Saint Paul
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saint Paul clear sky chart from 2005-11-06 to 2025-11-03.

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 4 4 5% 7% 38%	127310
	Night	12% 9% 4 9% 5% 4 4 4 5% 6% 38%	123022
Transparency	Day	43% 6% 13% 25% 11% 1	130874
	Night	45% 6% 13% 23% 12% 1	127535
Seeing	Day	16% 12% 32% 25% 12% 3	17416
	Night	16% 10% 33% 31% 10% 1	27239

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% 6% 19% 7% 7% 4 2 4 7% 22%	3617
	11th to 20th	Day	6% 12% 7% 13% 8% 7% 8% 9% 9% 4 19%	3638
	21st to end	Day	6% 16% 7% 13% 5% 4 5% 3 4 5% 31%	4488
February	1st to 10th	Day	9% 11% 5% 10% 7% 6% 6% 5% 5% 6% 29%	1800
	11th to 20th	Day	8% 11% 6% 10% 6% 5% 5% 4 6% 6% 34%	1754
	21st to end	Day	11% 11% 4 10% 6% 5% 4 4 5% 8% 32%	1555
March	1st to 10th	Day	12% 8% 3 6% 4 3 4 3 5% 8% 45%	4802
	11th to 20th	Day	10% 10% 3 7% 4 4 4 4 6% 8% 41%	4980
	21st to end	Day	22% 11% 4 10% 5% 4 4 4 4 6% 26%	5543
April	1st to 10th	Day	16% 11% 3 7% 5% 4 4 4 5% 8% 34%	2400
	11th to 20th	Day	20% 11% 4 7% 4 4 5% 4 5% 6% 31%	2374
	21st to end	Day	21% 12% 2 6% 4 4 5% 4 5% 6% 30%	2600
May	1st to 10th	Day	14% 7% 2 4 4 3 3 3 5% 6% 50%	6134
	11th to 20th	Day	17% 8% 2 5% 3 3 3 3 5% 7% 43%	6319
	21st to end	Day	18% 7% 2 6% 5% 4 4 3 5% 7% 38%	6935
June	1st to 10th	Day	12% 4 2 4 4 4 5% 4 6% 8% 46%	2800
	11th to 20th	Day	14% 7% 3 7% 5% 5% 4 5% 7% 9% 36%	2800
	21st to end	Day	12% 5% 2 5% 5% 6% 5% 5% 8% 9% 39%	2800
July	1st to 10th	Day	9% 4 2 5% 4 4 5% 4 7% 10% 45%	6360
	11th to 20th	Day	9% 3 1 4 3 3 3 3 5% 8% 57%	6360
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 7% 9% 47%	6879
August	1st to 10th	Day	13% 6% 2 5% 4 4 5% 4 6% 8% 43%	4234
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 4 6% 8% 44%	4171
	21st to end	Day	11% 6% 2 6% 4 4 4 4 5% 7% 47%	4454
September	1st to 10th	Day	12% 6% 2 4 4 4 5% 4 6% 7% 47%	2400
	11th to 20th	Day	13% 6% 2 5% 3 5% 5% 5% 7% 7% 44%	2382
	21st to end	Day	14% 6% 2 6% 4 3 4 3 6% 6% 45%	2095
October	1st to 10th	Day	16% 7% 3 5% 4 4 4 3 4 6% 45%	2000
	11th to 20th	Day	15% 10% 3 6% 4 4 4 3 5% 7% 39%	2000
	21st to end	Day	17% 12% 4 7% 4 3 4 3 4 5% 38%	2165
November	1st to 10th	Day	13% 11% 3 9% 5% 4 4 4 5% 5% 36%	1671
	11th to 20th	Day	11% 14% 6% 11% 7% 4 5% 2 6% 5% 29%	1600
	21st to end	Day	12% 12% 5% 9% 6% 4 3 4 6% 7% 34%	1600
December	1st to 10th	Day	8% 10% 5% 15% 12% 7% 5% 4 6% 7% 22%	2610
	11th to 20th	Day	11% 17% 6% 10% 6% 5% 5% 3 4 6% 26%	3008
	21st to end	Day	21% 19% 7% 19% 5% 4 3 2 3 4 13%	3982
January	1st to 10th	Night	7% 12% 6% 15% 9% 6% 4 3 5% 5% 29%	6348
	11th to 20th	Night	7% 11% 5% 13% 8% 6% 10% 9% 7% 5% 20%	6338
	21st to end	Night	8% 17% 6% 10% 5% 5% 4 3 5% 5% 32%	6490
February	1st to 10th	Night	8% 11% 5% 11% 7% 6% 5% 4 5% 6% 34%	2600
	11th to 20th	Night	6% 10% 4 8% 7% 5% 5% 4 5% 7% 39%	2533
	21st to end	Night	11% 10% 4 8% 5% 5% 5% 3 5% 6% 37%	2075
March	1st to 10th	Night	10% 7% 2 7% 4 4 4 3 6% 6% 47%	5083
	11th to 20th	Night	10% 7% 3 7% 5% 5% 5% 4 6% 8% 39%	4980
	21st to end	Night	24% 12% 4 9% 4 3 3 3 4 5% 28%	5385
April	1st to 10th	Night	17% 11% 3 6% 4 4 4 3 5% 7% 37%	2000
	11th to 20th	Night	20% 11% 3 7% 5% 3 3 4 4 6% 34%	1972
	21st to end	Night	20% 9% 3 7% 4 4 5% 4 4 6% 35%	1800
May	1st to 10th	Night	13% 7% 2 5% 4 3 3 3 5% 5% 51%	3779
	11th to 20th	Night	15% 5% 2 4 3 2 3 3 5% 7% 50%	3596
	21st to end	Night	16% 8% 3 6% 4 4 4 3 5% 6% 40%	3942
June	1st to 10th	Night	10% 5% 2 6% 4 3 4 4 6% 8% 49%	1600
	11th to 20th	Night	9% 6% 1 6% 5% 4 5% 5% 6% 7% 46%	1600
	21st to end	Night	8% 5% 2 5% 4 4 4 4 6% 8% 51%	1600
July	1st to 10th	Night	8% 3 2 5% 4 4 4 4 6% 9% 50%	3618
	11th to 20th	Night	6% 4 2 5% 4 4 4 4 6% 8% 55%	3617
	21st to end	Night	9% 4 2 5% 4 4 4 4 6% 7% 51%	3989
August	1st to 10th	Night	13% 5% 3 5% 4 4 4 4 5% 7% 47%	2926
	11th to 20th	Night	14% 5% 2 3 3 3 4 3 5% 8% 50%	2888
	21st to end	Night	9% 6% 2 7% 4 4 4 4 5% 6% 48%	3448
September	1st to 10th	Night	9% 4 2 5% 3 4 4 4 4 7% 53%	2000
	11th to 20th	Night	10% 5% 2 4 3 4 4 4 5% 8% 52%	2015
	21st to end	Night	13% 5% 2 4 4 3 4 3 4 5% 53%	2284
October	1st to 10th	Night	14% 6% 2 6% 4 3 3 3 4 6% 50%	2400
	11th to 20th	Night	16% 10% 2 6% 3 3 4 3 4 7% 41%	2400
	21st to end	Night	19% 11% 3 6% 3 3 4 3 4 5% 38%	2673
November	1st to 10th	Night	14% 9% 3 7% 4 3 4 3 5% 6% 41%	2668
	11th to 20th	Night	13% 11% 5% 11% 5% 5% 4 3 4 5% 34%	2800
	21st to end	Night	14% 10% 4 9% 6% 4 4 3 4 7% 36%	2800
December	1st to 10th	Night	7% 9% 4 15% 8% 8% 6% 4 5% 7% 29%	4580
	11th to 20th	Night	10% 16% 7% 14% 6% 5% 4 4 4 4 24%	5199
	21st to end	Night	22% 15% 8% 15% 5% 4 3 3 3 4 17%	6996

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	64% 4 9% 18% 5%	3618
	11th to 20th	Day	60% 5% 9% 16% 9%	3638
	21st to end	Day	55% 6% 15% 17% 7%	4488
February	1st to 10th	Day	53% 6% 14% 18% 8% 1	1800
	11th to 20th	Day	49% 5% 13% 24% 8% 1	1763
	21st to end	Day	50% 7% 13% 20% 10% 1	1555
March	1st to 10th	Day	38% 5% 18% 25% 12% 2	4802
	11th to 20th	Day	42% 5% 15% 29% 10% 1	4980
	21st to end	Day	59% 5% 10% 18% 7%	5545
April	1st to 10th	Day	48% 6% 13% 21% 12% 1	2400
	11th to 20th	Day	53% 6% 11% 17% 11% 1	2374
	21st to end	Day	54% 6% 12% 19% 9% 1	2600
May	1st to 10th	Day	35% 5% 12% 29% 17% 2	6172
	11th to 20th	Day	40% 6% 11% 23% 15% 5%	6323
	21st to end	Day	44% 7% 10% 29% 10% 1	6949
June	1st to 10th	Day	33% 8% 15% 30% 13% 1	2800
	11th to 20th	Day	43% 9% 14% 20% 13% 1	2800
	21st to end	Day	38% 10% 16% 26% 10% 2	2800
July	1st to 10th	Day	31% 9% 18% 32% 9%	6291
	11th to 20th	Day	25% 6% 16% 37% 15% 1	6285
	21st to end	Day	31% 8% 15% 29% 16% 1	6684
August	1st to 10th	Day	37% 7% 13% 29% 12% 2	4220
	11th to 20th	Day	35% 8% 13% 33% 10%	4210
	21st to end	Day	36% 7% 16% 28% 13% 1	4453
September	1st to 10th	Day	35% 6% 15% 31% 12%	2400
	11th to 20th	Day	35% 8% 17% 31% 8%	2382
	21st to end	Day	38% 6% 11% 32% 11%	2095
October	1st to 10th	Day	30% 3 9% 35% 22%	3260
	11th to 20th	Day	39% 5% 11% 27% 17% 1	3240
	21st to end	Day	43% 5% 15% 28% 9%	3479
November	1st to 10th	Day	48% 7% 13% 18% 12% 2	1671
	11th to 20th	Day	57% 5% 13% 16% 8% 1	1600
	21st to end	Day	50% 6% 17% 19% 6% 1	1600
December	1st to 10th	Day	61% 7% 16% 12% 5%	2610
	11th to 20th	Day	59% 5% 13% 17% 5%	3005
	21st to end	Day	76% 5% 8% 7% 4	3982
January	1st to 10th	Night	57% 5% 11% 20% 8%	6348
	11th to 20th	Night	60% 5% 11% 14% 9%	6338
	21st to end	Night	54% 5% 12% 22% 6%	6490
February	1st to 10th	Night	51% 6% 12% 21% 9% 1	2600
	11th to 20th	Night	45% 5% 15% 25% 8% 1	2534
	21st to end	Night	48% 6% 12% 22% 12% 1	2075
March	1st to 10th	Night	36% 6% 15% 25% 16% 3	5083
	11th to 20th	Night	38% 7% 16% 25% 13% 1	4980
	21st to end	Night	59% 4 10% 17% 9%	5385
April	1st to 10th	Night	47% 5% 10% 23% 15% 1	2000
	11th to 20th	Night	50% 5% 10% 19% 14% 2	1972
	21st to end	Night	49% 6% 9% 20% 14% 2	1800
May	1st to 10th	Night	35% 6% 10% 26% 21% 2	3806
	11th to 20th	Night	33% 5% 12% 22% 20% 7%	3597
	21st to end	Night	43% 7% 10% 27% 13% 1	3950
June	1st to 10th	Night	32% 7% 14% 28% 18% 2	1600
	11th to 20th	Night	35% 8% 13% 22% 19% 2	1600
	21st to end	Night	28% 8% 16% 29% 16% 3	1600
July	1st to 10th	Night	28% 8% 19% 31% 13% 1	3580
	11th to 20th	Night	25% 7% 16% 36% 15% 2	3572
	21st to end	Night	31% 7% 15% 27% 17% 2	3874
August	1st to 10th	Night	36% 7% 12% 27% 14% 4	2916
	11th to 20th	Night	32% 6% 15% 31% 15% 1	2915
	21st to end	Night	35% 8% 16% 27% 12% 2	3448
September	1st to 10th	Night	31% 6% 13% 33% 16% 1	2000
	11th to 20th	Night	30% 7% 17% 31% 15%	2015
	21st to end	Night	33% 5% 12% 32% 16% 1	2284
October	1st to 10th	Night	24% 3 7% 36% 26% 4	3920
	11th to 20th	Night	34% 5% 13% 24% 21% 3	3899
	21st to end	Night	43% 5% 12% 27% 12%	4309
November	1st to 10th	Night	43% 6% 14% 23% 13% 1	2668
	11th to 20th	Night	53% 6% 12% 18% 10% 1	2800
	21st to end	Night	50% 5% 16% 22% 6% 1	2800
December	1st to 10th	Night	54% 7% 18% 18% 4	4580
	11th to 20th	Night	63% 5% 10% 16% 4 1	5201
	21st to end	Night	72% 4 9% 12% 3	6996

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% 13% 33% 29% 10% 2	300
	11th to 20th	Day	17% 14% 40% 24% 5%	300
	21st to end	Day	16% 11% 42% 22% 8% 2	330
February	1st to 10th	Day	16% 15% 43% 21% 4 1	300
	11th to 20th	Day	14% 17% 39% 23% 5% 1	300
	21st to end	Day	17% 14% 43% 23% 2	249
March	1st to 10th	Day	17% 15% 43% 20% 6%	300
	11th to 20th	Day	19% 16% 36% 22% 6% 1	300
	21st to end	Day	27% 17% 28% 19% 7% 2	360
April	1st to 10th	Day	22% 18% 35% 20% 5% 1	500
	11th to 20th	Day	31% 14% 26% 21% 8%	492
	21st to end	Day	27% 15% 30% 19% 7% 1	700
May	1st to 10th	Day	19% 16% 31% 24% 10% 1	703
	11th to 20th	Day	18% 15% 29% 24% 11% 2	725
	21st to end	Day	18% 11% 28% 26% 14% 3	789
June	1st to 10th	Day	9% 10% 31% 32% 15% 2	730
	11th to 20th	Day	14% 12% 37% 27% 9% 2	730
	21st to end	Day	13% 12% 33% 25% 14% 4	730
July	1st to 10th	Day	8% 5% 25% 33% 21% 8%	721
	11th to 20th	Day	10% 7% 29% 28% 19% 6%	718
	21st to end	Day	6% 6% 30% 35% 18% 5%	794
August	1st to 10th	Day	10% 6% 25% 35% 19% 5%	726
	11th to 20th	Day	14% 6% 23% 30% 23% 4	715
	21st to end	Day	11% 7% 28% 32% 17% 5%	673
September	1st to 10th	Day	13% 10% 31% 26% 16% 4	530
	11th to 20th	Day	13% 8% 29% 30% 18% 2	512
	21st to end	Day	15% 15% 29% 21% 15% 4	330
October	1st to 10th	Day	18% 14% 29% 23% 12% 4	330
	11th to 20th	Day	19% 21% 38% 16% 5%	330
	21st to end	Day	23% 18% 38% 14% 6% 1	363
November	1st to 10th	Day	21% 17% 34% 21% 7% 1	306
	11th to 20th	Day	19% 23% 36% 19% 3	300
	21st to end	Day	23% 17% 41% 15% 4	300
December	1st to 10th	Day	14% 14% 40% 24% 7% 1	300
	11th to 20th	Day	20% 18% 33% 24% 4	300
	21st to end	Day	28% 15% 37% 16% 3 1	330
January	1st to 10th	Night	11% 13% 37% 31% 8%	1000
	11th to 20th	Night	16% 12% 37% 28% 5% 1	1000
	21st to end	Night	16% 12% 38% 28% 5% 1	1100
February	1st to 10th	Night	14% 13% 40% 27% 6% 1	1000
	11th to 20th	Night	12% 12% 42% 27% 6% 1	979
	21st to end	Night	17% 14% 34% 28% 8%	755
March	1st to 10th	Night	15% 11% 36% 29% 8%	678
	11th to 20th	Night	18% 12% 38% 26% 6%	600
	21st to end	Night	23% 13% 28% 24% 11% 1	660
April	1st to 10th	Night	24% 12% 33% 27% 5%	600
	11th to 20th	Night	25% 11% 32% 25% 6%	593
	21st to end	Night	23% 10% 34% 25% 8% 1	600
May	1st to 10th	Night	20% 12% 31% 30% 8% 1	600
	11th to 20th	Night	16% 9% 34% 31% 9% 1	591
	21st to end	Night	14% 9% 28% 36% 13%	650
June	1st to 10th	Night	11% 7% 31% 41% 11%	600
	11th to 20th	Night	10% 5% 33% 45% 7%	600
	21st to end	Night	10% 5% 28% 41% 15% 2	600
July	1st to 10th	Night	6% 2 23% 40% 28% 2	585
	11th to 20th	Night	6% 4 29% 42% 17% 1	582
	21st to end	Night	5% 3 28% 43% 19% 2	657
August	1st to 10th	Night	8% 4 19% 48% 20% 1	597
	11th to 20th	Night	13% 4 20% 37% 25% 2	594
	21st to end	Night	7% 5% 28% 36% 22% 2	660
September	1st to 10th	Night	10% 8% 25% 37% 17% 3	600
	11th to 20th	Night	11% 7% 32% 32% 17% 2	600
	21st to end	Night	14% 9% 31% 29% 15% 1	684
October	1st to 10th	Night	17% 11% 29% 30% 12% 1	800
	11th to 20th	Night	21% 13% 33% 26% 7% 1	800
	21st to end	Night	24% 12% 30% 27% 7%	880
November	1st to 10th	Night	19% 12% 33% 29% 6% 1	894
	11th to 20th	Night	19% 15% 35% 25% 7%	1000
	21st to end	Night	18% 16% 35% 24% 7%	1000
December	1st to 10th	Night	16% 11% 37% 30% 6% 1	1000
	11th to 20th	Night	20% 10% 38% 26% 6%	1000
	21st to end	Night	24% 12% 34% 25% 4	1100

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