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 2024-12-09.

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	13% 9% 3 8% 5% 4 4 4 6% 7% 37%	101710
	Night	14% 10% 4 7% 4 4 4 3 5% 6% 38%	98149
Transparency	Day	45% 4 12% 25% 13% 1	105249
	Night	46% 3 11% 24% 15% 2	102751
Seeing	Day	17% 11% 28% 26% 14% 5%	15984
	Night	18% 9% 30% 31% 11% 1	25873

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	11% 13% 9% 14% 6% 5% 4 3 4 4 26%	2527
	11th to 20th	Day	12% 13% 5% 15% 5% 4 5% 8% 7% 6% 19%	2530
	21st to end	Day	16% 18% 11% 12% 5% 3 3 2 4 6% 20%	2893
February	1st to 10th	Day	12% 14% 5% 8% 6% 4 5% 4 5% 8% 29%	1710
	11th to 20th	Day	13% 11% 3 8% 5% 5% 5% 3 4 5% 37%	1810
	21st to end	Day	13% 12% 5% 10% 5% 5% 4 4 4 6% 31%	1570
March	1st to 10th	Day	12% 8% 3 7% 4 5% 4 3 4 6% 42%	3120
	11th to 20th	Day	11% 7% 3 8% 5% 4 5% 4 5% 6% 42%	3318
	21st to end	Day	20% 12% 4 10% 5% 5% 4 3 5% 6% 26%	4150
April	1st to 10th	Day	18% 14% 4 7% 6% 4 4 3 5% 6% 30%	2280
	11th to 20th	Day	17% 11% 3 7% 6% 4 4 3 4 7% 34%	2254
	21st to end	Day	19% 9% 3 9% 5% 4 4 3 6% 6% 32%	2354
May	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 4 6% 7% 36%	4161
	11th to 20th	Day	15% 6% 2 6% 4 4 4 4 5% 7% 43%	4399
	21st to end	Day	12% 7% 3 6% 5% 4 5% 4 7% 8% 39%	4824
June	1st to 10th	Day	10% 5% 2 6% 4 5% 5% 4 6% 8% 43%	2660
	11th to 20th	Day	12% 5% 2 5% 4 5% 5% 4 7% 9% 43%	2660
	21st to end	Day	12% 5% 3 6% 5% 5% 5% 5% 8% 9% 37%	2660
July	1st to 10th	Day	11% 8% 3 7% 5% 5% 5% 5% 7% 10% 33%	4440
	11th to 20th	Day	5% 4 1 5% 4 5% 5% 4 7% 9% 51%	4440
	21st to end	Day	8% 7% 3 6% 5% 5% 4 4 7% 9% 42%	4813
August	1st to 10th	Day	9% 5% 2 6% 5% 4 6% 4 7% 9% 41%	4374
	11th to 20th	Day	11% 5% 2 5% 4 4 5% 4 6% 9% 46%	3767
	21st to end	Day	9% 6% 3 7% 4 3 4 3 6% 9% 46%	4180
September	1st to 10th	Day	12% 5% 3 5% 3 5% 5% 3 6% 8% 46%	2280
	11th to 20th	Day	12% 4 2 4 3 4 4 3 5% 8% 52%	2201
	21st to end	Day	11% 7% 3 6% 5% 3 4 3 5% 7% 44%	2090
October	1st to 10th	Day	14% 7% 2 5% 4 3 4 3 5% 7% 47%	1968
	11th to 20th	Day	19% 11% 2 7% 4 4 4 3 5% 6% 36%	1900
	21st to end	Day	19% 10% 3 7% 4 4 4 3 4 6% 37%	1900
November	1st to 10th	Day	12% 10% 3 6% 4 4 4 2 4 6% 44%	1762
	11th to 20th	Day	14% 13% 4 8% 5% 4 5% 4 5% 6% 32%	1800
	21st to end	Day	16% 14% 4 10% 5% 3 2 2 4 6% 34%	1630
December	1st to 10th	Day	14% 13% 4 10% 6% 5% 4 3 5% 7% 30%	1584
	11th to 20th	Day	12% 15% 6% 9% 6% 4 4 3 6% 6% 27%	1918
	21st to end	Day	19% 21% 9% 14% 5% 4 4 3 3 3 14%	2783
January	1st to 10th	Night	12% 15% 8% 12% 5% 4 3 2 4 3 31%	4428
	11th to 20th	Night	13% 16% 7% 14% 6% 4 5% 5% 7% 4 20%	4440
	21st to end	Night	16% 19% 8% 11% 5% 5% 4 2 4 5% 21%	4756
February	1st to 10th	Night	12% 15% 5% 8% 5% 6% 4 4 5% 5% 33%	2470
	11th to 20th	Night	12% 10% 4 9% 4 4 4 3 5% 6% 39%	2254
	21st to end	Night	17% 12% 3 8% 4 3 3 4 5% 5% 35%	1884
March	1st to 10th	Night	17% 9% 3 7% 4 4 4 3 3 5% 42%	3733
	11th to 20th	Night	10% 6% 2 6% 4 4 4 4 6% 8% 45%	3672
	21st to end	Night	24% 11% 4 9% 4 3 4 3 4 4 29%	3480
April	1st to 10th	Night	17% 9% 2 7% 5% 5% 3 3 5% 6% 37%	1900
	11th to 20th	Night	18% 9% 4 6% 4 4 4 3 4 6% 38%	1875
	21st to end	Night	18% 7% 3 7% 5% 4 4 3 6% 6% 38%	1824
May	1st to 10th	Night	16% 7% 2 7% 5% 4 4 4 6% 8% 37%	2734
	11th to 20th	Night	14% 7% 2 6% 4 5% 5% 4 7% 6% 40%	2506
	21st to end	Night	11% 8% 3 7% 4 4 4 4 6% 7% 42%	2743
June	1st to 10th	Night	8% 5% 2 5% 5% 4 5% 4 7% 8% 47%	1520
	11th to 20th	Night	11% 5% 1 6% 3 4 3 4 6% 9% 48%	1520
	21st to end	Night	11% 7% 2 5% 4 3 4 4 6% 8% 47%	1520
July	1st to 10th	Night	13% 7% 2 6% 4 4 5% 4 6% 8% 39%	2530
	11th to 20th	Night	5% 4 1 5% 3 3 4 4 6% 8% 56%	2530
	21st to end	Night	6% 5% 2 6% 4 5% 5% 5% 7% 8% 46%	2750
August	1st to 10th	Night	8% 5% 2 5% 4 4 4 4 6% 7% 52%	2562
	11th to 20th	Night	8% 7% 2 5% 4 4 4 3 6% 8% 49%	3062
	21st to end	Night	9% 5% 2 5% 4 4 4 4 5% 8% 50%	3476
September	1st to 10th	Night	8% 4 2 6% 4 3 4 3 4 7% 55%	1900
	11th to 20th	Night	11% 4 1 4 3 4 4 4 5% 8% 52%	1959
	21st to end	Night	11% 5% 2 6% 4 4 4 3 4 7% 49%	2090
October	1st to 10th	Night	12% 7% 2 5% 4 3 4 2 4 7% 50%	2209
	11th to 20th	Night	17% 9% 3 6% 3 3 3 3 4 5% 44%	2280
	21st to end	Night	19% 9% 3 6% 4 4 4 3 6% 7% 37%	2697
November	1st to 10th	Night	12% 8% 3 6% 4 3 2 3 5% 6% 47%	2536
	11th to 20th	Night	14% 11% 4 9% 5% 4 4 4 5% 6% 35%	2600
	21st to end	Night	16% 12% 4 8% 5% 4 3 3 4 5% 36%	2767
December	1st to 10th	Night	15% 12% 4 8% 5% 5% 5% 3 5% 5% 32%	2779
	11th to 20th	Night	16% 15% 4 10% 5% 5% 4 4 4 6% 29%	3279
	21st to end	Night	21% 18% 7% 10% 5% 5% 4 3 5% 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	64% 2 12% 16% 5%	2528
	11th to 20th	Day	64% 2 12% 14% 8%	2530
	21st to end	Day	69% 2 8% 15% 5%	2893
February	1st to 10th	Day	56% 2 11% 19% 10% 1	1710
	11th to 20th	Day	50% 3 11% 24% 10% 2	1820
	21st to end	Day	55% 3 9% 21% 10% 2	1570
March	1st to 10th	Day	45% 2 11% 28% 11% 3	3120
	11th to 20th	Day	42% 2 10% 32% 13% 1	3318
	21st to end	Day	62% 3 12% 17% 6% 1	4150
April	1st to 10th	Day	55% 4 10% 21% 10%	2280
	11th to 20th	Day	51% 3 9% 23% 12% 2	2254
	21st to end	Day	52% 4 11% 19% 13% 1	2354
May	1st to 10th	Day	49% 2 9% 24% 15% 1	4199
	11th to 20th	Day	41% 3 11% 30% 15%	4403
	21st to end	Day	42% 3 11% 24% 16% 3	4837
June	1st to 10th	Day	37% 5% 13% 28% 16% 1	2660
	11th to 20th	Day	36% 5% 13% 26% 18% 2	2660
	21st to end	Day	41% 5% 15% 23% 14% 2	2660
July	1st to 10th	Day	43% 7% 13% 26% 9% 2	4371
	11th to 20th	Day	28% 6% 16% 31% 18% 1	4365
	21st to end	Day	37% 7% 15% 19% 20% 2	4662
August	1st to 10th	Day	37% 6% 14% 29% 12% 1	4359
	11th to 20th	Day	34% 5% 13% 34% 13% 1	3803
	21st to end	Day	35% 4 13% 29% 18% 1	4179
September	1st to 10th	Day	37% 4 11% 27% 20% 2	2280
	11th to 20th	Day	32% 3 11% 34% 18% 2	2201
	21st to end	Day	40% 3 9% 30% 17% 1	2090
October	1st to 10th	Day	25% 2 6% 40% 25% 1	3267
	11th to 20th	Day	35% 4 9% 29% 23% 1	3140
	21st to end	Day	43% 3 9% 29% 13% 3	3112
November	1st to 10th	Day	42% 3 14% 25% 14% 2	1762
	11th to 20th	Day	53% 3 13% 20% 9% 1	1800
	21st to end	Day	53% 3 13% 24% 7%	1630
December	1st to 10th	Day	55% 3 16% 18% 7% 1	1584
	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	60% 2 9% 20% 9% 1	4428
	11th to 20th	Night	67% 2 9% 13% 8%	4440
	21st to end	Night	69% 2 8% 15% 5% 1	4756
February	1st to 10th	Night	54% 3 9% 20% 13% 1	2470
	11th to 20th	Night	47% 3 11% 23% 14% 1	2255
	21st to end	Night	50% 3 10% 21% 11% 4	1884
March	1st to 10th	Night	47% 2 12% 24% 9% 5%	3733
	11th to 20th	Night	38% 3 10% 30% 17% 2	3672
	21st to end	Night	60% 2 8% 19% 10% 1	3480
April	1st to 10th	Night	49% 3 10% 22% 14% 2	1900
	11th to 20th	Night	49% 3 6% 20% 19% 3	1875
	21st to end	Night	47% 3 11% 24% 13% 2	1824
May	1st to 10th	Night	46% 3 12% 19% 17% 2	2761
	11th to 20th	Night	44% 2 11% 29% 13% 1	2507
	21st to end	Night	41% 3 11% 20% 20% 5%	2751
June	1st to 10th	Night	33% 5% 13% 28% 20% 1	1520
	11th to 20th	Night	34% 5% 10% 24% 25% 3	1520
	21st to end	Night	35% 5% 15% 23% 19% 2	1520
July	1st to 10th	Night	42% 5% 15% 22% 12% 3	2490
	11th to 20th	Night	25% 6% 15% 35% 18% 2	2482
	21st to end	Night	32% 7% 15% 21% 22% 3	2662
August	1st to 10th	Night	31% 5% 14% 30% 19% 2	2553
	11th to 20th	Night	32% 6% 13% 32% 17% 1	3092
	21st to end	Night	32% 5% 13% 30% 18% 3	3476
September	1st to 10th	Night	32% 4 11% 26% 25% 3	1900
	11th to 20th	Night	30% 4 10% 34% 19% 2	1959
	21st to end	Night	36% 3 9% 32% 19% 1	2090
October	1st to 10th	Night	25% 3 6% 37% 27% 1	3690
	11th to 20th	Night	36% 3 9% 27% 23% 2	3779
	21st to end	Night	42% 3 9% 27% 16% 2	4435
November	1st to 10th	Night	39% 3 10% 28% 17% 3	2536
	11th to 20th	Night	50% 4 12% 22% 11% 1	2600
	21st to end	Night	51% 3 13% 22% 10% 1	2767
December	1st to 10th	Night	54% 4 12% 21% 9% 1	2779
	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% 14% 35% 25% 4 1	270
	21st to end	Day	22% 13% 33% 26% 5% 1	297
February	1st to 10th	Day	17% 17% 42% 19% 5% 1	270
	11th to 20th	Day	19% 20% 36% 21% 4 1	270
	21st to end	Day	21% 19% 41% 16% 2	225
March	1st to 10th	Day	14% 24% 39% 16% 6%	270
	11th to 20th	Day	22% 20% 33% 17% 7% 1	270
	21st to end	Day	26% 16% 29% 20% 6% 2	491
April	1st to 10th	Day	25% 14% 34% 21% 5%	460
	11th to 20th	Day	23% 20% 27% 19% 10% 3	452
	21st to end	Day	26% 13% 28% 21% 11% 2	460
May	1st to 10th	Day	21% 14% 29% 25% 9% 2	503
	11th to 20th	Day	22% 9% 29% 25% 11% 3	675
	21st to end	Day	16% 10% 27% 25% 16% 6%	734
June	1st to 10th	Day	10% 8% 29% 31% 17% 5%	680
	11th to 20th	Day	13% 6% 30% 29% 16% 5%	680
	21st to end	Day	14% 8% 28% 29% 16% 4	680
July	1st to 10th	Day	7% 6% 18% 31% 24% 13%	671
	11th to 20th	Day	9% 6% 25% 30% 20% 9%	668
	21st to end	Day	9% 3 23% 35% 21% 9%	739
August	1st to 10th	Day	9% 4 20% 33% 23% 12%	676
	11th to 20th	Day	12% 4 18% 28% 25% 14%	505
	21st to end	Day	10% 6% 17% 34% 24% 9%	539
September	1st to 10th	Day	14% 6% 23% 27% 22% 7%	490
	11th to 20th	Day	12% 2 19% 32% 23% 11%	490
	21st to end	Day	14% 11% 27% 24% 17% 7%	490
October	1st to 10th	Day	17% 9% 27% 26% 18% 4	368
	11th to 20th	Day	25% 17% 30% 21% 7% 1	300
	21st to end	Day	29% 14% 30% 21% 5% 1	330
November	1st to 10th	Day	19% 15% 36% 19% 9% 1	300
	11th to 20th	Day	22% 16% 38% 17% 8%	300
	21st to end	Day	27% 10% 39% 20% 5%	300
December	1st to 10th	Day	17% 19% 39% 16% 8% 1	294
	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	22% 12% 36% 23% 6% 1	950
	21st to end	Night	19% 11% 35% 29% 6%	1045
February	1st to 10th	Night	20% 10% 37% 27% 6%	950
	11th to 20th	Night	19% 13% 35% 28% 5%	779
	21st to end	Night	24% 13% 36% 22% 4	628
March	1st to 10th	Night	21% 11% 36% 26% 7%	760
	11th to 20th	Night	16% 12% 32% 30% 8%	684
	21st to end	Night	24% 10% 29% 28% 7% 2	627
April	1st to 10th	Night	22% 12% 38% 24% 4	570
	11th to 20th	Night	23% 11% 32% 28% 6%	563
	21st to end	Night	22% 9% 32% 27% 9% 1	570
May	1st to 10th	Night	18% 10% 34% 30% 7% 1	570
	11th to 20th	Night	19% 6% 28% 35% 11%	561
	21st to end	Night	14% 6% 25% 39% 15% 1	617
June	1st to 10th	Night	9% 4 26% 46% 14% 1	570
	11th to 20th	Night	13% 4 32% 40% 11% 1	570
	21st to end	Night	12% 4 26% 41% 17%	570
July	1st to 10th	Night	9% 3 14% 42% 30% 2	555
	11th to 20th	Night	9% 2 20% 43% 24% 3	552
	21st to end	Night	6% 3 16% 50% 23% 1	624
August	1st to 10th	Night	6% 3 13% 49% 25% 4	567
	11th to 20th	Night	9% 2 14% 40% 31% 5%	564
	21st to end	Night	10% 2 16% 44% 26% 3	627
September	1st to 10th	Night	11% 3 20% 37% 24% 5%	570
	11th to 20th	Night	12% 3 21% 35% 26% 3	629
	21st to end	Night	13% 8% 26% 32% 20% 2	760
October	1st to 10th	Night	13% 7% 31% 32% 15% 2	760
	11th to 20th	Night	22% 12% 28% 30% 8% 1	760
	21st to end	Night	24% 11% 31% 25% 8%	836
November	1st to 10th	Night	17% 11% 37% 25% 10% 1	780
	11th to 20th	Night	22% 14% 34% 24% 7%	800
	21st to end	Night	21% 12% 35% 25% 7%	967
December	1st to 10th	Night	21% 13% 37% 23% 6%	993
	11th to 20th	Night	24% 11% 34% 24% 6% 1	950
	21st to end	Night	30% 11% 35% 22% 3	1045

Page generated at 2024-12-06 02:54:49. Version ac07

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