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 2026-09-29.

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 7% 5% 5% 5% 4 6% 8% 39%	148647
	Night	14% 7% 3 6% 4 4 4 4 5% 7% 42%	142795
Transparency	Day	42% 5% 12% 20% 17% 5%	152422
	Night	40% 5% 11% 20% 19% 5%	147079
Seeing	Day	19% 12% 24% 23% 15% 7%	17339
	Night	17% 11% 23% 28% 19% 3	27293

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	21% 11% 3 5% 3 3 3 2 3 4 41%	5258
	11th to 20th	Day	11% 7% 4 6% 3 3 2 2 2 4 56%	5280
	21st to end	Day	21% 13% 3 7% 3 3 3 3 4 5% 34%	6056
February	1st to 10th	Day	17% 10% 2 5% 5% 4 3 3 5% 7% 38%	2100
	11th to 20th	Day	24% 8% 2 6% 3 3 3 3 5% 5% 38%	2048
	21st to end	Day	21% 7% 3 7% 4 3 4 2 5% 5% 39%	1730
March	1st to 10th	Day	20% 9% 3 8% 5% 4 4 3 5% 6% 33%	4668
	11th to 20th	Day	11% 7% 2 6% 3 4 3 4 5% 6% 49%	5090
	21st to end	Day	15% 6% 2 8% 5% 4 4 3 5% 5% 43%	5586
April	1st to 10th	Day	13% 5% 2 7% 5% 4 4 4 7% 7% 42%	2415
	11th to 20th	Day	12% 6% 2 6% 5% 4 4 3 5% 6% 48%	2494
	21st to end	Day	11% 4 2 6% 5% 5% 5% 4 5% 8% 45%	2672
May	1st to 10th	Day	18% 7% 2 7% 4 5% 5% 4 6% 8% 35%	7616
	11th to 20th	Day	14% 8% 3 8% 5% 6% 6% 5% 6% 7% 32%	7626
	21st to end	Day	18% 9% 3 9% 5% 5% 5% 4 5% 7% 30%	8391
June	1st to 10th	Day	11% 6% 3 7% 6% 6% 6% 5% 8% 10% 33%	2730
	11th to 20th	Day	6% 4 2 6% 5% 6% 7% 6% 10% 11% 38%	2730
	21st to end	Day	7% 5% 2 6% 5% 5% 7% 6% 9% 10% 37%	2730
July	1st to 10th	Day	6% 5% 2 6% 6% 6% 7% 6% 9% 13% 34%	7680
	11th to 20th	Day	8% 6% 2 7% 6% 6% 7% 6% 9% 13% 30%	7680
	21st to end	Day	11% 7% 3 9% 6% 7% 7% 6% 8% 11% 26%	8340
August	1st to 10th	Day	7% 6% 2 8% 5% 7% 7% 6% 8% 12% 31%	6014
	11th to 20th	Day	5% 4 2 5% 4 4 5% 5% 7% 12% 48%	5531
	21st to end	Day	6% 4 2 5% 5% 5% 6% 5% 6% 9% 48%	6080
September	1st to 10th	Day	9% 7% 3 5% 5% 4 5% 5% 7% 9% 40%	2343
	11th to 20th	Day	12% 7% 2 6% 5% 5% 5% 4 5% 7% 42%	2310
	21st to end	Day	12% 5% 2 6% 5% 5% 5% 4 5% 8% 44%	2288
October	1st to 10th	Day	11% 4 2 6% 3 4 4 3 4 5% 54%	2200
	11th to 20th	Day	12% 5% 1 4 3 3 3 3 4 6% 56%	2106
	21st to end	Day	13% 7% 2 5% 3 3 3 3 4 5% 53%	2175
November	1st to 10th	Day	12% 5% 2 5% 3 3 3 3 5% 5% 54%	1852
	11th to 20th	Day	13% 6% 2 5% 3 4 4 3 4 6% 52%	1890
	21st to end	Day	14% 8% 2 5% 4 4 4 3 5% 7% 45%	1890
December	1st to 10th	Day	21% 6% 2 3 3 3 4 3 5% 6% 44%	3020
	11th to 20th	Day	15% 9% 4 8% 5% 4 4 3 4 5% 38%	3463
	21st to end	Day	17% 8% 4 7% 4 4 4 4 5% 6% 37%	4565
January	1st to 10th	Night	18% 9% 3 6% 3 3 3 3 4 6% 41%	7635
	11th to 20th	Night	16% 8% 3 6% 3 3 2 2 4 5% 48%	7680
	21st to end	Night	20% 11% 3 7% 4 2 3 2 3 4 41%	8120
February	1st to 10th	Night	17% 7% 3 6% 4 4 4 3 5% 6% 42%	2520
	11th to 20th	Night	22% 8% 3 7% 4 4 3 3 3 5% 39%	2458
	21st to end	Night	22% 7% 2 6% 4 4 4 3 5% 6% 38%	2076
March	1st to 10th	Night	20% 11% 3 7% 4 4 4 4 5% 6% 32%	5404
	11th to 20th	Night	12% 6% 2 4 3 3 3 4 5% 7% 50%	5090
	21st to end	Night	14% 7% 3 7% 4 4 4 4 4 6% 44%	5588
April	1st to 10th	Night	12% 4 2 5% 4 5% 5% 4 6% 8% 47%	2221
	11th to 20th	Night	13% 5% 2 4 3 3 4 3 5% 7% 50%	2075
	21st to end	Night	9% 8% 2 6% 3 4 3 3 5% 7% 48%	1948
May	1st to 10th	Night	15% 8% 3 9% 5% 5% 5% 4 5% 8% 34%	5237
	11th to 20th	Night	16% 8% 2 8% 4 5% 5% 4 7% 7% 34%	5234
	21st to end	Night	16% 9% 3 8% 5% 5% 5% 4 7% 8% 31%	5761
June	1st to 10th	Night	7% 6% 2 7% 5% 6% 6% 5% 7% 11% 37%	1890
	11th to 20th	Night	6% 4 1 5% 5% 5% 5% 5% 8% 11% 45%	1890
	21st to end	Night	5% 5% 3 5% 4 4 6% 5% 7% 12% 44%	1890
July	1st to 10th	Night	7% 5% 2 6% 5% 5% 6% 6% 8% 13% 36%	5278
	11th to 20th	Night	8% 6% 3 8% 6% 6% 7% 6% 8% 12% 31%	5277
	21st to end	Night	11% 8% 3 9% 5% 6% 6% 5% 7% 10% 31%	5736
August	1st to 10th	Night	8% 5% 2 8% 6% 5% 6% 5% 8% 13% 35%	4135
	11th to 20th	Night	6% 5% 2 5% 3 4 4 4 7% 12% 47%	4510
	21st to end	Night	6% 5% 2 5% 3 4 5% 4 6% 9% 50%	5046
September	1st to 10th	Night	8% 5% 3 6% 5% 6% 4 5% 6% 9% 42%	2254
	11th to 20th	Night	11% 5% 2 7% 4 4 4 4 6% 8% 45%	2310
	21st to end	Night	11% 5% 1 6% 4 4 4 4 6% 7% 49%	2289
October	1st to 10th	Night	10% 5% 2 5% 3 3 2 3 5% 6% 57%	2200
	11th to 20th	Night	11% 5% 2 4 3 3 3 2 4 5% 58%	2292
	21st to end	Night	12% 7% 2 5% 3 3 3 2 4 5% 55%	2660
November	1st to 10th	Night	11% 6% 2 5% 3 3 3 4 4 5% 54%	2666
	11th to 20th	Night	12% 6% 3 4 3 3 3 3 4 6% 53%	2730
	21st to end	Night	15% 8% 2 5% 3 3 4 4 5% 5% 46%	2730
December	1st to 10th	Night	19% 7% 3 4 3 3 3 2 4 6% 46%	4380
	11th to 20th	Night	17% 10% 3 7% 3 4 4 3 4 5% 41%	4952
	21st to end	Night	18% 9% 3 7% 3 4 4 3 5% 6% 38%	6633

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	48% 2 6% 22% 19% 3	5259
	11th to 20th	Day	34% 2 5% 16% 32% 10%	5280
	21st to end	Day	52% 2 5% 15% 19% 7%	6056
February	1st to 10th	Day	45% 4 7% 19% 21% 4	2100
	11th to 20th	Day	49% 3 6% 18% 18% 5%	2058
	21st to end	Day	48% 3 7% 14% 21% 7%	1730
March	1st to 10th	Day	50% 4 8% 12% 19% 8%	4668
	11th to 20th	Day	36% 3 6% 15% 24% 16%	5090
	21st to end	Day	43% 3 8% 23% 19% 4	5586
April	1st to 10th	Day	40% 5% 10% 21% 19% 5%	2415
	11th to 20th	Day	37% 4 7% 19% 25% 7%	2494
	21st to end	Day	35% 5% 12% 27% 18% 3	2672
May	1st to 10th	Day	46% 5% 12% 22% 13% 2	7651
	11th to 20th	Day	49% 5% 15% 20% 9% 1	7630
	21st to end	Day	53% 6% 9% 17% 13% 1	8405
June	1st to 10th	Day	42% 9% 16% 20% 11% 2	2730
	11th to 20th	Day	34% 10% 18% 25% 11% 1	2730
	21st to end	Day	36% 11% 17% 22% 12% 2	2730
July	1st to 10th	Day	38% 7% 27% 22% 6%	7615
	11th to 20th	Day	44% 8% 28% 16% 3 1	7611
	21st to end	Day	50% 7% 19% 17% 7%	8156
August	1st to 10th	Day	44% 8% 16% 25% 7%	6001
	11th to 20th	Day	29% 5% 24% 28% 13% 1	5568
	21st to end	Day	32% 5% 14% 27% 19% 2	6079
September	1st to 10th	Day	38% 9% 13% 19% 17% 4	2343
	11th to 20th	Day	40% 6% 13% 21% 19% 1	2310
	21st to end	Day	39% 5% 13% 16% 21% 6%	2288
October	1st to 10th	Day	25% 4 6% 14% 39% 12%	3590
	11th to 20th	Day	21% 3 5% 17% 29% 26%	3411
	21st to end	Day	27% 2 5% 25% 28% 12%	3489
November	1st to 10th	Day	35% 3 6% 17% 31% 9%	1852
	11th to 20th	Day	34% 4 7% 19% 27% 10%	1890
	21st to end	Day	39% 4 6% 18% 26% 6%	1890
December	1st to 10th	Day	42% 4 5% 17% 26% 6%	3020
	11th to 20th	Day	50% 2 7% 17% 19% 5%	3460
	21st to end	Day	46% 3 9% 26% 14% 2	4565
January	1st to 10th	Night	44% 3 9% 19% 21% 3	7636
	11th to 20th	Night	40% 2 4 19% 27% 8%	7680
	21st to end	Night	49% 1 3 16% 22% 8%	8120
February	1st to 10th	Night	42% 4 7% 20% 21% 6%	2520
	11th to 20th	Night	49% 4 5% 18% 19% 6%	2459
	21st to end	Night	47% 4 7% 16% 19% 8%	2076
March	1st to 10th	Night	51% 4 8% 14% 18% 5%	5404
	11th to 20th	Night	33% 4 7% 16% 25% 14%	5090
	21st to end	Night	41% 3 7% 23% 20% 6%	5588
April	1st to 10th	Night	34% 6% 11% 19% 24% 6%	2221
	11th to 20th	Night	33% 4 7% 23% 23% 9%	2075
	21st to end	Night	35% 5% 10% 27% 19% 4	1948
May	1st to 10th	Night	48% 6% 13% 18% 13% 2	5264
	11th to 20th	Night	47% 5% 16% 20% 11%	5235
	21st to end	Night	49% 8% 11% 18% 12% 1	5771
June	1st to 10th	Night	39% 10% 16% 20% 13% 2	1890
	11th to 20th	Night	31% 9% 22% 24% 14% 1	1890
	21st to end	Night	31% 11% 18% 23% 13% 4	1890
July	1st to 10th	Night	39% 8% 26% 21% 6%	5235
	11th to 20th	Night	43% 10% 28% 15% 3 1	5226
	21st to end	Night	48% 8% 20% 16% 7% 1	5606
August	1st to 10th	Night	41% 10% 15% 25% 7%	4124
	11th to 20th	Night	30% 5% 23% 27% 14%	4539
	21st to end	Night	30% 5% 14% 26% 22% 2	5046
September	1st to 10th	Night	37% 7% 15% 19% 16% 5%	2254
	11th to 20th	Night	37% 8% 13% 22% 19% 2	2310
	21st to end	Night	34% 6% 11% 21% 20% 8%	2289
October	1st to 10th	Night	23% 3 8% 15% 38% 12%	3590
	11th to 20th	Night	19% 2 5% 18% 33% 23%	3726
	21st to end	Night	24% 3 3 25% 29% 16%	4284
November	1st to 10th	Night	33% 4 7% 18% 27% 11%	2666
	11th to 20th	Night	33% 3 5% 20% 28% 11%	2730
	21st to end	Night	39% 4 6% 20% 25% 6%	2730
December	1st to 10th	Night	41% 3 5% 19% 27% 6%	4380
	11th to 20th	Night	45% 3 8% 15% 23% 5%	4954
	21st to end	Night	47% 3 8% 27% 14% 1	6633

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% 23% 32% 9% 1	330
	11th to 20th	Day	34% 25% 25% 12% 3	330
	21st to end	Day	28% 34% 27% 9% 2 1	363
February	1st to 10th	Day	27% 24% 37% 10% 2	330
	11th to 20th	Day	45% 24% 22% 8% 1	330
	21st to end	Day	36% 22% 34% 6% 2	273
March	1st to 10th	Day	31% 20% 28% 17% 4	366
	11th to 20th	Day	27% 21% 29% 18% 5% 1	540
	21st to end	Day	23% 20% 33% 18% 5%	594
April	1st to 10th	Day	24% 15% 31% 20% 9% 1	540
	11th to 20th	Day	17% 16% 33% 23% 9% 1	532
	21st to end	Day	18% 13% 30% 24% 12% 3	540
May	1st to 10th	Day	20% 12% 30% 22% 12% 4	543
	11th to 20th	Day	15% 8% 27% 27% 14% 8%	567
	21st to end	Day	16% 8% 22% 28% 17% 8%	617
June	1st to 10th	Day	14% 5% 22% 28% 21% 10%	570
	11th to 20th	Day	8% 6% 19% 29% 22% 17%	570
	21st to end	Day	10% 4 18% 28% 23% 16%	570
July	1st to 10th	Day	11% 3 12% 27% 27% 21%	565
	11th to 20th	Day	8% 3 8% 26% 32% 22%	564
	21st to end	Day	10% 3 12% 29% 28% 18%	620
August	1st to 10th	Day	13% 5% 16% 25% 24% 17%	566
	11th to 20th	Day	11% 2 13% 31% 28% 15%	559
	21st to end	Day	13% 5% 10% 28% 29% 15%	627
September	1st to 10th	Day	8% 5% 18% 29% 26% 14%	570
	11th to 20th	Day	14% 6% 15% 26% 30% 10%	570
	21st to end	Day	13% 4 21% 30% 25% 7%	562
October	1st to 10th	Day	15% 6% 25% 32% 15% 7%	530
	11th to 20th	Day	14% 11% 24% 31% 18% 2	530
	21st to end	Day	19% 13% 26% 27% 13% 3	558
November	1st to 10th	Day	18% 16% 32% 22% 9% 3	330
	11th to 20th	Day	20% 20% 36% 18% 5% 1	330
	21st to end	Day	23% 21% 33% 17% 5% 1	330
December	1st to 10th	Day	35% 24% 23% 13% 4 1	330
	11th to 20th	Day	27% 21% 30% 18% 4	330
	21st to end	Day	28% 21% 34% 14% 3	363
January	1st to 10th	Night	27% 21% 28% 20% 4	840
	11th to 20th	Night	25% 19% 28% 21% 6%	840
	21st to end	Night	23% 20% 32% 23% 3	924
February	1st to 10th	Night	23% 15% 31% 26% 4	840
	11th to 20th	Night	29% 20% 29% 21% 1	823
	21st to end	Night	27% 19% 34% 18% 3	692
March	1st to 10th	Night	21% 16% 32% 26% 5%	840
	11th to 20th	Night	20% 17% 31% 24% 8%	840
	21st to end	Night	19% 14% 32% 27% 7%	924
April	1st to 10th	Night	16% 13% 31% 28% 11%	751
	11th to 20th	Night	17% 12% 28% 30% 12% 1	623
	21st to end	Night	13% 8% 26% 34% 18% 1	630
May	1st to 10th	Night	12% 9% 25% 35% 19% 1	630
	11th to 20th	Night	15% 6% 23% 30% 20% 5%	621
	21st to end	Night	12% 5% 16% 33% 29% 6%	683
June	1st to 10th	Night	9% 4 12% 38% 32% 4	630
	11th to 20th	Night	7% 3 13% 32% 33% 12%	630
	21st to end	Night	5% 2 9% 35% 41% 7%	630
July	1st to 10th	Night	9% 2 7% 25% 43% 14%	615
	11th to 20th	Night	10% 1 8% 25% 43% 14%	612
	21st to end	Night	7% 3 9% 28% 43% 11%	690
August	1st to 10th	Night	11% 2 9% 28% 40% 11%	627
	11th to 20th	Night	10% 3 10% 27% 40% 10%	624
	21st to end	Night	13% 3 11% 29% 35% 10%	693
September	1st to 10th	Night	10% 2 15% 29% 35% 9%	784
	11th to 20th	Night	13% 3 14% 32% 33% 4	840
	21st to end	Night	13% 4 17% 35% 28% 2	833
October	1st to 10th	Night	13% 6% 21% 33% 21% 6%	800
	11th to 20th	Night	13% 8% 26% 32% 20% 1	800
	21st to end	Night	15% 12% 22% 34% 16% 2	880
November	1st to 10th	Night	14% 10% 26% 30% 18% 1	820
	11th to 20th	Night	16% 14% 28% 30% 11% 1	840
	21st to end	Night	21% 16% 27% 25% 10% 1	840
December	1st to 10th	Night	24% 15% 28% 24% 7% 1	840
	11th to 20th	Night	25% 15% 26% 26% 7%	840
	21st to end	Night	27% 16% 27% 25% 5%	924

Page generated at 2026-09-26 04:18:39. Version ac07

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