Great Sand Dunes National Park and Preserve
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Great Sand Dunes National Park and Preserve clear sky chart from 2005-11-06 to 2024-02-20.

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 5% 5% 3 5% 5% 6% 8% 53%	78522
	Night	2 4 2 5% 5% 3 4 5% 6% 8% 57%	80728
Transparency	Day	27% 8% 13% 24% 22% 7%	78237
	Night	24% 8% 13% 26% 23% 6%	80535
Seeing	Day	13% 22% 31% 23% 9% 1	14355
	Night	8% 17% 32% 29% 13% 2	24580

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	2 2 5% 5% 4 4 5% 7% 9% 58%	2538
	11th to 20th	Day	4 3 5% 5% 3 4 4 5% 7% 60%	2828
	21st to end	Day	5% 4 8% 6% 3 3 5% 6% 8% 50%	3146
February	1st to 10th	Day	1 4 4 7% 4 3 4 4 5% 7% 57%	1712
	11th to 20th	Day	1 2 2 4 5% 3 4 4 6% 9% 59%	1839
	21st to end	Day	6% 3 6% 5% 3 4 5% 5% 8% 54%	1480
March	1st to 10th	Day	1 5% 3 5% 4 2 5% 4 6% 9% 54%	1818
	11th to 20th	Day	2 7% 3 6% 4 4 5% 5% 5% 9% 51%	1980
	21st to end	Day	1 8% 3 7% 6% 3 5% 4 5% 8% 50%	2286
April	1st to 10th	Day	3 6% 3 5% 5% 3 4 4 6% 9% 53%	2160
	11th to 20th	Day	3 7% 3 5% 6% 3 5% 6% 5% 9% 47%	2131
	21st to end	Day	3 8% 3 5% 6% 4 5% 5% 7% 8% 46%	2160
May	1st to 10th	Day	4 6% 3 6% 6% 3 5% 6% 5% 7% 47%	2171
	11th to 20th	Day	4 6% 3 7% 6% 4 6% 6% 6% 8% 42%	2414
	21st to end	Day	4 4 2 5% 5% 3 5% 4 6% 8% 54%	2724
June	1st to 10th	Day	3 3 1 3 5% 3 6% 7% 8% 10% 50%	2520
	11th to 20th	Day	2 3 1 3 4 3 5% 5% 6% 8% 60%	2520
	21st to end	Day	2 3 2 4 6% 4 6% 6% 8% 10% 50%	2520
July	1st to 10th	Day	4 4 2 5% 5% 4 7% 7% 8% 9% 45%	2520
	11th to 20th	Day	4 3 2 5% 6% 4 7% 7% 8% 9% 44%	2520
	21st to end	Day	5% 5% 3 7% 7% 5% 8% 8% 10% 10% 31%	2553
August	1st to 10th	Day	6% 5% 2 6% 6% 5% 6% 8% 9% 8% 38%	2298
	11th to 20th	Day	5% 4 1 4 5% 4 7% 6% 8% 10% 45%	2123
	21st to end	Day	4 5% 2 5% 6% 4 7% 6% 8% 10% 44%	2376
September	1st to 10th	Day	4 4 2 5% 5% 3 5% 6% 6% 8% 51%	2160
	11th to 20th	Day	4 3 1 3 4 2 4 6% 6% 6% 60%	2156
	21st to end	Day	3 2 1 4 4 3 4 3 5% 5% 65%	1976
October	1st to 10th	Day	3 6% 2 4 5% 3 4 4 5% 7% 56%	1800
	11th to 20th	Day	2 2 1 3 4 2 3 4 3 4 71%	1800
	21st to end	Day	3 5% 2 4 4 2 3 3 4 6% 64%	1980
November	1st to 10th	Day	3 1 3 3 3 3 2 4 9% 68%	1683
	11th to 20th	Day	1 3 2 2 3 2 2 4 5% 9% 66%	1710
	21st to end	Day	1 5% 2 5% 4 3 3 3 4 7% 63%	1680
December	1st to 10th	Day	1 4 2 5% 4 2 4 3 5% 8% 62%	1520
	11th to 20th	Day	1 4 2 4 4 2 4 5% 7% 11% 57%	1926
	21st to end	Day	4 3 5% 5% 3 4 5% 6% 8% 58%	2794
January	1st to 10th	Night	3 2 8% 6% 3 4 5% 5% 6% 57%	4417
	11th to 20th	Night	3 2 5% 5% 3 4 5% 5% 7% 61%	4170
	21st to end	Night	4 3 6% 6% 3 4 5% 5% 7% 55%	4521
February	1st to 10th	Night	1 6% 3 6% 4 2 3 3 4 8% 61%	2466
	11th to 20th	Night	1 6% 3 6% 4 2 3 4 5% 7% 59%	2212
	21st to end	Night	1 5% 3 6% 5% 3 4 4 5% 7% 58%	1776
March	1st to 10th	Night	1 5% 2 5% 4 2 4 4 6% 8% 59%	2138
	11th to 20th	Night	2 6% 3 5% 5% 2 4 5% 5% 9% 55%	1980
	21st to end	Night	2 5% 2 5% 5% 2 4 4 4 8% 58%	2069
April	1st to 10th	Night	2 6% 2 5% 4 3 4 4 5% 7% 59%	1800
	11th to 20th	Night	2 8% 3 4 5% 3 4 5% 5% 8% 52%	1777
	21st to end	Night	3 7% 2 5% 4 4 5% 5% 5% 8% 52%	1800
May	1st to 10th	Night	4 6% 3 6% 5% 3 6% 5% 4 6% 54%	1787
	11th to 20th	Night	7% 6% 3 5% 6% 4 5% 6% 5% 8% 46%	1478
	21st to end	Night	5% 5% 1 3 4 4 4 5% 6% 8% 54%	1552
June	1st to 10th	Night	2 3 2 4 5% 3 6% 6% 5% 9% 56%	1440
	11th to 20th	Night	1 2 1 3 3 2 4 4 6% 8% 65%	1440
	21st to end	Night	3 2 2 4 4 3 7% 7% 9% 8% 52%	1440
July	1st to 10th	Night	3 4 3 6% 8% 5% 7% 7% 7% 9% 42%	1440
	11th to 20th	Night	3 3 3 5% 5% 3 5% 7% 8% 10% 47%	1440
	21st to end	Night	5% 5% 3 5% 7% 5% 9% 9% 10% 11% 33%	1761
August	1st to 10th	Night	4 3 2 7% 6% 5% 6% 7% 8% 10% 42%	1639
	11th to 20th	Night	5% 4 3 6% 6% 4 6% 7% 8% 10% 41%	1778
	21st to end	Night	5% 4 2 5% 6% 4 7% 8% 8% 8% 43%	1980
September	1st to 10th	Night	5% 4 2 5% 6% 4 5% 6% 7% 8% 49%	1800
	11th to 20th	Night	4 3 1 4 4 2 5% 4 7% 8% 57%	1804
	21st to end	Night	3 3 1 3 3 2 3 4 6% 7% 63%	1980
October	1st to 10th	Night	3 3 2 4 4 2 4 5% 5% 8% 60%	2160
	11th to 20th	Night	1 2 1 2 2 1 3 3 4 6% 74%	2160
	21st to end	Night	3 5% 2 4 3 2 3 4 5% 5% 65%	2376
November	1st to 10th	Night	1 2 1 2 2 2 3 3 5% 7% 72%	2375
	11th to 20th	Night	1 2 2 2 2 2 3 3 4 7% 71%	2470
	21st to end	Night	2 4 2 4 4 2 4 3 5% 9% 62%	2498
December	1st to 10th	Night	1 3 3 5% 4 2 3 4 5% 8% 62%	2660
	11th to 20th	Night	1 4 2 4 4 2 4 5% 7% 9% 57%	3271
	21st to end	Night	1 4 2 5% 5% 3 5% 5% 5% 8% 58%	4873

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	21% 8% 17% 29% 22% 2	2539
	11th to 20th	Day	22% 7% 17% 31% 21% 1	2828
	21st to end	Day	29% 8% 11% 30% 19% 3	3146
February	1st to 10th	Day	26% 6% 17% 27% 18% 6%	1712
	11th to 20th	Day	22% 8% 12% 28% 25% 5%	1849
	21st to end	Day	29% 6% 9% 22% 25% 8%	1480
March	1st to 10th	Day	26% 6% 12% 24% 26% 6%	1818
	11th to 20th	Day	30% 6% 10% 27% 23% 4	1980
	21st to end	Day	32% 7% 11% 27% 19% 3	2286
April	1st to 10th	Day	29% 7% 11% 23% 21% 9%	2160
	11th to 20th	Day	33% 8% 10% 23% 20% 6%	2134
	21st to end	Day	32% 9% 13% 22% 21% 4	2160
May	1st to 10th	Day	33% 7% 11% 23% 20% 5%	2171
	11th to 20th	Day	36% 10% 14% 23% 15% 3	2418
	21st to end	Day	27% 9% 11% 19% 23% 10%	2724
June	1st to 10th	Day	25% 9% 16% 21% 20% 10%	2520
	11th to 20th	Day	20% 7% 8% 19% 24% 22%	2520
	21st to end	Day	25% 8% 12% 22% 21% 12%	2520
July	1st to 10th	Day	32% 10% 12% 16% 19% 11%	2451
	11th to 20th	Day	30% 11% 16% 26% 11% 6%	2445
	21st to end	Day	38% 16% 23% 17% 5%	2411
August	1st to 10th	Day	36% 14% 15% 15% 14% 6%	2283
	11th to 20th	Day	30% 10% 14% 21% 18% 6%	2123
	21st to end	Day	30% 10% 14% 23% 20% 3	2376
September	1st to 10th	Day	29% 9% 11% 22% 21% 9%	2160
	11th to 20th	Day	22% 8% 11% 19% 29% 11%	2156
	21st to end	Day	21% 6% 7% 25% 35% 7%	1976
October	1st to 10th	Day	28% 7% 8% 22% 26% 9%	1800
	11th to 20th	Day	18% 3 8% 22% 38% 11%	1800
	21st to end	Day	22% 4 9% 29% 29% 7%	1980
November	1st to 10th	Day	17% 4 11% 25% 36% 8%	1683
	11th to 20th	Day	15% 5% 12% 34% 28% 6%	1710
	21st to end	Day	22% 5% 9% 28% 27% 9%	1680
December	1st to 10th	Day	21% 6% 19% 29% 20% 6%	1520
	11th to 20th	Day	21% 9% 15% 28% 24% 4	1924
	21st to end	Day	24% 6% 12% 24% 26% 9%	2794
January	1st to 10th	Night	25% 7% 12% 29% 23% 3	4417
	11th to 20th	Night	21% 8% 15% 33% 19% 3	4170
	21st to end	Night	27% 7% 14% 31% 18% 3	4521
February	1st to 10th	Night	24% 5% 16% 27% 23% 5%	2466
	11th to 20th	Night	25% 6% 13% 29% 23% 4	2212
	21st to end	Night	26% 6% 9% 24% 30% 6%	1776
March	1st to 10th	Night	23% 7% 11% 26% 25% 7%	2138
	11th to 20th	Night	26% 6% 11% 28% 24% 4	1980
	21st to end	Night	26% 7% 11% 28% 25% 3	2069
April	1st to 10th	Night	25% 7% 10% 27% 23% 7%	1800
	11th to 20th	Night	28% 8% 11% 24% 24% 4	1777
	21st to end	Night	28% 7% 15% 27% 20% 3	1800
May	1st to 10th	Night	30% 7% 11% 27% 19% 6%	1787
	11th to 20th	Night	34% 10% 14% 20% 16% 5%	1479
	21st to end	Night	25% 9% 15% 20% 21% 10%	1552
June	1st to 10th	Night	23% 8% 15% 22% 18% 13%	1440
	11th to 20th	Night	16% 6% 11% 22% 24% 21%	1440
	21st to end	Night	24% 10% 13% 20% 22% 11%	1440
July	1st to 10th	Night	34% 11% 12% 16% 16% 11%	1400
	11th to 20th	Night	26% 12% 21% 25% 11% 6%	1392
	21st to end	Night	37% 19% 22% 17% 6%	1663
August	1st to 10th	Night	32% 15% 19% 15% 12% 6%	1630
	11th to 20th	Night	33% 10% 19% 21% 12% 6%	1778
	21st to end	Night	31% 11% 16% 22% 16% 4	1980
September	1st to 10th	Night	30% 9% 14% 21% 19% 8%	1800
	11th to 20th	Night	23% 8% 11% 20% 25% 12%	1804
	21st to end	Night	19% 7% 9% 24% 34% 7%	1980
October	1st to 10th	Night	23% 8% 11% 22% 28% 9%	2160
	11th to 20th	Night	13% 5% 7% 23% 41% 12%	2160
	21st to end	Night	21% 5% 7% 30% 30% 7%	2376
November	1st to 10th	Night	14% 4 11% 30% 34% 8%	2375
	11th to 20th	Night	14% 4 9% 35% 31% 7%	2470
	21st to end	Night	22% 5% 9% 25% 31% 9%	2498
December	1st to 10th	Night	20% 7% 17% 29% 22% 6%	2660
	11th to 20th	Night	22% 8% 14% 26% 26% 4	3272
	21st to end	Night	23% 8% 14% 22% 27% 6%	4873

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	19% 26% 30% 17% 7%	270
	11th to 20th	Day	17% 32% 33% 16% 3 1	270
	21st to end	Day	7% 28% 36% 21% 6% 1	297
February	1st to 10th	Day	20% 36% 30% 11% 2	270
	11th to 20th	Day	17% 42% 29% 9% 3	267
	21st to end	Day	31% 32% 25% 12%	198
March	1st to 10th	Day	24% 32% 26% 14% 4	258
	11th to 20th	Day	21% 31% 30% 13% 4	420
	21st to end	Day	27% 35% 31% 6% 1	462
April	1st to 10th	Day	24% 36% 28% 11% 1 1	420
	11th to 20th	Day	25% 39% 27% 8% 2	412
	21st to end	Day	22% 39% 28% 10% 1	420
May	1st to 10th	Day	17% 36% 32% 11% 3	434
	11th to 20th	Day	9% 24% 33% 24% 8% 1	625
	21st to end	Day	11% 25% 32% 21% 9% 1	679
June	1st to 10th	Day	6% 15% 33% 28% 16% 1	630
	11th to 20th	Day	8% 18% 36% 24% 12% 2	630
	21st to end	Day	6% 16% 33% 26% 16% 3	630
July	1st to 10th	Day	6% 7% 29% 36% 18% 4	621
	11th to 20th	Day	6% 5% 22% 40% 22% 4	618
	21st to end	Day	8% 4 26% 40% 21% 1	495
August	1st to 10th	Day	9% 8% 32% 36% 14% 2	447
	11th to 20th	Day	8% 8% 34% 35% 13% 2	437
	21st to end	Day	6% 8% 36% 36% 13% 2	495
September	1st to 10th	Day	8% 12% 34% 31% 12% 3	450
	11th to 20th	Day	6% 17% 40% 26% 9% 2	446
	21st to end	Day	7% 19% 28% 29% 13% 4	270
October	1st to 10th	Day	12% 26% 27% 22% 10% 4	270
	11th to 20th	Day	13% 24% 35% 16% 9% 3	270
	21st to end	Day	14% 28% 29% 19% 8% 2	297
November	1st to 10th	Day	16% 27% 32% 16% 7% 1	270
	11th to 20th	Day	14% 25% 32% 20% 9%	270
	21st to end	Day	10% 30% 32% 21% 7%	270
December	1st to 10th	Day	17% 28% 30% 18% 7%	270
	11th to 20th	Day	13% 33% 34% 13% 5% 1	270
	21st to end	Day	21% 32% 31% 14% 2	297
January	1st to 10th	Night	7% 19% 39% 26% 9% 1	950
	11th to 20th	Night	8% 19% 39% 24% 8% 2	794
	21st to end	Night	4 16% 40% 32% 8%	836
February	1st to 10th	Night	5% 22% 47% 21% 4	760
	11th to 20th	Night	8% 26% 44% 16% 6%	742
	21st to end	Night	10% 22% 49% 18% 1	592
March	1st to 10th	Night	10% 27% 34% 24% 5% 1	720
	11th to 20th	Night	7% 19% 39% 26% 8% 1	720
	21st to end	Night	12% 23% 40% 20% 5%	683
April	1st to 10th	Night	12% 26% 37% 23% 3	540
	11th to 20th	Night	11% 25% 32% 25% 5%	533
	21st to end	Night	11% 24% 35% 24% 6%	540
May	1st to 10th	Night	10% 19% 35% 26% 9% 1	540
	11th to 20th	Night	9% 19% 32% 27% 10% 2	531
	21st to end	Night	11% 20% 30% 25% 13% 1	584
June	1st to 10th	Night	5% 11% 29% 36% 18% 2	540
	11th to 20th	Night	3 16% 32% 34% 13% 1	540
	21st to end	Night	4 8% 24% 38% 24% 2	540
July	1st to 10th	Night	6% 3 19% 38% 30% 4	525
	11th to 20th	Night	4 2 14% 37% 38% 5%	522
	21st to end	Night	7% 2 13% 29% 44% 6%	591
August	1st to 10th	Night	7% 4 12% 38% 35% 5%	537
	11th to 20th	Night	7% 2 17% 46% 25% 4	534
	21st to end	Night	7% 2 16% 43% 28% 4	594
September	1st to 10th	Night	6% 6% 21% 39% 23% 5%	540
	11th to 20th	Night	6% 8% 24% 38% 22% 2	540
	21st to end	Night	6% 13% 23% 38% 18% 2	540
October	1st to 10th	Night	7% 19% 28% 31% 14% 2	720
	11th to 20th	Night	4 15% 36% 29% 13% 2	720
	21st to end	Night	8% 18% 28% 31% 14% 1	792
November	1st to 10th	Night	7% 18% 32% 31% 12%	895
	11th to 20th	Night	7% 17% 38% 27% 10% 1	950
	21st to end	Night	9% 20% 31% 29% 10% 1	950
December	1st to 10th	Night	8% 21% 36% 27% 7%	950
	11th to 20th	Night	8% 22% 38% 23% 8%	950
	21st to end	Night	10% 24% 39% 22% 4 1	1045

Page generated at 2024-02-17 04:28:42. Version ac07

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