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 2024-02-20.

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	8% 8% 3 6% 5% 3 4 5% 5% 7% 45%	78235
	Night	9% 9% 4 7% 6% 3 4 5% 5% 7% 41%	80909
Transparency	Day	38% 6% 12% 21% 17% 6%	77962
	Night	42% 7% 12% 20% 14% 5%	80762
Seeing	Day	9% 8% 22% 29% 23% 9%	13305
	Night	12% 5% 23% 36% 21% 3	22502

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	13% 20% 8% 10% 6% 3 4 4 4 4 23%	2539
	11th to 20th	Day	15% 15% 6% 10% 8% 4 3 5% 4 5% 24%	2516
	21st to end	Day	21% 21% 7% 13% 6% 3 3 4 4 4 13%	2794
February	1st to 10th	Day	11% 13% 5% 10% 8% 4 6% 6% 5% 7% 26%	1638
	11th to 20th	Day	9% 13% 5% 8% 7% 4 3 4 6% 8% 34%	1673
	21st to end	Day	7% 11% 4 7% 7% 5% 5% 6% 6% 8% 34%	1480
March	1st to 10th	Day	9% 10% 3 7% 6% 3 6% 7% 7% 9% 35%	1800
	11th to 20th	Day	7% 11% 4 7% 5% 4 5% 5% 6% 9% 37%	1894
	21st to end	Day	8% 8% 4 7% 6% 4 6% 7% 8% 8% 33%	2340
April	1st to 10th	Day	9% 8% 3 7% 6% 4 5% 6% 6% 9% 37%	2160
	11th to 20th	Day	6% 7% 3 7% 6% 3 6% 6% 7% 8% 42%	2132
	21st to end	Day	5% 6% 3 6% 7% 4 5% 5% 6% 9% 45%	2369
May	1st to 10th	Day	4 4 2 5% 4 4 5% 5% 7% 8% 52%	2520
	11th to 20th	Day	8% 5% 3 5% 6% 3 5% 7% 8% 9% 41%	2477
	21st to end	Day	8% 6% 2 6% 6% 4 6% 5% 5% 7% 44%	2723
June	1st to 10th	Day	8% 6% 3 5% 5% 4 6% 5% 6% 8% 45%	2520
	11th to 20th	Day	7% 4 2 5% 5% 3 5% 5% 6% 8% 49%	2520
	21st to end	Day	4 3 2 5% 3 2 3 4 5% 8% 62%	2520
July	1st to 10th	Day	2 2 1 2 3 2 4 4 5% 6% 69%	2520
	11th to 20th	Day	2 2 1 3 3 2 3 2 4 5% 72%	2520
	21st to end	Day	1 1 1 2 1 1 2 2 3 4 82%	2741
August	1st to 10th	Day	3 2 1 3 3 2 2 3 4 5% 72%	2507
	11th to 20th	Day	2 2 1 2 2 2 3 3 4 5% 73%	2378
	21st to end	Day	2 3 1 3 4 2 4 4 5% 6% 67%	2376
September	1st to 10th	Day	3 2 1 3 3 2 3 3 4 6% 70%	2160
	11th to 20th	Day	4 5% 2 5% 5% 3 5% 5% 6% 7% 55%	2142
	21st to end	Day	6% 5% 2 4 4 3 4 4 4 7% 55%	1968
October	1st to 10th	Day	6% 6% 3 4 4 4 4 5% 6% 6% 54%	1800
	11th to 20th	Day	8% 5% 3 4 5% 3 4 5% 6% 9% 48%	1787
	21st to end	Day	13% 7% 2 6% 5% 3 3 5% 6% 7% 44%	1782
November	1st to 10th	Day	13% 10% 4 8% 7% 4 6% 5% 5% 7% 33%	1660
	11th to 20th	Day	10% 15% 4 8% 6% 3 5% 5% 5% 6% 32%	1520
	21st to end	Day	11% 12% 7% 10% 6% 4 5% 5% 5% 7% 29%	1520
December	1st to 10th	Day	11% 13% 4 11% 8% 4 6% 5% 4 6% 27%	1520
	11th to 20th	Day	15% 15% 8% 16% 9% 4 4 4 5% 6% 15%	1925
	21st to end	Day	12% 18% 7% 12% 9% 6% 6% 5% 4 5% 17%	2794
January	1st to 10th	Night	13% 17% 7% 12% 7% 4 5% 4 5% 6% 19%	4406
	11th to 20th	Night	14% 14% 6% 10% 6% 3 4 4 5% 7% 27%	4382
	21st to end	Night	16% 19% 9% 15% 7% 4 4 4 4 5% 14%	4862
February	1st to 10th	Night	9% 14% 4 8% 6% 4 6% 6% 6% 6% 30%	2539
	11th to 20th	Night	10% 10% 3 6% 6% 3 5% 5% 7% 9% 36%	2377
	21st to end	Night	8% 11% 4 7% 6% 4 5% 5% 6% 8% 34%	1776
March	1st to 10th	Night	10% 11% 4 6% 6% 4 5% 6% 7% 8% 34%	2160
	11th to 20th	Night	6% 7% 4 8% 6% 4 5% 7% 6% 9% 38%	2061
	21st to end	Night	6% 8% 4 8% 7% 5% 6% 5% 6% 10% 34%	2015
April	1st to 10th	Night	9% 8% 4 6% 6% 2 5% 5% 6% 8% 40%	1800
	11th to 20th	Night	6% 7% 3 5% 7% 3 4 5% 6% 6% 48%	1779
	21st to end	Night	7% 6% 3 5% 5% 3 4 5% 6% 10% 45%	1588
May	1st to 10th	Night	5% 4 2 5% 4 3 6% 5% 7% 8% 53%	1440
	11th to 20th	Night	9% 5% 2 5% 4 3 5% 7% 6% 8% 46%	1416
	21st to end	Night	7% 4 3 5% 5% 3 5% 5% 7% 9% 48%	1552
June	1st to 10th	Night	8% 4 2 6% 6% 3 4 5% 6% 9% 49%	1440
	11th to 20th	Night	5% 4 2 4 4 2 4 5% 6% 7% 57%	1440
	21st to end	Night	3 3 1 4 4 2 4 4 4 7% 64%	1440
July	1st to 10th	Night	2 2 1 3 3 2 2 4 5% 7% 69%	1440
	11th to 20th	Night	2 2 1 2 2 1 2 3 3 4 78%	1440
	21st to end	Night	1 1 1 1 1 2 3 3 4 84%	1576
August	1st to 10th	Night	2 2 1 2 2 2 2 2 3 6% 77%	1432
	11th to 20th	Night	2 2 1 3 2 2 2 3 4 6% 74%	1516
	21st to end	Night	2 2 1 2 3 3 3 4 4 7% 68%	1980
September	1st to 10th	Night	3 2 1 2 3 2 3 4 5% 6% 69%	1800
	11th to 20th	Night	3 4 2 5% 4 2 4 4 5% 7% 59%	1818
	21st to end	Night	5% 4 2 4 4 3 4 4 6% 8% 57%	1988
October	1st to 10th	Night	8% 6% 3 5% 4 3 4 4 4 7% 52%	2160
	11th to 20th	Night	7% 5% 2 5% 6% 3 5% 5% 5% 8% 49%	2172
	21st to end	Night	11% 7% 2 7% 6% 2 4 6% 5% 7% 43%	2574
November	1st to 10th	Night	12% 9% 4 6% 6% 3 6% 5% 6% 8% 34%	2418
	11th to 20th	Night	10% 10% 4 7% 6% 4 5% 5% 6% 7% 35%	2660
	21st to end	Night	11% 11% 5% 10% 6% 4 5% 5% 5% 6% 32%	2660
December	1st to 10th	Night	12% 11% 5% 9% 7% 4 5% 5% 6% 7% 28%	2660
	11th to 20th	Night	15% 12% 6% 14% 9% 5% 6% 5% 5% 6% 16%	3280
	21st to end	Night	14% 19% 6% 10% 7% 4 4 4 5% 5% 22%	4862

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	65% 7% 8% 13% 7% 1	2539
	11th to 20th	Day	60% 7% 16% 14% 2	2540
	21st to end	Day	75% 7% 8% 7% 2	2794
February	1st to 10th	Day	55% 9% 16% 14% 4 1	1638
	11th to 20th	Day	47% 8% 17% 18% 10%	1682
	21st to end	Day	45% 9% 16% 19% 9% 1	1480
March	1st to 10th	Day	41% 9% 16% 22% 11% 1	1800
	11th to 20th	Day	43% 7% 12% 27% 11%	1894
	21st to end	Day	44% 11% 15% 20% 9% 1	2340
April	1st to 10th	Day	41% 8% 15% 21% 13% 2	2160
	11th to 20th	Day	36% 6% 16% 21% 16% 4	2132
	21st to end	Day	34% 7% 13% 24% 18% 4	2369
May	1st to 10th	Day	26% 6% 13% 32% 18% 4	2520
	11th to 20th	Day	35% 7% 14% 26% 16% 2	2480
	21st to end	Day	37% 7% 13% 26% 16% 2	2724
June	1st to 10th	Day	36% 6% 11% 23% 18% 5%	2520
	11th to 20th	Day	30% 6% 12% 28% 19% 5%	2520
	21st to end	Day	21% 4 10% 29% 26% 10%	2520
July	1st to 10th	Day	15% 4 8% 22% 33% 17%	2451
	11th to 20th	Day	15% 3 6% 18% 34% 24%	2445
	21st to end	Day	8% 3 4 18% 43% 25%	2589
August	1st to 10th	Day	15% 3 8% 21% 33% 20%	2490
	11th to 20th	Day	14% 3 7% 26% 37% 14%	2378
	21st to end	Day	17% 4 9% 29% 33% 8%	2376
September	1st to 10th	Day	16% 4 9% 29% 30% 13%	2160
	11th to 20th	Day	26% 6% 12% 22% 26% 8%	2142
	21st to end	Day	28% 5% 17% 27% 17% 5%	1968
October	1st to 10th	Day	30% 5% 13% 32% 17% 2	1800
	11th to 20th	Day	30% 8% 18% 30% 13% 1	1787
	21st to end	Day	38% 8% 15% 25% 13% 1	1782
November	1st to 10th	Day	50% 8% 15% 17% 10% 1	1660
	11th to 20th	Day	52% 7% 16% 17% 7% 1	1520
	21st to end	Day	54% 9% 16% 12% 7% 2	1520
December	1st to 10th	Day	56% 9% 14% 14% 6%	1520
	11th to 20th	Day	71% 9% 8% 8% 5%	1928
	21st to end	Day	69% 8% 9% 10% 4	2794
January	1st to 10th	Night	65% 7% 10% 13% 5%	4406
	11th to 20th	Night	56% 8% 14% 18% 4	4420
	21st to end	Night	72% 8% 10% 8% 2 1	4862
February	1st to 10th	Night	51% 10% 18% 15% 6% 1	2539
	11th to 20th	Night	43% 10% 19% 18% 10% 1	2379
	21st to end	Night	45% 9% 14% 19% 11% 1	1776
March	1st to 10th	Night	45% 6% 15% 23% 9% 1	2160
	11th to 20th	Night	40% 8% 13% 28% 10% 1	2062
	21st to end	Night	44% 9% 14% 24% 8% 1	2015
April	1st to 10th	Night	42% 6% 14% 25% 12% 2	1800
	11th to 20th	Night	35% 6% 12% 25% 18% 4	1779
	21st to end	Night	32% 8% 12% 26% 18% 3	1588
May	1st to 10th	Night	27% 6% 10% 31% 22% 4	1440
	11th to 20th	Night	33% 6% 11% 28% 19% 3	1416
	21st to end	Night	31% 7% 13% 30% 16% 3	1552
June	1st to 10th	Night	32% 6% 10% 25% 20% 6%	1440
	11th to 20th	Night	25% 6% 13% 32% 21% 4	1440
	21st to end	Night	21% 4 10% 27% 28% 9%	1440
July	1st to 10th	Night	15% 4 9% 22% 31% 20%	1400
	11th to 20th	Night	12% 2 6% 20% 33% 26%	1392
	21st to end	Night	6% 2 5% 15% 40% 32%	1488
August	1st to 10th	Night	12% 1 6% 19% 37% 25%	1424
	11th to 20th	Night	12% 3 8% 24% 36% 17%	1516
	21st to end	Night	15% 4 8% 24% 35% 13%	1980
September	1st to 10th	Night	15% 4 9% 26% 30% 17%	1800
	11th to 20th	Night	23% 6% 10% 23% 28% 11%	1818
	21st to end	Night	24% 6% 13% 31% 19% 8%	1988
October	1st to 10th	Night	32% 5% 9% 30% 23% 2	2160
	11th to 20th	Night	33% 6% 13% 28% 18% 2	2172
	21st to end	Night	39% 7% 11% 28% 14% 2	2574
November	1st to 10th	Night	45% 8% 17% 19% 9% 2	2418
	11th to 20th	Night	47% 9% 16% 18% 8% 2	2660
	21st to end	Night	53% 9% 14% 16% 8% 1	2660
December	1st to 10th	Night	54% 9% 15% 18% 4	2660
	11th to 20th	Night	67% 10% 13% 7% 3	3276
	21st to end	Night	62% 8% 12% 10% 7% 1	4862

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	24% 8% 24% 27% 16% 2	180
	11th to 20th	Day	24% 6% 17% 32% 15% 6%	180
	21st to end	Day	24% 2 17% 34% 18% 6%	198
February	1st to 10th	Day	15% 6% 28% 35% 13% 2	298
	11th to 20th	Day	15% 6% 26% 33% 17% 3	371
	21st to end	Day	10% 7% 29% 32% 20% 2	346
March	1st to 10th	Day	13% 7% 29% 30% 16% 5%	420
	11th to 20th	Day	13% 10% 22% 28% 22% 5%	420
	21st to end	Day	12% 13% 27% 29% 17% 3	462
April	1st to 10th	Day	14% 13% 25% 25% 17% 6%	420
	11th to 20th	Day	8% 18% 30% 22% 16% 6%	412
	21st to end	Day	8% 12% 26% 29% 17% 8%	420
May	1st to 10th	Day	5% 11% 27% 32% 19% 5%	423
	11th to 20th	Day	12% 8% 21% 26% 23% 11%	448
	21st to end	Day	9% 6% 21% 24% 27% 13%	485
June	1st to 10th	Day	8% 10% 22% 27% 22% 11%	450
	11th to 20th	Day	9% 10% 26% 33% 16% 5%	450
	21st to end	Day	3 6% 21% 27% 30% 13%	450
July	1st to 10th	Day	2 5% 16% 34% 34% 9%	446
	11th to 20th	Day	2 4 21% 33% 28% 12%	444
	21st to end	Day	3 15% 32% 33% 16%	487
August	1st to 10th	Day	4 3 14% 29% 31% 19%	447
	11th to 20th	Day	2 3 14% 28% 32% 21%	437
	21st to end	Day	3 6% 20% 27% 28% 16%	495
September	1st to 10th	Day	5% 5% 16% 32% 28% 14%	450
	11th to 20th	Day	6% 6% 19% 29% 28% 13%	450
	21st to end	Day	7% 10% 22% 28% 26% 7%	450
October	1st to 10th	Day	8% 8% 26% 28% 23% 7%	450
	11th to 20th	Day	9% 8% 19% 29% 26% 7%	437
	21st to end	Day	14% 9% 26% 30% 17% 4	297
November	1st to 10th	Day	16% 11% 20% 35% 16% 1	264
	11th to 20th	Day	17% 10% 27% 22% 18% 7%	180
	21st to end	Day	14% 4 17% 38% 23% 3	180
December	1st to 10th	Day	18% 7% 17% 26% 22% 9%	180
	11th to 20th	Day	17% 7% 24% 35% 15% 2	180
	21st to end	Day	17% 8% 21% 35% 15% 5%	198
January	1st to 10th	Night	23% 5% 25% 31% 15% 2	760
	11th to 20th	Night	20% 4 21% 32% 20% 3	760
	21st to end	Night	18% 3 19% 41% 16% 3	836
February	1st to 10th	Night	15% 5% 30% 34% 14% 2	760
	11th to 20th	Night	13% 5% 28% 34% 17% 3	742
	21st to end	Night	12% 7% 26% 36% 15% 4	592
March	1st to 10th	Night	15% 5% 22% 38% 18% 2	720
	11th to 20th	Night	8% 6% 27% 37% 21% 1	720
	21st to end	Night	9% 7% 29% 39% 14% 2	792
April	1st to 10th	Night	12% 6% 24% 36% 20% 2	720
	11th to 20th	Night	10% 9% 30% 31% 16% 4	711
	21st to end	Night	8% 7% 32% 33% 17% 3	508
May	1st to 10th	Night	5% 7% 33% 35% 18% 2	360
	11th to 20th	Night	10% 6% 20% 36% 25% 4	354
	21st to end	Night	7% 5% 24% 36% 24% 4	389
June	1st to 10th	Night	9% 6% 28% 34% 22% 2	360
	11th to 20th	Night	6% 8% 35% 34% 15% 2	360
	21st to end	Night	4 5% 27% 35% 26% 2	360
July	1st to 10th	Night	2 4 23% 40% 28% 2	350
	11th to 20th	Night	2 4 26% 40% 25% 2	348
	21st to end	Night	1 4 18% 40% 34% 3	394
August	1st to 10th	Night	2 3 18% 35% 37% 5%	358
	11th to 20th	Night	2 2 16% 33% 38% 9%	448
	21st to end	Night	3 5% 18% 38% 32% 5%	792
September	1st to 10th	Night	4 3 21% 36% 30% 6%	720
	11th to 20th	Night	5% 4 18% 28% 37% 8%	720
	21st to end	Night	7% 4 19% 36% 29% 5%	720
October	1st to 10th	Night	10% 5% 18% 37% 28% 2	720
	11th to 20th	Night	10% 5% 20% 35% 25% 5%	720
	21st to end	Night	15% 4 24% 37% 16% 4	792
November	1st to 10th	Night	18% 5% 21% 42% 13% 1	740
	11th to 20th	Night	16% 7% 27% 32% 15% 3	760
	21st to end	Night	17% 4 21% 33% 22% 3	760
December	1st to 10th	Night	17% 5% 21% 37% 17% 3	760
	11th to 20th	Night	19% 5% 20% 39% 15% 1	760
	21st to end	Night	21% 5% 23% 41% 10% 1	836

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