Victoria Beach
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Victoria Beach 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	11% 9% 3 9% 5% 5% 5% 4 6% 7% 36%	138423
	Night	10% 11% 4 10% 6% 5% 5% 4 6% 6% 31%	134266
Transparency	Day	46% 4 15% 25% 9% 1	141798
	Night	52% 4 12% 22% 9% 1	138979
Seeing	Day	15% 4 20% 34% 22% 5%	18590
	Night	17% 4 24% 35% 18% 3	28537

By Month

Percentage Cloud Cover NE (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% 16% 7% 15% 9% 9% 7% 5% 5% 6% 16%	4124
	11th to 20th	Day	6% 11% 5% 14% 8% 8% 11% 9% 10% 6% 12%	4112
	21st to end	Day	4 13% 6% 14% 8% 9% 8% 5% 9% 8% 17%	4984
February	1st to 10th	Day	7% 13% 6% 13% 7% 5% 8% 5% 8% 8% 20%	1794
	11th to 20th	Day	8% 9% 4 10% 6% 6% 8% 5% 6% 9% 27%	1844
	21st to end	Day	6% 12% 4 12% 8% 5% 6% 5% 7% 8% 28%	1595
March	1st to 10th	Day	7% 10% 4 13% 7% 5% 5% 5% 7% 8% 30%	4733
	11th to 20th	Day	8% 10% 4 11% 7% 6% 6% 4 6% 7% 32%	5090
	21st to end	Day	8% 10% 4 9% 5% 5% 5% 4 6% 6% 39%	5585
April	1st to 10th	Day	9% 10% 3 8% 6% 4 4 4 5% 7% 40%	2574
	11th to 20th	Day	11% 10% 3 7% 5% 5% 5% 4 6% 7% 39%	2702
	21st to end	Day	13% 7% 3 8% 5% 5% 4 5% 6% 8% 38%	2730
May	1st to 10th	Day	8% 7% 3 6% 4 4 4 3 6% 7% 48%	8077
	11th to 20th	Day	18% 8% 3 7% 5% 5% 5% 4 6% 7% 33%	8668
	21st to end	Day	13% 5% 2 5% 3 3 4 3 5% 6% 50%	9683
June	1st to 10th	Day	15% 7% 2 5% 4 4 5% 4 6% 7% 40%	3150
	11th to 20th	Day	14% 6% 2 6% 4 5% 5% 5% 7% 8% 38%	3150
	21st to end	Day	13% 6% 3 6% 4 5% 4 4 7% 9% 39%	3150
July	1st to 10th	Day	9% 5% 2 6% 4 5% 6% 4 6% 9% 46%	6800
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 6% 9% 48%	6800
	21st to end	Day	8% 4 2 5% 4 4 4 4 6% 9% 50%	7406
August	1st to 10th	Day	9% 4 2 5% 4 4 5% 4 6% 9% 46%	4481
	11th to 20th	Day	11% 4 2 5% 4 4 5% 4 6% 9% 47%	4171
	21st to end	Day	15% 6% 2 6% 3 3 4 4 5% 8% 43%	4675
September	1st to 10th	Day	12% 6% 2 6% 4 4 4 4 6% 8% 45%	2496
	11th to 20th	Day	16% 9% 3 6% 5% 5% 4 4 6% 9% 34%	2215
	21st to end	Day	13% 8% 3 7% 5% 3 4 4 5% 7% 41%	2200
October	1st to 10th	Day	19% 12% 3 7% 4 4 4 4 5% 7% 30%	2011
	11th to 20th	Day	16% 15% 3 7% 6% 4 4 4 5% 7% 27%	1970
	21st to end	Day	19% 16% 5% 11% 5% 6% 5% 3 5% 5% 20%	1954
November	1st to 10th	Day	16% 15% 4 14% 7% 5% 3 3 4 4 23%	1647
	11th to 20th	Day	11% 18% 5% 17% 8% 4 4 3 4 5% 21%	1680
	21st to end	Day	12% 17% 6% 15% 10% 6% 4 3 4 5% 18%	1528
December	1st to 10th	Day	10% 17% 8% 19% 13% 9% 5% 3 4 3 9%	2360
	11th to 20th	Day	9% 14% 5% 13% 8% 6% 7% 6% 7% 7% 19%	2709
	21st to end	Day	7% 14% 7% 17% 7% 8% 6% 5% 5% 6% 17%	3575
January	1st to 10th	Night	6% 15% 7% 15% 8% 8% 7% 6% 5% 5% 18%	8800
	11th to 20th	Night	6% 13% 7% 14% 10% 9% 9% 8% 6% 4 14%	8803
	21st to end	Night	5% 13% 5% 12% 7% 7% 8% 5% 8% 7% 21%	9229
February	1st to 10th	Night	7% 15% 5% 10% 7% 6% 7% 6% 6% 6% 25%	2824
	11th to 20th	Night	6% 11% 4 9% 5% 5% 5% 7% 8% 8% 32%	2663
	21st to end	Night	5% 12% 5% 12% 6% 6% 6% 5% 5% 6% 32%	2228
March	1st to 10th	Night	9% 12% 4 10% 5% 5% 6% 4 6% 6% 32%	5328
	11th to 20th	Night	6% 8% 4 8% 6% 5% 5% 5% 6% 8% 39%	5089
	21st to end	Night	10% 11% 4 9% 5% 5% 4 3 5% 6% 38%	5588
April	1st to 10th	Night	11% 8% 2 7% 5% 4 5% 4 5% 8% 41%	2043
	11th to 20th	Night	14% 9% 3 7% 5% 4 5% 4 6% 7% 36%	1869
	21st to end	Night	9% 8% 3 9% 4 5% 7% 5% 7% 7% 36%	1890
May	1st to 10th	Night	11% 7% 2 7% 4 4 4 4 7% 6% 45%	4849
	11th to 20th	Night	19% 7% 3 7% 4 3 5% 3 5% 8% 37%	4222
	21st to end	Night	12% 7% 3 6% 3 4 3 3 4 6% 49%	4526
June	1st to 10th	Night	14% 7% 3 7% 4 5% 6% 4 7% 8% 36%	1470
	11th to 20th	Night	15% 6% 2 5% 4 4 5% 4 6% 8% 41%	1470
	21st to end	Night	14% 5% 3 5% 4 5% 3 4 7% 11% 39%	1470
July	1st to 10th	Night	8% 4 2 5% 3 4 4 4 6% 8% 51%	3180
	11th to 20th	Night	9% 4 2 6% 4 5% 5% 4 6% 8% 46%	3180
	21st to end	Night	6% 3 2 5% 4 4 5% 3 7% 9% 52%	3469
August	1st to 10th	Night	11% 4 2 6% 4 4 5% 4 6% 8% 46%	2676
	11th to 20th	Night	9% 3 1 4 4 4 4 4 7% 9% 50%	2888
	21st to end	Night	11% 6% 2 6% 4 3 5% 4 5% 9% 44%	3234
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 8% 46%	1903
	11th to 20th	Night	16% 8% 2 7% 4 4 4 5% 5% 7% 39%	2181
	21st to end	Night	15% 6% 3 7% 5% 4 4 4 5% 8% 40%	2200
October	1st to 10th	Night	18% 11% 3 7% 5% 3 4 4 4 7% 34%	2368
	11th to 20th	Night	18% 15% 4 8% 5% 4 5% 3 5% 6% 27%	2430
	21st to end	Night	18% 16% 5% 9% 5% 4 4 4 5% 5% 25%	2885
November	1st to 10th	Night	14% 17% 5% 12% 6% 5% 5% 3 4 5% 24%	2871
	11th to 20th	Night	13% 18% 7% 15% 8% 5% 3 3 4 5% 19%	2940
	21st to end	Night	13% 16% 8% 16% 10% 6% 4 3 4 4 17%	3087
December	1st to 10th	Night	11% 22% 7% 16% 13% 7% 3 3 4 3 11%	5050
	11th to 20th	Night	8% 13% 5% 14% 8% 5% 8% 6% 5% 6% 22%	5718
	21st to end	Night	7% 12% 6% 19% 9% 6% 6% 4 5% 5% 21%	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	69% 3 9% 14% 5%	4125
	11th to 20th	Day	66% 3 9% 18% 4	4140
	21st to end	Day	62% 3 10% 19% 5%	4984
February	1st to 10th	Day	59% 5% 14% 15% 7% 1	1794
	11th to 20th	Day	51% 4 16% 22% 7%	1853
	21st to end	Day	52% 6% 13% 19% 9% 1	1595
March	1st to 10th	Day	50% 5% 15% 18% 11% 1	4735
	11th to 20th	Day	51% 5% 13% 21% 10%	5090
	21st to end	Day	45% 5% 11% 28% 10% 1	5585
April	1st to 10th	Day	44% 5% 12% 25% 13% 1	2574
	11th to 20th	Day	44% 5% 12% 23% 15% 2	2702
	21st to end	Day	44% 5% 14% 26% 10% 1	2730
May	1st to 10th	Day	36% 3 12% 33% 16% 1	8089
	11th to 20th	Day	51% 4 10% 24% 10% 1	8672
	21st to end	Day	35% 5% 8% 26% 21% 5%	9683
June	1st to 10th	Day	42% 7% 14% 26% 10% 1	3150
	11th to 20th	Day	42% 7% 15% 24% 10% 1	3150
	21st to end	Day	41% 7% 19% 25% 7%	3150
July	1st to 10th	Day	36% 4 23% 29% 8%	6727
	11th to 20th	Day	34% 3 22% 35% 5%	6719
	21st to end	Day	32% 3 24% 35% 6%	7193
August	1st to 10th	Day	34% 4 21% 32% 8%	4464
	11th to 20th	Day	34% 4 24% 32% 4	4210
	21st to end	Day	40% 4 24% 28% 4	4674
September	1st to 10th	Day	37% 6% 19% 30% 7%	2496
	11th to 20th	Day	47% 6% 20% 24% 3	2215
	21st to end	Day	42% 6% 17% 28% 7%	2200
October	1st to 10th	Day	46% 4 17% 27% 6%	3271
	11th to 20th	Day	47% 5% 13% 24% 10%	3188
	21st to end	Day	57% 4 20% 18% 2	3140
November	1st to 10th	Day	64% 6% 14% 13% 4 1	1647
	11th to 20th	Day	67% 5% 13% 11% 4	1680
	21st to end	Day	68% 4 15% 11% 2	1528
December	1st to 10th	Day	81% 4 7% 6% 2	2360
	11th to 20th	Day	62% 5% 14% 14% 5%	2710
	21st to end	Day	65% 7% 9% 14% 5%	3575
January	1st to 10th	Night	68% 4 8% 13% 7%	8800
	11th to 20th	Night	69% 3 7% 15% 5%	8850
	21st to end	Night	59% 4 10% 20% 7%	9229
February	1st to 10th	Night	56% 5% 12% 17% 8% 1	2824
	11th to 20th	Night	45% 5% 17% 24% 9%	2664
	21st to end	Night	52% 4 11% 21% 11%	2228
March	1st to 10th	Night	51% 5% 13% 16% 10% 5%	5339
	11th to 20th	Night	40% 5% 15% 26% 14% 1	5090
	21st to end	Night	48% 4 8% 27% 13% 1	5588
April	1st to 10th	Night	42% 4 9% 25% 17% 3	2043
	11th to 20th	Night	47% 4 9% 21% 15% 3	1869
	21st to end	Night	44% 5% 10% 25% 15% 1	1890
May	1st to 10th	Night	38% 3 9% 33% 16%	4857
	11th to 20th	Night	47% 3 10% 27% 11% 1	4223
	21st to end	Night	38% 3 8% 19% 27% 4	4526
June	1st to 10th	Night	45% 6% 13% 24% 11% 1	1470
	11th to 20th	Night	41% 5% 15% 26% 12% 2	1470
	21st to end	Night	38% 6% 20% 26% 9% 1	1470
July	1st to 10th	Night	32% 4 18% 36% 9% 1	3145
	11th to 20th	Night	36% 3 17% 37% 7% 1	3138
	21st to end	Night	29% 4 24% 34% 9%	3368
August	1st to 10th	Night	36% 4 15% 34% 11%	2669
	11th to 20th	Night	30% 4 27% 32% 6%	2915
	21st to end	Night	38% 3 21% 29% 7%	3234
September	1st to 10th	Night	37% 5% 18% 31% 10%	1903
	11th to 20th	Night	44% 6% 18% 24% 8% 1	2181
	21st to end	Night	42% 5% 15% 28% 9% 1	2200
October	1st to 10th	Night	42% 4 14% 29% 11%	3875
	11th to 20th	Night	49% 3 14% 25% 8%	3953
	21st to end	Night	53% 4 17% 23% 3	4659
November	1st to 10th	Night	62% 6% 13% 13% 5%	2871
	11th to 20th	Night	68% 6% 12% 10% 5%	2940
	21st to end	Night	72% 4 13% 9% 3	3087
December	1st to 10th	Night	78% 4 10% 6% 2	5050
	11th to 20th	Night	62% 4 12% 12% 10%	5716
	21st to end	Night	64% 4 9% 17% 6%	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	11% 3 31% 32% 18% 4	330
	11th to 20th	Day	10% 6% 21% 42% 19% 2	330
	21st to end	Day	15% 4 23% 36% 18% 4	363
February	1st to 10th	Day	14% 5% 29% 34% 15% 4	330
	11th to 20th	Day	11% 5% 25% 32% 21% 7%	330
	21st to end	Day	8% 4 22% 40% 24% 1	273
March	1st to 10th	Day	11% 4 23% 38% 22% 2	330
	11th to 20th	Day	13% 6% 22% 39% 17% 3	330
	21st to end	Day	16% 2 22% 36% 20% 4	363
April	1st to 10th	Day	12% 3 19% 39% 22% 4	594
	11th to 20th	Day	17% 4 21% 34% 21% 3	740
	21st to end	Day	14% 3 17% 37% 22% 6%	750
May	1st to 10th	Day	12% 3 19% 37% 26% 4	753
	11th to 20th	Day	18% 4 16% 34% 22% 6%	775
	21st to end	Day	18% 3 14% 28% 30% 7%	844
June	1st to 10th	Day	18% 3 16% 34% 22% 7%	780
	11th to 20th	Day	14% 3 20% 34% 25% 3	780
	21st to end	Day	15% 3 13% 35% 26% 8%	780
July	1st to 10th	Day	10% 4 16% 34% 26% 11%	722
	11th to 20th	Day	10% 5% 17% 32% 28% 9%	718
	21st to end	Day	9% 2 14% 35% 31% 9%	794
August	1st to 10th	Day	10% 3 16% 33% 29% 9%	726
	11th to 20th	Day	12% 3 13% 31% 30% 11%	715
	21st to end	Day	16% 3 16% 30% 28% 7%	803
September	1st to 10th	Day	14% 4 23% 33% 22% 5%	626
	11th to 20th	Day	19% 6% 18% 37% 17% 4	345
	21st to end	Day	20% 6% 22% 32% 17% 3	330
October	1st to 10th	Day	21% 7% 22% 30% 17% 3	330
	11th to 20th	Day	19% 7% 23% 39% 11% 1	330
	21st to end	Day	29% 7% 19% 28% 14% 2	363
November	1st to 10th	Day	20% 8% 26% 31% 14% 1	330
	11th to 20th	Day	19% 8% 34% 26% 12% 2	330
	21st to end	Day	20% 8% 25% 38% 9% 1	330
December	1st to 10th	Day	16% 4 28% 35% 13% 4	330
	11th to 20th	Day	17% 6% 34% 32% 8% 2	330
	21st to end	Day	13% 4 24% 38% 17% 4	363
January	1st to 10th	Night	13% 3 28% 35% 18% 3	1050
	11th to 20th	Night	14% 4 25% 39% 15% 2	1050
	21st to end	Night	15% 4 25% 39% 15% 2	1155
February	1st to 10th	Night	14% 3 24% 40% 18% 2	1050
	11th to 20th	Night	10% 3 23% 39% 21% 4	1029
	21st to end	Night	10% 4 27% 37% 21% 2	844
March	1st to 10th	Night	14% 3 23% 37% 20% 2	776
	11th to 20th	Night	12% 3 28% 41% 15% 2	630
	21st to end	Night	18% 3 21% 35% 18% 4	693
April	1st to 10th	Night	15% 2 23% 41% 17% 3	630
	11th to 20th	Night	17% 4 21% 37% 19% 3	623
	21st to end	Night	13% 2 22% 42% 18% 3	630
May	1st to 10th	Night	17% 3 22% 39% 16% 3	630
	11th to 20th	Night	18% 3 17% 40% 19% 4	621
	21st to end	Night	20% 2 16% 38% 21% 2	683
June	1st to 10th	Night	19% 2 17% 37% 22% 4	630
	11th to 20th	Night	17% 4 19% 34% 22% 3	630
	21st to end	Night	15% 3 12% 37% 28% 5%	630
July	1st to 10th	Night	7% 2 17% 39% 29% 6%	585
	11th to 20th	Night	10% 3 18% 37% 27% 6%	582
	21st to end	Night	9% 3 15% 35% 31% 7%	657
August	1st to 10th	Night	10% 4 16% 37% 29% 4	597
	11th to 20th	Night	10% 4 15% 35% 27% 9%	594
	21st to end	Night	17% 2 18% 34% 25% 4	660
September	1st to 10th	Night	17% 3 22% 35% 19% 4	600
	11th to 20th	Night	19% 4 22% 37% 16% 2	600
	21st to end	Night	19% 4 25% 33% 17% 3	600
October	1st to 10th	Night	25% 7% 26% 29% 12% 1	768
	11th to 20th	Night	25% 8% 24% 30% 11% 1	830
	21st to end	Night	29% 6% 26% 28% 10% 1	1100
November	1st to 10th	Night	23% 8% 29% 25% 14% 1	1025
	11th to 20th	Night	21% 7% 31% 29% 9% 3	1050
	21st to end	Night	21% 6% 32% 32% 8% 1	1050
December	1st to 10th	Night	16% 4 27% 36% 15% 2	1050
	11th to 20th	Night	17% 5% 31% 36% 10% 2	1050
	21st to end	Night	17% 3 27% 33% 18% 3	1155

Page generated at 2026-06-28 01:10:47. Version ac07

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