Webster State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Webster State Park clear sky chart from 2005-11-06 to 2026-03-03.

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	9% 5% 2 5% 3 3 3 3 5% 7% 55%	140128
	Night	8% 5% 2 5% 3 3 4 3 5% 7% 54%	138367
Transparency	Day	29% 4 12% 27% 22% 6%	134942
	Night	29% 4 12% 26% 23% 6%	134563
Seeing	Day	11% 8% 30% 32% 16% 3	17396
	Night	10% 8% 34% 37% 10%	27458

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	9% 9% 2 6% 3 3 3 3 5% 7% 50%	4720
	11th to 20th	Day	5% 8% 3 8% 5% 4 4 3 4 5% 51%	5119
	21st to end	Day	6% 10% 3 7% 4 3 3 2 4 5% 54%	5812
February	1st to 10th	Day	8% 10% 3 7% 5% 3 4 3 5% 7% 46%	1995
	11th to 20th	Day	6% 7% 2 7% 6% 4 5% 3 5% 7% 48%	2049
	21st to end	Day	6% 5% 1 6% 4 3 3 3 5% 6% 58%	1730
March	1st to 10th	Day	8% 7% 2 4 3 2 2 2 3 5% 60%	4556
	11th to 20th	Day	8% 6% 2 5% 3 3 3 2 4 5% 60%	4980
	21st to end	Day	9% 6% 2 4 3 3 4 3 5% 7% 54%	5464
April	1st to 10th	Day	10% 6% 1 4 3 3 4 4 5% 7% 54%	2342
	11th to 20th	Day	10% 6% 2 6% 4 4 3 4 5% 7% 49%	2429
	21st to end	Day	16% 6% 2 4 3 3 4 3 4 7% 47%	2600
May	1st to 10th	Day	11% 5% 2 4 4 3 4 3 6% 7% 52%	5900
	11th to 20th	Day	10% 4 1 3 3 3 3 3 5% 6% 58%	5862
	21st to end	Day	20% 5% 2 5% 3 3 4 3 6% 7% 42%	6446
June	1st to 10th	Day	6% 3 1 4 3 3 3 3 6% 7% 61%	2615
	11th to 20th	Day	7% 4 2 3 3 4 4 4 6% 7% 57%	2800
	21st to end	Day	5% 3 1 4 3 3 4 4 7% 6% 60%	2800
July	1st to 10th	Day	6% 4 2 5% 4 4 5% 4 6% 8% 54%	6339
	11th to 20th	Day	6% 3 2 4 4 3 4 4 7% 9% 55%	6149
	21st to end	Day	6% 4 1 4 3 4 4 4 7% 9% 55%	6424
August	1st to 10th	Day	11% 5% 2 6% 3 3 4 3 5% 8% 49%	5801
	11th to 20th	Day	8% 4 1 5% 3 4 4 4 6% 9% 52%	5821
	21st to end	Day	14% 5% 1 5% 3 3 4 3 5% 6% 50%	6035
September	1st to 10th	Day	11% 4 1 4 3 3 3 3 4 6% 59%	2297
	11th to 20th	Day	9% 4 1 4 4 4 3 2 5% 6% 58%	2200
	21st to end	Day	8% 4 1 5% 3 3 3 3 4 6% 62%	2200
October	1st to 10th	Day	10% 2 1 2 1 1 2 1 3 5% 71%	3590
	11th to 20th	Day	6% 3 1 3 3 3 4 3 4 7% 65%	3282
	21st to end	Day	9% 4 1 4 2 2 2 3 4 6% 63%	3288
November	1st to 10th	Day	8% 4 1 3 3 3 4 4 4 6% 62%	1853
	11th to 20th	Day	7% 4 1 4 2 3 3 3 4 5% 64%	1890
	21st to end	Day	10% 6% 2 4 2 3 2 3 4 6% 58%	1890
December	1st to 10th	Day	4 5% 2 4 2 2 3 3 5% 6% 64%	3030
	11th to 20th	Day	5% 5% 2 4 2 3 3 3 4 6% 63%	3481
	21st to end	Day	11% 12% 4 9% 3 3 4 3 4 6% 41%	4339
January	1st to 10th	Night	7% 8% 4 10% 4 3 3 3 5% 6% 47%	8201
	11th to 20th	Night	4 6% 2 6% 4 4 3 3 4 6% 58%	7838
	21st to end	Night	7% 10% 3 7% 4 4 4 3 4 5% 50%	8402
February	1st to 10th	Night	7% 8% 3 6% 5% 4 4 3 5% 6% 48%	2641
	11th to 20th	Night	6% 7% 3 6% 5% 4 4 4 6% 7% 48%	2458
	21st to end	Night	6% 5% 2 7% 4 3 3 3 4 5% 59%	2076
March	1st to 10th	Night	8% 5% 1 4 2 2 2 2 4 5% 64%	5357
	11th to 20th	Night	8% 4 2 4 3 4 3 3 6% 7% 58%	4980
	21st to end	Night	9% 6% 1 6% 4 5% 5% 4 7% 8% 46%	5467
April	1st to 10th	Night	9% 6% 2 5% 3 3 4 4 6% 7% 52%	2055
	11th to 20th	Night	12% 5% 2 5% 4 3 3 4 6% 8% 48%	1918
	21st to end	Night	16% 4 2 5% 4 3 4 3 5% 7% 49%	1800
May	1st to 10th	Night	15% 5% 2 5% 3 4 4 4 5% 6% 47%	4080
	11th to 20th	Night	8% 5% 1 4 3 4 4 3 5% 7% 56%	4053
	21st to end	Night	19% 5% 2 5% 3 3 4 3 6% 8% 41%	4451
June	1st to 10th	Night	6% 3 1 4 3 3 4 4 6% 10% 56%	1779
	11th to 20th	Night	7% 2 1 4 3 4 5% 3 6% 9% 55%	1600
	21st to end	Night	5% 3 1 5% 4 3 5% 5% 8% 8% 54%	1600
July	1st to 10th	Night	7% 4 1 4 4 4 4 4 6% 9% 53%	3640
	11th to 20th	Night	7% 5% 2 5% 4 5% 5% 4 7% 10% 45%	3815
	21st to end	Night	6% 4 1 4 4 3 4 4 7% 9% 55%	4449
August	1st to 10th	Night	6% 4 2 5% 3 4 4 4 8% 11% 47%	4011
	11th to 20th	Night	7% 5% 1 4 3 4 5% 4 6% 9% 52%	4028
	21st to end	Night	9% 6% 2 6% 4 5% 4 4 7% 8% 45%	4937
September	1st to 10th	Night	7% 3 1 3 3 3 3 3 5% 7% 63%	2102
	11th to 20th	Night	8% 3 2 4 3 3 4 4 4 6% 60%	2200
	21st to end	Night	8% 4 1 4 3 2 3 2 4 6% 63%	2200
October	1st to 10th	Night	6% 2 1 2 2 2 2 2 3 3 73%	3590
	11th to 20th	Night	6% 2 1 3 2 2 3 2 4 6% 68%	3823
	21st to end	Night	7% 3 1 3 2 2 2 2 4 7% 66%	4507
November	1st to 10th	Night	6% 3 1 3 3 3 2 2 4 6% 66%	2665
	11th to 20th	Night	7% 4 1 3 3 2 3 3 4 5% 65%	2730
	21st to end	Night	9% 6% 1 4 3 2 3 2 4 6% 60%	2730
December	1st to 10th	Night	3 5% 1 4 3 3 2 2 4 5% 67%	4380
	11th to 20th	Night	5% 4 1 4 3 3 3 3 5% 7% 62%	4946
	21st to end	Night	11% 12% 3 6% 4 4 3 3 4 6% 44%	6858

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	35% 3 11% 28% 21% 2	4723
	11th to 20th	Day	35% 4 9% 28% 20% 4	5119
	21st to end	Day	35% 2 13% 25% 22% 3	5812
February	1st to 10th	Day	37% 5% 14% 24% 14% 4	1995
	11th to 20th	Day	35% 4 15% 25% 16% 5%	2059
	21st to end	Day	27% 4 11% 26% 24% 8%	1730
March	1st to 10th	Day	29% 3 6% 20% 29% 13%	4556
	11th to 20th	Day	27% 4 7% 22% 27% 14%	4980
	21st to end	Day	29% 6% 18% 35% 12% 1	5464
April	1st to 10th	Day	29% 5% 12% 28% 22% 5%	2342
	11th to 20th	Day	34% 5% 13% 25% 18% 5%	2432
	21st to end	Day	38% 5% 11% 27% 17% 2	2600
May	1st to 10th	Day	31% 6% 12% 28% 17% 6%	5900
	11th to 20th	Day	26% 6% 11% 23% 23% 10%	5866
	21st to end	Day	39% 7% 12% 22% 17% 2	6447
June	1st to 10th	Day	21% 7% 19% 34% 16% 4	2615
	11th to 20th	Day	25% 6% 13% 28% 21% 7%	2800
	21st to end	Day	21% 7% 11% 28% 26% 7%	2800
July	1st to 10th	Day	28% 5% 9% 27% 25% 6%	6271
	11th to 20th	Day	25% 4 17% 27% 23% 4	6074
	21st to end	Day	25% 5% 13% 26% 23% 7%	6240
August	1st to 10th	Day	34% 4 13% 27% 19% 3	4220
	11th to 20th	Day	33% 5% 17% 23% 19% 3	4210
	21st to end	Day	23% 4 12% 27% 24% 9%	4349
September	1st to 10th	Day	28% 4 9% 26% 24% 9%	2297
	11th to 20th	Day	27% 4 9% 27% 26% 6%	2200
	21st to end	Day	26% 3 9% 29% 27% 6%	2200
October	1st to 10th	Day	20% 2 5% 21% 41% 11%	3590
	11th to 20th	Day	22% 3 10% 36% 20% 9%	3282
	21st to end	Day	24% 2 7% 28% 33% 6%	3288
November	1st to 10th	Day	24% 4 10% 29% 27% 6%	1853
	11th to 20th	Day	24% 2 9% 29% 31% 5%	1890
	21st to end	Day	29% 3 11% 27% 26% 5%	1890
December	1st to 10th	Day	22% 3 12% 35% 22% 6%	3030
	11th to 20th	Day	24% 2 12% 41% 19% 2	3479
	21st to end	Day	45% 4 9% 24% 16% 2	4339
January	1st to 10th	Night	39% 3 12% 24% 20% 3	8202
	11th to 20th	Night	28% 4 12% 27% 24% 6%	7838
	21st to end	Night	37% 3 10% 23% 19% 7%	8402
February	1st to 10th	Night	36% 5% 13% 23% 17% 6%	2641
	11th to 20th	Night	35% 5% 12% 28% 17% 4	2458
	21st to end	Night	29% 4 9% 22% 26% 11%	2076
March	1st to 10th	Night	24% 3 6% 22% 31% 14%	5357
	11th to 20th	Night	25% 4 7% 19% 26% 19%	4980
	21st to end	Night	35% 5% 16% 33% 10% 1	5467
April	1st to 10th	Night	30% 6% 13% 23% 23% 5%	2055
	11th to 20th	Night	34% 5% 13% 24% 20% 4	1918
	21st to end	Night	35% 6% 13% 26% 19% 2	1800
May	1st to 10th	Night	35% 6% 13% 25% 16% 5%	4080
	11th to 20th	Night	27% 6% 12% 25% 22% 7%	4054
	21st to end	Night	39% 7% 15% 22% 14% 2	4452
June	1st to 10th	Night	22% 8% 18% 29% 20% 4	1779
	11th to 20th	Night	25% 7% 14% 28% 21% 5%	1600
	21st to end	Night	24% 7% 14% 26% 24% 6%	1600
July	1st to 10th	Night	29% 4 17% 24% 23% 4	3600
	11th to 20th	Night	34% 4 16% 23% 20% 4	3767
	21st to end	Night	25% 4 16% 25% 22% 7%	4320
August	1st to 10th	Night	28% 5% 16% 25% 23% 3	2916
	11th to 20th	Night	32% 4 18% 26% 17% 3	2915
	21st to end	Night	26% 4 14% 28% 18% 9%	3554
September	1st to 10th	Night	22% 5% 11% 25% 26% 10%	2102
	11th to 20th	Night	24% 5% 10% 25% 27% 9%	2200
	21st to end	Night	24% 3 10% 24% 32% 8%	2200
October	1st to 10th	Night	18% 3 6% 18% 44% 12%	3590
	11th to 20th	Night	20% 2 10% 26% 29% 13%	3823
	21st to end	Night	21% 2 9% 26% 35% 8%	4507
November	1st to 10th	Night	20% 3 11% 29% 28% 10%	2665
	11th to 20th	Night	22% 3 9% 29% 29% 8%	2730
	21st to end	Night	27% 3 10% 28% 24% 7%	2730
December	1st to 10th	Night	22% 3 11% 36% 23% 5%	4380
	11th to 20th	Night	22% 3 10% 37% 24% 4	4947
	21st to end	Night	42% 4 9% 29% 15% 2	6858

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	12% 7% 38% 31% 12% 2	330
	11th to 20th	Day	12% 14% 34% 30% 10%	330
	21st to end	Day	12% 6% 42% 31% 9% 1	363
February	1st to 10th	Day	14% 11% 41% 26% 7%	330
	11th to 20th	Day	11% 13% 41% 25% 8% 2	330
	21st to end	Day	6% 13% 55% 21% 5%	273
March	1st to 10th	Day	12% 13% 41% 26% 8%	306
	11th to 20th	Day	19% 11% 34% 26% 9% 2	300
	21st to end	Day	17% 13% 42% 22% 5% 1	330
April	1st to 10th	Day	14% 18% 38% 24% 5% 1	442
	11th to 20th	Day	14% 15% 41% 24% 6%	550
	21st to end	Day	19% 14% 38% 21% 8% 1	700
May	1st to 10th	Day	15% 9% 30% 31% 13% 2	703
	11th to 20th	Day	16% 10% 31% 26% 14% 2	725
	21st to end	Day	16% 9% 29% 33% 12% 2	789
June	1st to 10th	Day	5% 5% 25% 36% 19% 9%	730
	11th to 20th	Day	7% 4 33% 35% 18% 2	730
	21st to end	Day	5% 6% 33% 39% 17% 1	730
July	1st to 10th	Day	7% 3 21% 38% 26% 6%	721
	11th to 20th	Day	4 3 16% 43% 29% 5%	718
	21st to end	Day	7% 2 16% 40% 29% 7%	794
August	1st to 10th	Day	10% 2 16% 39% 28% 5%	726
	11th to 20th	Day	7% 2 18% 42% 26% 4	715
	21st to end	Day	9% 1 19% 40% 26% 5%	608
September	1st to 10th	Day	11% 4 22% 37% 22% 4	427
	11th to 20th	Day	6% 4 25% 37% 21% 6%	330
	21st to end	Day	9% 6% 28% 29% 22% 6%	330
October	1st to 10th	Day	18% 7% 20% 34% 15% 7%	330
	11th to 20th	Day	6% 12% 42% 25% 12% 4	330
	21st to end	Day	20% 10% 32% 25% 10% 3	363
November	1st to 10th	Day	12% 11% 35% 29% 10% 3	330
	11th to 20th	Day	12% 10% 38% 26% 13% 1	330
	21st to end	Day	19% 8% 32% 26% 12% 2	330
December	1st to 10th	Day	7% 7% 42% 32% 11% 2	330
	11th to 20th	Day	12% 10% 41% 28% 9%	330
	21st to end	Day	17% 12% 32% 30% 9%	363
January	1st to 10th	Night	9% 8% 37% 39% 7%	1050
	11th to 20th	Night	9% 9% 37% 37% 7% 1	1050
	21st to end	Night	10% 8% 43% 34% 6%	1155
February	1st to 10th	Night	12% 9% 41% 32% 6%	961
	11th to 20th	Night	9% 11% 42% 34% 4	824
	21st to end	Night	8% 11% 42% 34% 4	692
March	1st to 10th	Night	12% 13% 38% 31% 5%	793
	11th to 20th	Night	14% 10% 36% 33% 7% 1	600
	21st to end	Night	15% 15% 39% 27% 4	660
April	1st to 10th	Night	12% 14% 43% 28% 3	600
	11th to 20th	Night	15% 15% 39% 27% 4	593
	21st to end	Night	16% 12% 33% 31% 7%	600
May	1st to 10th	Night	14% 8% 36% 36% 7% 1	600
	11th to 20th	Night	14% 10% 33% 34% 9% 1	591
	21st to end	Night	13% 10% 34% 33% 9% 1	650
June	1st to 10th	Night	6% 6% 35% 39% 12% 1	600
	11th to 20th	Night	7% 6% 38% 38% 11%	600
	21st to end	Night	6% 6% 36% 42% 11%	600
July	1st to 10th	Night	7% 2 24% 47% 19% 1	585
	11th to 20th	Night	4 2 23% 52% 18% 1	582
	21st to end	Night	7% 1 16% 51% 23% 1	657
August	1st to 10th	Night	7% 2 20% 50% 20%	597
	11th to 20th	Night	10% 2 20% 48% 20% 1	594
	21st to end	Night	5% 2 23% 50% 20% 1	660
September	1st to 10th	Night	7% 3 30% 46% 13% 2	600
	11th to 20th	Night	8% 3 32% 41% 16% 1	600
	21st to end	Night	10% 6% 29% 40% 15% 1	600
October	1st to 10th	Night	11% 8% 30% 38% 13%	600
	11th to 20th	Night	11% 9% 38% 35% 8%	750
	21st to end	Night	14% 9% 31% 33% 12%	1034
November	1st to 10th	Night	8% 9% 34% 41% 9%	1025
	11th to 20th	Night	10% 9% 39% 35% 8%	1050
	21st to end	Night	12% 7% 33% 37% 10% 1	1050
December	1st to 10th	Night	8% 8% 39% 38% 7%	1050
	11th to 20th	Night	11% 9% 38% 35% 7%	1050
	21st to end	Night	14% 9% 34% 35% 7%	1155

Page generated at 2026-02-28 00:40:26. Version ac07

Copyright © 2026 Attilla Danko.