Minneapolis
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Minneapolis clear sky chart from 2005-11-06 to 2024-11-04.

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% 9% 3 8% 5% 4 4 4 5% 7% 37%	101591
	Night	12% 10% 3 8% 5% 4 4 4 5% 6% 39%	97529
Transparency	Day	46% 3 13% 27% 11% 1	105197
	Night	45% 3 12% 26% 13% 1	102063
Seeing	Day	17% 13% 32% 25% 11% 2	16025
	Night	17% 11% 33% 28% 10% 1	25883

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% 6% 18% 6% 5% 4 2 5% 5% 20%	2527
	11th to 20th	Day	5% 12% 6% 15% 9% 7% 8% 7% 6% 5% 20%	2544
	21st to end	Day	8% 21% 8% 11% 6% 5% 4 3 5% 6% 23%	3135
February	1st to 10th	Day	9% 11% 6% 10% 7% 6% 6% 5% 6% 6% 30%	1710
	11th to 20th	Day	8% 12% 5% 9% 6% 6% 5% 4 6% 6% 33%	1664
	21st to end	Day	11% 13% 5% 11% 6% 5% 4 4 5% 7% 30%	1470
March	1st to 10th	Day	11% 12% 4 7% 5% 4 4 3 5% 7% 39%	3365
	11th to 20th	Day	10% 9% 3 9% 5% 4 4 3 5% 7% 40%	3480
	21st to end	Day	23% 11% 5% 11% 5% 4 4 3 3 5% 23%	3863
April	1st to 10th	Day	16% 10% 3 8% 5% 4 4 4 4 7% 35%	2280
	11th to 20th	Day	20% 11% 3 7% 4 5% 4 3 5% 5% 32%	2264
	21st to end	Day	21% 12% 3 6% 5% 4 4 4 5% 5% 30%	2470
May	1st to 10th	Day	17% 7% 2 5% 4 4 4 4 5% 8% 40%	4263
	11th to 20th	Day	14% 7% 2 6% 4 4 4 3 6% 7% 45%	4399
	21st to end	Day	17% 7% 2 7% 5% 5% 4 4 5% 8% 35%	4824
June	1st to 10th	Day	12% 5% 2 5% 3 4 4 4 6% 8% 46%	2660
	11th to 20th	Day	13% 7% 3 7% 5% 5% 5% 4 8% 8% 37%	2660
	21st to end	Day	11% 4 2 6% 5% 6% 5% 5% 7% 10% 39%	2660
July	1st to 10th	Day	11% 5% 2 6% 5% 5% 6% 5% 8% 10% 37%	4440
	11th to 20th	Day	6% 3 1 4 3 3 3 4 5% 8% 60%	4440
	21st to end	Day	7% 4 2 6% 4 5% 5% 5% 7% 9% 47%	4761
August	1st to 10th	Day	12% 6% 2 6% 4 4 4 5% 6% 8% 43%	4104
	11th to 20th	Day	13% 5% 2 6% 3 4 5% 4 6% 9% 44%	4041
	21st to end	Day	10% 6% 2 6% 5% 5% 4 3 6% 7% 46%	4324
September	1st to 10th	Day	11% 5% 2 5% 4 4 4 3 6% 8% 48%	2280
	11th to 20th	Day	13% 5% 1 4 4 4 4 4 7% 8% 45%	2252
	21st to end	Day	15% 6% 2 5% 4 4 4 4 5% 6% 44%	1998
October	1st to 10th	Day	17% 7% 3 6% 4 5% 3 4 4 6% 43%	1900
	11th to 20th	Day	15% 10% 3 7% 4 4 4 3 5% 7% 38%	1900
	21st to end	Day	17% 11% 3 7% 4 3 4 3 4 6% 37%	2066
November	1st to 10th	Day	12% 12% 4 9% 5% 4 4 4 5% 5% 37%	1586
	11th to 20th	Day	11% 14% 7% 12% 6% 4 4 3 5% 6% 28%	1520
	21st to end	Day	12% 12% 4 8% 6% 4 3 4 5% 7% 34%	1520
December	1st to 10th	Day	11% 13% 5% 13% 8% 6% 5% 3 4 6% 26%	1520
	11th to 20th	Day	11% 14% 6% 12% 7% 5% 5% 3 4 5% 28%	1918
	21st to end	Day	22% 15% 7% 17% 5% 4 3 3 3 4 17%	2783
January	1st to 10th	Night	10% 16% 7% 15% 6% 4 4 3 4 4 27%	4428
	11th to 20th	Night	7% 11% 6% 14% 7% 6% 9% 7% 7% 5% 21%	4412
	21st to end	Night	10% 22% 7% 11% 5% 5% 4 3 4 4 26%	4532
February	1st to 10th	Night	7% 12% 5% 11% 7% 6% 5% 3 4 6% 34%	2470
	11th to 20th	Night	6% 10% 3 9% 6% 6% 5% 4 5% 7% 39%	2403
	21st to end	Night	11% 11% 3 9% 7% 5% 4 3 5% 6% 37%	1984
March	1st to 10th	Night	8% 9% 3 7% 4 3 4 3 6% 7% 46%	3519
	11th to 20th	Night	9% 8% 3 8% 5% 5% 5% 4 6% 7% 40%	3480
	21st to end	Night	25% 12% 3 11% 4 3 3 2 4 4 28%	3768
April	1st to 10th	Night	15% 12% 3 6% 4 3 5% 3 6% 6% 37%	1900
	11th to 20th	Night	20% 11% 3 7% 4 3 3 3 5% 6% 34%	1862
	21st to end	Night	19% 10% 2 7% 4 4 4 4 4 6% 35%	1710
May	1st to 10th	Night	15% 7% 2 7% 5% 4 4 4 6% 5% 42%	2641
	11th to 20th	Night	14% 5% 2 4 3 3 4 3 4 8% 50%	2506
	21st to end	Night	14% 8% 3 6% 4 4 4 4 5% 7% 41%	2743
June	1st to 10th	Night	10% 6% 2 5% 4 3 4 3 6% 8% 49%	1520
	11th to 20th	Night	8% 6% 2 5% 5% 5% 5% 5% 6% 8% 46%	1520
	21st to end	Night	7% 5% 2 5% 3 4 4 3 7% 9% 51%	1520
July	1st to 10th	Night	11% 5% 2 4 4 3 5% 4 6% 10% 46%	2530
	11th to 20th	Night	4 2 1 4 3 3 4 4 6% 9% 59%	2530
	21st to end	Night	6% 4 2 4 4 4 4 4 6% 7% 56%	2800
August	1st to 10th	Night	12% 6% 2 6% 4 4 4 3 5% 7% 47%	2836
	11th to 20th	Night	14% 4 1 4 2 3 4 4 5% 9% 50%	2798
	21st to end	Night	9% 6% 3 7% 4 4 4 4 5% 6% 47%	3334
September	1st to 10th	Night	8% 4 2 5% 4 3 4 4 4 8% 53%	1900
	11th to 20th	Night	10% 5% 1 5% 3 3 4 3 6% 7% 53%	1924
	21st to end	Night	13% 6% 2 5% 3 3 3 3 5% 5% 52%	2161
October	1st to 10th	Night	14% 6% 2 6% 3 4 3 3 4 6% 49%	2280
	11th to 20th	Night	15% 11% 2 5% 4 4 4 4 5% 6% 41%	2280
	21st to end	Night	18% 11% 4 6% 3 4 4 3 5% 6% 38%	2532
November	1st to 10th	Night	14% 9% 3 7% 4 4 4 4 5% 6% 42%	2563
	11th to 20th	Night	13% 12% 5% 12% 5% 4 4 3 4 5% 33%	2660
	21st to end	Night	14% 10% 3 9% 5% 5% 4 3 5% 6% 36%	2660
December	1st to 10th	Night	10% 12% 4 12% 7% 4 5% 4 5% 7% 31%	2660
	11th to 20th	Night	11% 15% 5% 12% 7% 5% 4 4 5% 6% 27%	3279
	21st to end	Night	22% 15% 5% 12% 5% 4 3 3 4 4 22%	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	67% 2 11% 16% 4	2528
	11th to 20th	Day	66% 2 10% 17% 5%	2544
	21st to end	Day	62% 3 13% 17% 4	3135
February	1st to 10th	Day	53% 4 13% 21% 8% 1	1710
	11th to 20th	Day	51% 4 11% 26% 8% 1	1673
	21st to end	Day	53% 4 11% 21% 11%	1470
March	1st to 10th	Day	47% 1 14% 27% 11%	3365
	11th to 20th	Day	45% 2 10% 32% 9% 1	3480
	21st to end	Day	65% 2 10% 19% 5%	3863
April	1st to 10th	Day	49% 3 12% 22% 12% 1	2280
	11th to 20th	Day	55% 2 9% 20% 12% 2	2264
	21st to end	Day	56% 3 11% 22% 8% 1	2470
May	1st to 10th	Day	45% 2 10% 27% 14% 2	4301
	11th to 20th	Day	40% 2 10% 31% 15% 2	4403
	21st to end	Day	49% 2 10% 28% 10% 1	4837
June	1st to 10th	Day	34% 4 15% 33% 13% 2	2660
	11th to 20th	Day	44% 4 13% 24% 14% 2	2660
	21st to end	Day	38% 4 16% 29% 10% 2	2660
July	1st to 10th	Day	40% 6% 19% 23% 11% 1	4371
	11th to 20th	Day	23% 4 16% 38% 18% 2	4365
	21st to end	Day	31% 6% 14% 31% 18% 1	4611
August	1st to 10th	Day	39% 4 12% 30% 13% 2	4090
	11th to 20th	Day	36% 5% 13% 35% 11%	4080
	21st to end	Day	37% 4 16% 29% 14% 1	4323
September	1st to 10th	Day	35% 4 13% 34% 14%	2280
	11th to 20th	Day	37% 3 16% 35% 9%	2252
	21st to end	Day	40% 3 11% 35% 11% 1	1998
October	1st to 10th	Day	32% 1 8% 36% 23%	3160
	11th to 20th	Day	40% 3 10% 28% 17% 1	3140
	21st to end	Day	44% 2 14% 30% 9%	3380
November	1st to 10th	Day	49% 3 13% 20% 13% 2	1586
	11th to 20th	Day	58% 3 13% 17% 9%	1520
	21st to end	Day	50% 3 17% 22% 7% 1	1520
December	1st to 10th	Day	60% 4 16% 15% 5%	1520
	11th to 20th	Day	59% 2 19% 16% 4	1915
	21st to end	Day	73% 2 8% 11% 5%	2783
January	1st to 10th	Night	62% 2 11% 19% 6%	4428
	11th to 20th	Night	63% 2 12% 16% 6%	4412
	21st to end	Night	64% 2 9% 19% 5% 1	4532
February	1st to 10th	Night	52% 3 11% 23% 10% 1	2470
	11th to 20th	Night	46% 3 14% 27% 9% 1	2404
	21st to end	Night	49% 2 11% 24% 12% 1	1984
March	1st to 10th	Night	39% 2 13% 28% 17% 1	3519
	11th to 20th	Night	44% 1 8% 29% 17% 1	3480
	21st to end	Night	62% 2 7% 22% 7% 1	3768
April	1st to 10th	Night	48% 3 8% 25% 14% 1	1900
	11th to 20th	Night	52% 2 7% 20% 16% 3	1862
	21st to end	Night	50% 3 8% 23% 14% 2	1710
May	1st to 10th	Night	44% 2 10% 21% 21% 1	2668
	11th to 20th	Night	34% 3 10% 29% 21% 4	2507
	21st to end	Night	44% 2 11% 26% 16% 1	2751
June	1st to 10th	Night	34% 2 13% 30% 19% 2	1520
	11th to 20th	Night	36% 4 15% 24% 19% 2	1520
	21st to end	Night	29% 2 16% 33% 16% 3	1520
July	1st to 10th	Night	34% 5% 20% 26% 14% 1	2490
	11th to 20th	Night	22% 4 14% 39% 19% 2	2482
	21st to end	Night	26% 5% 14% 33% 19% 3	2711
August	1st to 10th	Night	38% 3 11% 30% 14% 4	2826
	11th to 20th	Night	31% 4 15% 33% 16% 1	2825
	21st to end	Night	36% 5% 16% 28% 13% 2	3334
September	1st to 10th	Night	30% 3 12% 36% 18% 1	1900
	11th to 20th	Night	31% 3 16% 32% 17%	1924
	21st to end	Night	35% 2 12% 33% 17% 1	2161
October	1st to 10th	Night	25% 2 5% 36% 28% 4	3800
	11th to 20th	Night	35% 3 12% 25% 22% 3	3779
	21st to end	Night	45% 2 12% 29% 13%	4168
November	1st to 10th	Night	44% 3 12% 26% 14% 2	2563
	11th to 20th	Night	53% 3 12% 20% 11% 1	2660
	21st to end	Night	50% 3 16% 24% 7% 1	2660
December	1st to 10th	Night	53% 3 15% 22% 6%	2660
	11th to 20th	Night	58% 3 13% 18% 6% 2	3281
	21st to end	Night	68% 1 10% 16% 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	15% 12% 30% 28% 11% 3	270
	11th to 20th	Day	16% 15% 36% 27% 4 1	270
	21st to end	Day	17% 10% 41% 20% 10% 2	297
February	1st to 10th	Day	17% 15% 42% 20% 5%	270
	11th to 20th	Day	15% 22% 33% 23% 6% 1	270
	21st to end	Day	20% 15% 39% 23% 4	225
March	1st to 10th	Day	16% 19% 39% 19% 7%	270
	11th to 20th	Day	20% 12% 36% 23% 7% 2	270
	21st to end	Day	27% 18% 25% 20% 8% 2	321
April	1st to 10th	Day	23% 17% 34% 20% 5%	460
	11th to 20th	Day	33% 13% 26% 19% 9%	462
	21st to end	Day	29% 16% 27% 19% 7% 1	650
May	1st to 10th	Day	22% 18% 33% 19% 7% 1	653
	11th to 20th	Day	22% 13% 29% 24% 10% 2	675
	21st to end	Day	19% 10% 29% 26% 13% 2	734
June	1st to 10th	Day	11% 10% 33% 31% 14% 2	680
	11th to 20th	Day	15% 15% 38% 24% 8% 1	680
	21st to end	Day	14% 12% 33% 25% 14% 3	680
July	1st to 10th	Day	9% 7% 26% 34% 18% 7%	671
	11th to 20th	Day	10% 10% 30% 30% 16% 4	668
	21st to end	Day	6% 10% 30% 33% 17% 5%	739
August	1st to 10th	Day	10% 7% 29% 31% 19% 3	676
	11th to 20th	Day	16% 7% 23% 31% 19% 5%	665
	21st to end	Day	12% 8% 29% 32% 15% 4	631
September	1st to 10th	Day	15% 11% 30% 27% 15% 2	490
	11th to 20th	Day	15% 8% 32% 28% 16% 2	462
	21st to end	Day	17% 17% 30% 21% 12% 2	300
October	1st to 10th	Day	22% 14% 29% 22% 11% 3	300
	11th to 20th	Day	20% 24% 38% 14% 4	300
	21st to end	Day	27% 18% 38% 11% 5%	330
November	1st to 10th	Day	21% 21% 34% 17% 6% 1	279
	11th to 20th	Day	19% 23% 38% 17% 3	270
	21st to end	Day	23% 18% 42% 12% 4	270
December	1st to 10th	Day	16% 17% 35% 24% 7% 1	270
	11th to 20th	Day	20% 19% 32% 24% 4	270
	21st to end	Day	30% 14% 34% 19% 2	297
January	1st to 10th	Night	13% 14% 37% 28% 7% 1	950
	11th to 20th	Night	17% 14% 35% 27% 5% 1	950
	21st to end	Night	19% 14% 34% 26% 6%	1045
February	1st to 10th	Night	15% 15% 38% 25% 7%	950
	11th to 20th	Night	12% 16% 40% 24% 7% 1	929
	21st to end	Night	19% 13% 35% 25% 8%	728
March	1st to 10th	Night	17% 12% 35% 26% 9% 1	636
	11th to 20th	Night	19% 13% 36% 26% 7%	570
	21st to end	Night	23% 11% 29% 23% 11% 2	627
April	1st to 10th	Night	22% 14% 33% 25% 5%	570
	11th to 20th	Night	26% 12% 29% 26% 6% 1	563
	21st to end	Night	24% 12% 32% 23% 9% 1	570
May	1st to 10th	Night	20% 13% 32% 29% 5% 1	570
	11th to 20th	Night	17% 9% 37% 27% 9% 1	561
	21st to end	Night	16% 10% 28% 34% 13%	617
June	1st to 10th	Night	13% 6% 32% 39% 10%	570
	11th to 20th	Night	11% 6% 36% 39% 7%	570
	21st to end	Night	11% 6% 28% 38% 15% 1	570
July	1st to 10th	Night	6% 3 26% 37% 25% 1	555
	11th to 20th	Night	6% 7% 30% 40% 16% 1	552
	21st to end	Night	6% 4 31% 39% 19% 2	624
August	1st to 10th	Night	7% 6% 22% 45% 19% 1	567
	11th to 20th	Night	13% 5% 21% 36% 23% 3	564
	21st to end	Night	10% 4 30% 33% 21% 1	627
September	1st to 10th	Night	9% 8% 28% 36% 16% 3	570
	11th to 20th	Night	11% 8% 36% 28% 15% 3	570
	21st to end	Night	15% 12% 31% 27% 14% 1	641
October	1st to 10th	Night	19% 11% 31% 26% 12% 1	760
	11th to 20th	Night	24% 11% 34% 23% 7% 1	760
	21st to end	Night	26% 13% 29% 25% 7%	836
November	1st to 10th	Night	20% 14% 32% 27% 6% 1	866
	11th to 20th	Night	20% 17% 32% 23% 7% 1	950
	21st to end	Night	20% 17% 34% 22% 7%	950
December	1st to 10th	Night	17% 13% 35% 27% 6% 1	950
	11th to 20th	Night	20% 14% 35% 25% 5% 1	950
	21st to end	Night	26% 14% 33% 22% 4	1045

Page generated at 2024-11-01 21:47:48. Version ac07

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