Rimrock Meadows
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rimrock Meadows clear sky chart from 2005-11-06 to 2026-08-15.

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	6% 7% 2 7% 4 4 4 3 5% 7% 51%	147989
	Night	7% 8% 3 7% 4 4 4 4 5% 7% 47%	142609
Transparency	Day	33% 4 10% 24% 21% 9%	147717
	Night	37% 5% 11% 24% 17% 6%	142463
Seeing	Day	9% 8% 22% 30% 23% 9%	16514
	Night	11% 5% 23% 37% 21% 3	25443

By Month

Percentage Cloud Cover NW (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	11% 18% 7% 14% 7% 6% 5% 3 4 5% 22%	4723
	11th to 20th	Day	8% 10% 3 8% 5% 5% 4 3 5% 7% 41%	4716
	21st to end	Day	13% 15% 5% 12% 5% 4 4 3 5% 5% 30%	5186
February	1st to 10th	Day	10% 15% 4 12% 7% 5% 5% 4 5% 7% 26%	1811
	11th to 20th	Day	9% 13% 5% 9% 6% 5% 3 4 6% 7% 34%	1864
	21st to end	Day	7% 11% 3 9% 5% 6% 5% 4 7% 7% 35%	1730
March	1st to 10th	Day	4 8% 2 7% 5% 7% 7% 5% 7% 9% 39%	4618
	11th to 20th	Day	4 8% 3 7% 5% 5% 5% 4 5% 8% 47%	4902
	21st to end	Day	7% 7% 3 9% 6% 6% 7% 5% 8% 10% 31%	6024
April	1st to 10th	Day	8% 8% 3 7% 6% 5% 6% 5% 7% 8% 38%	2520
	11th to 20th	Day	5% 7% 3 7% 5% 5% 5% 4 7% 8% 45%	2492
	21st to end	Day	4 6% 2 7% 6% 5% 5% 4 7% 8% 45%	2765
May	1st to 10th	Day	4 5% 2 5% 3 4 4 3 5% 8% 57%	8195
	11th to 20th	Day	6% 4 2 6% 4 4 5% 4 6% 8% 51%	8160
	21st to end	Day	6% 6% 2 7% 5% 5% 4 4 6% 9% 48%	8993
June	1st to 10th	Day	8% 6% 2 6% 5% 5% 5% 4 6% 7% 47%	2940
	11th to 20th	Day	6% 4 2 5% 4 4 5% 4 7% 7% 52%	2940
	21st to end	Day	4 4 2 6% 3 3 3 3 5% 7% 60%	2940
July	1st to 10th	Day	1 1 1 2 2 2 2 2 3 4 80%	8220
	11th to 20th	Day	2 3 1 2 2 2 2 2 2 3 79%	8220
	21st to end	Day	2 2 1 2 1 2 2 2 3 5% 77%	8916
August	1st to 10th	Day	2 2 1 3 2 2 3 2 5% 5% 72%	4681
	11th to 20th	Day	2 2 1 3 2 3 3 3 5% 6% 71%	4346
	21st to end	Day	4 4 1 5% 3 4 3 3 4 5% 63%	4312
September	1st to 10th	Day	3 2 1 3 2 3 3 2 5% 7% 69%	2400
	11th to 20th	Day	4 4 2 5% 4 4 5% 4 5% 7% 56%	2380
	21st to end	Day	6% 4 2 5% 3 4 3 3 5% 7% 56%	2186
October	1st to 10th	Day	4 4 2 3 3 3 3 3 6% 7% 62%	3280
	11th to 20th	Day	5% 5% 3 6% 5% 5% 6% 5% 6% 8% 46%	3234
	21st to end	Day	8% 6% 2 6% 5% 5% 5% 4 6% 7% 47%	3200
November	1st to 10th	Day	12% 10% 4 10% 5% 5% 5% 4 5% 6% 34%	1838
	11th to 20th	Day	10% 15% 4 9% 5% 5% 5% 4 6% 6% 30%	1680
	21st to end	Day	11% 13% 5% 12% 6% 6% 4 4 5% 7% 27%	1680
December	1st to 10th	Day	9% 10% 3 14% 7% 5% 5% 5% 5% 7% 29%	2700
	11th to 20th	Day	13% 19% 7% 17% 7% 5% 4 3 4 5% 16%	3105
	21st to end	Day	11% 20% 7% 15% 7% 7% 5% 4 4 5% 16%	4092
January	1st to 10th	Night	12% 19% 7% 12% 5% 5% 4 3 5% 6% 22%	8172
	11th to 20th	Night	7% 9% 4 8% 4 4 3 3 5% 7% 45%	8182
	21st to end	Night	10% 14% 6% 12% 5% 4 4 3 4 5% 33%	8994
February	1st to 10th	Night	8% 14% 4 10% 5% 5% 5% 5% 6% 7% 30%	2805
	11th to 20th	Night	9% 11% 3 8% 5% 5% 5% 4 7% 8% 35%	2642
	21st to end	Night	8% 12% 3 9% 6% 5% 6% 4 6% 8% 34%	2076
March	1st to 10th	Night	5% 8% 3 6% 5% 5% 5% 5% 8% 9% 41%	5496
	11th to 20th	Night	5% 9% 3 7% 4 4 4 4 5% 7% 47%	5300
	21st to end	Night	6% 7% 3 9% 6% 7% 6% 5% 8% 9% 33%	5192
April	1st to 10th	Night	8% 8% 3 7% 5% 4 4 4 6% 8% 42%	2100
	11th to 20th	Night	6% 7% 2 6% 6% 4 4 4 5% 7% 49%	2079
	21st to end	Night	6% 6% 2 6% 4 4 4 5% 6% 10% 47%	1851
May	1st to 10th	Night	3 3 2 4 3 4 5% 3 6% 7% 59%	4724
	11th to 20th	Night	4 4 2 4 3 3 5% 4 6% 8% 56%	4700
	21st to end	Night	5% 4 2 5% 3 3 4 3 6% 9% 54%	5178
June	1st to 10th	Night	7% 4 2 6% 5% 3 5% 3 6% 9% 50%	1680
	11th to 20th	Night	5% 4 1 5% 4 3 4 4 6% 7% 58%	1680
	21st to end	Night	3 3 1 5% 4 4 4 3 5% 7% 61%	1680
July	1st to 10th	Night	1 2 1 1 1 1 2 2 3 5% 80%	4740
	11th to 20th	Night	1 1 1 2 2 2 2 2 3 4 80%	4740
	21st to end	Night	1 1 1 2 2 2 2 2 4 5% 77%	5152
August	1st to 10th	Night	2 3 1 3 2 2 2 2 4 5% 74%	2689
	11th to 20th	Night	2 2 1 4 2 3 3 3 5% 6% 69%	2791
	21st to end	Night	3 3 2 4 3 3 3 3 4 6% 66%	3608
September	1st to 10th	Night	2 2 1 3 2 3 3 3 5% 6% 69%	2000
	11th to 20th	Night	3 4 1 6% 3 3 5% 3 5% 7% 59%	2020
	21st to end	Night	4 3 2 4 3 5% 3 4 6% 8% 58%	2210
October	1st to 10th	Night	4 4 1 4 2 3 4 4 6% 9% 60%	3920
	11th to 20th	Night	6% 5% 2 5% 4 5% 5% 5% 6% 8% 49%	3922
	21st to end	Night	9% 6% 2 8% 5% 4 4 4 6% 7% 45%	4600
November	1st to 10th	Night	12% 10% 4 7% 5% 4 5% 5% 6% 8% 34%	2680
	11th to 20th	Night	10% 11% 4 7% 6% 5% 6% 4 7% 7% 34%	2940
	21st to end	Night	11% 13% 4 11% 5% 5% 5% 4 5% 6% 30%	2940
December	1st to 10th	Night	7% 9% 3 9% 5% 5% 4 4 5% 7% 42%	4700
	11th to 20th	Night	14% 15% 5% 16% 8% 6% 6% 4 6% 6% 14%	5320
	21st to end	Night	15% 19% 5% 11% 5% 5% 5% 3 5% 5% 22%	7106

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	67% 4 7% 13% 8%	4723
	11th to 20th	Day	43% 4 16% 28% 9% 1	4740
	21st to end	Day	59% 4 11% 19% 7%	5187
February	1st to 10th	Day	56% 8% 15% 14% 5% 1	1811
	11th to 20th	Day	48% 7% 16% 18% 10%	1873
	21st to end	Day	45% 8% 16% 21% 8% 1	1730
March	1st to 10th	Day	38% 6% 12% 23% 20% 1	4618
	11th to 20th	Day	35% 5% 9% 34% 17% 1	4902
	21st to end	Day	44% 9% 16% 20% 10% 1	6024
April	1st to 10th	Day	40% 7% 15% 23% 13% 2	2520
	11th to 20th	Day	34% 6% 15% 23% 17% 6%	2492
	21st to end	Day	34% 6% 12% 24% 19% 4	2765
May	1st to 10th	Day	25% 3 5% 26% 34% 7%	8195
	11th to 20th	Day	29% 3 11% 30% 23% 4	8163
	21st to end	Day	32% 5% 12% 33% 17% 1	8994
June	1st to 10th	Day	35% 6% 10% 22% 21% 6%	2940
	11th to 20th	Day	29% 5% 11% 26% 23% 7%	2940
	21st to end	Day	24% 3 10% 29% 24% 9%	2940
July	1st to 10th	Day	11% 1 3 22% 33% 30%	8151
	11th to 20th	Day	14% 1 2 14% 30% 39%	8145
	21st to end	Day	13% 1 2 22% 39% 23%	8723
August	1st to 10th	Day	16% 2 4 18% 36% 25%	4664
	11th to 20th	Day	15% 2 7% 38% 30% 8%	4388
	21st to end	Day	24% 2 9% 27% 31% 8%	4311
September	1st to 10th	Day	16% 3 9% 29% 30% 13%	2400
	11th to 20th	Day	26% 6% 12% 24% 25% 8%	2380
	21st to end	Day	27% 5% 16% 29% 18% 5%	2186
October	1st to 10th	Day	22% 3 12% 38% 22% 2	3280
	11th to 20th	Day	36% 4 16% 25% 18% 1	3234
	21st to end	Day	36% 5% 13% 27% 13% 5%	3200
November	1st to 10th	Day	49% 7% 16% 17% 9% 1	1838
	11th to 20th	Day	53% 7% 16% 16% 7% 1	1680
	21st to end	Day	56% 8% 16% 11% 7% 1	1680
December	1st to 10th	Day	54% 6% 15% 20% 5%	2700
	11th to 20th	Day	72% 5% 7% 10% 6%	3108
	21st to end	Day	71% 6% 7% 11% 4	4092
January	1st to 10th	Night	65% 4 11% 15% 6%	8172
	11th to 20th	Night	40% 4 16% 29% 10%	8220
	21st to end	Night	55% 5% 13% 20% 7%	8994
February	1st to 10th	Night	51% 9% 17% 15% 7% 1	2805
	11th to 20th	Night	44% 9% 18% 18% 10% 1	2644
	21st to end	Night	46% 9% 14% 20% 10% 1	2076
March	1st to 10th	Night	34% 5% 12% 28% 18% 3	5496
	11th to 20th	Night	36% 4 9% 32% 18% 1	5301
	21st to end	Night	42% 9% 17% 24% 7% 1	5192
April	1st to 10th	Night	40% 5% 15% 27% 11% 2	2100
	11th to 20th	Night	33% 6% 13% 25% 19% 4	2079
	21st to end	Night	31% 7% 11% 28% 20% 3	1851
May	1st to 10th	Night	24% 2 5% 24% 39% 6%	4721
	11th to 20th	Night	25% 3 8% 33% 30% 2	4700
	21st to end	Night	26% 4 13% 37% 19% 1	5182
June	1st to 10th	Night	30% 5% 9% 26% 23% 6%	1680
	11th to 20th	Night	24% 5% 11% 29% 26% 5%	1680
	21st to end	Night	23% 4 10% 28% 28% 9%	1680
July	1st to 10th	Night	10% 1 3 23% 32% 31%	4700
	11th to 20th	Night	12% 1 2 16% 29% 41%	4692
	21st to end	Night	12% 1 3 21% 40% 23%	5040
August	1st to 10th	Night	15% 1 4 14% 39% 27%	2681
	11th to 20th	Night	18% 1 6% 37% 27% 10%	2815
	21st to end	Night	21% 2 6% 27% 31% 13%	3608
September	1st to 10th	Night	15% 3 8% 26% 29% 18%	2000
	11th to 20th	Night	23% 5% 10% 26% 27% 10%	2020
	21st to end	Night	23% 5% 12% 32% 20% 8%	2210
October	1st to 10th	Night	22% 3 8% 44% 22% 1	3920
	11th to 20th	Night	32% 4 14% 28% 20% 2	3922
	21st to end	Night	39% 4 11% 27% 16% 2	4600
November	1st to 10th	Night	46% 7% 17% 19% 9% 2	2680
	11th to 20th	Night	48% 9% 15% 19% 8% 2	2940
	21st to end	Night	54% 8% 14% 15% 7% 1	2940
December	1st to 10th	Night	42% 7% 18% 26% 6%	4700
	11th to 20th	Night	71% 7% 11% 7% 4	5316
	21st to end	Night	64% 6% 10% 12% 7% 1	7106

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	22% 6% 24% 30% 15% 1	220
	11th to 20th	Day	20% 5% 18% 32% 19% 7%	220
	21st to end	Day	21% 1 16% 35% 21% 6%	242
February	1st to 10th	Day	16% 6% 28% 33% 15% 3	351
	11th to 20th	Day	15% 6% 26% 32% 18% 4	436
	21st to end	Day	12% 8% 31% 30% 17% 2	446
March	1st to 10th	Day	11% 8% 29% 31% 16% 4	540
	11th to 20th	Day	12% 12% 24% 26% 20% 6%	540
	21st to end	Day	12% 11% 28% 28% 18% 2	594
April	1st to 10th	Day	13% 12% 25% 24% 19% 7%	540
	11th to 20th	Day	8% 17% 29% 23% 16% 6%	532
	21st to end	Day	7% 11% 24% 30% 19% 9%	540
May	1st to 10th	Day	6% 10% 26% 32% 20% 6%	543
	11th to 20th	Day	11% 9% 22% 26% 21% 11%	568
	21st to end	Day	8% 6% 21% 25% 27% 13%	617
June	1st to 10th	Day	8% 10% 23% 27% 21% 11%	570
	11th to 20th	Day	7% 10% 27% 32% 18% 6%	570
	21st to end	Day	4 6% 21% 28% 28% 14%	570
July	1st to 10th	Day	2 4 17% 34% 33% 10%	566
	11th to 20th	Day	2 4 21% 32% 28% 13%	564
	21st to end	Day	1 3 14% 33% 32% 17%	619
August	1st to 10th	Day	4 3 14% 30% 30% 19%	567
	11th to 20th	Day	2 3 13% 29% 31% 20%	534
	21st to end	Day	4 5% 19% 27% 28% 17%	583
September	1st to 10th	Day	5% 4 14% 29% 28% 20%	530
	11th to 20th	Day	6% 5% 19% 29% 27% 13%	530
	21st to end	Day	7% 10% 21% 28% 27% 7%	530
October	1st to 10th	Day	7% 8% 24% 30% 23% 7%	530
	11th to 20th	Day	10% 9% 21% 28% 26% 6%	515
	21st to end	Day	13% 8% 25% 34% 17% 3	363
November	1st to 10th	Day	17% 10% 21% 34% 16% 1	322
	11th to 20th	Day	18% 9% 25% 21% 20% 7%	220
	21st to end	Day	16% 5% 17% 37% 22% 4	220
December	1st to 10th	Day	19% 7% 16% 26% 22% 10%	220
	11th to 20th	Day	20% 9% 24% 32% 14% 1	220
	21st to end	Day	17% 7% 20% 36% 15% 5%	242
January	1st to 10th	Night	23% 5% 24% 32% 15% 1	840
	11th to 20th	Night	19% 3 21% 34% 20% 3	840
	21st to end	Night	17% 3 18% 42% 18% 3	924
February	1st to 10th	Night	14% 5% 30% 35% 14% 2	840
	11th to 20th	Night	13% 4 26% 36% 17% 3	824
	21st to end	Night	13% 7% 27% 36% 15% 3	692
March	1st to 10th	Night	13% 5% 22% 39% 19% 2	840
	11th to 20th	Night	9% 5% 27% 38% 20% 1	840
	21st to end	Night	9% 7% 29% 39% 14% 2	924
April	1st to 10th	Night	11% 6% 24% 37% 20% 2	840
	11th to 20th	Night	9% 9% 30% 32% 17% 3	831
	21st to end	Night	8% 7% 31% 34% 17% 3	591
May	1st to 10th	Night	5% 7% 31% 35% 20% 2	420
	11th to 20th	Night	9% 6% 23% 36% 23% 4	414
	21st to end	Night	7% 4 24% 38% 24% 3	455
June	1st to 10th	Night	8% 5% 29% 35% 22% 2	420
	11th to 20th	Night	6% 8% 35% 35% 15% 1	420
	21st to end	Night	5% 5% 26% 37% 25% 2	420
July	1st to 10th	Night	2 4 23% 42% 27% 2	410
	11th to 20th	Night	2 4 26% 42% 24% 2	408
	21st to end	Night	2 3 18% 40% 34% 3	460
August	1st to 10th	Night	2 3 17% 39% 35% 5%	418
	11th to 20th	Night	3 2 15% 35% 37% 8%	508
	21st to end	Night	4 4 17% 38% 33% 5%	880
September	1st to 10th	Night	4 3 20% 35% 33% 6%	800
	11th to 20th	Night	5% 4 18% 30% 36% 8%	800
	21st to end	Night	7% 4 19% 35% 30% 5%	800
October	1st to 10th	Night	9% 5% 18% 39% 27% 2	800
	11th to 20th	Night	11% 4 21% 36% 24% 4	800
	21st to end	Night	14% 4 24% 39% 15% 4	880
November	1st to 10th	Night	18% 5% 20% 43% 13% 1	820
	11th to 20th	Night	16% 7% 27% 32% 15% 3	840
	21st to end	Night	19% 4 20% 33% 21% 3	840
December	1st to 10th	Night	16% 5% 21% 37% 18% 3	840
	11th to 20th	Night	19% 5% 21% 40% 14% 1	840
	21st to end	Night	20% 4 23% 41% 10% 1	924

Page generated at 2026-08-12 00:37:13. Version ac07

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