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 2025-03-27.

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	16% 10% 3 8% 5% 5% 5% 4 6% 6% 32%	113751
	Night	16% 11% 3 9% 5% 5% 4 4 5% 6% 33%	114244
Transparency	Day	51% 9% 12% 17% 10% 2	113511
	Night	51% 10% 13% 17% 8% 2	114130
Seeing	Day	23% 14% 22% 25% 13% 3	15440
	Night	24% 11% 17% 27% 19% 2	23959

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	24% 16% 5% 13% 7% 6% 5% 4 5% 6% 8%	3639
	11th to 20th	Day	18% 13% 4 9% 5% 5% 5% 3 5% 6% 27%	3616
	21st to end	Day	16% 11% 4 9% 6% 5% 5% 4 6% 5% 29%	4216
February	1st to 10th	Day	23% 16% 5% 10% 6% 5% 4 4 5% 6% 16%	1800
	11th to 20th	Day	24% 16% 5% 11% 6% 5% 4 3 4 5% 16%	1755
	21st to end	Day	23% 20% 5% 9% 5% 5% 4 3 4 4 17%	1551
March	1st to 10th	Day	12% 13% 5% 12% 8% 7% 7% 6% 7% 6% 17%	3356
	11th to 20th	Day	15% 13% 4 8% 5% 5% 4 3 3 4 35%	3600
	21st to end	Day	17% 15% 5% 13% 9% 6% 6% 4 6% 5% 14%	4002
April	1st to 10th	Day	23% 16% 4 11% 7% 5% 5% 3 5% 6% 15%	2280
	11th to 20th	Day	19% 14% 4 10% 7% 5% 4 4 5% 5% 23%	2270
	21st to end	Day	20% 14% 5% 10% 6% 6% 4 4 5% 5% 22%	2479
May	1st to 10th	Day	19% 9% 3 7% 4 5% 5% 3 4 5% 35%	4420
	11th to 20th	Day	11% 9% 3 8% 6% 6% 6% 4 7% 8% 33%	4377
	21st to end	Day	23% 11% 4 10% 6% 6% 5% 4 7% 6% 18%	4813
June	1st to 10th	Day	23% 10% 3 8% 5% 5% 4 5% 5% 7% 24%	2660
	11th to 20th	Day	20% 11% 4 10% 6% 5% 6% 5% 6% 7% 21%	2829
	21st to end	Day	11% 7% 3 8% 6% 5% 4 4 6% 7% 38%	2850
July	1st to 10th	Day	6% 4 2 4 3 3 2 2 4 5% 65%	4740
	11th to 20th	Day	5% 3 1 3 3 2 2 3 4 5% 67%	4434
	21st to end	Day	9% 5% 2 4 3 3 3 3 5% 6% 56%	4790
August	1st to 10th	Day	5% 4 1 4 3 3 3 2 5% 7% 64%	4251
	11th to 20th	Day	7% 6% 2 6% 4 4 6% 5% 7% 9% 44%	4026
	21st to end	Day	13% 7% 2 6% 5% 4 4 3 5% 6% 45%	4322
September	1st to 10th	Day	9% 5% 2 6% 5% 4 4 4 6% 7% 49%	2280
	11th to 20th	Day	11% 8% 3 8% 5% 5% 5% 4 6% 7% 38%	2280
	21st to end	Day	14% 8% 3 7% 5% 4 4 3 6% 6% 39%	2004
October	1st to 10th	Day	14% 8% 2 6% 4 4 4 4 6% 9% 41%	3180
	11th to 20th	Day	20% 8% 4 8% 5% 5% 5% 4 6% 7% 27%	3161
	21st to end	Day	18% 9% 3 9% 6% 5% 6% 4 6% 8% 26%	3301
November	1st to 10th	Day	23% 14% 4 10% 6% 5% 7% 4 6% 6% 16%	1620
	11th to 20th	Day	25% 13% 4 9% 8% 5% 5% 4 6% 6% 17%	1600
	21st to end	Day	22% 16% 4 7% 5% 5% 5% 4 6% 7% 19%	1600
December	1st to 10th	Day	16% 9% 3 9% 6% 6% 5% 4 5% 6% 32%	2620
	11th to 20th	Day	22% 12% 4 11% 7% 7% 6% 5% 7% 8% 13%	3025
	21st to end	Day	21% 16% 4 11% 7% 7% 5% 4 7% 5% 13%	4004
January	1st to 10th	Night	25% 18% 6% 13% 7% 6% 4 4 4 4 10%	6306
	11th to 20th	Night	15% 15% 4 9% 4 4 4 3 5% 7% 28%	6282
	21st to end	Night	18% 11% 4 9% 5% 5% 4 3 5% 6% 31%	6733
February	1st to 10th	Night	23% 14% 4 11% 6% 5% 5% 3 4 6% 19%	2600
	11th to 20th	Night	21% 15% 4 11% 6% 4 4 3 4 4 24%	2532
	21st to end	Night	20% 17% 5% 9% 5% 5% 6% 4 4 6% 20%	2078
March	1st to 10th	Night	11% 14% 4 11% 7% 7% 6% 6% 8% 6% 20%	3738
	11th to 20th	Night	12% 9% 3 8% 5% 5% 5% 4 5% 6% 39%	3599
	21st to end	Night	21% 17% 4 11% 7% 6% 5% 4 5% 5% 15%	3789
April	1st to 10th	Night	18% 15% 4 11% 7% 5% 5% 4 4 5% 21%	1900
	11th to 20th	Night	16% 13% 4 8% 6% 5% 5% 5% 6% 6% 27%	1856
	21st to end	Night	17% 11% 3 8% 5% 6% 6% 4 4 8% 27%	1701
May	1st to 10th	Night	17% 10% 4 8% 5% 4 3 3 4 4 40%	2540
	11th to 20th	Night	9% 7% 3 8% 5% 5% 5% 4 6% 6% 42%	2516
	21st to end	Night	12% 14% 3 8% 6% 5% 6% 4 6% 7% 30%	2762
June	1st to 10th	Night	15% 7% 3 7% 6% 5% 6% 4 5% 8% 34%	1520
	11th to 20th	Night	15% 10% 4 8% 4 4 4 4 7% 6% 33%	1345
	21st to end	Night	8% 6% 3 6% 4 3 4 4 6% 6% 51%	1330
July	1st to 10th	Night	3 3 1 3 2 2 2 2 4 5% 73%	2220
	11th to 20th	Night	4 2 1 3 2 2 2 2 3 5% 75%	2524
	21st to end	Night	4 3 1 4 2 3 2 2 4 6% 70%	2762
August	1st to 10th	Night	3 2 1 3 3 2 2 2 3 5% 74%	2680
	11th to 20th	Night	7% 4 1 4 4 4 3 4 6% 8% 55%	2812
	21st to end	Night	13% 6% 2 6% 3 3 4 3 4 5% 52%	3338
September	1st to 10th	Night	7% 4 2 4 3 3 4 3 5% 7% 58%	1900
	11th to 20th	Night	12% 8% 3 7% 5% 4 5% 3 5% 6% 44%	1900
	21st to end	Night	10% 7% 2 8% 5% 4 4 3 5% 6% 46%	2174
October	1st to 10th	Night	11% 8% 2 6% 5% 4 4 3 5% 7% 45%	3800
	11th to 20th	Night	18% 8% 3 8% 5% 5% 4 3 5% 7% 34%	3777
	21st to end	Night	15% 7% 3 9% 6% 5% 6% 4 6% 8% 30%	4263
November	1st to 10th	Night	26% 10% 3 9% 5% 5% 6% 4 5% 6% 21%	2675
	11th to 20th	Night	23% 13% 3 10% 7% 5% 4 4 5% 5% 20%	2800
	21st to end	Night	19% 14% 4 9% 6% 5% 5% 5% 5% 6% 22%	2800
December	1st to 10th	Night	13% 11% 3 9% 5% 4 5% 4 6% 6% 32%	4560
	11th to 20th	Night	22% 14% 5% 11% 7% 6% 5% 4 5% 5% 15%	5180
	21st to end	Night	21% 12% 4 11% 7% 6% 6% 5% 6% 5% 18%	6952

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	74% 10% 8% 5% 2	3639
	11th to 20th	Day	55% 9% 11% 17% 7% 1	3640
	21st to end	Day	57% 8% 7% 15% 12%	4216
February	1st to 10th	Day	68% 9% 9% 9% 5%	1800
	11th to 20th	Day	69% 10% 7% 8% 5% 1	1764
	21st to end	Day	70% 7% 9% 10% 5%	1551
March	1st to 10th	Day	61% 12% 14% 10% 3	3356
	11th to 20th	Day	55% 7% 10% 27% 2 1	3600
	21st to end	Day	69% 11% 11% 9%	4002
April	1st to 10th	Day	71% 9% 12% 8% 1	2280
	11th to 20th	Day	63% 8% 10% 11% 7% 1	2270
	21st to end	Day	65% 8% 11% 11% 4	2479
May	1st to 10th	Day	49% 10% 14% 18% 9%	4420
	11th to 20th	Day	46% 14% 20% 17% 3	4380
	21st to end	Day	64% 13% 14% 8% 1	4814
June	1st to 10th	Day	59% 8% 16% 11% 6%	2660
	11th to 20th	Day	62% 11% 14% 10% 3	2829
	21st to end	Day	44% 8% 18% 20% 8% 2	2850
July	1st to 10th	Day	23% 6% 9% 20% 22% 20%	4666
	11th to 20th	Day	20% 5% 7% 24% 37% 6%	4358
	21st to end	Day	26% 7% 13% 32% 20% 3	4639
August	1st to 10th	Day	21% 6% 11% 35% 23% 5%	4234
	11th to 20th	Day	33% 11% 20% 24% 9% 2	4065
	21st to end	Day	40% 7% 13% 26% 15% 1	4321
September	1st to 10th	Day	33% 7% 14% 25% 15% 5%	2280
	11th to 20th	Day	43% 11% 13% 16% 14% 3	2280
	21st to end	Day	44% 9% 16% 16% 13% 2	2004
October	1st to 10th	Day	38% 7% 13% 31% 10% 1	3180
	11th to 20th	Day	53% 8% 15% 14% 8% 1	3161
	21st to end	Day	55% 9% 13% 12% 10% 1	3301
November	1st to 10th	Day	68% 9% 9% 11% 3	1620
	11th to 20th	Day	67% 10% 9% 7% 6% 2	1600
	21st to end	Day	63% 9% 9% 10% 9% 1	1600
December	1st to 10th	Day	51% 8% 9% 17% 14% 1	2620
	11th to 20th	Day	66% 9% 14% 9% 2	3028
	21st to end	Day	70% 10% 12% 7% 2	4004
January	1st to 10th	Night	74% 10% 7% 6% 2 1	6306
	11th to 20th	Night	53% 9% 12% 20% 6% 1	6320
	21st to end	Night	55% 8% 8% 19% 10% 1	6733
February	1st to 10th	Night	66% 9% 10% 9% 5%	2600
	11th to 20th	Night	64% 8% 11% 8% 6% 2	2534
	21st to end	Night	65% 8% 11% 10% 5%	2078
March	1st to 10th	Night	60% 11% 13% 12% 4	3738
	11th to 20th	Night	45% 12% 17% 23% 2 1	3600
	21st to end	Night	70% 12% 9% 8%	3789
April	1st to 10th	Night	66% 9% 14% 10% 2	1900
	11th to 20th	Night	56% 10% 14% 11% 8% 1	1856
	21st to end	Night	58% 9% 15% 13% 5% 1	1701
May	1st to 10th	Night	47% 11% 13% 21% 8%	2540
	11th to 20th	Night	38% 17% 22% 17% 5% 1	2516
	21st to end	Night	53% 19% 17% 9% 2	2762
June	1st to 10th	Night	48% 10% 18% 19% 5%	1520
	11th to 20th	Night	50% 11% 20% 16% 3	1345
	21st to end	Night	35% 9% 23% 23% 8% 2	1330
July	1st to 10th	Night	17% 6% 11% 29% 15% 22%	2185
	11th to 20th	Night	16% 3 9% 27% 37% 7%	2477
	21st to end	Night	17% 6% 14% 35% 23% 5%	2674
August	1st to 10th	Night	16% 4 11% 36% 28% 4	2672
	11th to 20th	Night	25% 11% 30% 22% 9% 3	2839
	21st to end	Night	34% 8% 16% 30% 11% 1	3338
September	1st to 10th	Night	26% 9% 16% 27% 17% 5%	1900
	11th to 20th	Night	41% 10% 11% 19% 14% 4	1900
	21st to end	Night	39% 9% 15% 20% 15% 2	2174
October	1st to 10th	Night	36% 7% 19% 31% 6% 1	3800
	11th to 20th	Night	51% 8% 14% 21% 6% 1	3777
	21st to end	Night	49% 10% 15% 17% 9%	4263
November	1st to 10th	Night	64% 9% 11% 12% 4 1	2675
	11th to 20th	Night	66% 9% 9% 9% 5% 2	2800
	21st to end	Night	62% 9% 9% 10% 9% 1	2800
December	1st to 10th	Night	49% 9% 13% 20% 9% 1	4560
	11th to 20th	Night	70% 8% 11% 8% 2	5176
	21st to end	Night	65% 13% 12% 8% 2	6952

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	36% 15% 20% 14% 11% 5%	200
	11th to 20th	Day	32% 17% 19% 20% 10% 4	200
	21st to end	Day	31% 17% 17% 18% 14% 4	315
February	1st to 10th	Day	38% 17% 19% 14% 10% 2	400
	11th to 20th	Day	38% 17% 22% 17% 6% 1	395
	21st to end	Day	39% 16% 23% 15% 6% 1	365
March	1st to 10th	Day	29% 23% 24% 17% 6% 1	500
	11th to 20th	Day	29% 17% 20% 20% 12% 2	500
	21st to end	Day	30% 20% 25% 17% 7% 1	531
April	1st to 10th	Day	32% 18% 22% 17% 9% 2	460
	11th to 20th	Day	27% 23% 24% 15% 6% 4	452
	21st to end	Day	28% 18% 25% 20% 8% 1	460
May	1st to 10th	Day	19% 17% 25% 24% 12% 2	463
	11th to 20th	Day	28% 13% 22% 22% 11% 4	488
	21st to end	Day	23% 13% 24% 25% 12% 3	529
June	1st to 10th	Day	24% 11% 23% 26% 13% 3	490
	11th to 20th	Day	20% 16% 32% 22% 10% 1	659
	21st to end	Day	12% 12% 23% 35% 15% 3	680
July	1st to 10th	Day	11% 8% 22% 39% 18% 3	671
	11th to 20th	Day	7% 7% 24% 39% 19% 3	497
	21st to end	Day	7% 6% 20% 39% 23% 5%	531
August	1st to 10th	Day	7% 8% 18% 40% 20% 6%	487
	11th to 20th	Day	8% 4 17% 41% 23% 7%	477
	21st to end	Day	12% 10% 24% 32% 16% 6%	539
September	1st to 10th	Day	12% 9% 25% 34% 15% 4	490
	11th to 20th	Day	15% 10% 21% 32% 18% 4	490
	21st to end	Day	17% 15% 22% 26% 18% 3	490
October	1st to 10th	Day	23% 15% 19% 22% 19% 3	490
	11th to 20th	Day	26% 14% 20% 20% 14% 6%	490
	21st to end	Day	31% 16% 19% 20% 10% 4	454
November	1st to 10th	Day	32% 23% 15% 15% 13% 2	227
	11th to 20th	Day	32% 18% 17% 14% 14% 6%	200
	21st to end	Day	28% 18% 20% 16% 10% 9%	200
December	1st to 10th	Day	32% 16% 12% 17% 15% 9%	200
	11th to 20th	Day	37% 17% 25% 12% 8% 2	200
	21st to end	Day	40% 18% 13% 18% 10% 1	220
January	1st to 10th	Night	40% 14% 15% 17% 12% 2	800
	11th to 20th	Night	30% 14% 15% 23% 16% 2	800
	21st to end	Night	30% 12% 16% 24% 16% 2	880
February	1st to 10th	Night	32% 14% 16% 26% 11% 1	800
	11th to 20th	Night	31% 12% 16% 27% 13% 1	784
	21st to end	Night	32% 14% 18% 25% 9% 1	660
March	1st to 10th	Night	27% 14% 20% 26% 13% 2	800
	11th to 20th	Night	27% 15% 20% 25% 12% 1	800
	21st to end	Night	31% 15% 23% 22% 9% 1	862
April	1st to 10th	Night	26% 13% 21% 23% 14% 2	760
	11th to 20th	Night	23% 14% 22% 25% 15% 2	728
	21st to end	Night	23% 12% 19% 30% 14% 1	561
May	1st to 10th	Night	17% 12% 21% 30% 20%	380
	11th to 20th	Night	16% 7% 17% 33% 25% 2	374
	21st to end	Night	20% 6% 19% 31% 22% 2	411
June	1st to 10th	Night	18% 6% 24% 28% 24% 1	380
	11th to 20th	Night	20% 8% 23% 30% 19% 1	380
	21st to end	Night	9% 4 19% 37% 28% 2	380
July	1st to 10th	Night	6% 4 13% 41% 33% 2	370
	11th to 20th	Night	7% 4 10% 46% 32% 2	368
	21st to end	Night	4 2 13% 37% 42% 4	416
August	1st to 10th	Night	8% 2 11% 31% 42% 6%	464
	11th to 20th	Night	7% 2 7% 33% 44% 7%	564
	21st to end	Night	10% 5% 12% 38% 32% 3	741
September	1st to 10th	Night	10% 4 14% 35% 31% 5%	760
	11th to 20th	Night	14% 6% 17% 22% 36% 6%	760
	21st to end	Night	15% 8% 16% 31% 27% 3	760
October	1st to 10th	Night	18% 9% 14% 29% 27% 3	760
	11th to 20th	Night	24% 11% 14% 26% 21% 5%	760
	21st to end	Night	25% 12% 18% 28% 15% 2	836
November	1st to 10th	Night	33% 11% 20% 25% 10% 1	780
	11th to 20th	Night	36% 12% 19% 19% 12% 2	800
	21st to end	Night	30% 12% 19% 22% 14% 4	800
December	1st to 10th	Night	28% 13% 15% 25% 17% 2	800
	11th to 20th	Night	36% 13% 20% 22% 9% 2	800
	21st to end	Night	41% 15% 18% 18% 7% 1	880

Page generated at 2025-03-24 06:04:32. Version ac07

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