Weyburn
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Weyburn clear sky chart from 2005-11-06 to 2026-07-31.

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	9% 8% 3 8% 5% 5% 5% 4 6% 8% 38%	147850
	Night	7% 8% 4 9% 6% 5% 5% 4 6% 8% 37%	142592
Transparency	Day	43% 7% 15% 24% 10% 1	142415
	Night	44% 6% 15% 23% 10% 1	139040
Seeing	Day	12% 9% 30% 30% 15% 3	18656
	Night	12% 8% 32% 35% 12% 1	28163

By Month

Percentage Cloud Cover SW (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	7% 12% 5% 15% 8% 8% 7% 5% 6% 7% 20%	4720
	11th to 20th	Day	3 7% 4 13% 10% 9% 10% 9% 10% 7% 17%	4740
	21st to end	Day	5% 9% 5% 12% 7% 7% 5% 4 6% 8% 31%	5188
February	1st to 10th	Day	9% 13% 5% 12% 9% 6% 8% 5% 6% 6% 21%	1714
	11th to 20th	Day	7% 11% 5% 11% 8% 8% 8% 6% 6% 7% 23%	1859
	21st to end	Day	5% 11% 5% 11% 9% 8% 6% 6% 7% 8% 24%	1730
March	1st to 10th	Day	6% 13% 6% 15% 6% 5% 6% 4 5% 7% 28%	4600
	11th to 20th	Day	6% 11% 6% 15% 7% 7% 5% 4 6% 8% 25%	4772
	21st to end	Day	8% 13% 7% 16% 6% 6% 5% 4 6% 7% 24%	6097
April	1st to 10th	Day	7% 8% 3 7% 6% 5% 5% 4 7% 8% 40%	2520
	11th to 20th	Day	13% 14% 3 10% 5% 5% 5% 4 6% 7% 28%	2537
	21st to end	Day	13% 9% 3 8% 5% 5% 4 4 5% 8% 37%	2829
May	1st to 10th	Day	11% 7% 3 6% 4 4 4 4 6% 7% 43%	8224
	11th to 20th	Day	18% 7% 2 6% 4 4 4 4 6% 8% 35%	8191
	21st to end	Day	11% 5% 2 6% 4 4 5% 4 5% 8% 47%	9224
June	1st to 10th	Day	12% 5% 2 6% 5% 5% 5% 4 7% 9% 40%	3150
	11th to 20th	Day	15% 7% 2 7% 5% 5% 5% 5% 6% 9% 34%	3245
	21st to end	Day	10% 5% 2 5% 5% 4 4 5% 7% 9% 43%	3360
July	1st to 10th	Day	5% 4 2 5% 5% 5% 5% 5% 8% 9% 47%	6932
	11th to 20th	Day	7% 5% 2 5% 4 4 5% 5% 7% 9% 46%	6480
	21st to end	Day	5% 4 2 5% 4 4 4 4 7% 8% 52%	7044
August	1st to 10th	Day	12% 6% 2 6% 5% 5% 5% 4 6% 8% 42%	6232
	11th to 20th	Day	5% 3 2 5% 4 5% 5% 4 6% 9% 52%	6253
	21st to end	Day	7% 3 2 5% 4 4 4 4 5% 8% 57%	6036
September	1st to 10th	Day	11% 4 2 5% 3 4 4 4 5% 8% 50%	2400
	11th to 20th	Day	13% 7% 3 7% 4 4 4 3 5% 7% 43%	2352
	21st to end	Day	12% 6% 2 5% 3 3 3 3 5% 8% 51%	2200
October	1st to 10th	Day	9% 7% 2 5% 3 4 4 3 5% 6% 51%	3303
	11th to 20th	Day	8% 7% 2 5% 4 3 3 3 6% 9% 49%	3069
	21st to end	Day	7% 10% 3 9% 5% 4 4 3 6% 8% 41%	3190
November	1st to 10th	Day	12% 14% 4 9% 6% 5% 5% 4 5% 6% 31%	1799
	11th to 20th	Day	7% 13% 4 12% 8% 6% 6% 4 5% 6% 29%	1680
	21st to end	Day	7% 15% 6% 11% 7% 7% 6% 4 5% 6% 27%	1503
December	1st to 10th	Day	5% 13% 6% 15% 8% 6% 7% 5% 6% 8% 22%	2360
	11th to 20th	Day	8% 17% 5% 12% 9% 8% 7% 4 5% 6% 19%	2713
	21st to end	Day	5% 8% 4 12% 7% 5% 5% 5% 6% 7% 35%	3604
January	1st to 10th	Night	3 11% 5% 14% 10% 7% 7% 5% 6% 6% 23%	8201
	11th to 20th	Night	4 8% 4 13% 9% 9% 10% 7% 9% 7% 22%	8250
	21st to end	Night	4 9% 6% 12% 8% 5% 6% 4 6% 9% 30%	9026
February	1st to 10th	Night	7% 13% 5% 10% 8% 7% 7% 6% 7% 8% 22%	2924
	11th to 20th	Night	6% 11% 4 12% 7% 6% 6% 5% 7% 7% 29%	2647
	21st to end	Night	3 9% 4 11% 7% 6% 6% 4 6% 8% 35%	2076
March	1st to 10th	Night	6% 11% 4 12% 6% 5% 5% 4 7% 9% 30%	5494
	11th to 20th	Night	6% 10% 4 11% 8% 6% 6% 4 6% 8% 31%	5430
	21st to end	Night	7% 13% 7% 16% 6% 5% 5% 3 5% 7% 25%	5097
April	1st to 10th	Night	6% 9% 3 7% 5% 4 4 4 6% 8% 44%	2100
	11th to 20th	Night	12% 11% 4 9% 5% 4 5% 4 7% 7% 33%	2031
	21st to end	Night	11% 9% 3 8% 5% 4 4 5% 6% 7% 38%	1789
May	1st to 10th	Night	10% 6% 2 5% 3 3 4 3 6% 8% 51%	4723
	11th to 20th	Night	18% 7% 2 6% 5% 4 5% 4 5% 8% 36%	4701
	21st to end	Night	12% 5% 2 5% 4 4 4 4 6% 8% 47%	4968
June	1st to 10th	Night	12% 4 2 5% 4 4 4 3 6% 8% 47%	1470
	11th to 20th	Night	12% 6% 2 6% 5% 4 3 4 5% 10% 42%	1367
	21st to end	Night	10% 4 2 6% 4 4 3 5% 7% 9% 46%	1260
July	1st to 10th	Night	5% 4 2 5% 4 4 5% 4 7% 11% 48%	3233
	11th to 20th	Night	11% 5% 2 6% 4 4 4 3 5% 6% 50%	3720
	21st to end	Night	5% 2 1 4 3 3 4 3 5% 8% 62%	4050
August	1st to 10th	Night	10% 5% 2 5% 5% 4 4 4 5% 9% 47%	3580
	11th to 20th	Night	5% 3 1 4 4 3 4 4 6% 9% 56%	3596
	21st to end	Night	5% 3 2 4 3 3 3 4 6% 9% 58%	4938
September	1st to 10th	Night	9% 4 2 5% 3 3 4 3 5% 7% 56%	2000
	11th to 20th	Night	11% 6% 2 5% 4 4 4 3 5% 7% 49%	2047
	21st to end	Night	11% 5% 2 5% 4 4 4 4 5% 6% 50%	2200
October	1st to 10th	Night	9% 6% 3 6% 4 4 3 3 5% 6% 51%	3882
	11th to 20th	Night	6% 6% 2 5% 4 4 4 4 7% 10% 48%	4047
	21st to end	Night	7% 8% 3 8% 5% 5% 5% 4 6% 8% 43%	4610
November	1st to 10th	Night	12% 14% 3 10% 5% 4 4 3 5% 6% 34%	2718
	11th to 20th	Night	8% 12% 4 11% 7% 7% 5% 4 6% 7% 30%	2940
	21st to end	Night	7% 12% 5% 12% 6% 6% 5% 4 5% 7% 30%	3113
December	1st to 10th	Night	7% 14% 6% 14% 7% 9% 6% 4 6% 7% 21%	5050
	11th to 20th	Night	7% 14% 6% 13% 9% 7% 7% 4 6% 6% 21%	5714
	21st to end	Night	4 8% 4 12% 7% 6% 6% 5% 6% 7% 35%	7600

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	62% 6% 13% 12% 7%	4723
	11th to 20th	Day	58% 6% 14% 14% 8%	4740
	21st to end	Day	50% 5% 19% 19% 7%	5188
February	1st to 10th	Day	62% 5% 11% 16% 7%	1714
	11th to 20th	Day	58% 6% 11% 14% 11%	1868
	21st to end	Day	55% 7% 14% 17% 7% 1	1730
March	1st to 10th	Day	55% 6% 18% 16% 5%	4600
	11th to 20th	Day	56% 8% 15% 17% 4	4772
	21st to end	Day	57% 8% 13% 16% 5%	6097
April	1st to 10th	Day	40% 8% 16% 25% 9% 1	2520
	11th to 20th	Day	53% 7% 15% 18% 7% 1	2540
	21st to end	Day	45% 7% 16% 24% 8% 1	2829
May	1st to 10th	Day	37% 6% 12% 29% 16%	8224
	11th to 20th	Day	45% 7% 14% 21% 13% 1	8195
	21st to end	Day	34% 7% 10% 29% 19% 1	9225
June	1st to 10th	Day	39% 8% 16% 26% 9% 2	3150
	11th to 20th	Day	45% 9% 16% 20% 10% 1	3245
	21st to end	Day	35% 9% 19% 28% 8% 1	3360
July	1st to 10th	Day	30% 9% 23% 28% 10% 1	6863
	11th to 20th	Day	31% 7% 17% 33% 10% 1	6405
	21st to end	Day	27% 7% 16% 32% 14% 3	6846
August	1st to 10th	Day	32% 7% 17% 25% 17% 1	4536
	11th to 20th	Day	28% 7% 20% 36% 9% 1	4525
	21st to end	Day	29% 6% 14% 39% 11% 1	4350
September	1st to 10th	Day	32% 6% 14% 30% 16% 3	2400
	11th to 20th	Day	41% 6% 14% 26% 11% 2	2352
	21st to end	Day	33% 5% 13% 31% 16% 2	2200
October	1st to 10th	Day	34% 4 13% 34% 13% 2	3303
	11th to 20th	Day	32% 4 17% 35% 12% 1	3069
	21st to end	Day	41% 5% 15% 31% 8%	3190
November	1st to 10th	Day	54% 5% 14% 19% 6% 1	1799
	11th to 20th	Day	54% 7% 15% 16% 7% 1	1680
	21st to end	Day	58% 7% 15% 14% 5%	1503
December	1st to 10th	Day	61% 7% 16% 12% 4	2360
	11th to 20th	Day	65% 5% 17% 10% 2	2710
	21st to end	Day	46% 5% 10% 25% 13% 2	3604
January	1st to 10th	Night	58% 6% 13% 17% 6%	8202
	11th to 20th	Night	56% 6% 15% 14% 8%	8250
	21st to end	Night	50% 6% 20% 16% 8%	9026
February	1st to 10th	Night	57% 7% 11% 17% 7%	2924
	11th to 20th	Night	52% 6% 13% 18% 11% 1	2648
	21st to end	Night	45% 6% 16% 23% 10%	2076
March	1st to 10th	Night	48% 6% 22% 20% 4	5494
	11th to 20th	Night	48% 8% 19% 21% 4	5430
	21st to end	Night	56% 7% 12% 19% 6%	5097
April	1st to 10th	Night	37% 6% 16% 24% 17% 1	2100
	11th to 20th	Night	49% 5% 12% 22% 11% 2	2031
	21st to end	Night	42% 7% 13% 26% 11% 1	1789
May	1st to 10th	Night	31% 4 11% 33% 19% 1	4724
	11th to 20th	Night	45% 6% 14% 20% 13% 2	4702
	21st to end	Night	32% 7% 11% 28% 20% 2	4969
June	1st to 10th	Night	33% 7% 17% 28% 12% 3	1470
	11th to 20th	Night	37% 8% 18% 21% 13% 2	1367
	21st to end	Night	32% 9% 18% 32% 9%	1260
July	1st to 10th	Night	28% 9% 23% 31% 8% 1	3195
	11th to 20th	Night	35% 5% 13% 34% 11% 1	3672
	21st to end	Night	22% 5% 19% 32% 17% 6%	3936
August	1st to 10th	Night	30% 6% 16% 31% 16% 1	2600
	11th to 20th	Night	23% 5% 19% 39% 13% 1	2600
	21st to end	Night	24% 5% 19% 34% 17% 2	3555
September	1st to 10th	Night	27% 5% 11% 31% 22% 3	2000
	11th to 20th	Night	35% 6% 15% 26% 17% 2	2047
	21st to end	Night	35% 5% 12% 31% 16% 2	2200
October	1st to 10th	Night	35% 3 13% 32% 12% 3	3882
	11th to 20th	Night	32% 4 14% 36% 13% 2	4047
	21st to end	Night	39% 4 12% 34% 10% 1	4610
November	1st to 10th	Night	51% 5% 14% 19% 8% 2	2718
	11th to 20th	Night	51% 7% 17% 18% 6% 1	2940
	21st to end	Night	52% 7% 18% 18% 5%	3113
December	1st to 10th	Night	62% 7% 17% 11% 3	5050
	11th to 20th	Night	63% 5% 17% 10% 4	5716
	21st to end	Night	46% 6% 11% 21% 12% 3	7600

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% 36% 31% 14% 3	330
	11th to 20th	Day	9% 12% 36% 32% 11% 1	330
	21st to end	Day	10% 12% 34% 32% 10% 1	363
February	1st to 10th	Day	15% 10% 36% 29% 9%	330
	11th to 20th	Day	9% 7% 35% 30% 15% 4	330
	21st to end	Day	4 8% 33% 36% 18% 1	273
March	1st to 10th	Day	15% 6% 37% 29% 12% 2	330
	11th to 20th	Day	12% 12% 36% 28% 10% 2	384
	21st to end	Day	12% 13% 34% 26% 13% 1	594
April	1st to 10th	Day	10% 14% 41% 27% 7% 1	540
	11th to 20th	Day	19% 15% 30% 27% 8% 1	578
	21st to end	Day	15% 10% 31% 28% 14% 2	750
May	1st to 10th	Day	12% 9% 27% 34% 15% 3	753
	11th to 20th	Day	16% 10% 28% 24% 16% 6%	775
	21st to end	Day	16% 9% 27% 27% 18% 4	844
June	1st to 10th	Day	11% 13% 31% 25% 17% 3	780
	11th to 20th	Day	17% 11% 32% 27% 13% 2	780
	21st to end	Day	11% 8% 26% 32% 19% 4	780
July	1st to 10th	Day	8% 4 23% 37% 24% 4	771
	11th to 20th	Day	6% 7% 29% 33% 21% 5%	768
	21st to end	Day	4 5% 28% 36% 19% 8%	845
August	1st to 10th	Day	9% 7% 21% 38% 20% 6%	726
	11th to 20th	Day	9% 5% 23% 33% 24% 6%	715
	21st to end	Day	8% 7% 24% 34% 21% 5%	609
September	1st to 10th	Day	12% 9% 28% 30% 15% 5%	530
	11th to 20th	Day	18% 10% 25% 28% 18% 1	482
	21st to end	Day	16% 7% 28% 30% 17% 2	330
October	1st to 10th	Day	18% 8% 28% 25% 17% 3	330
	11th to 20th	Day	13% 11% 36% 23% 14% 2	330
	21st to end	Day	16% 12% 36% 28% 7% 1	363
November	1st to 10th	Day	21% 8% 32% 24% 13% 2	330
	11th to 20th	Day	14% 12% 34% 31% 8% 1	330
	21st to end	Day	9% 11% 36% 33% 10% 1	330
December	1st to 10th	Day	13% 11% 35% 28% 10% 3	330
	11th to 20th	Day	12% 16% 38% 26% 5% 1	330
	21st to end	Day	10% 7% 33% 34% 13% 2	363
January	1st to 10th	Night	8% 10% 37% 33% 11% 1	1050
	11th to 20th	Night	13% 12% 35% 31% 8%	1050
	21st to end	Night	10% 12% 38% 31% 9% 1	1155
February	1st to 10th	Night	14% 10% 33% 32% 11% 1	1034
	11th to 20th	Night	10% 7% 34% 36% 11% 2	824
	21st to end	Night	5% 9% 29% 38% 17% 3	692
March	1st to 10th	Night	11% 8% 33% 35% 11% 2	840
	11th to 20th	Night	10% 8% 35% 33% 12% 1	840
	21st to end	Night	14% 8% 30% 34% 14% 1	696
April	1st to 10th	Night	8% 9% 36% 36% 10%	630
	11th to 20th	Night	17% 8% 38% 31% 5% 1	623
	21st to end	Night	17% 10% 33% 32% 9% 1	630
May	1st to 10th	Night	14% 5% 27% 41% 12% 1	630
	11th to 20th	Night	16% 6% 30% 33% 13% 1	621
	21st to end	Night	17% 7% 26% 33% 16% 1	683
June	1st to 10th	Night	15% 6% 29% 35% 15%	630
	11th to 20th	Night	15% 4 35% 32% 14%	527
	21st to end	Night	11% 4 30% 40% 15% 1	420
July	1st to 10th	Night	7% 4 23% 46% 19% 1	498
	11th to 20th	Night	8% 4 29% 45% 13% 1	612
	21st to end	Night	3 3 28% 47% 17% 2	687
August	1st to 10th	Night	8% 4 23% 49% 15% 2	597
	11th to 20th	Night	8% 3 24% 42% 21% 2	594
	21st to end	Night	7% 5% 26% 43% 19% 1	660
September	1st to 10th	Night	11% 6% 25% 39% 19% 1	600
	11th to 20th	Night	12% 4 30% 36% 16% 1	600
	21st to end	Night	13% 6% 31% 39% 11% 1	600
October	1st to 10th	Night	16% 8% 27% 36% 13% 1	775
	11th to 20th	Night	14% 9% 29% 36% 11% 1	885
	21st to end	Night	14% 9% 34% 35% 7% 1	1100
November	1st to 10th	Night	18% 10% 34% 31% 7% 1	1025
	11th to 20th	Night	13% 10% 37% 30% 9% 2	1050
	21st to end	Night	13% 10% 37% 31% 9%	1050
December	1st to 10th	Night	12% 8% 35% 32% 11% 2	1050
	11th to 20th	Night	14% 11% 36% 30% 8% 1	1050
	21st to end	Night	12% 7% 34% 33% 12% 2	1155

Page generated at 2026-07-28 01:25:23. Version ac07

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