Beaver Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Beaver Creek 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	9% 11% 5% 12% 8% 7% 7% 5% 7% 8% 21%	106878
	Night	6% 12% 5% 14% 9% 8% 8% 6% 8% 9% 17%	101422
Transparency	Day	54% 12% 17% 13% 4	106560
	Night	53% 11% 14% 14% 6% 1	101387
Seeing	Day	14% 6% 19% 29% 24% 9%	17793
	Night	10% 3 14% 36% 28% 8%	22933

By Month

Percentage Cloud Cover NW (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 7% 6% 16% 9% 9% 12% 6% 10% 14% 12%	1465
	11th to 20th	Day	2 12% 5% 15% 9% 9% 8% 5% 8% 12% 14%	1565
	21st to end	Day	3 12% 7% 15% 9% 7% 10% 8% 9% 10% 10%	1878
February	1st to 10th	Day	2 11% 5% 12% 11% 9% 7% 7% 10% 10% 16%	1330
	11th to 20th	Day	1 12% 6% 14% 10% 10% 7% 5% 10% 8% 16%	1384
	21st to end	Day	2 10% 6% 16% 9% 7% 7% 6% 10% 10% 19%	1413
March	1st to 10th	Day	1 9% 6% 19% 12% 6% 6% 5% 6% 7% 23%	2872
	11th to 20th	Day	1 9% 6% 16% 9% 9% 6% 5% 8% 8% 23%	3480
	21st to end	Day	2 10% 4 12% 8% 7% 7% 6% 8% 8% 28%	3936
April	1st to 10th	Day	3 12% 6% 14% 7% 6% 6% 5% 8% 8% 24%	2470
	11th to 20th	Day	4 13% 5% 10% 8% 6% 6% 4 7% 8% 28%	2521
	21st to end	Day	6% 12% 5% 12% 7% 7% 7% 4 6% 7% 28%	2835
May	1st to 10th	Day	6% 11% 5% 14% 8% 7% 7% 6% 7% 8% 20%	4920
	11th to 20th	Day	9% 10% 4 11% 8% 7% 7% 5% 7% 7% 25%	5259
	21st to end	Day	16% 12% 4 9% 6% 6% 7% 5% 6% 7% 20%	5946
June	1st to 10th	Day	12% 11% 4 11% 7% 7% 6% 5% 7% 8% 22%	3479
	11th to 20th	Day	14% 10% 4 11% 8% 8% 6% 5% 6% 7% 21%	3610
	21st to end	Day	16% 9% 4 10% 7% 6% 7% 6% 8% 9% 19%	3610
July	1st to 10th	Day	16% 10% 4 11% 7% 7% 6% 5% 7% 8% 19%	5938
	11th to 20th	Day	14% 10% 4 10% 8% 6% 7% 6% 8% 9% 19%	5380
	21st to end	Day	16% 10% 4 9% 6% 6% 6% 5% 6% 9% 23%	5834
August	1st to 10th	Day	10% 7% 3 9% 7% 6% 5% 5% 6% 7% 35%	4880
	11th to 20th	Day	11% 9% 4 9% 6% 6% 6% 5% 9% 8% 29%	4654
	21st to end	Day	18% 11% 4 10% 7% 7% 7% 6% 7% 6% 17%	4743
September	1st to 10th	Day	14% 12% 4 12% 7% 6% 6% 5% 6% 6% 22%	2465
	11th to 20th	Day	10% 10% 5% 10% 7% 7% 7% 5% 7% 7% 25%	2215
	21st to end	Day	11% 16% 5% 12% 6% 5% 5% 5% 6% 7% 21%	2049
October	1st to 10th	Day	8% 12% 5% 12% 7% 7% 7% 6% 7% 8% 21%	3140
	11th to 20th	Day	5% 13% 5% 15% 7% 7% 6% 5% 6% 9% 23%	2716
	21st to end	Day	8% 19% 7% 15% 7% 7% 6% 5% 6% 7% 13%	2728
November	1st to 10th	Day	4 17% 9% 15% 8% 7% 6% 5% 8% 7% 13%	1264
	11th to 20th	Day	4 16% 7% 18% 12% 8% 7% 5% 6% 5% 11%	1190
	21st to end	Day	4 12% 6% 15% 10% 9% 9% 8% 9% 10% 8%	955
December	1st to 10th	Day	2 14% 5% 15% 11% 10% 7% 7% 8% 10% 11%	792
	11th to 20th	Day	2 12% 4 14% 8% 9% 9% 7% 10% 15% 9%	917
	21st to end	Day	2 4 4 13% 11% 11% 9% 7% 13% 12% 14%	1045
January	1st to 10th	Night	1 11% 5% 12% 9% 10% 10% 6% 11% 15% 10%	5496
	11th to 20th	Night	3 14% 5% 16% 9% 7% 7% 6% 10% 11% 11%	5333
	21st to end	Night	2 11% 6% 15% 10% 10% 10% 7% 9% 10% 9%	5781
February	1st to 10th	Night	2 9% 5% 15% 10% 8% 8% 6% 8% 9% 20%	2850
	11th to 20th	Night	1 12% 6% 12% 8% 8% 7% 7% 10% 11% 19%	2682
	21st to end	Night	2 9% 7% 17% 12% 7% 6% 4 7% 8% 22%	2041
March	1st to 10th	Night	1 7% 6% 21% 14% 9% 7% 4 5% 6% 20%	3976
	11th to 20th	Night	3 12% 8% 18% 9% 7% 7% 5% 6% 7% 19%	3478
	21st to end	Night	2 11% 5% 13% 8% 7% 8% 6% 7% 8% 25%	3682
April	1st to 10th	Night	4 12% 7% 13% 9% 6% 7% 4 7% 7% 24%	1710
	11th to 20th	Night	5% 15% 4 11% 7% 7% 7% 5% 6% 7% 27%	1608
	21st to end	Night	4 11% 4 10% 8% 7% 6% 6% 9% 10% 25%	1344
May	1st to 10th	Night	9% 10% 4 12% 9% 7% 7% 5% 6% 8% 23%	2043
	11th to 20th	Night	9% 16% 5% 11% 7% 6% 7% 4 7% 7% 18%	1634
	21st to end	Night	20% 13% 4 11% 7% 7% 6% 5% 5% 5% 16%	1628
June	1st to 10th	Night	15% 11% 4 9% 10% 7% 10% 6% 6% 6% 16%	698
	11th to 20th	Night	20% 12% 5% 12% 10% 6% 5% 5% 4 5% 17%	570
	21st to end	Night	16% 10% 5% 11% 9% 7% 6% 6% 8% 8% 15%	570
July	1st to 10th	Night	24% 11% 4 11% 6% 6% 4 4 5% 7% 17%	1029
	11th to 20th	Night	16% 9% 4 13% 7% 6% 6% 5% 8% 8% 18%	1580
	21st to end	Night	20% 8% 3 9% 6% 5% 6% 5% 6% 9% 23%	1718
August	1st to 10th	Night	12% 8% 3 9% 6% 6% 4 3 4 6% 39%	2057
	11th to 20th	Night	15% 9% 3 9% 6% 6% 6% 5% 8% 9% 23%	2184
	21st to end	Night	19% 12% 4 12% 7% 6% 7% 5% 5% 6% 18%	2922
September	1st to 10th	Night	13% 12% 4 12% 7% 6% 7% 6% 7% 7% 19%	1715
	11th to 20th	Night	11% 11% 4 13% 7% 7% 7% 4 6% 8% 23%	1962
	21st to end	Night	14% 17% 5% 12% 8% 5% 6% 5% 6% 5% 19%	2131
October	1st to 10th	Night	9% 12% 4 12% 7% 7% 7% 5% 7% 9% 22%	3827
	11th to 20th	Night	7% 13% 6% 13% 8% 7% 6% 5% 6% 7% 21%	4212
	21st to end	Night	6% 16% 6% 12% 10% 8% 7% 6% 8% 7% 15%	4831
November	1st to 10th	Night	4 16% 7% 16% 10% 8% 8% 6% 6% 7% 13%	3034
	11th to 20th	Night	4 15% 8% 18% 12% 9% 7% 5% 7% 6% 10%	3210
	21st to end	Night	4 12% 6% 15% 11% 9% 9% 8% 8% 8% 9%	3425
December	1st to 10th	Night	4 13% 6% 15% 9% 9% 8% 7% 9% 9% 12%	3571
	11th to 20th	Night	2 10% 6% 16% 11% 10% 10% 6% 9% 10% 11%	4271
	21st to end	Night	2 9% 5% 13% 10% 9% 9% 8% 10% 14% 10%	6619

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	46% 11% 13% 15% 13% 1	1465
	11th to 20th	Day	49% 13% 12% 16% 6% 3	1580
	21st to end	Day	52% 13% 17% 10% 7% 1	1878
February	1st to 10th	Day	48% 9% 12% 16% 12% 2	1330
	11th to 20th	Day	53% 11% 12% 13% 10% 1	1391
	21st to end	Day	51% 9% 15% 14% 10% 1	1413
March	1st to 10th	Day	53% 8% 11% 19% 8%	2872
	11th to 20th	Day	45% 13% 17% 14% 8% 3	3480
	21st to end	Day	40% 17% 21% 14% 7% 1	3936
April	1st to 10th	Day	52% 12% 20% 11% 4 1	2470
	11th to 20th	Day	51% 13% 14% 13% 8%	2521
	21st to end	Day	52% 11% 15% 15% 7%	2835
May	1st to 10th	Day	50% 17% 16% 13% 4 1	4920
	11th to 20th	Day	48% 14% 16% 15% 6%	5262
	21st to end	Day	56% 13% 15% 13% 2	5947
June	1st to 10th	Day	58% 14% 14% 9% 4	3479
	11th to 20th	Day	61% 13% 13% 11% 2	3610
	21st to end	Day	60% 14% 16% 10% 1	3610
July	1st to 10th	Day	61% 10% 20% 8% 1	5845
	11th to 20th	Day	59% 12% 19% 9% 1	5287
	21st to end	Day	58% 10% 21% 10%	5650
August	1st to 10th	Day	47% 10% 21% 16% 5%	4860
	11th to 20th	Day	51% 10% 18% 17% 4	4699
	21st to end	Day	64% 9% 16% 10% 1	4742
September	1st to 10th	Day	59% 11% 15% 12% 3	2465
	11th to 20th	Day	51% 14% 17% 16% 2	2215
	21st to end	Day	56% 13% 15% 14% 2	2049
October	1st to 10th	Day	55% 9% 15% 18% 3	3140
	11th to 20th	Day	55% 8% 15% 17% 5%	2716
	21st to end	Day	63% 8% 16% 11% 3	2728
November	1st to 10th	Day	59% 11% 13% 14% 3	1264
	11th to 20th	Day	67% 8% 12% 9% 4	1190
	21st to end	Day	55% 8% 16% 14% 6%	955
December	1st to 10th	Day	57% 12% 13% 13% 5%	792
	11th to 20th	Day	45% 12% 12% 19% 11% 1	919
	21st to end	Day	37% 15% 19% 12% 15% 2	1045
January	1st to 10th	Night	45% 12% 14% 20% 9% 1	5496
	11th to 20th	Night	49% 13% 12% 15% 10% 2	5380
	21st to end	Night	51% 13% 15% 12% 7% 2	5781
February	1st to 10th	Night	49% 9% 12% 16% 13% 2	2850
	11th to 20th	Night	48% 10% 13% 17% 10% 2	2686
	21st to end	Night	54% 8% 12% 16% 9% 1	2041
March	1st to 10th	Night	57% 9% 10% 14% 10%	3976
	11th to 20th	Night	51% 14% 13% 12% 8% 1	3480
	21st to end	Night	39% 17% 19% 16% 7% 1	3682
April	1st to 10th	Night	51% 11% 18% 14% 6%	1710
	11th to 20th	Night	51% 12% 14% 13% 10%	1608
	21st to end	Night	48% 14% 16% 15% 7%	1344
May	1st to 10th	Night	50% 15% 14% 16% 5%	2043
	11th to 20th	Night	51% 18% 12% 13% 6%	1634
	21st to end	Night	62% 14% 13% 9% 2	1628
June	1st to 10th	Night	63% 14% 11% 8% 4	698
	11th to 20th	Night	64% 9% 14% 12% 1	570
	21st to end	Night	64% 13% 13% 9% 1	570
July	1st to 10th	Night	65% 9% 18% 6% 2	1013
	11th to 20th	Night	61% 10% 16% 11% 2	1550
	21st to end	Night	58% 8% 22% 12%	1663
August	1st to 10th	Night	46% 7% 18% 22% 6%	2052
	11th to 20th	Night	54% 11% 13% 18% 4	2205
	21st to end	Night	66% 9% 13% 11% 1	2922
September	1st to 10th	Night	58% 13% 16% 13% 1	1715
	11th to 20th	Night	54% 12% 17% 15% 2	1962
	21st to end	Night	60% 12% 13% 12% 3	2131
October	1st to 10th	Night	57% 7% 14% 18% 4	3827
	11th to 20th	Night	58% 7% 13% 17% 4 1	4212
	21st to end	Night	59% 8% 18% 13% 2	4831
November	1st to 10th	Night	61% 9% 13% 14% 3	3034
	11th to 20th	Night	66% 9% 11% 10% 4	3210
	21st to end	Night	56% 11% 14% 15% 4	3425
December	1st to 10th	Night	56% 11% 14% 14% 5%	3571
	11th to 20th	Night	51% 12% 12% 13% 9% 3	4268
	21st to end	Night	45% 13% 13% 14% 11% 5%	6619

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 1 9% 33% 37% 16%	90
	11th to 20th	Day	3 3 8% 37% 27% 22%	90
	21st to end	Day	5% 4 15% 36% 24% 16%	183
February	1st to 10th	Day	4 2 14% 38% 28% 15%	370
	11th to 20th	Day	5% 2 25% 37% 23% 8%	365
	21st to end	Day	4 7% 27% 34% 21% 7%	307
March	1st to 10th	Day	3 4 19% 34% 28% 12%	370
	11th to 20th	Day	2 2 26% 35% 24% 10%	370
	21st to end	Day	4 5% 25% 33% 27% 6%	452
April	1st to 10th	Day	4 7% 23% 34% 27% 4	650
	11th to 20th	Day	9% 7% 21% 32% 26% 5%	640
	21st to end	Day	11% 6% 20% 31% 26% 6%	650
May	1st to 10th	Day	12% 9% 26% 29% 19% 5%	653
	11th to 20th	Day	15% 7% 20% 30% 21% 7%	675
	21st to end	Day	17% 8% 21% 29% 19% 5%	785
June	1st to 10th	Day	17% 5% 16% 28% 25% 8%	929
	11th to 20th	Day	19% 6% 18% 24% 26% 8%	1060
	21st to end	Day	19% 5% 17% 24% 26% 9%	1060
July	1st to 10th	Day	19% 4 14% 28% 27% 8%	999
	11th to 20th	Day	20% 6% 14% 26% 25% 9%	668
	21st to end	Day	20% 4 11% 26% 28% 12%	739
August	1st to 10th	Day	19% 6% 14% 25% 24% 12%	676
	11th to 20th	Day	18% 6% 20% 27% 22% 7%	665
	21st to end	Day	23% 7% 16% 27% 21% 5%	748
September	1st to 10th	Day	17% 8% 18% 24% 23% 10%	675
	11th to 20th	Day	12% 7% 21% 27% 27% 6%	455
	21st to end	Day	14% 5% 27% 25% 21% 8%	390
October	1st to 10th	Day	14% 8% 23% 26% 20% 9%	390
	11th to 20th	Day	14% 6% 17% 27% 22% 13%	390
	21st to end	Day	11% 3 16% 34% 26% 10%	429
November	1st to 10th	Day	11% 3 14% 39% 24% 9%	288
	11th to 20th	Day	10% 1 18% 31% 25% 15%	195
	21st to end	Day	5% 2 14% 40% 20% 19%	100
December	1st to 10th	Day	7% 2 13% 35% 31% 12%	98
	11th to 20th	Day	4 2 11% 39% 27% 17%	90
	21st to end	Day	2 3 16% 35% 20% 23%	99
January	1st to 10th	Night	3 1 8% 39% 38% 12%	928
	11th to 20th	Night	6% 3 13% 43% 27% 8%	850
	21st to end	Night	5% 2 14% 44% 25% 10%	935
February	1st to 10th	Night	4 2 14% 41% 32% 8%	850
	11th to 20th	Night	4 4 17% 44% 24% 7%	834
	21st to end	Night	4 1 14% 45% 28% 7%	703
March	1st to 10th	Night	3 2 17% 33% 34% 10%	811
	11th to 20th	Night	4 1 12% 37% 33% 13%	570
	21st to end	Night	5% 3 17% 30% 36% 10%	627
April	1st to 10th	Night	8% 3 18% 33% 30% 7%	570
	11th to 20th	Night	11% 4 16% 33% 28% 8%	563
	21st to end	Night	7% 3 14% 32% 37% 7%	570
May	1st to 10th	Night	14% 5% 17% 34% 25% 4	471
	11th to 20th	Night	16% 7% 19% 35% 20% 3	230
	21st to end	Night	15% 6% 21% 30% 26% 2	206
June	1st to 10th	Night	19% 4 15% 33% 27% 2	190
	11th to 20th	Night	25% 5% 17% 27% 24% 2	190
	21st to end	Night	18% 7% 14% 25% 32% 3	190
July	1st to 10th	Night	28% 3 10% 33% 25% 2	185
	11th to 20th	Night	23% 5% 13% 31% 25% 2	184
	21st to end	Night	23% 3 12% 29% 30% 2	208
August	1st to 10th	Night	21% 3 16% 27% 26% 6%	463
	11th to 20th	Night	21% 5% 15% 29% 26% 4	564
	21st to end	Night	25% 4 11% 31% 25% 4	627
September	1st to 10th	Night	17% 4 19% 31% 24% 4	570
	11th to 20th	Night	15% 5% 21% 26% 29% 5%	570
	21st to end	Night	18% 4 17% 32% 21% 8%	611
October	1st to 10th	Night	19% 5% 18% 31% 22% 5%	767
	11th to 20th	Night	17% 4 12% 33% 25% 8%	860
	21st to end	Night	11% 3 13% 36% 30% 7%	946
November	1st to 10th	Night	9% 3 14% 35% 30% 9%	880
	11th to 20th	Night	8% 2 13% 37% 28% 11%	900
	21st to end	Night	8% 2 15% 38% 25% 13%	925
December	1st to 10th	Night	7% 2 13% 41% 27% 10%	1091
	11th to 20th	Night	6% 3 12% 40% 29% 11%	1053
	21st to end	Night	4 2 12% 36% 28% 17%	1241

Page generated at 2024-12-06 00:54:50. Version ac07

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