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 2024-11-02.

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 3 5% 6% 46%	101301
	Night	13% 9% 3 7% 4 4 4 4 5% 6% 41%	97750
Transparency	Day	39% 7% 11% 21% 15% 7%	101069
	Night	43% 6% 11% 19% 13% 7%	97628
Seeing	Day	14% 9% 23% 26% 20% 8%	14653
	Night	17% 6% 21% 33% 19% 3	23859

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% 21% 6% 9% 5% 4 5% 4 6% 6% 16%	2539
	11th to 20th	Day	22% 14% 5% 11% 5% 5% 5% 4 5% 5% 20%	2516
	21st to end	Day	23% 18% 6% 10% 5% 5% 4 3 4 5% 17%	2794
February	1st to 10th	Day	18% 16% 4 8% 6% 3 5% 4 6% 6% 24%	1534
	11th to 20th	Day	17% 15% 4 9% 6% 4 5% 2 5% 6% 25%	1797
	21st to end	Day	16% 17% 4 9% 6% 5% 4 4 5% 6% 24%	1570
March	1st to 10th	Day	10% 11% 4 9% 5% 5% 5% 5% 8% 8% 30%	3138
	11th to 20th	Day	8% 8% 2 6% 5% 4 5% 4 5% 7% 47%	3271
	21st to end	Day	14% 15% 4 11% 7% 6% 6% 5% 5% 5% 22%	4124
April	1st to 10th	Day	13% 11% 4 9% 6% 5% 5% 4 7% 7% 27%	2280
	11th to 20th	Day	11% 10% 3 8% 6% 5% 4 5% 6% 6% 36%	2307
	21st to end	Day	11% 8% 3 8% 6% 5% 5% 4 6% 7% 37%	2470
May	1st to 10th	Day	10% 7% 3 6% 4 5% 5% 4 6% 8% 44%	4288
	11th to 20th	Day	7% 5% 2 5% 4 4 5% 4 6% 9% 50%	4377
	21st to end	Day	9% 7% 3 8% 6% 5% 6% 5% 7% 8% 36%	4813
June	1st to 10th	Day	14% 8% 3 6% 5% 4 4 4 6% 7% 40%	2769
	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	12% 6% 2 5% 4 4 5% 3 5% 5% 49%	2025
	11th to 20th	Day	13% 6% 2 6% 3 4 5% 4 5% 6% 46%	1794
	21st to end	Day	17% 10% 3 7% 4 4 4 4 4 6% 37%	1881
November	1st to 10th	Day	22% 9% 3 7% 5% 4 5% 3 6% 7% 28%	1683
	11th to 20th	Day	20% 14% 4 7% 5% 4 5% 4 5% 6% 25%	1649
	21st to end	Day	17% 15% 5% 10% 5% 5% 4 2 5% 6% 25%	1447
December	1st to 10th	Day	20% 13% 5% 12% 6% 5% 5% 4 5% 5% 20%	1330
	11th to 20th	Day	21% 15% 5% 11% 7% 5% 6% 4 4 5% 17%	1682
	21st to end	Day	18% 16% 4 10% 5% 5% 5% 4 6% 7% 21%	2674
January	1st to 10th	Night	23% 18% 4 10% 5% 5% 4 3 5% 5% 17%	4406
	11th to 20th	Night	20% 16% 5% 9% 4 4 4 4 5% 5% 24%	4382
	21st to end	Night	22% 15% 5% 8% 5% 4 5% 4 5% 6% 22%	4862
February	1st to 10th	Night	20% 16% 4 8% 5% 4 4 4 5% 5% 26%	2642
	11th to 20th	Night	16% 14% 3 8% 4 4 5% 4 5% 5% 31%	2270
	21st to end	Night	15% 14% 4 8% 7% 4 4 5% 5% 6% 29%	1884
March	1st to 10th	Night	10% 10% 3 7% 6% 5% 5% 4 5% 8% 37%	3736
	11th to 20th	Night	10% 9% 3 6% 3 3 4 3 5% 6% 50%	3707
	21st to end	Night	12% 10% 4 9% 7% 7% 6% 6% 7% 9% 24%	3527
April	1st to 10th	Night	12% 11% 3 8% 5% 5% 5% 5% 6% 8% 32%	1900
	11th to 20th	Night	11% 9% 4 7% 6% 4 4 3 6% 5% 41%	1824
	21st to end	Night	11% 8% 3 6% 6% 5% 4 4 6% 8% 39%	1710
May	1st to 10th	Night	11% 6% 2 6% 4 5% 4 4 7% 7% 43%	2673
	11th to 20th	Night	7% 6% 2 5% 5% 4 4 3 6% 9% 50%	2516
	21st to end	Night	12% 6% 2 7% 5% 4 6% 5% 6% 7% 39%	2762
June	1st to 10th	Night	11% 5% 2 6% 4 4 5% 4 6% 8% 43%	1406
	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	11% 5% 3 5% 4 3 3 4 5% 6% 50%	2152
	11th to 20th	Night	13% 6% 2 6% 4 4 4 3 4 7% 46%	2385
	21st to end	Night	15% 8% 3 6% 5% 4 3 3 5% 6% 42%	2717
November	1st to 10th	Night	20% 11% 3 8% 5% 4 4 4 6% 6% 30%	2430
	11th to 20th	Night	20% 11% 4 7% 5% 4 5% 3 5% 5% 29%	2531
	21st to end	Night	19% 12% 4 9% 5% 3 4 4 6% 5% 30%	2710
December	1st to 10th	Night	17% 12% 3 9% 6% 4 4 4 5% 7% 28%	2850
	11th to 20th	Night	21% 17% 5% 11% 6% 5% 5% 4 6% 5% 16%	3510
	21st to end	Night	19% 14% 4 9% 6% 5% 4 4 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	48% 8% 10% 24% 10%	3138
	11th to 20th	Day	38% 9% 14% 33% 6%	3271
	21st to end	Day	62% 10% 12% 10% 5% 1	4124
April	1st to 10th	Day	54% 8% 16% 17% 6%	2280
	11th to 20th	Day	49% 7% 12% 19% 12% 2	2307
	21st to end	Day	46% 9% 11% 23% 10% 1	2470
May	1st to 10th	Day	36% 9% 12% 30% 13% 1	4288
	11th to 20th	Day	30% 7% 13% 34% 14% 2	4380
	21st to end	Day	41% 11% 18% 23% 6% 1	4814
June	1st to 10th	Day	44% 7% 11% 24% 13% 1	2769
	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	38% 5% 13% 27% 16% 1	2025
	11th to 20th	Day	39% 5% 16% 28% 11% 1	1794
	21st to end	Day	50% 6% 14% 21% 8% 1	1881
November	1st to 10th	Day	57% 9% 12% 17% 4 1	1683
	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	44% 7% 9% 26% 12% 1	3736
	11th to 20th	Night	37% 7% 11% 35% 11%	3708
	21st to end	Night	54% 12% 13% 17% 4	3527
April	1st to 10th	Night	48% 8% 14% 22% 8%	1900
	11th to 20th	Night	45% 6% 11% 22% 15% 3	1824
	21st to end	Night	43% 6% 12% 21% 14% 3	1710
May	1st to 10th	Night	37% 8% 10% 27% 17% 1	2673
	11th to 20th	Night	30% 7% 10% 30% 22% 2	2516
	21st to end	Night	41% 10% 16% 24% 8% 1	2762
June	1st to 10th	Night	37% 7% 11% 25% 17% 3	1406
	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	35% 5% 12% 28% 20% 2	2152
	11th to 20th	Night	40% 6% 11% 23% 18% 2	2385
	21st to end	Night	43% 7% 11% 24% 13% 2	2717
November	1st to 10th	Night	54% 7% 13% 19% 6% 1	2430
	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% 14% 29% 22% 14% 2	460
	11th to 20th	Day	16% 10% 22% 25% 20% 6%	460
	21st to end	Day	19% 16% 29% 22% 11% 2	506
April	1st to 10th	Day	19% 12% 28% 24% 13% 4	460
	11th to 20th	Day	15% 11% 33% 24% 13% 5%	452
	21st to end	Day	12% 12% 29% 26% 17% 4	460
May	1st to 10th	Day	11% 10% 22% 31% 22% 4	463
	11th to 20th	Day	15% 7% 20% 25% 20% 13%	488
	21st to end	Day	10% 9% 19% 25% 24% 13%	529
June	1st to 10th	Day	14% 7% 18% 28% 23% 10%	599
	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% 10% 23% 30% 11%	273
	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	760
	11th to 20th	Night	16% 9% 23% 28% 22% 1	760
	21st to end	Night	20% 6% 27% 33% 11% 2	836
April	1st to 10th	Night	16% 5% 27% 33% 17% 2	760
	11th to 20th	Night	14% 8% 29% 33% 14% 3	696
	21st to end	Night	13% 7% 26% 32% 19% 2	570
May	1st to 10th	Night	9% 6% 26% 33% 23% 3	461
	11th to 20th	Night	11% 4 16% 34% 27% 8%	374
	21st to end	Night	11% 7% 19% 34% 25% 4	411
June	1st to 10th	Night	11% 5% 23% 36% 20% 6%	380
	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% 11%	748
	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

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