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 2024-12-09.

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% 9% 3 8% 5% 4 5% 4 5% 7% 37%	101892
	Night	13% 9% 3 8% 5% 4 4 4 5% 6% 38%	98006
Transparency	Day	46% 4 13% 26% 11% 1	105474
	Night	46% 3 12% 25% 12% 1	102564
Seeing	Day	17% 8% 31% 27% 13% 4	16153
	Night	17% 8% 31% 32% 11% 1	26079

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	12% 16% 5% 18% 6% 4 5% 4 4 5% 21%	2527
	11th to 20th	Day	6% 10% 7% 13% 10% 10% 9% 7% 6% 5% 19%	2530
	21st to end	Day	8% 19% 8% 13% 5% 4 5% 4 5% 5% 23%	3070
February	1st to 10th	Day	8% 12% 4 10% 7% 4 5% 4 6% 7% 31%	1710
	11th to 20th	Day	8% 12% 5% 9% 7% 6% 5% 3 5% 6% 34%	1664
	21st to end	Day	10% 11% 5% 11% 5% 4 5% 4 4 7% 34%	1492
March	1st to 10th	Day	11% 11% 4 7% 5% 4 4 3 4 7% 39%	3299
	11th to 20th	Day	10% 9% 3 8% 5% 5% 4 3 5% 8% 40%	3480
	21st to end	Day	20% 12% 4 11% 6% 5% 4 3 5% 6% 24%	3902
April	1st to 10th	Day	17% 11% 3 7% 5% 4 4 4 5% 7% 33%	2280
	11th to 20th	Day	20% 13% 4 7% 4 4 4 4 4 5% 31%	2254
	21st to end	Day	21% 11% 3 8% 5% 4 4 3 5% 5% 30%	2456
May	1st to 10th	Day	19% 6% 2 6% 4 4 4 3 5% 6% 40%	4335
	11th to 20th	Day	15% 6% 2 6% 4 4 4 3 5% 7% 43%	4399
	21st to end	Day	18% 7% 3 7% 5% 4 4 3 5% 7% 35%	4824
June	1st to 10th	Day	13% 6% 2 4 4 4 4 5% 6% 7% 46%	2660
	11th to 20th	Day	13% 7% 2 6% 5% 5% 4 5% 7% 9% 37%	2660
	21st to end	Day	11% 5% 2 5% 5% 5% 5% 5% 8% 9% 40%	2660
July	1st to 10th	Day	12% 5% 2 6% 5% 5% 6% 5% 7% 10% 38%	4440
	11th to 20th	Day	6% 3 1 4 3 3 4 4 6% 9% 59%	4440
	21st to end	Day	9% 4 2 5% 4 3 4 4 7% 8% 49%	4813
August	1st to 10th	Day	13% 6% 2 5% 4 4 5% 4 6% 9% 43%	4150
	11th to 20th	Day	12% 5% 2 5% 4 5% 5% 4 6% 8% 43%	4041
	21st to end	Day	12% 6% 3 6% 5% 4 4 4 5% 7% 44%	4291
September	1st to 10th	Day	11% 5% 2 6% 5% 4 4 4 5% 8% 47%	2280
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 4 5% 8% 45%	2280
	21st to end	Day	16% 6% 2 5% 3 3 3 4 5% 8% 43%	1984
October	1st to 10th	Day	17% 7% 2 5% 4 4 4 4 5% 6% 43%	1900
	11th to 20th	Day	16% 12% 2 7% 5% 4 4 3 4 6% 36%	1900
	21st to end	Day	17% 11% 3 8% 4 4 4 3 4 6% 36%	2024
November	1st to 10th	Day	11% 15% 4 8% 6% 4 4 3 6% 5% 34%	1662
	11th to 20th	Day	13% 15% 6% 10% 8% 5% 5% 3 4 6% 27%	1600
	21st to end	Day	14% 12% 5% 7% 5% 5% 5% 3 6% 6% 32%	1600
December	1st to 10th	Day	10% 15% 5% 12% 8% 6% 5% 5% 6% 6% 22%	1584
	11th to 20th	Day	12% 13% 8% 12% 6% 5% 5% 3 5% 5% 26%	1918
	21st to end	Day	22% 16% 6% 15% 6% 3 4 2 3 4 18%	2783
January	1st to 10th	Night	11% 14% 6% 15% 7% 4 4 3 5% 4 27%	4428
	11th to 20th	Night	7% 10% 5% 13% 9% 7% 8% 8% 6% 5% 21%	4440
	21st to end	Night	10% 19% 8% 13% 5% 5% 4 3 4 5% 23%	4596
February	1st to 10th	Night	6% 11% 5% 10% 7% 5% 5% 4 5% 6% 35%	2470
	11th to 20th	Night	6% 10% 4 10% 6% 5% 5% 4 5% 6% 38%	2403
	21st to end	Night	11% 12% 4 8% 5% 5% 5% 4 5% 5% 35%	1960
March	1st to 10th	Night	9% 8% 2 7% 5% 4 4 3 5% 7% 45%	3583
	11th to 20th	Night	9% 7% 3 10% 5% 6% 5% 4 6% 6% 40%	3480
	21st to end	Night	25% 11% 4 10% 5% 3 3 2 3 4 30%	3727
April	1st to 10th	Night	19% 11% 3 7% 5% 4 3 4 5% 6% 34%	1900
	11th to 20th	Night	22% 9% 4 6% 4 4 3 3 4 5% 36%	1875
	21st to end	Night	19% 10% 2 7% 4 4 4 3 6% 7% 34%	1723
May	1st to 10th	Night	14% 8% 2 7% 5% 5% 4 3 5% 4 41%	2569
	11th to 20th	Night	14% 5% 1 4 3 3 3 3 5% 7% 51%	2506
	21st to end	Night	13% 7% 3 7% 5% 4 4 3 5% 8% 40%	2743
June	1st to 10th	Night	12% 5% 2 5% 3 4 3 4 7% 9% 46%	1520
	11th to 20th	Night	10% 5% 3 6% 5% 4 4 4 6% 7% 47%	1520
	21st to end	Night	8% 5% 2 5% 4 4 4 4 7% 9% 48%	1520
July	1st to 10th	Night	12% 4 2 5% 3 4 3 4 7% 8% 49%	2530
	11th to 20th	Night	4 3 1 3 3 4 3 3 5% 10% 59%	2530
	21st to end	Night	6% 3 1 5% 3 3 3 3 5% 8% 59%	2750
August	1st to 10th	Night	12% 6% 2 6% 4 4 3 3 5% 7% 48%	2787
	11th to 20th	Night	13% 5% 2 5% 4 4 4 3 6% 7% 47%	2798
	21st to end	Night	12% 7% 3 6% 4 3 4 4 5% 7% 45%	3366
September	1st to 10th	Night	9% 4 2 5% 4 3 4 3 4 8% 53%	1900
	11th to 20th	Night	10% 4 1 5% 4 3 4 4 5% 7% 53%	1900
	21st to end	Night	14% 5% 1 5% 4 3 4 3 4 7% 49%	2174
October	1st to 10th	Night	15% 6% 2 5% 3 3 4 3 5% 6% 49%	2280
	11th to 20th	Night	16% 10% 2 5% 4 4 5% 3 4 6% 40%	2280
	21st to end	Night	17% 11% 3 7% 4 4 4 3 5% 6% 36%	2574
November	1st to 10th	Night	15% 10% 3 7% 5% 3 4 4 5% 6% 38%	2632
	11th to 20th	Night	14% 12% 5% 11% 5% 4 4 3 5% 5% 33%	2800
	21st to end	Night	14% 10% 4 10% 6% 4 4 3 6% 6% 34%	2800
December	1st to 10th	Night	8% 15% 5% 12% 7% 6% 4 3 5% 7% 28%	2779
	11th to 20th	Night	11% 16% 5% 12% 7% 6% 5% 4 5% 5% 25%	3279
	21st to end	Night	23% 17% 5% 11% 6% 4 3 3 4 4 21%	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	65% 3 10% 17% 5%	2528
	11th to 20th	Day	66% 3 10% 16% 5%	2530
	21st to end	Day	63% 3 13% 16% 4	3070
February	1st to 10th	Day	52% 3 13% 21% 9% 1	1710
	11th to 20th	Day	51% 3 11% 25% 9% 1	1673
	21st to end	Day	52% 5% 10% 22% 10% 1	1492
March	1st to 10th	Day	46% 3 15% 23% 12% 1	3299
	11th to 20th	Day	43% 4 12% 31% 10% 1	3480
	21st to end	Day	63% 2 9% 20% 5%	3902
April	1st to 10th	Day	50% 4 11% 21% 13% 1	2280
	11th to 20th	Day	55% 4 8% 19% 13% 1	2254
	21st to end	Day	55% 4 12% 21% 9%	2456
May	1st to 10th	Day	44% 4 10% 28% 14% 2	4375
	11th to 20th	Day	41% 3 13% 27% 13% 2	4403
	21st to end	Day	49% 4 11% 25% 10% 1	4837
June	1st to 10th	Day	36% 5% 15% 31% 12% 1	2660
	11th to 20th	Day	42% 5% 15% 25% 12% 1	2660
	21st to end	Day	38% 5% 17% 29% 9% 2	2660
July	1st to 10th	Day	41% 3 19% 25% 12%	4371
	11th to 20th	Day	24% 3 17% 38% 17% 1	4365
	21st to end	Day	31% 4 15% 31% 18% 1	4662
August	1st to 10th	Day	39% 3 13% 30% 13% 1	4135
	11th to 20th	Day	39% 3 13% 35% 9%	4080
	21st to end	Day	41% 3 17% 26% 13% 1	4290
September	1st to 10th	Day	35% 6% 12% 35% 11%	2280
	11th to 20th	Day	37% 4 19% 32% 8%	2280
	21st to end	Day	40% 5% 12% 33% 10% 1	1984
October	1st to 10th	Day	30% 2 10% 38% 20%	3160
	11th to 20th	Day	41% 2 10% 28% 17% 2	3140
	21st to end	Day	46% 2 16% 26% 9%	3314
November	1st to 10th	Day	51% 4 13% 19% 12% 1	1662
	11th to 20th	Day	60% 4 12% 16% 7% 1	1600
	21st to end	Day	52% 5% 16% 21% 5% 2	1600
December	1st to 10th	Day	61% 5% 14% 16% 4	1584
	11th to 20th	Day	60% 3 16% 15% 5% 1	1915
	21st to end	Day	72% 3 8% 11% 7%	2783
January	1st to 10th	Night	60% 3 12% 19% 6% 1	4428
	11th to 20th	Night	62% 4 12% 15% 6%	4440
	21st to end	Night	65% 3 9% 18% 4 1	4596
February	1st to 10th	Night	49% 3 12% 24% 10% 2	2470
	11th to 20th	Night	46% 5% 13% 26% 9% 1	2404
	21st to end	Night	51% 4 11% 22% 11% 1	1960
March	1st to 10th	Night	39% 4 14% 25% 17% 1	3583
	11th to 20th	Night	45% 3 10% 28% 15% 1	3480
	21st to end	Night	61% 2 8% 19% 9%	3727
April	1st to 10th	Night	50% 4 8% 21% 16% 1	1900
	11th to 20th	Night	51% 3 8% 21% 15% 2	1875
	21st to end	Night	49% 4 9% 23% 14% 2	1723
May	1st to 10th	Night	46% 3 11% 20% 19% 1	2594
	11th to 20th	Night	33% 4 10% 28% 21% 3	2507
	21st to end	Night	43% 4 14% 23% 15% 1	2751
June	1st to 10th	Night	34% 5% 14% 31% 15% 1	1520
	11th to 20th	Night	36% 4 14% 26% 18% 3	1520
	21st to end	Night	30% 5% 17% 31% 14% 3	1520
July	1st to 10th	Night	33% 4 22% 27% 13% 1	2490
	11th to 20th	Night	21% 4 13% 39% 20% 2	2482
	21st to end	Night	23% 4 16% 34% 21% 2	2662
August	1st to 10th	Night	37% 3 12% 30% 15% 3	2778
	11th to 20th	Night	36% 4 13% 34% 12% 1	2825
	21st to end	Night	39% 4 16% 29% 10% 2	3366
September	1st to 10th	Night	30% 4 15% 35% 15% 1	1900
	11th to 20th	Night	30% 4 17% 34% 15%	1900
	21st to end	Night	36% 3 13% 35% 12% 1	2174
October	1st to 10th	Night	26% 2 7% 37% 25% 4	3800
	11th to 20th	Night	39% 2 11% 24% 23% 2	3779
	21st to end	Night	48% 3 11% 25% 12%	4234
November	1st to 10th	Night	46% 3 12% 25% 13% 1	2632
	11th to 20th	Night	54% 3 12% 18% 11% 1	2800
	21st to end	Night	50% 4 15% 23% 6% 1	2800
December	1st to 10th	Night	57% 4 15% 19% 5%	2779
	11th to 20th	Night	61% 4 12% 18% 5% 1	3281
	21st to end	Night	67% 2 11% 15% 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	17% 7% 34% 30% 10% 3	270
	11th to 20th	Day	17% 9% 39% 28% 7% 1	270
	21st to end	Day	15% 7% 39% 28% 9% 1	297
February	1st to 10th	Day	17% 12% 48% 16% 6% 1	270
	11th to 20th	Day	16% 16% 41% 20% 6% 1	270
	21st to end	Day	16% 14% 42% 25% 2	225
March	1st to 10th	Day	18% 11% 43% 20% 7% 1	270
	11th to 20th	Day	20% 8% 39% 24% 9% 1	270
	21st to end	Day	23% 12% 32% 20% 9% 3	347
April	1st to 10th	Day	24% 12% 36% 22% 6% 1	460
	11th to 20th	Day	30% 10% 26% 25% 7% 1	452
	21st to end	Day	26% 10% 32% 21% 9% 2	636
May	1st to 10th	Day	22% 11% 31% 26% 8% 2	653
	11th to 20th	Day	19% 10% 28% 26% 13% 4	675
	21st to end	Day	20% 7% 27% 25% 16% 4	734
June	1st to 10th	Day	11% 8% 27% 33% 17% 4	680
	11th to 20th	Day	15% 9% 35% 29% 10% 2	680
	21st to end	Day	14% 6% 31% 28% 16% 6%	680
July	1st to 10th	Day	10% 3 23% 28% 24% 11%	671
	11th to 20th	Day	10% 6% 25% 31% 19% 9%	668
	21st to end	Day	8% 3 24% 36% 21% 9%	739
August	1st to 10th	Day	12% 4 22% 33% 23% 7%	676
	11th to 20th	Day	14% 3 19% 32% 26% 6%	665
	21st to end	Day	13% 6% 23% 33% 20% 4	611
September	1st to 10th	Day	14% 5% 30% 30% 17% 5%	490
	11th to 20th	Day	13% 4 28% 32% 19% 3	490
	21st to end	Day	19% 9% 29% 26% 13% 4	313
October	1st to 10th	Day	21% 10% 28% 23% 15% 3	300
	11th to 20th	Day	19% 17% 32% 24% 7%	300
	21st to end	Day	23% 13% 40% 17% 6% 2	330
November	1st to 10th	Day	23% 11% 36% 20% 8% 1	300
	11th to 20th	Day	22% 16% 38% 21% 3	300
	21st to end	Day	24% 12% 38% 20% 5%	300
December	1st to 10th	Day	17% 8% 44% 22% 8% 1	294
	11th to 20th	Day	20% 15% 36% 23% 6%	270
	21st to end	Day	28% 13% 39% 18% 2	297
January	1st to 10th	Night	13% 11% 37% 30% 9% 1	950
	11th to 20th	Night	17% 8% 38% 29% 7% 1	950
	21st to end	Night	18% 9% 34% 30% 8% 1	1045
February	1st to 10th	Night	12% 10% 41% 30% 7% 1	950
	11th to 20th	Night	11% 12% 40% 28% 7% 1	929
	21st to end	Night	18% 12% 34% 28% 8%	704
March	1st to 10th	Night	16% 12% 38% 27% 7% 1	675
	11th to 20th	Night	17% 9% 38% 29% 6%	570
	21st to end	Night	22% 10% 30% 26% 10% 2	627
April	1st to 10th	Night	27% 8% 33% 26% 6%	570
	11th to 20th	Night	27% 7% 31% 27% 6% 1	563
	21st to end	Night	25% 8% 29% 29% 8% 1	570
May	1st to 10th	Night	21% 7% 35% 30% 7%	570
	11th to 20th	Night	17% 7% 31% 33% 10% 2	561
	21st to end	Night	12% 7% 27% 39% 14% 1	617
June	1st to 10th	Night	13% 5% 28% 41% 12% 1	570
	11th to 20th	Night	12% 4 31% 43% 9%	570
	21st to end	Night	9% 4 25% 44% 16% 2	570
July	1st to 10th	Night	8% 1 21% 41% 28% 2	555
	11th to 20th	Night	9% 4 20% 44% 22% 2	552
	21st to end	Night	5% 2 22% 46% 23% 2	624
August	1st to 10th	Night	10% 2 14% 54% 18% 2	567
	11th to 20th	Night	14% 1 19% 37% 26% 4	564
	21st to end	Night	11% 4 22% 37% 24% 2	627
September	1st to 10th	Night	11% 5% 23% 39% 18% 3	570
	11th to 20th	Night	12% 2 29% 36% 18% 2	570
	21st to end	Night	16% 9% 30% 29% 15% 1	669
October	1st to 10th	Night	18% 7% 28% 32% 13% 1	760
	11th to 20th	Night	22% 10% 30% 29% 8% 1	760
	21st to end	Night	25% 10% 28% 29% 8%	836
November	1st to 10th	Night	21% 9% 32% 30% 7% 1	876
	11th to 20th	Night	20% 12% 33% 27% 8%	1000
	21st to end	Night	19% 14% 36% 25% 6%	1000
December	1st to 10th	Night	16% 10% 36% 29% 8% 1	993
	11th to 20th	Night	21% 8% 38% 25% 7% 1	950
	21st to end	Night	25% 10% 33% 26% 6%	1045

Page generated at 2024-12-06 02:54:49. Version ac07

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