Steptoe Butte State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Steptoe Butte State Park clear sky chart from 2005-11-06 to 2026-10-14.

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% 7% 3 6% 4 4 4 3 5% 7% 48%	153099
	Night	11% 9% 3 7% 4 4 4 4 5% 6% 43%	147401
Transparency	Day	36% 5% 11% 24% 17% 7%	152826
	Night	41% 5% 11% 21% 15% 6%	147256
Seeing	Day	14% 9% 23% 26% 20% 8%	17147
	Night	17% 6% 21% 33% 19% 3	26297

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	18% 19% 8% 11% 5% 4 5% 4 5% 5% 15%	4723
	11th to 20th	Day	12% 8% 4 11% 4 4 5% 3 5% 6% 38%	4716
	21st to end	Day	15% 13% 4 10% 5% 5% 4 3 5% 6% 31%	5186
February	1st to 10th	Day	17% 16% 4 9% 6% 4 5% 4 7% 6% 23%	1696
	11th to 20th	Day	17% 17% 4 10% 6% 4 5% 2 5% 6% 24%	1992
	21st to end	Day	16% 16% 4 9% 5% 5% 4 4 5% 6% 26%	1730
March	1st to 10th	Day	8% 9% 3 8% 5% 5% 6% 5% 8% 8% 32%	4618
	11th to 20th	Day	10% 9% 3 8% 5% 4 5% 4 6% 8% 39%	4793
	21st to end	Day	14% 14% 4 11% 7% 6% 5% 4 6% 6% 23%	6045
April	1st to 10th	Day	12% 11% 4 9% 6% 5% 5% 4 7% 8% 29%	2520
	11th to 20th	Day	11% 10% 3 8% 6% 5% 4 5% 6% 6% 36%	2553
	21st to end	Day	11% 7% 3 7% 6% 5% 5% 4 6% 7% 38%	2730
May	1st to 10th	Day	6% 5% 2 4 3 4 4 4 6% 8% 54%	7959
	11th to 20th	Day	8% 6% 2 7% 5% 5% 5% 5% 7% 9% 41%	8160
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 4 7% 8% 45%	8993
June	1st to 10th	Day	13% 8% 3 7% 5% 4 5% 4 6% 7% 40%	3061
	11th to 20th	Day	11% 6% 2 5% 4 4 4 4 7% 7% 46%	3150
	21st to end	Day	6% 3 2 5% 3 4 4 3 5% 7% 59%	3064
July	1st to 10th	Day	2 2 1 2 2 2 3 2 4 5% 75%	8220
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 4 76%	8220
	21st to end	Day	2 1 1 2 2 2 2 2 4 6% 76%	8916
August	1st to 10th	Day	2 2 1 2 2 2 2 2 3 5% 78%	6441
	11th to 20th	Day	2 2 1 3 3 3 4 3 5% 7% 67%	6056
	21st to end	Day	2 2 1 3 2 3 3 3 6% 8% 67%	6166
September	1st to 10th	Day	5% 2 1 3 2 3 3 3 5% 7% 66%	2520
	11th to 20th	Day	7% 6% 2 6% 3 3 4 4 6% 7% 53%	2395
	21st to end	Day	7% 5% 3 5% 3 4 4 4 6% 7% 51%	2310
October	1st to 10th	Day	7% 4 1 4 3 3 4 2 4 7% 59%	3590
	11th to 20th	Day	10% 6% 2 5% 4 5% 5% 4 6% 7% 46%	3103
	21st to end	Day	15% 10% 4 7% 4 4 4 3 5% 6% 40%	3200
November	1st to 10th	Day	22% 9% 4 7% 5% 4 5% 3 6% 7% 29%	1854
	11th to 20th	Day	20% 14% 4 8% 5% 4 5% 4 5% 6% 24%	1821
	21st to end	Day	17% 15% 5% 10% 6% 5% 4 3 5% 6% 24%	1599
December	1st to 10th	Day	16% 9% 4 10% 5% 5% 5% 4 5% 6% 31%	2360
	11th to 20th	Day	20% 17% 5% 10% 6% 5% 6% 4 4 5% 17%	2712
	21st to end	Day	21% 17% 5% 9% 6% 4 5% 4 5% 6% 17%	3927
January	1st to 10th	Night	22% 17% 6% 11% 6% 5% 5% 4 5% 5% 15%	8172
	11th to 20th	Night	11% 10% 3 8% 5% 4 4 4 5% 6% 40%	8182
	21st to end	Night	14% 11% 4 7% 4 4 5% 4 5% 6% 36%	8994
February	1st to 10th	Night	19% 16% 4 8% 5% 4 4 3 5% 5% 26%	2920
	11th to 20th	Night	17% 15% 4 8% 4 4 5% 3 4 5% 31%	2515
	21st to end	Night	15% 14% 4 8% 7% 4 4 4 5% 6% 30%	2076
March	1st to 10th	Night	9% 9% 3 8% 5% 4 5% 4 5% 8% 39%	5496
	11th to 20th	Night	12% 13% 4 8% 4 4 4 3 5% 5% 40%	5425
	21st to end	Night	11% 11% 4 9% 7% 7% 7% 5% 8% 9% 23%	5169
April	1st to 10th	Night	12% 10% 3 7% 5% 5% 6% 5% 6% 8% 33%	2100
	11th to 20th	Night	11% 9% 4 7% 5% 4 4 3 6% 5% 42%	2018
	21st to end	Night	10% 8% 3 6% 6% 5% 5% 4 7% 8% 39%	1890
May	1st to 10th	Night	7% 4 1 5% 3 4 4 4 6% 8% 53%	4969
	11th to 20th	Night	8% 7% 3 8% 5% 5% 5% 5% 7% 9% 39%	4700
	21st to end	Night	8% 6% 2 7% 5% 4 5% 4 6% 8% 45%	5178
June	1st to 10th	Night	11% 5% 3 6% 4 4 5% 4 6% 8% 44%	1554
	11th to 20th	Night	8% 6% 2 6% 5% 5% 4 4 7% 5% 48%	1470
	21st to end	Night	8% 5% 1 6% 4 4 4 3 5% 6% 54%	1548
July	1st to 10th	Night	2 1 2 1 2 3 3 4 6% 75%	4740
	11th to 20th	Night	1 2 1 3 2 2 2 2 5% 6% 74%	4740
	21st to end	Night	2 3 1 2 2 2 2 2 3 6% 76%	5152
August	1st to 10th	Night	3 2 1 3 1 2 2 3 3 5% 76%	3709
	11th to 20th	Night	1 2 1 4 3 3 4 4 5% 6% 65%	4002
	21st to end	Night	3 3 1 4 3 3 4 2 4 6% 66%	4996
September	1st to 10th	Night	4 2 1 3 3 3 4 3 4 7% 65%	2100
	11th to 20th	Night	6% 5% 2 5% 4 3 4 4 6% 8% 54%	2224
	21st to end	Night	8% 4 2 5% 4 3 4 3 6% 7% 54%	2310
October	1st to 10th	Night	7% 4 2 5% 3 3 3 3 5% 6% 60%	3826
	11th to 20th	Night	10% 5% 2 6% 4 4 4 4 5% 8% 47%	4115
	21st to end	Night	13% 7% 3 6% 4 4 4 4 5% 7% 44%	4600
November	1st to 10th	Night	19% 11% 2 7% 5% 4 4 4 6% 6% 30%	2665
	11th to 20th	Night	20% 12% 5% 8% 5% 4 5% 3 6% 5% 28%	2798
	21st to end	Night	19% 12% 4 10% 5% 4 4 4 5% 6% 28%	2996
December	1st to 10th	Night	12% 8% 3 7% 5% 4 4 3 5% 7% 42%	5040
	11th to 20th	Night	20% 18% 5% 11% 6% 5% 5% 3 6% 6% 14%	5700
	21st to end	Night	21% 16% 6% 9% 6% 5% 4 3 5% 6% 20%	7312

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	69% 7% 11% 11% 1	4723
	11th to 20th	Day	47% 5% 18% 22% 8% 1	4740
	21st to end	Day	55% 5% 14% 18% 8%	5187
February	1st to 10th	Day	61% 9% 13% 12% 5% 1	1696
	11th to 20th	Day	63% 7% 11% 13% 6%	2002
	21st to end	Day	60% 7% 8% 17% 6% 1	1730
March	1st to 10th	Day	46% 7% 10% 23% 14% 1	4618
	11th to 20th	Day	44% 8% 13% 29% 7%	4793
	21st to end	Day	61% 8% 12% 15% 4 1	6045
April	1st to 10th	Day	52% 8% 16% 19% 6%	2520
	11th to 20th	Day	48% 7% 12% 21% 11% 2	2553
	21st to end	Day	44% 9% 11% 24% 11% 1	2730
May	1st to 10th	Day	28% 5% 9% 35% 23% 1	7959
	11th to 20th	Day	37% 6% 14% 29% 12% 1	8163
	21st to end	Day	34% 7% 18% 30% 11% 1	8994
June	1st to 10th	Day	43% 7% 11% 24% 15% 1	3061
	11th to 20th	Day	37% 7% 13% 24% 17% 3	3150
	21st to end	Day	26% 4 11% 31% 23% 4	3064
July	1st to 10th	Day	13% 2 5% 25% 31% 25%	8151
	11th to 20th	Day	15% 2 4 16% 32% 31%	8145
	21st to end	Day	12% 2 4 26% 35% 20%	8723
August	1st to 10th	Day	12% 2 3 15% 40% 28%	6424
	11th to 20th	Day	17% 4 6% 38% 29% 6%	6097
	21st to end	Day	17% 3 9% 35% 31% 6%	6165
September	1st to 10th	Day	18% 5% 10% 29% 26% 12%	2520
	11th to 20th	Day	32% 5% 12% 25% 21% 6%	2395
	21st to end	Day	32% 6% 15% 28% 15% 4	2310
October	1st to 10th	Day	27% 3 11% 34% 22% 2	3590
	11th to 20th	Day	38% 5% 18% 24% 14% 1	3103
	21st to end	Day	47% 5% 13% 25% 9% 2	3200
November	1st to 10th	Day	57% 8% 13% 18% 4 1	1854
	11th to 20th	Day	61% 8% 14% 13% 3 1	1821
	21st to end	Day	60% 8% 15% 12% 4 1	1599
December	1st to 10th	Day	53% 7% 19% 18% 2 1	2360
	11th to 20th	Day	70% 7% 11% 10% 1	2714
	21st to end	Day	66% 8% 14% 9% 3	3927
January	1st to 10th	Night	69% 7% 11% 11% 1	8172
	11th to 20th	Night	46% 5% 18% 21% 9% 2	8220
	21st to end	Night	49% 6% 15% 21% 9%	8994
February	1st to 10th	Night	61% 6% 13% 13% 6% 1	2920
	11th to 20th	Night	56% 6% 15% 14% 8% 1	2516
	21st to end	Night	56% 6% 12% 18% 7% 1	2076
March	1st to 10th	Night	42% 5% 9% 23% 18% 2	5496
	11th to 20th	Night	47% 5% 8% 30% 9%	5426
	21st to end	Night	55% 10% 11% 20% 4	5169
April	1st to 10th	Night	46% 8% 15% 22% 9%	2100
	11th to 20th	Night	43% 5% 11% 23% 15% 2	2018
	21st to end	Night	42% 6% 11% 21% 16% 3	1890
May	1st to 10th	Night	29% 5% 7% 31% 27% 2	4966
	11th to 20th	Night	38% 7% 10% 26% 18% 1	4700
	21st to end	Night	35% 7% 15% 27% 14% 1	5182
June	1st to 10th	Night	36% 6% 12% 25% 18% 3	1554
	11th to 20th	Night	36% 5% 8% 24% 21% 6%	1470
	21st to end	Night	31% 4 9% 23% 26% 7%	1548
July	1st to 10th	Night	12% 1 4 19% 35% 29%	4700
	11th to 20th	Night	13% 2 4 12% 30% 40%	4692
	21st to end	Night	13% 2 3 17% 38% 26%	5040
August	1st to 10th	Night	14% 2 2 9% 35% 38%	3701
	11th to 20th	Night	18% 3 4 32% 33% 9%	4027
	21st to end	Night	21% 3 6% 26% 32% 12%	4996
September	1st to 10th	Night	18% 4 8% 26% 27% 17%	2100
	11th to 20th	Night	30% 5% 9% 24% 24% 8%	2224
	21st to end	Night	29% 5% 12% 29% 18% 7%	2310
October	1st to 10th	Night	27% 3 9% 31% 27% 2	3826
	11th to 20th	Night	37% 5% 14% 22% 21% 1	4115
	21st to end	Night	40% 6% 8% 32% 13% 1	4600
November	1st to 10th	Night	54% 6% 15% 19% 6% 1	2665
	11th to 20th	Night	58% 6% 14% 15% 5% 1	2798
	21st to end	Night	57% 6% 15% 16% 5%	2996
December	1st to 10th	Night	43% 7% 21% 24% 5%	5040
	11th to 20th	Night	70% 6% 13% 10% 1	5697
	21st to end	Night	65% 8% 12% 12% 4	7312

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	27% 13% 27% 17% 10% 5%	220
	11th to 20th	Day	24% 8% 25% 21% 16% 6%	220
	21st to end	Day	28% 7% 29% 23% 11% 3	242
February	1st to 10th	Day	27% 12% 31% 20% 8% 3	236
	11th to 20th	Day	28% 14% 23% 23% 11% 2	505
	21st to end	Day	23% 15% 25% 26% 9% 2	446
March	1st to 10th	Day	19% 14% 30% 22% 14% 2	540
	11th to 20th	Day	20% 12% 22% 24% 18% 5%	540
	21st to end	Day	20% 16% 29% 23% 11% 2	594
April	1st to 10th	Day	18% 11% 27% 25% 14% 5%	540
	11th to 20th	Day	15% 11% 32% 24% 13% 5%	532
	21st to end	Day	11% 11% 27% 26% 19% 6%	540
May	1st to 10th	Day	10% 8% 22% 31% 23% 5%	543
	11th to 20th	Day	15% 8% 22% 25% 19% 12%	568
	21st to end	Day	10% 8% 18% 26% 24% 14%	617
June	1st to 10th	Day	14% 8% 19% 26% 23% 10%	691
	11th to 20th	Day	13% 9% 29% 27% 17% 5%	780
	21st to end	Day	7% 4 21% 29% 28% 11%	694
July	1st to 10th	Day	4 2 18% 34% 34% 8%	566
	11th to 20th	Day	4 3 20% 36% 29% 9%	564
	21st to end	Day	2 3 15% 36% 31% 13%	619
August	1st to 10th	Day	4 4 17% 30% 32% 13%	567
	11th to 20th	Day	3 2 13% 34% 32% 15%	557
	21st to end	Day	7% 6% 20% 27% 26% 15%	627
September	1st to 10th	Day	5% 2 24% 25% 28% 16%	570
	11th to 20th	Day	11% 5% 22% 24% 26% 12%	570
	21st to end	Day	10% 7% 21% 29% 26% 7%	570
October	1st to 10th	Day	11% 8% 22% 29% 23% 8%	570
	11th to 20th	Day	17% 10% 21% 25% 19% 8%	431
	21st to end	Day	22% 10% 28% 24% 12% 4	363
November	1st to 10th	Day	27% 10% 23% 28% 12%	330
	11th to 20th	Day	22% 17% 24% 21% 13% 5%	293
	21st to end	Day	17% 14% 31% 23% 12% 3	220
December	1st to 10th	Day	29% 12% 20% 20% 12% 8%	220
	11th to 20th	Day	35% 14% 24% 15% 10% 2	220
	21st to end	Day	29% 11% 30% 18% 11% 2	242
January	1st to 10th	Night	32% 10% 21% 25% 9% 2	840
	11th to 20th	Night	25% 7% 21% 29% 14% 3	840
	21st to end	Night	21% 5% 22% 33% 17% 2	924
February	1st to 10th	Night	25% 9% 23% 30% 11% 1	840
	11th to 20th	Night	25% 9% 20% 32% 13% 2	824
	21st to end	Night	21% 11% 21% 32% 12% 3	692
March	1st to 10th	Night	18% 9% 25% 33% 12% 3	840
	11th to 20th	Night	18% 10% 24% 28% 20% 1	840
	21st to end	Night	20% 7% 27% 34% 10% 2	924
April	1st to 10th	Night	15% 5% 27% 34% 17% 2	840
	11th to 20th	Night	15% 8% 28% 33% 14% 2	770
	21st to end	Night	13% 7% 25% 32% 21% 2	630
May	1st to 10th	Night	8% 6% 26% 34% 24% 3	509
	11th to 20th	Night	10% 5% 18% 34% 25% 7%	414
	21st to end	Night	11% 7% 20% 34% 25% 4	455
June	1st to 10th	Night	11% 6% 23% 35% 21% 5%	420
	11th to 20th	Night	11% 5% 28% 38% 17% 2	420
	21st to end	Night	9% 4 18% 40% 25% 4	420
July	1st to 10th	Night	3 1 13% 45% 33% 4	410
	11th to 20th	Night	2 3 17% 48% 28% 2	408
	21st to end	Night	1 2 13% 44% 36% 4	460
August	1st to 10th	Night	4 3 12% 40% 35% 6%	418
	11th to 20th	Night	3 2 11% 40% 36% 9%	560
	21st to end	Night	5% 2 17% 39% 32% 4	878
September	1st to 10th	Night	6% 2 15% 41% 29% 7%	840
	11th to 20th	Night	8% 4 17% 33% 29% 9%	840
	21st to end	Night	10% 4 18% 34% 28% 6%	840
October	1st to 10th	Night	12% 5% 17% 40% 24% 3	840
	11th to 20th	Night	15% 7% 20% 30% 24% 3	812
	21st to end	Night	18% 6% 26% 31% 15% 4	880
November	1st to 10th	Night	26% 7% 20% 36% 11%	820
	11th to 20th	Night	25% 10% 25% 26% 12% 2	840
	21st to end	Night	24% 9% 20% 29% 16% 3	896
December	1st to 10th	Night	23% 8% 18% 34% 16% 2	1050
	11th to 20th	Night	31% 7% 23% 29% 10% 1	1050
	21st to end	Night	35% 10% 20% 26% 8%	1013

Page generated at 2026-10-11 02:06:30. Version ac07

Copyright © 2026 Attilla Danko.