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 2024-10-24.

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	7% 8% 3 7% 4 4 4 3 5% 6% 50%	101486
	Night	8% 9% 3 7% 4 4 4 4 5% 7% 45%	97370
Transparency	Day	33% 6% 11% 22% 19% 9%	101255
	Night	38% 6% 11% 21% 16% 7%	97247
Seeing	Day	9% 8% 22% 29% 23% 9%	14288
	Night	11% 5% 23% 36% 21% 3	23257

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% 11% 6% 5% 4 3 4 4 23%	2539
	11th to 20th	Day	15% 16% 5% 12% 7% 5% 3 4 4 5% 24%	2516
	21st to end	Day	21% 22% 7% 14% 5% 4 3 3 4 4 13%	2794
February	1st to 10th	Day	10% 14% 4 11% 7% 6% 5% 5% 5% 7% 26%	1638
	11th to 20th	Day	9% 13% 5% 9% 6% 5% 3 4 6% 7% 34%	1682
	21st to end	Day	7% 11% 3 9% 5% 6% 5% 4 7% 7% 34%	1570
March	1st to 10th	Day	6% 9% 3 7% 5% 5% 6% 5% 6% 9% 38%	3138
	11th to 20th	Day	3 7% 2 5% 4 3 3 3 5% 7% 56%	3352
	21st to end	Day	9% 8% 3 8% 6% 6% 6% 5% 8% 8% 34%	4116
April	1st to 10th	Day	9% 9% 3 7% 6% 5% 5% 5% 6% 8% 37%	2280
	11th to 20th	Day	6% 7% 3 7% 5% 5% 6% 4 7% 8% 43%	2252
	21st to end	Day	4 6% 2 8% 6% 5% 5% 4 7% 9% 43%	2501
May	1st to 10th	Day	6% 7% 2 4 3 4 4 3 5% 8% 56%	4420
	11th to 20th	Day	4 4 1 4 3 3 4 4 6% 7% 58%	4377
	21st to end	Day	7% 8% 3 8% 6% 6% 5% 4 6% 7% 40%	4813
June	1st to 10th	Day	8% 7% 2 6% 5% 5% 5% 4 6% 7% 45%	2660
	11th to 20th	Day	7% 4 2 6% 5% 5% 5% 4 7% 7% 49%	2660
	21st to end	Day	4 4 2 5% 3 3 3 3 5% 7% 61%	2660
July	1st to 10th	Day	1 1 2 2 2 2 2 3 4 81%	4420
	11th to 20th	Day	1 2 1 2 2 2 2 2 3 3 80%	4420
	21st to end	Day	1 1 1 2 1 2 2 2 3 4 80%	4790
August	1st to 10th	Day	2 2 1 3 2 2 3 2 5% 5% 73%	4401
	11th to 20th	Day	1 2 1 3 2 3 3 3 5% 7% 71%	4155
	21st to end	Day	4 4 1 5% 3 4 3 3 4 5% 64%	4180
September	1st to 10th	Day	3 2 1 3 2 2 3 2 5% 7% 70%	2280
	11th to 20th	Day	4 5% 2 5% 4 5% 5% 4 5% 7% 55%	2261
	21st to end	Day	6% 4 2 5% 3 4 3 3 5% 7% 56%	2077
October	1st to 10th	Day	6% 6% 2 4 4 4 4 4 6% 6% 55%	1900
	11th to 20th	Day	7% 5% 2 6% 4 4 5% 4 6% 8% 48%	1886
	21st to end	Day	12% 7% 2 7% 4 3 4 4 6% 7% 45%	1809
November	1st to 10th	Day	13% 10% 4 9% 5% 6% 5% 4 5% 6% 33%	1660
	11th to 20th	Day	10% 16% 4 9% 4 5% 5% 4 6% 6% 32%	1520
	21st to end	Day	11% 13% 5% 11% 5% 6% 5% 4 5% 7% 28%	1520
December	1st to 10th	Day	11% 15% 3 12% 8% 6% 5% 4 4 6% 27%	1520
	11th to 20th	Day	14% 17% 7% 18% 7% 5% 4 3 4 6% 15%	1925
	21st to end	Day	11% 19% 6% 14% 7% 7% 5% 4 4 5% 16%	2794
January	1st to 10th	Night	13% 18% 7% 13% 6% 5% 4 3 6% 6% 19%	4406
	11th to 20th	Night	13% 15% 6% 11% 5% 4 4 3 5% 7% 27%	4382
	21st to end	Night	16% 20% 8% 16% 6% 5% 3 3 4 5% 14%	4862
February	1st to 10th	Night	8% 15% 4 9% 5% 5% 5% 5% 6% 6% 30%	2539
	11th to 20th	Night	10% 11% 2 7% 5% 5% 5% 4 7% 8% 36%	2384
	21st to end	Night	8% 12% 3 8% 6% 6% 5% 4 7% 8% 33%	1884
March	1st to 10th	Night	6% 9% 3 6% 5% 4 5% 6% 7% 10% 38%	3736
	11th to 20th	Night	4 6% 2 5% 3 3 3 3 4 7% 58%	3623
	21st to end	Night	6% 8% 3 9% 6% 7% 7% 5% 8% 10% 32%	3536
April	1st to 10th	Night	8% 9% 3 7% 6% 4 5% 4 6% 8% 40%	1900
	11th to 20th	Night	6% 8% 3 6% 6% 4 4 4 5% 6% 48%	1879
	21st to end	Night	6% 6% 2 7% 4 4 4 5% 6% 10% 46%	1675
May	1st to 10th	Night	5% 6% 2 5% 3 3 4 3 5% 6% 58%	2540
	11th to 20th	Night	5% 3 1 3 3 3 4 4 5% 7% 61%	2516
	21st to end	Night	5% 4 2 5% 4 4 4 4 7% 10% 53%	2762
June	1st to 10th	Night	7% 5% 2 6% 5% 3 5% 3 6% 9% 49%	1520
	11th to 20th	Night	5% 4 1 5% 4 3 4 4 6% 7% 56%	1520
	21st to end	Night	3 3 1 5% 4 3 4 3 5% 7% 63%	1520
July	1st to 10th	Night	1 1 1 1 2 1 1 2 3 4 82%	2540
	11th to 20th	Night	1 1 1 1 1 1 2 3 3 85%	2540
	21st to end	Night	1 1 2 1 2 2 2 3 4 82%	2762
August	1st to 10th	Night	2 3 1 3 2 2 2 2 4 6% 74%	2529
	11th to 20th	Night	2 2 1 4 2 3 3 3 5% 6% 69%	2673
	21st to end	Night	2 3 2 4 3 3 3 3 4 6% 67%	3498
September	1st to 10th	Night	2 2 1 3 2 3 3 3 5% 6% 69%	1900
	11th to 20th	Night	3 4 2 6% 4 3 5% 3 5% 7% 59%	1919
	21st to end	Night	5% 3 2 4 3 5% 3 4 6% 8% 57%	2099
October	1st to 10th	Night	8% 6% 2 6% 3 3 4 4 4 7% 54%	2280
	11th to 20th	Night	7% 5% 2 6% 5% 4 4 4 5% 8% 49%	2293
	21st to end	Night	11% 7% 2 8% 4 3 5% 5% 6% 7% 43%	2613
November	1st to 10th	Night	12% 10% 4 7% 5% 4 5% 4 6% 8% 34%	2418
	11th to 20th	Night	10% 11% 4 7% 6% 5% 5% 4 7% 7% 35%	2660
	21st to end	Night	11% 13% 4 11% 5% 5% 5% 4 5% 6% 32%	2660
December	1st to 10th	Night	12% 13% 4 10% 6% 5% 4 4 6% 6% 28%	2660
	11th to 20th	Night	15% 13% 5% 15% 8% 6% 6% 4 5% 6% 16%	3280
	21st to end	Night	13% 20% 5% 11% 6% 5% 4 3 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%	1691
	21st to end	Day	45% 9% 16% 19% 9% 1	1570
March	1st to 10th	Day	36% 9% 14% 24% 16% 1	3138
	11th to 20th	Day	27% 6% 12% 43% 11% 1	3352
	21st to end	Day	41% 12% 16% 18% 12% 1	4116
April	1st to 10th	Day	41% 8% 15% 22% 12% 2	2280
	11th to 20th	Day	35% 6% 15% 21% 16% 5%	2252
	21st to end	Day	34% 7% 13% 24% 18% 4	2501
May	1st to 10th	Day	25% 5% 9% 23% 29% 9%	4420
	11th to 20th	Day	21% 6% 11% 33% 24% 6%	4380
	21st to end	Day	37% 9% 14% 26% 12% 1	4814
June	1st to 10th	Day	36% 6% 10% 23% 19% 6%	2660
	11th to 20th	Day	30% 5% 12% 28% 19% 6%	2660
	21st to end	Day	22% 3 10% 29% 26% 10%	2660
July	1st to 10th	Day	10% 2 5% 13% 30% 40%	4351
	11th to 20th	Day	12% 2 3 10% 23% 49%	4345
	21st to end	Day	10% 1 3 19% 36% 30%	4639
August	1st to 10th	Day	15% 2 5% 17% 36% 25%	4384
	11th to 20th	Day	15% 2 7% 38% 30% 8%	4197
	21st to end	Day	24% 3 9% 27% 31% 8%	4179
September	1st to 10th	Day	16% 4 8% 29% 31% 13%	2280
	11th to 20th	Day	27% 6% 12% 23% 25% 8%	2261
	21st to end	Day	27% 5% 17% 28% 18% 6%	2077
October	1st to 10th	Day	29% 5% 13% 32% 18% 2	1900
	11th to 20th	Day	31% 7% 18% 29% 14% 1	1886
	21st to end	Day	38% 8% 15% 25% 13% 2	1809
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	2386
	21st to end	Night	46% 10% 14% 19% 11% 1	1884
March	1st to 10th	Night	35% 7% 14% 25% 15% 3	3736
	11th to 20th	Night	26% 5% 11% 41% 15% 1	3624
	21st to end	Night	41% 12% 17% 24% 6%	3536
April	1st to 10th	Night	41% 6% 15% 25% 11% 2	1900
	11th to 20th	Night	34% 6% 13% 24% 19% 4	1879
	21st to end	Night	32% 8% 12% 26% 19% 3	1675
May	1st to 10th	Night	26% 4 7% 20% 34% 8%	2540
	11th to 20th	Night	19% 5% 8% 32% 31% 4	2516
	21st to end	Night	23% 8% 18% 38% 11% 2	2762
June	1st to 10th	Night	32% 6% 10% 25% 21% 6%	1520
	11th to 20th	Night	25% 5% 13% 31% 22% 4	1520
	21st to end	Night	21% 4 10% 28% 28% 9%	1520
July	1st to 10th	Night	8% 2 5% 14% 29% 41%	2500
	11th to 20th	Night	7% 1 3 11% 23% 54%	2492
	21st to end	Night	8% 1 3 17% 36% 35%	2674
August	1st to 10th	Night	15% 1 4 14% 39% 27%	2521
	11th to 20th	Night	18% 1 6% 37% 28% 10%	2697
	21st to end	Night	20% 2 7% 28% 31% 12%	3498
September	1st to 10th	Night	15% 3 9% 25% 29% 18%	1900
	11th to 20th	Night	23% 5% 10% 25% 26% 10%	1919
	21st to end	Night	23% 5% 13% 32% 19% 8%	2099
October	1st to 10th	Night	30% 4 9% 31% 23% 2	2280
	11th to 20th	Night	32% 5% 13% 28% 19% 2	2293
	21st to end	Night	39% 7% 10% 27% 14% 2	2613
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	16% 6% 26% 33% 16% 3	374
	21st to end	Day	10% 9% 30% 30% 19% 3	382
March	1st to 10th	Day	12% 7% 29% 30% 17% 5%	460
	11th to 20th	Day	12% 10% 22% 27% 22% 7%	460
	21st to end	Day	12% 12% 26% 29% 18% 2	506
April	1st to 10th	Day	13% 13% 25% 25% 17% 6%	460
	11th to 20th	Day	8% 18% 31% 22% 15% 6%	452
	21st to end	Day	7% 12% 26% 29% 17% 8%	460
May	1st to 10th	Day	6% 11% 27% 32% 19% 5%	463
	11th to 20th	Day	11% 9% 22% 25% 22% 11%	488
	21st to end	Day	9% 7% 21% 24% 26% 12%	529
June	1st to 10th	Day	9% 10% 22% 28% 21% 10%	490
	11th to 20th	Day	8% 10% 26% 33% 17% 6%	490
	21st to end	Day	3 6% 21% 27% 30% 13%	490
July	1st to 10th	Day	2 5% 17% 34% 34% 9%	486
	11th to 20th	Day	2 4 20% 32% 29% 14%	484
	21st to end	Day	3 14% 33% 33% 16%	531
August	1st to 10th	Day	4 3 14% 30% 31% 19%	487
	11th to 20th	Day	2 3 13% 28% 31% 22%	477
	21st to end	Day	4 6% 20% 27% 27% 17%	539
September	1st to 10th	Day	5% 4 15% 30% 28% 18%	490
	11th to 20th	Day	6% 6% 20% 29% 27% 12%	490
	21st to end	Day	7% 10% 21% 28% 26% 7%	490
October	1st to 10th	Day	7% 9% 24% 30% 23% 7%	490
	11th to 20th	Day	9% 8% 20% 29% 27% 7%	476
	21st to end	Day	14% 9% 26% 31% 16% 4	306
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	744
	21st to end	Night	12% 7% 26% 35% 15% 4	628
March	1st to 10th	Night	14% 5% 22% 38% 19% 2	760
	11th to 20th	Night	8% 6% 26% 37% 22% 1	760
	21st to end	Night	9% 7% 28% 39% 14% 2	836
April	1st to 10th	Night	11% 7% 25% 36% 19% 2	760
	11th to 20th	Night	9% 9% 31% 32% 15% 4	751
	21st to end	Night	8% 7% 32% 34% 16% 3	535
May	1st to 10th	Night	5% 8% 32% 35% 18% 2	380
	11th to 20th	Night	9% 6% 22% 35% 24% 4	374
	21st to end	Night	7% 5% 25% 36% 24% 4	411
June	1st to 10th	Night	8% 5% 29% 34% 21% 2	380
	11th to 20th	Night	6% 8% 35% 33% 15% 2	380
	21st to end	Night	4 6% 27% 35% 26% 2	380
July	1st to 10th	Night	2 4 23% 41% 27% 2	370
	11th to 20th	Night	2 4 25% 41% 26% 2	368
	21st to end	Night	1 4 19% 39% 34% 3	416
August	1st to 10th	Night	2 3 17% 36% 37% 5%	378
	11th to 20th	Night	3 2 16% 33% 38% 9%	474
	21st to end	Night	3 4 18% 38% 32% 5%	836
September	1st to 10th	Night	4 3 20% 35% 32% 6%	760
	11th to 20th	Night	5% 4 19% 29% 36% 8%	760
	21st to end	Night	7% 4 19% 36% 29% 5%	760
October	1st to 10th	Night	10% 5% 18% 38% 28% 2	760
	11th to 20th	Night	10% 4 20% 36% 25% 5%	760
	21st to end	Night	15% 4 24% 38% 15% 4	804
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

Page generated at 2024-10-20 23:20:01. Version ac07

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