LaGrange
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the LaGrange clear sky chart from 2005-11-06 to 2024-01-22.

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	15% 10% 4 7% 6% 3 5% 5% 5% 7% 31%	75004
	Night	16% 11% 4 7% 6% 3 5% 5% 5% 7% 32%	74904
Transparency	Day	51% 7% 12% 18% 11% 1	74723
	Night	51% 7% 12% 18% 11% 2	74705
Seeing	Day	19% 14% 28% 22% 12% 5%	13871
	Night	20% 11% 28% 27% 12% 1	23594

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	18% 16% 8% 10% 8% 4 5% 4 5% 4 17%	1706
	11th to 20th	Day	19% 18% 9% 12% 8% 3 5% 4 3 5% 14%	1710
	21st to end	Day	17% 18% 9% 13% 10% 3 4 4 4 4 14%	1791
February	1st to 10th	Day	19% 18% 6% 10% 8% 4 4 3 3 5% 21%	1620
	11th to 20th	Day	15% 13% 8% 15% 8% 4 5% 5% 4 4 19%	1658
	21st to end	Day	18% 14% 4 11% 7% 3 6% 4 4 6% 23%	1480
March	1st to 10th	Day	20% 13% 6% 8% 5% 4 4 4 5% 6% 26%	1904
	11th to 20th	Day	16% 13% 5% 10% 6% 3 4 4 3 5% 29%	1980
	21st to end	Day	21% 13% 5% 8% 6% 3 4 4 4 6% 26%	2178
April	1st to 10th	Day	14% 13% 3 8% 6% 4 4 5% 5% 6% 32%	1996
	11th to 20th	Day	17% 11% 4 6% 6% 3 5% 4 5% 6% 33%	2312
	21st to end	Day	21% 9% 3 6% 5% 3 4 4 4 7% 33%	2340
May	1st to 10th	Day	18% 9% 3 7% 7% 3 6% 4 6% 6% 31%	2340
	11th to 20th	Day	19% 8% 3 6% 5% 4 5% 5% 7% 7% 32%	2301
	21st to end	Day	9% 5% 3 6% 6% 3 6% 5% 8% 9% 39%	2531
June	1st to 10th	Day	14% 6% 3 6% 5% 4 5% 5% 6% 9% 38%	2438
	11th to 20th	Day	12% 6% 3 6% 6% 4 5% 5% 6% 9% 38%	2570
	21st to end	Day	11% 4 2 5% 5% 4 5% 6% 6% 10% 40%	2575
July	1st to 10th	Day	10% 6% 3 5% 6% 3 5% 5% 5% 8% 43%	2476
	11th to 20th	Day	10% 5% 3 5% 5% 3 6% 6% 6% 12% 41%	2340
	21st to end	Day	9% 5% 2 5% 6% 4 6% 6% 7% 8% 40%	2547
August	1st to 10th	Day	8% 6% 3 6% 6% 4 6% 5% 7% 8% 41%	2327
	11th to 20th	Day	11% 6% 3 6% 6% 3 6% 6% 6% 10% 36%	2303
	21st to end	Day	11% 5% 2 5% 5% 4 5% 6% 5% 9% 41%	2560
September	1st to 10th	Day	14% 6% 2 5% 5% 3 6% 5% 6% 7% 41%	2023
	11th to 20th	Day	11% 6% 3 5% 6% 3 5% 4 7% 8% 42%	1980
	21st to end	Day	17% 8% 2 6% 5% 2 4 4 5% 7% 40%	1980
October	1st to 10th	Day	13% 8% 2 6% 5% 4 5% 5% 7% 7% 39%	1886
	11th to 20th	Day	18% 9% 3 6% 5% 3 5% 5% 6% 5% 36%	1800
	21st to end	Day	22% 12% 3 6% 6% 3 4 5% 5% 5% 28%	1942
November	1st to 10th	Day	13% 10% 4 7% 5% 3 5% 3 5% 7% 38%	1672
	11th to 20th	Day	18% 14% 5% 7% 6% 3 4 4 3 6% 30%	1710
	21st to end	Day	18% 16% 5% 9% 6% 4 5% 5% 5% 7% 21%	1564
December	1st to 10th	Day	18% 19% 7% 10% 7% 3 4 4 4 5% 19%	1520
	11th to 20th	Day	17% 17% 8% 13% 7% 3 4 4 4 6% 17%	1910
	21st to end	Day	23% 23% 8% 10% 7% 3 4 3 4 5% 10%	3034
January	1st to 10th	Night	18% 16% 7% 11% 7% 4 4 4 4 4 21%	2459
	11th to 20th	Night	18% 19% 7% 12% 8% 4 4 3 3 4 16%	2470
	21st to end	Night	17% 17% 7% 11% 7% 3 5% 3 4 5% 20%	2599
February	1st to 10th	Night	21% 14% 6% 10% 7% 4 5% 3 4 5% 21%	2340
	11th to 20th	Night	17% 15% 7% 9% 6% 4 6% 5% 5% 5% 21%	2188
	21st to end	Night	20% 14% 6% 9% 7% 4 4 4 3 5% 25%	1776
March	1st to 10th	Night	17% 11% 6% 8% 6% 4 4 4 4 5% 32%	2054
	11th to 20th	Night	16% 9% 4 6% 5% 3 4 5% 6% 7% 34%	1980
	21st to end	Night	20% 11% 4 7% 5% 3 4 4 5% 6% 31%	2178
April	1st to 10th	Night	15% 12% 4 6% 6% 3 5% 5% 6% 7% 32%	1972
	11th to 20th	Night	16% 10% 3 6% 6% 3 5% 5% 5% 7% 34%	1603
	21st to end	Night	17% 8% 4 6% 5% 3 4 5% 5% 7% 36%	1620
May	1st to 10th	Night	17% 9% 3 8% 7% 3 6% 5% 6% 8% 29%	1620
	11th to 20th	Night	15% 8% 4 6% 4 3 4 4 6% 9% 36%	1592
	21st to end	Night	9% 5% 3 5% 4 3 5% 6% 6% 11% 43%	1744
June	1st to 10th	Night	10% 5% 3 5% 5% 3 5% 6% 5% 8% 44%	1512
	11th to 20th	Night	10% 5% 2 6% 7% 2 5% 6% 6% 10% 41%	1382
	21st to end	Night	10% 4 2 5% 4 4 6% 4 6% 11% 44%	1375
July	1st to 10th	Night	8% 5% 2 5% 5% 3 5% 5% 6% 8% 47%	1476
	11th to 20th	Night	8% 4 2 4 5% 3 4 6% 6% 11% 47%	1620
	21st to end	Night	8% 5% 2 5% 6% 3 5% 5% 7% 9% 45%	1771
August	1st to 10th	Night	6% 4 2 5% 5% 3 4 6% 6% 9% 48%	1611
	11th to 20th	Night	9% 6% 1 6% 5% 3 5% 5% 6% 9% 45%	1598
	21st to end	Night	8% 5% 3 4 5% 4 5% 5% 6% 9% 46%	1782
September	1st to 10th	Night	11% 5% 2 5% 6% 3 5% 5% 6% 7% 46%	1929
	11th to 20th	Night	10% 4 1 4 5% 2 4 4 5% 7% 52%	1980
	21st to end	Night	15% 6% 3 5% 5% 4 5% 5% 5% 6% 42%	1980
October	1st to 10th	Night	14% 6% 2 6% 5% 3 4 4 5% 8% 43%	2074
	11th to 20th	Night	20% 7% 3 6% 6% 3 4 4 5% 6% 36%	2160
	21st to end	Night	24% 10% 3 6% 5% 4 4 4 6% 5% 29%	2412
November	1st to 10th	Night	15% 9% 3 5% 5% 3 4 6% 5% 7% 38%	2406
	11th to 20th	Night	16% 14% 5% 8% 6% 3 4 4 4 5% 30%	2470
	21st to end	Night	21% 14% 5% 8% 6% 4 5% 4 5% 6% 24%	2612
December	1st to 10th	Night	20% 17% 7% 9% 6% 3 4 4 4 5% 20%	2660
	11th to 20th	Night	17% 16% 7% 10% 6% 3 5% 5% 5% 6% 22%	3285
	21st to end	Night	24% 20% 7% 9% 7% 3 4 4 4 5% 12%	4614

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	69% 6% 11% 10% 4	1707
	11th to 20th	Day	74% 6% 10% 8% 2	1710
	21st to end	Day	74% 5% 10% 8% 3	1791
February	1st to 10th	Day	67% 5% 11% 12% 5%	1620
	11th to 20th	Day	67% 6% 9% 12% 5% 1	1667
	21st to end	Day	61% 6% 13% 11% 6% 2	1480
March	1st to 10th	Day	59% 6% 11% 19% 6%	1904
	11th to 20th	Day	58% 6% 10% 15% 10% 1	1980
	21st to end	Day	59% 6% 8% 18% 8% 1	2178
April	1st to 10th	Day	51% 7% 12% 17% 11% 1	1996
	11th to 20th	Day	52% 6% 11% 16% 13% 2	2312
	21st to end	Day	51% 6% 12% 20% 10% 2	2340
May	1st to 10th	Day	52% 8% 12% 18% 9% 2	2340
	11th to 20th	Day	48% 9% 11% 17% 13% 2	2305
	21st to end	Day	39% 9% 14% 23% 13% 1	2531
June	1st to 10th	Day	42% 8% 11% 24% 14% 1	2438
	11th to 20th	Day	41% 9% 15% 21% 13% 2	2570
	21st to end	Day	36% 9% 14% 22% 16% 2	2575
July	1st to 10th	Day	39% 8% 11% 22% 18% 2	2409
	11th to 20th	Day	34% 8% 16% 25% 15% 2	2271
	21st to end	Day	36% 10% 15% 22% 15% 2	2405
August	1st to 10th	Day	38% 9% 15% 24% 14%	2314
	11th to 20th	Day	40% 9% 16% 22% 11% 2	2303
	21st to end	Day	37% 9% 14% 22% 15% 3	2560
September	1st to 10th	Day	39% 8% 16% 19% 15% 3	2023
	11th to 20th	Day	38% 8% 15% 22% 15% 2	1980
	21st to end	Day	43% 7% 11% 20% 18% 1	1980
October	1st to 10th	Day	42% 8% 12% 22% 15% 1	1886
	11th to 20th	Day	48% 8% 12% 20% 12% 1	1800
	21st to end	Day	56% 7% 14% 14% 9% 1	1942
November	1st to 10th	Day	46% 5% 13% 20% 15% 1	1672
	11th to 20th	Day	55% 5% 11% 18% 8% 2	1710
	21st to end	Day	62% 7% 13% 12% 6%	1564
December	1st to 10th	Day	69% 7% 10% 12% 3	1520
	11th to 20th	Day	67% 7% 10% 13% 3	1906
	21st to end	Day	78% 6% 8% 6% 2	3034
January	1st to 10th	Night	67% 4 10% 13% 6%	2459
	11th to 20th	Night	72% 6% 10% 10% 3	2470
	21st to end	Night	66% 5% 12% 12% 4 1	2599
February	1st to 10th	Night	66% 5% 11% 13% 4	2340
	11th to 20th	Night	63% 7% 9% 14% 7%	2190
	21st to end	Night	63% 5% 10% 13% 7% 2	1776
March	1st to 10th	Night	55% 5% 11% 21% 8% 1	2054
	11th to 20th	Night	48% 7% 12% 19% 12% 2	1980
	21st to end	Night	53% 7% 8% 21% 10% 2	2178
April	1st to 10th	Night	50% 6% 13% 16% 13% 2	1972
	11th to 20th	Night	47% 8% 11% 16% 15% 3	1603
	21st to end	Night	46% 6% 12% 19% 14% 3	1620
May	1st to 10th	Night	53% 8% 11% 14% 11% 3	1620
	11th to 20th	Night	43% 9% 12% 16% 16% 3	1593
	21st to end	Night	33% 9% 17% 25% 15% 2	1745
June	1st to 10th	Night	37% 9% 12% 25% 14% 4	1512
	11th to 20th	Night	36% 9% 15% 21% 18% 2	1382
	21st to end	Night	34% 9% 13% 26% 15% 3	1375
July	1st to 10th	Night	33% 8% 13% 22% 19% 5%	1434
	11th to 20th	Night	29% 10% 16% 24% 19% 2	1566
	21st to end	Night	32% 9% 17% 22% 17% 4	1672
August	1st to 10th	Night	29% 9% 16% 26% 19% 1	1600
	11th to 20th	Night	33% 9% 17% 26% 13% 2	1598
	21st to end	Night	32% 9% 15% 23% 18% 3	1782
September	1st to 10th	Night	36% 8% 14% 23% 15% 4	1929
	11th to 20th	Night	30% 8% 13% 27% 21% 1	1980
	21st to end	Night	40% 8% 12% 20% 19% 1	1980
October	1st to 10th	Night	39% 7% 14% 20% 19% 1	2074
	11th to 20th	Night	48% 7% 12% 20% 13% 1	2160
	21st to end	Night	55% 6% 11% 18% 9% 1	2412
November	1st to 10th	Night	44% 7% 13% 20% 14% 2	2406
	11th to 20th	Night	55% 6% 11% 16% 10% 2	2470
	21st to end	Night	60% 6% 13% 15% 6%	2612
December	1st to 10th	Night	66% 7% 10% 12% 5%	2660
	11th to 20th	Night	61% 8% 13% 15% 3	3288
	21st to end	Night	73% 8% 10% 8% 2	4614

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	29% 23% 31% 11% 5% 1	270
	11th to 20th	Day	29% 28% 31% 8% 3	270
	21st to end	Day	28% 25% 33% 12% 1 1	267
February	1st to 10th	Day	35% 22% 33% 10%	240
	11th to 20th	Day	32% 26% 32% 10%	240
	21st to end	Day	29% 32% 31% 7% 1	198
March	1st to 10th	Day	27% 21% 34% 13% 5%	344
	11th to 20th	Day	25% 17% 33% 18% 6%	420
	21st to end	Day	31% 17% 28% 19% 5% 1	462
April	1st to 10th	Day	22% 18% 32% 18% 8% 1	420
	11th to 20th	Day	25% 18% 26% 19% 8% 4	412
	21st to end	Day	27% 16% 31% 16% 8% 2	420
May	1st to 10th	Day	26% 14% 30% 21% 6% 3	423
	11th to 20th	Day	21% 10% 32% 23% 10% 4	447
	21st to end	Day	13% 8% 27% 28% 19% 5%	485
June	1st to 10th	Day	13% 8% 30% 32% 15% 3	450
	11th to 20th	Day	13% 10% 26% 32% 17% 3	500
	21st to end	Day	10% 10% 30% 32% 15% 3	630
July	1st to 10th	Day	10% 5% 23% 29% 22% 11%	579
	11th to 20th	Day	13% 5% 24% 28% 20% 10%	444
	21st to end	Day	10% 6% 23% 33% 20% 8%	488
August	1st to 10th	Day	10% 4 20% 32% 24% 11%	446
	11th to 20th	Day	14% 6% 23% 25% 21% 10%	439
	21st to end	Day	10% 7% 18% 30% 22% 12%	495
September	1st to 10th	Day	15% 6% 23% 24% 20% 12%	450
	11th to 20th	Day	11% 5% 18% 26% 26% 13%	450
	21st to end	Day	17% 14% 25% 21% 15% 8%	450
October	1st to 10th	Day	12% 11% 27% 25% 19% 6%	450
	11th to 20th	Day	19% 18% 33% 22% 7% 1	450
	21st to end	Day	29% 21% 30% 16% 4	457
November	1st to 10th	Day	18% 22% 33% 17% 8% 2	270
	11th to 20th	Day	27% 24% 27% 14% 7% 1	270
	21st to end	Day	25% 23% 39% 11%	201
December	1st to 10th	Day	22% 26% 33% 14% 3 2	180
	11th to 20th	Day	24% 27% 38% 11% 1	180
	21st to end	Day	27% 24% 35% 11% 2	274
January	1st to 10th	Night	27% 22% 33% 15% 4	760
	11th to 20th	Night	30% 19% 30% 16% 4	760
	21st to end	Night	25% 16% 34% 22% 3	800
February	1st to 10th	Night	29% 16% 34% 19% 2	720
	11th to 20th	Night	26% 18% 32% 20% 3	703
	21st to end	Night	27% 17% 35% 19% 2	592
March	1st to 10th	Night	23% 15% 33% 23% 5%	720
	11th to 20th	Night	20% 15% 33% 25% 6% 1	720
	21st to end	Night	26% 10% 30% 25% 9% 1	792
April	1st to 10th	Night	20% 15% 33% 27% 5%	720
	11th to 20th	Night	21% 11% 33% 24% 9% 1	539
	21st to end	Night	19% 9% 36% 29% 7% 1	540
May	1st to 10th	Night	21% 9% 28% 32% 9% 1	540
	11th to 20th	Night	19% 6% 27% 33% 13% 2	531
	21st to end	Night	11% 4 22% 38% 23% 2	584
June	1st to 10th	Night	11% 3 28% 42% 15% 1	432
	11th to 20th	Night	11% 3 27% 42% 16% 1	360
	21st to end	Night	11% 3 25% 39% 21% 1	475
July	1st to 10th	Night	10% 2 14% 40% 30% 3	525
	11th to 20th	Night	9% 3 18% 42% 24% 3	522
	21st to end	Night	9% 2 18% 42% 27% 2	591
August	1st to 10th	Night	9% 1 16% 44% 27% 4	537
	11th to 20th	Night	9% 5% 16% 39% 28% 4	534
	21st to end	Night	9% 4 18% 34% 31% 4	594
September	1st to 10th	Night	13% 5% 16% 36% 25% 4	715
	11th to 20th	Night	12% 4 14% 36% 30% 5%	720
	21st to end	Night	16% 9% 23% 30% 19% 3	720
October	1st to 10th	Night	16% 9% 23% 31% 19% 3	720
	11th to 20th	Night	22% 14% 29% 26% 8% 1	720
	21st to end	Night	29% 14% 28% 24% 5%	792
November	1st to 10th	Night	20% 12% 32% 25% 10% 1	740
	11th to 20th	Night	25% 15% 33% 19% 6% 1	760
	21st to end	Night	29% 16% 31% 19% 6%	760
December	1st to 10th	Night	29% 17% 31% 18% 4	760
	11th to 20th	Night	26% 17% 37% 18% 3	760
	21st to end	Night	29% 16% 34% 18% 2	836

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