Klickitat County Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Klickitat County Star Party clear sky chart from 2005-11-06 to 2024-04-25.

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% 8% 3 6% 5% 3 5% 5% 5% 7% 45%	83239
	Night	10% 8% 3 6% 6% 3 5% 5% 5% 7% 42%	85958
Transparency	Day	38% 8% 13% 21% 15% 5%	82942
	Night	41% 9% 14% 20% 12% 3	85776
Seeing	Day	14% 18% 29% 24% 12% 3	13730
	Night	14% 13% 25% 28% 17% 3	22933

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	15% 21% 8% 12% 9% 4 5% 4 5% 5% 13%	2539
	11th to 20th	Day	18% 16% 7% 9% 6% 3 5% 5% 5% 8% 18%	2540
	21st to end	Day	25% 12% 5% 9% 8% 4 6% 5% 5% 6% 15%	2837
February	1st to 10th	Day	13% 14% 5% 8% 7% 3 5% 5% 5% 7% 27%	1710
	11th to 20th	Day	12% 10% 4 7% 8% 4 5% 6% 6% 7% 32%	1669
	21st to end	Day	8% 10% 5% 9% 8% 6% 6% 6% 6% 8% 29%	1570
March	1st to 10th	Day	7% 9% 3 7% 6% 4 6% 6% 8% 11% 32%	3138
	11th to 20th	Day	6% 7% 4 6% 5% 3 4 4 5% 8% 48%	3449
	21st to end	Day	8% 11% 4 9% 8% 5% 6% 6% 7% 8% 27%	4041
April	1st to 10th	Day	8% 9% 3 7% 7% 4 7% 7% 7% 9% 33%	2280
	11th to 20th	Day	7% 9% 3 7% 5% 4 6% 5% 6% 8% 40%	2249
	21st to end	Day	5% 6% 3 5% 6% 3 6% 5% 7% 9% 45%	2345
May	1st to 10th	Day	6% 5% 2 4 6% 3 4 5% 7% 9% 48%	2520
	11th to 20th	Day	8% 6% 3 6% 6% 3 6% 6% 8% 10% 39%	2477
	21st to end	Day	8% 5% 2 4 5% 3 6% 6% 7% 9% 45%	2723
June	1st to 10th	Day	9% 5% 2 5% 4 3 5% 6% 6% 8% 47%	2520
	11th to 20th	Day	5% 4 2 4 4 3 5% 5% 5% 8% 55%	2520
	21st to end	Day	3 3 2 3 2 2 3 3 4 6% 68%	2520
July	1st to 10th	Day	2 2 1 2 2 1 2 3 4 6% 76%	2520
	11th to 20th	Day	3 2 2 1 1 3 3 3 5% 76%	2520
	21st to end	Day	2 1 1 1 1 1 2 2 3 84%	2741
August	1st to 10th	Day	3 2 1 1 2 1 2 3 4 5% 76%	2496
	11th to 20th	Day	2 2 1 2 2 1 2 2 3 5% 78%	2294
	21st to end	Day	2 3 1 2 3 2 3 4 3 6% 71%	2376
September	1st to 10th	Day	3 2 1 2 2 1 2 3 4 6% 74%	2160
	11th to 20th	Day	4 4 2 4 4 3 4 5% 5% 7% 59%	2160
	21st to end	Day	7% 6% 2 4 4 3 3 4 4 7% 56%	1938
October	1st to 10th	Day	8% 5% 3 5% 4 3 5% 4 6% 7% 50%	1800
	11th to 20th	Day	9% 7% 2 5% 6% 3 4 5% 7% 7% 44%	1800
	21st to end	Day	13% 8% 3 7% 6% 4 4 5% 6% 6% 39%	1836
November	1st to 10th	Day	11% 11% 4 7% 8% 4 5% 6% 6% 9% 29%	1669
	11th to 20th	Day	13% 10% 6% 9% 9% 4 6% 6% 7% 8% 23%	1520
	21st to end	Day	10% 11% 4 9% 7% 4 5% 5% 7% 8% 29%	1520
December	1st to 10th	Day	13% 11% 6% 10% 7% 4 5% 5% 6% 6% 28%	1520
	11th to 20th	Day	14% 16% 6% 12% 10% 5% 8% 5% 5% 6% 13%	1928
	21st to end	Day	15% 16% 6% 12% 9% 4 6% 4 4 5% 18%	2794
January	1st to 10th	Night	16% 15% 5% 10% 8% 4 6% 6% 6% 6% 18%	4406
	11th to 20th	Night	19% 14% 5% 9% 6% 3 5% 5% 4 6% 24%	4420
	21st to end	Night	22% 12% 4 8% 8% 4 6% 5% 6% 7% 18%	4817
February	1st to 10th	Night	12% 14% 5% 9% 7% 3 5% 5% 5% 7% 29%	2470
	11th to 20th	Night	11% 11% 4 7% 7% 3 5% 5% 5% 6% 37%	2398
	21st to end	Night	9% 13% 6% 8% 6% 4 5% 6% 6% 7% 32%	1884
March	1st to 10th	Night	7% 8% 4 7% 7% 4 5% 6% 7% 9% 35%	3736
	11th to 20th	Night	6% 6% 3 5% 4 3 4 5% 5% 7% 53%	3530
	21st to end	Night	8% 8% 4 7% 7% 5% 6% 6% 7% 9% 32%	3612
April	1st to 10th	Night	8% 8% 3 7% 5% 3 5% 5% 7% 10% 38%	1900
	11th to 20th	Night	8% 6% 3 4 6% 3 4 4 5% 8% 50%	1879
	21st to end	Night	6% 5% 3 6% 5% 3 6% 5% 7% 10% 45%	1709
May	1st to 10th	Night	5% 4 2 3 5% 3 5% 4 6% 8% 56%	1440
	11th to 20th	Night	8% 5% 2 3 4 2 5% 5% 8% 10% 49%	1416
	21st to end	Night	5% 6% 2 4 4 3 4 6% 7% 10% 48%	1552
June	1st to 10th	Night	10% 4 2 4 4 4 3 5% 6% 8% 50%	1440
	11th to 20th	Night	7% 5% 2 3 4 2 4 3 5% 7% 60%	1440
	21st to end	Night	3 3 1 4 4 2 3 3 4 5% 68%	1440
July	1st to 10th	Night	3 2 1 2 2 1 2 3 3 5% 75%	1440
	11th to 20th	Night	2 2 1 1 2 2 2 3 3 4 78%	1440
	21st to end	Night	1 1 1 2 1 1 2 2 3 3 83%	1576
August	1st to 10th	Night	2 2 1 2 2 2 2 3 3 6% 75%	1440
	11th to 20th	Night	3 2 1 2 2 2 2 2 3 4 77%	1606
	21st to end	Night	2 2 1 3 3 1 2 3 3 6% 74%	1980
September	1st to 10th	Night	3 1 1 2 3 1 2 3 5% 5% 75%	1800
	11th to 20th	Night	4 3 2 3 4 3 5% 4 4 5% 64%	1800
	21st to end	Night	6% 3 2 3 3 2 3 5% 6% 7% 59%	2020
October	1st to 10th	Night	7% 5% 3 5% 5% 2 4 5% 4 6% 55%	2160
	11th to 20th	Night	9% 6% 2 6% 5% 3 5% 5% 6% 7% 47%	2160
	21st to end	Night	11% 7% 3 6% 4 3 4 4 5% 7% 46%	2520
November	1st to 10th	Night	14% 9% 3 7% 6% 3 5% 5% 6% 7% 35%	2409
	11th to 20th	Night	14% 11% 5% 6% 6% 4 6% 5% 6% 8% 30%	2660
	21st to end	Night	10% 9% 3 8% 7% 4 5% 5% 6% 8% 34%	2660
December	1st to 10th	Night	13% 10% 5% 9% 8% 4 5% 5% 5% 6% 29%	2660
	11th to 20th	Night	17% 14% 5% 10% 9% 5% 6% 5% 6% 7% 17%	3276
	21st to end	Night	15% 12% 6% 11% 8% 3 5% 5% 4 7% 25%	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	68% 9% 12% 9% 1	2539
	11th to 20th	Day	63% 11% 16% 8% 1	2540
	21st to end	Day	68% 12% 12% 6% 2	2837
February	1st to 10th	Day	57% 10% 16% 14% 3	1710
	11th to 20th	Day	50% 12% 15% 17% 6%	1678
	21st to end	Day	51% 10% 18% 13% 7% 1	1570
March	1st to 10th	Day	42% 8% 17% 23% 10% 1	3138
	11th to 20th	Day	34% 7% 15% 33% 10%	3449
	21st to end	Day	50% 10% 16% 17% 7%	4041
April	1st to 10th	Day	45% 9% 16% 19% 10%	2280
	11th to 20th	Day	41% 8% 16% 19% 13% 3	2252
	21st to end	Day	33% 11% 15% 25% 14% 2	2345
May	1st to 10th	Day	31% 7% 15% 28% 17% 1	2520
	11th to 20th	Day	38% 9% 14% 24% 13% 2	2480
	21st to end	Day	33% 9% 19% 26% 12% 1	2724
June	1st to 10th	Day	33% 9% 12% 29% 15% 3	2520
	11th to 20th	Day	26% 7% 15% 33% 17% 3	2520
	21st to end	Day	18% 5% 12% 32% 24% 9%	2520
July	1st to 10th	Day	11% 4 10% 26% 33% 17%	2451
	11th to 20th	Day	12% 4 8% 17% 36% 24%	2445
	21st to end	Day	8% 2 5% 18% 43% 24%	2589
August	1st to 10th	Day	13% 3 8% 24% 36% 16%	2479
	11th to 20th	Day	11% 3 9% 27% 36% 14%	2294
	21st to end	Day	16% 3 10% 29% 34% 8%	2376
September	1st to 10th	Day	14% 5% 8% 30% 30% 14%	2160
	11th to 20th	Day	25% 6% 11% 25% 24% 8%	2160
	21st to end	Day	30% 6% 15% 26% 19% 5%	1938
October	1st to 10th	Day	33% 8% 13% 26% 17% 3	1800
	11th to 20th	Day	37% 10% 15% 22% 15% 2	1800
	21st to end	Day	44% 9% 13% 21% 12%	1836
November	1st to 10th	Day	52% 9% 14% 18% 6% 1	1669
	11th to 20th	Day	58% 12% 16% 11% 3 1	1520
	21st to end	Day	52% 11% 15% 13% 8% 1	1520
December	1st to 10th	Day	56% 8% 16% 14% 5%	1520
	11th to 20th	Day	67% 15% 10% 6% 2	1928
	21st to end	Day	66% 11% 12% 9% 2	2794
January	1st to 10th	Night	63% 14% 12% 9% 2	4406
	11th to 20th	Night	59% 10% 18% 10% 3	4420
	21st to end	Night	65% 13% 12% 8% 2	4817
February	1st to 10th	Night	54% 10% 18% 15% 3	2470
	11th to 20th	Night	48% 9% 15% 19% 8% 1	2400
	21st to end	Night	48% 11% 16% 17% 7% 1	1884
March	1st to 10th	Night	40% 8% 19% 26% 7% 1	3736
	11th to 20th	Night	31% 8% 17% 31% 12% 1	3530
	21st to end	Night	43% 13% 20% 21% 3	3612
April	1st to 10th	Night	40% 11% 17% 21% 10% 1	1900
	11th to 20th	Night	34% 7% 17% 26% 13% 3	1879
	21st to end	Night	34% 10% 16% 25% 13% 2	1709
May	1st to 10th	Night	26% 7% 17% 34% 16% 1	1440
	11th to 20th	Night	29% 8% 18% 28% 14% 3	1416
	21st to end	Night	29% 10% 20% 28% 12% 1	1552
June	1st to 10th	Night	32% 9% 12% 31% 13% 3	1440
	11th to 20th	Night	25% 5% 16% 35% 18% 1	1440
	21st to end	Night	20% 4 11% 33% 25% 8%	1440
July	1st to 10th	Night	13% 4 10% 24% 33% 16%	1400
	11th to 20th	Night	11% 3 9% 21% 31% 25%	1392
	21st to end	Night	8% 1 5% 16% 44% 26%	1488
August	1st to 10th	Night	13% 2 7% 27% 35% 16%	1432
	11th to 20th	Night	13% 2 8% 26% 36% 15%	1606
	21st to end	Night	14% 4 8% 28% 36% 10%	1980
September	1st to 10th	Night	11% 4 11% 28% 30% 15%	1800
	11th to 20th	Night	23% 6% 9% 29% 22% 12%	1800
	21st to end	Night	23% 7% 13% 27% 21% 8%	2020
October	1st to 10th	Night	30% 7% 11% 24% 25% 3	2160
	11th to 20th	Night	36% 7% 12% 25% 17% 2	2160
	21st to end	Night	39% 8% 11% 24% 17% 1	2520
November	1st to 10th	Night	47% 9% 13% 21% 9%	2409
	11th to 20th	Night	53% 11% 14% 17% 5%	2660
	21st to end	Night	47% 13% 14% 18% 8%	2660
December	1st to 10th	Night	56% 9% 16% 15% 3	2660
	11th to 20th	Night	63% 13% 14% 8% 2	3276
	21st to end	Night	57% 14% 12% 11% 6%	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	26% 24% 23% 16% 8% 3	180
	11th to 20th	Day	26% 18% 24% 22% 9% 1	180
	21st to end	Day	22% 19% 28% 19% 11% 1	228
February	1st to 10th	Day	28% 16% 30% 19% 6% 1	370
	11th to 20th	Day	28% 20% 28% 19% 4 1	367
	21st to end	Day	20% 27% 26% 19% 7% 1	382
March	1st to 10th	Day	20% 23% 32% 18% 6% 1	460
	11th to 20th	Day	20% 21% 29% 21% 9% 1	460
	21st to end	Day	21% 26% 28% 17% 7%	506
April	1st to 10th	Day	22% 21% 32% 15% 7% 2	460
	11th to 20th	Day	19% 28% 28% 15% 8% 2	452
	21st to end	Day	13% 27% 33% 18% 6% 2	437
May	1st to 10th	Day	12% 19% 33% 23% 10% 2	423
	11th to 20th	Day	18% 16% 29% 21% 12% 3	448
	21st to end	Day	10% 18% 27% 28% 12% 4	485
June	1st to 10th	Day	13% 22% 24% 25% 13% 3	450
	11th to 20th	Day	10% 26% 35% 20% 7% 2	450
	21st to end	Day	6% 18% 27% 32% 15% 3	450
July	1st to 10th	Day	2 11% 38% 33% 14% 1	446
	11th to 20th	Day	3 13% 35% 32% 15% 2	444
	21st to end	Day	2 8% 32% 33% 21% 4	487
August	1st to 10th	Day	5% 8% 28% 29% 21% 9%	447
	11th to 20th	Day	3 8% 24% 32% 26% 8%	437
	21st to end	Day	8% 12% 32% 26% 17% 5%	495
September	1st to 10th	Day	7% 10% 31% 31% 15% 6%	450
	11th to 20th	Day	9% 10% 31% 30% 17% 3	450
	21st to end	Day	10% 19% 26% 27% 16% 2	450
October	1st to 10th	Day	13% 18% 28% 22% 16% 3	450
	11th to 20th	Day	18% 16% 23% 24% 14% 4	450
	21st to end	Day	20% 22% 25% 17% 13% 4	351
November	1st to 10th	Day	19% 19% 28% 24% 10%	267
	11th to 20th	Day	21% 25% 18% 24% 9% 3	180
	21st to end	Day	18% 21% 27% 20% 12% 2	180
December	1st to 10th	Day	23% 18% 28% 15% 10% 7%	180
	11th to 20th	Day	24% 23% 27% 19% 6% 1	180
	21st to end	Day	21% 25% 24% 19% 11% 1	198
January	1st to 10th	Night	25% 16% 22% 28% 8% 1	760
	11th to 20th	Night	22% 11% 25% 24% 16% 3	760
	21st to end	Night	22% 10% 20% 29% 16% 2	836
February	1st to 10th	Night	20% 17% 25% 24% 13% 2	760
	11th to 20th	Night	18% 18% 23% 28% 12% 1	744
	21st to end	Night	19% 19% 26% 25% 10% 1	628
March	1st to 10th	Night	16% 15% 29% 23% 16% 2	760
	11th to 20th	Night	13% 16% 27% 30% 12% 2	760
	21st to end	Night	14% 22% 31% 21% 10% 2	836
April	1st to 10th	Night	17% 17% 28% 24% 12% 3	760
	11th to 20th	Night	15% 20% 29% 20% 13% 3	751
	21st to end	Night	11% 19% 30% 26% 14% 2	599
May	1st to 10th	Night	9% 16% 26% 30% 17% 3	360
	11th to 20th	Night	14% 7% 25% 31% 20% 3	354
	21st to end	Night	9% 6% 31% 33% 17% 4	389
June	1st to 10th	Night	14% 14% 25% 29% 16% 2	360
	11th to 20th	Night	11% 16% 32% 29% 12% 1	360
	21st to end	Night	6% 11% 23% 37% 21% 2	360
July	1st to 10th	Night	4 5% 27% 40% 22% 2	350
	11th to 20th	Night	2 7% 33% 40% 16% 3	348
	21st to end	Night	2 8% 19% 43% 27% 3	394
August	1st to 10th	Night	3 6% 16% 43% 27% 5%	366
	11th to 20th	Night	5% 3 16% 31% 31% 14%	538
	21st to end	Night	4 9% 26% 33% 23% 6%	792
September	1st to 10th	Night	3 7% 23% 36% 27% 4	720
	11th to 20th	Night	5% 7% 22% 28% 29% 8%	720
	21st to end	Night	8% 11% 20% 27% 28% 5%	720
October	1st to 10th	Night	11% 10% 24% 32% 20% 4	720
	11th to 20th	Night	15% 12% 21% 27% 21% 4	720
	21st to end	Night	17% 15% 22% 26% 16% 4	792
November	1st to 10th	Night	19% 13% 26% 30% 12%	740
	11th to 20th	Night	23% 14% 24% 24% 13% 2	760
	21st to end	Night	14% 15% 23% 28% 16% 3	760
December	1st to 10th	Night	18% 13% 26% 26% 15% 2	760
	11th to 20th	Night	24% 11% 24% 27% 11% 2	760
	21st to end	Night	22% 17% 27% 24% 9% 1	836

Page generated at 2024-04-22 06:25:41. Version ac07

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