Lewis County Fairgrounds
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lewis County Fairgrounds clear sky chart from 2005-11-06 to 2024-01-27.

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	15% 11% 5% 8% 7% 4 5% 5% 5% 6% 29%	74852
	Night	14% 12% 5% 9% 7% 4 5% 5% 5% 6% 29%	75189
Transparency	Day	55% 7% 11% 17% 9% 1	74557
	Night	56% 8% 10% 16% 8% 1	75018
Seeing	Day	23% 21% 30% 17% 7% 2	13533
	Night	22% 20% 30% 21% 7% 1	22813

By Month

Percentage Cloud Cover NE (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	10% 18% 8% 15% 11% 4 5% 5% 3 4 15%	1517
	11th to 20th	Day	12% 18% 7% 12% 11% 4 6% 5% 5% 4 17%	1520
	21st to end	Day	8% 15% 8% 13% 11% 6% 7% 5% 5% 5% 16%	1741
February	1st to 10th	Day	13% 16% 6% 17% 11% 6% 6% 5% 4 4 13%	1620
	11th to 20th	Day	9% 15% 8% 14% 11% 5% 5% 3 4 3 21%	1620
	21st to end	Day	14% 18% 7% 13% 8% 4 4 4 4 5% 19%	1480
March	1st to 10th	Day	12% 14% 8% 14% 8% 3 4 4 4 5% 24%	1797
	11th to 20th	Day	13% 15% 7% 9% 7% 3 5% 4 5% 5% 26%	1970
	21st to end	Day	16% 12% 5% 8% 7% 3 4 3 4 4 33%	2303
April	1st to 10th	Day	16% 14% 5% 7% 6% 4 4 3 5% 5% 32%	2160
	11th to 20th	Day	15% 11% 4 7% 5% 3 4 5% 5% 6% 35%	2134
	21st to end	Day	19% 12% 3 7% 6% 3 4 4 5% 7% 31%	2190
May	1st to 10th	Day	17% 10% 4 7% 6% 4 5% 5% 5% 6% 32%	2520
	11th to 20th	Day	15% 8% 4 6% 5% 3 5% 4 6% 7% 37%	2478
	21st to end	Day	14% 7% 2 5% 6% 3 5% 5% 6% 9% 37%	2725
June	1st to 10th	Day	20% 8% 3 6% 6% 3 5% 5% 6% 8% 30%	2520
	11th to 20th	Day	17% 7% 3 5% 4 3 5% 6% 6% 8% 36%	2520
	21st to end	Day	17% 7% 3 6% 6% 4 5% 5% 6% 8% 32%	2520
July	1st to 10th	Day	11% 5% 3 6% 6% 3 5% 5% 8% 8% 39%	2520
	11th to 20th	Day	12% 6% 3 6% 6% 4 5% 6% 6% 9% 37%	2520
	21st to end	Day	13% 5% 3 6% 6% 4 6% 6% 8% 9% 36%	2744
August	1st to 10th	Day	12% 6% 2 6% 6% 4 5% 6% 7% 9% 37%	2431
	11th to 20th	Day	12% 7% 3 6% 6% 4 5% 7% 7% 9% 35%	2231
	21st to end	Day	14% 6% 3 5% 6% 4 5% 5% 6% 9% 36%	2376
September	1st to 10th	Day	14% 6% 3 5% 6% 3 6% 5% 6% 8% 39%	2160
	11th to 20th	Day	14% 6% 3 7% 5% 3 4 5% 6% 7% 41%	2147
	21st to end	Day	17% 7% 2 5% 5% 3 5% 5% 6% 7% 36%	1945
October	1st to 10th	Day	21% 10% 4 6% 7% 4 4 4 5% 5% 31%	1800
	11th to 20th	Day	19% 12% 3 7% 5% 4 6% 6% 6% 7% 27%	1800
	21st to end	Day	25% 14% 4 7% 4 3 5% 6% 4 5% 23%	1850
November	1st to 10th	Day	14% 14% 4 8% 8% 4 5% 4 5% 6% 28%	1671
	11th to 20th	Day	12% 16% 4 8% 8% 4 5% 5% 5% 6% 28%	1604
	21st to end	Day	14% 18% 7% 11% 8% 4 5% 4 5% 5% 19%	1520
December	1st to 10th	Day	15% 22% 9% 13% 9% 3 5% 4 4 5% 12%	1520
	11th to 20th	Day	14% 21% 11% 12% 8% 3 4 4 4 4 15%	1906
	21st to end	Day	19% 16% 10% 13% 8% 3 4 4 4 5% 15%	2772
January	1st to 10th	Night	11% 17% 10% 16% 10% 4 5% 4 4 3 15%	2649
	11th to 20th	Night	10% 16% 9% 16% 10% 5% 7% 5% 4 4 15%	2660
	21st to end	Night	9% 13% 8% 14% 9% 6% 6% 5% 5% 5% 20%	2756
February	1st to 10th	Night	11% 16% 8% 16% 12% 5% 6% 4 5% 3 15%	2340
	11th to 20th	Night	10% 12% 8% 14% 10% 6% 6% 5% 4 5% 21%	2225
	21st to end	Night	12% 13% 6% 11% 9% 3 5% 5% 6% 7% 22%	1776
March	1st to 10th	Night	12% 13% 7% 11% 8% 4 6% 4 4 6% 25%	2150
	11th to 20th	Night	12% 15% 6% 9% 7% 5% 4 5% 5% 5% 29%	1988
	21st to end	Night	14% 14% 5% 8% 7% 3 5% 4 4 6% 31%	2052
April	1st to 10th	Night	16% 13% 5% 8% 6% 3 4 4 4 6% 32%	1800
	11th to 20th	Night	17% 12% 4 5% 5% 3 5% 4 5% 6% 34%	1775
	21st to end	Night	18% 10% 3 6% 5% 3 5% 5% 5% 6% 33%	1776
May	1st to 10th	Night	19% 9% 3 6% 6% 4 5% 4 5% 6% 33%	1446
	11th to 20th	Night	10% 9% 3 6% 5% 3 5% 5% 6% 8% 40%	1415
	21st to end	Night	11% 6% 3 6% 6% 4 5% 5% 7% 8% 40%	1550
June	1st to 10th	Night	17% 6% 2 5% 5% 3 5% 7% 6% 7% 37%	1440
	11th to 20th	Night	16% 4 3 4 5% 3 5% 6% 5% 8% 40%	1440
	21st to end	Night	13% 7% 2 5% 6% 3 5% 5% 7% 9% 38%	1440
July	1st to 10th	Night	8% 4 3 5% 5% 3 5% 5% 6% 8% 48%	1440
	11th to 20th	Night	10% 5% 2 5% 4 3 5% 6% 6% 8% 46%	1440
	21st to end	Night	10% 5% 2 6% 5% 3 3 5% 6% 8% 46%	1574
August	1st to 10th	Night	10% 5% 2 5% 5% 3 5% 5% 6% 10% 45%	1504
	11th to 20th	Night	11% 5% 3 6% 5% 4 4 5% 6% 9% 42%	1652
	21st to end	Night	10% 6% 2 5% 5% 3 5% 6% 6% 8% 44%	1980
September	1st to 10th	Night	14% 6% 2 5% 4 3 5% 5% 5% 8% 44%	1800
	11th to 20th	Night	13% 6% 2 5% 4 3 3 4 4 7% 49%	1812
	21st to end	Night	15% 7% 3 6% 5% 3 5% 4 6% 8% 40%	2011
October	1st to 10th	Night	21% 10% 3 7% 6% 3 5% 4 5% 6% 31%	2160
	11th to 20th	Night	18% 9% 3 6% 6% 4 6% 4 6% 7% 32%	2160
	21st to end	Night	23% 12% 3 8% 7% 3 5% 5% 5% 5% 23%	2505
November	1st to 10th	Night	14% 13% 4 8% 7% 4 5% 5% 5% 5% 31%	2407
	11th to 20th	Night	14% 13% 4 9% 7% 3 5% 5% 5% 7% 28%	2574
	21st to end	Night	13% 17% 7% 11% 8% 5% 5% 4 5% 5% 20%	2660
December	1st to 10th	Night	13% 22% 9% 12% 8% 4 6% 5% 4 4 13%	2660
	11th to 20th	Night	16% 17% 8% 12% 7% 4 5% 4 4 4 18%	3288
	21st to end	Night	20% 17% 8% 14% 7% 3 4 3 4 5% 13%	4884

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	73% 6% 7% 11% 3	1518
	11th to 20th	Day	70% 7% 6% 8% 6% 2	1520
	21st to end	Day	70% 7% 7% 9% 5% 2	1741
February	1st to 10th	Day	75% 5% 6% 9% 4 1	1620
	11th to 20th	Day	69% 5% 7% 11% 7% 1	1629
	21st to end	Day	68% 7% 8% 10% 7%	1480
March	1st to 10th	Day	63% 6% 9% 13% 7% 1	1800
	11th to 20th	Day	61% 6% 9% 13% 9% 2	1970
	21st to end	Day	56% 4 8% 16% 14% 3	2303
April	1st to 10th	Day	56% 5% 8% 18% 11% 2	2160
	11th to 20th	Day	49% 8% 8% 21% 13% 1	2134
	21st to end	Day	54% 7% 9% 16% 11% 3	2190
May	1st to 10th	Day	53% 6% 9% 17% 13% 2	2520
	11th to 20th	Day	46% 8% 10% 23% 12% 1	2482
	21st to end	Day	44% 9% 16% 20% 10% 1	2725
June	1st to 10th	Day	51% 8% 12% 18% 11%	2520
	11th to 20th	Day	45% 8% 12% 24% 9% 1	2520
	21st to end	Day	49% 9% 13% 19% 9% 1	2520
July	1st to 10th	Day	40% 9% 14% 24% 12% 1	2450
	11th to 20th	Day	42% 9% 16% 26% 7%	2445
	21st to end	Day	43% 10% 16% 21% 11%	2591
August	1st to 10th	Day	41% 11% 16% 23% 10%	2417
	11th to 20th	Day	44% 11% 15% 23% 7%	2231
	21st to end	Day	44% 9% 12% 24% 8% 1	2376
September	1st to 10th	Day	43% 8% 12% 24% 11% 1	2160
	11th to 20th	Day	42% 6% 10% 26% 14% 1	2147
	21st to end	Day	46% 8% 11% 23% 11% 1	1945
October	1st to 10th	Day	56% 6% 10% 18% 9% 1	1800
	11th to 20th	Day	55% 9% 13% 16% 5% 1	1800
	21st to end	Day	64% 6% 10% 12% 7% 2	1850
November	1st to 10th	Day	58% 7% 11% 15% 8% 1	1671
	11th to 20th	Day	59% 7% 12% 13% 7% 3	1604
	21st to end	Day	69% 7% 12% 8% 4	1520
December	1st to 10th	Day	76% 6% 10% 6% 2	1520
	11th to 20th	Day	74% 7% 7% 9% 4	1906
	21st to end	Day	74% 6% 6% 7% 7%	2772
January	1st to 10th	Night	74% 6% 6% 9% 4	2649
	11th to 20th	Night	74% 7% 6% 8% 4 2	2660
	21st to end	Night	65% 7% 7% 12% 8% 1	2756
February	1st to 10th	Night	74% 7% 7% 8% 4	2340
	11th to 20th	Night	66% 7% 7% 13% 6%	2227
	21st to end	Night	61% 7% 11% 13% 6% 1	1776
March	1st to 10th	Night	62% 6% 9% 14% 7% 1	2160
	11th to 20th	Night	57% 7% 10% 17% 9% 1	1989
	21st to end	Night	55% 5% 9% 16% 12% 3	2052
April	1st to 10th	Night	55% 7% 10% 18% 9% 1	1800
	11th to 20th	Night	51% 8% 9% 18% 12% 1	1775
	21st to end	Night	51% 7% 10% 18% 13% 2	1776
May	1st to 10th	Night	52% 8% 9% 15% 15% 2	1446
	11th to 20th	Night	43% 7% 12% 22% 14% 2	1416
	21st to end	Night	40% 9% 16% 20% 13% 1	1551
June	1st to 10th	Night	44% 9% 15% 21% 9% 1	1440
	11th to 20th	Night	42% 9% 13% 22% 13% 2	1440
	21st to end	Night	43% 9% 13% 23% 11%	1440
July	1st to 10th	Night	33% 10% 15% 25% 15% 2	1400
	11th to 20th	Night	35% 11% 13% 30% 11% 1	1392
	21st to end	Night	36% 9% 15% 29% 9% 1	1486
August	1st to 10th	Night	35% 11% 18% 28% 8%	1494
	11th to 20th	Night	40% 10% 15% 25% 10%	1652
	21st to end	Night	36% 11% 14% 29% 10%	1980
September	1st to 10th	Night	39% 9% 13% 28% 10% 1	1800
	11th to 20th	Night	37% 6% 13% 30% 13% 1	1812
	21st to end	Night	42% 8% 12% 25% 12% 1	2011
October	1st to 10th	Night	53% 7% 11% 17% 10% 1	2160
	11th to 20th	Night	51% 9% 14% 19% 6% 1	2160
	21st to end	Night	63% 8% 10% 11% 6% 1	2505
November	1st to 10th	Night	54% 8% 11% 16% 9% 2	2407
	11th to 20th	Night	57% 8% 10% 15% 7% 2	2574
	21st to end	Night	67% 9% 9% 12% 3	2660
December	1st to 10th	Night	74% 7% 8% 8% 2	2660
	11th to 20th	Night	71% 7% 8% 9% 5%	3288
	21st to end	Night	74% 6% 8% 6% 5%	4884

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% 25% 31% 13% 4 1	180
	11th to 20th	Day	28% 29% 33% 8% 1 1	180
	21st to end	Day	21% 31% 35% 11% 2	237
February	1st to 10th	Day	38% 31% 28% 3	240
	11th to 20th	Day	31% 34% 31% 4	287
	21st to end	Day	35% 26% 30% 8% 1	346
March	1st to 10th	Day	25% 27% 33% 11% 3	420
	11th to 20th	Day	28% 27% 31% 11% 2	420
	21st to end	Day	33% 24% 26% 12% 5% 1	462
April	1st to 10th	Day	33% 27% 23% 13% 5%	420
	11th to 20th	Day	31% 23% 23% 14% 7% 3	412
	21st to end	Day	31% 22% 27% 12% 5% 2	420
May	1st to 10th	Day	27% 25% 28% 12% 8% 2	423
	11th to 20th	Day	21% 17% 33% 21% 5% 2	447
	21st to end	Day	19% 16% 35% 17% 12% 2	485
June	1st to 10th	Day	24% 17% 31% 21% 5% 1	450
	11th to 20th	Day	18% 18% 35% 18% 9% 2	450
	21st to end	Day	18% 19% 34% 20% 7% 1	450
July	1st to 10th	Day	12% 12% 35% 24% 14% 3	445
	11th to 20th	Day	13% 11% 33% 28% 14% 2	444
	21st to end	Day	14% 12% 40% 26% 7% 1	488
August	1st to 10th	Day	12% 12% 32% 28% 12% 5%	446
	11th to 20th	Day	13% 11% 29% 28% 13% 5%	439
	21st to end	Day	17% 15% 30% 21% 12% 5%	495
September	1st to 10th	Day	14% 16% 28% 23% 12% 6%	450
	11th to 20th	Day	14% 14% 28% 19% 16% 9%	450
	21st to end	Day	18% 17% 29% 21% 12% 3	450
October	1st to 10th	Day	26% 17% 28% 14% 11% 4	450
	11th to 20th	Day	22% 28% 30% 14% 4 1	450
	21st to end	Day	33% 22% 28% 16% 2	430
November	1st to 10th	Day	27% 24% 29% 16% 5%	365
	11th to 20th	Day	28% 29% 27% 13% 2 1	264
	21st to end	Day	27% 25% 41% 7%	180
December	1st to 10th	Day	37% 27% 23% 13% 1	180
	11th to 20th	Day	31% 34% 27% 8% 1	180
	21st to end	Day	29% 33% 31% 7% 1	198
January	1st to 10th	Night	25% 28% 32% 13% 2	760
	11th to 20th	Night	21% 33% 30% 13% 3	760
	21st to end	Night	17% 28% 35% 16% 3	820
February	1st to 10th	Night	23% 28% 37% 12% 1	720
	11th to 20th	Night	21% 30% 35% 13% 2	703
	21st to end	Night	24% 27% 31% 15% 2	592
March	1st to 10th	Night	23% 26% 34% 15% 2	720
	11th to 20th	Night	27% 25% 27% 18% 3	720
	21st to end	Night	23% 24% 30% 16% 6% 1	792
April	1st to 10th	Night	25% 22% 33% 18% 1	720
	11th to 20th	Night	23% 23% 30% 17% 6% 1	711
	21st to end	Night	26% 17% 29% 21% 6% 1	696
May	1st to 10th	Night	23% 13% 30% 27% 6% 1	366
	11th to 20th	Night	15% 18% 33% 27% 6% 1	354
	21st to end	Night	14% 9% 36% 29% 10% 1	389
June	1st to 10th	Night	19% 12% 28% 33% 8% 1	360
	11th to 20th	Night	17% 10% 29% 32% 12%	360
	21st to end	Night	17% 8% 34% 34% 7%	360
July	1st to 10th	Night	6% 7% 31% 43% 12% 1	350
	11th to 20th	Night	11% 6% 28% 36% 18% 1	348
	21st to end	Night	10% 7% 32% 39% 11% 1	394
August	1st to 10th	Night	14% 7% 25% 38% 15% 1	430
	11th to 20th	Night	14% 5% 24% 34% 21% 2	588
	21st to end	Night	13% 7% 28% 36% 15% 1	792
September	1st to 10th	Night	15% 11% 28% 29% 15% 2	720
	11th to 20th	Night	17% 8% 25% 30% 16% 4	720
	21st to end	Night	18% 13% 27% 23% 17% 1	720
October	1st to 10th	Night	26% 16% 26% 19% 13% 2	720
	11th to 20th	Night	23% 19% 29% 23% 6% 1	720
	21st to end	Night	31% 20% 31% 17% 2	792
November	1st to 10th	Night	25% 18% 32% 20% 6%	740
	11th to 20th	Night	24% 24% 30% 15% 6% 1	760
	21st to end	Night	26% 27% 27% 16% 3	760
December	1st to 10th	Night	27% 28% 31% 12% 2	760
	11th to 20th	Night	27% 28% 30% 13% 2 1	760
	21st to end	Night	28% 30% 29% 10% 1	836

Page generated at 2024-01-24 09:37:28. Version ac07

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