Janesville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Janesville clear sky chart from 2005-11-06 to 2024-01-16.

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% 4 7% 6% 3 5% 5% 5% 7% 37%	74818
	Night	14% 9% 4 6% 5% 3 4 4 5% 7% 39%	75014
Transparency	Day	47% 4 12% 23% 12% 1	74519
	Night	46% 4 11% 23% 14% 2	74834
Seeing	Day	17% 10% 28% 26% 14% 5%	14709
	Night	18% 9% 30% 31% 12% 1	24702

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	12% 10% 7% 9% 6% 4 6% 5% 5% 6% 30%	1517
	11th to 20th	Day	13% 15% 7% 11% 8% 4 4 4 6% 6% 22%	1485
	21st to end	Day	13% 15% 9% 11% 7% 3 5% 4 5% 7% 22%	1652
February	1st to 10th	Day	13% 14% 5% 7% 7% 3 5% 5% 5% 7% 28%	1620
	11th to 20th	Day	14% 11% 4 6% 6% 4 6% 4 4 5% 36%	1712
	21st to end	Day	14% 12% 6% 9% 6% 4 4 4 4 6% 31%	1480
March	1st to 10th	Day	13% 10% 5% 8% 7% 5% 5% 4 4 7% 34%	1800
	11th to 20th	Day	12% 9% 3 7% 6% 3 4 5% 4 8% 38%	1888
	21st to end	Day	19% 10% 4 7% 6% 4 5% 5% 6% 7% 28%	2361
April	1st to 10th	Day	18% 11% 5% 6% 6% 3 5% 4 5% 6% 30%	2160
	11th to 20th	Day	17% 10% 4 6% 6% 3 4 4 4 8% 33%	2134
	21st to end	Day	20% 9% 3 8% 6% 3 4 4 6% 6% 32%	2230
May	1st to 10th	Day	18% 8% 3 7% 6% 4 5% 5% 6% 7% 29%	2377
	11th to 20th	Day	19% 6% 3 5% 6% 3 5% 5% 5% 7% 36%	2479
	21st to end	Day	13% 7% 3 6% 5% 3 6% 4 7% 8% 37%	2725
June	1st to 10th	Day	10% 5% 2 5% 5% 4 6% 5% 6% 9% 43%	2520
	11th to 20th	Day	13% 4 2 4 4 3 5% 5% 8% 9% 43%	2520
	21st to end	Day	12% 5% 3 5% 6% 3 5% 6% 8% 10% 37%	2520
July	1st to 10th	Day	7% 4 2 5% 5% 3 5% 6% 7% 11% 46%	2520
	11th to 20th	Day	8% 4 1 4 6% 3 5% 7% 8% 9% 44%	2520
	21st to end	Day	8% 5% 2 4 5% 3 4 6% 7% 11% 45%	2743
August	1st to 10th	Day	7% 4 2 5% 6% 3 6% 7% 8% 10% 42%	2486
	11th to 20th	Day	11% 5% 3 5% 5% 3 5% 6% 5% 9% 43%	2150
	21st to end	Day	10% 5% 2 5% 5% 3 4 4 6% 8% 48%	2376
September	1st to 10th	Day	13% 6% 3 4 4 4 5% 4 6% 8% 44%	2160
	11th to 20th	Day	13% 4 2 4 3 2 4 4 5% 7% 52%	2086
	21st to end	Day	11% 7% 3 6% 6% 3 4 4 5% 7% 44%	1980
October	1st to 10th	Day	15% 7% 3 5% 4 2 4 4 4 7% 45%	1865
	11th to 20th	Day	20% 10% 3 6% 5% 3 3 4 5% 6% 35%	1800
	21st to end	Day	20% 9% 4 6% 5% 3 4 4 4 6% 37%	1800
November	1st to 10th	Day	11% 9% 3 6% 5% 3 4 4 4 6% 45%	1672
	11th to 20th	Day	14% 11% 5% 7% 6% 3 5% 5% 5% 7% 32%	1710
	21st to end	Day	17% 12% 4 7% 6% 2 3 2 4 7% 36%	1549
December	1st to 10th	Day	14% 13% 4 8% 7% 4 5% 5% 4 6% 29%	1520
	11th to 20th	Day	13% 14% 6% 9% 7% 3 5% 5% 6% 6% 28%	1918
	21st to end	Day	19% 20% 10% 12% 7% 3 5% 4 3 3 14%	2783
January	1st to 10th	Night	13% 12% 5% 9% 7% 3 4 3 4 4 36%	2648
	11th to 20th	Night	15% 13% 7% 11% 6% 3 5% 4 5% 5% 26%	2603
	21st to end	Night	13% 13% 6% 11% 8% 3 5% 4 4 7% 25%	2700
February	1st to 10th	Night	13% 14% 6% 8% 5% 4 5% 4 4 5% 32%	2340
	11th to 20th	Night	13% 10% 4 8% 5% 3 5% 4 4 6% 37%	2132
	21st to end	Night	18% 11% 4 7% 4 3 3 5% 5% 6% 34%	1776
March	1st to 10th	Night	17% 9% 4 6% 6% 3 4 5% 4 6% 36%	2160
	11th to 20th	Night	12% 8% 3 5% 5% 3 5% 5% 5% 8% 41%	2088
	21st to end	Night	20% 10% 4 7% 5% 3 4 4 5% 5% 33%	1994
April	1st to 10th	Night	17% 8% 3 6% 7% 4 4 4 5% 7% 36%	1800
	11th to 20th	Night	19% 9% 4 5% 5% 3 4 4 4 5% 38%	1775
	21st to end	Night	18% 7% 3 6% 6% 3 5% 4 5% 7% 37%	1728
May	1st to 10th	Night	16% 7% 2 6% 6% 3 5% 6% 6% 9% 35%	1580
	11th to 20th	Night	16% 8% 3 6% 4 4 4 5% 7% 7% 38%	1416
	21st to end	Night	11% 6% 3 6% 6% 3 5% 4 7% 9% 41%	1551
June	1st to 10th	Night	8% 4 2 4 5% 3 5% 6% 6% 9% 47%	1440
	11th to 20th	Night	12% 5% 1 5% 4 3 3 5% 5% 9% 48%	1440
	21st to end	Night	10% 6% 3 4 4 3 3 4 6% 9% 48%	1440
July	1st to 10th	Night	6% 4 2 4 4 3 4 6% 6% 10% 52%	1440
	11th to 20th	Night	7% 4 2 5% 4 2 4 5% 4 8% 56%	1440
	21st to end	Night	6% 4 1 4 3 3 5% 5% 8% 9% 50%	1575
August	1st to 10th	Night	4 4 2 5% 5% 2 6% 5% 6% 9% 51%	1449
	11th to 20th	Night	8% 4 2 4 4 3 3 4 5% 9% 54%	1750
	21st to end	Night	9% 4 2 4 5% 3 4 4 5% 7% 53%	1980
September	1st to 10th	Night	9% 4 2 5% 5% 3 4 5% 4 7% 53%	1800
	11th to 20th	Night	12% 4 2 3 3 3 4 5% 5% 7% 53%	1855
	21st to end	Night	12% 5% 2 5% 5% 3 4 3 4 8% 49%	1980
October	1st to 10th	Night	12% 6% 2 5% 4 2 4 4 4 7% 49%	2092
	11th to 20th	Night	18% 8% 3 5% 4 2 3 3 4 5% 43%	2160
	21st to end	Night	20% 9% 3 5% 4 3 4 4 5% 7% 37%	2555
November	1st to 10th	Night	12% 8% 3 5% 5% 2 3 4 5% 6% 48%	2406
	11th to 20th	Night	14% 11% 4 8% 6% 3 4 4 5% 6% 35%	2470
	21st to end	Night	17% 10% 4 6% 5% 3 3 4 4 5% 37%	2628
December	1st to 10th	Night	16% 12% 5% 7% 6% 4 5% 5% 5% 5% 31%	2660
	11th to 20th	Night	16% 14% 5% 9% 5% 3 4 4 4 6% 30%	3279
	21st to end	Night	21% 18% 7% 9% 6% 4 4 3 4 5% 19%	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	56% 4 13% 18% 9%	1518
	11th to 20th	Day	63% 4 11% 15% 6%	1485
	21st to end	Day	64% 4 10% 14% 8% 1	1652
February	1st to 10th	Day	57% 2 12% 19% 8% 1	1620
	11th to 20th	Day	51% 3 11% 22% 10% 2	1722
	21st to end	Day	56% 3 9% 20% 11% 1	1480
March	1st to 10th	Day	52% 3 13% 23% 8% 1	1800
	11th to 20th	Day	46% 4 12% 23% 13% 2	1888
	21st to end	Day	57% 5% 12% 19% 7% 1	2361
April	1st to 10th	Day	54% 4 10% 21% 10%	2160
	11th to 20th	Day	51% 3 9% 22% 12% 2	2134
	21st to end	Day	53% 4 11% 19% 12% 1	2230
May	1st to 10th	Day	53% 4 12% 23% 7%	2377
	11th to 20th	Day	48% 4 13% 23% 12%	2483
	21st to end	Day	45% 5% 12% 22% 14% 2	2725
June	1st to 10th	Day	37% 5% 13% 28% 16% 1	2520
	11th to 20th	Day	36% 5% 13% 25% 18% 2	2520
	21st to end	Day	41% 5% 15% 23% 14% 2	2520
July	1st to 10th	Day	31% 5% 15% 33% 13% 2	2451
	11th to 20th	Day	34% 6% 15% 26% 17% 2	2445
	21st to end	Day	33% 5% 15% 28% 16% 3	2591
August	1st to 10th	Day	35% 5% 15% 31% 13% 1	2471
	11th to 20th	Day	38% 4 15% 28% 14% 1	2150
	21st to end	Day	34% 4 12% 28% 20% 2	2376
September	1st to 10th	Day	39% 4 11% 26% 19% 2	2160
	11th to 20th	Day	33% 3 11% 34% 17% 2	2086
	21st to end	Day	41% 3 9% 30% 15% 1	1980
October	1st to 10th	Day	41% 4 9% 30% 16% 1	1865
	11th to 20th	Day	51% 3 11% 23% 12% 1	1800
	21st to end	Day	51% 2 9% 24% 12% 1	1800
November	1st to 10th	Day	42% 3 14% 25% 15% 2	1672
	11th to 20th	Day	52% 4 14% 20% 9% 1	1710
	21st to end	Day	52% 3 13% 25% 7% 1	1549
December	1st to 10th	Day	56% 3 14% 18% 7% 1	1520
	11th to 20th	Day	57% 2 15% 16% 7% 2	1915
	21st to end	Day	77% 3 7% 9% 5%	2783
January	1st to 10th	Night	53% 3 10% 21% 12% 1	2648
	11th to 20th	Night	61% 4 12% 15% 8%	2603
	21st to end	Night	60% 4 11% 16% 9% 1	2700
February	1st to 10th	Night	56% 3 9% 19% 12% 1	2340
	11th to 20th	Night	49% 3 12% 21% 14% 1	2133
	21st to end	Night	51% 3 10% 20% 11% 4	1776
March	1st to 10th	Night	50% 4 13% 21% 9% 2	2160
	11th to 20th	Night	42% 5% 12% 22% 17% 2	2088
	21st to end	Night	54% 3 10% 21% 11% 2	1994
April	1st to 10th	Night	49% 3 10% 21% 14% 2	1800
	11th to 20th	Night	49% 3 6% 20% 19% 3	1775
	21st to end	Night	47% 3 12% 23% 13% 2	1728
May	1st to 10th	Night	46% 4 13% 23% 13% 1	1580
	11th to 20th	Night	45% 4 11% 24% 13% 2	1417
	21st to end	Night	41% 5% 14% 22% 16% 2	1552
June	1st to 10th	Night	33% 5% 13% 28% 20% 1	1440
	11th to 20th	Night	35% 5% 10% 24% 25% 3	1440
	21st to end	Night	34% 5% 16% 24% 18% 3	1440
July	1st to 10th	Night	27% 4 16% 31% 18% 4	1400
	11th to 20th	Night	29% 5% 11% 32% 21% 3	1392
	21st to end	Night	28% 4 16% 29% 18% 5%	1487
August	1st to 10th	Night	30% 5% 15% 32% 15% 3	1440
	11th to 20th	Night	28% 5% 15% 31% 20% 1	1750
	21st to end	Night	31% 4 12% 28% 21% 4	1980
September	1st to 10th	Night	33% 4 11% 25% 24% 3	1800
	11th to 20th	Night	31% 4 10% 34% 19% 2	1855
	21st to end	Night	36% 3 10% 32% 18% 1	1980
October	1st to 10th	Night	37% 4 9% 29% 20% 2	2092
	11th to 20th	Night	45% 2 11% 23% 18% 1	2160
	21st to end	Night	48% 3 11% 25% 12% 1	2555
November	1st to 10th	Night	38% 3 10% 29% 18% 3	2406
	11th to 20th	Night	50% 4 12% 22% 11% 1	2470
	21st to end	Night	50% 3 13% 23% 10% 1	2628
December	1st to 10th	Night	55% 4 11% 20% 8% 1	2660
	11th to 20th	Night	58% 3 12% 18% 8% 1	3281
	21st to end	Night	70% 2 8% 15% 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	19% 13% 31% 29% 9% 1	270
	11th to 20th	Day	21% 15% 33% 25% 4 1	257
	21st to end	Day	20% 14% 34% 25% 5% 1	264
February	1st to 10th	Day	18% 17% 43% 18% 4	240
	11th to 20th	Day	20% 20% 33% 21% 5%	240
	21st to end	Day	23% 20% 39% 16% 2 1	198
March	1st to 10th	Day	14% 24% 37% 18% 7%	240
	11th to 20th	Day	21% 18% 33% 19% 8% 2	240
	21st to end	Day	26% 16% 28% 19% 7% 3	447
April	1st to 10th	Day	24% 13% 35% 22% 5%	420
	11th to 20th	Day	22% 19% 27% 19% 10% 3	412
	21st to end	Day	26% 12% 28% 20% 11% 2	420
May	1st to 10th	Day	23% 13% 29% 25% 9% 2	460
	11th to 20th	Day	23% 9% 29% 24% 11% 3	625
	21st to end	Day	17% 10% 27% 24% 16% 6%	679
June	1st to 10th	Day	9% 7% 28% 32% 17% 6%	630
	11th to 20th	Day	13% 6% 29% 30% 17% 6%	630
	21st to end	Day	14% 7% 26% 30% 17% 4	630
July	1st to 10th	Day	7% 5% 17% 32% 24% 14%	621
	11th to 20th	Day	9% 6% 25% 31% 20% 9%	618
	21st to end	Day	8% 3 24% 35% 20% 8%	684
August	1st to 10th	Day	8% 4 19% 33% 24% 12%	626
	11th to 20th	Day	12% 3 16% 27% 26% 15%	464
	21st to end	Day	11% 6% 18% 34% 22% 9%	495
September	1st to 10th	Day	15% 6% 22% 28% 22% 7%	450
	11th to 20th	Day	13% 3 20% 31% 22% 11%	450
	21st to end	Day	14% 11% 26% 23% 18% 7%	450
October	1st to 10th	Day	18% 8% 26% 26% 18% 4	335
	11th to 20th	Day	27% 17% 30% 19% 6% 1	270
	21st to end	Day	30% 14% 29% 20% 5% 1	297
November	1st to 10th	Day	17% 16% 36% 20% 10% 1	270
	11th to 20th	Day	21% 16% 38% 18% 7%	270
	21st to end	Day	26% 10% 38% 21% 5%	270
December	1st to 10th	Day	18% 19% 37% 16% 8% 1	270
	11th to 20th	Day	19% 11% 41% 19% 9% 1	270
	21st to end	Day	25% 18% 38% 18% 2	297
January	1st to 10th	Night	17% 13% 35% 27% 7%	950
	11th to 20th	Night	23% 11% 35% 24% 6% 1	930
	21st to end	Night	19% 11% 35% 28% 6% 1	990
February	1st to 10th	Night	21% 10% 37% 26% 6%	900
	11th to 20th	Night	19% 13% 35% 28% 5%	737
	21st to end	Night	25% 13% 35% 23% 4	592
March	1st to 10th	Night	21% 10% 35% 26% 7%	720
	11th to 20th	Night	17% 11% 32% 31% 9%	648
	21st to end	Night	23% 10% 29% 28% 8% 2	594
April	1st to 10th	Night	22% 11% 37% 24% 4	540
	11th to 20th	Night	24% 10% 31% 29% 7%	533
	21st to end	Night	21% 9% 32% 28% 9% 1	540
May	1st to 10th	Night	19% 9% 34% 30% 7% 1	540
	11th to 20th	Night	20% 7% 28% 34% 12%	531
	21st to end	Night	14% 5% 26% 39% 16% 1	584
June	1st to 10th	Night	9% 3 26% 46% 14% 1	540
	11th to 20th	Night	13% 4 29% 41% 12% 1	540
	21st to end	Night	11% 4 25% 42% 18%	540
July	1st to 10th	Night	8% 2 14% 42% 32% 2	525
	11th to 20th	Night	8% 2 20% 43% 24% 3	522
	21st to end	Night	7% 3 16% 50% 23% 1	591
August	1st to 10th	Night	6% 3 12% 48% 26% 4	537
	11th to 20th	Night	9% 2 13% 39% 32% 6%	534
	21st to end	Night	10% 2 16% 43% 26% 3	594
September	1st to 10th	Night	11% 3 20% 37% 23% 5%	540
	11th to 20th	Night	13% 3 21% 34% 25% 3	595
	21st to end	Night	13% 8% 26% 31% 20% 2	720
October	1st to 10th	Night	14% 7% 31% 31% 16% 2	720
	11th to 20th	Night	22% 12% 28% 29% 8% 1	720
	21st to end	Night	25% 10% 31% 26% 8% 1	792
November	1st to 10th	Night	16% 10% 38% 25% 11% 1	740
	11th to 20th	Night	21% 14% 34% 24% 7%	760
	21st to end	Night	22% 12% 35% 25% 7%	918
December	1st to 10th	Night	22% 13% 36% 23% 6%	950
	11th to 20th	Night	24% 11% 34% 24% 6% 1	950
	21st to end	Night	30% 11% 35% 22% 3	1045

Page generated at 2024-01-13 18:28:32. Version ac07

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