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 2024-02-15.

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	18% 11% 4 7% 7% 4 5% 5% 5% 6% 28%	78756
	Night	18% 11% 4 8% 7% 3 5% 5% 5% 6% 30%	80269
Transparency	Day	56% 9% 12% 15% 7% 1	78477
	Night	56% 9% 12% 15% 7% 1	80128
Seeing	Day	23% 14% 22% 25% 13% 3	14004
	Night	25% 10% 17% 27% 19% 2	22562

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	28% 17% 5% 10% 8% 4 5% 5% 4 5% 10%	2539
	11th to 20th	Day	26% 14% 4 7% 6% 3 4 4 4 6% 22%	2516
	21st to end	Day	23% 13% 5% 10% 8% 5% 6% 6% 7% 6% 13%	2936
February	1st to 10th	Day	24% 15% 5% 10% 6% 4 4 4 5% 6% 15%	1710
	11th to 20th	Day	25% 15% 5% 9% 7% 3 5% 3 5% 5% 17%	1612
	21st to end	Day	24% 19% 6% 8% 6% 4 5% 4 3 4 18%	1390
March	1st to 10th	Day	20% 16% 5% 8% 9% 4 5% 6% 5% 5% 17%	1862
	11th to 20th	Day	24% 14% 5% 9% 6% 4 5% 4 4 6% 18%	1980
	21st to end	Day	22% 16% 7% 11% 9% 4 5% 6% 5% 5% 11%	2236
April	1st to 10th	Day	24% 15% 4 10% 8% 4 6% 4 5% 6% 14%	2160
	11th to 20th	Day	21% 13% 4 9% 8% 3 5% 5% 5% 5% 21%	2149
	21st to end	Day	21% 13% 5% 8% 7% 4 5% 5% 4 6% 22%	2348
May	1st to 10th	Day	18% 11% 4 7% 5% 4 6% 5% 5% 5% 30%	2520
	11th to 20th	Day	18% 11% 4 7% 7% 4 6% 6% 8% 7% 24%	2477
	21st to end	Day	21% 9% 5% 9% 7% 3 5% 6% 5% 6% 23%	2723
June	1st to 10th	Day	24% 10% 4 7% 6% 3 5% 6% 5% 7% 24%	2520
	11th to 20th	Day	21% 11% 4 8% 8% 4 6% 6% 6% 7% 20%	2680
	21st to end	Day	11% 7% 4 7% 7% 3 4 5% 6% 7% 39%	2700
July	1st to 10th	Day	9% 6% 3 6% 5% 4 4 4 6% 6% 49%	2700
	11th to 20th	Day	9% 5% 2 5% 5% 3 4 5% 7% 7% 49%	2534
	21st to end	Day	7% 5% 2 3 3 2 2 3 5% 7% 61%	2741
August	1st to 10th	Day	8% 5% 2 4 5% 3 4 4 6% 8% 51%	2422
	11th to 20th	Day	7% 5% 2 4 3 2 4 5% 5% 7% 56%	2298
	21st to end	Day	10% 6% 2 6% 6% 4 5% 4 5% 8% 44%	2466
September	1st to 10th	Day	9% 5% 2 6% 5% 3 4 4 5% 7% 49%	2160
	11th to 20th	Day	11% 7% 3 7% 6% 4 5% 5% 6% 7% 39%	2160
	21st to end	Day	14% 8% 3 6% 6% 3 5% 3 6% 6% 39%	1900
October	1st to 10th	Day	18% 11% 4 7% 5% 3 4 4 6% 6% 31%	1800
	11th to 20th	Day	19% 9% 4 8% 6% 3 4 5% 5% 7% 29%	1800
	21st to end	Day	23% 9% 4 8% 7% 3 4 5% 5% 6% 26%	1900
November	1st to 10th	Day	23% 13% 6% 9% 7% 4 6% 5% 6% 5% 16%	1538
	11th to 20th	Day	25% 12% 5% 8% 8% 3 6% 5% 5% 6% 18%	1520
	21st to end	Day	23% 14% 5% 6% 6% 4 5% 5% 5% 6% 19%	1520
December	1st to 10th	Day	19% 12% 5% 9% 7% 4 4 5% 4 5% 25%	1520
	11th to 20th	Day	21% 13% 5% 9% 9% 4 5% 6% 6% 8% 15%	1925
	21st to end	Day	20% 16% 5% 10% 8% 4 6% 5% 6% 6% 14%	2794
January	1st to 10th	Night	25% 19% 6% 10% 9% 5% 5% 4 4 3 10%	4406
	11th to 20th	Night	22% 14% 5% 9% 6% 3 4 4 5% 7% 21%	4382
	21st to end	Night	24% 13% 5% 10% 8% 4 6% 5% 5% 6% 13%	4708
February	1st to 10th	Night	24% 13% 5% 9% 7% 4 5% 4 4 6% 19%	2470
	11th to 20th	Night	21% 14% 5% 9% 7% 3 4 3 4 4 23%	2329
	21st to end	Night	20% 17% 6% 8% 6% 4 6% 5% 4 5% 19%	1865
March	1st to 10th	Night	19% 14% 5% 8% 6% 4 5% 5% 6% 6% 23%	2098
	11th to 20th	Night	20% 11% 5% 10% 7% 5% 6% 5% 4 6% 22%	1979
	21st to end	Night	21% 15% 5% 9% 9% 4 5% 5% 5% 5% 17%	2120
April	1st to 10th	Night	19% 14% 5% 9% 8% 4 6% 5% 4 6% 21%	1800
	11th to 20th	Night	17% 11% 5% 7% 6% 4 6% 5% 6% 7% 26%	1758
	21st to end	Night	18% 10% 3 7% 6% 4 7% 5% 4 8% 28%	1612
May	1st to 10th	Night	14% 9% 3 7% 6% 3 4 5% 5% 6% 38%	1440
	11th to 20th	Night	14% 7% 4 7% 6% 5% 6% 6% 7% 6% 31%	1416
	21st to end	Night	14% 10% 3 7% 7% 3 6% 5% 6% 7% 32%	1552
June	1st to 10th	Night	15% 5% 4 6% 7% 4 6% 5% 5% 8% 34%	1440
	11th to 20th	Night	16% 10% 4 8% 5% 4 5% 5% 7% 7% 32%	1275
	21st to end	Night	8% 6% 3 5% 5% 2 3 4 5% 6% 52%	1260
July	1st to 10th	Night	6% 4 2 4 4 1 4 4 5% 7% 59%	1260
	11th to 20th	Night	6% 3 3 4 4 2 3 4 4 5% 63%	1424
	21st to end	Night	3 2 1 3 2 2 2 2 4 5% 74%	1576
August	1st to 10th	Night	6% 3 1 4 4 1 3 3 4 7% 63%	1513
	11th to 20th	Night	5% 3 1 2 3 2 3 4 4 7% 67%	1602
	21st to end	Night	8% 5% 1 5% 4 3 3 4 5% 5% 57%	1890
September	1st to 10th	Night	7% 4 2 4 4 2 4 4 4 7% 58%	1800
	11th to 20th	Night	11% 8% 3 6% 5% 4 5% 4 5% 6% 45%	1800
	21st to end	Night	11% 7% 2 7% 6% 3 4 4 5% 6% 45%	2059
October	1st to 10th	Night	15% 8% 3 6% 6% 3 3 4 4 6% 39%	2160
	11th to 20th	Night	19% 8% 3 8% 6% 4 5% 3 4 6% 34%	2160
	21st to end	Night	20% 8% 3 7% 7% 3 4 4 5% 7% 32%	2456
November	1st to 10th	Night	27% 9% 4 7% 6% 4 6% 5% 5% 6% 22%	2537
	11th to 20th	Night	24% 12% 4 8% 8% 4 5% 5% 5% 5% 21%	2660
	21st to end	Night	20% 13% 4 8% 7% 4 5% 6% 5% 6% 23%	2660
December	1st to 10th	Night	21% 12% 4 8% 7% 3 5% 5% 5% 6% 24%	2660
	11th to 20th	Night	22% 13% 5% 9% 7% 4 6% 5% 5% 5% 20%	3280
	21st to end	Night	21% 12% 5% 11% 9% 4 5% 5% 5% 5% 17%	4862

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	77% 10% 6% 5% 3 1	2539
	11th to 20th	Day	64% 7% 11% 13% 4 2	2540
	21st to end	Day	73% 9% 7% 7% 4 1	2936
February	1st to 10th	Day	69% 9% 8% 9% 4	1710
	11th to 20th	Day	69% 10% 8% 9% 5% 1	1621
	21st to end	Day	70% 7% 9% 9% 5%	1390
March	1st to 10th	Day	68% 8% 10% 11% 3	1862
	11th to 20th	Day	70% 6% 9% 12% 2 1	1980
	21st to end	Day	76% 9% 9% 7%	2236
April	1st to 10th	Day	72% 8% 12% 8% 1	2160
	11th to 20th	Day	65% 8% 10% 11% 6% 1	2149
	21st to end	Day	65% 8% 11% 11% 4	2348
May	1st to 10th	Day	55% 9% 15% 17% 5%	2520
	11th to 20th	Day	58% 10% 15% 13% 4	2480
	21st to end	Day	62% 9% 13% 14% 2	2724
June	1st to 10th	Day	60% 8% 16% 11% 5%	2520
	11th to 20th	Day	63% 11% 14% 10% 3	2680
	21st to end	Day	44% 8% 18% 19% 9% 2	2700
July	1st to 10th	Day	37% 9% 14% 24% 15% 2	2626
	11th to 20th	Day	33% 8% 12% 28% 18% 2	2458
	21st to end	Day	22% 6% 13% 34% 20% 4	2589
August	1st to 10th	Day	31% 8% 15% 27% 15% 3	2405
	11th to 20th	Day	26% 8% 17% 29% 15% 4	2298
	21st to end	Day	38% 7% 13% 29% 11% 2	2466
September	1st to 10th	Day	34% 7% 14% 26% 14% 5%	2160
	11th to 20th	Day	42% 11% 13% 17% 15% 3	2160
	21st to end	Day	45% 10% 15% 16% 13% 2	1900
October	1st to 10th	Day	52% 7% 10% 20% 9% 1	1800
	11th to 20th	Day	53% 8% 15% 15% 7% 1	1800
	21st to end	Day	59% 8% 9% 14% 10%	1900
November	1st to 10th	Day	68% 9% 9% 11% 3 1	1538
	11th to 20th	Day	67% 9% 9% 7% 6% 2	1520
	21st to end	Day	64% 8% 8% 10% 9% 1	1520
December	1st to 10th	Day	62% 9% 8% 11% 8% 2	1520
	11th to 20th	Day	66% 10% 11% 9% 3	1928
	21st to end	Day	69% 10% 10% 8% 3	2794
January	1st to 10th	Night	77% 9% 6% 5% 2 1	4406
	11th to 20th	Night	62% 8% 11% 15% 4 1	4420
	21st to end	Night	71% 10% 7% 7% 4 1	4708
February	1st to 10th	Night	67% 8% 10% 9% 5%	2470
	11th to 20th	Night	65% 8% 11% 9% 6% 2	2331
	21st to end	Night	67% 8% 9% 10% 5%	1865
March	1st to 10th	Night	62% 8% 13% 13% 4	2098
	11th to 20th	Night	64% 8% 11% 13% 4 1	1980
	21st to end	Night	69% 12% 11% 9%	2120
April	1st to 10th	Night	66% 9% 13% 10% 2	1800
	11th to 20th	Night	58% 9% 14% 11% 7% 1	1758
	21st to end	Night	58% 8% 15% 14% 5% 1	1612
May	1st to 10th	Night	48% 10% 17% 18% 8% 1	1440
	11th to 20th	Night	51% 11% 16% 15% 4 2	1416
	21st to end	Night	51% 13% 18% 16% 3	1552
June	1st to 10th	Night	48% 10% 18% 18% 4	1440
	11th to 20th	Night	52% 12% 20% 14% 3	1275
	21st to end	Night	35% 9% 23% 23% 9% 2	1260
July	1st to 10th	Night	28% 10% 17% 26% 15% 5%	1225
	11th to 20th	Night	26% 5% 15% 31% 20% 3	1377
	21st to end	Night	15% 6% 13% 38% 21% 7%	1488
August	1st to 10th	Night	23% 7% 17% 29% 20% 4	1505
	11th to 20th	Night	18% 8% 20% 33% 16% 5%	1602
	21st to end	Night	29% 9% 16% 32% 14% 1	1890
September	1st to 10th	Night	26% 10% 15% 28% 16% 5%	1800
	11th to 20th	Night	41% 9% 11% 20% 15% 5%	1800
	21st to end	Night	40% 9% 13% 20% 15% 2	2059
October	1st to 10th	Night	46% 7% 13% 23% 9% 1	2160
	11th to 20th	Night	53% 7% 12% 19% 8% 1	2160
	21st to end	Night	52% 8% 11% 17% 11%	2456
November	1st to 10th	Night	64% 9% 11% 12% 4 1	2537
	11th to 20th	Night	66% 10% 9% 9% 5% 2	2660
	21st to end	Night	62% 8% 8% 11% 10% 1	2660
December	1st to 10th	Night	63% 8% 10% 12% 6% 1	2660
	11th to 20th	Night	65% 10% 12% 10% 3	3276
	21st to end	Night	67% 14% 8% 8% 2	4862

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	37% 14% 18% 14% 11% 6%	180
	11th to 20th	Day	34% 17% 19% 18% 9% 3	180
	21st to end	Day	34% 18% 16% 17% 13% 2	288
February	1st to 10th	Day	39% 16% 19% 14% 10% 2	370
	11th to 20th	Day	40% 18% 19% 17% 6% 1	348
	21st to end	Day	38% 17% 23% 15% 7% 1	306
March	1st to 10th	Day	29% 23% 24% 17% 6% 1	420
	11th to 20th	Day	30% 17% 20% 20% 12% 1	420
	21st to end	Day	31% 18% 25% 17% 6% 1	462
April	1st to 10th	Day	34% 17% 21% 18% 9% 2	420
	11th to 20th	Day	29% 21% 24% 15% 7% 5%	412
	21st to end	Day	28% 17% 25% 21% 8% 1	420
May	1st to 10th	Day	20% 16% 24% 26% 12% 2	423
	11th to 20th	Day	30% 11% 22% 22% 10% 4	448
	21st to end	Day	23% 12% 24% 26% 12% 3	485
June	1st to 10th	Day	24% 12% 24% 24% 13% 3	450
	11th to 20th	Day	20% 16% 32% 21% 10% 1	610
	21st to end	Day	12% 11% 24% 35% 15% 3	630
July	1st to 10th	Day	12% 8% 20% 39% 18% 3	621
	11th to 20th	Day	8% 7% 26% 38% 18% 3	457
	21st to end	Day	7% 5% 21% 39% 23% 5%	487
August	1st to 10th	Day	8% 9% 18% 38% 21% 6%	447
	11th to 20th	Day	7% 4 16% 41% 24% 8%	437
	21st to end	Day	11% 10% 25% 33% 16% 5%	495
September	1st to 10th	Day	13% 10% 25% 33% 15% 4	450
	11th to 20th	Day	16% 9% 20% 32% 20% 4	450
	21st to end	Day	18% 15% 20% 26% 18% 3	450
October	1st to 10th	Day	23% 15% 19% 21% 19% 3	450
	11th to 20th	Day	26% 14% 19% 20% 15% 6%	450
	21st to end	Day	33% 15% 17% 20% 11% 4	415
November	1st to 10th	Day	33% 23% 14% 15% 14% 1	205
	11th to 20th	Day	29% 19% 17% 14% 15% 7%	180
	21st to end	Day	29% 19% 18% 14% 9% 9%	180
December	1st to 10th	Day	34% 17% 13% 16% 13% 7%	180
	11th to 20th	Day	36% 17% 24% 13% 8% 2	180
	21st to end	Day	38% 17% 14% 19% 11% 1	198
January	1st to 10th	Night	41% 14% 15% 16% 12% 3	760
	11th to 20th	Night	31% 14% 15% 21% 16% 2	760
	21st to end	Night	32% 12% 16% 23% 15% 2	836
February	1st to 10th	Night	33% 13% 15% 26% 11% 1	760
	11th to 20th	Night	32% 13% 15% 26% 14% 1	722
	21st to end	Night	32% 14% 19% 24% 10% 1	592
March	1st to 10th	Night	28% 14% 18% 24% 13% 2	720
	11th to 20th	Night	28% 14% 20% 26% 12% 1	720
	21st to end	Night	31% 14% 22% 23% 9% 1	792
April	1st to 10th	Night	27% 13% 21% 23% 14% 2	720
	11th to 20th	Night	24% 14% 20% 26% 15% 2	690
	21st to end	Night	24% 11% 19% 30% 15% 1	532
May	1st to 10th	Night	17% 12% 19% 31% 21%	360
	11th to 20th	Night	17% 7% 16% 33% 25% 2	354
	21st to end	Night	20% 6% 18% 32% 22% 2	389
June	1st to 10th	Night	17% 6% 24% 28% 24% 1	360
	11th to 20th	Night	20% 8% 22% 30% 19% 1	360
	21st to end	Night	10% 4 20% 37% 28% 2	360
July	1st to 10th	Night	7% 4 14% 39% 33% 3	350
	11th to 20th	Night	7% 4 10% 45% 32% 2	348
	21st to end	Night	3 2 13% 36% 43% 4	394
August	1st to 10th	Night	8% 2 12% 30% 41% 7%	439
	11th to 20th	Night	6% 2 6% 33% 45% 7%	534
	21st to end	Night	10% 5% 12% 38% 32% 3	702
September	1st to 10th	Night	10% 4 14% 36% 30% 5%	720
	11th to 20th	Night	14% 6% 16% 22% 37% 6%	720
	21st to end	Night	16% 8% 15% 31% 27% 3	720
October	1st to 10th	Night	18% 9% 14% 28% 27% 3	720
	11th to 20th	Night	25% 11% 14% 25% 21% 5%	720
	21st to end	Night	26% 13% 16% 27% 16% 3	792
November	1st to 10th	Night	33% 11% 20% 25% 10% 1	740
	11th to 20th	Night	35% 12% 19% 19% 12% 2	760
	21st to end	Night	31% 12% 19% 21% 14% 4	760
December	1st to 10th	Night	29% 13% 16% 25% 16% 2	760
	11th to 20th	Night	36% 12% 20% 21% 9% 1	760
	21st to end	Night	42% 15% 17% 18% 8% 1	836

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