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 2024-01-27.

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% 6% 2 5% 5% 3 4 5% 5% 7% 45%	74776
	Night	12% 6% 2 5% 4 2 4 4 5% 7% 49%	75286
Transparency	Day	38% 6% 11% 24% 17% 4	74499
	Night	36% 5% 11% 25% 20% 4	75083
Seeing	Day	16% 10% 24% 25% 19% 6%	14354
	Night	16% 9% 26% 31% 16% 2	24323

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% 8% 3 5% 4 2 3 3 3 5% 48%	1707
	11th to 20th	Day	16% 9% 3 5% 5% 3 3 4 4 6% 43%	1710
	21st to end	Day	16% 9% 3 5% 4 2 3 3 4 6% 47%	1836
February	1st to 10th	Day	17% 8% 4 5% 6% 2 3 3 3 5% 43%	1620
	11th to 20th	Day	16% 6% 3 7% 4 2 4 4 5% 5% 43%	1667
	21st to end	Day	18% 10% 3 4 5% 3 4 4 4 5% 38%	1495
March	1st to 10th	Day	17% 8% 3 4 4 2 4 3 5% 5% 46%	1980
	11th to 20th	Day	20% 7% 3 5% 4 2 4 4 5% 5% 40%	1980
	21st to end	Day	20% 8% 2 6% 5% 4 4 4 5% 6% 36%	2187
April	1st to 10th	Day	11% 6% 3 5% 6% 3 4 4 5% 6% 46%	2160
	11th to 20th	Day	16% 6% 3 5% 5% 3 4 4 5% 6% 41%	2134
	21st to end	Day	18% 9% 3 6% 5% 3 4 4 4 6% 39%	2160
May	1st to 10th	Day	15% 7% 3 7% 6% 3 5% 5% 6% 7% 39%	2190
	11th to 20th	Day	13% 5% 2 5% 6% 4 5% 5% 6% 8% 42%	2302
	21st to end	Day	9% 6% 3 7% 6% 4 6% 5% 7% 9% 38%	2663
June	1st to 10th	Day	8% 5% 2 5% 5% 3 6% 6% 6% 9% 45%	2520
	11th to 20th	Day	6% 3 2 3 6% 3 6% 6% 8% 10% 47%	2520
	21st to end	Day	4 3 2 4 5% 4 5% 6% 6% 9% 52%	2520
July	1st to 10th	Day	8% 4 3 6% 6% 4 6% 7% 8% 11% 37%	2392
	11th to 20th	Day	4 3 1 4 5% 4 6% 7% 8% 11% 46%	2340
	21st to end	Day	6% 5% 2 5% 5% 3 6% 7% 7% 11% 42%	2546
August	1st to 10th	Day	7% 4 2 6% 5% 4 5% 6% 8% 12% 42%	2328
	11th to 20th	Day	9% 5% 2 6% 4 3 5% 5% 8% 9% 43%	2172
	21st to end	Day	7% 3 2 4 5% 3 5% 6% 6% 8% 49%	2376
September	1st to 10th	Day	12% 4 3 4 4 3 5% 5% 6% 7% 48%	2160
	11th to 20th	Day	11% 6% 2 5% 5% 3 4 6% 6% 8% 45%	2160
	21st to end	Day	10% 4 2 4 4 2 4 4 5% 7% 55%	1885
October	1st to 10th	Day	8% 5% 2 5% 4 3 3 4 5% 7% 55%	1800
	11th to 20th	Day	16% 4 2 5% 3 2 2 3 3 6% 55%	1800
	21st to end	Day	18% 7% 2 4 4 2 2 3 4 6% 48%	1980
November	1st to 10th	Day	12% 5% 2 4 3 2 3 3 3 5% 58%	1858
	11th to 20th	Day	11% 6% 2 5% 4 4 3 4 4 5% 52%	1739
	21st to end	Day	19% 7% 2 5% 3 2 3 3 4 5% 47%	1604
December	1st to 10th	Day	15% 6% 2 5% 5% 3 4 4 4 6% 45%	1520
	11th to 20th	Day	15% 8% 4 6% 6% 3 3 4 4 4 43%	1918
	21st to end	Day	12% 14% 3 8% 5% 4 5% 4 5% 6% 33%	2847
January	1st to 10th	Night	16% 6% 3 4 4 3 5% 3 4 6% 46%	2458
	11th to 20th	Night	15% 7% 3 5% 4 2 3 4 3 6% 47%	2470
	21st to end	Night	15% 8% 3 5% 4 2 3 3 3 5% 48%	2665
February	1st to 10th	Night	16% 9% 3 6% 5% 2 4 3 4 6% 42%	2340
	11th to 20th	Night	16% 6% 3 6% 5% 2 4 4 4 6% 45%	2180
	21st to end	Night	17% 8% 2 4 5% 3 4 3 3 5% 46%	1776
March	1st to 10th	Night	17% 7% 2 5% 4 2 3 3 4 5% 46%	1980
	11th to 20th	Night	19% 8% 2 5% 5% 3 4 3 4 5% 41%	1980
	21st to end	Night	18% 7% 3 6% 5% 3 5% 5% 5% 6% 37%	2167
April	1st to 10th	Night	10% 5% 3 5% 5% 2 4 5% 4 7% 52%	1800
	11th to 20th	Night	13% 5% 2 5% 5% 3 4 5% 5% 6% 49%	1775
	21st to end	Night	17% 5% 2 5% 4 3 4 5% 5% 7% 43%	1800
May	1st to 10th	Night	14% 5% 2 4 5% 2 4 4 4 7% 49%	1765
	11th to 20th	Night	15% 7% 3 3 3 2 3 3 4 7% 49%	1593
	21st to end	Night	9% 6% 3 5% 5% 2 5% 5% 7% 10% 42%	1610
June	1st to 10th	Night	8% 3 2 4 5% 2 3 4 6% 11% 52%	1440
	11th to 20th	Night	4 3 1 3 3 2 4 4 5% 12% 59%	1440
	21st to end	Night	3 3 2 3 4 2 4 4 6% 10% 60%	1440
July	1st to 10th	Night	4 3 2 4 6% 4 5% 6% 7% 11% 48%	1562
	11th to 20th	Night	3 2 1 2 4 2 5% 5% 6% 11% 58%	1620
	21st to end	Night	5% 3 3 4 5% 3 5% 6% 7% 8% 51%	1772
August	1st to 10th	Night	4 4 2 3 5% 3 5% 6% 7% 10% 51%	1611
	11th to 20th	Night	6% 4 2 5% 5% 2 5% 5% 6% 10% 50%	1729
	21st to end	Night	6% 4 2 4 3 3 4 5% 6% 8% 55%	1980
September	1st to 10th	Night	8% 4 2 3 3 2 3 5% 6% 8% 56%	1800
	11th to 20th	Night	10% 5% 2 4 5% 3 4 5% 6% 7% 49%	1800
	21st to end	Night	7% 4 2 4 3 2 3 4 3 6% 61%	2051
October	1st to 10th	Night	7% 4 1 4 4 2 3 4 5% 7% 60%	2160
	11th to 20th	Night	13% 5% 2 4 3 2 4 4 4 5% 57%	2160
	21st to end	Night	17% 5% 2 4 4 3 3 3 3 5% 51%	2376
November	1st to 10th	Night	11% 4 2 4 3 2 3 4 3 5% 58%	2220
	11th to 20th	Night	12% 6% 2 3 3 2 3 4 4 5% 56%	2437
	21st to end	Night	16% 6% 3 4 3 2 4 4 4 6% 48%	2574
December	1st to 10th	Night	17% 7% 2 4 5% 2 3 3 4 7% 47%	2660
	11th to 20th	Night	17% 8% 3 6% 5% 3 4 3 4 5% 44%	3279
	21st to end	Night	17% 12% 4 7% 6% 3 4 4 4 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	41% 3 8% 25% 19% 4	1708
	11th to 20th	Day	43% 3 9% 26% 17% 1	1710
	21st to end	Day	40% 3 11% 28% 15% 4	1836
February	1st to 10th	Day	46% 4 10% 24% 14% 3	1620
	11th to 20th	Day	43% 4 9% 24% 16% 4	1676
	21st to end	Day	48% 4 7% 20% 13% 7%	1495
March	1st to 10th	Day	41% 4 9% 20% 19% 8%	1980
	11th to 20th	Day	47% 4 8% 22% 15% 4	1980
	21st to end	Day	49% 5% 11% 21% 12% 2	2187
April	1st to 10th	Day	38% 5% 9% 27% 19% 2	2160
	11th to 20th	Day	42% 5% 11% 22% 15% 5%	2134
	21st to end	Day	47% 4 9% 22% 15% 2	2160
May	1st to 10th	Day	45% 6% 11% 23% 14% 1	2190
	11th to 20th	Day	40% 6% 14% 24% 13% 2	2306
	21st to end	Day	43% 9% 13% 23% 11% 2	2663
June	1st to 10th	Day	35% 8% 15% 24% 16% 1	2520
	11th to 20th	Day	29% 8% 15% 29% 16% 3	2520
	21st to end	Day	27% 7% 16% 27% 20% 4	2520
July	1st to 10th	Day	38% 8% 16% 22% 13% 2	2328
	11th to 20th	Day	29% 8% 13% 29% 18% 4	2271
	21st to end	Day	33% 9% 15% 30% 12% 1	2405
August	1st to 10th	Day	32% 9% 18% 27% 13% 1	2314
	11th to 20th	Day	36% 7% 13% 28% 16% 1	2172
	21st to end	Day	31% 7% 15% 24% 17% 5%	2376
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	41% 4 9% 23% 20% 4	2458
	11th to 20th	Night	40% 4 10% 26% 18% 3	2470
	21st to end	Night	39% 3 9% 28% 18% 3	2665
February	1st to 10th	Night	44% 4 9% 24% 16% 3	2340
	11th to 20th	Night	41% 4 9% 24% 18% 3	2181
	21st to end	Night	41% 4 9% 22% 17% 7%	1776
March	1st to 10th	Night	41% 4 9% 19% 19% 9%	1980
	11th to 20th	Night	46% 5% 9% 19% 18% 3	1980
	21st to end	Night	48% 4 10% 23% 14% 1	2167
April	1st to 10th	Night	34% 5% 11% 23% 22% 5%	1800
	11th to 20th	Night	35% 5% 10% 25% 19% 6%	1775
	21st to end	Night	39% 5% 10% 27% 16% 2	1800
May	1st to 10th	Night	37% 6% 12% 24% 18% 3	1765
	11th to 20th	Night	35% 6% 13% 25% 16% 4	1594
	21st to end	Night	36% 8% 17% 24% 14% 1	1611
June	1st to 10th	Night	26% 6% 13% 33% 20% 2	1440
	11th to 20th	Night	20% 5% 15% 37% 20% 4	1440
	21st to end	Night	20% 6% 16% 30% 20% 8%	1440
July	1st to 10th	Night	28% 8% 18% 26% 19% 2	1517
	11th to 20th	Night	21% 7% 14% 32% 21% 5%	1566
	21st to end	Night	27% 7% 16% 33% 17% 1	1673
August	1st to 10th	Night	25% 9% 16% 36% 13% 1	1601
	11th to 20th	Night	29% 6% 16% 28% 19% 2	1729
	21st to end	Night	26% 6% 16% 26% 20% 5%	1980
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	25% 23% 33% 17% 2	282
February	1st to 10th	Day	28% 19% 37% 13% 4	240
	11th to 20th	Day	31% 23% 31% 12% 3 1	240
	21st to end	Day	37% 23% 28% 10% 3	198
March	1st to 10th	Day	30% 20% 31% 15% 4	240
	11th to 20th	Day	35% 19% 30% 13% 3	240
	21st to end	Day	28% 25% 38% 7% 3	273
April	1st to 10th	Day	20% 18% 32% 20% 9% 1	420
	11th to 20th	Day	24% 16% 33% 20% 7% 1	412
	21st to end	Day	23% 15% 35% 20% 5% 1	420
May	1st to 10th	Day	20% 16% 31% 23% 9%	453
	11th to 20th	Day	16% 11% 31% 23% 16% 3	625
	21st to end	Day	11% 7% 33% 27% 17% 5%	679
June	1st to 10th	Day	10% 4 21% 28% 29% 9%	630
	11th to 20th	Day	7% 2 19% 38% 29% 6%	630
	21st to end	Day	5% 4 25% 33% 27% 7%	630
July	1st to 10th	Day	9% 2 14% 31% 34% 10%	621
	11th to 20th	Day	4 3 13% 34% 33% 14%	618
	21st to end	Day	7% 1 12% 30% 33% 16%	684
August	1st to 10th	Day	8% 2 12% 36% 34% 7%	626
	11th to 20th	Day	11% 3 12% 31% 33% 10%	486
	21st to end	Day	11% 2 7% 28% 36% 16%	495
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	1025
February	1st to 10th	Night	24% 12% 36% 24% 4	900
	11th to 20th	Night	22% 16% 38% 24% 1	786
	21st to end	Night	25% 18% 35% 20% 2	592
March	1st to 10th	Night	22% 14% 31% 30% 3	540
	11th to 20th	Night	24% 13% 31% 28% 5%	540
	21st to end	Night	22% 13% 33% 27% 5%	594
April	1st to 10th	Night	13% 15% 38% 29% 5%	540
	11th to 20th	Night	14% 16% 31% 30% 8%	533
	21st to end	Night	18% 9% 37% 27% 8% 1	540
May	1st to 10th	Night	15% 8% 29% 38% 9%	540
	11th to 20th	Night	17% 7% 26% 29% 19% 2	531
	21st to end	Night	10% 6% 22% 36% 22% 4	584
June	1st to 10th	Night	10% 3 13% 37% 34% 2	540
	11th to 20th	Night	5% 2 14% 46% 31% 3	540
	21st to end	Night	5% 1 18% 40% 33% 3	540
July	1st to 10th	Night	6% 2 10% 36% 38% 8%	525
	11th to 20th	Night	4 1 9% 37% 41% 8%	522
	21st to end	Night	5% 1 7% 38% 41% 8%	591
August	1st to 10th	Night	6% 1 8% 38% 41% 6%	537
	11th to 20th	Night	6% 1 13% 39% 36% 4	534
	21st to end	Night	9% 1 7% 34% 41% 8%	594
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 2024-01-24 08:37:27. Version ac07

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