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 2026-10-29.

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	3 4 2 4 3 4 5% 4 7% 10% 53%	158925
	Night	4 5% 2 5% 4 4 5% 4 7% 9% 50%	150789
Transparency	Day	24% 6% 12% 27% 21% 10%	153731
	Night	27% 6% 14% 28% 18% 8%	146992
Seeing	Day	6% 6% 20% 35% 24% 8%	18472
	Night	6% 4 26% 46% 17% 1	28494

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	3 2 8% 6% 6% 7% 6% 11% 13% 36%	4720
	11th to 20th	Day	4 2 6% 5% 5% 5% 5% 8% 12% 47%	5096
	21st to end	Day	3 2 6% 4 5% 7% 7% 11% 14% 41%	5844
February	1st to 10th	Day	1 6% 2 7% 5% 4 6% 5% 8% 10% 44%	1890
	11th to 20th	Day	2 5% 3 8% 5% 5% 5% 6% 8% 10% 43%	1845
	21st to end	Day	1 4 3 5% 5% 5% 6% 4 7% 10% 50%	1646
March	1st to 10th	Day	2 6% 2 4 3 4 5% 5% 9% 12% 48%	4990
	11th to 20th	Day	2 7% 2 5% 3 4 5% 4 6% 9% 52%	5110
	21st to end	Day	4 7% 3 7% 5% 5% 5% 5% 7% 11% 41%	5637
April	1st to 10th	Day	5% 7% 2 5% 4 4 4 5% 6% 10% 48%	2520
	11th to 20th	Day	6% 7% 3 7% 4 4 5% 4 7% 9% 43%	2491
	21st to end	Day	9% 8% 3 6% 6% 5% 5% 4 6% 8% 39%	2693
May	1st to 10th	Day	8% 8% 2 6% 3 4 5% 4 6% 7% 49%	7703
	11th to 20th	Day	8% 5% 1 4 3 4 4 4 6% 9% 52%	8191
	21st to end	Day	6% 5% 2 5% 4 4 5% 5% 8% 10% 46%	9026
June	1st to 10th	Day	4 3 2 4 4 3 5% 4 7% 10% 54%	2940
	11th to 20th	Day	4 3 1 4 3 3 4 4 6% 8% 60%	2940
	21st to end	Day	2 3 1 3 3 3 4 4 7% 8% 64%	2940
July	1st to 10th	Day	1 2 1 2 2 3 4 4 7% 9% 65%	8249
	11th to 20th	Day	1 2 1 3 3 3 4 4 7% 9% 66%	8250
	21st to end	Day	2 2 1 3 3 4 6% 5% 8% 10% 56%	8504
August	1st to 10th	Day	2 2 1 3 3 3 4 4 6% 7% 66%	7549
	11th to 20th	Day	2 2 1 4 3 3 5% 5% 7% 10% 58%	7565
	21st to end	Day	2 2 1 4 3 3 5% 4 8% 10% 56%	7924
September	1st to 10th	Day	3 3 1 3 3 3 3 3 5% 7% 66%	2520
	11th to 20th	Day	5% 2 1 3 3 2 4 3 5% 8% 64%	2473
	21st to end	Day	6% 3 1 4 2 2 3 3 5% 5% 66%	2237
October	1st to 10th	Day	5% 3 1 3 2 2 2 2 4 5% 71%	3370
	11th to 20th	Day	7% 5% 2 4 3 3 3 2 4 6% 60%	3350
	21st to end	Day	6% 5% 2 5% 3 3 3 3 5% 8% 56%	3628
November	1st to 10th	Day	2 4 2 5% 3 4 4 5% 6% 9% 56%	1826
	11th to 20th	Day	2 4 2 4 4 4 6% 5% 7% 9% 53%	1680
	21st to end	Day	1 7% 3 6% 4 3 5% 5% 5% 10% 51%	1680
December	1st to 10th	Day	1 3 2 4 3 3 4 4 9% 10% 58%	2700
	11th to 20th	Day	1 4 2 5% 4 4 5% 5% 8% 12% 48%	3106
	21st to end	Day	2 7% 3 7% 4 5% 5% 5% 10% 13% 38%	4092
January	1st to 10th	Night	1 8% 3 6% 5% 5% 7% 6% 9% 13% 37%	8201
	11th to 20th	Night	1 4 3 9% 5% 5% 5% 4 9% 13% 42%	7950
	21st to end	Night	1 4 2 7% 5% 5% 7% 8% 12% 14% 36%	8370
February	1st to 10th	Night	2 6% 3 8% 5% 4 6% 4 7% 9% 47%	2730
	11th to 20th	Night	2 5% 3 7% 5% 6% 7% 5% 8% 9% 44%	2662
	21st to end	Night	1 6% 3 7% 4 4 4 4 7% 8% 50%	2160
March	1st to 10th	Night	3 9% 3 6% 3 5% 5% 5% 6% 8% 48%	5106
	11th to 20th	Night	3 8% 2 6% 3 4 4 4 6% 9% 51%	5110
	21st to end	Night	5% 8% 3 7% 5% 4 6% 4 7% 9% 42%	5576
April	1st to 10th	Night	6% 7% 2 5% 4 4 4 4 6% 8% 49%	2100
	11th to 20th	Night	7% 9% 3 7% 5% 5% 5% 4 6% 8% 41%	2077
	21st to end	Night	9% 10% 3 6% 4 4 4 4 6% 8% 42%	1922
May	1st to 10th	Night	13% 8% 2 6% 3 4 4 3 4 6% 46%	5229
	11th to 20th	Night	10% 6% 2 5% 4 4 4 4 6% 8% 47%	4701
	21st to end	Night	8% 5% 2 5% 5% 5% 5% 5% 7% 9% 45%	5181
June	1st to 10th	Night	4 4 1 4 4 4 4 4 6% 9% 55%	1680
	11th to 20th	Night	7% 3 1 4 4 3 4 3 6% 8% 56%	1680
	21st to end	Night	4 3 1 4 2 2 3 3 5% 7% 67%	1680
July	1st to 10th	Night	2 2 1 4 3 4 5% 4 8% 9% 59%	4740
	11th to 20th	Night	1 1 1 3 3 3 5% 5% 7% 10% 59%	4740
	21st to end	Night	3 3 1 4 3 3 4 3 6% 10% 60%	5601
August	1st to 10th	Night	2 2 1 3 3 3 3 3 5% 6% 69%	5273
	11th to 20th	Night	2 2 1 4 3 4 5% 4 7% 9% 59%	5291
	21st to end	Night	3 4 2 5% 4 4 5% 4 6% 11% 53%	6290
September	1st to 10th	Night	4 3 1 4 3 3 4 4 4 7% 63%	2100
	11th to 20th	Night	5% 3 2 3 3 3 3 4 6% 7% 59%	2144
	21st to end	Night	7% 3 1 3 2 3 2 2 4 6% 66%	2382
October	1st to 10th	Night	6% 4 1 3 2 2 2 2 3 4 71%	4040
	11th to 20th	Night	7% 4 2 5% 3 4 3 3 5% 7% 57%	4018
	21st to end	Night	6% 7% 2 5% 3 4 4 3 5% 8% 52%	4348
November	1st to 10th	Night	3 4 2 5% 4 3 4 5% 7% 9% 54%	2668
	11th to 20th	Night	2 5% 2 5% 5% 5% 5% 5% 7% 8% 51%	2940
	21st to end	Night	3 7% 3 6% 4 4 4 4 6% 8% 52%	2940
December	1st to 10th	Night	1 4 2 5% 3 3 3 3 7% 10% 58%	4710
	11th to 20th	Night	1 4 2 6% 4 4 4 4 7% 12% 52%	5321
	21st to end	Night	2 7% 3 7% 4 5% 5% 5% 10% 14% 38%	7128

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	32% 8% 21% 29% 9%	4723
	11th to 20th	Day	26% 8% 20% 28% 15% 3	5096
	21st to end	Day	24% 11% 19% 33% 13% 1	5844
February	1st to 10th	Day	31% 7% 18% 30% 12% 2	1890
	11th to 20th	Day	32% 7% 19% 26% 13% 3	1854
	21st to end	Day	26% 5% 19% 27% 19% 3	1646
March	1st to 10th	Day	23% 6% 12% 35% 16% 8%	4990
	11th to 20th	Day	26% 6% 16% 33% 18% 1	5110
	21st to end	Day	33% 8% 18% 31% 10% 1	5637
April	1st to 10th	Day	30% 7% 18% 28% 14% 2	2520
	11th to 20th	Day	33% 6% 14% 27% 18% 1	2494
	21st to end	Day	39% 7% 12% 26% 15% 1	2693
May	1st to 10th	Day	32% 6% 13% 27% 19% 4	7703
	11th to 20th	Day	27% 6% 9% 27% 24% 7%	8195
	21st to end	Day	28% 6% 13% 34% 16% 2	9027
June	1st to 10th	Day	23% 7% 16% 27% 21% 6%	2940
	11th to 20th	Day	20% 6% 12% 22% 26% 14%	2940
	21st to end	Day	16% 5% 9% 24% 30% 17%	2940
July	1st to 10th	Day	14% 4 5% 21% 31% 25%	8181
	11th to 20th	Day	14% 4 7% 21% 29% 26%	8175
	21st to end	Day	19% 5% 9% 20% 25% 22%	8316
August	1st to 10th	Day	16% 4 6% 17% 25% 33%	5978
	11th to 20th	Day	22% 5% 9% 24% 29% 11%	5964
	21st to end	Day	17% 4 11% 24% 27% 17%	6215
September	1st to 10th	Day	19% 3 8% 19% 32% 18%	2520
	11th to 20th	Day	19% 4 8% 28% 26% 15%	2473
	21st to end	Day	19% 4 7% 29% 32% 9%	2237
October	1st to 10th	Day	18% 4 7% 21% 28% 22%	3370
	11th to 20th	Day	26% 3 8% 32% 24% 7%	3350
	21st to end	Day	26% 4 11% 36% 20% 3	3628
November	1st to 10th	Day	24% 6% 16% 29% 21% 4	1826
	11th to 20th	Day	24% 7% 17% 32% 17% 4	1680
	21st to end	Day	28% 5% 18% 29% 18% 2	1680
December	1st to 10th	Day	19% 6% 19% 39% 16% 1	2700
	11th to 20th	Day	25% 7% 25% 32% 9% 2	3104
	21st to end	Day	33% 6% 14% 32% 15% 1	4092
January	1st to 10th	Night	34% 7% 20% 29% 10% 1	8202
	11th to 20th	Night	30% 9% 19% 29% 11% 3	7950
	21st to end	Night	27% 10% 20% 29% 14% 1	8370
February	1st to 10th	Night	31% 7% 18% 30% 12% 2	2730
	11th to 20th	Night	31% 9% 16% 28% 13% 2	2663
	21st to end	Night	29% 5% 17% 26% 20% 3	2160
March	1st to 10th	Night	30% 5% 12% 29% 16% 8%	5106
	11th to 20th	Night	28% 4 15% 35% 17% 1	5110
	21st to end	Night	36% 7% 20% 28% 8% 1	5576
April	1st to 10th	Night	33% 6% 15% 28% 14% 4	2100
	11th to 20th	Night	39% 7% 13% 22% 17% 1	2077
	21st to end	Night	39% 5% 11% 29% 15% 1	1922
May	1st to 10th	Night	37% 4 10% 29% 17% 3	5227
	11th to 20th	Night	32% 5% 11% 25% 17% 10%	4702
	21st to end	Night	33% 5% 12% 39% 10% 1	5182
June	1st to 10th	Night	23% 8% 18% 25% 19% 7%	1680
	11th to 20th	Night	24% 6% 10% 19% 26% 14%	1680
	21st to end	Night	16% 5% 8% 21% 31% 20%	1680
July	1st to 10th	Night	20% 5% 8% 22% 30% 16%	4700
	11th to 20th	Night	17% 5% 7% 19% 26% 26%	4692
	21st to end	Night	19% 4 9% 23% 25% 19%	5477
August	1st to 10th	Night	15% 3 5% 21% 22% 33%	4168
	11th to 20th	Night	23% 6% 14% 25% 22% 11%	4168
	21st to end	Night	17% 4 14% 25% 19% 20%	4930
September	1st to 10th	Night	21% 4 8% 17% 30% 20%	2100
	11th to 20th	Night	22% 5% 9% 23% 27% 14%	2144
	21st to end	Night	20% 4 8% 26% 31% 11%	2382
October	1st to 10th	Night	18% 4 6% 20% 34% 18%	4040
	11th to 20th	Night	27% 3 8% 29% 25% 7%	4018
	21st to end	Night	29% 4 9% 32% 19% 7%	4348
November	1st to 10th	Night	24% 7% 16% 30% 20% 4	2668
	11th to 20th	Night	29% 6% 13% 34% 16% 3	2940
	21st to end	Night	29% 6% 15% 32% 16% 2	2940
December	1st to 10th	Night	21% 5% 17% 39% 17% 2	4710
	11th to 20th	Night	24% 6% 19% 38% 10% 2	5322
	21st to end	Night	31% 7% 15% 30% 14% 3	7128

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	4 3 20% 45% 22% 5%	330
	11th to 20th	Day	3 5% 20% 44% 24% 5%	330
	21st to end	Day	4 3 16% 50% 21% 6%	363
February	1st to 10th	Day	2 4 36% 42% 13% 2	330
	11th to 20th	Day	2 4 25% 47% 19% 3	330
	21st to end	Day	2 7% 21% 47% 19% 3	273
March	1st to 10th	Day	7% 9% 27% 40% 14% 3	503
	11th to 20th	Day	7% 11% 28% 36% 15% 2	540
	21st to end	Day	9% 12% 28% 33% 15% 2	594
April	1st to 10th	Day	8% 14% 25% 32% 16% 6%	540
	11th to 20th	Day	10% 15% 29% 30% 14% 2	532
	21st to end	Day	14% 14% 21% 26% 20% 4	540
May	1st to 10th	Day	13% 12% 22% 26% 18% 8%	569
	11th to 20th	Day	14% 6% 18% 32% 23% 7%	775
	21st to end	Day	12% 5% 20% 27% 25% 11%	844
June	1st to 10th	Day	4 6% 21% 30% 28% 10%	780
	11th to 20th	Day	6% 7% 23% 35% 22% 6%	780
	21st to end	Day	3 5% 19% 38% 28% 7%	780
July	1st to 10th	Day	3 2 13% 34% 35% 12%	771
	11th to 20th	Day	3 2 12% 37% 35% 11%	768
	21st to end	Day	3 3 16% 31% 33% 14%	692
August	1st to 10th	Day	4 3 16% 34% 30% 12%	567
	11th to 20th	Day	2 3 15% 33% 33% 14%	557
	21st to end	Day	4 4 16% 30% 31% 15%	627
September	1st to 10th	Day	4 4 17% 33% 28% 14%	570
	11th to 20th	Day	5% 7% 20% 30% 26% 13%	570
	21st to end	Day	8% 5% 14% 28% 29% 15%	497
October	1st to 10th	Day	9% 5% 12% 27% 30% 17%	360
	11th to 20th	Day	7% 6% 23% 29% 23% 12%	360
	21st to end	Day	7% 5% 20% 40% 23% 6%	387
November	1st to 10th	Day	5% 6% 23% 41% 20% 6%	330
	11th to 20th	Day	5% 5% 22% 41% 22% 6%	330
	21st to end	Day	5% 3 19% 42% 26% 5%	330
December	1st to 10th	Day	2 2 20% 52% 19% 5%	330
	11th to 20th	Day	7% 3 21% 48% 18% 3	330
	21st to end	Day	4 6% 20% 48% 16% 6%	363
January	1st to 10th	Night	3 4 29% 48% 15% 2	1050
	11th to 20th	Night	3 4 33% 45% 13% 2	945
	21st to end	Night	4 3 27% 51% 14% 1	924
February	1st to 10th	Night	5% 4 35% 44% 11%	840
	11th to 20th	Night	3 4 29% 50% 13% 2	824
	21st to end	Night	3 5% 37% 45% 10% 1	692
March	1st to 10th	Night	5% 4 32% 45% 13% 1	840
	11th to 20th	Night	5% 4 33% 45% 13%	840
	21st to end	Night	7% 5% 33% 43% 11% 1	915
April	1st to 10th	Night	11% 7% 32% 40% 9%	630
	11th to 20th	Night	12% 6% 30% 41% 11%	623
	21st to end	Night	12% 7% 27% 41% 12% 1	630
May	1st to 10th	Night	14% 5% 22% 38% 20% 1	630
	11th to 20th	Night	14% 4 20% 38% 23% 1	621
	21st to end	Night	12% 4 20% 41% 22% 1	683
June	1st to 10th	Night	5% 4 22% 41% 25% 3	630
	11th to 20th	Night	8% 3 26% 49% 14%	630
	21st to end	Night	4 3 18% 49% 24% 1	630
July	1st to 10th	Night	4 1 14% 50% 30% 1	615
	11th to 20th	Night	2 1 15% 57% 24% 1	612
	21st to end	Night	3 1 12% 52% 31% 1	690
August	1st to 10th	Night	3 1 15% 51% 30% 1	627
	11th to 20th	Night	3 1 12% 52% 30% 1	624
	21st to end	Night	3 2 15% 46% 32% 1	693
September	1st to 10th	Night	6% 2 16% 47% 25% 2	630
	11th to 20th	Night	6% 2 20% 45% 24% 3	674
	21st to end	Night	8% 3 16% 40% 28% 5%	840
October	1st to 10th	Night	12% 2 19% 43% 21% 3	840
	11th to 20th	Night	8% 4 25% 41% 20% 2	840
	21st to end	Night	7% 4 25% 47% 15% 1	912
November	1st to 10th	Night	4 4 30% 47% 13% 1	965
	11th to 20th	Night	4 6% 32% 45% 11% 1	1050
	21st to end	Night	6% 3 27% 48% 14% 1	1050
December	1st to 10th	Night	4 3 32% 49% 12% 1	1050
	11th to 20th	Night	4 4 32% 49% 10%	1050
	21st to end	Night	6% 5% 31% 46% 10% 1	1155

Page generated at 2026-10-26 02:37:48. Version ac07

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