Victoria
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Victoria clear sky chart from 2005-11-06 to 2026-02-01.

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	13% 6% 2 6% 5% 5% 5% 4 6% 8% 41%	127512
	Night	15% 6% 2 5% 4 3 4 3 5% 7% 45%	124793
Transparency	Day	39% 7% 11% 21% 14% 8%	131255
	Night	37% 5% 12% 20% 15% 9%	129113
Seeing	Day	13% 7% 22% 29% 21% 8%	16270
	Night	16% 5% 21% 34% 22% 2	26289

By Month

Percentage Cloud Cover SE (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	21% 11% 3 7% 4 3 3 3 3 4 38%	4167
	11th to 20th	Day	17% 6% 2 6% 3 2 3 3 4 6% 49%	4170
	21st to end	Day	29% 7% 3 5% 3 3 3 3 5% 6% 33%	4799
February	1st to 10th	Day	21% 9% 3 7% 3 3 3 4 4 4 39%	2000
	11th to 20th	Day	20% 9% 2 7% 4 3 4 3 5% 5% 39%	1949
	21st to end	Day	19% 8% 2 6% 4 3 3 3 5% 6% 41%	1725
March	1st to 10th	Day	13% 6% 3 7% 4 4 4 3 6% 8% 41%	4936
	11th to 20th	Day	15% 7% 3 7% 4 4 4 3 4 5% 46%	4980
	21st to end	Day	17% 7% 3 7% 5% 4 4 3 5% 6% 40%	5462
April	1st to 10th	Day	13% 8% 2 6% 5% 4 5% 4 6% 6% 41%	2200
	11th to 20th	Day	17% 7% 3 6% 6% 4 4 3 5% 6% 39%	2191
	21st to end	Day	13% 8% 2 7% 5% 4 5% 5% 5% 6% 40%	2400
May	1st to 10th	Day	19% 7% 2 7% 5% 5% 5% 4 6% 8% 31%	5857
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 6% 7% 46%	5862
	21st to end	Day	9% 6% 2 7% 5% 5% 6% 5% 7% 11% 38%	6434
June	1st to 10th	Day	5% 4 2 5% 5% 5% 6% 5% 9% 11% 44%	2600
	11th to 20th	Day	5% 4 2 6% 5% 5% 6% 5% 9% 11% 42%	2600
	21st to end	Day	7% 6% 3 8% 7% 7% 7% 5% 9% 11% 32%	2600
July	1st to 10th	Day	8% 6% 3 9% 6% 7% 7% 6% 7% 10% 32%	5900
	11th to 20th	Day	5% 6% 3 7% 6% 6% 7% 5% 9% 12% 33%	5900
	21st to end	Day	9% 6% 2 6% 5% 5% 6% 5% 7% 11% 38%	6422
August	1st to 10th	Day	1 2 1 3 3 3 4 4 6% 10% 62%	4234
	11th to 20th	Day	2 3 2 4 4 5% 6% 6% 9% 13% 46%	3987
	21st to end	Day	7% 4 2 7% 6% 7% 7% 5% 8% 11% 36%	3949
September	1st to 10th	Day	8% 6% 3 10% 6% 7% 6% 5% 7% 9% 33%	2200
	11th to 20th	Day	10% 7% 2 8% 6% 6% 6% 5% 6% 8% 37%	2200
	21st to end	Day	8% 5% 2 5% 5% 5% 6% 5% 7% 9% 44%	2200
October	1st to 10th	Day	5% 4 2 5% 4 5% 5% 5% 6% 7% 53%	2200
	11th to 20th	Day	11% 6% 2 4 3 4 4 3 5% 6% 51%	2000
	21st to end	Day	10% 4 2 4 4 4 5% 3 4 7% 52%	2200
November	1st to 10th	Day	12% 6% 2 6% 5% 5% 4 4 5% 7% 44%	2058
	11th to 20th	Day	13% 6% 2 6% 4 4 3 4 5% 6% 48%	2100
	21st to end	Day	16% 8% 2 7% 6% 4 4 3 5% 5% 39%	1932
December	1st to 10th	Day	32% 9% 3 6% 3 3 3 2 4 4 31%	3030
	11th to 20th	Day	15% 7% 3 6% 5% 5% 4 4 5% 7% 40%	3481
	21st to end	Day	13% 6% 2 7% 3 3 3 2 4 6% 49%	4587
January	1st to 10th	Night	24% 9% 2 5% 3 2 2 2 4 5% 41%	6018
	11th to 20th	Night	15% 5% 2 5% 3 3 3 2 4 7% 51%	6030
	21st to end	Night	32% 6% 2 5% 3 3 3 3 5% 6% 33%	6464
February	1st to 10th	Night	21% 8% 3 7% 4 4 3 3 4 5% 39%	2400
	11th to 20th	Night	22% 6% 2 5% 3 3 3 3 4 6% 43%	2338
	21st to end	Night	22% 8% 2 6% 3 4 3 3 4 5% 40%	1903
March	1st to 10th	Night	22% 9% 2 6% 3 3 3 4 4 6% 37%	4919
	11th to 20th	Night	20% 7% 2 5% 3 3 3 3 3 5% 45%	4980
	21st to end	Night	21% 8% 2 5% 3 2 3 3 4 5% 44%	5467
April	1st to 10th	Night	17% 8% 2 5% 4 4 4 4 6% 7% 39%	2200
	11th to 20th	Night	19% 6% 2 5% 4 4 4 3 5% 7% 42%	2157
	21st to end	Night	18% 8% 3 6% 4 4 3 4 6% 6% 38%	2000
May	1st to 10th	Night	30% 8% 3 6% 5% 4 4 3 5% 6% 27%	4053
	11th to 20th	Night	15% 6% 2 5% 3 3 4 3 5% 8% 45%	4053
	21st to end	Night	18% 7% 3 7% 5% 5% 4 4 6% 10% 30%	4443
June	1st to 10th	Night	6% 3 2 4 3 3 3 4 6% 11% 54%	1800
	11th to 20th	Night	5% 3 2 4 4 4 5% 4 8% 9% 52%	1800
	21st to end	Night	6% 4 2 6% 4 4 6% 5% 8% 11% 45%	1800
July	1st to 10th	Night	6% 5% 2 7% 6% 5% 6% 4 7% 9% 43%	4078
	11th to 20th	Night	4 4 2 6% 4 5% 6% 5% 8% 10% 46%	4077
	21st to end	Night	7% 5% 2 6% 4 4 5% 4 6% 10% 45%	4449
August	1st to 10th	Night	1 1 2 1 2 3 2 4 8% 77%	2926
	11th to 20th	Night	2 2 1 3 2 3 4 4 7% 11% 61%	3053
	21st to end	Night	4 2 1 4 4 4 4 3 8% 12% 55%	3945
September	1st to 10th	Night	6% 4 2 6% 5% 4 5% 4 7% 10% 46%	2200
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 5% 8% 50%	2200
	21st to end	Night	7% 3 2 4 3 3 4 4 5% 8% 55%	2200
October	1st to 10th	Night	4 4 1 4 3 3 4 3 5% 7% 62%	2200
	11th to 20th	Night	8% 5% 1 4 3 2 2 2 4 5% 62%	2378
	21st to end	Night	10% 4 1 3 3 2 3 3 4 4 64%	2640
November	1st to 10th	Night	10% 5% 2 5% 4 3 3 3 4 6% 55%	2460
	11th to 20th	Night	14% 6% 2 5% 3 3 4 3 4 5% 52%	2520
	21st to end	Night	16% 6% 2 6% 4 4 5% 4 5% 6% 43%	2683
December	1st to 10th	Night	32% 11% 3 6% 3 3 3 2 3 4 30%	4380
	11th to 20th	Night	16% 7% 3 7% 4 3 3 3 4 5% 44%	4946
	21st to end	Night	14% 6% 3 6% 4 3 3 2 4 5% 50%	6633

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	51% 4 5% 16% 16% 8%	4168
	11th to 20th	Day	38% 4 5% 22% 20% 12%	4170
	21st to end	Day	51% 3 5% 12% 18% 11%	4799
February	1st to 10th	Day	48% 4 6% 10% 18% 14%	2000
	11th to 20th	Day	48% 3 8% 15% 14% 11%	1959
	21st to end	Day	44% 6% 8% 16% 16% 11%	1725
March	1st to 10th	Day	41% 6% 8% 18% 11% 16%	4936
	11th to 20th	Day	42% 4 6% 10% 16% 22%	4980
	21st to end	Day	43% 5% 8% 18% 17% 8%	5464
April	1st to 10th	Day	42% 6% 9% 16% 17% 11%	2200
	11th to 20th	Day	45% 6% 7% 15% 15% 11%	2191
	21st to end	Day	43% 7% 8% 19% 16% 8%	2400
May	1st to 10th	Day	50% 7% 11% 18% 11% 3	5895
	11th to 20th	Day	35% 7% 12% 22% 17% 7%	5866
	21st to end	Day	37% 7% 12% 33% 9% 1	6447
June	1st to 10th	Day	30% 9% 16% 28% 17% 1	2600
	11th to 20th	Day	33% 8% 13% 26% 16% 4	2600
	21st to end	Day	42% 10% 14% 24% 9% 1	2600
July	1st to 10th	Day	43% 10% 20% 23% 3	5836
	11th to 20th	Day	39% 10% 21% 25% 6%	5831
	21st to end	Day	37% 9% 19% 25% 9%	6240
August	1st to 10th	Day	17% 7% 13% 49% 14%	4220
	11th to 20th	Day	25% 11% 26% 31% 6% 1	4026
	21st to end	Day	38% 11% 16% 23% 10% 1	3948
September	1st to 10th	Day	44% 11% 12% 15% 14% 4	2200
	11th to 20th	Day	42% 8% 12% 20% 14% 3	2200
	21st to end	Day	34% 8% 13% 19% 16% 11%	2200
October	1st to 10th	Day	21% 4 8% 13% 19% 35%	3590
	11th to 20th	Day	26% 4 8% 20% 25% 18%	3240
	21st to end	Day	29% 4 8% 18% 27% 14%	3538
November	1st to 10th	Day	38% 6% 10% 15% 21% 10%	2058
	11th to 20th	Day	38% 5% 9% 17% 18% 14%	2100
	21st to end	Day	46% 5% 9% 15% 15% 11%	1932
December	1st to 10th	Day	59% 3 5% 13% 16% 5%	3030
	11th to 20th	Day	43% 6% 7% 15% 17% 11%	3479
	21st to end	Day	37% 4 5% 21% 19% 15%	4587
January	1st to 10th	Night	47% 3 6% 15% 16% 13%	6018
	11th to 20th	Night	34% 3 6% 20% 22% 15%	6030
	21st to end	Night	53% 3 5% 12% 17% 11%	6464
February	1st to 10th	Night	48% 3 9% 10% 16% 15%	2400
	11th to 20th	Night	44% 5% 7% 16% 16% 13%	2338
	21st to end	Night	47% 4 7% 15% 16% 11%	1903
March	1st to 10th	Night	48% 5% 8% 15% 13% 11%	4919
	11th to 20th	Night	43% 4 6% 11% 16% 19%	4980
	21st to end	Night	43% 3 10% 17% 18% 9%	5467
April	1st to 10th	Night	43% 6% 12% 16% 13% 10%	2200
	11th to 20th	Night	43% 4 10% 15% 13% 14%	2157
	21st to end	Night	45% 6% 11% 17% 13% 8%	2000
May	1st to 10th	Night	58% 5% 9% 14% 9% 4	4080
	11th to 20th	Night	36% 6% 11% 24% 16% 7%	4054
	21st to end	Night	47% 8% 16% 22% 6%	4452
June	1st to 10th	Night	24% 7% 20% 32% 16% 1	1800
	11th to 20th	Night	26% 7% 12% 34% 18% 3	1800
	21st to end	Night	31% 9% 22% 29% 9% 1	1800
July	1st to 10th	Night	37% 8% 26% 26% 2	4035
	11th to 20th	Night	30% 9% 30% 25% 6%	4026
	21st to end	Night	34% 9% 23% 24% 10%	4320
August	1st to 10th	Night	9% 4 18% 56% 12%	2916
	11th to 20th	Night	16% 7% 39% 33% 4	3080
	21st to end	Night	21% 12% 26% 31% 9% 1	3945
September	1st to 10th	Night	32% 10% 22% 20% 13% 4	2200
	11th to 20th	Night	33% 8% 17% 25% 14% 4	2200
	21st to end	Night	27% 7% 14% 26% 17% 9%	2200
October	1st to 10th	Night	16% 4 9% 18% 20% 34%	3590
	11th to 20th	Night	19% 3 9% 23% 30% 17%	3864
	21st to end	Night	20% 4 6% 26% 30% 15%	4252
November	1st to 10th	Night	31% 6% 11% 19% 22% 11%	2460
	11th to 20th	Night	35% 5% 12% 16% 18% 14%	2520
	21st to end	Night	41% 5% 9% 17% 17% 10%	2683
December	1st to 10th	Night	61% 3 6% 13% 12% 6%	4380
	11th to 20th	Night	43% 4 9% 13% 17% 14%	4947
	21st to end	Night	37% 4 6% 17% 24% 12%	6633

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	25% 10% 32% 22% 9% 2	330
	11th to 20th	Day	27% 12% 31% 22% 7% 1	330
	21st to end	Day	22% 14% 32% 20% 11%	363
February	1st to 10th	Day	25% 15% 27% 22% 10% 1	300
	11th to 20th	Day	27% 19% 27% 21% 6%	300
	21st to end	Day	24% 13% 41% 17% 5%	249
March	1st to 10th	Day	20% 17% 36% 21% 5%	300
	11th to 20th	Day	19% 17% 41% 18% 5%	300
	21st to end	Day	16% 15% 40% 20% 8%	330
April	1st to 10th	Day	16% 19% 37% 21% 7% 1	300
	11th to 20th	Day	18% 16% 35% 23% 7% 2	309
	21st to end	Day	18% 12% 35% 26% 10%	500
May	1st to 10th	Day	14% 11% 44% 23% 8%	698
	11th to 20th	Day	14% 7% 34% 32% 12% 2	725
	21st to end	Day	9% 6% 33% 34% 16% 2	789
June	1st to 10th	Day	6% 2 19% 36% 29% 8%	730
	11th to 20th	Day	7% 2 18% 41% 26% 6%	730
	21st to end	Day	8% 3 13% 34% 29% 12%	730
July	1st to 10th	Day	9% 2 9% 36% 29% 14%	721
	11th to 20th	Day	5% 2 6% 35% 37% 15%	718
	21st to end	Day	6% 2 5% 35% 35% 17%	794
August	1st to 10th	Day	3 1 3 33% 37% 23%	726
	11th to 20th	Day	3 1 4 34% 35% 22%	609
	21st to end	Day	9% 2 4 20% 30% 35%	363
September	1st to 10th	Day	8% 2 9% 23% 38% 20%	330
	11th to 20th	Day	8% 2 5% 27% 38% 20%	330
	21st to end	Day	8% 1 7% 33% 38% 14%	330
October	1st to 10th	Day	5% 2 12% 32% 38% 11%	330
	11th to 20th	Day	10% 4 13% 37% 25% 11%	330
	21st to end	Day	14% 7% 25% 28% 21% 6%	363
November	1st to 10th	Day	14% 5% 22% 31% 22% 6%	330
	11th to 20th	Day	20% 3 22% 32% 18% 5%	330
	21st to end	Day	22% 14% 30% 19% 11% 3	330
December	1st to 10th	Day	24% 8% 28% 24% 10% 5%	330
	11th to 20th	Day	24% 11% 28% 25% 11% 2	330
	21st to end	Day	21% 8% 33% 24% 11% 2	363
January	1st to 10th	Night	23% 9% 30% 28% 9% 1	1050
	11th to 20th	Night	22% 8% 28% 34% 8%	1050
	21st to end	Night	25% 7% 30% 33% 6%	1077
February	1st to 10th	Night	26% 11% 28% 30% 6%	800
	11th to 20th	Night	24% 11% 28% 32% 5%	784
	21st to end	Night	27% 9% 35% 26% 4	583
March	1st to 10th	Night	24% 8% 30% 32% 6%	600
	11th to 20th	Night	22% 10% 31% 32% 5%	600
	21st to end	Night	19% 7% 34% 32% 7%	660
April	1st to 10th	Night	21% 7% 36% 31% 6%	600
	11th to 20th	Night	22% 9% 28% 33% 8%	593
	21st to end	Night	22% 7% 35% 28% 8%	600
May	1st to 10th	Night	18% 6% 37% 33% 6%	600
	11th to 20th	Night	13% 4 30% 39% 13% 1	591
	21st to end	Night	11% 4 26% 42% 17%	650
June	1st to 10th	Night	7% 2 11% 48% 32% 1	600
	11th to 20th	Night	6% 2 14% 53% 25% 1	600
	21st to end	Night	8% 1 11% 38% 37% 6%	600
July	1st to 10th	Night	6% 1 6% 39% 43% 5%	585
	11th to 20th	Night	3 2 5% 35% 49% 7%	582
	21st to end	Night	4 1 5% 35% 49% 6%	657
August	1st to 10th	Night	1 3 34% 55% 7%	597
	11th to 20th	Night	4 1 3 32% 55% 5%	594
	21st to end	Night	5% 1 3 25% 53% 12%	660
September	1st to 10th	Night	8% 1 3 28% 52% 9%	600
	11th to 20th	Night	10% 2 3 31% 47% 8%	600
	21st to end	Night	8% 7% 31% 50% 4	600
October	1st to 10th	Night	6% 2 7% 37% 45% 4	600
	11th to 20th	Night	10% 3 17% 44% 25% 2	778
	21st to end	Night	10% 5% 23% 39% 21% 1	880
November	1st to 10th	Night	10% 5% 17% 40% 25% 2	820
	11th to 20th	Night	18% 5% 22% 35% 18% 1	840
	21st to end	Night	18% 8% 27% 32% 15% 1	1003
December	1st to 10th	Night	24% 8% 23% 31% 14% 1	1050
	11th to 20th	Night	23% 8% 27% 31% 11%	1050
	21st to end	Night	20% 8% 28% 33% 11%	1155

Page generated at 2026-01-29 00:21:43. Version ac07

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