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 2025-08-05.

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%	126189
	Night	12% 9% 3 9% 5% 4 4 3 5% 6% 39%	122168
Transparency	Day	44% 6% 13% 24% 12% 1	129783
	Night	44% 6% 13% 23% 14% 1	126650
Seeing	Day	17% 10% 31% 27% 12% 3	17009
	Night	16% 10% 34% 29% 10% 1	26853

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	6% 14% 5% 20% 11% 8% 6% 4 6% 5% 15%	3617
	11th to 20th	Day	6% 11% 5% 13% 7% 7% 9% 7% 12% 6% 17%	3822
	21st to end	Day	8% 14% 8% 13% 7% 4 5% 4 4 5% 28%	4488
February	1st to 10th	Day	8% 13% 5% 13% 9% 7% 6% 5% 5% 7% 24%	1800
	11th to 20th	Day	9% 13% 3 10% 6% 6% 6% 4 6% 7% 29%	1754
	21st to end	Day	13% 10% 3 12% 6% 4 4 3 5% 7% 32%	1560
March	1st to 10th	Day	13% 7% 3 7% 4 3 4 3 5% 6% 45%	4886
	11th to 20th	Day	11% 7% 3 6% 4 3 4 4 5% 9% 45%	4980
	21st to end	Day	22% 12% 4 10% 6% 4 4 3 4 6% 25%	5497
April	1st to 10th	Day	18% 12% 3 8% 5% 4 4 3 5% 8% 29%	2400
	11th to 20th	Day	18% 12% 4 7% 5% 5% 4 3 5% 6% 32%	2374
	21st to end	Day	21% 11% 3 7% 4 4 4 4 5% 5% 30%	2582
May	1st to 10th	Day	13% 7% 2 6% 4 4 4 3 6% 7% 45%	5990
	11th to 20th	Day	14% 7% 2 5% 4 4 3 3 5% 6% 46%	6319
	21st to end	Day	19% 7% 2 6% 4 5% 4 3 5% 7% 37%	6935
June	1st to 10th	Day	11% 6% 2 7% 4 4 4 4 6% 7% 46%	2800
	11th to 20th	Day	13% 7% 2 6% 4 4 5% 4 6% 9% 39%	2800
	21st to end	Day	12% 5% 3 5% 5% 4 5% 4 7% 8% 40%	2800
July	1st to 10th	Day	9% 5% 2 6% 4 5% 5% 4 7% 9% 43%	6360
	11th to 20th	Day	8% 5% 2 5% 4 3 4 4 5% 8% 53%	6360
	21st to end	Day	8% 5% 2 6% 5% 4 6% 4 7% 10% 43%	6660
August	1st to 10th	Day	10% 7% 3 7% 4 4 4 4 6% 7% 44%	4157
	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	12% 10% 3 6% 4 4 3 5% 5% 8% 40%	1698
	11th to 20th	Day	11% 12% 6% 12% 6% 4 5% 4 5% 5% 31%	1600
	21st to end	Day	12% 12% 5% 8% 6% 4 3 3 5% 8% 35%	1600
December	1st to 10th	Day	7% 7% 3 11% 9% 8% 6% 5% 7% 8% 29%	2610
	11th to 20th	Day	10% 14% 6% 13% 12% 8% 6% 4 4 5% 18%	3008
	21st to end	Day	19% 19% 7% 19% 5% 4 3 3 3 4 14%	3982
January	1st to 10th	Night	7% 10% 5% 22% 8% 8% 7% 4 5% 5% 20%	6348
	11th to 20th	Night	6% 10% 4 12% 8% 7% 9% 8% 9% 7% 20%	6157
	21st to end	Night	10% 12% 6% 12% 6% 5% 5% 3 5% 6% 31%	6490
February	1st to 10th	Night	8% 13% 5% 11% 7% 7% 4 4 6% 6% 30%	2600
	11th to 20th	Night	7% 11% 4 9% 6% 5% 5% 4 7% 6% 36%	2533
	21st to end	Night	12% 9% 3 9% 7% 5% 4 4 6% 7% 36%	2070
March	1st to 10th	Night	12% 7% 3 5% 4 3 3 3 4 6% 51%	5011
	11th to 20th	Night	10% 7% 3 6% 4 4 4 3 6% 8% 47%	4980
	21st to end	Night	23% 10% 4 10% 4 3 3 3 3 5% 29%	5431
April	1st to 10th	Night	14% 11% 3 7% 5% 4 5% 3 4 5% 38%	2000
	11th to 20th	Night	17% 10% 3 6% 4 3 4 3 5% 6% 37%	1975
	21st to end	Night	19% 9% 3 6% 5% 4 4 3 4 6% 37%	1815
May	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 5% 6% 51%	3923
	11th to 20th	Night	12% 7% 2 6% 4 3 4 3 4 6% 50%	3596
	21st to end	Night	18% 9% 3 6% 4 3 4 3 4 6% 40%	3942
June	1st to 10th	Night	9% 4 2 5% 4 4 4 4 7% 8% 50%	1600
	11th to 20th	Night	11% 5% 2 7% 5% 4 4 4 6% 8% 45%	1600
	21st to end	Night	11% 5% 2 4 3 3 3 4 5% 9% 52%	1600
July	1st to 10th	Night	7% 4 2 5% 4 3 4 4 8% 10% 48%	3618
	11th to 20th	Night	6% 5% 1 4 4 3 3 3 6% 9% 55%	3617
	21st to end	Night	9% 4 2 5% 3 4 4 4 6% 7% 52%	4208
August	1st to 10th	Night	10% 6% 3 6% 4 3 4 4 5% 7% 49%	2872
	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% 9% 3 6% 4 4 4 4 5% 5% 45%	2597
	11th to 20th	Night	11% 10% 4 10% 5% 5% 5% 3 5% 6% 36%	2800
	21st to end	Night	13% 11% 3 8% 5% 5% 4 3 4 6% 38%	2800
December	1st to 10th	Night	6% 7% 3 11% 9% 8% 5% 4 6% 7% 32%	4580
	11th to 20th	Night	12% 13% 5% 14% 7% 5% 5% 3 4 6% 26%	5199
	21st to end	Night	20% 16% 7% 19% 6% 4 3 3 3 4 15%	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	70% 5% 9% 12% 4	3618
	11th to 20th	Day	59% 5% 9% 15% 13%	3822
	21st to end	Day	59% 5% 14% 14% 8% 1	4488
February	1st to 10th	Day	58% 7% 12% 14% 9% 1	1800
	11th to 20th	Day	52% 6% 12% 21% 7% 2	1763
	21st to end	Day	53% 5% 13% 19% 10% 1	1560
March	1st to 10th	Day	39% 5% 15% 28% 11% 2	4886
	11th to 20th	Day	36% 6% 13% 30% 13% 2	4980
	21st to end	Day	61% 5% 12% 15% 6%	5499
April	1st to 10th	Day	53% 6% 13% 19% 8% 1	2400
	11th to 20th	Day	51% 6% 12% 17% 12% 1	2374
	21st to end	Day	54% 6% 12% 18% 8% 1	2582
May	1st to 10th	Day	36% 7% 13% 27% 16%	6028
	11th to 20th	Day	37% 7% 12% 26% 15% 3	6323
	21st to end	Day	44% 7% 11% 27% 10%	6949
June	1st to 10th	Day	35% 8% 14% 28% 14% 1	2800
	11th to 20th	Day	39% 9% 14% 20% 16% 1	2800
	21st to end	Day	38% 9% 17% 23% 12% 1	2800
July	1st to 10th	Day	35% 8% 17% 32% 8%	6291
	11th to 20th	Day	29% 6% 15% 32% 16% 1	6285
	21st to end	Day	34% 9% 16% 28% 13% 1	6471
August	1st to 10th	Day	39% 7% 12% 28% 12% 2	4143
	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	41% 7% 13% 21% 15% 3	1698
	11th to 20th	Day	54% 5% 12% 19% 10% 1	1600
	21st to end	Day	49% 5% 17% 21% 8% 1	1600
December	1st to 10th	Day	50% 8% 16% 18% 7% 1	2610
	11th to 20th	Day	68% 5% 12% 10% 5%	3005
	21st to end	Day	74% 5% 8% 9% 3	3982
January	1st to 10th	Night	65% 5% 10% 14% 6%	6348
	11th to 20th	Night	58% 5% 12% 13% 12% 1	6157
	21st to end	Night	53% 5% 13% 17% 11%	6490
February	1st to 10th	Night	53% 6% 12% 20% 9% 1	2600
	11th to 20th	Night	46% 6% 14% 23% 10% 2	2534
	21st to end	Night	46% 6% 12% 20% 13% 2	2070
March	1st to 10th	Night	35% 4 10% 33% 15% 2	5011
	11th to 20th	Night	34% 5% 12% 30% 17% 2	4980
	21st to end	Night	57% 6% 12% 14% 10% 1	5431
April	1st to 10th	Night	48% 6% 11% 21% 14% 1	2000
	11th to 20th	Night	45% 6% 12% 19% 15% 2	1975
	21st to end	Night	48% 6% 10% 21% 13% 2	1815
May	1st to 10th	Night	33% 6% 10% 29% 21% 1	3950
	11th to 20th	Night	34% 6% 11% 23% 19% 6%	3597
	21st to end	Night	44% 6% 10% 26% 13% 1	3950
June	1st to 10th	Night	30% 9% 14% 30% 15% 2	1600
	11th to 20th	Night	36% 8% 14% 21% 18% 3	1600
	21st to end	Night	28% 7% 17% 29% 17% 3	1600
July	1st to 10th	Night	29% 7% 21% 29% 13% 1	3580
	11th to 20th	Night	26% 6% 17% 34% 15% 1	3572
	21st to end	Night	31% 7% 17% 29% 16% 1	4086
August	1st to 10th	Night	34% 6% 13% 28% 17% 3	2862
	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% 15% 3	2597
	11th to 20th	Night	48% 6% 12% 20% 12% 2	2800
	21st to end	Night	47% 5% 14% 24% 9% 1	2800
December	1st to 10th	Night	49% 6% 17% 21% 7%	4580
	11th to 20th	Night	60% 5% 13% 18% 4	5201
	21st to end	Night	73% 5% 8% 10% 3	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	16% 15% 38% 21% 8% 3	300
	11th to 20th	Day	18% 13% 45% 18% 4 1	300
	21st to end	Day	13% 13% 42% 25% 6% 2	330
February	1st to 10th	Day	14% 15% 43% 23% 4 1	300
	11th to 20th	Day	17% 15% 39% 24% 4 1	300
	21st to end	Day	21% 15% 40% 22% 2	249
March	1st to 10th	Day	17% 16% 40% 22% 5%	300
	11th to 20th	Day	22% 10% 35% 26% 6% 1	300
	21st to end	Day	30% 12% 31% 18% 7% 1	340
April	1st to 10th	Day	28% 13% 33% 21% 4	500
	11th to 20th	Day	29% 15% 26% 22% 8% 1	492
	21st to end	Day	27% 15% 27% 21% 8% 2	682
May	1st to 10th	Day	20% 12% 34% 24% 9% 1	703
	11th to 20th	Day	22% 11% 26% 25% 12% 4	725
	21st to end	Day	21% 7% 29% 26% 13% 3	789
June	1st to 10th	Day	11% 8% 27% 30% 19% 5%	730
	11th to 20th	Day	13% 7% 33% 32% 13% 3	730
	21st to end	Day	14% 9% 31% 28% 14% 4	730
July	1st to 10th	Day	8% 4 21% 35% 23% 10%	721
	11th to 20th	Day	9% 5% 29% 32% 19% 7%	718
	21st to end	Day	7% 4 26% 37% 20% 6%	794
August	1st to 10th	Day	10% 5% 21% 32% 27% 6%	697
	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	18% 17% 35% 23% 6% 2	300
	11th to 20th	Day	18% 23% 39% 15% 6%	300
	21st to end	Day	20% 15% 41% 21% 2	300
December	1st to 10th	Day	14% 12% 44% 25% 5% 1	300
	11th to 20th	Day	16% 16% 40% 21% 6% 1	300
	21st to end	Day	27% 17% 34% 19% 2 1	330
January	1st to 10th	Night	12% 13% 43% 24% 8%	1000
	11th to 20th	Night	15% 14% 38% 28% 5% 1	1000
	21st to end	Night	18% 14% 37% 25% 6%	1100
February	1st to 10th	Night	15% 14% 41% 25% 5% 1	1000
	11th to 20th	Night	13% 15% 42% 23% 6% 1	979
	21st to end	Night	17% 15% 38% 24% 6% 1	750
March	1st to 10th	Night	17% 13% 39% 24% 7%	644
	11th to 20th	Night	18% 11% 39% 24% 8%	600
	21st to end	Night	25% 10% 34% 23% 7% 2	660
April	1st to 10th	Night	18% 16% 35% 27% 4	600
	11th to 20th	Night	22% 15% 32% 24% 6% 1	593
	21st to end	Night	24% 11% 31% 25% 7% 2	600
May	1st to 10th	Night	18% 11% 32% 30% 10% 1	600
	11th to 20th	Night	16% 10% 31% 32% 9% 1	591
	21st to end	Night	20% 7% 27% 32% 13%	650
June	1st to 10th	Night	10% 5% 30% 40% 14% 1	600
	11th to 20th	Night	12% 5% 33% 39% 11%	600
	21st to end	Night	13% 4 25% 43% 14% 1	600
July	1st to 10th	Night	7% 2 21% 39% 30% 2	585
	11th to 20th	Night	5% 3 24% 42% 24% 2	582
	21st to end	Night	7% 2 19% 48% 21% 3	657
August	1st to 10th	Night	7% 2 18% 46% 25% 2	579
	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% 12% 38% 27% 6% 1	860
	11th to 20th	Night	16% 15% 41% 23% 5%	1000
	21st to end	Night	18% 15% 38% 22% 7%	1000
December	1st to 10th	Night	15% 13% 40% 26% 6%	1000
	11th to 20th	Night	19% 12% 40% 23% 6%	1000
	21st to end	Night	24% 13% 36% 23% 4	1100

Page generated at 2025-08-02 00:32:27. Version ac07

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