Marshfield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Marshfield clear sky chart from 2005-11-06 to 2024-02-15.

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% 7% 3 6% 5% 3 4 4 5% 7% 43%	78470
	Night	12% 7% 3 5% 5% 2 4 4 5% 7% 46%	80655
Transparency	Day	40% 7% 11% 23% 16% 3	78193
	Night	38% 6% 11% 24% 18% 3	80452
Seeing	Day	15% 13% 27% 26% 15% 3	14486
	Night	16% 13% 32% 27% 12% 1	24505

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	14% 11% 4 5% 5% 3 3 3 4 4 44%	2847
	11th to 20th	Day	10% 11% 5% 7% 6% 3 4 3 4 5% 42%	2850
	21st to end	Day	21% 10% 4 7% 4 2 3 3 4 5% 38%	3135
February	1st to 10th	Day	14% 10% 5% 7% 6% 4 4 4 4 6% 35%	1710
	11th to 20th	Day	14% 8% 4 6% 5% 3 5% 4 4 5% 40%	1650
	21st to end	Day	15% 11% 3 6% 5% 3 5% 4 5% 6% 37%	1517
March	1st to 10th	Day	12% 10% 5% 6% 3 3 4 4 4 7% 42%	1980
	11th to 20th	Day	19% 10% 4 6% 4 2 3 4 4 6% 36%	1980
	21st to end	Day	19% 11% 4 6% 6% 3 6% 5% 4 6% 31%	2178
April	1st to 10th	Day	11% 7% 3 6% 4 3 5% 4 5% 7% 45%	2150
	11th to 20th	Day	16% 9% 3 6% 5% 2 4 4 4 7% 40%	2134
	21st to end	Day	20% 7% 3 6% 5% 3 4 5% 5% 6% 36%	2160
May	1st to 10th	Day	19% 7% 3 6% 6% 3 5% 4 5% 5% 36%	2274
	11th to 20th	Day	15% 6% 3 5% 5% 3 4 4 5% 7% 42%	2302
	21st to end	Day	11% 6% 3 6% 6% 4 7% 7% 6% 9% 35%	2675
June	1st to 10th	Day	9% 4 2 5% 5% 3 4 5% 6% 11% 46%	2520
	11th to 20th	Day	7% 4 2 5% 4 4 5% 5% 7% 10% 47%	2520
	21st to end	Day	6% 3 2 4 4 3 5% 5% 6% 9% 53%	2520
July	1st to 10th	Day	9% 4 2 5% 5% 4 6% 6% 7% 12% 40%	2418
	11th to 20th	Day	4 3 1 4 5% 4 6% 6% 8% 10% 48%	2340
	21st to end	Day	9% 4 3 5% 6% 4 6% 5% 8% 9% 40%	2546
August	1st to 10th	Day	8% 5% 2 6% 6% 4 6% 5% 8% 9% 41%	2328
	11th to 20th	Day	9% 5% 3 6% 6% 3 5% 6% 7% 9% 42%	2226
	21st to end	Day	7% 4 2 5% 6% 3 5% 5% 6% 8% 49%	2376
September	1st to 10th	Day	12% 4 2 4 5% 3 4 4 5% 8% 48%	2160
	11th to 20th	Day	10% 5% 3 6% 5% 3 5% 4 4 6% 47%	2134
	21st to end	Day	8% 5% 2 4 4 3 4 6% 6% 6% 52%	1890
October	1st to 10th	Day	11% 5% 2 4 4 3 3 4 4 7% 54%	1800
	11th to 20th	Day	13% 6% 3 4 4 2 3 3 4 5% 52%	1800
	21st to end	Day	18% 7% 2 5% 4 2 2 3 4 5% 47%	1980
November	1st to 10th	Day	11% 6% 2 4 3 2 3 3 3 5% 57%	1858
	11th to 20th	Day	13% 6% 3 5% 4 2 2 3 5% 8% 47%	1739
	21st to end	Day	14% 8% 3 6% 4 2 3 3 4 6% 48%	1520
December	1st to 10th	Day	12% 9% 4 5% 4 4 4 5% 5% 7% 42%	1520
	11th to 20th	Day	11% 10% 5% 8% 5% 3 3 4 3 5% 42%	1918
	21st to end	Day	13% 16% 6% 9% 6% 3 5% 4 4 5% 29%	2815
January	1st to 10th	Night	11% 9% 4 10% 6% 3 4 3 4 5% 39%	4108
	11th to 20th	Night	10% 7% 3 7% 9% 3 6% 5% 5% 5% 39%	4120
	21st to end	Night	20% 13% 5% 7% 3 2 2 4 3 4 37%	4532
February	1st to 10th	Night	14% 9% 3 6% 5% 2 4 4 4 6% 41%	2470
	11th to 20th	Night	14% 8% 3 7% 5% 2 3 3 4 6% 44%	2289
	21st to end	Night	14% 10% 3 5% 7% 2 4 4 4 5% 42%	1754
March	1st to 10th	Night	15% 8% 4 5% 4 2 3 3 4 6% 46%	1980
	11th to 20th	Night	18% 10% 3 6% 4 3 4 4 4 5% 39%	1980
	21st to end	Night	18% 9% 4 7% 6% 2 5% 5% 4 6% 34%	2178
April	1st to 10th	Night	10% 5% 2 4 4 3 3 4 5% 8% 52%	1810
	11th to 20th	Night	13% 8% 2 6% 3 2 3 4 5% 9% 45%	1775
	21st to end	Night	18% 7% 3 6% 5% 3 3 4 6% 6% 40%	1800
May	1st to 10th	Night	13% 6% 2 5% 4 2 4 4 4 8% 46%	1683
	11th to 20th	Night	15% 5% 2 5% 5% 2 4 4 5% 8% 46%	1593
	21st to end	Night	11% 6% 4 5% 5% 3 5% 6% 7% 9% 40%	1599
June	1st to 10th	Night	7% 4 2 4 3 3 4 5% 5% 9% 53%	1440
	11th to 20th	Night	5% 3 2 3 4 3 4 5% 7% 10% 55%	1440
	21st to end	Night	3 1 1 3 3 2 4 3 5% 9% 65%	1440
July	1st to 10th	Night	7% 3 2 3 4 3 3 6% 8% 9% 51%	1537
	11th to 20th	Night	3 2 1 3 4 2 3 5% 7% 11% 58%	1620
	21st to end	Night	5% 3 2 4 5% 3 5% 5% 6% 10% 52%	1772
August	1st to 10th	Night	5% 4 1 4 5% 4 5% 5% 6% 9% 52%	1611
	11th to 20th	Night	7% 3 1 4 4 3 4 4 6% 8% 56%	1673
	21st to end	Night	5% 3 1 4 5% 3 3 4 5% 8% 57%	1980
September	1st to 10th	Night	9% 4 2 3 4 3 3 4 4 7% 56%	1800
	11th to 20th	Night	9% 4 2 4 4 3 4 4 5% 8% 53%	1822
	21st to end	Night	8% 3 1 4 4 2 4 3 4 7% 59%	2052
October	1st to 10th	Night	8% 4 1 3 4 2 3 4 5% 8% 59%	2160
	11th to 20th	Night	14% 5% 2 3 3 2 3 4 4 6% 54%	2160
	21st to end	Night	16% 7% 2 4 4 2 3 4 4 5% 49%	2376
November	1st to 10th	Night	11% 5% 2 4 3 2 3 3 4 5% 59%	2220
	11th to 20th	Night	12% 7% 2 5% 3 2 3 3 4 6% 51%	2437
	21st to end	Night	14% 8% 3 5% 4 2 3 4 4 6% 47%	2657
December	1st to 10th	Night	14% 9% 4 6% 5% 2 3 4 5% 7% 41%	2660
	11th to 20th	Night	13% 9% 4 7% 5% 2 4 4 4 6% 42%	3279
	21st to end	Night	15% 17% 6% 8% 5% 3 4 4 4 5% 30%	4848

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	43% 5% 7% 26% 18% 2	2848
	11th to 20th	Day	44% 5% 9% 27% 12% 4	2850
	21st to end	Day	50% 4 9% 17% 16% 5%	3135
February	1st to 10th	Day	50% 5% 11% 20% 13% 1	1710
	11th to 20th	Day	46% 4 11% 20% 15% 4	1659
	21st to end	Day	48% 4 8% 21% 14% 6%	1517
March	1st to 10th	Day	43% 5% 9% 18% 19% 5%	1980
	11th to 20th	Day	50% 5% 9% 18% 13% 4	1980
	21st to end	Day	53% 7% 11% 17% 9% 1	2178
April	1st to 10th	Day	38% 7% 13% 23% 18% 1	2150
	11th to 20th	Day	46% 6% 11% 20% 14% 3	2134
	21st to end	Day	49% 7% 9% 23% 11% 1	2160
May	1st to 10th	Day	49% 7% 11% 20% 12% 1	2274
	11th to 20th	Day	42% 8% 14% 23% 13% 1	2306
	21st to end	Day	43% 12% 13% 21% 11% 1	2675
June	1st to 10th	Day	32% 9% 16% 26% 15% 1	2520
	11th to 20th	Day	30% 9% 15% 30% 13% 2	2520
	21st to end	Day	25% 9% 17% 28% 16% 4	2520
July	1st to 10th	Day	34% 12% 18% 22% 12% 3	2354
	11th to 20th	Day	27% 10% 16% 25% 19% 3	2271
	21st to end	Day	37% 10% 14% 29% 10% 1	2405
August	1st to 10th	Day	36% 10% 18% 23% 13% 1	2314
	11th to 20th	Day	36% 9% 14% 26% 13% 1	2226
	21st to end	Day	31% 7% 13% 23% 18% 6%	2376
September	1st to 10th	Day	33% 7% 13% 25% 14% 7%	2160
	11th to 20th	Day	37% 7% 8% 22% 24% 1	2134
	21st to end	Day	30% 7% 10% 26% 24% 3	1890
October	1st to 10th	Day	31% 6% 9% 25% 24% 5%	1800
	11th to 20th	Day	36% 3 8% 25% 22% 7%	1800
	21st to end	Day	40% 4 9% 24% 17% 6%	1980
November	1st to 10th	Day	32% 4 9% 26% 23% 6%	1858
	11th to 20th	Day	36% 5% 9% 20% 24% 6%	1739
	21st to end	Day	40% 4 9% 23% 21% 3	1520
December	1st to 10th	Day	42% 6% 10% 26% 14% 2	1520
	11th to 20th	Day	46% 6% 6% 18% 22% 2	1915
	21st to end	Day	56% 6% 8% 16% 12% 2	2815
January	1st to 10th	Night	46% 6% 10% 22% 15% 1	4108
	11th to 20th	Night	43% 7% 11% 24% 13% 2	4120
	21st to end	Night	51% 5% 9% 19% 14% 2	4532
February	1st to 10th	Night	44% 5% 11% 23% 14% 3	2470
	11th to 20th	Night	43% 5% 10% 22% 17% 3	2290
	21st to end	Night	45% 4 9% 22% 15% 5%	1754
March	1st to 10th	Night	41% 5% 9% 20% 19% 7%	1980
	11th to 20th	Night	47% 7% 9% 19% 15% 3	1980
	21st to end	Night	51% 7% 10% 20% 10% 1	2178
April	1st to 10th	Night	30% 6% 13% 25% 22% 4	1810
	11th to 20th	Night	36% 7% 13% 23% 16% 6%	1775
	21st to end	Night	44% 6% 11% 24% 15% 1	1800
May	1st to 10th	Night	38% 7% 13% 24% 17% 1	1683
	11th to 20th	Night	37% 7% 14% 24% 16% 3	1594
	21st to end	Night	39% 10% 16% 23% 12% 1	1600
June	1st to 10th	Night	26% 7% 17% 29% 18% 2	1440
	11th to 20th	Night	23% 7% 16% 32% 20% 3	1440
	21st to end	Night	16% 6% 20% 32% 20% 6%	1440
July	1st to 10th	Night	26% 11% 15% 27% 16% 4	1492
	11th to 20th	Night	19% 8% 16% 29% 25% 3	1566
	21st to end	Night	25% 8% 15% 37% 14% 1	1673
August	1st to 10th	Night	27% 8% 16% 35% 13% 1	1601
	11th to 20th	Night	26% 7% 15% 32% 19% 2	1673
	21st to end	Night	25% 6% 16% 26% 21% 6%	1980
September	1st to 10th	Night	29% 6% 12% 28% 19% 6%	1800
	11th to 20th	Night	30% 6% 11% 24% 26% 3	1822
	21st to end	Night	26% 6% 11% 23% 31% 4	2052
October	1st to 10th	Night	24% 7% 11% 27% 25% 6%	2160
	11th to 20th	Night	32% 5% 8% 25% 24% 7%	2160
	21st to end	Night	38% 5% 8% 22% 21% 6%	2376
November	1st to 10th	Night	29% 4 10% 26% 23% 7%	2220
	11th to 20th	Night	34% 4 8% 24% 25% 5%	2437
	21st to end	Night	40% 5% 8% 23% 21% 3	2657
December	1st to 10th	Night	42% 5% 12% 21% 17% 2	2660
	11th to 20th	Night	46% 4 8% 20% 20% 2	3281
	21st to end	Night	57% 7% 10% 15% 9% 2	4848

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	21% 28% 36% 14% 2	270
	11th to 20th	Day	28% 29% 35% 9%	270
	21st to end	Day	18% 32% 36% 13% 1	297
February	1st to 10th	Day	20% 28% 40% 10% 2	270
	11th to 20th	Day	27% 31% 29% 10% 3	252
	21st to end	Day	31% 28% 33% 7% 2	198
March	1st to 10th	Day	20% 30% 39% 10% 1	240
	11th to 20th	Day	31% 19% 34% 13% 3	240
	21st to end	Day	33% 25% 33% 8% 2	264
April	1st to 10th	Day	18% 21% 37% 19% 3 1	410
	11th to 20th	Day	24% 22% 32% 18% 5%	412
	21st to end	Day	25% 18% 35% 18% 4	420
May	1st to 10th	Day	21% 18% 33% 22% 6%	537
	11th to 20th	Day	19% 12% 31% 24% 13% 1	625
	21st to end	Day	13% 9% 35% 25% 15% 4	679
June	1st to 10th	Day	9% 6% 20% 33% 26% 6%	630
	11th to 20th	Day	7% 3 25% 38% 24% 4	630
	21st to end	Day	6% 5% 30% 37% 18% 4	630
July	1st to 10th	Day	10% 2 17% 33% 29% 9%	621
	11th to 20th	Day	4 3 17% 41% 31% 5%	618
	21st to end	Day	10% 1 14% 35% 31% 9%	684
August	1st to 10th	Day	11% 3 14% 41% 26% 5%	626
	11th to 20th	Day	9% 4 17% 36% 28% 6%	540
	21st to end	Day	11% 2 13% 33% 32% 10%	495
September	1st to 10th	Day	11% 3 12% 40% 27% 7%	450
	11th to 20th	Day	8% 2 20% 42% 21% 7%	424
	21st to end	Day	11% 7% 29% 30% 20% 4	270
October	1st to 10th	Day	12% 9% 35% 30% 11% 3	270
	11th to 20th	Day	18% 17% 41% 19% 5%	270
	21st to end	Day	30% 20% 29% 19% 1	297
November	1st to 10th	Day	14% 16% 43% 20% 6% 1	270
	11th to 20th	Day	19% 22% 33% 20% 4 1	270
	21st to end	Day	23% 22% 31% 20% 4	270
December	1st to 10th	Day	16% 30% 31% 16% 4 2	270
	11th to 20th	Day	22% 23% 36% 14% 4	270
	21st to end	Day	19% 36% 34% 10% 2	297
January	1st to 10th	Night	18% 23% 38% 17% 4	950
	11th to 20th	Night	20% 24% 39% 14% 3	950
	21st to end	Night	19% 22% 40% 18% 1	1045
February	1st to 10th	Night	19% 21% 42% 15% 2	950
	11th to 20th	Night	21% 21% 41% 16% 2	859
	21st to end	Night	21% 24% 38% 15% 1	570
March	1st to 10th	Night	20% 18% 38% 21% 3	540
	11th to 20th	Night	25% 16% 35% 19% 5%	540
	21st to end	Night	22% 17% 38% 19% 4	594
April	1st to 10th	Night	14% 18% 38% 26% 4	540
	11th to 20th	Night	17% 15% 39% 23% 5%	533
	21st to end	Night	20% 14% 41% 19% 6%	540
May	1st to 10th	Night	16% 9% 39% 29% 7%	540
	11th to 20th	Night	16% 7% 32% 29% 14% 1	531
	21st to end	Night	13% 7% 31% 29% 18% 3	584
June	1st to 10th	Night	9% 4 20% 40% 26% 2	540
	11th to 20th	Night	6% 2 26% 43% 21% 2	540
	21st to end	Night	3 1 24% 49% 22% 1	540
July	1st to 10th	Night	9% 1 11% 42% 32% 5%	525
	11th to 20th	Night	3 1 15% 43% 34% 3	522
	21st to end	Night	5% 1 14% 45% 32% 3	591
August	1st to 10th	Night	7% 2 14% 43% 31% 3	537
	11th to 20th	Night	8% 1 16% 43% 28% 3	534
	21st to end	Night	6% 2 14% 40% 34% 5%	594
September	1st to 10th	Night	10% 2 15% 41% 29% 3	540
	11th to 20th	Night	11% 1 15% 44% 25% 3	540
	21st to end	Night	10% 5% 26% 37% 20% 3	612
October	1st to 10th	Night	9% 6% 32% 30% 20% 3	720
	11th to 20th	Night	16% 13% 37% 26% 7%	720
	21st to end	Night	22% 12% 34% 25% 7%	792
November	1st to 10th	Night	12% 13% 42% 25% 8%	740
	11th to 20th	Night	17% 17% 38% 22% 7%	760
	21st to end	Night	19% 16% 36% 21% 7%	947
December	1st to 10th	Night	21% 17% 38% 20% 4	950
	11th to 20th	Night	22% 17% 38% 21% 3	950
	21st to end	Night	20% 22% 39% 17% 2	1045

Page generated at 2024-02-12 05:35:33. Version ac07

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