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 2024-11-04.

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% 3 7% 5% 4 5% 4 6% 7% 38%	101306
	Night	15% 9% 3 7% 5% 4 4 4 5% 6% 37%	97787
Transparency	Day	43% 6% 13% 24% 13% 2	104851
	Night	46% 6% 11% 22% 14% 2	102370
Seeing	Day	15% 4 18% 34% 23% 6%	15859
	Night	18% 6% 25% 30% 17% 3	25700

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% 9% 6% 4 4 4 4 6% 27%	2527
	11th to 20th	Day	13% 13% 6% 13% 5% 4 9% 8% 7% 5% 17%	2530
	21st to end	Day	19% 18% 7% 10% 4 5% 4 3 5% 6% 20%	2783
February	1st to 10th	Day	12% 14% 5% 9% 5% 6% 6% 5% 7% 7% 26%	1743
	11th to 20th	Day	12% 12% 3 7% 5% 5% 5% 4 6% 6% 33%	1848
	21st to end	Day	12% 11% 4 12% 6% 5% 5% 4 6% 6% 28%	1570
March	1st to 10th	Day	13% 10% 3 8% 5% 4 4 4 5% 6% 39%	3120
	11th to 20th	Day	11% 5% 3 7% 6% 6% 5% 4 5% 7% 41%	3249
	21st to end	Day	20% 11% 4 9% 6% 5% 5% 4 4 6% 27%	4165
April	1st to 10th	Day	16% 10% 3 8% 6% 4 5% 4 5% 7% 31%	2280
	11th to 20th	Day	16% 8% 3 7% 5% 5% 4 4 6% 7% 37%	2254
	21st to end	Day	18% 8% 3 7% 5% 5% 5% 4 5% 6% 36%	2418
May	1st to 10th	Day	16% 7% 3 8% 5% 4 4 4 6% 7% 36%	4082
	11th to 20th	Day	14% 6% 2 6% 5% 4 5% 4 6% 7% 41%	4327
	21st to end	Day	11% 6% 2 5% 4 4 4 4 6% 9% 44%	4824
June	1st to 10th	Day	10% 5% 2 6% 5% 4 4 4 6% 8% 45%	2660
	11th to 20th	Day	10% 5% 2 6% 4 4 4 3 6% 9% 46%	2660
	21st to end	Day	9% 5% 3 7% 6% 5% 4 4 7% 9% 42%	2660
July	1st to 10th	Day	12% 6% 2 7% 5% 4 5% 4 7% 9% 39%	4440
	11th to 20th	Day	5% 3 1 4 4 4 4 5% 7% 10% 53%	4440
	21st to end	Day	7% 5% 2 7% 5% 5% 5% 4 6% 8% 47%	4813
August	1st to 10th	Day	11% 5% 2 5% 4 4 4 4 7% 9% 45%	4341
	11th to 20th	Day	10% 3 2 5% 3 4 4 4 6% 7% 52%	3830
	21st to end	Day	8% 5% 2 7% 4 4 5% 4 6% 8% 48%	4180
September	1st to 10th	Day	12% 5% 2 5% 4 4 4 3 6% 8% 48%	2280
	11th to 20th	Day	11% 5% 1 4 3 3 4 4 5% 7% 53%	2149
	21st to end	Day	12% 6% 2 7% 4 4 5% 4 6% 8% 42%	2090
October	1st to 10th	Day	13% 6% 2 6% 4 4 4 2 5% 7% 46%	2050
	11th to 20th	Day	18% 8% 3 7% 5% 4 6% 4 5% 6% 33%	1857
	21st to end	Day	19% 9% 3 6% 5% 5% 5% 3 5% 6% 36%	1881
November	1st to 10th	Day	10% 10% 2 7% 4 4 4 4 6% 6% 42%	1699
	11th to 20th	Day	13% 12% 5% 8% 6% 5% 4 4 7% 8% 29%	1710
	21st to end	Day	20% 11% 3 6% 5% 3 4 3 4 5% 36%	1625
December	1st to 10th	Day	16% 14% 4 8% 7% 7% 5% 5% 6% 6% 22%	1520
	11th to 20th	Day	13% 12% 4 10% 6% 5% 4 4 7% 8% 26%	1918
	21st to end	Day	20% 22% 8% 12% 6% 4 4 3 3 3 16%	2783
January	1st to 10th	Night	16% 15% 7% 8% 5% 4 4 3 4 6% 28%	4428
	11th to 20th	Night	16% 16% 6% 14% 5% 5% 7% 7% 5% 4 16%	4440
	21st to end	Night	20% 18% 6% 9% 5% 4 4 3 4 5% 22%	4881
February	1st to 10th	Night	13% 15% 4 9% 6% 4 4 4 4 6% 30%	2436
	11th to 20th	Night	13% 10% 3 7% 5% 5% 4 3 6% 6% 37%	2218
	21st to end	Night	19% 12% 3 7% 4 4 4 3 4 5% 35%	1884
March	1st to 10th	Night	17% 10% 3 7% 4 4 4 3 4 5% 40%	3733
	11th to 20th	Night	10% 6% 2 5% 4 4 4 4 6% 8% 46%	3736
	21st to end	Night	19% 12% 6% 9% 5% 5% 4 3 4 4 28%	3470
April	1st to 10th	Night	16% 9% 2 5% 5% 5% 5% 4 5% 6% 37%	1900
	11th to 20th	Night	19% 8% 3 7% 5% 4 4 4 3 5% 39%	1875
	21st to end	Night	19% 7% 3 7% 3 4 4 3 5% 6% 40%	1761
May	1st to 10th	Night	16% 7% 2 7% 5% 4 4 4 6% 7% 36%	2813
	11th to 20th	Night	17% 6% 2 6% 5% 4 5% 4 6% 9% 35%	2573
	21st to end	Night	13% 8% 2 7% 5% 4 3 3 5% 7% 43%	2743
June	1st to 10th	Night	9% 6% 1 6% 4 5% 5% 4 5% 8% 47%	1520
	11th to 20th	Night	10% 6% 2 6% 4 4 4 4 6% 9% 44%	1520
	21st to end	Night	9% 6% 2 7% 5% 5% 5% 4 6% 8% 44%	1520
July	1st to 10th	Night	12% 6% 2 6% 6% 5% 5% 5% 6% 7% 39%	2530
	11th to 20th	Night	6% 3 2 4 3 5% 4 4 6% 10% 54%	2530
	21st to end	Night	6% 4 2 6% 5% 5% 5% 5% 7% 7% 49%	2750
August	1st to 10th	Night	11% 4 1 5% 4 4 4 3 5% 8% 52%	2593
	11th to 20th	Night	11% 3 2 6% 3 3 4 3 5% 8% 52%	2995
	21st to end	Night	8% 4 2 5% 4 4 4 3 6% 9% 51%	3476
September	1st to 10th	Night	10% 4 2 6% 4 4 5% 3 5% 7% 51%	1900
	11th to 20th	Night	11% 4 1 4 3 4 4 3 6% 7% 53%	2011
	21st to end	Night	14% 6% 2 7% 4 3 4 3 5% 6% 45%	2090
October	1st to 10th	Night	13% 6% 2 5% 4 3 5% 4 5% 6% 48%	2127
	11th to 20th	Night	17% 8% 3 6% 4 4 4 3 4 6% 41%	2322
	21st to end	Night	21% 7% 2 6% 5% 3 4 4 5% 8% 35%	2717
November	1st to 10th	Night	14% 7% 2 6% 4 4 4 3 5% 6% 45%	2452
	11th to 20th	Night	14% 12% 3 8% 5% 5% 5% 4 5% 6% 34%	2470
	21st to end	Night	18% 9% 3 6% 5% 5% 4 3 4 7% 35%	2550
December	1st to 10th	Night	16% 14% 4 9% 6% 6% 5% 5% 5% 5% 25%	2660
	11th to 20th	Night	16% 13% 4 9% 5% 6% 4 4 6% 6% 27%	3279
	21st to end	Night	24% 17% 4 8% 5% 4 5% 3 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	45% 6% 12% 23% 11% 3	3120
	11th to 20th	Day	42% 7% 11% 26% 12% 1	3249
	21st to end	Day	58% 6% 13% 15% 6% 1	4165
April	1st to 10th	Day	52% 6% 11% 19% 11%	2280
	11th to 20th	Day	45% 7% 11% 21% 13% 3	2254
	21st to end	Day	48% 5% 14% 18% 13% 2	2418
May	1st to 10th	Day	45% 7% 12% 21% 14% 2	4120
	11th to 20th	Day	39% 9% 13% 24% 14% 1	4331
	21st to end	Day	35% 7% 13% 23% 18% 4	4837
June	1st to 10th	Day	36% 7% 12% 25% 17% 3	2660
	11th to 20th	Day	34% 5% 15% 23% 20% 2	2660
	21st to end	Day	37% 7% 15% 24% 15% 2	2660
July	1st to 10th	Day	42% 4 13% 25% 13% 3	4371
	11th to 20th	Day	27% 4 17% 34% 16% 1	4365
	21st to end	Day	35% 5% 17% 21% 19% 3	4662
August	1st to 10th	Day	35% 5% 15% 30% 13% 1	4326
	11th to 20th	Day	31% 5% 15% 36% 13% 1	3869
	21st to end	Day	34% 5% 14% 25% 20% 2	4179
September	1st to 10th	Day	34% 5% 15% 28% 16% 2	2280
	11th to 20th	Day	30% 6% 13% 32% 17% 2	2149
	21st to end	Day	38% 6% 12% 28% 14% 1	2090
October	1st to 10th	Day	25% 3 7% 42% 21% 1	3401
	11th to 20th	Day	39% 4 10% 29% 17% 1	3060
	21st to end	Day	44% 4 9% 29% 12% 3	3081
November	1st to 10th	Day	42% 7% 13% 23% 15% 1	1699
	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	47% 5% 12% 25% 9% 2	3733
	11th to 20th	Night	34% 7% 14% 25% 17% 3	3736
	21st to end	Night	60% 5% 8% 16% 10% 1	3470
April	1st to 10th	Night	46% 7% 10% 21% 15% 1	1900
	11th to 20th	Night	48% 5% 7% 18% 18% 4	1875
	21st to end	Night	45% 5% 12% 20% 16% 2	1761
May	1st to 10th	Night	44% 7% 12% 19% 15% 3	2840
	11th to 20th	Night	43% 9% 12% 23% 12% 1	2574
	21st to end	Night	41% 7% 9% 18% 18% 7%	2751
June	1st to 10th	Night	34% 7% 10% 28% 17% 3	1520
	11th to 20th	Night	36% 7% 9% 25% 21% 3	1520
	21st to end	Night	37% 7% 13% 24% 15% 3	1520
July	1st to 10th	Night	43% 4 14% 22% 11% 5%	2490
	11th to 20th	Night	26% 4 15% 36% 16% 3	2482
	21st to end	Night	32% 5% 15% 20% 24% 3	2662
August	1st to 10th	Night	31% 5% 15% 28% 19% 2	2584
	11th to 20th	Night	32% 4 11% 35% 17% 1	3022
	21st to end	Night	30% 4 12% 30% 20% 3	3476
September	1st to 10th	Night	33% 6% 11% 25% 22% 3	1900
	11th to 20th	Night	30% 6% 8% 34% 19% 2	2011
	21st to end	Night	40% 5% 8% 30% 16% 2	2090
October	1st to 10th	Night	26% 4 7% 38% 24% 1	3543
	11th to 20th	Night	38% 5% 10% 23% 23% 1	3858
	21st to end	Night	42% 4 10% 25% 17% 2	4467
November	1st to 10th	Night	40% 7% 9% 24% 17% 3	2452
	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	25% 5% 27% 32% 10% 2	506
April	1st to 10th	Day	21% 6% 24% 38% 11%	460
	11th to 20th	Day	19% 5% 25% 34% 12% 5%	452
	21st to end	Day	20% 4 23% 33% 17% 3	460
May	1st to 10th	Day	19% 3 19% 42% 16% 2	463
	11th to 20th	Day	18% 3 14% 40% 22% 3	629
	21st to end	Day	13% 2 13% 36% 26% 11%	734
June	1st to 10th	Day	10% 3 12% 40% 28% 8%	680
	11th to 20th	Day	12% 1 11% 41% 27% 9%	680
	21st to end	Day	11% 2 11% 41% 30% 5%	680
July	1st to 10th	Day	8% 1 6% 31% 39% 15%	671
	11th to 20th	Day	9% 2 9% 35% 36% 11%	668
	21st to end	Day	8% 1 7% 40% 36% 8%	739
August	1st to 10th	Day	7% 2 8% 35% 36% 12%	633
	11th to 20th	Day	10% 3 9% 32% 34% 13%	479
	21st to end	Day	9% 2 10% 31% 37% 12%	539
September	1st to 10th	Day	13% 3 14% 27% 31% 12%	490
	11th to 20th	Day	10% 2 10% 29% 34% 15%	490
	21st to end	Day	15% 4 18% 28% 24% 11%	490
October	1st to 10th	Day	16% 4 19% 29% 24% 8%	450
	11th to 20th	Day	21% 6% 24% 30% 17% 2	300
	21st to end	Day	26% 8% 24% 30% 12% 1	330
November	1st to 10th	Day	13% 7% 29% 29% 21% 2	279
	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	20% 6% 29% 34% 10% 1	570
	11th to 20th	Night	23% 3 25% 33% 14% 2	563
	21st to end	Night	22% 4 20% 37% 17% 1	570
May	1st to 10th	Night	19% 4 14% 45% 17% 2	570
	11th to 20th	Night	19% 2 16% 34% 25% 4	561
	21st to end	Night	15% 2 13% 30% 31% 9%	617
June	1st to 10th	Night	11% 2 9% 43% 29% 6%	570
	11th to 20th	Night	14% 1 13% 38% 29% 5%	570
	21st to end	Night	10% 1 12% 40% 32% 5%	570
July	1st to 10th	Night	10% 2 4 33% 37% 14%	555
	11th to 20th	Night	8% 2 9% 37% 35% 10%	552
	21st to end	Night	7% 1 8% 37% 41% 5%	624
August	1st to 10th	Night	8% 2 7% 37% 38% 8%	567
	11th to 20th	Night	9% 1 10% 32% 37% 10%	564
	21st to end	Night	8% 2 11% 32% 41% 6%	627
September	1st to 10th	Night	10% 4 13% 32% 30% 11%	570
	11th to 20th	Night	11% 3 11% 30% 33% 11%	681
	21st to end	Night	14% 6% 20% 27% 24% 9%	760
October	1st to 10th	Night	15% 4 22% 32% 21% 6%	760
	11th to 20th	Night	22% 8% 28% 27% 14% 1	760
	21st to end	Night	24% 8% 28% 28% 10% 2	836
November	1st to 10th	Night	17% 8% 32% 26% 15% 2	755
	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

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