Michigan City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Michigan City clear sky chart from 2005-11-06 to 2025-07-21.

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% 10% 4 9% 5% 4 4 4 5% 7% 35%	119825
	Night	15% 12% 5% 10% 5% 4 4 3 5% 6% 32%	119501
Transparency	Day	29% 41% 7% 14% 8% 1	123409
	Night	33% 40% 6% 12% 8% 1	124045
Seeing	Day	17% 12% 30% 24% 13% 4	16734
	Night	20% 11% 29% 26% 12% 1	26580

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	12% 17% 12% 19% 8% 5% 4 3 3 5% 13%	3617
	11th to 20th	Day	11% 17% 10% 16% 8% 7% 5% 8% 3 3 11%	3620
	21st to end	Day	18% 19% 6% 9% 5% 3 3 3 5% 5% 23%	3982
February	1st to 10th	Day	15% 17% 6% 12% 6% 5% 4 3 4 6% 21%	1910
	11th to 20th	Day	14% 13% 4 13% 9% 5% 3 4 4 4 27%	1948
	21st to end	Day	14% 16% 6% 12% 4 3 5% 4 3 6% 27%	1650
March	1st to 10th	Day	17% 11% 5% 10% 4 3 3 3 4 5% 34%	4480
	11th to 20th	Day	8% 9% 5% 8% 5% 4 5% 3 6% 7% 39%	4719
	21st to end	Day	17% 15% 7% 11% 5% 5% 5% 3 5% 5% 23%	5865
April	1st to 10th	Day	17% 12% 4 7% 5% 4 4 3 5% 7% 33%	2400
	11th to 20th	Day	15% 11% 3 6% 4 3 4 3 5% 6% 38%	2374
	21st to end	Day	17% 9% 3 7% 4 4 4 4 6% 8% 33%	2570
May	1st to 10th	Day	18% 9% 2 6% 4 4 5% 4 6% 8% 34%	5862
	11th to 20th	Day	13% 7% 2 6% 4 4 5% 4 6% 8% 41%	5942
	21st to end	Day	14% 8% 3 6% 3 3 4 3 5% 8% 42%	6935
June	1st to 10th	Day	11% 5% 2 7% 4 4 5% 3 5% 8% 45%	2800
	11th to 20th	Day	9% 5% 2 5% 5% 5% 5% 4 7% 9% 45%	2800
	21st to end	Day	10% 6% 2 5% 4 4 6% 4 7% 8% 44%	2800
July	1st to 10th	Day	12% 7% 3 7% 5% 5% 5% 4 6% 9% 38%	4580
	11th to 20th	Day	7% 4 2 5% 3 4 5% 4 6% 10% 49%	4580
	21st to end	Day	7% 6% 2 7% 5% 4 5% 4 7% 8% 45%	4814
August	1st to 10th	Day	10% 6% 2 5% 4 4 4 3 6% 8% 49%	4199
	11th to 20th	Day	10% 5% 2 6% 4 4 4 3 5% 7% 49%	3885
	21st to end	Day	7% 4 2 6% 4 4 5% 4 6% 8% 50%	4180
September	1st to 10th	Day	10% 5% 3 5% 5% 4 5% 4 5% 7% 46%	2280
	11th to 20th	Day	11% 5% 2 5% 3 5% 4 4 6% 6% 48%	2104
	21st to end	Day	12% 8% 2 7% 4 4 5% 4 5% 8% 41%	2090
October	1st to 10th	Day	14% 8% 2 6% 4 4 4 3 5% 6% 45%	2090
	11th to 20th	Day	20% 10% 2 7% 5% 4 4 4 5% 6% 34%	1863
	21st to end	Day	22% 11% 4 8% 5% 5% 4 4 5% 6% 26%	1881
November	1st to 10th	Day	14% 12% 3 7% 3 4 4 4 5% 7% 37%	1762
	11th to 20th	Day	17% 16% 5% 10% 5% 4 4 3 5% 6% 25%	1800
	21st to end	Day	19% 17% 5% 11% 5% 4 4 3 3 5% 26%	1800
December	1st to 10th	Day	10% 17% 6% 19% 6% 4 3 2 3 5% 25%	2653
	11th to 20th	Day	15% 18% 10% 14% 5% 5% 4 3 5% 5% 15%	3008
	21st to end	Day	23% 21% 7% 15% 6% 5% 4 2 3 3 11%	3982
January	1st to 10th	Night	14% 19% 11% 19% 7% 4 3 3 3 4 14%	6348
	11th to 20th	Night	14% 20% 9% 17% 6% 6% 6% 5% 4 3 10%	6360
	21st to end	Night	19% 17% 7% 9% 5% 4 4 3 4 4 22%	6996
February	1st to 10th	Night	17% 16% 6% 10% 7% 5% 4 3 4 5% 24%	2483
	11th to 20th	Night	15% 13% 5% 9% 8% 5% 5% 3 5% 6% 27%	2338
	21st to end	Night	18% 14% 4 11% 5% 4 3 3 4 5% 29%	1980
March	1st to 10th	Night	15% 13% 6% 10% 5% 4 4 3 4 5% 33%	5373
	11th to 20th	Night	11% 8% 4 7% 4 4 4 3 5% 6% 43%	5239
	21st to end	Night	18% 13% 6% 9% 4 4 4 3 5% 6% 29%	5109
April	1st to 10th	Night	15% 12% 3 7% 5% 4 4 3 5% 7% 36%	2000
	11th to 20th	Night	18% 9% 2 6% 5% 4 4 4 5% 5% 37%	1975
	21st to end	Night	17% 8% 3 8% 6% 5% 4 3 5% 5% 36%	1829
May	1st to 10th	Night	19% 10% 3 7% 4 5% 4 3 5% 7% 33%	4033
	11th to 20th	Night	15% 7% 2 6% 3 4 4 3 5% 8% 42%	3953
	21st to end	Night	17% 9% 3 7% 4 4 4 3 4 5% 41%	3942
June	1st to 10th	Night	9% 5% 2 5% 4 4 3 4 6% 9% 48%	1600
	11th to 20th	Night	9% 6% 2 6% 5% 4 5% 4 7% 9% 44%	1600
	21st to end	Night	9% 5% 3 7% 5% 5% 5% 4 6% 9% 42%	1600
July	1st to 10th	Night	10% 5% 2 6% 5% 5% 6% 4 7% 10% 41%	2610
	11th to 20th	Night	8% 4 2 5% 3 3 4 4 6% 7% 53%	2610
	21st to end	Night	6% 5% 2 6% 5% 4 5% 5% 9% 9% 45%	2750
August	1st to 10th	Night	9% 6% 2 7% 4 5% 4 4 7% 8% 45%	2731
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 5% 7% 51%	2940
	21st to end	Night	10% 4 2 5% 4 5% 4 3 5% 7% 51%	3476
September	1st to 10th	Night	11% 6% 3 5% 4 4 4 3 5% 7% 49%	1900
	11th to 20th	Night	11% 4 2 5% 3 3 4 3 5% 9% 52%	2056
	21st to end	Night	12% 6% 2 6% 4 5% 4 3 5% 8% 44%	2090
October	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 6% 48%	2090
	11th to 20th	Night	20% 10% 3 6% 3 3 3 3 5% 6% 38%	2310
	21st to end	Night	23% 11% 3 6% 4 3 4 3 4 6% 33%	2717
November	1st to 10th	Night	15% 13% 4 8% 4 3 4 3 5% 5% 38%	2536
	11th to 20th	Night	14% 19% 5% 10% 4 4 4 3 5% 5% 26%	2600
	21st to end	Night	18% 17% 5% 11% 5% 2 4 3 4 6% 26%	2600
December	1st to 10th	Night	12% 15% 7% 20% 7% 4 3 3 3 5% 20%	4532
	11th to 20th	Night	15% 20% 9% 16% 8% 5% 4 3 4 4 13%	5199
	21st to end	Night	23% 21% 8% 12% 6% 5% 4 3 4 4 11%	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	55% 31% 6% 7% 1	3618
	11th to 20th	Day	54% 32% 7% 2 4 1	3620
	21st to end	Day	44% 29% 10% 12% 5%	3982
February	1st to 10th	Day	25% 62% 5% 5% 3	1910
	11th to 20th	Day	25% 61% 4 7% 3	1958
	21st to end	Day	20% 62% 6% 8% 3 1	1650
March	1st to 10th	Day	37% 29% 7% 17% 9% 1	4480
	11th to 20th	Day	28% 31% 10% 26% 5%	4719
	21st to end	Day	47% 31% 9% 8% 5%	5867
April	1st to 10th	Day	23% 62% 4 7% 3	2400
	11th to 20th	Day	17% 63% 5% 9% 5% 1	2374
	21st to end	Day	18% 63% 5% 8% 6% 1	2570
May	1st to 10th	Day	33% 32% 8% 16% 9% 1	5897
	11th to 20th	Day	27% 32% 10% 20% 9% 1	5946
	21st to end	Day	28% 30% 8% 20% 13% 1	6949
June	1st to 10th	Day	13% 63% 4 10% 9% 1	2800
	11th to 20th	Day	16% 64% 5% 9% 5% 1	2800
	21st to end	Day	13% 62% 6% 11% 6% 1	2800
July	1st to 10th	Day	31% 38% 9% 12% 9% 2	4511
	11th to 20th	Day	17% 37% 12% 24% 10%	4505
	21st to end	Day	24% 38% 11% 10% 15% 2	4663
August	1st to 10th	Day	21% 39% 10% 21% 10%	4184
	11th to 20th	Day	22% 39% 7% 23% 9%	3924
	21st to end	Day	21% 40% 9% 16% 13% 1	4179
September	1st to 10th	Day	14% 62% 6% 10% 7% 1	2280
	11th to 20th	Day	12% 61% 5% 12% 8% 1	2104
	21st to end	Day	19% 61% 4 9% 6% 1	2090
October	1st to 10th	Day	15% 37% 5% 25% 16% 1	3480
	11th to 20th	Day	21% 39% 7% 15% 18%	3066
	21st to end	Day	31% 37% 5% 18% 7% 1	3081
November	1st to 10th	Day	23% 58% 6% 6% 6% 1	1762
	11th to 20th	Day	27% 58% 3 6% 5% 1	1800
	21st to end	Day	31% 57% 4 6% 2	1800
December	1st to 10th	Day	39% 38% 11% 11% 2	2653
	11th to 20th	Day	47% 35% 10% 8% 1	3005
	21st to end	Day	62% 27% 4 6% 1	3982
January	1st to 10th	Night	57% 29% 6% 6% 1	6348
	11th to 20th	Night	57% 32% 5% 3 3	6360
	21st to end	Night	44% 31% 9% 10% 6%	6996
February	1st to 10th	Night	25% 61% 5% 6% 3	2483
	11th to 20th	Night	24% 60% 3 8% 4	2339
	21st to end	Night	21% 61% 4 9% 4 1	1980
March	1st to 10th	Night	38% 31% 7% 19% 5% 1	5373
	11th to 20th	Night	29% 30% 8% 22% 10% 1	5239
	21st to end	Night	40% 31% 7% 15% 7%	5109
April	1st to 10th	Night	21% 62% 5% 8% 4	2000
	11th to 20th	Night	19% 63% 4 7% 5% 1	1975
	21st to end	Night	18% 63% 4 7% 6% 1	1829
May	1st to 10th	Night	38% 31% 6% 11% 11% 4	4060
	11th to 20th	Night	29% 31% 11% 19% 9% 2	3954
	21st to end	Night	35% 30% 5% 13% 15% 2	3950
June	1st to 10th	Night	13% 63% 4 12% 7% 1	1600
	11th to 20th	Night	18% 62% 5% 9% 6% 1	1600
	21st to end	Night	13% 62% 6% 12% 7% 1	1600
July	1st to 10th	Night	28% 38% 9% 16% 6% 4	2570
	11th to 20th	Night	19% 37% 8% 15% 20% 1	2562
	21st to end	Night	22% 39% 11% 11% 15% 3	2662
August	1st to 10th	Night	23% 40% 9% 19% 9%	2722
	11th to 20th	Night	22% 40% 8% 18% 13%	2967
	21st to end	Night	22% 39% 7% 19% 12%	3476
September	1st to 10th	Night	12% 61% 6% 10% 10% 1	1900
	11th to 20th	Night	10% 61% 3 13% 12% 1	2056
	21st to end	Night	17% 61% 5% 10% 6%	2090
October	1st to 10th	Night	12% 37% 7% 25% 18% 1	3480
	11th to 20th	Night	27% 37% 3 12% 20%	3833
	21st to end	Night	25% 37% 6% 17% 15% 1	4467
November	1st to 10th	Night	27% 56% 4 7% 4 1	2536
	11th to 20th	Night	26% 57% 3 7% 5% 1	2600
	21st to end	Night	30% 57% 5% 6% 2	2600
December	1st to 10th	Night	39% 42% 9% 8% 2	4532
	11th to 20th	Night	52% 35% 7% 4 2	5201
	21st to end	Night	58% 27% 7% 5% 2	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	22% 18% 39% 17% 3 1	300
	11th to 20th	Day	27% 19% 35% 14% 3 1	300
	21st to end	Day	26% 19% 38% 15% 2	330
February	1st to 10th	Day	21% 27% 34% 13% 4	300
	11th to 20th	Day	25% 26% 31% 15% 3	300
	21st to end	Day	24% 26% 38% 12% 1	249
March	1st to 10th	Day	22% 23% 40% 13% 2	300
	11th to 20th	Day	23% 19% 33% 19% 5% 1	382
	21st to end	Day	28% 18% 31% 17% 6%	550
April	1st to 10th	Day	24% 17% 34% 19% 5% 1	500
	11th to 20th	Day	22% 22% 29% 18% 7% 3	492
	21st to end	Day	22% 15% 36% 18% 8% 1	500
May	1st to 10th	Day	24% 11% 34% 20% 9% 2	503
	11th to 20th	Day	20% 10% 32% 22% 13% 3	556
	21st to end	Day	14% 9% 31% 27% 14% 5%	789
June	1st to 10th	Day	12% 8% 28% 32% 16% 3	730
	11th to 20th	Day	11% 6% 32% 31% 16% 3	730
	21st to end	Day	12% 8% 30% 33% 14% 4	730
July	1st to 10th	Day	10% 5% 22% 30% 22% 11%	721
	11th to 20th	Day	10% 4 26% 33% 20% 8%	718
	21st to end	Day	8% 4 24% 39% 19% 5%	740
August	1st to 10th	Day	8% 3 18% 31% 28% 12%	543
	11th to 20th	Day	9% 4 26% 28% 26% 8%	479
	21st to end	Day	11% 3 18% 34% 28% 7%	539
September	1st to 10th	Day	12% 6% 21% 30% 24% 6%	490
	11th to 20th	Day	9% 6% 18% 30% 26% 10%	490
	21st to end	Day	16% 12% 22% 24% 19% 6%	490
October	1st to 10th	Day	16% 9% 28% 29% 16% 3	490
	11th to 20th	Day	23% 17% 30% 22% 7%	333
	21st to end	Day	29% 17% 34% 16% 3	330
November	1st to 10th	Day	18% 19% 35% 19% 8% 2	300
	11th to 20th	Day	25% 21% 34% 15% 5%	300
	21st to end	Day	30% 15% 39% 14% 2	300
December	1st to 10th	Day	18% 28% 34% 14% 6%	300
	11th to 20th	Day	20% 26% 37% 13% 3	300
	21st to end	Day	26% 25% 36% 13% 1	330
January	1st to 10th	Night	24% 19% 36% 19% 3	1000
	11th to 20th	Night	24% 19% 37% 17% 3 1	1000
	21st to end	Night	24% 16% 36% 21% 3	1100
February	1st to 10th	Night	27% 13% 37% 20% 4	868
	11th to 20th	Night	23% 17% 34% 20% 5%	783
	21st to end	Night	25% 18% 38% 16% 3	660
March	1st to 10th	Night	22% 15% 36% 21% 6% 1	800
	11th to 20th	Night	18% 12% 38% 25% 7%	800
	21st to end	Night	26% 10% 31% 27% 6%	729
April	1st to 10th	Night	20% 15% 34% 24% 6% 1	600
	11th to 20th	Night	23% 12% 30% 26% 9% 1	593
	21st to end	Night	20% 10% 32% 28% 8% 1	600
May	1st to 10th	Night	21% 7% 30% 30% 11% 1	600
	11th to 20th	Night	20% 5% 26% 32% 16% 1	591
	21st to end	Night	13% 5% 23% 36% 21% 2	650
June	1st to 10th	Night	11% 4 23% 40% 21% 1	600
	11th to 20th	Night	10% 4 27% 39% 18% 2	600
	21st to end	Night	10% 4 26% 39% 19% 2	600
July	1st to 10th	Night	9% 2 14% 39% 30% 6%	585
	11th to 20th	Night	9% 3 20% 36% 26% 5%	582
	21st to end	Night	6% 1 17% 44% 30% 2	624
August	1st to 10th	Night	7% 2 12% 43% 32% 4	567
	11th to 20th	Night	7% 3 17% 39% 29% 5%	564
	21st to end	Night	10% 3 17% 38% 28% 4	627
September	1st to 10th	Night	13% 5% 18% 36% 25% 4	570
	11th to 20th	Night	11% 5% 16% 35% 28% 4	726
	21st to end	Night	13% 8% 25% 28% 22% 4	760
October	1st to 10th	Night	14% 8% 27% 30% 19% 1	760
	11th to 20th	Night	25% 13% 29% 25% 8%	760
	21st to end	Night	29% 14% 30% 22% 6%	836
November	1st to 10th	Night	23% 14% 32% 19% 10% 1	780
	11th to 20th	Night	25% 22% 30% 19% 5%	800
	21st to end	Night	28% 17% 32% 19% 4	800
December	1st to 10th	Night	26% 20% 36% 16% 3	965
	11th to 20th	Night	24% 17% 36% 20% 2	1000
	21st to end	Night	29% 18% 35% 16% 2	1100

Page generated at 2025-07-18 01:10:03. Version ac07

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