Kemptville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kemptville 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	17% 10% 3 8% 5% 5% 5% 4 5% 6% 31%	138259
	Night	17% 12% 4 9% 5% 4 4 3 5% 6% 30%	134072
Transparency	Day	51% 7% 11% 21% 10% 1	141726
	Night	53% 6% 11% 19% 10% 1	138694
Seeing	Day	23% 16% 31% 20% 8% 2	16550
	Night	23% 14% 30% 25% 8% 1	25653

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% 18% 6% 14% 6% 6% 4 3 5% 5% 20%	4661
	11th to 20th	Day	12% 18% 7% 15% 7% 5% 4 3 4 5% 19%	4650
	21st to end	Day	10% 15% 6% 14% 9% 9% 5% 3 5% 4 19%	5364
February	1st to 10th	Day	16% 15% 4 12% 7% 4 4 3 4 5% 24%	1890
	11th to 20th	Day	13% 16% 5% 11% 7% 5% 5% 3 4 5% 26%	1864
	21st to end	Day	19% 15% 5% 11% 6% 5% 4 3 5% 5% 22%	1730
March	1st to 10th	Day	19% 14% 4 10% 5% 4 5% 3 4 6% 25%	4576
	11th to 20th	Day	11% 13% 4 9% 6% 5% 6% 4 6% 6% 30%	5079
	21st to end	Day	18% 11% 4 8% 5% 4 3 3 4 5% 37%	5909
April	1st to 10th	Day	22% 12% 4 7% 4 5% 4 3 4 5% 31%	2520
	11th to 20th	Day	22% 10% 3 7% 4 3 3 3 4 5% 35%	2494
	21st to end	Day	23% 10% 3 7% 5% 4 4 3 5% 5% 32%	2643
May	1st to 10th	Day	22% 10% 3 8% 5% 5% 5% 4 5% 7% 26%	8237
	11th to 20th	Day	17% 9% 3 8% 5% 4 4 4 6% 8% 32%	8221
	21st to end	Day	20% 9% 3 6% 4 4 4 3 5% 7% 34%	9060
June	1st to 10th	Day	21% 8% 3 7% 5% 5% 5% 4 6% 6% 31%	2940
	11th to 20th	Day	15% 5% 2 7% 4 5% 5% 6% 6% 7% 37%	2940
	21st to end	Day	19% 8% 2 7% 5% 5% 5% 4 6% 7% 32%	2940
July	1st to 10th	Day	13% 7% 3 7% 5% 5% 6% 5% 7% 9% 34%	6360
	11th to 20th	Day	11% 5% 2 6% 5% 5% 5% 4 6% 8% 42%	6360
	21st to end	Day	10% 5% 2 5% 4 4 4 4 7% 10% 44%	6926
August	1st to 10th	Day	15% 8% 3 7% 5% 5% 4 4 5% 7% 37%	4480
	11th to 20th	Day	16% 7% 2 6% 4 5% 5% 4 5% 8% 39%	4090
	21st to end	Day	15% 6% 2 6% 4 4 5% 3 7% 9% 38%	4312
September	1st to 10th	Day	13% 5% 3 6% 4 5% 4 4 6% 8% 42%	2400
	11th to 20th	Day	13% 4 2 6% 4 4 4 4 5% 8% 48%	2394
	21st to end	Day	18% 6% 2 5% 4 4 4 4 6% 7% 39%	2145
October	1st to 10th	Day	19% 8% 3 6% 6% 4 4 3 5% 5% 38%	2000
	11th to 20th	Day	19% 10% 3 9% 5% 5% 5% 4 5% 6% 30%	2000
	21st to end	Day	25% 11% 3 6% 5% 4 5% 3 4 5% 28%	2038
November	1st to 10th	Day	17% 10% 2 7% 5% 5% 5% 4 5% 6% 33%	1851
	11th to 20th	Day	17% 14% 4 8% 6% 5% 4 4 5% 6% 28%	1711
	21st to end	Day	21% 16% 5% 9% 5% 4 5% 3 5% 5% 21%	1680
December	1st to 10th	Day	20% 21% 5% 11% 6% 4 4 4 4 5% 15%	2680
	11th to 20th	Day	18% 15% 5% 13% 6% 5% 4 4 4 4 24%	3066
	21st to end	Day	22% 17% 5% 12% 6% 4 4 3 3 4 21%	4048
January	1st to 10th	Night	14% 19% 8% 13% 6% 4 4 3 4 5% 20%	8234
	11th to 20th	Night	12% 17% 7% 16% 7% 5% 5% 3 4 5% 17%	8235
	21st to end	Night	13% 15% 5% 12% 7% 6% 5% 4 5% 5% 23%	8799
February	1st to 10th	Night	14% 15% 6% 12% 7% 5% 4 4 5% 6% 22%	2730
	11th to 20th	Night	14% 14% 5% 13% 6% 4 4 3 5% 4 28%	2642
	21st to end	Night	15% 14% 4 11% 7% 4 4 4 4 5% 28%	2076
March	1st to 10th	Night	22% 14% 4 9% 5% 4 4 3 4 4 28%	5484
	11th to 20th	Night	14% 13% 4 8% 4 4 4 4 7% 7% 31%	5095
	21st to end	Night	19% 11% 3 8% 5% 4 3 3 4 5% 34%	5265
April	1st to 10th	Night	20% 11% 3 7% 6% 4 3 2 5% 5% 33%	2100
	11th to 20th	Night	21% 10% 2 8% 4 4 4 3 3 5% 35%	2075
	21st to end	Night	21% 9% 3 8% 4 4 3 3 4 6% 35%	1993
May	1st to 10th	Night	22% 10% 3 8% 5% 6% 6% 4 6% 7% 23%	4660
	11th to 20th	Night	15% 9% 3 7% 5% 4 4 3 5% 7% 37%	4639
	21st to end	Night	18% 8% 3 6% 5% 4 5% 4 6% 8% 33%	5114
June	1st to 10th	Night	16% 8% 3 8% 5% 5% 5% 4 6% 8% 33%	1680
	11th to 20th	Night	15% 6% 3 6% 4 5% 3 4 7% 7% 40%	1680
	21st to end	Night	18% 7% 3 6% 5% 4 4 4 6% 7% 35%	1680
July	1st to 10th	Night	13% 7% 3 8% 5% 5% 5% 4 7% 10% 34%	3600
	11th to 20th	Night	12% 6% 3 6% 4 4 4 4 5% 8% 44%	3600
	21st to end	Night	9% 6% 2 6% 4 4 5% 4 6% 8% 45%	3926
August	1st to 10th	Night	12% 7% 3 7% 4 4 5% 4 6% 8% 40%	2665
	11th to 20th	Night	13% 6% 3 7% 4 5% 4 4 5% 8% 41%	2926
	21st to end	Night	10% 6% 2 7% 4 5% 5% 4 6% 8% 41%	3586
September	1st to 10th	Night	12% 6% 2 6% 5% 4 4 3 5% 6% 47%	2000
	11th to 20th	Night	14% 5% 2 4 3 3 3 3 6% 6% 51%	2005
	21st to end	Night	16% 7% 2 7% 4 4 4 3 5% 7% 42%	2251
October	1st to 10th	Night	17% 6% 3 7% 5% 4 4 3 6% 7% 39%	2400
	11th to 20th	Night	20% 9% 3 6% 5% 4 5% 3 6% 6% 33%	2400
	21st to end	Night	24% 11% 2 7% 4 5% 4 4 5% 7% 28%	2801
November	1st to 10th	Night	19% 10% 3 7% 5% 4 4 2 4 6% 35%	2667
	11th to 20th	Night	18% 12% 4 7% 6% 5% 4 4 4 5% 32%	2906
	21st to end	Night	21% 15% 4 9% 5% 5% 4 3 5% 5% 23%	2940
December	1st to 10th	Night	19% 18% 5% 12% 7% 5% 5% 3 4 5% 17%	4720
	11th to 20th	Night	23% 15% 5% 10% 5% 4 4 3 3 4 25%	5348
	21st to end	Night	26% 17% 4 11% 5% 3 4 3 4 4 19%	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% 7% 11% 12% 4	4662
	11th to 20th	Day	66% 6% 9% 9% 9% 1	4680
	21st to end	Day	67% 6% 8% 9% 8% 1	5364
February	1st to 10th	Day	62% 5% 9% 19% 5% 1	1890
	11th to 20th	Day	59% 6% 11% 16% 7% 1	1873
	21st to end	Day	63% 6% 9% 13% 8% 1	1730
March	1st to 10th	Day	59% 6% 10% 13% 10% 3	4579
	11th to 20th	Day	50% 8% 17% 15% 9% 1	5079
	21st to end	Day	49% 6% 7% 18% 18% 3	5909
April	1st to 10th	Day	54% 5% 7% 18% 13% 2	2520
	11th to 20th	Day	51% 6% 8% 19% 15% 2	2494
	21st to end	Day	53% 6% 9% 16% 14% 4	2643
May	1st to 10th	Day	55% 7% 8% 19% 9% 1	8249
	11th to 20th	Day	49% 7% 12% 21% 10% 1	8225
	21st to end	Day	49% 6% 11% 24% 10% 1	9061
June	1st to 10th	Day	51% 8% 10% 18% 12% 1	2940
	11th to 20th	Day	43% 8% 11% 24% 12% 2	2940
	21st to end	Day	49% 9% 11% 20% 10% 1	2940
July	1st to 10th	Day	44% 7% 13% 26% 10%	6290
	11th to 20th	Day	37% 8% 13% 28% 14%	6285
	21st to end	Day	34% 7% 13% 36% 9%	6728
August	1st to 10th	Day	46% 6% 15% 24% 9%	4466
	11th to 20th	Day	42% 6% 14% 29% 8% 1	4129
	21st to end	Day	40% 7% 16% 26% 11%	4312
September	1st to 10th	Day	38% 9% 14% 27% 12%	2400
	11th to 20th	Day	35% 6% 13% 32% 14%	2394
	21st to end	Day	42% 8% 14% 25% 10%	2145
October	1st to 10th	Day	45% 5% 11% 30% 9%	3260
	11th to 20th	Day	46% 6% 15% 25% 7% 1	3240
	21st to end	Day	48% 6% 17% 22% 8%	3263
November	1st to 10th	Day	49% 8% 14% 21% 7% 1	1851
	11th to 20th	Day	56% 7% 11% 16% 10% 1	1711
	21st to end	Day	64% 8% 12% 11% 5%	1680
December	1st to 10th	Day	71% 6% 12% 10% 1	2680
	11th to 20th	Day	64% 6% 10% 14% 6%	3066
	21st to end	Day	68% 5% 8% 15% 5%	4048
January	1st to 10th	Night	67% 6% 11% 12% 5% 1	8234
	11th to 20th	Night	68% 7% 8% 10% 7%	8280
	21st to end	Night	63% 5% 7% 13% 12% 1	8799
February	1st to 10th	Night	62% 5% 11% 15% 6% 1	2730
	11th to 20th	Night	58% 6% 11% 19% 6%	2644
	21st to end	Night	58% 5% 9% 18% 9% 1	2076
March	1st to 10th	Night	59% 5% 7% 15% 11% 2	5494
	11th to 20th	Night	49% 7% 18% 16% 7% 3	5096
	21st to end	Night	51% 4 8% 21% 13% 2	5265
April	1st to 10th	Night	53% 5% 9% 19% 12% 2	2100
	11th to 20th	Night	51% 6% 7% 20% 15% 1	2075
	21st to end	Night	50% 5% 8% 17% 16% 3	1993
May	1st to 10th	Night	56% 8% 10% 17% 7% 2	4666
	11th to 20th	Night	44% 8% 12% 22% 13% 1	4640
	21st to end	Night	47% 7% 12% 19% 15% 1	5115
June	1st to 10th	Night	46% 9% 13% 19% 12% 1	1680
	11th to 20th	Night	40% 7% 13% 21% 16% 2	1680
	21st to end	Night	47% 8% 12% 19% 12% 1	1680
July	1st to 10th	Night	43% 7% 16% 20% 13% 1	3560
	11th to 20th	Night	37% 7% 13% 31% 12%	3552
	21st to end	Night	36% 8% 12% 29% 16%	3809
August	1st to 10th	Night	40% 8% 14% 26% 11%	2655
	11th to 20th	Night	41% 6% 16% 29% 8% 1	2953
	21st to end	Night	38% 8% 14% 27% 12% 1	3586
September	1st to 10th	Night	37% 8% 11% 29% 14% 1	2000
	11th to 20th	Night	32% 7% 14% 34% 12% 1	2005
	21st to end	Night	41% 7% 12% 27% 13% 1	2251
October	1st to 10th	Night	40% 6% 13% 29% 11% 1	3920
	11th to 20th	Night	42% 5% 16% 27% 10%	3899
	21st to end	Night	49% 5% 16% 21% 8%	4526
November	1st to 10th	Night	51% 6% 13% 20% 9% 1	2667
	11th to 20th	Night	54% 6% 12% 18% 9% 1	2906
	21st to end	Night	61% 7% 12% 15% 5%	2940
December	1st to 10th	Night	68% 6% 11% 12% 3	4720
	11th to 20th	Night	63% 5% 8% 14% 10% 1	5348
	21st to end	Night	68% 5% 6% 12% 9%	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	25% 20% 35% 15% 4	220
	11th to 20th	Day	33% 18% 33% 12% 3 1	220
	21st to end	Day	23% 22% 35% 13% 6%	286
February	1st to 10th	Day	30% 21% 32% 15% 2	330
	11th to 20th	Day	28% 24% 38% 11%	351
	21st to end	Day	30% 19% 35% 14% 1	446
March	1st to 10th	Day	27% 19% 35% 15% 4	540
	11th to 20th	Day	28% 19% 33% 16% 3 1	540
	21st to end	Day	30% 22% 27% 15% 5% 1	594
April	1st to 10th	Day	34% 18% 30% 13% 4 1	540
	11th to 20th	Day	35% 19% 23% 15% 6% 2	532
	21st to end	Day	31% 19% 30% 13% 5% 1	540
May	1st to 10th	Day	26% 18% 30% 17% 6% 1	543
	11th to 20th	Day	19% 18% 35% 19% 8% 2	567
	21st to end	Day	23% 17% 29% 21% 9% 1	617
June	1st to 10th	Day	24% 14% 31% 22% 8% 1	570
	11th to 20th	Day	17% 15% 36% 21% 9% 2	570
	21st to end	Day	21% 15% 34% 19% 9% 2	570
July	1st to 10th	Day	13% 9% 33% 30% 13% 2	525
	11th to 20th	Day	12% 10% 34% 28% 13% 3	524
	21st to end	Day	14% 8% 36% 29% 11% 2	576
August	1st to 10th	Day	14% 9% 27% 33% 14% 3	526
	11th to 20th	Day	16% 7% 26% 29% 15% 7%	519
	21st to end	Day	15% 12% 31% 23% 13% 7%	583
September	1st to 10th	Day	16% 12% 28% 24% 13% 7%	530
	11th to 20th	Day	12% 8% 25% 25% 18% 12%	530
	21st to end	Day	19% 11% 31% 20% 15% 4	530
October	1st to 10th	Day	23% 15% 27% 19% 12% 5%	530
	11th to 20th	Day	27% 18% 28% 21% 5% 1	530
	21st to end	Day	32% 14% 28% 22% 4	493
November	1st to 10th	Day	28% 21% 27% 18% 5% 1	425
	11th to 20th	Day	27% 21% 32% 14% 4 2	251
	21st to end	Day	31% 22% 33% 11% 3	220
December	1st to 10th	Day	33% 16% 35% 12% 3	220
	11th to 20th	Day	31% 25% 33% 6% 4	220
	21st to end	Day	34% 17% 30% 15% 2 1	242
January	1st to 10th	Night	26% 18% 33% 19% 4	840
	11th to 20th	Night	31% 18% 26% 20% 4	840
	21st to end	Night	22% 14% 35% 24% 5%	924
February	1st to 10th	Night	22% 19% 35% 21% 3	840
	11th to 20th	Night	22% 20% 37% 18% 3	823
	21st to end	Night	24% 20% 32% 21% 3	692
March	1st to 10th	Night	26% 15% 35% 20% 4	840
	11th to 20th	Night	25% 21% 30% 19% 4	840
	21st to end	Night	26% 16% 29% 23% 7%	924
April	1st to 10th	Night	27% 15% 30% 24% 3	840
	11th to 20th	Night	27% 17% 29% 21% 6%	831
	21st to end	Night	26% 14% 29% 24% 6%	733
May	1st to 10th	Night	26% 9% 27% 27% 8% 2	420
	11th to 20th	Night	19% 12% 35% 27% 8%	414
	21st to end	Night	15% 11% 38% 25% 11%	455
June	1st to 10th	Night	17% 8% 34% 35% 7%	420
	11th to 20th	Night	16% 13% 31% 30% 10%	420
	21st to end	Night	18% 9% 34% 29% 11%	420
July	1st to 10th	Night	8% 9% 28% 44% 10% 1	390
	11th to 20th	Night	14% 5% 26% 40% 14% 1	388
	21st to end	Night	9% 4 31% 43% 11% 1	438
August	1st to 10th	Night	14% 4 24% 41% 17%	438
	11th to 20th	Night	14% 4 21% 38% 22% 1	619
	21st to end	Night	14% 7% 29% 31% 18% 2	880
September	1st to 10th	Night	14% 8% 30% 31% 16% 1	800
	11th to 20th	Night	16% 6% 22% 30% 23% 4	800
	21st to end	Night	18% 9% 24% 28% 20% 1	800
October	1st to 10th	Night	21% 10% 30% 23% 16% 2	800
	11th to 20th	Night	25% 13% 30% 25% 7% 1	800
	21st to end	Night	30% 14% 28% 23% 5%	880
November	1st to 10th	Night	28% 15% 27% 22% 8%	820
	11th to 20th	Night	25% 18% 30% 18% 9%	840
	21st to end	Night	31% 17% 27% 20% 5%	840
December	1st to 10th	Night	31% 16% 31% 19% 4	840
	11th to 20th	Night	29% 19% 30% 17% 4 1	840
	21st to end	Night	33% 17% 29% 18% 3	924

Page generated at 2026-06-28 02:10:43. Version ac07

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