Souris
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Souris clear sky chart from 2005-11-06 to 2026-06-16.

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	10% 8% 3 9% 6% 5% 5% 4 6% 8% 36%	141810
	Night	8% 9% 4 10% 6% 5% 6% 4 6% 8% 34%	139068
Transparency	Day	44% 8% 15% 24% 9% 1	141525
	Night	46% 7% 14% 23% 9% 1	138938
Seeing	Day	14% 9% 31% 29% 14% 3	18449
	Night	14% 7% 33% 33% 12% 1	28440

By Month

Percentage Cloud Cover NW (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	4 13% 7% 15% 9% 7% 6% 5% 7% 9% 18%	4125
	11th to 20th	Day	3 11% 5% 13% 12% 8% 11% 8% 7% 8% 14%	4638
	21st to end	Day	5% 10% 6% 11% 5% 6% 5% 4 6% 9% 31%	5188
February	1st to 10th	Day	9% 13% 6% 14% 7% 6% 5% 4 6% 6% 23%	1680
	11th to 20th	Day	6% 12% 4 10% 9% 7% 8% 5% 6% 8% 24%	1882
	21st to end	Day	6% 11% 4 12% 9% 7% 7% 5% 6% 7% 25%	1730
March	1st to 10th	Day	7% 12% 5% 13% 8% 7% 6% 4 7% 9% 23%	4600
	11th to 20th	Day	7% 14% 6% 13% 9% 6% 6% 4 6% 7% 22%	4942
	21st to end	Day	10% 12% 5% 14% 7% 6% 5% 4 5% 7% 24%	5806
April	1st to 10th	Day	10% 9% 3 9% 5% 5% 5% 4 5% 8% 38%	2520
	11th to 20th	Day	13% 12% 5% 9% 5% 4 5% 4 5% 6% 31%	2687
	21st to end	Day	14% 9% 4 8% 6% 5% 4 3 6% 8% 34%	2730
May	1st to 10th	Day	11% 7% 3 6% 4 4 4 3 5% 8% 45%	7939
	11th to 20th	Day	21% 10% 3 7% 4 4 4 3 5% 6% 31%	8504
	21st to end	Day	12% 6% 2 6% 4 3 4 3 5% 7% 48%	9683
June	1st to 10th	Day	13% 7% 2 7% 5% 5% 4 4 7% 8% 38%	3150
	11th to 20th	Day	14% 7% 2 7% 5% 5% 5% 5% 6% 8% 35%	3076
	21st to end	Day	12% 6% 2 6% 5% 6% 5% 4 7% 9% 39%	3000
July	1st to 10th	Day	7% 5% 2 6% 4 5% 5% 5% 8% 10% 43%	6800
	11th to 20th	Day	10% 5% 2 5% 4 4 5% 4 7% 9% 44%	6754
	21st to end	Day	6% 4 2 6% 4 4 5% 5% 7% 10% 46%	6898
August	1st to 10th	Day	8% 6% 2 6% 4 4 5% 4 6% 10% 44%	4552
	11th to 20th	Day	10% 5% 2 5% 3 3 4 3 6% 9% 49%	4236
	21st to end	Day	9% 5% 2 5% 3 3 4 4 6% 9% 50%	4675
September	1st to 10th	Day	10% 6% 2 6% 3 4 4 3 5% 8% 51%	2402
	11th to 20th	Day	14% 6% 3 6% 5% 4 4 4 5% 6% 43%	2220
	21st to end	Day	14% 5% 2 5% 4 3 3 3 5% 7% 48%	2200
October	1st to 10th	Day	11% 9% 3 6% 4 4 4 3 5% 6% 46%	3506
	11th to 20th	Day	8% 7% 2 7% 4 4 4 3 6% 9% 47%	2932
	21st to end	Day	11% 11% 5% 9% 5% 3 4 3 4 7% 37%	3190
November	1st to 10th	Day	17% 14% 4 10% 5% 4 4 3 5% 6% 29%	1848
	11th to 20th	Day	10% 16% 5% 11% 7% 4 4 4 5% 6% 28%	1603
	21st to end	Day	9% 13% 5% 10% 7% 6% 5% 5% 5% 6% 28%	1470
December	1st to 10th	Day	6% 14% 7% 18% 9% 11% 8% 4 4 4 16%	2360
	11th to 20th	Day	8% 12% 5% 13% 8% 7% 5% 5% 7% 9% 20%	2709
	21st to end	Day	5% 9% 4 16% 7% 6% 7% 5% 6% 7% 28%	3575
January	1st to 10th	Night	5% 11% 6% 17% 9% 8% 8% 5% 5% 7% 19%	8799
	11th to 20th	Night	5% 11% 4 13% 10% 8% 9% 7% 9% 7% 18%	8272
	21st to end	Night	4 11% 6% 13% 7% 6% 8% 5% 7% 9% 25%	9026
February	1st to 10th	Night	8% 14% 4 12% 7% 7% 6% 4 6% 6% 25%	2940
	11th to 20th	Night	6% 10% 4 9% 7% 6% 7% 5% 6% 6% 34%	2640
	21st to end	Night	6% 9% 4 10% 7% 5% 6% 4 6% 7% 34%	2076
March	1st to 10th	Night	6% 11% 4 12% 7% 5% 5% 5% 7% 9% 29%	5494
	11th to 20th	Night	7% 11% 4 11% 6% 5% 5% 4 6% 8% 33%	5241
	21st to end	Night	8% 13% 6% 14% 7% 5% 4 3 5% 7% 27%	5375
April	1st to 10th	Night	6% 8% 3 8% 5% 4 6% 4 7% 8% 41%	2100
	11th to 20th	Night	13% 12% 4 7% 5% 4 5% 4 6% 7% 32%	1883
	21st to end	Night	14% 9% 3 7% 6% 5% 5% 3 6% 6% 36%	1890
May	1st to 10th	Night	11% 7% 3 7% 4 4 5% 4 5% 7% 43%	4994
	11th to 20th	Night	17% 8% 2 6% 4 4 5% 4 7% 8% 36%	4387
	21st to end	Night	11% 7% 2 6% 4 4 3 3 5% 7% 48%	4523
June	1st to 10th	Night	12% 6% 2 5% 5% 4 4 4 7% 8% 44%	1470
	11th to 20th	Night	13% 5% 3 6% 4 5% 5% 3 6% 9% 41%	1435
	21st to end	Night	11% 4 2 7% 3 4 4 5% 7% 9% 45%	1400
July	1st to 10th	Night	6% 4 2 4 4 4 4 5% 8% 11% 49%	3180
	11th to 20th	Night	7% 4 2 5% 3 4 4 4 5% 9% 52%	3223
	21st to end	Night	6% 5% 2 6% 4 4 4 4 6% 9% 50%	3968
August	1st to 10th	Night	6% 4 2 5% 4 3 4 3 5% 9% 54%	2608
	11th to 20th	Night	5% 3 1 5% 4 5% 5% 4 7% 9% 50%	2823
	21st to end	Night	8% 4 2 5% 3 4 4 3 6% 8% 52%	3234
September	1st to 10th	Night	9% 4 2 5% 3 3 3 4 5% 8% 53%	1995
	11th to 20th	Night	13% 6% 2 5% 4 3 4 3 5% 8% 46%	2180
	21st to end	Night	14% 7% 2 6% 4 4 4 4 4 7% 46%	2200
October	1st to 10th	Night	12% 8% 2 6% 3 4 4 3 5% 6% 49%	3640
	11th to 20th	Night	10% 7% 2 5% 5% 5% 5% 5% 6% 8% 43%	4216
	21st to end	Night	8% 9% 4 7% 5% 4 4 4 6% 7% 43%	4610
November	1st to 10th	Night	12% 12% 4 9% 5% 5% 5% 4 5% 6% 33%	2669
	11th to 20th	Night	9% 14% 5% 11% 7% 5% 5% 3 5% 6% 30%	3014
	21st to end	Night	8% 13% 4 11% 7% 6% 5% 4 6% 6% 30%	3150
December	1st to 10th	Night	6% 14% 5% 15% 10% 8% 8% 6% 6% 5% 18%	5050
	11th to 20th	Night	9% 15% 5% 11% 8% 6% 6% 4 6% 8% 21%	5718
	21st to end	Night	5% 8% 3 13% 8% 7% 7% 6% 7% 8% 27%	7645

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	58% 9% 10% 16% 7%	4125
	11th to 20th	Day	61% 9% 10% 14% 7%	4662
	21st to end	Day	48% 6% 14% 25% 7%	5188
February	1st to 10th	Day	59% 6% 12% 16% 6% 1	1680
	11th to 20th	Day	54% 7% 12% 18% 9%	1891
	21st to end	Day	54% 8% 15% 16% 6%	1730
March	1st to 10th	Day	53% 9% 18% 14% 6%	4600
	11th to 20th	Day	56% 10% 14% 15% 5%	4944
	21st to end	Day	55% 8% 13% 18% 6%	5806
April	1st to 10th	Day	44% 8% 16% 22% 10% 1	2520
	11th to 20th	Day	51% 7% 13% 17% 10% 1	2687
	21st to end	Day	48% 8% 15% 21% 8% 1	2730
May	1st to 10th	Day	36% 6% 15% 29% 12% 2	7939
	11th to 20th	Day	51% 7% 11% 20% 10% 2	8508
	21st to end	Day	35% 7% 10% 25% 23% 1	9683
June	1st to 10th	Day	42% 9% 18% 21% 10% 1	3150
	11th to 20th	Day	45% 9% 16% 20% 9% 1	3076
	21st to end	Day	39% 10% 19% 25% 6% 1	3000
July	1st to 10th	Day	32% 10% 26% 27% 4	6726
	11th to 20th	Day	34% 8% 20% 32% 6%	6673
	21st to end	Day	29% 9% 23% 29% 9%	6705
August	1st to 10th	Day	34% 8% 19% 29% 11%	4536
	11th to 20th	Day	31% 7% 21% 33% 7%	4276
	21st to end	Day	30% 7% 21% 34% 9%	4674
September	1st to 10th	Day	32% 7% 15% 33% 11% 1	2402
	11th to 20th	Day	41% 7% 17% 25% 9% 1	2220
	21st to end	Day	36% 6% 13% 31% 13%	2200
October	1st to 10th	Day	40% 4 13% 35% 8%	3506
	11th to 20th	Day	35% 5% 13% 36% 10%	2932
	21st to end	Day	47% 5% 10% 29% 8%	3190
November	1st to 10th	Day	56% 7% 12% 16% 7% 1	1848
	11th to 20th	Day	55% 7% 17% 13% 7% 1	1603
	21st to end	Day	55% 7% 16% 16% 5%	1470
December	1st to 10th	Day	69% 8% 12% 8% 3	2360
	11th to 20th	Day	57% 9% 16% 15% 3	2710
	21st to end	Day	51% 8% 11% 19% 10% 1	3575
January	1st to 10th	Night	61% 7% 10% 16% 5%	8800
	11th to 20th	Night	58% 9% 11% 16% 6%	8310
	21st to end	Night	53% 8% 13% 20% 7%	9026
February	1st to 10th	Night	57% 6% 13% 16% 7% 1	2940
	11th to 20th	Night	45% 9% 12% 20% 13%	2641
	21st to end	Night	46% 7% 14% 22% 9%	2076
March	1st to 10th	Night	47% 8% 20% 19% 7%	5494
	11th to 20th	Night	45% 8% 16% 21% 9%	5241
	21st to end	Night	55% 7% 11% 22% 5%	5375
April	1st to 10th	Night	38% 7% 14% 24% 14% 2	2100
	11th to 20th	Night	49% 7% 13% 20% 11%	1883
	21st to end	Night	45% 7% 14% 22% 11% 2	1890
May	1st to 10th	Night	38% 7% 10% 27% 18%	4994
	11th to 20th	Night	43% 7% 11% 27% 10% 2	4387
	21st to end	Night	35% 6% 10% 24% 25%	4526
June	1st to 10th	Night	35% 8% 19% 24% 12% 2	1470
	11th to 20th	Night	38% 9% 17% 23% 12% 1	1435
	21st to end	Night	33% 10% 20% 30% 6% 1	1400
July	1st to 10th	Night	26% 11% 26% 30% 7% 1	3145
	11th to 20th	Night	29% 7% 18% 39% 7%	3181
	21st to end	Night	28% 8% 22% 29% 12% 1	3856
August	1st to 10th	Night	27% 8% 18% 32% 14% 2	2600
	11th to 20th	Night	28% 9% 18% 35% 9% 1	2849
	21st to end	Night	29% 6% 19% 34% 12% 1	3234
September	1st to 10th	Night	28% 7% 14% 33% 16% 2	1995
	11th to 20th	Night	35% 8% 17% 26% 12% 1	2180
	21st to end	Night	38% 6% 13% 29% 12% 2	2200
October	1st to 10th	Night	37% 4 12% 30% 14% 3	3640
	11th to 20th	Night	38% 5% 12% 32% 13% 1	4216
	21st to end	Night	40% 6% 13% 32% 9%	4610
November	1st to 10th	Night	50% 7% 14% 19% 7% 2	2669
	11th to 20th	Night	54% 8% 15% 17% 6% 1	3014
	21st to end	Night	52% 9% 16% 17% 6%	3150
December	1st to 10th	Night	63% 8% 15% 11% 4	5050
	11th to 20th	Night	58% 7% 15% 16% 4	5716
	21st to end	Night	49% 9% 14% 17% 10% 1	7645

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	10% 7% 41% 28% 13% 2	330
	11th to 20th	Day	8% 9% 41% 30% 12% 1	330
	21st to end	Day	13% 9% 38% 26% 11% 2	363
February	1st to 10th	Day	15% 13% 38% 26% 6% 1	330
	11th to 20th	Day	9% 7% 36% 33% 13% 2	330
	21st to end	Day	4 8% 39% 32% 15% 1	273
March	1st to 10th	Day	11% 12% 35% 29% 12% 2	330
	11th to 20th	Day	11% 13% 27% 33% 14% 2	330
	21st to end	Day	15% 10% 33% 28% 11% 2	455
April	1st to 10th	Day	14% 13% 33% 30% 9% 1	540
	11th to 20th	Day	19% 12% 32% 25% 12% 1	725
	21st to end	Day	17% 9% 30% 31% 11% 1	750
May	1st to 10th	Day	14% 10% 27% 30% 16% 2	753
	11th to 20th	Day	21% 8% 29% 25% 14% 2	775
	21st to end	Day	18% 9% 23% 31% 17% 2	844
June	1st to 10th	Day	14% 12% 30% 27% 12% 5%	780
	11th to 20th	Day	15% 9% 35% 28% 11% 3	756
	21st to end	Day	12% 10% 28% 32% 15% 4	730
July	1st to 10th	Day	9% 4 25% 35% 19% 8%	721
	11th to 20th	Day	11% 7% 30% 27% 19% 6%	718
	21st to end	Day	6% 5% 24% 35% 22% 7%	794
August	1st to 10th	Day	11% 6% 23% 34% 19% 7%	726
	11th to 20th	Day	10% 7% 23% 29% 23% 8%	715
	21st to end	Day	11% 7% 25% 33% 19% 5%	803
September	1st to 10th	Day	11% 10% 33% 26% 15% 5%	532
	11th to 20th	Day	19% 10% 27% 33% 9% 3	350
	21st to end	Day	20% 9% 29% 26% 13% 3	330
October	1st to 10th	Day	22% 15% 24% 23% 14% 3	330
	11th to 20th	Day	15% 13% 35% 26% 8% 3	330
	21st to end	Day	20% 9% 40% 21% 9% 2	363
November	1st to 10th	Day	23% 12% 33% 21% 10% 2	330
	11th to 20th	Day	17% 12% 37% 26% 7% 1	330
	21st to end	Day	12% 12% 39% 27% 8% 2	330
December	1st to 10th	Day	14% 10% 40% 22% 12% 2	330
	11th to 20th	Day	15% 12% 40% 26% 6% 1	330
	21st to end	Day	12% 7% 36% 29% 14% 2	363
January	1st to 10th	Night	12% 9% 36% 32% 10% 1	1050
	11th to 20th	Night	16% 9% 36% 30% 8% 1	1050
	21st to end	Night	12% 8% 41% 30% 8%	1155
February	1st to 10th	Night	14% 10% 34% 30% 10% 1	1050
	11th to 20th	Night	11% 6% 34% 34% 12% 3	977
	21st to end	Night	10% 7% 33% 35% 14% 2	692
March	1st to 10th	Night	13% 9% 30% 36% 11% 2	840
	11th to 20th	Night	8% 8% 36% 35% 11% 2	703
	21st to end	Night	15% 6% 30% 35% 12% 2	693
April	1st to 10th	Night	10% 5% 37% 38% 10% 1	630
	11th to 20th	Night	18% 8% 33% 34% 8%	623
	21st to end	Night	17% 7% 33% 32% 10% 1	630
May	1st to 10th	Night	17% 6% 31% 33% 12%	630
	11th to 20th	Night	18% 7% 31% 31% 13%	621
	21st to end	Night	21% 6% 24% 36% 12%	683
June	1st to 10th	Night	15% 6% 35% 29% 14% 1	630
	11th to 20th	Night	14% 6% 35% 35% 9%	615
	21st to end	Night	11% 5% 28% 40% 16%	600
July	1st to 10th	Night	7% 3 24% 42% 22% 1	585
	11th to 20th	Night	8% 3 28% 42% 18% 1	582
	21st to end	Night	7% 3 22% 48% 18% 3	657
August	1st to 10th	Night	8% 3 24% 45% 18% 1	597
	11th to 20th	Night	7% 4 24% 39% 23% 2	594
	21st to end	Night	13% 4 26% 40% 17% 1	660
September	1st to 10th	Night	10% 4 29% 36% 19% 2	600
	11th to 20th	Night	16% 8% 28% 39% 9%	600
	21st to end	Night	17% 8% 28% 36% 11% 1	600
October	1st to 10th	Night	20% 7% 33% 30% 9%	624
	11th to 20th	Night	21% 9% 29% 32% 9%	989
	21st to end	Night	17% 8% 38% 28% 9%	1100
November	1st to 10th	Night	17% 11% 35% 28% 8% 1	1025
	11th to 20th	Night	16% 9% 37% 26% 10% 1	1050
	21st to end	Night	15% 10% 38% 28% 7% 1	1050
December	1st to 10th	Night	11% 8% 39% 29% 11% 1	1050
	11th to 20th	Night	15% 12% 34% 29% 8% 2	1050
	21st to end	Night	15% 5% 34% 32% 11% 2	1155

Page generated at 2026-06-13 01:31:41. Version ac07

Copyright © 2026 Attilla Danko.