AUGO Fort Vermillion
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the AUGO Fort Vermillion clear sky chart from 2005-11-06 to 2026-10-14.

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	8% 8% 3 9% 6% 5% 6% 4 7% 8% 36%	155178
	Night	7% 10% 4 11% 7% 6% 5% 4 6% 8% 31%	145203
Transparency	Day	43% 8% 19% 23% 7%	154841
	Night	49% 7% 16% 21% 7%	145125
Seeing	Day	12% 8% 25% 31% 19% 6%	19612
	Night	13% 6% 25% 35% 18% 3	27348

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	5% 11% 6% 17% 11% 8% 6% 5% 7% 8% 17%	3365
	11th to 20th	Day	5% 10% 4 9% 6% 5% 5% 5% 7% 9% 36%	3522
	21st to end	Day	7% 17% 7% 14% 7% 6% 5% 3 6% 7% 20%	3994
February	1st to 10th	Day	7% 13% 5% 10% 8% 7% 6% 4 5% 7% 27%	1680
	11th to 20th	Day	6% 12% 5% 10% 7% 7% 7% 4 6% 8% 29%	1640
	21st to end	Day	4 13% 5% 12% 7% 7% 7% 6% 7% 9% 24%	1562
March	1st to 10th	Day	2 8% 6% 14% 8% 7% 7% 5% 8% 9% 26%	4618
	11th to 20th	Day	4 10% 5% 13% 8% 7% 7% 4 6% 6% 30%	4854
	21st to end	Day	3 8% 3 9% 6% 5% 5% 4 6% 7% 43%	5966
April	1st to 10th	Day	5% 10% 3 10% 6% 6% 6% 5% 6% 8% 35%	2604
	11th to 20th	Day	5% 8% 3 8% 6% 6% 6% 5% 8% 8% 38%	2728
	21st to end	Day	9% 9% 3 8% 6% 7% 6% 5% 6% 7% 34%	2977
May	1st to 10th	Day	5% 5% 2 6% 4 4 5% 5% 7% 10% 48%	8793
	11th to 20th	Day	12% 9% 4 9% 6% 6% 6% 5% 6% 7% 31%	9013
	21st to end	Day	11% 7% 2 8% 6% 5% 5% 4 7% 8% 36%	10540
June	1st to 10th	Day	13% 9% 3 8% 6% 5% 6% 5% 7% 8% 32%	3570
	11th to 20th	Day	14% 8% 3 8% 6% 5% 6% 5% 7% 8% 30%	3570
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 4 7% 10% 38%	3570
July	1st to 10th	Day	7% 5% 2 7% 5% 6% 7% 6% 9% 12% 35%	9961
	11th to 20th	Day	6% 4 2 6% 5% 5% 6% 5% 8% 10% 45%	9420
	21st to end	Day	12% 6% 2 6% 4 5% 5% 4 6% 9% 40%	10220
August	1st to 10th	Day	8% 5% 2 5% 4 5% 5% 3 7% 10% 46%	6897
	11th to 20th	Day	7% 5% 2 6% 4 5% 6% 4 7% 9% 45%	6367
	21st to end	Day	12% 5% 2 6% 5% 5% 6% 5% 7% 7% 41%	6770
September	1st to 10th	Day	13% 5% 2 6% 4 4 4 4 6% 9% 41%	2646
	11th to 20th	Day	9% 7% 2 8% 5% 4 5% 4 6% 8% 42%	2414
	21st to end	Day	10% 8% 3 7% 5% 6% 5% 4 7% 8% 39%	2310
October	1st to 10th	Day	9% 10% 5% 9% 6% 4 5% 4 7% 7% 34%	3338
	11th to 20th	Day	10% 13% 3 7% 5% 5% 5% 4 6% 8% 35%	2959
	21st to end	Day	8% 15% 4 10% 5% 5% 7% 5% 7% 6% 28%	3015
November	1st to 10th	Day	12% 12% 5% 11% 9% 5% 5% 3 5% 7% 26%	1442
	11th to 20th	Day	11% 17% 4 14% 8% 5% 5% 5% 5% 7% 21%	1470
	21st to end	Day	9% 12% 5% 12% 8% 7% 6% 4 6% 7% 25%	1233
December	1st to 10th	Day	7% 15% 6% 16% 10% 7% 4 4 6% 5% 19%	1680
	11th to 20th	Day	8% 20% 7% 11% 7% 6% 6% 3 5% 6% 21%	1929
	21st to end	Day	6% 12% 5% 15% 7% 6% 6% 4 5% 5% 28%	2541
January	1st to 10th	Night	6% 14% 7% 19% 10% 7% 6% 4 6% 6% 15%	9526
	11th to 20th	Night	5% 9% 3 10% 7% 5% 6% 5% 8% 8% 33%	9376
	21st to end	Night	6% 15% 5% 14% 9% 7% 5% 4 5% 6% 23%	10173
February	1st to 10th	Night	5% 10% 5% 12% 7% 6% 5% 4 6% 7% 32%	2960
	11th to 20th	Night	5% 14% 5% 10% 7% 4 5% 5% 6% 7% 32%	2866
	21st to end	Night	5% 11% 5% 12% 6% 7% 6% 5% 6% 7% 30%	2240
March	1st to 10th	Night	4 9% 6% 13% 7% 6% 6% 4 6% 8% 32%	5496
	11th to 20th	Night	4 10% 6% 14% 7% 6% 6% 5% 6% 8% 27%	5365
	21st to end	Night	3 7% 4 12% 6% 6% 5% 4 6% 6% 40%	5251
April	1st to 10th	Night	7% 11% 4 9% 6% 5% 6% 4 7% 7% 34%	2016
	11th to 20th	Night	7% 10% 4 8% 5% 5% 5% 5% 7% 7% 36%	1840
	21st to end	Night	11% 10% 3 7% 6% 5% 6% 4 7% 9% 31%	1643
May	1st to 10th	Night	6% 7% 2 7% 5% 5% 6% 4 7% 8% 42%	4126
	11th to 20th	Night	11% 8% 3 9% 6% 7% 6% 4 7% 8% 31%	3835
	21st to end	Night	11% 8% 3 7% 6% 5% 5% 5% 7% 9% 34%	3628
June	1st to 10th	Night	13% 9% 4 7% 6% 6% 8% 6% 6% 8% 29%	1050
	11th to 20th	Night	14% 7% 2 8% 5% 4 6% 5% 7% 7% 35%	1050
	21st to end	Night	10% 6% 2 7% 6% 4 6% 4 8% 8% 39%	1050
July	1st to 10th	Night	9% 6% 3 8% 6% 7% 8% 5% 9% 10% 29%	2995
	11th to 20th	Night	7% 5% 2 5% 4 5% 5% 4 7% 9% 47%	3540
	21st to end	Night	11% 6% 2 6% 4 5% 5% 4 7% 9% 42%	3848
August	1st to 10th	Night	7% 3 1 4 4 4 5% 5% 7% 9% 51%	3250
	11th to 20th	Night	6% 5% 3 8% 5% 5% 6% 4 7% 8% 44%	3677
	21st to end	Night	11% 6% 2 6% 4 5% 4 3 6% 9% 44%	4368
September	1st to 10th	Night	13% 5% 3 7% 5% 4 4 4 6% 8% 40%	1973
	11th to 20th	Night	12% 7% 3 7% 5% 5% 5% 5% 6% 7% 39%	2205
	21st to end	Night	11% 6% 3 7% 5% 5% 5% 4 6% 9% 37%	2310
October	1st to 10th	Night	7% 8% 3 7% 5% 5% 5% 4 7% 9% 40%	4075
	11th to 20th	Night	9% 11% 3 8% 4 5% 5% 4 7% 8% 36%	4255
	21st to end	Night	9% 15% 4 13% 7% 5% 4 3 5% 6% 28%	4746
November	1st to 10th	Night	12% 15% 5% 11% 6% 5% 5% 4 6% 7% 26%	3075
	11th to 20th	Night	12% 15% 5% 13% 7% 6% 5% 4 6% 7% 21%	3150
	21st to end	Night	8% 14% 6% 13% 7% 5% 5% 4 6% 8% 24%	3385
December	1st to 10th	Night	8% 14% 6% 13% 9% 7% 6% 5% 6% 7% 19%	5720
	11th to 20th	Night	9% 18% 6% 13% 7% 6% 5% 4 5% 6% 21%	6483
	21st to end	Night	4 11% 5% 13% 8% 6% 6% 4 6% 7% 28%	8657

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% 14% 4	3365
	11th to 20th	Day	43% 8% 17% 20% 12%	3540
	21st to end	Day	62% 7% 14% 10% 6%	3994
February	1st to 10th	Day	55% 7% 12% 17% 9%	1680
	11th to 20th	Day	51% 8% 18% 18% 6%	1648
	21st to end	Day	52% 11% 15% 16% 5%	1562
March	1st to 10th	Day	49% 8% 15% 22% 5%	4618
	11th to 20th	Day	52% 7% 16% 21% 3	4855
	21st to end	Day	37% 7% 15% 22% 18% 1	5966
April	1st to 10th	Day	44% 9% 17% 20% 10%	2604
	11th to 20th	Day	40% 8% 13% 25% 13% 1	2728
	21st to end	Day	46% 8% 16% 20% 8% 1	2977
May	1st to 10th	Day	29% 6% 19% 29% 16% 1	8793
	11th to 20th	Day	49% 6% 11% 24% 9% 1	9017
	21st to end	Day	42% 7% 17% 23% 10% 2	10541
June	1st to 10th	Day	46% 8% 15% 19% 10% 1	3570
	11th to 20th	Day	48% 9% 16% 21% 6%	3570
	21st to end	Day	38% 11% 18% 25% 8%	3570
July	1st to 10th	Day	38% 9% 28% 20% 4	9877
	11th to 20th	Day	31% 7% 17% 34% 10%	9333
	21st to end	Day	39% 7% 20% 31% 2	9999
August	1st to 10th	Day	32% 9% 26% 29% 4	6878
	11th to 20th	Day	33% 9% 26% 25% 7% 1	6409
	21st to end	Day	40% 8% 27% 23% 2	6769
September	1st to 10th	Day	39% 9% 26% 20% 5%	2646
	11th to 20th	Day	39% 8% 25% 26% 3	2414
	21st to end	Day	41% 9% 20% 24% 6%	2310
October	1st to 10th	Day	49% 7% 18% 23% 3	3338
	11th to 20th	Day	46% 7% 21% 23% 3	2959
	21st to end	Day	54% 8% 20% 15% 3	3015
November	1st to 10th	Day	56% 9% 17% 15% 3	1442
	11th to 20th	Day	61% 10% 14% 13% 2	1470
	21st to end	Day	57% 8% 15% 16% 4	1233
December	1st to 10th	Day	64% 7% 14% 11% 3	1680
	11th to 20th	Day	64% 6% 10% 19% 2	1930
	21st to end	Day	55% 7% 13% 19% 5%	2541
January	1st to 10th	Night	67% 6% 9% 13% 4	9527
	11th to 20th	Night	45% 8% 16% 19% 11%	9420
	21st to end	Night	58% 8% 16% 14% 4	10173
February	1st to 10th	Night	50% 6% 16% 19% 9%	2960
	11th to 20th	Night	49% 7% 16% 22% 6%	2868
	21st to end	Night	50% 9% 15% 21% 5%	2240
March	1st to 10th	Night	48% 6% 14% 26% 6%	5496
	11th to 20th	Night	52% 7% 14% 24% 3	5365
	21st to end	Night	41% 6% 11% 26% 15% 2	5251
April	1st to 10th	Night	45% 9% 12% 22% 10% 2	2016
	11th to 20th	Night	43% 7% 12% 21% 16% 2	1840
	21st to end	Night	46% 9% 12% 21% 11% 1	1643
May	1st to 10th	Night	35% 6% 16% 28% 13% 1	4126
	11th to 20th	Night	48% 7% 8% 21% 15% 1	3835
	21st to end	Night	43% 7% 16% 22% 11%	3632
June	1st to 10th	Night	48% 10% 11% 22% 9% 1	1050
	11th to 20th	Night	45% 10% 15% 22% 8% 1	1050
	21st to end	Night	39% 11% 16% 24% 9% 1	1050
July	1st to 10th	Night	45% 9% 22% 19% 5%	2970
	11th to 20th	Night	32% 6% 16% 37% 9%	3504
	21st to end	Night	37% 7% 17% 36% 3	3764
August	1st to 10th	Night	28% 8% 23% 35% 5%	3244
	11th to 20th	Night	35% 8% 25% 21% 9% 1	3701
	21st to end	Night	37% 6% 24% 29% 3	4368
September	1st to 10th	Night	40% 9% 21% 23% 6%	1973
	11th to 20th	Night	41% 9% 19% 25% 7%	2205
	21st to end	Night	42% 7% 19% 23% 9%	2310
October	1st to 10th	Night	40% 7% 19% 28% 6%	4075
	11th to 20th	Night	44% 7% 20% 23% 5%	4255
	21st to end	Night	56% 7% 18% 17% 2	4746
November	1st to 10th	Night	57% 8% 15% 17% 3	3075
	11th to 20th	Night	60% 9% 13% 15% 3	3150
	21st to end	Night	57% 7% 15% 16% 4 1	3385
December	1st to 10th	Night	61% 7% 15% 13% 4	5720
	11th to 20th	Night	63% 6% 13% 15% 3	6481
	21st to end	Night	52% 7% 17% 17% 5%	8657

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% 8% 24% 35% 17% 6%	220
	11th to 20th	Day	19% 9% 20% 40% 11% 1	220
	21st to end	Day	16% 9% 29% 34% 10% 2	242
February	1st to 10th	Day	10% 11% 30% 29% 14% 7%	220
	11th to 20th	Day	10% 6% 30% 32% 17% 5%	220
	21st to end	Day	7% 10% 30% 30% 19% 4	304
March	1st to 10th	Day	5% 11% 28% 30% 21% 4	540
	11th to 20th	Day	9% 10% 32% 34% 10% 4	540
	21st to end	Day	8% 10% 29% 33% 17% 3	594
April	1st to 10th	Day	8% 12% 33% 30% 15% 3	540
	11th to 20th	Day	10% 8% 31% 32% 15% 4	532
	21st to end	Day	12% 12% 26% 30% 18% 1	577
May	1st to 10th	Day	10% 13% 29% 30% 15% 4	753
	11th to 20th	Day	13% 10% 24% 28% 19% 6%	862
	21st to end	Day	12% 7% 22% 33% 21% 4	1072
June	1st to 10th	Day	16% 9% 26% 29% 16% 3	990
	11th to 20th	Day	16% 6% 22% 29% 21% 6%	990
	21st to end	Day	9% 5% 18% 30% 30% 7%	990
July	1st to 10th	Day	10% 7% 22% 31% 24% 6%	976
	11th to 20th	Day	10% 5% 18% 32% 26% 10%	972
	21st to end	Day	13% 5% 17% 27% 29% 10%	1079
August	1st to 10th	Day	12% 3 17% 30% 26% 11%	776
	11th to 20th	Day	13% 8% 29% 29% 15% 6%	557
	21st to end	Day	15% 6% 22% 30% 19% 8%	627
September	1st to 10th	Day	15% 8% 26% 27% 16% 7%	570
	11th to 20th	Day	10% 7% 24% 29% 23% 7%	570
	21st to end	Day	12% 11% 30% 28% 14% 4	570
October	1st to 10th	Day	16% 11% 28% 27% 14% 3	484
	11th to 20th	Day	15% 6% 34% 31% 11% 3	339
	21st to end	Day	18% 11% 32% 25% 9% 4	344
November	1st to 10th	Day	15% 7% 29% 33% 15% 3	220
	11th to 20th	Day	16% 7% 27% 35% 12% 3	220
	21st to end	Day	13% 7% 25% 30% 18% 5%	220
December	1st to 10th	Day	14% 8% 19% 36% 21% 2	220
	11th to 20th	Day	8% 12% 28% 37% 11% 5%	220
	21st to end	Day	10% 5% 23% 34% 22% 6%	242
January	1st to 10th	Night	15% 6% 23% 36% 17% 3	1160
	11th to 20th	Night	14% 8% 27% 36% 13% 2	1160
	21st to end	Night	15% 10% 30% 32% 11% 2	1253
February	1st to 10th	Night	9% 6% 27% 34% 19% 4	860
	11th to 20th	Night	12% 7% 24% 36% 17% 2	824
	21st to end	Night	8% 6% 26% 38% 18% 3	692
March	1st to 10th	Night	7% 8% 26% 34% 22% 3	840
	11th to 20th	Night	12% 8% 28% 35% 15% 2	840
	21st to end	Night	8% 5% 26% 40% 19% 2	924
April	1st to 10th	Night	11% 9% 26% 34% 18% 1	756
	11th to 20th	Night	11% 6% 30% 35% 16% 2	592
	21st to end	Night	14% 8% 27% 35% 16% 1	420
May	1st to 10th	Night	12% 6% 28% 36% 16% 1	420
	11th to 20th	Night	10% 8% 26% 34% 20% 1	414
	21st to end	Night	13% 6% 19% 38% 22% 1	455
June	1st to 10th	Night	15% 6% 21% 36% 20% 2	420
	11th to 20th	Night	17% 3 17% 32% 30% 1	420
	21st to end	Night	10% 3 15% 41% 25% 6%	420
July	1st to 10th	Night	12% 4 16% 39% 28% 2	410
	11th to 20th	Night	12% 2 15% 37% 29% 5%	408
	21st to end	Night	10% 3 15% 32% 36% 5%	460
August	1st to 10th	Night	10% 4 13% 38% 30% 6%	418
	11th to 20th	Night	8% 4 17% 44% 23% 3	416
	21st to end	Night	15% 2 18% 36% 27% 2	596
September	1st to 10th	Night	15% 3 20% 37% 22% 3	713
	11th to 20th	Night	14% 5% 19% 38% 20% 3	840
	21st to end	Night	13% 7% 27% 35% 15% 3	840
October	1st to 10th	Night	12% 7% 29% 35% 15% 2	840
	11th to 20th	Night	14% 6% 29% 36% 14% 2	812
	21st to end	Night	19% 9% 28% 31% 12% 1	938
November	1st to 10th	Night	18% 7% 28% 31% 15% 2	1025
	11th to 20th	Night	18% 7% 26% 32% 15% 1	1050
	21st to end	Night	14% 6% 29% 34% 15% 2	1116
December	1st to 10th	Night	14% 6% 25% 37% 15% 3	1160
	11th to 20th	Night	14% 9% 27% 33% 13% 3	1160
	21st to end	Night	12% 5% 21% 36% 23% 4	1276

Page generated at 2026-10-11 03:06:27. Version ac07

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