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 2025-02-25.

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%	112144
	Night	7% 9% 4 9% 6% 5% 5% 4 6% 7% 37%	115324
Transparency	Day	43% 5% 15% 26% 10% 1	111887
	Night	45% 5% 15% 24% 10% 1	115171
Seeing	Day	13% 8% 30% 29% 16% 4	16527
	Night	13% 7% 31% 35% 13% 1	26692

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	5% 13% 5% 16% 10% 9% 8% 4 6% 6% 18%	3618
	11th to 20th	Day	3 8% 4 14% 9% 9% 9% 8% 11% 8% 17%	3640
	21st to end	Day	6% 9% 6% 14% 7% 6% 4 3 5% 6% 33%	4004
February	1st to 10th	Day	9% 12% 6% 11% 8% 6% 8% 5% 6% 6% 23%	1607
	11th to 20th	Day	6% 13% 5% 10% 8% 8% 6% 6% 7% 7% 23%	1815
	21st to end	Day	6% 11% 5% 12% 9% 6% 5% 5% 6% 8% 26%	1610
March	1st to 10th	Day	9% 14% 5% 12% 7% 5% 5% 4 5% 5% 28%	3130
	11th to 20th	Day	6% 12% 7% 11% 6% 5% 5% 4 6% 8% 29%	3243
	21st to end	Day	11% 14% 5% 13% 6% 5% 5% 4 5% 7% 27%	4165
April	1st to 10th	Day	7% 8% 4 7% 6% 4 5% 5% 7% 8% 40%	2280
	11th to 20th	Day	13% 14% 4 9% 5% 4 5% 4 5% 8% 29%	2315
	21st to end	Day	14% 9% 3 8% 5% 3 4 3 6% 7% 37%	2498
May	1st to 10th	Day	18% 9% 2 6% 4 4 4 4 6% 8% 35%	4430
	11th to 20th	Day	14% 6% 2 6% 5% 5% 6% 4 7% 7% 37%	4388
	21st to end	Day	15% 6% 2 7% 5% 4 5% 4 5% 8% 40%	4977
June	1st to 10th	Day	13% 6% 2 6% 4 4 5% 4 6% 10% 41%	2850
	11th to 20th	Day	15% 7% 2 6% 5% 4 5% 4 6% 8% 37%	2850
	21st to end	Day	11% 5% 2 5% 5% 5% 5% 4 6% 9% 45%	2850
July	1st to 10th	Day	6% 4 2 6% 4 5% 5% 5% 7% 10% 46%	4626
	11th to 20th	Day	4 3 1 4 4 4 5% 4 7% 10% 55%	4430
	21st to end	Day	4 3 1 4 4 4 4 5% 7% 9% 55%	4802
August	1st to 10th	Day	9% 5% 2 5% 4 4 5% 4 6% 9% 49%	4411
	11th to 20th	Day	7% 3 2 5% 4 4 6% 4 7% 10% 49%	4260
	21st to end	Day	8% 5% 2 5% 4 4 4 4 5% 8% 52%	4262
September	1st to 10th	Day	12% 4 2 4 3 3 3 4 4 8% 53%	2280
	11th to 20th	Day	13% 6% 2 6% 3 4 4 3 5% 6% 47%	2204
	21st to end	Day	15% 5% 2 4 3 4 3 3 4 7% 49%	2090
October	1st to 10th	Day	10% 6% 2 6% 3 3 4 3 5% 7% 52%	3274
	11th to 20th	Day	7% 6% 3 6% 3 3 3 3 5% 9% 51%	2937
	21st to end	Day	8% 9% 3 10% 5% 4 5% 4 5% 8% 40%	3091
November	1st to 10th	Day	13% 14% 5% 7% 5% 4 5% 4 5% 5% 33%	1763
	11th to 20th	Day	9% 13% 5% 12% 6% 5% 4 4 5% 5% 33%	1610
	21st to end	Day	9% 15% 6% 11% 6% 5% 7% 3 5% 7% 27%	1403
December	1st to 10th	Day	6% 14% 6% 15% 7% 5% 6% 4 6% 6% 25%	2290
	11th to 20th	Day	7% 18% 6% 12% 7% 6% 7% 4 5% 7% 20%	2643
	21st to end	Day	6% 9% 4 10% 8% 4 5% 4 5% 5% 40%	3498
January	1st to 10th	Night	4 12% 5% 13% 12% 8% 7% 5% 7% 6% 21%	6331
	11th to 20th	Night	4 8% 4 13% 8% 8% 10% 8% 10% 7% 21%	6340
	21st to end	Night	5% 11% 6% 12% 7% 6% 5% 4 6% 7% 30%	6974
February	1st to 10th	Night	8% 13% 4 11% 8% 6% 6% 6% 7% 8% 23%	2800
	11th to 20th	Night	6% 12% 4 12% 7% 6% 6% 5% 7% 7% 29%	2481
	21st to end	Night	5% 10% 4 11% 7% 5% 5% 4 6% 8% 35%	1938
March	1st to 10th	Night	6% 11% 5% 13% 8% 6% 4 3 5% 8% 31%	3734
	11th to 20th	Night	6% 10% 5% 9% 5% 4 5% 4 7% 8% 38%	3725
	21st to end	Night	8% 13% 7% 12% 5% 4 4 4 5% 6% 32%	3477
April	1st to 10th	Night	6% 9% 3 6% 5% 4 4 4 7% 9% 44%	1900
	11th to 20th	Night	13% 13% 4 8% 5% 4 5% 5% 5% 7% 32%	1813
	21st to end	Night	12% 8% 3 8% 5% 5% 5% 3 7% 6% 38%	1679
May	1st to 10th	Night	16% 11% 3 7% 5% 3 4 3 5% 5% 38%	2540
	11th to 20th	Night	13% 7% 2 6% 4 4 5% 4 6% 8% 41%	2517
	21st to end	Night	15% 7% 2 6% 4 4 5% 3 6% 8% 41%	2607
June	1st to 10th	Night	13% 4 2 4 3 4 4 5% 7% 10% 44%	1330
	11th to 20th	Night	11% 5% 3 6% 4 5% 4 4 6% 8% 44%	1330
	21st to end	Night	10% 4 1 5% 4 4 4 4 7% 8% 49%	1330
July	1st to 10th	Night	4 3 2 6% 4 5% 5% 5% 8% 11% 47%	2339
	11th to 20th	Night	6% 3 2 5% 4 4 5% 3 6% 7% 54%	2540
	21st to end	Night	2 2 2 4 3 3 3 3 6% 9% 62%	2761
August	1st to 10th	Night	6% 4 2 5% 4 4 4 4 6% 7% 53%	2528
	11th to 20th	Night	6% 3 1 3 4 4 4 4 6% 10% 56%	2579
	21st to end	Night	7% 3 1 4 2 3 4 3 5% 8% 59%	3389
September	1st to 10th	Night	10% 4 1 4 2 3 4 3 5% 7% 57%	1900
	11th to 20th	Night	11% 5% 1 5% 3 3 4 3 6% 6% 51%	1976
	21st to end	Night	12% 6% 2 7% 4 4 3 3 4 7% 47%	2090
October	1st to 10th	Night	9% 6% 3 6% 3 3 3 2 4 7% 54%	3690
	11th to 20th	Night	7% 7% 2 5% 4 3 4 4 7% 9% 48%	3959
	21st to end	Night	7% 8% 3 6% 4 4 5% 4 5% 8% 45%	4467
November	1st to 10th	Night	12% 12% 4 8% 6% 4 5% 4 5% 7% 35%	2535
	11th to 20th	Night	9% 11% 4 11% 8% 6% 5% 4 5% 6% 32%	2786
	21st to end	Night	7% 12% 4 11% 7% 5% 5% 4 6% 7% 33%	2995
December	1st to 10th	Night	6% 15% 5% 13% 7% 7% 6% 4 6% 7% 23%	4900
	11th to 20th	Night	9% 14% 5% 12% 9% 7% 7% 4 5% 6% 22%	5564
	21st to end	Night	5% 8% 4 12% 6% 6% 6% 5% 6% 7% 34%	7480

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	66% 5% 11% 14% 4	3619
	11th to 20th	Day	60% 4 13% 14% 9%	3640
	21st to end	Day	52% 4 21% 20% 3	4004
February	1st to 10th	Day	61% 4 12% 16% 7%	1607
	11th to 20th	Day	57% 5% 10% 16% 11%	1824
	21st to end	Day	54% 5% 15% 18% 7% 1	1610
March	1st to 10th	Day	57% 6% 14% 20% 3	3130
	11th to 20th	Day	52% 6% 19% 19% 4	3243
	21st to end	Day	57% 4 13% 17% 8%	4165
April	1st to 10th	Day	40% 6% 16% 25% 13% 1	2280
	11th to 20th	Day	53% 4 14% 19% 9% 1	2318
	21st to end	Day	46% 4 15% 25% 9%	2498
May	1st to 10th	Day	47% 5% 14% 23% 11% 1	4430
	11th to 20th	Day	42% 5% 13% 25% 13% 1	4392
	21st to end	Day	42% 5% 12% 30% 10% 1	4977
June	1st to 10th	Day	38% 5% 18% 27% 11% 2	2850
	11th to 20th	Day	43% 5% 15% 25% 10% 1	2850
	21st to end	Day	36% 6% 19% 30% 9% 1	2850
July	1st to 10th	Day	31% 8% 23% 31% 7% 1	4555
	11th to 20th	Day	23% 6% 16% 40% 14% 1	4355
	21st to end	Day	23% 6% 15% 37% 16% 3	4651
August	1st to 10th	Day	31% 6% 16% 28% 18% 1	4396
	11th to 20th	Day	29% 6% 19% 36% 10% 1	4302
	21st to end	Day	30% 4 14% 39% 12% 1	4261
September	1st to 10th	Day	31% 4 14% 32% 18% 2	2280
	11th to 20th	Day	38% 5% 14% 27% 14% 2	2204
	21st to end	Day	35% 4 11% 33% 16% 1	2090
October	1st to 10th	Day	34% 3 12% 34% 15% 2	3274
	11th to 20th	Day	32% 3 17% 35% 13%	2937
	21st to end	Day	42% 5% 12% 32% 8%	3091
November	1st to 10th	Day	53% 5% 12% 22% 7% 1	1763
	11th to 20th	Day	52% 4 18% 16% 9% 1	1610
	21st to end	Day	57% 6% 17% 14% 5%	1403
December	1st to 10th	Day	58% 5% 19% 15% 3	2290
	11th to 20th	Day	63% 5% 18% 12% 2	2640
	21st to end	Day	46% 3 9% 29% 12% 1	3498
January	1st to 10th	Night	61% 5% 13% 16% 5%	6331
	11th to 20th	Night	56% 5% 16% 15% 7%	6340
	21st to end	Night	52% 5% 21% 19% 3	6974
February	1st to 10th	Night	57% 6% 11% 19% 8%	2800
	11th to 20th	Night	51% 5% 13% 19% 11% 1	2482
	21st to end	Night	46% 4 16% 23% 11%	1938
March	1st to 10th	Night	52% 4 15% 23% 6%	3734
	11th to 20th	Night	43% 4 23% 24% 6%	3725
	21st to end	Night	53% 3 13% 21% 9% 1	3477
April	1st to 10th	Night	35% 5% 14% 25% 19% 2	1900
	11th to 20th	Night	52% 4 10% 23% 11% 1	1813
	21st to end	Night	45% 4 12% 27% 11% 1	1679
May	1st to 10th	Night	46% 4 11% 24% 13% 1	2540
	11th to 20th	Night	40% 5% 14% 24% 16% 1	2518
	21st to end	Night	40% 6% 11% 31% 11%	2607
June	1st to 10th	Night	34% 6% 17% 28% 13% 3	1330
	11th to 20th	Night	38% 5% 20% 22% 14% 2	1330
	21st to end	Night	32% 6% 18% 34% 10% 1	1330
July	1st to 10th	Night	28% 10% 24% 30% 8% 1	2301
	11th to 20th	Night	28% 6% 14% 35% 15% 2	2492
	21st to end	Night	18% 5% 18% 34% 18% 7%	2674
August	1st to 10th	Night	27% 6% 17% 32% 16% 2	2520
	11th to 20th	Night	24% 5% 18% 39% 12% 1	2603
	21st to end	Night	24% 5% 17% 36% 18% 2	3389
September	1st to 10th	Night	26% 5% 10% 33% 25% 2	1900
	11th to 20th	Night	32% 5% 15% 28% 18% 2	1976
	21st to end	Night	37% 4 11% 31% 15% 2	2090
October	1st to 10th	Night	33% 3 12% 35% 13% 5%	3690
	11th to 20th	Night	33% 3 12% 37% 14% 1	3959
	21st to end	Night	38% 3 11% 37% 10% 1	4467
November	1st to 10th	Night	49% 5% 14% 21% 10% 2	2535
	11th to 20th	Night	53% 4 17% 19% 7% 1	2786
	21st to end	Night	51% 5% 18% 20% 6%	2995
December	1st to 10th	Night	60% 6% 18% 12% 3	4900
	11th to 20th	Night	62% 4 18% 12% 4	5566
	21st to end	Night	47% 5% 11% 22% 13% 2	7480

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% 30% 12% 6%	300
	11th to 20th	Day	10% 8% 38% 32% 10% 2	300
	21st to end	Day	11% 11% 32% 33% 12% 1	330
February	1st to 10th	Day	14% 10% 35% 31% 9% 1	300
	11th to 20th	Day	13% 5% 37% 30% 12% 4	300
	21st to end	Day	7% 4 33% 36% 18% 2	237
March	1st to 10th	Day	15% 9% 37% 26% 11% 1	270
	11th to 20th	Day	15% 9% 33% 27% 12% 4	278
	21st to end	Day	16% 10% 31% 29% 10% 3	506
April	1st to 10th	Day	10% 15% 39% 27% 7% 2	460
	11th to 20th	Day	21% 12% 32% 24% 9% 2	516
	21st to end	Day	15% 10% 29% 32% 13% 2	650
May	1st to 10th	Day	15% 7% 29% 29% 16% 3	653
	11th to 20th	Day	16% 6% 27% 28% 17% 6%	675
	21st to end	Day	19% 7% 25% 23% 21% 5%	734
June	1st to 10th	Day	13% 10% 27% 27% 17% 5%	680
	11th to 20th	Day	15% 11% 34% 25% 13% 3	680
	21st to end	Day	11% 7% 26% 32% 19% 5%	680
July	1st to 10th	Day	8% 5% 20% 38% 23% 6%	671
	11th to 20th	Day	8% 7% 27% 33% 19% 6%	668
	21st to end	Day	4 5% 27% 34% 21% 8%	739
August	1st to 10th	Day	11% 4 23% 33% 22% 7%	676
	11th to 20th	Day	10% 5% 23% 33% 24% 6%	665
	21st to end	Day	10% 7% 24% 33% 20% 5%	595
September	1st to 10th	Day	13% 9% 28% 30% 16% 4	490
	11th to 20th	Day	17% 11% 26% 29% 15% 1	414
	21st to end	Day	22% 6% 29% 26% 14% 2	300
October	1st to 10th	Day	21% 9% 25% 27% 16% 2	300
	11th to 20th	Day	13% 12% 31% 26% 14% 4	300
	21st to end	Day	20% 9% 34% 26% 10% 1	330
November	1st to 10th	Day	24% 8% 29% 24% 12% 3	300
	11th to 20th	Day	16% 11% 33% 30% 9% 1	300
	21st to end	Day	15% 11% 35% 28% 11% 1	300
December	1st to 10th	Day	13% 10% 38% 24% 10% 4	300
	11th to 20th	Day	14% 10% 42% 27% 6% 1	300
	21st to end	Day	10% 6% 34% 27% 18% 5%	330
January	1st to 10th	Night	10% 10% 36% 31% 11% 1	1000
	11th to 20th	Night	13% 12% 33% 32% 9% 1	1000
	21st to end	Night	12% 10% 38% 30% 9% 1	1100
February	1st to 10th	Night	13% 9% 33% 32% 12% 1	1000
	11th to 20th	Night	12% 6% 35% 34% 11% 3	794
	21st to end	Night	8% 6% 28% 38% 17% 4	646
March	1st to 10th	Night	12% 8% 32% 33% 12% 3	760
	11th to 20th	Night	12% 6% 36% 35% 11% 1	732
	21st to end	Night	14% 5% 32% 35% 12% 1	627
April	1st to 10th	Night	10% 7% 36% 35% 11%	570
	11th to 20th	Night	19% 9% 34% 30% 7%	563
	21st to end	Night	17% 5% 34% 32% 11% 1	570
May	1st to 10th	Night	15% 7% 25% 40% 13% 1	570
	11th to 20th	Night	15% 6% 24% 40% 15%	561
	21st to end	Night	19% 5% 25% 35% 15% 1	617
June	1st to 10th	Night	17% 5% 26% 35% 17% 1	570
	11th to 20th	Night	15% 6% 31% 36% 12%	570
	21st to end	Night	11% 4 26% 43% 16% 1	570
July	1st to 10th	Night	6% 4 24% 46% 20% 1	555
	11th to 20th	Night	7% 3 27% 47% 15% 1	552
	21st to end	Night	4 2 30% 42% 20% 1	624
August	1st to 10th	Night	7% 4 22% 49% 16% 2	567
	11th to 20th	Night	7% 3 23% 43% 23% 1	564
	21st to end	Night	9% 3 29% 41% 18% 1	627
September	1st to 10th	Night	12% 4 26% 39% 18% 1	570
	11th to 20th	Night	13% 4 28% 39% 15% 1	570
	21st to end	Night	14% 6% 29% 39% 11% 1	570
October	1st to 10th	Night	16% 8% 26% 35% 15% 1	689
	11th to 20th	Night	16% 9% 26% 35% 14% 1	864
	21st to end	Night	16% 8% 31% 33% 10% 1	1045
November	1st to 10th	Night	17% 9% 33% 30% 10% 1	975
	11th to 20th	Night	15% 9% 36% 30% 9% 2	1000
	21st to end	Night	13% 10% 36% 31% 9%	1000
December	1st to 10th	Night	13% 7% 35% 32% 11% 3	1000
	11th to 20th	Night	16% 11% 33% 31% 8% 2	1000
	21st to end	Night	15% 6% 33% 33% 13% 1	1100

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