St Croix Falls
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the St Croix Falls clear sky chart from 2005-11-06 to 2026-04-02.

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% 9% 3 8% 5% 4 4 4 5% 7% 38%	131873
	Night	12% 9% 4 9% 5% 5% 4 4 5% 6% 37%	130293
Transparency	Day	46% 3 13% 26% 11% 1	135412
	Night	48% 3 12% 24% 12% 1	134830
Seeing	Day	17% 9% 31% 26% 13% 4	17895
	Night	17% 8% 32% 32% 11% 1	27951

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% 13% 5% 20% 8% 5% 5% 3 4 5% 22%	4691
	11th to 20th	Day	5% 11% 7% 13% 8% 7% 7% 7% 8% 5% 20%	4710
	21st to end	Day	5% 12% 6% 12% 5% 5% 6% 4 6% 7% 33%	5691
February	1st to 10th	Day	8% 13% 5% 11% 7% 5% 5% 4 6% 7% 30%	1890
	11th to 20th	Day	7% 12% 5% 10% 7% 6% 5% 3 5% 6% 36%	1844
	21st to end	Day	9% 11% 5% 10% 6% 5% 5% 4 4 7% 34%	1644
March	1st to 10th	Day	12% 9% 3 6% 4 4 4 3 5% 8% 44%	4848
	11th to 20th	Day	9% 10% 3 8% 5% 5% 5% 3 5% 8% 40%	5090
	21st to end	Day	20% 10% 3 9% 6% 5% 4 3 5% 6% 28%	5716
April	1st to 10th	Day	18% 11% 3 6% 5% 4 4 4 5% 7% 32%	2412
	11th to 20th	Day	20% 13% 4 7% 5% 4 4 4 4 5% 31%	2374
	21st to end	Day	21% 11% 3 8% 5% 4 4 3 5% 5% 30%	2585
May	1st to 10th	Day	14% 6% 2 5% 4 3 4 3 4 6% 50%	6227
	11th to 20th	Day	16% 8% 3 6% 4 4 4 3 5% 6% 41%	6319
	21st to end	Day	17% 8% 2 7% 4 4 4 3 5% 7% 38%	6935
June	1st to 10th	Day	13% 6% 2 4 4 4 5% 5% 6% 7% 45%	2800
	11th to 20th	Day	14% 8% 2 7% 5% 5% 4 4 7% 9% 36%	2800
	21st to end	Day	12% 5% 2 5% 5% 5% 5% 5% 8% 9% 40%	2800
July	1st to 10th	Day	10% 4 2 5% 4 4 5% 4 6% 10% 47%	6360
	11th to 20th	Day	9% 4 1 4 3 3 3 3 5% 8% 56%	6360
	21st to end	Day	10% 5% 2 5% 4 4 4 4 6% 9% 47%	6924
August	1st to 10th	Day	12% 6% 2 5% 4 4 5% 4 6% 9% 43%	4282
	11th to 20th	Day	13% 5% 2 5% 4 5% 5% 4 6% 8% 43%	4171
	21st to end	Day	12% 6% 3 6% 5% 4 4 4 5% 7% 44%	4427
September	1st to 10th	Day	11% 5% 2 6% 5% 4 4 4 5% 8% 46%	2400
	11th to 20th	Day	12% 5% 2 6% 4 4 5% 4 5% 8% 44%	2400
	21st to end	Day	15% 7% 2 5% 3 3 3 4 5% 8% 44%	2088
October	1st to 10th	Day	16% 6% 2 5% 4 4 4 4 5% 7% 43%	2000
	11th to 20th	Day	16% 12% 3 7% 5% 4 4 3 4 6% 36%	2000
	21st to end	Day	17% 12% 3 8% 4 4 3 3 4 6% 36%	2130
November	1st to 10th	Day	11% 14% 4 9% 6% 4 4 4 6% 5% 34%	1747
	11th to 20th	Day	12% 15% 6% 9% 8% 4 5% 3 4 6% 28%	1680
	21st to end	Day	14% 12% 5% 8% 5% 5% 5% 3 6% 6% 31%	1680
December	1st to 10th	Day	7% 13% 6% 14% 14% 7% 5% 4 5% 5% 20%	2690
	11th to 20th	Day	11% 16% 7% 11% 6% 4 4 3 5% 6% 27%	3088
	21st to end	Day	20% 19% 8% 19% 6% 4 3 2 3 3 14%	4070
January	1st to 10th	Night	8% 13% 5% 14% 9% 5% 4 3 5% 5% 28%	8232
	11th to 20th	Night	5% 11% 5% 13% 8% 7% 8% 8% 7% 6% 20%	8280
	21st to end	Night	6% 13% 6% 11% 5% 5% 6% 4 5% 6% 34%	8522
February	1st to 10th	Night	6% 11% 5% 10% 7% 6% 5% 4 6% 6% 34%	2730
	11th to 20th	Night	6% 10% 4 10% 6% 5% 5% 4 6% 6% 38%	2663
	21st to end	Night	10% 12% 4 9% 5% 5% 5% 4 5% 5% 35%	2160
March	1st to 10th	Night	10% 7% 2 7% 5% 4 4 3 5% 7% 46%	5269
	11th to 20th	Night	10% 7% 3 9% 5% 5% 5% 4 7% 9% 36%	5090
	21st to end	Night	23% 11% 4 9% 5% 4 4 2 4 5% 29%	5453
April	1st to 10th	Night	18% 12% 3 7% 5% 4 3 4 5% 6% 34%	2010
	11th to 20th	Night	21% 9% 3 6% 4 4 4 3 4 5% 36%	1975
	21st to end	Night	19% 9% 3 7% 4 4 4 4 6% 7% 34%	1813
May	1st to 10th	Night	12% 7% 2 6% 4 4 4 3 4 4 50%	3687
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 5% 7% 50%	3596
	21st to end	Night	15% 9% 2 7% 4 4 4 3 5% 7% 39%	3942
June	1st to 10th	Night	12% 5% 2 5% 3 4 3 4 6% 9% 45%	1600
	11th to 20th	Night	11% 5% 3 6% 5% 4 4 4 6% 7% 46%	1600
	21st to end	Night	9% 5% 2 5% 4 4 4 4 7% 9% 48%	1600
July	1st to 10th	Night	9% 3 1 5% 3 4 4 4 6% 8% 52%	3618
	11th to 20th	Night	7% 4 1 4 3 4 4 4 6% 9% 55%	3617
	21st to end	Night	8% 5% 2 6% 3 4 4 4 5% 8% 52%	3947
August	1st to 10th	Night	12% 5% 2 6% 4 4 3 3 5% 7% 48%	2875
	11th to 20th	Night	13% 5% 2 5% 3 4 4 3 6% 7% 47%	2888
	21st to end	Night	12% 6% 3 6% 4 3 4 4 6% 7% 46%	3472
September	1st to 10th	Night	10% 4 2 5% 4 3 4 3 4 8% 53%	2000
	11th to 20th	Night	10% 4 1 5% 4 3 4 4 6% 7% 52%	2000
	21st to end	Night	13% 5% 2 5% 4 3 4 3 4 7% 50%	2288
October	1st to 10th	Night	14% 6% 2 5% 3 3 4 3 5% 6% 49%	2400
	11th to 20th	Night	16% 11% 2 6% 4 4 5% 3 4 6% 40%	2400
	21st to end	Night	17% 11% 3 7% 4 4 4 3 5% 6% 36%	2710
November	1st to 10th	Night	14% 10% 3 7% 5% 3 4 4 5% 6% 38%	2767
	11th to 20th	Night	13% 12% 5% 11% 5% 4 4 3 4 4 34%	2940
	21st to end	Night	14% 10% 4 10% 6% 4 4 3 6% 6% 34%	2940
December	1st to 10th	Night	6% 11% 5% 15% 8% 9% 6% 4 5% 6% 26%	4720
	11th to 20th	Night	10% 17% 6% 14% 6% 5% 5% 6% 5% 5% 21%	5339
	21st to end	Night	21% 16% 6% 16% 5% 4 3 3 4 4 17%	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	66% 2 8% 15% 8%	4692
	11th to 20th	Day	62% 2 8% 17% 10%	4710
	21st to end	Day	52% 2 13% 23% 10%	5691
February	1st to 10th	Day	53% 3 13% 21% 9% 1	1890
	11th to 20th	Day	50% 3 11% 26% 9% 1	1853
	21st to end	Day	51% 4 11% 23% 10% 1	1644
March	1st to 10th	Day	41% 2 17% 25% 12% 3	4848
	11th to 20th	Day	44% 3 14% 28% 10% 1	5090
	21st to end	Day	59% 2 10% 19% 9% 1	5718
April	1st to 10th	Day	50% 4 11% 20% 13% 1	2412
	11th to 20th	Day	56% 3 9% 18% 12% 1	2374
	21st to end	Day	55% 4 11% 21% 9%	2585
May	1st to 10th	Day	37% 3 11% 29% 17% 2	6266
	11th to 20th	Day	44% 2 12% 23% 14% 5%	6323
	21st to end	Day	47% 3 9% 29% 11% 1	6949
June	1st to 10th	Day	36% 4 15% 31% 12% 1	2800
	11th to 20th	Day	44% 5% 15% 23% 12% 1	2800
	21st to end	Day	39% 5% 17% 29% 9% 2	2800
July	1st to 10th	Day	34% 3 18% 36% 9%	6291
	11th to 20th	Day	28% 2 16% 38% 15% 1	6285
	21st to end	Day	34% 3 15% 31% 17%	6728
August	1st to 10th	Day	39% 3 14% 29% 14% 1	4267
	11th to 20th	Day	39% 3 13% 35% 9%	4210
	21st to end	Day	40% 3 17% 27% 12% 1	4426
September	1st to 10th	Day	36% 5% 12% 35% 11%	2400
	11th to 20th	Day	38% 4 20% 31% 8%	2400
	21st to end	Day	39% 5% 12% 34% 10% 1	2088
October	1st to 10th	Day	30% 2 10% 38% 20%	3260
	11th to 20th	Day	42% 2 10% 27% 17% 2	3240
	21st to end	Day	46% 2 16% 27% 9%	3420
November	1st to 10th	Day	51% 3 13% 19% 12% 1	1747
	11th to 20th	Day	58% 3 13% 18% 7% 1	1680
	21st to end	Day	53% 4 15% 20% 5% 2	1680
December	1st to 10th	Day	66% 3 11% 15% 4	2690
	11th to 20th	Day	60% 2 11% 20% 7%	3085
	21st to end	Day	78% 2 6% 9% 5%	4070
January	1st to 10th	Night	60% 2 14% 15% 9%	8233
	11th to 20th	Night	62% 3 8% 16% 10%	8280
	21st to end	Night	52% 2 10% 25% 10%	8522
February	1st to 10th	Night	51% 3 12% 23% 10% 1	2730
	11th to 20th	Night	46% 4 13% 26% 10% 1	2664
	21st to end	Night	51% 4 12% 22% 11% 1	2160
March	1st to 10th	Night	39% 3 15% 22% 18% 4	5269
	11th to 20th	Night	45% 2 15% 24% 14% 1	5090
	21st to end	Night	60% 2 10% 15% 13%	5453
April	1st to 10th	Night	50% 4 8% 22% 16% 1	2010
	11th to 20th	Night	51% 3 8% 21% 14% 2	1975
	21st to end	Night	49% 4 9% 22% 14% 1	1813
May	1st to 10th	Night	40% 2 10% 28% 19% 2	3712
	11th to 20th	Night	35% 3 12% 23% 20% 7%	3597
	21st to end	Night	44% 3 11% 28% 12% 1	3950
June	1st to 10th	Night	35% 5% 13% 30% 15% 1	1600
	11th to 20th	Night	37% 4 14% 25% 17% 3	1600
	21st to end	Night	31% 5% 16% 30% 15% 3	1600
July	1st to 10th	Night	31% 3 20% 34% 12% 1	3580
	11th to 20th	Night	27% 3 14% 38% 16% 2	3572
	21st to end	Night	32% 3 16% 30% 17% 2	3832
August	1st to 10th	Night	37% 3 12% 30% 15% 3	2866
	11th to 20th	Night	36% 4 13% 34% 11% 1	2915
	21st to end	Night	39% 3 16% 29% 11% 2	3472
September	1st to 10th	Night	31% 4 15% 35% 15% 1	2000
	11th to 20th	Night	31% 4 18% 33% 14%	2000
	21st to end	Night	35% 3 12% 35% 13% 1	2288
October	1st to 10th	Night	26% 2 7% 36% 24% 4	3920
	11th to 20th	Night	39% 2 11% 24% 22% 2	3899
	21st to end	Night	48% 2 11% 26% 12%	4370
November	1st to 10th	Night	46% 3 12% 26% 12% 1	2767
	11th to 20th	Night	54% 3 12% 19% 11% 1	2940
	21st to end	Night	51% 4 15% 23% 6% 1	2940
December	1st to 10th	Night	59% 4 15% 18% 4	4720
	11th to 20th	Night	65% 3 9% 17% 6% 1	5341
	21st to end	Night	72% 2 8% 12% 5%	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	16% 7% 35% 29% 9% 2	330
	11th to 20th	Day	16% 10% 40% 28% 6% 1	330
	21st to end	Day	13% 9% 42% 26% 8% 1	363
February	1st to 10th	Day	16% 14% 47% 16% 5% 2	330
	11th to 20th	Day	15% 14% 43% 21% 7% 1	330
	21st to end	Day	16% 16% 41% 23% 3	273
March	1st to 10th	Day	18% 12% 43% 20% 6% 1	330
	11th to 20th	Day	20% 11% 39% 21% 7% 1	330
	21st to end	Day	24% 13% 34% 19% 8% 2	419
April	1st to 10th	Day	25% 13% 35% 22% 5% 1	504
	11th to 20th	Day	30% 12% 26% 24% 7% 1	492
	21st to end	Day	26% 11% 32% 21% 8% 2	685
May	1st to 10th	Day	21% 11% 30% 27% 10% 2	703
	11th to 20th	Day	20% 10% 27% 26% 13% 5%	725
	21st to end	Day	21% 7% 27% 25% 16% 4	789
June	1st to 10th	Day	11% 8% 28% 33% 16% 3	730
	11th to 20th	Day	16% 8% 35% 28% 10% 2	730
	21st to end	Day	15% 6% 31% 27% 15% 6%	730
July	1st to 10th	Day	10% 3 23% 29% 25% 10%	721
	11th to 20th	Day	9% 6% 26% 31% 19% 9%	718
	21st to end	Day	8% 3 25% 36% 20% 8%	794
August	1st to 10th	Day	12% 3 22% 33% 23% 7%	726
	11th to 20th	Day	15% 3 20% 31% 25% 6%	715
	21st to end	Day	13% 5% 23% 34% 21% 4	659
September	1st to 10th	Day	15% 5% 29% 28% 17% 6%	530
	11th to 20th	Day	13% 5% 28% 32% 19% 3	530
	21st to end	Day	18% 9% 27% 25% 15% 6%	343
October	1st to 10th	Day	20% 10% 30% 22% 15% 3	330
	11th to 20th	Day	21% 17% 32% 23% 7%	330
	21st to end	Day	23% 13% 39% 17% 6% 2	363
November	1st to 10th	Day	23% 14% 35% 20% 8% 1	330
	11th to 20th	Day	21% 16% 38% 21% 4	330
	21st to end	Day	24% 13% 36% 21% 5%	330
December	1st to 10th	Day	17% 8% 42% 25% 8% 1	330
	11th to 20th	Day	21% 15% 36% 22% 6%	330
	21st to end	Day	28% 13% 39% 16% 3 1	363
January	1st to 10th	Night	13% 11% 36% 31% 8% 1	1050
	11th to 20th	Night	16% 9% 39% 29% 7% 1	1050
	21st to end	Night	17% 10% 35% 30% 7% 1	1155
February	1st to 10th	Night	13% 11% 40% 29% 7% 1	1050
	11th to 20th	Night	11% 12% 41% 29% 7% 1	1029
	21st to end	Night	17% 12% 35% 28% 8%	776
March	1st to 10th	Night	16% 12% 38% 27% 7% 1	746
	11th to 20th	Night	17% 9% 40% 28% 6%	630
	21st to end	Night	22% 10% 31% 25% 9% 2	693
April	1st to 10th	Night	27% 8% 32% 27% 6%	603
	11th to 20th	Night	27% 7% 32% 27% 7% 1	593
	21st to end	Night	25% 7% 30% 29% 8% 1	600
May	1st to 10th	Night	21% 7% 35% 30% 7%	600
	11th to 20th	Night	17% 8% 30% 33% 10% 2	591
	21st to end	Night	13% 7% 26% 40% 13% 1	650
June	1st to 10th	Night	14% 4 28% 41% 12% 1	600
	11th to 20th	Night	13% 4 31% 43% 9%	600
	21st to end	Night	10% 4 26% 43% 15% 2	600
July	1st to 10th	Night	8% 2 20% 42% 27% 2	585
	11th to 20th	Night	9% 3 20% 45% 21% 2	582
	21st to end	Night	5% 2 22% 46% 23% 2	657
August	1st to 10th	Night	10% 2 14% 54% 19% 2	597
	11th to 20th	Night	14% 1 18% 37% 26% 3	594
	21st to end	Night	11% 4 23% 37% 23% 2	660
September	1st to 10th	Night	12% 5% 23% 39% 18% 3	600
	11th to 20th	Night	13% 2 29% 37% 18% 2	600
	21st to end	Night	15% 8% 29% 30% 16% 1	704
October	1st to 10th	Night	18% 7% 28% 33% 13% 1	800
	11th to 20th	Night	22% 10% 31% 28% 8% 1	800
	21st to end	Night	24% 10% 29% 29% 8%	880
November	1st to 10th	Night	20% 9% 33% 31% 7% 1	921
	11th to 20th	Night	20% 12% 33% 27% 8%	1050
	21st to end	Night	19% 14% 36% 25% 6%	1050
December	1st to 10th	Night	16% 9% 37% 29% 8% 1	1050
	11th to 20th	Night	21% 10% 37% 24% 7% 1	1050
	21st to end	Night	26% 9% 33% 26% 6% 1	1155

Page generated at 2026-03-30 01:18:41. Version ac07

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