Rio Vista
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rio Vista clear sky chart from 2005-11-06 to 2024-02-25.

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% 4 2 3 3 2 3 3 4 6% 62%	78560
	Night	9% 4 2 4 3 2 3 3 4 6% 59%	80760
Transparency	Day	24% 4 9% 19% 24% 19%	78275
	Night	26% 5% 10% 19% 22% 17%	80566
Seeing	Day	8% 7% 24% 33% 21% 7%	14294
	Night	9% 5% 24% 39% 21% 3	23766

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	19% 10% 4 6% 5% 4 4 4 5% 7% 34%	2585
	11th to 20th	Day	18% 12% 3 7% 6% 3 4 3 4 5% 34%	2860
	21st to end	Day	21% 9% 4 7% 6% 3 5% 5% 5% 6% 30%	3146
February	1st to 10th	Day	16% 5% 2 6% 6% 2 4 3 4 5% 46%	1710
	11th to 20th	Day	14% 5% 3 4 4 2 5% 5% 5% 6% 46%	1768
	21st to end	Day	14% 4 2 4 4 3 4 3 5% 6% 51%	1521
March	1st to 10th	Day	13% 7% 3 7% 5% 3 4 5% 6% 7% 40%	1903
	11th to 20th	Day	15% 6% 3 6% 5% 3 4 4 6% 7% 42%	1980
	21st to end	Day	11% 4 2 5% 5% 3 5% 5% 5% 6% 50%	2232
April	1st to 10th	Day	13% 6% 2 4 4 2 4 4 6% 7% 48%	2160
	11th to 20th	Day	8% 3 1 3 3 2 3 4 4 6% 61%	2129
	21st to end	Day	5% 3 1 2 4 2 3 3 4 9% 65%	2160
May	1st to 10th	Day	4 2 1 2 3 2 2 4 5% 7% 69%	2210
	11th to 20th	Day	3 2 1 2 2 1 3 3 4 7% 71%	2413
	21st to end	Day	3 1 1 2 2 2 3 4 3 8% 71%	2723
June	1st to 10th	Day	3 3 1 2 2 2 3 3 4 8% 69%	2520
	11th to 20th	Day	1 2 1 2 2 3 6% 83%	2520
	21st to end	Day	2 1 1 1 1 1 1 2 2 4 84%	2520
July	1st to 10th	Day	1 1 1 2 3 5% 86%	2520
	11th to 20th	Day	1 1 1 1 1 1 2 3 4 86%	2439
	21st to end	Day	1 1 1 1 1 2 2 3 6% 83%	2546
August	1st to 10th	Day	1 1 1 1 1 2 2 2 4 84%	2328
	11th to 20th	Day	1 1 1 1 1 2 3 5% 85%	2172
	21st to end	Day	1 1 1 1 1 2 2 4 87%	2376
September	1st to 10th	Day	1 1 1 1 1 1 1 2 4 87%	2160
	11th to 20th	Day	2 2 1 1 2 1 2 3 4 5% 77%	2160
	21st to end	Day	2 2 1 2 2 2 2 2 3 5% 79%	1927
October	1st to 10th	Day	2 2 1 3 3 1 3 3 3 5% 75%	1800
	11th to 20th	Day	5% 2 1 3 2 2 4 4 4 6% 69%	1800
	21st to end	Day	5% 3 2 3 3 2 3 3 4 6% 66%	1980
November	1st to 10th	Day	7% 4 2 3 4 3 4 4 5% 8% 57%	1769
	11th to 20th	Day	9% 7% 2 6% 5% 4 4 4 4 7% 49%	1710
	21st to end	Day	11% 4 2 4 5% 3 3 4 5% 6% 53%	1571
December	1st to 10th	Day	13% 7% 3 7% 5% 3 3 4 4 6% 45%	1520
	11th to 20th	Day	25% 10% 4 7% 5% 2 4 3 4 6% 30%	1928
	21st to end	Day	16% 9% 3 7% 6% 4 5% 5% 6% 8% 31%	2794
January	1st to 10th	Night	13% 7% 3 6% 5% 3 4 4 5% 6% 43%	4344
	11th to 20th	Night	21% 8% 3 7% 6% 3 4 4 5% 6% 33%	4110
	21st to end	Night	19% 7% 3 7% 5% 3 4 5% 5% 7% 35%	4521
February	1st to 10th	Night	15% 5% 3 4 4 2 4 4 4 4 51%	2470
	11th to 20th	Night	12% 4 2 5% 4 3 3 4 5% 8% 51%	2299
	21st to end	Night	13% 4 1 3 3 2 3 4 4 6% 55%	1829
March	1st to 10th	Night	13% 6% 2 6% 5% 3 4 4 5% 6% 46%	2054
	11th to 20th	Night	15% 5% 1 4 4 2 5% 4 4 7% 48%	1980
	21st to end	Night	12% 4 3 4 3 2 3 4 4 6% 56%	2122
April	1st to 10th	Night	10% 4 2 4 4 3 3 4 5% 8% 54%	1800
	11th to 20th	Night	8% 3 2 2 4 2 3 3 4 7% 62%	1779
	21st to end	Night	4 2 1 2 2 1 2 4 5% 8% 68%	1800
May	1st to 10th	Night	4 2 1 3 2 1 3 3 3 7% 71%	1746
	11th to 20th	Night	3 1 1 2 2 2 2 3 5% 8% 73%	1477
	21st to end	Night	2 2 1 1 2 2 3 3 3 7% 75%	1552
June	1st to 10th	Night	4 2 2 2 2 3 2 4 7% 72%	1440
	11th to 20th	Night	1 1 1 2 2 3 4 85%	1440
	21st to end	Night	1 1 1 1 1 1 2 2 3 3 84%	1440
July	1st to 10th	Night	1 1 1 1 1 2 4 88%	1440
	11th to 20th	Night	1 1 1 1 1 1 1 2 4 86%	1517
	21st to end	Night	1 1 1 1 2 1 2 2 5% 8% 76%	1773
August	1st to 10th	Night	2 1 1 1 2 2 2 3 3 7% 77%	1611
	11th to 20th	Night	1 1 2 2 4 7% 81%	1728
	21st to end	Night	1 1 1 1 2 1 2 6% 85%	1980
September	1st to 10th	Night	1 1 1 1 1 2 3 6% 85%	1800
	11th to 20th	Night	2 1 1 1 1 1 2 2 4 7% 78%	1800
	21st to end	Night	1 1 2 2 1 2 2 3 5% 81%	2029
October	1st to 10th	Night	3 2 2 2 1 2 3 4 4 75%	2160
	11th to 20th	Night	3 2 1 2 3 2 2 3 4 7% 71%	2160
	21st to end	Night	5% 2 2 3 1 3 3 5% 6% 70%	2376
November	1st to 10th	Night	7% 4 1 3 3 2 4 3 4 9% 60%	2308
	11th to 20th	Night	8% 4 2 4 4 2 3 5% 5% 7% 57%	2470
	21st to end	Night	10% 4 2 3 3 2 4 3 5% 6% 58%	2607
December	1st to 10th	Night	14% 6% 2 5% 4 3 3 4 4 6% 48%	2660
	11th to 20th	Night	22% 7% 3 5% 5% 3 5% 4 6% 8% 32%	3276
	21st to end	Night	17% 6% 3 7% 6% 4 5% 5% 5% 6% 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	48% 9% 12% 22% 8% 1	2585
	11th to 20th	Day	53% 7% 10% 14% 13% 4	2860
	21st to end	Day	52% 8% 11% 16% 11% 3	3146
February	1st to 10th	Day	40% 5% 9% 21% 18% 6%	1710
	11th to 20th	Day	36% 6% 12% 19% 20% 6%	1777
	21st to end	Day	33% 6% 11% 24% 19% 7%	1521
March	1st to 10th	Day	42% 5% 13% 21% 16% 4	1903
	11th to 20th	Day	41% 6% 10% 22% 16% 5%	1980
	21st to end	Day	34% 7% 14% 20% 20% 5%	2232
April	1st to 10th	Day	35% 6% 12% 22% 19% 6%	2160
	11th to 20th	Day	24% 5% 13% 26% 24% 8%	2132
	21st to end	Day	18% 5% 13% 29% 29% 7%	2160
May	1st to 10th	Day	16% 4 10% 27% 33% 11%	2210
	11th to 20th	Day	15% 4 9% 30% 32% 12%	2416
	21st to end	Day	14% 5% 14% 33% 26% 8%	2724
June	1st to 10th	Day	15% 5% 11% 26% 31% 13%	2520
	11th to 20th	Day	6% 2 8% 22% 36% 26%	2520
	21st to end	Day	7% 1 4 12% 36% 40%	2520
July	1st to 10th	Day	4 1 4 9% 26% 56%	2451
	11th to 20th	Day	5% 1 5% 13% 26% 51%	2364
	21st to end	Day	5% 1 4 9% 27% 54%	2405
August	1st to 10th	Day	7% 2 4 12% 32% 42%	2312
	11th to 20th	Day	5% 1 3 13% 34% 44%	2172
	21st to end	Day	4 1 3 13% 36% 44%	2376
September	1st to 10th	Day	5% 1 3 8% 31% 51%	2160
	11th to 20th	Day	10% 3 7% 21% 40% 20%	2160
	21st to end	Day	11% 2 5% 18% 35% 28%	1927
October	1st to 10th	Day	13% 4 6% 18% 31% 28%	1800
	11th to 20th	Day	17% 4 10% 21% 24% 25%	1800
	21st to end	Day	20% 4 9% 21% 27% 20%	1980
November	1st to 10th	Day	26% 5% 10% 26% 22% 11%	1769
	11th to 20th	Day	35% 5% 11% 25% 19% 5%	1710
	21st to end	Day	30% 6% 12% 23% 23% 8%	1571
December	1st to 10th	Day	39% 6% 12% 19% 16% 7%	1520
	11th to 20th	Day	56% 6% 9% 13% 14% 2	1928
	21st to end	Day	47% 10% 14% 16% 11% 2	2794
January	1st to 10th	Night	37% 11% 17% 24% 9% 3	4344
	11th to 20th	Night	50% 8% 14% 12% 10% 6%	4110
	21st to end	Night	48% 8% 12% 15% 12% 4	4521
February	1st to 10th	Night	37% 4 8% 21% 21% 8%	2470
	11th to 20th	Night	31% 5% 12% 21% 23% 8%	2301
	21st to end	Night	30% 4 10% 27% 21% 6%	1829
March	1st to 10th	Night	38% 6% 13% 18% 18% 6%	2054
	11th to 20th	Night	36% 5% 8% 24% 20% 7%	1980
	21st to end	Night	29% 7% 13% 23% 22% 7%	2122
April	1st to 10th	Night	30% 5% 15% 20% 22% 8%	1800
	11th to 20th	Night	23% 5% 12% 27% 21% 12%	1779
	21st to end	Night	16% 5% 13% 29% 30% 7%	1800
May	1st to 10th	Night	15% 4 10% 23% 35% 12%	1746
	11th to 20th	Night	12% 4 11% 29% 33% 12%	1477
	21st to end	Night	10% 5% 14% 36% 26% 10%	1552
June	1st to 10th	Night	13% 6% 10% 24% 32% 14%	1440
	11th to 20th	Night	6% 2 8% 20% 35% 28%	1440
	21st to end	Night	7% 2 4 11% 35% 42%	1440
July	1st to 10th	Night	4 1 2 10% 25% 58%	1400
	11th to 20th	Night	5% 2 4 10% 22% 57%	1469
	21st to end	Night	6% 2 3 9% 25% 54%	1674
August	1st to 10th	Night	8% 1 3 14% 28% 45%	1602
	11th to 20th	Night	4 2 4 11% 31% 48%	1728
	21st to end	Night	5% 1 4 10% 32% 48%	1980
September	1st to 10th	Night	4 2 5% 8% 30% 52%	1800
	11th to 20th	Night	8% 2 7% 20% 36% 27%	1800
	21st to end	Night	8% 2 5% 19% 34% 32%	2029
October	1st to 10th	Night	12% 4 8% 17% 28% 30%	2160
	11th to 20th	Night	15% 4 7% 19% 27% 28%	2160
	21st to end	Night	16% 4 7% 22% 28% 23%	2376
November	1st to 10th	Night	23% 5% 10% 26% 21% 16%	2308
	11th to 20th	Night	26% 5% 12% 25% 24% 8%	2470
	21st to end	Night	27% 4 9% 22% 27% 10%	2607
December	1st to 10th	Night	37% 6% 11% 20% 17% 10%	2660
	11th to 20th	Night	49% 7% 12% 14% 15% 3	3276
	21st to end	Night	46% 10% 12% 17% 12% 3	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	30% 8% 19% 23% 15% 6%	213
	11th to 20th	Day	18% 7% 19% 22% 24% 10%	370
	21st to end	Day	15% 7% 18% 25% 22% 14%	407
February	1st to 10th	Day	18% 9% 19% 17% 24% 12%	370
	11th to 20th	Day	14% 13% 26% 20% 18% 8%	414
	21st to end	Day	12% 13% 20% 33% 17% 5%	363
March	1st to 10th	Day	17% 10% 26% 27% 13% 6%	420
	11th to 20th	Day	18% 11% 24% 23% 15% 9%	420
	21st to end	Day	13% 13% 29% 27% 15% 3	462
April	1st to 10th	Day	14% 14% 28% 23% 15% 6%	420
	11th to 20th	Day	11% 13% 33% 24% 13% 6%	412
	21st to end	Day	4 16% 28% 29% 17% 6%	420
May	1st to 10th	Day	6% 11% 31% 33% 16% 3	423
	11th to 20th	Day	5% 8% 33% 29% 21% 3	448
	21st to end	Day	4 9% 26% 35% 22% 4	485
June	1st to 10th	Day	4 11% 28% 34% 18% 4	450
	11th to 20th	Day	1 9% 30% 44% 15% 2	450
	21st to end	Day	1 3 28% 45% 21% 2	450
July	1st to 10th	Day	1 2 24% 52% 20% 1	446
	11th to 20th	Day	1 20% 48% 29% 2	444
	21st to end	Day	1 1 22% 52% 22% 3	487
August	1st to 10th	Day	2 3 23% 49% 19% 3	447
	11th to 20th	Day	2 26% 45% 22% 4	437
	21st to end	Day	1 1 21% 48% 25% 4	495
September	1st to 10th	Day	1 3 18% 43% 29% 6%	450
	11th to 20th	Day	2 7% 21% 41% 21% 8%	450
	21st to end	Day	2 5% 20% 36% 24% 13%	450
October	1st to 10th	Day	3 5% 24% 28% 25% 14%	450
	11th to 20th	Day	5% 6% 18% 26% 26% 19%	450
	21st to end	Day	7% 6% 18% 27% 24% 17%	495
November	1st to 10th	Day	8% 7% 21% 16% 28% 20%	365
	11th to 20th	Day	9% 6% 16% 25% 29% 16%	270
	21st to end	Day	11% 4 17% 30% 28% 11%	203
December	1st to 10th	Day	19% 8% 17% 22% 22% 12%	180
	11th to 20th	Day	20% 7% 18% 20% 27% 9%	180
	21st to end	Day	20% 10% 20% 24% 23% 4	198
January	1st to 10th	Night	18% 4 16% 34% 24% 4	760
	11th to 20th	Night	14% 5% 15% 36% 24% 6%	760
	21st to end	Night	16% 4 16% 33% 28% 3	836
February	1st to 10th	Night	18% 5% 15% 37% 22% 3	760
	11th to 20th	Night	13% 8% 20% 32% 23% 3	744
	21st to end	Night	13% 8% 23% 35% 18% 2	610
March	1st to 10th	Night	15% 8% 23% 33% 19% 3	720
	11th to 20th	Night	15% 8% 24% 33% 19% 2	720
	21st to end	Night	12% 7% 32% 33% 16%	792
April	1st to 10th	Night	10% 6% 32% 34% 16% 1	720
	11th to 20th	Night	8% 10% 37% 29% 14% 2	711
	21st to end	Night	5% 8% 38% 33% 15% 1	720
May	1st to 10th	Night	5% 6% 34% 39% 14% 2	666
	11th to 20th	Night	3 4 33% 47% 12%	415
	21st to end	Night	3 7% 34% 48% 8%	389
June	1st to 10th	Night	4 4 38% 47% 7% 1	360
	11th to 20th	Night	1 5% 38% 47% 10%	360
	21st to end	Night	1 3 36% 48% 12%	360
July	1st to 10th	Night	1 34% 55% 11%	350
	11th to 20th	Night	1 25% 58% 15% 1	425
	21st to end	Night	2 1 24% 56% 17% 1	591
August	1st to 10th	Night	3 1 25% 51% 19% 1	537
	11th to 20th	Night	1 32% 51% 16%	660
	21st to end	Night	1 1 24% 54% 19% 1	792
September	1st to 10th	Night	1 2 25% 48% 24% 1	720
	11th to 20th	Night	2 3 27% 47% 19% 2	720
	21st to end	Night	2 3 22% 42% 27% 4	720
October	1st to 10th	Night	3 4 24% 39% 25% 5%	720
	11th to 20th	Night	3 4 22% 36% 30% 4	720
	21st to end	Night	6% 3 18% 35% 30% 8%	792
November	1st to 10th	Night	6% 4 20% 34% 31% 5%	740
	11th to 20th	Night	9% 2 16% 38% 30% 5%	760
	21st to end	Night	10% 3 16% 38% 27% 5%	760
December	1st to 10th	Night	15% 5% 16% 37% 22% 5%	760
	11th to 20th	Night	22% 4 13% 34% 23% 3	760
	21st to end	Night	19% 7% 20% 33% 20% 1	836

Page generated at 2024-02-22 03:05:46. Version ac07

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