Estevan
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Estevan clear sky chart from 2005-11-06 to 2026-07-01.

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% 39%	146950
	Night	7% 8% 3 9% 6% 5% 5% 4 6% 8% 37%	142859
Transparency	Day	43% 5% 15% 25% 11% 1	141524
	Night	45% 5% 15% 24% 11% 1	139297
Seeing	Day	13% 9% 30% 29% 15% 4	18487
	Night	13% 7% 31% 35% 12% 1	28470

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	6% 11% 5% 13% 10% 9% 8% 4 6% 6% 22%	4700
	11th to 20th	Day	2 8% 5% 15% 8% 9% 9% 8% 10% 8% 18%	4740
	21st to end	Day	6% 8% 5% 12% 7% 7% 4 4 6% 8% 32%	5188
February	1st to 10th	Day	9% 12% 6% 12% 8% 6% 8% 5% 6% 6% 23%	1688
	11th to 20th	Day	7% 13% 5% 10% 8% 7% 6% 5% 7% 7% 24%	1908
	21st to end	Day	5% 11% 5% 12% 9% 7% 5% 5% 6% 8% 27%	1730
March	1st to 10th	Day	7% 12% 5% 14% 7% 5% 5% 3 5% 6% 31%	4600
	11th to 20th	Day	7% 12% 7% 12% 7% 6% 6% 5% 6% 8% 26%	4754
	21st to end	Day	10% 14% 6% 14% 6% 5% 4 3 5% 6% 26%	6101
April	1st to 10th	Day	7% 9% 4 8% 5% 5% 5% 5% 7% 8% 39%	2520
	11th to 20th	Day	13% 13% 4 9% 5% 4 4 4 5% 8% 29%	2562
	21st to end	Day	13% 10% 3 8% 5% 3 4 3 6% 7% 37%	2761
May	1st to 10th	Day	11% 7% 2 7% 5% 4 4 4 5% 8% 44%	8224
	11th to 20th	Day	19% 7% 2 6% 4 4 5% 4 6% 7% 34%	8191
	21st to end	Day	12% 6% 2 6% 4 4 4 3 4 8% 48%	9318
June	1st to 10th	Day	12% 5% 2 6% 4 4 5% 4 6% 9% 41%	3150
	11th to 20th	Day	14% 7% 2 6% 5% 5% 6% 4 6% 8% 36%	3150
	21st to end	Day	11% 5% 2 5% 4 5% 5% 5% 6% 9% 43%	3150
July	1st to 10th	Day	6% 4 2 6% 5% 5% 5% 5% 6% 9% 47%	6620
	11th to 20th	Day	6% 4 2 5% 5% 4 5% 4 8% 10% 47%	6340
	21st to end	Day	5% 5% 2 6% 4 4 5% 5% 7% 10% 48%	6903
August	1st to 10th	Day	10% 6% 2 7% 4 5% 5% 4 6% 9% 42%	6232
	11th to 20th	Day	6% 3 2 5% 4 4 5% 4 7% 10% 50%	6131
	21st to end	Day	6% 4 1 4 3 4 4 4 6% 9% 56%	6108
September	1st to 10th	Day	11% 4 2 4 3 4 4 4 5% 7% 53%	2400
	11th to 20th	Day	14% 7% 2 6% 4 4 4 3 5% 6% 45%	2320
	21st to end	Day	14% 5% 2 4 3 3 3 3 4 7% 51%	2200
October	1st to 10th	Day	10% 6% 2 6% 3 3 4 3 5% 7% 52%	3377
	11th to 20th	Day	8% 7% 3 6% 3 3 3 3 5% 9% 50%	3030
	21st to end	Day	8% 9% 3 10% 5% 4 4 4 5% 8% 40%	3190
November	1st to 10th	Day	13% 13% 5% 7% 5% 4 5% 4 5% 5% 33%	1853
	11th to 20th	Day	8% 13% 5% 12% 6% 5% 4 5% 5% 6% 33%	1690
	21st to end	Day	9% 14% 6% 11% 6% 6% 7% 3 5% 7% 27%	1473
December	1st to 10th	Day	6% 15% 6% 15% 7% 5% 6% 4 6% 6% 25%	2360
	11th to 20th	Day	7% 17% 6% 12% 7% 6% 7% 4 5% 7% 20%	2713
	21st to end	Day	6% 9% 4 11% 8% 4 5% 4 5% 5% 39%	3575
January	1st to 10th	Night	4 11% 5% 14% 11% 8% 7% 5% 7% 6% 23%	8205
	11th to 20th	Night	4 8% 4 13% 8% 8% 10% 8% 9% 7% 21%	8250
	21st to end	Night	4 9% 5% 12% 8% 6% 6% 5% 6% 8% 30%	9026
February	1st to 10th	Night	8% 13% 4 12% 8% 6% 6% 6% 7% 7% 23%	2940
	11th to 20th	Night	6% 12% 4 11% 7% 5% 5% 5% 7% 7% 30%	2608
	21st to end	Night	5% 9% 4 11% 7% 5% 5% 5% 6% 8% 36%	2076
March	1st to 10th	Night	6% 11% 4 12% 7% 6% 5% 4 5% 8% 31%	5494
	11th to 20th	Night	7% 10% 5% 11% 8% 5% 5% 4 7% 7% 31%	5443
	21st to end	Night	7% 14% 7% 14% 6% 4 5% 4 5% 6% 27%	5094
April	1st to 10th	Night	7% 9% 3 6% 5% 4 4 4 7% 9% 43%	2100
	11th to 20th	Night	12% 12% 4 8% 5% 4 5% 5% 5% 7% 32%	2006
	21st to end	Night	13% 9% 3 8% 5% 4 5% 3 6% 6% 39%	1855
May	1st to 10th	Night	9% 7% 2 5% 4 4 5% 3 5% 7% 50%	4723
	11th to 20th	Night	17% 8% 2 6% 4 4 5% 4 6% 8% 36%	4701
	21st to end	Night	13% 5% 2 5% 3 3 4 3 5% 8% 48%	4886
June	1st to 10th	Night	13% 5% 1 5% 3 4 4 5% 7% 10% 43%	1470
	11th to 20th	Night	10% 5% 3 6% 4 5% 5% 4 7% 8% 42%	1470
	21st to end	Night	11% 4 1 6% 4 4 4 4 6% 8% 47%	1470
July	1st to 10th	Night	4 3 2 6% 4 5% 5% 5% 8% 11% 48%	3355
	11th to 20th	Night	10% 5% 2 5% 4 4 5% 3 6% 6% 48%	3640
	21st to end	Night	4 3 2 4 4 4 4 4 6% 9% 56%	3970
August	1st to 10th	Night	8% 5% 2 5% 4 4 4 4 6% 9% 49%	3580
	11th to 20th	Night	5% 3 2 4 3 4 4 4 6% 10% 56%	3718
	21st to end	Night	5% 3 1 4 2 3 4 3 5% 8% 61%	4853
September	1st to 10th	Night	9% 4 1 4 3 3 4 3 5% 7% 57%	2000
	11th to 20th	Night	12% 5% 1 5% 4 4 4 4 6% 7% 49%	2080
	21st to end	Night	11% 6% 2 6% 4 4 3 3 4 7% 50%	2200
October	1st to 10th	Night	9% 6% 2 6% 3 3 3 2 4 6% 54%	3806
	11th to 20th	Night	8% 7% 2 5% 4 3 4 4 7% 9% 47%	4085
	21st to end	Night	7% 8% 3 6% 4 4 5% 4 5% 8% 45%	4610
November	1st to 10th	Night	12% 12% 4 8% 6% 4 5% 4 5% 6% 35%	2665
	11th to 20th	Night	8% 11% 4 11% 8% 6% 5% 4 5% 6% 33%	2926
	21st to end	Night	7% 12% 4 11% 7% 6% 5% 3 6% 7% 32%	3145
December	1st to 10th	Night	6% 15% 5% 13% 8% 7% 6% 4 6% 7% 23%	5050
	11th to 20th	Night	9% 14% 5% 11% 9% 7% 7% 4 6% 6% 22%	5714
	21st to end	Night	5% 8% 4 12% 7% 6% 6% 5% 7% 7% 34%	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	61% 5% 13% 14% 7%	4703
	11th to 20th	Day	60% 4 13% 15% 7%	4740
	21st to end	Day	49% 4 21% 19% 7%	5188
February	1st to 10th	Day	61% 4 12% 16% 7%	1688
	11th to 20th	Day	58% 5% 10% 16% 11%	1917
	21st to end	Day	53% 5% 15% 18% 7% 1	1730
March	1st to 10th	Day	53% 5% 18% 18% 6%	4600
	11th to 20th	Day	54% 6% 18% 19% 3	4754
	21st to end	Day	59% 5% 12% 17% 7%	6101
April	1st to 10th	Day	41% 6% 16% 24% 12% 1	2520
	11th to 20th	Day	53% 4 14% 19% 9% 1	2565
	21st to end	Day	46% 4 15% 26% 8% 1	2761
May	1st to 10th	Day	38% 4 11% 30% 16% 1	8224
	11th to 20th	Day	47% 5% 12% 22% 13% 1	8195
	21st to end	Day	36% 4 9% 29% 22% 1	9319
June	1st to 10th	Day	38% 5% 17% 27% 11% 2	3150
	11th to 20th	Day	44% 6% 15% 25% 9% 1	3150
	21st to end	Day	37% 7% 18% 29% 8% 1	3150
July	1st to 10th	Day	31% 7% 21% 29% 10% 1	6550
	11th to 20th	Day	30% 8% 18% 34% 11% 1	6265
	21st to end	Day	30% 7% 16% 32% 13% 2	6705
August	1st to 10th	Day	31% 6% 16% 27% 18% 1	4536
	11th to 20th	Day	28% 6% 20% 35% 10% 1	4439
	21st to end	Day	29% 4 14% 39% 12% 1	4396
September	1st to 10th	Day	31% 4 14% 32% 18% 2	2400
	11th to 20th	Day	40% 5% 14% 26% 14% 2	2320
	21st to end	Day	34% 4 11% 34% 17% 1	2200
October	1st to 10th	Day	33% 3 12% 34% 15% 2	3377
	11th to 20th	Day	33% 3 16% 35% 13%	3030
	21st to end	Day	42% 5% 12% 33% 8%	3190
November	1st to 10th	Day	53% 5% 12% 22% 7% 1	1853
	11th to 20th	Day	52% 4 19% 16% 9% 1	1690
	21st to end	Day	58% 6% 17% 14% 5%	1473
December	1st to 10th	Day	58% 5% 18% 15% 4	2360
	11th to 20th	Day	62% 5% 18% 12% 2	2710
	21st to end	Day	46% 4 9% 28% 12% 1	3575
January	1st to 10th	Night	59% 5% 12% 18% 6%	8206
	11th to 20th	Night	56% 6% 15% 15% 8%	8250
	21st to end	Night	51% 5% 19% 17% 8%	9026
February	1st to 10th	Night	57% 6% 11% 18% 7%	2940
	11th to 20th	Night	50% 5% 13% 19% 11% 1	2609
	21st to end	Night	46% 4 16% 24% 10%	2076
March	1st to 10th	Night	50% 5% 19% 21% 6%	5494
	11th to 20th	Night	50% 5% 19% 22% 5%	5443
	21st to end	Night	57% 4 11% 20% 6% 1	5094
April	1st to 10th	Night	36% 5% 14% 25% 18% 2	2100
	11th to 20th	Night	50% 4 10% 24% 10% 1	2006
	21st to end	Night	45% 4 11% 27% 11% 1	1855
May	1st to 10th	Night	33% 4 9% 33% 20% 1	4724
	11th to 20th	Night	45% 5% 12% 22% 14% 1	4702
	21st to end	Night	34% 5% 9% 29% 22% 1	4887
June	1st to 10th	Night	34% 6% 16% 29% 13% 2	1470
	11th to 20th	Night	39% 5% 19% 22% 13% 1	1470
	21st to end	Night	33% 7% 17% 33% 9% 1	1470
July	1st to 10th	Night	28% 9% 21% 32% 10% 1	3317
	11th to 20th	Night	35% 7% 13% 34% 10% 1	3592
	21st to end	Night	23% 7% 20% 31% 15% 5%	3856
August	1st to 10th	Night	27% 6% 17% 31% 16% 2	2600
	11th to 20th	Night	24% 5% 19% 39% 12% 1	2686
	21st to end	Night	23% 5% 17% 36% 18% 2	3496
September	1st to 10th	Night	26% 5% 10% 33% 24% 2	2000
	11th to 20th	Night	34% 5% 16% 27% 17% 2	2080
	21st to end	Night	36% 4 11% 32% 16% 2	2200
October	1st to 10th	Night	32% 3 12% 35% 13% 5%	3806
	11th to 20th	Night	33% 3 12% 36% 14% 1	4085
	21st to end	Night	38% 3 11% 37% 10% 1	4610
November	1st to 10th	Night	48% 5% 14% 21% 10% 2	2665
	11th to 20th	Night	52% 4 17% 19% 6% 1	2926
	21st to end	Night	52% 5% 18% 19% 6%	3145
December	1st to 10th	Night	60% 6% 18% 12% 3	5050
	11th to 20th	Night	62% 5% 18% 12% 4	5716
	21st to end	Night	47% 5% 11% 22% 12% 2	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	12% 6% 35% 31% 11% 5%	330
	11th to 20th	Day	11% 9% 39% 30% 9% 2	330
	21st to end	Day	11% 12% 32% 33% 12% 1	363
February	1st to 10th	Day	13% 11% 36% 30% 8% 1	330
	11th to 20th	Day	14% 5% 35% 30% 12% 4	330
	21st to end	Day	6% 6% 36% 34% 16% 2	273
March	1st to 10th	Day	13% 11% 38% 27% 11% 1	330
	11th to 20th	Day	15% 10% 34% 27% 11% 3	339
	21st to end	Day	16% 11% 33% 28% 9% 2	594
April	1st to 10th	Day	10% 16% 37% 28% 8% 1	540
	11th to 20th	Day	20% 14% 31% 25% 8% 1	603
	21st to end	Day	15% 11% 28% 31% 13% 2	750
May	1st to 10th	Day	14% 9% 28% 30% 16% 3	753
	11th to 20th	Day	19% 7% 27% 26% 16% 5%	775
	21st to end	Day	18% 7% 25% 24% 21% 5%	844
June	1st to 10th	Day	12% 11% 29% 26% 16% 5%	780
	11th to 20th	Day	15% 11% 32% 27% 13% 2	780
	21st to end	Day	12% 7% 27% 31% 18% 5%	780
July	1st to 10th	Day	8% 5% 21% 38% 23% 6%	722
	11th to 20th	Day	8% 7% 27% 34% 19% 5%	718
	21st to end	Day	5% 5% 26% 35% 22% 8%	794
August	1st to 10th	Day	10% 5% 23% 33% 23% 6%	726
	11th to 20th	Day	9% 5% 24% 33% 23% 6%	715
	21st to end	Day	10% 7% 23% 33% 20% 6%	642
September	1st to 10th	Day	13% 9% 27% 29% 17% 5%	530
	11th to 20th	Day	17% 10% 26% 29% 15% 2	450
	21st to end	Day	20% 6% 27% 28% 15% 2	330
October	1st to 10th	Day	19% 10% 24% 29% 16% 2	330
	11th to 20th	Day	14% 12% 32% 25% 12% 4	330
	21st to end	Day	19% 9% 34% 26% 10% 1	363
November	1st to 10th	Day	23% 8% 31% 24% 11% 2	330
	11th to 20th	Day	15% 10% 34% 29% 10% 1	330
	21st to end	Day	15% 10% 36% 28% 10% 1	330
December	1st to 10th	Day	13% 10% 40% 24% 9% 4	330
	11th to 20th	Day	15% 12% 40% 26% 6% 1	330
	21st to end	Day	10% 7% 35% 27% 17% 4	363
January	1st to 10th	Night	10% 10% 37% 31% 11% 1	1050
	11th to 20th	Night	13% 13% 33% 31% 8% 1	1050
	21st to end	Night	11% 11% 38% 29% 10% 1	1155
February	1st to 10th	Night	13% 10% 33% 32% 12% 1	1050
	11th to 20th	Night	12% 6% 34% 34% 11% 3	834
	21st to end	Night	8% 7% 29% 37% 16% 3	692
March	1st to 10th	Night	12% 9% 33% 32% 11% 3	840
	11th to 20th	Night	12% 7% 35% 35% 10% 1	809
	21st to end	Night	14% 7% 32% 35% 11% 1	693
April	1st to 10th	Night	11% 7% 36% 35% 11%	630
	11th to 20th	Night	18% 9% 35% 31% 7%	623
	21st to end	Night	17% 6% 32% 33% 11%	630
May	1st to 10th	Night	13% 7% 25% 42% 12% 1	630
	11th to 20th	Night	17% 7% 25% 38% 13%	621
	21st to end	Night	19% 5% 25% 35% 15% 1	683
June	1st to 10th	Night	16% 7% 27% 35% 15%	630
	11th to 20th	Night	14% 6% 31% 37% 12%	630
	21st to end	Night	11% 4 28% 42% 14%	630
July	1st to 10th	Night	6% 4 23% 46% 19% 1	585
	11th to 20th	Night	8% 3 27% 47% 14% 1	582
	21st to end	Night	4 2 29% 44% 20% 1	657
August	1st to 10th	Night	7% 4 22% 49% 16% 2	597
	11th to 20th	Night	7% 3 23% 43% 22% 1	594
	21st to end	Night	9% 3 28% 41% 18% 1	660
September	1st to 10th	Night	12% 4 26% 39% 18% 2	600
	11th to 20th	Night	14% 4 28% 39% 15% 1	600
	21st to end	Night	14% 6% 29% 40% 11% 1	600
October	1st to 10th	Night	16% 8% 25% 36% 15% 1	725
	11th to 20th	Night	17% 9% 26% 34% 13% 1	910
	21st to end	Night	16% 9% 32% 33% 10% 1	1100
November	1st to 10th	Night	17% 9% 33% 30% 9% 1	1025
	11th to 20th	Night	14% 9% 36% 30% 9% 1	1050
	21st to end	Night	13% 10% 36% 31% 10%	1050
December	1st to 10th	Night	13% 7% 35% 32% 11% 3	1050
	11th to 20th	Night	16% 12% 33% 30% 8% 2	1050
	21st to end	Night	14% 7% 33% 33% 13% 1	1155

Page generated at 2026-06-28 00:10:44. Version ac07

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