Wynyard
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wynyard clear sky chart from 2005-11-06 to 2024-02-05.

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% 4 8% 7% 4 5% 5% 6% 8% 34%	77597
	Night	8% 9% 4 8% 8% 4 6% 6% 6% 7% 34%	81213
Transparency	Day	46% 8% 16% 21% 8% 1	77302
	Night	47% 7% 15% 21% 9% 1	81088
Seeing	Day	13% 9% 29% 29% 16% 4	14851
	Night	13% 7% 32% 33% 13% 2	24481

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% 12% 7% 14% 11% 5% 8% 7% 6% 7% 19%	1997
	11th to 20th	Day	4 7% 4 11% 13% 8% 9% 11% 11% 8% 13%	2327
	21st to end	Day	7% 10% 6% 11% 8% 4 6% 5% 7% 7% 27%	2794
February	1st to 10th	Day	7% 9% 5% 11% 9% 7% 8% 10% 7% 7% 20%	1472
	11th to 20th	Day	6% 12% 5% 9% 8% 6% 9% 9% 8% 8% 22%	1561
	21st to end	Day	4 9% 7% 14% 11% 5% 8% 6% 8% 8% 20%	1444
March	1st to 10th	Day	9% 12% 6% 11% 10% 6% 9% 5% 5% 6% 19%	1800
	11th to 20th	Day	7% 14% 7% 8% 7% 4 5% 5% 6% 8% 29%	1856
	21st to end	Day	10% 10% 5% 9% 7% 4 5% 5% 6% 7% 31%	2363
April	1st to 10th	Day	7% 9% 4 9% 7% 3 5% 4 5% 8% 38%	2160
	11th to 20th	Day	14% 13% 5% 9% 8% 3 4 5% 5% 7% 28%	2196
	21st to end	Day	13% 9% 4 7% 7% 4 4 5% 6% 8% 33%	2495
May	1st to 10th	Day	12% 8% 3 6% 5% 3 5% 5% 6% 8% 38%	2520
	11th to 20th	Day	9% 6% 3 6% 5% 4 6% 5% 5% 7% 44%	2478
	21st to end	Day	18% 7% 3 6% 5% 3 4 5% 5% 7% 35%	2913
June	1st to 10th	Day	14% 6% 3 6% 6% 3 5% 5% 6% 9% 36%	2870
	11th to 20th	Day	22% 8% 3 6% 6% 3 5% 5% 6% 7% 28%	2880
	21st to end	Day	15% 5% 2 4 5% 4 4 6% 7% 9% 40%	2880
July	1st to 10th	Day	7% 5% 2 5% 5% 3 4 5% 7% 11% 46%	2880
	11th to 20th	Day	11% 5% 2 5% 5% 4 5% 5% 6% 7% 44%	2750
	21st to end	Day	8% 4 2 4 4 3 5% 5% 6% 8% 49%	2742
August	1st to 10th	Day	8% 4 2 5% 5% 3 6% 6% 6% 10% 45%	2507
	11th to 20th	Day	12% 5% 2 4 5% 3 5% 5% 7% 9% 44%	2477
	21st to end	Day	15% 5% 2 4 3 3 4 5% 5% 7% 47%	2490
September	1st to 10th	Day	13% 6% 2 4 4 4 4 5% 5% 7% 45%	2160
	11th to 20th	Day	14% 9% 3 6% 4 2 4 4 5% 7% 42%	2134
	21st to end	Day	11% 7% 2 4 4 3 4 5% 5% 8% 48%	1972
October	1st to 10th	Day	16% 13% 3 5% 4 3 4 5% 5% 6% 36%	1800
	11th to 20th	Day	11% 10% 5% 6% 6% 3 4 4 4 6% 40%	1690
	21st to end	Day	12% 15% 4 11% 7% 4 4 4 6% 6% 28%	1782
November	1st to 10th	Day	19% 15% 5% 10% 6% 3 5% 3 5% 7% 23%	1542
	11th to 20th	Day	9% 16% 5% 11% 12% 5% 6% 5% 5% 5% 22%	1438
	21st to end	Day	9% 13% 7% 11% 10% 4 6% 6% 4 6% 24%	1330
December	1st to 10th	Day	6% 9% 6% 11% 12% 6% 8% 9% 6% 6% 21%	1330
	11th to 20th	Day	6% 13% 6% 17% 11% 6% 6% 6% 5% 6% 17%	1477
	21st to end	Day	4 7% 4 7% 7% 4 5% 5% 6% 6% 45%	2090
January	1st to 10th	Night	5% 12% 6% 13% 13% 5% 7% 6% 5% 7% 20%	4946
	11th to 20th	Night	4 8% 4 11% 14% 10% 11% 8% 7% 7% 15%	4573
	21st to end	Night	6% 10% 5% 11% 10% 5% 6% 5% 6% 7% 30%	4873
February	1st to 10th	Night	8% 9% 4 9% 9% 6% 8% 8% 7% 7% 25%	2583
	11th to 20th	Night	5% 9% 5% 11% 9% 5% 8% 6% 7% 6% 29%	2300
	21st to end	Night	4 6% 5% 11% 9% 4 6% 7% 5% 8% 34%	1812
March	1st to 10th	Night	9% 10% 5% 8% 7% 5% 6% 7% 7% 8% 29%	2160
	11th to 20th	Night	7% 10% 5% 7% 7% 4 6% 6% 6% 8% 34%	2102
	21st to end	Night	9% 8% 4 9% 7% 4 5% 6% 6% 7% 34%	1993
April	1st to 10th	Night	6% 10% 3 7% 5% 4 5% 5% 6% 8% 42%	1800
	11th to 20th	Night	13% 9% 4 8% 7% 3 5% 4 5% 7% 34%	1714
	21st to end	Night	17% 8% 4 8% 5% 3 4 5% 5% 7% 34%	1463
May	1st to 10th	Night	11% 9% 4 6% 6% 3 5% 4 4 7% 42%	1440
	11th to 20th	Night	11% 7% 3 5% 4 3 4 4 6% 8% 44%	1418
	21st to end	Night	19% 5% 1 4 4 3 5% 6% 7% 7% 39%	1362
June	1st to 10th	Night	11% 6% 3 5% 5% 2 4 5% 6% 9% 43%	1086
	11th to 20th	Night	19% 5% 2 6% 5% 4 5% 6% 6% 8% 35%	1080
	21st to end	Night	13% 5% 2 4 5% 4 5% 4 5% 9% 45%	1080
July	1st to 10th	Night	8% 4 2 4 3 4 5% 6% 7% 9% 48%	1080
	11th to 20th	Night	7% 4 1 4 5% 3 4 5% 7% 9% 51%	1206
	21st to end	Night	6% 3 1 2 3 2 4 4 5% 9% 60%	1576
August	1st to 10th	Night	6% 3 1 3 4 3 4 5% 6% 9% 58%	1432
	11th to 20th	Night	8% 3 1 3 4 3 4 5% 6% 8% 54%	1424
	21st to end	Night	11% 5% 2 5% 4 3 4 4 5% 7% 50%	1862
September	1st to 10th	Night	11% 7% 2 5% 5% 3 4 5% 6% 8% 47%	1800
	11th to 20th	Night	13% 7% 2 5% 5% 3 4 4 5% 7% 45%	1826
	21st to end	Night	10% 6% 2 5% 5% 3 4 4 5% 7% 49%	1985
October	1st to 10th	Night	16% 11% 2 4 4 2 3 4 7% 7% 39%	2160
	11th to 20th	Night	10% 9% 4 5% 5% 3 5% 5% 5% 7% 42%	2251
	21st to end	Night	10% 15% 6% 9% 7% 3 5% 5% 4 6% 31%	2574
November	1st to 10th	Night	16% 13% 5% 9% 9% 4 5% 5% 4 6% 24%	2534
	11th to 20th	Night	8% 14% 7% 11% 10% 5% 5% 4 5% 6% 24%	2740
	21st to end	Night	8% 12% 6% 10% 10% 4 7% 6% 6% 6% 25%	2850
December	1st to 10th	Night	6% 10% 6% 13% 10% 5% 7% 7% 5% 6% 25%	2850
	11th to 20th	Night	7% 13% 6% 12% 10% 6% 6% 7% 6% 6% 20%	3712
	21st to end	Night	4 7% 3 8% 7% 3 5% 5% 5% 6% 47%	5566

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	63% 8% 14% 10% 6%	1997
	11th to 20th	Day	58% 10% 15% 12% 4	2349
	21st to end	Day	54% 8% 12% 20% 6%	2794
February	1st to 10th	Day	58% 8% 14% 12% 7%	1472
	11th to 20th	Day	55% 8% 11% 17% 10%	1570
	21st to end	Day	57% 8% 11% 15% 9%	1444
March	1st to 10th	Day	63% 8% 10% 13% 6%	1800
	11th to 20th	Day	53% 7% 13% 18% 8%	1857
	21st to end	Day	52% 8% 15% 18% 8%	2363
April	1st to 10th	Day	43% 7% 15% 23% 11% 1	2160
	11th to 20th	Day	55% 7% 13% 16% 7% 2	2196
	21st to end	Day	47% 8% 17% 21% 7%	2495
May	1st to 10th	Day	42% 7% 13% 25% 13%	2520
	11th to 20th	Day	38% 8% 13% 27% 12% 1	2482
	21st to end	Day	46% 8% 15% 19% 11% 1	2913
June	1st to 10th	Day	43% 8% 16% 23% 9% 1	2870
	11th to 20th	Day	54% 8% 14% 17% 7%	2880
	21st to end	Day	39% 10% 18% 26% 7%	2880
July	1st to 10th	Day	29% 11% 23% 29% 7%	2801
	11th to 20th	Day	37% 9% 20% 25% 8%	2665
	21st to end	Day	30% 10% 22% 30% 8%	2590
August	1st to 10th	Day	32% 10% 23% 26% 9%	2491
	11th to 20th	Day	34% 10% 23% 27% 5% 1	2477
	21st to end	Day	35% 8% 16% 32% 9%	2490
September	1st to 10th	Day	37% 8% 15% 27% 12% 1	2160
	11th to 20th	Day	41% 7% 17% 26% 9% 1	2134
	21st to end	Day	35% 6% 16% 30% 12% 1	1972
October	1st to 10th	Day	47% 7% 17% 22% 7%	1800
	11th to 20th	Day	44% 7% 13% 26% 9%	1690
	21st to end	Day	57% 6% 15% 17% 4 1	1782
November	1st to 10th	Day	62% 6% 12% 15% 5% 1	1542
	11th to 20th	Day	64% 8% 13% 9% 5%	1438
	21st to end	Day	61% 6% 12% 16% 4	1330
December	1st to 10th	Day	59% 10% 14% 11% 6% 1	1330
	11th to 20th	Day	65% 8% 16% 8% 3	1478
	21st to end	Day	39% 5% 13% 22% 11% 9%	2090
January	1st to 10th	Night	62% 7% 13% 14% 4	4946
	11th to 20th	Night	63% 8% 13% 12% 3	4613
	21st to end	Night	52% 9% 14% 18% 6%	4873
February	1st to 10th	Night	55% 7% 13% 17% 8% 1	2583
	11th to 20th	Night	50% 7% 14% 19% 10% 1	2301
	21st to end	Night	45% 8% 15% 22% 10%	1812
March	1st to 10th	Night	50% 9% 14% 20% 6% 1	2160
	11th to 20th	Night	46% 8% 14% 23% 9% 1	2102
	21st to end	Night	47% 8% 14% 19% 11%	1993
April	1st to 10th	Night	39% 6% 13% 24% 16% 1	1800
	11th to 20th	Night	49% 6% 12% 18% 12% 3	1714
	21st to end	Night	48% 7% 13% 21% 10% 1	1463
May	1st to 10th	Night	41% 6% 11% 26% 16% 1	1440
	11th to 20th	Night	38% 6% 13% 22% 19% 1	1418
	21st to end	Night	41% 7% 17% 21% 14% 1	1362
June	1st to 10th	Night	35% 9% 17% 26% 12% 2	1086
	11th to 20th	Night	44% 10% 16% 19% 10% 2	1080
	21st to end	Night	36% 8% 21% 26% 8% 1	1080
July	1st to 10th	Night	28% 10% 21% 30% 10%	1050
	11th to 20th	Night	29% 10% 19% 34% 7% 1	1168
	21st to end	Night	22% 7% 23% 36% 11% 1	1488
August	1st to 10th	Night	22% 9% 23% 35% 11%	1424
	11th to 20th	Night	27% 8% 20% 35% 9% 1	1424
	21st to end	Night	33% 6% 14% 34% 12%	1862
September	1st to 10th	Night	34% 7% 17% 26% 15% 1	1800
	11th to 20th	Night	39% 6% 15% 28% 11% 1	1826
	21st to end	Night	34% 6% 16% 27% 15% 1	1985
October	1st to 10th	Night	43% 7% 17% 26% 7%	2160
	11th to 20th	Night	41% 7% 15% 27% 10%	2251
	21st to end	Night	54% 7% 13% 19% 7%	2574
November	1st to 10th	Night	61% 7% 12% 13% 6% 1	2534
	11th to 20th	Night	62% 7% 15% 12% 4	2740
	21st to end	Night	58% 9% 15% 15% 3	2850
December	1st to 10th	Night	57% 8% 14% 15% 5% 1	2850
	11th to 20th	Night	61% 10% 12% 12% 5%	3710
	21st to end	Night	38% 5% 13% 23% 16% 6%	5566

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% 12% 36% 22% 17% 2	180
	11th to 20th	Day	6% 8% 38% 36% 10% 1	217
	21st to end	Day	13% 10% 34% 29% 12% 1	297
February	1st to 10th	Day	7% 10% 39% 32% 10% 2	252
	11th to 20th	Day	8% 10% 31% 34% 13% 3	240
	21st to end	Day	7% 7% 30% 37% 17% 3	198
March	1st to 10th	Day	12% 9% 33% 32% 13% 1	240
	11th to 20th	Day	11% 9% 30% 33% 14% 3	297
	21st to end	Day	15% 10% 33% 29% 12% 2	462
April	1st to 10th	Day	9% 12% 36% 29% 12% 2	420
	11th to 20th	Day	17% 12% 29% 24% 15% 3	474
	21st to end	Day	15% 10% 28% 31% 14% 2	600
May	1st to 10th	Day	13% 8% 32% 25% 18% 4	603
	11th to 20th	Day	12% 9% 29% 26% 20% 4	625
	21st to end	Day	17% 9% 22% 30% 16% 6%	679
June	1st to 10th	Day	14% 12% 31% 25% 14% 5%	630
	11th to 20th	Day	23% 12% 27% 22% 14% 3	630
	21st to end	Day	16% 7% 23% 29% 20% 6%	630
July	1st to 10th	Day	9% 7% 23% 35% 20% 5%	621
	11th to 20th	Day	11% 7% 25% 31% 20% 6%	618
	21st to end	Day	8% 6% 26% 31% 20% 10%	684
August	1st to 10th	Day	8% 5% 23% 33% 22% 8%	626
	11th to 20th	Day	11% 7% 20% 34% 20% 8%	615
	21st to end	Day	16% 6% 24% 30% 20% 5%	556
September	1st to 10th	Day	14% 13% 32% 23% 15% 2	450
	11th to 20th	Day	20% 9% 29% 28% 12% 3	424
	21st to end	Day	14% 7% 31% 32% 14% 2	270
October	1st to 10th	Day	21% 6% 28% 23% 19% 3	270
	11th to 20th	Day	16% 13% 33% 22% 13% 3	270
	21st to end	Day	20% 14% 30% 26% 8% 2	297
November	1st to 10th	Day	25% 9% 30% 24% 8% 3	270
	11th to 20th	Day	15% 13% 42% 24% 6% 1	270
	21st to end	Day	12% 11% 40% 27% 7% 2	270
December	1st to 10th	Day	6% 8% 39% 33% 13% 1	270
	11th to 20th	Day	13% 8% 45% 30% 4 1	198
	21st to end	Day	7% 5% 32% 34% 18% 4	198
January	1st to 10th	Night	12% 8% 36% 31% 12% 1	950
	11th to 20th	Night	12% 9% 40% 30% 8% 1	950
	21st to end	Night	13% 9% 40% 30% 8% 1	1045
February	1st to 10th	Night	13% 7% 32% 35% 11% 2	923
	11th to 20th	Night	8% 8% 35% 37% 10% 2	732
	21st to end	Night	6% 6% 26% 38% 21% 2	592
March	1st to 10th	Night	14% 6% 30% 33% 15% 2	720
	11th to 20th	Night	9% 7% 35% 34% 13% 1	720
	21st to end	Night	12% 8% 29% 34% 15% 3	607
April	1st to 10th	Night	9% 9% 31% 34% 16% 2	540
	11th to 20th	Night	18% 7% 30% 33% 11% 1	533
	21st to end	Night	21% 8% 29% 34% 8%	540
May	1st to 10th	Night	13% 8% 29% 35% 13% 1	540
	11th to 20th	Night	16% 6% 29% 32% 16% 1	531
	21st to end	Night	20% 7% 23% 33% 15% 2	584
June	1st to 10th	Night	13% 6% 28% 36% 16% 1	366
	11th to 20th	Night	20% 5% 27% 32% 16% 1	360
	21st to end	Night	16% 3 22% 39% 19% 1	360
July	1st to 10th	Night	8% 5% 23% 41% 22% 1	350
	11th to 20th	Night	10% 4 29% 37% 17% 3	366
	21st to end	Night	7% 4 26% 37% 23% 4	591
August	1st to 10th	Night	7% 5% 23% 39% 22% 4	537
	11th to 20th	Night	9% 3 19% 38% 27% 4	534
	21st to end	Night	13% 6% 25% 39% 16% 2	594
September	1st to 10th	Night	14% 5% 26% 36% 19% 1	540
	11th to 20th	Night	16% 5% 25% 36% 15% 2	540
	21st to end	Night	11% 8% 31% 37% 12% 1	545
October	1st to 10th	Night	20% 7% 25% 34% 13% 1	720
	11th to 20th	Night	14% 8% 30% 36% 11% 1	811
	21st to end	Night	19% 9% 32% 29% 10% 1	990
November	1st to 10th	Night	24% 7% 34% 28% 7% 1	925
	11th to 20th	Night	14% 11% 38% 27% 9% 2	950
	21st to end	Night	14% 13% 41% 25% 7% 1	950
December	1st to 10th	Night	10% 7% 40% 27% 13% 3	950
	11th to 20th	Night	11% 10% 40% 28% 10% 1	950
	21st to end	Night	12% 4 33% 33% 16% 2	1045

Page generated at 2024-02-02 04:20:29. Version ac07

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