Green River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Green River clear sky chart from 2005-11-06 to 2024-12-09.

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 4 2 5% 4 4 4 4 6% 8% 57%	105171
	Night	4 5% 2 5% 4 4 4 4 6% 8% 54%	103354
Transparency	Day	24% 5% 8% 21% 23% 18%	104936
	Night	28% 5% 9% 22% 21% 15%	103178
Seeing	Day	5% 6% 15% 32% 30% 13%	15145
	Night	6% 3 17% 43% 28% 3	25511

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 6% 3 8% 6% 8% 6% 6% 9% 8% 37%	2858
	11th to 20th	Day	3 5% 2 7% 7% 7% 7% 5% 6% 9% 43%	2860
	21st to end	Day	6% 8% 2 7% 5% 6% 6% 4 6% 8% 42%	3146
February	1st to 10th	Day	3 6% 2 7% 6% 6% 7% 5% 10% 10% 40%	1710
	11th to 20th	Day	5% 7% 3 6% 6% 5% 5% 4 5% 8% 47%	1665
	21st to end	Day	5% 6% 2 7% 5% 4 5% 4 7% 9% 45%	1610
March	1st to 10th	Day	3 6% 2 5% 4 5% 4 4 6% 8% 52%	3444
	11th to 20th	Day	7% 9% 3 7% 5% 4 4 4 6% 7% 44%	3490
	21st to end	Day	8% 10% 3 8% 5% 5% 5% 3 6% 7% 40%	3825
April	1st to 10th	Day	3 4 2 5% 4 4 4 3 6% 7% 58%	2171
	11th to 20th	Day	4 5% 2 5% 4 4 4 4 6% 7% 56%	2251
	21st to end	Day	3 4 1 5% 4 4 4 3 5% 7% 59%	2452
May	1st to 10th	Day	6% 4 2 5% 4 4 4 3 6% 8% 54%	4110
	11th to 20th	Day	3 3 1 4 3 4 4 4 7% 8% 59%	4071
	21st to end	Day	4 3 2 4 3 3 3 3 6% 7% 62%	4477
June	1st to 10th	Day	3 3 1 3 2 3 3 3 6% 8% 66%	2636
	11th to 20th	Day	2 3 1 2 2 3 3 3 4 5% 72%	2660
	21st to end	Day	2 2 1 2 2 3 3 4 5% 6% 71%	2563
July	1st to 10th	Day	2 2 1 2 2 2 2 2 4 6% 76%	4110
	11th to 20th	Day	1 2 1 4 3 4 6% 5% 9% 13% 51%	4110
	21st to end	Day	2 2 1 3 3 3 4 4 7% 9% 61%	4454
August	1st to 10th	Day	2 2 1 3 3 4 5% 5% 9% 11% 55%	4092
	11th to 20th	Day	2 2 1 3 3 4 4 5% 7% 8% 61%	4028
	21st to end	Day	4 2 1 3 2 3 4 4 6% 7% 63%	4309
September	1st to 10th	Day	4 2 1 2 3 2 3 3 4 6% 69%	2256
	11th to 20th	Day	3 2 1 3 3 2 4 3 4 6% 68%	2090
	21st to end	Day	5% 2 1 3 2 2 2 2 3 5% 74%	2090
October	1st to 10th	Day	4 2 1 2 1 2 2 2 2 4 79%	3212
	11th to 20th	Day	5% 3 2 5% 4 3 4 3 4 8% 59%	3150
	21st to end	Day	3 4 2 3 2 3 4 4 5% 6% 64%	3438
November	1st to 10th	Day	4 4 1 3 3 2 2 2 4 6% 67%	1924
	11th to 20th	Day	3 3 2 3 2 2 3 2 4 7% 68%	1778
	21st to end	Day	5% 4 2 5% 3 3 3 3 3 7% 62%	1600
December	1st to 10th	Day	5% 6% 2 6% 4 4 5% 3 6% 8% 51%	1584
	11th to 20th	Day	7% 7% 2 10% 8% 7% 7% 5% 6% 7% 34%	1926
	21st to end	Day	6% 9% 3 7% 5% 5% 4 5% 9% 8% 37%	3021
January	1st to 10th	Night	4 7% 3 8% 5% 6% 5% 4 6% 8% 43%	4097
	11th to 20th	Night	4 6% 2 7% 4 6% 7% 5% 6% 10% 43%	4110
	21st to end	Night	8% 8% 3 8% 5% 6% 5% 4 5% 7% 43%	4521
February	1st to 10th	Night	3 5% 3 7% 6% 5% 5% 4 6% 9% 47%	2470
	11th to 20th	Night	4 7% 3 8% 6% 5% 5% 5% 6% 8% 42%	2402
	21st to end	Night	4 6% 3 6% 5% 5% 5% 5% 6% 8% 47%	1837
March	1st to 10th	Night	6% 8% 2 6% 4 5% 5% 4 5% 8% 47%	3430
	11th to 20th	Night	7% 8% 2 7% 4 4 5% 4 5% 8% 47%	3490
	21st to end	Night	6% 8% 3 7% 5% 5% 5% 5% 6% 6% 45%	3828
April	1st to 10th	Night	4 6% 2 5% 3 5% 4 4 5% 7% 55%	2008
	11th to 20th	Night	6% 5% 2 5% 4 4 4 4 5% 5% 54%	1877
	21st to end	Night	4 5% 2 5% 2 4 5% 3 6% 8% 57%	1724
May	1st to 10th	Night	6% 6% 2 5% 4 4 5% 3 5% 7% 53%	2860
	11th to 20th	Night	3 3 2 4 4 4 5% 5% 6% 8% 57%	2834
	21st to end	Night	4 5% 2 5% 3 3 4 3 5% 7% 59%	3110
June	1st to 10th	Night	4 4 1 4 3 4 4 4 6% 7% 59%	1535
	11th to 20th	Night	4 2 1 4 3 3 4 3 5% 6% 64%	1520
	21st to end	Night	2 2 1 2 3 4 5% 3 6% 6% 66%	1607
July	1st to 10th	Night	2 2 1 2 2 3 3 3 5% 7% 69%	2860
	11th to 20th	Night	2 3 1 6% 5% 7% 7% 6% 11% 12% 40%	2860
	21st to end	Night	2 2 1 6% 5% 5% 6% 5% 8% 9% 49%	3109
August	1st to 10th	Night	2 3 1 5% 5% 6% 6% 6% 8% 10% 47%	2847
	11th to 20th	Night	4 3 2 5% 4 4 5% 4 7% 8% 55%	2811
	21st to end	Night	2 2 1 4 3 3 4 3 6% 7% 63%	3358
September	1st to 10th	Night	3 2 1 3 3 3 4 3 5% 7% 65%	1920
	11th to 20th	Night	3 3 1 4 2 3 3 3 4 6% 68%	2090
	21st to end	Night	3 2 1 3 2 2 3 2 3 4 73%	2090
October	1st to 10th	Night	4 2 1 3 2 2 2 2 3 5% 74%	3759
	11th to 20th	Night	4 3 2 5% 3 4 4 3 5% 7% 60%	3778
	21st to end	Night	4 5% 2 4 2 2 3 2 4 7% 64%	4120
November	1st to 10th	Night	3 4 2 3 2 3 3 2 4 6% 67%	2372
	11th to 20th	Night	3 3 1 3 3 2 3 3 4 6% 69%	2600
	21st to end	Night	5% 5% 2 4 4 3 3 3 5% 6% 61%	2798
December	1st to 10th	Night	4 5% 2 4 4 4 3 3 6% 7% 56%	2779
	11th to 20th	Night	5% 6% 3 7% 7% 5% 5% 5% 7% 10% 39%	3271
	21st to end	Night	7% 7% 3 7% 5% 5% 5% 5% 7% 8% 40%	4672

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	38% 10% 17% 25% 9% 1	2859
	11th to 20th	Day	36% 9% 21% 26% 5% 3	2860
	21st to end	Day	39% 6% 19% 23% 12%	3146
February	1st to 10th	Day	34% 9% 19% 23% 13% 2	1710
	11th to 20th	Day	34% 6% 14% 30% 15% 2	1674
	21st to end	Day	32% 9% 9% 27% 19% 5%	1610
March	1st to 10th	Day	26% 9% 8% 31% 21% 5%	3444
	11th to 20th	Day	38% 6% 9% 28% 15% 4	3490
	21st to end	Day	38% 8% 7% 26% 18% 3	3825
April	1st to 10th	Day	25% 5% 6% 24% 28% 13%	2171
	11th to 20th	Day	25% 5% 7% 24% 26% 13%	2254
	21st to end	Day	23% 5% 6% 23% 30% 13%	2452
May	1st to 10th	Day	24% 8% 4 17% 32% 16%	4110
	11th to 20th	Day	18% 6% 6% 21% 32% 16%	4074
	21st to end	Day	19% 5% 4 16% 35% 20%	4477
June	1st to 10th	Day	15% 4 4 16% 32% 29%	2636
	11th to 20th	Day	15% 3 4 11% 23% 45%	2660
	21st to end	Day	13% 3 2 10% 24% 48%	2563
July	1st to 10th	Day	11% 2 3 7% 13% 63%	4046
	11th to 20th	Day	21% 4 4 14% 28% 28%	4041
	21st to end	Day	18% 4 6% 17% 22% 34%	4314
August	1st to 10th	Day	21% 3 8% 26% 21% 21%	4078
	11th to 20th	Day	21% 3 9% 19% 23% 25%	4067
	21st to end	Day	20% 3 7% 19% 27% 25%	4308
September	1st to 10th	Day	17% 3 5% 12% 28% 35%	2256
	11th to 20th	Day	17% 3 8% 18% 23% 30%	2090
	21st to end	Day	16% 3 3 15% 36% 28%	2090
October	1st to 10th	Day	12% 2 4 15% 32% 35%	3212
	11th to 20th	Day	26% 2 3 25% 34% 10%	3150
	21st to end	Day	22% 3 9% 31% 30% 6%	3438
November	1st to 10th	Day	19% 3 11% 30% 30% 6%	1924
	11th to 20th	Day	18% 4 12% 39% 26% 3	1778
	21st to end	Day	26% 4 13% 34% 20% 3	1600
December	1st to 10th	Day	30% 6% 25% 25% 11% 3	1584
	11th to 20th	Day	46% 9% 16% 23% 5%	1924
	21st to end	Day	39% 8% 14% 21% 16% 1	3021
January	1st to 10th	Night	35% 9% 13% 33% 9%	4097
	11th to 20th	Night	32% 10% 20% 29% 9% 1	4110
	21st to end	Night	40% 6% 19% 24% 9% 1	4521
February	1st to 10th	Night	31% 6% 19% 27% 14% 3	2470
	11th to 20th	Night	38% 7% 8% 24% 20% 2	2403
	21st to end	Night	32% 6% 10% 26% 21% 5%	1837
March	1st to 10th	Night	35% 7% 5% 26% 20% 7%	3430
	11th to 20th	Night	34% 7% 6% 29% 18% 5%	3490
	21st to end	Night	37% 7% 6% 22% 24% 4	3828
April	1st to 10th	Night	29% 5% 6% 20% 25% 16%	2008
	11th to 20th	Night	30% 5% 5% 19% 27% 14%	1877
	21st to end	Night	24% 6% 5% 22% 30% 13%	1724
May	1st to 10th	Night	30% 7% 5% 11% 30% 18%	2860
	11th to 20th	Night	20% 9% 5% 21% 33% 12%	2835
	21st to end	Night	22% 6% 4 16% 37% 16%	3110
June	1st to 10th	Night	21% 5% 3 12% 30% 28%	1535
	11th to 20th	Night	21% 3 4 9% 18% 44%	1520
	21st to end	Night	17% 5% 3 8% 19% 48%	1607
July	1st to 10th	Night	15% 4 4 7% 9% 60%	2815
	11th to 20th	Night	30% 5% 4 12% 27% 21%	2806
	21st to end	Night	27% 5% 7% 14% 18% 30%	3011
August	1st to 10th	Night	29% 4 7% 24% 14% 21%	2838
	11th to 20th	Night	27% 4 8% 15% 19% 27%	2838
	21st to end	Night	21% 4 8% 17% 20% 31%	3358
September	1st to 10th	Night	18% 4 5% 13% 18% 41%	1920
	11th to 20th	Night	19% 4 6% 18% 21% 32%	2090
	21st to end	Night	16% 3 3 12% 29% 37%	2090
October	1st to 10th	Night	15% 2 3 11% 26% 42%	3759
	11th to 20th	Night	24% 2 5% 19% 36% 14%	3778
	21st to end	Night	22% 2 5% 32% 31% 7%	4120
November	1st to 10th	Night	21% 3 6% 25% 34% 12%	2372
	11th to 20th	Night	18% 3 7% 35% 31% 5%	2600
	21st to end	Night	26% 3 7% 30% 29% 5%	2798
December	1st to 10th	Night	27% 5% 17% 31% 17% 3	2779
	11th to 20th	Night	35% 8% 21% 27% 8% 1	3272
	21st to end	Night	38% 7% 15% 23% 15% 2	4672

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% 3 9% 41% 25% 11%	270
	11th to 20th	Day	8% 1 15% 41% 28% 7%	270
	21st to end	Day	4 3 9% 42% 31% 10%	297
February	1st to 10th	Day	7% 2 11% 51% 22% 7%	270
	11th to 20th	Day	8% 2 13% 44% 28% 5%	270
	21st to end	Day	7% 10% 15% 42% 24% 3	377
March	1st to 10th	Day	8% 9% 17% 35% 24% 7%	460
	11th to 20th	Day	8% 7% 17% 38% 23% 7%	460
	21st to end	Day	8% 13% 25% 35% 17% 2	506
April	1st to 10th	Day	6% 13% 21% 30% 23% 7%	460
	11th to 20th	Day	8% 16% 21% 33% 17% 5%	452
	21st to end	Day	6% 13% 24% 29% 22% 7%	460
May	1st to 10th	Day	7% 12% 23% 32% 21% 5%	463
	11th to 20th	Day	4 6% 22% 28% 26% 14%	488
	21st to end	Day	5% 10% 19% 29% 26% 11%	529
June	1st to 10th	Day	3 6% 15% 31% 34% 11%	656
	11th to 20th	Day	4 7% 18% 32% 30% 9%	680
	21st to end	Day	4 3 18% 35% 33% 7%	583
July	1st to 10th	Day	2 2 12% 29% 38% 17%	486
	11th to 20th	Day	2 14% 21% 39% 24%	484
	21st to end	Day	2 2 8% 22% 39% 27%	531
August	1st to 10th	Day	3 3 8% 29% 37% 21%	487
	11th to 20th	Day	4 1 9% 30% 35% 21%	477
	21st to end	Day	4 2 10% 23% 42% 19%	539
September	1st to 10th	Day	3 3 12% 19% 37% 26%	490
	11th to 20th	Day	2 6% 16% 23% 35% 18%	490
	21st to end	Day	6% 6% 12% 21% 34% 21%	490
October	1st to 10th	Day	6% 4 13% 23% 26% 27%	329
	11th to 20th	Day	5% 5% 11% 27% 34% 18%	300
	21st to end	Day	5% 6% 12% 35% 35% 8%	330
November	1st to 10th	Day	6% 6% 15% 33% 27% 14%	300
	11th to 20th	Day	1 2 11% 45% 29% 12%	300
	21st to end	Day	9% 3 11% 34% 31% 12%	300
December	1st to 10th	Day	8% 2 12% 42% 23% 13%	294
	11th to 20th	Day	6% 2 12% 40% 35% 6%	270
	21st to end	Day	12% 5% 15% 43% 19% 7%	297
January	1st to 10th	Night	8% 3 11% 47% 26% 6%	760
	11th to 20th	Night	8% 2 14% 44% 28% 4	760
	21st to end	Night	9% 1 15% 48% 23% 4	836
February	1st to 10th	Night	5% 1 18% 52% 20% 3	760
	11th to 20th	Night	6% 2 19% 51% 19% 2	744
	21st to end	Night	5% 4 23% 52% 15% 1	628
March	1st to 10th	Night	7% 3 23% 45% 21% 1	760
	11th to 20th	Night	5% 4 18% 46% 25% 1	760
	21st to end	Night	6% 6% 27% 45% 16% 1	836
April	1st to 10th	Night	6% 7% 27% 40% 18% 1	678
	11th to 20th	Night	8% 7% 30% 38% 16% 1	563
	21st to end	Night	5% 8% 28% 35% 22% 3	570
May	1st to 10th	Night	6% 7% 28% 42% 16% 2	570
	11th to 20th	Night	5% 3 19% 43% 26% 4	561
	21st to end	Night	5% 7% 23% 38% 25% 2	617
June	1st to 10th	Night	4 5% 17% 44% 29% 1	570
	11th to 20th	Night	4 4 24% 45% 22% 1	570
	21st to end	Night	2 3 16% 47% 31% 1	570
July	1st to 10th	Night	4 1 12% 37% 43% 3	555
	11th to 20th	Night	2 1 6% 36% 49% 5%	552
	21st to end	Night	2 1 4 33% 56% 5%	624
August	1st to 10th	Night	4 1 8% 38% 45% 4	567
	11th to 20th	Night	4 1 11% 41% 41% 3	564
	21st to end	Night	3 1 9% 38% 44% 5%	627
September	1st to 10th	Night	5% 1 11% 36% 42% 5%	590
	11th to 20th	Night	4 1 13% 39% 38% 5%	760
	21st to end	Night	4 2 16% 31% 39% 8%	760
October	1st to 10th	Night	7% 2 16% 42% 28% 5%	760
	11th to 20th	Night	5% 2 15% 42% 32% 4	760
	21st to end	Night	7% 3 17% 36% 32% 4	836
November	1st to 10th	Night	4 3 14% 45% 31% 3	780
	11th to 20th	Night	4 2 16% 48% 26% 5%	800
	21st to end	Night	7% 4 15% 41% 28% 5%	998
December	1st to 10th	Night	5% 2 14% 51% 24% 4	993
	11th to 20th	Night	8% 2 16% 47% 25% 2	950
	21st to end	Night	11% 3 15% 48% 20% 2	922

Page generated at 2024-12-06 01:54:49. Version ac07

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