Berrysville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Berrysville clear sky chart from 2005-11-06 to 2026-08-15.

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	14% 9% 3 8% 5% 5% 5% 4 6% 7% 35%	143835
	Night	14% 10% 3 8% 5% 4 4 3 5% 7% 36%	138032
Transparency	Day	46% 6% 11% 22% 13% 1	147496
	Night	46% 6% 10% 22% 14% 2	142430
Seeing	Day	18% 13% 27% 22% 13% 6%	17419
	Night	18% 11% 27% 28% 14% 2	27152

By Month

Percentage Cloud Cover SE (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	17% 16% 8% 12% 5% 4 3 3 4 6% 22%	5258
	11th to 20th	Day	13% 15% 5% 16% 6% 6% 4 3 4 3 25%	5280
	21st to end	Day	19% 13% 7% 10% 7% 7% 5% 4 4 5% 20%	5780
February	1st to 10th	Day	19% 13% 4 9% 5% 4 4 4 4 5% 28%	1941
	11th to 20th	Day	19% 12% 4 10% 5% 4 4 3 4 6% 28%	2048
	21st to end	Day	20% 11% 5% 11% 5% 3 4 2 4 6% 30%	1730
March	1st to 10th	Day	17% 13% 7% 9% 4 4 4 3 4 5% 30%	4721
	11th to 20th	Day	12% 8% 3 7% 5% 4 5% 4 6% 7% 38%	5090
	21st to end	Day	17% 10% 3 8% 5% 4 4 4 5% 7% 34%	5586
April	1st to 10th	Day	15% 11% 3 7% 5% 4 4 3 5% 7% 36%	2399
	11th to 20th	Day	16% 8% 2 7% 5% 4 4 4 5% 7% 38%	2602
	21st to end	Day	18% 8% 2 7% 6% 4 5% 3 5% 7% 35%	2730
May	1st to 10th	Day	18% 9% 3 7% 5% 5% 5% 4 6% 7% 31%	7616
	11th to 20th	Day	17% 9% 3 7% 4 5% 4 4 6% 7% 34%	7626
	21st to end	Day	19% 7% 3 7% 5% 5% 6% 5% 7% 8% 28%	8391
June	1st to 10th	Day	12% 5% 2 6% 5% 5% 5% 4 7% 9% 40%	2730
	11th to 20th	Day	9% 5% 2 7% 5% 5% 5% 4 7% 9% 41%	2730
	21st to end	Day	9% 6% 3 6% 5% 4 5% 4 8% 10% 40%	2917
July	1st to 10th	Day	10% 6% 3 7% 5% 5% 5% 4 6% 8% 42%	7980
	11th to 20th	Day	11% 6% 2 7% 5% 5% 5% 5% 7% 10% 37%	7680
	21st to end	Day	9% 7% 3 8% 6% 6% 6% 5% 8% 9% 33%	8340
August	1st to 10th	Day	7% 5% 2 6% 5% 5% 5% 5% 7% 10% 42%	4364
	11th to 20th	Day	8% 6% 2 7% 5% 5% 5% 5% 8% 10% 39%	4226
	21st to end	Day	5% 4 2 5% 4 4 5% 4 6% 9% 54%	4459
September	1st to 10th	Day	13% 5% 2 5% 3 4 4 3 5% 7% 49%	2230
	11th to 20th	Day	8% 5% 1 5% 4 4 4 4 6% 8% 50%	2200
	21st to end	Day	17% 6% 2 6% 4 4 3 3 4 6% 44%	2200
October	1st to 10th	Day	12% 4 2 4 4 4 4 4 6% 6% 49%	2185
	11th to 20th	Day	14% 7% 2 5% 5% 3 4 3 4 6% 47%	2000
	21st to end	Day	20% 8% 3 6% 4 3 3 3 4 6% 39%	2116
November	1st to 10th	Day	11% 8% 2 6% 4 3 4 3 5% 6% 49%	1852
	11th to 20th	Day	15% 12% 4 7% 4 4 4 3 5% 6% 36%	1890
	21st to end	Day	18% 11% 4 8% 5% 4 3 3 4 6% 33%	1890
December	1st to 10th	Day	18% 13% 3 8% 4 4 5% 3 3 4 33%	3020
	11th to 20th	Day	21% 14% 5% 9% 5% 5% 4 4 5% 5% 24%	3463
	21st to end	Day	20% 19% 5% 12% 5% 4 4 3 4 5% 18%	4565
January	1st to 10th	Night	14% 15% 5% 14% 7% 6% 5% 4 5% 5% 20%	7635
	11th to 20th	Night	13% 15% 7% 15% 7% 4 5% 3 4 4 24%	7680
	21st to end	Night	17% 12% 5% 10% 5% 6% 4 3 4 5% 31%	8401
February	1st to 10th	Night	19% 14% 4 8% 5% 3 4 3 5% 5% 29%	2677
	11th to 20th	Night	19% 12% 4 9% 5% 4 4 3 4 6% 31%	2458
	21st to end	Night	20% 13% 5% 8% 5% 4 3 3 4 6% 30%	2076
March	1st to 10th	Night	18% 13% 3 6% 4 4 4 3 4 5% 36%	5338
	11th to 20th	Night	12% 7% 3 6% 4 3 5% 4 6% 8% 41%	5090
	21st to end	Night	17% 9% 4 8% 6% 5% 4 4 4 6% 33%	5588
April	1st to 10th	Night	15% 9% 3 6% 5% 5% 5% 4 7% 6% 37%	2238
	11th to 20th	Night	14% 7% 3 7% 4 3 5% 4 6% 7% 40%	1967
	21st to end	Night	16% 8% 3 6% 4 3 4 4 6% 8% 38%	1890
May	1st to 10th	Night	20% 9% 3 7% 5% 4 4 4 6% 8% 31%	5237
	11th to 20th	Night	14% 8% 3 6% 5% 4 5% 4 7% 9% 36%	5234
	21st to end	Night	17% 8% 3 7% 5% 4 4 4 7% 9% 33%	5761
June	1st to 10th	Night	8% 5% 2 5% 4 5% 4 4 6% 9% 48%	1890
	11th to 20th	Night	9% 5% 2 5% 4 4 4 4 6% 10% 47%	1890
	21st to end	Night	8% 5% 2 4 4 4 4 5% 9% 12% 43%	1687
July	1st to 10th	Night	8% 6% 2 8% 4 5% 5% 4 5% 9% 45%	4970
	11th to 20th	Night	9% 7% 2 8% 5% 5% 5% 4 5% 9% 41%	5277
	21st to end	Night	8% 6% 2 7% 5% 6% 5% 5% 7% 9% 39%	5736
August	1st to 10th	Night	6% 7% 2 7% 5% 5% 5% 4 6% 9% 44%	3005
	11th to 20th	Night	9% 7% 3 7% 6% 5% 5% 3 5% 7% 43%	2911
	21st to end	Night	4 2 1 4 3 4 3 4 7% 11% 57%	3421
September	1st to 10th	Night	11% 5% 2 5% 4 4 4 3 5% 7% 52%	2150
	11th to 20th	Night	8% 4 2 5% 4 3 4 3 4 7% 55%	2200
	21st to end	Night	14% 6% 2 6% 4 4 3 3 6% 5% 47%	2200
October	1st to 10th	Night	9% 4 2 5% 4 4 4 3 5% 6% 55%	2214
	11th to 20th	Night	14% 6% 2 5% 3 4 4 3 5% 6% 47%	2400
	21st to end	Night	19% 8% 2 5% 4 4 4 3 5% 5% 41%	2720
November	1st to 10th	Night	13% 6% 2 6% 3 3 3 3 5% 7% 47%	2666
	11th to 20th	Night	15% 10% 3 6% 4 4 4 3 5% 6% 40%	2730
	21st to end	Night	19% 13% 3 7% 5% 4 4 3 5% 6% 32%	2730
December	1st to 10th	Night	17% 12% 4 8% 4 3 4 2 4 5% 36%	4380
	11th to 20th	Night	19% 14% 6% 9% 5% 4 4 3 5% 5% 26%	4952
	21st to end	Night	21% 19% 6% 10% 6% 5% 4 3 4 5% 18%	6633

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	63% 5% 12% 15% 5%	5259
	11th to 20th	Day	61% 5% 8% 13% 11% 1	5280
	21st to end	Day	65% 4 8% 15% 6% 1	5780
February	1st to 10th	Day	59% 4 10% 18% 9% 1	1941
	11th to 20th	Day	58% 4 10% 17% 10% 1	2058
	21st to end	Day	56% 3 10% 21% 8% 1	1730
March	1st to 10th	Day	56% 4 7% 21% 11% 2	4721
	11th to 20th	Day	43% 5% 9% 28% 14% 1	5090
	21st to end	Day	49% 5% 10% 22% 12% 2	5586
April	1st to 10th	Day	46% 6% 12% 23% 11% 2	2399
	11th to 20th	Day	45% 5% 10% 22% 15% 3	2602
	21st to end	Day	48% 5% 12% 22% 12% 2	2730
May	1st to 10th	Day	50% 7% 11% 21% 10% 1	7651
	11th to 20th	Day	47% 7% 11% 23% 12% 1	7630
	21st to end	Day	49% 8% 11% 17% 12% 3	8405
June	1st to 10th	Day	39% 8% 12% 23% 16% 2	2730
	11th to 20th	Day	37% 9% 15% 22% 16% 1	2730
	21st to end	Day	37% 9% 13% 24% 14% 3	2917
July	1st to 10th	Day	38% 8% 12% 26% 15% 1	7915
	11th to 20th	Day	39% 9% 12% 28% 11%	7611
	21st to end	Day	43% 8% 12% 21% 15% 2	8156
August	1st to 10th	Day	34% 8% 14% 32% 11% 1	4351
	11th to 20th	Day	35% 8% 12% 29% 16% 1	4265
	21st to end	Day	26% 7% 15% 28% 21% 3	4458
September	1st to 10th	Day	35% 6% 11% 23% 20% 6%	2230
	11th to 20th	Day	31% 6% 13% 23% 25% 3	2200
	21st to end	Day	41% 6% 9% 22% 21% 2	2200
October	1st to 10th	Day	23% 4 9% 30% 32% 2	3562
	11th to 20th	Day	29% 4 8% 31% 26% 2	3240
	21st to end	Day	35% 4 10% 25% 23% 3	3392
November	1st to 10th	Day	36% 6% 9% 28% 19% 2	1852
	11th to 20th	Day	48% 4 7% 22% 15% 3	1890
	21st to end	Day	52% 4 9% 21% 13% 1	1890
December	1st to 10th	Day	54% 5% 9% 23% 8%	3020
	11th to 20th	Day	61% 6% 8% 18% 6%	3460
	21st to end	Day	68% 4 9% 13% 6% 1	4565
January	1st to 10th	Night	65% 5% 9% 14% 7%	7636
	11th to 20th	Night	64% 4 7% 13% 10% 2	7680
	21st to end	Night	56% 5% 10% 20% 9% 1	8401
February	1st to 10th	Night	57% 5% 10% 19% 9% 1	2677
	11th to 20th	Night	56% 4 8% 20% 11% 1	2459
	21st to end	Night	57% 4 10% 17% 10% 2	2076
March	1st to 10th	Night	50% 4 6% 26% 12% 2	5338
	11th to 20th	Night	38% 6% 9% 30% 16% 1	5090
	21st to end	Night	52% 5% 8% 22% 12% 1	5588
April	1st to 10th	Night	45% 6% 10% 24% 13% 2	2238
	11th to 20th	Night	42% 5% 11% 20% 17% 5%	1967
	21st to end	Night	44% 6% 10% 23% 14% 2	1890
May	1st to 10th	Night	50% 7% 12% 20% 9% 3	5264
	11th to 20th	Night	43% 8% 13% 22% 12% 1	5235
	21st to end	Night	45% 7% 14% 19% 11% 4	5771
June	1st to 10th	Night	32% 7% 13% 25% 21% 2	1890
	11th to 20th	Night	31% 7% 16% 23% 20% 4	1890
	21st to end	Night	30% 9% 18% 23% 17% 3	1687
July	1st to 10th	Night	37% 7% 11% 25% 17% 3	4928
	11th to 20th	Night	38% 9% 13% 26% 13% 1	5226
	21st to end	Night	37% 9% 13% 23% 16% 3	5606
August	1st to 10th	Night	33% 9% 14% 31% 11% 1	2994
	11th to 20th	Night	38% 8% 10% 25% 17% 1	2938
	21st to end	Night	20% 7% 17% 31% 22% 3	3421
September	1st to 10th	Night	31% 6% 12% 23% 21% 6%	2150
	11th to 20th	Night	28% 6% 10% 25% 28% 3	2200
	21st to end	Night	38% 5% 9% 20% 27% 2	2200
October	1st to 10th	Night	23% 4 8% 26% 37% 3	3617
	11th to 20th	Night	28% 4 8% 27% 30% 4	3899
	21st to end	Night	33% 3 9% 22% 26% 7%	4381
November	1st to 10th	Night	37% 3 10% 24% 22% 3	2666
	11th to 20th	Night	46% 4 8% 22% 18% 3	2730
	21st to end	Night	54% 4 9% 20% 11% 1	2730
December	1st to 10th	Night	51% 4 11% 24% 10% 1	4380
	11th to 20th	Night	59% 4 11% 19% 7% 1	4954
	21st to end	Night	68% 4 9% 15% 4	6633

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	24% 24% 35% 13% 4	330
	11th to 20th	Day	30% 26% 32% 10% 1	330
	21st to end	Day	29% 24% 33% 11% 3	363
February	1st to 10th	Day	27% 22% 34% 12% 5%	330
	11th to 20th	Day	32% 25% 34% 6% 2	330
	21st to end	Day	30% 20% 41% 8%	273
March	1st to 10th	Day	27% 25% 32% 13% 3	393
	11th to 20th	Day	26% 21% 34% 16% 3	540
	21st to end	Day	30% 19% 31% 15% 4	594
April	1st to 10th	Day	22% 21% 31% 17% 8% 1	540
	11th to 20th	Day	22% 23% 26% 18% 8% 3	532
	21st to end	Day	21% 16% 35% 15% 10% 2	540
May	1st to 10th	Day	25% 18% 29% 17% 7% 3	543
	11th to 20th	Day	19% 13% 31% 21% 13% 4	567
	21st to end	Day	16% 10% 25% 25% 18% 7%	617
June	1st to 10th	Day	13% 9% 22% 31% 18% 7%	570
	11th to 20th	Day	11% 7% 24% 31% 18% 7%	570
	21st to end	Day	10% 7% 28% 31% 17% 8%	757
July	1st to 10th	Day	12% 5% 17% 25% 22% 19%	670
	11th to 20th	Day	9% 6% 21% 28% 24% 11%	564
	21st to end	Day	11% 3 20% 30% 22% 14%	620
August	1st to 10th	Day	11% 5% 17% 28% 24% 15%	566
	11th to 20th	Day	11% 4 21% 31% 21% 11%	535
	21st to end	Day	8% 4 15% 34% 25% 14%	583
September	1st to 10th	Day	12% 5% 17% 28% 27% 11%	530
	11th to 20th	Day	8% 3 16% 27% 32% 14%	530
	21st to end	Day	22% 7% 20% 24% 23% 4	530
October	1st to 10th	Day	11% 6% 24% 32% 18% 9%	530
	11th to 20th	Day	14% 14% 34% 21% 12% 4	530
	21st to end	Day	23% 17% 31% 23% 6% 1	499
November	1st to 10th	Day	16% 15% 36% 23% 8% 2	330
	11th to 20th	Day	24% 20% 30% 19% 6% 2	330
	21st to end	Day	25% 21% 34% 16% 4	330
December	1st to 10th	Day	25% 22% 35% 13% 5%	330
	11th to 20th	Day	22% 24% 36% 14% 4	330
	21st to end	Day	28% 23% 33% 13% 3	363
January	1st to 10th	Night	23% 21% 32% 20% 4	840
	11th to 20th	Night	27% 19% 34% 18% 2	840
	21st to end	Night	24% 18% 35% 21% 2	924
February	1st to 10th	Night	28% 13% 34% 23% 1	840
	11th to 20th	Night	26% 19% 33% 20% 2	823
	21st to end	Night	27% 17% 34% 20% 1	692
March	1st to 10th	Night	21% 18% 32% 23% 5%	840
	11th to 20th	Night	21% 17% 35% 20% 7%	840
	21st to end	Night	22% 15% 32% 25% 6%	924
April	1st to 10th	Night	19% 16% 35% 24% 6%	768
	11th to 20th	Night	17% 12% 35% 25% 10% 1	623
	21st to end	Night	18% 8% 39% 27% 7%	630
May	1st to 10th	Night	20% 10% 30% 28% 11% 1	630
	11th to 20th	Night	17% 8% 26% 32% 16% 1	621
	21st to end	Night	10% 5% 23% 33% 24% 4	683
June	1st to 10th	Night	9% 2 24% 40% 23% 2	630
	11th to 20th	Night	10% 4 18% 41% 24% 3	630
	21st to end	Night	7% 4 23% 37% 27% 3	630
July	1st to 10th	Night	11% 3 14% 32% 31% 10%	615
	11th to 20th	Night	6% 3 16% 36% 35% 4	612
	21st to end	Night	10% 2 12% 39% 32% 4	690
August	1st to 10th	Night	7% 3 13% 40% 33% 4	627
	11th to 20th	Night	9% 3 13% 38% 31% 5%	606
	21st to end	Night	6% 1 16% 36% 33% 9%	660
September	1st to 10th	Night	12% 3 14% 33% 31% 6%	750
	11th to 20th	Night	9% 3 14% 33% 35% 6%	800
	21st to end	Night	16% 5% 18% 36% 24% 2	800
October	1st to 10th	Night	11% 6% 23% 34% 24% 4	800
	11th to 20th	Night	17% 9% 26% 34% 13% 2	800
	21st to end	Night	21% 13% 28% 27% 10% 1	880
November	1st to 10th	Night	17% 9% 30% 27% 16% 1	820
	11th to 20th	Night	20% 17% 29% 25% 8% 1	840
	21st to end	Night	25% 14% 28% 27% 6% 1	840
December	1st to 10th	Night	27% 16% 31% 21% 5%	840
	11th to 20th	Night	25% 13% 32% 23% 6% 1	840
	21st to end	Night	29% 15% 31% 23% 3	924

Page generated at 2026-08-12 03:37:15. Version ac07

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