Benton Harbor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Benton Harbor 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	14% 11% 4 9% 5% 4 4 3 5% 7% 35%	119807
	Night	16% 13% 5% 10% 5% 4 4 3 4 5% 30%	119499
Transparency	Day	51% 2 11% 23% 12% 1	123391
	Night	57% 2 9% 19% 12% 1	124043
Seeing	Day	19% 11% 29% 24% 12% 4	16752
	Night	23% 9% 27% 28% 12% 1	26599

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% 21% 11% 22% 5% 4 3 2 3 4 13%	3617
	11th to 20th	Day	11% 19% 8% 19% 13% 10% 6% 2 2 3 7%	3620
	21st to end	Day	19% 19% 6% 15% 5% 3 6% 3 3 4 17%	3982
February	1st to 10th	Day	13% 17% 6% 13% 11% 5% 4 4 3 4 19%	1885
	11th to 20th	Day	14% 15% 8% 15% 9% 5% 3 3 4 5% 20%	1948
	21st to end	Day	15% 15% 6% 12% 5% 5% 5% 3 5% 5% 23%	1650
March	1st to 10th	Day	15% 11% 6% 12% 5% 4 3 3 4 6% 32%	4480
	11th to 20th	Day	10% 9% 7% 9% 4 4 4 4 6% 8% 36%	4765
	21st to end	Day	17% 15% 7% 11% 5% 5% 4 3 4 5% 24%	5782
April	1st to 10th	Day	17% 13% 3 7% 4 4 3 3 5% 7% 33%	2400
	11th to 20th	Day	15% 11% 3 5% 4 3 4 3 5% 7% 39%	2378
	21st to end	Day	17% 9% 3 7% 5% 4 4 3 5% 8% 36%	2600
May	1st to 10th	Day	18% 8% 3 6% 4 4 4 4 6% 7% 36%	5862
	11th to 20th	Day	13% 8% 3 6% 4 4 4 3 5% 8% 42%	5902
	21st to end	Day	16% 6% 2 5% 3 4 3 3 5% 8% 45%	6935
June	1st to 10th	Day	9% 6% 2 5% 4 4 5% 3 6% 8% 48%	2800
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 6% 9% 47%	2800
	21st to end	Day	11% 5% 2 6% 4 4 4 4 6% 8% 46%	2800
July	1st to 10th	Day	12% 7% 2 7% 4 5% 5% 4 5% 8% 41%	4580
	11th to 20th	Day	7% 3 2 4 4 3 4 4 6% 10% 52%	4580
	21st to end	Day	6% 6% 2 6% 4 4 5% 4 6% 8% 48%	4814
August	1st to 10th	Day	11% 5% 2 5% 3 4 4 3 6% 8% 48%	4174
	11th to 20th	Day	11% 5% 2 5% 3 4 4 4 5% 7% 50%	3958
	21st to end	Day	8% 5% 2 6% 5% 4 4 4 6% 8% 50%	4180
September	1st to 10th	Day	10% 5% 2 6% 4 3 5% 3 6% 7% 48%	2278
	11th to 20th	Day	12% 4 2 4 4 5% 3 3 7% 8% 48%	2090
	21st to end	Day	14% 6% 2 7% 4 4 4 4 6% 8% 40%	2090
October	1st to 10th	Day	16% 8% 3 6% 3 3 4 3 4 4 45%	2090
	11th to 20th	Day	23% 9% 3 7% 4 4 3 4 6% 7% 31%	1860
	21st to end	Day	24% 10% 3 8% 5% 5% 5% 3 5% 6% 24%	1881
November	1st to 10th	Day	15% 14% 3 6% 4 3 4 3 5% 5% 36%	1762
	11th to 20th	Day	17% 20% 4 10% 5% 4 4 3 4 5% 22%	1800
	21st to end	Day	22% 18% 6% 10% 4 3 3 3 4 5% 21%	1800
December	1st to 10th	Day	12% 22% 13% 16% 4 3 3 2 4 4 18%	2674
	11th to 20th	Day	15% 23% 12% 14% 7% 3 3 2 4 4 12%	3008
	21st to end	Day	24% 22% 8% 13% 6% 4 3 3 3 4 10%	3982
January	1st to 10th	Night	15% 23% 11% 21% 5% 3 3 2 4 4 9%	6348
	11th to 20th	Night	13% 21% 10% 21% 8% 11% 3 2 2 2 7%	6360
	21st to end	Night	19% 19% 9% 14% 6% 4 6% 2 3 3 16%	6996
February	1st to 10th	Night	15% 17% 5% 14% 10% 4 3 3 3 5% 21%	2508
	11th to 20th	Night	14% 17% 6% 15% 8% 5% 4 3 4 4 20%	2338
	21st to end	Night	18% 16% 6% 12% 5% 3 4 2 3 5% 26%	1980
March	1st to 10th	Night	15% 12% 5% 10% 4 4 4 2 4 5% 33%	5373
	11th to 20th	Night	11% 9% 3 8% 5% 5% 4 3 5% 6% 42%	5194
	21st to end	Night	19% 12% 5% 9% 4 4 4 3 4 5% 30%	5177
April	1st to 10th	Night	16% 10% 3 7% 5% 5% 4 3 5% 6% 35%	2000
	11th to 20th	Night	20% 9% 2 7% 3 4 4 4 4 5% 37%	1970
	21st to end	Night	19% 7% 3 7% 5% 4 4 3 5% 6% 37%	1800
May	1st to 10th	Night	18% 9% 3 7% 5% 4 4 3 5% 7% 34%	4033
	11th to 20th	Night	16% 7% 3 7% 4 3 4 3 5% 8% 42%	3989
	21st to end	Night	17% 8% 3 7% 4 3 3 3 4 6% 41%	3942
June	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 6% 10% 47%	1600
	11th to 20th	Night	10% 6% 1 5% 5% 4 5% 5% 6% 9% 43%	1600
	21st to end	Night	9% 5% 2 6% 4 6% 5% 4 8% 9% 42%	1600
July	1st to 10th	Night	10% 5% 2 6% 5% 4 5% 4 7% 9% 42%	2610
	11th to 20th	Night	8% 4 2 4 4 3 3 4 5% 8% 55%	2610
	21st to end	Night	7% 5% 2 5% 5% 5% 5% 5% 8% 8% 47%	2750
August	1st to 10th	Night	9% 5% 2 6% 4 5% 5% 4 6% 8% 47%	2754
	11th to 20th	Night	10% 4 2 5% 4 4 4 4 6% 7% 51%	2868
	21st to end	Night	10% 5% 2 6% 4 4 5% 4 5% 7% 48%	3476
September	1st to 10th	Night	11% 5% 2 6% 4 3 4 3 5% 6% 50%	1900
	11th to 20th	Night	12% 4 2 4 3 3 4 3 6% 8% 52%	2072
	21st to end	Night	13% 7% 2 7% 4 4 5% 4 6% 7% 42%	2090
October	1st to 10th	Night	16% 7% 2 6% 4 3 3 3 5% 5% 46%	2090
	11th to 20th	Night	22% 11% 3 6% 4 4 4 3 4 6% 35%	2314
	21st to end	Night	26% 11% 3 7% 4 3 4 3 4 5% 30%	2717
November	1st to 10th	Night	17% 13% 3 7% 4 3 4 3 4 5% 37%	2536
	11th to 20th	Night	18% 20% 5% 9% 4 4 4 3 5% 5% 24%	2600
	21st to end	Night	20% 21% 6% 8% 4 4 3 2 3 5% 23%	2600
December	1st to 10th	Night	13% 20% 10% 18% 6% 4 4 3 4 4 14%	4509
	11th to 20th	Night	17% 24% 12% 15% 6% 4 3 2 3 4 10%	5199
	21st to end	Night	24% 23% 7% 12% 5% 5% 4 3 3 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	78% 1 9% 11% 2	3618
	11th to 20th	Day	87% 1 6% 4 1	3620
	21st to end	Day	74% 1 9% 13% 3	3982
February	1st to 10th	Day	71% 2 9% 13% 5% 1	1885
	11th to 20th	Day	69% 1 8% 14% 7%	1958
	21st to end	Day	64% 2 10% 16% 8% 1	1650
March	1st to 10th	Day	57% 1 10% 22% 9%	4480
	11th to 20th	Day	48% 1 14% 29% 8% 1	4765
	21st to end	Day	65% 1 8% 18% 8%	5784
April	1st to 10th	Day	53% 3 9% 22% 13%	2400
	11th to 20th	Day	47% 2 9% 25% 14% 3	2378
	21st to end	Day	49% 1 11% 22% 14% 2	2600
May	1st to 10th	Day	49% 2 10% 25% 14% 1	5897
	11th to 20th	Day	43% 2 12% 27% 15% 1	5906
	21st to end	Day	40% 1 9% 28% 19% 1	6949
June	1st to 10th	Day	36% 3 12% 27% 20% 2	2800
	11th to 20th	Day	35% 3 12% 27% 20% 3	2800
	21st to end	Day	37% 3 15% 24% 18% 3	2800
July	1st to 10th	Day	44% 2 12% 23% 16% 3	4511
	11th to 20th	Day	29% 2 15% 35% 17% 2	4505
	21st to end	Day	36% 3 16% 21% 21% 3	4663
August	1st to 10th	Day	35% 2 13% 32% 15% 1	4159
	11th to 20th	Day	34% 2 13% 34% 15% 1	3997
	21st to end	Day	34% 2 12% 29% 20% 2	4179
September	1st to 10th	Day	36% 3 14% 27% 17% 4	2278
	11th to 20th	Day	35% 2 11% 32% 18% 2	2090
	21st to end	Day	42% 3 9% 27% 17% 1	2090
October	1st to 10th	Day	31% 2 8% 39% 19% 1	3480
	11th to 20th	Day	43% 1 11% 25% 20%	3063
	21st to end	Day	53% 1 9% 25% 10% 1	3081
November	1st to 10th	Day	50% 3 12% 21% 13% 1	1762
	11th to 20th	Day	65% 1 10% 17% 6% 1	1800
	21st to end	Day	67% 2 10% 17% 4	1800
December	1st to 10th	Day	73% 1 14% 10% 2	2674
	11th to 20th	Day	79% 1 10% 9% 1	3005
	21st to end	Day	81% 1 6% 9% 2	3982
January	1st to 10th	Night	82% 1 6% 10% 2	6348
	11th to 20th	Night	88% 1 5% 4 2	6360
	21st to end	Night	77% 1 11% 9% 3	6996
February	1st to 10th	Night	69% 2 9% 13% 7% 1	2508
	11th to 20th	Night	69% 2 7% 17% 6%	2339
	21st to end	Night	64% 2 9% 17% 7% 2	1980
March	1st to 10th	Night	56% 1 11% 24% 7% 1	5373
	11th to 20th	Night	46% 1 11% 29% 11% 2	5194
	21st to end	Night	59% 1 9% 20% 11% 1	5177
April	1st to 10th	Night	50% 3 11% 22% 13% 1	2000
	11th to 20th	Night	50% 2 7% 21% 18% 3	1970
	21st to end	Night	49% 2 11% 21% 15% 3	1800
May	1st to 10th	Night	52% 1 10% 20% 12% 4	4060
	11th to 20th	Night	44% 2 11% 23% 18% 2	3990
	21st to end	Night	46% 2 7% 23% 21% 1	3950
June	1st to 10th	Night	34% 3 11% 30% 18% 3	1600
	11th to 20th	Night	38% 3 12% 25% 20% 2	1600
	21st to end	Night	38% 4 16% 25% 15% 2	1600
July	1st to 10th	Night	41% 2 12% 27% 13% 6%	2570
	11th to 20th	Night	29% 2 14% 24% 28% 3	2562
	21st to end	Night	35% 4 15% 18% 25% 2	2662
August	1st to 10th	Night	36% 2 13% 30% 18% 1	2745
	11th to 20th	Night	34% 3 10% 32% 20% 1	2895
	21st to end	Night	36% 2 8% 31% 20% 3	3476
September	1st to 10th	Night	36% 3 11% 27% 19% 4	1900
	11th to 20th	Night	32% 2 7% 32% 24% 2	2072
	21st to end	Night	42% 3 9% 26% 18% 2	2090
October	1st to 10th	Night	30% 1 9% 33% 26% 1	3480
	11th to 20th	Night	45% 1 8% 22% 22% 1	3837
	21st to end	Night	47% 1 8% 27% 16% 1	4467
November	1st to 10th	Night	51% 3 8% 23% 14% 2	2536
	11th to 20th	Night	63% 2 10% 17% 7% 1	2600
	21st to end	Night	67% 2 11% 17% 4	2600
December	1st to 10th	Night	76% 1 10% 10% 2	4509
	11th to 20th	Night	81% 1 8% 8% 1	5201
	21st to end	Night	80% 1 8% 9% 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	21% 18% 36% 17% 6% 1	300
	11th to 20th	Day	24% 16% 39% 17% 4 1	300
	21st to end	Day	26% 15% 34% 21% 3	330
February	1st to 10th	Day	24% 22% 32% 16% 5% 1	300
	11th to 20th	Day	24% 27% 31% 15% 3	300
	21st to end	Day	26% 27% 36% 10% 2	249
March	1st to 10th	Day	22% 23% 38% 12% 4	300
	11th to 20th	Day	25% 19% 31% 18% 5% 1	402
	21st to end	Day	30% 16% 30% 18% 5% 1	550
April	1st to 10th	Day	27% 16% 33% 18% 5% 1	500
	11th to 20th	Day	24% 22% 28% 17% 7% 2	492
	21st to end	Day	26% 12% 34% 18% 9% 2	500
May	1st to 10th	Day	26% 13% 31% 20% 8% 2	503
	11th to 20th	Day	20% 9% 31% 23% 12% 4	542
	21st to end	Day	16% 8% 32% 25% 13% 5%	789
June	1st to 10th	Day	12% 9% 33% 29% 13% 4	730
	11th to 20th	Day	13% 8% 29% 31% 16% 4	730
	21st to end	Day	13% 6% 31% 30% 15% 4	730
July	1st to 10th	Day	10% 4 25% 30% 22% 9%	721
	11th to 20th	Day	11% 4 30% 32% 16% 7%	718
	21st to end	Day	8% 3 26% 36% 21% 6%	740
August	1st to 10th	Day	11% 3 19% 32% 25% 11%	531
	11th to 20th	Day	12% 4 25% 24% 27% 8%	479
	21st to end	Day	10% 4 19% 33% 24% 9%	539
September	1st to 10th	Day	15% 5% 20% 32% 20% 8%	490
	11th to 20th	Day	11% 3 18% 29% 26% 13%	490
	21st to end	Day	18% 11% 20% 24% 18% 9%	490
October	1st to 10th	Day	20% 8% 24% 29% 16% 3	490
	11th to 20th	Day	26% 13% 31% 24% 6%	357
	21st to end	Day	38% 10% 30% 18% 4	330
November	1st to 10th	Day	23% 16% 29% 24% 8% 1	300
	11th to 20th	Day	29% 20% 29% 17% 5%	300
	21st to end	Day	36% 13% 36% 13% 2	300
December	1st to 10th	Day	26% 22% 31% 15% 6%	300
	11th to 20th	Day	24% 27% 32% 13% 3 1	300
	21st to end	Day	28% 24% 30% 17% 2	330
January	1st to 10th	Night	27% 15% 32% 21% 5%	1000
	11th to 20th	Night	28% 16% 33% 19% 4 1	1000
	21st to end	Night	26% 14% 32% 24% 4	1100
February	1st to 10th	Night	28% 12% 35% 23% 3	852
	11th to 20th	Night	25% 15% 31% 24% 4	783
	21st to end	Night	27% 15% 37% 17% 3	660
March	1st to 10th	Night	24% 14% 31% 25% 6% 1	800
	11th to 20th	Night	20% 13% 34% 25% 7% 1	800
	21st to end	Night	26% 8% 30% 28% 7% 1	758
April	1st to 10th	Night	22% 13% 34% 25% 7% 1	600
	11th to 20th	Night	26% 10% 30% 26% 7% 1	593
	21st to end	Night	22% 10% 31% 28% 9% 1	600
May	1st to 10th	Night	21% 5% 30% 33% 10% 1	600
	11th to 20th	Night	22% 4 24% 34% 15% 1	591
	21st to end	Night	14% 3 25% 39% 18% 2	650
June	1st to 10th	Night	13% 3 22% 42% 18% 1	600
	11th to 20th	Night	14% 2 27% 40% 17% 1	600
	21st to end	Night	11% 3 23% 38% 23% 1	600
July	1st to 10th	Night	10% 1 16% 40% 28% 4	585
	11th to 20th	Night	11% 2 16% 40% 27% 4	582
	21st to end	Night	10% 1 14% 44% 29% 3	624
August	1st to 10th	Night	10% 1 12% 45% 30% 3	567
	11th to 20th	Night	10% 2 13% 40% 29% 5%	564
	21st to end	Night	12% 2 13% 38% 31% 4	627
September	1st to 10th	Night	14% 4 15% 38% 24% 5%	570
	11th to 20th	Night	12% 5% 15% 36% 28% 4	742
	21st to end	Night	18% 5% 23% 28% 21% 5%	760
October	1st to 10th	Night	20% 5% 22% 32% 20% 1	760
	11th to 20th	Night	30% 11% 24% 26% 8% 1	760
	21st to end	Night	34% 12% 27% 22% 6%	836
November	1st to 10th	Night	27% 12% 29% 22% 10% 1	780
	11th to 20th	Night	31% 16% 29% 21% 4 1	800
	21st to end	Night	33% 11% 30% 22% 4	800
December	1st to 10th	Night	29% 18% 31% 18% 4	955
	11th to 20th	Night	30% 13% 33% 20% 3	1000
	21st to end	Night	34% 14% 32% 17% 2	1100

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

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