Riverton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Riverton clear sky chart from 2005-11-06 to 2025-07-06.

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 5% 2 5% 4 4 5% 4 7% 9% 52%	124260
	Night	4 5% 2 6% 4 4 5% 4 7% 9% 50%	123484
Transparency	Day	25% 6% 13% 27% 21% 8%	124012
	Night	27% 6% 14% 28% 18% 7%	123320
Seeing	Day	6% 6% 20% 35% 24% 8%	16647
	Night	6% 4 25% 46% 18% 1	26747

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 9% 7% 7% 7% 7% 12% 14% 31%	3638
	11th to 20th	Day	1 6% 3 8% 6% 6% 6% 6% 9% 11% 39%	3912
	21st to end	Day	1 3 2 6% 4 5% 7% 8% 12% 16% 36%	4510
February	1st to 10th	Day	1 7% 3 7% 6% 5% 6% 5% 8% 10% 44%	1800
	11th to 20th	Day	2 6% 3 8% 5% 5% 5% 6% 8% 10% 42%	1755
	21st to end	Day	1 5% 3 5% 5% 5% 6% 4 7% 10% 49%	1570
March	1st to 10th	Day	2 6% 2 4 3 4 5% 5% 9% 12% 48%	4882
	11th to 20th	Day	2 7% 2 5% 3 4 5% 4 6% 9% 52%	5000
	21st to end	Day	4 7% 3 7% 5% 5% 6% 5% 8% 11% 40%	5516
April	1st to 10th	Day	6% 7% 2 5% 4 4 5% 5% 6% 10% 48%	2400
	11th to 20th	Day	6% 8% 3 7% 4 5% 5% 4 7% 8% 42%	2371
	21st to end	Day	9% 8% 3 6% 6% 5% 5% 4 7% 8% 39%	2565
May	1st to 10th	Day	9% 9% 2 6% 4 4 5% 4 5% 7% 46%	5944
	11th to 20th	Day	7% 5% 1 4 4 4 4 4 7% 9% 51%	6298
	21st to end	Day	6% 5% 1 4 3 4 5% 5% 7% 10% 50%	6925
June	1st to 10th	Day	4 3 2 4 4 3 5% 4 7% 10% 54%	2800
	11th to 20th	Day	5% 3 1 4 3 3 4 4 6% 8% 59%	2800
	21st to end	Day	2 3 1 3 3 3 3 4 6% 8% 65%	2800
July	1st to 10th	Day	2 2 1 2 2 2 3 3 6% 8% 69%	4501
	11th to 20th	Day	1 2 1 3 2 3 4 4 7% 9% 64%	4430
	21st to end	Day	2 2 1 3 3 4 4 4 7% 9% 61%	4559
August	1st to 10th	Day	3 2 1 3 3 4 5% 5% 7% 9% 57%	4092
	11th to 20th	Day	2 2 1 3 2 3 5% 4 7% 9% 61%	4028
	21st to end	Day	1 2 1 2 2 2 3 3 5% 7% 71%	4278
September	1st to 10th	Day	3 3 1 3 3 4 4 3 5% 6% 64%	2280
	11th to 20th	Day	5% 2 1 3 3 2 3 3 5% 7% 66%	2237
	21st to end	Day	6% 3 1 4 2 2 3 2 5% 5% 67%	2024
October	1st to 10th	Day	5% 3 1 3 2 2 2 2 4 5% 71%	3170
	11th to 20th	Day	6% 5% 2 4 3 3 3 2 4 7% 60%	3150
	21st to end	Day	6% 6% 2 5% 3 3 3 3 5% 8% 56%	3438
November	1st to 10th	Day	2 4 2 5% 3 4 4 5% 6% 9% 56%	1737
	11th to 20th	Day	1 4 2 4 4 4 6% 5% 7% 9% 53%	1600
	21st to end	Day	1 7% 3 6% 4 3 5% 6% 5% 10% 50%	1600
December	1st to 10th	Day	1 3 2 4 3 3 4 4 9% 10% 58%	2620
	11th to 20th	Day	1 4 2 5% 4 4 5% 5% 9% 12% 48%	3026
	21st to end	Day	3 8% 3 7% 4 5% 5% 5% 10% 13% 37%	4004
January	1st to 10th	Night	1 8% 4 6% 5% 5% 7% 6% 10% 14% 34%	6327
	11th to 20th	Night	1 3 3 12% 7% 6% 6% 5% 11% 14% 33%	6110
	21st to end	Night	1 4 2 7% 5% 5% 8% 9% 13% 14% 32%	6468
February	1st to 10th	Night	2 7% 3 8% 5% 4 6% 4 7% 9% 46%	2600
	11th to 20th	Night	2 5% 3 7% 5% 6% 7% 5% 8% 10% 43%	2532
	21st to end	Night	2 7% 3 7% 5% 4 4 4 7% 8% 50%	2060
March	1st to 10th	Night	3 9% 3 6% 3 5% 5% 5% 6% 8% 48%	4994
	11th to 20th	Night	3 8% 2 6% 3 4 4 4 6% 9% 51%	5000
	21st to end	Night	5% 8% 3 7% 5% 4 5% 5% 7% 9% 42%	5455
April	1st to 10th	Night	6% 7% 2 5% 4 4 4 4 6% 8% 49%	2000
	11th to 20th	Night	8% 9% 3 7% 5% 5% 5% 4 6% 8% 40%	1977
	21st to end	Night	9% 10% 3 6% 4 4 4 4 6% 8% 43%	1830
May	1st to 10th	Night	14% 9% 3 6% 3 4 3 3 4 6% 45%	4021
	11th to 20th	Night	11% 6% 3 5% 4 4 5% 4 7% 8% 45%	3617
	21st to end	Night	9% 5% 2 5% 4 4 4 4 6% 9% 48%	3972
June	1st to 10th	Night	5% 4 1 4 4 4 5% 4 7% 9% 54%	1600
	11th to 20th	Night	7% 3 1 4 3 3 4 3 6% 8% 56%	1600
	21st to end	Night	3 3 1 4 2 2 3 3 6% 7% 67%	1600
July	1st to 10th	Night	2 1 1 3 3 3 3 3 7% 8% 65%	2580
	11th to 20th	Night	1 1 1 2 2 3 4 4 7% 9% 66%	2540
	21st to end	Night	2 2 1 2 2 3 3 3 6% 11% 65%	3000
August	1st to 10th	Night	4 3 1 4 3 4 3 4 6% 7% 60%	2847
	11th to 20th	Night	2 2 1 4 4 4 5% 5% 7% 8% 60%	2811
	21st to end	Night	1 2 1 2 2 2 3 3 4 9% 69%	3387
September	1st to 10th	Night	4 3 1 4 3 3 4 4 4 7% 64%	1900
	11th to 20th	Night	5% 3 2 3 3 3 3 4 6% 6% 62%	1940
	21st to end	Night	7% 3 1 3 2 3 2 2 4 6% 67%	2155
October	1st to 10th	Night	6% 4 1 3 2 2 2 2 3 4 71%	3800
	11th to 20th	Night	6% 4 2 5% 3 4 3 3 5% 7% 57%	3778
	21st to end	Night	6% 8% 2 5% 3 4 4 3 5% 8% 51%	4120
November	1st to 10th	Night	3 4 2 5% 4 4 4 5% 7% 9% 54%	2538
	11th to 20th	Night	2 5% 2 4 5% 5% 5% 5% 7% 8% 52%	2800
	21st to end	Night	3 7% 3 6% 4 4 4 4 6% 8% 52%	2800
December	1st to 10th	Night	1 4 2 5% 3 3 3 3 7% 10% 58%	4570
	11th to 20th	Night	1 4 2 6% 4 4 4 4 8% 12% 51%	5181
	21st to end	Night	2 7% 3 7% 4 5% 6% 5% 10% 14% 37%	6974

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	34% 9% 20% 26% 10%	3639
	11th to 20th	Day	33% 9% 18% 23% 16% 1	3912
	21st to end	Day	24% 13% 21% 30% 12% 1	4510
February	1st to 10th	Day	32% 7% 19% 29% 11% 2	1800
	11th to 20th	Day	32% 7% 20% 26% 13% 2	1764
	21st to end	Day	27% 6% 19% 27% 18% 3	1570
March	1st to 10th	Day	23% 6% 12% 35% 16% 8%	4882
	11th to 20th	Day	27% 6% 17% 33% 18%	5000
	21st to end	Day	34% 8% 18% 31% 10% 1	5516
April	1st to 10th	Day	30% 7% 18% 28% 15% 2	2400
	11th to 20th	Day	35% 7% 15% 27% 16% 1	2374
	21st to end	Day	40% 7% 12% 26% 15% 1	2565
May	1st to 10th	Day	34% 6% 14% 24% 18% 4	5944
	11th to 20th	Day	27% 6% 11% 29% 22% 5%	6302
	21st to end	Day	25% 7% 15% 34% 18% 2	6926
June	1st to 10th	Day	23% 7% 17% 28% 21% 5%	2800
	11th to 20th	Day	20% 6% 13% 22% 26% 14%	2800
	21st to end	Day	15% 5% 8% 24% 30% 17%	2800
July	1st to 10th	Day	12% 4 7% 20% 34% 23%	4432
	11th to 20th	Day	14% 4 5% 17% 33% 27%	4355
	21st to end	Day	17% 4 6% 16% 31% 26%	4415
August	1st to 10th	Day	21% 5% 8% 23% 24% 19%	4078
	11th to 20th	Day	18% 5% 6% 22% 33% 16%	4067
	21st to end	Day	13% 4 6% 19% 35% 24%	4277
September	1st to 10th	Day	20% 4 8% 18% 31% 18%	2280
	11th to 20th	Day	18% 4 8% 27% 27% 16%	2237
	21st to end	Day	19% 4 7% 28% 33% 9%	2024
October	1st to 10th	Day	17% 4 7% 21% 27% 23%	3170
	11th to 20th	Day	26% 4 8% 32% 24% 6%	3150
	21st to end	Day	27% 4 11% 36% 19% 3	3438
November	1st to 10th	Day	24% 6% 16% 29% 21% 4	1737
	11th to 20th	Day	23% 8% 17% 31% 17% 4	1600
	21st to end	Day	28% 6% 17% 29% 18% 2	1600
December	1st to 10th	Day	19% 6% 19% 39% 16% 1	2620
	11th to 20th	Day	26% 7% 25% 32% 9% 2	3024
	21st to end	Day	33% 6% 13% 31% 15% 1	4004
January	1st to 10th	Night	34% 7% 21% 29% 8% 1	6327
	11th to 20th	Night	34% 11% 18% 23% 12% 2	6110
	21st to end	Night	27% 11% 22% 28% 11% 1	6468
February	1st to 10th	Night	32% 7% 18% 29% 11% 3	2600
	11th to 20th	Night	31% 9% 17% 28% 13% 2	2533
	21st to end	Night	30% 5% 18% 25% 19% 3	2060
March	1st to 10th	Night	30% 5% 12% 30% 16% 8%	4994
	11th to 20th	Night	28% 4 15% 35% 17% 1	5000
	21st to end	Night	36% 8% 20% 28% 7% 1	5455
April	1st to 10th	Night	33% 6% 16% 28% 14% 4	2000
	11th to 20th	Night	40% 7% 14% 22% 16% 1	1977
	21st to end	Night	38% 5% 11% 30% 15% 1	1830
May	1st to 10th	Night	38% 4 11% 27% 17% 3	4018
	11th to 20th	Night	33% 6% 13% 26% 16% 6%	3618
	21st to end	Night	30% 5% 13% 40% 11% 1	3972
June	1st to 10th	Night	23% 8% 19% 26% 19% 5%	1600
	11th to 20th	Night	25% 6% 10% 19% 26% 14%	1600
	21st to end	Night	15% 5% 7% 20% 32% 21%	1600
July	1st to 10th	Night	15% 4 9% 19% 36% 17%	2540
	11th to 20th	Night	13% 4 6% 18% 33% 26%	2492
	21st to end	Night	12% 3 5% 20% 37% 23%	2906
August	1st to 10th	Night	21% 5% 8% 29% 17% 21%	2838
	11th to 20th	Night	21% 5% 8% 26% 26% 15%	2838
	21st to end	Night	13% 4 9% 22% 25% 28%	3387
September	1st to 10th	Night	20% 5% 8% 17% 31% 20%	1900
	11th to 20th	Night	20% 6% 9% 22% 29% 15%	1940
	21st to end	Night	20% 4 8% 26% 31% 12%	2155
October	1st to 10th	Night	19% 4 6% 20% 33% 18%	3800
	11th to 20th	Night	27% 3 8% 30% 25% 7%	3778
	21st to end	Night	30% 4 9% 32% 19% 7%	4120
November	1st to 10th	Night	24% 7% 16% 29% 20% 4	2538
	11th to 20th	Night	28% 6% 13% 34% 16% 3	2800
	21st to end	Night	29% 6% 15% 31% 17% 2	2800
December	1st to 10th	Night	20% 5% 17% 39% 17% 2	4570
	11th to 20th	Night	25% 7% 19% 38% 10% 1	5182
	21st to end	Night	32% 7% 15% 29% 14% 3	6974

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	5% 3 20% 45% 22% 5%	300
	11th to 20th	Day	3 4 19% 43% 25% 5%	300
	21st to end	Day	4 3 15% 49% 23% 6%	330
February	1st to 10th	Day	3 4 38% 44% 10% 2	300
	11th to 20th	Day	2 3 27% 48% 18% 2	300
	21st to end	Day	2 7% 21% 48% 19% 3	249
March	1st to 10th	Day	7% 8% 27% 41% 14% 3	465
	11th to 20th	Day	7% 9% 29% 37% 15% 3	500
	21st to end	Day	10% 12% 29% 32% 15% 2	550
April	1st to 10th	Day	8% 15% 25% 31% 15% 5%	500
	11th to 20th	Day	11% 15% 30% 30% 13% 1	492
	21st to end	Day	15% 14% 21% 26% 21% 4	500
May	1st to 10th	Day	13% 13% 22% 26% 17% 8%	528
	11th to 20th	Day	14% 6% 18% 33% 23% 6%	725
	21st to end	Day	12% 5% 21% 26% 25% 11%	789
June	1st to 10th	Day	4 5% 22% 29% 29% 11%	730
	11th to 20th	Day	7% 7% 23% 34% 23% 6%	730
	21st to end	Day	3 5% 19% 38% 28% 7%	730
July	1st to 10th	Day	3 3 13% 33% 35% 12%	697
	11th to 20th	Day	3 2 14% 38% 34% 9%	668
	21st to end	Day	3 3 15% 33% 33% 13%	597
August	1st to 10th	Day	4 4 15% 36% 29% 13%	487
	11th to 20th	Day	3 3 16% 32% 32% 14%	477
	21st to end	Day	3 4 17% 32% 30% 14%	539
September	1st to 10th	Day	5% 4 17% 33% 28% 14%	490
	11th to 20th	Day	5% 8% 20% 28% 27% 13%	490
	21st to end	Day	8% 6% 16% 28% 28% 13%	424
October	1st to 10th	Day	10% 6% 12% 28% 27% 16%	300
	11th to 20th	Day	6% 7% 21% 30% 25% 11%	300
	21st to end	Day	8% 5% 22% 41% 21% 4	330
November	1st to 10th	Day	5% 6% 24% 40% 18% 7%	300
	11th to 20th	Day	5% 4 23% 42% 20% 6%	300
	21st to end	Day	6% 3 20% 44% 24% 4	300
December	1st to 10th	Day	2 2 18% 52% 20% 6%	300
	11th to 20th	Day	7% 2 21% 49% 18% 3	300
	21st to end	Day	4 5% 20% 48% 16% 7%	330
January	1st to 10th	Night	3 4 28% 49% 15% 2	1000
	11th to 20th	Night	3 4 32% 46% 13% 3	900
	21st to end	Night	5% 3 26% 51% 14% 1	880
February	1st to 10th	Night	5% 4 36% 44% 11% 1	800
	11th to 20th	Night	3 3 29% 49% 13% 2	784
	21st to end	Night	4 5% 36% 45% 10% 1	660
March	1st to 10th	Night	5% 4 32% 45% 14% 1	800
	11th to 20th	Night	5% 4 31% 47% 13%	800
	21st to end	Night	7% 5% 32% 43% 12% 1	871
April	1st to 10th	Night	11% 7% 33% 40% 9% 1	600
	11th to 20th	Night	12% 7% 30% 41% 11%	593
	21st to end	Night	12% 7% 27% 42% 13% 1	600
May	1st to 10th	Night	14% 5% 22% 37% 20% 1	600
	11th to 20th	Night	14% 4 19% 38% 23% 1	591
	21st to end	Night	12% 4 20% 40% 23% 1	650
June	1st to 10th	Night	5% 4 22% 40% 26% 3	600
	11th to 20th	Night	9% 3 25% 49% 14%	600
	21st to end	Night	4 3 17% 50% 25% 1	600
July	1st to 10th	Night	4 1 14% 48% 32% 1	570
	11th to 20th	Night	2 1 16% 55% 25% 1	552
	21st to end	Night	3 1 11% 51% 33% 2	624
August	1st to 10th	Night	3 1 13% 50% 32% 1	567
	11th to 20th	Night	2 1 13% 50% 31% 1	564
	21st to end	Night	3 2 15% 45% 34% 1	627
September	1st to 10th	Night	6% 2 16% 47% 26% 3	570
	11th to 20th	Night	5% 2 20% 44% 26% 3	610
	21st to end	Night	9% 3 16% 40% 27% 5%	760
October	1st to 10th	Night	13% 3 20% 41% 21% 3	760
	11th to 20th	Night	8% 4 24% 43% 21% 2	760
	21st to end	Night	8% 4 24% 48% 15% 1	836
November	1st to 10th	Night	4 4 30% 47% 14% 1	918
	11th to 20th	Night	5% 6% 33% 45% 11% 1	1000
	21st to end	Night	6% 3 27% 48% 14% 1	1000
December	1st to 10th	Night	4 3 31% 50% 12% 1	1000
	11th to 20th	Night	4 4 31% 50% 11% 1	1000
	21st to end	Night	6% 5% 30% 47% 11% 1	1100

Page generated at 2025-07-02 23:30:12. Version ac07

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