Garland Mountain Trailhead
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Garland Mountain Trailhead clear sky chart from 2005-11-06 to 2025-05-26.

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	13% 7% 3 6% 4 4 5% 4 6% 7% 41%	114328
	Night	13% 7% 3 6% 4 4 4 3 5% 7% 43%	114972
Transparency	Day	40% 6% 10% 20% 19% 5%	118147
	Night	39% 5% 9% 20% 21% 6%	119279
Seeing	Day	19% 12% 23% 23% 15% 8%	15504
	Night	17% 11% 23% 28% 19% 3	25580

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	17% 11% 4 4 3 3 3 2 3 4 45%	4056
	11th to 20th	Day	13% 8% 4 7% 3 3 2 2 2 4 51%	4060
	21st to end	Day	20% 13% 3 6% 3 3 3 3 4 5% 37%	4673
February	1st to 10th	Day	18% 10% 2 5% 5% 4 3 3 5% 7% 38%	2000
	11th to 20th	Day	24% 8% 2 6% 3 3 3 3 5% 5% 37%	1948
	21st to end	Day	21% 7% 3 7% 4 3 4 2 4 4 40%	1650
March	1st to 10th	Day	20% 9% 3 8% 5% 4 4 3 5% 6% 33%	4566
	11th to 20th	Day	11% 7% 2 6% 3 3 3 4 5% 6% 49%	4980
	21st to end	Day	15% 6% 2 8% 5% 4 4 3 5% 5% 43%	5465
April	1st to 10th	Day	13% 6% 2 6% 5% 4 4 4 7% 7% 42%	2300
	11th to 20th	Day	13% 6% 2 6% 5% 4 4 3 5% 6% 46%	2374
	21st to end	Day	11% 4 2 6% 5% 5% 5% 4 5% 8% 45%	2545
May	1st to 10th	Day	13% 7% 2 7% 4 5% 5% 4 6% 8% 39%	4212
	11th to 20th	Day	17% 9% 3 8% 5% 5% 4 4 6% 7% 33%	4211
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 4 7% 9% 42%	4541
June	1st to 10th	Day	10% 7% 3 7% 6% 6% 6% 5% 7% 10% 33%	2470
	11th to 20th	Day	5% 4 2 5% 5% 5% 7% 6% 10% 11% 40%	2470
	21st to end	Day	7% 6% 2 6% 5% 6% 7% 6% 8% 9% 37%	2470
July	1st to 10th	Day	7% 7% 2 7% 6% 6% 8% 6% 9% 12% 28%	4120
	11th to 20th	Day	8% 5% 2 7% 6% 6% 7% 6% 8% 10% 34%	4120
	21st to end	Day	14% 8% 4 11% 8% 8% 7% 6% 7% 8% 19%	4466
August	1st to 10th	Day	5% 4 2 7% 5% 6% 6% 5% 8% 11% 40%	4104
	11th to 20th	Day	8% 5% 2 6% 5% 5% 6% 5% 7% 11% 41%	3759
	21st to end	Day	7% 4 2 5% 5% 5% 6% 5% 5% 7% 48%	4180
September	1st to 10th	Day	10% 7% 3 6% 6% 4 5% 5% 7% 9% 39%	2120
	11th to 20th	Day	13% 8% 3 7% 5% 5% 5% 4 5% 7% 40%	2090
	21st to end	Day	12% 5% 2 6% 4 5% 4 3 4 7% 46%	2090
October	1st to 10th	Day	11% 4 1 5% 3 4 4 3 4 5% 55%	2090
	11th to 20th	Day	12% 5% 1 4 3 3 3 3 4 6% 55%	2001
	21st to end	Day	13% 6% 2 5% 3 3 3 3 4 5% 53%	2066
November	1st to 10th	Day	13% 5% 2 5% 3 3 3 3 5% 5% 53%	1762
	11th to 20th	Day	13% 6% 2 5% 3 4 4 3 4 6% 51%	1800
	21st to end	Day	14% 8% 2 5% 4 4 4 3 5% 7% 45%	1800
December	1st to 10th	Day	21% 6% 2 3 3 3 4 3 5% 6% 45%	2930
	11th to 20th	Day	16% 10% 4 8% 5% 4 5% 3 4 5% 37%	3373
	21st to end	Day	17% 8% 4 7% 4 4 4 4 5% 6% 37%	4466
January	1st to 10th	Night	15% 10% 3 6% 3 3 3 3 4 5% 44%	5889
	11th to 20th	Night	16% 9% 4 6% 3 3 2 2 4 5% 46%	5900
	21st to end	Night	18% 11% 3 6% 3 3 3 2 4 4 43%	6278
February	1st to 10th	Night	17% 8% 3 5% 4 4 4 3 5% 6% 42%	2400
	11th to 20th	Night	22% 8% 3 6% 4 4 3 3 3 5% 39%	2338
	21st to end	Night	22% 7% 2 6% 4 3 4 3 5% 7% 39%	1980
March	1st to 10th	Night	20% 11% 3 7% 4 4 4 4 5% 6% 33%	5286
	11th to 20th	Night	12% 6% 2 4 3 3 3 4 5% 7% 50%	4980
	21st to end	Night	14% 7% 3 7% 4 4 4 4 4 6% 44%	5467
April	1st to 10th	Night	12% 4 2 5% 4 4 5% 4 6% 8% 47%	2115
	11th to 20th	Night	14% 6% 2 4 3 3 4 4 5% 7% 49%	1975
	21st to end	Night	9% 8% 2 6% 3 4 3 4 5% 7% 49%	1855
May	1st to 10th	Night	12% 7% 3 7% 5% 5% 5% 3 5% 8% 40%	2903
	11th to 20th	Night	18% 8% 2 6% 4 4 4 4 6% 7% 35%	2902
	21st to end	Night	6% 5% 2 6% 5% 5% 5% 5% 8% 10% 45%	3130
June	1st to 10th	Night	7% 6% 2 7% 6% 6% 6% 5% 8% 11% 36%	1710
	11th to 20th	Night	5% 4 1 5% 5% 5% 5% 6% 8% 11% 46%	1710
	21st to end	Night	5% 5% 3 6% 4 5% 6% 5% 7% 12% 42%	1710
July	1st to 10th	Night	9% 7% 3 7% 6% 5% 7% 5% 7% 12% 32%	2840
	11th to 20th	Night	8% 5% 2 6% 5% 5% 7% 6% 8% 12% 36%	2840
	21st to end	Night	13% 10% 4 11% 6% 6% 6% 5% 7% 9% 23%	3087
August	1st to 10th	Night	5% 4 2 7% 4 5% 6% 4 7% 13% 43%	2825
	11th to 20th	Night	8% 6% 2 6% 4 4 4 4 5% 9% 47%	3065
	21st to end	Night	7% 5% 2 5% 3 3 4 4 6% 7% 53%	3476
September	1st to 10th	Night	8% 5% 3 6% 6% 6% 4 4 6% 9% 43%	2039
	11th to 20th	Night	12% 6% 2 7% 4 4 4 4 6% 8% 43%	2090
	21st to end	Night	12% 5% 1 5% 3 3 4 3 5% 7% 51%	2090
October	1st to 10th	Night	10% 4 2 4 3 2 2 3 5% 6% 58%	2090
	11th to 20th	Night	11% 5% 2 4 3 3 3 2 4 5% 57%	2177
	21st to end	Night	12% 7% 2 5% 3 3 3 2 4 5% 55%	2527
November	1st to 10th	Night	11% 6% 2 5% 3 3 3 4 4 5% 54%	2536
	11th to 20th	Night	13% 6% 2 5% 3 3 3 3 5% 6% 52%	2600
	21st to end	Night	15% 8% 2 5% 3 3 4 4 5% 5% 46%	2600
December	1st to 10th	Night	19% 7% 3 5% 3 3 3 2 4 6% 46%	4250
	11th to 20th	Night	17% 10% 3 7% 3 4 4 3 4 5% 40%	4822
	21st to end	Night	18% 9% 3 7% 3 4 4 3 5% 6% 38%	6490

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	44% 3 5% 21% 24% 4	4057
	11th to 20th	Day	39% 3 5% 19% 28% 6%	4060
	21st to end	Day	49% 2 5% 16% 22% 5%	4673
February	1st to 10th	Day	46% 4 7% 19% 20% 4	2000
	11th to 20th	Day	49% 4 6% 17% 19% 6%	1958
	21st to end	Day	48% 3 7% 14% 21% 7%	1650
March	1st to 10th	Day	51% 4 7% 12% 19% 8%	4566
	11th to 20th	Day	36% 4 6% 14% 24% 16%	4980
	21st to end	Day	43% 3 7% 23% 19% 4	5465
April	1st to 10th	Day	39% 5% 10% 22% 19% 5%	2300
	11th to 20th	Day	38% 5% 7% 19% 25% 7%	2374
	21st to end	Day	35% 5% 11% 27% 18% 3	2545
May	1st to 10th	Day	39% 8% 12% 22% 16% 2	4250
	11th to 20th	Day	47% 8% 11% 22% 10% 1	4215
	21st to end	Day	35% 8% 13% 22% 20% 1	4554
June	1st to 10th	Day	42% 10% 17% 20% 10% 2	2470
	11th to 20th	Day	32% 11% 18% 26% 12% 1	2470
	21st to end	Day	38% 12% 16% 20% 12% 2	2470
July	1st to 10th	Day	44% 10% 21% 19% 6% 1	4055
	11th to 20th	Day	43% 8% 22% 20% 5% 2	4051
	21st to end	Day	60% 11% 13% 11% 5%	4324
August	1st to 10th	Day	34% 8% 14% 33% 10%	4091
	11th to 20th	Day	35% 7% 18% 24% 15% 2	3796
	21st to end	Day	34% 6% 13% 25% 20% 3	4179
September	1st to 10th	Day	40% 10% 12% 17% 18% 5%	2120
	11th to 20th	Day	43% 6% 11% 18% 20% 2	2090
	21st to end	Day	38% 5% 13% 15% 22% 7%	2090
October	1st to 10th	Day	25% 4 6% 14% 40% 12%	3480
	11th to 20th	Day	21% 3 5% 17% 28% 26%	3306
	21st to end	Day	27% 2 6% 25% 28% 12%	3380
November	1st to 10th	Day	35% 3 6% 17% 31% 9%	1762
	11th to 20th	Day	35% 4 7% 18% 27% 10%	1800
	21st to end	Day	40% 5% 6% 17% 26% 6%	1800
December	1st to 10th	Day	41% 3 5% 17% 27% 6%	2930
	11th to 20th	Day	51% 2 7% 17% 18% 5%	3370
	21st to end	Day	46% 3 9% 25% 14% 2	4466
January	1st to 10th	Night	41% 3 6% 18% 27% 5%	5889
	11th to 20th	Night	42% 3 5% 19% 25% 7%	5900
	21st to end	Night	46% 2 4 17% 25% 6%	6278
February	1st to 10th	Night	42% 5% 7% 19% 20% 6%	2400
	11th to 20th	Night	49% 4 5% 17% 19% 6%	2339
	21st to end	Night	46% 4 7% 16% 19% 8%	1980
March	1st to 10th	Night	51% 4 7% 14% 18% 5%	5286
	11th to 20th	Night	33% 4 7% 16% 25% 15%	4980
	21st to end	Night	41% 4 6% 22% 20% 6%	5467
April	1st to 10th	Night	34% 6% 11% 19% 24% 6%	2115
	11th to 20th	Night	34% 4 7% 22% 23% 9%	1975
	21st to end	Night	34% 5% 11% 27% 19% 4	1855
May	1st to 10th	Night	40% 9% 14% 21% 15% 2	2930
	11th to 20th	Night	44% 7% 16% 21% 11%	2903
	21st to end	Night	30% 10% 15% 26% 18% 2	3138
June	1st to 10th	Night	39% 11% 17% 20% 12% 2	1710
	11th to 20th	Night	28% 9% 23% 25% 14% 1	1710
	21st to end	Night	33% 11% 17% 21% 14% 4	1710
July	1st to 10th	Night	45% 9% 19% 19% 7% 1	2795
	11th to 20th	Night	38% 10% 22% 22% 6% 2	2786
	21st to end	Night	55% 12% 14% 13% 5% 1	2988
August	1st to 10th	Night	34% 8% 15% 33% 9%	2814
	11th to 20th	Night	35% 7% 14% 28% 16% 1	3094
	21st to end	Night	30% 6% 13% 22% 26% 3	3476
September	1st to 10th	Night	38% 8% 15% 18% 16% 5%	2039
	11th to 20th	Night	38% 8% 13% 20% 19% 2	2090
	21st to end	Night	33% 6% 11% 22% 20% 8%	2090
October	1st to 10th	Night	22% 3 9% 15% 39% 12%	3480
	11th to 20th	Night	19% 2 5% 17% 33% 23%	3611
	21st to end	Night	24% 3 3 25% 29% 16%	4151
November	1st to 10th	Night	33% 4 7% 18% 26% 12%	2536
	11th to 20th	Night	33% 4 5% 19% 28% 11%	2600
	21st to end	Night	39% 4 7% 20% 25% 6%	2600
December	1st to 10th	Night	40% 3 5% 19% 27% 6%	4250
	11th to 20th	Night	46% 4 8% 15% 23% 5%	4824
	21st to end	Night	47% 3 8% 26% 14% 1	6490

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	35% 24% 31% 9% 1	300
	11th to 20th	Day	34% 25% 27% 12% 3	300
	21st to end	Day	25% 33% 28% 10% 3 1	330
February	1st to 10th	Day	28% 23% 37% 10% 2	300
	11th to 20th	Day	47% 23% 21% 8% 1	300
	21st to end	Day	35% 24% 33% 6% 2	249
March	1st to 10th	Day	32% 21% 27% 16% 4	334
	11th to 20th	Day	27% 21% 28% 18% 5%	500
	21st to end	Day	25% 21% 32% 17% 6%	550
April	1st to 10th	Day	26% 15% 30% 19% 9% 1	500
	11th to 20th	Day	18% 16% 34% 23% 9% 1	492
	21st to end	Day	18% 12% 31% 24% 12% 3	500
May	1st to 10th	Day	19% 13% 30% 22% 12% 4	503
	11th to 20th	Day	16% 8% 27% 26% 14% 9%	527
	21st to end	Day	15% 7% 20% 29% 19% 9%	549
June	1st to 10th	Day	14% 4 21% 28% 22% 11%	490
	11th to 20th	Day	7% 5% 18% 27% 23% 20%	490
	21st to end	Day	12% 4 19% 27% 22% 16%	490
July	1st to 10th	Day	12% 4 11% 26% 25% 22%	485
	11th to 20th	Day	8% 3 9% 24% 32% 24%	484
	21st to end	Day	10% 3 10% 27% 29% 20%	532
August	1st to 10th	Day	12% 3 16% 25% 24% 20%	486
	11th to 20th	Day	12% 2 14% 30% 27% 15%	479
	21st to end	Day	14% 4 9% 26% 31% 16%	539
September	1st to 10th	Day	9% 5% 17% 29% 26% 14%	490
	11th to 20th	Day	16% 7% 15% 25% 28% 9%	490
	21st to end	Day	14% 4 19% 29% 27% 6%	490
October	1st to 10th	Day	15% 6% 23% 32% 16% 7%	490
	11th to 20th	Day	14% 12% 24% 29% 18% 2	490
	21st to end	Day	18% 11% 26% 28% 14% 3	515
November	1st to 10th	Day	18% 16% 32% 22% 10% 3	300
	11th to 20th	Day	21% 19% 36% 19% 5% 1	300
	21st to end	Day	22% 19% 34% 18% 6% 1	300
December	1st to 10th	Day	33% 24% 25% 13% 4 1	300
	11th to 20th	Day	27% 21% 31% 18% 4	300
	21st to end	Day	30% 21% 33% 13% 3	330
January	1st to 10th	Night	26% 22% 28% 19% 5%	800
	11th to 20th	Night	26% 19% 28% 21% 6%	800
	21st to end	Night	22% 19% 32% 23% 3	880
February	1st to 10th	Night	22% 15% 31% 27% 5%	800
	11th to 20th	Night	30% 19% 28% 21% 1	783
	21st to end	Night	26% 19% 34% 18% 3	660
March	1st to 10th	Night	22% 17% 32% 25% 5%	800
	11th to 20th	Night	20% 17% 31% 23% 9%	800
	21st to end	Night	20% 14% 31% 27% 8%	880
April	1st to 10th	Night	16% 13% 31% 28% 11%	715
	11th to 20th	Night	18% 12% 29% 29% 11% 1	593
	21st to end	Night	13% 8% 27% 34% 17% 1	600
May	1st to 10th	Night	11% 10% 24% 35% 19% 1	600
	11th to 20th	Night	16% 6% 23% 30% 20% 5%	591
	21st to end	Night	9% 4 15% 34% 31% 6%	634
June	1st to 10th	Night	9% 4 12% 38% 33% 5%	570
	11th to 20th	Night	5% 3 13% 31% 34% 14%	570
	21st to end	Night	5% 2 10% 35% 40% 8%	570
July	1st to 10th	Night	10% 3 8% 25% 41% 14%	555
	11th to 20th	Night	10% 1 7% 25% 43% 14%	552
	21st to end	Night	7% 2 9% 27% 43% 12%	624
August	1st to 10th	Night	9% 1 7% 29% 41% 12%	567
	11th to 20th	Night	10% 2 10% 29% 40% 9%	564
	21st to end	Night	14% 3 10% 26% 37% 11%	627
September	1st to 10th	Night	10% 2 14% 28% 36% 9%	709
	11th to 20th	Night	14% 3 15% 30% 33% 4	760
	21st to end	Night	14% 4 16% 34% 30% 2	760
October	1st to 10th	Night	13% 5% 20% 33% 23% 6%	760
	11th to 20th	Night	14% 8% 26% 31% 20% 1	760
	21st to end	Night	14% 12% 21% 34% 16% 2	836
November	1st to 10th	Night	13% 11% 27% 29% 18% 2	780
	11th to 20th	Night	16% 15% 28% 30% 11% 1	800
	21st to end	Night	20% 15% 28% 25% 11% 1	800
December	1st to 10th	Night	24% 16% 29% 23% 7% 1	800
	11th to 20th	Night	25% 15% 26% 26% 7% 1	800
	21st to end	Night	27% 16% 27% 25% 5%	880

Page generated at 2025-05-23 09:20:59. Version ac07

Copyright © 2025 Attilla Danko.