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 2024-03-08.

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	12% 9% 3 6% 5% 3 4 4 5% 7% 41%	78197
	Night	15% 10% 3 6% 5% 3 4 4 5% 6% 37%	81303
Transparency	Day	44% 7% 12% 20% 14% 4	77924
	Night	47% 7% 12% 18% 12% 4	81156
Seeing	Day	15% 8% 23% 26% 20% 8%	13695
	Night	18% 6% 21% 33% 19% 3	23129

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% 20% 6% 8% 5% 3 5% 5% 6% 6% 16%	2539
	11th to 20th	Day	22% 13% 5% 10% 6% 3 5% 5% 5% 5% 20%	2516
	21st to end	Day	24% 18% 6% 9% 7% 4 4 4 4 5% 17%	2794
February	1st to 10th	Day	18% 15% 4 7% 6% 2 6% 4 6% 6% 25%	1534
	11th to 20th	Day	18% 15% 5% 8% 7% 3 5% 4 5% 6% 26%	1797
	21st to end	Day	17% 16% 4 8% 6% 3 5% 5% 5% 6% 24%	1570
March	1st to 10th	Day	15% 11% 5% 8% 6% 3 6% 5% 6% 7% 27%	1871
	11th to 20th	Day	14% 12% 4 8% 6% 4 7% 5% 5% 8% 27%	1852
	21st to end	Day	18% 13% 4 9% 6% 4 6% 6% 5% 5% 23%	2348
April	1st to 10th	Day	13% 11% 4 8% 8% 4 5% 5% 7% 8% 27%	2160
	11th to 20th	Day	13% 9% 4 7% 7% 3 4 5% 6% 6% 36%	2184
	21st to end	Day	12% 7% 3 6% 7% 3 5% 5% 5% 7% 38%	2340
May	1st to 10th	Day	8% 7% 3 5% 5% 3 4 5% 6% 8% 45%	2440
	11th to 20th	Day	12% 7% 2 7% 6% 4 6% 5% 7% 10% 36%	2477
	21st to end	Day	11% 7% 3 6% 6% 4 5% 6% 7% 7% 37%	2723
June	1st to 10th	Day	14% 7% 4 6% 5% 3 4 5% 5% 7% 39%	2623
	11th to 20th	Day	12% 6% 2 5% 4 3 4 5% 6% 8% 43%	2700
	21st to end	Day	6% 3 1 4 4 3 4 4 4 7% 61%	2627
July	1st to 10th	Day	3 2 1 2 3 2 3 4 5% 6% 70%	2520
	11th to 20th	Day	3 1 1 2 3 2 3 3 4 5% 73%	2520
	21st to end	Day	1 1 1 1 2 1 2 2 3 4 81%	2741
August	1st to 10th	Day	3 3 1 3 3 1 2 3 4 6% 72%	2507
	11th to 20th	Day	4 2 1 2 2 2 3 3 4 8% 70%	2352
	21st to end	Day	5% 5% 1 3 3 2 3 3 6% 7% 62%	2412
September	1st to 10th	Day	5% 2 1 3 2 2 3 3 4 7% 69%	2160
	11th to 20th	Day	7% 4 2 5% 4 3 4 5% 6% 8% 53%	2053
	21st to end	Day	8% 5% 3 4 4 3 4 5% 6% 8% 50%	1980
October	1st to 10th	Day	13% 6% 2 5% 5% 3 5% 4 5% 5% 48%	1919
	11th to 20th	Day	13% 6% 2 5% 4 3 4 5% 5% 6% 47%	1700
	21st to end	Day	17% 10% 3 6% 5% 3 5% 5% 4 6% 37%	1782
November	1st to 10th	Day	22% 8% 3 6% 6% 3 5% 5% 5% 8% 28%	1674
	11th to 20th	Day	21% 13% 5% 7% 5% 3 5% 5% 5% 6% 25%	1649
	21st to end	Day	17% 13% 6% 8% 7% 4 5% 3 5% 7% 25%	1447
December	1st to 10th	Day	21% 12% 5% 10% 8% 4 6% 5% 5% 5% 20%	1330
	11th to 20th	Day	21% 15% 6% 10% 7% 4 6% 6% 4 5% 18%	1682
	21st to end	Day	18% 15% 4 9% 7% 3 5% 5% 6% 7% 21%	2674
January	1st to 10th	Night	23% 17% 5% 9% 7% 3 5% 4 5% 5% 17%	4406
	11th to 20th	Night	20% 16% 5% 8% 5% 3 4 5% 5% 5% 24%	4382
	21st to end	Night	23% 14% 5% 7% 6% 3 5% 4 5% 6% 22%	4862
February	1st to 10th	Night	20% 15% 4 7% 5% 3 4 4 5% 5% 26%	2642
	11th to 20th	Night	16% 13% 4 7% 5% 4 5% 4 4 6% 31%	2270
	21st to end	Night	15% 13% 4 7% 7% 4 4 6% 5% 6% 29%	1884
March	1st to 10th	Night	16% 10% 3 7% 7% 3 6% 5% 5% 7% 31%	2249
	11th to 20th	Night	14% 10% 4 7% 5% 3 5% 5% 6% 8% 33%	2106
	21st to end	Night	16% 10% 4 6% 7% 4 6% 5% 6% 9% 26%	2006
April	1st to 10th	Night	13% 9% 3 7% 6% 4 5% 6% 6% 9% 31%	1800
	11th to 20th	Night	11% 8% 4 7% 6% 3 6% 4 5% 5% 40%	1727
	21st to end	Night	11% 8% 3 5% 7% 3 5% 5% 6% 9% 39%	1620
May	1st to 10th	Night	9% 7% 2 5% 5% 3 5% 5% 5% 7% 47%	1517
	11th to 20th	Night	10% 6% 3 5% 6% 3 6% 5% 7% 10% 41%	1416
	21st to end	Night	9% 6% 2 5% 6% 4 6% 6% 6% 8% 41%	1552
June	1st to 10th	Night	12% 5% 3 5% 5% 3 5% 5% 6% 8% 43%	1332
	11th to 20th	Night	10% 6% 3 5% 6% 4 5% 5% 6% 5% 46%	1260
	21st to end	Night	7% 4 1 4 5% 4 4 4 5% 6% 56%	1326
July	1st to 10th	Night	3 2 2 3 1 4 4 4 7% 70%	1440
	11th to 20th	Night	3 1 1 2 2 2 2 3 5% 6% 72%	1440
	21st to end	Night	1 1 1 2 2 1 3 3 3 4 79%	1576
August	1st to 10th	Night	3 2 1 3 2 2 3 4 4 7% 68%	1432
	11th to 20th	Night	3 3 1 3 3 2 3 3 3 6% 70%	1547
	21st to end	Night	4 3 1 2 3 2 3 3 5% 6% 66%	1940
September	1st to 10th	Night	4 2 1 3 3 2 4 3 4 6% 68%	1800
	11th to 20th	Night	6% 4 2 5% 4 3 4 4 5% 8% 55%	1906
	21st to end	Night	9% 4 2 4 4 2 4 4 6% 8% 53%	1980
October	1st to 10th	Night	11% 6% 3 5% 5% 3 3 5% 5% 6% 48%	2038
	11th to 20th	Night	14% 6% 3 5% 5% 2 4 5% 4 7% 46%	2259
	21st to end	Night	15% 8% 3 5% 6% 3 3 4 5% 6% 42%	2574
November	1st to 10th	Night	20% 10% 3 7% 6% 3 4 5% 6% 6% 30%	2405
	11th to 20th	Night	21% 10% 5% 7% 6% 3 5% 4 5% 5% 29%	2531
	21st to end	Night	19% 11% 4 8% 6% 3 4 5% 6% 6% 30%	2710
December	1st to 10th	Night	18% 11% 4 8% 6% 3 5% 5% 5% 7% 29%	2850
	11th to 20th	Night	21% 16% 5% 10% 7% 4 6% 5% 6% 5% 16%	3510
	21st to end	Night	19% 13% 4 8% 7% 4 5% 5% 5% 6% 23%	5008

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	68% 9% 13% 9% 1	2539
	11th to 20th	Day	64% 6% 12% 14% 2 1	2540
	21st to end	Day	70% 6% 13% 9% 1 1	2794
February	1st to 10th	Day	60% 9% 14% 12% 4	1534
	11th to 20th	Day	62% 7% 12% 13% 6%	1807
	21st to end	Day	61% 8% 8% 16% 6% 1	1570
March	1st to 10th	Day	55% 8% 13% 17% 6% 1	1871
	11th to 20th	Day	57% 8% 13% 17% 6%	1852
	21st to end	Day	64% 8% 14% 11% 3	2348
April	1st to 10th	Day	54% 8% 15% 17% 6%	2160
	11th to 20th	Day	50% 7% 12% 19% 11% 2	2184
	21st to end	Day	46% 9% 11% 23% 10% 1	2340
May	1st to 10th	Day	36% 6% 14% 30% 13% 1	2440
	11th to 20th	Day	43% 7% 15% 24% 11% 1	2480
	21st to end	Day	44% 7% 15% 25% 8% 1	2724
June	1st to 10th	Day	44% 7% 11% 25% 12%	2623
	11th to 20th	Day	39% 7% 14% 25% 13% 2	2700
	21st to end	Day	25% 5% 11% 32% 23% 4	2627
July	1st to 10th	Day	17% 4 8% 26% 30% 15%	2451
	11th to 20th	Day	15% 4 8% 18% 37% 17%	2445
	21st to end	Day	8% 2 4 20% 45% 19%	2589
August	1st to 10th	Day	17% 4 7% 23% 35% 15%	2490
	11th to 20th	Day	16% 4 8% 26% 34% 11%	2352
	21st to end	Day	22% 4 10% 29% 28% 7%	2412
September	1st to 10th	Day	17% 5% 10% 30% 26% 12%	2160
	11th to 20th	Day	30% 5% 12% 24% 23% 6%	2053
	21st to end	Day	32% 7% 16% 27% 14% 4	1980
October	1st to 10th	Day	39% 6% 13% 27% 14% 1	1919
	11th to 20th	Day	39% 6% 16% 29% 11% 1	1700
	21st to end	Day	50% 6% 14% 21% 8%	1782
November	1st to 10th	Day	57% 9% 13% 17% 4 1	1674
	11th to 20th	Day	60% 8% 14% 13% 3 1	1649
	21st to end	Day	59% 8% 15% 13% 5% 1	1447
December	1st to 10th	Day	65% 8% 12% 12% 2 1	1330
	11th to 20th	Day	70% 9% 11% 9% 1	1684
	21st to end	Day	59% 10% 14% 12% 4	2674
January	1st to 10th	Night	68% 9% 11% 11% 1 1	4406
	11th to 20th	Night	61% 5% 13% 14% 5% 1	4420
	21st to end	Night	62% 9% 16% 12% 2	4862
February	1st to 10th	Night	61% 7% 13% 14% 5% 1	2642
	11th to 20th	Night	56% 6% 15% 14% 8%	2271
	21st to end	Night	56% 7% 11% 18% 7% 1	1884
March	1st to 10th	Night	53% 7% 12% 19% 9% 1	2249
	11th to 20th	Night	49% 7% 11% 23% 9%	2107
	21st to end	Night	55% 8% 13% 18% 5%	2006
April	1st to 10th	Night	48% 8% 14% 22% 8%	1800
	11th to 20th	Night	46% 6% 10% 22% 14% 2	1727
	21st to end	Night	44% 6% 12% 22% 13% 3	1620
May	1st to 10th	Night	37% 6% 9% 30% 18% 1	1517
	11th to 20th	Night	37% 6% 14% 26% 16% 2	1416
	21st to end	Night	38% 8% 14% 30% 9% 1	1552
June	1st to 10th	Night	38% 7% 11% 25% 17% 2	1332
	11th to 20th	Night	39% 6% 9% 26% 16% 4	1260
	21st to end	Night	29% 4 9% 24% 26% 7%	1326
July	1st to 10th	Night	16% 2 6% 22% 34% 20%	1400
	11th to 20th	Night	14% 4 7% 18% 30% 27%	1392
	21st to end	Night	11% 3 4 11% 39% 32%	1488
August	1st to 10th	Night	16% 4 5% 16% 36% 22%	1424
	11th to 20th	Night	18% 4 5% 20% 34% 19%	1547
	21st to end	Night	19% 4 8% 23% 31% 15%	1940
September	1st to 10th	Night	18% 4 9% 26% 27% 17%	1800
	11th to 20th	Night	29% 5% 8% 23% 26% 9%	1906
	21st to end	Night	30% 5% 13% 28% 16% 8%	1980
October	1st to 10th	Night	36% 5% 12% 28% 18% 2	2038
	11th to 20th	Night	40% 6% 11% 24% 17% 2	2259
	21st to end	Night	43% 8% 11% 23% 14% 2	2574
November	1st to 10th	Night	54% 7% 13% 19% 6% 1	2405
	11th to 20th	Night	57% 6% 14% 15% 6% 1	2531
	21st to end	Night	54% 6% 16% 18% 6%	2710
December	1st to 10th	Night	56% 8% 14% 17% 4	2850
	11th to 20th	Night	68% 8% 13% 10% 1	3507
	21st to end	Night	58% 10% 13% 13% 5%	5008

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% 24% 19% 11% 7%	180
	11th to 20th	Day	29% 9% 26% 17% 14% 6%	180
	21st to end	Day	32% 7% 31% 21% 8% 1	198
February	1st to 10th	Day	28% 14% 33% 19% 5% 1	194
	11th to 20th	Day	28% 15% 23% 23% 9% 2	430
	21st to end	Day	23% 16% 24% 25% 10% 2	382
March	1st to 10th	Day	19% 13% 29% 22% 14% 2	449
	11th to 20th	Day	17% 11% 22% 25% 21% 4	420
	21st to end	Day	21% 16% 29% 22% 11% 2	462
April	1st to 10th	Day	19% 10% 28% 25% 13% 4	420
	11th to 20th	Day	17% 11% 33% 22% 12% 5%	412
	21st to end	Day	13% 12% 27% 27% 16% 5%	420
May	1st to 10th	Day	11% 9% 22% 32% 23% 4	423
	11th to 20th	Day	16% 6% 19% 25% 20% 14%	448
	21st to end	Day	11% 8% 18% 25% 25% 13%	485
June	1st to 10th	Day	14% 7% 19% 28% 22% 11%	553
	11th to 20th	Day	14% 9% 29% 24% 17% 6%	630
	21st to end	Day	6% 4 21% 27% 29% 12%	557
July	1st to 10th	Day	4 2 17% 33% 35% 8%	446
	11th to 20th	Day	4 4 18% 36% 30% 9%	444
	21st to end	Day	1 3 15% 36% 31% 13%	487
August	1st to 10th	Day	4 4 16% 30% 32% 14%	447
	11th to 20th	Day	3 2 12% 32% 33% 18%	437
	21st to end	Day	7% 5% 21% 27% 25% 15%	495
September	1st to 10th	Day	6% 2 27% 26% 28% 12%	450
	11th to 20th	Day	9% 5% 24% 22% 27% 13%	450
	21st to end	Day	11% 8% 21% 28% 26% 6%	450
October	1st to 10th	Day	14% 8% 22% 29% 19% 8%	450
	11th to 20th	Day	17% 10% 21% 25% 20% 8%	350
	21st to end	Day	24% 11% 27% 22% 11% 5%	297
November	1st to 10th	Day	26% 9% 23% 30% 11%	270
	11th to 20th	Day	23% 15% 22% 22% 12% 5%	241
	21st to end	Day	18% 12% 30% 22% 15% 3	180
December	1st to 10th	Day	27% 13% 22% 21% 10% 6%	180
	11th to 20th	Day	36% 13% 23% 15% 11% 3	180
	21st to end	Day	27% 11% 29% 20% 11% 3	198
January	1st to 10th	Night	32% 10% 21% 24% 10% 3	760
	11th to 20th	Night	28% 8% 20% 27% 14% 3	760
	21st to end	Night	23% 6% 23% 31% 16% 2	836
February	1st to 10th	Night	25% 10% 24% 31% 10% 1	760
	11th to 20th	Night	24% 9% 21% 31% 14% 2	744
	21st to end	Night	21% 10% 20% 33% 13% 3	628
March	1st to 10th	Night	19% 8% 25% 32% 13% 3	750
	11th to 20th	Night	17% 9% 23% 29% 20% 1	720
	21st to end	Night	21% 6% 28% 33% 11% 2	792
April	1st to 10th	Night	15% 5% 27% 33% 17% 2	720
	11th to 20th	Night	15% 8% 29% 31% 15% 3	659
	21st to end	Night	14% 7% 25% 32% 20% 3	540
May	1st to 10th	Night	9% 6% 26% 33% 23% 3	437
	11th to 20th	Night	11% 4 16% 33% 27% 8%	354
	21st to end	Night	11% 6% 19% 34% 25% 5%	389
June	1st to 10th	Night	11% 5% 23% 35% 20% 6%	360
	11th to 20th	Night	12% 4 28% 34% 19% 3	360
	21st to end	Night	8% 3 18% 40% 26% 4	360
July	1st to 10th	Night	3 1 13% 44% 34% 4	350
	11th to 20th	Night	3 3 18% 46% 28% 2	348
	21st to end	Night	1 1 12% 44% 37% 5%	394
August	1st to 10th	Night	4 3 12% 38% 36% 7%	358
	11th to 20th	Night	3 2 10% 38% 38% 10%	479
	21st to end	Night	4 2 17% 39% 33% 5%	752
September	1st to 10th	Night	5% 2 17% 42% 27% 7%	720
	11th to 20th	Night	7% 3 18% 31% 30% 11%	720
	21st to end	Night	12% 3 18% 33% 28% 7%	720
October	1st to 10th	Night	14% 5% 18% 37% 24% 3	720
	11th to 20th	Night	16% 7% 19% 29% 26% 4	720
	21st to end	Night	19% 6% 25% 29% 16% 4	792
November	1st to 10th	Night	26% 7% 19% 36% 12%	740
	11th to 20th	Night	25% 9% 26% 26% 12% 2	760
	21st to end	Night	23% 8% 20% 28% 17% 3	810
December	1st to 10th	Night	22% 7% 19% 34% 15% 1	950
	11th to 20th	Night	31% 6% 22% 30% 10% 1	950
	21st to end	Night	36% 10% 20% 26% 9%	917

Page generated at 2024-03-05 04:24:02. Version ac07

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