Windy Point Observation Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Windy Point Observation Site clear sky chart from 2005-11-06 to 2026-07-01.

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 7% 3 9% 5% 5% 5% 4 5% 6% 47%	146537
	Night	1 4 2 6% 4 4 4 4 6% 8% 58%	143371
Transparency	Day	33% 8% 10% 19% 21% 9%	141458
	Night	21% 8% 12% 24% 25% 10%	139458
Seeing	Day	18% 22% 26% 21% 11% 3	17551
	Night	7% 12% 29% 32% 18% 2	27679

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 3 13% 6% 4 4 3 6% 7% 50%	5061
	11th to 20th	Day	1 2 6% 5% 4 3 3 4 7% 63%	5340
	21st to end	Day	4 3 10% 5% 5% 4 3 4 7% 55%	5844
February	1st to 10th	Day	4 4 12% 5% 3 3 3 5% 8% 53%	1890
	11th to 20th	Day	4 5% 11% 6% 5% 4 3 6% 9% 47%	1925
	21st to end	Day	3 4 12% 5% 5% 5% 3 5% 6% 52%	1730
March	1st to 10th	Day	5% 6% 16% 6% 4 4 2 4 5% 48%	4974
	11th to 20th	Day	1 8% 8% 18% 6% 5% 5% 3 5% 6% 36%	5110
	21st to end	Day	1 11% 6% 11% 6% 6% 5% 4 5% 6% 39%	5685
April	1st to 10th	Day	2 9% 3 8% 6% 4 5% 4 5% 6% 48%	2520
	11th to 20th	Day	2 10% 5% 9% 6% 5% 5% 3 5% 8% 43%	2491
	21st to end	Day	1 10% 4 7% 5% 5% 5% 4 6% 8% 44%	2520
May	1st to 10th	Day	2 13% 4 10% 6% 5% 5% 4 5% 6% 40%	7337
	11th to 20th	Day	2 8% 3 8% 6% 5% 6% 4 7% 6% 44%	7807
	21st to end	Day	2 5% 2 7% 5% 6% 7% 5% 6% 7% 48%	9026
June	1st to 10th	Day	5% 6% 2 7% 5% 5% 5% 4 6% 7% 48%	2940
	11th to 20th	Day	5% 5% 2 6% 4 4 5% 4 5% 5% 56%	2940
	21st to end	Day	5% 5% 3 7% 5% 5% 5% 4 5% 6% 50%	2940
July	1st to 10th	Day	6% 5% 2 7% 5% 5% 5% 4 5% 5% 50%	6340
	11th to 20th	Day	6% 6% 3 9% 7% 8% 8% 6% 8% 8% 31%	5938
	21st to end	Day	9% 8% 4 11% 7% 7% 6% 5% 6% 6% 31%	6401
August	1st to 10th	Day	9% 8% 3 10% 7% 7% 6% 5% 6% 9% 31%	5779
	11th to 20th	Day	8% 8% 3 10% 6% 7% 6% 5% 6% 6% 35%	5545
	21st to end	Day	9% 10% 5% 12% 7% 7% 6% 5% 6% 7% 26%	5984
September	1st to 10th	Day	11% 8% 3 9% 6% 5% 5% 4 5% 5% 39%	2400
	11th to 20th	Day	9% 7% 4 8% 5% 5% 5% 3 4 5% 46%	2400
	21st to end	Day	8% 8% 3 7% 4 4 3 3 4 5% 52%	2119
October	1st to 10th	Day	6% 7% 3 6% 4 3 3 2 3 4 58%	3270
	11th to 20th	Day	4 11% 3 9% 5% 4 4 3 4 4 48%	3250
	21st to end	Day	2 5% 2 5% 3 2 3 2 3 5% 69%	3548
November	1st to 10th	Day	1 4 2 5% 3 3 3 2 4 6% 68%	1994
	11th to 20th	Day	4 1 4 3 3 2 3 4 7% 70%	1890
	21st to end	Day	5% 3 7% 4 3 3 2 4 6% 63%	1701
December	1st to 10th	Day	4 2 4 4 3 3 2 3 8% 68%	2700
	11th to 20th	Day	3 1 7% 3 3 3 3 4 7% 65%	3106
	21st to end	Day	4 2 9% 4 3 4 3 6% 8% 58%	4092
January	1st to 10th	Night	2 2 9% 7% 6% 6% 5% 8% 9% 45%	7904
	11th to 20th	Night	1 1 6% 5% 4 3 3 5% 6% 67%	7650
	21st to end	Night	2 2 7% 4 5% 4 3 6% 6% 60%	8370
February	1st to 10th	Night	1 2 8% 5% 4 4 3 5% 7% 60%	2730
	11th to 20th	Night	3 2 7% 4 5% 5% 5% 6% 8% 55%	2580
	21st to end	Night	3 2 7% 4 5% 5% 3 5% 7% 60%	2076
March	1st to 10th	Night	3 3 8% 6% 5% 4 3 5% 7% 57%	5122
	11th to 20th	Night	5% 4 12% 6% 6% 5% 3 5% 8% 47%	5110
	21st to end	Night	5% 3 8% 5% 5% 5% 5% 7% 8% 48%	5526
April	1st to 10th	Night	5% 2 5% 3 5% 4 4 7% 7% 58%	2100
	11th to 20th	Night	1 6% 3 6% 4 5% 5% 4 6% 8% 53%	2077
	21st to end	Night	1 5% 2 6% 4 4 4 3 6% 7% 58%	2100
May	1st to 10th	Night	1 9% 3 7% 5% 4 5% 4 6% 7% 49%	5606
	11th to 20th	Night	1 4 2 4 3 3 4 4 6% 8% 61%	5081
	21st to end	Night	1 4 1 3 2 2 2 3 4 6% 69%	5181
June	1st to 10th	Night	1 3 1 3 3 3 3 4 6% 7% 67%	1680
	11th to 20th	Night	2 3 1 2 2 2 4 3 4 6% 70%	1680
	21st to end	Night	2 3 1 4 3 4 4 4 6% 7% 62%	1680
July	1st to 10th	Night	3 3 1 4 3 3 4 4 6% 6% 63%	3640
	11th to 20th	Night	2 2 1 5% 4 4 5% 5% 8% 13% 52%	4023
	21st to end	Night	3 4 2 7% 6% 5% 6% 5% 8% 10% 44%	4472
August	1st to 10th	Night	4 4 2 5% 4 5% 5% 4 7% 12% 49%	4033
	11th to 20th	Night	3 3 1 4 3 4 5% 5% 8% 11% 53%	4304
	21st to end	Night	5% 7% 3 10% 6% 6% 6% 5% 7% 10% 36%	4993
September	1st to 10th	Night	4 4 2 6% 4 4 5% 4 6% 8% 52%	2000
	11th to 20th	Night	4 4 2 5% 3 3 4 4 6% 9% 58%	2000
	21st to end	Night	3 4 1 4 3 3 3 3 5% 7% 64%	2276
October	1st to 10th	Night	3 4 1 3 2 2 2 2 3 4 74%	3920
	11th to 20th	Night	3 6% 2 6% 4 4 3 3 4 6% 58%	3898
	21st to end	Night	1 4 1 4 2 3 2 2 4 6% 71%	4252
November	1st to 10th	Night	1 4 2 4 3 3 3 3 4 8% 65%	2502
	11th to 20th	Night	2 1 3 2 2 3 3 4 6% 72%	2730
	21st to end	Night	4 3 7% 4 3 2 3 6% 6% 61%	2916
December	1st to 10th	Night	1 1 4 4 3 3 2 3 6% 73%	4710
	11th to 20th	Night	3 1 4 3 2 3 3 5% 9% 67%	5321
	21st to end	Night	3 2 8% 5% 4 4 4 6% 8% 56%	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	27% 7% 13% 26% 20% 7%	5064
	11th to 20th	Day	19% 5% 12% 22% 25% 16%	5340
	21st to end	Day	25% 7% 8% 22% 25% 13%	5844
February	1st to 10th	Day	30% 5% 14% 21% 19% 11%	1890
	11th to 20th	Day	33% 6% 9% 20% 23% 10%	1934
	21st to end	Day	32% 4 9% 19% 22% 13%	1730
March	1st to 10th	Day	34% 7% 8% 15% 21% 15%	4974
	11th to 20th	Day	42% 8% 8% 22% 16% 4	5110
	21st to end	Day	41% 8% 11% 25% 13% 3	5685
April	1st to 10th	Day	34% 7% 11% 21% 20% 8%	2520
	11th to 20th	Day	38% 6% 10% 21% 20% 5%	2494
	21st to end	Day	35% 7% 12% 26% 17% 3	2520
May	1st to 10th	Day	37% 8% 11% 21% 17% 5%	7337
	11th to 20th	Day	31% 10% 10% 20% 23% 5%	7810
	21st to end	Day	25% 11% 11% 20% 28% 5%	9027
June	1st to 10th	Day	30% 8% 11% 23% 20% 9%	2940
	11th to 20th	Day	27% 6% 8% 16% 26% 16%	2940
	21st to end	Day	32% 7% 7% 15% 22% 17%	2940
July	1st to 10th	Day	31% 7% 8% 10% 15% 30%	6272
	11th to 20th	Day	41% 13% 14% 15% 11% 6%	5867
	21st to end	Day	44% 13% 12% 12% 13% 7%	6217
August	1st to 10th	Day	54% 10% 14% 9% 9% 3	4208
	11th to 20th	Day	47% 10% 11% 11% 16% 5%	4016
	21st to end	Day	50% 10% 10% 12% 14% 4	4311
September	1st to 10th	Day	44% 7% 10% 12% 19% 8%	2400
	11th to 20th	Day	38% 7% 8% 15% 23% 9%	2400
	21st to end	Day	34% 5% 7% 19% 28% 8%	2119
October	1st to 10th	Day	29% 5% 5% 17% 33% 11%	3270
	11th to 20th	Day	34% 7% 7% 19% 25% 8%	3250
	21st to end	Day	20% 3 6% 22% 39% 10%	3548
November	1st to 10th	Day	18% 4 10% 25% 32% 11%	1994
	11th to 20th	Day	16% 4 9% 30% 30% 10%	1890
	21st to end	Day	23% 5% 9% 25% 26% 14%	1701
December	1st to 10th	Day	16% 5% 11% 29% 29% 10%	2700
	11th to 20th	Day	19% 6% 12% 28% 28% 7%	3104
	21st to end	Day	22% 6% 11% 22% 25% 14%	4092
January	1st to 10th	Night	25% 10% 12% 26% 21% 6%	7905
	11th to 20th	Night	12% 6% 15% 25% 23% 19%	7650
	21st to end	Night	19% 7% 9% 22% 28% 16%	8370
February	1st to 10th	Night	23% 5% 15% 22% 24% 11%	2730
	11th to 20th	Night	23% 8% 12% 24% 25% 9%	2581
	21st to end	Night	22% 7% 9% 22% 28% 12%	2076
March	1st to 10th	Night	22% 6% 10% 18% 34% 10%	5122
	11th to 20th	Night	28% 10% 11% 21% 22% 7%	5110
	21st to end	Night	27% 10% 14% 33% 13% 2	5526
April	1st to 10th	Night	21% 8% 15% 26% 23% 7%	2100
	11th to 20th	Night	26% 8% 12% 26% 24% 5%	2077
	21st to end	Night	22% 8% 13% 33% 22% 3	2100
May	1st to 10th	Night	27% 9% 13% 25% 23% 3	5604
	11th to 20th	Night	17% 7% 11% 32% 31% 2	5082
	21st to end	Night	14% 5% 11% 27% 35% 7%	5182
June	1st to 10th	Night	15% 5% 12% 30% 29% 8%	1680
	11th to 20th	Night	15% 4 9% 19% 34% 19%	1680
	21st to end	Night	19% 5% 10% 20% 26% 19%	1680
July	1st to 10th	Night	19% 7% 11% 12% 17% 35%	3600
	11th to 20th	Night	19% 10% 21% 29% 14% 7%	3971
	21st to end	Night	29% 13% 20% 17% 13% 7%	4344
August	1st to 10th	Night	33% 14% 23% 12% 12% 5%	2928
	11th to 20th	Night	23% 12% 25% 12% 21% 7%	3109
	21st to end	Night	37% 10% 15% 16% 17% 5%	3597
September	1st to 10th	Night	27% 9% 16% 19% 23% 7%	2000
	11th to 20th	Night	22% 8% 12% 21% 28% 9%	2000
	21st to end	Night	19% 5% 8% 29% 31% 6%	2276
October	1st to 10th	Night	16% 3 8% 20% 39% 14%	3920
	11th to 20th	Night	21% 9% 8% 29% 26% 7%	3898
	21st to end	Night	15% 5% 6% 22% 40% 12%	4252
November	1st to 10th	Night	18% 5% 12% 25% 31% 10%	2502
	11th to 20th	Night	12% 6% 9% 32% 31% 11%	2730
	21st to end	Night	22% 5% 9% 24% 27% 12%	2916
December	1st to 10th	Night	13% 4 11% 30% 32% 10%	4710
	11th to 20th	Night	14% 7% 10% 28% 32% 10%	5322
	21st to end	Night	22% 8% 12% 21% 24% 12%	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	18% 21% 32% 20% 8% 1	330
	11th to 20th	Day	22% 25% 23% 25% 5%	330
	21st to end	Day	13% 24% 31% 24% 7% 1	363
February	1st to 10th	Day	21% 32% 29% 15% 3 1	330
	11th to 20th	Day	25% 33% 24% 13% 4	330
	21st to end	Day	26% 32% 22% 16% 4	273
March	1st to 10th	Day	25% 30% 24% 17% 4 1	498
	11th to 20th	Day	24% 29% 26% 15% 5% 1	540
	21st to end	Day	27% 32% 25% 13% 3	594
April	1st to 10th	Day	24% 28% 29% 14% 4 1	540
	11th to 20th	Day	30% 34% 24% 7% 3 1	532
	21st to end	Day	24% 33% 25% 13% 4 1	540
May	1st to 10th	Day	22% 33% 30% 10% 5%	543
	11th to 20th	Day	18% 29% 29% 16% 7% 2	636
	21st to end	Day	19% 24% 24% 19% 11% 2	844
June	1st to 10th	Day	11% 17% 26% 26% 16% 4	780
	11th to 20th	Day	11% 19% 30% 23% 13% 3	780
	21st to end	Day	9% 19% 26% 23% 18% 5%	780
July	1st to 10th	Day	9% 9% 23% 30% 23% 6%	722
	11th to 20th	Day	12% 7% 20% 32% 22% 7%	554
	21st to end	Day	18% 8% 20% 29% 19% 6%	575
August	1st to 10th	Day	19% 13% 21% 24% 17% 6%	527
	11th to 20th	Day	12% 12% 23% 31% 16% 7%	517
	21st to end	Day	14% 11% 28% 25% 18% 4	583
September	1st to 10th	Day	14% 14% 23% 26% 16% 7%	530
	11th to 20th	Day	15% 20% 30% 22% 11% 3	530
	21st to end	Day	19% 18% 23% 19% 14% 7%	414
October	1st to 10th	Day	19% 18% 22% 18% 16% 6%	330
	11th to 20th	Day	19% 24% 25% 18% 12% 2	330
	21st to end	Day	17% 22% 25% 23% 12% 1	363
November	1st to 10th	Day	19% 24% 25% 21% 9% 2	330
	11th to 20th	Day	13% 25% 28% 23% 9% 2	330
	21st to end	Day	16% 23% 28% 20% 12% 2	330
December	1st to 10th	Day	16% 24% 30% 17% 11% 2	330
	11th to 20th	Day	18% 25% 27% 22% 7% 2	330
	21st to end	Day	23% 23% 29% 20% 3 2	363
January	1st to 10th	Night	6% 15% 34% 30% 12% 2	948
	11th to 20th	Night	8% 15% 34% 29% 13% 1	840
	21st to end	Night	5% 12% 38% 34% 8% 3	924
February	1st to 10th	Night	7% 16% 40% 30% 7% 1	840
	11th to 20th	Night	7% 16% 44% 25% 7%	824
	21st to end	Night	9% 14% 45% 28% 4	692
March	1st to 10th	Night	9% 19% 33% 30% 9% 1	840
	11th to 20th	Night	7% 15% 35% 29% 14% 1	840
	21st to end	Night	8% 15% 38% 32% 7%	891
April	1st to 10th	Night	9% 20% 35% 30% 7%	630
	11th to 20th	Night	10% 20% 34% 27% 8%	623
	21st to end	Night	5% 20% 34% 30% 10% 1	630
May	1st to 10th	Night	8% 13% 34% 33% 12%	630
	11th to 20th	Night	6% 12% 27% 35% 17% 3	621
	21st to end	Night	10% 13% 27% 29% 19% 2	683
June	1st to 10th	Night	3 9% 21% 40% 25% 1	630
	11th to 20th	Night	7% 9% 23% 41% 18% 2	630
	21st to end	Night	3 6% 20% 38% 29% 3	630
July	1st to 10th	Night	5% 2 12% 37% 40% 3	585
	11th to 20th	Night	4 1 9% 32% 46% 8%	582
	21st to end	Night	7% 1 5% 33% 47% 7%	657
August	1st to 10th	Night	8% 2 9% 31% 45% 6%	597
	11th to 20th	Night	7% 2 8% 34% 44% 5%	594
	21st to end	Night	7% 5% 9% 34% 39% 6%	660
September	1st to 10th	Night	5% 3 13% 38% 37% 4	600
	11th to 20th	Night	5% 6% 20% 36% 29% 4	600
	21st to end	Night	7% 8% 17% 32% 29% 7%	761
October	1st to 10th	Night	9% 12% 24% 34% 20% 2	800
	11th to 20th	Night	8% 12% 29% 31% 17% 3	800
	21st to end	Night	8% 11% 25% 35% 17% 4	880
November	1st to 10th	Night	7% 13% 30% 31% 17% 2	862
	11th to 20th	Night	7% 13% 35% 33% 11% 2	1050
	21st to end	Night	9% 14% 29% 32% 12% 2	1050
December	1st to 10th	Night	6% 14% 39% 30% 10% 1	1050
	11th to 20th	Night	8% 18% 36% 27% 10% 1	1050
	21st to end	Night	9% 15% 40% 29% 6% 1	1155

Page generated at 2026-06-28 00:10:48. Version ac07

Copyright © 2026 Attilla Danko.