Weeksville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Weeksville clear sky chart from 2005-11-06 to 2025-01-07.

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	12% 6% 2 6% 4 4 5% 4 6% 8% 42%	104552
	Night	13% 6% 2 6% 4 4 4 4 6% 7% 43%	104437
Transparency	Day	22% 46% 8% 13% 9% 2	108189
	Night	23% 45% 7% 13% 10% 3	108939
Seeing	Day	15% 11% 26% 26% 17% 5%	15538
	Night	16% 9% 27% 31% 15% 2	25230

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	13% 6% 2 5% 3 3 3 3 4 6% 52%	2763
	11th to 20th	Day	12% 6% 2 6% 4 3 3 3 4 7% 49%	2840
	21st to end	Day	11% 10% 3 7% 5% 4 5% 4 5% 6% 40%	3124
February	1st to 10th	Day	14% 8% 2 6% 4 4 4 4 6% 7% 42%	1710
	11th to 20th	Day	18% 7% 3 5% 4 4 3 3 4 5% 44%	1847
	21st to end	Day	16% 7% 2 7% 4 4 5% 3 5% 7% 41%	1570
March	1st to 10th	Day	22% 9% 3 6% 4 4 3 3 4 6% 37%	3304
	11th to 20th	Day	11% 5% 2 5% 4 3 3 2 4 6% 55%	3480
	21st to end	Day	15% 6% 2 6% 4 3 4 2 5% 6% 46%	3941
April	1st to 10th	Day	12% 5% 2 5% 4 3 3 3 5% 7% 52%	2280
	11th to 20th	Day	8% 6% 1 5% 4 4 4 4 6% 7% 51%	2254
	21st to end	Day	10% 5% 2 5% 5% 4 5% 4 6% 7% 48%	2280
May	1st to 10th	Day	9% 5% 2 8% 5% 6% 6% 5% 7% 9% 37%	3765
	11th to 20th	Day	17% 7% 3 8% 5% 5% 5% 4 6% 8% 32%	4090
	21st to end	Day	7% 5% 3 6% 4 5% 5% 5% 8% 9% 43%	4823
June	1st to 10th	Day	10% 4 2 5% 4 5% 5% 5% 8% 11% 40%	2660
	11th to 20th	Day	9% 5% 1 5% 4 4 6% 5% 9% 10% 41%	2660
	21st to end	Day	6% 4 2 7% 6% 4 7% 6% 8% 11% 38%	2660
July	1st to 10th	Day	8% 5% 2 6% 4 5% 6% 5% 9% 13% 37%	4440
	11th to 20th	Day	10% 6% 3 8% 6% 6% 6% 5% 8% 11% 31%	4154
	21st to end	Day	11% 7% 3 8% 6% 6% 6% 5% 8% 10% 30%	4466
August	1st to 10th	Day	17% 9% 3 9% 6% 5% 6% 4 7% 10% 24%	4011
	11th to 20th	Day	9% 6% 2 7% 5% 5% 6% 5% 7% 10% 38%	3730
	21st to end	Day	7% 4 2 6% 5% 6% 5% 6% 7% 11% 42%	4180
September	1st to 10th	Day	11% 6% 2 7% 5% 5% 5% 5% 7% 8% 40%	2280
	11th to 20th	Day	13% 6% 3 7% 4 4 5% 3 6% 9% 38%	2280
	21st to end	Day	18% 8% 3 7% 4 4 4 4 6% 8% 34%	2046
October	1st to 10th	Day	14% 7% 3 5% 4 4 4 2 4 7% 46%	1900
	11th to 20th	Day	11% 5% 2 6% 4 4 4 3 5% 5% 50%	1900
	21st to end	Day	11% 5% 2 6% 4 3 4 3 4 5% 51%	2090
November	1st to 10th	Day	15% 6% 2 5% 3 4 4 4 5% 6% 46%	1874
	11th to 20th	Day	14% 7% 2 4 3 3 3 3 5% 7% 49%	1800
	21st to end	Day	13% 5% 2 4 3 3 4 3 5% 7% 49%	1800
December	1st to 10th	Day	11% 5% 2 5% 4 3 4 3 5% 5% 54%	2600
	11th to 20th	Day	13% 7% 3 7% 4 4 4 3 4 6% 45%	2990
	21st to end	Day	13% 5% 2 5% 4 3 4 3 5% 8% 49%	3960
January	1st to 10th	Night	14% 6% 2 5% 4 4 4 3 4 6% 47%	4314
	11th to 20th	Night	13% 7% 3 7% 5% 5% 4 4 6% 6% 41%	4120
	21st to end	Night	14% 8% 3 8% 4 4 4 3 5% 5% 42%	4532
February	1st to 10th	Night	17% 8% 2 5% 3 3 4 4 6% 7% 41%	2470
	11th to 20th	Night	19% 8% 3 5% 4 3 4 3 5% 6% 40%	2218
	21st to end	Night	14% 8% 2 6% 4 4 3 3 5% 6% 45%	1884
March	1st to 10th	Night	23% 10% 3 7% 5% 4 4 3 5% 5% 31%	3546
	11th to 20th	Night	13% 7% 2 5% 4 3 4 3 4 5% 51%	3480
	21st to end	Night	17% 6% 3 6% 3 3 3 2 4 5% 47%	3690
April	1st to 10th	Night	13% 5% 2 6% 4 4 4 4 5% 7% 47%	1900
	11th to 20th	Night	9% 8% 2 6% 4 4 4 4 5% 6% 47%	1875
	21st to end	Night	12% 6% 2 6% 4 3 3 4 5% 6% 48%	1900
May	1st to 10th	Night	10% 7% 3 7% 5% 6% 6% 4 6% 8% 37%	3130
	11th to 20th	Night	19% 8% 2 6% 5% 4 5% 4 6% 7% 35%	2827
	21st to end	Night	7% 7% 3 7% 5% 5% 4 4 7% 10% 41%	2732
June	1st to 10th	Night	11% 6% 2 6% 5% 4 5% 4 7% 9% 41%	1520
	11th to 20th	Night	8% 5% 3 6% 3 6% 5% 5% 9% 11% 39%	1520
	21st to end	Night	9% 4 2 6% 5% 4 5% 6% 8% 10% 42%	1520
July	1st to 10th	Night	8% 4 2 7% 4 5% 6% 5% 9% 14% 36%	2520
	11th to 20th	Night	10% 5% 2 8% 6% 6% 6% 5% 8% 11% 33%	2800
	21st to end	Night	16% 7% 3 8% 5% 5% 7% 5% 7% 8% 30%	3087
August	1st to 10th	Night	16% 8% 3 8% 5% 5% 6% 5% 6% 10% 29%	2885
	11th to 20th	Night	10% 6% 3 8% 5% 6% 6% 4 6% 9% 38%	3097
	21st to end	Night	9% 4 2 7% 5% 4 5% 4 7% 10% 43%	3476
September	1st to 10th	Night	11% 5% 3 7% 5% 5% 5% 4 6% 8% 42%	1900
	11th to 20th	Night	14% 8% 2 6% 5% 4 4 4 4 8% 40%	1900
	21st to end	Night	17% 8% 3 7% 5% 5% 5% 3 5% 8% 34%	2127
October	1st to 10th	Night	13% 5% 2 6% 4 3 4 3 5% 6% 47%	2280
	11th to 20th	Night	13% 5% 2 6% 3 3 3 3 4 6% 51%	2280
	21st to end	Night	11% 5% 1 5% 3 3 3 3 5% 7% 53%	2508
November	1st to 10th	Night	15% 6% 1 5% 4 3 4 3 5% 7% 48%	2421
	11th to 20th	Night	15% 7% 2 5% 4 4 4 3 5% 6% 45%	2600
	21st to end	Night	12% 5% 2 5% 4 3 3 3 5% 7% 50%	2600
December	1st to 10th	Night	10% 5% 2 5% 3 4 4 4 5% 5% 53%	4577
	11th to 20th	Night	16% 6% 2 7% 5% 4 5% 4 5% 6% 39%	5205
	21st to end	Night	12% 5% 2 5% 3 3 4 3 5% 8% 50%	6996

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	23% 36% 3 20% 15% 2	2764
	11th to 20th	Day	23% 37% 4 10% 21% 5%	2840
	21st to end	Day	30% 41% 5% 9% 10% 4	3124
February	1st to 10th	Day	16% 64% 5% 8% 5% 1	1710
	11th to 20th	Day	18% 64% 4 5% 7% 3	1856
	21st to end	Day	16% 64% 4 7% 6% 2	1570
March	1st to 10th	Day	37% 42% 5% 7% 4 4	3304
	11th to 20th	Day	15% 41% 3 11% 19% 10%	3480
	21st to end	Day	24% 40% 7% 14% 11% 4	3941
April	1st to 10th	Day	12% 65% 5% 8% 9% 1	2280
	11th to 20th	Day	12% 66% 4 10% 6% 2	2254
	21st to end	Day	13% 65% 6% 10% 6% 2	2280
May	1st to 10th	Day	27% 45% 11% 12% 4 1	3800
	11th to 20th	Day	32% 42% 8% 14% 4	4094
	21st to end	Day	19% 43% 10% 19% 8% 1	4837
June	1st to 10th	Day	14% 67% 5% 8% 5% 1	2660
	11th to 20th	Day	9% 66% 9% 10% 6%	2660
	21st to end	Day	12% 65% 8% 10% 5%	2660
July	1st to 10th	Day	24% 42% 16% 13% 5% 1	4370
	11th to 20th	Day	33% 40% 17% 9% 1	4083
	21st to end	Day	34% 40% 7% 11% 8% 1	4324
August	1st to 10th	Day	41% 39% 12% 7% 2	3998
	11th to 20th	Day	21% 41% 13% 17% 8%	3766
	21st to end	Day	20% 39% 12% 20% 9% 1	4180
September	1st to 10th	Day	17% 63% 8% 7% 5% 1	2280
	11th to 20th	Day	17% 61% 5% 9% 6% 2	2280
	21st to end	Day	22% 61% 5% 8% 4	2046
October	1st to 10th	Day	18% 38% 6% 18% 17% 2	3160
	11th to 20th	Day	13% 37% 3 14% 22% 12%	3140
	21st to end	Day	9% 36% 5% 22% 22% 6%	3428
November	1st to 10th	Day	19% 56% 5% 11% 8% 2	1874
	11th to 20th	Day	17% 57% 3 9% 11% 3	1800
	21st to end	Day	14% 57% 4 12% 11% 2	1800
December	1st to 10th	Day	21% 36% 5% 19% 16% 3	2600
	11th to 20th	Day	31% 32% 8% 14% 10% 5%	2986
	21st to end	Day	25% 28% 9% 23% 14%	3960
January	1st to 10th	Night	26% 36% 4 15% 15% 4	4314
	11th to 20th	Night	28% 37% 4 13% 15% 4	4120
	21st to end	Night	29% 41% 4 9% 12% 5%	4532
February	1st to 10th	Night	14% 65% 5% 11% 5% 1	2470
	11th to 20th	Night	19% 64% 3 6% 6% 2	2220
	21st to end	Night	15% 65% 2 9% 6% 2	1884
March	1st to 10th	Night	41% 43% 4 6% 4 1	3546
	11th to 20th	Night	19% 41% 4 8% 17% 12%	3480
	21st to end	Night	25% 40% 3 18% 10% 4	3690
April	1st to 10th	Night	14% 67% 4 6% 8% 1	1900
	11th to 20th	Night	15% 66% 4 10% 5% 1	1875
	21st to end	Night	13% 65% 5% 11% 6% 1	1900
May	1st to 10th	Night	28% 45% 11% 12% 4 1	3160
	11th to 20th	Night	31% 41% 7% 17% 4	2828
	21st to end	Night	23% 43% 11% 15% 7% 1	2739
June	1st to 10th	Night	15% 66% 6% 8% 5% 1	1520
	11th to 20th	Night	9% 67% 7% 11% 6%	1520
	21st to end	Night	11% 65% 7% 12% 5%	1520
July	1st to 10th	Night	24% 42% 16% 11% 5% 1	2480
	11th to 20th	Night	32% 40% 18% 10% 1	2748
	21st to end	Night	39% 39% 6% 7% 9%	2988
August	1st to 10th	Night	37% 40% 12% 10% 1	2874
	11th to 20th	Night	26% 40% 11% 15% 8%	3127
	21st to end	Night	20% 38% 11% 20% 11% 1	3476
September	1st to 10th	Night	17% 61% 9% 7% 4 1	1900
	11th to 20th	Night	19% 61% 4 8% 6% 2	1900
	21st to end	Night	23% 61% 6% 7% 3	2127
October	1st to 10th	Night	24% 37% 5% 16% 17% 1	3800
	11th to 20th	Night	11% 37% 4 11% 22% 14%	3779
	21st to end	Night	8% 36% 5% 23% 18% 10%	4120
November	1st to 10th	Night	21% 56% 3 11% 8% 1	2421
	11th to 20th	Night	20% 57% 3 6% 10% 5%	2600
	21st to end	Night	14% 57% 5% 13% 10% 2	2600
December	1st to 10th	Night	20% 36% 4 14% 20% 7%	4577
	11th to 20th	Night	34% 32% 9% 10% 11% 5%	5208
	21st to end	Night	24% 28% 12% 22% 13% 1	6996

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	18% 22% 41% 16% 3	251
	11th to 20th	Day	18% 27% 33% 20% 3	270
	21st to end	Day	19% 22% 38% 16% 4 1	297
February	1st to 10th	Day	19% 19% 40% 18% 4	270
	11th to 20th	Day	28% 21% 35% 14% 2	455
	21st to end	Day	20% 19% 34% 23% 2 1	382
March	1st to 10th	Day	17% 21% 34% 22% 5%	460
	11th to 20th	Day	22% 17% 36% 17% 6% 2	460
	21st to end	Day	18% 17% 38% 20% 7% 1	506
April	1st to 10th	Day	16% 20% 35% 22% 6% 2	460
	11th to 20th	Day	12% 17% 34% 24% 10% 4	452
	21st to end	Day	14% 13% 31% 28% 13% 2	460
May	1st to 10th	Day	15% 14% 31% 27% 11% 3	463
	11th to 20th	Day	15% 8% 27% 32% 14% 3	487
	21st to end	Day	13% 5% 22% 31% 20% 8%	529
June	1st to 10th	Day	11% 3 25% 31% 25% 5%	490
	11th to 20th	Day	10% 4 20% 32% 24% 10%	490
	21st to end	Day	7% 3 18% 35% 29% 7%	490
July	1st to 10th	Day	9% 1 14% 33% 29% 13%	485
	11th to 20th	Day	8% 2 10% 33% 37% 10%	484
	21st to end	Day	9% 5% 14% 35% 30% 6%	532
August	1st to 10th	Day	15% 4 15% 30% 27% 9%	486
	11th to 20th	Day	12% 1 12% 31% 29% 15%	479
	21st to end	Day	11% 3 15% 31% 29% 12%	539
September	1st to 10th	Day	13% 3 19% 27% 24% 14%	490
	11th to 20th	Day	15% 4 20% 29% 24% 8%	490
	21st to end	Day	21% 7% 20% 25% 20% 7%	490
October	1st to 10th	Day	18% 7% 20% 25% 22% 8%	490
	11th to 20th	Day	14% 9% 27% 27% 18% 4	490
	21st to end	Day	12% 11% 25% 27% 19% 5%	539
November	1st to 10th	Day	18% 10% 27% 29% 12% 4	452
	11th to 20th	Day	17% 15% 30% 26% 11% 1	400
	21st to end	Day	14% 16% 30% 23% 15% 2	400
December	1st to 10th	Day	16% 16% 44% 17% 7% 2	200
	11th to 20th	Day	17% 18% 34% 20% 11% 1	200
	21st to end	Day	20% 15% 30% 21% 13% 1	220
January	1st to 10th	Night	18% 21% 33% 23% 5%	785
	11th to 20th	Night	19% 16% 32% 26% 7%	760
	21st to end	Night	18% 17% 38% 24% 3	836
February	1st to 10th	Night	22% 14% 33% 28% 3	760
	11th to 20th	Night	24% 18% 39% 18% 2	743
	21st to end	Night	17% 16% 38% 24% 5%	628
March	1st to 10th	Night	17% 15% 39% 24% 6%	760
	11th to 20th	Night	19% 14% 40% 20% 6%	760
	21st to end	Night	17% 14% 36% 27% 5%	836
April	1st to 10th	Night	16% 14% 39% 26% 4	760
	11th to 20th	Night	13% 12% 37% 29% 9% 1	751
	21st to end	Night	14% 8% 37% 34% 6% 1	760
May	1st to 10th	Night	14% 10% 34% 32% 9% 1	760
	11th to 20th	Night	16% 7% 26% 38% 12% 1	576
	21st to end	Night	12% 2 16% 41% 26% 3	411
June	1st to 10th	Night	13% 2 19% 44% 19% 2	380
	11th to 20th	Night	8% 3 17% 45% 24% 3	380
	21st to end	Night	7% 2 16% 51% 23% 1	380
July	1st to 10th	Night	8% 2 12% 43% 32% 3	370
	11th to 20th	Night	8% 2 8% 41% 35% 7%	527
	21st to end	Night	9% 2 14% 44% 27% 4	624
August	1st to 10th	Night	14% 2 12% 37% 31% 4	601
	11th to 20th	Night	11% 1 13% 38% 32% 5%	750
	21st to end	Night	13% 2 12% 31% 36% 7%	836
September	1st to 10th	Night	12% 2 15% 32% 30% 9%	760
	11th to 20th	Night	17% 4 14% 34% 27% 4	760
	21st to end	Night	20% 5% 18% 31% 24% 3	760
October	1st to 10th	Night	15% 5% 20% 30% 25% 5%	760
	11th to 20th	Night	17% 8% 24% 30% 20% 2	760
	21st to end	Night	13% 8% 25% 30% 19% 4	836
November	1st to 10th	Night	18% 7% 23% 33% 14% 4	780
	11th to 20th	Night	20% 10% 28% 30% 11% 1	800
	21st to end	Night	13% 13% 30% 28% 15% 1	800
December	1st to 10th	Night	19% 14% 32% 26% 9%	800
	11th to 20th	Night	17% 10% 35% 28% 9%	800
	21st to end	Night	16% 12% 34% 30% 8%	880

Page generated at 2025-01-04 03:24:00. Version ac07

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