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 2024-04-10.

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% 10% 5% 7% 6% 3 4 5% 5% 7% 34%	83011
	Night	16% 12% 5% 8% 6% 3 4 4 5% 6% 31%	85828
Transparency	Day	49% 7% 12% 20% 11% 1	82712
	Night	52% 6% 11% 18% 11% 1	85648
Seeing	Day	17% 11% 29% 25% 14% 4	14882
	Night	20% 11% 29% 27% 12% 1	24925

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% 14% 11% 8% 4 4 4 4 5% 14%	2527
	11th to 20th	Day	13% 18% 10% 14% 10% 4 5% 11% 4 3 8%	2530
	21st to end	Day	23% 24% 7% 8% 5% 3 3 3 3 6% 15%	2783
February	1st to 10th	Day	15% 16% 6% 9% 8% 4 5% 4 4 6% 22%	1814
	11th to 20th	Day	14% 12% 5% 10% 10% 4 4 4 4 5% 28%	1848
	21st to end	Day	15% 15% 8% 11% 5% 2 4 4 3 6% 27%	1570
March	1st to 10th	Day	18% 12% 6% 8% 5% 2 4 5% 5% 6% 30%	3120
	11th to 20th	Day	10% 8% 6% 8% 7% 3 5% 5% 6% 7% 35%	3303
	21st to end	Day	18% 11% 7% 10% 6% 4 5% 4 5% 5% 25%	4091
April	1st to 10th	Day	16% 11% 4 6% 6% 3 5% 4 5% 7% 33%	2269
	11th to 20th	Day	16% 11% 3 5% 5% 3 4 4 4 7% 38%	2134
	21st to end	Day	18% 9% 3 6% 5% 3 4 5% 5% 8% 33%	2312
May	1st to 10th	Day	16% 9% 3 6% 5% 3 5% 5% 6% 8% 34%	2340
	11th to 20th	Day	18% 9% 3 5% 5% 3 4 4 4 7% 38%	2326
	21st to end	Day	11% 6% 3 6% 5% 3 5% 5% 6% 9% 40%	2725
June	1st to 10th	Day	10% 5% 2 6% 5% 3 5% 5% 5% 8% 46%	2520
	11th to 20th	Day	9% 4 3 5% 6% 3 5% 5% 6% 9% 46%	2520
	21st to end	Day	11% 5% 3 5% 5% 3 5% 6% 7% 8% 43%	2520
July	1st to 10th	Day	7% 5% 2 5% 5% 3 5% 5% 6% 8% 49%	2520
	11th to 20th	Day	9% 5% 2 5% 3 3 5% 5% 5% 10% 47%	2520
	21st to end	Day	6% 4 2 5% 5% 3 5% 6% 7% 10% 47%	2743
August	1st to 10th	Day	7% 4 2 4 5% 4 5% 5% 7% 10% 47%	2381
	11th to 20th	Day	8% 4 2 5% 5% 3 5% 5% 7% 9% 45%	2214
	21st to end	Day	8% 4 2 4 4 3 4 5% 6% 9% 50%	2376
September	1st to 10th	Day	10% 5% 3 4 6% 3 5% 6% 6% 7% 44%	2160
	11th to 20th	Day	11% 5% 2 5% 5% 3 5% 5% 6% 7% 47%	1994
	21st to end	Day	12% 7% 3 5% 5% 3 4 5% 5% 8% 42%	1980
October	1st to 10th	Day	14% 8% 2 5% 5% 3 4 4 5% 6% 44%	1980
	11th to 20th	Day	21% 10% 3 6% 6% 3 4 4 5% 6% 32%	1766
	21st to end	Day	23% 11% 5% 7% 6% 3 4 5% 5% 6% 25%	1782
November	1st to 10th	Day	14% 11% 4 6% 4 2 5% 4 5% 8% 37%	1672
	11th to 20th	Day	18% 15% 6% 8% 7% 3 4 4 5% 6% 25%	1710
	21st to end	Day	20% 15% 6% 9% 5% 3 5% 4 3 5% 27%	1710
December	1st to 10th	Day	15% 18% 9% 12% 7% 3 4 3 3 5% 21%	1550
	11th to 20th	Day	14% 19% 10% 11% 6% 3 4 3 5% 5% 20%	1918
	21st to end	Day	20% 21% 7% 14% 8% 5% 4 3 3 4 11%	2783
January	1st to 10th	Night	16% 19% 10% 12% 8% 4 3 4 4 4 17%	4428
	11th to 20th	Night	16% 20% 10% 14% 7% 3 4 8% 4 3 11%	4440
	21st to end	Night	24% 20% 9% 9% 7% 3 4 3 3 4 12%	4884
February	1st to 10th	Night	18% 14% 6% 8% 8% 4 5% 4 4 5% 24%	2360
	11th to 20th	Night	15% 12% 6% 7% 9% 4 6% 4 5% 6% 27%	2218
	21st to end	Night	19% 13% 5% 10% 6% 3 3 3 4 5% 28%	1884
March	1st to 10th	Night	17% 11% 5% 8% 5% 3 4 4 4 5% 32%	3733
	11th to 20th	Night	9% 8% 5% 7% 6% 3 5% 4 5% 6% 42%	3655
	21st to end	Night	20% 12% 7% 8% 6% 2 5% 4 5% 6% 26%	3571
April	1st to 10th	Night	15% 11% 3 6% 5% 3 4 4 4 7% 37%	1900
	11th to 20th	Night	19% 9% 2 5% 5% 3 4 5% 5% 5% 37%	1775
	21st to end	Night	18% 8% 3 7% 6% 4 5% 4 5% 5% 36%	1647
May	1st to 10th	Night	17% 8% 4 5% 5% 4 5% 5% 5% 8% 34%	1620
	11th to 20th	Night	18% 8% 2 6% 5% 3 4 4 5% 8% 38%	1565
	21st to end	Night	10% 6% 2 6% 5% 3 6% 5% 7% 7% 42%	1551
June	1st to 10th	Night	9% 4 2 4 5% 3 3 5% 6% 9% 49%	1440
	11th to 20th	Night	8% 5% 3 5% 6% 4 5% 5% 6% 8% 46%	1440
	21st to end	Night	9% 5% 3 6% 7% 4 5% 5% 6% 8% 42%	1440
July	1st to 10th	Night	7% 4 1 4 5% 3 4 6% 7% 10% 50%	1440
	11th to 20th	Night	9% 4 2 4 4 3 4 5% 7% 8% 51%	1440
	21st to end	Night	5% 3 2 4 5% 3 6% 6% 8% 10% 49%	1575
August	1st to 10th	Night	6% 4 2 4 5% 3 4 6% 7% 10% 49%	1555
	11th to 20th	Night	7% 5% 2 4 5% 3 5% 5% 6% 8% 50%	1683
	21st to end	Night	8% 4 2 4 5% 4 5% 4 5% 7% 52%	1980
September	1st to 10th	Night	12% 6% 3 5% 5% 2 4 4 5% 7% 48%	1800
	11th to 20th	Night	12% 4 2 4 4 3 4 4 5% 9% 51%	1947
	21st to end	Night	11% 6% 2 6% 5% 4 4 4 5% 8% 45%	1980
October	1st to 10th	Night	13% 6% 3 5% 5% 3 4 4 5% 5% 46%	1980
	11th to 20th	Night	20% 10% 3 5% 4 2 3 4 5% 6% 37%	2188
	21st to end	Night	24% 12% 3 5% 5% 3 4 4 4 6% 32%	2574
November	1st to 10th	Night	15% 12% 5% 7% 5% 2 4 4 4 5% 38%	2406
	11th to 20th	Night	15% 17% 6% 9% 6% 3 4 4 4 6% 27%	2470
	21st to end	Night	19% 16% 5% 9% 6% 2 3 3 3 6% 27%	2470
December	1st to 10th	Night	17% 19% 8% 11% 6% 3 3 4 4 5% 19%	2626
	11th to 20th	Night	14% 19% 9% 12% 8% 3 3 5% 4 5% 18%	3279
	21st to end	Night	24% 20% 7% 10% 7% 4 4 4 4 5% 12%	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% 3	2528
	11th to 20th	Day	74% 9% 9% 6% 1	2530
	21st to end	Day	72% 4 10% 11% 3	2783
February	1st to 10th	Day	63% 5% 12% 12% 6% 1	1814
	11th to 20th	Day	58% 4 11% 18% 8%	1858
	21st to end	Day	58% 5% 12% 16% 7% 2	1570
March	1st to 10th	Day	54% 6% 12% 18% 9% 1	3120
	11th to 20th	Day	44% 7% 14% 27% 8% 1	3303
	21st to end	Day	60% 7% 15% 15% 3	4091
April	1st to 10th	Day	50% 5% 11% 21% 12%	2269
	11th to 20th	Day	47% 5% 11% 21% 13% 3	2134
	21st to end	Day	48% 7% 13% 17% 12% 3	2312
May	1st to 10th	Day	48% 7% 13% 23% 9% 1	2340
	11th to 20th	Day	47% 6% 12% 21% 13% 1	2330
	21st to end	Day	41% 8% 13% 23% 15% 2	2725
June	1st to 10th	Day	36% 7% 11% 25% 19% 2	2520
	11th to 20th	Day	35% 7% 12% 24% 20% 3	2520
	21st to end	Day	37% 9% 15% 21% 16% 2	2520
July	1st to 10th	Day	32% 7% 13% 26% 18% 4	2451
	11th to 20th	Day	32% 8% 15% 27% 16% 2	2445
	21st to end	Day	31% 9% 15% 25% 16% 3	2591
August	1st to 10th	Day	31% 9% 15% 30% 14% 2	2366
	11th to 20th	Day	33% 7% 16% 26% 16% 2	2214
	21st to end	Day	30% 7% 14% 25% 19% 4	2376
September	1st to 10th	Day	37% 7% 14% 22% 16% 4	2160
	11th to 20th	Day	34% 7% 13% 27% 17% 2	1994
	21st to end	Day	39% 7% 10% 23% 18% 2	1980
October	1st to 10th	Day	41% 6% 12% 24% 16% 2	1980
	11th to 20th	Day	51% 6% 11% 20% 12% 1	1766
	21st to end	Day	58% 6% 12% 15% 8% 1	1782
November	1st to 10th	Day	44% 7% 13% 20% 15% 1	1672
	11th to 20th	Day	59% 6% 10% 17% 8%	1710
	21st to end	Day	61% 5% 9% 18% 6%	1710
December	1st to 10th	Day	67% 5% 9% 13% 5%	1550
	11th to 20th	Day	65% 4 12% 16% 3	1915
	21st to end	Day	78% 6% 8% 7% 2	2783
January	1st to 10th	Night	68% 8% 9% 12% 3	4428
	11th to 20th	Night	75% 8% 9% 6% 2	4440
	21st to end	Night	73% 5% 9% 10% 3	4884
February	1st to 10th	Night	62% 5% 9% 15% 7% 1	2360
	11th to 20th	Night	56% 5% 11% 18% 9% 1	2219
	21st to end	Night	60% 4 9% 17% 9% 2	1884
March	1st to 10th	Night	52% 6% 11% 22% 8% 1	3733
	11th to 20th	Night	40% 6% 12% 25% 15% 2	3655
	21st to end	Night	58% 7% 11% 18% 6%	3571
April	1st to 10th	Night	47% 6% 12% 20% 13% 1	1900
	11th to 20th	Night	49% 5% 7% 19% 18% 3	1775
	21st to end	Night	49% 7% 10% 18% 14% 3	1647
May	1st to 10th	Night	48% 7% 12% 22% 11% 1	1620
	11th to 20th	Night	46% 6% 11% 21% 16% 1	1566
	21st to end	Night	40% 7% 15% 21% 15% 3	1552
June	1st to 10th	Night	31% 7% 14% 27% 20% 2	1440
	11th to 20th	Night	35% 6% 12% 24% 21% 2	1440
	21st to end	Night	38% 9% 15% 22% 14% 3	1440
July	1st to 10th	Night	29% 8% 15% 26% 18% 4	1400
	11th to 20th	Night	29% 7% 14% 24% 22% 4	1392
	21st to end	Night	27% 9% 17% 25% 18% 5%	1487
August	1st to 10th	Night	27% 9% 15% 30% 18% 1	1546
	11th to 20th	Night	30% 8% 15% 25% 20% 2	1683
	21st to end	Night	30% 7% 10% 26% 21% 5%	1980
September	1st to 10th	Night	35% 7% 12% 22% 19% 6%	1800
	11th to 20th	Night	32% 6% 8% 29% 24% 2	1947
	21st to end	Night	37% 7% 11% 26% 18% 2	1980
October	1st to 10th	Night	38% 7% 10% 25% 19% 1	1980
	11th to 20th	Night	47% 5% 9% 21% 16% 1	2188
	21st to end	Night	54% 5% 11% 20% 9% 1	2574
November	1st to 10th	Night	48% 5% 9% 20% 15% 2	2406
	11th to 20th	Night	57% 7% 10% 17% 9% 1	2470
	21st to end	Night	59% 4 12% 19% 6%	2470
December	1st to 10th	Night	67% 5% 9% 13% 6%	2626
	11th to 20th	Night	67% 6% 11% 13% 4	3281
	21st to end	Night	75% 5% 9% 8% 2	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	21% 18% 37% 19% 3 1	270
	11th to 20th	Day	27% 17% 36% 16% 3 1	270
	21st to end	Day	27% 16% 38% 16% 2	297
February	1st to 10th	Day	21% 26% 34% 14% 5%	270
	11th to 20th	Day	23% 24% 33% 17% 3	270
	21st to end	Day	22% 26% 38% 12% 1	225
March	1st to 10th	Day	21% 24% 38% 14% 3	270
	11th to 20th	Day	22% 18% 34% 20% 5% 1	348
	21st to end	Day	27% 17% 31% 18% 6%	506
April	1st to 10th	Day	23% 16% 35% 20% 5% 1	457
	11th to 20th	Day	21% 20% 29% 18% 8% 4	412
	21st to end	Day	21% 15% 36% 17% 9% 1	420
May	1st to 10th	Day	24% 10% 32% 22% 9% 2	423
	11th to 20th	Day	22% 8% 33% 22% 14% 2	472
	21st to end	Day	13% 6% 30% 29% 16% 6%	679
June	1st to 10th	Day	11% 6% 28% 33% 18% 4	630
	11th to 20th	Day	11% 6% 32% 31% 18% 4	630
	21st to end	Day	12% 6% 30% 33% 15% 4	630
July	1st to 10th	Day	9% 4 22% 30% 24% 12%	621
	11th to 20th	Day	10% 3 25% 33% 21% 8%	618
	21st to end	Day	8% 4 25% 38% 20% 6%	684
August	1st to 10th	Day	8% 2 16% 31% 29% 13%	500
	11th to 20th	Day	8% 4 24% 30% 27% 8%	439
	21st to end	Day	11% 3 18% 33% 28% 7%	495
September	1st to 10th	Day	12% 6% 20% 31% 24% 6%	450
	11th to 20th	Day	10% 6% 18% 29% 26% 11%	450
	21st to end	Day	15% 12% 22% 24% 20% 7%	450
October	1st to 10th	Day	16% 7% 28% 29% 16% 4	450
	11th to 20th	Day	25% 17% 31% 21% 6%	302
	21st to end	Day	31% 16% 35% 15% 2	297
November	1st to 10th	Day	16% 18% 36% 20% 9% 2	270
	11th to 20th	Day	24% 19% 33% 17% 6%	270
	21st to end	Day	28% 14% 40% 16% 2	270
December	1st to 10th	Day	19% 26% 34% 14% 7%	270
	11th to 20th	Day	19% 26% 37% 14% 4	270
	21st to end	Day	24% 25% 37% 13% 1	297
January	1st to 10th	Night	24% 18% 36% 19% 3	950
	11th to 20th	Night	25% 17% 37% 17% 3 1	950
	21st to end	Night	24% 15% 36% 22% 3	1045
February	1st to 10th	Night	26% 12% 37% 20% 4	825
	11th to 20th	Night	23% 16% 35% 21% 5%	743
	21st to end	Night	25% 18% 36% 16% 3	628
March	1st to 10th	Night	21% 16% 35% 21% 6% 1	760
	11th to 20th	Night	17% 11% 39% 25% 7%	760
	21st to end	Night	26% 9% 31% 27% 7%	693
April	1st to 10th	Night	19% 14% 34% 24% 6% 1	570
	11th to 20th	Night	23% 11% 30% 26% 9% 1	533
	21st to end	Night	21% 8% 33% 28% 9% 1	540
May	1st to 10th	Night	22% 6% 30% 31% 10% 1	540
	11th to 20th	Night	21% 4 26% 33% 16% 1	531
	21st to end	Night	13% 4 23% 35% 23% 3	584
June	1st to 10th	Night	11% 3 21% 41% 22% 1	540
	11th to 20th	Night	9% 4 26% 41% 19% 2	540
	21st to end	Night	10% 4 24% 39% 20% 2	540
July	1st to 10th	Night	9% 1 14% 38% 32% 7%	525
	11th to 20th	Night	9% 2 19% 37% 27% 5%	522
	21st to end	Night	6% 2 17% 42% 31% 2	591
August	1st to 10th	Night	7% 2 12% 43% 32% 4	537
	11th to 20th	Night	7% 3 16% 39% 30% 5%	534
	21st to end	Night	10% 3 18% 37% 29% 4	594
September	1st to 10th	Night	13% 5% 17% 36% 25% 4	540
	11th to 20th	Night	11% 5% 17% 34% 28% 5%	687
	21st to end	Night	12% 8% 25% 28% 23% 4	720
October	1st to 10th	Night	15% 8% 26% 29% 20% 1	720
	11th to 20th	Night	25% 14% 29% 24% 7%	720
	21st to end	Night	30% 14% 29% 21% 6%	792
November	1st to 10th	Night	23% 14% 33% 19% 10% 1	740
	11th to 20th	Night	23% 21% 31% 19% 5%	760
	21st to end	Night	27% 16% 32% 20% 5%	760
December	1st to 10th	Night	26% 19% 36% 16% 3	916
	11th to 20th	Night	23% 16% 37% 21% 3	950
	21st to end	Night	29% 18% 35% 16% 2	1045

Page generated at 2024-04-07 09:28:10. Version ac07

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