Green Bay
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Green Bay clear sky chart from 2005-11-06 to 2024-03-23.

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% 6% 7% 37%	78584
	Night	13% 10% 4 7% 6% 3 4 4 5% 6% 37%	81360
Transparency	Day	46% 6% 13% 23% 11% 1	78285
	Night	47% 5% 12% 23% 12% 1	81180
Seeing	Day	15% 11% 30% 27% 14% 4	15003
	Night	17% 8% 32% 31% 11% 1	25101

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	11% 11% 6% 11% 7% 4 6% 5% 5% 5% 29%	2527
	11th to 20th	Day	12% 12% 5% 9% 8% 5% 7% 6% 6% 7% 22%	2530
	21st to end	Day	16% 16% 7% 12% 7% 4 5% 3 4 4 22%	2783
February	1st to 10th	Day	10% 11% 5% 9% 8% 3 5% 4 5% 7% 33%	1663
	11th to 20th	Day	11% 10% 5% 7% 5% 2 4 5% 5% 6% 38%	1819
	21st to end	Day	12% 13% 4 8% 6% 3 5% 5% 5% 6% 33%	1570
March	1st to 10th	Day	13% 10% 4 6% 5% 3 4 5% 5% 8% 38%	1900
	11th to 20th	Day	11% 9% 4 6% 6% 4 5% 6% 5% 6% 39%	1955
	21st to end	Day	16% 11% 4 7% 6% 4 5% 5% 5% 6% 32%	2400
April	1st to 10th	Day	15% 10% 5% 8% 6% 4 5% 5% 6% 7% 29%	2160
	11th to 20th	Day	20% 8% 3 5% 5% 3 4 4 4 6% 36%	2134
	21st to end	Day	17% 9% 4 6% 6% 3 5% 5% 5% 7% 33%	2317
May	1st to 10th	Day	15% 8% 3 7% 6% 3 5% 5% 5% 7% 37%	2386
	11th to 20th	Day	14% 7% 3 6% 6% 4 4 4 5% 7% 40%	2479
	21st to end	Day	11% 6% 2 5% 5% 4 6% 6% 6% 9% 40%	2725
June	1st to 10th	Day	10% 5% 3 5% 5% 3 5% 5% 6% 7% 46%	2520
	11th to 20th	Day	12% 5% 2 5% 5% 3 4 5% 7% 8% 43%	2520
	21st to end	Day	10% 5% 2 5% 5% 3 5% 5% 6% 9% 43%	2520
July	1st to 10th	Day	6% 4 1 4 4 3 5% 5% 7% 11% 49%	2520
	11th to 20th	Day	7% 4 2 5% 5% 3 4 5% 7% 10% 47%	2520
	21st to end	Day	8% 4 2 5% 4 3 5% 5% 6% 9% 48%	2743
August	1st to 10th	Day	7% 5% 2 5% 6% 4 6% 6% 7% 10% 43%	2507
	11th to 20th	Day	10% 5% 2 5% 5% 3 5% 5% 6% 8% 45%	2253
	21st to end	Day	11% 6% 2 5% 5% 3 4 4 6% 8% 45%	2376
September	1st to 10th	Day	13% 7% 2 6% 5% 2 5% 5% 6% 9% 41%	2160
	11th to 20th	Day	12% 5% 2 5% 4 3 4 4 6% 8% 47%	2052
	21st to end	Day	11% 8% 3 7% 6% 3 5% 5% 6% 7% 38%	1980
October	1st to 10th	Day	15% 7% 3 6% 5% 3 4 4 5% 6% 43%	1908
	11th to 20th	Day	20% 10% 4 7% 6% 4 5% 3 5% 6% 30%	1746
	21st to end	Day	17% 9% 4 8% 6% 3 4 4 4 7% 33%	1782
November	1st to 10th	Day	14% 8% 3 5% 6% 3 4 4 5% 8% 40%	1672
	11th to 20th	Day	12% 10% 5% 9% 7% 3 5% 5% 5% 7% 31%	1710
	21st to end	Day	16% 10% 4 7% 5% 3 5% 4 5% 7% 33%	1526
December	1st to 10th	Day	13% 11% 4 8% 7% 3 5% 6% 7% 6% 30%	1520
	11th to 20th	Day	13% 13% 5% 9% 7% 4 5% 6% 5% 6% 26%	1918
	21st to end	Day	18% 16% 6% 12% 8% 4 5% 4 4 5% 17%	2783
January	1st to 10th	Night	13% 15% 7% 9% 7% 3 4 3 3 4 32%	4428
	11th to 20th	Night	11% 12% 6% 11% 8% 4 6% 5% 5% 6% 25%	4440
	21st to end	Night	13% 17% 7% 11% 8% 4 4 4 4 5% 24%	4884
February	1st to 10th	Night	9% 13% 6% 9% 7% 4 5% 4 5% 5% 34%	2513
	11th to 20th	Night	9% 10% 4 9% 7% 4 5% 5% 4 6% 37%	2247
	21st to end	Night	15% 12% 4 8% 6% 3 4 5% 4 5% 35%	1884
March	1st to 10th	Night	14% 8% 3 6% 5% 4 5% 5% 5% 7% 40%	2280
	11th to 20th	Night	12% 8% 3 6% 6% 3 5% 4 5% 6% 43%	2241
	21st to end	Night	18% 9% 4 6% 4 3 5% 5% 4 7% 36%	2000
April	1st to 10th	Night	17% 10% 4 7% 6% 4 5% 4 6% 6% 33%	1800
	11th to 20th	Night	21% 7% 2 5% 5% 3 4 3 5% 6% 39%	1775
	21st to end	Night	16% 10% 3 7% 6% 2 4 5% 5% 6% 36%	1643
May	1st to 10th	Night	16% 7% 3 8% 6% 3 5% 4 6% 8% 34%	1571
	11th to 20th	Night	16% 6% 2 6% 4 4 5% 5% 5% 7% 39%	1416
	21st to end	Night	11% 5% 2 4 6% 3 3 6% 6% 10% 42%	1551
June	1st to 10th	Night	10% 6% 3 4 5% 4 4 5% 6% 8% 45%	1440
	11th to 20th	Night	13% 6% 2 5% 6% 2 4 4 6% 10% 43%	1440
	21st to end	Night	8% 5% 2 4 5% 3 5% 6% 7% 9% 48%	1440
July	1st to 10th	Night	6% 3 2 5% 4 3 4 5% 7% 8% 54%	1440
	11th to 20th	Night	7% 4 2 4 4 3 4 4 7% 10% 51%	1440
	21st to end	Night	6% 3 2 4 5% 3 5% 5% 5% 8% 55%	1575
August	1st to 10th	Night	7% 5% 2 5% 4 3 5% 6% 7% 11% 47%	1432
	11th to 20th	Night	7% 4 2 4 5% 3 5% 4 6% 9% 50%	1645
	21st to end	Night	9% 6% 2 5% 4 3 4 4 5% 7% 51%	1980
September	1st to 10th	Night	10% 4 2 4 4 3 4 5% 5% 7% 53%	1800
	11th to 20th	Night	12% 4 2 5% 4 3 4 3 5% 7% 52%	1889
	21st to end	Night	13% 7% 3 6% 6% 2 4 3 5% 7% 44%	1980
October	1st to 10th	Night	13% 7% 2 5% 5% 2 4 4 6% 6% 46%	2049
	11th to 20th	Night	16% 9% 3 7% 6% 4 4 4 4 6% 37%	2214
	21st to end	Night	18% 11% 4 7% 5% 4 3 4 5% 6% 33%	2574
November	1st to 10th	Night	12% 8% 3 5% 5% 3 4 4 4 8% 44%	2406
	11th to 20th	Night	13% 10% 4 7% 7% 4 5% 4 5% 6% 34%	2470
	21st to end	Night	15% 10% 4 6% 6% 3 4 4 5% 6% 36%	2650
December	1st to 10th	Night	13% 11% 5% 8% 7% 4 5% 4 5% 7% 31%	2660
	11th to 20th	Night	12% 14% 6% 9% 6% 4 5% 4 4 5% 31%	3279
	21st to end	Night	20% 19% 6% 9% 6% 4 4 4 4 4 20%	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	57% 5% 15% 16% 7% 1	2528
	11th to 20th	Day	59% 6% 12% 18% 4 1	2530
	21st to end	Day	66% 5% 11% 14% 5%	2783
February	1st to 10th	Day	50% 6% 12% 21% 11% 1	1663
	11th to 20th	Day	46% 5% 12% 23% 13% 2	1829
	21st to end	Day	51% 5% 12% 21% 9% 2	1570
March	1st to 10th	Day	45% 6% 14% 23% 10% 2	1900
	11th to 20th	Day	45% 6% 13% 21% 12% 2	1955
	21st to end	Day	52% 5% 12% 21% 9% 1	2400
April	1st to 10th	Day	52% 7% 11% 19% 11%	2160
	11th to 20th	Day	50% 5% 9% 21% 13% 2	2134
	21st to end	Day	51% 5% 11% 19% 12% 2	2317
May	1st to 10th	Day	46% 6% 14% 23% 10% 1	2386
	11th to 20th	Day	43% 6% 13% 22% 15% 2	2483
	21st to end	Day	39% 7% 13% 25% 13% 2	2725
June	1st to 10th	Day	37% 6% 12% 28% 15% 2	2520
	11th to 20th	Day	38% 5% 15% 25% 15% 1	2520
	21st to end	Day	36% 7% 15% 25% 15% 1	2520
July	1st to 10th	Day	28% 8% 14% 31% 17% 3	2451
	11th to 20th	Day	31% 7% 14% 29% 16% 3	2445
	21st to end	Day	31% 8% 14% 28% 17% 3	2591
August	1st to 10th	Day	35% 7% 15% 29% 12% 2	2492
	11th to 20th	Day	35% 8% 15% 29% 12% 1	2253
	21st to end	Day	37% 7% 13% 26% 16% 1	2376
September	1st to 10th	Day	40% 6% 12% 26% 14% 1	2160
	11th to 20th	Day	35% 5% 18% 31% 10% 1	2052
	21st to end	Day	43% 7% 14% 27% 9%	1980
October	1st to 10th	Day	42% 5% 14% 28% 10% 1	1908
	11th to 20th	Day	54% 6% 11% 20% 8% 1	1746
	21st to end	Day	52% 6% 13% 19% 10%	1782
November	1st to 10th	Day	42% 6% 13% 25% 14% 1	1672
	11th to 20th	Day	52% 5% 15% 18% 9%	1710
	21st to end	Day	51% 5% 16% 21% 6% 1	1526
December	1st to 10th	Day	50% 7% 14% 23% 5%	1520
	11th to 20th	Day	57% 5% 14% 14% 8% 3	1915
	21st to end	Day	71% 4 8% 12% 5%	2783
January	1st to 10th	Night	56% 5% 10% 20% 9% 1	4428
	11th to 20th	Night	60% 5% 10% 19% 6%	4440
	21st to end	Night	63% 4 12% 15% 5%	4884
February	1st to 10th	Night	52% 5% 9% 21% 11% 2	2513
	11th to 20th	Night	49% 4 10% 24% 11% 2	2248
	21st to end	Night	51% 4 12% 21% 10% 2	1884
March	1st to 10th	Night	44% 5% 15% 24% 11% 1	2280
	11th to 20th	Night	42% 5% 12% 24% 16% 2	2241
	21st to end	Night	49% 5% 10% 22% 12% 2	2000
April	1st to 10th	Night	51% 6% 7% 19% 17% 1	1800
	11th to 20th	Night	47% 4 8% 23% 14% 4	1775
	21st to end	Night	48% 5% 11% 20% 14% 1	1643
May	1st to 10th	Night	48% 6% 12% 21% 11% 2	1571
	11th to 20th	Night	44% 6% 11% 24% 13% 2	1417
	21st to end	Night	36% 7% 15% 25% 15% 2	1552
June	1st to 10th	Night	36% 7% 12% 29% 15% 1	1440
	11th to 20th	Night	38% 5% 11% 27% 17% 2	1440
	21st to end	Night	31% 8% 16% 27% 14% 3	1440
July	1st to 10th	Night	26% 6% 13% 35% 16% 4	1400
	11th to 20th	Night	29% 7% 15% 28% 18% 4	1392
	21st to end	Night	27% 5% 17% 29% 18% 3	1487
August	1st to 10th	Night	30% 8% 16% 29% 15% 2	1423
	11th to 20th	Night	31% 7% 15% 30% 16% 1	1645
	21st to end	Night	32% 6% 12% 27% 21% 2	1980
September	1st to 10th	Night	31% 6% 12% 29% 20% 1	1800
	11th to 20th	Night	31% 5% 14% 35% 14% 1	1889
	21st to end	Night	39% 5% 13% 29% 13% 1	1980
October	1st to 10th	Night	38% 6% 10% 31% 14% 2	2049
	11th to 20th	Night	47% 6% 14% 22% 10% 1	2214
	21st to end	Night	51% 6% 13% 19% 11%	2574
November	1st to 10th	Night	40% 5% 11% 27% 15% 2	2406
	11th to 20th	Night	51% 5% 12% 19% 12% 1	2470
	21st to end	Night	48% 5% 14% 25% 7% 1	2650
December	1st to 10th	Night	52% 5% 15% 20% 7% 1	2660
	11th to 20th	Night	56% 4 13% 17% 9% 1	3281
	21st to end	Night	67% 6% 8% 14% 5%	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	14% 14% 32% 28% 11% 1	270
	11th to 20th	Day	23% 14% 31% 26% 6%	270
	21st to end	Day	20% 11% 34% 28% 6% 1	297
February	1st to 10th	Day	13% 16% 40% 22% 7% 1	270
	11th to 20th	Day	11% 23% 39% 19% 7%	270
	21st to end	Day	20% 18% 41% 17% 3	225
March	1st to 10th	Day	14% 23% 38% 20% 5%	270
	11th to 20th	Day	19% 16% 31% 23% 9% 2	297
	21st to end	Day	24% 14% 27% 25% 9% 1	470
April	1st to 10th	Day	22% 14% 32% 23% 8% 1	420
	11th to 20th	Day	24% 18% 25% 21% 9% 2	412
	21st to end	Day	20% 11% 31% 21% 14% 2	420
May	1st to 10th	Day	17% 12% 34% 24% 9% 3	469
	11th to 20th	Day	17% 10% 34% 27% 10% 3	625
	21st to end	Day	14% 9% 28% 29% 16% 5%	679
June	1st to 10th	Day	10% 7% 33% 32% 15% 3	630
	11th to 20th	Day	16% 6% 31% 31% 13% 3	630
	21st to end	Day	12% 7% 28% 33% 17% 3	630
July	1st to 10th	Day	8% 4 21% 35% 24% 9%	621
	11th to 20th	Day	8% 6% 26% 34% 19% 7%	618
	21st to end	Day	7% 4 26% 34% 21% 8%	684
August	1st to 10th	Day	9% 4 22% 34% 24% 7%	626
	11th to 20th	Day	12% 4 19% 29% 25% 11%	463
	21st to end	Day	15% 6% 21% 27% 24% 7%	495
September	1st to 10th	Day	15% 9% 24% 28% 18% 7%	450
	11th to 20th	Day	12% 5% 22% 35% 20% 6%	450
	21st to end	Day	16% 12% 25% 25% 17% 6%	450
October	1st to 10th	Day	17% 13% 25% 25% 17% 3	378
	11th to 20th	Day	20% 21% 31% 22% 6%	270
	21st to end	Day	24% 19% 36% 16% 4 1	297
November	1st to 10th	Day	17% 14% 36% 23% 9% 1	270
	11th to 20th	Day	15% 19% 38% 22% 6% 1	270
	21st to end	Day	21% 15% 42% 17% 5%	270
December	1st to 10th	Day	16% 16% 43% 21% 3	270
	11th to 20th	Day	19% 18% 39% 18% 5% 1	270
	21st to end	Day	26% 14% 38% 16% 5%	297
January	1st to 10th	Night	16% 11% 41% 26% 7%	950
	11th to 20th	Night	19% 12% 35% 26% 8% 1	950
	21st to end	Night	17% 8% 36% 30% 8%	1045
February	1st to 10th	Night	15% 12% 37% 28% 7% 1	950
	11th to 20th	Night	14% 11% 41% 28% 6%	772
	21st to end	Night	21% 11% 37% 27% 4	628
March	1st to 10th	Night	16% 10% 35% 30% 8% 1	760
	11th to 20th	Night	16% 10% 39% 28% 6% 1	749
	21st to end	Night	23% 7% 29% 30% 11% 1	600
April	1st to 10th	Night	22% 8% 38% 26% 6%	540
	11th to 20th	Night	25% 8% 29% 30% 7% 1	533
	21st to end	Night	18% 9% 33% 30% 9% 1	540
May	1st to 10th	Night	19% 8% 34% 29% 9% 1	540
	11th to 20th	Night	18% 5% 34% 33% 9% 1	531
	21st to end	Night	12% 5% 26% 41% 15% 1	584
June	1st to 10th	Night	12% 5% 28% 41% 14% 1	540
	11th to 20th	Night	16% 5% 26% 39% 13% 1	540
	21st to end	Night	10% 4 25% 46% 16%	540
July	1st to 10th	Night	8% 2 19% 46% 24% 2	525
	11th to 20th	Night	10% 2 21% 42% 24% 1	522
	21st to end	Night	7% 2 23% 43% 23% 2	591
August	1st to 10th	Night	9% 2 17% 43% 27% 2	537
	11th to 20th	Night	8% 3 18% 39% 29% 3	534
	21st to end	Night	9% 3 22% 41% 22% 2	594
September	1st to 10th	Night	10% 4 25% 34% 23% 4	540
	11th to 20th	Night	13% 6% 24% 33% 21% 4	629
	21st to end	Night	15% 8% 23% 33% 19% 2	720
October	1st to 10th	Night	17% 7% 27% 30% 18% 1	720
	11th to 20th	Night	20% 11% 33% 29% 7%	720
	21st to end	Night	23% 10% 33% 24% 9% 1	792
November	1st to 10th	Night	15% 11% 38% 29% 7% 1	740
	11th to 20th	Night	18% 14% 39% 24% 5% 1	760
	21st to end	Night	20% 13% 35% 25% 7%	940
December	1st to 10th	Night	19% 12% 39% 23% 6%	950
	11th to 20th	Night	20% 12% 36% 25% 6% 1	950
	21st to end	Night	26% 11% 35% 24% 4	1045

Page generated at 2024-03-19 22:31:08. Version ac07

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