Nicolet
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nicolet clear sky chart from 2005-11-06 to 2024-01-16.

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	18% 9% 4 6% 5% 3 5% 5% 5% 7% 33%	74798
	Night	20% 10% 4 7% 6% 3 4 4 5% 6% 32%	75007
Transparency	Day	35% 35% 8% 14% 6% 1	74503
	Night	37% 35% 7% 13% 6% 1	74836
Seeing	Day	22% 10% 28% 24% 12% 3	13475
	Night	24% 8% 29% 29% 9% 1	22489

By Month

Percentage Cloud Cover NE (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	22% 16% 5% 9% 5% 3 4 4 4 5% 23%	1517
	11th to 20th	Day	18% 16% 6% 7% 7% 4 5% 4 4 5% 24%	1480
	21st to end	Day	11% 13% 5% 9% 7% 3 5% 5% 6% 7% 30%	1584
February	1st to 10th	Day	15% 16% 6% 8% 7% 4 5% 4 4 5% 26%	1508
	11th to 20th	Day	15% 15% 5% 7% 6% 4 6% 5% 6% 5% 27%	1699
	21st to end	Day	16% 12% 6% 9% 6% 4 5% 3 5% 5% 28%	1480
March	1st to 10th	Day	16% 10% 4 7% 7% 4 4 5% 6% 6% 32%	1797
	11th to 20th	Day	16% 12% 5% 6% 5% 2 4 5% 4 7% 34%	1843
	21st to end	Day	17% 10% 3 6% 6% 3 6% 5% 5% 6% 34%	2376
April	1st to 10th	Day	22% 9% 3 7% 4 3 4 4 5% 6% 32%	2160
	11th to 20th	Day	21% 6% 2 4 5% 4 5% 4 5% 6% 39%	2159
	21st to end	Day	23% 10% 4 5% 5% 3 4 4 5% 5% 32%	2340
May	1st to 10th	Day	20% 7% 3 5% 5% 3 5% 4 5% 7% 36%	2445
	11th to 20th	Day	17% 7% 2 5% 6% 3 5% 4 6% 7% 38%	2478
	21st to end	Day	19% 6% 3 6% 6% 3 5% 5% 5% 7% 35%	2725
June	1st to 10th	Day	22% 6% 3 5% 5% 3 5% 5% 6% 7% 31%	2520
	11th to 20th	Day	16% 6% 3 5% 6% 3 5% 4 6% 9% 37%	2520
	21st to end	Day	19% 7% 4 6% 6% 4 5% 6% 5% 7% 31%	2520
July	1st to 10th	Day	13% 6% 3 4 5% 4 6% 6% 7% 10% 38%	2520
	11th to 20th	Day	12% 6% 2 5% 6% 4 5% 5% 7% 9% 38%	2520
	21st to end	Day	12% 6% 3 5% 6% 3 6% 6% 7% 9% 36%	2744
August	1st to 10th	Day	15% 5% 3 6% 5% 4 5% 6% 8% 11% 33%	2506
	11th to 20th	Day	11% 5% 3 5% 6% 3 5% 5% 7% 8% 41%	2336
	21st to end	Day	13% 5% 2 5% 5% 3 5% 5% 6% 10% 42%	2376
September	1st to 10th	Day	14% 6% 2 5% 6% 3 4 5% 6% 9% 41%	2160
	11th to 20th	Day	16% 5% 2 4 4 2 3 4 5% 6% 47%	2047
	21st to end	Day	19% 6% 1 4 5% 2 5% 5% 5% 6% 41%	1980
October	1st to 10th	Day	21% 7% 3 5% 5% 3 4 4 5% 7% 36%	1913
	11th to 20th	Day	23% 7% 3 7% 7% 4 6% 5% 5% 6% 28%	1706
	21st to end	Day	27% 10% 3 8% 3 2 4 4 4 6% 29%	1782
November	1st to 10th	Day	19% 9% 4 6% 7% 3 4 4 5% 6% 34%	1671
	11th to 20th	Day	21% 11% 5% 8% 6% 3 4 4 5% 6% 28%	1668
	21st to end	Day	23% 13% 3 5% 5% 4 5% 4 5% 7% 26%	1520
December	1st to 10th	Day	28% 12% 5% 7% 6% 3 4 3 4 4 24%	1520
	11th to 20th	Day	23% 13% 6% 8% 5% 3 4 4 3 4 26%	1906
	21st to end	Day	25% 17% 5% 9% 5% 2 3 3 3 5% 22%	2772
January	1st to 10th	Night	20% 17% 7% 9% 6% 4 4 4 5% 4 21%	2649
	11th to 20th	Night	19% 16% 6% 9% 7% 3 5% 4 4 5% 23%	2602
	21st to end	Night	12% 13% 5% 10% 8% 4 6% 3 5% 6% 29%	2772
February	1st to 10th	Night	15% 14% 5% 11% 7% 4 6% 5% 4 5% 24%	2452
	11th to 20th	Night	15% 13% 5% 10% 7% 4 5% 4 3 5% 27%	2147
	21st to end	Night	16% 13% 4 7% 6% 4 5% 3 4 4 33%	1776
March	1st to 10th	Night	17% 12% 4 10% 7% 3 4 4 5% 5% 28%	2150
	11th to 20th	Night	19% 12% 5% 7% 6% 3 4 4 4 5% 31%	2113
	21st to end	Night	19% 11% 4 6% 4 2 5% 4 5% 4 36%	1980
April	1st to 10th	Night	24% 10% 4 7% 5% 2 4 4 5% 6% 28%	1800
	11th to 20th	Night	22% 7% 2 5% 6% 2 4 5% 5% 6% 36%	1749
	21st to end	Night	23% 10% 5% 5% 5% 2 4 3 3 7% 34%	1620
May	1st to 10th	Night	24% 7% 3 7% 6% 2 5% 4 4 5% 33%	1530
	11th to 20th	Night	20% 7% 3 7% 5% 3 4 4 5% 6% 34%	1415
	21st to end	Night	20% 6% 3 6% 4 3 4 4 4 8% 38%	1550
June	1st to 10th	Night	21% 7% 3 4 5% 3 4 5% 7% 8% 33%	1440
	11th to 20th	Night	19% 6% 3 5% 5% 2 5% 5% 5% 9% 37%	1440
	21st to end	Night	19% 6% 3 5% 5% 3 6% 6% 6% 8% 32%	1440
July	1st to 10th	Night	12% 4 3 5% 7% 3 5% 6% 6% 12% 36%	1440
	11th to 20th	Night	13% 5% 3 6% 5% 4 5% 6% 7% 8% 39%	1440
	21st to end	Night	13% 5% 3 5% 6% 3 4 5% 7% 7% 40%	1574
August	1st to 10th	Night	14% 4 3 5% 4 4 5% 5% 8% 8% 39%	1432
	11th to 20th	Night	14% 6% 1 6% 6% 4 5% 5% 6% 7% 40%	1545
	21st to end	Night	15% 5% 2 5% 4 3 5% 5% 5% 8% 42%	1977
September	1st to 10th	Night	15% 5% 2 5% 5% 3 4 4 5% 8% 44%	1800
	11th to 20th	Night	18% 5% 1 4 4 2 3 3 5% 7% 48%	1912
	21st to end	Night	19% 6% 3 5% 4 3 4 5% 4 6% 43%	1980
October	1st to 10th	Night	19% 7% 2 5% 5% 3 4 5% 4 5% 40%	2043
	11th to 20th	Night	23% 8% 3 6% 5% 3 4 4 4 6% 33%	2254
	21st to end	Night	27% 8% 3 7% 5% 4 3 5% 4 6% 29%	2574
November	1st to 10th	Night	21% 9% 3 7% 6% 3 5% 4 5% 5% 32%	2407
	11th to 20th	Night	21% 11% 4 8% 7% 3 4 4 4 5% 29%	2512
	21st to end	Night	25% 14% 3 7% 5% 3 4 3 4 5% 27%	2660
December	1st to 10th	Night	23% 14% 5% 9% 7% 3 4 5% 4 4 22%	2660
	11th to 20th	Night	23% 14% 6% 8% 6% 3 3 4 4 5% 25%	3288
	21st to end	Night	27% 17% 5% 8% 4 2 3 3 3 4 24%	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	42% 38% 6% 11% 4	1518
	11th to 20th	Day	41% 39% 5% 10% 4	1480
	21st to end	Day	36% 36% 6% 14% 7% 1	1584
February	1st to 10th	Day	42% 34% 6% 13% 4 1	1508
	11th to 20th	Day	40% 36% 10% 8% 5% 1	1708
	21st to end	Day	40% 35% 7% 14% 5%	1480
March	1st to 10th	Day	37% 35% 9% 13% 6% 1	1800
	11th to 20th	Day	37% 35% 10% 12% 6%	1843
	21st to end	Day	34% 36% 7% 15% 8% 1	2376
April	1st to 10th	Day	38% 35% 7% 13% 6% 1	2160
	11th to 20th	Day	31% 34% 8% 15% 10% 1	2159
	21st to end	Day	36% 35% 6% 13% 8% 3	2340
May	1st to 10th	Day	31% 35% 6% 14% 12% 2	2445
	11th to 20th	Day	32% 35% 6% 14% 10% 2	2482
	21st to end	Day	32% 36% 6% 14% 11% 1	2725
June	1st to 10th	Day	36% 36% 7% 14% 5% 1	2520
	11th to 20th	Day	30% 36% 9% 17% 7% 1	2520
	21st to end	Day	38% 36% 8% 11% 5%	2520
July	1st to 10th	Day	28% 38% 11% 18% 5%	2450
	11th to 20th	Day	30% 37% 10% 17% 6%	2445
	21st to end	Day	30% 37% 13% 16% 4	2591
August	1st to 10th	Day	32% 36% 12% 16% 4	2492
	11th to 20th	Day	27% 35% 14% 19% 6%	2336
	21st to end	Day	28% 35% 11% 16% 9%	2376
September	1st to 10th	Day	29% 35% 9% 19% 7%	2160
	11th to 20th	Day	27% 35% 8% 21% 9%	2047
	21st to end	Day	31% 35% 11% 16% 6%	1980
October	1st to 10th	Day	33% 35% 8% 18% 5%	1913
	11th to 20th	Day	39% 36% 10% 13% 2	1706
	21st to end	Day	37% 36% 8% 13% 5% 1	1782
November	1st to 10th	Day	30% 39% 9% 16% 6% 1	1671
	11th to 20th	Day	39% 39% 7% 10% 6%	1668
	21st to end	Day	38% 39% 9% 12% 2	1520
December	1st to 10th	Day	43% 38% 7% 10% 3	1520
	11th to 20th	Day	45% 31% 4 16% 3	1906
	21st to end	Day	54% 23% 10% 8% 5%	2772
January	1st to 10th	Night	44% 39% 7% 9% 2	2649
	11th to 20th	Night	42% 40% 5% 9% 3 1	2602
	21st to end	Night	40% 36% 6% 11% 6%	2772
February	1st to 10th	Night	42% 35% 5% 11% 6% 1	2452
	11th to 20th	Night	42% 36% 6% 9% 6%	2149
	21st to end	Night	40% 35% 7% 11% 6% 1	1776
March	1st to 10th	Night	41% 35% 6% 13% 5%	2160
	11th to 20th	Night	41% 35% 6% 11% 7%	2114
	21st to end	Night	34% 36% 6% 15% 8% 2	1980
April	1st to 10th	Night	39% 34% 7% 13% 6% 1	1800
	11th to 20th	Night	31% 35% 6% 16% 11% 1	1749
	21st to end	Night	35% 35% 4 14% 9% 3	1620
May	1st to 10th	Night	36% 35% 4 10% 12% 3	1530
	11th to 20th	Night	35% 35% 5% 11% 11% 3	1416
	21st to end	Night	32% 35% 7% 12% 12% 2	1551
June	1st to 10th	Night	33% 35% 9% 15% 6% 1	1440
	11th to 20th	Night	31% 37% 8% 14% 8% 2	1440
	21st to end	Night	35% 37% 8% 12% 7%	1440
July	1st to 10th	Night	29% 36% 11% 16% 7%	1400
	11th to 20th	Night	29% 38% 10% 16% 7% 1	1392
	21st to end	Night	30% 38% 12% 14% 7%	1486
August	1st to 10th	Night	29% 36% 11% 18% 6%	1422
	11th to 20th	Night	28% 34% 12% 19% 7%	1545
	21st to end	Night	30% 35% 9% 18% 8%	1977
September	1st to 10th	Night	28% 35% 10% 19% 8%	1800
	11th to 20th	Night	28% 35% 7% 21% 9%	1912
	21st to end	Night	31% 36% 6% 18% 8% 1	1980
October	1st to 10th	Night	33% 35% 6% 18% 7%	2043
	11th to 20th	Night	36% 35% 10% 15% 4	2254
	21st to end	Night	38% 36% 8% 12% 6%	2574
November	1st to 10th	Night	33% 39% 8% 15% 4	2407
	11th to 20th	Night	37% 38% 7% 12% 6% 1	2512
	21st to end	Night	41% 38% 7% 12% 3	2660
December	1st to 10th	Night	44% 39% 7% 8% 2	2660
	11th to 20th	Night	44% 31% 5% 15% 4	3288
	21st to end	Night	53% 23% 7% 14% 3	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	28% 14% 30% 22% 5% 1	180
	11th to 20th	Day	26% 12% 32% 22% 6% 1	170
	21st to end	Day	22% 9% 34% 27% 6% 2	176
February	1st to 10th	Day	32% 16% 36% 13% 3	190
	11th to 20th	Day	23% 11% 35% 27% 4	367
	21st to end	Day	24% 13% 33% 25% 5%	346
March	1st to 10th	Day	23% 10% 31% 28% 8%	420
	11th to 20th	Day	21% 15% 32% 23% 7% 1	420
	21st to end	Day	26% 9% 27% 24% 11% 2	462
April	1st to 10th	Day	26% 11% 24% 27% 10% 1	420
	11th to 20th	Day	27% 14% 25% 21% 10% 2	412
	21st to end	Day	28% 11% 32% 18% 9% 2	420
May	1st to 10th	Day	24% 13% 33% 18% 11% 2	423
	11th to 20th	Day	19% 8% 30% 25% 14% 3	447
	21st to end	Day	21% 11% 34% 19% 12% 3	485
June	1st to 10th	Day	23% 10% 27% 27% 11% 3	450
	11th to 20th	Day	18% 10% 27% 24% 17% 4	450
	21st to end	Day	21% 9% 25% 25% 16% 4	450
July	1st to 10th	Day	15% 6% 24% 29% 21% 5%	445
	11th to 20th	Day	15% 5% 29% 32% 16% 3	444
	21st to end	Day	14% 8% 24% 31% 20% 3	488
August	1st to 10th	Day	17% 7% 19% 32% 21% 6%	446
	11th to 20th	Day	15% 4 22% 32% 18% 9%	439
	21st to end	Day	16% 8% 26% 22% 16% 12%	495
September	1st to 10th	Day	16% 7% 26% 28% 15% 9%	450
	11th to 20th	Day	18% 8% 21% 26% 18% 9%	450
	21st to end	Day	19% 8% 25% 23% 18% 6%	450
October	1st to 10th	Day	20% 10% 26% 25% 15% 4	450
	11th to 20th	Day	25% 13% 27% 21% 12% 2	403
	21st to end	Day	32% 11% 26% 22% 9%	396
November	1st to 10th	Day	30% 12% 27% 23% 8% 1	365
	11th to 20th	Day	26% 13% 28% 23% 9%	328
	21st to end	Day	31% 14% 29% 16% 9%	180
December	1st to 10th	Day	34% 12% 22% 21% 8% 3	180
	11th to 20th	Day	26% 18% 33% 18% 4 1	180
	21st to end	Day	32% 18% 26% 15% 9% 1	198
January	1st to 10th	Night	28% 11% 30% 25% 6%	760
	11th to 20th	Night	27% 10% 28% 27% 6%	744
	21st to end	Night	18% 6% 32% 35% 7% 1	792
February	1st to 10th	Night	23% 8% 35% 28% 6% 1	720
	11th to 20th	Night	22% 10% 37% 24% 5% 1	703
	21st to end	Night	23% 10% 32% 30% 5%	592
March	1st to 10th	Night	24% 9% 31% 31% 5%	720
	11th to 20th	Night	26% 9% 33% 24% 7% 1	720
	21st to end	Night	22% 8% 31% 30% 8% 1	792
April	1st to 10th	Night	30% 8% 27% 29% 7%	720
	11th to 20th	Night	25% 10% 30% 27% 7%	685
	21st to end	Night	27% 12% 29% 26% 7%	540
May	1st to 10th	Night	27% 7% 30% 29% 7%	450
	11th to 20th	Night	24% 6% 29% 32% 7% 1	354
	21st to end	Night	22% 6% 35% 29% 9%	389
June	1st to 10th	Night	25% 4 29% 34% 7% 1	360
	11th to 20th	Night	21% 4 26% 35% 13%	360
	21st to end	Night	20% 4 27% 36% 12% 1	360
July	1st to 10th	Night	13% 5% 26% 41% 14% 1	350
	11th to 20th	Night	11% 3 23% 47% 15% 1	348
	21st to end	Night	15% 4 21% 45% 14% 1	394
August	1st to 10th	Night	15% 4 17% 42% 20% 1	358
	11th to 20th	Night	14% 4 22% 39% 20% 2	481
	21st to end	Night	17% 5% 24% 33% 20% 2	789
September	1st to 10th	Night	17% 5% 24% 38% 13% 2	720
	11th to 20th	Night	21% 5% 19% 33% 20% 2	720
	21st to end	Night	20% 6% 27% 30% 14% 3	720
October	1st to 10th	Night	22% 6% 31% 30% 12% 1	720
	11th to 20th	Night	26% 7% 27% 29% 10% 1	720
	21st to end	Night	29% 9% 31% 26% 5%	792
November	1st to 10th	Night	26% 11% 29% 25% 8%	740
	11th to 20th	Night	24% 11% 33% 20% 11% 1	760
	21st to end	Night	30% 11% 28% 24% 6% 1	760
December	1st to 10th	Night	33% 9% 29% 23% 6% 1	760
	11th to 20th	Night	26% 11% 31% 24% 7% 1	760
	21st to end	Night	33% 13% 28% 20% 7%	836

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