Mountain Home
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mountain Home clear sky chart from 2005-11-06 to 2024-08-30.

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	12% 7% 2 6% 4 4 4 4 6% 7% 44%	95354
	Night	13% 6% 2 5% 4 3 4 3 5% 7% 48%	93721
Transparency	Day	38% 5% 11% 25% 17% 4	95126
	Night	36% 5% 11% 25% 19% 4	93555
Seeing	Day	16% 10% 24% 25% 19% 5%	15251
	Night	16% 9% 26% 31% 16% 2	25023

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	16% 10% 3 6% 3 3 3 2 3 4 47%	2847
	11th to 20th	Day	12% 9% 2 6% 4 3 3 3 4 5% 49%	2850
	21st to end	Day	24% 8% 4 5% 2 2 2 2 3 4 44%	3135
February	1st to 10th	Day	17% 9% 3 6% 5% 3 4 3 3 5% 42%	1710
	11th to 20th	Day	16% 7% 2 7% 3 3 3 3 5% 5% 44%	1762
	21st to end	Day	17% 11% 3 5% 5% 4 5% 3 5% 5% 38%	1586
March	1st to 10th	Day	18% 10% 3 6% 3 4 3 2 4 4 44%	3436
	11th to 20th	Day	13% 6% 2 5% 3 3 3 3 5% 6% 51%	3480
	21st to end	Day	16% 7% 2 7% 5% 4 4 3 5% 6% 40%	3836
April	1st to 10th	Day	11% 6% 3 6% 5% 4 4 3 5% 6% 46%	2280
	11th to 20th	Day	15% 6% 3 6% 4 4 4 4 5% 6% 41%	2254
	21st to end	Day	18% 10% 3 7% 4 4 4 4 4 6% 39%	2280
May	1st to 10th	Day	13% 7% 3 7% 5% 4 5% 5% 7% 8% 37%	3823
	11th to 20th	Day	13% 6% 2 7% 5% 5% 4 4 6% 8% 40%	4082
	21st to end	Day	13% 7% 3 7% 5% 5% 5% 4 6% 7% 38%	4720
June	1st to 10th	Day	8% 5% 2 5% 5% 5% 6% 4 6% 10% 44%	2660
	11th to 20th	Day	6% 4 1 4 5% 5% 6% 5% 8% 11% 47%	2660
	21st to end	Day	4 4 1 5% 5% 5% 5% 5% 7% 9% 51%	2660
July	1st to 10th	Day	10% 5% 2 6% 5% 5% 5% 4 7% 10% 42%	4200
	11th to 20th	Day	5% 3 1 4 4 5% 5% 5% 7% 12% 49%	4120
	21st to end	Day	7% 6% 2 7% 5% 6% 7% 6% 8% 10% 35%	4465
August	1st to 10th	Day	7% 5% 2 6% 4 5% 6% 4 7% 11% 43%	2458
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 8% 9% 43%	2294
	21st to end	Day	7% 4 2 5% 4 4 4 5% 6% 8% 49%	2485
September	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 6% 6% 48%	2160
	11th to 20th	Day	11% 6% 2 5% 4 4 4 4 6% 7% 45%	2160
	21st to end	Day	10% 4 2 5% 4 3 5% 3 5% 6% 55%	1885
October	1st to 10th	Day	8% 5% 2 5% 3 4 4 3 5% 7% 54%	1800
	11th to 20th	Day	16% 4 2 5% 3 3 2 2 3 6% 54%	1800
	21st to end	Day	18% 7% 2 5% 3 2 3 2 5% 6% 48%	1980
November	1st to 10th	Day	12% 5% 2 4 3 3 2 3 3 5% 58%	1858
	11th to 20th	Day	11% 7% 1 6% 4 4 3 3 4 5% 52%	1739
	21st to end	Day	19% 7% 2 5% 3 3 3 3 4 5% 47%	1604
December	1st to 10th	Day	15% 7% 2 5% 5% 4 3 3 4 6% 45%	1520
	11th to 20th	Day	14% 9% 4 7% 4 4 3 4 4 4 43%	1918
	21st to end	Day	12% 14% 3 9% 4 5% 5% 4 5% 6% 33%	2847
January	1st to 10th	Night	15% 7% 3 6% 4 5% 5% 4 6% 6% 39%	4108
	11th to 20th	Night	13% 6% 2 8% 3 3 3 3 4 6% 48%	4120
	21st to end	Night	22% 11% 3 5% 3 2 2 2 3 4 43%	4532
February	1st to 10th	Night	16% 9% 3 6% 4 3 3 3 5% 6% 41%	2470
	11th to 20th	Night	16% 7% 3 7% 4 3 3 3 4 5% 45%	2305
	21st to end	Night	16% 8% 2 4 4 4 3 2 4 5% 47%	1884
March	1st to 10th	Night	22% 8% 2 5% 3 2 3 2 4 5% 43%	3419
	11th to 20th	Night	13% 7% 2 5% 3 3 3 2 4 5% 52%	3480
	21st to end	Night	13% 7% 3 6% 5% 4 5% 4 5% 6% 41%	3793
April	1st to 10th	Night	11% 6% 2 5% 4 3 4 4 4 6% 51%	1900
	11th to 20th	Night	13% 5% 2 5% 4 3 4 4 5% 6% 49%	1875
	21st to end	Night	17% 6% 2 5% 4 4 3 4 5% 7% 43%	1900
May	1st to 10th	Night	16% 6% 2 5% 4 3 4 3 5% 7% 45%	3069
	11th to 20th	Night	12% 7% 3 5% 4 4 4 4 6% 9% 43%	2823
	21st to end	Night	11% 7% 3 7% 5% 3 4 4 6% 8% 42%	2844
June	1st to 10th	Night	8% 3 2 5% 4 3 3 4 6% 11% 52%	1520
	11th to 20th	Night	4 3 1 3 3 3 4 3 6% 11% 58%	1520
	21st to end	Night	3 3 2 3 4 3 4 3 6% 9% 59%	1520
July	1st to 10th	Night	8% 4 2 5% 4 5% 5% 4 7% 10% 48%	2750
	11th to 20th	Night	4 3 2 3 4 4 4 4 6% 8% 60%	2850
	21st to end	Night	5% 6% 3 7% 6% 5% 5% 5% 7% 8% 43%	3098
August	1st to 10th	Night	4 4 1 4 4 4 5% 5% 6% 11% 52%	1701
	11th to 20th	Night	6% 4 2 7% 4 4 5% 4 6% 10% 49%	1827
	21st to end	Night	6% 4 1 4 3 4 4 4 6% 8% 56%	2080
September	1st to 10th	Night	8% 4 2 4 3 3 3 4 6% 8% 56%	1800
	11th to 20th	Night	10% 5% 2 5% 4 5% 4 4 6% 7% 49%	1800
	21st to end	Night	7% 4 2 5% 3 3 3 3 3 6% 60%	2051
October	1st to 10th	Night	7% 4 1 5% 3 2 3 3 5% 7% 60%	2160
	11th to 20th	Night	13% 5% 2 4 2 2 4 2 4 5% 57%	2160
	21st to end	Night	17% 5% 2 4 3 3 3 2 3 5% 51%	2376
November	1st to 10th	Night	11% 5% 2 4 3 2 3 3 4 5% 58%	2220
	11th to 20th	Night	12% 6% 2 4 3 3 3 4 4 5% 56%	2437
	21st to end	Night	16% 7% 2 4 3 3 3 3 4 6% 48%	2574
December	1st to 10th	Night	16% 7% 2 5% 4 3 3 2 4 7% 47%	2660
	11th to 20th	Night	17% 8% 3 6% 4 4 4 3 4 5% 44%	3279
	21st to end	Night	17% 12% 4 8% 5% 4 4 3 5% 5% 33%	4816

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	43% 2 6% 27% 19% 3	2848
	11th to 20th	Day	38% 3 10% 28% 17% 3	2850
	21st to end	Day	46% 2 9% 20% 19% 5%	3135
February	1st to 10th	Day	46% 4 9% 24% 14% 3	1710
	11th to 20th	Day	42% 4 8% 24% 17% 4	1771
	21st to end	Day	47% 4 8% 20% 14% 8%	1586
March	1st to 10th	Day	45% 3 7% 18% 17% 10%	3436
	11th to 20th	Day	35% 4 9% 27% 20% 6%	3480
	21st to end	Day	44% 4 11% 24% 16% 1	3836
April	1st to 10th	Day	38% 5% 8% 26% 20% 3	2280
	11th to 20th	Day	42% 5% 11% 21% 16% 5%	2254
	21st to end	Day	47% 5% 9% 22% 15% 2	2280
May	1st to 10th	Day	44% 6% 12% 23% 14% 1	3858
	11th to 20th	Day	41% 7% 14% 25% 12% 1	4086
	21st to end	Day	44% 7% 11% 23% 14% 2	4733
June	1st to 10th	Day	35% 8% 16% 24% 17% 1	2660
	11th to 20th	Day	29% 8% 15% 29% 17% 3	2660
	21st to end	Day	27% 7% 16% 27% 20% 4	2660
July	1st to 10th	Day	36% 7% 15% 27% 13% 2	4136
	11th to 20th	Day	25% 7% 11% 34% 21% 2	4051
	21st to end	Day	40% 9% 16% 26% 8% 1	4325
August	1st to 10th	Day	31% 9% 18% 27% 14% 1	2444
	11th to 20th	Day	36% 7% 13% 28% 15% 1	2294
	21st to end	Day	31% 7% 15% 26% 17% 5%	2485
September	1st to 10th	Day	35% 6% 11% 25% 16% 6%	2160
	11th to 20th	Day	35% 7% 8% 22% 24% 3	2160
	21st to end	Day	30% 6% 7% 26% 28% 4	1885
October	1st to 10th	Day	30% 5% 9% 25% 25% 6%	1800
	11th to 20th	Day	33% 3 5% 25% 27% 7%	1800
	21st to end	Day	39% 4 7% 27% 17% 7%	1980
November	1st to 10th	Day	31% 3 8% 27% 24% 7%	1858
	11th to 20th	Day	35% 4 6% 25% 23% 8%	1739
	21st to end	Day	40% 3 9% 20% 24% 3	1604
December	1st to 10th	Day	41% 3 9% 28% 16% 3	1520
	11th to 20th	Day	44% 4 6% 21% 23% 2	1915
	21st to end	Day	49% 6% 10% 19% 11% 5%	2847
January	1st to 10th	Night	43% 5% 8% 24% 18% 2	4108
	11th to 20th	Night	39% 5% 10% 24% 19% 3	4120
	21st to end	Night	47% 2 10% 21% 17% 2	4532
February	1st to 10th	Night	44% 4 9% 24% 16% 3	2470
	11th to 20th	Night	41% 4 9% 24% 19% 4	2306
	21st to end	Night	39% 4 9% 22% 18% 7%	1884
March	1st to 10th	Night	45% 3 9% 17% 16% 9%	3419
	11th to 20th	Night	36% 4 9% 28% 20% 4	3480
	21st to end	Night	42% 4 9% 29% 14% 1	3793
April	1st to 10th	Night	34% 5% 10% 23% 22% 6%	1900
	11th to 20th	Night	35% 5% 10% 25% 19% 6%	1875
	21st to end	Night	40% 5% 10% 26% 15% 3	1900
May	1st to 10th	Night	40% 6% 14% 25% 14% 2	3099
	11th to 20th	Night	38% 6% 16% 26% 13% 2	2824
	21st to end	Night	38% 7% 14% 28% 13% 1	2852
June	1st to 10th	Night	27% 6% 13% 33% 20% 2	1520
	11th to 20th	Night	20% 5% 14% 36% 21% 4	1520
	21st to end	Night	21% 6% 16% 30% 20% 7%	1520
July	1st to 10th	Night	30% 7% 18% 25% 17% 3	2705
	11th to 20th	Night	21% 6% 12% 35% 24% 3	2796
	21st to end	Night	36% 7% 17% 28% 12%	2999
August	1st to 10th	Night	24% 9% 16% 36% 14% 1	1691
	11th to 20th	Night	29% 6% 16% 27% 19% 2	1827
	21st to end	Night	25% 6% 17% 27% 20% 5%	2080
September	1st to 10th	Night	26% 6% 11% 31% 18% 8%	1800
	11th to 20th	Night	33% 7% 10% 22% 24% 5%	1800
	21st to end	Night	25% 4 9% 23% 32% 5%	2051
October	1st to 10th	Night	24% 5% 12% 26% 26% 7%	2160
	11th to 20th	Night	30% 4 8% 21% 31% 7%	2160
	21st to end	Night	38% 3 8% 22% 21% 8%	2376
November	1st to 10th	Night	29% 3 9% 26% 26% 7%	2220
	11th to 20th	Night	31% 4 8% 24% 27% 7%	2437
	21st to end	Night	38% 4 8% 23% 24% 4	2574
December	1st to 10th	Night	39% 3 11% 24% 20% 3	2660
	11th to 20th	Night	43% 3 7% 23% 20% 3	3281
	21st to end	Night	51% 6% 10% 20% 11% 2	4816

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	30% 16% 32% 17% 3 1	270
	11th to 20th	Day	29% 20% 33% 15% 2	270
	21st to end	Day	24% 23% 33% 17% 3	297
February	1st to 10th	Day	28% 18% 37% 13% 4	270
	11th to 20th	Day	30% 22% 30% 13% 4 1	270
	21st to end	Day	36% 24% 29% 8% 2	225
March	1st to 10th	Day	30% 18% 33% 16% 3	270
	11th to 20th	Day	33% 21% 31% 13% 3	270
	21st to end	Day	28% 24% 37% 8% 3	307
April	1st to 10th	Day	22% 18% 31% 20% 8% 1	460
	11th to 20th	Day	23% 17% 33% 19% 6% 1	452
	21st to end	Day	23% 15% 34% 20% 5% 2	460
May	1st to 10th	Day	21% 17% 30% 22% 9%	495
	11th to 20th	Day	16% 12% 31% 23% 16% 3	675
	21st to end	Day	11% 8% 34% 26% 16% 5%	734
June	1st to 10th	Day	10% 5% 22% 28% 27% 8%	680
	11th to 20th	Day	7% 2 19% 38% 29% 6%	680
	21st to end	Day	5% 4 24% 34% 27% 7%	680
July	1st to 10th	Day	8% 3 14% 33% 32% 10%	671
	11th to 20th	Day	4 3 13% 35% 32% 13%	668
	21st to end	Day	7% 1 13% 31% 32% 15%	739
August	1st to 10th	Day	8% 3 13% 37% 32% 8%	676
	11th to 20th	Day	12% 3 13% 32% 32% 9%	528
	21st to end	Day	10% 2 8% 29% 35% 17%	532
September	1st to 10th	Day	11% 3 11% 31% 33% 11%	450
	11th to 20th	Day	10% 2 11% 32% 31% 14%	450
	21st to end	Day	11% 7% 20% 30% 26% 7%	288
October	1st to 10th	Day	11% 8% 26% 31% 20% 3	270
	11th to 20th	Day	17% 15% 36% 23% 7% 1	270
	21st to end	Day	33% 14% 27% 19% 6% 1	297
November	1st to 10th	Day	16% 11% 34% 23% 13% 4	270
	11th to 20th	Day	21% 13% 32% 21% 11% 1	270
	21st to end	Day	30% 15% 25% 20% 9% 2	270
December	1st to 10th	Day	21% 25% 28% 14% 9% 3	270
	11th to 20th	Day	27% 21% 25% 20% 7%	270
	21st to end	Day	25% 24% 33% 14% 4	297
January	1st to 10th	Night	23% 16% 33% 24% 4	950
	11th to 20th	Night	23% 16% 33% 24% 3 1	950
	21st to end	Night	21% 15% 36% 25% 3	1045
February	1st to 10th	Night	23% 13% 35% 25% 4	950
	11th to 20th	Night	22% 16% 37% 23% 1	831
	21st to end	Night	24% 18% 36% 20% 2	628
March	1st to 10th	Night	22% 14% 31% 29% 3	570
	11th to 20th	Night	23% 13% 31% 28% 5%	570
	21st to end	Night	22% 13% 34% 27% 5%	627
April	1st to 10th	Night	14% 16% 38% 27% 5%	570
	11th to 20th	Night	15% 16% 31% 30% 8%	563
	21st to end	Night	18% 10% 37% 26% 8% 1	570
May	1st to 10th	Night	15% 8% 30% 38% 9%	570
	11th to 20th	Night	17% 7% 26% 30% 19% 2	561
	21st to end	Night	11% 7% 22% 35% 21% 4	617
June	1st to 10th	Night	10% 3 14% 38% 33% 2	570
	11th to 20th	Night	5% 2 14% 46% 31% 3	570
	21st to end	Night	5% 1 18% 41% 32% 3	570
July	1st to 10th	Night	6% 2 10% 36% 37% 8%	555
	11th to 20th	Night	4 1 9% 38% 40% 7%	552
	21st to end	Night	5% 1 8% 38% 40% 8%	624
August	1st to 10th	Night	5% 1 9% 39% 40% 6%	567
	11th to 20th	Night	7% 1 13% 40% 36% 4	564
	21st to end	Night	9% 1 7% 34% 42% 7%	624
September	1st to 10th	Night	9% 2 11% 35% 40% 3	540
	11th to 20th	Night	12% 1 9% 35% 35% 7%	540
	21st to end	Night	9% 5% 16% 35% 32% 3	634
October	1st to 10th	Night	9% 3 19% 37% 28% 3	720
	11th to 20th	Night	16% 8% 29% 31% 15%	720
	21st to end	Night	22% 10% 27% 30% 11%	792
November	1st to 10th	Night	14% 8% 31% 33% 14%	740
	11th to 20th	Night	17% 10% 29% 34% 10%	760
	21st to end	Night	21% 11% 29% 29% 10%	864
December	1st to 10th	Night	23% 11% 29% 30% 7%	950
	11th to 20th	Night	24% 12% 27% 30% 6%	950
	21st to end	Night	24% 17% 29% 27% 3	1045

Page generated at 2024-08-27 08:49:38. Version ac07

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