	26% 5% 14% 28% 21% 6%	3632
	21st to end	Night	28% 6% 14% 26% 21% 6%	3856
August	1st to 10th	Night	29% 8% 17% 22% 19% 6%	2644
	11th to 20th	Night	30% 6% 17% 23% 21% 4	3040
	21st to end	Night	25% 6% 13% 23% 24% 9%	3597
September	1st to 10th	Night	22% 4 10% 29% 27% 8%	2000
	11th to 20th	Night	24% 5% 14% 25% 25% 6%	2123
	21st to end	Night	25% 4 8% 30% 26% 7%	2200
October	1st to 10th	Night	20% 3 7% 20% 30% 19%	3655
	11th to 20th	Night	26% 5% 11% 32% 22% 4	3988
	21st to end	Night	32% 4 12% 27% 19% 7%	4610
November	1st to 10th	Night	31% 6% 14% 24% 19% 5%	2665
	11th to 20th	Night	32% 5% 13% 25% 19% 5%	2730
	21st to end	Night	30% 6% 16% 27% 19% 3	2861
December	1st to 10th	Night	31% 5% 17% 28% 17% 2	4710
	11th to 20th	Night	33% 6% 17% 31% 11% 2	5322
	21st to end	Night	40% 4 11% 30% 13% 1	7128

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	8% 7% 26% 35% 20% 4	330
	11th to 20th	Day	14% 7% 30% 36% 11% 2	330
	21st to end	Day	7% 10% 39% 32% 11% 1	363
February	1st to 10th	Day	12% 11% 34% 36% 6%	330
	11th to 20th	Day	12% 8% 38% 32% 10%	330
	21st to end	Day	7% 14% 40% 30% 9% 1	273
March	1st to 10th	Day	11% 12% 32% 31% 12% 2	330
	11th to 20th	Day	12% 8% 37% 27% 13% 2	330
	21st to end	Day	18% 13% 29% 27% 12% 2	573
April	1st to 10th	Day	17% 13% 34% 28% 9%	540
	11th to 20th	Day	19% 17% 31% 25% 8% 1	532
	21st to end	Day	19% 11% 23% 32% 14% 1	731
May	1st to 10th	Day	15% 10% 25% 30% 17% 3	753
	11th to 20th	Day	20% 7% 23% 30% 15% 4	775
	21st to end	Day	16% 9% 27% 29% 16% 4	844
June	1st to 10th	Day	7% 7% 24% 32% 23% 8%	780
	11th to 20th	Day	11% 7% 31% 35% 14% 3	780
	21st to end	Day	7% 6% 27% 35% 22% 4	780
July	1st to 10th	Day	5% 3 20% 40% 27% 5%	771
	11th to 20th	Day	6% 3 21% 44% 24% 3	744
	21st to end	Day	6% 3 20% 40% 29% 4	794
August	1st to 10th	Day	6% 3 20% 41% 27% 4	726
	11th to 20th	Day	6% 3 21% 36% 27% 7%	639
	21st to end	Day	6% 5% 19% 35% 27% 8%	583
September	1st to 10th	Day	7% 5% 23% 32% 27% 6%	530
	11th to 20th	Day	9% 4 18% 33% 28% 7%	405
	21st to end	Day	11% 7% 25% 30% 20% 7%	330
October	1st to 10th	Day	16% 5% 22% 27% 19% 11%	330
	11th to 20th	Day	14% 13% 32% 25% 13% 2	330
	21st to end	Day	13% 15% 31% 25% 15% 2	363
November	1st to 10th	Day	11% 10% 35% 29% 13% 2	330
	11th to 20th	Day	11% 8% 34% 33% 12% 2	330
	21st to end	Day	12% 7% 28% 39% 12% 2	330
December	1st to 10th	Day	7% 12% 35% 33% 12% 2	330
	11th to 20th	Day	11% 10% 37% 33% 9% 1	330
	21st to end	Day	13% 10% 34% 29% 12% 2	363
January	1st to 10th	Night	8% 8% 33% 38% 12% 1	1050
	11th to 20th	Night	10% 11% 35% 36% 8%	1050
	21st to end	Night	9% 8% 37% 38% 8%	1155
February	1st to 10th	Night	12% 8% 40% 33% 6%	908
	11th to 20th	Night	8% 6% 38% 41% 8%	824
	21st to end	Night	9% 7% 40% 37% 7%	692
March	1st to 10th	Night	11% 9% 33% 39% 7%	840
	11th to 20th	Night	11% 6% 33% 39% 10% 1	788
	21st to end	Night	16% 10% 28% 37% 8%	693
April	1st to 10th	Night	16% 9% 34% 35% 6%	630
	11th to 20th	Night	16% 10% 36% 33% 5%	623
	21st to end	Night	17% 10% 27% 36% 10%	630
May	1st to 10th	Night	12% 8% 28% 38% 13% 1	630
	11th to 20th	Night	17% 7% 28% 35% 13%	621
	21st to end	Night	14% 8% 34% 34% 9%	683
June	1st to 10th	Night	8% 7% 29% 41% 13% 1	630
	11th to 20th	Night	11% 6% 37% 39% 7%	630
	21st to end	Night	7% 7% 29% 46% 11%	630
July	1st to 10th	Night	6% 3 28% 45% 18% 1	615
	11th to 20th	Night	5% 3 24% 52% 16%	597
	21st to end	Night	4 2 25% 53% 16%	657
August	1st to 10th	Night	5% 3 24% 52% 15%	597
	11th to 20th	Night	5% 3 25% 47% 20%	594
	21st to end	Night	3 5% 26% 49% 17%	660
September	1st to 10th	Night	7% 4 26% 46% 17% 1	600
	11th to 20th	Night	8% 4 26% 44% 17% 1	600
	21st to end	Night	11% 6% 27% 42% 14% 1	600
October	1st to 10th	Night	16% 6% 25% 36% 16%	639
	11th to 20th	Night	12% 6% 31% 37% 13%	852
	21st to end	Night	14% 7% 30% 37% 10%	1100
November	1st to 10th	Night	11% 6% 35% 40% 8% 1	1025
	11th to 20th	Night	10% 7% 35% 40% 8%	1050
	21st to end	Night	9% 7% 33% 42% 9%	1050
December	1st to 10th	Night	9% 8% 39% 36% 8%	1050
	11th to 20th	Night	9% 7% 35% 41% 8%	1050
	21st to end	Night	14% 9% 33% 36% 8%	1155

Page generated at 2026-07-13 01:14:47. Version ac07

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