City of Rocks National Reserve
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the City of Rocks National Reserve clear sky chart from 2005-11-06 to 2024-05-10.

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	4 7% 3 7% 6% 4 5% 5% 6% 7% 46%	83423
	Night	3 6% 3 7% 6% 4 6% 6% 6% 7% 46%	86074
Transparency	Day	25% 34% 7% 14% 12% 6%	83135
	Night	25% 34% 8% 15% 12% 5%	85883
Seeing	Day	14% 20% 30% 23% 11% 3	13854
	Night	12% 13% 20% 31% 20% 4	23747

By Month

Percentage Cloud Cover SW (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	2 9% 5% 13% 12% 6% 8% 6% 5% 6% 27%	2539
	11th to 20th	Day	2 9% 8% 15% 10% 6% 5% 6% 6% 6% 28%	2540
	21st to end	Day	3 9% 5% 11% 9% 4 6% 6% 5% 8% 35%	3091
February	1st to 10th	Day	3 9% 6% 12% 9% 5% 6% 6% 6% 6% 31%	1710
	11th to 20th	Day	3 10% 6% 10% 9% 5% 7% 5% 7% 6% 32%	1807
	21st to end	Day	3 8% 5% 10% 11% 5% 6% 6% 6% 8% 31%	1570
March	1st to 10th	Day	2 10% 5% 11% 10% 5% 6% 6% 5% 6% 33%	3195
	11th to 20th	Day	3 7% 4 7% 5% 3 4 4 5% 5% 52%	3490
	21st to end	Day	5% 11% 5% 11% 10% 6% 7% 8% 8% 7% 23%	3825
April	1st to 10th	Day	5% 10% 5% 9% 6% 4 6% 5% 6% 6% 38%	2207
	11th to 20th	Day	6% 9% 4 7% 7% 4 5% 6% 5% 6% 41%	2385
	21st to end	Day	5% 9% 3 8% 7% 3 5% 5% 5% 8% 43%	2470
May	1st to 10th	Day	5% 6% 2 6% 6% 4 6% 6% 7% 8% 43%	2459
	11th to 20th	Day	7% 6% 2 6% 7% 4 6% 6% 7% 10% 40%	2301
	21st to end	Day	7% 8% 4 8% 7% 5% 7% 6% 7% 8% 34%	2530
June	1st to 10th	Day	5% 5% 2 5% 6% 3 5% 5% 7% 9% 49%	2505
	11th to 20th	Day	5% 5% 1 4 3 3 4 5% 4 9% 56%	2520
	21st to end	Day	2 2 1 3 2 2 4 4 5% 6% 70%	2520
July	1st to 10th	Day	2 2 1 3 4 3 5% 5% 7% 8% 61%	2520
	11th to 20th	Day	3 2 1 3 2 2 3 4 5% 7% 67%	2520
	21st to end	Day	3 3 2 4 4 3 5% 5% 5% 7% 60%	2585
August	1st to 10th	Day	4 4 2 4 4 2 5% 6% 6% 8% 56%	2328
	11th to 20th	Day	2 2 1 3 3 2 4 4 5% 7% 68%	2299
	21st to end	Day	2 2 1 3 3 3 4 5% 6% 7% 63%	2519
September	1st to 10th	Day	3 2 1 3 3 2 4 4 4 7% 68%	2061
	11th to 20th	Day	3 4 2 4 4 2 3 4 5% 7% 62%	1980
	21st to end	Day	5% 4 2 4 4 2 4 4 3 5% 64%	1980
October	1st to 10th	Day	6% 7% 3 5% 5% 3 4 4 6% 7% 51%	1963
	11th to 20th	Day	4 6% 2 6% 4 3 4 4 5% 7% 55%	1800
	21st to end	Day	2 5% 2 5% 5% 3 5% 5% 6% 8% 53%	1824
November	1st to 10th	Day	5% 10% 4 7% 6% 3 5% 5% 6% 7% 42%	1674
	11th to 20th	Day	5% 8% 3 8% 6% 4 6% 5% 7% 8% 41%	1710
	21st to end	Day	4 10% 4 8% 7% 5% 5% 5% 5% 7% 40%	1710
December	1st to 10th	Day	3 10% 6% 9% 8% 5% 4 6% 5% 7% 37%	1549
	11th to 20th	Day	3 9% 4 10% 9% 6% 7% 7% 7% 9% 29%	1943
	21st to end	Day	3 8% 4 10% 8% 4 6% 6% 6% 8% 35%	2794
January	1st to 10th	Night	3 7% 4 9% 9% 5% 8% 9% 8% 8% 31%	4406
	11th to 20th	Night	2 9% 5% 13% 11% 5% 7% 10% 6% 7% 25%	4420
	21st to end	Night	2 8% 5% 9% 7% 4 7% 7% 8% 7% 36%	4570
February	1st to 10th	Night	2 8% 5% 11% 8% 5% 7% 7% 7% 8% 32%	2470
	11th to 20th	Night	2 7% 4 8% 8% 4 5% 5% 7% 7% 42%	2259
	21st to end	Night	2 6% 5% 8% 7% 4 7% 6% 7% 9% 38%	1884
March	1st to 10th	Night	2 7% 4 8% 8% 5% 7% 6% 8% 8% 38%	3679
	11th to 20th	Night	1 5% 3 6% 6% 3 5% 5% 6% 8% 52%	3490
	21st to end	Night	4 7% 3 7% 7% 4 7% 8% 8% 10% 34%	3828
April	1st to 10th	Night	4 7% 3 6% 7% 4 5% 5% 7% 7% 45%	1971
	11th to 20th	Night	5% 6% 3 5% 5% 3 6% 6% 6% 7% 49%	1743
	21st to end	Night	6% 5% 2 5% 6% 3 5% 5% 6% 8% 50%	1710
May	1st to 10th	Night	4 5% 2 6% 5% 3 4 5% 7% 8% 52%	1705
	11th to 20th	Night	3 6% 3 5% 6% 4 6% 7% 8% 9% 44%	1594
	21st to end	Night	8% 7% 3 5% 5% 3 6% 6% 5% 9% 43%	1746
June	1st to 10th	Night	3 3 2 4 5% 4 4 6% 7% 9% 53%	1451
	11th to 20th	Night	5% 4 2 3 3 3 4 5% 4 7% 61%	1440
	21st to end	Night	2 1 1 3 4 2 3 3 5% 7% 69%	1440
July	1st to 10th	Night	1 2 1 4 4 3 5% 6% 7% 7% 61%	1440
	11th to 20th	Night	1 2 1 4 3 2 4 4 4 5% 70%	1440
	21st to end	Night	3 3 2 4 5% 2 3 6% 5% 6% 62%	1729
August	1st to 10th	Night	3 4 2 4 4 3 5% 5% 6% 7% 57%	1611
	11th to 20th	Night	3 2 1 3 4 3 4 4 4 7% 64%	1602
	21st to end	Night	4 3 1 3 2 2 4 4 5% 6% 65%	1834
September	1st to 10th	Night	2 2 1 3 3 2 3 3 4 5% 71%	1898
	11th to 20th	Night	5% 3 1 2 2 2 3 4 4 5% 68%	1980
	21st to end	Night	5% 3 1 3 2 2 3 3 3 5% 70%	1980
October	1st to 10th	Night	6% 4 3 5% 4 2 3 3 5% 6% 59%	1995
	11th to 20th	Night	5% 4 1 4 3 3 5% 4 6% 7% 58%	2160
	21st to end	Night	2 4 2 5% 5% 3 5% 5% 6% 8% 54%	2528
November	1st to 10th	Night	6% 6% 3 6% 5% 3 6% 6% 6% 7% 44%	2405
	11th to 20th	Night	4 5% 3 6% 7% 4 6% 7% 6% 8% 44%	2470
	21st to end	Night	2 6% 4 6% 6% 4 6% 6% 7% 8% 44%	2470
December	1st to 10th	Night	4 7% 5% 8% 8% 4 6% 6% 7% 8% 37%	2602
	11th to 20th	Night	4 8% 4 9% 8% 6% 7% 7% 9% 8% 30%	3262
	21st to end	Night	3 8% 4 9% 9% 5% 7% 7% 6% 7% 36%	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	43% 29% 8% 13% 7%	2539
	11th to 20th	Day	46% 27% 7% 15% 3 1	2540
	21st to end	Day	39% 25% 13% 14% 6% 2	3091
February	1st to 10th	Day	33% 35% 10% 13% 8% 1	1710
	11th to 20th	Day	32% 38% 9% 13% 6% 2	1817
	21st to end	Day	32% 38% 10% 13% 5% 1	1570
March	1st to 10th	Day	36% 26% 7% 16% 15%	3195
	11th to 20th	Day	25% 24% 10% 28% 12% 1	3490
	21st to end	Day	42% 28% 12% 16% 3	3825
April	1st to 10th	Day	28% 36% 9% 14% 10% 3	2207
	11th to 20th	Day	29% 35% 7% 19% 9% 1	2388
	21st to end	Day	26% 34% 10% 18% 10% 1	2470
May	1st to 10th	Day	25% 35% 5% 18% 15% 2	2459
	11th to 20th	Day	21% 37% 8% 20% 12% 2	2304
	21st to end	Day	32% 38% 7% 16% 7%	2530
June	1st to 10th	Day	24% 38% 8% 18% 10% 2	2505
	11th to 20th	Day	18% 36% 5% 13% 17% 10%	2520
	21st to end	Day	10% 36% 2 12% 24% 15%	2520
July	1st to 10th	Day	12% 38% 1 10% 17% 22%	2451
	11th to 20th	Day	11% 37% 2 7% 16% 26%	2445
	21st to end	Day	15% 38% 3 7% 17% 21%	2441
August	1st to 10th	Day	15% 37% 3 10% 18% 18%	2313
	11th to 20th	Day	11% 35% 2 9% 24% 19%	2299
	21st to end	Day	14% 36% 3 9% 19% 18%	2519
September	1st to 10th	Day	11% 37% 4 10% 19% 19%	2061
	11th to 20th	Day	15% 36% 5% 13% 16% 16%	1980
	21st to end	Day	11% 36% 4 15% 26% 9%	1980
October	1st to 10th	Day	23% 36% 7% 15% 13% 6%	1963
	11th to 20th	Day	20% 36% 8% 21% 12% 2	1800
	21st to end	Day	17% 39% 10% 19% 14% 2	1824
November	1st to 10th	Day	27% 42% 6% 14% 9% 3	1674
	11th to 20th	Day	25% 41% 11% 15% 8% 1	1710
	21st to end	Day	25% 39% 9% 15% 9% 2	1710
December	1st to 10th	Day	27% 41% 9% 14% 6% 3	1549
	11th to 20th	Day	37% 33% 14% 8% 9%	1942
	21st to end	Day	33% 29% 12% 11% 13% 3	2794
January	1st to 10th	Night	35% 31% 7% 17% 10%	4406
	11th to 20th	Night	43% 33% 7% 11% 5% 1	4420
	21st to end	Night	37% 27% 12% 16% 6% 2	4570
February	1st to 10th	Night	31% 36% 9% 16% 7% 1	2470
	11th to 20th	Night	26% 36% 10% 16% 10% 2	2260
	21st to end	Night	26% 38% 8% 18% 7% 2	1884
March	1st to 10th	Night	33% 26% 9% 15% 14% 2	3679
	11th to 20th	Night	22% 24% 13% 26% 14% 1	3490
	21st to end	Night	30% 27% 12% 25% 5%	3828
April	1st to 10th	Night	27% 36% 6% 16% 10% 5%	1971
	11th to 20th	Night	23% 35% 9% 18% 13% 2	1743
	21st to end	Night	20% 35% 10% 20% 13%	1710
May	1st to 10th	Night	20% 36% 8% 16% 18% 2	1705
	11th to 20th	Night	19% 37% 8% 19% 13% 3	1595
	21st to end	Night	26% 37% 7% 18% 10% 1	1746
June	1st to 10th	Night	21% 38% 11% 16% 12% 2	1451
	11th to 20th	Night	17% 36% 8% 13% 19% 8%	1440
	21st to end	Night	11% 36% 3 10% 23% 17%	1440
July	1st to 10th	Night	12% 39% 2 8% 20% 20%	1400
	11th to 20th	Night	12% 37% 2 5% 16% 28%	1392
	21st to end	Night	14% 38% 2 7% 17% 22%	1633
August	1st to 10th	Night	16% 36% 2 11% 18% 16%	1602
	11th to 20th	Night	15% 35% 1 9% 22% 17%	1602
	21st to end	Night	12% 36% 3 9% 21% 19%	1834
September	1st to 10th	Night	11% 36% 4 9% 19% 22%	1898
	11th to 20th	Night	12% 36% 5% 13% 17% 17%	1980
	21st to end	Night	10% 35% 4 13% 26% 12%	1980
October	1st to 10th	Night	19% 35% 7% 15% 17% 6%	1995
	11th to 20th	Night	17% 36% 8% 21% 14% 4	2160
	21st to end	Night	17% 37% 9% 22% 12% 3	2528
November	1st to 10th	Night	25% 42% 7% 11% 10% 4	2405
	11th to 20th	Night	22% 42% 11% 13% 10% 1	2470
	21st to end	Night	19% 41% 9% 16% 12% 3	2470
December	1st to 10th	Night	25% 41% 10% 14% 5% 4	2602
	11th to 20th	Night	34% 34% 10% 11% 10% 1	3262
	21st to end	Night	33% 29% 13% 11% 11% 4	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	26% 23% 24% 17% 9% 1	180
	11th to 20th	Day	16% 27% 24% 21% 11% 2	180
	21st to end	Day	14% 25% 25% 24% 8% 2	283
February	1st to 10th	Day	23% 36% 22% 13% 5% 1	270
	11th to 20th	Day	23% 29% 25% 16% 6%	412
	21st to end	Day	18% 30% 30% 17% 4	382
March	1st to 10th	Day	22% 25% 34% 16% 3	460
	11th to 20th	Day	16% 27% 29% 18% 9% 1	460
	21st to end	Day	24% 32% 29% 12% 3 1	506
April	1st to 10th	Day	24% 25% 27% 15% 7% 1	460
	11th to 20th	Day	22% 29% 30% 13% 5%	452
	21st to end	Day	22% 25% 27% 19% 4 2	460
May	1st to 10th	Day	17% 25% 31% 19% 7% 1	460
	11th to 20th	Day	19% 20% 28% 22% 8% 2	448
	21st to end	Day	16% 17% 28% 23% 13% 3	485
June	1st to 10th	Day	11% 16% 31% 26% 13% 3	450
	11th to 20th	Day	15% 21% 37% 18% 8% 1	450
	21st to end	Day	4 16% 39% 26% 13% 3	450
July	1st to 10th	Day	3 11% 37% 34% 13% 2	446
	11th to 20th	Day	4 13% 44% 28% 10% 2	444
	21st to end	Day	4 8% 32% 35% 17% 5%	487
August	1st to 10th	Day	7% 11% 33% 32% 14% 3	447
	11th to 20th	Day	3 9% 32% 31% 17% 7%	437
	21st to end	Day	5% 11% 28% 30% 21% 5%	495
September	1st to 10th	Day	6% 11% 27% 32% 16% 9%	450
	11th to 20th	Day	9% 12% 31% 26% 16% 6%	450
	21st to end	Day	11% 15% 28% 27% 15% 5%	450
October	1st to 10th	Day	15% 15% 23% 24% 17% 5%	433
	11th to 20th	Day	14% 20% 20% 21% 21% 4	270
	21st to end	Day	13% 22% 30% 24% 9% 1	297
November	1st to 10th	Day	22% 19% 24% 21% 12% 1	270
	11th to 20th	Day	13% 21% 29% 23% 11% 3	270
	21st to end	Day	19% 20% 19% 27% 12% 3	270
December	1st to 10th	Day	22% 19% 27% 20% 10% 2	270
	11th to 20th	Day	15% 27% 27% 21% 9% 2	222
	21st to end	Day	22% 25% 26% 19% 8% 1	198
January	1st to 10th	Night	18% 14% 19% 28% 17% 3	760
	11th to 20th	Night	16% 15% 21% 27% 16% 4	760
	21st to end	Night	16% 15% 20% 26% 18% 4	836
February	1st to 10th	Night	16% 23% 24% 21% 14% 2	760
	11th to 20th	Night	14% 18% 23% 28% 15% 2	744
	21st to end	Night	13% 19% 26% 27% 13% 2	628
March	1st to 10th	Night	14% 16% 26% 31% 11% 3	760
	11th to 20th	Night	10% 16% 23% 30% 18% 3	760
	21st to end	Night	19% 19% 24% 25% 13% 1	836
April	1st to 10th	Night	17% 16% 21% 30% 13% 2	760
	11th to 20th	Night	11% 20% 29% 26% 11% 2	615
	21st to end	Night	12% 17% 25% 30% 14% 2	570
May	1st to 10th	Night	12% 13% 27% 28% 18% 2	569
	11th to 20th	Night	10% 11% 19% 32% 24% 4	531
	21st to end	Night	14% 10% 17% 28% 26% 4	584
June	1st to 10th	Night	8% 8% 14% 39% 26% 5%	371
	11th to 20th	Night	9% 11% 20% 41% 18% 2	360
	21st to end	Night	4 4 20% 39% 28% 6%	360
July	1st to 10th	Night	3 1 9% 49% 32% 6%	350
	11th to 20th	Night	3 2 17% 48% 28% 2	348
	21st to end	Night	3 2 12% 42% 37% 4	547
August	1st to 10th	Night	5% 4 13% 45% 29% 4	537
	11th to 20th	Night	4 3 12% 44% 32% 4	534
	21st to end	Night	6% 4 17% 41% 29% 3	646
September	1st to 10th	Night	5% 4 14% 37% 30% 9%	720
	11th to 20th	Night	7% 4 15% 32% 32% 10%	720
	21st to end	Night	9% 6% 15% 32% 27% 11%	720
October	1st to 10th	Night	11% 9% 19% 32% 23% 7%	720
	11th to 20th	Night	10% 12% 15% 29% 28% 5%	720
	21st to end	Night	12% 13% 21% 28% 22% 5%	792
November	1st to 10th	Night	16% 14% 18% 29% 20% 4	740
	11th to 20th	Night	14% 14% 23% 31% 16% 2	760
	21st to end	Night	11% 16% 19% 29% 18% 6%	760
December	1st to 10th	Night	16% 15% 22% 30% 16% 1	892
	11th to 20th	Night	18% 15% 22% 29% 13% 3	841
	21st to end	Night	20% 19% 24% 27% 8% 2	836

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