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 2025-01-22.

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% 11% 4 8% 5% 5% 5% 4 5% 7% 31%	105279
	Night	16% 12% 4 9% 5% 4 4 4 5% 6% 31%	103993
Transparency	Day	50% 7% 12% 19% 11% 1	108942
	Night	51% 7% 11% 19% 11% 1	108458
Seeing	Day	19% 14% 28% 22% 12% 5%	15197
	Night	20% 11% 28% 27% 12% 1	24893

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	19% 23% 7% 14% 5% 4 4 2 4 4 14%	2926
	11th to 20th	Day	15% 24% 8% 12% 6% 6% 6% 3 4 5% 12%	2930
	21st to end	Day	27% 20% 12% 12% 7% 3 2 2 3 3 8%	3133
February	1st to 10th	Day	17% 19% 5% 11% 6% 5% 4 3 4 5% 22%	1710
	11th to 20th	Day	14% 14% 7% 15% 8% 5% 5% 3 4 4 20%	1752
	21st to end	Day	18% 14% 4 12% 6% 4 4 3 5% 6% 23%	1570
March	1st to 10th	Day	21% 15% 6% 9% 4 4 3 3 4 6% 25%	3308
	11th to 20th	Day	13% 14% 5% 11% 5% 4 4 3 3 5% 33%	3480
	21st to end	Day	20% 13% 6% 9% 5% 4 4 3 4 6% 28%	3815
April	1st to 10th	Day	14% 14% 3 9% 5% 5% 4 4 6% 6% 31%	2108
	11th to 20th	Day	17% 12% 3 6% 5% 4 4 3 5% 6% 33%	2442
	21st to end	Day	20% 10% 3 7% 4 4 4 3 4 6% 33%	2470
May	1st to 10th	Day	19% 9% 3 8% 5% 4 5% 3 6% 6% 30%	4082
	11th to 20th	Day	18% 8% 3 6% 5% 4 5% 4 6% 8% 34%	4081
	21st to end	Day	10% 6% 3 7% 5% 5% 5% 5% 8% 8% 39%	4476
June	1st to 10th	Day	13% 7% 3 7% 4 5% 5% 3 7% 8% 37%	2574
	11th to 20th	Day	12% 6% 3 7% 6% 4 5% 4 6% 9% 39%	2713
	21st to end	Day	11% 5% 2 6% 5% 5% 5% 5% 7% 10% 40%	2717
July	1st to 10th	Day	10% 6% 3 7% 5% 5% 5% 4 7% 10% 39%	4354
	11th to 20th	Day	9% 5% 2 5% 4 5% 5% 4 6% 10% 44%	4120
	21st to end	Day	10% 7% 2 7% 5% 5% 6% 5% 7% 7% 40%	4466
August	1st to 10th	Day	12% 7% 2 7% 5% 5% 5% 4 6% 9% 37%	4104
	11th to 20th	Day	11% 6% 3 6% 4 4 6% 5% 7% 10% 37%	4044
	21st to end	Day	9% 5% 2 6% 5% 5% 6% 5% 6% 10% 41%	4504
September	1st to 10th	Day	13% 6% 2 6% 4 4 5% 4 6% 7% 43%	2135
	11th to 20th	Day	11% 7% 2 5% 5% 4 5% 3 6% 8% 43%	2090
	21st to end	Day	18% 9% 2 6% 4 4 4 3 5% 7% 38%	2090
October	1st to 10th	Day	12% 8% 2 6% 5% 5% 4 4 7% 7% 40%	1990
	11th to 20th	Day	18% 9% 3 8% 3 4 4 4 6% 5% 36%	1900
	21st to end	Day	20% 12% 3 7% 5% 4 4 4 5% 5% 30%	2049
November	1st to 10th	Day	13% 11% 3 8% 5% 4 4 3 5% 7% 37%	1762
	11th to 20th	Day	18% 15% 4 8% 5% 4 4 3 3 6% 30%	1800
	21st to end	Day	18% 18% 5% 9% 5% 5% 4 4 5% 6% 20%	1646
December	1st to 10th	Day	18% 15% 6% 15% 6% 4 4 3 5% 4 20%	2600
	11th to 20th	Day	20% 19% 8% 11% 5% 4 3 3 3 5% 18%	2990
	21st to end	Day	23% 23% 6% 13% 6% 5% 4 3 3 4 11%	4348
January	1st to 10th	Night	16% 22% 8% 14% 5% 4 3 3 4 4 16%	4239
	11th to 20th	Night	13% 22% 10% 16% 6% 5% 7% 4 3 3 10%	4250
	21st to end	Night	27% 19% 7% 13% 5% 3 3 2 3 3 15%	4546
February	1st to 10th	Night	20% 15% 5% 11% 6% 5% 4 2 5% 5% 21%	2470
	11th to 20th	Night	16% 16% 6% 10% 6% 6% 5% 4 5% 5% 22%	2313
	21st to end	Night	19% 14% 5% 12% 6% 5% 4 2 4 5% 24%	1884
March	1st to 10th	Night	21% 14% 5% 6% 4 3 3 2 4 5% 33%	3543
	11th to 20th	Night	14% 10% 3 7% 4 4 4 4 6% 7% 36%	3480
	21st to end	Night	18% 11% 3 9% 4 4 4 3 5% 6% 32%	3817
April	1st to 10th	Night	15% 13% 3 7% 5% 5% 4 4 6% 7% 32%	2081
	11th to 20th	Night	16% 11% 3 7% 5% 4 5% 4 6% 7% 34%	1693
	21st to end	Night	16% 9% 3 7% 4 4 4 4 6% 7% 36%	1710
May	1st to 10th	Night	20% 10% 4 8% 5% 5% 5% 3 6% 7% 27%	2813
	11th to 20th	Night	16% 8% 3 7% 4 4 4 3 6% 8% 36%	2812
	21st to end	Night	9% 5% 2 5% 3 4 4 4 7% 10% 47%	3079
June	1st to 10th	Night	10% 7% 2 6% 5% 5% 5% 4 5% 8% 43%	1596
	11th to 20th	Night	9% 5% 2 7% 5% 4 5% 5% 7% 9% 41%	1458
	21st to end	Night	10% 5% 2 6% 3 5% 5% 4 6% 11% 43%	1452
July	1st to 10th	Night	10% 6% 2 6% 4 4 4 4 6% 9% 47%	2592
	11th to 20th	Night	9% 4 2 5% 4 4 5% 4 6% 9% 48%	2840
	21st to end	Night	7% 5% 2 6% 5% 4 5% 4 7% 10% 44%	3087
August	1st to 10th	Night	11% 7% 3 7% 4 4 4 4 6% 9% 41%	2825
	11th to 20th	Night	12% 7% 2 7% 4 4 4 4 5% 7% 44%	2785
	21st to end	Night	7% 5% 2 6% 4 5% 5% 4 7% 8% 45%	3124
September	1st to 10th	Night	11% 5% 2 6% 5% 4 5% 3 6% 6% 47%	2037
	11th to 20th	Night	10% 4 2 5% 4 3 4 3 6% 7% 52%	2090
	21st to end	Night	16% 7% 3 6% 4 5% 5% 4 4 6% 41%	2090
October	1st to 10th	Night	13% 6% 2 7% 5% 4 4 4 5% 7% 44%	2190
	11th to 20th	Night	19% 7% 3 8% 5% 4 4 4 5% 6% 36%	2280
	21st to end	Night	23% 10% 3 7% 4 4 4 3 6% 6% 30%	2546
November	1st to 10th	Night	15% 9% 3 6% 4 4 4 4 5% 6% 38%	2536
	11th to 20th	Night	16% 15% 4 9% 5% 5% 4 3 4 5% 30%	2600
	21st to end	Night	21% 15% 4 9% 5% 5% 4 3 6% 6% 23%	2750
December	1st to 10th	Night	16% 16% 7% 12% 6% 5% 4 4 4 5% 20%	4580
	11th to 20th	Night	18% 20% 7% 11% 5% 4 4 3 5% 5% 19%	5205
	21st to end	Night	22% 20% 6% 12% 5% 5% 4 3 5% 5% 13%	6600

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% 5% 10% 9% 2	2927
	11th to 20th	Day	74% 6% 9% 8% 3	2930
	21st to end	Day	83% 4 6% 5% 2	3133
February	1st to 10th	Day	65% 5% 11% 13% 6%	1710
	11th to 20th	Day	65% 7% 9% 13% 5% 1	1761
	21st to end	Day	60% 7% 14% 12% 6% 2	1570
March	1st to 10th	Day	60% 6% 9% 20% 4	3308
	11th to 20th	Day	52% 8% 13% 21% 6% 1	3480
	21st to end	Day	56% 7% 11% 16% 9% 1	3815
April	1st to 10th	Day	52% 7% 12% 17% 11% 1	2108
	11th to 20th	Day	51% 6% 12% 17% 13% 2	2442
	21st to end	Day	50% 7% 11% 20% 10% 2	2470
May	1st to 10th	Day	51% 8% 11% 21% 8% 1	4120
	11th to 20th	Day	45% 9% 13% 23% 9% 1	4085
	21st to end	Day	37% 10% 14% 19% 15% 5%	4489
June	1st to 10th	Day	42% 8% 11% 25% 13% 1	2574
	11th to 20th	Day	40% 9% 15% 21% 14% 2	2713
	21st to end	Day	37% 9% 14% 22% 16% 2	2717
July	1st to 10th	Day	40% 6% 12% 23% 17% 2	4287
	11th to 20th	Day	33% 6% 14% 27% 18% 2	4051
	21st to end	Day	39% 7% 15% 16% 20% 2	4324
August	1st to 10th	Day	42% 7% 15% 23% 13%	4091
	11th to 20th	Day	38% 8% 13% 31% 10% 1	4083
	21st to end	Day	37% 7% 15% 27% 11% 2	4504
September	1st to 10th	Day	38% 7% 15% 20% 16% 3	2135
	11th to 20th	Day	37% 7% 15% 22% 17% 2	2090
	21st to end	Day	45% 7% 11% 19% 18% 1	2090
October	1st to 10th	Day	32% 6% 15% 28% 19% 1	3302
	11th to 20th	Day	44% 6% 10% 20% 18% 1	3140
	21st to end	Day	42% 5% 12% 23% 17% 1	3351
November	1st to 10th	Day	46% 5% 13% 22% 14% 1	1762
	11th to 20th	Day	56% 5% 11% 17% 9% 2	1800
	21st to end	Day	63% 7% 12% 12% 6%	1646
December	1st to 10th	Day	66% 6% 13% 13% 2	2600
	11th to 20th	Day	70% 5% 9% 12% 4	2986
	21st to end	Day	78% 5% 7% 8% 2	4348
January	1st to 10th	Night	70% 6% 9% 11% 4	4239
	11th to 20th	Night	78% 6% 8% 7% 2	4250
	21st to end	Night	75% 4 8% 9% 2	4546
February	1st to 10th	Night	65% 5% 11% 13% 5% 1	2470
	11th to 20th	Night	61% 8% 9% 15% 7%	2315
	21st to end	Night	63% 6% 9% 13% 8% 2	1884
March	1st to 10th	Night	54% 5% 12% 21% 8%	3543
	11th to 20th	Night	43% 10% 17% 19% 10% 1	3480
	21st to end	Night	48% 10% 9% 24% 8% 1	3817
April	1st to 10th	Night	50% 6% 13% 16% 12% 2	2081
	11th to 20th	Night	47% 8% 12% 16% 15% 3	1693
	21st to end	Night	46% 7% 12% 20% 14% 3	1710
May	1st to 10th	Night	53% 9% 10% 17% 9% 2	2840
	11th to 20th	Night	41% 10% 12% 21% 13% 2	2813
	21st to end	Night	30% 8% 15% 26% 17% 4	3087
June	1st to 10th	Night	38% 8% 11% 24% 15% 3	1596
	11th to 20th	Night	35% 8% 15% 22% 17% 2	1458
	21st to end	Night	34% 9% 13% 26% 15% 3	1452
July	1st to 10th	Night	35% 6% 13% 24% 17% 6%	2550
	11th to 20th	Night	31% 7% 14% 27% 18% 3	2786
	21st to end	Night	33% 7% 17% 19% 21% 2	2988
August	1st to 10th	Night	39% 7% 14% 24% 15% 1	2814
	11th to 20th	Night	38% 7% 12% 29% 14% 1	2812
	21st to end	Night	34% 7% 14% 28% 14% 2	3124
September	1st to 10th	Night	35% 8% 14% 24% 16% 4	2037
	11th to 20th	Night	29% 8% 12% 27% 22% 2	2090
	21st to end	Night	43% 7% 11% 20% 18% 1	2090
October	1st to 10th	Night	30% 5% 9% 30% 25% 1	3658
	11th to 20th	Night	45% 5% 10% 20% 19% 2	3779
	21st to end	Night	40% 5% 11% 26% 17% 2	4182
November	1st to 10th	Night	44% 7% 13% 21% 14% 2	2536
	11th to 20th	Night	55% 6% 11% 16% 10% 2	2600
	21st to end	Night	60% 6% 13% 15% 5% 1	2750
December	1st to 10th	Night	64% 6% 11% 15% 4	4580
	11th to 20th	Night	67% 6% 11% 14% 3	5208
	21st to end	Night	72% 7% 10% 10% 1	6600

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	28% 22% 33% 11% 4 1	300
	11th to 20th	Day	29% 28% 33% 7% 3	300
	21st to end	Day	29% 26% 31% 13% 1 1	300
February	1st to 10th	Day	32% 22% 33% 11% 2	270
	11th to 20th	Day	30% 25% 33% 10% 1	270
	21st to end	Day	30% 31% 31% 8%	225
March	1st to 10th	Day	27% 21% 34% 14% 5%	380
	11th to 20th	Day	26% 18% 33% 18% 5%	460
	21st to end	Day	31% 17% 29% 18% 4 1	506
April	1st to 10th	Day	22% 20% 33% 17% 7% 1	460
	11th to 20th	Day	25% 20% 25% 18% 7% 4	452
	21st to end	Day	26% 17% 32% 16% 8% 2	460
May	1st to 10th	Day	24% 15% 30% 22% 6% 3	463
	11th to 20th	Day	20% 10% 32% 22% 10% 5%	487
	21st to end	Day	13% 9% 27% 27% 19% 5%	529
June	1st to 10th	Day	13% 9% 30% 31% 15% 2	490
	11th to 20th	Day	13% 10% 25% 34% 16% 2	543
	21st to end	Day	11% 10% 30% 31% 14% 3	680
July	1st to 10th	Day	11% 5% 24% 29% 21% 11%	626
	11th to 20th	Day	12% 5% 25% 29% 20% 9%	484
	21st to end	Day	10% 5% 22% 33% 21% 8%	532
August	1st to 10th	Day	11% 5% 21% 31% 22% 10%	486
	11th to 20th	Day	14% 5% 25% 25% 21% 10%	479
	21st to end	Day	10% 7% 18% 30% 24% 12%	539
September	1st to 10th	Day	15% 6% 23% 24% 21% 12%	490
	11th to 20th	Day	10% 4 17% 27% 28% 14%	490
	21st to end	Day	20% 13% 24% 21% 13% 8%	490
October	1st to 10th	Day	11% 11% 27% 26% 18% 7%	490
	11th to 20th	Day	19% 17% 31% 22% 8% 3	490
	21st to end	Day	27% 20% 30% 17% 4	498
November	1st to 10th	Day	18% 22% 33% 17% 7% 2	300
	11th to 20th	Day	28% 23% 28% 14% 6% 1	300
	21st to end	Day	29% 24% 37% 10%	223
December	1st to 10th	Day	23% 26% 33% 15% 4 2	200
	11th to 20th	Day	26% 26% 35% 12% 2	200
	21st to end	Day	28% 23% 36% 10% 2	305
January	1st to 10th	Night	26% 22% 33% 16% 4	800
	11th to 20th	Night	30% 19% 32% 15% 4	800
	21st to end	Night	26% 17% 33% 21% 3	841
February	1st to 10th	Night	28% 17% 33% 20% 2	760
	11th to 20th	Night	25% 19% 32% 21% 3	743
	21st to end	Night	27% 17% 34% 19% 2	628
March	1st to 10th	Night	24% 15% 32% 24% 5%	760
	11th to 20th	Night	20% 17% 33% 24% 6% 1	760
	21st to end	Night	25% 10% 31% 25% 8% 1	836
April	1st to 10th	Night	21% 16% 33% 26% 5%	760
	11th to 20th	Night	22% 11% 33% 24% 9% 1	569
	21st to end	Night	18% 9% 36% 29% 6% 1	570
May	1st to 10th	Night	20% 10% 28% 32% 9% 2	570
	11th to 20th	Night	19% 7% 27% 32% 13% 2	561
	21st to end	Night	11% 4 22% 38% 23% 2	617
June	1st to 10th	Night	11% 4 28% 42% 15% 1	456
	11th to 20th	Night	10% 3 27% 43% 16% 1	380
	21st to end	Night	11% 3 26% 38% 20% 1	502
July	1st to 10th	Night	10% 2 15% 41% 29% 3	555
	11th to 20th	Night	9% 3 18% 42% 24% 3	552
	21st to end	Night	9% 2 17% 42% 28% 2	624
August	1st to 10th	Night	10% 2 16% 43% 26% 4	567
	11th to 20th	Night	9% 5% 17% 38% 27% 4	564
	21st to end	Night	8% 3 18% 35% 32% 4	627
September	1st to 10th	Night	12% 5% 17% 37% 25% 4	755
	11th to 20th	Night	11% 4 14% 36% 31% 5%	760
	21st to end	Night	17% 9% 23% 30% 18% 3	760
October	1st to 10th	Night	16% 9% 23% 32% 18% 3	760
	11th to 20th	Night	22% 14% 29% 26% 9% 1	760
	21st to end	Night	28% 14% 29% 24% 5%	836
November	1st to 10th	Night	20% 12% 33% 25% 9% 1	780
	11th to 20th	Night	26% 15% 33% 19% 6% 1	800
	21st to end	Night	29% 16% 31% 18% 6%	800
December	1st to 10th	Night	29% 17% 31% 18% 4	800
	11th to 20th	Night	26% 17% 36% 18% 3	800
	21st to end	Night	29% 16% 34% 19% 3	880

Page generated at 2025-01-19 03:06:46. Version ac07

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