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 2026-03-18.

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	17% 10% 3 8% 5% 4 4 4 5% 7% 32%	131190
	Night	18% 12% 4 9% 5% 5% 4 3 5% 6% 29%	130323
Transparency	Day	52% 4 14% 21% 9% 1	134633
	Night	57% 4 11% 18% 9% 1	134967
Seeing	Day	22% 11% 28% 24% 12% 3	16187
	Night	24% 8% 29% 29% 9% 1	25207

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	17% 17% 5% 10% 4 3 3 3 5% 7% 26%	4661
	11th to 20th	Day	12% 17% 6% 13% 8% 5% 4 3 5% 5% 23%	4650
	21st to end	Day	8% 12% 5% 12% 7% 6% 6% 4 6% 8% 27%	5124
February	1st to 10th	Day	13% 15% 4 10% 7% 5% 4 3 4 5% 28%	1759
	11th to 20th	Day	14% 15% 5% 9% 5% 5% 5% 3 6% 5% 27%	1991
	21st to end	Day	15% 13% 5% 9% 6% 6% 4 3 5% 5% 29%	1730
March	1st to 10th	Day	21% 12% 4 9% 6% 5% 4 3 4 5% 27%	4576
	11th to 20th	Day	13% 13% 4 9% 5% 4 4 4 5% 7% 34%	4717
	21st to end	Day	18% 12% 4 8% 4 4 4 3 4 5% 33%	5970
April	1st to 10th	Day	22% 10% 3 7% 4 4 4 3 5% 6% 33%	2400
	11th to 20th	Day	20% 7% 2 5% 4 5% 5% 3 5% 6% 38%	2403
	21st to end	Day	23% 10% 3 6% 4 4 4 4 6% 5% 32%	2600
May	1st to 10th	Day	26% 8% 3 7% 5% 5% 4 3 5% 6% 27%	6159
	11th to 20th	Day	20% 8% 3 8% 5% 4 4 3 5% 7% 33%	6318
	21st to end	Day	19% 9% 3 7% 5% 4 5% 4 5% 7% 32%	6949
June	1st to 10th	Day	21% 7% 3 6% 5% 5% 5% 4 6% 7% 31%	2800
	11th to 20th	Day	16% 6% 3 6% 4 4 5% 4 6% 9% 37%	2800
	21st to end	Day	20% 8% 3 7% 5% 5% 5% 5% 5% 7% 31%	2800
July	1st to 10th	Day	14% 6% 2 7% 5% 5% 5% 5% 7% 9% 33%	6360
	11th to 20th	Day	11% 7% 3 6% 4 5% 5% 4 7% 9% 39%	6360
	21st to end	Day	11% 5% 2 5% 4 4 5% 4 7% 9% 45%	6926
August	1st to 10th	Day	14% 5% 2 7% 4 5% 6% 5% 8% 11% 33%	4563
	11th to 20th	Day	17% 6% 3 6% 4 4 4 4 6% 9% 37%	4222
	21st to end	Day	18% 6% 2 6% 4 4 4 3 5% 7% 40%	4312
September	1st to 10th	Day	13% 6% 2 6% 4 4 4 4 6% 9% 42%	2400
	11th to 20th	Day	14% 5% 2 5% 3 3 4 3 5% 6% 48%	2273
	21st to end	Day	19% 6% 1 5% 4 3 5% 4 5% 6% 41%	2200
October	1st to 10th	Day	19% 7% 3 6% 4 3 4 4 5% 7% 38%	2125
	11th to 20th	Day	21% 8% 3 8% 5% 5% 5% 4 5% 7% 29%	1895
	21st to end	Day	25% 11% 3 8% 3 3 4 3 4 7% 29%	1980
November	1st to 10th	Day	19% 11% 3 7% 6% 4 3 3 5% 6% 33%	1851
	11th to 20th	Day	19% 13% 4 9% 5% 4 4 3 4 6% 28%	1842
	21st to end	Day	24% 15% 3 6% 5% 5% 4 3 5% 6% 24%	1680
December	1st to 10th	Day	22% 16% 5% 10% 5% 5% 4 3 4 4 23%	2680
	11th to 20th	Day	19% 14% 5% 10% 5% 4 4 3 4 6% 27%	3066
	21st to end	Day	22% 14% 4 9% 5% 5% 4 4 6% 6% 21%	4048
January	1st to 10th	Night	15% 18% 7% 12% 5% 5% 4 3 4 4 22%	8234
	11th to 20th	Night	13% 19% 7% 16% 7% 5% 4 3 4 4 17%	8235
	21st to end	Night	9% 12% 5% 14% 9% 6% 5% 4 6% 6% 24%	9057
February	1st to 10th	Night	13% 14% 5% 12% 7% 5% 4 4 5% 5% 26%	2860
	11th to 20th	Night	14% 15% 5% 12% 7% 5% 4 3 3 4 27%	2514
	21st to end	Night	15% 15% 3 8% 6% 5% 4 3 4 4 32%	2076
March	1st to 10th	Night	24% 13% 3 10% 6% 4 4 3 4 4 26%	5484
	11th to 20th	Night	16% 13% 4 9% 6% 5% 5% 4 5% 6% 27%	5380
	21st to end	Night	17% 12% 5% 10% 4 4 5% 3 4 5% 30%	4962
April	1st to 10th	Night	23% 11% 3 8% 4 3 4 3 5% 6% 29%	2000
	11th to 20th	Night	22% 8% 2 7% 5% 3 5% 4 5% 5% 34%	1945
	21st to end	Night	23% 10% 5% 6% 4 3 3 3 4 6% 35%	1800
May	1st to 10th	Night	26% 10% 4 9% 5% 4 4 3 5% 5% 25%	3824
	11th to 20th	Night	23% 8% 3 8% 5% 5% 4 3 5% 6% 31%	3575
	21st to end	Night	19% 8% 3 8% 5% 5% 4 3 5% 8% 30%	3926
June	1st to 10th	Night	21% 7% 3 5% 4 4 4 4 7% 8% 33%	1600
	11th to 20th	Night	18% 6% 2 6% 4 4 5% 4 6% 8% 37%	1600
	21st to end	Night	20% 7% 3 6% 5% 4 5% 5% 6% 8% 32%	1600
July	1st to 10th	Night	14% 5% 3 7% 6% 6% 7% 5% 7% 11% 31%	3600
	11th to 20th	Night	17% 6% 2 6% 4 4 4 5% 6% 7% 39%	3600
	21st to end	Night	11% 5% 2 7% 4 5% 5% 4 6% 8% 43%	3926
August	1st to 10th	Night	15% 7% 3 7% 6% 5% 5% 4 7% 7% 34%	2586
	11th to 20th	Night	17% 6% 2 7% 5% 4 4 4 5% 7% 38%	2792
	21st to end	Night	19% 6% 3 7% 4 4 4 4 5% 6% 38%	3583
September	1st to 10th	Night	15% 5% 2 6% 4 3 4 3 5% 8% 45%	2000
	11th to 20th	Night	16% 5% 1 5% 4 3 3 2 5% 6% 49%	2126
	21st to end	Night	18% 6% 3 6% 4 4 4 4 4 6% 42%	2200
October	1st to 10th	Night	18% 7% 2 6% 5% 4 4 3 5% 5% 41%	2271
	11th to 20th	Night	21% 8% 3 7% 4 4 4 4 4 6% 35%	2505
	21st to end	Night	25% 9% 3 8% 4 5% 4 4 4 6% 30%	2860
November	1st to 10th	Night	21% 10% 3 8% 5% 5% 4 3 5% 5% 31%	2667
	11th to 20th	Night	20% 12% 4 9% 5% 5% 3 3 5% 5% 29%	2777
	21st to end	Night	24% 15% 3 9% 5% 4 4 2 4 4 25%	2940
December	1st to 10th	Night	18% 16% 5% 11% 7% 6% 5% 3 5% 5% 19%	4720
	11th to 20th	Night	23% 14% 4 9% 5% 4 3 4 5% 5% 23%	5348
	21st to end	Night	24% 16% 5% 9% 4 3 4 4 5% 5% 23%	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	63% 3 11% 18% 4	4662
	11th to 20th	Day	66% 4 7% 15% 8%	4680
	21st to end	Day	58% 3 10% 16% 12% 1	5124
February	1st to 10th	Day	60% 4 9% 19% 6% 2	1759
	11th to 20th	Day	59% 4 13% 16% 8% 1	2000
	21st to end	Day	58% 5% 10% 18% 9% 1	1730
March	1st to 10th	Day	61% 5% 8% 14% 9% 3	4579
	11th to 20th	Day	52% 4 18% 13% 11% 1	4717
	21st to end	Day	55% 3 8% 19% 14% 2	5970
April	1st to 10th	Day	54% 5% 10% 18% 11% 2	2400
	11th to 20th	Day	49% 4 10% 22% 13% 2	2403
	21st to end	Day	54% 4 10% 18% 12% 3	2600
May	1st to 10th	Day	59% 3 10% 19% 8% 1	6170
	11th to 20th	Day	51% 6% 17% 17% 8% 2	6322
	21st to end	Day	51% 5% 13% 18% 12% 1	6949
June	1st to 10th	Day	50% 7% 12% 20% 10% 2	2800
	11th to 20th	Day	43% 7% 14% 23% 11% 1	2800
	21st to end	Day	52% 6% 13% 20% 9%	2800
July	1st to 10th	Day	48% 4 17% 25% 6%	6290
	11th to 20th	Day	42% 4 18% 29% 7%	6285
	21st to end	Day	36% 4 17% 34% 9%	6728
August	1st to 10th	Day	46% 5% 20% 22% 6%	4549
	11th to 20th	Day	45% 4 22% 22% 6%	4262
	21st to end	Day	44% 5% 16% 21% 13% 1	4312
September	1st to 10th	Day	38% 6% 18% 27% 10% 1	2400
	11th to 20th	Day	36% 5% 16% 31% 12%	2273
	21st to end	Day	42% 6% 14% 27% 11%	2200
October	1st to 10th	Day	45% 3 16% 30% 6%	3463
	11th to 20th	Day	49% 5% 18% 24% 4	3059
	21st to end	Day	48% 3 21% 22% 7%	3180
November	1st to 10th	Day	54% 5% 13% 21% 7%	1851
	11th to 20th	Day	57% 4 13% 17% 8%	1842
	21st to end	Day	63% 5% 14% 14% 4	1680
December	1st to 10th	Day	68% 2 11% 14% 5%	2680
	11th to 20th	Day	61% 4 8% 18% 9%	3066
	21st to end	Day	65% 4 10% 12% 8%	4048
January	1st to 10th	Night	67% 3 12% 13% 5% 1	8234
	11th to 20th	Night	73% 3 8% 12% 4	8280
	21st to end	Night	63% 3 8% 14% 12%	9057
February	1st to 10th	Night	61% 4 9% 17% 8% 1	2860
	11th to 20th	Night	60% 4 10% 16% 9% 1	2516
	21st to end	Night	56% 4 10% 16% 12% 1	2076
March	1st to 10th	Night	62% 4 8% 13% 11% 3	5494
	11th to 20th	Night	58% 4 13% 14% 10% 1	5381
	21st to end	Night	58% 3 7% 22% 9% 2	4962
April	1st to 10th	Night	56% 4 9% 17% 12% 2	2000
	11th to 20th	Night	51% 5% 8% 19% 14% 2	1945
	21st to end	Night	52% 4 9% 20% 13% 2	1800
May	1st to 10th	Night	61% 4 10% 16% 8% 1	3830
	11th to 20th	Night	54% 5% 12% 19% 9% 1	3576
	21st to end	Night	52% 5% 11% 15% 16% 1	3927
June	1st to 10th	Night	48% 5% 12% 22% 12% 1	1600
	11th to 20th	Night	44% 7% 12% 21% 14% 3	1600
	21st to end	Night	49% 7% 10% 20% 13% 1	1600
July	1st to 10th	Night	48% 4 19% 21% 7%	3560
	11th to 20th	Night	44% 4 17% 26% 8%	3552
	21st to end	Night	40% 4 18% 27% 10%	3809
August	1st to 10th	Night	49% 5% 14% 25% 6%	2576
	11th to 20th	Night	46% 6% 17% 24% 7%	2818
	21st to end	Night	47% 4 13% 23% 13%	3583
September	1st to 10th	Night	38% 5% 16% 28% 13% 1	2000
	11th to 20th	Night	37% 4 14% 33% 11% 1	2126
	21st to end	Night	44% 5% 10% 27% 14% 1	2200
October	1st to 10th	Night	48% 4 13% 25% 10%	3713
	11th to 20th	Night	48% 4 14% 28% 6%	4080
	21st to end	Night	50% 3 15% 20% 10% 2	4610
November	1st to 10th	Night	55% 5% 13% 19% 7% 1	2667
	11th to 20th	Night	58% 4 12% 17% 8% 1	2777
	21st to end	Night	63% 4 12% 15% 5%	2940
December	1st to 10th	Night	70% 2 13% 12% 3	4720
	11th to 20th	Night	63% 3 8% 18% 7%	5348
	21st to end	Night	65% 3 8% 16% 8%	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	29% 14% 30% 21% 5%	220
	11th to 20th	Day	27% 12% 34% 20% 5% 1	220
	21st to end	Day	21% 12% 33% 26% 6% 2	242
February	1st to 10th	Day	26% 14% 37% 17% 6% 1	261
	11th to 20th	Day	22% 12% 34% 26% 5%	479
	21st to end	Day	22% 14% 35% 24% 4	446
March	1st to 10th	Day	24% 12% 31% 25% 7%	540
	11th to 20th	Day	23% 15% 33% 22% 6% 1	528
	21st to end	Day	27% 10% 29% 22% 9% 2	550
April	1st to 10th	Day	27% 13% 23% 27% 9% 1	500
	11th to 20th	Day	28% 16% 25% 20% 9% 2	492
	21st to end	Day	28% 12% 33% 16% 9% 2	500
May	1st to 10th	Day	25% 11% 32% 20% 10% 2	503
	11th to 20th	Day	20% 9% 28% 24% 15% 4	527
	21st to end	Day	22% 12% 32% 20% 12% 3	573
June	1st to 10th	Day	23% 9% 26% 28% 11% 3	530
	11th to 20th	Day	18% 11% 28% 25% 15% 3	530
	21st to end	Day	22% 9% 28% 23% 15% 3	530
July	1st to 10th	Day	16% 6% 27% 28% 19% 5%	525
	11th to 20th	Day	15% 6% 30% 31% 14% 3	524
	21st to end	Day	13% 9% 26% 31% 19% 3	576
August	1st to 10th	Day	16% 6% 19% 34% 20% 6%	526
	11th to 20th	Day	15% 4 21% 32% 19% 8%	519
	21st to end	Day	16% 8% 26% 22% 17% 10%	583
September	1st to 10th	Day	15% 8% 26% 28% 15% 8%	530
	11th to 20th	Day	15% 7% 19% 28% 21% 10%	530
	21st to end	Day	19% 9% 25% 23% 19% 6%	530
October	1st to 10th	Day	19% 9% 28% 26% 14% 4	530
	11th to 20th	Day	25% 13% 27% 21% 12% 3	472
	21st to end	Day	30% 11% 27% 22% 9%	462
November	1st to 10th	Day	30% 13% 27% 22% 7%	425
	11th to 20th	Day	27% 12% 28% 24% 9%	382
	21st to end	Day	35% 13% 31% 13% 8%	220
December	1st to 10th	Day	32% 11% 25% 20% 8% 3	220
	11th to 20th	Day	25% 19% 33% 18% 4 1	220
	21st to end	Day	30% 16% 28% 17% 8% 2	242
January	1st to 10th	Night	28% 10% 30% 26% 6%	840
	11th to 20th	Night	28% 10% 28% 27% 6%	840
	21st to end	Night	18% 7% 33% 34% 7% 1	924
February	1st to 10th	Night	21% 9% 34% 28% 7% 1	840
	11th to 20th	Night	22% 11% 39% 24% 5%	823
	21st to end	Night	24% 10% 32% 30% 4	692
March	1st to 10th	Night	25% 11% 31% 29% 5%	840
	11th to 20th	Night	26% 9% 35% 23% 6%	829
	21st to end	Night	23% 9% 31% 29% 7% 1	880
April	1st to 10th	Night	30% 9% 27% 28% 6%	800
	11th to 20th	Night	26% 11% 30% 27% 6%	761
	21st to end	Night	27% 12% 29% 26% 6%	600
May	1st to 10th	Night	26% 8% 30% 29% 6%	500
	11th to 20th	Night	24% 6% 29% 32% 8% 1	394
	21st to end	Night	22% 6% 34% 30% 9%	433
June	1st to 10th	Night	25% 4 29% 35% 7% 1	400
	11th to 20th	Night	20% 5% 27% 36% 12%	400
	21st to end	Night	22% 4 27% 35% 11% 1	400
July	1st to 10th	Night	13% 5% 26% 42% 14% 1	390
	11th to 20th	Night	13% 3 23% 47% 13% 1	388
	21st to end	Night	15% 4 21% 46% 14%	438
August	1st to 10th	Night	15% 4 17% 42% 21% 1	398
	11th to 20th	Night	14% 4 21% 39% 20% 2	536
	21st to end	Night	17% 5% 24% 32% 19% 2	877
September	1st to 10th	Night	17% 6% 25% 38% 14% 1	800
	11th to 20th	Night	19% 4 18% 34% 23% 2	800
	21st to end	Night	20% 6% 26% 32% 15% 2	800
October	1st to 10th	Night	21% 5% 31% 30% 13% 1	800
	11th to 20th	Night	25% 7% 28% 30% 9% 1	800
	21st to end	Night	28% 9% 31% 27% 5%	880
November	1st to 10th	Night	28% 11% 29% 25% 7%	820
	11th to 20th	Night	25% 10% 33% 21% 11% 1	840
	21st to end	Night	30% 12% 29% 23% 5% 1	840
December	1st to 10th	Night	31% 9% 30% 24% 6% 1	840
	11th to 20th	Night	27% 12% 32% 23% 7% 1	840
	21st to end	Night	32% 12% 28% 20% 7%	924

Page generated at 2026-03-15 02:23:53. Version ac07

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