Yakima
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Yakima clear sky chart from 2005-11-06 to 2024-11-04.

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	7% 7% 2 6% 4 4 4 3 5% 6% 52%	105343
	Night	8% 8% 3 6% 4 4 4 4 5% 7% 48%	102340
Transparency	Day	31% 6% 10% 23% 20% 10%	105087
	Night	35% 6% 13% 24% 17% 6%	102185
Seeing	Day	10% 9% 19% 30% 24% 8%	14422
	Night	11% 4 20% 41% 21% 3	23401

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	14% 17% 4 11% 6% 4 4 5% 5% 6% 22%	2539
	11th to 20th	Day	17% 16% 4 8% 4 5% 4 4 5% 6% 28%	2540
	21st to end	Day	23% 17% 5% 15% 6% 5% 3 3 4 6% 14%	2794
February	1st to 10th	Day	11% 10% 4 9% 6% 4 6% 4 6% 8% 32%	1705
	11th to 20th	Day	9% 11% 4 8% 4 5% 5% 4 6% 7% 38%	1665
	21st to end	Day	7% 10% 3 7% 5% 4 5% 4 8% 8% 39%	1570
March	1st to 10th	Day	7% 7% 3 7% 5% 6% 6% 5% 8% 9% 37%	3138
	11th to 20th	Day	5% 6% 2 5% 4 4 3 4 5% 7% 55%	3422
	21st to end	Day	7% 8% 4 9% 7% 7% 6% 5% 6% 8% 33%	4061
April	1st to 10th	Day	8% 9% 2 7% 7% 7% 5% 4 7% 7% 36%	2280
	11th to 20th	Day	6% 9% 3 6% 5% 4 5% 4 6% 9% 43%	2249
	21st to end	Day	5% 6% 3 7% 5% 5% 5% 5% 7% 8% 45%	2465
May	1st to 10th	Day	7% 5% 2 5% 4 4 4 3 5% 6% 56%	4420
	11th to 20th	Day	5% 4 2 4 3 3 3 3 4 7% 62%	4377
	21st to end	Day	8% 8% 2 7% 5% 5% 6% 5% 7% 8% 40%	4813
June	1st to 10th	Day	8% 5% 2 6% 4 5% 4 3 7% 8% 47%	2660
	11th to 20th	Day	5% 4 2 5% 4 5% 5% 5% 6% 7% 53%	2660
	21st to end	Day	4 3 1 4 4 3 3 3 5% 6% 65%	2660
July	1st to 10th	Day	1 1 1 1 1 2 2 2 3 4 82%	4420
	11th to 20th	Day	2 1 1 2 1 2 2 2 2 3 82%	4420
	21st to end	Day	1 2 2 1 2 2 2 3 4 81%	4790
August	1st to 10th	Day	2 2 1 2 2 2 2 2 4 5% 75%	4400
	11th to 20th	Day	2 1 1 3 3 2 3 3 4 6% 72%	4060
	21st to end	Day	4 5% 2 4 2 2 3 2 4 5% 66%	4181
September	1st to 10th	Day	3 2 1 2 2 2 3 3 4 6% 71%	2280
	11th to 20th	Day	4 4 2 5% 4 4 4 4 5% 6% 59%	2280
	21st to end	Day	6% 4 2 5% 3 4 4 2 5% 6% 60%	2046
October	1st to 10th	Day	5% 3 2 3 3 3 3 3 6% 8% 63%	3180
	11th to 20th	Day	5% 5% 2 5% 4 4 6% 5% 6% 9% 49%	3161
	21st to end	Day	8% 6% 2 7% 6% 6% 5% 4 6% 7% 43%	3147
November	1st to 10th	Day	10% 10% 2 7% 6% 5% 5% 4 6% 7% 38%	1678
	11th to 20th	Day	9% 11% 3 11% 6% 5% 5% 4 6% 6% 34%	1520
	21st to end	Day	11% 11% 4 9% 5% 5% 6% 4 6% 8% 31%	1520
December	1st to 10th	Day	10% 13% 5% 11% 6% 5% 4 4 6% 6% 31%	1520
	11th to 20th	Day	14% 15% 7% 14% 8% 5% 4 4 4 6% 19%	1928
	21st to end	Day	12% 18% 6% 13% 6% 5% 5% 4 5% 5% 21%	2794
January	1st to 10th	Night	12% 19% 5% 10% 6% 5% 6% 4 6% 6% 21%	4406
	11th to 20th	Night	16% 13% 4 8% 5% 4 4 3 5% 8% 30%	4420
	21st to end	Night	20% 17% 6% 15% 5% 4 4 3 4 5% 18%	4862
February	1st to 10th	Night	11% 12% 3 7% 5% 5% 5% 5% 6% 8% 34%	2470
	11th to 20th	Night	10% 9% 3 7% 5% 4 4 4 6% 7% 41%	2402
	21st to end	Night	7% 10% 4 8% 5% 4 4 5% 7% 8% 38%	1884
March	1st to 10th	Night	6% 8% 2 6% 5% 6% 6% 5% 8% 9% 38%	3736
	11th to 20th	Night	5% 5% 2 5% 3 3 3 3 6% 6% 59%	3556
	21st to end	Night	6% 7% 3 8% 6% 5% 6% 6% 7% 9% 37%	3591
April	1st to 10th	Night	9% 7% 3 6% 5% 4 6% 3 7% 9% 41%	1900
	11th to 20th	Night	6% 7% 2 7% 4 3 4 4 6% 6% 51%	1879
	21st to end	Night	5% 5% 2 6% 4 4 5% 5% 7% 9% 47%	1712
May	1st to 10th	Night	5% 5% 2 5% 4 3 4 3 4 5% 60%	2540
	11th to 20th	Night	4 2 1 3 3 2 4 3 5% 7% 66%	2516
	21st to end	Night	3 4 1 4 4 4 4 4 6% 8% 57%	2762
June	1st to 10th	Night	8% 4 1 6% 3 3 5% 4 6% 8% 51%	1520
	11th to 20th	Night	5% 4 1 3 3 3 4 3 4 7% 62%	1520
	21st to end	Night	2 3 1 3 4 3 3 3 5% 5% 67%	1520
July	1st to 10th	Night	1 1 1 1 1 1 1 1 3 3 86%	2540
	11th to 20th	Night	1 1 1 1 1 2 2 3 4 84%	2540
	21st to end	Night	1 1 1 1 1 1 1 3 3 85%	2761
August	1st to 10th	Night	2 2 1 2 2 2 2 2 3 5% 78%	2529
	11th to 20th	Night	2 2 1 2 2 2 3 3 4 6% 74%	2774
	21st to end	Night	2 2 1 4 3 3 3 3 5% 5% 69%	3495
September	1st to 10th	Night	3 2 1 2 1 2 2 3 4 6% 74%	1900
	11th to 20th	Night	3 3 2 4 3 4 3 3 5% 7% 64%	1900
	21st to end	Night	5% 3 1 4 3 3 3 4 5% 7% 62%	2130
October	1st to 10th	Night	4 3 1 3 3 2 4 3 6% 7% 64%	3800
	11th to 20th	Night	5% 4 1 5% 3 4 4 5% 8% 8% 52%	3777
	21st to end	Night	9% 6% 3 6% 4 4 5% 4 5% 8% 46%	4410
November	1st to 10th	Night	12% 9% 2 7% 5% 4 5% 3 6% 8% 39%	2470
	11th to 20th	Night	10% 9% 3 8% 6% 5% 5% 4 6% 7% 37%	2660
	21st to end	Night	11% 10% 3 8% 5% 4 4 4 5% 7% 37%	2660
December	1st to 10th	Night	12% 13% 4 10% 6% 4 5% 4 5% 6% 31%	2660
	11th to 20th	Night	16% 13% 6% 16% 6% 5% 4 4 5% 5% 18%	3276
	21st to end	Night	13% 18% 6% 9% 6% 5% 5% 4 5% 5% 26%	4862

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	59% 8% 13% 12% 7%	2539
	11th to 20th	Day	57% 6% 17% 17% 3	2540
	21st to end	Day	73% 5% 9% 9% 4	2794
February	1st to 10th	Day	48% 9% 19% 19% 4 1	1705
	11th to 20th	Day	43% 7% 17% 23% 9% 1	1674
	21st to end	Day	38% 9% 19% 23% 9% 2	1570
March	1st to 10th	Day	36% 10% 11% 26% 16% 1	3138
	11th to 20th	Day	28% 6% 10% 43% 13% 1	3422
	21st to end	Day	44% 9% 15% 20% 11% 1	4061
April	1st to 10th	Day	41% 9% 14% 21% 14% 1	2280
	11th to 20th	Day	35% 7% 14% 23% 18% 4	2252
	21st to end	Day	33% 8% 11% 26% 19% 3	2465
May	1st to 10th	Day	26% 6% 7% 24% 29% 8%	4420
	11th to 20th	Day	20% 4 9% 34% 28% 5%	4380
	21st to end	Day	37% 9% 14% 28% 10% 2	4814
June	1st to 10th	Day	33% 6% 9% 28% 19% 5%	2660
	11th to 20th	Day	27% 6% 10% 30% 23% 4	2660
	21st to end	Day	19% 4 8% 33% 27% 10%	2660
July	1st to 10th	Day	8% 2 4 14% 26% 45%	4351
	11th to 20th	Day	9% 2 3 10% 23% 52%	4345
	21st to end	Day	9% 3 4 17% 36% 32%	4639
August	1st to 10th	Day	12% 3 5% 14% 39% 28%	4384
	11th to 20th	Day	13% 3 7% 36% 32% 9%	4100
	21st to end	Day	22% 3 8% 25% 35% 7%	4180
September	1st to 10th	Day	13% 4 7% 30% 32% 14%	2280
	11th to 20th	Day	24% 6% 10% 26% 25% 10%	2280
	21st to end	Day	25% 4 12% 32% 21% 6%	2046
October	1st to 10th	Day	21% 3 11% 37% 26% 2	3180
	11th to 20th	Day	31% 5% 18% 26% 18% 2	3161
	21st to end	Day	37% 6% 12% 28% 14% 3	3147
November	1st to 10th	Day	42% 8% 16% 21% 10% 2	1678
	11th to 20th	Day	47% 8% 18% 19% 7% 1	1520
	21st to end	Day	49% 8% 18% 16% 8% 1	1520
December	1st to 10th	Day	53% 7% 14% 18% 7% 1	1520
	11th to 20th	Day	66% 7% 12% 10% 4	1928
	21st to end	Day	65% 6% 11% 13% 5% 1	2794
January	1st to 10th	Night	61% 7% 14% 11% 6%	4406
	11th to 20th	Night	52% 6% 18% 18% 6%	4420
	21st to end	Night	70% 5% 11% 10% 2 1	4862
February	1st to 10th	Night	46% 7% 22% 18% 6% 1	2470
	11th to 20th	Night	41% 8% 17% 22% 11% 1	2404
	21st to end	Night	40% 9% 16% 21% 12% 2	1884
March	1st to 10th	Night	35% 9% 13% 27% 14% 2	3736
	11th to 20th	Night	25% 5% 12% 41% 16% 1	3556
	21st to end	Night	40% 7% 16% 30% 7%	3591
April	1st to 10th	Night	36% 8% 15% 26% 13% 2	1900
	11th to 20th	Night	32% 5% 15% 26% 19% 3	1879
	21st to end	Night	29% 8% 13% 30% 16% 3	1712
May	1st to 10th	Night	27% 4 6% 25% 32% 6%	2540
	11th to 20th	Night	18% 4 8% 36% 29% 5%	2516
	21st to end	Night	20% 7% 23% 37% 11% 2	2762
June	1st to 10th	Night	29% 5% 9% 32% 21% 4	1520
	11th to 20th	Night	23% 5% 11% 36% 23% 3	1520
	21st to end	Night	18% 5% 7% 34% 27% 9%	1520
July	1st to 10th	Night	6% 2 5% 16% 27% 43%	2500
	11th to 20th	Night	7% 2 4 11% 27% 49%	2492
	21st to end	Night	6% 2 4 20% 37% 32%	2674
August	1st to 10th	Night	11% 2 4 13% 42% 28%	2521
	11th to 20th	Night	13% 3 9% 39% 25% 10%	2800
	21st to end	Night	16% 4 10% 26% 35% 9%	3495
September	1st to 10th	Night	12% 3 7% 30% 30% 17%	1900
	11th to 20th	Night	20% 4 12% 27% 26% 12%	1900
	21st to end	Night	20% 4 12% 33% 23% 8%	2130
October	1st to 10th	Night	19% 4 9% 42% 25% 1	3800
	11th to 20th	Night	26% 7% 17% 30% 18% 2	3777
	21st to end	Night	35% 5% 12% 30% 16% 1	4410
November	1st to 10th	Night	43% 7% 15% 22% 13% 1	2470
	11th to 20th	Night	44% 8% 18% 21% 8% 1	2660
	21st to end	Night	45% 6% 19% 18% 11% 1	2660
December	1st to 10th	Night	54% 6% 17% 19% 4	2660
	11th to 20th	Night	66% 7% 15% 9% 4	3276
	21st to end	Night	59% 6% 14% 13% 7% 1	4862

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	23% 7% 18% 26% 20% 6%	180
	11th to 20th	Day	23% 8% 11% 27% 26% 6%	180
	21st to end	Day	21% 3 8% 38% 26% 5%	198
February	1st to 10th	Day	17% 9% 19% 37% 16% 2	365
	11th to 20th	Day	19% 10% 23% 30% 16% 2	365
	21st to end	Day	14% 9% 26% 32% 14% 4	382
March	1st to 10th	Day	15% 11% 27% 28% 16% 3	460
	11th to 20th	Day	11% 14% 18% 31% 21% 5%	460
	21st to end	Day	13% 16% 23% 31% 14% 3	506
April	1st to 10th	Day	18% 13% 23% 24% 17% 4	460
	11th to 20th	Day	13% 17% 24% 26% 14% 6%	452
	21st to end	Day	9% 15% 27% 26% 16% 7%	460
May	1st to 10th	Day	9% 13% 25% 31% 17% 5%	463
	11th to 20th	Day	12% 9% 22% 28% 20% 9%	488
	21st to end	Day	11% 9% 19% 27% 26% 9%	529
June	1st to 10th	Day	10% 9% 20% 26% 25% 10%	490
	11th to 20th	Day	8% 12% 26% 32% 16% 6%	490
	21st to end	Day	3 9% 19% 28% 33% 7%	490
July	1st to 10th	Day	2 5% 15% 36% 33% 8%	486
	11th to 20th	Day	2 4 19% 32% 32% 10%	484
	21st to end	Day	1 3 15% 30% 37% 14%	531
August	1st to 10th	Day	5% 3 12% 29% 37% 15%	487
	11th to 20th	Day	1 3 12% 26% 38% 19%	477
	21st to end	Day	4 7% 18% 29% 27% 15%	539
September	1st to 10th	Day	4 5% 14% 30% 31% 16%	490
	11th to 20th	Day	7% 6% 15% 33% 28% 11%	490
	21st to end	Day	8% 8% 19% 31% 28% 7%	490
October	1st to 10th	Day	10% 9% 22% 26% 26% 8%	490
	11th to 20th	Day	12% 8% 18% 28% 26% 8%	490
	21st to end	Day	15% 6% 25% 30% 16% 7%	364
November	1st to 10th	Day	19% 8% 18% 38% 13% 4	268
	11th to 20th	Day	19% 7% 18% 27% 18% 10%	180
	21st to end	Day	14% 4 13% 34% 27% 8%	180
December	1st to 10th	Day	17% 2 13% 34% 21% 14%	180
	11th to 20th	Day	14% 4 9% 49% 21% 2	180
	21st to end	Day	18% 5% 14% 39% 19% 5%	198
January	1st to 10th	Night	19% 6% 19% 37% 16% 3	760
	11th to 20th	Night	19% 4 16% 37% 22% 2	760
	21st to end	Night	19% 3 14% 40% 22% 2	836
February	1st to 10th	Night	15% 6% 22% 41% 14% 2	760
	11th to 20th	Night	15% 3 22% 39% 18% 3	744
	21st to end	Night	11% 11% 18% 42% 17% 2	628
March	1st to 10th	Night	13% 5% 19% 44% 16% 2	760
	11th to 20th	Night	9% 7% 21% 42% 19% 1	760
	21st to end	Night	8% 8% 24% 43% 15% 2	836
April	1st to 10th	Night	12% 6% 22% 40% 18% 2	760
	11th to 20th	Night	9% 7% 29% 36% 17% 3	751
	21st to end	Night	7% 5% 28% 40% 18% 2	572
May	1st to 10th	Night	4 4 28% 44% 18% 2	380
	11th to 20th	Night	8% 6% 21% 39% 26% 1	374
	21st to end	Night	6% 2 20% 45% 24% 3	411
June	1st to 10th	Night	9% 4 25% 38% 22% 1	380
	11th to 20th	Night	8% 4 32% 40% 15% 1	380
	21st to end	Night	3 4 30% 44% 18% 1	380
July	1st to 10th	Night	2 2 24% 51% 20% 1	370
	11th to 20th	Night	1 3 27% 49% 18% 1	368
	21st to end	Night	1 2 23% 44% 28% 1	416
August	1st to 10th	Night	2 1 22% 45% 27% 3	378
	11th to 20th	Night	2 1 13% 38% 37% 8%	538
	21st to end	Night	3 4 18% 39% 32% 4	833
September	1st to 10th	Night	5% 2 15% 39% 35% 4	760
	11th to 20th	Night	4 2 13% 37% 34% 9%	760
	21st to end	Night	7% 3 17% 39% 29% 5%	760
October	1st to 10th	Night	10% 3 16% 42% 25% 3	760
	11th to 20th	Night	9% 3 16% 40% 26% 5%	760
	21st to end	Night	12% 3 19% 44% 17% 4	836
November	1st to 10th	Night	14% 4 17% 48% 16% 2	754
	11th to 20th	Night	15% 6% 22% 37% 18% 3	760
	21st to end	Night	14% 5% 19% 41% 18% 4	760
December	1st to 10th	Night	17% 4 16% 39% 22% 4	760
	11th to 20th	Night	20% 4 13% 45% 17% 1	760
	21st to end	Night	18% 5% 19% 43% 14% 1	836

Page generated at 2024-11-01 19:47:40. Version ac07

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