Mineral Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mineral Point clear sky chart from 2005-11-06 to 2024-01-14.

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% 8% 4 7% 6% 3 5% 5% 5% 7% 37%	74780
	Night	13% 9% 4 6% 6% 3 5% 4 5% 7% 39%	75004
Transparency	Day	46% 6% 13% 22% 12% 1	74480
	Night	45% 5% 12% 22% 14% 2	74824
Seeing	Day	17% 10% 29% 26% 14% 4	14720
	Night	17% 10% 32% 30% 11% 1	24713

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	10% 11% 7% 9% 6% 4 5% 4 6% 7% 30%	1517
	11th to 20th	Day	11% 14% 7% 13% 7% 3 6% 5% 4 7% 22%	1464
	21st to end	Day	12% 14% 6% 12% 8% 4 5% 5% 4 8% 22%	1710
February	1st to 10th	Day	12% 12% 6% 9% 5% 3 5% 6% 5% 7% 29%	1620
	11th to 20th	Day	14% 11% 4 6% 6% 3 6% 5% 5% 6% 34%	1655
	21st to end	Day	13% 14% 5% 7% 7% 3 5% 4 4 6% 32%	1480
March	1st to 10th	Day	13% 10% 5% 10% 5% 3 5% 4 5% 7% 34%	1800
	11th to 20th	Day	12% 9% 4 7% 5% 3 4 4 5% 8% 39%	1957
	21st to end	Day	20% 10% 4 7% 6% 3 4 4 5% 6% 30%	2312
April	1st to 10th	Day	18% 10% 4 7% 6% 3 6% 5% 5% 7% 30%	2160
	11th to 20th	Day	16% 11% 4 7% 6% 3 4 4 5% 5% 34%	2134
	21st to end	Day	19% 9% 4 7% 6% 4 4 4 5% 6% 32%	2176
May	1st to 10th	Day	16% 7% 4 7% 7% 4 6% 6% 7% 7% 30%	2460
	11th to 20th	Day	16% 8% 3 7% 5% 4 4 5% 6% 9% 33%	2479
	21st to end	Day	15% 6% 3 6% 6% 3 6% 6% 6% 8% 36%	2725
June	1st to 10th	Day	11% 4 2 5% 5% 3 5% 5% 6% 9% 45%	2520
	11th to 20th	Day	11% 6% 2 5% 5% 3 5% 5% 6% 9% 42%	2520
	21st to end	Day	10% 6% 3 6% 6% 4 6% 5% 6% 9% 40%	2520
July	1st to 10th	Day	7% 5% 2 5% 5% 3 5% 6% 7% 9% 47%	2520
	11th to 20th	Day	7% 4 2 5% 6% 4 5% 6% 7% 8% 46%	2520
	21st to end	Day	7% 5% 2 5% 5% 4 5% 5% 7% 10% 45%	2743
August	1st to 10th	Day	7% 4 3 5% 6% 4 7% 7% 8% 10% 40%	2414
	11th to 20th	Day	10% 6% 3 6% 5% 3 5% 5% 5% 8% 44%	2210
	21st to end	Day	10% 6% 3 6% 5% 3 5% 5% 7% 8% 46%	2376
September	1st to 10th	Day	13% 6% 2 5% 6% 3 4 5% 6% 7% 43%	2160
	11th to 20th	Day	12% 5% 2 4 4 2 3 4 5% 8% 50%	2134
	21st to end	Day	13% 6% 3 5% 5% 3 4 4 6% 7% 43%	1970
October	1st to 10th	Day	14% 7% 3 6% 4 3 4 5% 4 6% 45%	1800
	11th to 20th	Day	19% 9% 3 5% 6% 3 3 4 5% 6% 37%	1800
	21st to end	Day	18% 9% 4 6% 5% 3 3 4 4 5% 40%	1853
November	1st to 10th	Day	10% 8% 4 7% 6% 3 4 4 5% 7% 43%	1672
	11th to 20th	Day	15% 11% 5% 7% 6% 3 5% 4 5% 7% 33%	1658
	21st to end	Day	15% 10% 5% 7% 5% 2 4 4 4 6% 38%	1520
December	1st to 10th	Day	12% 14% 5% 9% 6% 3 5% 5% 5% 6% 31%	1520
	11th to 20th	Day	13% 11% 5% 9% 7% 3 5% 5% 6% 7% 28%	1918
	21st to end	Day	16% 20% 10% 11% 6% 3 4 5% 4 4 16%	2783
January	1st to 10th	Night	11% 11% 5% 9% 6% 4 5% 4 5% 5% 35%	2648
	11th to 20th	Night	13% 12% 6% 10% 8% 4 6% 4 4 6% 27%	2575
	21st to end	Night	13% 13% 6% 10% 7% 4 5% 4 5% 7% 26%	2644
February	1st to 10th	Night	11% 12% 5% 9% 7% 4 5% 4 4 6% 31%	2340
	11th to 20th	Night	10% 10% 4 7% 7% 3 5% 5% 5% 6% 38%	2191
	21st to end	Night	15% 13% 4 6% 6% 3 3 3 6% 5% 36%	1776
March	1st to 10th	Night	16% 10% 4 6% 5% 4 4 5% 4 6% 35%	2160
	11th to 20th	Night	13% 6% 3 6% 5% 3 6% 5% 6% 7% 41%	2017
	21st to end	Night	19% 12% 4 6% 6% 3 5% 5% 4 6% 30%	2043
April	1st to 10th	Night	17% 8% 4 6% 6% 3 4 4 5% 5% 38%	1800
	11th to 20th	Night	19% 8% 3 6% 5% 3 5% 5% 4 5% 38%	1775
	21st to end	Night	16% 8% 3 6% 6% 3 5% 4 6% 8% 35%	1782
May	1st to 10th	Night	16% 7% 3 6% 7% 3 5% 6% 5% 8% 35%	1497
	11th to 20th	Night	14% 11% 3 5% 5% 3 4 4 6% 8% 37%	1416
	21st to end	Night	12% 5% 3 5% 4 2 4 6% 5% 8% 45%	1551
June	1st to 10th	Night	9% 4 3 4 6% 3 5% 6% 5% 9% 47%	1440
	11th to 20th	Night	12% 6% 2 4 5% 3 5% 4 5% 10% 45%	1440
	21st to end	Night	9% 5% 3 4 4 3 4 5% 5% 8% 50%	1440
July	1st to 10th	Night	6% 3 2 4 4 3 4 4 5% 10% 55%	1440
	11th to 20th	Night	6% 4 2 4 4 3 4 5% 5% 8% 56%	1440
	21st to end	Night	6% 3 2 4 5% 3 5% 4 7% 9% 52%	1575
August	1st to 10th	Night	5% 4 2 4 5% 3 5% 6% 8% 9% 50%	1521
	11th to 20th	Night	9% 4 2 5% 4 3 3 5% 5% 9% 51%	1689
	21st to end	Night	8% 5% 3 4 4 3 3 4 4 7% 55%	1980
September	1st to 10th	Night	9% 5% 2 4 3 3 4 4 5% 7% 55%	1800
	11th to 20th	Night	11% 4 2 3 5% 3 4 5% 4 7% 53%	1808
	21st to end	Night	9% 5% 3 4 4 3 5% 5% 4 6% 51%	1988
October	1st to 10th	Night	12% 5% 2 4 4 3 4 4 5% 5% 51%	2160
	11th to 20th	Night	16% 6% 2 5% 6% 2 4 4 5% 7% 42%	2160
	21st to end	Night	17% 8% 3 6% 5% 3 4 4 5% 7% 37%	2502
November	1st to 10th	Night	12% 7% 3 6% 4 2 3 4 4 6% 49%	2406
	11th to 20th	Night	15% 10% 4 7% 6% 3 5% 4 5% 6% 35%	2517
	21st to end	Night	16% 9% 3 7% 5% 3 4 3 5% 6% 39%	2660
December	1st to 10th	Night	13% 11% 4 9% 6% 4 5% 5% 5% 6% 30%	2660
	11th to 20th	Night	14% 11% 5% 9% 7% 5% 6% 5% 4 6% 29%	3279
	21st to end	Night	19% 15% 6% 10% 8% 4 5% 4 4 4 19%	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	53% 5% 14% 16% 11%	1518
	11th to 20th	Day	61% 6% 11% 15% 7% 1	1464
	21st to end	Day	61% 5% 12% 13% 7% 1	1710
February	1st to 10th	Day	54% 4 13% 19% 8% 1	1620
	11th to 20th	Day	49% 6% 11% 23% 9% 2	1664
	21st to end	Day	54% 6% 9% 19% 10% 2	1480
March	1st to 10th	Day	51% 5% 13% 21% 8% 1	1800
	11th to 20th	Day	45% 5% 12% 23% 13% 2	1957
	21st to end	Day	56% 4 11% 20% 8% 1	2312
April	1st to 10th	Day	54% 6% 10% 20% 11% 1	2160
	11th to 20th	Day	51% 5% 9% 21% 12% 2	2134
	21st to end	Day	51% 6% 11% 19% 12% 1	2176
May	1st to 10th	Day	51% 7% 13% 21% 7% 1	2460
	11th to 20th	Day	48% 7% 12% 21% 11%	2483
	21st to end	Day	46% 7% 11% 20% 14% 2	2725
June	1st to 10th	Day	35% 7% 15% 27% 15% 1	2520
	11th to 20th	Day	37% 8% 13% 23% 18% 1	2520
	21st to end	Day	40% 8% 14% 24% 13% 1	2520
July	1st to 10th	Day	32% 8% 16% 29% 13% 2	2451
	11th to 20th	Day	34% 8% 16% 26% 14% 2	2445
	21st to end	Day	32% 8% 15% 27% 14% 3	2591
August	1st to 10th	Day	34% 10% 16% 28% 11% 1	2399
	11th to 20th	Day	37% 7% 13% 26% 14% 2	2210
	21st to end	Day	34% 6% 13% 27% 18% 2	2376
September	1st to 10th	Day	39% 7% 11% 25% 17% 2	2160
	11th to 20th	Day	33% 6% 12% 32% 15% 2	2134
	21st to end	Day	39% 5% 11% 28% 16% 1	1970
October	1st to 10th	Day	40% 5% 10% 30% 15%	1800
	11th to 20th	Day	48% 5% 11% 23% 13% 1	1800
	21st to end	Day	47% 5% 12% 23% 13% 1	1853
November	1st to 10th	Day	41% 4 14% 25% 13% 3	1672
	11th to 20th	Day	51% 4 13% 21% 10% 1	1658
	21st to end	Day	48% 5% 16% 22% 8% 1	1520
December	1st to 10th	Day	53% 5% 13% 18% 8% 2	1520
	11th to 20th	Day	55% 5% 16% 14% 8% 1	1915
	21st to end	Day	72% 5% 9% 10% 5%	2783
January	1st to 10th	Night	50% 4 11% 20% 13% 1	2648
	11th to 20th	Night	60% 4 13% 14% 8%	2575
	21st to end	Night	57% 6% 11% 16% 9% 1	2644
February	1st to 10th	Night	54% 5% 10% 18% 11% 2	2340
	11th to 20th	Night	47% 5% 12% 22% 13% 2	2192
	21st to end	Night	51% 4 11% 21% 10% 3	1776
March	1st to 10th	Night	50% 6% 13% 21% 10% 2	2160
	11th to 20th	Night	40% 6% 14% 22% 17% 2	2017
	21st to end	Night	56% 5% 9% 20% 9% 2	2043
April	1st to 10th	Night	47% 4 11% 22% 14% 2	1800
	11th to 20th	Night	49% 4 8% 19% 17% 3	1775
	21st to end	Night	47% 5% 12% 20% 13% 3	1782
May	1st to 10th	Night	46% 8% 13% 21% 13%	1497
	11th to 20th	Night	45% 6% 11% 23% 14% 1	1417
	21st to end	Night	36% 7% 14% 24% 17% 2	1552
June	1st to 10th	Night	33% 7% 13% 27% 18% 1	1440
	11th to 20th	Night	33% 7% 11% 25% 21% 3	1440
	21st to end	Night	32% 8% 15% 25% 17% 3	1440
July	1st to 10th	Night	24% 7% 15% 33% 18% 3	1400
	11th to 20th	Night	26% 7% 13% 30% 20% 4	1392
	21st to end	Night	26% 6% 20% 28% 17% 3	1487
August	1st to 10th	Night	28% 8% 15% 32% 15% 2	1512
	11th to 20th	Night	30% 6% 14% 30% 18% 1	1689
	21st to end	Night	29% 6% 12% 28% 20% 5%	1980
September	1st to 10th	Night	30% 6% 12% 26% 24% 2	1800
	11th to 20th	Night	32% 5% 11% 31% 18% 3	1808
	21st to end	Night	33% 6% 10% 29% 20% 1	1988
October	1st to 10th	Night	34% 6% 9% 28% 21% 2	2160
	11th to 20th	Night	42% 5% 13% 22% 18% 1	2160
	21st to end	Night	47% 5% 11% 23% 13% 1	2502
November	1st to 10th	Night	37% 4 12% 26% 18% 2	2406
	11th to 20th	Night	50% 5% 13% 20% 12% 1	2517
	21st to end	Night	47% 5% 13% 25% 10% 1	2660
December	1st to 10th	Night	54% 6% 12% 20% 8% 1	2660
	11th to 20th	Night	56% 5% 12% 18% 7% 1	3281
	21st to end	Night	68% 5% 8% 15% 4	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	17% 16% 31% 26% 9% 2	270
	11th to 20th	Day	21% 12% 39% 22% 4 2	249
	21st to end	Day	22% 12% 39% 22% 5%	264
February	1st to 10th	Day	16% 19% 43% 18% 4	240
	11th to 20th	Day	26% 20% 31% 18% 5%	240
	21st to end	Day	24% 22% 40% 12% 2	198
March	1st to 10th	Day	17% 18% 43% 16% 6%	240
	11th to 20th	Day	17% 20% 38% 16% 6% 3	240
	21st to end	Day	29% 12% 33% 17% 7% 2	398
April	1st to 10th	Day	26% 14% 35% 20% 6%	420
	11th to 20th	Day	26% 16% 26% 19% 12% 1	412
	21st to end	Day	23% 14% 26% 24% 11% 2	420
May	1st to 10th	Day	21% 13% 32% 25% 7% 1	543
	11th to 20th	Day	21% 12% 29% 24% 12% 3	625
	21st to end	Day	17% 9% 27% 24% 15% 8%	679
June	1st to 10th	Day	10% 7% 27% 32% 20% 5%	630
	11th to 20th	Day	15% 5% 31% 30% 15% 4	630
	21st to end	Day	12% 7% 29% 32% 14% 6%	630
July	1st to 10th	Day	9% 3 16% 32% 27% 12%	621
	11th to 20th	Day	9% 5% 26% 31% 21% 8%	618
	21st to end	Day	8% 4 27% 34% 21% 7%	684
August	1st to 10th	Day	7% 3 22% 35% 24% 10%	626
	11th to 20th	Day	11% 7% 19% 27% 23% 12%	524
	21st to end	Day	10% 7% 22% 32% 21% 8%	495
September	1st to 10th	Day	17% 6% 23% 30% 18% 6%	450
	11th to 20th	Day	13% 3 22% 32% 21% 8%	450
	21st to end	Day	15% 11% 29% 23% 19% 4	440
October	1st to 10th	Day	18% 8% 30% 30% 13% 1	270
	11th to 20th	Day	26% 17% 31% 19% 6%	270
	21st to end	Day	26% 18% 28% 21% 6% 2	297
November	1st to 10th	Day	15% 16% 38% 22% 7% 2	270
	11th to 20th	Day	17% 21% 36% 17% 8% 1	270
	21st to end	Day	24% 9% 40% 22% 5%	270
December	1st to 10th	Day	16% 17% 41% 18% 7% 1	270
	11th to 20th	Day	18% 13% 40% 23% 7% 1	270
	21st to end	Day	26% 18% 36% 19% 2	297
January	1st to 10th	Night	15% 16% 36% 25% 7% 1	950
	11th to 20th	Night	19% 13% 38% 25% 5%	920
	21st to end	Night	20% 12% 37% 26% 5%	990
February	1st to 10th	Night	18% 13% 39% 25% 5%	900
	11th to 20th	Night	16% 15% 39% 25% 5%	797
	21st to end	Night	23% 17% 36% 21% 4	592
March	1st to 10th	Night	22% 13% 37% 22% 6% 1	720
	11th to 20th	Night	18% 10% 36% 28% 7% 1	577
	21st to end	Night	24% 11% 32% 26% 7% 1	594
April	1st to 10th	Night	19% 14% 37% 24% 5%	540
	11th to 20th	Night	22% 13% 29% 29% 7% 1	533
	21st to end	Night	18% 9% 34% 29% 9% 1	540
May	1st to 10th	Night	19% 7% 36% 29% 8% 1	540
	11th to 20th	Night	18% 8% 30% 34% 10%	531
	21st to end	Night	15% 4 27% 35% 17% 1	584
June	1st to 10th	Night	11% 5% 25% 44% 15% 1	540
	11th to 20th	Night	15% 4 31% 36% 15%	540
	21st to end	Night	12% 3 24% 43% 16% 2	540
July	1st to 10th	Night	6% 3 16% 40% 33% 4	525
	11th to 20th	Night	8% 3 20% 44% 22% 3	522
	21st to end	Night	8% 3 17% 45% 25% 2	591
August	1st to 10th	Night	6% 2 16% 45% 27% 3	537
	11th to 20th	Night	10% 2 15% 40% 27% 6%	534
	21st to end	Night	11% 2 18% 44% 21% 4	594
September	1st to 10th	Night	12% 4 22% 37% 20% 6%	540
	11th to 20th	Night	12% 2 23% 35% 23% 5%	548
	21st to end	Night	12% 8% 26% 33% 19% 1	720
October	1st to 10th	Night	16% 7% 27% 31% 19% 1	720
	11th to 20th	Night	18% 11% 32% 29% 8%	720
	21st to end	Night	21% 12% 33% 26% 8%	792
November	1st to 10th	Night	16% 11% 39% 25% 9% 1	740
	11th to 20th	Night	18% 15% 38% 21% 6%	807
	21st to end	Night	20% 13% 36% 24% 7%	950
December	1st to 10th	Night	20% 13% 39% 23% 5%	950
	11th to 20th	Night	23% 10% 37% 24% 6% 1	950
	21st to end	Night	26% 14% 37% 20% 3	1045

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