Indiana Dunes State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Indiana Dunes State Park 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% 10% 4 8% 5% 4 4 4 5% 7% 36%	101192
	Night	15% 12% 4 8% 5% 4 4 3 5% 6% 34%	97862
Transparency	Day	45% 6% 12% 22% 13% 1	104776
	Night	48% 6% 10% 20% 13% 2	102419
Seeing	Day	18% 12% 30% 24% 12% 4	15772
	Night	20% 12% 29% 26% 12% 1	25599

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% 18% 13% 12% 7% 5% 3 4 4 4 15%	2527
	11th to 20th	Day	14% 18% 8% 16% 7% 6% 5% 9% 5% 3 9%	2530
	21st to end	Day	23% 25% 5% 9% 5% 4 3 2 3 6% 15%	2783
February	1st to 10th	Day	15% 15% 6% 11% 7% 5% 4 4 4 7% 22%	1818
	11th to 20th	Day	14% 13% 4 12% 7% 5% 3 3 5% 5% 30%	1848
	21st to end	Day	14% 16% 5% 12% 4 4 4 3 4 6% 28%	1570
March	1st to 10th	Day	19% 12% 5% 8% 4 3 3 3 4 6% 31%	3120
	11th to 20th	Day	10% 8% 5% 10% 5% 4 5% 3 6% 7% 37%	3283
	21st to end	Day	17% 12% 6% 12% 6% 4 5% 4 5% 5% 24%	4101
April	1st to 10th	Day	16% 12% 3 7% 5% 4 3 4 5% 7% 34%	2280
	11th to 20th	Day	16% 11% 3 6% 4 4 4 3 4 8% 38%	2254
	21st to end	Day	18% 9% 3 7% 4 4 4 4 6% 7% 33%	2432
May	1st to 10th	Day	17% 8% 3 6% 4 5% 4 4 6% 9% 35%	4082
	11th to 20th	Day	14% 8% 2 5% 4 3 4 3 6% 8% 43%	4145
	21st to end	Day	10% 7% 3 5% 4 4 4 4 6% 9% 46%	4824
June	1st to 10th	Day	10% 6% 2 6% 5% 4 4 4 6% 8% 45%	2660
	11th to 20th	Day	9% 5% 1 6% 5% 5% 5% 5% 6% 8% 47%	2660
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 5% 7% 9% 41%	2660
July	1st to 10th	Day	12% 7% 3 7% 5% 4 5% 5% 7% 9% 37%	4440
	11th to 20th	Day	7% 4 2 4 4 4 5% 4 6% 11% 50%	4440
	21st to end	Day	7% 6% 2 7% 4 5% 5% 4 6% 9% 45%	4813
August	1st to 10th	Day	10% 6% 2 5% 4 4 4 3 6% 8% 48%	4209
	11th to 20th	Day	10% 5% 2 6% 4 4 4 3 5% 8% 49%	3858
	21st to end	Day	7% 4 2 6% 4 4 5% 3 6% 9% 50%	4180
September	1st to 10th	Day	11% 5% 2 5% 5% 4 5% 3 6% 7% 47%	2280
	11th to 20th	Day	11% 5% 2 5% 3 5% 4 4 6% 8% 48%	2113
	21st to end	Day	12% 7% 4 6% 4 4 5% 4 6% 9% 40%	2090
October	1st to 10th	Day	13% 7% 3 6% 4 4 4 3 5% 6% 46%	2090
	11th to 20th	Day	19% 9% 3 7% 5% 4 4 3 5% 6% 34%	1862
	21st to end	Day	21% 11% 4 8% 4 5% 5% 3 5% 7% 27%	1881
November	1st to 10th	Day	13% 11% 2 6% 4 4 5% 3 6% 6% 39%	1699
	11th to 20th	Day	17% 15% 5% 9% 6% 4 4 3 5% 6% 27%	1710
	21st to end	Day	19% 15% 5% 10% 5% 3 3 3 4 5% 28%	1710
December	1st to 10th	Day	14% 20% 6% 11% 7% 5% 3 3 4 5% 22%	1539
	11th to 20th	Day	13% 20% 7% 12% 5% 4 3 3 6% 5% 21%	1918
	21st to end	Day	21% 21% 8% 14% 6% 5% 5% 3 3 4 11%	2783
January	1st to 10th	Night	16% 20% 9% 11% 6% 4 4 3 4 4 18%	4428
	11th to 20th	Night	16% 21% 9% 14% 6% 3 5% 6% 4 3 11%	4440
	21st to end	Night	24% 19% 8% 10% 5% 4 4 2 3 5% 15%	4884
February	1st to 10th	Night	17% 15% 5% 9% 6% 4 5% 4 4 6% 25%	2359
	11th to 20th	Night	14% 13% 5% 9% 7% 5% 5% 4 5% 5% 29%	2218
	21st to end	Night	19% 14% 5% 10% 5% 3 4 3 4 4 29%	1884
March	1st to 10th	Night	17% 12% 5% 7% 5% 4 4 3 4 6% 33%	3733
	11th to 20th	Night	10% 7% 4 7% 5% 4 4 4 5% 6% 44%	3677
	21st to end	Night	19% 12% 8% 8% 5% 4 4 4 4 5% 27%	3544
April	1st to 10th	Night	14% 12% 4 6% 4 4 4 4 5% 7% 36%	1900
	11th to 20th	Night	18% 10% 3 5% 5% 5% 3 4 4 5% 38%	1875
	21st to end	Night	17% 9% 4 8% 5% 5% 4 3 4 6% 36%	1747
May	1st to 10th	Night	17% 9% 3 6% 5% 4 5% 3 5% 8% 34%	2813
	11th to 20th	Night	18% 7% 2 6% 3 3 4 3 5% 8% 40%	2735
	21st to end	Night	13% 7% 2 6% 4 4 4 3 5% 6% 44%	2743
June	1st to 10th	Night	9% 6% 1 5% 4 3 3 3 7% 10% 48%	1520
	11th to 20th	Night	8% 6% 3 6% 5% 4 4 3 6% 9% 45%	1520
	21st to end	Night	9% 7% 2 7% 5% 5% 5% 5% 5% 8% 41%	1520
July	1st to 10th	Night	10% 4 2 6% 5% 4 6% 4 7% 8% 42%	2530
	11th to 20th	Night	7% 5% 2 4 4 3 4 4 5% 8% 54%	2530
	21st to end	Night	5% 4 2 7% 5% 5% 6% 4 9% 9% 45%	2750
August	1st to 10th	Night	9% 5% 2 6% 5% 4 5% 4 7% 9% 45%	2722
	11th to 20th	Night	9% 4 2 6% 4 4 4 3 5% 7% 51%	2967
	21st to end	Night	10% 5% 2 5% 3 4 4 3 5% 7% 51%	3476
September	1st to 10th	Night	12% 5% 2 6% 3 4 4 2 5% 7% 50%	1900
	11th to 20th	Night	10% 6% 2 5% 4 3 4 3 5% 8% 53%	2047
	21st to end	Night	12% 7% 2 5% 4 4 5% 4 6% 7% 44%	2090
October	1st to 10th	Night	12% 6% 2 5% 4 5% 4 3 5% 6% 48%	2090
	11th to 20th	Night	21% 9% 2 7% 3 4 3 3 4 6% 39%	2312
	21st to end	Night	23% 11% 3 6% 4 3 4 3 4 7% 33%	2717
November	1st to 10th	Night	13% 13% 4 7% 4 4 4 3 4 6% 39%	2452
	11th to 20th	Night	14% 17% 4 10% 5% 4 4 4 5% 6% 27%	2470
	21st to end	Night	19% 14% 4 10% 5% 3 4 3 4 6% 28%	2470
December	1st to 10th	Night	17% 19% 6% 11% 7% 4 5% 2 4 5% 20%	2636
	11th to 20th	Night	14% 19% 8% 13% 6% 4 4 3 4 5% 20%	3279
	21st to end	Night	24% 21% 7% 11% 6% 5% 4 3 4 4 13%	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	70% 8% 10% 9% 4	2528
	11th to 20th	Day	72% 11% 9% 7% 1	2530
	21st to end	Day	71% 4 9% 12% 3	2783
February	1st to 10th	Day	62% 6% 12% 12% 7% 1	1818
	11th to 20th	Day	55% 6% 11% 19% 9% 1	1858
	21st to end	Day	58% 5% 11% 17% 6% 2	1570
March	1st to 10th	Day	53% 7% 10% 20% 9% 1	3120
	11th to 20th	Day	41% 9% 12% 29% 7% 1	3283
	21st to end	Day	60% 7% 15% 14% 3	4101
April	1st to 10th	Day	49% 6% 11% 22% 12%	2280
	11th to 20th	Day	46% 5% 11% 22% 13% 3	2254
	21st to end	Day	49% 5% 13% 17% 13% 2	2432
May	1st to 10th	Day	45% 7% 12% 26% 10% 1	4120
	11th to 20th	Day	39% 6% 13% 30% 11% 1	4149
	21st to end	Day	34% 7% 12% 23% 23% 2	4837
June	1st to 10th	Day	37% 6% 11% 25% 18% 3	2660
	11th to 20th	Day	35% 5% 12% 26% 20% 3	2660
	21st to end	Day	38% 7% 17% 20% 16% 2	2660
July	1st to 10th	Day	43% 6% 13% 22% 14% 3	4371
	11th to 20th	Day	30% 4 17% 32% 16% 1	4365
	21st to end	Day	36% 6% 18% 17% 20% 3	4662
August	1st to 10th	Day	33% 5% 15% 31% 14% 1	4194
	11th to 20th	Day	34% 5% 11% 33% 16% 1	3897
	21st to end	Day	30% 6% 13% 27% 20% 3	4179
September	1st to 10th	Day	35% 6% 13% 25% 17% 4	2280
	11th to 20th	Day	33% 5% 13% 28% 20% 2	2113
	21st to end	Day	39% 7% 10% 24% 18% 1	2090
October	1st to 10th	Day	28% 4 9% 34% 24% 1	3480
	11th to 20th	Day	41% 4 11% 21% 21%	3065
	21st to end	Day	48% 4 9% 25% 11% 2	3081
November	1st to 10th	Day	42% 7% 14% 21% 15% 1	1699
	11th to 20th	Day	57% 6% 10% 18% 8% 1	1710
	21st to end	Day	58% 6% 10% 19% 7%	1710
December	1st to 10th	Day	65% 7% 9% 13% 6%	1539
	11th to 20th	Day	64% 5% 11% 17% 4	1915
	21st to end	Day	78% 6% 8% 7% 2	2783
January	1st to 10th	Night	67% 8% 9% 12% 4	4428
	11th to 20th	Night	73% 9% 8% 7% 2	4440
	21st to end	Night	71% 6% 8% 11% 4	4884
February	1st to 10th	Night	60% 6% 10% 15% 8% 2	2359
	11th to 20th	Night	54% 7% 10% 19% 10% 1	2219
	21st to end	Night	58% 6% 8% 17% 9% 2	1884
March	1st to 10th	Night	51% 6% 11% 23% 8% 1	3733
	11th to 20th	Night	38% 8% 11% 26% 15% 2	3677
	21st to end	Night	58% 7% 11% 18% 6% 1	3544
April	1st to 10th	Night	47% 5% 12% 21% 13% 1	1900
	11th to 20th	Night	48% 5% 8% 19% 17% 3	1875
	21st to end	Night	49% 6% 10% 18% 14% 3	1747
May	1st to 10th	Night	47% 6% 10% 23% 12% 2	2840
	11th to 20th	Night	42% 6% 13% 26% 12% 1	2736
	21st to end	Night	40% 7% 10% 16% 23% 4	2751
June	1st to 10th	Night	30% 7% 13% 28% 20% 2	1520
	11th to 20th	Night	34% 6% 13% 24% 21% 2	1520
	21st to end	Night	39% 8% 14% 21% 15% 3	1520
July	1st to 10th	Night	38% 6% 13% 25% 12% 5%	2490
	11th to 20th	Night	28% 6% 13% 24% 27% 2	2482
	21st to end	Night	32% 8% 17% 19% 20% 4	2662
August	1st to 10th	Night	35% 6% 14% 29% 15% 1	2713
	11th to 20th	Night	32% 5% 13% 27% 22% 1	2994
	21st to end	Night	33% 5% 10% 29% 20% 3	3476
September	1st to 10th	Night	34% 5% 12% 24% 20% 5%	1900
	11th to 20th	Night	30% 6% 8% 28% 26% 2	2047
	21st to end	Night	38% 6% 9% 27% 18% 3	2090
October	1st to 10th	Night	23% 5% 8% 35% 27% 2	3480
	11th to 20th	Night	44% 4 6% 20% 25% 1	3848
	21st to end	Night	42% 4 9% 25% 19% 1	4467
November	1st to 10th	Night	46% 6% 8% 22% 16% 2	2452
	11th to 20th	Night	54% 9% 10% 18% 9% 1	2470
	21st to end	Night	57% 6% 11% 20% 7%	2470
December	1st to 10th	Night	64% 7% 8% 14% 6% 1	2636
	11th to 20th	Night	60% 11% 10% 14% 4	3281
	21st to end	Night	74% 6% 8% 8% 3	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	24% 19% 34% 18% 3	270
	11th to 20th	Day	30% 15% 37% 13% 3 1	270
	21st to end	Day	26% 19% 36% 18% 2	297
February	1st to 10th	Day	22% 26% 34% 14% 4	270
	11th to 20th	Day	24% 25% 32% 15% 3	270
	21st to end	Day	24% 27% 37% 11% 1	225
March	1st to 10th	Day	25% 24% 34% 16% 1	270
	11th to 20th	Day	24% 18% 34% 18% 6% 1	341
	21st to end	Day	28% 17% 30% 18% 6%	506
April	1st to 10th	Day	25% 16% 35% 18% 6% 1	460
	11th to 20th	Day	22% 21% 31% 17% 6% 3	452
	21st to end	Day	24% 15% 34% 18% 8% 1	460
May	1st to 10th	Day	23% 12% 34% 20% 9% 2	463
	11th to 20th	Day	20% 9% 33% 22% 14% 2	525
	21st to end	Day	14% 8% 31% 28% 14% 5%	734
June	1st to 10th	Day	11% 8% 30% 31% 16% 4	680
	11th to 20th	Day	11% 8% 33% 30% 16% 3	680
	21st to end	Day	13% 7% 33% 30% 12% 5%	680
July	1st to 10th	Day	12% 4 24% 27% 21% 11%	671
	11th to 20th	Day	10% 5% 26% 32% 19% 7%	668
	21st to end	Day	9% 4 25% 37% 19% 6%	739
August	1st to 10th	Day	10% 2 20% 32% 25% 12%	553
	11th to 20th	Day	9% 5% 26% 30% 22% 8%	479
	21st to end	Day	11% 4 19% 35% 23% 8%	539
September	1st to 10th	Day	14% 5% 23% 32% 20% 6%	490
	11th to 20th	Day	11% 5% 17% 33% 23% 11%	490
	21st to end	Day	18% 12% 20% 25% 18% 7%	490
October	1st to 10th	Day	16% 8% 29% 29% 15% 3	490
	11th to 20th	Day	23% 19% 30% 22% 7%	324
	21st to end	Day	32% 15% 35% 15% 3	330
November	1st to 10th	Day	15% 16% 39% 21% 7% 2	279
	11th to 20th	Day	26% 17% 34% 18% 4	270
	21st to end	Day	31% 13% 40% 14% 2	270
December	1st to 10th	Day	22% 23% 34% 15% 6%	270
	11th to 20th	Day	21% 23% 38% 14% 3	270
	21st to end	Day	25% 24% 38% 12% 1	297
January	1st to 10th	Night	24% 21% 35% 18% 3	950
	11th to 20th	Night	25% 19% 34% 17% 4 1	950
	21st to end	Night	24% 17% 36% 20% 3	1045
February	1st to 10th	Night	26% 14% 37% 20% 3	835
	11th to 20th	Night	22% 19% 35% 21% 4	743
	21st to end	Night	27% 18% 37% 15% 3	628
March	1st to 10th	Night	23% 16% 36% 20% 6% 1	760
	11th to 20th	Night	18% 12% 39% 25% 6%	760
	21st to end	Night	25% 12% 30% 26% 6%	679
April	1st to 10th	Night	20% 15% 35% 23% 6% 1	570
	11th to 20th	Night	23% 12% 31% 25% 8% 1	563
	21st to end	Night	21% 11% 31% 28% 8% 1	570
May	1st to 10th	Night	22% 6% 33% 28% 11% 1	570
	11th to 20th	Night	21% 4 27% 33% 15% 1	561
	21st to end	Night	12% 5% 22% 38% 21% 3	617
June	1st to 10th	Night	11% 4 23% 41% 20% 1	570
	11th to 20th	Night	11% 4 28% 36% 19% 2	570
	21st to end	Night	11% 6% 25% 38% 19% 2	570
July	1st to 10th	Night	9% 2 15% 39% 29% 6%	555
	11th to 20th	Night	9% 3 20% 36% 26% 5%	552
	21st to end	Night	6% 2 17% 42% 31% 2	624
August	1st to 10th	Night	7% 2 12% 44% 30% 5%	567
	11th to 20th	Night	9% 4 15% 38% 29% 6%	564
	21st to end	Night	10% 3 17% 39% 27% 4	627
September	1st to 10th	Night	13% 5% 17% 35% 26% 3	570
	11th to 20th	Night	10% 7% 17% 35% 27% 5%	717
	21st to end	Night	14% 6% 25% 29% 21% 4	760
October	1st to 10th	Night	15% 7% 28% 30% 19% 2	760
	11th to 20th	Night	25% 15% 29% 23% 8%	760
	21st to end	Night	27% 17% 29% 21% 6%	836
November	1st to 10th	Night	22% 16% 33% 19% 10% 1	755
	11th to 20th	Night	23% 22% 32% 18% 5%	760
	21st to end	Night	27% 17% 33% 18% 5%	760
December	1st to 10th	Night	26% 20% 35% 17% 3	926
	11th to 20th	Night	24% 18% 36% 20% 2	950
	21st to end	Night	30% 18% 35% 15% 2	1045

Page generated at 2024-11-01 21:47:35. Version ac07

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