Vaughan
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vaughan 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	15% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	138374
	Night	15% 10% 4 8% 5% 5% 5% 4 6% 7% 33%	133920
Transparency	Day	47% 7% 12% 21% 11% 1	141969
	Night	47% 7% 12% 20% 12% 1	138413
Seeing	Day	19% 13% 30% 24% 11% 4	16662
	Night	19% 9% 31% 29% 11% 1	25893

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	17% 10% 4 13% 7% 5% 5% 4 5% 7% 23%	4661
	11th to 20th	Day	10% 18% 8% 18% 9% 8% 5% 4 4 4 14%	5101
	21st to end	Day	13% 14% 6% 13% 8% 6% 6% 4 5% 6% 19%	5780
February	1st to 10th	Day	14% 17% 4 12% 6% 6% 5% 4 4 5% 23%	1890
	11th to 20th	Day	12% 15% 6% 12% 8% 4 5% 3 5% 6% 24%	1843
	21st to end	Day	16% 16% 4 10% 6% 4 6% 4 4 5% 25%	1615
March	1st to 10th	Day	18% 10% 4 8% 6% 5% 4 4 5% 5% 32%	5042
	11th to 20th	Day	11% 12% 4 9% 6% 5% 4 4 6% 7% 30%	5090
	21st to end	Day	18% 11% 4 9% 5% 5% 4 3 4 5% 33%	5586
April	1st to 10th	Day	17% 13% 4 8% 5% 4 4 4 5% 6% 29%	2478
	11th to 20th	Day	20% 9% 3 8% 4 4 5% 3 5% 5% 35%	2579
	21st to end	Day	20% 9% 2 7% 5% 5% 4 3 6% 6% 33%	2730
May	1st to 10th	Day	19% 9% 3 8% 4 4 4 4 5% 7% 32%	7642
	11th to 20th	Day	14% 8% 3 7% 5% 5% 5% 4 5% 8% 36%	8177
	21st to end	Day	17% 6% 2 5% 4 4 4 3 5% 8% 43%	9060
June	1st to 10th	Day	14% 7% 2 6% 5% 5% 5% 4 7% 8% 38%	2940
	11th to 20th	Day	12% 5% 2 7% 4 4 5% 5% 7% 10% 38%	2940
	21st to end	Day	14% 5% 2 6% 5% 5% 4 4 7% 8% 39%	3100
July	1st to 10th	Day	9% 5% 2 7% 5% 5% 5% 4 7% 10% 39%	6411
	11th to 20th	Day	8% 5% 1 5% 4 5% 5% 4 7% 10% 46%	6360
	21st to end	Day	7% 4 2 6% 4 5% 5% 5% 7% 9% 45%	6480
August	1st to 10th	Day	16% 7% 2 6% 5% 4 5% 4 6% 8% 38%	4234
	11th to 20th	Day	10% 7% 3 8% 5% 5% 6% 5% 7% 9% 35%	4174
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 4 7% 9% 42%	4493
September	1st to 10th	Day	13% 6% 2 6% 4 4 5% 4 6% 8% 42%	2400
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 3 6% 8% 46%	2280
	21st to end	Day	14% 6% 3 7% 6% 4 6% 3 6% 8% 36%	2160
October	1st to 10th	Day	17% 8% 3 6% 4 4 4 4 5% 8% 37%	2000
	11th to 20th	Day	20% 8% 3 7% 6% 5% 5% 4 6% 6% 31%	2000
	21st to end	Day	23% 12% 3 8% 5% 5% 5% 5% 5% 6% 23%	2200
November	1st to 10th	Day	15% 10% 3 8% 6% 4 5% 4 6% 6% 33%	1774
	11th to 20th	Day	14% 12% 3 11% 6% 5% 7% 5% 6% 6% 26%	1680
	21st to end	Day	17% 15% 5% 10% 6% 5% 5% 4 7% 6% 21%	1680
December	1st to 10th	Day	18% 17% 5% 11% 6% 6% 6% 4 6% 5% 16%	2680
	11th to 20th	Day	20% 16% 5% 10% 6% 5% 4 3 5% 5% 21%	3066
	21st to end	Day	26% 16% 7% 13% 5% 4 4 3 4 4 14%	4048
January	1st to 10th	Night	14% 11% 5% 11% 6% 6% 5% 5% 6% 7% 23%	8234
	11th to 20th	Night	11% 15% 6% 14% 10% 7% 6% 4 6% 5% 15%	7782
	21st to end	Night	13% 12% 5% 11% 8% 6% 6% 4 6% 7% 22%	8401
February	1st to 10th	Night	13% 14% 5% 10% 7% 4 5% 4 5% 6% 26%	2730
	11th to 20th	Night	14% 14% 4 10% 7% 5% 5% 4 6% 5% 27%	2663
	21st to end	Night	13% 13% 4 10% 6% 4 5% 5% 6% 6% 28%	2186
March	1st to 10th	Night	16% 10% 5% 9% 6% 5% 5% 4 5% 6% 31%	5018
	11th to 20th	Night	10% 8% 3 8% 4 5% 5% 5% 7% 8% 36%	5089
	21st to end	Night	21% 8% 3 6% 4 4 4 3 4 6% 38%	5588
April	1st to 10th	Night	18% 10% 3 8% 5% 4 5% 4 6% 6% 31%	2141
	11th to 20th	Night	16% 9% 3 7% 5% 5% 4 3 5% 6% 37%	2008
	21st to end	Night	16% 8% 3 6% 4 4 5% 4 6% 7% 37%	1890
May	1st to 10th	Night	20% 8% 2 6% 4 4 4 4 5% 6% 36%	5257
	11th to 20th	Night	13% 9% 3 7% 4 4 4 4 5% 7% 39%	4680
	21st to end	Night	18% 5% 2 5% 3 3 3 3 5% 7% 46%	5114
June	1st to 10th	Night	13% 5% 2 6% 5% 4 4 4 6% 9% 43%	1680
	11th to 20th	Night	8% 6% 2 6% 4 5% 4 5% 7% 10% 42%	1680
	21st to end	Night	10% 6% 2 5% 5% 5% 4 4 6% 7% 45%	1501
July	1st to 10th	Night	7% 5% 3 6% 4 4 4 4 6% 10% 47%	3512
	11th to 20th	Night	9% 4 1 5% 4 4 5% 4 6% 9% 50%	3600
	21st to end	Night	8% 4 2 5% 3 4 4 4 5% 8% 52%	4370
August	1st to 10th	Night	9% 5% 2 7% 4 5% 4 3 6% 8% 47%	2915
	11th to 20th	Night	11% 4 2 5% 4 4 4 4 5% 8% 50%	2875
	21st to end	Night	10% 5% 2 5% 4 4 4 4 7% 8% 47%	3371
September	1st to 10th	Night	8% 5% 2 6% 4 4 5% 4 6% 8% 48%	2000
	11th to 20th	Night	10% 4 2 4 3 3 4 3 6% 7% 55%	2117
	21st to end	Night	16% 6% 3 7% 4 3 4 3 5% 6% 43%	2240
October	1st to 10th	Night	15% 7% 3 7% 4 4 4 4 5% 6% 41%	2400
	11th to 20th	Night	18% 7% 3 7% 5% 5% 5% 4 6% 6% 35%	2400
	21st to end	Night	19% 9% 4 8% 5% 4 5% 4 6% 6% 31%	2640
November	1st to 10th	Night	16% 9% 3 6% 4 4 4 3 6% 6% 37%	2740
	11th to 20th	Night	16% 11% 3 8% 6% 5% 5% 4 6% 7% 30%	2940
	21st to end	Night	20% 12% 4 8% 5% 5% 5% 4 5% 6% 25%	2940
December	1st to 10th	Night	17% 15% 5% 11% 6% 6% 5% 4 6% 6% 18%	4720
	11th to 20th	Night	16% 17% 5% 10% 6% 5% 5% 4 5% 5% 22%	5348
	21st to end	Night	25% 14% 6% 12% 5% 5% 4 3 4 5% 15%	7150

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	57% 8% 13% 13% 9%	4662
	11th to 20th	Day	70% 6% 9% 11% 4	5135
	21st to end	Day	62% 6% 12% 11% 8%	5780
February	1st to 10th	Day	61% 6% 10% 17% 5% 1	1890
	11th to 20th	Day	60% 5% 12% 15% 7% 1	1852
	21st to end	Day	59% 7% 10% 16% 7% 1	1615
March	1st to 10th	Day	52% 6% 15% 15% 12% 1	5045
	11th to 20th	Day	50% 6% 17% 17% 8% 2	5090
	21st to end	Day	52% 5% 10% 18% 13% 1	5586
April	1st to 10th	Day	55% 4 11% 18% 11% 1	2478
	11th to 20th	Day	50% 5% 10% 21% 14% 1	2579
	21st to end	Day	51% 5% 11% 19% 11% 3	2730
May	1st to 10th	Day	49% 7% 12% 17% 11% 4	7651
	11th to 20th	Day	44% 8% 12% 20% 14% 1	8181
	21st to end	Day	40% 5% 10% 28% 15% 2	9061
June	1st to 10th	Day	42% 7% 11% 22% 16% 1	2940
	11th to 20th	Day	38% 8% 13% 25% 15% 2	2940
	21st to end	Day	40% 7% 13% 24% 14% 1	3100
July	1st to 10th	Day	37% 8% 14% 25% 15% 2	6342
	11th to 20th	Day	31% 7% 13% 32% 16% 1	6285
	21st to end	Day	32% 8% 14% 28% 17% 1	6294
August	1st to 10th	Day	42% 8% 14% 21% 14% 1	4221
	11th to 20th	Day	40% 8% 15% 25% 10%	4213
	21st to end	Day	35% 8% 13% 34% 10% 1	4493
September	1st to 10th	Day	38% 7% 14% 29% 11% 1	2400
	11th to 20th	Day	34% 6% 14% 31% 15% 1	2280
	21st to end	Day	44% 7% 12% 26% 10%	2160
October	1st to 10th	Day	36% 7% 16% 27% 13% 1	3260
	11th to 20th	Day	39% 6% 15% 26% 14%	3240
	21st to end	Day	53% 7% 14% 20% 7%	3538
November	1st to 10th	Day	49% 7% 13% 21% 9% 1	1774
	11th to 20th	Day	54% 8% 14% 15% 9% 1	1680
	21st to end	Day	60% 7% 15% 15% 3	1680
December	1st to 10th	Day	66% 7% 14% 9% 4	2680
	11th to 20th	Day	62% 8% 13% 9% 8%	3066
	21st to end	Day	72% 6% 6% 9% 6%	4048
January	1st to 10th	Night	54% 9% 13% 18% 5%	8234
	11th to 20th	Night	64% 8% 10% 13% 5%	7823
	21st to end	Night	57% 7% 12% 12% 12% 1	8401
February	1st to 10th	Night	57% 5% 11% 20% 7% 1	2730
	11th to 20th	Night	57% 6% 12% 17% 9% 1	2665
	21st to end	Night	54% 6% 14% 18% 8%	2186
March	1st to 10th	Night	51% 6% 12% 17% 11% 2	5028
	11th to 20th	Night	42% 6% 19% 21% 11% 2	5090
	21st to end	Night	46% 5% 10% 19% 18% 2	5588
April	1st to 10th	Night	51% 5% 11% 18% 13% 2	2141
	11th to 20th	Night	48% 5% 8% 21% 15% 2	2008
	21st to end	Night	44% 6% 11% 20% 16% 2	1890
May	1st to 10th	Night	48% 6% 10% 16% 15% 5%	5264
	11th to 20th	Night	43% 7% 13% 20% 14% 2	4681
	21st to end	Night	38% 5% 12% 26% 17% 2	5115
June	1st to 10th	Night	37% 6% 10% 25% 19% 2	1680
	11th to 20th	Night	36% 6% 13% 23% 21% 2	1680
	21st to end	Night	37% 6% 13% 26% 17% 1	1501
July	1st to 10th	Night	32% 6% 14% 25% 20% 2	3472
	11th to 20th	Night	30% 7% 13% 31% 19% 1	3552
	21st to end	Night	29% 7% 11% 30% 21% 1	4241
August	1st to 10th	Night	35% 6% 13% 28% 16% 2	2904
	11th to 20th	Night	32% 6% 15% 33% 13% 1	2902
	21st to end	Night	32% 7% 14% 32% 13% 1	3371
September	1st to 10th	Night	33% 7% 15% 30% 14% 1	2000
	11th to 20th	Night	29% 5% 11% 37% 18% 1	2117
	21st to end	Night	42% 6% 12% 28% 12% 1	2240
October	1st to 10th	Night	32% 6% 10% 28% 24% 1	3920
	11th to 20th	Night	42% 6% 13% 27% 12%	3899
	21st to end	Night	39% 7% 16% 26% 11% 1	4252
November	1st to 10th	Night	45% 5% 12% 24% 12% 1	2740
	11th to 20th	Night	51% 7% 13% 18% 10% 1	2940
	21st to end	Night	56% 7% 17% 16% 4	2940
December	1st to 10th	Night	62% 8% 12% 14% 4	4720
	11th to 20th	Night	61% 7% 11% 13% 8%	5348
	21st to end	Night	68% 7% 10% 9% 5%	7150

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% 33% 21% 5% 1	220
	11th to 20th	Day	23% 24% 32% 15% 4 1	303
	21st to end	Day	23% 20% 36% 18% 4	363
February	1st to 10th	Day	25% 22% 35% 15% 3 1	330
	11th to 20th	Day	22% 23% 39% 13% 2	330
	21st to end	Day	30% 24% 31% 14% 1	289
March	1st to 10th	Day	21% 16% 37% 21% 5%	540
	11th to 20th	Day	22% 18% 37% 18% 4 1	540
	21st to end	Day	27% 18% 30% 20% 5% 1	594
April	1st to 10th	Day	22% 22% 32% 18% 5%	540
	11th to 20th	Day	28% 16% 28% 18% 7% 3	532
	21st to end	Day	24% 15% 33% 19% 7% 2	540
May	1st to 10th	Day	24% 10% 32% 21% 8% 4	543
	11th to 20th	Day	16% 10% 32% 26% 11% 5%	567
	21st to end	Day	17% 10% 28% 27% 13% 5%	617
June	1st to 10th	Day	13% 12% 33% 29% 11% 2	570
	11th to 20th	Day	15% 10% 28% 31% 14% 2	570
	21st to end	Day	17% 7% 29% 33% 10% 3	730
July	1st to 10th	Day	10% 5% 24% 34% 21% 5%	551
	11th to 20th	Day	12% 4 24% 32% 19% 8%	524
	21st to end	Day	9% 3 27% 35% 18% 7%	576
August	1st to 10th	Day	12% 5% 21% 30% 21% 10%	526
	11th to 20th	Day	10% 4 24% 29% 23% 11%	519
	21st to end	Day	11% 7% 23% 30% 19% 9%	583
September	1st to 10th	Day	12% 8% 27% 25% 17% 12%	530
	11th to 20th	Day	9% 5% 21% 25% 24% 16%	530
	21st to end	Day	15% 9% 27% 25% 18% 6%	530
October	1st to 10th	Day	19% 10% 27% 23% 14% 6%	530
	11th to 20th	Day	19% 15% 36% 20% 8% 2	530
	21st to end	Day	28% 13% 29% 24% 5%	583
November	1st to 10th	Day	20% 20% 30% 21% 8% 1	310
	11th to 20th	Day	23% 22% 32% 16% 5% 2	220
	21st to end	Day	24% 15% 43% 17% 2	220
December	1st to 10th	Day	26% 15% 36% 17% 5%	220
	11th to 20th	Day	26% 24% 26% 19% 5%	220
	21st to end	Day	29% 18% 38% 13% 2 1	242
January	1st to 10th	Night	23% 14% 38% 21% 5%	840
	11th to 20th	Night	25% 15% 32% 23% 4	840
	21st to end	Night	19% 11% 40% 24% 6%	924
February	1st to 10th	Night	19% 15% 39% 24% 3	840
	11th to 20th	Night	21% 14% 36% 25% 3	823
	21st to end	Night	20% 15% 39% 22% 4	692
March	1st to 10th	Night	19% 14% 37% 25% 4	840
	11th to 20th	Night	21% 16% 36% 21% 5%	840
	21st to end	Night	22% 11% 35% 25% 7%	924
April	1st to 10th	Night	23% 13% 35% 25% 3	840
	11th to 20th	Night	18% 12% 37% 25% 8% 1	764
	21st to end	Night	18% 9% 33% 31% 9%	630
May	1st to 10th	Night	18% 5% 30% 32% 13% 2	630
	11th to 20th	Night	17% 3 34% 34% 11% 1	430
	21st to end	Night	13% 5% 29% 36% 17%	455
June	1st to 10th	Night	15% 3 29% 39% 14% 1	420
	11th to 20th	Night	11% 6% 30% 38% 15%	420
	21st to end	Night	11% 6% 24% 45% 14%	420
July	1st to 10th	Night	7% 3 23% 46% 20% 1	390
	11th to 20th	Night	11% 2 24% 41% 21% 2	388
	21st to end	Night	7% 3 19% 48% 21% 1	625
August	1st to 10th	Night	10% 1 16% 43% 28% 2	597
	11th to 20th	Night	8% 2 16% 43% 27% 3	594
	21st to end	Night	11% 4 22% 36% 25% 3	743
September	1st to 10th	Night	11% 5% 25% 35% 20% 5%	800
	11th to 20th	Night	12% 3 19% 33% 27% 5%	800
	21st to end	Night	18% 6% 22% 31% 20% 4	800
October	1st to 10th	Night	17% 6% 28% 29% 18% 3	800
	11th to 20th	Night	21% 9% 31% 29% 9% 1	800
	21st to end	Night	24% 9% 32% 30% 5%	880
November	1st to 10th	Night	21% 11% 29% 29% 9% 1	820
	11th to 20th	Night	21% 13% 34% 24% 7% 1	840
	21st to end	Night	26% 10% 34% 25% 5%	840
December	1st to 10th	Night	27% 12% 36% 20% 5%	840
	11th to 20th	Night	23% 14% 40% 21% 3	840
	21st to end	Night	30% 12% 35% 21% 2	924

Page generated at 2026-06-28 02:10:44. Version ac07

Copyright © 2026 Attilla Danko.