Brantford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brantford clear sky chart from 2005-11-06 to 2026-06-16.

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	14% 10% 4 9% 5% 5% 5% 4 5% 7% 32%	138157
	Night	14% 10% 4 9% 5% 4 5% 4 5% 7% 33%	133785
Transparency	Day	49% 7% 12% 20% 11% 1	141754
	Night	48% 7% 12% 19% 12% 1	138276
Seeing	Day	19% 13% 28% 22% 12% 5%	16730
	Night	19% 11% 30% 28% 11% 1	26009

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% 15% 6% 16% 6% 5% 5% 4 4 5% 19%	4781
	11th to 20th	Day	9% 22% 9% 19% 9% 7% 4 3 3 4 12%	5246
	21st to end	Day	15% 16% 6% 17% 7% 7% 5% 3 3 4 16%	5780
February	1st to 10th	Day	15% 15% 5% 12% 7% 6% 5% 3 5% 6% 21%	1890
	11th to 20th	Day	14% 14% 7% 13% 7% 5% 4 4 4 6% 23%	1843
	21st to end	Day	16% 15% 4 11% 6% 5% 5% 3 5% 5% 23%	1662
March	1st to 10th	Day	18% 12% 5% 11% 6% 4 4 3 4 5% 29%	5030
	11th to 20th	Day	11% 12% 4 10% 6% 5% 5% 4 6% 7% 30%	5090
	21st to end	Day	17% 11% 4 10% 5% 5% 4 3 4 5% 30%	5586
April	1st to 10th	Day	17% 13% 4 9% 6% 4 5% 3 5% 6% 29%	2436
	11th to 20th	Day	18% 10% 3 8% 5% 5% 4 4 5% 6% 34%	2615
	21st to end	Day	19% 10% 3 8% 4 4 5% 3 5% 5% 34%	2730
May	1st to 10th	Day	18% 9% 3 8% 5% 5% 5% 4 5% 6% 32%	7642
	11th to 20th	Day	15% 9% 3 8% 5% 5% 4 4 5% 8% 34%	7900
	21st to end	Day	16% 5% 2 6% 4 4 5% 4 5% 6% 43%	9060
June	1st to 10th	Day	12% 6% 3 6% 5% 4 5% 5% 7% 8% 40%	2940
	11th to 20th	Day	10% 7% 2 7% 6% 5% 6% 4 7% 9% 38%	2870
	21st to end	Day	12% 5% 2 5% 5% 5% 5% 4 7% 10% 40%	2998
July	1st to 10th	Day	9% 5% 2 6% 5% 5% 5% 5% 7% 10% 41%	6527
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 5% 7% 9% 43%	6158
	21st to end	Day	8% 4 2 6% 4 4 6% 4 6% 9% 47%	6424
August	1st to 10th	Day	16% 6% 2 6% 4 5% 5% 5% 6% 9% 37%	4234
	11th to 20th	Day	10% 7% 3 6% 5% 5% 5% 6% 7% 10% 35%	4174
	21st to end	Day	8% 6% 2 6% 4 5% 6% 5% 7% 10% 41%	4543
September	1st to 10th	Day	12% 6% 2 6% 5% 5% 5% 4 6% 9% 40%	2400
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 6% 8% 48%	2218
	21st to end	Day	14% 6% 2 8% 5% 5% 5% 5% 6% 8% 34%	2196
October	1st to 10th	Day	17% 7% 4 7% 4 4 4 4 5% 7% 38%	2000
	11th to 20th	Day	20% 8% 3 7% 5% 4 5% 4 7% 7% 31%	2000
	21st to end	Day	23% 10% 3 8% 6% 5% 5% 4 5% 7% 25%	2200
November	1st to 10th	Day	14% 10% 3 8% 6% 5% 5% 4 6% 7% 33%	1830
	11th to 20th	Day	14% 13% 4 8% 6% 4 5% 4 7% 8% 27%	1680
	21st to end	Day	18% 15% 4 10% 6% 5% 5% 4 6% 6% 22%	1680
December	1st to 10th	Day	17% 18% 5% 12% 7% 6% 6% 5% 6% 6% 14%	2680
	11th to 20th	Day	21% 19% 5% 9% 4 3 4 4 5% 5% 21%	3066
	21st to end	Day	26% 19% 6% 11% 6% 4 5% 3 4 4 13%	4048
January	1st to 10th	Night	14% 14% 5% 14% 7% 5% 5% 4 6% 6% 21%	8096
	11th to 20th	Night	10% 17% 7% 16% 8% 5% 5% 4 5% 5% 16%	7639
	21st to end	Night	14% 14% 6% 14% 6% 6% 5% 4 5% 6% 21%	8401
February	1st to 10th	Night	16% 15% 4 10% 8% 5% 5% 4 5% 6% 23%	2730
	11th to 20th	Night	15% 12% 4 10% 6% 5% 5% 4 6% 7% 25%	2663
	21st to end	Night	15% 13% 5% 12% 5% 5% 5% 3 6% 6% 24%	2141
March	1st to 10th	Night	15% 10% 3 8% 7% 4 5% 4 6% 6% 33%	5029
	11th to 20th	Night	10% 9% 3 8% 5% 4 5% 4 6% 9% 37%	5089
	21st to end	Night	18% 11% 3 7% 4 3 4 3 5% 5% 37%	5588
April	1st to 10th	Night	18% 9% 4 8% 5% 5% 4 4 5% 6% 31%	2184
	11th to 20th	Night	17% 9% 3 7% 5% 4 5% 4 5% 6% 36%	1972
	21st to end	Night	14% 7% 2 8% 5% 5% 4 3 6% 8% 37%	1890
May	1st to 10th	Night	19% 7% 3 7% 5% 4 4 4 5% 6% 35%	5257
	11th to 20th	Night	14% 9% 3 9% 5% 5% 5% 4 5% 6% 35%	4943
	21st to end	Night	19% 5% 2 5% 3 4 4 3 5% 7% 44%	5114
June	1st to 10th	Night	11% 5% 2 5% 4 5% 4 4 7% 8% 44%	1680
	11th to 20th	Night	9% 5% 3 5% 4 5% 6% 5% 6% 9% 43%	1630
	21st to end	Night	11% 5% 2 5% 5% 4 5% 4 6% 7% 46%	1400
July	1st to 10th	Night	6% 5% 2 6% 4 4 5% 4 5% 9% 49%	3414
	11th to 20th	Night	9% 5% 3 6% 3 4 4 4 5% 8% 49%	3784
	21st to end	Night	7% 4 2 5% 4 4 5% 4 6% 7% 51%	4428
August	1st to 10th	Night	10% 5% 2 7% 4 4 5% 3 7% 8% 45%	2915
	11th to 20th	Night	11% 5% 2 5% 3 4 5% 3 6% 7% 47%	2875
	21st to end	Night	8% 4 2 6% 3 4 5% 3 6% 9% 49%	3320
September	1st to 10th	Night	10% 5% 3 7% 5% 4 4 3 5% 8% 47%	2000
	11th to 20th	Night	9% 3 2 4 4 3 4 3 5% 6% 55%	2179
	21st to end	Night	16% 6% 3 6% 5% 4 4 3 5% 6% 41%	2203
October	1st to 10th	Night	15% 7% 3 5% 4 4 3 3 5% 7% 45%	2400
	11th to 20th	Night	17% 9% 2 6% 5% 4 5% 3 5% 7% 36%	2400
	21st to end	Night	21% 8% 3 8% 5% 5% 5% 3 5% 6% 32%	2640
November	1st to 10th	Night	14% 8% 3 6% 4 3 4 5% 6% 7% 39%	2683
	11th to 20th	Night	16% 12% 2 8% 6% 5% 5% 4 6% 7% 29%	2940
	21st to end	Night	20% 12% 3 8% 5% 5% 4 5% 6% 8% 25%	2940
December	1st to 10th	Night	15% 15% 4 11% 6% 5% 6% 5% 7% 8% 19%	4720
	11th to 20th	Night	17% 18% 4 10% 5% 5% 4 3 5% 6% 25%	5348
	21st to end	Night	25% 18% 6% 10% 5% 4 4 3 4 5% 16%	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	65% 8% 9% 10% 8%	4782
	11th to 20th	Day	77% 5% 7% 7% 4	5280
	21st to end	Day	70% 7% 10% 8% 5%	5780
February	1st to 10th	Day	65% 6% 10% 13% 5%	1890
	11th to 20th	Day	63% 5% 10% 15% 6% 1	1852
	21st to end	Day	62% 6% 11% 14% 6% 1	1662
March	1st to 10th	Day	56% 6% 14% 16% 7%	5033
	11th to 20th	Day	50% 7% 17% 18% 6% 2	5090
	21st to end	Day	54% 7% 10% 19% 10% 1	5586
April	1st to 10th	Day	55% 6% 11% 16% 11% 1	2436
	11th to 20th	Day	51% 6% 11% 21% 11% 1	2615
	21st to end	Day	52% 6% 11% 19% 10% 2	2730
May	1st to 10th	Day	50% 7% 11% 18% 9% 4	7651
	11th to 20th	Day	46% 8% 12% 21% 11% 2	7904
	21st to end	Day	40% 7% 10% 24% 18% 2	9061
June	1st to 10th	Day	40% 8% 12% 23% 16% 2	2940
	11th to 20th	Day	39% 9% 14% 22% 15% 1	2870
	21st to end	Day	39% 8% 14% 24% 16%	2998
July	1st to 10th	Day	34% 8% 14% 25% 16% 2	6458
	11th to 20th	Day	32% 8% 14% 29% 15% 1	6083
	21st to end	Day	32% 8% 13% 27% 19% 1	6240
August	1st to 10th	Day	42% 9% 13% 22% 13% 1	4221
	11th to 20th	Day	40% 9% 17% 24% 9% 1	4213
	21st to end	Day	35% 9% 13% 32% 11% 1	4543
September	1st to 10th	Day	39% 8% 15% 25% 12% 1	2400
	11th to 20th	Day	33% 7% 13% 31% 15%	2218
	21st to end	Day	44% 9% 14% 23% 9% 1	2196
October	1st to 10th	Day	37% 7% 15% 25% 15% 1	3260
	11th to 20th	Day	39% 6% 16% 22% 17%	3240
	21st to end	Day	49% 7% 15% 22% 8%	3538
November	1st to 10th	Day	48% 8% 13% 22% 8% 1	1830
	11th to 20th	Day	53% 8% 15% 15% 9% 1	1680
	21st to end	Day	60% 8% 15% 13% 4	1680
December	1st to 10th	Day	67% 9% 12% 9% 3	2680
	11th to 20th	Day	64% 7% 10% 11% 7%	3066
	21st to end	Day	73% 7% 7% 7% 5%	4048
January	1st to 10th	Night	60% 9% 11% 14% 6% 1	8096
	11th to 20th	Night	66% 7% 9% 10% 6% 1	7680
	21st to end	Night	62% 7% 9% 13% 9% 1	8401
February	1st to 10th	Night	61% 7% 11% 16% 5% 1	2730
	11th to 20th	Night	56% 7% 14% 16% 7%	2665
	21st to end	Night	58% 6% 12% 16% 7%	2141
March	1st to 10th	Night	49% 7% 15% 18% 9% 2	5039
	11th to 20th	Night	41% 7% 19% 21% 11% 1	5090
	21st to end	Night	48% 6% 10% 19% 16% 2	5588
April	1st to 10th	Night	51% 7% 11% 17% 12% 1	2184
	11th to 20th	Night	47% 6% 9% 20% 15% 2	1972
	21st to end	Night	44% 7% 12% 19% 15% 3	1890
May	1st to 10th	Night	47% 7% 11% 15% 15% 6%	5264
	11th to 20th	Night	46% 9% 12% 21% 11% 2	4944
	21st to end	Night	39% 6% 10% 25% 18% 2	5115
June	1st to 10th	Night	36% 8% 10% 25% 18% 3	1680
	11th to 20th	Night	35% 8% 14% 25% 17% 2	1630
	21st to end	Night	36% 7% 15% 22% 19% 1	1400
July	1st to 10th	Night	31% 7% 13% 25% 20% 4	3374
	11th to 20th	Night	32% 7% 12% 29% 18% 3	3736
	21st to end	Night	30% 7% 13% 25% 23% 3	4297
August	1st to 10th	Night	35% 8% 14% 25% 16% 2	2904
	11th to 20th	Night	33% 8% 17% 29% 12% 1	2902
	21st to end	Night	30% 8% 13% 32% 16% 1	3320
September	1st to 10th	Night	35% 6% 13% 28% 16% 2	2000
	11th to 20th	Night	28% 6% 13% 32% 19% 1	2179
	21st to end	Night	43% 6% 12% 25% 12% 1	2203
October	1st to 10th	Night	31% 6% 9% 29% 23% 1	3920
	11th to 20th	Night	41% 6% 13% 25% 15%	3899
	21st to end	Night	39% 6% 15% 27% 12% 1	4252
November	1st to 10th	Night	42% 7% 14% 23% 13% 1	2683
	11th to 20th	Night	52% 8% 13% 17% 9% 1	2940
	21st to end	Night	56% 8% 16% 14% 5%	2940
December	1st to 10th	Night	60% 9% 16% 12% 3	4720
	11th to 20th	Night	60% 6% 11% 14% 9% 1	5348
	21st to end	Night	70% 7% 9% 8% 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	26% 21% 30% 15% 7%	242
	11th to 20th	Day	28% 22% 36% 10% 3 1	330
	21st to end	Day	25% 20% 34% 17% 4 1	363
February	1st to 10th	Day	23% 25% 34% 12% 5%	330
	11th to 20th	Day	27% 22% 35% 15% 1	330
	21st to end	Day	33% 24% 31% 11% 1	273
March	1st to 10th	Day	25% 15% 34% 19% 6%	528
	11th to 20th	Day	26% 16% 34% 17% 5% 1	540
	21st to end	Day	30% 15% 31% 17% 7%	594
April	1st to 10th	Day	23% 20% 31% 19% 5% 1	540
	11th to 20th	Day	25% 19% 25% 19% 9% 3	532
	21st to end	Day	26% 12% 31% 21% 7% 3	540
May	1st to 10th	Day	24% 14% 27% 22% 8% 4	543
	11th to 20th	Day	18% 11% 28% 24% 14% 4	567
	21st to end	Day	14% 10% 27% 27% 16% 6%	617
June	1st to 10th	Day	12% 14% 32% 26% 13% 3	570
	11th to 20th	Day	13% 11% 29% 28% 14% 5%	550
	21st to end	Day	14% 8% 31% 32% 11% 4	728
July	1st to 10th	Day	8% 7% 23% 28% 24% 9%	602
	11th to 20th	Day	12% 6% 26% 26% 20% 11%	524
	21st to end	Day	9% 3 26% 35% 21% 6%	576
August	1st to 10th	Day	11% 5% 20% 29% 23% 12%	526
	11th to 20th	Day	12% 5% 21% 27% 22% 14%	519
	21st to end	Day	11% 6% 22% 29% 21% 11%	583
September	1st to 10th	Day	12% 10% 21% 25% 18% 14%	530
	11th to 20th	Day	9% 5% 17% 25% 28% 17%	530
	21st to end	Day	15% 11% 25% 25% 17% 7%	530
October	1st to 10th	Day	19% 11% 26% 23% 15% 6%	530
	11th to 20th	Day	19% 15% 35% 20% 7% 3	530
	21st to end	Day	27% 14% 31% 20% 7% 1	583
November	1st to 10th	Day	23% 22% 30% 16% 6% 2	328
	11th to 20th	Day	25% 23% 27% 16% 6% 2	220
	21st to end	Day	29% 22% 31% 16% 2	220
December	1st to 10th	Day	26% 22% 33% 14% 5% 1	220
	11th to 20th	Day	27% 25% 30% 15% 3	220
	21st to end	Day	31% 19% 37% 10% 3 1	242
January	1st to 10th	Night	22% 18% 36% 18% 5% 1	840
	11th to 20th	Night	28% 17% 32% 19% 3	840
	21st to end	Night	20% 15% 37% 23% 5%	924
February	1st to 10th	Night	23% 16% 36% 23% 2	840
	11th to 20th	Night	22% 15% 37% 22% 4	823
	21st to end	Night	23% 18% 35% 22% 2	692
March	1st to 10th	Night	19% 14% 36% 24% 6%	840
	11th to 20th	Night	23% 14% 34% 23% 5%	840
	21st to end	Night	21% 13% 33% 25% 9% 1	924
April	1st to 10th	Night	23% 14% 32% 27% 4	840
	11th to 20th	Night	21% 13% 32% 25% 8% 1	728
	21st to end	Night	16% 9% 33% 33% 9%	630
May	1st to 10th	Night	19% 7% 32% 28% 13% 2	630
	11th to 20th	Night	15% 5% 30% 37% 11% 1	525
	21st to end	Night	15% 5% 29% 34% 17% 1	455
June	1st to 10th	Night	12% 5% 33% 39% 11%	420
	11th to 20th	Night	11% 6% 31% 39% 12% 1	410
	21st to end	Night	12% 5% 27% 42% 14%	400
July	1st to 10th	Night	6% 1 25% 46% 20% 2	390
	11th to 20th	Night	9% 2 24% 40% 22% 2	468
	21st to end	Night	9% 3 18% 47% 21% 2	657
August	1st to 10th	Night	7% 2 18% 43% 28% 3	597
	11th to 20th	Night	9% 2 16% 39% 31% 2	594
	21st to end	Night	10% 3 21% 36% 28% 2	718
September	1st to 10th	Night	11% 5% 22% 34% 23% 5%	800
	11th to 20th	Night	10% 5% 16% 34% 31% 4	800
	21st to end	Night	17% 7% 22% 29% 21% 5%	800
October	1st to 10th	Night	16% 8% 27% 28% 19% 3	800
	11th to 20th	Night	22% 11% 29% 28% 9% 1	800
	21st to end	Night	25% 11% 31% 29% 4	880
November	1st to 10th	Night	19% 13% 30% 27% 10% 2	820
	11th to 20th	Night	21% 17% 32% 22% 8% 1	840
	21st to end	Night	26% 13% 33% 22% 6%	840
December	1st to 10th	Night	27% 17% 32% 19% 6%	840
	11th to 20th	Night	23% 19% 37% 17% 4	840
	21st to end	Night	31% 12% 34% 20% 3	924

Page generated at 2026-06-13 02:31:44. Version ac07

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