Evansville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Evansville clear sky chart from 2005-11-06 to 2025-02-21.

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% 7% 3 7% 5% 4 4 4 6% 7% 41%	108519
	Night	15% 8% 3 6% 4 4 4 3 5% 6% 43%	110213
Transparency	Day	41% 4 11% 25% 16% 2	112179
	Night	41% 4 10% 24% 18% 3	114694
Seeing	Day	16% 9% 24% 25% 19% 8%	15805
	Night	17% 8% 26% 31% 16% 2	25746

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	15% 11% 6% 11% 6% 6% 4 4 5% 5% 27%	3617
	11th to 20th	Day	14% 9% 4 12% 7% 6% 6% 3 4 7% 29%	3620
	21st to end	Day	20% 11% 6% 8% 4 4 3 3 5% 6% 32%	4471
February	1st to 10th	Day	18% 12% 4 7% 4 4 3 3 4 7% 36%	2000
	11th to 20th	Day	18% 10% 4 7% 5% 4 4 3 5% 6% 34%	1948
	21st to end	Day	15% 10% 4 10% 5% 5% 4 4 5% 5% 33%	1570
March	1st to 10th	Day	23% 12% 3 6% 4 3 3 2 3 5% 35%	3120
	11th to 20th	Day	14% 7% 3 6% 3 3 4 3 4 7% 47%	3251
	21st to end	Day	13% 8% 2 7% 5% 4 4 4 5% 6% 40%	4155
April	1st to 10th	Day	12% 6% 3 6% 4 4 4 4 6% 8% 42%	2280
	11th to 20th	Day	15% 7% 2 6% 5% 4 4 4 5% 7% 41%	2254
	21st to end	Day	17% 6% 2 6% 4 3 4 4 5% 8% 40%	2317
May	1st to 10th	Day	17% 7% 2 7% 6% 4 6% 4 8% 9% 31%	4082
	11th to 20th	Day	18% 7% 3 6% 4 4 4 4 6% 7% 37%	4081
	21st to end	Day	10% 6% 3 7% 4 5% 5% 4 6% 8% 41%	4596
June	1st to 10th	Day	12% 4 2 5% 4 4 5% 3 7% 9% 45%	2660
	11th to 20th	Day	5% 3 2 5% 6% 5% 6% 5% 7% 8% 49%	2660
	21st to end	Day	7% 5% 2 5% 4 5% 4 5% 8% 10% 46%	2660
July	1st to 10th	Day	12% 6% 2 6% 4 4 5% 4 6% 10% 41%	4440
	11th to 20th	Day	5% 3 2 6% 4 4 5% 4 7% 11% 48%	4440
	21st to end	Day	9% 6% 4 10% 7% 7% 6% 6% 8% 9% 29%	4720
August	1st to 10th	Day	5% 4 2 4 3 4 4 4 6% 10% 54%	3923
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 10% 43%	3729
	21st to end	Day	5% 3 2 5% 4 4 4 3 6% 8% 56%	4180
September	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 6% 6% 48%	2280
	11th to 20th	Day	9% 4 2 6% 5% 5% 4 4 5% 8% 49%	2114
	21st to end	Day	12% 4 2 5% 4 3 4 4 5% 5% 51%	2090
October	1st to 10th	Day	10% 4 1 4 3 3 3 3 4 6% 58%	2090
	11th to 20th	Day	12% 5% 2 6% 3 3 4 3 5% 7% 50%	1948
	21st to end	Day	17% 6% 2 6% 4 3 3 2 5% 5% 46%	1909
November	1st to 10th	Day	9% 6% 2 5% 4 3 4 3 5% 6% 52%	1762
	11th to 20th	Day	16% 8% 3 6% 4 3 3 3 4 6% 45%	1800
	21st to end	Day	19% 9% 3 5% 4 3 3 3 4 6% 40%	1800
December	1st to 10th	Day	15% 10% 3 7% 3 3 3 2 3 5% 46%	2930
	11th to 20th	Day	15% 10% 5% 10% 5% 5% 4 3 5% 6% 32%	3040
	21st to end	Day	25% 16% 5% 9% 5% 4 4 3 4 4 22%	3982
January	1st to 10th	Night	17% 12% 6% 8% 4 4 4 4 5% 6% 30%	6348
	11th to 20th	Night	15% 12% 4 8% 5% 6% 5% 3 3 5% 35%	6360
	21st to end	Night	20% 10% 4 6% 4 4 3 2 4 6% 37%	6495
February	1st to 10th	Night	20% 11% 4 8% 4 3 3 4 5% 6% 31%	2400
	11th to 20th	Night	17% 9% 3 8% 5% 4 3 3 4 5% 38%	2338
	21st to end	Night	20% 9% 3 7% 4 4 3 4 5% 6% 35%	1885
March	1st to 10th	Night	24% 10% 3 6% 5% 3 3 3 4 5% 34%	3733
	11th to 20th	Night	12% 6% 2 6% 4 4 3 3 5% 6% 49%	3709
	21st to end	Night	17% 7% 3 8% 4 4 4 3 4 6% 39%	3503
April	1st to 10th	Night	12% 6% 2 6% 4 4 3 3 4 7% 46%	1900
	11th to 20th	Night	17% 7% 2 5% 4 3 3 3 5% 7% 44%	1875
	21st to end	Night	18% 6% 2 7% 4 3 3 4 6% 7% 39%	1862
May	1st to 10th	Night	16% 9% 2 7% 4 4 4 3 6% 9% 35%	2813
	11th to 20th	Night	15% 7% 2 6% 4 4 4 4 5% 6% 43%	2812
	21st to end	Night	9% 5% 2 6% 5% 5% 4 5% 7% 10% 42%	2958
June	1st to 10th	Night	10% 5% 2 5% 3 4 5% 5% 6% 9% 46%	1520
	11th to 20th	Night	6% 3 1 5% 4 3 4 4 7% 8% 54%	1520
	21st to end	Night	4 3 1 4 4 3 4 4 8% 10% 53%	1520
July	1st to 10th	Night	8% 5% 2 6% 4 4 3 4 6% 8% 49%	2530
	11th to 20th	Night	5% 4 2 5% 4 4 4 3 6% 8% 56%	2530
	21st to end	Night	9% 6% 4 9% 5% 6% 6% 6% 8% 9% 33%	2838
August	1st to 10th	Night	4 3 1 5% 3 3 3 3 5% 8% 61%	3002
	11th to 20th	Night	6% 5% 2 5% 3 4 4 4 7% 9% 52%	3100
	21st to end	Night	4 3 1 4 3 3 3 3 6% 9% 60%	3476
September	1st to 10th	Night	10% 4 2 5% 4 3 4 3 5% 7% 54%	1900
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 6% 8% 51%	2047
	21st to end	Night	12% 5% 2 5% 3 3 3 4 4 7% 51%	2090
October	1st to 10th	Night	8% 4 2 6% 3 3 2 2 5% 5% 59%	2090
	11th to 20th	Night	14% 4 2 5% 4 4 3 3 3 4 54%	2228
	21st to end	Night	17% 7% 2 5% 3 3 4 3 4 5% 46%	2688
November	1st to 10th	Night	11% 6% 2 6% 3 3 3 3 5% 6% 53%	2536
	11th to 20th	Night	14% 6% 2 6% 4 3 3 3 4 7% 48%	2600
	21st to end	Night	18% 8% 3 5% 4 3 2 4 4 5% 44%	2600
December	1st to 10th	Night	18% 9% 3 7% 3 3 3 3 4 4 44%	4250
	11th to 20th	Night	18% 8% 3 6% 4 4 4 4 5% 5% 39%	5161
	21st to end	Night	26% 14% 4 8% 4 4 4 3 3 4 25%	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	58% 3 11% 21% 7% 1	3618
	11th to 20th	Day	57% 2 8% 23% 10% 1	3620
	21st to end	Day	56% 2 9% 18% 10% 4	4471
February	1st to 10th	Day	51% 3 11% 22% 11% 2	2000
	11th to 20th	Day	51% 4 9% 21% 13% 2	1958
	21st to end	Day	51% 5% 9% 19% 13% 3	1570
March	1st to 10th	Day	55% 3 6% 19% 14% 4	3120
	11th to 20th	Day	38% 4 10% 28% 16% 3	3251
	21st to end	Day	43% 5% 12% 24% 14% 1	4155
April	1st to 10th	Day	39% 6% 14% 25% 16% 1	2280
	11th to 20th	Day	43% 5% 10% 23% 16% 3	2254
	21st to end	Day	43% 5% 12% 26% 12% 2	2317
May	1st to 10th	Day	46% 8% 15% 22% 9% 1	4120
	11th to 20th	Day	45% 6% 10% 25% 12% 1	4085
	21st to end	Day	39% 7% 12% 20% 21% 2	4609
June	1st to 10th	Day	35% 6% 12% 25% 19% 3	2660
	11th to 20th	Day	30% 8% 12% 26% 21% 3	2660
	21st to end	Day	31% 8% 15% 24% 17% 6%	2660
July	1st to 10th	Day	38% 5% 12% 27% 15% 3	4371
	11th to 20th	Day	30% 5% 12% 35% 16% 2	4365
	21st to end	Day	49% 5% 16% 20% 9% 1	4571
August	1st to 10th	Day	26% 4 15% 37% 17% 1	3910
	11th to 20th	Day	36% 4 13% 27% 18% 1	3765
	21st to end	Day	27% 3 13% 37% 17% 3	4179
September	1st to 10th	Day	34% 7% 9% 25% 20% 5%	2280
	11th to 20th	Day	33% 5% 9% 26% 23% 3	2114
	21st to end	Day	34% 5% 7% 24% 26% 4	2090
October	1st to 10th	Day	18% 3 5% 25% 43% 6%	3480
	11th to 20th	Day	24% 2 9% 26% 34% 6%	3214
	21st to end	Day	32% 2 7% 26% 28% 5%	3121
November	1st to 10th	Day	33% 4 10% 30% 17% 6%	1762
	11th to 20th	Day	41% 4 7% 25% 19% 5%	1800
	21st to end	Day	47% 3 8% 24% 16% 2	1800
December	1st to 10th	Day	43% 2 12% 27% 16%	2930
	11th to 20th	Day	54% 3 10% 21% 11% 1	3037
	21st to end	Day	66% 3 11% 13% 6%	3982
January	1st to 10th	Night	54% 3 10% 23% 8% 1	6348
	11th to 20th	Night	54% 3 6% 20% 14% 3	6360
	21st to end	Night	50% 2 8% 20% 19% 1	6495
February	1st to 10th	Night	54% 4 11% 21% 10% 1	2400
	11th to 20th	Night	49% 4 8% 22% 15% 2	2339
	21st to end	Night	49% 4 11% 20% 13% 4	1885
March	1st to 10th	Night	53% 5% 7% 18% 15% 3	3733
	11th to 20th	Night	37% 5% 12% 24% 17% 6%	3709
	21st to end	Night	46% 5% 11% 25% 12% 1	3503
April	1st to 10th	Night	38% 5% 11% 26% 17% 3	1900
	11th to 20th	Night	40% 4 9% 23% 19% 5%	1875
	21st to end	Night	43% 6% 10% 23% 15% 2	1862
May	1st to 10th	Night	45% 7% 16% 23% 8% 1	2840
	11th to 20th	Night	41% 7% 12% 25% 14% 1	2813
	21st to end	Night	34% 8% 15% 23% 17% 3	2966
June	1st to 10th	Night	33% 6% 12% 25% 21% 4	1520
	11th to 20th	Night	26% 6% 14% 22% 26% 5%	1520
	21st to end	Night	23% 7% 17% 26% 19% 8%	1520
July	1st to 10th	Night	34% 5% 11% 27% 19% 4	2490
	11th to 20th	Night	27% 4 12% 36% 19% 3	2482
	21st to end	Night	45% 5% 15% 22% 11% 1	2748
August	1st to 10th	Night	24% 3 14% 43% 15% 1	2991
	11th to 20th	Night	30% 4 13% 29% 22% 1	3130
	21st to end	Night	22% 4 12% 35% 24% 3	3476
September	1st to 10th	Night	30% 6% 8% 27% 23% 6%	1900
	11th to 20th	Night	30% 5% 9% 26% 25% 5%	2047
	21st to end	Night	33% 5% 9% 24% 23% 7%	2090
October	1st to 10th	Night	19% 3 5% 15% 51% 7%	3480
	11th to 20th	Night	24% 2 5% 26% 37% 6%	3701
	21st to end	Night	31% 2 7% 23% 27% 9%	4426
November	1st to 10th	Night	33% 3 9% 24% 24% 6%	2536
	11th to 20th	Night	37% 4 7% 24% 22% 6%	2600
	21st to end	Night	43% 3 9% 25% 18% 2	2600
December	1st to 10th	Night	45% 3 10% 25% 17% 1	4250
	11th to 20th	Night	47% 3 12% 22% 15% 1	5163
	21st to end	Night	64% 3 9% 17% 6% 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	25% 16% 32% 20% 7% 1	300
	11th to 20th	Day	24% 22% 32% 18% 4	300
	21st to end	Day	22% 22% 39% 13% 4	330
February	1st to 10th	Day	25% 15% 39% 18% 2 1	300
	11th to 20th	Day	28% 19% 38% 12% 2 1	300
	21st to end	Day	29% 18% 31% 19% 4	225
March	1st to 10th	Day	23% 16% 40% 17% 4	270
	11th to 20th	Day	23% 18% 37% 16% 6% 1	322
	21st to end	Day	26% 15% 32% 20% 7% 1	506
April	1st to 10th	Day	18% 15% 33% 25% 8% 1	460
	11th to 20th	Day	22% 14% 25% 23% 15% 1	452
	21st to end	Day	19% 12% 34% 23% 9% 3	460
May	1st to 10th	Day	17% 14% 27% 29% 10% 4	463
	11th to 20th	Day	22% 5% 23% 28% 16% 8%	487
	21st to end	Day	9% 5% 26% 27% 21% 12%	597
June	1st to 10th	Day	13% 5% 18% 26% 29% 10%	680
	11th to 20th	Day	6% 3 20% 33% 27% 12%	680
	21st to end	Day	9% 4 21% 33% 22% 11%	680
July	1st to 10th	Day	11% 3 13% 24% 27% 23%	671
	11th to 20th	Day	7% 4 12% 31% 31% 15%	668
	21st to end	Day	10% 2 12% 31% 32% 14%	682
August	1st to 10th	Day	9% 3 11% 28% 31% 17%	486
	11th to 20th	Day	14% 2 13% 28% 32% 12%	479
	21st to end	Day	8% 1 11% 23% 39% 18%	539
September	1st to 10th	Day	9% 3 15% 25% 33% 15%	490
	11th to 20th	Day	9% 3 10% 29% 33% 17%	490
	21st to end	Day	16% 5% 21% 22% 24% 12%	490
October	1st to 10th	Day	10% 3 20% 34% 24% 8%	490
	11th to 20th	Day	14% 10% 33% 25% 14% 5%	348
	21st to end	Day	23% 13% 27% 27% 9%	330
November	1st to 10th	Day	14% 7% 35% 27% 12% 5%	300
	11th to 20th	Day	16% 20% 30% 23% 11% 1	300
	21st to end	Day	26% 7% 33% 24% 8% 2	300
December	1st to 10th	Day	21% 19% 31% 20% 7% 2	300
	11th to 20th	Day	26% 14% 29% 23% 8% 1	300
	21st to end	Day	29% 19% 29% 17% 6%	330
January	1st to 10th	Night	22% 13% 34% 27% 4	1000
	11th to 20th	Night	26% 14% 35% 21% 4	1000
	21st to end	Night	20% 13% 38% 26% 2	1055
February	1st to 10th	Night	26% 11% 36% 24% 3	800
	11th to 20th	Night	23% 15% 36% 24% 2	783
	21st to end	Night	25% 14% 39% 21% 2	629
March	1st to 10th	Night	23% 11% 33% 28% 5%	760
	11th to 20th	Night	20% 11% 33% 28% 7%	760
	21st to end	Night	23% 10% 28% 32% 6%	651
April	1st to 10th	Night	15% 10% 32% 34% 8% 1	570
	11th to 20th	Night	21% 7% 31% 28% 12% 1	563
	21st to end	Night	21% 7% 30% 32% 9% 2	570
May	1st to 10th	Night	17% 7% 29% 33% 14% 1	570
	11th to 20th	Night	14% 6% 21% 36% 20% 3	561
	21st to end	Night	7% 2 20% 37% 29% 5%	617
June	1st to 10th	Night	12% 3 15% 40% 27% 3	570
	11th to 20th	Night	7% 1 16% 44% 30% 2	570
	21st to end	Night	4 2 19% 40% 32% 4	570
July	1st to 10th	Night	9% 1 11% 32% 38% 8%	555
	11th to 20th	Night	4 3 10% 36% 42% 5%	552
	21st to end	Night	8% 2 10% 36% 37% 7%	624
August	1st to 10th	Night	8% 2 6% 37% 41% 6%	567
	11th to 20th	Night	7% 2 10% 39% 37% 6%	564
	21st to end	Night	6% 1 6% 37% 42% 7%	627
September	1st to 10th	Night	12% 2 10% 32% 38% 6%	570
	11th to 20th	Night	9% 2 12% 33% 38% 5%	717
	21st to end	Night	14% 3 19% 31% 29% 5%	760
October	1st to 10th	Night	11% 4 20% 34% 27% 6%	760
	11th to 20th	Night	16% 7% 28% 31% 17% 2	760
	21st to end	Night	21% 8% 31% 29% 11% 1	836
November	1st to 10th	Night	14% 7% 30% 34% 14% 1	780
	11th to 20th	Night	17% 10% 33% 30% 11%	800
	21st to end	Night	23% 10% 27% 30% 9% 1	800
December	1st to 10th	Night	24% 8% 31% 31% 6%	800
	11th to 20th	Night	23% 8% 33% 29% 6% 1	975
	21st to end	Night	28% 14% 32% 23% 4	1100

Page generated at 2025-02-18 02:26:29. Version ac07

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