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 2024-03-28.

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	8% 7% 3 6% 5% 3 4 5% 5% 7% 47%	78647
	Night	9% 8% 3 6% 5% 3 4 4 5% 7% 44%	81364
Transparency	Day	35% 6% 11% 23% 18% 6%	78350
	Night	39% 6% 13% 22% 15% 4	81182
Seeing	Day	11% 9% 19% 30% 24% 8%	13552
	Night	11% 4 19% 41% 21% 3	22741

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% 16% 5% 10% 8% 4 4 6% 5% 7% 22%	2539
	11th to 20th	Day	17% 15% 4 8% 5% 3 5% 5% 5% 6% 28%	2540
	21st to end	Day	23% 16% 6% 13% 8% 3 4 3 3 6% 14%	2794
February	1st to 10th	Day	11% 10% 4 8% 7% 4 6% 5% 6% 8% 32%	1705
	11th to 20th	Day	9% 10% 5% 7% 5% 3 5% 5% 5% 7% 38%	1665
	21st to end	Day	7% 9% 4 6% 6% 3 5% 5% 7% 9% 39%	1570
March	1st to 10th	Day	9% 7% 3 6% 6% 3 7% 6% 8% 10% 35%	1900
	11th to 20th	Day	8% 9% 3 6% 7% 4 5% 6% 6% 8% 38%	2046
	21st to end	Day	6% 8% 4 8% 8% 5% 7% 6% 7% 9% 32%	2393
April	1st to 10th	Day	8% 8% 3 6% 8% 5% 6% 6% 7% 8% 37%	2160
	11th to 20th	Day	7% 9% 3 5% 5% 3 5% 6% 6% 8% 43%	2129
	21st to end	Day	5% 6% 2 6% 5% 4 5% 5% 7% 9% 46%	2334
May	1st to 10th	Day	5% 4 2 4 5% 4 5% 5% 7% 8% 53%	2520
	11th to 20th	Day	8% 6% 3 5% 5% 3 5% 6% 7% 9% 43%	2477
	21st to end	Day	7% 7% 3 6% 5% 3 5% 5% 6% 8% 43%	2723
June	1st to 10th	Day	9% 4 2 5% 5% 3 5% 4 6% 8% 47%	2520
	11th to 20th	Day	5% 4 2 5% 4 3 5% 6% 6% 7% 52%	2520
	21st to end	Day	4 2 2 3 4 2 3 3 4 7% 65%	2520
July	1st to 10th	Day	2 2 1 2 2 2 3 3 5% 6% 72%	2520
	11th to 20th	Day	3 2 1 2 2 1 3 3 3 5% 76%	2520
	21st to end	Day	1 1 1 1 1 2 2 3 4 83%	2741
August	1st to 10th	Day	3 2 1 2 2 1 2 3 4 6% 75%	2507
	11th to 20th	Day	2 1 1 2 2 1 3 3 3 6% 76%	2320
	21st to end	Day	2 2 2 2 3 1 3 5% 5% 6% 70%	2377
September	1st to 10th	Day	3 1 1 2 3 2 2 3 4 6% 72%	2160
	11th to 20th	Day	4 4 2 5% 4 3 4 5% 4 6% 59%	2160
	21st to end	Day	6% 4 2 4 4 3 4 3 5% 6% 59%	1939
October	1st to 10th	Day	7% 5% 3 4 4 3 3 4 6% 8% 54%	1800
	11th to 20th	Day	7% 6% 2 4 5% 2 4 4 5% 10% 51%	1800
	21st to end	Day	10% 7% 2 6% 5% 4 5% 5% 5% 6% 44%	1815
November	1st to 10th	Day	10% 9% 3 6% 6% 4 6% 5% 6% 7% 38%	1651
	11th to 20th	Day	10% 10% 4 10% 7% 4 5% 4 6% 6% 34%	1520
	21st to end	Day	11% 9% 5% 8% 6% 4 6% 5% 5% 8% 31%	1520
December	1st to 10th	Day	11% 11% 5% 10% 7% 4 4 5% 5% 7% 31%	1520
	11th to 20th	Day	14% 14% 7% 13% 8% 4 5% 5% 5% 6% 19%	1928
	21st to end	Day	13% 17% 6% 11% 7% 4 5% 5% 5% 5% 21%	2794
January	1st to 10th	Night	12% 18% 6% 9% 7% 4 5% 5% 6% 7% 21%	4406
	11th to 20th	Night	17% 12% 4 7% 6% 3 4 4 5% 8% 30%	4420
	21st to end	Night	20% 17% 6% 13% 6% 3 4 3 4 5% 18%	4862
February	1st to 10th	Night	11% 11% 4 6% 6% 3 5% 6% 6% 8% 34%	2470
	11th to 20th	Night	10% 9% 3 6% 5% 3 5% 5% 6% 7% 41%	2402
	21st to end	Night	8% 10% 4 7% 6% 3 5% 6% 6% 8% 38%	1884
March	1st to 10th	Night	9% 9% 3 5% 6% 3 5% 6% 6% 8% 39%	2280
	11th to 20th	Night	7% 7% 3 6% 5% 3 5% 6% 8% 9% 41%	2132
	21st to end	Night	6% 7% 3 8% 6% 3 6% 6% 6% 9% 39%	2117
April	1st to 10th	Night	10% 7% 3 5% 6% 3 5% 4 7% 10% 40%	1800
	11th to 20th	Night	6% 7% 3 6% 5% 3 4 4 5% 6% 51%	1779
	21st to end	Night	6% 4 3 5% 5% 3 5% 6% 7% 9% 47%	1623
May	1st to 10th	Night	4 4 2 4 5% 3 4 5% 5% 6% 59%	1440
	11th to 20th	Night	8% 3 2 4 5% 2 5% 4 6% 9% 50%	1416
	21st to end	Night	4 4 2 5% 5% 3 6% 6% 7% 8% 50%	1552
June	1st to 10th	Night	8% 4 2 5% 4 2 5% 5% 6% 8% 52%	1440
	11th to 20th	Night	5% 5% 1 3 3 2 5% 4 4 7% 62%	1440
	21st to end	Night	3 3 1 2 4 2 4 4 5% 5% 67%	1440
July	1st to 10th	Night	2 1 1 2 2 2 2 3 5% 6% 76%	1440
	11th to 20th	Night	1 1 1 2 2 1 3 3 3 4 80%	1440
	21st to end	Night	1 1 1 1 1 1 2 1 3 3 85%	1576
August	1st to 10th	Night	2 2 1 2 2 1 2 2 2 6% 77%	1432
	11th to 20th	Night	2 1 1 1 2 1 2 2 4 5% 78%	1577
	21st to end	Night	2 1 1 2 3 2 3 3 5% 6% 73%	1977
September	1st to 10th	Night	3 2 1 2 1 1 2 3 4 6% 75%	1800
	11th to 20th	Night	3 3 2 3 4 3 4 4 5% 7% 64%	1800
	21st to end	Night	6% 3 1 3 3 2 3 4 5% 7% 62%	2017
October	1st to 10th	Night	8% 5% 2 4 4 3 4 3 4 7% 57%	2160
	11th to 20th	Night	7% 4 2 5% 4 3 4 5% 6% 7% 51%	2160
	21st to end	Night	9% 6% 3 5% 5% 3 4 4 4 7% 49%	2539
November	1st to 10th	Night	12% 8% 3 6% 6% 4 4 5% 6% 8% 39%	2425
	11th to 20th	Night	10% 9% 3 7% 6% 4 5% 5% 6% 8% 37%	2660
	21st to end	Night	11% 9% 4 8% 5% 3 5% 5% 5% 7% 38%	2660
December	1st to 10th	Night	12% 12% 5% 9% 6% 3 5% 4 5% 6% 31%	2660
	11th to 20th	Night	16% 12% 7% 16% 8% 3 5% 5% 5% 5% 19%	3276
	21st to end	Night	13% 18% 6% 7% 7% 4 5% 5% 4 6% 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	40% 9% 13% 25% 12% 1	1900
	11th to 20th	Day	41% 7% 12% 29% 10%	2046
	21st to end	Day	45% 9% 17% 21% 8% 1	2393
April	1st to 10th	Day	41% 8% 13% 21% 15% 1	2160
	11th to 20th	Day	36% 7% 14% 23% 18% 3	2132
	21st to end	Day	32% 8% 11% 26% 19% 4	2334
May	1st to 10th	Day	26% 7% 11% 33% 21% 2	2520
	11th to 20th	Day	35% 6% 11% 27% 19% 2	2480
	21st to end	Day	36% 7% 13% 28% 14% 2	2724
June	1st to 10th	Day	33% 6% 10% 28% 19% 5%	2520
	11th to 20th	Day	27% 6% 10% 31% 23% 3	2520
	21st to end	Day	19% 4 8% 33% 26% 10%	2520
July	1st to 10th	Day	14% 4 6% 24% 34% 19%	2451
	11th to 20th	Day	13% 3 5% 17% 35% 27%	2445
	21st to end	Day	7% 3 2 16% 41% 30%	2589
August	1st to 10th	Day	12% 3 6% 21% 38% 19%	2490
	11th to 20th	Day	12% 3 5% 24% 40% 16%	2320
	21st to end	Day	14% 4 6% 30% 35% 10%	2377
September	1st to 10th	Day	13% 4 7% 30% 31% 14%	2160
	11th to 20th	Day	24% 6% 10% 24% 26% 11%	2160
	21st to end	Day	26% 4 12% 31% 22% 6%	1939
October	1st to 10th	Day	29% 4 13% 32% 19% 3	1800
	11th to 20th	Day	30% 5% 18% 31% 15% 2	1800
	21st to end	Day	38% 7% 13% 27% 14% 1	1815
November	1st to 10th	Day	42% 8% 16% 21% 10% 2	1651
	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	40% 8% 14% 26% 11% 2	2280
	11th to 20th	Night	37% 6% 15% 30% 10% 1	2132
	21st to end	Night	41% 6% 17% 26% 9% 1	2117
April	1st to 10th	Night	36% 8% 14% 26% 14% 2	1800
	11th to 20th	Night	33% 5% 14% 27% 19% 2	1779
	21st to end	Night	30% 8% 13% 29% 17% 3	1623
May	1st to 10th	Night	25% 6% 10% 35% 22% 3	1440
	11th to 20th	Night	29% 5% 13% 31% 19% 3	1416
	21st to end	Night	29% 6% 15% 33% 15% 3	1552
June	1st to 10th	Night	29% 5% 9% 32% 20% 3	1440
	11th to 20th	Night	23% 5% 11% 37% 22% 3	1440
	21st to end	Night	18% 5% 7% 34% 27% 10%	1440
July	1st to 10th	Night	11% 3 9% 25% 32% 20%	1400
	11th to 20th	Night	9% 3 6% 20% 36% 26%	1392
	21st to end	Night	7% 2 3 16% 44% 29%	1488
August	1st to 10th	Night	11% 3 5% 21% 39% 21%	1424
	11th to 20th	Night	10% 2 7% 27% 35% 19%	1577
	21st to end	Night	11% 4 7% 28% 39% 11%	1977
September	1st to 10th	Night	12% 3 7% 31% 31% 16%	1800
	11th to 20th	Night	20% 4 12% 26% 27% 12%	1800
	21st to end	Night	21% 4 12% 33% 23% 8%	2017
October	1st to 10th	Night	29% 5% 9% 29% 26% 2	2160
	11th to 20th	Night	29% 7% 12% 31% 17% 3	2160
	21st to end	Night	34% 5% 13% 29% 17% 1	2539
November	1st to 10th	Night	42% 7% 15% 22% 13% 1	2425
	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% 17% 23% 30% 14% 2	491
April	1st to 10th	Day	19% 14% 21% 24% 17% 5%	420
	11th to 20th	Day	13% 17% 23% 25% 15% 6%	412
	21st to end	Day	10% 16% 26% 26% 15% 7%	420
May	1st to 10th	Day	8% 13% 25% 31% 18% 4	423
	11th to 20th	Day	13% 9% 21% 27% 21% 8%	448
	21st to end	Day	10% 8% 19% 27% 26% 10%	485
June	1st to 10th	Day	9% 9% 21% 26% 25% 11%	450
	11th to 20th	Day	8% 12% 26% 31% 16% 6%	450
	21st to end	Day	3 9% 20% 28% 34% 7%	450
July	1st to 10th	Day	3 5% 15% 37% 32% 8%	446
	11th to 20th	Day	2 5% 20% 33% 30% 10%	444
	21st to end	Day	1 3 15% 30% 36% 15%	487
August	1st to 10th	Day	5% 4 13% 27% 38% 15%	447
	11th to 20th	Day	1 3 12% 26% 38% 19%	437
	21st to end	Day	4 7% 18% 28% 28% 15%	495
September	1st to 10th	Day	4 5% 15% 32% 31% 13%	450
	11th to 20th	Day	8% 6% 15% 33% 28% 11%	450
	21st to end	Day	8% 8% 20% 30% 27% 6%	450
October	1st to 10th	Day	11% 8% 24% 25% 25% 8%	450
	11th to 20th	Day	12% 8% 17% 30% 25% 8%	450
	21st to end	Day	16% 6% 25% 28% 16% 8%	330
November	1st to 10th	Day	19% 8% 18% 37% 14% 4	259
	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% 23% 43% 15% 2	820
April	1st to 10th	Night	13% 6% 21% 41% 18% 2	720
	11th to 20th	Night	9% 6% 27% 36% 18% 3	711
	21st to end	Night	8% 5% 29% 39% 18% 2	543
May	1st to 10th	Night	4 4 28% 43% 18% 2	360
	11th to 20th	Night	8% 5% 20% 40% 26% 1	354
	21st to end	Night	6% 2 19% 43% 26% 3	389
June	1st to 10th	Night	8% 5% 25% 38% 22% 1	360
	11th to 20th	Night	8% 4 31% 40% 15% 1	360
	21st to end	Night	3 4 29% 44% 18% 1	360
July	1st to 10th	Night	3 2 23% 50% 21% 1	350
	11th to 20th	Night	1 3 28% 48% 18% 1	348
	21st to end	Night	1 2 23% 43% 29% 2	394
August	1st to 10th	Night	2 1 21% 45% 27% 3	358
	11th to 20th	Night	2 1 13% 38% 37% 9%	509
	21st to end	Night	3 4 18% 39% 32% 4	789
September	1st to 10th	Night	5% 3 15% 39% 34% 4	720
	11th to 20th	Night	4 2 12% 37% 35% 9%	720
	21st to end	Night	7% 3 17% 39% 29% 6%	720
October	1st to 10th	Night	10% 3 15% 42% 26% 3	720
	11th to 20th	Night	9% 3 16% 39% 27% 5%	720
	21st to end	Night	12% 3 20% 43% 18% 4	792
November	1st to 10th	Night	14% 4 16% 48% 16% 2	740
	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 2024-03-24 20:37:01. Version ac07

Copyright © 2024 Attilla Danko.