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 2024-11-25.

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	12% 9% 3 8% 5% 4 4 4 6% 7% 37%	101679
	Night	13% 9% 3 8% 5% 4 4 3 5% 6% 39%	97893
Transparency	Day	44% 6% 12% 24% 13% 1	105208
	Night	44% 5% 11% 23% 15% 2	102491
Seeing	Day	16% 11% 30% 26% 13% 4	15961
	Night	17% 10% 32% 30% 11% 1	25825

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% 14% 10% 16% 5% 5% 3 2 4 5% 26%	2527
	11th to 20th	Day	10% 11% 5% 15% 6% 5% 6% 9% 8% 7% 19%	2530
	21st to end	Day	15% 18% 8% 13% 5% 3 4 3 3 6% 20%	3007
February	1st to 10th	Day	11% 13% 4 10% 5% 4 5% 5% 5% 7% 31%	1710
	11th to 20th	Day	13% 11% 3 7% 5% 4 5% 4 5% 7% 36%	1749
	21st to end	Day	12% 14% 4 8% 6% 4 4 4 4 6% 33%	1570
March	1st to 10th	Day	14% 8% 3 7% 4 3 4 3 4 6% 44%	3120
	11th to 20th	Day	10% 7% 3 8% 5% 4 5% 3 6% 7% 43%	3443
	21st to end	Day	21% 13% 3 10% 5% 4 4 3 5% 5% 26%	4059
April	1st to 10th	Day	18% 12% 3 8% 5% 5% 4 4 5% 6% 31%	2280
	11th to 20th	Day	16% 11% 4 8% 5% 4 4 3 5% 5% 34%	2254
	21st to end	Day	19% 9% 3 7% 5% 5% 4 3 5% 6% 33%	2297
May	1st to 10th	Day	15% 7% 3 8% 5% 4 5% 3 6% 6% 37%	4299
	11th to 20th	Day	12% 7% 3 7% 4 5% 4 4 5% 7% 42%	4399
	21st to end	Day	14% 7% 3 7% 5% 4 5% 4 6% 8% 39%	4824
June	1st to 10th	Day	11% 5% 2 5% 4 5% 5% 4 6% 9% 44%	2660
	11th to 20th	Day	11% 6% 2 6% 4 5% 5% 4 6% 9% 41%	2660
	21st to end	Day	11% 7% 3 7% 5% 5% 4 4 7% 8% 39%	2660
July	1st to 10th	Day	10% 7% 3 8% 5% 5% 6% 5% 8% 9% 34%	4440
	11th to 20th	Day	4 4 2 6% 4 4 5% 5% 7% 8% 51%	4440
	21st to end	Day	7% 6% 3 8% 5% 6% 5% 5% 7% 8% 40%	4813
August	1st to 10th	Day	9% 6% 2 6% 5% 5% 6% 5% 7% 9% 40%	4246
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 4 5% 8% 46%	3866
	21st to end	Day	8% 6% 2 6% 4 4 4 4 7% 9% 46%	4180
September	1st to 10th	Day	13% 5% 2 6% 5% 4 4 3 6% 7% 44%	2280
	11th to 20th	Day	12% 5% 2 5% 4 3 3 4 5% 8% 49%	2252
	21st to end	Day	13% 6% 2 6% 4 4 4 4 6% 7% 44%	2079
October	1st to 10th	Day	13% 7% 3 6% 4 4 3 4 4 6% 47%	1900
	11th to 20th	Day	18% 9% 3 6% 5% 3 4 3 5% 6% 38%	1900
	21st to end	Day	17% 9% 3 6% 4 4 3 3 4 5% 41%	1955
November	1st to 10th	Day	11% 9% 3 8% 5% 4 3 3 5% 7% 42%	1762
	11th to 20th	Day	14% 13% 3 8% 5% 5% 4 3 5% 6% 33%	1745
	21st to end	Day	14% 11% 4 8% 4 4 4 3 4 6% 37%	1552
December	1st to 10th	Day	12% 15% 4 10% 6% 4 4 4 5% 5% 31%	1520
	11th to 20th	Day	13% 12% 5% 11% 6% 4 5% 4 6% 7% 28%	1918
	21st to end	Day	16% 22% 9% 12% 5% 4 4 4 4 4 16%	2783
January	1st to 10th	Night	10% 12% 8% 13% 6% 5% 4 3 4 4 30%	4428
	11th to 20th	Night	11% 15% 6% 14% 7% 4 5% 4 8% 6% 21%	4440
	21st to end	Night	15% 18% 8% 11% 5% 5% 4 3 4 5% 22%	4658
February	1st to 10th	Night	11% 13% 4 10% 6% 6% 4 4 4 6% 32%	2470
	11th to 20th	Night	9% 11% 3 8% 6% 4 4 4 5% 6% 39%	2317
	21st to end	Night	15% 13% 3 8% 5% 4 3 3 5% 5% 36%	1884
March	1st to 10th	Night	16% 10% 3 6% 4 4 3 3 4 5% 41%	3733
	11th to 20th	Night	10% 6% 2 6% 4 4 4 4 6% 8% 47%	3545
	21st to end	Night	24% 13% 4 10% 5% 4 3 3 4 5% 26%	3571
April	1st to 10th	Night	17% 9% 3 7% 5% 4 4 3 5% 5% 38%	1900
	11th to 20th	Night	18% 8% 3 7% 4 4 4 4 4 5% 38%	1875
	21st to end	Night	16% 8% 2 7% 5% 5% 5% 3 6% 7% 36%	1881
May	1st to 10th	Night	16% 8% 3 7% 5% 4 4 4 6% 6% 36%	2600
	11th to 20th	Night	10% 9% 3 6% 5% 4 4 3 6% 7% 42%	2506
	21st to end	Night	9% 6% 3 7% 4 4 4 5% 6% 8% 45%	2743
June	1st to 10th	Night	9% 4 2 5% 5% 5% 5% 5% 6% 8% 46%	1520
	11th to 20th	Night	11% 6% 2 5% 4 3 5% 4 6% 10% 45%	1520
	21st to end	Night	9% 6% 2 5% 4 3 5% 4 5% 8% 49%	1520
July	1st to 10th	Night	13% 7% 3 6% 4 4 4 4 6% 8% 42%	2530
	11th to 20th	Night	4 3 1 5% 4 4 5% 4 5% 8% 58%	2530
	21st to end	Night	6% 5% 2 7% 4 4 4 4 7% 8% 49%	2750
August	1st to 10th	Night	8% 5% 2 5% 5% 4 5% 4 6% 8% 49%	2690
	11th to 20th	Night	9% 5% 2 5% 4 4 4 4 5% 8% 50%	2965
	21st to end	Night	9% 5% 2 6% 4 4 4 4 5% 8% 50%	3476
September	1st to 10th	Night	9% 5% 1 4 3 4 4 3 5% 7% 56%	1900
	11th to 20th	Night	10% 4 2 5% 4 4 5% 3 5% 7% 52%	1909
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 5% 6% 51%	2099
October	1st to 10th	Night	12% 6% 2 4 3 4 4 3 5% 5% 52%	2280
	11th to 20th	Night	15% 6% 2 6% 5% 3 4 3 5% 7% 43%	2280
	21st to end	Night	17% 9% 3 7% 4 4 4 4 5% 7% 37%	2641
November	1st to 10th	Night	12% 8% 3 6% 3 3 3 3 4 6% 48%	2536
	11th to 20th	Night	14% 11% 3 9% 5% 5% 4 4 5% 6% 35%	2650
	21st to end	Night	16% 10% 3 8% 4 4 3 3 5% 6% 38%	2723
December	1st to 10th	Night	13% 12% 4 10% 6% 5% 5% 4 5% 6% 30%	2660
	11th to 20th	Night	14% 12% 4 10% 6% 6% 5% 3 4 6% 29%	3279
	21st to end	Night	19% 16% 6% 12% 6% 5% 5% 3 5% 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	62% 4 12% 15% 7%	2528
	11th to 20th	Day	58% 7% 12% 14% 8% 1	2530
	21st to end	Day	66% 4 11% 14% 5%	3007
February	1st to 10th	Day	52% 4 13% 19% 11% 1	1710
	11th to 20th	Day	47% 6% 11% 25% 9% 2	1758
	21st to end	Day	52% 6% 9% 20% 10% 3	1570
March	1st to 10th	Day	42% 5% 10% 28% 13% 3	3120
	11th to 20th	Day	39% 5% 11% 32% 12% 1	3443
	21st to end	Day	60% 6% 12% 15% 6% 1	4059
April	1st to 10th	Day	54% 6% 9% 21% 10%	2280
	11th to 20th	Day	51% 5% 9% 21% 12% 2	2254
	21st to end	Day	50% 6% 11% 19% 12% 1	2297
May	1st to 10th	Day	46% 6% 11% 21% 16% 1	4338
	11th to 20th	Day	40% 7% 10% 31% 11%	4403
	21st to end	Day	42% 7% 10% 24% 14% 3	4837
June	1st to 10th	Day	35% 7% 14% 26% 16% 1	2660
	11th to 20th	Day	37% 8% 13% 23% 18% 1	2660
	21st to end	Day	41% 7% 13% 24% 13% 2	2660
July	1st to 10th	Day	43% 8% 14% 26% 8% 1	4371
	11th to 20th	Day	28% 6% 15% 32% 17% 1	4365
	21st to end	Day	39% 8% 13% 20% 18% 2	4662
August	1st to 10th	Day	38% 8% 14% 26% 13% 1	4231
	11th to 20th	Day	35% 6% 13% 31% 14% 1	3905
	21st to end	Day	34% 5% 14% 31% 15% 1	4179
September	1st to 10th	Day	38% 7% 11% 25% 18% 2	2280
	11th to 20th	Day	32% 6% 12% 32% 16% 2	2252
	21st to end	Day	39% 5% 11% 28% 16% 1	2079
October	1st to 10th	Day	24% 3 6% 39% 26% 1	3160
	11th to 20th	Day	34% 4 9% 27% 24% 3	3140
	21st to end	Day	42% 4 10% 27% 14% 3	3193
November	1st to 10th	Day	42% 4 14% 25% 12% 2	1762
	11th to 20th	Day	52% 4 12% 21% 10% 1	1745
	21st to end	Day	49% 5% 16% 22% 8% 1	1552
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	56% 5% 11% 19% 9% 1	4428
	11th to 20th	Night	61% 4 11% 15% 9%	4440
	21st to end	Night	65% 5% 8% 15% 5% 1	4658
February	1st to 10th	Night	53% 5% 10% 18% 12% 2	2470
	11th to 20th	Night	46% 5% 11% 23% 14% 1	2318
	21st to end	Night	50% 4 11% 21% 10% 3	1884
March	1st to 10th	Night	46% 5% 10% 24% 11% 4	3733
	11th to 20th	Night	33% 5% 11% 31% 17% 2	3545
	21st to end	Night	62% 4 7% 17% 9% 1	3571
April	1st to 10th	Night	47% 4 11% 23% 14% 2	1900
	11th to 20th	Night	48% 4 8% 19% 18% 3	1875
	21st to end	Night	46% 5% 12% 21% 13% 2	1881
May	1st to 10th	Night	46% 6% 11% 16% 19% 1	2626
	11th to 20th	Night	40% 7% 10% 25% 17% 1	2507
	21st to end	Night	33% 9% 13% 23% 20% 2	2751
June	1st to 10th	Night	33% 8% 13% 28% 18% 2	1520
	11th to 20th	Night	33% 7% 11% 25% 21% 3	1520
	21st to end	Night	34% 7% 14% 23% 18% 4	1520
July	1st to 10th	Night	39% 6% 17% 24% 12% 2	2490
	11th to 20th	Night	25% 6% 14% 35% 18% 2	2482
	21st to end	Night	30% 7% 18% 21% 20% 3	2662
August	1st to 10th	Night	32% 6% 13% 29% 19% 1	2681
	11th to 20th	Night	32% 6% 13% 32% 17% 1	2992
	21st to end	Night	32% 6% 13% 27% 18% 4	3476
September	1st to 10th	Night	28% 5% 12% 28% 25% 2	1900
	11th to 20th	Night	32% 5% 11% 31% 18% 2	1909
	21st to end	Night	32% 6% 10% 29% 21% 1	2099
October	1st to 10th	Night	24% 4 6% 36% 29% 1	3800
	11th to 20th	Night	31% 4 10% 26% 27% 2	3779
	21st to end	Night	44% 4 9% 27% 15% 2	4340
November	1st to 10th	Night	38% 4 12% 26% 17% 2	2536
	11th to 20th	Night	50% 5% 12% 20% 12% 2	2650
	21st to end	Night	48% 5% 13% 24% 10% 1	2723
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	19% 14% 41% 21% 3 1	270
	21st to end	Day	22% 13% 36% 24% 5%	297
February	1st to 10th	Day	15% 19% 42% 19% 5%	270
	11th to 20th	Day	23% 20% 34% 17% 6%	270
	21st to end	Day	22% 20% 43% 12% 2	225
March	1st to 10th	Day	16% 19% 44% 16% 5%	270
	11th to 20th	Day	17% 21% 38% 15% 6% 3	270
	21st to end	Day	29% 12% 33% 17% 7% 1	439
April	1st to 10th	Day	27% 14% 34% 19% 5%	460
	11th to 20th	Day	26% 17% 26% 19% 12% 1	452
	21st to end	Day	23% 15% 26% 24% 10% 2	460
May	1st to 10th	Day	21% 13% 32% 25% 8% 1	590
	11th to 20th	Day	20% 11% 29% 25% 13% 3	675
	21st to end	Day	17% 10% 27% 25% 14% 7%	734
June	1st to 10th	Day	11% 8% 28% 31% 18% 4	680
	11th to 20th	Day	14% 6% 33% 29% 14% 4	680
	21st to end	Day	13% 8% 30% 31% 13% 5%	680
July	1st to 10th	Day	9% 4 17% 32% 26% 12%	671
	11th to 20th	Day	8% 5% 26% 31% 21% 9%	668
	21st to end	Day	8% 4 26% 34% 21% 7%	739
August	1st to 10th	Day	7% 4 23% 34% 23% 9%	676
	11th to 20th	Day	12% 7% 20% 28% 22% 11%	568
	21st to end	Day	9% 7% 21% 33% 22% 8%	539
September	1st to 10th	Day	16% 6% 24% 29% 19% 6%	490
	11th to 20th	Day	12% 3 21% 33% 22% 8%	490
	21st to end	Day	15% 10% 29% 24% 18% 3	479
October	1st to 10th	Day	17% 8% 31% 30% 13% 1	300
	11th to 20th	Day	25% 17% 32% 20% 6%	300
	21st to end	Day	25% 18% 29% 21% 5% 2	330
November	1st to 10th	Day	16% 16% 38% 21% 7% 2	300
	11th to 20th	Day	18% 21% 36% 16% 8% 1	300
	21st to end	Day	24% 9% 39% 22% 5%	282
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	18% 13% 39% 24% 5%	950
	21st to end	Night	20% 11% 36% 27% 5%	1045
February	1st to 10th	Night	17% 13% 39% 26% 5%	950
	11th to 20th	Night	16% 15% 40% 26% 4	843
	21st to end	Night	22% 16% 37% 20% 4	628
March	1st to 10th	Night	21% 13% 37% 22% 6% 1	760
	11th to 20th	Night	17% 11% 36% 28% 7% 1	609
	21st to end	Night	25% 11% 32% 25% 6%	627
April	1st to 10th	Night	20% 15% 37% 24% 4	570
	11th to 20th	Night	21% 14% 30% 29% 6% 1	563
	21st to end	Night	18% 9% 34% 28% 9% 1	570
May	1st to 10th	Night	19% 7% 36% 29% 7% 1	570
	11th to 20th	Night	17% 8% 30% 34% 10%	561
	21st to end	Night	15% 4 27% 36% 17% 1	617
June	1st to 10th	Night	11% 5% 26% 43% 15% 1	570
	11th to 20th	Night	14% 4 31% 36% 14%	570
	21st to end	Night	13% 3 25% 42% 16% 2	570
July	1st to 10th	Night	7% 3 16% 40% 31% 3	555
	11th to 20th	Night	8% 3 20% 43% 23% 3	552
	21st to end	Night	8% 3 17% 45% 26% 2	624
August	1st to 10th	Night	6% 3 17% 46% 26% 3	567
	11th to 20th	Night	10% 2 15% 40% 26% 6%	564
	21st to end	Night	11% 2 18% 44% 21% 4	627
September	1st to 10th	Night	11% 4 22% 37% 21% 6%	570
	11th to 20th	Night	12% 3 22% 35% 24% 5%	579
	21st to end	Night	12% 8% 26% 34% 19% 1	760
October	1st to 10th	Night	15% 7% 26% 33% 18% 1	760
	11th to 20th	Night	18% 11% 33% 29% 9%	760
	21st to end	Night	20% 12% 33% 26% 8%	836
November	1st to 10th	Night	17% 11% 38% 25% 9% 1	780
	11th to 20th	Night	19% 15% 38% 21% 6%	850
	21st to end	Night	20% 14% 35% 24% 7%	973
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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