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 2024-01-17.

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	13% 8% 4 7% 6% 3 5% 5% 5% 7% 37%	74739
	Night	12% 8% 3 7% 6% 3 4 4 5% 7% 40%	75106
Transparency	Day	45% 6% 13% 22% 12% 1	74446
	Night	43% 6% 13% 23% 13% 2	74919
Seeing	Day	17% 10% 30% 27% 13% 4	14756
	Night	16% 9% 32% 31% 11% 1	24770

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	9% 11% 7% 9% 8% 6% 7% 6% 5% 6% 26%	1517
	11th to 20th	Day	10% 14% 6% 12% 9% 4 7% 5% 5% 7% 23%	1576
	21st to end	Day	12% 10% 6% 12% 9% 5% 7% 6% 6% 7% 20%	1782
February	1st to 10th	Day	9% 12% 5% 10% 9% 5% 6% 5% 5% 8% 25%	1620
	11th to 20th	Day	12% 11% 4 7% 6% 4 7% 6% 5% 8% 30%	1574
	21st to end	Day	16% 10% 4 9% 8% 3 5% 4 5% 7% 30%	1412
March	1st to 10th	Day	14% 9% 5% 10% 6% 3 5% 5% 5% 7% 30%	1952
	11th to 20th	Day	14% 9% 3 8% 6% 4 4 5% 6% 7% 34%	1980
	21st to end	Day	20% 11% 4 8% 7% 3 4 4 4 6% 27%	2191
April	1st to 10th	Day	19% 10% 5% 8% 5% 3 4 5% 5% 6% 30%	2160
	11th to 20th	Day	18% 10% 3 6% 6% 3 5% 5% 5% 6% 34%	2134
	21st to end	Day	22% 9% 4 6% 6% 3 4 4 4 6% 32%	2299
May	1st to 10th	Day	18% 9% 4 6% 6% 4 5% 5% 6% 7% 29%	2376
	11th to 20th	Day	19% 8% 3 5% 5% 3 5% 5% 4 7% 36%	2479
	21st to end	Day	17% 8% 3 6% 5% 3 6% 4 5% 7% 37%	2725
June	1st to 10th	Day	11% 6% 2 5% 4 3 5% 5% 5% 9% 44%	2520
	11th to 20th	Day	12% 6% 2 5% 4 3 4 5% 6% 9% 43%	2520
	21st to end	Day	10% 5% 2 5% 5% 3 6% 6% 7% 10% 40%	2520
July	1st to 10th	Day	7% 4 2 4 4 3 5% 5% 7% 10% 47%	2520
	11th to 20th	Day	7% 4 2 5% 5% 3 5% 5% 6% 8% 50%	2520
	21st to end	Day	6% 4 2 5% 4 3 6% 6% 7% 10% 48%	2631
August	1st to 10th	Day	8% 6% 3 6% 5% 3 6% 5% 7% 9% 42%	2328
	11th to 20th	Day	11% 6% 3 6% 4 3 5% 5% 6% 8% 43%	2301
	21st to end	Day	9% 4 2 5% 4 3 4 5% 7% 8% 49%	2430
September	1st to 10th	Day	12% 5% 2 5% 5% 3 4 3 5% 7% 49%	2160
	11th to 20th	Day	11% 5% 2 5% 6% 3 3 3 5% 8% 49%	2134
	21st to end	Day	12% 6% 3 5% 5% 3 5% 5% 5% 7% 45%	1894
October	1st to 10th	Day	17% 6% 3 5% 4 3 4 4 4 7% 44%	1800
	11th to 20th	Day	16% 8% 3 5% 4 2 3 4 5% 6% 42%	1800
	21st to end	Day	17% 11% 4 5% 5% 2 4 4 4 6% 39%	1980
November	1st to 10th	Day	10% 9% 3 4 5% 2 4 4 6% 8% 44%	1643
	11th to 20th	Day	13% 8% 4 9% 8% 4 5% 5% 6% 7% 32%	1520
	21st to end	Day	14% 11% 4 6% 5% 3 4 3 4 7% 39%	1520
December	1st to 10th	Day	13% 9% 4 10% 9% 4 6% 5% 5% 8% 27%	1520
	11th to 20th	Day	12% 13% 6% 9% 7% 3 6% 5% 5% 8% 27%	1918
	21st to end	Day	20% 14% 8% 16% 6% 2 3 4 3 5% 18%	2783
January	1st to 10th	Night	8% 9% 4 10% 9% 4 5% 6% 5% 7% 33%	2648
	11th to 20th	Night	10% 12% 5% 11% 8% 5% 5% 6% 6% 7% 26%	2520
	21st to end	Night	13% 12% 5% 10% 7% 3 5% 5% 5% 8% 27%	2574
February	1st to 10th	Night	10% 11% 5% 10% 8% 4 6% 4 6% 6% 31%	2340
	11th to 20th	Night	9% 10% 3 7% 7% 3 5% 5% 5% 7% 38%	2273
	21st to end	Night	13% 9% 4 8% 6% 3 6% 4 4 5% 37%	1844
March	1st to 10th	Night	14% 9% 4 6% 5% 2 4 5% 4 7% 40%	2022
	11th to 20th	Night	13% 9% 4 7% 5% 3 4 4 5% 7% 38%	1980
	21st to end	Night	18% 11% 4 7% 6% 4 4 5% 5% 6% 31%	2165
April	1st to 10th	Night	15% 9% 4 7% 5% 3 4 4 5% 6% 39%	1800
	11th to 20th	Night	19% 8% 3 5% 5% 2 5% 5% 5% 6% 38%	1775
	21st to end	Night	19% 8% 3 5% 3 3 4 4 6% 6% 41%	1656
May	1st to 10th	Night	17% 8% 2 5% 6% 3 4 5% 5% 6% 40%	1581
	11th to 20th	Night	16% 6% 3 5% 6% 2 4 5% 5% 7% 41%	1416
	21st to end	Night	14% 7% 3 4 5% 3 4 4 5% 8% 43%	1551
June	1st to 10th	Night	9% 3 2 4 5% 3 5% 7% 6% 8% 48%	1440
	11th to 20th	Night	11% 4 2 4 5% 2 4 5% 6% 9% 47%	1440
	21st to end	Night	10% 5% 2 4 4 2 3 3 4 11% 52%	1440
July	1st to 10th	Night	5% 4 2 4 4 2 4 5% 5% 8% 56%	1440
	11th to 20th	Night	4 2 2 3 4 3 4 4 5% 10% 59%	1440
	21st to end	Night	5% 3 1 3 3 2 3 4 7% 9% 60%	1685
August	1st to 10th	Night	5% 4 2 5% 5% 3 4 6% 5% 10% 51%	1611
	11th to 20th	Night	9% 5% 2 4 3 2 4 5% 5% 9% 52%	1600
	21st to end	Night	7% 4 2 4 4 2 4 4 5% 6% 58%	1925
September	1st to 10th	Night	9% 4 3 5% 4 2 3 5% 4 5% 57%	1800
	11th to 20th	Night	11% 6% 2 4 4 3 2 4 4 8% 53%	1824
	21st to end	Night	11% 6% 2 4 3 2 4 3 5% 6% 54%	2047
October	1st to 10th	Night	13% 6% 2 4 5% 3 4 4 5% 6% 49%	2160
	11th to 20th	Night	16% 6% 3 6% 5% 3 4 4 4 6% 45%	2160
	21st to end	Night	15% 9% 3 6% 5% 3 4 4 4 5% 41%	2376
November	1st to 10th	Night	12% 7% 3 5% 4 2 4 4 6% 6% 48%	2430
	11th to 20th	Night	12% 9% 5% 8% 7% 3 4 4 5% 6% 37%	2660
	21st to end	Night	14% 9% 3 7% 5% 2 4 4 4 6% 41%	2660
December	1st to 10th	Night	10% 10% 5% 10% 8% 3 5% 5% 5% 7% 32%	2660
	11th to 20th	Night	13% 10% 4 9% 8% 4 5% 5% 5% 7% 30%	3279
	21st to end	Night	20% 15% 6% 13% 7% 4 4 4 4 5% 19%	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	58% 5% 12% 15% 10%	1518
	11th to 20th	Day	61% 4 13% 14% 7% 1	1576
	21st to end	Day	63% 6% 12% 12% 6% 1	1782
February	1st to 10th	Day	56% 5% 13% 17% 8% 1	1620
	11th to 20th	Day	51% 6% 12% 21% 8% 2	1583
	21st to end	Day	55% 6% 10% 18% 10% 2	1412
March	1st to 10th	Day	52% 6% 14% 20% 6% 1	1952
	11th to 20th	Day	48% 7% 14% 22% 9% 1	1980
	21st to end	Day	57% 7% 11% 18% 6% 1	2191
April	1st to 10th	Day	54% 5% 13% 19% 8% 1	2160
	11th to 20th	Day	51% 6% 11% 19% 13% 1	2134
	21st to end	Day	53% 5% 11% 20% 9% 1	2299
May	1st to 10th	Day	53% 6% 13% 18% 8% 1	2376
	11th to 20th	Day	48% 6% 13% 22% 10% 1	2483
	21st to end	Day	46% 6% 13% 20% 12% 2	2725
June	1st to 10th	Day	36% 7% 15% 28% 14% 1	2520
	11th to 20th	Day	36% 7% 14% 22% 19% 1	2520
	21st to end	Day	37% 9% 16% 24% 13% 1	2520
July	1st to 10th	Day	31% 7% 16% 31% 13% 2	2451
	11th to 20th	Day	31% 7% 15% 26% 17% 3	2445
	21st to end	Day	29% 9% 17% 29% 15% 2	2485
August	1st to 10th	Day	36% 8% 14% 27% 12% 2	2314
	11th to 20th	Day	37% 8% 13% 28% 13% 1	2301
	21st to end	Day	32% 8% 12% 27% 20% 1	2430
September	1st to 10th	Day	34% 6% 13% 28% 16% 2	2160
	11th to 20th	Day	34% 6% 14% 33% 13%	2134
	21st to end	Day	38% 5% 11% 29% 15% 1	1894
October	1st to 10th	Day	41% 5% 11% 26% 15% 1	1800
	11th to 20th	Day	42% 4 13% 25% 15% 1	1800
	21st to end	Day	48% 4 12% 24% 12%	1980
November	1st to 10th	Day	38% 6% 14% 24% 16% 2	1643
	11th to 20th	Day	51% 7% 12% 21% 9% 1	1520
	21st to end	Day	47% 4 16% 22% 10% 1	1520
December	1st to 10th	Day	55% 6% 15% 15% 9% 1	1520
	11th to 20th	Day	54% 5% 19% 15% 6%	1915
	21st to end	Day	70% 4 8% 13% 5% 1	2783
January	1st to 10th	Night	50% 5% 13% 21% 11% 1	2648
	11th to 20th	Night	56% 6% 15% 15% 8%	2520
	21st to end	Night	57% 5% 12% 18% 8% 1	2574
February	1st to 10th	Night	54% 5% 11% 20% 10% 1	2340
	11th to 20th	Night	45% 5% 13% 23% 11% 2	2274
	21st to end	Night	48% 4 12% 21% 13% 2	1844
March	1st to 10th	Night	45% 6% 15% 26% 8% 1	2022
	11th to 20th	Night	46% 5% 12% 24% 13% 1	1980
	21st to end	Night	54% 7% 12% 18% 8% 2	2165
April	1st to 10th	Night	46% 5% 11% 23% 13% 1	1800
	11th to 20th	Night	47% 5% 11% 19% 16% 2	1775
	21st to end	Night	43% 5% 11% 25% 13% 2	1656
May	1st to 10th	Night	45% 6% 12% 22% 15% 1	1581
	11th to 20th	Night	42% 7% 11% 25% 13% 2	1417
	21st to end	Night	40% 6% 13% 25% 15% 2	1552
June	1st to 10th	Night	30% 9% 15% 28% 16% 2	1440
	11th to 20th	Night	32% 8% 15% 21% 20% 4	1440
	21st to end	Night	28% 7% 16% 29% 17% 2	1440
July	1st to 10th	Night	26% 6% 14% 34% 17% 3	1400
	11th to 20th	Night	21% 7% 18% 30% 20% 4	1392
	21st to end	Night	20% 6% 17% 33% 20% 3	1591
August	1st to 10th	Night	28% 7% 15% 29% 18% 3	1601
	11th to 20th	Night	29% 7% 14% 31% 17% 2	1600
	21st to end	Night	26% 7% 14% 28% 21% 4	1925
September	1st to 10th	Night	29% 6% 11% 27% 25% 1	1800
	11th to 20th	Night	31% 5% 11% 31% 20% 1	1824
	21st to end	Night	32% 5% 11% 30% 21% 2	2047
October	1st to 10th	Night	35% 6% 12% 27% 19% 2	2160
	11th to 20th	Night	39% 5% 12% 24% 18% 2	2160
	21st to end	Night	46% 4 12% 22% 15% 1	2376
November	1st to 10th	Night	37% 5% 13% 25% 17% 3	2430
	11th to 20th	Night	47% 6% 12% 22% 12% 1	2660
	21st to end	Night	46% 5% 12% 26% 10% 1	2660
December	1st to 10th	Night	51% 5% 16% 19% 8% 1	2660
	11th to 20th	Night	52% 6% 15% 21% 5% 1	3281
	21st to end	Night	68% 5% 8% 13% 6%	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% 11% 35% 25% 10% 1	270
	11th to 20th	Day	19% 10% 42% 24% 4 1	258
	21st to end	Day	19% 10% 39% 24% 6% 2	264
February	1st to 10th	Day	13% 20% 35% 25% 4 2	240
	11th to 20th	Day	17% 19% 39% 19% 5% 1	240
	21st to end	Day	26% 14% 33% 23% 4	198
March	1st to 10th	Day	17% 16% 43% 16% 8%	240
	11th to 20th	Day	23% 12% 32% 26% 5% 2	240
	21st to end	Day	33% 14% 27% 19% 6% 1	277
April	1st to 10th	Day	27% 13% 35% 21% 4	420
	11th to 20th	Day	26% 16% 28% 21% 8% 1	412
	21st to end	Day	26% 14% 30% 19% 8% 2	559
May	1st to 10th	Day	23% 13% 34% 22% 7% 1	603
	11th to 20th	Day	24% 12% 28% 22% 10% 4	625
	21st to end	Day	21% 8% 27% 25% 15% 4	679
June	1st to 10th	Day	10% 6% 26% 32% 21% 4	630
	11th to 20th	Day	13% 7% 29% 34% 14% 3	630
	21st to end	Day	12% 6% 34% 30% 14% 4	630
July	1st to 10th	Day	8% 4 18% 34% 25% 11%	621
	11th to 20th	Day	9% 3 29% 32% 21% 6%	618
	21st to end	Day	7% 2 26% 38% 22% 5%	684
August	1st to 10th	Day	8% 3 21% 35% 24% 8%	626
	11th to 20th	Day	11% 4 21% 30% 26% 7%	615
	21st to end	Day	10% 6% 22% 34% 21% 6%	549
September	1st to 10th	Day	16% 7% 24% 28% 20% 5%	450
	11th to 20th	Day	10% 4 30% 32% 18% 5%	424
	21st to end	Day	14% 13% 31% 30% 8% 4	270
October	1st to 10th	Day	22% 9% 26% 25% 14% 4	270
	11th to 20th	Day	19% 20% 35% 18% 8% 1	270
	21st to end	Day	25% 16% 33% 17% 6% 3	297
November	1st to 10th	Day	17% 14% 35% 24% 7% 1	270
	11th to 20th	Day	17% 21% 35% 17% 9%	270
	21st to end	Day	23% 16% 38% 18% 5%	270
December	1st to 10th	Day	13% 14% 40% 25% 6% 1	270
	11th to 20th	Day	19% 13% 35% 24% 9% 1	270
	21st to end	Day	27% 15% 38% 18% 2	297
January	1st to 10th	Night	12% 15% 38% 27% 8%	950
	11th to 20th	Night	16% 12% 37% 29% 5% 1	933
	21st to end	Night	20% 12% 36% 25% 7%	990
February	1st to 10th	Night	16% 12% 39% 27% 6% 1	900
	11th to 20th	Night	15% 14% 39% 25% 5% 1	879
	21st to end	Night	18% 14% 35% 25% 6% 1	660
March	1st to 10th	Night	21% 12% 34% 26% 7%	582
	11th to 20th	Night	19% 8% 39% 24% 9%	540
	21st to end	Night	23% 10% 35% 24% 7% 2	594
April	1st to 10th	Night	19% 14% 39% 24% 4	540
	11th to 20th	Night	24% 11% 34% 24% 6%	533
	21st to end	Night	22% 8% 36% 26% 7% 2	540
May	1st to 10th	Night	19% 8% 32% 32% 8%	540
	11th to 20th	Night	17% 9% 33% 31% 9% 1	531
	21st to end	Night	19% 5% 29% 33% 13% 1	584
June	1st to 10th	Night	9% 4 28% 43% 15% 1	540
	11th to 20th	Night	13% 3 27% 46% 11%	540
	21st to end	Night	11% 3 27% 42% 16% 1	540
July	1st to 10th	Night	6% 2 17% 42% 31% 2	525
	11th to 20th	Night	4 2 23% 43% 26% 2	522
	21st to end	Night	5% 2 18% 51% 21% 3	591
August	1st to 10th	Night	7% 2 17% 49% 25% 1	537
	11th to 20th	Night	10% 4 18% 40% 25% 4	534
	21st to end	Night	8% 3 22% 43% 21% 3	594
September	1st to 10th	Night	10% 4 23% 40% 19% 3	540
	11th to 20th	Night	14% 3 27% 37% 18% 2	540
	21st to end	Night	15% 9% 30% 32% 14%	607
October	1st to 10th	Night	15% 8% 33% 31% 13% 1	720
	11th to 20th	Night	19% 12% 35% 27% 8%	720
	21st to end	Night	20% 13% 32% 26% 8%	792
November	1st to 10th	Night	15% 12% 36% 29% 7% 1	787
	11th to 20th	Night	16% 15% 41% 21% 6%	950
	21st to end	Night	18% 13% 36% 25% 7%	950
December	1st to 10th	Night	17% 11% 40% 24% 7% 1	950
	11th to 20th	Night	21% 10% 34% 29% 6%	950
	21st to end	Night	25% 12% 34% 23% 6%	1045

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