Patoka Lake Observing Sites
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Patoka Lake Observing Sites clear sky chart from 2005-11-06 to 2026-04-17.

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% 8% 3 7% 5% 4 4 4 5% 7% 38%	131166
	Night	15% 9% 3 7% 4 4 4 3 5% 6% 39%	131172
Transparency	Day	43% 5% 11% 23% 15% 2	134789
	Night	44% 5% 10% 22% 16% 2	135610
Seeing	Day	18% 13% 27% 23% 13% 5%	17352
	Night	19% 12% 26% 26% 14% 2	27252

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% 4 5% 4 3 6% 5% 29%	4691
	11th to 20th	Day	11% 10% 4 13% 7% 5% 4 3 4 5% 33%	4710
	21st to end	Day	19% 13% 5% 9% 5% 4 4 3 5% 5% 28%	5746
February	1st to 10th	Day	17% 12% 5% 8% 4 3 3 3 5% 6% 33%	2100
	11th to 20th	Day	17% 9% 4 8% 4 4 4 3 5% 7% 35%	2048
	21st to end	Day	15% 13% 4 9% 4 4 4 4 4 6% 33%	1730
March	1st to 10th	Day	18% 12% 4 7% 4 3 3 2 3 4 40%	4580
	11th to 20th	Day	13% 9% 2 6% 4 3 4 4 5% 7% 43%	4855
	21st to end	Day	15% 8% 3 8% 5% 5% 5% 3 6% 7% 35%	5907
April	1st to 10th	Day	15% 8% 2 6% 5% 4 5% 4 5% 7% 39%	2520
	11th to 20th	Day	17% 8% 3 6% 4 4 4 4 5% 7% 38%	2446
	21st to end	Day	18% 6% 2 7% 5% 4 5% 4 4 6% 39%	2508
May	1st to 10th	Day	21% 8% 2 8% 5% 5% 5% 5% 6% 8% 28%	5862
	11th to 20th	Day	18% 7% 3 6% 5% 5% 4 4 6% 7% 35%	5861
	21st to end	Day	13% 7% 3 7% 5% 5% 6% 5% 7% 9% 34%	6465
June	1st to 10th	Day	12% 6% 2 5% 4 4 5% 4 5% 8% 45%	2800
	11th to 20th	Day	9% 5% 2 5% 5% 5% 5% 4 7% 8% 45%	2800
	21st to end	Day	9% 5% 2 5% 4 4 5% 4 7% 10% 45%	2800
July	1st to 10th	Day	12% 5% 2 6% 4 4 5% 4 6% 9% 43%	6360
	11th to 20th	Day	10% 5% 2 6% 5% 5% 5% 5% 7% 10% 40%	6360
	21st to end	Day	10% 6% 3 9% 6% 6% 7% 6% 7% 10% 31%	6652
August	1st to 10th	Day	8% 4 2 5% 3 3 5% 4 6% 10% 50%	4213
	11th to 20th	Day	8% 5% 2 6% 5% 5% 6% 5% 7% 10% 40%	3849
	21st to end	Day	5% 4 1 4 4 4 4 4 6% 10% 55%	4312
September	1st to 10th	Day	11% 5% 2 5% 5% 4 4 3 6% 7% 47%	2382
	11th to 20th	Day	9% 4 2 6% 4 4 4 3 6% 8% 50%	2200
	21st to end	Day	14% 5% 2 6% 4 4 3 3 4 6% 49%	2200
October	1st to 10th	Day	10% 5% 2 4 3 4 4 3 5% 6% 54%	2200
	11th to 20th	Day	13% 6% 2 6% 3 4 5% 3 4 7% 48%	2082
	21st to end	Day	21% 8% 2 6% 3 3 3 3 5% 5% 42%	1980
November	1st to 10th	Day	11% 6% 2 4 5% 3 4 3 5% 6% 51%	1852
	11th to 20th	Day	17% 10% 2 5% 4 3 3 3 5% 6% 42%	1890
	21st to end	Day	21% 10% 3 5% 3 3 4 3 4 5% 38%	1890
December	1st to 10th	Day	15% 12% 3 6% 3 3 4 3 4 5% 43%	3020
	11th to 20th	Day	17% 12% 6% 9% 4 4 4 3 5% 6% 30%	3225
	21st to end	Day	23% 18% 6% 9% 5% 4 4 3 4 5% 20%	4070
January	1st to 10th	Night	16% 13% 5% 10% 4 4 4 3 4 6% 31%	8232
	11th to 20th	Night	12% 13% 6% 12% 5% 6% 6% 3 3 4 30%	8280
	21st to end	Night	19% 12% 4 6% 5% 4 3 3 4 6% 34%	8442
February	1st to 10th	Night	21% 11% 4 10% 5% 4 4 4 4 5% 28%	2520
	11th to 20th	Night	18% 10% 4 9% 4 3 3 3 4 6% 34%	2458
	21st to end	Night	20% 11% 3 8% 4 4 3 3 5% 5% 34%	2076
March	1st to 10th	Night	21% 13% 3 6% 3 4 4 3 4 5% 36%	5493
	11th to 20th	Night	13% 7% 3 6% 3 4 4 3 5% 6% 47%	5310
	21st to end	Night	17% 8% 3 8% 6% 5% 4 4 4 5% 34%	5307
April	1st to 10th	Night	14% 8% 2 6% 4 4 4 4 6% 7% 41%	2100
	11th to 20th	Night	16% 6% 3 7% 4 3 4 3 5% 7% 42%	2035
	21st to end	Night	18% 7% 2 6% 4 4 5% 3 6% 8% 37%	1890
May	1st to 10th	Night	20% 11% 3 7% 5% 4 4 3 5% 8% 29%	4033
	11th to 20th	Night	18% 6% 2 7% 5% 4 5% 4 7% 8% 34%	4032
	21st to end	Night	14% 6% 2 7% 5% 5% 5% 4 7% 9% 35%	4387
June	1st to 10th	Night	9% 6% 2 6% 5% 3 3 4 7% 7% 48%	1600
	11th to 20th	Night	7% 5% 2 5% 4 5% 5% 4 5% 9% 49%	1600
	21st to end	Night	5% 4 2 5% 4 5% 4 4 6% 10% 51%	1600
July	1st to 10th	Night	9% 5% 2 6% 4 4 5% 3 6% 8% 48%	3618
	11th to 20th	Night	8% 5% 2 6% 3 5% 5% 4 7% 9% 47%	3617
	21st to end	Night	9% 5% 2 7% 6% 6% 6% 5% 8% 11% 35%	4207
August	1st to 10th	Night	8% 4 1 5% 3 4 4 3 5% 8% 55%	2932
	11th to 20th	Night	7% 4 2 6% 4 5% 6% 4 6% 9% 49%	3200
	21st to end	Night	3 3 1 4 3 3 4 3 6% 9% 60%	3586
September	1st to 10th	Night	12% 5% 2 5% 3 4 3 3 5% 6% 52%	2000
	11th to 20th	Night	8% 4 2 5% 3 3 3 3 6% 8% 54%	2197
	21st to end	Night	14% 5% 2 5% 4 3 4 3 5% 7% 50%	2200
October	1st to 10th	Night	9% 4 2 5% 3 4 2 2 4 6% 59%	2200
	11th to 20th	Night	14% 5% 2 6% 3 3 4 3 4 5% 51%	2311
	21st to end	Night	19% 8% 2 6% 3 3 3 2 4 5% 45%	2860
November	1st to 10th	Night	13% 6% 2 6% 4 3 3 3 5% 5% 50%	2666
	11th to 20th	Night	15% 8% 3 6% 3 3 3 3 4 7% 44%	2730
	21st to end	Night	19% 11% 3 6% 4 3 3 2 4 5% 39%	2730
December	1st to 10th	Night	18% 11% 3 9% 4 3 3 2 3 4 39%	4380
	11th to 20th	Night	20% 11% 4 8% 3 3 4 3 4 5% 34%	5193
	21st to end	Night	26% 18% 5% 9% 5% 4 4 3 4 4 20%	7150

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	57% 3 11% 21% 7% 1	4692
	11th to 20th	Day	53% 3 9% 21% 13% 1	4710
	21st to end	Day	60% 3 8% 18% 7% 5%	5746
February	1st to 10th	Day	52% 4 10% 22% 11% 2	2100
	11th to 20th	Day	50% 4 9% 22% 13% 2	2058
	21st to end	Day	53% 4 10% 20% 11% 3	1730
March	1st to 10th	Day	50% 3 5% 19% 18% 5%	4580
	11th to 20th	Day	41% 4 9% 27% 17% 2	4855
	21st to end	Day	47% 6% 12% 22% 12% 1	5909
April	1st to 10th	Day	44% 6% 13% 21% 16% 1	2520
	11th to 20th	Day	45% 5% 10% 23% 14% 3	2446
	21st to end	Day	45% 6% 10% 25% 12% 2	2508
May	1st to 10th	Day	52% 6% 12% 18% 11% 1	5897
	11th to 20th	Day	48% 7% 10% 23% 11% 1	5865
	21st to end	Day	45% 6% 13% 19% 16% 2	6479
June	1st to 10th	Day	37% 6% 10% 26% 18% 3	2800
	11th to 20th	Day	34% 8% 13% 24% 18% 3	2800
	21st to end	Day	34% 7% 14% 23% 18% 4	2800
July	1st to 10th	Day	38% 6% 10% 24% 21% 2	6291
	11th to 20th	Day	37% 8% 14% 26% 13% 1	6285
	21st to end	Day	46% 9% 15% 20% 9% 1	6463
August	1st to 10th	Day	28% 7% 14% 34% 15% 1	4200
	11th to 20th	Day	37% 7% 12% 26% 17% 1	3885
	21st to end	Day	25% 6% 13% 36% 16% 3	4311
September	1st to 10th	Day	36% 5% 9% 24% 21% 4	2382
	11th to 20th	Day	32% 6% 9% 29% 21% 3	2200
	21st to end	Day	36% 4 8% 23% 25% 3	2200
October	1st to 10th	Day	21% 3 5% 27% 42% 2	3590
	11th to 20th	Day	26% 4 9% 26% 32% 4	3363
	21st to end	Day	35% 3 8% 25% 26% 4	3180
November	1st to 10th	Day	35% 4 10% 29% 17% 5%	1852
	11th to 20th	Day	44% 3 7% 23% 17% 4	1890
	21st to end	Day	49% 3 8% 23% 16% 2	1890
December	1st to 10th	Day	44% 4 11% 26% 14%	3020
	11th to 20th	Day	56% 4 9% 21% 10% 1	3222
	21st to end	Day	67% 5% 11% 12% 6%	4070
January	1st to 10th	Night	56% 3 11% 21% 8%	8233
	11th to 20th	Night	58% 4 5% 16% 15% 2	8280
	21st to end	Night	52% 3 10% 21% 13% 1	8442
February	1st to 10th	Night	58% 4 9% 20% 7% 1	2520
	11th to 20th	Night	52% 3 8% 22% 13% 1	2459
	21st to end	Night	52% 4 10% 20% 12% 3	2076
March	1st to 10th	Night	53% 3 6% 20% 15% 4	5493
	11th to 20th	Night	39% 4 9% 25% 21% 2	5310
	21st to end	Night	51% 5% 8% 24% 11% 1	5307
April	1st to 10th	Night	41% 7% 10% 25% 15% 3	2100
	11th to 20th	Night	42% 4 11% 21% 18% 5%	2035
	21st to end	Night	45% 6% 9% 23% 15% 2	1890
May	1st to 10th	Night	53% 7% 11% 20% 8% 1	4060
	11th to 20th	Night	48% 6% 11% 24% 10%	4033
	21st to end	Night	43% 7% 14% 21% 13% 3	4395
June	1st to 10th	Night	33% 7% 11% 25% 21% 4	1600
	11th to 20th	Night	32% 7% 13% 21% 22% 7%	1600
	21st to end	Night	27% 6% 16% 24% 19% 7%	1600
July	1st to 10th	Night	35% 7% 10% 26% 20% 2	3580
	11th to 20th	Night	33% 9% 14% 28% 14% 2	3572
	21st to end	Night	40% 9% 16% 22% 11% 1	4084
August	1st to 10th	Night	26% 7% 14% 38% 14% 1	2921
	11th to 20th	Night	31% 6% 13% 31% 17% 1	3230
	21st to end	Night	20% 5% 14% 33% 25% 4	3586
September	1st to 10th	Night	33% 5% 8% 26% 21% 6%	2000
	11th to 20th	Night	28% 6% 8% 27% 27% 5%	2197
	21st to end	Night	35% 4 9% 22% 25% 5%	2200
October	1st to 10th	Night	19% 2 6% 17% 51% 5%	3590
	11th to 20th	Night	25% 3 6% 24% 38% 5%	3756
	21st to end	Night	33% 3 7% 22% 29% 6%	4610
November	1st to 10th	Night	36% 4 9% 24% 23% 5%	2666
	11th to 20th	Night	40% 4 8% 22% 21% 5%	2730
	21st to end	Night	48% 4 8% 22% 16% 2	2730
December	1st to 10th	Night	50% 3 9% 23% 14%	4380
	11th to 20th	Night	52% 4 12% 20% 12% 1	5195
	21st to end	Night	69% 4 7% 14% 5% 1	7150

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	26% 23% 30% 16% 4	330
	11th to 20th	Day	30% 26% 32% 10% 2	330
	21st to end	Day	28% 26% 33% 12% 1	363
February	1st to 10th	Day	24% 29% 32% 12% 2	330
	11th to 20th	Day	30% 30% 30% 8% 1	330
	21st to end	Day	29% 21% 40% 9% 1	273
March	1st to 10th	Day	24% 28% 34% 12% 1	330
	11th to 20th	Day	30% 23% 33% 9% 3 2	435
	21st to end	Day	28% 22% 32% 13% 4	594
April	1st to 10th	Day	23% 21% 30% 20% 5% 1	540
	11th to 20th	Day	22% 22% 29% 19% 8% 1	516
	21st to end	Day	20% 20% 37% 13% 8% 1	500
May	1st to 10th	Day	22% 16% 32% 20% 6% 3	503
	11th to 20th	Day	19% 14% 30% 24% 9% 5%	527
	21st to end	Day	13% 11% 30% 28% 12% 7%	579
June	1st to 10th	Day	15% 7% 26% 30% 16% 5%	730
	11th to 20th	Day	10% 8% 24% 34% 17% 7%	730
	21st to end	Day	10% 7% 28% 28% 18% 8%	730
July	1st to 10th	Day	15% 4 18% 26% 25% 12%	721
	11th to 20th	Day	9% 5% 23% 33% 21% 9%	718
	21st to end	Day	10% 4 20% 35% 23% 8%	674
August	1st to 10th	Day	11% 3 18% 33% 24% 11%	526
	11th to 20th	Day	12% 4 21% 33% 22% 8%	519
	21st to end	Day	9% 3 15% 31% 27% 14%	583
September	1st to 10th	Day	11% 5% 21% 27% 28% 8%	530
	11th to 20th	Day	9% 3 14% 35% 25% 14%	530
	21st to end	Day	17% 9% 18% 26% 22% 8%	530
October	1st to 10th	Day	11% 7% 25% 32% 19% 6%	530
	11th to 20th	Day	18% 14% 33% 20% 11% 4	445
	21st to end	Day	28% 16% 37% 17% 2 1	363
November	1st to 10th	Day	16% 18% 36% 20% 8% 2	330
	11th to 20th	Day	25% 22% 31% 17% 4 1	330
	21st to end	Day	31% 12% 35% 17% 5%	330
December	1st to 10th	Day	22% 29% 31% 13% 3 2	330
	11th to 20th	Day	28% 19% 37% 12% 3	330
	21st to end	Day	36% 23% 28% 12% 2	363
January	1st to 10th	Night	25% 21% 30% 22% 2	1050
	11th to 20th	Night	29% 22% 32% 15% 2	1050
	21st to end	Night	23% 23% 33% 18% 2	1034
February	1st to 10th	Night	27% 18% 35% 18% 2	840
	11th to 20th	Night	26% 22% 32% 18% 2	823
	21st to end	Night	27% 19% 37% 15% 1	692
March	1st to 10th	Night	25% 19% 31% 22% 3	840
	11th to 20th	Night	25% 17% 33% 18% 6%	840
	21st to end	Night	25% 14% 33% 24% 4 1	798
April	1st to 10th	Night	19% 14% 34% 25% 6%	630
	11th to 20th	Night	22% 13% 30% 24% 11%	611
	21st to end	Night	21% 11% 32% 28% 7% 1	600
May	1st to 10th	Night	19% 10% 32% 26% 13% 1	600
	11th to 20th	Night	16% 8% 24% 31% 18% 2	591
	21st to end	Night	10% 7% 23% 31% 24% 5%	650
June	1st to 10th	Night	11% 3 22% 36% 26% 2	600
	11th to 20th	Night	8% 4 20% 41% 25% 2	600
	21st to end	Night	6% 2 23% 36% 31% 2	600
July	1st to 10th	Night	11% 3 12% 31% 33% 10%	585
	11th to 20th	Night	7% 2 13% 36% 37% 5%	582
	21st to end	Night	10% 3 13% 35% 34% 6%	657
August	1st to 10th	Night	9% 1 11% 37% 35% 7%	597
	11th to 20th	Night	7% 2 12% 38% 35% 6%	594
	21st to end	Night	6% 2 13% 35% 38% 6%	660
September	1st to 10th	Night	15% 3 13% 33% 30% 6%	600
	11th to 20th	Night	9% 3 16% 31% 35% 6%	797
	21st to end	Night	16% 5% 19% 30% 26% 4	800
October	1st to 10th	Night	12% 6% 20% 33% 24% 6%	800
	11th to 20th	Night	17% 11% 27% 28% 16% 2	800
	21st to end	Night	24% 14% 31% 22% 9%	880
November	1st to 10th	Night	16% 11% 32% 28% 12% 1	820
	11th to 20th	Night	20% 18% 30% 23% 8%	840
	21st to end	Night	26% 17% 24% 24% 9%	840
December	1st to 10th	Night	26% 16% 32% 20% 5%	840
	11th to 20th	Night	27% 16% 29% 22% 6% 1	956
	21st to end	Night	30% 18% 31% 18% 3	1155

Page generated at 2026-04-14 02:44:23. Version ac07

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