Fergus Falls
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fergus Falls clear sky chart from 2005-11-06 to 2026-07-31.

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	11% 8% 3 8% 5% 5% 5% 4 6% 7% 37%	138415
	Night	10% 9% 4 9% 6% 5% 5% 4 6% 7% 35%	134936
Transparency	Day	44% 7% 14% 25% 10% 1	141927
	Night	45% 7% 13% 23% 11% 1	139497
Seeing	Day	15% 10% 31% 28% 13% 2	18520
	Night	14% 9% 34% 32% 10% 1	28374

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% 13% 5% 16% 13% 9% 8% 5% 5% 5% 14%	4124
	11th to 20th	Day	4 10% 4 14% 8% 7% 14% 8% 9% 8% 14%	4499
	21st to end	Day	3 8% 7% 15% 8% 7% 7% 6% 8% 9% 23%	5619
February	1st to 10th	Day	8% 13% 6% 10% 8% 6% 7% 6% 8% 7% 23%	1890
	11th to 20th	Day	7% 11% 4 10% 8% 7% 7% 5% 7% 8% 27%	1844
	21st to end	Day	7% 12% 4 11% 7% 9% 7% 4 7% 8% 24%	1651
March	1st to 10th	Day	11% 9% 3 8% 6% 5% 4 4 5% 7% 39%	4870
	11th to 20th	Day	10% 10% 4 8% 6% 4 5% 4 7% 9% 35%	5090
	21st to end	Day	17% 14% 5% 11% 7% 5% 4 4 4 6% 22%	5583
April	1st to 10th	Day	15% 12% 4 8% 5% 4 4 4 5% 7% 33%	2447
	11th to 20th	Day	16% 10% 4 10% 5% 4 4 4 5% 6% 32%	2702
	21st to end	Day	22% 10% 4 6% 4 4 4 4 4 6% 32%	2730
May	1st to 10th	Day	10% 5% 2 6% 4 4 4 3 5% 6% 51%	7617
	11th to 20th	Day	16% 9% 2 5% 3 3 4 3 5% 6% 44%	8213
	21st to end	Day	15% 6% 2 6% 4 4 5% 4 6% 8% 41%	9265
June	1st to 10th	Day	13% 6% 2 5% 4 4 5% 4 7% 9% 41%	3150
	11th to 20th	Day	14% 7% 3 6% 4 5% 5% 4 5% 8% 39%	3150
	21st to end	Day	11% 5% 2 5% 4 5% 5% 5% 7% 9% 41%	3150
July	1st to 10th	Day	7% 4 2 5% 4 4 5% 5% 7% 10% 48%	6950
	11th to 20th	Day	9% 5% 2 5% 3 3 4 4 6% 8% 51%	6950
	21st to end	Day	8% 4 2 6% 4 5% 5% 4 8% 10% 45%	6884
August	1st to 10th	Day	11% 5% 2 4 3 4 5% 4 7% 10% 46%	4234
	11th to 20th	Day	12% 7% 2 7% 4 5% 4 4 7% 10% 39%	4171
	21st to end	Day	11% 5% 2 5% 4 3 4 3 5% 7% 50%	4675
September	1st to 10th	Day	11% 4 1 5% 3 4 5% 3 6% 7% 51%	2418
	11th to 20th	Day	12% 5% 2 6% 5% 5% 4 4 6% 7% 46%	2200
	21st to end	Day	14% 5% 2 6% 3 3 4 4 5% 7% 47%	2200
October	1st to 10th	Day	15% 9% 3 5% 4 3 5% 4 6% 5% 41%	2015
	11th to 20th	Day	16% 12% 4 5% 4 4 4 2 4 5% 41%	2000
	21st to end	Day	19% 12% 4 7% 3 3 4 4 5% 7% 34%	2081
November	1st to 10th	Day	14% 13% 4 10% 5% 4 4 3 4 5% 33%	1738
	11th to 20th	Day	10% 14% 6% 14% 7% 5% 3 4 4 6% 28%	1680
	21st to end	Day	10% 11% 5% 12% 7% 6% 5% 3 5% 6% 29%	1680
December	1st to 10th	Day	7% 12% 5% 14% 11% 11% 8% 5% 6% 5% 16%	2657
	11th to 20th	Day	7% 17% 8% 11% 6% 6% 5% 4 6% 6% 23%	2713
	21st to end	Day	15% 16% 5% 17% 10% 5% 4 2 4 5% 18%	3575
January	1st to 10th	Night	5% 10% 4 16% 12% 9% 8% 5% 6% 7% 17%	8799
	11th to 20th	Night	4 10% 5% 12% 8% 9% 12% 9% 8% 6% 17%	8490
	21st to end	Night	3 9% 9% 11% 6% 5% 8% 5% 7% 8% 29%	8592
February	1st to 10th	Night	7% 11% 5% 11% 7% 6% 6% 5% 7% 7% 28%	2730
	11th to 20th	Night	6% 10% 4 9% 6% 5% 7% 5% 7% 8% 33%	2663
	21st to end	Night	9% 10% 4 9% 8% 6% 6% 5% 5% 7% 31%	2175
March	1st to 10th	Night	10% 7% 2 6% 4 4 5% 4 6% 9% 43%	5212
	11th to 20th	Night	9% 9% 3 9% 8% 6% 7% 4 6% 7% 33%	5090
	21st to end	Night	18% 12% 4 11% 5% 4 3 3 5% 5% 29%	5588
April	1st to 10th	Night	15% 10% 3 7% 4 4 4 3 6% 7% 37%	2170
	11th to 20th	Night	19% 10% 3 7% 4 4 3 4 4 6% 37%	1869
	21st to end	Night	18% 9% 3 7% 4 4 4 4 5% 6% 37%	1890
May	1st to 10th	Night	10% 6% 2 5% 3 3 3 3 4 6% 53%	5266
	11th to 20th	Night	15% 7% 2 5% 3 3 3 3 4 5% 50%	4676
	21st to end	Night	14% 7% 2 6% 4 4 4 4 6% 8% 41%	4916
June	1st to 10th	Night	11% 4 2 5% 3 3 4 4 5% 10% 49%	1470
	11th to 20th	Night	10% 5% 2 5% 4 3 4 4 7% 8% 47%	1470
	21st to end	Night	8% 4 2 5% 4 3 3 3 6% 11% 50%	1470
July	1st to 10th	Night	8% 4 1 5% 5% 4 5% 4 6% 9% 49%	3248
	11th to 20th	Night	6% 3 1 4 2 3 3 4 5% 8% 61%	3247
	21st to end	Night	7% 4 2 6% 5% 5% 5% 4 7% 9% 46%	4192
August	1st to 10th	Night	9% 5% 2 5% 4 3 4 4 6% 6% 53%	2926
	11th to 20th	Night	11% 5% 2 5% 3 4 3 3 6% 7% 51%	2888
	21st to end	Night	10% 5% 2 4 4 3 4 3 6% 7% 52%	3234
September	1st to 10th	Night	10% 4 1 4 3 3 3 3 5% 7% 56%	1977
	11th to 20th	Night	8% 5% 1 6% 5% 3 5% 3 5% 6% 53%	2200
	21st to end	Night	11% 5% 2 5% 3 3 3 3 5% 6% 55%	2200
October	1st to 10th	Night	12% 7% 2 7% 3 4 4 4 5% 7% 45%	2365
	11th to 20th	Night	15% 9% 3 6% 4 4 4 3 5% 6% 41%	2400
	21st to end	Night	16% 10% 3 8% 4 4 3 3 5% 6% 37%	2755
November	1st to 10th	Night	10% 11% 4 9% 5% 4 6% 4 5% 7% 35%	2780
	11th to 20th	Night	10% 12% 5% 12% 5% 5% 4 3 6% 7% 30%	2940
	21st to end	Night	10% 11% 4 10% 7% 5% 4 4 6% 8% 33%	2940
December	1st to 10th	Night	5% 9% 5% 12% 12% 9% 7% 5% 7% 7% 22%	4749
	11th to 20th	Night	9% 13% 6% 16% 8% 7% 5% 4 6% 6% 21%	5714
	21st to end	Night	15% 16% 6% 15% 9% 6% 5% 4 4 5% 15%	7645

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% 9% 11% 4	4125
	11th to 20th	Day	63% 6% 10% 16% 4	4499
	21st to end	Day	53% 7% 11% 19% 9%	5619
February	1st to 10th	Day	56% 7% 12% 18% 7%	1890
	11th to 20th	Day	52% 7% 13% 21% 5% 1	1853
	21st to end	Day	55% 7% 15% 16% 7%	1651
March	1st to 10th	Day	42% 7% 17% 25% 7% 1	4870
	11th to 20th	Day	43% 6% 16% 27% 8%	5090
	21st to end	Day	62% 6% 12% 16% 3	5585
April	1st to 10th	Day	49% 7% 10% 22% 10% 1	2447
	11th to 20th	Day	51% 7% 13% 17% 11% 1	2702
	21st to end	Day	51% 7% 11% 22% 8% 1	2730
May	1st to 10th	Day	31% 7% 13% 31% 19%	7655
	11th to 20th	Day	39% 6% 9% 25% 15% 5%	8217
	21st to end	Day	38% 8% 12% 30% 11% 1	9279
June	1st to 10th	Day	37% 9% 17% 28% 10% 1	3150
	11th to 20th	Day	41% 8% 15% 22% 13% 1	3150
	21st to end	Day	36% 10% 18% 25% 12%	3150
July	1st to 10th	Day	29% 9% 20% 31% 11%	6876
	11th to 20th	Day	29% 6% 16% 35% 12% 1	6869
	21st to end	Day	32% 8% 20% 31% 9% 1	6693
August	1st to 10th	Day	32% 7% 16% 30% 12% 2	4220
	11th to 20th	Day	38% 8% 15% 31% 7% 1	4210
	21st to end	Day	33% 7% 18% 31% 10% 1	4674
September	1st to 10th	Day	31% 7% 16% 34% 12% 1	2418
	11th to 20th	Day	36% 7% 18% 29% 10%	2200
	21st to end	Day	35% 7% 15% 31% 11% 1	2200
October	1st to 10th	Day	33% 5% 9% 33% 18% 1	3275
	11th to 20th	Day	42% 4 8% 24% 20% 1	3240
	21st to end	Day	49% 5% 14% 24% 7%	3350
November	1st to 10th	Day	52% 6% 11% 20% 10% 1	1738
	11th to 20th	Day	58% 6% 13% 16% 7%	1680
	21st to end	Day	55% 7% 15% 16% 6% 1	1680
December	1st to 10th	Day	67% 7% 14% 10% 3	2657
	11th to 20th	Day	60% 5% 13% 16% 6%	2710
	21st to end	Day	70% 4 9% 13% 4	3575
January	1st to 10th	Night	63% 7% 12% 11% 7%	8800
	11th to 20th	Night	61% 8% 9% 15% 7% 1	8490
	21st to end	Night	49% 7% 14% 21% 8%	8592
February	1st to 10th	Night	52% 7% 13% 18% 9% 1	2730
	11th to 20th	Night	46% 7% 11% 23% 11% 1	2664
	21st to end	Night	50% 7% 13% 18% 10% 1	2175
March	1st to 10th	Night	35% 7% 18% 26% 12% 2	5212
	11th to 20th	Night	46% 8% 13% 23% 10%	5090
	21st to end	Night	56% 5% 12% 19% 7% 1	5588
April	1st to 10th	Night	44% 7% 12% 23% 12% 2	2170
	11th to 20th	Night	48% 5% 10% 23% 12% 2	1869
	21st to end	Night	47% 7% 11% 24% 11% 1	1890
May	1st to 10th	Night	31% 6% 11% 33% 19% 1	5293
	11th to 20th	Night	36% 6% 7% 22% 22% 7%	4677
	21st to end	Night	38% 8% 11% 29% 14% 1	4926
June	1st to 10th	Night	31% 6% 16% 32% 13% 2	1470
	11th to 20th	Night	33% 8% 16% 25% 14% 4	1470
	21st to end	Night	27% 8% 19% 30% 14% 2	1470
July	1st to 10th	Night	30% 8% 18% 30% 13%	3215
	11th to 20th	Night	21% 5% 18% 41% 13% 2	3208
	21st to end	Night	32% 8% 19% 29% 11% 1	4073
August	1st to 10th	Night	30% 6% 15% 30% 16% 3	2916
	11th to 20th	Night	31% 7% 16% 34% 11% 1	2915
	21st to end	Night	30% 8% 16% 31% 14% 1	3234
September	1st to 10th	Night	26% 6% 16% 35% 15% 1	1977
	11th to 20th	Night	31% 8% 18% 30% 14%	2200
	21st to end	Night	29% 6% 14% 34% 17% 1	2200
October	1st to 10th	Night	26% 4 8% 35% 21% 5%	3872
	11th to 20th	Night	38% 4 11% 27% 18% 2	3899
	21st to end	Night	45% 5% 14% 25% 11%	4442
November	1st to 10th	Night	46% 7% 12% 23% 10% 2	2780
	11th to 20th	Night	52% 7% 14% 17% 9% 1	2940
	21st to end	Night	49% 8% 18% 19% 5% 1	2940
December	1st to 10th	Night	58% 7% 16% 15% 4	4749
	11th to 20th	Night	61% 7% 11% 17% 4	5716
	21st to end	Night	70% 6% 10% 11% 3	7645

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	11% 13% 36% 29% 9% 2	330
	11th to 20th	Day	13% 13% 38% 28% 8%	330
	21st to end	Day	10% 15% 39% 21% 13% 2	363
February	1st to 10th	Day	15% 16% 37% 27% 5% 1	330
	11th to 20th	Day	15% 12% 38% 25% 8% 1	330
	21st to end	Day	10% 10% 41% 33% 5%	273
March	1st to 10th	Day	17% 14% 35% 28% 5% 1	330
	11th to 20th	Day	18% 12% 35% 25% 8% 2	330
	21st to end	Day	21% 13% 33% 21% 10% 2	363
April	1st to 10th	Day	24% 15% 31% 23% 7%	467
	11th to 20th	Day	23% 16% 30% 22% 8% 1	740
	21st to end	Day	23% 13% 32% 19% 11% 1	750
May	1st to 10th	Day	18% 13% 32% 24% 11% 2	753
	11th to 20th	Day	20% 10% 29% 28% 11% 2	775
	21st to end	Day	17% 8% 29% 30% 14% 3	844
June	1st to 10th	Day	11% 10% 29% 29% 18% 3	780
	11th to 20th	Day	16% 10% 36% 25% 11% 1	780
	21st to end	Day	13% 9% 29% 30% 14% 3	780
July	1st to 10th	Day	7% 5% 21% 37% 25% 5%	771
	11th to 20th	Day	9% 7% 28% 34% 18% 5%	768
	21st to end	Day	6% 4 29% 34% 23% 4	845
August	1st to 10th	Day	10% 4 25% 33% 24% 3	726
	11th to 20th	Day	13% 6% 21% 34% 20% 7%	715
	21st to end	Day	10% 7% 27% 31% 21% 4	803
September	1st to 10th	Day	11% 7% 28% 35% 16% 3	548
	11th to 20th	Day	10% 8% 35% 31% 12% 4	330
	21st to end	Day	17% 13% 30% 26% 11% 3	330
October	1st to 10th	Day	18% 12% 29% 28% 12% 1	330
	11th to 20th	Day	18% 16% 35% 24% 5% 1	330
	21st to end	Day	23% 16% 38% 17% 6% 1	363
November	1st to 10th	Day	25% 14% 25% 28% 8%	330
	11th to 20th	Day	19% 13% 41% 21% 5%	330
	21st to end	Day	16% 14% 37% 27% 5%	330
December	1st to 10th	Day	15% 11% 40% 25% 8% 1	330
	11th to 20th	Day	18% 15% 39% 25% 4	330
	21st to end	Day	23% 11% 39% 21% 5% 1	363
January	1st to 10th	Night	10% 10% 40% 29% 9% 2	1050
	11th to 20th	Night	13% 12% 37% 29% 8% 1	1050
	21st to end	Night	13% 10% 40% 30% 6% 1	1155
February	1st to 10th	Night	11% 11% 38% 31% 7% 1	1050
	11th to 20th	Night	11% 10% 40% 28% 9% 2	1029
	21st to end	Night	14% 10% 35% 30% 10% 2	791
March	1st to 10th	Night	14% 10% 38% 30% 8% 1	714
	11th to 20th	Night	14% 12% 39% 28% 6% 1	630
	21st to end	Night	18% 11% 32% 27% 10% 2	693
April	1st to 10th	Night	19% 9% 37% 30% 5%	630
	11th to 20th	Night	23% 13% 29% 26% 8%	623
	21st to end	Night	23% 8% 32% 27% 10%	630
May	1st to 10th	Night	17% 10% 34% 30% 9%	630
	11th to 20th	Night	15% 9% 34% 32% 9% 1	621
	21st to end	Night	13% 8% 32% 34% 12%	683
June	1st to 10th	Night	13% 7% 28% 36% 15% 1	630
	11th to 20th	Night	13% 6% 33% 40% 7%	630
	21st to end	Night	10% 6% 27% 44% 14%	630
July	1st to 10th	Night	5% 3 22% 45% 23% 2	615
	11th to 20th	Night	5% 3 28% 47% 16% 1	612
	21st to end	Night	4 3 25% 46% 19% 2	687
August	1st to 10th	Night	9% 3 19% 50% 18% 1	597
	11th to 20th	Night	10% 5% 21% 40% 22% 3	594
	21st to end	Night	8% 3 30% 40% 18% 1	660
September	1st to 10th	Night	12% 5% 26% 41% 15% 2	600
	11th to 20th	Night	10% 6% 31% 38% 14% 2	600
	21st to end	Night	13% 6% 35% 32% 13% 1	600
October	1st to 10th	Night	16% 10% 34% 29% 10%	765
	11th to 20th	Night	20% 11% 33% 28% 7% 1	800
	21st to end	Night	21% 11% 34% 28% 6%	995
November	1st to 10th	Night	16% 11% 34% 31% 8%	1025
	11th to 20th	Night	17% 13% 35% 28% 7% 1	1050
	21st to end	Night	15% 12% 40% 28% 5%	1050
December	1st to 10th	Night	13% 10% 38% 31% 8% 1	1050
	11th to 20th	Night	17% 12% 36% 29% 5% 1	1050
	21st to end	Night	22% 10% 36% 25% 7% 1	1155

Page generated at 2026-07-28 02:25:20. Version ac07

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