Peyton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Peyton clear sky chart from 2005-11-06 to 2025-12-18.

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	4 5% 2 5% 4 4 4 4 6% 8% 54%	135746
	Night	4 5% 2 5% 4 4 4 4 6% 7% 56%	132700
Transparency	Day	25% 6% 10% 23% 24% 11%	130728
	Night	25% 6% 11% 24% 24% 10%	128722
Seeing	Day	7% 10% 29% 30% 19% 6%	17052
	Night	6% 6% 31% 40% 15% 2	27098

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	1 4 2 5% 2 3 4 4 6% 10% 59%	3638
	11th to 20th	Day	1 2 2 5% 5% 4 4 4 7% 8% 57%	3732
	21st to end	Day	1 4 2 7% 3 3 3 2 5% 6% 62%	4510
February	1st to 10th	Day	1 8% 2 5% 4 3 4 3 6% 7% 58%	1838
	11th to 20th	Day	1 4 2 6% 5% 4 4 4 5% 8% 56%	1949
	21st to end	Day	1 5% 3 7% 4 3 3 3 5% 6% 59%	1650
March	1st to 10th	Day	1 5% 2 5% 3 3 3 3 5% 6% 63%	4500
	11th to 20th	Day	3 8% 3 6% 4 4 4 3 6% 8% 51%	4852
	21st to end	Day	2 6% 2 5% 4 4 5% 4 7% 8% 52%	5878
April	1st to 10th	Day	5% 7% 2 5% 3 4 5% 3 5% 8% 54%	2400
	11th to 20th	Day	6% 9% 3 6% 3 4 4 4 6% 8% 47%	2371
	21st to end	Day	8% 7% 2 6% 4 4 4 4 6% 8% 47%	2400
May	1st to 10th	Day	11% 7% 3 6% 4 4 4 3 5% 6% 47%	5762
	11th to 20th	Day	6% 5% 2 6% 3 4 4 5% 7% 9% 48%	6095
	21st to end	Day	6% 5% 2 5% 4 4 5% 5% 8% 10% 46%	6925
June	1st to 10th	Day	6% 5% 1 4 4 5% 5% 5% 7% 9% 48%	2800
	11th to 20th	Day	4 4 2 4 3 4 5% 4 8% 9% 54%	2800
	21st to end	Day	3 3 1 5% 5% 5% 5% 5% 9% 9% 48%	2800
July	1st to 10th	Day	3 2 1 4 4 4 5% 5% 9% 11% 51%	6339
	11th to 20th	Day	3 4 1 5% 5% 6% 6% 5% 8% 10% 45%	6340
	21st to end	Day	4 4 2 6% 5% 6% 7% 5% 8% 9% 45%	6817
August	1st to 10th	Day	6% 4 2 6% 5% 5% 6% 5% 8% 11% 42%	5636
	11th to 20th	Day	3 3 1 5% 4 5% 6% 5% 8% 11% 49%	5366
	21st to end	Day	5% 5% 2 6% 4 6% 6% 5% 8% 9% 43%	5984
September	1st to 10th	Day	4 4 1 4 4 3 4 4 6% 9% 57%	2400
	11th to 20th	Day	5% 3 1 4 3 3 4 3 6% 8% 59%	2346
	21st to end	Day	4 4 1 4 3 3 3 3 5% 6% 64%	2200
October	1st to 10th	Day	4 4 1 3 2 2 2 2 3 5% 74%	3378
	11th to 20th	Day	4 5% 2 4 3 3 3 3 4 6% 61%	3250
	21st to end	Day	3 3 1 3 3 2 2 2 4 5% 71%	3392
November	1st to 10th	Day	2 4 1 4 3 2 3 4 5% 8% 65%	1853
	11th to 20th	Day	2 6% 2 4 2 3 4 2 3 7% 66%	1890
	21st to end	Day	2 6% 2 5% 3 2 3 3 5% 7% 63%	1869
December	1st to 10th	Day	1 5% 2 3 3 3 3 3 3 5% 69%	2700
	11th to 20th	Day	1 3 2 4 3 2 4 3 5% 7% 67%	3082
	21st to end	Day	2 5% 2 6% 3 3 4 3 5% 7% 60%	4004
January	1st to 10th	Night	1 5% 3 7% 4 4 4 4 6% 8% 55%	6327
	11th to 20th	Night	1 3 2 5% 5% 4 4 4 6% 7% 60%	6276
	21st to end	Night	1 4 2 6% 4 3 4 3 4 6% 63%	6468
February	1st to 10th	Night	2 6% 2 5% 4 4 4 3 5% 8% 57%	2560
	11th to 20th	Night	2 6% 3 7% 5% 4 4 4 6% 7% 51%	2338
	21st to end	Night	2 6% 2 4 4 4 3 3 4 6% 62%	1980
March	1st to 10th	Night	1 5% 2 6% 4 3 4 3 5% 7% 60%	5374
	11th to 20th	Night	4 7% 3 6% 4 4 4 3 5% 6% 54%	5140
	21st to end	Night	4 6% 3 6% 4 5% 4 4 6% 7% 52%	5078
April	1st to 10th	Night	5% 6% 2 5% 4 4 3 3 6% 7% 56%	2000
	11th to 20th	Night	7% 10% 2 5% 4 4 3 3 6% 7% 49%	1977
	21st to end	Night	9% 8% 2 4 4 4 4 5% 5% 8% 47%	2000
May	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 5% 6% 48%	4202
	11th to 20th	Night	6% 6% 3 5% 4 4 4 4 6% 9% 49%	3804
	21st to end	Night	8% 6% 2 6% 4 4 5% 4 5% 7% 48%	3972
June	1st to 10th	Night	5% 4 2 5% 3 4 4 4 7% 10% 51%	1600
	11th to 20th	Night	3 3 1 3 3 4 4 5% 7% 8% 59%	1600
	21st to end	Night	5% 5% 2 6% 4 4 6% 5% 7% 9% 50%	1600
July	1st to 10th	Night	4 4 2 5% 5% 5% 5% 5% 7% 9% 49%	3640
	11th to 20th	Night	3 3 1 6% 5% 5% 6% 5% 8% 12% 45%	3640
	21st to end	Night	4 5% 2 6% 5% 6% 5% 5% 7% 9% 47%	4052
August	1st to 10th	Night	6% 6% 2 6% 5% 5% 6% 5% 7% 9% 43%	4161
	11th to 20th	Night	4 4 2 6% 4 5% 6% 5% 8% 10% 47%	4483
	21st to end	Night	8% 5% 2 6% 4 5% 6% 5% 8% 10% 41%	4993
September	1st to 10th	Night	5% 5% 2 6% 4 4 4 5% 6% 9% 51%	2000
	11th to 20th	Night	6% 4 2 4 4 4 3 3 5% 8% 59%	2053
	21st to end	Night	5% 4 1 5% 3 4 4 3 4 6% 62%	2200
October	1st to 10th	Night	4 3 1 4 2 3 3 2 3 5% 69%	3805
	11th to 20th	Night	6% 4 2 5% 3 3 4 4 5% 7% 58%	3898
	21st to end	Night	3 4 1 3 2 3 3 3 4 5% 69%	4374
November	1st to 10th	Night	2 5% 2 3 3 2 3 2 5% 7% 67%	2665
	11th to 20th	Night	1 3 2 4 3 3 3 3 4 6% 68%	2730
	21st to end	Night	3 5% 2 5% 3 3 3 3 5% 7% 60%	2746
December	1st to 10th	Night	1 3 2 4 3 2 2 2 4 6% 72%	4710
	11th to 20th	Night	1 3 2 4 3 3 4 3 5% 8% 64%	5280
	21st to end	Night	2 5% 2 5% 4 4 5% 4 6% 8% 56%	6974

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	19% 5% 9% 31% 25% 11%	3639
	11th to 20th	Day	22% 5% 10% 22% 28% 12%	3732
	21st to end	Day	23% 4 7% 26% 27% 13%	4510
February	1st to 10th	Day	25% 4 11% 27% 22% 11%	1838
	11th to 20th	Day	24% 6% 8% 27% 26% 8%	1959
	21st to end	Day	25% 4 8% 21% 24% 19%	1650
March	1st to 10th	Day	18% 6% 7% 16% 32% 21%	4500
	11th to 20th	Day	29% 6% 9% 22% 27% 8%	4852
	21st to end	Day	24% 8% 10% 38% 18% 3	5878
April	1st to 10th	Day	27% 6% 12% 25% 22% 9%	2400
	11th to 20th	Day	32% 7% 11% 22% 19% 10%	2374
	21st to end	Day	31% 7% 12% 26% 20% 4	2400
May	1st to 10th	Day	34% 6% 10% 25% 18% 8%	5762
	11th to 20th	Day	27% 7% 12% 19% 23% 11%	6099
	21st to end	Day	27% 10% 15% 23% 20% 7%	6926
June	1st to 10th	Day	27% 8% 16% 24% 17% 9%	2800
	11th to 20th	Day	23% 7% 12% 18% 24% 17%	2800
	21st to end	Day	25% 8% 12% 21% 21% 13%	2800
July	1st to 10th	Day	21% 8% 9% 20% 26% 15%	6271
	11th to 20th	Day	27% 9% 13% 25% 17% 9%	6265
	21st to end	Day	32% 7% 13% 16% 17% 15%	6620
August	1st to 10th	Day	34% 9% 17% 23% 12% 5%	4098
	11th to 20th	Day	27% 8% 13% 18% 22% 12%	3882
	21st to end	Day	28% 6% 13% 21% 25% 7%	4311
September	1st to 10th	Day	23% 6% 10% 22% 25% 15%	2400
	11th to 20th	Day	21% 6% 9% 18% 29% 17%	2346
	21st to end	Day	20% 4 7% 20% 34% 14%	2200
October	1st to 10th	Day	15% 4 6% 15% 39% 21%	3378
	11th to 20th	Day	23% 4 7% 24% 32% 10%	3250
	21st to end	Day	16% 3 4 23% 38% 15%	3392
November	1st to 10th	Day	17% 4 10% 24% 28% 17%	1853
	11th to 20th	Day	19% 4 6% 26% 34% 12%	1890
	21st to end	Day	21% 3 9% 24% 27% 16%	1869
December	1st to 10th	Day	19% 3 8% 30% 31% 10%	2700
	11th to 20th	Day	17% 4 7% 30% 32% 11%	3080
	21st to end	Day	22% 5% 9% 29% 25% 11%	4004
January	1st to 10th	Night	25% 6% 9% 29% 24% 7%	6327
	11th to 20th	Night	21% 6% 9% 25% 25% 14%	6276
	21st to end	Night	22% 5% 9% 26% 26% 12%	6468
February	1st to 10th	Night	25% 5% 10% 27% 24% 10%	2560
	11th to 20th	Night	30% 5% 11% 27% 20% 7%	2338
	21st to end	Night	22% 4 7% 25% 26% 16%	1980
March	1st to 10th	Night	22% 5% 8% 15% 36% 14%	5374
	11th to 20th	Night	29% 5% 11% 15% 29% 11%	5140
	21st to end	Night	28% 7% 12% 33% 19% 2	5078
April	1st to 10th	Night	26% 6% 13% 24% 22% 10%	2000
	11th to 20th	Night	32% 5% 13% 23% 19% 7%	1977
	21st to end	Night	33% 8% 13% 25% 16% 5%	2000
May	1st to 10th	Night	32% 8% 14% 28% 11% 6%	4199
	11th to 20th	Night	29% 8% 13% 24% 17% 9%	3805
	21st to end	Night	31% 10% 15% 23% 16% 5%	3972
June	1st to 10th	Night	26% 8% 21% 23% 14% 8%	1600
	11th to 20th	Night	20% 7% 16% 23% 18% 15%	1600
	21st to end	Night	27% 9% 10% 22% 21% 11%	1600
July	1st to 10th	Night	28% 7% 11% 22% 27% 5%	3600
	11th to 20th	Night	28% 9% 19% 26% 15% 3	3592
	21st to end	Night	31% 8% 15% 18% 18% 10%	3937
August	1st to 10th	Night	40% 9% 18% 19% 9% 5%	3023
	11th to 20th	Night	31% 9% 16% 20% 18% 4	3243
	21st to end	Night	27% 8% 18% 27% 16% 4	3597
September	1st to 10th	Night	27% 7% 11% 22% 23% 10%	2000
	11th to 20th	Night	23% 5% 10% 22% 25% 15%	2053
	21st to end	Night	22% 5% 8% 23% 31% 11%	2200
October	1st to 10th	Night	17% 5% 8% 19% 34% 17%	3805
	11th to 20th	Night	25% 4 8% 28% 27% 9%	3898
	21st to end	Night	17% 3 7% 27% 30% 15%	4374
November	1st to 10th	Night	17% 3 10% 24% 28% 16%	2665
	11th to 20th	Night	17% 4 7% 28% 32% 12%	2730
	21st to end	Night	23% 4 10% 22% 29% 12%	2746
December	1st to 10th	Night	16% 3 7% 32% 32% 10%	4710
	11th to 20th	Night	19% 4 6% 27% 35% 8%	5281
	21st to end	Night	24% 5% 10% 23% 26% 11%	6974

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	6% 7% 33% 35% 16% 4	300
	11th to 20th	Day	7% 12% 31% 35% 14% 2	300
	21st to end	Day	3 12% 35% 32% 15% 3	330
February	1st to 10th	Day	4 13% 46% 27% 8% 2	300
	11th to 20th	Day	4 12% 46% 28% 9% 1	300
	21st to end	Day	14% 48% 27% 8% 2	249
March	1st to 10th	Day	3 13% 37% 28% 14% 4	300
	11th to 20th	Day	9% 17% 36% 25% 10% 3	430
	21st to end	Day	9% 21% 42% 19% 7% 2	550
April	1st to 10th	Day	10% 18% 39% 21% 10% 2	500
	11th to 20th	Day	13% 21% 38% 19% 6% 3	492
	21st to end	Day	13% 18% 34% 24% 10% 1	500
May	1st to 10th	Day	14% 16% 31% 26% 10% 3	643
	11th to 20th	Day	13% 10% 30% 26% 16% 4	725
	21st to end	Day	9% 11% 31% 26% 18% 5%	789
June	1st to 10th	Day	7% 8% 23% 32% 22% 8%	730
	11th to 20th	Day	5% 8% 30% 31% 20% 5%	730
	21st to end	Day	4 6% 25% 35% 22% 7%	730
July	1st to 10th	Day	6% 3 18% 32% 30% 10%	721
	11th to 20th	Day	5% 2 14% 33% 33% 13%	718
	21st to end	Day	6% 2 14% 29% 35% 14%	758
August	1st to 10th	Day	8% 2 19% 35% 27% 9%	527
	11th to 20th	Day	4 3 21% 33% 26% 12%	517
	21st to end	Day	4 4 23% 35% 24% 9%	583
September	1st to 10th	Day	6% 3 24% 33% 24% 10%	530
	11th to 20th	Day	4 5% 28% 29% 22% 11%	476
	21st to end	Day	8% 7% 18% 31% 23% 14%	330
October	1st to 10th	Day	8% 9% 19% 28% 20% 15%	330
	11th to 20th	Day	3 12% 30% 31% 16% 9%	330
	21st to end	Day	7% 12% 29% 31% 16% 6%	363
November	1st to 10th	Day	4 10% 36% 26% 18% 7%	330
	11th to 20th	Day	5% 6% 32% 36% 17% 4	330
	21st to end	Day	4 12% 33% 32% 13% 5%	330
December	1st to 10th	Day	3 12% 37% 30% 15% 3	330
	11th to 20th	Day	3 11% 37% 34% 14% 2	321
	21st to end	Day	5% 14% 37% 33% 11% 1	330
January	1st to 10th	Night	4 6% 35% 40% 11% 3	1000
	11th to 20th	Night	3 7% 38% 39% 10% 3	975
	21st to end	Night	3 4 39% 43% 10% 1	880
February	1st to 10th	Night	4 6% 47% 38% 5% 1	800
	11th to 20th	Night	4 7% 46% 35% 8% 1	784
	21st to end	Night	5% 8% 45% 36% 6%	660
March	1st to 10th	Night	4 7% 40% 39% 8% 1	800
	11th to 20th	Night	7% 7% 35% 39% 10% 1	800
	21st to end	Night	7% 8% 44% 34% 8%	702
April	1st to 10th	Night	8% 10% 45% 31% 7%	600
	11th to 20th	Night	13% 12% 33% 34% 7% 1	593
	21st to end	Night	13% 12% 30% 36% 8% 1	600
May	1st to 10th	Night	9% 11% 33% 35% 11% 1	600
	11th to 20th	Night	11% 7% 28% 40% 13% 1	591
	21st to end	Night	11% 7% 34% 33% 14% 1	650
June	1st to 10th	Night	6% 4 26% 42% 19% 2	600
	11th to 20th	Night	4 5% 28% 47% 15% 1	600
	21st to end	Night	5% 4 23% 46% 21% 2	600
July	1st to 10th	Night	7% 3 17% 45% 27% 2	585
	11th to 20th	Night	5% 1 11% 45% 36% 3	582
	21st to end	Night	7% 3 12% 39% 37% 2	657
August	1st to 10th	Night	7% 3 13% 43% 31% 3	597
	11th to 20th	Night	6% 2 13% 51% 25% 2	594
	21st to end	Night	7% 2 13% 45% 30% 3	660
September	1st to 10th	Night	7% 3 14% 49% 25% 3	600
	11th to 20th	Night	8% 3 19% 45% 23% 3	600
	21st to end	Night	6% 5% 23% 43% 21% 3	600
October	1st to 10th	Night	8% 6% 28% 35% 19% 3	724
	11th to 20th	Night	5% 5% 32% 39% 16% 4	800
	21st to end	Night	5% 8% 29% 38% 16% 3	953
November	1st to 10th	Night	3 6% 30% 44% 16% 2	1025
	11th to 20th	Night	3 6% 35% 44% 11% 2	1050
	21st to end	Night	6% 7% 33% 38% 14% 2	1050
December	1st to 10th	Night	2 6% 38% 41% 11% 2	1050
	11th to 20th	Night	3 6% 40% 39% 11% 2	1036
	21st to end	Night	5% 8% 40% 37% 8% 1	1100

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