Val Marie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Val Marie 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	7% 7% 3 8% 5% 5% 5% 4 6% 8% 42%	146923
	Night	6% 7% 3 8% 5% 5% 5% 4 6% 8% 41%	142827
Transparency	Day	39% 6% 15% 26% 12% 2	141531
	Night	39% 6% 15% 25% 13% 2	139230
Seeing	Day	11% 10% 30% 30% 16% 3	17995
	Night	10% 8% 33% 36% 12% 1	27384

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	4 12% 5% 15% 9% 7% 6% 4 5% 7% 27%	4124
	11th to 20th	Day	1 6% 5% 13% 7% 6% 8% 5% 7% 8% 35%	4140
	21st to end	Day	3 8% 4 10% 7% 6% 6% 5% 6% 8% 38%	5285
February	1st to 10th	Day	7% 12% 5% 12% 8% 7% 5% 3 7% 7% 27%	1890
	11th to 20th	Day	5% 11% 4 14% 7% 7% 5% 5% 7% 8% 26%	1845
	21st to end	Day	4 12% 4 11% 8% 7% 7% 6% 6% 7% 28%	1583
March	1st to 10th	Day	4 10% 4 12% 7% 5% 5% 4 6% 9% 36%	4731
	11th to 20th	Day	5% 7% 3 8% 6% 6% 6% 5% 7% 11% 36%	5110
	21st to end	Day	7% 16% 7% 15% 7% 6% 5% 4 6% 7% 22%	5775
April	1st to 10th	Day	8% 9% 4 9% 6% 5% 5% 5% 6% 7% 36%	2520
	11th to 20th	Day	12% 13% 4 8% 5% 6% 5% 4 6% 6% 31%	2580
	21st to end	Day	12% 10% 3 7% 5% 4 4 4 6% 8% 36%	2803
May	1st to 10th	Day	10% 8% 3 7% 4 5% 4 4 6% 7% 42%	8224
	11th to 20th	Day	15% 8% 3 9% 6% 6% 6% 4 6% 8% 30%	8191
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 5% 7% 9% 42%	9138
June	1st to 10th	Day	14% 6% 2 7% 5% 5% 5% 5% 6% 9% 37%	3150
	11th to 20th	Day	14% 6% 2 7% 5% 5% 6% 4 7% 8% 36%	3150
	21st to end	Day	7% 4 2 5% 5% 5% 5% 4 8% 8% 48%	3150
July	1st to 10th	Day	4 3 1 4 5% 5% 6% 4 7% 9% 53%	6780
	11th to 20th	Day	4 3 1 4 4 4 4 4 6% 9% 55%	6780
	21st to end	Day	5% 4 2 5% 3 3 3 3 5% 7% 61%	6992
August	1st to 10th	Day	9% 5% 2 5% 4 4 4 4 6% 8% 48%	6214
	11th to 20th	Day	3 3 1 4 3 3 4 3 6% 9% 60%	5798
	21st to end	Day	7% 3 1 4 3 3 3 3 4 6% 63%	6300
September	1st to 10th	Day	9% 6% 2 5% 4 4 4 4 5% 6% 52%	2400
	11th to 20th	Day	11% 6% 2 5% 4 3 4 3 6% 7% 49%	2400
	21st to end	Day	10% 6% 2 5% 3 3 3 3 5% 7% 53%	2108
October	1st to 10th	Day	7% 6% 2 5% 4 3 3 3 5% 7% 55%	3270
	11th to 20th	Day	5% 5% 2 6% 3 3 5% 3 5% 10% 52%	3250
	21st to end	Day	4 7% 2 5% 3 5% 5% 4 7% 8% 50%	3244
November	1st to 10th	Day	9% 13% 4 8% 5% 4 4 3 6% 7% 37%	1648
	11th to 20th	Day	5% 8% 5% 10% 5% 5% 5% 4 6% 8% 38%	1680
	21st to end	Day	6% 12% 4 10% 6% 5% 6% 4 6% 8% 35%	1680
December	1st to 10th	Day	5% 8% 4 14% 10% 9% 6% 5% 6% 7% 27%	2700
	11th to 20th	Day	7% 11% 6% 15% 7% 6% 4 4 5% 5% 28%	2715
	21st to end	Day	4 7% 3 11% 7% 5% 5% 5% 7% 8% 38%	3575
January	1st to 10th	Night	3 9% 4 12% 8% 7% 7% 5% 8% 8% 29%	8768
	11th to 20th	Night	2 8% 5% 13% 7% 6% 6% 5% 7% 9% 31%	8805
	21st to end	Night	3 7% 5% 12% 7% 6% 5% 5% 7% 8% 36%	8988
February	1st to 10th	Night	5% 10% 5% 10% 7% 7% 5% 5% 6% 8% 33%	2730
	11th to 20th	Night	4 10% 4 11% 7% 6% 6% 5% 7% 9% 34%	2662
	21st to end	Night	4 9% 4 10% 7% 5% 6% 4 6% 8% 35%	2222
March	1st to 10th	Night	5% 8% 3 10% 7% 5% 5% 4 7% 10% 36%	5364
	11th to 20th	Night	6% 7% 3 8% 4 5% 5% 4 7% 10% 41%	5110
	21st to end	Night	9% 14% 6% 16% 7% 6% 5% 4 6% 7% 20%	5433
April	1st to 10th	Night	7% 8% 3 7% 6% 6% 6% 5% 7% 7% 39%	2100
	11th to 20th	Night	10% 12% 3 7% 5% 5% 5% 5% 6% 8% 34%	1986
	21st to end	Night	9% 9% 4 8% 6% 6% 5% 5% 5% 7% 37%	1817
May	1st to 10th	Night	9% 6% 2 6% 4 4 5% 4 6% 7% 48%	4723
	11th to 20th	Night	15% 8% 2 7% 5% 5% 5% 4 6% 8% 35%	4701
	21st to end	Night	9% 5% 2 6% 4 4 5% 4 7% 9% 46%	5046
June	1st to 10th	Night	12% 6% 2 6% 4 5% 4 4 6% 8% 43%	1470
	11th to 20th	Night	14% 4 2 5% 4 4 5% 5% 7% 8% 43%	1470
	21st to end	Night	6% 4 2 5% 5% 3 5% 4 4 8% 55%	1470
July	1st to 10th	Night	4 3 1 4 3 3 4 4 6% 9% 58%	3180
	11th to 20th	Night	6% 4 2 4 3 4 4 4 6% 7% 56%	3180
	21st to end	Night	6% 3 1 4 3 4 4 4 6% 7% 57%	3874
August	1st to 10th	Night	10% 5% 2 5% 4 4 4 3 7% 7% 49%	3595
	11th to 20th	Night	4 3 1 4 3 4 4 4 7% 9% 57%	4051
	21st to end	Night	9% 4 2 4 3 3 3 2 4 6% 59%	4676
September	1st to 10th	Night	8% 4 2 4 3 3 3 3 6% 6% 58%	2000
	11th to 20th	Night	8% 7% 2 6% 4 3 4 3 5% 8% 51%	2000
	21st to end	Night	8% 5% 2 4 3 3 3 3 6% 9% 55%	2290
October	1st to 10th	Night	7% 5% 2 5% 3 3 4 3 5% 8% 55%	3920
	11th to 20th	Night	5% 5% 2 4 3 3 3 3 5% 9% 56%	3898
	21st to end	Night	5% 6% 2 7% 4 4 4 4 7% 8% 48%	4521
November	1st to 10th	Night	10% 11% 4 8% 6% 4 5% 3 5% 7% 37%	2870
	11th to 20th	Night	5% 9% 4 9% 6% 5% 5% 4 7% 7% 39%	2940
	21st to end	Night	5% 10% 4 11% 5% 5% 5% 4 6% 8% 36%	2940
December	1st to 10th	Night	6% 12% 6% 13% 8% 6% 5% 4 6% 8% 26%	4710
	11th to 20th	Night	5% 12% 5% 14% 7% 5% 6% 5% 7% 8% 27%	5694
	21st to end	Night	4 7% 3 8% 6% 5% 5% 4 5% 7% 46%	7623

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	56% 7% 17% 15% 6%	4125
	11th to 20th	Day	45% 6% 18% 18% 13% 1	4140
	21st to end	Day	43% 7% 22% 23% 5%	5285
February	1st to 10th	Day	55% 6% 13% 16% 10%	1890
	11th to 20th	Day	52% 6% 15% 15% 11% 1	1854
	21st to end	Day	52% 7% 16% 16% 8%	1583
March	1st to 10th	Day	45% 6% 18% 24% 8%	4731
	11th to 20th	Day	40% 6% 19% 27% 8%	5110
	21st to end	Day	60% 8% 15% 12% 4	5775
April	1st to 10th	Day	46% 7% 15% 22% 9%	2520
	11th to 20th	Day	52% 6% 14% 21% 7% 1	2583
	21st to end	Day	45% 5% 13% 26% 9% 1	2803
May	1st to 10th	Day	40% 4 11% 28% 16% 2	8224
	11th to 20th	Day	49% 6% 11% 22% 12%	8195
	21st to end	Day	35% 7% 13% 31% 13% 1	9139
June	1st to 10th	Day	42% 8% 16% 22% 11% 1	3150
	11th to 20th	Day	42% 7% 14% 24% 11% 1	3150
	21st to end	Day	30% 7% 15% 34% 13% 1	3150
July	1st to 10th	Day	26% 7% 19% 23% 19% 6%	6707
	11th to 20th	Day	25% 7% 16% 30% 18% 4	6699
	21st to end	Day	24% 5% 11% 29% 23% 9%	6791
August	1st to 10th	Day	27% 5% 11% 33% 21% 3	4518
	11th to 20th	Day	23% 5% 17% 35% 17% 2	4197
	21st to end	Day	23% 4 12% 38% 19% 3	4543
September	1st to 10th	Day	31% 5% 11% 30% 17% 6%	2400
	11th to 20th	Day	33% 6% 16% 29% 13% 3	2400
	21st to end	Day	32% 4 12% 31% 18% 3	2108
October	1st to 10th	Day	30% 3 12% 35% 16% 3	3270
	11th to 20th	Day	29% 4 13% 39% 12% 3	3250
	21st to end	Day	30% 5% 16% 37% 12%	3244
November	1st to 10th	Day	46% 5% 16% 23% 8% 2	1648
	11th to 20th	Day	43% 7% 18% 24% 7% 1	1680
	21st to end	Day	46% 7% 20% 19% 7% 1	1680
December	1st to 10th	Day	55% 8% 17% 17% 3	2700
	11th to 20th	Day	56% 6% 19% 16% 2	2714
	21st to end	Day	42% 6% 13% 21% 13% 5%	3575
January	1st to 10th	Night	48% 8% 16% 18% 9%	8769
	11th to 20th	Night	47% 5% 18% 15% 15% 1	8805
	21st to end	Night	44% 5% 21% 23% 8%	8988
February	1st to 10th	Night	47% 6% 16% 20% 10% 1	2730
	11th to 20th	Night	45% 8% 16% 19% 12% 1	2663
	21st to end	Night	45% 6% 14% 23% 10% 1	2222
March	1st to 10th	Night	40% 6% 19% 22% 13%	5364
	11th to 20th	Night	37% 5% 21% 28% 9%	5110
	21st to end	Night	61% 7% 13% 12% 6%	5433
April	1st to 10th	Night	42% 7% 15% 25% 11% 1	2100
	11th to 20th	Night	46% 7% 12% 23% 10% 2	1986
	21st to end	Night	45% 6% 13% 24% 12%	1817
May	1st to 10th	Night	34% 6% 9% 30% 20% 1	4724
	11th to 20th	Night	44% 7% 13% 22% 14% 1	4702
	21st to end	Night	32% 7% 13% 33% 12% 2	5047
June	1st to 10th	Night	39% 7% 15% 24% 14% 1	1470
	11th to 20th	Night	36% 6% 14% 27% 15% 2	1470
	21st to end	Night	27% 6% 17% 32% 16% 1	1470
July	1st to 10th	Night	21% 6% 20% 27% 22% 4	3145
	11th to 20th	Night	27% 5% 17% 29% 16% 6%	3138
	21st to end	Night	24% 4 14% 28% 24% 6%	3763
August	1st to 10th	Night	25% 3 11% 32% 24% 4	2615
	11th to 20th	Night	23% 5% 16% 34% 19% 2	2928
	21st to end	Night	28% 5% 11% 34% 19% 4	3364
September	1st to 10th	Night	27% 4 10% 31% 20% 8%	2000
	11th to 20th	Night	32% 5% 13% 28% 18% 5%	2000
	21st to end	Night	27% 4 12% 32% 22% 3	2290
October	1st to 10th	Night	29% 5% 10% 34% 21% 1	3920
	11th to 20th	Night	26% 4 12% 40% 17% 1	3898
	21st to end	Night	32% 6% 12% 37% 13% 1	4521
November	1st to 10th	Night	46% 6% 15% 21% 10% 2	2870
	11th to 20th	Night	41% 6% 19% 23% 10% 1	2940
	21st to end	Night	45% 6% 21% 20% 8%	2940
December	1st to 10th	Night	55% 7% 19% 14% 5%	4710
	11th to 20th	Night	54% 7% 20% 16% 3	5695
	21st to end	Night	38% 5% 11% 26% 15% 4	7623

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	9% 10% 34% 26% 15% 5%	220
	11th to 20th	Day	7% 14% 38% 24% 17% 1	220
	21st to end	Day	8% 14% 34% 30% 13% 1	363
February	1st to 10th	Day	13% 11% 42% 26% 7% 1	330
	11th to 20th	Day	6% 11% 37% 32% 13% 2	330
	21st to end	Day	8% 9% 34% 37% 8% 4	273
March	1st to 10th	Day	11% 10% 34% 30% 14% 2	383
	11th to 20th	Day	8% 13% 39% 25% 12% 3	540
	21st to end	Day	11% 13% 34% 25% 15% 3	594
April	1st to 10th	Day	11% 15% 37% 29% 8% 1	540
	11th to 20th	Day	14% 17% 33% 26% 8% 2	532
	21st to end	Day	17% 13% 28% 28% 12% 2	613
May	1st to 10th	Day	14% 10% 26% 28% 18% 3	753
	11th to 20th	Day	15% 9% 27% 27% 17% 5%	775
	21st to end	Day	15% 10% 26% 26% 19% 5%	844
June	1st to 10th	Day	15% 12% 26% 27% 18% 3	780
	11th to 20th	Day	15% 12% 35% 24% 12% 2	780
	21st to end	Day	10% 8% 27% 31% 19% 5%	780
July	1st to 10th	Day	5% 5% 25% 38% 22% 5%	722
	11th to 20th	Day	4 6% 28% 37% 19% 5%	718
	21st to end	Day	4 5% 24% 38% 24% 5%	794
August	1st to 10th	Day	8% 5% 22% 36% 22% 7%	721
	11th to 20th	Day	7% 7% 22% 35% 21% 8%	517
	21st to end	Day	7% 8% 24% 35% 20% 6%	583
September	1st to 10th	Day	11% 8% 29% 33% 15% 4	530
	11th to 20th	Day	12% 8% 26% 31% 19% 3	530
	21st to end	Day	14% 11% 26% 29% 17% 3	425
October	1st to 10th	Day	20% 11% 22% 21% 22% 4	330
	11th to 20th	Day	10% 8% 38% 26% 16% 2	330
	21st to end	Day	11% 14% 40% 23% 10% 1	363
November	1st to 10th	Day	17% 15% 34% 26% 8%	330
	11th to 20th	Day	10% 15% 38% 27% 8% 2	330
	21st to end	Day	9% 10% 38% 28% 12% 2	330
December	1st to 10th	Day	11% 9% 42% 29% 8% 2	330
	11th to 20th	Day	9% 14% 38% 30% 8% 2	220
	21st to end	Day	8% 7% 36% 29% 17% 2	242
January	1st to 10th	Night	7% 10% 38% 33% 10% 1	1050
	11th to 20th	Night	10% 13% 38% 32% 6% 2	1050
	21st to end	Night	7% 13% 39% 30% 10% 1	1143
February	1st to 10th	Night	8% 9% 33% 36% 13% 1	840
	11th to 20th	Night	8% 7% 38% 38% 9%	824
	21st to end	Night	7% 8% 32% 36% 16% 2	692
March	1st to 10th	Night	9% 9% 36% 34% 11% 1	840
	11th to 20th	Night	10% 8% 37% 34% 9% 2	840
	21st to end	Night	11% 9% 34% 33% 11% 2	850
April	1st to 10th	Night	10% 7% 37% 37% 9%	630
	11th to 20th	Night	17% 8% 34% 32% 8%	623
	21st to end	Night	13% 10% 30% 38% 9%	630
May	1st to 10th	Night	12% 8% 26% 40% 12% 1	630
	11th to 20th	Night	13% 5% 30% 36% 15% 1	621
	21st to end	Night	16% 7% 26% 32% 17% 2	639
June	1st to 10th	Night	14% 10% 25% 33% 17% 1	420
	11th to 20th	Night	14% 6% 33% 38% 9%	420
	21st to end	Night	8% 5% 24% 45% 17%	420
July	1st to 10th	Night	6% 3 22% 47% 21%	390
	11th to 20th	Night	6% 3 27% 49% 15% 1	388
	21st to end	Night	4 4 25% 48% 18% 1	613
August	1st to 10th	Night	7% 3 25% 45% 18% 2	597
	11th to 20th	Night	6% 3 20% 47% 22% 1	594
	21st to end	Night	9% 5% 23% 43% 19% 1	660
September	1st to 10th	Night	11% 3 25% 41% 19% 1	600
	11th to 20th	Night	11% 5% 26% 40% 17% 1	600
	21st to end	Night	10% 6% 31% 37% 15% 1	785
October	1st to 10th	Night	13% 7% 29% 35% 15% 1	800
	11th to 20th	Night	10% 10% 32% 34% 13% 1	800
	21st to end	Night	12% 9% 39% 33% 7% 1	1015
November	1st to 10th	Night	17% 11% 36% 29% 8%	1025
	11th to 20th	Night	8% 12% 40% 30% 9% 1	1050
	21st to end	Night	9% 10% 42% 31% 8%	1050
December	1st to 10th	Night	10% 9% 38% 31% 11% 1	1050
	11th to 20th	Night	10% 10% 40% 30% 9%	1050
	21st to end	Night	11% 6% 36% 35% 9% 1	1155

Page generated at 2026-06-28 00:10:50. Version ac07

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