Lee & Rose Warner Nature Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lee & Rose Warner Nature Center clear sky chart from 2005-11-06 to 2026-05-02.

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	12% 9% 3 8% 5% 4 4 4 5% 7% 38%	132241
	Night	12% 9% 4 9% 5% 4 4 4 5% 6% 38%	130558
Transparency	Day	45% 4 13% 26% 11% 1	135792
	Night	47% 4 12% 24% 12% 1	135084
Seeing	Day	17% 10% 30% 26% 13% 4	18013
	Night	16% 9% 31% 32% 11% 1	28026

By Month

Percentage Cloud Cover SE (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% 14% 6% 20% 7% 5% 4 3 5% 5% 22%	4691
	11th to 20th	Day	6% 12% 6% 13% 7% 7% 8% 8% 7% 5% 22%	4710
	21st to end	Day	5% 12% 5% 11% 5% 4 7% 4 6% 7% 34%	5752
February	1st to 10th	Day	8% 12% 5% 10% 7% 6% 5% 5% 6% 6% 30%	1890
	11th to 20th	Day	8% 12% 5% 10% 5% 5% 4 4 5% 6% 36%	1844
	21st to end	Day	10% 12% 5% 10% 5% 5% 5% 4 5% 7% 33%	1638
March	1st to 10th	Day	12% 8% 3 6% 4 4 3 3 4 8% 45%	4862
	11th to 20th	Day	10% 9% 3 8% 5% 5% 4 4 5% 8% 40%	5090
	21st to end	Day	21% 11% 4 9% 5% 5% 4 4 5% 6% 27%	5694
April	1st to 10th	Day	16% 12% 3 7% 5% 4 4 3 5% 7% 34%	2520
	11th to 20th	Day	19% 13% 4 7% 4 4 4 3 5% 5% 31%	2494
	21st to end	Day	21% 11% 3 6% 5% 5% 4 4 4 6% 31%	2719
May	1st to 10th	Day	14% 7% 2 5% 4 3 3 2 4 6% 50%	6197
	11th to 20th	Day	16% 7% 2 6% 4 4 4 3 4 6% 44%	6319
	21st to end	Day	17% 8% 3 6% 4 5% 4 4 5% 7% 38%	6935
June	1st to 10th	Day	12% 5% 2 4 3 4 5% 4 7% 9% 45%	2800
	11th to 20th	Day	13% 7% 3 6% 5% 5% 5% 6% 6% 8% 36%	2800
	21st to end	Day	12% 5% 2 6% 5% 5% 6% 5% 7% 9% 40%	2800
July	1st to 10th	Day	9% 5% 2 5% 3 4 5% 5% 7% 10% 46%	6360
	11th to 20th	Day	9% 3 1 4 3 3 3 3 5% 8% 58%	6360
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 6% 9% 47%	6924
August	1st to 10th	Day	11% 5% 2 6% 4 5% 5% 4 6% 9% 43%	4244
	11th to 20th	Day	13% 5% 2 5% 4 3 4 4 7% 7% 45%	4171
	21st to end	Day	11% 5% 2 7% 4 4 4 3 6% 8% 46%	4444
September	1st to 10th	Day	11% 6% 2 5% 3 4 4 4 6% 9% 46%	2400
	11th to 20th	Day	12% 6% 2 5% 4 5% 5% 5% 6% 7% 44%	2400
	21st to end	Day	13% 6% 2 6% 4 4 4 4 5% 7% 45%	2085
October	1st to 10th	Day	16% 7% 2 5% 3 4 4 3 5% 6% 45%	2000
	11th to 20th	Day	15% 11% 3 7% 3 5% 5% 3 4 6% 38%	2000
	21st to end	Day	16% 12% 4 8% 4 3 3 3 4 6% 37%	2145
November	1st to 10th	Day	11% 12% 4 9% 5% 5% 5% 3 5% 5% 36%	1745
	11th to 20th	Day	12% 15% 7% 10% 7% 4 4 3 5% 5% 29%	1680
	21st to end	Day	14% 12% 4 9% 6% 4 4 4 5% 7% 32%	1680
December	1st to 10th	Day	7% 12% 4 15% 12% 7% 6% 4 6% 5% 22%	2690
	11th to 20th	Day	10% 17% 7% 11% 6% 4 4 3 4 5% 29%	3088
	21st to end	Day	19% 20% 8% 19% 5% 3 3 2 3 3 14%	4070
January	1st to 10th	Night	8% 13% 6% 13% 8% 5% 4 3 5% 6% 29%	8232
	11th to 20th	Night	6% 12% 5% 13% 8% 7% 9% 8% 7% 5% 21%	8280
	21st to end	Night	7% 13% 5% 9% 6% 5% 5% 3 6% 6% 35%	8445
February	1st to 10th	Night	6% 11% 6% 10% 7% 6% 5% 3 5% 6% 34%	2730
	11th to 20th	Night	7% 10% 4 8% 5% 6% 5% 4 5% 8% 38%	2663
	21st to end	Night	11% 10% 4 9% 6% 6% 5% 3 4 7% 36%	2166
March	1st to 10th	Night	10% 7% 3 6% 4 4 4 3 5% 7% 46%	5240
	11th to 20th	Night	10% 7% 3 8% 5% 5% 5% 4 6% 9% 39%	5090
	21st to end	Night	24% 11% 4 10% 5% 3 3 3 4 5% 29%	5477
April	1st to 10th	Night	17% 12% 3 6% 4 4 4 4 5% 6% 35%	2100
	11th to 20th	Night	20% 10% 3 7% 4 4 4 3 4 5% 36%	2075
	21st to end	Night	20% 9% 3 6% 5% 4 4 3 5% 6% 35%	1898
May	1st to 10th	Night	11% 7% 2 7% 4 3 3 3 4 5% 50%	3741
	11th to 20th	Night	14% 6% 2 5% 3 2 3 3 5% 7% 51%	3596
	21st to end	Night	15% 8% 3 7% 4 3 4 3 6% 6% 40%	3942
June	1st to 10th	Night	11% 5% 2 5% 4 4 4 5% 6% 8% 47%	1600
	11th to 20th	Night	9% 6% 2 6% 4 4 6% 3 7% 7% 46%	1600
	21st to end	Night	8% 5% 1 5% 4 4 4 4 6% 8% 51%	1600
July	1st to 10th	Night	9% 4 1 4 4 3 4 4 7% 8% 52%	3618
	11th to 20th	Night	6% 3 2 4 3 4 4 4 6% 9% 55%	3617
	21st to end	Night	8% 5% 2 5% 4 4 4 4 6% 8% 52%	3947
August	1st to 10th	Night	13% 5% 2 6% 4 4 4 3 6% 6% 47%	2913
	11th to 20th	Night	13% 4 2 4 4 3 4 3 6% 9% 48%	2888
	21st to end	Night	9% 6% 3 7% 4 4 4 3 6% 7% 47%	3456
September	1st to 10th	Night	10% 4 1 6% 3 4 4 4 5% 7% 53%	2000
	11th to 20th	Night	9% 5% 1 4 3 4 3 4 5% 8% 53%	2000
	21st to end	Night	13% 5% 1 3 4 3 4 3 4 6% 52%	2291
October	1st to 10th	Night	14% 6% 2 5% 3 3 3 3 5% 6% 50%	2400
	11th to 20th	Night	17% 9% 2 5% 4 4 4 3 5% 6% 41%	2400
	21st to end	Night	18% 11% 4 7% 3 3 3 3 5% 6% 37%	2693
November	1st to 10th	Night	13% 10% 4 6% 4 4 4 3 5% 6% 40%	2771
	11th to 20th	Night	13% 12% 4 11% 5% 4 4 3 5% 5% 34%	2940
	21st to end	Night	14% 10% 4 10% 5% 4 4 3 5% 7% 34%	2940
December	1st to 10th	Night	6% 10% 4 16% 7% 7% 5% 3 5% 7% 29%	4720
	11th to 20th	Night	10% 17% 6% 15% 6% 4 5% 4 5% 4 24%	5339
	21st to end	Night	21% 15% 8% 16% 5% 3 4 2 3 4 18%	7150

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	66% 3 9% 16% 6%	4692
	11th to 20th	Day	62% 3 9% 16% 10%	4710
	21st to end	Day	50% 3 14% 22% 10%	5752
February	1st to 10th	Day	54% 4 13% 19% 8% 1	1890
	11th to 20th	Day	49% 4 12% 26% 9% 1	1853
	21st to end	Day	51% 5% 12% 22% 9% 1	1638
March	1st to 10th	Day	40% 2 18% 25% 12% 3	4862
	11th to 20th	Day	43% 4 13% 29% 9% 1	5090
	21st to end	Day	59% 3 10% 19% 9% 1	5696
April	1st to 10th	Day	50% 4 10% 22% 13% 1	2520
	11th to 20th	Day	55% 3 10% 18% 12% 1	2494
	21st to end	Day	54% 4 11% 21% 10%	2719
May	1st to 10th	Day	37% 3 11% 30% 17% 2	6236
	11th to 20th	Day	42% 4 11% 24% 15% 5%	6323
	21st to end	Day	46% 3 9% 30% 11%	6949
June	1st to 10th	Day	34% 5% 16% 31% 13% 1	2800
	11th to 20th	Day	44% 6% 14% 23% 12% 1	2800
	21st to end	Day	39% 6% 16% 29% 9% 2	2800
July	1st to 10th	Day	32% 6% 17% 35% 9%	6291
	11th to 20th	Day	26% 4 15% 38% 16% 1	6285
	21st to end	Day	33% 6% 14% 30% 16% 1	6728
August	1st to 10th	Day	38% 5% 14% 29% 14% 1	4229
	11th to 20th	Day	36% 5% 14% 35% 10%	4210
	21st to end	Day	37% 4 17% 28% 13% 1	4443
September	1st to 10th	Day	35% 6% 13% 34% 12%	2400
	11th to 20th	Day	37% 5% 18% 31% 8%	2400
	21st to end	Day	40% 4 11% 34% 11%	2085
October	1st to 10th	Day	29% 3 9% 38% 21%	3260
	11th to 20th	Day	40% 4 11% 26% 17% 2	3240
	21st to end	Day	45% 2 15% 28% 9%	3447
November	1st to 10th	Day	50% 4 13% 19% 12% 2	1745
	11th to 20th	Day	57% 4 13% 18% 8% 1	1680
	21st to end	Day	52% 4 16% 20% 6% 2	1680
December	1st to 10th	Day	64% 5% 12% 14% 4	2690
	11th to 20th	Day	60% 2 13% 19% 7%	3085
	21st to end	Day	78% 2 7% 9% 4	4070
January	1st to 10th	Night	59% 3 14% 17% 7%	8233
	11th to 20th	Night	63% 3 10% 15% 9%	8280
	21st to end	Night	51% 3 12% 24% 10%	8445
February	1st to 10th	Night	51% 4 12% 23% 9% 1	2730
	11th to 20th	Night	46% 4 14% 27% 9% 1	2664
	21st to end	Night	50% 3 12% 22% 11% 1	2166
March	1st to 10th	Night	39% 3 15% 23% 17% 3	5240
	11th to 20th	Night	42% 3 15% 25% 14% 1	5090
	21st to end	Night	60% 3 10% 16% 11%	5477
April	1st to 10th	Night	49% 4 8% 23% 15% 1	2100
	11th to 20th	Night	50% 3 9% 22% 14% 2	2075
	21st to end	Night	49% 5% 9% 21% 14% 2	1898
May	1st to 10th	Night	37% 3 10% 28% 20% 2	3767
	11th to 20th	Night	34% 4 11% 24% 20% 7%	3597
	21st to end	Night	45% 3 11% 28% 13% 1	3950
June	1st to 10th	Night	33% 5% 14% 29% 17% 2	1600
	11th to 20th	Night	36% 4 15% 25% 17% 2	1600
	21st to end	Night	31% 4 16% 31% 16% 3	1600
July	1st to 10th	Night	29% 6% 19% 32% 13% 1	3580
	11th to 20th	Night	25% 6% 15% 37% 16% 1	3572
	21st to end	Night	31% 5% 15% 29% 18% 2	3832
August	1st to 10th	Night	36% 5% 12% 29% 15% 3	2904
	11th to 20th	Night	34% 5% 15% 32% 13% 1	2915
	21st to end	Night	36% 6% 16% 29% 12% 2	3456
September	1st to 10th	Night	31% 5% 13% 34% 16% 1	2000
	11th to 20th	Night	30% 4 18% 34% 15%	2000
	21st to end	Night	34% 4 14% 34% 14% 1	2291
October	1st to 10th	Night	25% 2 7% 36% 26% 4	3920
	11th to 20th	Night	36% 3 12% 25% 22% 2	3899
	21st to end	Night	46% 3 11% 27% 12%	4341
November	1st to 10th	Night	45% 4 12% 25% 13% 1	2771
	11th to 20th	Night	53% 4 12% 19% 10% 1	2940
	21st to end	Night	50% 4 15% 22% 7% 1	2940
December	1st to 10th	Night	58% 5% 15% 19% 4	4720
	11th to 20th	Night	64% 3 10% 16% 5% 1	5341
	21st to end	Night	73% 2 9% 12% 4	7150

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	15% 12% 35% 26% 10% 2	330
	11th to 20th	Day	17% 10% 41% 26% 5%	330
	21st to end	Day	15% 10% 39% 25% 10% 2	363
February	1st to 10th	Day	15% 16% 46% 17% 4 1	330
	11th to 20th	Day	14% 16% 42% 20% 7% 1	330
	21st to end	Day	16% 16% 38% 26% 3	273
March	1st to 10th	Day	18% 12% 45% 17% 8% 1	330
	11th to 20th	Day	18% 14% 40% 20% 7% 2	330
	21st to end	Day	25% 14% 31% 20% 8% 2	410
April	1st to 10th	Day	22% 15% 34% 24% 5% 1	540
	11th to 20th	Day	29% 14% 24% 24% 8% 1	532
	21st to end	Day	26% 13% 30% 20% 9% 2	739
May	1st to 10th	Day	21% 11% 29% 25% 11% 2	709
	11th to 20th	Day	20% 12% 26% 25% 13% 4	725
	21st to end	Day	19% 9% 25% 27% 16% 4	789
June	1st to 10th	Day	11% 7% 29% 31% 18% 4	730
	11th to 20th	Day	17% 8% 34% 28% 11% 3	730
	21st to end	Day	15% 8% 30% 28% 15% 5%	730
July	1st to 10th	Day	8% 4 21% 33% 24% 10%	721
	11th to 20th	Day	9% 6% 27% 30% 20% 8%	718
	21st to end	Day	7% 4 26% 35% 21% 7%	794
August	1st to 10th	Day	10% 5% 22% 33% 24% 6%	726
	11th to 20th	Day	14% 5% 20% 30% 25% 7%	715
	21st to end	Day	12% 6% 24% 34% 20% 5%	663
September	1st to 10th	Day	14% 7% 28% 28% 16% 7%	530
	11th to 20th	Day	12% 6% 28% 32% 20% 3	530
	21st to end	Day	15% 12% 27% 21% 17% 7%	330
October	1st to 10th	Day	17% 12% 28% 25% 14% 4	330
	11th to 20th	Day	21% 19% 33% 19% 7% 1	330
	21st to end	Day	22% 13% 37% 20% 6% 1	363
November	1st to 10th	Day	18% 16% 34% 23% 8% 1	330
	11th to 20th	Day	19% 19% 37% 20% 5%	330
	21st to end	Day	24% 12% 39% 20% 5%	330
December	1st to 10th	Day	17% 10% 43% 22% 8% 1	330
	11th to 20th	Day	22% 15% 37% 22% 5%	330
	21st to end	Day	28% 15% 37% 16% 2 1	363
January	1st to 10th	Night	13% 12% 34% 32% 8% 1	1050
	11th to 20th	Night	16% 11% 36% 29% 6% 1	1050
	21st to end	Night	17% 11% 34% 30% 7% 1	1155
February	1st to 10th	Night	13% 12% 40% 28% 7% 1	1050
	11th to 20th	Night	12% 12% 39% 29% 6% 1	1029
	21st to end	Night	17% 13% 33% 29% 7%	782
March	1st to 10th	Night	16% 11% 37% 28% 8% 1	730
	11th to 20th	Night	19% 10% 39% 27% 5%	630
	21st to end	Night	23% 10% 30% 26% 9% 2	693
April	1st to 10th	Night	23% 12% 32% 26% 6%	630
	11th to 20th	Night	25% 9% 32% 27% 7%	623
	21st to end	Night	24% 9% 30% 29% 7% 1	630
May	1st to 10th	Night	22% 7% 32% 32% 7% 1	603
	11th to 20th	Night	18% 6% 30% 33% 11% 1	591
	21st to end	Night	13% 7% 25% 39% 14% 1	650
June	1st to 10th	Night	13% 5% 27% 43% 12% 1	600
	11th to 20th	Night	11% 4 31% 43% 10% 1	600
	21st to end	Night	11% 4 25% 44% 15% 2	600
July	1st to 10th	Night	6% 2 20% 42% 28% 2	585
	11th to 20th	Night	7% 4 22% 43% 21% 2	582
	21st to end	Night	6% 2 22% 46% 22% 2	657
August	1st to 10th	Night	9% 2 16% 50% 22% 2	597
	11th to 20th	Night	15% 3 18% 36% 27% 3	594
	21st to end	Night	9% 4 24% 38% 23% 2	660
September	1st to 10th	Night	11% 6% 22% 40% 18% 3	600
	11th to 20th	Night	11% 6% 25% 38% 19% 2	600
	21st to end	Night	16% 7% 28% 32% 16% 2	695
October	1st to 10th	Night	17% 8% 29% 32% 13% 1	800
	11th to 20th	Night	22% 10% 32% 29% 7% 1	800
	21st to end	Night	25% 9% 29% 30% 7%	880
November	1st to 10th	Night	19% 10% 34% 30% 6% 1	925
	11th to 20th	Night	19% 14% 34% 26% 7%	1050
	21st to end	Night	18% 15% 35% 25% 6%	1050
December	1st to 10th	Night	16% 10% 36% 29% 7% 1	1050
	11th to 20th	Night	20% 11% 36% 26% 6% 1	1050
	21st to end	Night	26% 10% 32% 26% 5%	1155

Page generated at 2026-04-29 01:21:42. Version ac07

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