Wiarton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wiarton clear sky chart from 2005-11-06 to 2024-03-06.

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	16% 11% 5% 8% 6% 3 4 4 5% 6% 31%	78328
	Night	16% 13% 6% 10% 7% 3 5% 4 4 5% 25%	81197
Transparency	Day	53% 7% 12% 17% 9% 1	78034
	Night	60% 7% 11% 14% 7% 1	81025
Seeing	Day	18% 10% 26% 27% 14% 4	14169
	Night	20% 11% 28% 26% 12% 2	23599

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	15% 23% 15% 15% 10% 3 4 3 2 3 6%	2214
	11th to 20th	Day	12% 19% 12% 23% 13% 4 4 3 2 1 5%	2591
	21st to end	Day	18% 20% 12% 14% 8% 4 4 4 3 4 9%	3124
February	1st to 10th	Day	13% 20% 9% 16% 11% 5% 5% 4 4 4 12%	1710
	11th to 20th	Day	13% 15% 8% 13% 10% 4 6% 5% 5% 5% 17%	1663
	21st to end	Day	15% 16% 8% 10% 7% 4 6% 5% 4 5% 19%	1527
March	1st to 10th	Day	14% 10% 4 10% 7% 5% 5% 5% 5% 6% 30%	1965
	11th to 20th	Day	12% 12% 5% 9% 8% 3 5% 5% 5% 6% 30%	1980
	21st to end	Day	17% 9% 4 6% 6% 3 5% 4 5% 6% 34%	2178
April	1st to 10th	Day	20% 11% 4 8% 6% 3 4 4 5% 7% 29%	2073
	11th to 20th	Day	19% 9% 2 6% 5% 3 3 3 4 6% 39%	2312
	21st to end	Day	20% 8% 4 6% 4 3 4 5% 5% 7% 34%	2340
May	1st to 10th	Day	18% 7% 3 5% 5% 2 5% 5% 5% 8% 37%	2340
	11th to 20th	Day	16% 7% 3 5% 4 3 5% 5% 4 6% 43%	2396
	21st to end	Day	11% 5% 2 5% 5% 3 4 5% 5% 9% 46%	2725
June	1st to 10th	Day	12% 7% 3 4 4 3 5% 6% 7% 8% 41%	2654
	11th to 20th	Day	12% 5% 3 5% 5% 3 5% 5% 6% 8% 44%	2700
	21st to end	Day	14% 6% 2 5% 5% 3 4 4 6% 8% 43%	2700
July	1st to 10th	Day	10% 5% 2 4 4 2 3 5% 6% 9% 50%	2700
	11th to 20th	Day	11% 6% 2 5% 5% 3 4 5% 6% 8% 46%	2658
	21st to end	Day	10% 5% 2 5% 4 3 4 5% 6% 10% 45%	2547
August	1st to 10th	Day	12% 5% 2 4 4 2 4 4 6% 9% 48%	2327
	11th to 20th	Day	12% 5% 2 4 4 3 5% 5% 6% 8% 46%	2303
	21st to end	Day	13% 6% 3 5% 5% 3 5% 5% 6% 8% 40%	2561
September	1st to 10th	Day	13% 6% 3 6% 5% 3 4 5% 5% 8% 41%	2138
	11th to 20th	Day	13% 5% 2 6% 5% 3 4 4 6% 9% 42%	1980
	21st to end	Day	18% 6% 3 6% 5% 4 6% 5% 6% 6% 35%	1980
October	1st to 10th	Day	20% 9% 3 7% 5% 4 4 4 5% 6% 33%	1825
	11th to 20th	Day	25% 14% 4 9% 6% 4 4 4 5% 5% 20%	1800
	21st to end	Day	30% 14% 5% 8% 7% 2 4 3 4 5% 17%	1908
November	1st to 10th	Day	18% 18% 5% 8% 7% 3 4 5% 4 7% 21%	1630
	11th to 20th	Day	18% 19% 4 10% 7% 4 5% 6% 4 5% 18%	1520
	21st to end	Day	21% 23% 8% 9% 7% 4 4 5% 4 4 11%	1520
December	1st to 10th	Day	16% 27% 11% 13% 8% 3 4 4 3 4 8%	1520
	11th to 20th	Day	18% 24% 8% 15% 7% 3 4 3 3 5% 9%	1788
	21st to end	Day	28% 22% 8% 13% 7% 3 4 3 3 3 6%	2431
January	1st to 10th	Night	15% 24% 12% 16% 10% 4 4 3 3 3 7%	4739
	11th to 20th	Night	15% 17% 10% 18% 16% 4 5% 3 3 3 6%	4374
	21st to end	Night	17% 19% 10% 14% 8% 4 4 4 3 4 12%	4532
February	1st to 10th	Night	13% 18% 7% 14% 11% 5% 5% 5% 5% 3 14%	2470
	11th to 20th	Night	13% 14% 9% 14% 10% 4 4 4 4 6% 19%	2403
	21st to end	Night	16% 13% 7% 10% 8% 4 6% 5% 5% 5% 23%	1922
March	1st to 10th	Night	13% 12% 6% 9% 7% 4 5% 4 5% 5% 32%	2099
	11th to 20th	Night	14% 11% 6% 9% 7% 3 4 4 4 6% 33%	1979
	21st to end	Night	16% 11% 4 7% 5% 3 4 5% 4 5% 36%	2178
April	1st to 10th	Night	20% 10% 3 6% 6% 3 4 4 5% 6% 32%	1893
	11th to 20th	Night	18% 8% 3 6% 5% 2 5% 4 5% 7% 37%	1604
	21st to end	Night	20% 9% 3 8% 6% 2 4 5% 5% 5% 33%	1620
May	1st to 10th	Night	15% 6% 3 7% 6% 3 5% 4 5% 8% 38%	1620
	11th to 20th	Night	14% 6% 3 6% 6% 3 4 5% 6% 6% 41%	1493
	21st to end	Night	10% 4 2 5% 5% 4 5% 5% 6% 8% 46%	1550
June	1st to 10th	Night	13% 7% 2 6% 6% 4 5% 4 6% 8% 40%	1301
	11th to 20th	Night	11% 5% 2 4 4 3 5% 6% 6% 10% 43%	1260
	21st to end	Night	15% 5% 3 4 5% 3 4 6% 6% 8% 41%	1260
July	1st to 10th	Night	10% 4 2 3 4 3 3 4 5% 9% 54%	1260
	11th to 20th	Night	9% 4 2 5% 5% 4 5% 4 6% 9% 46%	1298
	21st to end	Night	8% 5% 3 4 5% 4 6% 5% 6% 7% 48%	1771
August	1st to 10th	Night	10% 5% 2 5% 4 3 4 4 5% 8% 49%	1611
	11th to 20th	Night	9% 5% 2 5% 6% 3 5% 5% 6% 8% 47%	1598
	21st to end	Night	11% 7% 3 6% 5% 3 4 5% 5% 7% 43%	1782
September	1st to 10th	Night	11% 4 2 6% 5% 2 4 6% 7% 8% 46%	1813
	11th to 20th	Night	12% 5% 2 6% 4 3 5% 5% 4 7% 46%	1980
	21st to end	Night	17% 7% 3 7% 6% 4 5% 4 4 6% 37%	1980
October	1st to 10th	Night	19% 8% 3 7% 6% 4 5% 4 6% 6% 34%	2134
	11th to 20th	Night	26% 11% 4 8% 6% 3 5% 4 6% 6% 21%	2160
	21st to end	Night	27% 14% 4 9% 7% 3 5% 4 3 6% 19%	2445
November	1st to 10th	Night	19% 15% 5% 8% 7% 3 5% 4 5% 5% 25%	2448
	11th to 20th	Night	18% 18% 6% 9% 6% 4 6% 5% 5% 6% 17%	2660
	21st to end	Night	23% 21% 6% 8% 6% 3 4 4 4 5% 14%	2660
December	1st to 10th	Night	20% 24% 10% 11% 6% 4 4 5% 4 4 7%	2660
	11th to 20th	Night	15% 22% 9% 16% 7% 3 5% 4 4 4 11%	3404
	21st to end	Night	25% 21% 9% 15% 7% 3 3 3 3 3 8%	5236

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	84% 7% 7% 3	2215
	11th to 20th	Day	88% 6% 4 2 1	2591
	21st to end	Day	79% 8% 9% 3 1	3124
February	1st to 10th	Day	77% 6% 8% 7% 1	1710
	11th to 20th	Day	69% 8% 11% 7% 4	1672
	21st to end	Day	66% 6% 11% 12% 4	1527
March	1st to 10th	Day	54% 7% 15% 15% 8% 1	1968
	11th to 20th	Day	54% 7% 10% 17% 10% 2	1980
	21st to end	Day	51% 5% 12% 18% 12% 2	2178
April	1st to 10th	Day	55% 6% 11% 18% 10%	2073
	11th to 20th	Day	48% 4 8% 22% 16% 1	2312
	21st to end	Day	48% 7% 12% 19% 11% 3	2340
May	1st to 10th	Day	43% 6% 10% 24% 14% 3	2340
	11th to 20th	Day	42% 5% 11% 23% 17% 1	2400
	21st to end	Day	35% 7% 15% 24% 15% 3	2725
June	1st to 10th	Day	39% 8% 11% 25% 16% 1	2654
	11th to 20th	Day	36% 7% 13% 25% 18% 1	2700
	21st to end	Day	39% 7% 13% 25% 14% 2	2700
July	1st to 10th	Day	29% 8% 15% 26% 20% 2	2626
	11th to 20th	Day	34% 7% 14% 31% 11% 2	2577
	21st to end	Day	35% 8% 14% 26% 15% 1	2405
August	1st to 10th	Day	33% 7% 18% 27% 14% 2	2314
	11th to 20th	Day	35% 9% 16% 27% 13%	2303
	21st to end	Day	39% 8% 16% 24% 12% 1	2561
September	1st to 10th	Day	41% 8% 14% 24% 13% 1	2138
	11th to 20th	Day	37% 8% 16% 28% 10%	1980
	21st to end	Day	49% 8% 13% 23% 7% 1	1980
October	1st to 10th	Day	51% 8% 12% 19% 9% 1	1825
	11th to 20th	Day	64% 7% 12% 11% 5% 1	1800
	21st to end	Day	70% 6% 10% 11% 3	1908
November	1st to 10th	Day	63% 7% 12% 13% 5%	1630
	11th to 20th	Day	66% 10% 12% 7% 5%	1520
	21st to end	Day	75% 9% 10% 5%	1520
December	1st to 10th	Day	82% 8% 6% 3 1	1520
	11th to 20th	Day	79% 9% 8% 5%	1787
	21st to end	Day	84% 6% 7% 3	2431
January	1st to 10th	Night	82% 8% 7% 3	4739
	11th to 20th	Night	84% 7% 5% 2 1	4374
	21st to end	Night	78% 8% 9% 3 1	4532
February	1st to 10th	Night	73% 7% 8% 9% 2	2470
	11th to 20th	Night	67% 7% 11% 11% 4	2405
	21st to end	Night	61% 8% 13% 11% 6% 1	1922
March	1st to 10th	Night	54% 7% 13% 17% 9% 1	2109
	11th to 20th	Night	54% 6% 9% 18% 11% 2	1980
	21st to end	Night	50% 6% 10% 19% 13% 2	2178
April	1st to 10th	Night	53% 5% 11% 20% 10% 1	1893
	11th to 20th	Night	46% 5% 9% 21% 18% 2	1604
	21st to end	Night	52% 5% 10% 16% 15% 2	1620
May	1st to 10th	Night	45% 5% 11% 20% 17% 2	1620
	11th to 20th	Night	42% 6% 7% 22% 20% 3	1494
	21st to end	Night	35% 7% 14% 23% 16% 4	1551
June	1st to 10th	Night	41% 6% 11% 21% 18% 3	1301
	11th to 20th	Night	36% 6% 13% 24% 19% 2	1260
	21st to end	Night	39% 6% 12% 27% 13% 2	1260
July	1st to 10th	Night	27% 6% 12% 28% 22% 4	1225
	11th to 20th	Night	33% 8% 12% 30% 15% 2	1256
	21st to end	Night	33% 9% 14% 26% 17% 1	1672
August	1st to 10th	Night	32% 7% 18% 26% 15% 2	1600
	11th to 20th	Night	33% 8% 16% 25% 16% 2	1598
	21st to end	Night	38% 7% 15% 26% 12% 1	1782
September	1st to 10th	Night	33% 9% 14% 28% 14% 1	1813
	11th to 20th	Night	36% 8% 15% 29% 11%	1980
	21st to end	Night	47% 8% 13% 23% 8%	1980
October	1st to 10th	Night	50% 9% 10% 20% 10% 1	2134
	11th to 20th	Night	62% 8% 12% 15% 4	2160
	21st to end	Night	68% 7% 10% 10% 5%	2445
November	1st to 10th	Night	59% 7% 13% 16% 5%	2448
	11th to 20th	Night	65% 9% 14% 7% 3 1	2660
	21st to end	Night	72% 10% 12% 6% 1	2660
December	1st to 10th	Night	80% 9% 7% 3 1	2660
	11th to 20th	Night	77% 8% 10% 4	3404
	21st to end	Night	84% 5% 8% 2	5236

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	22% 18% 37% 15% 5% 2	184
	11th to 20th	Day	20% 16% 36% 20% 7% 1	270
	21st to end	Day	26% 13% 32% 23% 6% 1	297
February	1st to 10th	Day	20% 25% 34% 17% 4	270
	11th to 20th	Day	18% 20% 39% 19% 4	270
	21st to end	Day	18% 26% 39% 16% 1	225
March	1st to 10th	Day	20% 14% 34% 23% 7% 1	373
	11th to 20th	Day	19% 14% 33% 26% 7% 1	420
	21st to end	Day	23% 12% 29% 27% 7% 2	462
April	1st to 10th	Day	19% 12% 35% 22% 11% 1	420
	11th to 20th	Day	25% 12% 27% 20% 11% 5%	412
	21st to end	Day	25% 7% 31% 25% 11% 1	420
May	1st to 10th	Day	22% 5% 28% 30% 13% 2	423
	11th to 20th	Day	17% 7% 26% 28% 18% 4	447
	21st to end	Day	13% 6% 22% 33% 21% 6%	485
June	1st to 10th	Day	13% 5% 26% 36% 17% 3	584
	11th to 20th	Day	13% 5% 25% 37% 17% 4	630
	21st to end	Day	16% 5% 25% 34% 17% 4	630
July	1st to 10th	Day	10% 2 21% 38% 24% 5%	621
	11th to 20th	Day	13% 4 24% 33% 19% 7%	617
	21st to end	Day	12% 3 18% 41% 20% 6%	488
August	1st to 10th	Day	14% 3 17% 31% 27% 8%	446
	11th to 20th	Day	14% 3 12% 35% 27% 9%	439
	21st to end	Day	15% 8% 20% 30% 19% 8%	495
September	1st to 10th	Day	14% 8% 21% 30% 19% 7%	450
	11th to 20th	Day	11% 8% 19% 26% 25% 11%	450
	21st to end	Day	18% 11% 20% 25% 21% 5%	450
October	1st to 10th	Day	22% 12% 24% 22% 16% 5%	450
	11th to 20th	Day	23% 17% 31% 23% 5% 1	450
	21st to end	Day	34% 16% 26% 18% 5%	423
November	1st to 10th	Day	22% 19% 30% 19% 8% 2	250
	11th to 20th	Day	25% 18% 32% 19% 4 2	180
	21st to end	Day	23% 19% 40% 16% 2	180
December	1st to 10th	Day	23% 25% 33% 15% 4	180
	11th to 20th	Day	28% 23% 32% 13% 5%	180
	21st to end	Day	35% 20% 33% 9% 3	198
January	1st to 10th	Night	23% 17% 33% 21% 5% 1	950
	11th to 20th	Night	26% 17% 31% 18% 6% 1	910
	21st to end	Night	20% 12% 33% 27% 7% 1	836
February	1st to 10th	Night	20% 17% 37% 21% 4	760
	11th to 20th	Night	17% 16% 34% 25% 7%	743
	21st to end	Night	21% 15% 36% 24% 4	628
March	1st to 10th	Night	16% 13% 38% 26% 7%	743
	11th to 20th	Night	18% 12% 37% 25% 7% 1	720
	21st to end	Night	19% 10% 29% 29% 12% 1	792
April	1st to 10th	Night	22% 11% 29% 30% 7% 1	720
	11th to 20th	Night	20% 8% 31% 27% 12% 3	540
	21st to end	Night	24% 6% 25% 29% 14% 1	540
May	1st to 10th	Night	17% 4 23% 36% 17% 2	540
	11th to 20th	Night	18% 4 18% 38% 21% 1	432
	21st to end	Night	12% 3 24% 37% 22% 3	389
June	1st to 10th	Night	15% 3 26% 37% 16% 3	360
	11th to 20th	Night	11% 6% 22% 37% 23%	360
	21st to end	Night	13% 4 21% 37% 25% 1	360
July	1st to 10th	Night	10% 3 14% 48% 23% 2	350
	11th to 20th	Night	10% 3 23% 31% 30% 3	386
	21st to end	Night	9% 3 18% 43% 24% 3	591
August	1st to 10th	Night	11% 2 20% 33% 31% 3	537
	11th to 20th	Night	10% 3 15% 34% 31% 7%	534
	21st to end	Night	14% 6% 19% 31% 26% 4	594
September	1st to 10th	Night	11% 6% 20% 35% 20% 7%	715
	11th to 20th	Night	13% 6% 21% 32% 23% 6%	720
	21st to end	Night	18% 8% 21% 25% 20% 7%	720
October	1st to 10th	Night	22% 8% 26% 26% 16% 3	720
	11th to 20th	Night	29% 15% 24% 23% 8% 2	720
	21st to end	Night	33% 14% 27% 21% 5% 1	792
November	1st to 10th	Night	26% 14% 29% 22% 8% 1	740
	11th to 20th	Night	25% 19% 31% 17% 8%	760
	21st to end	Night	32% 15% 31% 18% 3	760
December	1st to 10th	Night	28% 22% 32% 14% 4 1	760
	11th to 20th	Night	23% 20% 38% 15% 4	832
	21st to end	Night	33% 15% 32% 16% 4	1045

Page generated at 2024-03-03 06:28:57. Version ac07

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