Lake Katherine Nature Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Katherine Nature Center clear sky chart from 2005-11-06 to 2026-02-16.

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	13% 9% 3 8% 5% 5% 5% 4 6% 7% 36%	130668
	Night	13% 10% 4 8% 5% 4 4 3 5% 6% 37%	130431
Transparency	Day	46% 5% 12% 23% 13% 2	134192
	Night	46% 5% 11% 22% 14% 2	134982
Seeing	Day	17% 12% 31% 25% 12% 4	17483
	Night	18% 11% 30% 29% 11% 1	27455

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	12% 13% 7% 12% 6% 5% 5% 4 6% 6% 24%	4691
	11th to 20th	Day	8% 11% 7% 14% 6% 5% 6% 5% 5% 4 27%	4710
	21st to end	Day	14% 17% 4 10% 5% 4 3 3 5% 6% 29%	5276
February	1st to 10th	Day	14% 14% 6% 10% 6% 5% 5% 3 5% 6% 26%	1962
	11th to 20th	Day	14% 11% 5% 9% 6% 4 4 3 5% 5% 34%	1998
	21st to end	Day	15% 14% 4 9% 6% 4 4 3 6% 6% 30%	1650
March	1st to 10th	Day	17% 12% 3 7% 3 4 3 3 4 5% 40%	4480
	11th to 20th	Day	8% 8% 3 7% 5% 5% 5% 4 6% 7% 41%	4653
	21st to end	Day	18% 15% 6% 12% 6% 5% 5% 4 5% 5% 19%	5967
April	1st to 10th	Day	17% 14% 3 8% 5% 5% 5% 3 5% 5% 31%	2400
	11th to 20th	Day	16% 10% 2 6% 5% 5% 5% 4 5% 6% 35%	2374
	21st to end	Day	19% 8% 3 8% 5% 4 4 3 6% 7% 33%	2520
May	1st to 10th	Day	17% 9% 2 6% 5% 4 5% 4 6% 8% 33%	5862
	11th to 20th	Day	14% 6% 2 6% 5% 5% 5% 4 6% 9% 39%	6089
	21st to end	Day	13% 7% 3 7% 5% 4 4 4 6% 8% 39%	6935
June	1st to 10th	Day	9% 6% 2 6% 5% 4 5% 4 6% 8% 45%	2800
	11th to 20th	Day	9% 6% 2 6% 5% 5% 5% 3 6% 8% 44%	2800
	21st to end	Day	10% 6% 2 7% 6% 5% 5% 6% 7% 9% 38%	2800
July	1st to 10th	Day	9% 6% 3 7% 6% 5% 7% 5% 8% 9% 35%	6360
	11th to 20th	Day	9% 5% 2 7% 4 5% 5% 5% 7% 11% 40%	6360
	21st to end	Day	9% 7% 3 7% 5% 5% 5% 4 7% 9% 38%	6924
August	1st to 10th	Day	8% 5% 3 7% 4 5% 5% 4 6% 9% 44%	4431
	11th to 20th	Day	9% 5% 2 6% 3 4 5% 4 7% 9% 45%	3889
	21st to end	Day	6% 5% 2 6% 4 5% 5% 4 6% 10% 47%	4312
September	1st to 10th	Day	12% 4 2 5% 5% 5% 4 3 5% 7% 47%	2400
	11th to 20th	Day	10% 5% 2 4 3 3 4 3 6% 7% 52%	2257
	21st to end	Day	11% 6% 2 7% 4 4 5% 4 7% 8% 42%	2200
October	1st to 10th	Day	12% 7% 2 7% 3 5% 4 3 5% 5% 47%	2170
	11th to 20th	Day	18% 9% 3 7% 5% 5% 3 3 4 6% 37%	1975
	21st to end	Day	18% 9% 3 7% 4 4 4 3 5% 6% 35%	1980
November	1st to 10th	Day	12% 9% 3 6% 4 3 3 3 5% 7% 45%	1852
	11th to 20th	Day	15% 12% 3 8% 5% 4 4 3 5% 7% 34%	1890
	21st to end	Day	18% 11% 4 9% 5% 4 4 3 4 5% 34%	1853
December	1st to 10th	Day	9% 12% 3 9% 5% 4 4 3 4 6% 41%	2690
	11th to 20th	Day	12% 17% 6% 11% 6% 6% 5% 4 5% 6% 24%	3088
	21st to end	Day	24% 22% 7% 11% 6% 5% 4 3 4 4 11%	4070
January	1st to 10th	Night	13% 14% 6% 13% 6% 4 4 3 4 4 29%	8232
	11th to 20th	Night	11% 14% 6% 14% 7% 6% 5% 4 6% 4 22%	8280
	21st to end	Night	15% 14% 5% 8% 5% 5% 5% 3 5% 5% 31%	8923
February	1st to 10th	Night	16% 13% 4 8% 7% 5% 4 3 4 6% 31%	2656
	11th to 20th	Night	13% 12% 4 7% 5% 4 4 3 5% 6% 36%	2399
	21st to end	Night	18% 11% 5% 8% 5% 3 4 2 5% 5% 34%	1980
March	1st to 10th	Night	15% 12% 4 7% 4 3 4 3 4 5% 40%	5373
	11th to 20th	Night	11% 7% 2 6% 4 4 4 3 5% 7% 47%	5348
	21st to end	Night	18% 11% 6% 10% 6% 5% 5% 3 4 5% 27%	4965
April	1st to 10th	Night	15% 9% 3 7% 4 4 5% 3 6% 7% 37%	2000
	11th to 20th	Night	18% 8% 3 6% 4 4 3 4 6% 6% 39%	1975
	21st to end	Night	16% 9% 3 8% 4 4 4 4 5% 7% 35%	1879
May	1st to 10th	Night	18% 8% 3 7% 5% 4 4 4 5% 7% 34%	4033
	11th to 20th	Night	12% 7% 3 6% 4 4 4 3 6% 8% 42%	3799
	21st to end	Night	15% 8% 4 7% 4 4 4 3 4 6% 40%	3942
June	1st to 10th	Night	9% 5% 2 6% 4 4 4 4 5% 8% 49%	1600
	11th to 20th	Night	8% 7% 2 5% 4 4 5% 4 6% 10% 45%	1600
	21st to end	Night	10% 6% 2 6% 5% 5% 5% 4 6% 9% 43%	1600
July	1st to 10th	Night	10% 5% 2 7% 5% 6% 6% 5% 6% 8% 41%	3618
	11th to 20th	Night	6% 6% 2 7% 4 4 5% 3 6% 8% 49%	3617
	21st to end	Night	8% 5% 3 7% 5% 5% 5% 4 7% 9% 43%	3947
August	1st to 10th	Night	6% 5% 2 6% 4 5% 5% 4 6% 8% 47%	2723
	11th to 20th	Night	8% 5% 2 5% 4 4 4 4 6% 8% 51%	3158
	21st to end	Night	8% 5% 2 5% 3 3 4 3 5% 9% 52%	3586
September	1st to 10th	Night	9% 5% 2 7% 3 3 3 3 5% 7% 53%	2000
	11th to 20th	Night	8% 5% 2 4 4 3 4 3 5% 7% 55%	2121
	21st to end	Night	10% 5% 2 9% 4 3 4 4 6% 7% 46%	2200
October	1st to 10th	Night	11% 5% 2 5% 3 4 3 3 5% 7% 51%	2225
	11th to 20th	Night	16% 7% 3 6% 4 3 4 2 4 6% 45%	2425
	21st to end	Night	19% 9% 3 7% 4 3 4 3 5% 7% 36%	2860
November	1st to 10th	Night	12% 9% 3 6% 4 3 4 3 4 6% 46%	2666
	11th to 20th	Night	14% 10% 3 9% 5% 4 4 3 5% 6% 36%	2730
	21st to end	Night	17% 10% 4 8% 5% 4 3 3 4 6% 36%	2762
December	1st to 10th	Night	12% 9% 3 8% 4 4 4 3 5% 5% 42%	4720
	11th to 20th	Night	17% 15% 4 9% 5% 4 4 3 4 5% 29%	5339
	21st to end	Night	24% 19% 6% 9% 5% 5% 4 3 4 5% 16%	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	60% 4 16% 13% 6%	4692
	11th to 20th	Day	58% 4 9% 15% 12% 3	4710
	21st to end	Day	58% 3 12% 19% 8% 1	5276
February	1st to 10th	Day	59% 5% 12% 14% 8% 2	1962
	11th to 20th	Day	52% 4 11% 22% 10% 2	2008
	21st to end	Day	54% 6% 10% 19% 8% 2	1650
March	1st to 10th	Day	48% 4 7% 25% 12% 4	4480
	11th to 20th	Day	40% 5% 13% 32% 10% 1	4653
	21st to end	Day	65% 6% 10% 11% 6% 1	5969
April	1st to 10th	Day	54% 6% 9% 19% 11%	2400
	11th to 20th	Day	48% 6% 10% 21% 11% 4	2374
	21st to end	Day	49% 6% 13% 19% 11% 2	2520
May	1st to 10th	Day	47% 6% 12% 22% 11% 2	5897
	11th to 20th	Day	41% 7% 12% 25% 14% 1	6093
	21st to end	Day	41% 5% 12% 24% 15% 3	6949
June	1st to 10th	Day	35% 7% 12% 26% 18% 2	2800
	11th to 20th	Day	36% 6% 12% 25% 19% 2	2800
	21st to end	Day	40% 9% 14% 20% 15% 3	2800
July	1st to 10th	Day	42% 6% 13% 23% 14% 2	6291
	11th to 20th	Day	37% 6% 16% 26% 15% 1	6285
	21st to end	Day	40% 6% 16% 22% 15% 2	6728
August	1st to 10th	Day	35% 7% 16% 28% 14% 1	4416
	11th to 20th	Day	33% 7% 11% 32% 15% 1	3926
	21st to end	Day	31% 6% 13% 27% 19% 3	4311
September	1st to 10th	Day	35% 6% 12% 26% 18% 3	2400
	11th to 20th	Day	30% 5% 12% 29% 21% 3	2257
	21st to end	Day	37% 7% 10% 26% 19% 1	2200
October	1st to 10th	Day	27% 4 7% 33% 28% 2	3534
	11th to 20th	Day	37% 3 11% 27% 22% 1	3191
	21st to end	Day	44% 3 10% 25% 15% 3	3180
November	1st to 10th	Day	39% 5% 14% 24% 15% 2	1852
	11th to 20th	Day	50% 5% 12% 21% 11% 1	1890
	21st to end	Day	54% 5% 9% 23% 9%	1853
December	1st to 10th	Day	46% 4 16% 26% 8%	2690
	11th to 20th	Day	60% 4 11% 18% 6%	3085
	21st to end	Day	78% 3 6% 8% 4	4070
January	1st to 10th	Night	58% 4 11% 19% 8%	8233
	11th to 20th	Night	63% 4 10% 11% 11% 1	8280
	21st to end	Night	56% 3 11% 21% 9%	8923
February	1st to 10th	Night	57% 3 11% 17% 10% 2	2656
	11th to 20th	Night	49% 4 11% 22% 13% 1	2400
	21st to end	Night	52% 4 11% 19% 11% 2	1980
March	1st to 10th	Night	48% 4 9% 25% 11% 3	5373
	11th to 20th	Night	37% 5% 12% 29% 15% 3	5348
	21st to end	Night	58% 5% 8% 19% 9% 1	4965
April	1st to 10th	Night	45% 5% 12% 23% 13% 1	2000
	11th to 20th	Night	46% 5% 9% 20% 16% 4	1975
	21st to end	Night	48% 7% 9% 21% 13% 2	1879
May	1st to 10th	Night	49% 5% 12% 17% 14% 4	4060
	11th to 20th	Night	39% 6% 14% 26% 13% 3	3800
	21st to end	Night	44% 6% 10% 20% 16% 4	3950
June	1st to 10th	Night	33% 7% 13% 25% 20% 3	1600
	11th to 20th	Night	33% 6% 14% 23% 22% 2	1600
	21st to end	Night	37% 8% 13% 23% 16% 3	1600
July	1st to 10th	Night	39% 5% 13% 26% 12% 4	3580
	11th to 20th	Night	32% 5% 14% 26% 21% 1	3572
	21st to end	Night	36% 6% 16% 24% 17% 3	3832
August	1st to 10th	Night	32% 8% 16% 28% 16% 1	2714
	11th to 20th	Night	31% 6% 14% 28% 20% 1	3187
	21st to end	Night	30% 6% 11% 33% 17% 3	3586
September	1st to 10th	Night	32% 5% 11% 27% 22% 3	2000
	11th to 20th	Night	28% 5% 8% 29% 28% 2	2121
	21st to end	Night	37% 6% 10% 27% 18% 2	2200
October	1st to 10th	Night	22% 4 7% 36% 28% 2	3641
	11th to 20th	Night	37% 3 7% 24% 28% 2	3948
	21st to end	Night	40% 4 9% 25% 19% 3	4610
November	1st to 10th	Night	39% 4 10% 25% 18% 3	2666
	11th to 20th	Night	48% 5% 11% 22% 12% 1	2730
	21st to end	Night	51% 4 11% 23% 10%	2762
December	1st to 10th	Night	44% 4 14% 26% 10% 1	4720
	11th to 20th	Night	58% 4 12% 16% 10% 1	5341
	21st to end	Night	72% 4 8% 11% 5%	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	21% 16% 37% 21% 5%	330
	11th to 20th	Day	23% 22% 37% 12% 4 1	330
	21st to end	Day	23% 20% 39% 16% 2 1	363
February	1st to 10th	Day	22% 18% 42% 15% 2	330
	11th to 20th	Day	26% 18% 36% 17% 3 1	315
	21st to end	Day	25% 20% 41% 12% 2	249
March	1st to 10th	Day	20% 23% 41% 13% 2	300
	11th to 20th	Day	27% 17% 35% 16% 5%	340
	21st to end	Day	29% 17% 30% 18% 5% 1	550
April	1st to 10th	Day	27% 16% 31% 20% 6%	500
	11th to 20th	Day	24% 20% 26% 20% 9% 1	492
	21st to end	Day	23% 15% 37% 16% 8% 1	500
May	1st to 10th	Day	23% 15% 31% 22% 7% 2	503
	11th to 20th	Day	19% 12% 32% 24% 11% 2	625
	21st to end	Day	14% 9% 34% 26% 12% 5%	789
June	1st to 10th	Day	11% 10% 32% 30% 12% 5%	730
	11th to 20th	Day	12% 6% 33% 30% 15% 3	730
	21st to end	Day	11% 9% 35% 29% 12% 4	730
July	1st to 10th	Day	9% 4 24% 32% 19% 11%	721
	11th to 20th	Day	11% 4 28% 32% 16% 9%	718
	21st to end	Day	9% 5% 27% 35% 19% 5%	794
August	1st to 10th	Day	6% 3 23% 35% 22% 11%	646
	11th to 20th	Day	10% 5% 19% 31% 24% 10%	519
	21st to end	Day	7% 3 20% 38% 23% 9%	583
September	1st to 10th	Day	13% 6% 22% 30% 21% 6%	530
	11th to 20th	Day	9% 4 18% 32% 26% 11%	530
	21st to end	Day	13% 10% 25% 28% 18% 7%	530
October	1st to 10th	Day	16% 7% 28% 29% 16% 4	500
	11th to 20th	Day	19% 21% 31% 21% 6% 1	330
	21st to end	Day	27% 14% 38% 17% 4	363
November	1st to 10th	Day	18% 15% 37% 22% 6% 2	330
	11th to 20th	Day	24% 19% 35% 15% 6%	330
	21st to end	Day	26% 14% 40% 18% 3	330
December	1st to 10th	Day	18% 24% 36% 17% 5% 1	330
	11th to 20th	Day	22% 17% 40% 18% 2	330
	21st to end	Day	29% 20% 37% 13% 1	363
January	1st to 10th	Night	20% 17% 36% 23% 3	1050
	11th to 20th	Night	22% 18% 36% 19% 4 1	1050
	21st to end	Night	22% 15% 37% 23% 3	1155
February	1st to 10th	Night	23% 13% 38% 22% 4	976
	11th to 20th	Night	21% 15% 36% 25% 3	804
	21st to end	Night	23% 16% 38% 20% 3	660
March	1st to 10th	Night	21% 15% 38% 21% 5%	800
	11th to 20th	Night	17% 14% 38% 25% 6% 1	800
	21st to end	Night	24% 14% 30% 25% 7% 1	663
April	1st to 10th	Night	20% 14% 34% 25% 6% 1	600
	11th to 20th	Night	22% 13% 33% 23% 9% 1	593
	21st to end	Night	21% 11% 32% 28% 8% 1	600
May	1st to 10th	Night	20% 6% 34% 30% 9%	600
	11th to 20th	Night	18% 5% 29% 34% 14% 1	591
	21st to end	Night	13% 6% 26% 36% 18% 1	650
June	1st to 10th	Night	10% 5% 25% 45% 15% 1	600
	11th to 20th	Night	12% 5% 28% 40% 15% 1	600
	21st to end	Night	12% 3 26% 40% 19% 1	600
July	1st to 10th	Night	8% 2 20% 39% 27% 4	585
	11th to 20th	Night	8% 2 22% 39% 26% 3	582
	21st to end	Night	6% 2 18% 46% 26% 2	657
August	1st to 10th	Night	5% 1 13% 49% 28% 4	597
	11th to 20th	Night	8% 3 13% 40% 31% 4	594
	21st to end	Night	9% 2 17% 40% 29% 3	660
September	1st to 10th	Night	11% 3 19% 34% 28% 4	600
	11th to 20th	Night	9% 4 16% 37% 30% 4	721
	21st to end	Night	11% 7% 23% 34% 22% 3	800
October	1st to 10th	Night	14% 6% 25% 36% 19% 2	800
	11th to 20th	Night	19% 13% 30% 28% 8% 1	800
	21st to end	Night	25% 14% 29% 24% 7%	880
November	1st to 10th	Night	18% 12% 39% 21% 9% 1	820
	11th to 20th	Night	19% 19% 35% 23% 4	840
	21st to end	Night	24% 15% 35% 21% 5%	872
December	1st to 10th	Night	21% 16% 38% 21% 4	1050
	11th to 20th	Night	23% 14% 37% 22% 3	1050
	21st to end	Night	31% 16% 33% 18% 2	1155

Page generated at 2026-02-13 00:42:13. Version ac07

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