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 2025-02-21.

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% 10% 4 9% 5% 5% 5% 4 6% 7% 31%	109051
	Night	15% 10% 4 9% 5% 4 5% 4 5% 7% 33%	109456
Transparency	Day	49% 8% 13% 19% 10% 1	112691
	Night	48% 7% 13% 19% 11% 1	113979
Seeing	Day	19% 13% 28% 23% 12% 5%	14985
	Night	19% 11% 30% 28% 11% 1	24379

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	12% 15% 6% 15% 6% 5% 5% 4 4 5% 23%	3689
	11th to 20th	Day	10% 20% 8% 20% 9% 6% 4 3 3 4 13%	4026
	21st to end	Day	19% 17% 7% 16% 6% 5% 4 3 3 4 16%	4466
February	1st to 10th	Day	16% 15% 5% 12% 7% 6% 5% 3 4 6% 20%	1800
	11th to 20th	Day	13% 14% 7% 14% 7% 4 4 4 4 6% 23%	1753
	21st to end	Day	17% 14% 4 11% 6% 5% 5% 3 4 5% 25%	1508
March	1st to 10th	Day	20% 13% 4 9% 5% 4 4 3 4 6% 28%	3421
	11th to 20th	Day	11% 14% 5% 10% 6% 5% 4 4 6% 6% 29%	3480
	21st to end	Day	17% 10% 3 10% 5% 5% 4 3 5% 6% 32%	3815
April	1st to 10th	Day	16% 13% 4 9% 6% 4 5% 3 5% 6% 29%	2204
	11th to 20th	Day	19% 9% 3 7% 5% 5% 4 4 5% 7% 34%	2363
	21st to end	Day	20% 10% 3 8% 4 4 5% 3 4 5% 33%	2470
May	1st to 10th	Day	18% 7% 2 8% 6% 5% 5% 4 5% 7% 33%	4108
	11th to 20th	Day	16% 10% 3 8% 5% 5% 5% 4 6% 8% 31%	4229
	21st to end	Day	11% 5% 3 6% 4 4 5% 4 5% 7% 47%	4837
June	1st to 10th	Day	13% 6% 3 6% 5% 4 5% 5% 7% 8% 38%	2660
	11th to 20th	Day	11% 7% 2 7% 6% 5% 5% 5% 7% 9% 38%	2660
	21st to end	Day	13% 5% 2 5% 5% 5% 5% 4 7% 9% 40%	2848
July	1st to 10th	Day	10% 4 2 6% 5% 5% 5% 5% 7% 11% 40%	4552
	11th to 20th	Day	10% 5% 2 5% 4 4 6% 5% 8% 10% 42%	4294
	21st to end	Day	7% 5% 2 7% 5% 5% 6% 5% 7% 10% 41%	4466
August	1st to 10th	Day	16% 6% 2 6% 4 5% 5% 5% 6% 9% 36%	4104
	11th to 20th	Day	10% 7% 3 6% 5% 5% 5% 6% 7% 10% 35%	4044
	21st to end	Day	8% 6% 2 6% 4 5% 6% 5% 7% 10% 41%	4404
September	1st to 10th	Day	12% 7% 3 6% 5% 5% 5% 4 6% 9% 39%	2280
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 6% 8% 46%	2107
	21st to end	Day	14% 6% 2 8% 5% 5% 5% 5% 6% 8% 34%	2086
October	1st to 10th	Day	17% 7% 4 8% 4 4 4 4 5% 6% 36%	1900
	11th to 20th	Day	20% 8% 3 8% 5% 4 5% 4 6% 7% 31%	1900
	21st to end	Day	23% 10% 3 8% 6% 4 5% 4 5% 7% 24%	2090
November	1st to 10th	Day	14% 9% 3 8% 6% 5% 5% 4 6% 7% 34%	1741
	11th to 20th	Day	15% 13% 4 7% 6% 4 5% 4 7% 8% 27%	1600
	21st to end	Day	19% 15% 4 9% 5% 5% 5% 3 6% 6% 22%	1600
December	1st to 10th	Day	17% 17% 5% 12% 7% 6% 6% 5% 6% 6% 14%	2600
	11th to 20th	Day	21% 19% 5% 9% 4 3 4 4 5% 5% 21%	2986
	21st to end	Day	26% 19% 6% 10% 5% 4 5% 3 4 4 13%	3960
January	1st to 10th	Night	14% 12% 4 13% 7% 5% 5% 4 6% 6% 24%	6239
	11th to 20th	Night	12% 15% 7% 17% 9% 6% 6% 4 6% 5% 15%	5859
	21st to end	Night	18% 15% 6% 13% 5% 4 4 3 5% 5% 22%	6490
February	1st to 10th	Night	17% 15% 4 10% 8% 5% 5% 4 5% 6% 22%	2600
	11th to 20th	Night	15% 12% 4 10% 7% 5% 5% 4 6% 7% 25%	2533
	21st to end	Night	16% 12% 5% 11% 5% 5% 5% 3 6% 6% 25%	1944
March	1st to 10th	Night	18% 10% 3 7% 6% 4 4 4 5% 5% 33%	3418
	11th to 20th	Night	12% 11% 4 7% 5% 4 4 3 5% 8% 37%	3479
	21st to end	Night	16% 11% 2 7% 4 4 4 3 5% 5% 40%	3817
April	1st to 10th	Night	19% 9% 3 7% 5% 5% 5% 4 5% 6% 33%	1976
	11th to 20th	Night	17% 9% 3 6% 5% 4 5% 4 4 6% 37%	1782
	21st to end	Night	15% 7% 3 8% 5% 5% 4 3 6% 9% 36%	1710
May	1st to 10th	Night	18% 8% 3 6% 4 4 3 3 5% 6% 39%	2833
	11th to 20th	Night	12% 9% 3 9% 5% 5% 5% 5% 6% 7% 34%	2661
	21st to end	Night	11% 4 2 5% 3 4 4 4 6% 8% 50%	2738
June	1st to 10th	Night	11% 5% 2 6% 4 5% 4 5% 7% 8% 43%	1520
	11th to 20th	Night	10% 5% 3 5% 4 5% 6% 5% 6% 9% 44%	1511
	21st to end	Night	11% 5% 2 5% 5% 4 5% 4 6% 7% 46%	1330
July	1st to 10th	Night	6% 4 2 6% 4 4 4 3 5% 9% 53%	2386
	11th to 20th	Night	10% 4 2 5% 3 3 4 3 5% 9% 51%	2648
	21st to end	Night	6% 4 2 5% 5% 4 5% 4 7% 8% 50%	3087
August	1st to 10th	Night	10% 5% 2 7% 4 4 5% 3 7% 8% 44%	2825
	11th to 20th	Night	11% 6% 2 5% 4 4 5% 3 6% 7% 47%	2785
	21st to end	Night	8% 4 2 6% 3 4 5% 3 6% 9% 49%	3218
September	1st to 10th	Night	10% 5% 3 7% 5% 4 4 3 5% 8% 47%	1900
	11th to 20th	Night	10% 3 2 5% 4 3 4 3 5% 7% 54%	2070
	21st to end	Night	16% 6% 3 6% 5% 4 5% 3 5% 6% 40%	2093
October	1st to 10th	Night	15% 7% 3 6% 4 4 4 3 5% 7% 43%	2280
	11th to 20th	Night	18% 9% 2 6% 5% 4 5% 3 5% 7% 36%	2280
	21st to end	Night	21% 8% 3 8% 5% 5% 5% 3 5% 6% 31%	2508
November	1st to 10th	Night	14% 8% 3 6% 4 3 4 5% 6% 7% 39%	2552
	11th to 20th	Night	16% 12% 2 8% 5% 5% 5% 4 6% 7% 29%	2800
	21st to end	Night	20% 11% 3 8% 5% 5% 5% 5% 6% 8% 26%	2800
December	1st to 10th	Night	15% 14% 4 11% 6% 6% 6% 5% 7% 8% 18%	4580
	11th to 20th	Night	17% 18% 4 9% 5% 5% 4 3 4 6% 25%	5208
	21st to end	Night	25% 18% 6% 10% 5% 4 4 3 4 5% 16%	6996

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	61% 8% 9% 11% 10%	3690
	11th to 20th	Day	75% 5% 9% 7% 3	4060
	21st to end	Day	71% 7% 9% 7% 6%	4466
February	1st to 10th	Day	66% 7% 11% 13% 4	1800
	11th to 20th	Day	63% 5% 10% 15% 6% 1	1762
	21st to end	Day	62% 6% 10% 13% 6% 1	1508
March	1st to 10th	Day	58% 6% 11% 20% 5%	3424
	11th to 20th	Day	52% 8% 15% 18% 6% 2	3480
	21st to end	Day	50% 8% 11% 19% 10% 1	3815
April	1st to 10th	Day	55% 6% 11% 15% 12%	2204
	11th to 20th	Day	50% 6% 11% 20% 11% 1	2363
	21st to end	Day	52% 6% 11% 18% 11% 2	2470
May	1st to 10th	Day	47% 8% 13% 18% 11% 3	4120
	11th to 20th	Day	48% 10% 14% 20% 7% 1	4233
	21st to end	Day	35% 8% 13% 21% 19% 4	4837
June	1st to 10th	Day	40% 8% 13% 23% 14% 2	2660
	11th to 20th	Day	39% 9% 14% 22% 15% 1	2660
	21st to end	Day	39% 8% 14% 24% 15%	2848
July	1st to 10th	Day	34% 8% 16% 25% 14% 2	4482
	11th to 20th	Day	33% 8% 15% 32% 12%	4219
	21st to end	Day	35% 9% 14% 21% 18% 1	4324
August	1st to 10th	Day	43% 9% 13% 22% 13% 1	4091
	11th to 20th	Day	40% 10% 17% 24% 9% 1	4083
	21st to end	Day	35% 9% 13% 31% 11% 1	4404
September	1st to 10th	Day	40% 8% 15% 24% 12% 1	2280
	11th to 20th	Day	34% 7% 13% 29% 16%	2107
	21st to end	Day	44% 9% 14% 23% 9% 1	2086
October	1st to 10th	Day	38% 7% 15% 24% 15% 1	3160
	11th to 20th	Day	39% 6% 16% 22% 16%	3140
	21st to end	Day	49% 7% 15% 22% 7%	3428
November	1st to 10th	Day	48% 8% 13% 22% 8% 1	1741
	11th to 20th	Day	53% 9% 15% 15% 9%	1600
	21st to end	Day	60% 8% 15% 13% 4	1600
December	1st to 10th	Day	67% 9% 13% 8% 3	2600
	11th to 20th	Day	64% 7% 10% 11% 7%	2986
	21st to end	Day	73% 7% 7% 7% 5%	3960
January	1st to 10th	Night	57% 9% 11% 15% 7% 1	6239
	11th to 20th	Night	67% 8% 11% 10% 4	5900
	21st to end	Night	63% 7% 9% 11% 9% 1	6490
February	1st to 10th	Night	61% 7% 11% 15% 5%	2600
	11th to 20th	Night	56% 7% 14% 15% 8%	2535
	21st to end	Night	58% 6% 12% 16% 8%	1944
March	1st to 10th	Night	51% 7% 13% 22% 6% 1	3428
	11th to 20th	Night	43% 7% 18% 19% 12% 1	3480
	21st to end	Night	44% 7% 10% 22% 16% 2	3817
April	1st to 10th	Night	50% 7% 11% 18% 13% 1	1976
	11th to 20th	Night	47% 7% 9% 20% 16% 2	1782
	21st to end	Night	45% 7% 11% 18% 15% 3	1710
May	1st to 10th	Night	44% 6% 12% 18% 15% 4	2840
	11th to 20th	Night	44% 10% 16% 20% 7% 2	2662
	21st to end	Night	30% 8% 14% 23% 24% 2	2739
June	1st to 10th	Night	37% 8% 11% 25% 17% 2	1520
	11th to 20th	Night	35% 8% 13% 25% 17% 2	1511
	21st to end	Night	36% 7% 15% 23% 18% 1	1330
July	1st to 10th	Night	29% 6% 12% 26% 22% 5%	2346
	11th to 20th	Night	30% 7% 14% 32% 17% 1	2600
	21st to end	Night	30% 9% 16% 25% 18% 2	2988
August	1st to 10th	Night	35% 9% 13% 26% 16% 2	2814
	11th to 20th	Night	34% 8% 17% 28% 12% 1	2812
	21st to end	Night	30% 8% 13% 32% 17% 1	3218
September	1st to 10th	Night	36% 6% 13% 26% 16% 2	1900
	11th to 20th	Night	29% 7% 13% 31% 19% 1	2070
	21st to end	Night	43% 7% 13% 26% 12% 1	2093
October	1st to 10th	Night	31% 6% 10% 28% 23% 1	3800
	11th to 20th	Night	41% 6% 13% 25% 15%	3779
	21st to end	Night	40% 7% 15% 26% 12% 1	4120
November	1st to 10th	Night	41% 8% 14% 23% 13% 1	2552
	11th to 20th	Night	52% 8% 13% 17% 9% 1	2800
	21st to end	Night	55% 8% 17% 15% 5%	2800
December	1st to 10th	Night	61% 9% 16% 11% 3	4580
	11th to 20th	Night	60% 6% 11% 13% 9% 1	5208
	21st to end	Night	70% 7% 10% 8% 5%	6996

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	25% 21% 29% 16% 8%	220
	11th to 20th	Day	26% 22% 37% 10% 4 1	300
	21st to end	Day	24% 20% 34% 18% 3 1	330
February	1st to 10th	Day	25% 25% 35% 11% 5%	300
	11th to 20th	Day	27% 23% 34% 15% 1	300
	21st to end	Day	36% 25% 28% 11%	225
March	1st to 10th	Day	24% 13% 36% 20% 6%	449
	11th to 20th	Day	25% 14% 37% 19% 5% 1	460
	21st to end	Day	30% 14% 30% 18% 8%	506
April	1st to 10th	Day	21% 19% 33% 20% 6% 1	460
	11th to 20th	Day	26% 17% 26% 19% 9% 3	452
	21st to end	Day	25% 12% 31% 21% 8% 3	460
May	1st to 10th	Day	24% 13% 25% 24% 9% 5%	463
	11th to 20th	Day	18% 10% 27% 25% 16% 5%	487
	21st to end	Day	12% 9% 25% 30% 17% 7%	529
June	1st to 10th	Day	13% 14% 31% 26% 13% 3	490
	11th to 20th	Day	13% 10% 27% 29% 16% 5%	490
	21st to end	Day	14% 8% 31% 32% 11% 4	678
July	1st to 10th	Day	8% 7% 22% 29% 24% 9%	558
	11th to 20th	Day	12% 5% 25% 26% 19% 11%	484
	21st to end	Day	8% 3 27% 35% 21% 6%	532
August	1st to 10th	Day	12% 5% 21% 28% 23% 12%	486
	11th to 20th	Day	12% 4 22% 26% 22% 14%	479
	21st to end	Day	11% 6% 22% 28% 21% 11%	539
September	1st to 10th	Day	12% 10% 21% 26% 18% 13%	490
	11th to 20th	Day	9% 5% 18% 25% 27% 17%	490
	21st to end	Day	15% 12% 26% 24% 16% 7%	490
October	1st to 10th	Day	20% 11% 27% 22% 13% 6%	490
	11th to 20th	Day	20% 15% 34% 20% 8% 3	490
	21st to end	Day	27% 14% 31% 20% 8% 1	539
November	1st to 10th	Day	22% 22% 32% 16% 6% 2	299
	11th to 20th	Day	26% 23% 29% 16% 6% 2	200
	21st to end	Day	29% 20% 33% 17% 2 1	200
December	1st to 10th	Day	27% 22% 34% 12% 5% 1	200
	11th to 20th	Day	28% 25% 30% 15% 3	200
	21st to end	Day	30% 19% 37% 10% 4 1	220
January	1st to 10th	Night	22% 18% 35% 18% 6% 1	800
	11th to 20th	Night	29% 16% 33% 20% 3	800
	21st to end	Night	20% 14% 37% 24% 5%	880
February	1st to 10th	Night	24% 16% 36% 22% 2	800
	11th to 20th	Night	22% 15% 36% 21% 5%	783
	21st to end	Night	23% 18% 34% 22% 3	629
March	1st to 10th	Night	19% 13% 37% 25% 7%	760
	11th to 20th	Night	22% 14% 34% 23% 6% 1	760
	21st to end	Night	20% 12% 33% 25% 9% 1	836
April	1st to 10th	Night	23% 13% 32% 28% 5%	760
	11th to 20th	Night	21% 13% 33% 24% 9% 1	658
	21st to end	Night	17% 9% 33% 32% 9%	570
May	1st to 10th	Night	18% 6% 31% 29% 14% 2	570
	11th to 20th	Night	14% 5% 30% 39% 11% 1	475
	21st to end	Night	13% 5% 28% 35% 18% 1	411
June	1st to 10th	Night	12% 5% 33% 38% 12% 1	380
	11th to 20th	Night	11% 5% 29% 40% 13% 1	380
	21st to end	Night	12% 5% 27% 42% 14%	380
July	1st to 10th	Night	6% 1 25% 45% 21% 2	370
	11th to 20th	Night	10% 2 24% 40% 22% 2	444
	21st to end	Night	9% 3 18% 47% 21% 2	624
August	1st to 10th	Night	7% 2 18% 43% 26% 3	567
	11th to 20th	Night	9% 2 17% 38% 32% 2	564
	21st to end	Night	11% 3 21% 35% 29% 2	682
September	1st to 10th	Night	11% 5% 22% 34% 22% 5%	760
	11th to 20th	Night	11% 5% 17% 34% 29% 5%	760
	21st to end	Night	17% 7% 22% 29% 20% 5%	760
October	1st to 10th	Night	17% 8% 28% 27% 18% 3	760
	11th to 20th	Night	22% 11% 29% 28% 9% 1	760
	21st to end	Night	25% 11% 31% 28% 4	836
November	1st to 10th	Night	19% 12% 31% 27% 10% 2	780
	11th to 20th	Night	21% 16% 32% 22% 8% 1	800
	21st to end	Night	26% 12% 34% 22% 6%	800
December	1st to 10th	Night	27% 17% 32% 19% 6%	800
	11th to 20th	Night	24% 19% 36% 18% 4	800
	21st to end	Night	31% 12% 34% 21% 3	880

Page generated at 2025-02-18 03:26:26. Version ac07

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