Devils Tower National Monument
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Devils Tower National Monument clear sky chart from 2005-11-06 to 2024-12-06.

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	8% 7% 2 6% 4 4 4 4 5% 7% 49%	105567
	Night	7% 8% 3 6% 4 4 4 4 5% 7% 47%	102860
Transparency	Day	33% 5% 13% 27% 18% 4	105310
	Night	35% 5% 13% 26% 17% 4	102707
Seeing	Day	13% 14% 34% 27% 10% 2	16023
	Night	13% 12% 35% 32% 9% 1	26063

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	4 10% 4 8% 5% 5% 4 4 6% 9% 41%	2538
	11th to 20th	Day	4 10% 5% 8% 5% 6% 7% 5% 6% 8% 36%	2540
	21st to end	Day	3 9% 4 7% 4 4 4 3 4 6% 50%	2862
February	1st to 10th	Day	7% 16% 7% 10% 7% 5% 4 4 4 5% 31%	1710
	11th to 20th	Day	7% 14% 4 10% 5% 4 5% 3 5% 7% 38%	1738
	21st to end	Day	6% 13% 5% 8% 6% 4 4 4 7% 8% 37%	1570
March	1st to 10th	Day	3 12% 3 7% 4 3 4 3 4 7% 49%	3130
	11th to 20th	Day	6% 8% 2 5% 4 3 3 4 6% 7% 51%	3358
	21st to end	Day	13% 13% 3 10% 6% 4 4 4 5% 6% 32%	4098
April	1st to 10th	Day	12% 11% 4 6% 4 3 4 4 6% 7% 39%	2280
	11th to 20th	Day	14% 14% 4 8% 4 4 5% 4 6% 7% 32%	2251
	21st to end	Day	17% 12% 2 6% 4 4 3 3 6% 7% 36%	2365
May	1st to 10th	Day	18% 12% 3 6% 4 4 4 3 6% 7% 33%	4389
	11th to 20th	Day	13% 6% 2 6% 4 4 4 4 6% 8% 43%	4388
	21st to end	Day	13% 7% 3 6% 4 4 5% 4 6% 9% 40%	4825
June	1st to 10th	Day	9% 4 2 4 4 4 5% 5% 6% 9% 49%	2660
	11th to 20th	Day	10% 4 2 5% 3 4 5% 5% 7% 9% 47%	2660
	21st to end	Day	7% 3 1 4 2 3 4 3 5% 8% 61%	2660
July	1st to 10th	Day	5% 5% 2 5% 3 4 5% 4 6% 8% 55%	4430
	11th to 20th	Day	2 2 1 3 3 3 3 4 5% 8% 67%	4430
	21st to end	Day	2 2 1 3 3 3 5% 4 6% 9% 61%	4802
August	1st to 10th	Day	6% 5% 1 5% 4 4 5% 4 6% 9% 52%	4411
	11th to 20th	Day	6% 4 2 5% 3 4 4 4 6% 8% 54%	3890
	21st to end	Day	3 3 1 3 3 3 2 3 5% 7% 68%	4180
September	1st to 10th	Day	7% 4 1 3 2 2 3 3 4 7% 65%	2280
	11th to 20th	Day	8% 4 1 4 3 3 3 3 4 6% 60%	2254
	21st to end	Day	10% 6% 2 4 3 3 2 3 4 5% 60%	2090
October	1st to 10th	Day	8% 4 1 3 3 3 3 2 4 5% 65%	3176
	11th to 20th	Day	10% 6% 2 3 2 3 3 2 5% 5% 59%	3150
	21st to end	Day	11% 9% 2 5% 3 3 3 3 5% 7% 48%	3109
November	1st to 10th	Day	8% 8% 3 5% 5% 4 4 4 6% 8% 46%	1763
	11th to 20th	Day	6% 11% 3 7% 5% 3 4 3 5% 7% 46%	1700
	21st to end	Day	5% 9% 3 7% 4 4 5% 4 5% 7% 46%	1600
December	1st to 10th	Day	6% 12% 4 9% 6% 4 4 3 5% 7% 40%	1560
	11th to 20th	Day	4 7% 3 7% 4 3 4 5% 7% 9% 47%	1926
	21st to end	Day	5% 9% 4 11% 5% 5% 5% 3 4 6% 43%	2794
January	1st to 10th	Night	4 13% 4 8% 5% 5% 4 4 5% 7% 43%	4417
	11th to 20th	Night	5% 11% 3 9% 7% 5% 7% 5% 6% 6% 35%	4430
	21st to end	Night	4 10% 4 7% 5% 4 4 3 6% 8% 47%	4832
February	1st to 10th	Night	8% 16% 6% 10% 6% 4 4 4 5% 6% 33%	2470
	11th to 20th	Night	6% 13% 5% 11% 5% 4 4 4 6% 7% 36%	2327
	21st to end	Night	5% 13% 3 8% 6% 4 4 3 6% 8% 39%	1884
March	1st to 10th	Night	5% 10% 4 7% 5% 4 4 3 5% 8% 45%	3734
	11th to 20th	Night	6% 7% 3 6% 4 4 4 3 4 9% 50%	3614
	21st to end	Night	10% 13% 4 9% 6% 5% 5% 5% 6% 8% 30%	3545
April	1st to 10th	Night	15% 10% 3 4 4 5% 3 4 6% 7% 39%	1900
	11th to 20th	Night	13% 11% 3 8% 5% 4 4 3 5% 6% 38%	1877
	21st to end	Night	12% 11% 3 5% 5% 4 4 4 5% 7% 39%	1814
May	1st to 10th	Night	18% 11% 3 5% 3 3 4 3 4 6% 41%	2578
	11th to 20th	Night	9% 9% 2 5% 3 3 4 4 7% 10% 43%	2517
	21st to end	Night	17% 9% 2 4 4 3 4 4 6% 7% 40%	2762
June	1st to 10th	Night	9% 5% 2 6% 3 4 3 3 7% 10% 48%	1520
	11th to 20th	Night	11% 4 2 6% 5% 5% 4 3 6% 7% 46%	1520
	21st to end	Night	6% 3 1 4 4 3 5% 4 6% 8% 57%	1520
July	1st to 10th	Night	4 4 1 4 4 2 4 4 6% 8% 59%	2540
	11th to 20th	Night	3 3 1 3 3 3 4 4 7% 10% 57%	2540
	21st to end	Night	3 4 2 4 3 3 4 3 6% 8% 61%	2761
August	1st to 10th	Night	5% 4 2 6% 5% 5% 5% 4 8% 8% 51%	2528
	11th to 20th	Night	6% 3 1 4 3 4 4 4 8% 12% 52%	2942
	21st to end	Night	4 4 1 4 3 4 5% 3 5% 6% 61%	3487
September	1st to 10th	Night	7% 4 1 3 3 2 4 3 4 7% 62%	1900
	11th to 20th	Night	8% 4 2 4 3 3 4 4 6% 6% 57%	1925
	21st to end	Night	10% 4 1 4 3 3 3 3 4 7% 59%	2090
October	1st to 10th	Night	9% 5% 1 3 2 2 2 2 3 5% 67%	3790
	11th to 20th	Night	10% 5% 1 4 3 3 4 3 5% 6% 56%	3778
	21st to end	Night	10% 7% 2 5% 4 4 4 3 5% 7% 51%	4405
November	1st to 10th	Night	9% 7% 3 5% 4 3 4 4 6% 9% 45%	2535
	11th to 20th	Night	8% 10% 3 7% 4 4 4 3 5% 8% 45%	2697
	21st to end	Night	6% 9% 3 5% 4 4 4 4 5% 8% 48%	2800
December	1st to 10th	Night	5% 12% 5% 10% 6% 5% 4 3 5% 7% 40%	2737
	11th to 20th	Night	3 8% 3 8% 4 5% 4 5% 6% 8% 47%	3271
	21st to end	Night	7% 10% 3 9% 5% 4 4 3 4 6% 43%	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	39% 5% 17% 29% 9% 1	2539
	11th to 20th	Day	45% 5% 14% 24% 9% 3	2540
	21st to end	Day	35% 5% 17% 29% 13% 1	2862
February	1st to 10th	Day	56% 5% 10% 19% 9% 1	1710
	11th to 20th	Day	46% 6% 14% 22% 10% 2	1747
	21st to end	Day	44% 5% 13% 22% 12% 3	1570
March	1st to 10th	Day	34% 5% 10% 26% 22% 2	3130
	11th to 20th	Day	30% 6% 22% 33% 9% 1	3358
	21st to end	Day	52% 6% 18% 21% 4	4098
April	1st to 10th	Day	43% 6% 16% 24% 10% 2	2280
	11th to 20th	Day	51% 6% 13% 20% 10% 1	2254
	21st to end	Day	47% 5% 14% 25% 9% 1	2365
May	1st to 10th	Day	50% 6% 12% 21% 11% 1	4389
	11th to 20th	Day	36% 7% 13% 30% 14% 1	4392
	21st to end	Day	38% 8% 15% 30% 8% 1	4825
June	1st to 10th	Day	30% 8% 22% 26% 12% 2	2660
	11th to 20th	Day	32% 6% 17% 27% 17% 2	2660
	21st to end	Day	21% 6% 15% 29% 22% 7%	2660
July	1st to 10th	Day	24% 6% 10% 31% 24% 5%	4361
	11th to 20th	Day	14% 5% 8% 30% 30% 13%	4355
	21st to end	Day	17% 5% 8% 25% 31% 14%	4651
August	1st to 10th	Day	27% 7% 12% 23% 20% 12%	4396
	11th to 20th	Day	26% 5% 11% 29% 24% 4	3929
	21st to end	Day	16% 4 10% 25% 36% 10%	4179
September	1st to 10th	Day	21% 4 8% 27% 30% 10%	2280
	11th to 20th	Day	25% 5% 9% 28% 26% 7%	2254
	21st to end	Day	28% 3 10% 32% 24% 3	2090
October	1st to 10th	Day	24% 2 7% 21% 32% 14%	3176
	11th to 20th	Day	28% 3 11% 29% 26% 2	3150
	21st to end	Day	36% 4 12% 29% 17% 2	3109
November	1st to 10th	Day	36% 6% 11% 23% 21% 3	1763
	11th to 20th	Day	38% 4 13% 26% 16% 3	1700
	21st to end	Day	35% 6% 17% 27% 14% 2	1600
December	1st to 10th	Day	43% 5% 15% 22% 12% 1	1560
	11th to 20th	Day	31% 5% 23% 34% 6% 1	1924
	21st to end	Day	42% 4 7% 27% 16% 3	2794
January	1st to 10th	Night	41% 5% 12% 32% 9% 1	4417
	11th to 20th	Night	48% 6% 12% 20% 11% 2	4430
	21st to end	Night	36% 4 20% 27% 12% 1	4832
February	1st to 10th	Night	52% 5% 13% 19% 10% 1	2470
	11th to 20th	Night	47% 5% 13% 22% 12% 2	2328
	21st to end	Night	42% 5% 13% 23% 13% 4	1884
March	1st to 10th	Night	36% 6% 11% 28% 18% 2	3734
	11th to 20th	Night	33% 5% 22% 25% 13% 2	3614
	21st to end	Night	50% 7% 18% 19% 6%	3545
April	1st to 10th	Night	43% 8% 14% 24% 10% 2	1900
	11th to 20th	Night	47% 4 10% 26% 12% 1	1877
	21st to end	Night	44% 5% 13% 27% 10% 1	1814
May	1st to 10th	Night	45% 5% 11% 22% 16%	2578
	11th to 20th	Night	36% 6% 15% 33% 10%	2518
	21st to end	Night	42% 7% 13% 32% 6%	2762
June	1st to 10th	Night	32% 6% 23% 26% 12% 1	1520
	11th to 20th	Night	37% 5% 18% 23% 14% 3	1520
	21st to end	Night	24% 6% 15% 28% 23% 5%	1520
July	1st to 10th	Night	21% 5% 13% 33% 24% 4	2500
	11th to 20th	Night	20% 5% 10% 32% 27% 6%	2492
	21st to end	Night	21% 5% 9% 28% 31% 7%	2674
August	1st to 10th	Night	28% 7% 12% 23% 20% 10%	2520
	11th to 20th	Night	24% 5% 16% 30% 20% 5%	2969
	21st to end	Night	22% 5% 10% 20% 32% 11%	3487
September	1st to 10th	Night	23% 4 6% 28% 27% 12%	1900
	11th to 20th	Night	26% 6% 9% 26% 25% 7%	1925
	21st to end	Night	27% 4 9% 29% 26% 6%	2090
October	1st to 10th	Night	23% 3 8% 23% 29% 14%	3790
	11th to 20th	Night	30% 4 9% 27% 28% 2	3778
	21st to end	Night	34% 4 12% 29% 15% 6%	4405
November	1st to 10th	Night	35% 6% 15% 24% 16% 5%	2535
	11th to 20th	Night	39% 4 11% 27% 16% 3	2697
	21st to end	Night	34% 5% 15% 27% 16% 2	2800
December	1st to 10th	Night	45% 4 14% 22% 13% 2	2737
	11th to 20th	Night	34% 5% 18% 34% 9%	3272
	21st to end	Night	42% 5% 10% 26% 15% 3	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	10% 19% 34% 23% 10% 4	270
	11th to 20th	Day	15% 19% 34% 24% 6% 1	270
	21st to end	Day	15% 27% 36% 15% 6% 1	297
February	1st to 10th	Day	18% 18% 47% 14% 2	270
	11th to 20th	Day	14% 20% 47% 16% 2	270
	21st to end	Day	13% 20% 46% 16% 4 1	225
March	1st to 10th	Day	13% 26% 40% 17% 3 1	270
	11th to 20th	Day	14% 19% 39% 23% 4 1	380
	21st to end	Day	22% 17% 34% 18% 9% 1	506
April	1st to 10th	Day	20% 21% 39% 17% 2	460
	11th to 20th	Day	24% 24% 35% 15% 2	452
	21st to end	Day	23% 15% 31% 23% 6% 2	545
May	1st to 10th	Day	20% 17% 27% 23% 11% 2	653
	11th to 20th	Day	20% 11% 29% 25% 14% 1	675
	21st to end	Day	19% 12% 32% 25% 11% 1	734
June	1st to 10th	Day	9% 11% 27% 34% 16% 2	680
	11th to 20th	Day	12% 18% 37% 24% 8%	680
	21st to end	Day	9% 9% 34% 31% 16% 2	680
July	1st to 10th	Day	6% 5% 30% 40% 18% 1	671
	11th to 20th	Day	2 8% 35% 41% 12% 1	668
	21st to end	Day	4 8% 30% 39% 15% 3	739
August	1st to 10th	Day	7% 6% 30% 39% 17% 1	676
	11th to 20th	Day	8% 6% 34% 33% 17% 2	477
	21st to end	Day	4 10% 32% 36% 14% 4	539
September	1st to 10th	Day	6% 9% 36% 33% 14% 2	490
	11th to 20th	Day	9% 10% 30% 33% 16% 2	464
	21st to end	Day	18% 12% 31% 24% 12% 4	300
October	1st to 10th	Day	18% 13% 28% 24% 12% 5%	300
	11th to 20th	Day	18% 19% 33% 20% 8% 2	300
	21st to end	Day	15% 23% 32% 22% 7% 1	330
November	1st to 10th	Day	16% 18% 43% 16% 7%	300
	11th to 20th	Day	15% 17% 43% 20% 4 1	300
	21st to end	Day	11% 18% 44% 22% 5% 1	300
December	1st to 10th	Day	15% 23% 35% 20% 5%	285
	11th to 20th	Day	14% 21% 47% 14% 3	270
	21st to end	Day	16% 22% 37% 21% 4 1	297
January	1st to 10th	Night	11% 15% 35% 29% 9% 1	950
	11th to 20th	Night	15% 17% 37% 23% 7%	950
	21st to end	Night	13% 17% 40% 25% 5%	1017
February	1st to 10th	Night	15% 18% 40% 21% 6% 1	760
	11th to 20th	Night	12% 14% 41% 28% 5%	744
	21st to end	Night	12% 15% 36% 30% 7% 1	628
March	1st to 10th	Night	11% 16% 37% 28% 6% 1	760
	11th to 20th	Night	11% 11% 39% 31% 8% 1	760
	21st to end	Night	16% 12% 32% 31% 7% 1	669
April	1st to 10th	Night	20% 12% 34% 29% 6%	570
	11th to 20th	Night	22% 13% 30% 29% 5%	563
	21st to end	Night	19% 11% 28% 32% 9% 1	570
May	1st to 10th	Night	16% 9% 28% 33% 12% 2	570
	11th to 20th	Night	16% 11% 26% 35% 12%	561
	21st to end	Night	16% 11% 34% 28% 10%	617
June	1st to 10th	Night	10% 12% 29% 36% 13% 1	570
	11th to 20th	Night	12% 13% 38% 31% 7%	570
	21st to end	Night	6% 7% 32% 42% 12%	570
July	1st to 10th	Night	5% 5% 34% 37% 17% 1	555
	11th to 20th	Night	6% 5% 36% 42% 11%	552
	21st to end	Night	4 4 35% 47% 11%	624
August	1st to 10th	Night	6% 4 33% 42% 14%	567
	11th to 20th	Night	8% 5% 23% 47% 16% 1	564
	21st to end	Night	5% 5% 29% 46% 13% 1	627
September	1st to 10th	Night	8% 4 28% 41% 17% 1	570
	11th to 20th	Night	11% 9% 26% 39% 14% 1	570
	21st to end	Night	12% 8% 32% 34% 13% 1	570
October	1st to 10th	Night	19% 9% 27% 30% 14% 1	750
	11th to 20th	Night	14% 11% 29% 35% 10%	760
	21st to end	Night	16% 11% 36% 29% 8% 1	1007
November	1st to 10th	Night	14% 11% 39% 27% 8% 1	975
	11th to 20th	Night	14% 16% 37% 27% 6%	1000
	21st to end	Night	12% 14% 40% 31% 4	1000
December	1st to 10th	Night	11% 16% 40% 26% 6%	978
	11th to 20th	Night	8% 13% 43% 30% 6%	950
	21st to end	Night	16% 15% 37% 25% 6%	1045

Page generated at 2024-12-03 04:45:12. Version ac07

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