Reno
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Reno clear sky chart from 2005-11-06 to 2024-03-28.

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	2 4 2 4 4 3 4 4 5% 7% 62%	78833
	Night	2 4 2 4 4 3 4 4 6% 8% 60%	81189
Transparency	Day	22% 5% 9% 22% 23% 18%	78540
	Night	24% 5% 11% 24% 22% 13%	81004
Seeing	Day	8% 15% 27% 28% 17% 5%	14140
	Night	4 7% 23% 37% 23% 4	23624

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	1 4 2 6% 6% 4 7% 7% 8% 10% 45%	2539
	11th to 20th	Day	1 6% 4 6% 7% 4 6% 6% 5% 9% 45%	2573
	21st to end	Day	4 8% 3 7% 7% 4 7% 7% 7% 10% 36%	3146
February	1st to 10th	Day	2 5% 3 5% 5% 3 5% 5% 7% 10% 50%	1710
	11th to 20th	Day	2 3 3 4 6% 3 5% 4 7% 10% 52%	1850
	21st to end	Day	1 4 1 4 3 4 3 5% 7% 11% 56%	1570
March	1st to 10th	Day	2 6% 2 6% 7% 4 5% 6% 7% 11% 45%	1900
	11th to 20th	Day	2 4 3 5% 5% 4 4 6% 6% 8% 52%	2045
	21st to end	Day	1 4 2 4 5% 3 5% 5% 6% 9% 55%	2406
April	1st to 10th	Day	2 4 4 4 5% 3 5% 5% 6% 9% 54%	2160
	11th to 20th	Day	2 3 2 4 5% 3 4 5% 5% 7% 59%	2129
	21st to end	Day	2 5% 2 3 4 1 4 4 5% 6% 64%	2160
May	1st to 10th	Day	3 3 1 3 4 3 4 4 5% 8% 62%	2281
	11th to 20th	Day	4 4 2 3 4 2 3 4 5% 8% 60%	2440
	21st to end	Day	5% 5% 2 6% 5% 4 5% 5% 6% 6% 53%	2723
June	1st to 10th	Day	3 3 2 4 3 2 4 4 6% 8% 61%	2520
	11th to 20th	Day	1 2 1 2 3 2 3 2 4 5% 76%	2520
	21st to end	Day	2 2 1 3 3 2 3 3 3 4 75%	2520
July	1st to 10th	Day	1 1 1 1 2 1 3 3 4 5% 79%	2520
	11th to 20th	Day	1 1 2 2 1 3 3 3 5% 79%	2520
	21st to end	Day	1 2 1 2 3 2 3 3 4 6% 71%	2705
August	1st to 10th	Day	2 2 1 3 2 2 3 4 4 5% 72%	2307
	11th to 20th	Day	1 1 2 2 2 2 3 3 4 79%	2122
	21st to end	Day	1 1 1 1 1 2 2 2 4 84%	2376
September	1st to 10th	Day	1 1 1 2 2 1 1 2 2 4 84%	2160
	11th to 20th	Day	2 2 1 2 3 2 2 3 4 4 75%	2127
	21st to end	Day	2 2 1 2 2 1 2 3 3 5% 77%	1980
October	1st to 10th	Day	4 3 1 3 3 2 2 4 3 6% 69%	1836
	11th to 20th	Day	2 2 1 2 3 2 3 2 4 6% 74%	1800
	21st to end	Day	1 2 1 3 3 2 3 3 4 7% 70%	1921
November	1st to 10th	Day	3 4 2 3 4 2 3 5% 7% 7% 60%	1674
	11th to 20th	Day	2 3 1 2 3 2 4 6% 7% 10% 60%	1710
	21st to end	Day	1 3 2 4 4 3 4 5% 5% 9% 59%	1641
December	1st to 10th	Day	2 4 2 4 5% 3 5% 6% 5% 11% 52%	1520
	11th to 20th	Day	3 8% 4 8% 6% 3 5% 7% 9% 10% 36%	1928
	21st to end	Day	2 7% 4 6% 5% 4 6% 6% 8% 13% 40%	2794
January	1st to 10th	Night	1 4 2 6% 6% 4 5% 6% 7% 10% 49%	4406
	11th to 20th	Night	1 6% 3 8% 7% 4 6% 6% 8% 9% 41%	4385
	21st to end	Night	4 8% 4 7% 7% 4 6% 6% 7% 8% 39%	4521
February	1st to 10th	Night	2 4 3 4 5% 3 5% 5% 6% 9% 54%	2469
	11th to 20th	Night	2 4 3 4 4 3 5% 4 7% 11% 54%	2218
	21st to end	Night	1 4 1 5% 4 3 3 4 6% 10% 58%	1884
March	1st to 10th	Night	2 6% 2 5% 6% 3 5% 6% 6% 9% 51%	2280
	11th to 20th	Night	1 4 2 4 3 3 5% 5% 7% 10% 56%	2133
	21st to end	Night	2 4 2 4 4 3 4 4 5% 9% 59%	2103
April	1st to 10th	Night	2 3 2 3 4 3 4 6% 7% 10% 56%	1800
	11th to 20th	Night	2 3 2 4 4 2 4 5% 5% 8% 63%	1779
	21st to end	Night	4 3 1 3 3 3 4 3 4 7% 65%	1800
May	1st to 10th	Night	4 4 2 3 3 2 4 3 5% 6% 64%	1677
	11th to 20th	Night	2 4 2 4 3 3 3 5% 5% 8% 62%	1450
	21st to end	Night	4 4 2 4 4 3 4 4 6% 7% 58%	1552
June	1st to 10th	Night	4 3 2 3 2 2 3 3 4 8% 65%	1440
	11th to 20th	Night	1 1 1 2 3 1 2 2 5% 5% 77%	1440
	21st to end	Night	2 1 1 2 2 1 2 3 4 4 78%	1440
July	1st to 10th	Night	1 1 2 1 3 2 4 6% 80%	1440
	11th to 20th	Night	1 1 2 2 2 3 3 3 5% 80%	1440
	21st to end	Night	2 3 2 2 2 2 3 4 5% 74%	1608
August	1st to 10th	Night	2 2 1 3 3 2 3 4 5% 5% 70%	1629
	11th to 20th	Night	2 1 1 1 2 2 2 3 3 4 79%	1780
	21st to end	Night	2 2 2 2 1 1 2 2 4 83%	1980
September	1st to 10th	Night	1 1 1 2 1 2 1 2 4 85%	1800
	11th to 20th	Night	2 2 1 1 2 1 2 3 3 4 78%	1831
	21st to end	Night	2 2 2 3 2 2 3 3 5% 77%	1980
October	1st to 10th	Night	4 3 1 2 3 2 3 3 4 4 71%	2121
	11th to 20th	Night	2 2 1 2 2 1 2 2 4 6% 76%	2160
	21st to end	Night	2 3 1 2 2 1 2 3 4 6% 73%	2434
November	1st to 10th	Night	2 3 1 4 4 2 3 4 6% 8% 63%	2405
	11th to 20th	Night	1 3 1 3 3 2 4 3 6% 10% 62%	2470
	21st to end	Night	2 3 2 3 4 3 3 5% 6% 7% 60%	2536
December	1st to 10th	Night	3 4 2 5% 5% 3 5% 4 5% 8% 56%	2660
	11th to 20th	Night	4 7% 3 6% 6% 3 5% 6% 7% 12% 40%	3276
	21st to end	Night	2 6% 3 7% 7% 4 6% 6% 8% 10% 41%	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	35% 7% 17% 32% 9%	2539
	11th to 20th	Day	38% 7% 14% 29% 10% 2	2573
	21st to end	Day	44% 8% 13% 25% 10% 1	3146
February	1st to 10th	Day	29% 7% 14% 28% 16% 5%	1710
	11th to 20th	Day	28% 4 14% 32% 18% 4	1860
	21st to end	Day	22% 6% 17% 33% 18% 4	1570
March	1st to 10th	Day	33% 6% 15% 28% 15% 2	1900
	11th to 20th	Day	29% 6% 15% 24% 21% 4	2045
	21st to end	Day	26% 8% 20% 29% 14% 3	2406
April	1st to 10th	Day	28% 5% 15% 27% 20% 6%	2160
	11th to 20th	Day	23% 7% 10% 30% 23% 7%	2132
	21st to end	Day	22% 4 11% 32% 26% 5%	2160
May	1st to 10th	Day	20% 4 8% 30% 30% 7%	2281
	11th to 20th	Day	23% 4 7% 27% 30% 9%	2443
	21st to end	Day	30% 4 10% 25% 24% 6%	2724
June	1st to 10th	Day	21% 4 8% 22% 31% 14%	2520
	11th to 20th	Day	13% 3 4 21% 33% 27%	2520
	21st to end	Day	13% 4 1 11% 30% 41%	2520
July	1st to 10th	Day	8% 3 2 7% 25% 55%	2451
	11th to 20th	Day	10% 3 1 9% 24% 53%	2445
	21st to end	Day	15% 4 1 7% 23% 49%	2555
August	1st to 10th	Day	15% 4 1 10% 23% 46%	2291
	11th to 20th	Day	10% 3 1 7% 27% 52%	2122
	21st to end	Day	8% 2 1 6% 32% 52%	2376
September	1st to 10th	Day	8% 1 1 9% 28% 53%	2160
	11th to 20th	Day	13% 3 3 16% 34% 30%	2127
	21st to end	Day	13% 3 3 19% 35% 27%	1980
October	1st to 10th	Day	18% 2 7% 20% 31% 22%	1836
	11th to 20th	Day	13% 2 7% 26% 32% 19%	1800
	21st to end	Day	16% 3 8% 30% 30% 13%	1921
November	1st to 10th	Day	23% 5% 11% 27% 26% 8%	1674
	11th to 20th	Day	20% 6% 17% 29% 25% 4	1710
	21st to end	Day	24% 5% 11% 29% 26% 4	1641
December	1st to 10th	Day	28% 6% 14% 31% 17% 4	1520
	11th to 20th	Day	42% 10% 11% 25% 11% 2	1928
	21st to end	Day	35% 9% 19% 26% 10% 1	2794
January	1st to 10th	Night	31% 6% 22% 30% 10% 1	4406
	11th to 20th	Night	39% 8% 17% 24% 10% 3	4385
	21st to end	Night	42% 9% 13% 23% 11% 1	4521
February	1st to 10th	Night	28% 6% 14% 29% 18% 5%	2469
	11th to 20th	Night	24% 5% 14% 34% 20% 2	2219
	21st to end	Night	23% 7% 15% 34% 16% 4	1884
March	1st to 10th	Night	29% 7% 16% 29% 16% 4	2280
	11th to 20th	Night	24% 6% 15% 29% 22% 5%	2133
	21st to end	Night	24% 6% 22% 30% 15% 3	2103
April	1st to 10th	Night	23% 7% 17% 30% 18% 5%	1800
	11th to 20th	Night	20% 6% 15% 31% 20% 8%	1779
	21st to end	Night	20% 5% 14% 34% 22% 4	1800
May	1st to 10th	Night	21% 4 9% 29% 30% 7%	1677
	11th to 20th	Night	22% 4 11% 30% 25% 9%	1450
	21st to end	Night	26% 4 13% 29% 23% 5%	1552
June	1st to 10th	Night	21% 4 10% 22% 29% 13%	1440
	11th to 20th	Night	12% 2 6% 21% 34% 25%	1440
	21st to end	Night	11% 3 3 14% 32% 37%	1440
July	1st to 10th	Night	8% 3 1 8% 29% 50%	1400
	11th to 20th	Night	10% 2 2 10% 26% 50%	1392
	21st to end	Night	13% 3 3 7% 26% 47%	1519
August	1st to 10th	Night	16% 4 3 14% 24% 39%	1620
	11th to 20th	Night	10% 3 1 10% 29% 46%	1780
	21st to end	Night	9% 2 1 8% 34% 46%	1980
September	1st to 10th	Night	8% 2 2 7% 32% 50%	1800
	11th to 20th	Night	11% 3 4 19% 36% 27%	1831
	21st to end	Night	12% 2 3 21% 34% 28%	1980
October	1st to 10th	Night	18% 2 7% 21% 29% 23%	2121
	11th to 20th	Night	13% 3 7% 24% 34% 19%	2160
	21st to end	Night	15% 2 8% 29% 33% 14%	2434
November	1st to 10th	Night	21% 5% 11% 30% 23% 10%	2405
	11th to 20th	Night	19% 5% 13% 32% 26% 5%	2470
	21st to end	Night	23% 5% 11% 30% 25% 6%	2536
December	1st to 10th	Night	28% 8% 14% 27% 20% 4	2660
	11th to 20th	Night	37% 9% 13% 25% 14% 2	3276
	21st to end	Night	39% 8% 16% 24% 12% 2	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	11% 18% 27% 29% 12% 2	180
	11th to 20th	Day	8% 17% 28% 29% 15% 5%	200
	21st to end	Day	7% 11% 31% 31% 15% 4	407
February	1st to 10th	Day	9% 18% 29% 28% 14% 2	370
	11th to 20th	Day	8% 20% 27% 31% 13% 1	455
	21st to end	Day	8% 20% 29% 32% 10% 1	382
March	1st to 10th	Day	11% 21% 35% 22% 9% 2	460
	11th to 20th	Day	9% 22% 31% 22% 15% 2	460
	21st to end	Day	11% 25% 30% 26% 8%	491
April	1st to 10th	Day	10% 23% 30% 22% 12% 2	420
	11th to 20th	Day	12% 26% 27% 21% 11% 2	412
	21st to end	Day	13% 20% 25% 25% 12% 5%	420
May	1st to 10th	Day	10% 20% 30% 26% 11% 4	423
	11th to 20th	Day	15% 20% 25% 20% 13% 6%	448
	21st to end	Day	11% 15% 24% 23% 19% 8%	485
June	1st to 10th	Day	8% 18% 26% 22% 20% 6%	450
	11th to 20th	Day	9% 18% 30% 24% 13% 6%	450
	21st to end	Day	4 13% 25% 30% 22% 7%	450
July	1st to 10th	Day	2 9% 31% 32% 17% 9%	446
	11th to 20th	Day	2 9% 28% 30% 24% 8%	444
	21st to end	Day	2 6% 27% 32% 22% 11%	487
August	1st to 10th	Day	4 9% 25% 29% 22% 11%	447
	11th to 20th	Day	3 8% 26% 29% 22% 12%	437
	21st to end	Day	2 6% 29% 32% 24% 6%	495
September	1st to 10th	Day	3 8% 28% 30% 25% 7%	450
	11th to 20th	Day	7% 13% 24% 29% 23% 4	450
	21st to end	Day	5% 12% 24% 38% 18% 3	450
October	1st to 10th	Day	8% 12% 25% 27% 22% 6%	450
	11th to 20th	Day	8% 11% 22% 27% 26% 6%	450
	21st to end	Day	7% 13% 21% 33% 19% 6%	436
November	1st to 10th	Day	11% 10% 22% 27% 20% 9%	270
	11th to 20th	Day	4 11% 23% 31% 23% 9%	270
	21st to end	Day	5% 11% 25% 30% 23% 6%	237
December	1st to 10th	Day	9% 11% 32% 22% 17% 9%	180
	11th to 20th	Day	6% 12% 34% 24% 16% 7%	180
	21st to end	Day	15% 15% 22% 30% 16% 2	198
January	1st to 10th	Night	5% 10% 28% 32% 19% 6%	760
	11th to 20th	Night	4 9% 24% 39% 20% 4	760
	21st to end	Night	6% 6% 25% 37% 20% 5%	836
February	1st to 10th	Night	4 8% 28% 36% 20% 3	760
	11th to 20th	Night	4 10% 26% 37% 18% 5%	744
	21st to end	Night	4 13% 27% 40% 14% 3	628
March	1st to 10th	Night	6% 13% 31% 31% 15% 3	760
	11th to 20th	Night	4 11% 29% 31% 23% 3	760
	21st to end	Night	3 14% 33% 32% 16% 2	820
April	1st to 10th	Night	5% 11% 30% 35% 18% 1	720
	11th to 20th	Night	4 16% 27% 31% 18% 4	711
	21st to end	Night	6% 13% 24% 34% 20% 4	720
May	1st to 10th	Night	8% 11% 26% 34% 19% 3	597
	11th to 20th	Night	5% 7% 24% 39% 22% 2	388
	21st to end	Night	8% 5% 19% 38% 28% 3	389
June	1st to 10th	Night	7% 5% 19% 43% 23% 3	360
	11th to 20th	Night	2 4 25% 40% 28% 1	360
	21st to end	Night	2 2 18% 51% 26% 2	360
July	1st to 10th	Night	1 1 16% 52% 28% 3	350
	11th to 20th	Night	1 1 19% 53% 26% 1	348
	21st to end	Night	3 1 9% 50% 34% 4	426
August	1st to 10th	Night	3 1 12% 45% 35% 4	555
	11th to 20th	Night	2 2 16% 43% 32% 4	712
	21st to end	Night	2 3 18% 47% 28% 3	792
September	1st to 10th	Night	1 2 16% 38% 37% 5%	720
	11th to 20th	Night	3 5% 16% 34% 35% 7%	720
	21st to end	Night	2 5% 19% 36% 29% 10%	720
October	1st to 10th	Night	5% 4 19% 38% 26% 7%	720
	11th to 20th	Night	4 6% 16% 38% 30% 6%	720
	21st to end	Night	6% 4 20% 30% 29% 11%	792
November	1st to 10th	Night	5% 8% 22% 31% 28% 6%	740
	11th to 20th	Night	5% 6% 24% 39% 21% 5%	760
	21st to end	Night	4 7% 25% 33% 25% 6%	760
December	1st to 10th	Night	6% 7% 26% 38% 17% 6%	760
	11th to 20th	Night	6% 9% 28% 33% 18% 5%	760
	21st to end	Night	7% 10% 31% 35% 14% 1	836

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