Kawartha Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kawartha Observatory clear sky chart from 2005-11-06 to 2026-07-16.

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 8% 5% 5% 5% 4 5% 7% 33%	138483
	Night	14% 11% 4 9% 6% 5% 5% 4 5% 6% 32%	134179
Transparency	Day	48% 7% 12% 20% 11% 1	142067
	Night	49% 7% 12% 19% 11% 1	138682
Seeing	Day	20% 16% 31% 20% 9% 3	16516
	Night	19% 13% 32% 26% 10% 1	25820

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	14% 13% 6% 13% 6% 5% 5% 4 5% 5% 24%	4661
	11th to 20th	Day	8% 18% 8% 18% 10% 8% 5% 3 4 4 13%	4866
	21st to end	Day	12% 16% 6% 14% 7% 7% 6% 4 5% 6% 19%	5780
February	1st to 10th	Day	12% 16% 5% 13% 7% 5% 5% 3 5% 4 23%	1890
	11th to 20th	Day	12% 14% 7% 12% 6% 6% 5% 4 5% 6% 24%	1843
	21st to end	Day	16% 15% 6% 9% 6% 6% 5% 3 5% 5% 24%	1604
March	1st to 10th	Day	18% 12% 5% 9% 5% 4 4 3 4 5% 30%	5013
	11th to 20th	Day	11% 13% 5% 9% 5% 6% 5% 5% 6% 7% 28%	5090
	21st to end	Day	18% 12% 3 8% 4 3 3 3 4 5% 35%	5586
April	1st to 10th	Day	19% 11% 4 9% 5% 5% 4 3 5% 5% 30%	2519
	11th to 20th	Day	21% 10% 3 7% 3 4 4 2 4 5% 37%	2540
	21st to end	Day	19% 10% 3 7% 5% 5% 4 3 5% 6% 34%	2730
May	1st to 10th	Day	18% 8% 3 7% 5% 5% 5% 3 5% 7% 35%	7815
	11th to 20th	Day	15% 10% 3 8% 4 5% 4 3 5% 7% 36%	8221
	21st to end	Day	18% 8% 2 6% 4 4 3 3 5% 7% 40%	9060
June	1st to 10th	Day	16% 8% 2 7% 5% 5% 5% 4 6% 8% 36%	2940
	11th to 20th	Day	13% 7% 2 6% 5% 5% 5% 5% 7% 8% 38%	2940
	21st to end	Day	14% 7% 3 6% 5% 4 5% 4 7% 7% 37%	2940
July	1st to 10th	Day	11% 7% 2 6% 4 5% 5% 4 7% 10% 39%	6500
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 4 6% 8% 46%	6430
	21st to end	Day	6% 4 2 6% 4 5% 5% 5% 6% 10% 47%	6700
August	1st to 10th	Day	14% 9% 3 6% 4 4 4 4 7% 8% 37%	4234
	11th to 20th	Day	13% 7% 2 6% 5% 5% 5% 4 7% 10% 36%	4174
	21st to end	Day	9% 7% 2 6% 5% 4 5% 4 7% 9% 43%	4454
September	1st to 10th	Day	12% 6% 3 7% 4 4 5% 4 6% 7% 42%	2400
	11th to 20th	Day	11% 5% 2 5% 4 5% 4 4 6% 8% 47%	2336
	21st to end	Day	15% 7% 3 7% 6% 5% 5% 3 5% 7% 38%	2125
October	1st to 10th	Day	18% 9% 3 7% 5% 4 4 4 5% 7% 35%	2000
	11th to 20th	Day	20% 10% 4 9% 5% 4 4 3 5% 6% 29%	2000
	21st to end	Day	23% 11% 4 8% 5% 6% 4 3 5% 6% 25%	2200
November	1st to 10th	Day	14% 12% 3 7% 5% 4 5% 4 5% 6% 33%	1738
	11th to 20th	Day	13% 13% 4 10% 6% 5% 4 5% 7% 7% 26%	1680
	21st to end	Day	17% 17% 5% 10% 6% 5% 5% 3 5% 6% 20%	1680
December	1st to 10th	Day	15% 21% 6% 14% 7% 5% 4 4 5% 6% 14%	2680
	11th to 20th	Day	17% 18% 5% 10% 6% 4 4 3 4 6% 23%	3066
	21st to end	Day	22% 18% 5% 14% 5% 4 4 3 4 4 17%	4048
January	1st to 10th	Night	13% 15% 7% 15% 7% 5% 5% 4 5% 6% 19%	8234
	11th to 20th	Night	10% 16% 7% 16% 10% 7% 5% 4 4 5% 16%	8014
	21st to end	Night	11% 13% 6% 12% 6% 6% 6% 4 6% 6% 24%	8401
February	1st to 10th	Night	11% 15% 5% 11% 8% 6% 5% 4 5% 6% 23%	2730
	11th to 20th	Night	13% 13% 5% 11% 6% 5% 5% 4 5% 6% 26%	2663
	21st to end	Night	13% 12% 5% 12% 6% 5% 6% 4 6% 6% 26%	2201
March	1st to 10th	Night	16% 10% 4 10% 6% 5% 5% 3 5% 6% 30%	5030
	11th to 20th	Night	10% 10% 4 9% 6% 6% 5% 4 7% 8% 32%	5089
	21st to end	Night	20% 8% 4 7% 5% 4 4 3 5% 6% 35%	5588
April	1st to 10th	Night	19% 11% 4 7% 5% 4 5% 4 6% 6% 30%	2100
	11th to 20th	Night	17% 8% 3 7% 5% 4 4 4 5% 8% 36%	2045
	21st to end	Night	14% 9% 4 9% 5% 5% 5% 3 5% 7% 35%	1890
May	1st to 10th	Night	20% 8% 3 6% 4 4 4 3 5% 7% 36%	5083
	11th to 20th	Night	14% 7% 3 6% 4 4 4 3 6% 7% 41%	4639
	21st to end	Night	18% 6% 2 6% 4 3 4 3 5% 7% 42%	5114
June	1st to 10th	Night	13% 6% 3 7% 5% 3 4 4 7% 8% 40%	1680
	11th to 20th	Night	9% 5% 2 6% 4 5% 6% 4 6% 8% 44%	1680
	21st to end	Night	12% 7% 3 6% 4 5% 5% 5% 6% 8% 39%	1680
July	1st to 10th	Night	8% 6% 2 7% 5% 5% 5% 4 6% 7% 44%	3680
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 5% 8% 50%	3640
	21st to end	Night	8% 5% 1 5% 3 4 4 4 6% 8% 51%	4148
August	1st to 10th	Night	9% 5% 2 6% 4 3 5% 4 5% 7% 48%	2915
	11th to 20th	Night	12% 6% 2 5% 3 3 4 3 6% 8% 48%	2875
	21st to end	Night	10% 6% 2 6% 5% 3 5% 4 6% 7% 47%	3411
September	1st to 10th	Night	10% 5% 3 7% 4 4 4 4 6% 8% 46%	2000
	11th to 20th	Night	10% 4 2 5% 4 4 3 3 5% 6% 54%	2060
	21st to end	Night	15% 7% 3 6% 4 5% 4 3 5% 6% 42%	2274
October	1st to 10th	Night	17% 6% 3 8% 4 5% 4 3 5% 7% 38%	2400
	11th to 20th	Night	19% 10% 3 8% 6% 4 4 4 5% 6% 32%	2400
	21st to end	Night	20% 11% 3 8% 5% 4 4 4 5% 6% 29%	2640
November	1st to 10th	Night	16% 10% 4 8% 5% 4 4 3 6% 6% 34%	2777
	11th to 20th	Night	15% 14% 4 9% 5% 5% 5% 4 6% 7% 27%	2940
	21st to end	Night	17% 14% 5% 9% 6% 5% 5% 4 6% 6% 22%	2940
December	1st to 10th	Night	15% 17% 6% 12% 7% 6% 5% 4 6% 6% 16%	4720
	11th to 20th	Night	15% 16% 6% 13% 7% 6% 5% 4 5% 5% 18%	5348
	21st to end	Night	21% 18% 5% 16% 6% 4 4 3 3 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	59% 7% 12% 14% 8%	4662
	11th to 20th	Day	73% 6% 8% 8% 4	4897
	21st to end	Day	65% 6% 10% 10% 8% 1	5780
February	1st to 10th	Day	63% 6% 10% 16% 4 1	1890
	11th to 20th	Day	61% 7% 9% 14% 8% 1	1852
	21st to end	Day	61% 6% 10% 15% 8%	1604
March	1st to 10th	Day	55% 6% 13% 12% 14%	5016
	11th to 20th	Day	52% 7% 15% 17% 7% 2	5090
	21st to end	Day	51% 5% 8% 20% 16% 1	5586
April	1st to 10th	Day	55% 5% 10% 19% 10% 1	2519
	11th to 20th	Day	50% 4 10% 21% 14% 1	2540
	21st to end	Day	51% 6% 10% 18% 13% 3	2730
May	1st to 10th	Day	47% 7% 12% 19% 12% 3	7824
	11th to 20th	Day	46% 8% 10% 19% 16%	8225
	21st to end	Day	43% 6% 11% 26% 13% 2	9061
June	1st to 10th	Day	45% 8% 11% 20% 15% 1	2940
	11th to 20th	Day	41% 8% 13% 24% 13% 1	2940
	21st to end	Day	44% 8% 14% 22% 12% 1	2940
July	1st to 10th	Day	37% 8% 16% 24% 14% 1	6430
	11th to 20th	Day	33% 7% 14% 29% 16% 1	6355
	21st to end	Day	31% 8% 15% 33% 13%	6507
August	1st to 10th	Day	43% 7% 15% 23% 10% 1	4221
	11th to 20th	Day	40% 8% 16% 26% 9%	4213
	21st to end	Day	34% 8% 15% 32% 10% 1	4454
September	1st to 10th	Day	39% 8% 15% 27% 10% 1	2400
	11th to 20th	Day	34% 7% 14% 31% 14% 1	2336
	21st to end	Day	44% 8% 14% 24% 10%	2125
October	1st to 10th	Day	39% 8% 14% 27% 11% 1	3260
	11th to 20th	Day	44% 7% 16% 20% 12%	3240
	21st to end	Day	51% 8% 15% 19% 7%	3538
November	1st to 10th	Day	49% 8% 14% 19% 8% 1	1738
	11th to 20th	Day	53% 10% 14% 14% 7% 2	1680
	21st to end	Day	63% 8% 12% 13% 4	1680
December	1st to 10th	Day	70% 7% 13% 8% 2	2680
	11th to 20th	Day	62% 7% 11% 13% 7%	3066
	21st to end	Day	69% 7% 8% 10% 7%	4048
January	1st to 10th	Night	62% 8% 11% 12% 7%	8234
	11th to 20th	Night	68% 7% 10% 10% 5% 1	8058
	21st to end	Night	57% 7% 11% 12% 13% 1	8401
February	1st to 10th	Night	60% 7% 10% 17% 5% 1	2730
	11th to 20th	Night	57% 6% 11% 18% 7%	2665
	21st to end	Night	55% 7% 13% 18% 7% 1	2201
March	1st to 10th	Night	52% 7% 10% 17% 12% 3	5040
	11th to 20th	Night	45% 8% 19% 19% 8% 1	5090
	21st to end	Night	47% 6% 11% 19% 15% 2	5588
April	1st to 10th	Night	52% 6% 10% 19% 11% 1	2100
	11th to 20th	Night	45% 7% 10% 21% 15% 2	2045
	21st to end	Night	48% 6% 12% 18% 14% 2	1890
May	1st to 10th	Night	48% 6% 11% 18% 15% 3	5090
	11th to 20th	Night	42% 7% 12% 23% 15% 1	4640
	21st to end	Night	41% 6% 12% 24% 15% 2	5115
June	1st to 10th	Night	40% 7% 11% 24% 16% 2	1680
	11th to 20th	Night	35% 8% 13% 22% 19% 2	1680
	21st to end	Night	40% 8% 14% 23% 14% 1	1680
July	1st to 10th	Night	35% 8% 16% 23% 17% 1	3640
	11th to 20th	Night	31% 7% 14% 31% 17%	3592
	21st to end	Night	29% 8% 12% 34% 16% 1	4026
August	1st to 10th	Night	34% 6% 16% 26% 17% 1	2904
	11th to 20th	Night	34% 6% 18% 28% 13% 1	2902
	21st to end	Night	32% 8% 14% 32% 13% 1	3411
September	1st to 10th	Night	35% 7% 15% 29% 13% 1	2000
	11th to 20th	Night	29% 7% 13% 32% 17% 1	2060
	21st to end	Night	41% 8% 12% 28% 12% 1	2274
October	1st to 10th	Night	34% 7% 11% 28% 20% 1	3920
	11th to 20th	Night	43% 8% 16% 25% 9%	3899
	21st to end	Night	44% 9% 15% 24% 7%	4252
November	1st to 10th	Night	48% 8% 13% 21% 10% 1	2777
	11th to 20th	Night	53% 9% 14% 15% 8% 2	2940
	21st to end	Night	59% 10% 15% 12% 4	2940
December	1st to 10th	Night	64% 8% 15% 9% 3	4720
	11th to 20th	Night	64% 9% 11% 11% 5%	5348
	21st to end	Night	71% 7% 8% 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	21% 25% 35% 15% 5% 1	220
	11th to 20th	Day	21% 31% 30% 13% 5% 1	259
	21st to end	Day	23% 25% 33% 15% 3	363
February	1st to 10th	Day	30% 23% 31% 13% 3 1	330
	11th to 20th	Day	26% 30% 34% 9% 1	330
	21st to end	Day	35% 22% 34% 8%	320
March	1st to 10th	Day	22% 23% 36% 16% 3	540
	11th to 20th	Day	28% 21% 32% 15% 3	540
	21st to end	Day	32% 18% 32% 13% 5% 1	594
April	1st to 10th	Day	26% 21% 33% 13% 5% 1	540
	11th to 20th	Day	30% 20% 25% 13% 9% 3	532
	21st to end	Day	26% 17% 35% 12% 9% 1	540
May	1st to 10th	Day	22% 16% 32% 19% 7% 3	543
	11th to 20th	Day	17% 14% 36% 19% 10% 3	567
	21st to end	Day	18% 13% 32% 21% 11% 5%	617
June	1st to 10th	Day	17% 12% 37% 22% 9% 2	570
	11th to 20th	Day	15% 15% 29% 26% 12% 4	570
	21st to end	Day	17% 12% 33% 25% 10% 3	570
July	1st to 10th	Day	9% 8% 29% 33% 17% 4	565
	11th to 20th	Day	12% 10% 27% 26% 17% 7%	544
	21st to end	Day	8% 6% 36% 32% 13% 5%	576
August	1st to 10th	Day	10% 8% 29% 30% 17% 8%	526
	11th to 20th	Day	10% 9% 25% 26% 23% 7%	519
	21st to end	Day	13% 9% 29% 26% 16% 7%	583
September	1st to 10th	Day	13% 9% 28% 24% 16% 9%	530
	11th to 20th	Day	9% 7% 26% 24% 19% 15%	530
	21st to end	Day	15% 13% 29% 23% 14% 5%	530
October	1st to 10th	Day	20% 14% 30% 18% 13% 5%	530
	11th to 20th	Day	21% 21% 35% 16% 6% 2	530
	21st to end	Day	27% 21% 30% 18% 4	583
November	1st to 10th	Day	28% 19% 28% 19% 5%	303
	11th to 20th	Day	23% 24% 37% 11% 4 1	220
	21st to end	Day	25% 22% 40% 11% 2	220
December	1st to 10th	Day	25% 26% 32% 12% 3 1	220
	11th to 20th	Day	30% 28% 27% 12% 2 1	220
	21st to end	Day	30% 23% 33% 12% 2 1	242
January	1st to 10th	Night	21% 21% 35% 17% 5%	840
	11th to 20th	Night	26% 17% 32% 19% 5% 1	840
	21st to end	Night	18% 17% 36% 24% 5% 1	924
February	1st to 10th	Night	19% 18% 40% 21% 2	840
	11th to 20th	Night	22% 19% 38% 18% 4	823
	21st to end	Night	21% 20% 37% 20% 3	692
March	1st to 10th	Night	20% 19% 37% 21% 3	840
	11th to 20th	Night	21% 20% 35% 20% 4 1	840
	21st to end	Night	20% 14% 36% 22% 7% 1	924
April	1st to 10th	Night	25% 17% 33% 21% 4	840
	11th to 20th	Night	21% 15% 33% 22% 8% 1	801
	21st to end	Night	18% 12% 35% 26% 9%	630
May	1st to 10th	Night	20% 7% 28% 31% 12% 2	571
	11th to 20th	Night	15% 9% 33% 33% 9%	414
	21st to end	Night	13% 8% 31% 34% 13% 1	455
June	1st to 10th	Night	13% 7% 33% 35% 11%	420
	11th to 20th	Night	10% 10% 27% 40% 13% 1	420
	21st to end	Night	12% 7% 28% 39% 14%	420
July	1st to 10th	Night	5% 4 24% 48% 18%	410
	11th to 20th	Night	9% 4 28% 37% 21% 1	398
	21st to end	Night	9% 3 27% 42% 18% 1	533
August	1st to 10th	Night	9% 4 19% 40% 26% 2	597
	11th to 20th	Night	9% 4 19% 37% 27% 3	594
	21st to end	Night	11% 5% 26% 34% 22% 2	770
September	1st to 10th	Night	11% 6% 27% 33% 19% 3	800
	11th to 20th	Night	11% 5% 21% 33% 24% 6%	800
	21st to end	Night	17% 10% 22% 31% 17% 4	800
October	1st to 10th	Night	18% 8% 29% 27% 16% 2	800
	11th to 20th	Night	23% 15% 33% 20% 8% 1	800
	21st to end	Night	26% 14% 33% 22% 5%	880
November	1st to 10th	Night	22% 15% 30% 24% 8%	820
	11th to 20th	Night	22% 18% 34% 19% 6% 1	840
	21st to end	Night	24% 18% 33% 21% 4	840
December	1st to 10th	Night	25% 18% 37% 17% 3	840
	11th to 20th	Night	22% 21% 35% 18% 3 1	840
	21st to end	Night	28% 18% 34% 18% 3	924

Page generated at 2026-07-13 03:14:53. Version ac07

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