Mason City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mason City clear sky chart from 2005-11-06 to 2026-04-17.

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% 8% 3 8% 5% 4 5% 4 6% 7% 37%	131998
	Night	11% 9% 3 9% 5% 4 4 4 5% 7% 39%	130480
Transparency	Day	44% 6% 13% 24% 12% 1	135594
	Night	43% 5% 12% 24% 14% 2	134962
Seeing	Day	16% 11% 30% 26% 13% 3	17826
	Night	16% 10% 33% 30% 10% 1	27845

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	7% 14% 6% 21% 10% 8% 5% 3 4 4 17%	4691
	11th to 20th	Day	5% 10% 5% 13% 7% 8% 8% 7% 8% 6% 23%	5007
	21st to end	Day	7% 11% 6% 11% 6% 5% 8% 4 5% 6% 30%	5812
February	1st to 10th	Day	8% 13% 5% 12% 7% 7% 5% 4 6% 7% 24%	1890
	11th to 20th	Day	11% 11% 3 8% 6% 6% 6% 4 6% 7% 31%	1844
	21st to end	Day	14% 10% 3 10% 6% 5% 4 4 6% 7% 31%	1651
March	1st to 10th	Day	14% 8% 3 7% 4 3 3 3 4 6% 46%	4990
	11th to 20th	Day	12% 7% 2 5% 4 3 3 4 6% 8% 47%	5090
	21st to end	Day	22% 12% 5% 11% 5% 4 4 3 4 6% 25%	5624
April	1st to 10th	Day	19% 11% 4 8% 5% 5% 4 3 6% 6% 30%	2520
	11th to 20th	Day	18% 10% 3 8% 5% 4 5% 4 5% 6% 32%	2446
	21st to end	Day	22% 10% 3 7% 5% 4 4 3 4 6% 31%	2555
May	1st to 10th	Day	14% 7% 2 6% 4 5% 4 4 5% 7% 42%	5968
	11th to 20th	Day	15% 6% 2 5% 3 3 3 3 4 7% 48%	6319
	21st to end	Day	18% 8% 2 6% 4 4 5% 4 5% 8% 37%	6935
June	1st to 10th	Day	11% 6% 2 6% 4 4 5% 4 6% 8% 44%	2800
	11th to 20th	Day	12% 7% 2 6% 4 4 4 4 6% 9% 41%	2800
	21st to end	Day	11% 6% 2 6% 5% 5% 5% 4 8% 9% 39%	2800
July	1st to 10th	Day	8% 6% 3 6% 4 4 5% 5% 8% 10% 41%	6360
	11th to 20th	Day	8% 5% 2 6% 4 4 4 4 5% 8% 52%	6360
	21st to end	Day	8% 5% 2 7% 4 5% 6% 5% 8% 10% 40%	6619
August	1st to 10th	Day	9% 6% 2 7% 4 5% 5% 4 6% 9% 42%	4234
	11th to 20th	Day	10% 6% 3 7% 4 5% 6% 5% 7% 9% 39%	4171
	21st to end	Day	7% 5% 2 6% 4 4 5% 4 6% 7% 49%	4411
September	1st to 10th	Day	11% 5% 2 6% 4 3 4 3 5% 7% 51%	2400
	11th to 20th	Day	10% 5% 2 6% 5% 3 3 3 6% 8% 47%	2370
	21st to end	Day	11% 6% 3 5% 4 4 5% 4 6% 7% 46%	2104
October	1st to 10th	Day	15% 7% 2 5% 3 4 4 3 4 7% 47%	2000
	11th to 20th	Day	16% 8% 3 6% 3 3 4 3 6% 6% 42%	2000
	21st to end	Day	16% 11% 3 6% 4 4 4 3 4 6% 40%	2200
November	1st to 10th	Day	11% 9% 3 5% 4 4 4 3 6% 8% 43%	1819
	11th to 20th	Day	13% 10% 4 10% 6% 4 5% 4 5% 6% 33%	1680
	21st to end	Day	13% 13% 4 8% 5% 4 3 3 4 7% 36%	1680
December	1st to 10th	Day	7% 7% 3 10% 8% 5% 6% 5% 7% 8% 34%	2690
	11th to 20th	Day	12% 15% 6% 13% 9% 6% 5% 4 5% 6% 20%	3088
	21st to end	Day	20% 18% 9% 17% 4 3 3 2 3 4 15%	4070
January	1st to 10th	Night	8% 11% 5% 20% 8% 7% 5% 4 4 6% 22%	8232
	11th to 20th	Night	5% 10% 4 12% 8% 8% 8% 7% 7% 6% 24%	7980
	21st to end	Night	8% 10% 5% 10% 5% 5% 5% 4 5% 8% 34%	8402
February	1st to 10th	Night	9% 11% 5% 12% 7% 5% 5% 3 6% 6% 30%	2730
	11th to 20th	Night	9% 11% 3 8% 6% 5% 4 4 6% 7% 38%	2663
	21st to end	Night	12% 8% 3 8% 5% 5% 5% 3 4 6% 39%	2154
March	1st to 10th	Night	13% 8% 3 6% 3 2 3 3 4 6% 50%	5125
	11th to 20th	Night	9% 8% 3 6% 4 4 4 3 5% 8% 47%	5090
	21st to end	Night	22% 10% 3 10% 4 4 3 3 4 4 30%	5547
April	1st to 10th	Night	15% 10% 3 7% 5% 4 4 3 5% 5% 38%	2100
	11th to 20th	Night	18% 8% 2 6% 5% 4 4 4 5% 6% 38%	2035
	21st to end	Night	19% 8% 3 5% 3 4 3 3 5% 6% 40%	1840
May	1st to 10th	Night	14% 6% 2 5% 3 3 4 3 4 6% 50%	3944
	11th to 20th	Night	13% 6% 2 5% 4 3 4 3 4 7% 50%	3596
	21st to end	Night	16% 9% 2 7% 4 3 4 3 5% 6% 41%	3942
June	1st to 10th	Night	9% 4 2 5% 4 4 5% 6% 6% 7% 48%	1600
	11th to 20th	Night	11% 5% 2 6% 4 3 5% 4 7% 8% 45%	1600
	21st to end	Night	10% 6% 2 5% 3 3 3 3 5% 10% 50%	1600
July	1st to 10th	Night	7% 5% 2 5% 4 3 4 4 7% 9% 48%	3618
	11th to 20th	Night	6% 6% 2 4 3 4 4 4 5% 9% 55%	3617
	21st to end	Night	8% 5% 2 5% 3 5% 4 4 6% 9% 49%	4236
August	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 5% 8% 49%	2926
	11th to 20th	Night	11% 6% 1 4 3 3 4 3 5% 9% 51%	2888
	21st to end	Night	8% 5% 2 5% 4 3 4 3 5% 7% 54%	3489
September	1st to 10th	Night	9% 4 2 5% 3 3 3 4 4 5% 57%	2000
	11th to 20th	Night	11% 5% 2 5% 4 3 3 4 5% 8% 52%	2028
	21st to end	Night	10% 6% 2 5% 3 3 3 3 5% 6% 55%	2275
October	1st to 10th	Night	12% 6% 2 5% 3 3 4 3 5% 6% 51%	2400
	11th to 20th	Night	15% 6% 2 6% 3 4 4 3 4 6% 46%	2400
	21st to end	Night	15% 9% 3 7% 5% 3 4 4 5% 5% 41%	2640
November	1st to 10th	Night	12% 8% 2 6% 3 4 4 3 6% 6% 46%	2694
	11th to 20th	Night	12% 10% 4 9% 6% 4 4 3 5% 6% 38%	2940
	21st to end	Night	14% 10% 3 9% 4 4 4 3 3 6% 39%	2940
December	1st to 10th	Night	6% 8% 4 10% 7% 6% 6% 4 6% 7% 36%	4720
	11th to 20th	Night	13% 12% 5% 12% 6% 5% 4 4 5% 6% 27%	5339
	21st to end	Night	20% 17% 7% 18% 5% 4 3 3 3 4 16%	7150

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% 5% 10% 12% 5%	4692
	11th to 20th	Day	56% 4 10% 17% 13%	5007
	21st to end	Day	54% 5% 13% 21% 8% 1	5812
February	1st to 10th	Day	57% 5% 12% 17% 8% 1	1890
	11th to 20th	Day	50% 5% 12% 23% 8% 2	1853
	21st to end	Day	51% 5% 13% 20% 9% 2	1651
March	1st to 10th	Day	41% 4 13% 28% 12% 2	4990
	11th to 20th	Day	35% 4 13% 32% 14% 2	5090
	21st to end	Day	60% 6% 13% 15% 6%	5626
April	1st to 10th	Day	53% 5% 13% 20% 8% 1	2520
	11th to 20th	Day	51% 6% 11% 19% 12% 1	2446
	21st to end	Day	53% 5% 11% 20% 9% 1	2555
May	1st to 10th	Day	40% 6% 11% 24% 18%	6006
	11th to 20th	Day	37% 5% 12% 27% 16% 2	6323
	21st to end	Day	44% 6% 12% 27% 11% 1	6949
June	1st to 10th	Day	36% 6% 14% 28% 15% 1	2800
	11th to 20th	Day	38% 7% 14% 22% 18% 1	2800
	21st to end	Day	38% 8% 16% 23% 13% 1	2800
July	1st to 10th	Day	35% 8% 17% 31% 9% 1	6291
	11th to 20th	Day	31% 7% 13% 32% 16% 1	6285
	21st to end	Day	34% 10% 16% 25% 13% 1	6432
August	1st to 10th	Day	37% 7% 14% 26% 13% 2	4220
	11th to 20th	Day	39% 8% 16% 27% 10%	4210
	21st to end	Day	32% 8% 15% 27% 17% 1	4410
September	1st to 10th	Day	33% 6% 14% 30% 17% 2	2400
	11th to 20th	Day	35% 6% 15% 31% 13%	2370
	21st to end	Day	37% 6% 11% 29% 17% 1	2104
October	1st to 10th	Day	25% 4 7% 36% 28% 1	3260
	11th to 20th	Day	32% 4 13% 27% 23% 2	3240
	21st to end	Day	42% 3 10% 31% 13% 1	3538
November	1st to 10th	Day	38% 6% 14% 24% 16% 2	1819
	11th to 20th	Day	50% 6% 12% 21% 10% 1	1680
	21st to end	Day	49% 4 15% 21% 9% 1	1680
December	1st to 10th	Day	45% 6% 16% 24% 8% 1	2690
	11th to 20th	Day	64% 5% 14% 11% 6%	3085
	21st to end	Day	74% 4 8% 11% 3	4070
January	1st to 10th	Night	62% 5% 12% 14% 6%	8233
	11th to 20th	Night	55% 5% 13% 15% 11% 1	7980
	21st to end	Night	47% 5% 13% 23% 11%	8402
February	1st to 10th	Night	54% 4 12% 20% 9% 1	2730
	11th to 20th	Night	45% 5% 13% 24% 11% 2	2664
	21st to end	Night	46% 4 12% 23% 14% 2	2154
March	1st to 10th	Night	36% 4 9% 32% 16% 2	5125
	11th to 20th	Night	35% 4 10% 31% 17% 3	5090
	21st to end	Night	57% 6% 12% 15% 9% 1	5547
April	1st to 10th	Night	46% 5% 11% 23% 13% 1	2100
	11th to 20th	Night	46% 5% 12% 20% 16% 2	2035
	21st to end	Night	44% 5% 11% 25% 13% 2	1840
May	1st to 10th	Night	35% 5% 9% 28% 23%	3971
	11th to 20th	Night	34% 5% 10% 25% 20% 7%	3597
	21st to end	Night	43% 6% 9% 29% 12% 1	3950
June	1st to 10th	Night	31% 9% 14% 28% 16% 2	1600
	11th to 20th	Night	35% 8% 14% 20% 20% 4	1600
	21st to end	Night	31% 6% 15% 28% 18% 3	1600
July	1st to 10th	Night	30% 7% 19% 31% 13% 1	3580
	11th to 20th	Night	26% 7% 16% 35% 15% 1	3572
	21st to end	Night	30% 8% 17% 28% 16% 1	4113
August	1st to 10th	Night	32% 7% 13% 29% 17% 2	2916
	11th to 20th	Night	30% 7% 16% 33% 13% 1	2915
	21st to end	Night	29% 6% 16% 28% 18% 3	3489
September	1st to 10th	Night	28% 6% 11% 29% 24% 1	2000
	11th to 20th	Night	31% 6% 12% 30% 20% 1	2028
	21st to end	Night	31% 4 10% 29% 24% 2	2275
October	1st to 10th	Night	22% 4 7% 31% 33% 2	3920
	11th to 20th	Night	27% 4 12% 27% 25% 5%	3899
	21st to end	Night	44% 4 10% 25% 15% 1	4252
November	1st to 10th	Night	38% 5% 14% 25% 16% 3	2694
	11th to 20th	Night	47% 6% 12% 22% 12% 2	2940
	21st to end	Night	48% 5% 12% 25% 10% 1	2940
December	1st to 10th	Night	45% 6% 18% 23% 8% 1	4720
	11th to 20th	Night	56% 6% 14% 20% 4 1	5341
	21st to end	Night	73% 4 8% 11% 4	7150

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% 12% 35% 25% 10% 2	330
	11th to 20th	Day	16% 13% 44% 23% 4 1	330
	21st to end	Day	17% 11% 40% 23% 7% 2	363
February	1st to 10th	Day	13% 19% 37% 24% 5% 2	330
	11th to 20th	Day	16% 19% 37% 22% 5% 1	330
	21st to end	Day	21% 16% 36% 23% 4	273
March	1st to 10th	Day	17% 14% 44% 17% 7%	330
	11th to 20th	Day	23% 15% 31% 25% 4 1	330
	21st to end	Day	31% 15% 30% 17% 5% 1	379
April	1st to 10th	Day	27% 15% 34% 20% 4	540
	11th to 20th	Day	28% 18% 28% 20% 7% 1	516
	21st to end	Day	26% 15% 31% 18% 7% 2	655
May	1st to 10th	Day	22% 13% 32% 23% 9% 2	703
	11th to 20th	Day	23% 12% 26% 24% 11% 3	725
	21st to end	Day	20% 9% 29% 25% 14% 3	789
June	1st to 10th	Day	11% 8% 26% 32% 20% 4	730
	11th to 20th	Day	13% 7% 30% 34% 13% 2	730
	21st to end	Day	13% 7% 35% 28% 13% 4	730
July	1st to 10th	Day	8% 4 20% 33% 24% 11%	721
	11th to 20th	Day	9% 3 30% 31% 20% 7%	718
	21st to end	Day	7% 2 25% 39% 21% 6%	794
August	1st to 10th	Day	9% 4 22% 34% 23% 8%	726
	11th to 20th	Day	10% 4 22% 31% 26% 7%	715
	21st to end	Day	10% 5% 23% 35% 21% 6%	643
September	1st to 10th	Day	14% 8% 24% 28% 20% 6%	530
	11th to 20th	Day	9% 5% 28% 34% 19% 5%	500
	21st to end	Day	12% 12% 30% 29% 12% 5%	330
October	1st to 10th	Day	18% 10% 28% 25% 15% 4	330
	11th to 20th	Day	20% 20% 35% 17% 7% 1	330
	21st to end	Day	24% 15% 33% 19% 6% 2	363
November	1st to 10th	Day	18% 15% 38% 22% 6% 1	330
	11th to 20th	Day	19% 20% 37% 16% 8%	330
	21st to end	Day	23% 18% 36% 18% 5%	330
December	1st to 10th	Day	13% 15% 41% 24% 6% 1	330
	11th to 20th	Day	19% 16% 36% 22% 7% 1	330
	21st to end	Day	29% 14% 37% 17% 2 1	363
January	1st to 10th	Night	12% 14% 38% 27% 8%	1050
	11th to 20th	Night	16% 14% 37% 28% 5% 1	1050
	21st to end	Night	18% 13% 37% 26% 6%	1155
February	1st to 10th	Night	15% 12% 39% 27% 6% 1	1050
	11th to 20th	Night	15% 14% 41% 25% 5% 1	1029
	21st to end	Night	17% 14% 38% 25% 5% 1	770
March	1st to 10th	Night	21% 13% 34% 26% 7%	678
	11th to 20th	Night	20% 10% 40% 23% 8%	630
	21st to end	Night	23% 11% 36% 23% 6% 1	693
April	1st to 10th	Night	20% 15% 39% 22% 4	630
	11th to 20th	Night	22% 13% 34% 24% 6%	611
	21st to end	Night	23% 9% 35% 26% 6% 2	600
May	1st to 10th	Night	19% 8% 32% 32% 9%	600
	11th to 20th	Night	17% 10% 32% 31% 9% 1	591
	21st to end	Night	19% 6% 29% 33% 12% 1	650
June	1st to 10th	Night	10% 4 29% 42% 15% 1	600
	11th to 20th	Night	13% 3 30% 44% 10%	600
	21st to end	Night	12% 4 27% 42% 15% 1	600
July	1st to 10th	Night	6% 2 17% 43% 29% 2	585
	11th to 20th	Night	5% 2 22% 43% 26% 2	582
	21st to end	Night	6% 2 18% 50% 21% 3	657
August	1st to 10th	Night	7% 2 17% 48% 24% 1	597
	11th to 20th	Night	10% 4 18% 41% 24% 4	594
	21st to end	Night	8% 3 22% 43% 21% 3	660
September	1st to 10th	Night	9% 5% 24% 40% 19% 3	600
	11th to 20th	Night	14% 3 26% 38% 18% 2	600
	21st to end	Night	13% 8% 27% 33% 17% 1	675
October	1st to 10th	Night	14% 8% 32% 32% 12% 1	800
	11th to 20th	Night	18% 11% 36% 28% 7%	800
	21st to end	Night	20% 13% 33% 26% 7%	880
November	1st to 10th	Night	15% 13% 36% 29% 7% 1	873
	11th to 20th	Night	16% 16% 40% 22% 6%	1050
	21st to end	Night	18% 14% 36% 24% 7%	1050
December	1st to 10th	Night	16% 12% 41% 24% 6% 1	1050
	11th to 20th	Night	20% 12% 34% 28% 6%	1050
	21st to end	Night	25% 12% 34% 23% 6%	1155

Page generated at 2026-04-14 01:44:27. Version ac07

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