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 2025-06-10.

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	10% 8% 3 6% 4 4 4 4 5% 7% 45%	122992
	Night	12% 9% 3 7% 4 4 4 3 5% 6% 41%	123956
Transparency	Day	39% 6% 11% 22% 15% 6%	122760
	Night	44% 6% 11% 20% 13% 5%	123831
Seeing	Day	14% 9% 23% 26% 20% 8%	15351
	Night	17% 6% 21% 33% 19% 3	24674

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	20% 21% 8% 10% 4 4 5% 4 5% 5% 14%	3639
	11th to 20th	Day	15% 10% 4 10% 4 4 5% 3 5% 6% 33%	3616
	21st to end	Day	18% 14% 4 8% 4 4 3 3 4 5% 33%	4004
February	1st to 10th	Day	18% 16% 4 9% 6% 4 5% 4 6% 6% 24%	1615
	11th to 20th	Day	17% 17% 4 9% 6% 4 5% 2 5% 6% 25%	1895
	21st to end	Day	16% 16% 4 9% 6% 5% 4 4 5% 6% 25%	1650
March	1st to 10th	Day	8% 9% 3 9% 5% 5% 6% 5% 8% 8% 32%	4518
	11th to 20th	Day	10% 9% 3 8% 5% 5% 5% 4 6% 8% 39%	4690
	21st to end	Day	14% 14% 4 11% 7% 6% 5% 5% 6% 6% 22%	5915
April	1st to 10th	Day	12% 11% 4 9% 6% 5% 5% 4 7% 8% 28%	2400
	11th to 20th	Day	11% 10% 3 8% 6% 4 4 5% 6% 6% 37%	2430
	21st to end	Day	11% 8% 3 8% 6% 5% 5% 4 6% 7% 38%	2600
May	1st to 10th	Day	8% 6% 2 5% 3 4 4 4 6% 8% 51%	6136
	11th to 20th	Day	9% 6% 2 8% 5% 5% 5% 5% 7% 9% 40%	6277
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 5% 7% 8% 46%	6903
June	1st to 10th	Day	13% 8% 3 6% 5% 4 4 4 6% 7% 41%	2903
	11th to 20th	Day	12% 6% 2 5% 4 4 4 4 7% 8% 44%	2850
	21st to end	Day	6% 3 1 4 3 4 4 3 5% 6% 61%	2772
July	1st to 10th	Day	2 1 1 1 2 2 2 2 3 4 80%	4420
	11th to 20th	Day	2 1 1 2 2 2 2 2 3 4 81%	4420
	21st to end	Day	1 1 1 2 2 2 3 3 4 6% 76%	4790
August	1st to 10th	Day	3 3 1 3 2 2 2 2 4 6% 72%	4401
	11th to 20th	Day	3 3 1 3 2 3 3 3 5% 8% 66%	4117
	21st to end	Day	3 3 1 3 2 3 3 3 5% 7% 67%	4242
September	1st to 10th	Day	5% 2 1 3 2 3 3 3 4 7% 69%	2280
	11th to 20th	Day	7% 5% 2 6% 3 3 4 4 6% 7% 52%	2167
	21st to end	Day	7% 5% 3 5% 3 4 4 4 7% 8% 51%	2090
October	1st to 10th	Day	8% 4 2 4 3 3 4 2 4 6% 59%	3377
	11th to 20th	Day	9% 6% 2 5% 4 5% 5% 4 6% 7% 46%	2978
	21st to end	Day	15% 10% 3 6% 4 4 4 3 4 6% 40%	3101
November	1st to 10th	Day	22% 9% 4 7% 5% 4 5% 3 6% 7% 28%	1764
	11th to 20th	Day	21% 14% 4 7% 5% 4 5% 4 5% 6% 24%	1735
	21st to end	Day	17% 16% 4 10% 6% 5% 4 2 5% 6% 24%	1523
December	1st to 10th	Day	15% 9% 3 10% 5% 5% 5% 4 5% 6% 32%	2290
	11th to 20th	Day	20% 17% 6% 10% 5% 5% 6% 4 4 5% 17%	2642
	21st to end	Day	21% 17% 5% 9% 6% 4 5% 4 5% 6% 17%	3842
January	1st to 10th	Night	24% 18% 6% 11% 5% 5% 5% 4 5% 5% 14%	6306
	11th to 20th	Night	14% 12% 4 8% 4 4 4 4 5% 6% 36%	6282
	21st to end	Night	16% 13% 4 7% 4 4 4 3 4 5% 37%	6952
February	1st to 10th	Night	19% 17% 4 8% 5% 4 4 3 5% 5% 25%	2781
	11th to 20th	Night	17% 15% 3 8% 4 4 5% 4 5% 5% 31%	2392
	21st to end	Night	15% 14% 4 8% 7% 4 4 4 5% 6% 30%	1980
March	1st to 10th	Night	8% 9% 3 8% 5% 4 5% 4 5% 8% 40%	5376
	11th to 20th	Night	11% 13% 3 8% 4 4 4 3 5% 5% 41%	5308
	21st to end	Night	11% 11% 4 9% 7% 7% 7% 5% 8% 9% 22%	5058
April	1st to 10th	Night	12% 11% 3 8% 5% 5% 6% 5% 6% 9% 32%	2000
	11th to 20th	Night	11% 8% 4 7% 5% 4 4 3 6% 5% 42%	1921
	21st to end	Night	10% 8% 3 6% 6% 5% 4 4 6% 8% 40%	1800
May	1st to 10th	Night	9% 5% 2 5% 3 4 4 4 6% 7% 52%	3829
	11th to 20th	Night	9% 7% 3 8% 6% 5% 5% 4 6% 8% 41%	3616
	21st to end	Night	9% 6% 2 6% 4 3 5% 4 5% 7% 49%	3972
June	1st to 10th	Night	11% 5% 2 6% 4 4 5% 4 6% 8% 45%	1476
	11th to 20th	Night	9% 7% 2 6% 5% 5% 5% 4 7% 5% 46%	1330
	21st to end	Night	7% 5% 1 5% 4 4 4 3 5% 6% 56%	1400
July	1st to 10th	Night	2 1 2 2 2 2 2 3 4 81%	2540
	11th to 20th	Night	2 1 2 1 2 2 2 4 4 81%	2540
	21st to end	Night	2 2 1 2 1 2 2 2 3 4 78%	2762
August	1st to 10th	Night	4 3 1 4 2 2 2 4 4 7% 67%	2529
	11th to 20th	Night	2 3 1 5% 3 4 4 3 5% 6% 64%	2717
	21st to end	Night	3 3 1 4 3 3 3 2 5% 6% 66%	3430
September	1st to 10th	Night	3 2 1 3 3 3 4 3 4 6% 68%	1900
	11th to 20th	Night	6% 4 2 5% 4 3 4 4 6% 8% 54%	2012
	21st to end	Night	9% 4 2 5% 3 3 4 3 6% 7% 53%	2090
October	1st to 10th	Night	7% 4 2 4 3 3 3 3 5% 6% 60%	3600
	11th to 20th	Night	10% 5% 2 5% 5% 5% 5% 4 6% 8% 47%	3953
	21st to end	Night	13% 7% 3 6% 4 4 4 4 5% 7% 44%	4457
November	1st to 10th	Night	19% 11% 3 7% 5% 4 4 4 6% 6% 31%	2535
	11th to 20th	Night	20% 12% 4 8% 5% 4 5% 3 5% 5% 28%	2665
	21st to end	Night	19% 12% 4 9% 5% 4 4 4 5% 5% 28%	2853
December	1st to 10th	Night	11% 8% 3 7% 5% 4 4 3 5% 7% 43%	4890
	11th to 20th	Night	20% 18% 5% 11% 6% 5% 5% 3 6% 6% 14%	5550
	21st to end	Night	21% 16% 6% 9% 6% 5% 4 3 5% 6% 20%	7154

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	70% 8% 12% 9% 1	3639
	11th to 20th	Day	53% 5% 16% 20% 5% 1	3640
	21st to end	Day	54% 5% 11% 21% 8%	4004
February	1st to 10th	Day	61% 9% 13% 12% 4 1	1615
	11th to 20th	Day	63% 7% 11% 13% 6%	1905
	21st to end	Day	61% 8% 8% 16% 6% 1	1650
March	1st to 10th	Day	46% 7% 10% 23% 14% 1	4518
	11th to 20th	Day	43% 8% 13% 29% 7%	4690
	21st to end	Day	61% 8% 12% 14% 4 1	5915
April	1st to 10th	Day	53% 8% 16% 18% 6%	2400
	11th to 20th	Day	47% 6% 12% 20% 12% 2	2430
	21st to end	Day	45% 9% 11% 23% 10% 1	2600
May	1st to 10th	Day	30% 7% 10% 30% 23% 1	6136
	11th to 20th	Day	38% 7% 13% 29% 11% 2	6280
	21st to end	Day	33% 8% 17% 29% 12% 1	6904
June	1st to 10th	Day	43% 7% 11% 24% 14% 1	2903
	11th to 20th	Day	38% 7% 14% 25% 14% 3	2850
	21st to end	Day	25% 4 11% 32% 24% 4	2772
July	1st to 10th	Day	10% 2 5% 18% 28% 36%	4351
	11th to 20th	Day	10% 2 5% 11% 28% 44%	4345
	21st to end	Day	11% 2 5% 19% 36% 26%	4639
August	1st to 10th	Day	17% 3 4 16% 40% 20%	4384
	11th to 20th	Day	19% 4 6% 36% 27% 7%	4158
	21st to end	Day	18% 3 10% 32% 29% 8%	4241
September	1st to 10th	Day	17% 5% 10% 30% 27% 13%	2280
	11th to 20th	Day	32% 5% 12% 24% 21% 6%	2167
	21st to end	Day	31% 7% 16% 28% 14% 4	2090
October	1st to 10th	Day	28% 4 11% 33% 22% 2	3377
	11th to 20th	Day	38% 5% 19% 24% 14%	2978
	21st to end	Day	47% 5% 13% 24% 9% 2	3101
November	1st to 10th	Day	57% 8% 13% 17% 4 1	1764
	11th to 20th	Day	61% 8% 14% 13% 3 1	1735
	21st to end	Day	60% 8% 15% 12% 4 1	1523
December	1st to 10th	Day	52% 7% 20% 18% 2 1	2290
	11th to 20th	Day	71% 7% 11% 10% 1	2644
	21st to end	Day	66% 9% 14% 9% 3	3842
January	1st to 10th	Night	71% 7% 11% 10% 1	6306
	11th to 20th	Night	50% 5% 17% 18% 8% 1	6320
	21st to end	Night	49% 6% 13% 21% 9%	6952
February	1st to 10th	Night	62% 6% 12% 13% 6% 1	2781
	11th to 20th	Night	56% 6% 15% 14% 8% 1	2393
	21st to end	Night	55% 6% 12% 18% 7% 1	1980
March	1st to 10th	Night	42% 5% 9% 23% 18% 2	5376
	11th to 20th	Night	46% 5% 8% 30% 10%	5309
	21st to end	Night	55% 10% 11% 20% 4	5058
April	1st to 10th	Night	47% 8% 14% 23% 8%	2000
	11th to 20th	Night	43% 6% 10% 23% 16% 3	1921
	21st to end	Night	43% 6% 12% 21% 16% 3	1800
May	1st to 10th	Night	32% 6% 8% 26% 26% 3	3826
	11th to 20th	Night	39% 6% 10% 26% 16% 2	3616
	21st to end	Night	33% 8% 15% 29% 15% 1	3972
June	1st to 10th	Night	36% 7% 11% 25% 18% 3	1476
	11th to 20th	Night	38% 5% 9% 26% 17% 5%	1330
	21st to end	Night	29% 4 9% 24% 26% 8%	1400
July	1st to 10th	Night	10% 1 4 14% 30% 41%	2500
	11th to 20th	Night	9% 2 4 10% 19% 55%	2492
	21st to end	Night	12% 2 3 13% 31% 39%	2674
August	1st to 10th	Night	19% 3 3 11% 38% 26%	2521
	11th to 20th	Night	21% 4 4 28% 31% 12%	2742
	21st to end	Night	21% 3 7% 25% 28% 15%	3430
September	1st to 10th	Night	17% 4 8% 26% 26% 18%	1900
	11th to 20th	Night	29% 5% 9% 23% 25% 9%	2012
	21st to end	Night	29% 5% 13% 29% 16% 8%	2090
October	1st to 10th	Night	26% 3 10% 31% 27% 3	3600
	11th to 20th	Night	36% 5% 15% 22% 20% 1	3953
	21st to end	Night	41% 6% 8% 31% 13% 2	4457
November	1st to 10th	Night	53% 6% 14% 19% 6% 1	2535
	11th to 20th	Night	58% 6% 14% 16% 5% 1	2665
	21st to end	Night	56% 6% 16% 17% 6%	2853
December	1st to 10th	Night	42% 7% 21% 24% 6%	4890
	11th to 20th	Night	70% 6% 13% 9% 1	5547
	21st to end	Night	65% 8% 12% 12% 4	7154

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	28% 12% 25% 19% 11% 6%	200
	11th to 20th	Day	27% 9% 26% 19% 14% 6%	200
	21st to end	Day	30% 7% 30% 21% 9% 3	220
February	1st to 10th	Day	27% 13% 32% 20% 7% 1	215
	11th to 20th	Day	28% 15% 22% 23% 10% 2	468
	21st to end	Day	23% 15% 24% 26% 10% 2	414
March	1st to 10th	Day	18% 13% 30% 23% 14% 2	500
	11th to 20th	Day	17% 11% 21% 25% 19% 5%	500
	21st to end	Day	20% 16% 29% 22% 11% 2	550
April	1st to 10th	Day	18% 11% 28% 25% 14% 4	500
	11th to 20th	Day	15% 11% 33% 24% 12% 5%	492
	21st to end	Day	11% 11% 28% 26% 18% 5%	500
May	1st to 10th	Day	10% 9% 23% 31% 22% 5%	503
	11th to 20th	Day	15% 7% 21% 25% 20% 12%	528
	21st to end	Day	10% 9% 18% 25% 24% 14%	573
June	1st to 10th	Day	13% 7% 19% 27% 24% 11%	641
	11th to 20th	Day	14% 9% 29% 25% 17% 6%	680
	21st to end	Day	6% 5% 21% 28% 29% 11%	602
July	1st to 10th	Day	4 2 18% 33% 35% 8%	486
	11th to 20th	Day	4 3 17% 36% 30% 10%	484
	21st to end	Day	1 3 15% 36% 31% 13%	531
August	1st to 10th	Day	4 4 16% 30% 32% 14%	487
	11th to 20th	Day	3 2 13% 32% 32% 17%	477
	21st to end	Day	6% 6% 22% 26% 25% 15%	539
September	1st to 10th	Day	5% 2 25% 25% 27% 15%	490
	11th to 20th	Day	10% 6% 23% 22% 27% 12%	490
	21st to end	Day	10% 8% 21% 28% 25% 7%	490
October	1st to 10th	Day	13% 8% 22% 29% 20% 8%	490
	11th to 20th	Day	16% 9% 21% 24% 20% 9%	384
	21st to end	Day	24% 10% 27% 24% 11% 5%	330
November	1st to 10th	Day	27% 9% 23% 30% 12%	300
	11th to 20th	Day	23% 17% 24% 20% 12% 5%	267
	21st to end	Day	17% 13% 30% 24% 14% 3	200
December	1st to 10th	Day	26% 13% 21% 21% 12% 9%	200
	11th to 20th	Day	35% 14% 24% 16% 11% 3	200
	21st to end	Day	29% 11% 30% 19% 10% 2	220
January	1st to 10th	Night	33% 10% 21% 25% 10% 2	800
	11th to 20th	Night	27% 8% 21% 28% 14% 3	800
	21st to end	Night	22% 5% 22% 32% 17% 2	880
February	1st to 10th	Night	25% 10% 24% 30% 10% 1	800
	11th to 20th	Night	24% 9% 20% 31% 14% 2	784
	21st to end	Night	21% 11% 20% 32% 13% 3	660
March	1st to 10th	Night	18% 8% 25% 33% 13% 3	800
	11th to 20th	Night	16% 10% 24% 29% 21% 1	800
	21st to end	Night	21% 6% 27% 34% 11% 2	880
April	1st to 10th	Night	16% 5% 27% 33% 17% 2	800
	11th to 20th	Night	14% 8% 29% 33% 14% 2	733
	21st to end	Night	13% 7% 26% 32% 20% 2	600
May	1st to 10th	Night	9% 6% 26% 33% 23% 3	485
	11th to 20th	Night	10% 5% 18% 34% 26% 8%	394
	21st to end	Night	11% 6% 19% 34% 25% 4	433
June	1st to 10th	Night	11% 5% 22% 35% 21% 5%	399
	11th to 20th	Night	12% 5% 27% 36% 18% 2	380
	21st to end	Night	8% 3 18% 40% 26% 4	380
July	1st to 10th	Night	3 1 14% 44% 34% 4	370
	11th to 20th	Night	3 3 17% 47% 29% 2	368
	21st to end	Night	1 2 13% 44% 36% 4	416
August	1st to 10th	Night	4 3 13% 39% 35% 7%	378
	11th to 20th	Night	3 2 11% 38% 37% 10%	506
	21st to end	Night	4 2 18% 38% 33% 5%	794
September	1st to 10th	Night	5% 2 16% 41% 29% 7%	760
	11th to 20th	Night	8% 4 18% 31% 29% 10%	760
	21st to end	Night	11% 4 18% 33% 27% 6%	760
October	1st to 10th	Night	13% 5% 18% 38% 23% 3	760
	11th to 20th	Night	15% 7% 19% 30% 25% 4	760
	21st to end	Night	18% 6% 26% 30% 16% 4	836
November	1st to 10th	Night	26% 7% 19% 36% 12%	780
	11th to 20th	Night	25% 10% 26% 25% 12% 2	800
	21st to end	Night	23% 9% 20% 28% 17% 3	853
December	1st to 10th	Night	21% 7% 19% 35% 16% 2	1000
	11th to 20th	Night	31% 6% 23% 30% 10% 1	1000
	21st to end	Night	36% 10% 20% 25% 8%	965

Page generated at 2025-06-07 07:28:17. Version ac07

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