Wray
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wray clear sky chart from 2005-11-06 to 2025-10-04.

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	7% 5% 2 4 3 3 3 3 5% 7% 57%	134918
	Night	7% 6% 2 5% 4 4 4 4 5% 7% 53%	131873
Transparency	Day	26% 5% 12% 26% 24% 8%	129843
	Night	30% 5% 12% 25% 22% 7%	127969
Seeing	Day	10% 7% 28% 32% 19% 5%	16961
	Night	9% 7% 34% 39% 10% 1	26825

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	8% 9% 3 5% 3 2 2 2 4 6% 55%	3638
	11th to 20th	Day	3 8% 3 7% 4 3 4 3 5% 6% 53%	3640
	21st to end	Day	3 6% 2 6% 4 3 3 3 4 7% 59%	4157
February	1st to 10th	Day	5% 8% 3 7% 5% 5% 5% 4 5% 6% 48%	1972
	11th to 20th	Day	4 9% 3 7% 4 4 4 4 4 7% 50%	1949
	21st to end	Day	4 8% 3 5% 3 3 3 2 4 6% 59%	1650
March	1st to 10th	Day	8% 7% 2 3 3 3 3 2 4 6% 59%	4500
	11th to 20th	Day	7% 5% 1 4 2 3 4 2 5% 6% 61%	4706
	21st to end	Day	6% 6% 1 4 3 3 4 4 6% 8% 55%	5867
April	1st to 10th	Day	8% 6% 2 4 3 3 3 3 5% 8% 54%	2400
	11th to 20th	Day	12% 5% 2 5% 3 4 3 3 5% 8% 49%	2371
	21st to end	Day	11% 7% 2 4 4 4 4 4 6% 7% 47%	2515
May	1st to 10th	Day	7% 5% 2 6% 4 4 5% 4 6% 6% 52%	5900
	11th to 20th	Day	8% 3 1 4 3 4 4 3 6% 9% 55%	5862
	21st to end	Day	15% 6% 2 5% 3 3 3 3 5% 7% 49%	6839
June	1st to 10th	Day	6% 3 1 4 3 3 3 5% 7% 9% 57%	2800
	11th to 20th	Day	7% 3 2 4 3 4 3 4 6% 7% 59%	2800
	21st to end	Day	4 2 1 3 3 3 5% 5% 7% 8% 59%	2800
July	1st to 10th	Day	5% 3 1 4 4 4 4 3 6% 7% 59%	6339
	11th to 20th	Day	5% 3 1 3 2 3 4 4 6% 10% 58%	6340
	21st to end	Day	5% 3 1 4 3 4 4 4 7% 9% 56%	6903
August	1st to 10th	Day	10% 4 2 3 3 3 4 3 6% 9% 52%	5828
	11th to 20th	Day	5% 4 2 4 3 4 4 4 5% 8% 58%	5376
	21st to end	Day	10% 6% 2 5% 3 3 3 3 5% 7% 53%	5984
September	1st to 10th	Day	5% 4 1 4 2 3 3 3 4 7% 64%	2400
	11th to 20th	Day	6% 4 1 3 3 3 3 3 4 7% 62%	2240
	21st to end	Day	9% 3 1 3 2 2 2 3 4 6% 65%	2200
October	1st to 10th	Day	7% 2 1 2 2 1 2 2 2 4 76%	3513
	11th to 20th	Day	7% 4 1 2 2 2 3 2 4 6% 66%	3160
	21st to end	Day	7% 4 1 3 2 2 2 2 4 7% 65%	3091
November	1st to 10th	Day	4 4 1 5% 3 2 3 3 5% 7% 63%	1763
	11th to 20th	Day	5% 5% 1 3 3 3 2 2 3 5% 66%	1800
	21st to end	Day	5% 7% 2 4 3 3 3 2 4 6% 61%	1800
December	1st to 10th	Day	2 4 2 4 2 2 2 2 4 6% 67%	2785
	11th to 20th	Day	3 5% 1 3 3 3 2 3 4 7% 65%	3026
	21st to end	Day	10% 8% 3 6% 4 3 3 4 5% 6% 50%	4004
January	1st to 10th	Night	4 9% 3 7% 3 3 3 3 4 6% 53%	6327
	11th to 20th	Night	2 5% 2 7% 6% 4 5% 3 5% 7% 52%	6340
	21st to end	Night	3 6% 3 6% 4 4 4 3 5% 5% 57%	6864
February	1st to 10th	Night	7% 9% 3 9% 3 4 3 3 4 5% 48%	2425
	11th to 20th	Night	4 9% 3 7% 6% 4 4 4 6% 7% 47%	2338
	21st to end	Night	4 7% 2 6% 4 4 4 3 5% 6% 54%	1980
March	1st to 10th	Night	7% 8% 2 4 3 3 3 3 4 5% 59%	5374
	11th to 20th	Night	8% 7% 2 4 3 3 3 3 5% 6% 56%	5266
	21st to end	Night	9% 8% 2 6% 4 4 5% 4 6% 9% 42%	5079
April	1st to 10th	Night	9% 8% 2 5% 4 3 3 3 5% 7% 50%	2000
	11th to 20th	Night	13% 6% 2 4 4 4 4 3 5% 6% 48%	1977
	21st to end	Night	15% 6% 2 5% 3 4 4 4 4 8% 44%	1884
May	1st to 10th	Night	12% 7% 2 7% 4 4 5% 4 5% 7% 43%	4080
	11th to 20th	Night	9% 5% 2 5% 4 4 5% 4 6% 8% 51%	4053
	21st to end	Night	16% 9% 2 5% 4 4 4 4 6% 7% 40%	4041
June	1st to 10th	Night	7% 4 1 5% 5% 4 4 5% 6% 10% 50%	1600
	11th to 20th	Night	7% 4 2 4 4 4 4 4 6% 8% 52%	1600
	21st to end	Night	3 4 1 5% 5% 6% 7% 5% 7% 9% 48%	1600
July	1st to 10th	Night	5% 4 2 6% 4 5% 5% 4 7% 9% 49%	3640
	11th to 20th	Night	8% 5% 2 5% 4 3 5% 4 7% 10% 47%	3640
	21st to end	Night	4 4 1 6% 5% 5% 5% 5% 7% 9% 47%	3970
August	1st to 10th	Night	9% 6% 3 8% 5% 6% 6% 5% 7% 9% 37%	3984
	11th to 20th	Night	7% 5% 2 7% 5% 5% 6% 5% 7% 9% 41%	4456
	21st to end	Night	11% 7% 2 6% 4 4 5% 4 5% 7% 45%	4993
September	1st to 10th	Night	5% 4 2 4 4 4 4 4 5% 8% 57%	2000
	11th to 20th	Night	7% 3 2 4 3 3 4 4 5% 7% 59%	2160
	21st to end	Night	7% 3 1 4 2 3 3 3 4 6% 63%	2200
October	1st to 10th	Night	6% 2 1 2 2 2 2 2 3 5% 72%	3513
	11th to 20th	Night	9% 4 1 3 2 3 3 2 4 6% 63%	3732
	21st to end	Night	5% 5% 2 4 3 3 3 3 3 5% 63%	4467
November	1st to 10th	Night	5% 4 1 4 2 3 4 3 4 7% 62%	2535
	11th to 20th	Night	5% 5% 2 4 3 3 3 3 5% 6% 62%	2600
	21st to end	Night	5% 6% 1 5% 3 3 3 3 4 7% 60%	2600
December	1st to 10th	Night	3 4 1 5% 3 3 3 3 4 5% 67%	4400
	11th to 20th	Night	3 4 2 4 3 3 3 3 5% 8% 61%	5181
	21st to end	Night	8% 9% 3 6% 4 4 4 3 5% 7% 46%	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	32% 3 10% 31% 17% 6%	3639
	11th to 20th	Day	32% 3 12% 22% 25% 5%	3640
	21st to end	Day	26% 4 12% 27% 23% 7%	4157
February	1st to 10th	Day	37% 5% 12% 24% 17% 6%	1972
	11th to 20th	Day	34% 5% 10% 25% 21% 5%	1959
	21st to end	Day	27% 4 9% 23% 26% 11%	1650
March	1st to 10th	Day	28% 3 7% 20% 31% 11%	4500
	11th to 20th	Day	25% 3 10% 23% 34% 6%	4706
	21st to end	Day	25% 5% 16% 36% 16% 2	5867
April	1st to 10th	Day	28% 5% 13% 26% 23% 6%	2400
	11th to 20th	Day	33% 5% 14% 22% 19% 6%	2374
	21st to end	Day	33% 6% 12% 28% 18% 3	2515
May	1st to 10th	Day	29% 7% 13% 27% 18% 6%	5900
	11th to 20th	Day	24% 6% 13% 26% 22% 8%	5866
	21st to end	Day	34% 6% 14% 25% 18% 3	6840
June	1st to 10th	Day	21% 8% 18% 32% 17% 4	2800
	11th to 20th	Day	23% 6% 12% 26% 23% 10%	2800
	21st to end	Day	20% 7% 11% 26% 27% 10%	2800
July	1st to 10th	Day	24% 5% 9% 23% 30% 10%	6271
	11th to 20th	Day	20% 5% 17% 30% 21% 7%	6265
	21st to end	Day	23% 6% 15% 22% 22% 13%	6705
August	1st to 10th	Day	30% 7% 14% 28% 15% 5%	4234
	11th to 20th	Day	28% 5% 14% 21% 27% 5%	3892
	21st to end	Day	21% 5% 16% 24% 21% 14%	4311
September	1st to 10th	Day	21% 4 8% 27% 27% 14%	2400
	11th to 20th	Day	21% 5% 8% 24% 30% 11%	2240
	21st to end	Day	22% 3 6% 24% 34% 11%	2200
October	1st to 10th	Day	16% 2 5% 18% 34% 25%	3513
	11th to 20th	Day	20% 3 8% 32% 26% 9%	3160
	21st to end	Day	22% 2 9% 27% 31% 10%	3091
November	1st to 10th	Day	22% 4 13% 26% 26% 10%	1763
	11th to 20th	Day	22% 3 8% 28% 30% 9%	1800
	21st to end	Day	26% 2 9% 26% 29% 8%	1800
December	1st to 10th	Day	20% 3 12% 30% 30% 6%	2785
	11th to 20th	Day	20% 3 8% 41% 25% 3	3024
	21st to end	Day	35% 3 10% 28% 19% 4	4004
January	1st to 10th	Night	32% 3 13% 29% 19% 4	6327
	11th to 20th	Night	31% 5% 11% 23% 24% 7%	6340
	21st to end	Night	29% 4 9% 28% 22% 8%	6864
February	1st to 10th	Night	38% 5% 12% 21% 19% 6%	2425
	11th to 20th	Night	36% 5% 12% 27% 17% 4	2338
	21st to end	Night	30% 4 9% 24% 25% 9%	1980
March	1st to 10th	Night	27% 3 7% 19% 31% 12%	5374
	11th to 20th	Night	30% 3 9% 16% 30% 12%	5266
	21st to end	Night	36% 7% 16% 28% 11% 1	5079
April	1st to 10th	Night	32% 6% 12% 24% 19% 6%	2000
	11th to 20th	Night	36% 5% 13% 23% 19% 4	1977
	21st to end	Night	37% 6% 12% 25% 18% 2	1884
May	1st to 10th	Night	37% 7% 15% 26% 12% 3	4080
	11th to 20th	Night	29% 7% 16% 25% 19% 4	4054
	21st to end	Night	41% 8% 15% 21% 12% 2	4042
June	1st to 10th	Night	28% 9% 23% 24% 13% 4	1600
	11th to 20th	Night	28% 8% 15% 22% 20% 8%	1600
	21st to end	Night	28% 10% 13% 23% 19% 8%	1600
July	1st to 10th	Night	29% 6% 13% 28% 22% 2	3600
	11th to 20th	Night	32% 6% 18% 20% 20% 4	3592
	21st to end	Night	31% 7% 15% 21% 16% 9%	3856
August	1st to 10th	Night	37% 9% 15% 22% 14% 3	2902
	11th to 20th	Night	40% 7% 13% 21% 15% 4	3229
	21st to end	Night	28% 6% 13% 27% 17% 10%	3597
September	1st to 10th	Night	25% 6% 10% 24% 23% 13%	2000
	11th to 20th	Night	23% 7% 10% 24% 24% 12%	2160
	21st to end	Night	23% 4 8% 24% 30% 11%	2200
October	1st to 10th	Night	17% 4 7% 17% 35% 21%	3513
	11th to 20th	Night	23% 3 7% 27% 28% 11%	3732
	21st to end	Night	25% 3 10% 24% 29% 9%	4467
November	1st to 10th	Night	21% 4 9% 27% 27% 11%	2535
	11th to 20th	Night	22% 4 9% 26% 29% 10%	2600
	21st to end	Night	26% 3 9% 25% 27% 9%	2600
December	1st to 10th	Night	21% 3 10% 34% 26% 7%	4400
	11th to 20th	Night	22% 3 8% 36% 27% 4	5182
	21st to end	Night	37% 4 10% 28% 20% 2	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	10% 7% 34% 34% 14% 2	300
	11th to 20th	Day	15% 7% 38% 31% 7% 2	300
	21st to end	Day	8% 8% 47% 27% 8% 3	330
February	1st to 10th	Day	12% 10% 47% 26% 3 2	300
	11th to 20th	Day	9% 10% 44% 26% 9% 3	300
	21st to end	Day	8% 13% 45% 25% 9% 1	249
March	1st to 10th	Day	11% 8% 32% 31% 16% 3	300
	11th to 20th	Day	13% 8% 33% 28% 17% 2	300
	21st to end	Day	13% 13% 35% 27% 11% 1	500
April	1st to 10th	Day	12% 16% 35% 24% 9% 3	500
	11th to 20th	Day	17% 14% 33% 25% 9% 1	492
	21st to end	Day	17% 12% 33% 26% 11% 2	615
May	1st to 10th	Day	13% 10% 29% 31% 14% 3	703
	11th to 20th	Day	15% 7% 27% 31% 16% 4	725
	21st to end	Day	13% 9% 28% 28% 18% 4	789
June	1st to 10th	Day	7% 5% 22% 30% 26% 9%	730
	11th to 20th	Day	7% 6% 27% 37% 20% 2	730
	21st to end	Day	7% 4 25% 38% 22% 6%	730
July	1st to 10th	Day	8% 3 20% 37% 26% 6%	721
	11th to 20th	Day	4 2 16% 38% 32% 8%	718
	21st to end	Day	6% 2 14% 37% 33% 9%	794
August	1st to 10th	Day	8% 2 15% 36% 31% 7%	726
	11th to 20th	Day	5% 2 22% 39% 23% 8%	527
	21st to end	Day	5% 2 18% 41% 27% 7%	583
September	1st to 10th	Day	5% 3 21% 36% 25% 9%	530
	11th to 20th	Day	4 3 19% 38% 24% 12%	370
	21st to end	Day	13% 3 18% 28% 26% 11%	330
October	1st to 10th	Day	14% 4 20% 28% 23% 12%	309
	11th to 20th	Day	7% 8% 33% 28% 19% 5%	300
	21st to end	Day	14% 7% 33% 25% 15% 5%	330
November	1st to 10th	Day	7% 8% 34% 31% 16% 4	300
	11th to 20th	Day	9% 7% 34% 33% 15% 2	300
	21st to end	Day	11% 8% 27% 40% 12% 3	300
December	1st to 10th	Day	5% 10% 37% 35% 11% 2	300
	11th to 20th	Day	12% 10% 36% 28% 13%	300
	21st to end	Day	17% 9% 37% 27% 8% 2	330
January	1st to 10th	Night	7% 9% 37% 34% 12% 1	1000
	11th to 20th	Night	8% 10% 37% 37% 7% 1	1000
	21st to end	Night	8% 7% 42% 35% 8%	1055
February	1st to 10th	Night	11% 9% 42% 33% 5%	800
	11th to 20th	Night	8% 7% 45% 34% 6% 1	784
	21st to end	Night	7% 8% 46% 34% 4	660
March	1st to 10th	Night	9% 9% 38% 37% 7%	800
	11th to 20th	Night	14% 7% 39% 33% 7% 1	730
	21st to end	Night	14% 9% 35% 36% 6%	660
April	1st to 10th	Night	13% 11% 41% 32% 4	600
	11th to 20th	Night	16% 7% 43% 31% 3	593
	21st to end	Night	18% 9% 31% 34% 7% 1	600
May	1st to 10th	Night	14% 7% 33% 38% 8%	600
	11th to 20th	Night	16% 6% 29% 38% 10% 1	591
	21st to end	Night	16% 7% 36% 31% 11%	650
June	1st to 10th	Night	8% 6% 30% 39% 15% 1	600
	11th to 20th	Night	9% 5% 39% 39% 8%	600
	21st to end	Night	4 4 30% 48% 14%	600
July	1st to 10th	Night	9% 3 25% 50% 14%	585
	11th to 20th	Night	6% 2 21% 54% 17% 1	582
	21st to end	Night	6% 1 19% 51% 23%	657
August	1st to 10th	Night	8% 2 20% 50% 20% 1	597
	11th to 20th	Night	6% 3 24% 51% 15%	594
	21st to end	Night	6% 2 22% 53% 16% 1	660
September	1st to 10th	Night	7% 2 26% 51% 13% 1	600
	11th to 20th	Night	9% 4 29% 44% 15% 1	600
	21st to end	Night	10% 4 28% 43% 16%	600
October	1st to 10th	Night	12% 8% 25% 39% 15% 1	579
	11th to 20th	Night	11% 6% 29% 38% 14% 1	728
	21st to end	Night	10% 8% 32% 36% 13% 1	1045
November	1st to 10th	Night	7% 6% 31% 44% 11% 1	975
	11th to 20th	Night	8% 7% 36% 39% 10%	1000
	21st to end	Night	8% 5% 35% 39% 12% 1	1000
December	1st to 10th	Night	8% 6% 41% 37% 8%	1000
	11th to 20th	Night	7% 9% 37% 39% 8% 1	1000
	21st to end	Night	11% 10% 38% 36% 5%	1100

Page generated at 2025-09-30 23:39:06. Version ac07

Copyright © 2025 Attilla Danko.