Kitchener-Waterloo
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kitchener-Waterloo clear sky chart from 2005-11-06 to 2025-09-04.

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% 6% 5% 5% 4 6% 7% 31%	126904
	Night	14% 11% 4 9% 5% 5% 5% 4 5% 6% 32%	121769
Transparency	Day	50% 7% 13% 18% 11% 1	130484
	Night	50% 7% 12% 19% 11% 1	126265
Seeing	Day	19% 14% 29% 22% 12% 5%	15959
	Night	19% 12% 30% 27% 10% 1	24920

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	11% 15% 7% 17% 7% 5% 5% 3 4 5% 22%	3687
	11th to 20th	Day	9% 20% 8% 22% 9% 8% 5% 3 4 4 8%	4026
	21st to end	Day	17% 17% 7% 17% 7% 5% 5% 3 4 4 13%	4466
February	1st to 10th	Day	15% 17% 5% 12% 9% 7% 6% 4 5% 5% 16%	1800
	11th to 20th	Day	13% 14% 6% 14% 9% 5% 3 3 6% 7% 19%	1753
	21st to end	Day	16% 16% 6% 11% 7% 5% 6% 3 5% 5% 21%	1591
March	1st to 10th	Day	18% 12% 5% 11% 7% 4 4 3 5% 5% 27%	4882
	11th to 20th	Day	11% 12% 5% 10% 5% 5% 5% 4 6% 8% 29%	4980
	21st to end	Day	17% 13% 4 10% 5% 5% 4 3 4 5% 29%	5465
April	1st to 10th	Day	17% 13% 4 8% 5% 5% 4 4 6% 6% 28%	2313
	11th to 20th	Day	18% 11% 3 6% 5% 4 4 3 5% 6% 35%	2512
	21st to end	Day	19% 10% 3 7% 5% 5% 4 3 5% 6% 33%	2600
May	1st to 10th	Day	18% 9% 3 8% 5% 4 4 3 5% 7% 33%	5888
	11th to 20th	Day	16% 10% 3 8% 5% 5% 4 4 5% 8% 32%	6079
	21st to end	Day	18% 7% 2 6% 4 4 5% 4 5% 7% 38%	6949
June	1st to 10th	Day	13% 6% 2 6% 5% 5% 6% 5% 6% 9% 37%	2800
	11th to 20th	Day	11% 5% 3 7% 5% 5% 5% 4 7% 8% 40%	2915
	21st to end	Day	13% 5% 2 7% 5% 5% 5% 5% 7% 8% 39%	3000
July	1st to 10th	Day	10% 5% 2 7% 4 5% 5% 5% 7% 9% 41%	6783
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 9% 44%	6162
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 6% 9% 47%	6424
August	1st to 10th	Day	15% 6% 2 6% 4 4 5% 4 6% 9% 37%	4234
	11th to 20th	Day	11% 7% 3 8% 5% 6% 5% 5% 7% 9% 35%	4174
	21st to end	Day	9% 6% 3 7% 5% 5% 5% 5% 7% 9% 41%	4558
September	1st to 10th	Day	11% 6% 2 7% 5% 5% 4 4 6% 9% 40%	2316
	11th to 20th	Day	11% 5% 3 6% 4 4 4 3 7% 10% 43%	2096
	21st to end	Day	14% 7% 3 7% 6% 5% 5% 4 7% 7% 34%	2090
October	1st to 10th	Day	18% 9% 3 8% 5% 4 3 4 6% 6% 33%	1905
	11th to 20th	Day	21% 9% 3 8% 6% 5% 5% 3 5% 6% 29%	1900
	21st to end	Day	23% 12% 4 9% 5% 5% 5% 5% 5% 7% 21%	2086
November	1st to 10th	Day	13% 11% 4 9% 5% 5% 6% 4 6% 7% 30%	1724
	11th to 20th	Day	14% 15% 4 11% 6% 5% 5% 4 7% 7% 23%	1600
	21st to end	Day	16% 18% 6% 11% 7% 4 5% 3 6% 6% 18%	1600
December	1st to 10th	Day	17% 19% 6% 14% 8% 6% 6% 4 5% 5% 11%	2600
	11th to 20th	Day	20% 20% 6% 10% 8% 5% 5% 3 4 4 16%	2986
	21st to end	Day	27% 19% 6% 13% 6% 5% 4 3 4 4 11%	3960
January	1st to 10th	Night	13% 14% 6% 18% 7% 6% 5% 3 5% 5% 19%	6243
	11th to 20th	Night	11% 15% 7% 17% 11% 7% 6% 5% 6% 5% 11%	5859
	21st to end	Night	16% 13% 8% 14% 6% 5% 5% 3 5% 6% 18%	6490
February	1st to 10th	Night	15% 15% 5% 11% 7% 6% 5% 4 5% 7% 20%	2600
	11th to 20th	Night	13% 14% 5% 11% 8% 5% 5% 4 6% 7% 23%	2533
	21st to end	Night	14% 12% 5% 12% 7% 6% 4 5% 5% 6% 24%	2035
March	1st to 10th	Night	14% 10% 4 9% 7% 6% 5% 4 5% 7% 30%	4957
	11th to 20th	Night	9% 8% 3 10% 5% 4 5% 5% 6% 9% 36%	4979
	21st to end	Night	19% 11% 4 7% 4 4 3 3 5% 5% 36%	5467
April	1st to 10th	Night	19% 10% 3 8% 5% 5% 5% 3 5% 5% 32%	2086
	11th to 20th	Night	17% 10% 3 6% 5% 4 4 4 5% 6% 37%	1854
	21st to end	Night	14% 10% 3 8% 5% 4 5% 3 6% 7% 36%	1800
May	1st to 10th	Night	19% 7% 2 7% 4 4 4 3 6% 6% 38%	4053
	11th to 20th	Night	13% 9% 3 8% 5% 5% 4 4 5% 7% 37%	3810
	21st to end	Night	17% 5% 2 5% 3 3 4 3 5% 8% 45%	3926
June	1st to 10th	Night	11% 6% 2 5% 4 4 5% 4 6% 6% 45%	1600
	11th to 20th	Night	10% 5% 2 6% 5% 4 5% 5% 7% 9% 43%	1477
	21st to end	Night	10% 5% 2 6% 5% 5% 4 5% 5% 7% 46%	1400
July	1st to 10th	Night	6% 5% 2 5% 4 4 5% 4 6% 9% 50%	3177
	11th to 20th	Night	10% 6% 2 5% 3 4 4 3 5% 8% 51%	3781
	21st to end	Night	8% 5% 2 6% 4 4 4 4 5% 7% 52%	4428
August	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 5% 7% 46%	2915
	11th to 20th	Night	11% 6% 2 5% 4 4 4 3 7% 9% 45%	2875
	21st to end	Night	10% 5% 2 5% 4 5% 4 4 5% 7% 49%	3305
September	1st to 10th	Night	9% 5% 2 6% 5% 4 5% 4 5% 7% 47%	1931
	11th to 20th	Night	10% 5% 1 5% 3 3 4 3 6% 7% 54%	2080
	21st to end	Night	16% 7% 2 7% 5% 5% 5% 3 5% 8% 39%	2090
October	1st to 10th	Night	15% 7% 4 7% 4 3 4 3 5% 7% 40%	2275
	11th to 20th	Night	16% 9% 3 8% 5% 4 4 4 5% 6% 35%	2280
	21st to end	Night	21% 9% 4 8% 5% 5% 5% 4 6% 6% 28%	2508
November	1st to 10th	Night	14% 9% 3 8% 5% 4 4 4 6% 6% 36%	2571
	11th to 20th	Night	15% 13% 4 9% 6% 5% 5% 4 6% 7% 25%	2800
	21st to end	Night	18% 13% 5% 9% 7% 5% 5% 4 5% 7% 22%	2800
December	1st to 10th	Night	14% 17% 7% 14% 7% 6% 5% 4 6% 5% 15%	4580
	11th to 20th	Night	14% 20% 6% 12% 6% 5% 5% 3 4 5% 19%	5208
	21st to end	Night	24% 20% 7% 11% 6% 4 4 3 4 4 13%	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	63% 8% 9% 9% 10% 1	3688
	11th to 20th	Day	79% 5% 8% 5% 2	4060
	21st to end	Day	73% 6% 9% 7% 5%	4466
February	1st to 10th	Day	67% 7% 10% 11% 4 1	1800
	11th to 20th	Day	63% 6% 10% 13% 6% 1	1762
	21st to end	Day	63% 6% 11% 13% 6% 1	1591
March	1st to 10th	Day	58% 5% 14% 14% 8% 1	4885
	11th to 20th	Day	49% 7% 17% 18% 6% 2	4980
	21st to end	Day	55% 6% 11% 17% 9% 1	5465
April	1st to 10th	Day	55% 6% 12% 16% 11% 1	2313
	11th to 20th	Day	50% 6% 11% 21% 12% 1	2512
	21st to end	Day	52% 7% 10% 18% 11% 2	2600
May	1st to 10th	Day	49% 7% 13% 16% 10% 6%	5897
	11th to 20th	Day	49% 8% 11% 18% 12% 2	6083
	21st to end	Day	44% 7% 11% 19% 15% 3	6949
June	1st to 10th	Day	42% 8% 13% 21% 15% 1	2800
	11th to 20th	Day	39% 8% 15% 22% 14% 1	2915
	21st to end	Day	40% 8% 15% 23% 14%	3000
July	1st to 10th	Day	36% 7% 15% 25% 16% 2	6710
	11th to 20th	Day	33% 7% 14% 30% 15% 1	6087
	21st to end	Day	33% 7% 13% 26% 19% 1	6240
August	1st to 10th	Day	42% 8% 15% 22% 13% 1	4221
	11th to 20th	Day	42% 8% 16% 23% 9%	4213
	21st to end	Day	36% 7% 13% 32% 10% 1	4558
September	1st to 10th	Day	39% 9% 15% 24% 11% 1	2316
	11th to 20th	Day	35% 7% 15% 28% 15%	2096
	21st to end	Day	44% 9% 14% 24% 8% 1	2090
October	1st to 10th	Day	41% 7% 14% 22% 15% 1	3165
	11th to 20th	Day	42% 6% 14% 20% 17%	3140
	21st to end	Day	52% 7% 15% 19% 7%	3412
November	1st to 10th	Day	51% 8% 13% 19% 7% 1	1724
	11th to 20th	Day	57% 8% 14% 13% 8% 1	1600
	21st to end	Day	64% 8% 13% 11% 4	1600
December	1st to 10th	Day	73% 7% 10% 7% 3	2600
	11th to 20th	Day	70% 7% 8% 10% 5%	2986
	21st to end	Day	76% 7% 6% 6% 6%	3960
January	1st to 10th	Night	62% 9% 9% 14% 6%	6243
	11th to 20th	Night	70% 10% 9% 8% 3	5900
	21st to end	Night	65% 7% 10% 10% 8% 1	6490
February	1st to 10th	Night	62% 8% 11% 14% 4	2600
	11th to 20th	Night	58% 7% 12% 15% 7% 1	2535
	21st to end	Night	58% 7% 12% 15% 7%	2035
March	1st to 10th	Night	51% 7% 16% 16% 10% 2	4967
	11th to 20th	Night	42% 7% 20% 20% 11% 1	4980
	21st to end	Night	48% 6% 10% 19% 15% 2	5467
April	1st to 10th	Night	53% 5% 10% 18% 13% 1	2086
	11th to 20th	Night	47% 7% 10% 19% 16% 2	1854
	21st to end	Night	46% 7% 11% 19% 16% 3	1800
May	1st to 10th	Night	46% 7% 12% 14% 13% 8%	4060
	11th to 20th	Night	45% 9% 13% 19% 11% 2	3811
	21st to end	Night	38% 6% 13% 24% 17% 2	3927
June	1st to 10th	Night	36% 8% 12% 26% 17% 2	1600
	11th to 20th	Night	35% 7% 14% 25% 16% 2	1477
	21st to end	Night	36% 8% 15% 23% 18% 1	1400
July	1st to 10th	Night	30% 6% 15% 25% 21% 4	3142
	11th to 20th	Night	32% 5% 13% 28% 19% 3	3733
	21st to end	Night	31% 7% 11% 27% 21% 2	4297
August	1st to 10th	Night	36% 7% 13% 26% 16% 2	2904
	11th to 20th	Night	35% 8% 16% 29% 12% 1	2902
	21st to end	Night	32% 8% 13% 32% 15% 1	3305
September	1st to 10th	Night	35% 8% 13% 28% 15% 2	1931
	11th to 20th	Night	29% 6% 13% 31% 20% 1	2080
	21st to end	Night	42% 9% 11% 26% 12%	2090
October	1st to 10th	Night	33% 6% 9% 27% 24% 1	3795
	11th to 20th	Night	43% 6% 14% 23% 14%	3779
	21st to end	Night	42% 6% 16% 26% 9%	4120
November	1st to 10th	Night	45% 8% 14% 20% 12% 1	2571
	11th to 20th	Night	55% 8% 15% 15% 6% 1	2800
	21st to end	Night	59% 8% 16% 13% 4	2800
December	1st to 10th	Night	68% 7% 13% 10% 2	4580
	11th to 20th	Night	66% 6% 9% 12% 7%	5208
	21st to end	Night	74% 7% 9% 6% 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	22% 23% 33% 15% 6%	220
	11th to 20th	Day	22% 25% 37% 11% 4 1	300
	21st to end	Day	25% 19% 37% 15% 4	330
February	1st to 10th	Day	26% 26% 33% 11% 4	300
	11th to 20th	Day	26% 26% 35% 11% 1	300
	21st to end	Day	33% 23% 32% 11%	249
March	1st to 10th	Day	24% 17% 35% 18% 6%	474
	11th to 20th	Day	23% 18% 34% 21% 4 1	500
	21st to end	Day	29% 16% 31% 19% 5% 1	550
April	1st to 10th	Day	22% 21% 31% 20% 6% 1	500
	11th to 20th	Day	27% 19% 25% 18% 9% 2	492
	21st to end	Day	24% 14% 35% 18% 8% 2	500
May	1st to 10th	Day	21% 15% 28% 23% 8% 4	503
	11th to 20th	Day	17% 11% 30% 23% 14% 5%	527
	21st to end	Day	15% 8% 30% 26% 14% 7%	573
June	1st to 10th	Day	14% 15% 31% 26% 12% 3	530
	11th to 20th	Day	12% 11% 30% 30% 14% 3	645
	21st to end	Day	15% 8% 31% 30% 12% 3	730
July	1st to 10th	Day	9% 7% 25% 31% 21% 7%	711
	11th to 20th	Day	13% 7% 24% 26% 21% 9%	524
	21st to end	Day	9% 4 28% 32% 19% 7%	576
August	1st to 10th	Day	10% 7% 20% 30% 22% 12%	526
	11th to 20th	Day	11% 6% 21% 26% 22% 13%	519
	21st to end	Day	13% 7% 23% 25% 21% 10%	583
September	1st to 10th	Day	10% 10% 23% 26% 18% 13%	502
	11th to 20th	Day	9% 6% 19% 25% 25% 16%	490
	21st to end	Day	17% 11% 26% 23% 16% 7%	490
October	1st to 10th	Day	21% 12% 26% 23% 10% 7%	490
	11th to 20th	Day	20% 19% 32% 18% 9% 2	490
	21st to end	Day	28% 16% 32% 19% 5%	535
November	1st to 10th	Day	25% 21% 32% 13% 7% 1	280
	11th to 20th	Day	26% 18% 35% 16% 5% 2	200
	21st to end	Day	27% 21% 34% 16% 3	200
December	1st to 10th	Day	29% 24% 31% 10% 6%	200
	11th to 20th	Day	30% 27% 29% 12% 3 1	200
	21st to end	Day	29% 22% 36% 11% 2	220
January	1st to 10th	Night	22% 19% 37% 16% 5% 1	800
	11th to 20th	Night	26% 19% 33% 19% 2	800
	21st to end	Night	20% 15% 38% 23% 5%	880
February	1st to 10th	Night	23% 18% 36% 21% 2	800
	11th to 20th	Night	22% 18% 35% 21% 4	783
	21st to end	Night	22% 19% 35% 21% 3	660
March	1st to 10th	Night	18% 16% 38% 23% 5%	800
	11th to 20th	Night	20% 18% 36% 21% 6%	800
	21st to end	Night	21% 15% 31% 25% 8% 1	880
April	1st to 10th	Night	24% 16% 33% 24% 4	800
	11th to 20th	Night	21% 16% 32% 22% 9% 1	670
	21st to end	Night	16% 12% 35% 30% 8%	600
May	1st to 10th	Night	16% 9% 32% 30% 12% 1	600
	11th to 20th	Night	15% 5% 31% 35% 12% 1	499
	21st to end	Night	12% 6% 28% 36% 17%	433
June	1st to 10th	Night	13% 5% 33% 38% 11% 1	400
	11th to 20th	Night	11% 6% 32% 40% 11% 1	400
	21st to end	Night	11% 6% 28% 41% 15%	400
July	1st to 10th	Night	4 3 24% 49% 19% 1	390
	11th to 20th	Night	10% 4 25% 38% 21% 2	465
	21st to end	Night	10% 3 20% 46% 20% 1	657
August	1st to 10th	Night	7% 3 20% 42% 26% 2	597
	11th to 20th	Night	8% 3 17% 40% 29% 3	594
	21st to end	Night	11% 3 23% 36% 25% 2	703
September	1st to 10th	Night	12% 7% 21% 34% 22% 4	773
	11th to 20th	Night	12% 5% 19% 32% 28% 4	760
	21st to end	Night	17% 9% 22% 29% 18% 5%	760
October	1st to 10th	Night	18% 8% 28% 28% 16% 3	760
	11th to 20th	Night	20% 12% 30% 28% 9% 1	760
	21st to end	Night	26% 14% 31% 25% 5%	836
November	1st to 10th	Night	19% 14% 29% 27% 9% 2	780
	11th to 20th	Night	22% 18% 32% 21% 6% 1	800
	21st to end	Night	26% 16% 34% 20% 5%	800
December	1st to 10th	Night	26% 20% 31% 18% 5%	800
	11th to 20th	Night	23% 21% 36% 17% 3	800
	21st to end	Night	30% 16% 34% 18% 3	880

Page generated at 2025-09-01 01:51:03. Version ac07

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