Racine
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Racine clear sky chart from 2005-11-06 to 2024-04-03.

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% 8% 4 6% 6% 3 5% 5% 6% 7% 37%	78729
	Night	15% 9% 4 6% 5% 3 5% 5% 5% 6% 36%	81451
Transparency	Day	45% 7% 13% 22% 11% 1	78430
	Night	48% 7% 11% 21% 12% 2	81271
Seeing	Day	15% 4 18% 33% 22% 6%	14939
	Night	18% 7% 25% 30% 17% 3	25002

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	14% 15% 8% 8% 7% 3 4 5% 4 6% 27%	2527
	11th to 20th	Day	13% 12% 6% 12% 6% 3 6% 12% 7% 5% 18%	2530
	21st to end	Day	19% 18% 7% 9% 5% 3 5% 4 5% 6% 20%	2783
February	1st to 10th	Day	12% 13% 5% 8% 6% 4 6% 6% 7% 7% 26%	1743
	11th to 20th	Day	12% 11% 4 6% 6% 5% 4 5% 6% 7% 33%	1848
	21st to end	Day	13% 10% 5% 11% 7% 4 6% 5% 5% 6% 28%	1570
March	1st to 10th	Day	13% 9% 4 9% 7% 3 4 5% 4 7% 34%	1900
	11th to 20th	Day	12% 8% 4 6% 6% 3 6% 5% 5% 7% 39%	1950
	21st to end	Day	18% 9% 5% 7% 6% 4 5% 5% 5% 7% 29%	2508
April	1st to 10th	Day	16% 9% 4 7% 7% 3 5% 5% 5% 8% 31%	2184
	11th to 20th	Day	16% 8% 3 6% 6% 3 5% 5% 5% 7% 36%	2134
	21st to end	Day	18% 7% 3 6% 5% 3 5% 4 5% 7% 36%	2290
May	1st to 10th	Day	15% 7% 3 8% 6% 3 5% 5% 6% 9% 33%	2340
	11th to 20th	Day	17% 6% 3 6% 5% 3 4 4 6% 7% 39%	2435
	21st to end	Day	12% 6% 3 5% 5% 4 5% 5% 6% 8% 41%	2725
June	1st to 10th	Day	10% 5% 3 6% 6% 4 4 5% 5% 8% 45%	2520
	11th to 20th	Day	11% 5% 2 5% 5% 3 4 4 6% 9% 47%	2520
	21st to end	Day	9% 4 2 6% 6% 3 5% 5% 7% 10% 42%	2520
July	1st to 10th	Day	6% 3 2 4 5% 3 5% 4 7% 10% 51%	2520
	11th to 20th	Day	8% 3 2 4 5% 3 4 5% 6% 10% 50%	2520
	21st to end	Day	6% 4 2 4 5% 4 5% 6% 7% 8% 50%	2743
August	1st to 10th	Day	7% 4 2 4 4 3 4 5% 7% 11% 47%	2467
	11th to 20th	Day	9% 4 3 5% 5% 3 4 5% 7% 8% 47%	2187
	21st to end	Day	8% 4 2 5% 5% 3 4 5% 6% 9% 49%	2376
September	1st to 10th	Day	13% 5% 2 5% 5% 2 4 4 6% 8% 47%	2160
	11th to 20th	Day	12% 5% 2 4 3 2 4 5% 5% 7% 52%	2036
	21st to end	Day	12% 5% 2 6% 5% 3 5% 5% 6% 9% 42%	1980
October	1st to 10th	Day	14% 6% 2 5% 6% 3 4 3 5% 8% 44%	1943
	11th to 20th	Day	19% 8% 4 6% 6% 4 6% 5% 6% 6% 32%	1760
	21st to end	Day	19% 9% 3 5% 5% 3 4 4 5% 6% 35%	1782
November	1st to 10th	Day	11% 9% 3 6% 5% 3 4 5% 6% 6% 42%	1672
	11th to 20th	Day	13% 10% 5% 8% 7% 4 4 5% 6% 8% 29%	1710
	21st to end	Day	21% 10% 4 6% 5% 3 4 4 4 5% 36%	1625
December	1st to 10th	Day	17% 14% 4 7% 7% 5% 7% 6% 5% 7% 22%	1520
	11th to 20th	Day	14% 12% 4 9% 7% 3 5% 5% 7% 8% 26%	1918
	21st to end	Day	20% 21% 8% 10% 7% 3 4 4 3 3 16%	2783
January	1st to 10th	Night	16% 14% 8% 7% 6% 3 4 4 4 6% 28%	4428
	11th to 20th	Night	16% 15% 6% 12% 7% 4 5% 9% 4 5% 16%	4440
	21st to end	Night	20% 17% 7% 9% 6% 3 4 4 4 5% 22%	4881
February	1st to 10th	Night	14% 14% 4 8% 7% 3 4 5% 5% 6% 30%	2436
	11th to 20th	Night	14% 10% 3 6% 6% 4 5% 4 5% 6% 38%	2218
	21st to end	Night	19% 11% 4 6% 5% 3 5% 4 4 5% 35%	1884
March	1st to 10th	Night	15% 10% 4 8% 6% 4 4 5% 5% 5% 34%	2280
	11th to 20th	Night	12% 7% 3 5% 5% 3 4 5% 5% 8% 42%	2242
	21st to end	Night	19% 10% 5% 7% 6% 4 5% 4 4 6% 31%	2094
April	1st to 10th	Night	16% 9% 3 5% 6% 4 5% 5% 6% 6% 37%	1820
	11th to 20th	Night	19% 7% 3 6% 5% 3 5% 4 3 5% 39%	1775
	21st to end	Night	20% 7% 3 6% 4 3 4 4 5% 6% 39%	1669
May	1st to 10th	Night	17% 7% 3 6% 6% 3 5% 5% 7% 7% 34%	1620
	11th to 20th	Night	19% 6% 3 5% 5% 3 4 4 5% 8% 38%	1457
	21st to end	Night	12% 7% 3 6% 5% 3 4 5% 5% 8% 42%	1551
June	1st to 10th	Night	9% 5% 2 5% 4 3 5% 5% 5% 8% 48%	1440
	11th to 20th	Night	11% 6% 2 6% 5% 2 5% 5% 6% 9% 44%	1440
	21st to end	Night	9% 5% 3 6% 5% 4 6% 5% 7% 8% 45%	1440
July	1st to 10th	Night	7% 4 1 3 5% 3 5% 6% 7% 9% 50%	1440
	11th to 20th	Night	8% 3 2 4 4 3 5% 4 7% 9% 51%	1440
	21st to end	Night	7% 3 1 3 5% 3 6% 5% 7% 8% 52%	1575
August	1st to 10th	Night	6% 3 1 5% 5% 3 6% 5% 6% 9% 51%	1469
	11th to 20th	Night	9% 3 2 6% 3 3 5% 4 6% 9% 52%	1710
	21st to end	Night	9% 4 2 3 4 3 4 4 6% 8% 53%	1980
September	1st to 10th	Night	10% 4 2 6% 4 3 5% 5% 5% 7% 50%	1800
	11th to 20th	Night	11% 4 1 4 4 2 4 4 5% 7% 54%	1905
	21st to end	Night	15% 5% 2 6% 5% 3 4 4 5% 6% 45%	1980
October	1st to 10th	Night	14% 6% 2 5% 5% 3 4 5% 5% 6% 46%	2015
	11th to 20th	Night	18% 8% 3 6% 5% 3 3 4 4 6% 40%	2199
	21st to end	Night	22% 7% 3 5% 6% 3 4 4 5% 8% 35%	2574
November	1st to 10th	Night	14% 6% 2 5% 5% 3 4 4 5% 6% 45%	2406
	11th to 20th	Night	15% 11% 3 7% 5% 4 5% 5% 4 6% 34%	2470
	21st to end	Night	18% 8% 4 6% 6% 4 4 4 4 7% 35%	2550
December	1st to 10th	Night	17% 13% 4 8% 6% 4 5% 6% 5% 5% 25%	2660
	11th to 20th	Night	16% 12% 5% 8% 6% 4 5% 5% 6% 6% 27%	3279
	21st to end	Night	25% 17% 5% 7% 6% 4 5% 4 5% 5% 18%	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	58% 8% 13% 15% 5%	2528
	11th to 20th	Day	60% 13% 11% 13% 2	2530
	21st to end	Day	67% 5% 8% 16% 4	2783
February	1st to 10th	Day	55% 7% 12% 16% 9% 1	1743
	11th to 20th	Day	48% 7% 11% 23% 9% 2	1858
	21st to end	Day	54% 7% 10% 18% 9% 2	1570
March	1st to 10th	Day	51% 6% 12% 20% 8% 2	1900
	11th to 20th	Day	45% 7% 12% 23% 12% 2	1950
	21st to end	Day	56% 6% 14% 18% 7% 1	2508
April	1st to 10th	Day	53% 6% 12% 19% 11%	2184
	11th to 20th	Day	46% 7% 11% 21% 12% 4	2134
	21st to end	Day	48% 6% 14% 18% 12% 2	2290
May	1st to 10th	Day	47% 6% 14% 23% 9% 1	2340
	11th to 20th	Day	45% 7% 13% 23% 12% 2	2439
	21st to end	Day	40% 7% 14% 23% 14% 1	2725
June	1st to 10th	Day	36% 7% 12% 26% 16% 3	2520
	11th to 20th	Day	34% 6% 15% 23% 20% 2	2520
	21st to end	Day	36% 8% 15% 24% 16% 2	2520
July	1st to 10th	Day	27% 7% 14% 32% 16% 4	2451
	11th to 20th	Day	29% 7% 15% 30% 18% 1	2445
	21st to end	Day	29% 7% 18% 28% 15% 4	2591
August	1st to 10th	Day	30% 8% 16% 31% 14% 2	2452
	11th to 20th	Day	32% 7% 18% 28% 13% 1	2187
	21st to end	Day	31% 7% 14% 27% 19% 2	2376
September	1st to 10th	Day	35% 5% 15% 26% 16% 2	2160
	11th to 20th	Day	31% 7% 13% 32% 15% 2	2036
	21st to end	Day	38% 7% 13% 28% 13% 1	1980
October	1st to 10th	Day	40% 6% 10% 28% 14% 1	1943
	11th to 20th	Day	51% 6% 11% 20% 11% 1	1760
	21st to end	Day	50% 6% 11% 22% 10% 1	1782
November	1st to 10th	Day	42% 7% 12% 23% 15% 1	1672
	11th to 20th	Day	51% 8% 13% 20% 7% 1	1710
	21st to end	Day	52% 6% 11% 23% 7%	1625
December	1st to 10th	Day	60% 10% 11% 12% 7% 1	1520
	11th to 20th	Day	54% 8% 16% 16% 6% 1	1915
	21st to end	Day	73% 6% 6% 12% 3	2783
January	1st to 10th	Night	57% 9% 11% 16% 7%	4428
	11th to 20th	Night	68% 10% 9% 9% 4	4440
	21st to end	Night	65% 6% 10% 15% 4	4881
February	1st to 10th	Night	55% 6% 10% 17% 11% 1	2436
	11th to 20th	Night	47% 6% 12% 21% 12% 1	2219
	21st to end	Night	51% 5% 10% 20% 11% 4	1884
March	1st to 10th	Night	51% 6% 12% 20% 9% 2	2280
	11th to 20th	Night	39% 7% 14% 23% 15% 3	2242
	21st to end	Night	55% 5% 10% 19% 10% 1	2094
April	1st to 10th	Night	47% 7% 10% 20% 15% 1	1820
	11th to 20th	Night	49% 5% 7% 18% 18% 4	1775
	21st to end	Night	46% 4 13% 19% 15% 2	1669
May	1st to 10th	Night	46% 7% 13% 21% 12% 1	1620
	11th to 20th	Night	44% 7% 11% 21% 16% 2	1458
	21st to end	Night	41% 6% 12% 23% 16% 2	1552
June	1st to 10th	Night	33% 7% 11% 29% 17% 3	1440
	11th to 20th	Night	36% 7% 9% 24% 21% 3	1440
	21st to end	Night	36% 8% 13% 25% 15% 3	1440
July	1st to 10th	Night	28% 7% 16% 28% 17% 5%	1400
	11th to 20th	Night	28% 6% 14% 30% 19% 4	1392
	21st to end	Night	27% 7% 16% 26% 20% 4	1487
August	1st to 10th	Night	29% 8% 15% 30% 16% 3	1460
	11th to 20th	Night	29% 6% 15% 32% 17% 1	1710
	21st to end	Night	29% 6% 11% 29% 21% 3	1980
September	1st to 10th	Night	34% 6% 11% 24% 22% 3	1800
	11th to 20th	Night	31% 6% 9% 35% 18% 2	1905
	21st to end	Night	40% 5% 8% 30% 16% 2	1980
October	1st to 10th	Night	38% 7% 9% 28% 17% 2	2015
	11th to 20th	Night	45% 7% 11% 20% 16% 1	2199
	21st to end	Night	49% 7% 12% 21% 10% 1	2574
November	1st to 10th	Night	40% 7% 9% 25% 17% 3	2406
	11th to 20th	Night	50% 8% 12% 19% 11% 1	2470
	21st to end	Night	50% 7% 14% 21% 8% 1	2550
December	1st to 10th	Night	58% 8% 10% 16% 7% 1	2660
	11th to 20th	Night	55% 8% 12% 17% 7% 1	3281
	21st to end	Night	68% 6% 10% 12% 4	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	20% 7% 27% 34% 10% 2	270
	11th to 20th	Day	20% 8% 27% 33% 11%	270
	21st to end	Day	21% 5% 31% 31% 11% 1	297
February	1st to 10th	Day	15% 6% 37% 30% 9% 2	270
	11th to 20th	Day	17% 9% 33% 30% 11%	270
	21st to end	Day	17% 7% 34% 36% 5%	225
March	1st to 10th	Day	15% 5% 35% 38% 7%	270
	11th to 20th	Day	21% 5% 26% 34% 13% 2	308
	21st to end	Day	24% 5% 27% 32% 10% 2	506
April	1st to 10th	Day	20% 6% 24% 38% 12%	428
	11th to 20th	Day	20% 5% 25% 33% 12% 5%	412
	21st to end	Day	20% 4 23% 32% 17% 3	420
May	1st to 10th	Day	19% 3 19% 41% 16% 2	423
	11th to 20th	Day	19% 2 14% 39% 21% 3	581
	21st to end	Day	14% 2 12% 35% 25% 11%	679
June	1st to 10th	Day	10% 3 10% 40% 28% 8%	630
	11th to 20th	Day	13% 1 10% 39% 27% 10%	630
	21st to end	Day	10% 2 11% 40% 31% 5%	630
July	1st to 10th	Day	7% 1 6% 30% 40% 16%	621
	11th to 20th	Day	9% 2 8% 35% 36% 11%	618
	21st to end	Day	8% 1 7% 41% 35% 7%	684
August	1st to 10th	Day	6% 2 8% 34% 37% 13%	586
	11th to 20th	Day	9% 3 9% 30% 34% 14%	439
	21st to end	Day	9% 2 11% 32% 35% 12%	495
September	1st to 10th	Day	14% 3 13% 27% 31% 11%	450
	11th to 20th	Day	11% 2 11% 29% 33% 15%	450
	21st to end	Day	14% 4 18% 27% 26% 12%	450
October	1st to 10th	Day	17% 4 18% 29% 23% 8%	413
	11th to 20th	Day	22% 7% 24% 31% 15% 1	270
	21st to end	Day	28% 7% 25% 28% 11% 1	297
November	1st to 10th	Day	13% 7% 28% 29% 21% 2	270
	11th to 20th	Day	17% 11% 32% 26% 13%	270
	21st to end	Day	26% 5% 27% 34% 7%	270
December	1st to 10th	Day	19% 10% 33% 26% 11% 1	270
	11th to 20th	Day	18% 11% 33% 28% 9% 1	270
	21st to end	Day	24% 10% 37% 22% 7% 1	297
January	1st to 10th	Night	20% 11% 37% 24% 7%	950
	11th to 20th	Night	22% 11% 34% 25% 7% 1	950
	21st to end	Night	20% 10% 35% 27% 7%	1045
February	1st to 10th	Night	20% 8% 37% 27% 7% 1	916
	11th to 20th	Night	19% 10% 36% 28% 8%	743
	21st to end	Night	25% 6% 36% 26% 5%	628
March	1st to 10th	Night	19% 5% 32% 32% 11% 1	760
	11th to 20th	Night	15% 6% 31% 36% 11% 2	760
	21st to end	Night	22% 4 26% 34% 12% 1	631
April	1st to 10th	Night	21% 6% 29% 33% 11% 1	546
	11th to 20th	Night	23% 3 25% 32% 14% 3	533
	21st to end	Night	22% 3 19% 36% 17% 1	540
May	1st to 10th	Night	19% 3 15% 44% 17% 2	540
	11th to 20th	Night	20% 2 17% 33% 24% 4	531
	21st to end	Night	16% 2 13% 29% 32% 9%	584
June	1st to 10th	Night	11% 2 9% 43% 29% 6%	540
	11th to 20th	Night	15% 1 13% 36% 29% 5%	540
	21st to end	Night	10% 1 11% 39% 33% 5%	540
July	1st to 10th	Night	10% 2 4 32% 38% 15%	525
	11th to 20th	Night	8% 2 9% 36% 35% 10%	522
	21st to end	Night	7% 1 8% 38% 40% 5%	591
August	1st to 10th	Night	8% 2 6% 38% 38% 8%	537
	11th to 20th	Night	9% 1 9% 31% 38% 11%	534
	21st to end	Night	8% 2 11% 31% 41% 6%	594
September	1st to 10th	Night	11% 3 13% 33% 30% 10%	540
	11th to 20th	Night	12% 3 12% 30% 33% 10%	645
	21st to end	Night	15% 6% 20% 26% 24% 10%	720
October	1st to 10th	Night	16% 4 21% 31% 22% 6%	720
	11th to 20th	Night	22% 8% 28% 27% 13% 1	720
	21st to end	Night	25% 8% 27% 28% 10% 2	792
November	1st to 10th	Night	17% 8% 32% 27% 15% 2	740
	11th to 20th	Night	20% 15% 33% 24% 7% 1	760
	21st to end	Night	22% 10% 35% 26% 8%	840
December	1st to 10th	Night	22% 14% 35% 24% 6%	950
	11th to 20th	Night	22% 11% 36% 23% 7%	950
	21st to end	Night	30% 10% 33% 24% 3	1045

Page generated at 2024-03-31 05:08:55. Version ac07

Copyright © 2024 Attilla Danko.