Albert Lea
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Albert Lea 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	12% 9% 3 8% 5% 4 5% 4 6% 7% 37%	101523
	Night	12% 9% 3 9% 5% 4 4 3 5% 6% 39%	97596
Transparency	Day	44% 7% 13% 23% 12% 1	105157
	Night	43% 6% 13% 23% 14% 2	102102
Seeing	Day	16% 10% 31% 27% 13% 3	15954
	Night	15% 10% 34% 29% 10% 1	25805

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	8% 17% 6% 20% 8% 6% 5% 4 6% 5% 15%	2527
	11th to 20th	Day	6% 13% 5% 12% 8% 8% 8% 5% 10% 7% 18%	2662
	21st to end	Day	11% 17% 8% 16% 9% 5% 4 3 4 5% 18%	3135
February	1st to 10th	Day	7% 13% 5% 13% 9% 7% 6% 5% 5% 7% 24%	1710
	11th to 20th	Day	9% 12% 4 10% 6% 6% 6% 4 6% 7% 29%	1664
	21st to end	Day	13% 11% 3 12% 6% 5% 4 3 5% 7% 30%	1484
March	1st to 10th	Day	13% 9% 3 8% 4 3 4 3 5% 6% 41%	3400
	11th to 20th	Day	11% 8% 3 7% 5% 4 4 4 5% 8% 41%	3480
	21st to end	Day	23% 14% 5% 11% 6% 4 4 3 4 5% 21%	3835
April	1st to 10th	Day	18% 12% 3 9% 5% 4 4 3 5% 8% 29%	2280
	11th to 20th	Day	18% 12% 4 7% 5% 5% 4 3 5% 6% 33%	2254
	21st to end	Day	21% 11% 3 8% 5% 4 4 4 5% 5% 30%	2453
May	1st to 10th	Day	17% 8% 3 7% 4 4 5% 4 6% 8% 34%	4168
	11th to 20th	Day	12% 7% 3 6% 4 5% 4 4 6% 7% 42%	4399
	21st to end	Day	18% 7% 2 6% 4 4 4 4 5% 7% 38%	4824
June	1st to 10th	Day	11% 6% 2 7% 4 4 4 4 6% 7% 46%	2660
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 6% 9% 40%	2660
	21st to end	Day	11% 5% 3 6% 5% 4 5% 4 7% 8% 41%	2660
July	1st to 10th	Day	10% 6% 2 6% 5% 5% 5% 4 8% 10% 38%	4440
	11th to 20th	Day	6% 4 2 5% 4 4 4 4 5% 9% 55%	4440
	21st to end	Day	5% 5% 2 5% 4 4 6% 5% 7% 10% 46%	4633
August	1st to 10th	Day	10% 7% 3 7% 4 5% 4 4 6% 7% 43%	4104
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 7% 9% 39%	4041
	21st to end	Day	7% 5% 2 6% 4 5% 4 3 6% 8% 49%	4293
September	1st to 10th	Day	13% 5% 3 5% 3 3 3 4 5% 7% 49%	2280
	11th to 20th	Day	10% 6% 2 7% 4 4 4 3 6% 8% 48%	2241
	21st to end	Day	12% 7% 2 7% 4 4 4 4 6% 7% 44%	2005
October	1st to 10th	Day	15% 7% 3 5% 4 4 4 4 5% 7% 44%	1900
	11th to 20th	Day	15% 8% 3 5% 3 4 4 3 5% 6% 43%	1900
	21st to end	Day	16% 11% 3 8% 4 3 3 3 5% 6% 38%	2090
November	1st to 10th	Day	11% 10% 3 6% 4 4 3 5% 5% 8% 42%	1640
	11th to 20th	Day	12% 11% 5% 12% 6% 4 4 4 5% 5% 31%	1520
	21st to end	Day	13% 12% 4 7% 6% 4 3 3 5% 8% 36%	1520
December	1st to 10th	Day	12% 11% 4 13% 9% 6% 6% 4 6% 6% 25%	1520
	11th to 20th	Day	10% 13% 5% 12% 7% 5% 6% 5% 5% 6% 25%	1918
	21st to end	Day	19% 16% 7% 17% 5% 4 4 3 4 5% 16%	2783
January	1st to 10th	Night	9% 13% 6% 22% 7% 5% 5% 3 5% 5% 20%	4428
	11th to 20th	Night	6% 12% 5% 14% 8% 6% 7% 6% 10% 7% 19%	4307
	21st to end	Night	13% 16% 7% 15% 7% 5% 4 3 4 6% 20%	4532
February	1st to 10th	Night	7% 13% 5% 11% 7% 7% 4 4 6% 6% 30%	2470
	11th to 20th	Night	7% 11% 4 8% 6% 5% 5% 4 7% 6% 37%	2403
	21st to end	Night	12% 9% 3 9% 7% 5% 4 4 6% 6% 35%	1970
March	1st to 10th	Night	11% 8% 3 6% 4 3 3 3 4 6% 48%	3483
	11th to 20th	Night	11% 7% 3 6% 4 4 4 3 5% 8% 45%	3480
	21st to end	Night	25% 11% 4 11% 5% 3 3 3 3 5% 27%	3795
April	1st to 10th	Night	14% 11% 3 7% 5% 4 5% 3 4 5% 38%	1900
	11th to 20th	Night	18% 10% 3 7% 4 3 4 3 5% 6% 37%	1875
	21st to end	Night	19% 9% 3 6% 5% 4 4 3 4 6% 37%	1724
May	1st to 10th	Night	16% 6% 3 6% 4 4 4 3 5% 6% 42%	2735
	11th to 20th	Night	12% 6% 2 5% 4 3 4 3 5% 6% 49%	2506
	21st to end	Night	14% 8% 2 6% 4 3 4 3 5% 7% 45%	2743
June	1st to 10th	Night	9% 4 2 5% 4 4 4 4 7% 8% 50%	1520
	11th to 20th	Night	11% 5% 2 7% 4 4 4 4 6% 7% 46%	1520
	21st to end	Night	10% 4 2 4 3 3 3 3 5% 9% 52%	1520
July	1st to 10th	Night	9% 5% 2 6% 4 3 4 4 7% 9% 47%	2530
	11th to 20th	Night	3 3 1 4 4 3 4 3 6% 9% 61%	2530
	21st to end	Night	5% 3 1 4 4 4 3 4 6% 8% 58%	2927
August	1st to 10th	Night	10% 6% 3 6% 4 3 4 4 5% 7% 49%	2836
	11th to 20th	Night	12% 5% 2 4 3 3 3 3 5% 8% 51%	2798
	21st to end	Night	8% 5% 2 5% 4 3 4 3 4 6% 55%	3352
September	1st to 10th	Night	9% 4 1 5% 2 4 3 3 4 7% 59%	1900
	11th to 20th	Night	11% 4 2 5% 3 3 3 3 5% 8% 53%	1936
	21st to end	Night	10% 6% 3 5% 3 3 3 2 5% 6% 54%	2156
October	1st to 10th	Night	13% 7% 2 6% 3 4 3 3 4 6% 50%	2280
	11th to 20th	Night	14% 8% 2 5% 4 3 4 3 4 6% 46%	2280
	21st to end	Night	16% 9% 4 7% 4 4 3 3 4 6% 39%	2508
November	1st to 10th	Night	12% 8% 3 5% 4 4 4 4 5% 5% 46%	2509
	11th to 20th	Night	11% 10% 4 11% 5% 5% 5% 3 5% 6% 36%	2660
	21st to end	Night	13% 11% 3 7% 5% 4 4 3 4 6% 40%	2660
December	1st to 10th	Night	9% 11% 4 10% 7% 6% 5% 4 5% 7% 30%	2660
	11th to 20th	Night	12% 11% 4 11% 7% 6% 5% 4 5% 6% 28%	3279
	21st to end	Night	19% 16% 5% 15% 6% 4 4 3 4 5% 18%	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	69% 6% 10% 10% 5%	2528
	11th to 20th	Day	60% 5% 11% 17% 7%	2662
	21st to end	Day	69% 5% 11% 11% 3 1	3135
February	1st to 10th	Day	57% 7% 13% 14% 9% 1	1710
	11th to 20th	Day	52% 6% 12% 21% 7% 2	1673
	21st to end	Day	54% 5% 12% 18% 10% 1	1484
March	1st to 10th	Day	42% 6% 12% 26% 12% 1	3400
	11th to 20th	Day	38% 8% 11% 30% 12% 2	3480
	21st to end	Day	65% 6% 10% 13% 5%	3835
April	1st to 10th	Day	53% 6% 13% 19% 8% 1	2280
	11th to 20th	Day	51% 7% 12% 18% 12% 1	2254
	21st to end	Day	55% 7% 11% 18% 8% 1	2453
May	1st to 10th	Day	44% 8% 15% 20% 11%	4206
	11th to 20th	Day	37% 10% 13% 28% 11% 1	4403
	21st to end	Day	43% 9% 12% 24% 12% 1	4837
June	1st to 10th	Day	35% 8% 14% 28% 14% 1	2660
	11th to 20th	Day	38% 9% 14% 20% 17% 1	2660
	21st to end	Day	37% 9% 17% 24% 12% 1	2660
July	1st to 10th	Day	39% 9% 19% 25% 8% 1	4371
	11th to 20th	Day	26% 6% 15% 32% 19% 1	4365
	21st to end	Day	29% 11% 17% 27% 15% 1	4487
August	1st to 10th	Day	39% 7% 12% 28% 12% 2	4090
	11th to 20th	Day	39% 8% 17% 27% 9%	4080
	21st to end	Day	32% 7% 17% 27% 16% 1	4292
September	1st to 10th	Day	34% 7% 12% 30% 16% 1	2280
	11th to 20th	Day	34% 7% 16% 31% 12%	2241
	21st to end	Day	38% 7% 12% 27% 16% 1	2005
October	1st to 10th	Day	26% 4 8% 37% 24% 1	3160
	11th to 20th	Day	35% 5% 14% 23% 22% 1	3140
	21st to end	Day	42% 4 11% 31% 11%	3428
November	1st to 10th	Day	40% 7% 14% 21% 15% 3	1640
	11th to 20th	Day	54% 5% 12% 18% 10% 1	1520
	21st to end	Day	48% 5% 17% 21% 9% 1	1520
December	1st to 10th	Day	57% 8% 15% 11% 8% 1	1520
	11th to 20th	Day	57% 6% 17% 13% 6%	1915
	21st to end	Day	69% 6% 10% 11% 4 1	2783
January	1st to 10th	Night	65% 6% 9% 14% 6%	4428
	11th to 20th	Night	59% 6% 11% 16% 8%	4307
	21st to end	Night	64% 6% 11% 13% 5% 1	4532
February	1st to 10th	Night	53% 6% 11% 20% 9% 1	2470
	11th to 20th	Night	45% 6% 14% 23% 10% 2	2404
	21st to end	Night	47% 6% 12% 20% 13% 2	1970
March	1st to 10th	Night	37% 6% 11% 31% 14% 1	3483
	11th to 20th	Night	36% 6% 10% 29% 18% 2	3480
	21st to end	Night	60% 6% 10% 15% 8% 2	3795
April	1st to 10th	Night	48% 6% 11% 21% 14% 1	1900
	11th to 20th	Night	46% 7% 12% 18% 16% 2	1875
	21st to end	Night	47% 6% 10% 21% 14% 2	1724
May	1st to 10th	Night	41% 7% 11% 19% 21% 1	2762
	11th to 20th	Night	34% 8% 12% 25% 17% 5%	2507
	21st to end	Night	38% 7% 11% 26% 17% 1	2751
June	1st to 10th	Night	30% 8% 14% 30% 16% 2	1520
	11th to 20th	Night	35% 8% 14% 22% 18% 3	1520
	21st to end	Night	28% 7% 17% 29% 17% 3	1520
July	1st to 10th	Night	31% 7% 21% 27% 12% 1	2490
	11th to 20th	Night	20% 6% 17% 35% 19% 2	2482
	21st to end	Night	23% 8% 18% 30% 20% 2	2834
August	1st to 10th	Night	34% 6% 13% 28% 17% 3	2826
	11th to 20th	Night	32% 7% 16% 30% 14% 1	2825
	21st to end	Night	30% 6% 18% 26% 18% 2	3352
September	1st to 10th	Night	26% 6% 13% 31% 22% 2	1900
	11th to 20th	Night	29% 7% 15% 31% 17% 1	1936
	21st to end	Night	32% 5% 11% 29% 21% 2	2156
October	1st to 10th	Night	24% 4 6% 32% 31% 3	3800
	11th to 20th	Night	27% 5% 14% 27% 23% 5%	3779
	21st to end	Night	45% 4 10% 26% 14% 1	4120
November	1st to 10th	Night	39% 6% 14% 23% 16% 3	2509
	11th to 20th	Night	49% 6% 12% 20% 12% 1	2660
	21st to end	Night	46% 5% 14% 24% 10% 1	2660
December	1st to 10th	Night	53% 7% 15% 17% 7% 1	2660
	11th to 20th	Night	54% 6% 15% 18% 5%	3281
	21st to end	Night	68% 6% 10% 12% 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% 14% 37% 20% 8% 3	270
	11th to 20th	Day	19% 12% 44% 20% 4 1	270
	21st to end	Day	14% 12% 39% 26% 7% 2	297
February	1st to 10th	Day	12% 16% 44% 23% 4 1	270
	11th to 20th	Day	17% 14% 40% 24% 5% 1	270
	21st to end	Day	22% 16% 39% 21% 2	225
March	1st to 10th	Day	16% 17% 39% 22% 6%	270
	11th to 20th	Day	23% 9% 36% 25% 7% 1	270
	21st to end	Day	31% 11% 31% 19% 8% 1	306
April	1st to 10th	Day	28% 12% 34% 20% 4	460
	11th to 20th	Day	27% 15% 26% 23% 8% 1	452
	21st to end	Day	27% 15% 26% 21% 9% 2	633
May	1st to 10th	Day	20% 13% 36% 23% 6% 2	653
	11th to 20th	Day	21% 11% 28% 25% 12% 4	675
	21st to end	Day	21% 8% 29% 25% 14% 3	734
June	1st to 10th	Day	11% 8% 27% 29% 20% 5%	680
	11th to 20th	Day	13% 7% 33% 31% 13% 3	680
	21st to end	Day	13% 8% 31% 29% 15% 4	680
July	1st to 10th	Day	8% 4 20% 35% 23% 10%	671
	11th to 20th	Day	9% 4 29% 31% 19% 7%	668
	21st to end	Day	6% 3 26% 37% 20% 7%	739
August	1st to 10th	Day	9% 5% 21% 32% 26% 6%	676
	11th to 20th	Day	13% 5% 22% 30% 25% 5%	665
	21st to end	Day	12% 5% 26% 34% 18% 6%	613
September	1st to 10th	Day	15% 6% 28% 31% 15% 5%	490
	11th to 20th	Day	11% 5% 31% 33% 16% 4	451
	21st to end	Day	17% 10% 31% 25% 13% 4	300
October	1st to 10th	Day	19% 11% 27% 26% 13% 3	300
	11th to 20th	Day	19% 17% 38% 19% 6% 1	300
	21st to end	Day	24% 17% 35% 18% 5% 1	330
November	1st to 10th	Day	16% 17% 35% 24% 6% 2	279
	11th to 20th	Day	16% 24% 39% 16% 6%	270
	21st to end	Day	21% 14% 41% 21% 2	270
December	1st to 10th	Day	15% 12% 40% 27% 6% 1	270
	11th to 20th	Day	16% 15% 40% 23% 6% 1	270
	21st to end	Day	27% 17% 33% 20% 2	297
January	1st to 10th	Night	12% 13% 43% 24% 8%	950
	11th to 20th	Night	16% 13% 38% 28% 5% 1	950
	21st to end	Night	19% 14% 36% 25% 6%	1045
February	1st to 10th	Night	15% 13% 40% 26% 5% 1	950
	11th to 20th	Night	14% 15% 41% 24% 6% 1	929
	21st to end	Night	17% 15% 37% 24% 6% 1	714
March	1st to 10th	Night	17% 13% 39% 24% 7%	612
	11th to 20th	Night	18% 11% 38% 25% 8%	570
	21st to end	Night	24% 9% 33% 24% 7% 2	627
April	1st to 10th	Night	18% 16% 35% 27% 3	570
	11th to 20th	Night	23% 14% 33% 24% 6% 1	563
	21st to end	Night	24% 11% 31% 25% 7% 2	570
May	1st to 10th	Night	18% 12% 32% 30% 8% 1	570
	11th to 20th	Night	16% 10% 32% 32% 9% 1	561
	21st to end	Night	20% 7% 28% 32% 13%	617
June	1st to 10th	Night	10% 5% 30% 40% 14% 1	570
	11th to 20th	Night	12% 5% 32% 39% 12%	570
	21st to end	Night	12% 4 25% 43% 15% 1	570
July	1st to 10th	Night	7% 2 20% 38% 31% 2	555
	11th to 20th	Night	4 3 25% 41% 25% 2	552
	21st to end	Night	5% 2 20% 49% 21% 3	624
August	1st to 10th	Night	7% 2 18% 46% 24% 2	567
	11th to 20th	Night	10% 3 17% 41% 25% 3	564
	21st to end	Night	8% 2 26% 41% 21% 2	627
September	1st to 10th	Night	11% 4 26% 38% 18% 3	570
	11th to 20th	Night	11% 5% 31% 35% 16% 2	570
	21st to end	Night	11% 9% 33% 31% 15% 1	636
October	1st to 10th	Night	15% 10% 31% 30% 13% 1	760
	11th to 20th	Night	18% 12% 35% 27% 7%	760
	21st to end	Night	22% 13% 30% 27% 8%	836
November	1st to 10th	Night	16% 13% 38% 26% 6% 1	831
	11th to 20th	Night	16% 15% 42% 22% 5%	950
	21st to end	Night	18% 14% 38% 23% 7%	950
December	1st to 10th	Night	15% 13% 39% 26% 7%	950
	11th to 20th	Night	20% 11% 40% 23% 6%	950
	21st to end	Night	24% 13% 37% 22% 4	1045

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