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 2025-03-27.

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% 9% 3 8% 5% 5% 5% 4 6% 7% 35%	108772
	Night	10% 9% 4 9% 6% 5% 5% 4 6% 7% 34%	110780
Transparency	Day	45% 7% 14% 24% 9% 1	112324
	Night	46% 7% 13% 22% 10% 1	115362
Seeing	Day	15% 10% 31% 28% 14% 2	16513
	Night	14% 9% 34% 33% 10% 1	26628

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% 12% 4 12% 12% 9% 10% 6% 6% 6% 16%	3178
	11th to 20th	Day	5% 8% 5% 14% 8% 7% 14% 8% 10% 9% 14%	3455
	21st to end	Day	4 10% 9% 18% 8% 7% 5% 5% 6% 6% 22%	4334
February	1st to 10th	Day	8% 13% 6% 10% 7% 6% 7% 6% 8% 7% 22%	1800
	11th to 20th	Day	6% 11% 4 10% 8% 7% 7% 5% 8% 8% 26%	1754
	21st to end	Day	7% 13% 4 11% 7% 9% 7% 4 7% 8% 24%	1575
March	1st to 10th	Day	12% 12% 3 10% 6% 5% 4 3 5% 5% 34%	3422
	11th to 20th	Day	8% 11% 4 9% 7% 4 5% 3 6% 8% 35%	3590
	21st to end	Day	18% 14% 5% 12% 8% 5% 5% 4 4 6% 19%	3880
April	1st to 10th	Day	14% 12% 4 8% 5% 4 4 4 5% 7% 33%	2213
	11th to 20th	Day	16% 11% 4 10% 5% 4 4 4 5% 6% 32%	2442
	21st to end	Day	22% 10% 4 6% 4 4 4 3 4 6% 33%	2470
May	1st to 10th	Day	17% 7% 2 6% 4 4 5% 4 5% 7% 38%	4082
	11th to 20th	Day	13% 7% 3 6% 4 4 5% 3 6% 7% 43%	4390
	21st to end	Day	18% 7% 2 6% 4 4 5% 4 6% 8% 36%	4938
June	1st to 10th	Day	13% 5% 2 5% 4 4 5% 4 6% 8% 43%	2850
	11th to 20th	Day	14% 7% 3 5% 4 5% 5% 4 5% 8% 40%	2850
	21st to end	Day	10% 5% 2 5% 4 5% 5% 5% 7% 10% 42%	2850
July	1st to 10th	Day	8% 5% 2 6% 4 4 5% 5% 7% 10% 43%	4750
	11th to 20th	Day	6% 3 1 4 3 3 4 4 7% 9% 57%	4750
	21st to end	Day	5% 3 2 6% 4 5% 5% 4 8% 9% 48%	4681
August	1st to 10th	Day	11% 5% 2 4 3 4 4 4 7% 10% 46%	4104
	11th to 20th	Day	12% 7% 2 7% 4 5% 4 4 7% 10% 39%	4041
	21st to end	Day	12% 5% 2 5% 4 3 4 3 5% 7% 50%	4532
September	1st to 10th	Day	12% 4 1 5% 3 3 4 3 5% 7% 52%	2297
	11th to 20th	Day	11% 5% 2 6% 5% 5% 4 4 5% 7% 47%	2090
	21st to end	Day	14% 5% 2 6% 3 3 4 4 5% 8% 46%	2090
October	1st to 10th	Day	15% 9% 3 5% 4 4 5% 4 6% 5% 40%	1914
	11th to 20th	Day	16% 12% 4 5% 4 3 4 3 4 5% 41%	1900
	21st to end	Day	18% 12% 3 7% 3 3 4 4 5% 7% 34%	1977
November	1st to 10th	Day	15% 13% 4 9% 4 4 4 3 4 6% 34%	1654
	11th to 20th	Day	11% 14% 6% 15% 7% 5% 3 4 4 6% 26%	1600
	21st to end	Day	11% 11% 5% 11% 8% 5% 5% 3 5% 7% 29%	1600
December	1st to 10th	Day	7% 12% 5% 14% 10% 11% 8% 5% 6% 5% 16%	2578
	11th to 20th	Day	7% 17% 8% 12% 6% 6% 5% 4 6% 6% 23%	2643
	21st to end	Day	15% 17% 5% 17% 10% 5% 4 2 4 5% 18%	3498
January	1st to 10th	Night	4 10% 4 16% 12% 9% 8% 6% 6% 7% 17%	6787
	11th to 20th	Night	5% 9% 5% 12% 8% 9% 12% 9% 9% 6% 16%	6524
	21st to end	Night	4 12% 11% 12% 6% 5% 7% 5% 7% 7% 24%	6641
February	1st to 10th	Night	7% 11% 5% 11% 7% 6% 6% 6% 7% 7% 28%	2600
	11th to 20th	Night	5% 10% 4 9% 6% 5% 8% 6% 7% 8% 33%	2533
	21st to end	Night	10% 10% 4 9% 7% 6% 6% 5% 5% 7% 32%	2075
March	1st to 10th	Night	8% 8% 3 7% 4 5% 5% 5% 7% 8% 40%	3656
	11th to 20th	Night	9% 10% 3 9% 8% 5% 5% 3 5% 7% 36%	3590
	21st to end	Night	19% 14% 4 11% 5% 4 3 2 5% 5% 27%	3889
April	1st to 10th	Night	14% 10% 3 7% 4 4 4 3 6% 7% 37%	1964
	11th to 20th	Night	20% 10% 3 7% 4 4 3 3 4 6% 36%	1689
	21st to end	Night	18% 9% 3 8% 4 4 4 4 5% 5% 36%	1710
May	1st to 10th	Night	16% 9% 2 6% 4 4 4 4 4 6% 41%	2823
	11th to 20th	Night	12% 6% 2 7% 4 4 4 3 6% 6% 46%	2512
	21st to end	Night	15% 7% 3 6% 5% 4 4 4 6% 8% 38%	2624
June	1st to 10th	Night	11% 4 2 4 4 3 4 3 6% 9% 50%	1330
	11th to 20th	Night	10% 5% 2 5% 4 3 4 4 7% 8% 47%	1330
	21st to end	Night	8% 4 2 5% 4 3 4 3 7% 11% 51%	1330
July	1st to 10th	Night	9% 4 2 6% 6% 5% 6% 4 7% 8% 43%	2220
	11th to 20th	Night	4 3 1 3 2 3 2 3 4 7% 68%	2220
	21st to end	Night	4 3 1 6% 4 5% 6% 4 7% 9% 52%	2866
August	1st to 10th	Night	9% 5% 2 5% 3 3 4 4 6% 7% 53%	2836
	11th to 20th	Night	11% 5% 2 5% 3 3 3 4 6% 8% 51%	2798
	21st to end	Night	10% 5% 2 4 4 3 4 3 5% 7% 52%	3135
September	1st to 10th	Night	10% 4 1 4 3 3 3 3 5% 8% 56%	1878
	11th to 20th	Night	8% 5% 1 6% 5% 3 5% 2 5% 6% 53%	2090
	21st to end	Night	12% 5% 2 5% 3 3 3 3 5% 6% 54%	2090
October	1st to 10th	Night	13% 7% 2 7% 3 4 4 4 5% 8% 43%	2247
	11th to 20th	Night	15% 10% 3 6% 4 4 4 3 5% 6% 42%	2280
	21st to end	Night	17% 10% 3 8% 4 4 3 3 5% 6% 36%	2617
November	1st to 10th	Night	10% 11% 4 8% 5% 4 5% 4 5% 7% 36%	2644
	11th to 20th	Night	11% 13% 5% 12% 5% 5% 4 3 5% 7% 30%	2800
	21st to end	Night	10% 11% 4 9% 7% 5% 4 4 6% 8% 34%	2800
December	1st to 10th	Night	5% 9% 5% 11% 12% 9% 7% 6% 7% 7% 23%	4608
	11th to 20th	Night	9% 13% 6% 16% 8% 7% 5% 4 6% 6% 21%	5564
	21st to end	Night	15% 16% 6% 15% 9% 6% 5% 4 4 5% 15%	7480

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	65% 7% 8% 14% 5%	3179
	11th to 20th	Day	60% 7% 10% 18% 4	3455
	21st to end	Day	59% 8% 12% 15% 5%	4334
February	1st to 10th	Day	55% 7% 12% 18% 7%	1800
	11th to 20th	Day	52% 7% 14% 21% 5% 1	1763
	21st to end	Day	55% 7% 14% 16% 7%	1575
March	1st to 10th	Day	50% 8% 12% 25% 6%	3422
	11th to 20th	Day	44% 7% 14% 27% 7%	3590
	21st to end	Day	66% 7% 10% 14% 3	3880
April	1st to 10th	Day	48% 7% 11% 22% 11% 1	2213
	11th to 20th	Day	52% 7% 11% 17% 11% 1	2442
	21st to end	Day	51% 7% 12% 21% 8% 1	2470
May	1st to 10th	Day	41% 9% 15% 23% 11% 1	4120
	11th to 20th	Day	37% 8% 13% 28% 11% 3	4394
	21st to end	Day	41% 11% 16% 25% 7% 1	4951
June	1st to 10th	Day	36% 9% 16% 28% 10% 1	2850
	11th to 20th	Day	41% 9% 15% 21% 13% 1	2850
	21st to end	Day	34% 10% 19% 25% 11%	2850
July	1st to 10th	Day	33% 11% 18% 27% 12% 1	4676
	11th to 20th	Day	22% 7% 19% 36% 15% 1	4669
	21st to end	Day	27% 9% 19% 33% 10% 1	4533
August	1st to 10th	Day	32% 7% 16% 30% 12% 2	4090
	11th to 20th	Day	38% 8% 15% 31% 7% 1	4080
	21st to end	Day	33% 7% 18% 31% 10% 1	4531
September	1st to 10th	Day	31% 7% 15% 34% 12% 1	2297
	11th to 20th	Day	35% 7% 18% 30% 10%	2090
	21st to end	Day	36% 7% 15% 30% 10% 1	2090
October	1st to 10th	Day	33% 5% 9% 33% 18% 1	3174
	11th to 20th	Day	42% 4 9% 25% 19% 1	3140
	21st to end	Day	49% 5% 14% 24% 7%	3246
November	1st to 10th	Day	52% 6% 12% 20% 10% 1	1654
	11th to 20th	Day	59% 6% 13% 15% 7%	1600
	21st to end	Day	54% 7% 15% 16% 6% 1	1600
December	1st to 10th	Day	66% 7% 14% 10% 3	2578
	11th to 20th	Day	60% 6% 13% 16% 6%	2640
	21st to end	Day	70% 4 9% 13% 4	3498
January	1st to 10th	Night	63% 8% 10% 13% 7%	6787
	11th to 20th	Night	60% 9% 10% 12% 9% 1	6524
	21st to end	Night	55% 8% 15% 17% 4	6641
February	1st to 10th	Night	51% 7% 13% 18% 9% 1	2600
	11th to 20th	Night	46% 7% 12% 22% 12% 1	2534
	21st to end	Night	50% 7% 13% 18% 11% 1	2075
March	1st to 10th	Night	38% 9% 17% 25% 10% 2	3656
	11th to 20th	Night	44% 9% 13% 25% 10%	3590
	21st to end	Night	58% 6% 11% 19% 6% 1	3889
April	1st to 10th	Night	43% 7% 13% 23% 12% 2	1964
	11th to 20th	Night	49% 5% 9% 23% 12% 2	1689
	21st to end	Night	47% 7% 11% 23% 10% 1	1710
May	1st to 10th	Night	41% 8% 12% 26% 12% 2	2850
	11th to 20th	Night	36% 8% 11% 25% 18% 3	2513
	21st to end	Night	40% 11% 13% 24% 11% 1	2632
June	1st to 10th	Night	30% 7% 17% 31% 13% 1	1330
	11th to 20th	Night	32% 9% 16% 24% 14% 4	1330
	21st to end	Night	26% 8% 20% 30% 14% 2	1330
July	1st to 10th	Night	35% 10% 18% 23% 13% 1	2185
	11th to 20th	Night	16% 6% 14% 46% 16% 3	2178
	21st to end	Night	26% 8% 19% 32% 13% 2	2776
August	1st to 10th	Night	29% 7% 15% 30% 16% 3	2826
	11th to 20th	Night	31% 7% 16% 34% 11% 1	2825
	21st to end	Night	30% 8% 16% 31% 14% 1	3135
September	1st to 10th	Night	26% 6% 16% 35% 15% 1	1878
	11th to 20th	Night	31% 7% 17% 30% 15%	2090
	21st to end	Night	30% 6% 14% 33% 16% 1	2090
October	1st to 10th	Night	27% 5% 8% 35% 21% 5%	3754
	11th to 20th	Night	37% 4 11% 27% 18% 2	3779
	21st to end	Night	45% 5% 13% 25% 11%	4304
November	1st to 10th	Night	45% 7% 12% 23% 10% 2	2644
	11th to 20th	Night	53% 7% 14% 17% 9% 1	2800
	21st to end	Night	48% 8% 19% 19% 5% 1	2800
December	1st to 10th	Night	58% 7% 16% 15% 4	4608
	11th to 20th	Night	61% 7% 11% 17% 4	5566
	21st to end	Night	70% 7% 9% 11% 3	7480

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	10% 13% 35% 30% 9% 3	300
	11th to 20th	Day	13% 12% 37% 29% 9%	300
	21st to end	Day	11% 14% 38% 21% 15% 2	330
February	1st to 10th	Day	15% 15% 36% 28% 4 1	300
	11th to 20th	Day	15% 12% 41% 24% 8%	300
	21st to end	Day	10% 10% 41% 34% 5%	249
March	1st to 10th	Day	17% 13% 34% 29% 5% 1	300
	11th to 20th	Day	16% 10% 37% 26% 8% 2	300
	21st to end	Day	22% 10% 32% 23% 11% 3	315
April	1st to 10th	Day	23% 15% 32% 22% 8%	393
	11th to 20th	Day	25% 15% 28% 23% 9% 1	640
	21st to end	Day	22% 12% 32% 20% 12% 2	650
May	1st to 10th	Day	19% 13% 32% 23% 11% 2	653
	11th to 20th	Day	18% 9% 30% 29% 12% 2	675
	21st to end	Day	17% 8% 29% 29% 14% 3	734
June	1st to 10th	Day	11% 8% 29% 30% 20% 3	680
	11th to 20th	Day	15% 9% 37% 25% 12% 1	680
	21st to end	Day	12% 9% 29% 31% 15% 4	680
July	1st to 10th	Day	8% 5% 21% 35% 26% 5%	671
	11th to 20th	Day	10% 6% 26% 34% 18% 5%	668
	21st to end	Day	6% 3 27% 34% 26% 4	739
August	1st to 10th	Day	9% 4 26% 33% 25% 3	676
	11th to 20th	Day	13% 6% 21% 34% 20% 7%	665
	21st to end	Day	10% 7% 27% 31% 21% 4	748
September	1st to 10th	Day	12% 6% 28% 36% 16% 2	507
	11th to 20th	Day	9% 7% 36% 32% 12% 4	300
	21st to end	Day	18% 14% 31% 24% 10% 2	300
October	1st to 10th	Day	19% 11% 28% 28% 12% 1	300
	11th to 20th	Day	17% 15% 35% 26% 6% 1	300
	21st to end	Day	22% 16% 38% 17% 7% 1	330
November	1st to 10th	Day	25% 11% 26% 30% 9%	300
	11th to 20th	Day	20% 13% 42% 20% 6%	300
	21st to end	Day	17% 13% 38% 28% 4	300
December	1st to 10th	Day	14% 10% 41% 26% 8% 1	300
	11th to 20th	Day	16% 13% 40% 27% 4	300
	21st to end	Day	23% 11% 38% 22% 5% 1	330
January	1st to 10th	Night	10% 10% 39% 29% 9% 2	1000
	11th to 20th	Night	13% 10% 38% 30% 8% 1	1000
	21st to end	Night	13% 10% 40% 30% 6% 1	1100
February	1st to 10th	Night	11% 11% 38% 32% 8% 1	1000
	11th to 20th	Night	11% 11% 40% 28% 9% 2	979
	21st to end	Night	14% 10% 34% 30% 10% 2	755
March	1st to 10th	Night	14% 9% 38% 30% 8% 1	680
	11th to 20th	Night	14% 12% 39% 29% 6% 1	600
	21st to end	Night	18% 11% 31% 28% 11% 2	647
April	1st to 10th	Night	19% 8% 37% 30% 5% 1	570
	11th to 20th	Night	24% 12% 29% 26% 9% 1	563
	21st to end	Night	22% 8% 32% 26% 12%	570
May	1st to 10th	Night	18% 10% 35% 29% 8%	570
	11th to 20th	Night	15% 8% 34% 32% 10% 1	561
	21st to end	Night	12% 9% 33% 34% 12%	617
June	1st to 10th	Night	12% 7% 28% 37% 15% 1	570
	11th to 20th	Night	13% 5% 33% 41% 8%	570
	21st to end	Night	9% 5% 26% 45% 15%	570
July	1st to 10th	Night	5% 3 22% 45% 23% 2	555
	11th to 20th	Night	5% 3 26% 48% 17% 1	552
	21st to end	Night	4 3 23% 47% 21% 2	624
August	1st to 10th	Night	8% 3 19% 51% 19% 1	567
	11th to 20th	Night	10% 5% 21% 41% 22% 3	564
	21st to end	Night	8% 3 30% 40% 18% 1	627
September	1st to 10th	Night	11% 4 27% 41% 14% 2	570
	11th to 20th	Night	9% 6% 31% 37% 14% 2	570
	21st to end	Night	13% 6% 36% 31% 12% 1	570
October	1st to 10th	Night	17% 10% 34% 30% 10%	727
	11th to 20th	Night	19% 11% 34% 28% 8% 1	760
	21st to end	Night	21% 11% 34% 28% 6%	945
November	1st to 10th	Night	16% 10% 34% 31% 8%	975
	11th to 20th	Night	17% 13% 35% 27% 7% 1	1000
	21st to end	Night	15% 12% 40% 28% 5%	1000
December	1st to 10th	Night	13% 10% 38% 31% 8% 1	1000
	11th to 20th	Night	17% 11% 37% 29% 5% 1	1000
	21st to end	Night	22% 10% 34% 26% 7% 1	1100

Page generated at 2025-03-24 08:04:27. Version ac07

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