Lake Lawrence
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Lawrence clear sky chart from 2005-11-06 to 2026-07-31.

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	14% 9% 3 8% 5% 5% 5% 4 6% 7% 34%	143495
	Night	15% 10% 3 8% 5% 5% 5% 4 5% 6% 34%	138213
Transparency	Day	48% 9% 14% 18% 9% 2	143214
	Night	49% 9% 14% 18% 8% 1	138076
Seeing	Day	22% 14% 22% 25% 13% 3	17257
	Night	24% 11% 17% 27% 19% 2	25502

By Month

Percentage Cloud Cover NW (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	21% 15% 5% 13% 8% 7% 6% 4 6% 6% 8%	4723
	11th to 20th	Day	16% 11% 4 9% 5% 4 4 3 5% 6% 32%	4716
	21st to end	Day	15% 10% 4 10% 6% 5% 5% 4 6% 5% 29%	5466
February	1st to 10th	Day	23% 16% 4 10% 6% 5% 4 4 6% 7% 16%	1890
	11th to 20th	Day	23% 16% 5% 11% 7% 5% 4 3 4 5% 17%	1845
	21st to end	Day	23% 20% 5% 9% 5% 5% 4 4 4 4 17%	1626
March	1st to 10th	Day	12% 13% 5% 11% 8% 8% 7% 6% 8% 7% 17%	4787
	11th to 20th	Day	16% 15% 4 10% 6% 5% 5% 3 4 5% 26%	5110
	21st to end	Day	15% 14% 5% 13% 9% 7% 7% 5% 7% 6% 12%	5758
April	1st to 10th	Day	22% 15% 4 10% 7% 6% 5% 3 6% 6% 16%	2520
	11th to 20th	Day	17% 14% 3 10% 7% 5% 4 5% 5% 5% 24%	2512
	21st to end	Day	19% 13% 4 9% 6% 5% 5% 4 5% 5% 24%	2740
May	1st to 10th	Day	12% 7% 2 6% 5% 5% 5% 4 5% 6% 43%	8195
	11th to 20th	Day	12% 9% 3 10% 7% 7% 6% 5% 7% 8% 25%	8160
	21st to end	Day	15% 7% 3 7% 5% 5% 5% 4 7% 9% 32%	8993
June	1st to 10th	Day	21% 10% 3 7% 5% 5% 4 5% 5% 7% 27%	2940
	11th to 20th	Day	18% 10% 3 9% 6% 5% 6% 5% 6% 7% 24%	3127
	21st to end	Day	11% 7% 3 8% 7% 5% 4 5% 6% 7% 37%	3150
July	1st to 10th	Day	6% 4 1 4 3 3 3 3 4 5% 65%	6930
	11th to 20th	Day	4 3 1 3 3 2 2 2 4 5% 72%	6475
	21st to end	Day	7% 4 1 4 3 3 3 3 4 6% 62%	7015
August	1st to 10th	Day	5% 4 1 4 3 3 3 3 5% 7% 63%	4386
	11th to 20th	Day	7% 6% 2 6% 4 4 6% 5% 7% 9% 44%	4156
	21st to end	Day	13% 7% 2 6% 5% 4 4 3 5% 6% 44%	4459
September	1st to 10th	Day	9% 6% 3 7% 5% 4 4 4 6% 7% 48%	2400
	11th to 20th	Day	11% 8% 3 8% 5% 5% 5% 4 6% 7% 39%	2400
	21st to end	Day	14% 8% 3 7% 5% 4 4 3 6% 6% 40%	2109
October	1st to 10th	Day	13% 8% 2 6% 4 4 4 4 6% 9% 41%	3280
	11th to 20th	Day	20% 8% 4 8% 5% 5% 5% 4 6% 7% 27%	3261
	21st to end	Day	18% 9% 3 9% 6% 5% 6% 4 6% 8% 25%	3406
November	1st to 10th	Day	23% 13% 4 10% 6% 5% 7% 4 6% 6% 16%	1703
	11th to 20th	Day	25% 13% 4 9% 7% 5% 5% 4 6% 6% 16%	1680
	21st to end	Day	22% 16% 4 7% 5% 5% 5% 4 6% 7% 19%	1680
December	1st to 10th	Day	16% 9% 4 9% 6% 6% 5% 4 5% 6% 31%	2700
	11th to 20th	Day	22% 12% 4 10% 7% 7% 6% 5% 7% 8% 13%	3105
	21st to end	Day	21% 15% 4 11% 7% 7% 6% 4 7% 5% 13%	4092
January	1st to 10th	Night	23% 16% 5% 13% 8% 7% 5% 4 5% 4 10%	8172
	11th to 20th	Night	14% 13% 5% 10% 4 4 4 3 5% 6% 32%	8182
	21st to end	Night	17% 10% 4 9% 6% 5% 4 3 5% 6% 32%	8712
February	1st to 10th	Night	22% 14% 4 11% 6% 5% 5% 4 5% 6% 20%	2730
	11th to 20th	Night	20% 15% 4 11% 5% 4 4 3 4 5% 24%	2662
	21st to end	Night	20% 16% 5% 9% 5% 5% 6% 4 4 5% 21%	2179
March	1st to 10th	Night	11% 12% 4 9% 6% 6% 6% 6% 8% 8% 22%	5326
	11th to 20th	Night	14% 9% 3 9% 5% 6% 5% 5% 6% 7% 31%	5109
	21st to end	Night	19% 15% 5% 12% 7% 6% 5% 4 6% 5% 15%	5446
April	1st to 10th	Night	17% 14% 4 10% 7% 6% 5% 4 5% 6% 23%	2100
	11th to 20th	Night	15% 12% 4 7% 5% 5% 5% 5% 7% 6% 28%	2054
	21st to end	Night	16% 11% 2 8% 5% 6% 6% 4 4 8% 30%	1880
May	1st to 10th	Night	10% 7% 2 7% 4 4 4 3 5% 6% 48%	4724
	11th to 20th	Night	12% 8% 3 9% 5% 6% 5% 5% 7% 7% 32%	4700
	21st to end	Night	8% 9% 2 6% 5% 5% 6% 4 6% 10% 39%	5178
June	1st to 10th	Night	14% 6% 3 7% 6% 5% 6% 4 5% 8% 36%	1680
	11th to 20th	Night	14% 9% 3 7% 4 4 4 4 6% 7% 37%	1487
	21st to end	Night	8% 6% 3 6% 5% 4 4 3 6% 6% 50%	1470
July	1st to 10th	Night	3 2 1 2 2 2 2 2 5% 6% 73%	3250
	11th to 20th	Night	3 2 1 2 2 2 2 2 3 5% 77%	3689
	21st to end	Night	3 2 1 3 2 3 2 2 4 7% 70%	4049
August	1st to 10th	Night	3 2 1 3 3 2 2 2 3 5% 73%	2765
	11th to 20th	Night	8% 4 2 4 4 4 4 4 5% 8% 55%	2902
	21st to end	Night	13% 6% 2 6% 3 3 4 3 4 5% 51%	3443
September	1st to 10th	Night	7% 4 2 4 3 3 4 3 5% 7% 58%	2000
	11th to 20th	Night	12% 8% 3 7% 5% 4 5% 3 5% 6% 44%	2000
	21st to end	Night	10% 7% 2 8% 5% 4 4 3 5% 6% 46%	2289
October	1st to 10th	Night	11% 8% 2 6% 5% 4 4 3 5% 7% 45%	3920
	11th to 20th	Night	17% 8% 3 8% 5% 5% 4 3 5% 7% 34%	3897
	21st to end	Night	15% 7% 3 9% 6% 5% 6% 4 6% 8% 30%	4400
November	1st to 10th	Night	27% 10% 3 9% 5% 5% 6% 4 5% 6% 21%	2812
	11th to 20th	Night	23% 13% 3 10% 7% 5% 4 4 4 5% 20%	2940
	21st to end	Night	20% 13% 4 9% 6% 5% 5% 5% 5% 6% 22%	2940
December	1st to 10th	Night	14% 11% 3 9% 5% 4 5% 4 6% 6% 31%	4700
	11th to 20th	Night	22% 14% 5% 11% 7% 6% 6% 4 5% 5% 15%	5320
	21st to end	Night	21% 12% 4 11% 6% 6% 6% 5% 6% 6% 18%	7106

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	73% 10% 8% 6% 2	4723
	11th to 20th	Day	48% 10% 10% 18% 11% 2	4740
	21st to end	Day	57% 7% 7% 16% 13%	5467
February	1st to 10th	Day	67% 9% 9% 10% 5%	1890
	11th to 20th	Day	69% 9% 7% 8% 6% 1	1854
	21st to end	Day	69% 8% 9% 9% 4	1626
March	1st to 10th	Day	59% 11% 16% 11% 4	4787
	11th to 20th	Day	61% 6% 10% 21% 2	5110
	21st to end	Day	68% 11% 13% 8% 1	5758
April	1st to 10th	Day	68% 8% 13% 9% 1	2520
	11th to 20th	Day	61% 8% 11% 13% 7%	2512
	21st to end	Day	62% 8% 12% 12% 5%	2740
May	1st to 10th	Day	39% 8% 17% 28% 8%	8195
	11th to 20th	Day	51% 14% 19% 14% 2	8163
	21st to end	Day	46% 10% 25% 16% 3	8994
June	1st to 10th	Day	56% 8% 16% 13% 6%	2940
	11th to 20th	Day	58% 10% 14% 14% 4	3127
	21st to end	Day	44% 9% 18% 20% 8% 2	3150
July	1st to 10th	Day	21% 6% 15% 24% 19% 14%	6856
	11th to 20th	Day	16% 4 11% 29% 35% 5%	6399
	21st to end	Day	22% 6% 21% 35% 15% 2	6822
August	1st to 10th	Day	22% 6% 11% 34% 22% 5%	4369
	11th to 20th	Day	33% 11% 20% 24% 10% 2	4195
	21st to end	Day	40% 7% 12% 25% 15% 1	4458
September	1st to 10th	Day	35% 8% 14% 25% 14% 5%	2400
	11th to 20th	Day	41% 11% 14% 17% 15% 3	2400
	21st to end	Day	43% 9% 16% 18% 13% 2	2109
October	1st to 10th	Day	38% 7% 13% 31% 10% 1	3280
	11th to 20th	Day	53% 9% 15% 14% 9% 1	3261
	21st to end	Day	54% 9% 13% 12% 10% 1	3406
November	1st to 10th	Day	66% 10% 10% 11% 2	1703
	11th to 20th	Day	67% 10% 9% 7% 5% 2	1680
	21st to end	Day	63% 9% 9% 9% 8% 1	1680
December	1st to 10th	Day	52% 8% 9% 16% 14% 1	2700
	11th to 20th	Day	66% 9% 14% 9% 2	3108
	21st to end	Day	69% 10% 12% 7% 2	4092
January	1st to 10th	Night	74% 10% 8% 6% 2 1	8172
	11th to 20th	Night	48% 10% 11% 20% 11% 1	8220
	21st to end	Night	53% 8% 8% 20% 11% 1	8712
February	1st to 10th	Night	65% 9% 11% 9% 6%	2730
	11th to 20th	Night	63% 8% 11% 9% 7% 2	2664
	21st to end	Night	65% 9% 11% 10% 5%	2179
March	1st to 10th	Night	56% 10% 15% 13% 5%	5326
	11th to 20th	Night	49% 11% 16% 20% 2	5110
	21st to end	Night	66% 13% 12% 9%	5446
April	1st to 10th	Night	63% 9% 15% 11% 2	2100
	11th to 20th	Night	54% 10% 15% 12% 7% 1	2054
	21st to end	Night	55% 8% 16% 15% 5%	1880
May	1st to 10th	Night	36% 8% 17% 30% 9%	4721
	11th to 20th	Night	46% 15% 23% 13% 3 1	4700
	21st to end	Night	40% 14% 27% 17% 1	5182
June	1st to 10th	Night	47% 10% 18% 19% 5% 1	1680
	11th to 20th	Night	46% 11% 18% 20% 5%	1487
	21st to end	Night	35% 9% 22% 23% 8% 2	1470
July	1st to 10th	Night	13% 6% 20% 31% 14% 16%	3215
	11th to 20th	Night	13% 3 12% 32% 34% 6%	3642
	21st to end	Night	16% 6% 22% 37% 16% 3	3937
August	1st to 10th	Night	16% 5% 12% 36% 27% 4	2757
	11th to 20th	Night	25% 11% 29% 22% 9% 3	2929
	21st to end	Night	34% 8% 16% 30% 12% 1	3443
September	1st to 10th	Night	26% 10% 17% 27% 16% 5%	2000
	11th to 20th	Night	40% 10% 11% 20% 15% 4	2000
	21st to end	Night	38% 9% 15% 22% 14% 2	2289
October	1st to 10th	Night	36% 8% 19% 31% 6% 1	3920
	11th to 20th	Night	50% 7% 14% 21% 7% 1	3897
	21st to end	Night	49% 10% 15% 17% 9%	4400
November	1st to 10th	Night	64% 9% 11% 12% 4 1	2812
	11th to 20th	Night	66% 9% 9% 9% 5% 2	2940
	21st to end	Night	62% 9% 10% 10% 9% 1	2940
December	1st to 10th	Night	50% 9% 13% 20% 8% 1	4700
	11th to 20th	Night	70% 8% 11% 8% 2	5316
	21st to end	Night	64% 13% 13% 8% 2	7106

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	33% 18% 20% 14% 10% 5%	220
	11th to 20th	Day	29% 18% 18% 20% 10% 6%	220
	21st to end	Day	31% 16% 17% 19% 13% 4	342
February	1st to 10th	Day	37% 17% 20% 15% 10% 2	430
	11th to 20th	Day	36% 17% 23% 18% 6%	425
	21st to end	Day	39% 17% 23% 14% 6% 1	392
March	1st to 10th	Day	30% 23% 24% 16% 6% 1	540
	11th to 20th	Day	33% 17% 19% 19% 11% 2	540
	21st to end	Day	29% 20% 27% 17% 6% 1	594
April	1st to 10th	Day	31% 17% 21% 19% 10% 2	540
	11th to 20th	Day	25% 22% 25% 17% 7% 4	532
	21st to end	Day	25% 18% 26% 22% 8% 1	540
May	1st to 10th	Day	17% 17% 26% 26% 13% 2	543
	11th to 20th	Day	27% 15% 22% 22% 10% 4	568
	21st to end	Day	21% 12% 25% 26% 12% 2	617
June	1st to 10th	Day	22% 11% 24% 26% 13% 3	570
	11th to 20th	Day	18% 15% 33% 24% 9% 1	757
	21st to end	Day	12% 12% 24% 34% 14% 3	780
July	1st to 10th	Day	10% 8% 23% 39% 18% 2	771
	11th to 20th	Day	7% 8% 26% 39% 17% 3	578
	21st to end	Day	6% 6% 21% 38% 22% 6%	616
August	1st to 10th	Day	7% 9% 18% 40% 20% 6%	527
	11th to 20th	Day	8% 4 19% 40% 22% 7%	517
	21st to end	Day	11% 10% 23% 33% 17% 6%	583
September	1st to 10th	Day	11% 9% 25% 35% 16% 5%	530
	11th to 20th	Day	14% 10% 22% 32% 18% 4	530
	21st to end	Day	17% 15% 23% 26% 17% 3	530
October	1st to 10th	Day	22% 15% 20% 23% 18% 3	530
	11th to 20th	Day	25% 16% 20% 20% 14% 5%	530
	21st to end	Day	31% 16% 19% 21% 10% 4	493
November	1st to 10th	Day	32% 22% 17% 16% 12% 2	250
	11th to 20th	Day	32% 18% 18% 15% 12% 5%	220
	21st to end	Day	26% 18% 21% 17% 9% 8%	220
December	1st to 10th	Day	35% 16% 12% 15% 14% 8%	220
	11th to 20th	Day	39% 16% 23% 12% 8% 2	220
	21st to end	Day	37% 19% 14% 18% 10% 2	242
January	1st to 10th	Night	39% 14% 16% 17% 11% 2	840
	11th to 20th	Night	29% 14% 15% 23% 17% 2	840
	21st to end	Night	30% 11% 16% 25% 16% 2	924
February	1st to 10th	Night	30% 13% 17% 27% 11% 1	840
	11th to 20th	Night	30% 12% 16% 27% 14% 1	824
	21st to end	Night	32% 14% 19% 25% 9% 1	692
March	1st to 10th	Night	26% 15% 20% 25% 13% 2	840
	11th to 20th	Night	28% 15% 20% 24% 11% 1	840
	21st to end	Night	30% 15% 23% 23% 8% 1	924
April	1st to 10th	Night	25% 13% 20% 25% 15% 2	840
	11th to 20th	Night	22% 13% 22% 27% 14% 1	806
	21st to end	Night	22% 12% 20% 31% 14% 1	620
May	1st to 10th	Night	16% 11% 19% 32% 21%	420
	11th to 20th	Night	17% 8% 18% 32% 23% 2	414
	21st to end	Night	18% 6% 19% 33% 22% 2	455
June	1st to 10th	Night	17% 6% 25% 28% 24% 1	420
	11th to 20th	Night	18% 8% 23% 33% 18%	420
	21st to end	Night	10% 4 21% 36% 28% 1	420
July	1st to 10th	Night	6% 4 14% 42% 32% 3	410
	11th to 20th	Night	6% 4 11% 46% 31% 2	408
	21st to end	Night	3 2 13% 37% 41% 3	458
August	1st to 10th	Night	8% 2 11% 33% 41% 6%	489
	11th to 20th	Night	7% 2 7% 34% 43% 6%	594
	21st to end	Night	10% 5% 11% 37% 33% 3	780
September	1st to 10th	Night	10% 4 14% 35% 32% 5%	800
	11th to 20th	Night	13% 6% 18% 23% 36% 5%	800
	21st to end	Night	15% 8% 16% 31% 27% 3	800
October	1st to 10th	Night	18% 9% 15% 29% 26% 3	800
	11th to 20th	Night	24% 11% 15% 27% 20% 4	800
	21st to end	Night	24% 13% 18% 29% 15% 2	880
November	1st to 10th	Night	33% 12% 20% 25% 10% 1	820
	11th to 20th	Night	35% 12% 20% 20% 12% 2	840
	21st to end	Night	30% 11% 19% 22% 14% 3	840
December	1st to 10th	Night	29% 12% 15% 25% 17% 2	840
	11th to 20th	Night	36% 14% 20% 21% 8% 1	840
	21st to end	Night	40% 15% 17% 19% 8% 1	924

Page generated at 2026-07-28 00:25:24. Version ac07

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