Petawawa Terrace Provincial Nature Reserve
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Petawawa Terrace Provincial Nature Reserve clear sky chart from 2005-11-06 to 2025-11-18.

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	16% 10% 4 9% 5% 5% 5% 4 5% 7% 32%	127343
	Night	16% 12% 4 10% 5% 5% 4 3 5% 6% 30%	123008
Transparency	Day	51% 6% 11% 21% 10% 1	130847
	Night	54% 6% 11% 19% 9% 1	127578
Seeing	Day	21% 13% 29% 22% 11% 4	15655
	Night	22% 10% 27% 28% 11% 1	24789

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% 15% 7% 18% 8% 6% 4 2 4 4 18%	3597
	11th to 20th	Day	11% 16% 6% 16% 9% 6% 4 3 4 5% 19%	3570
	21st to end	Day	10% 19% 8% 14% 7% 5% 4 3 5% 5% 21%	4264
February	1st to 10th	Day	11% 16% 7% 13% 6% 6% 7% 4 5% 5% 20%	1800
	11th to 20th	Day	11% 16% 6% 11% 6% 6% 5% 4 5% 6% 24%	1753
	21st to end	Day	17% 15% 5% 9% 6% 5% 4 4 5% 6% 24%	1578
March	1st to 10th	Day	20% 13% 5% 10% 5% 4 4 3 5% 6% 25%	4658
	11th to 20th	Day	13% 12% 5% 10% 6% 5% 5% 4 5% 7% 28%	4980
	21st to end	Day	16% 12% 4 8% 5% 5% 3 2 4 5% 37%	5638
April	1st to 10th	Day	21% 13% 3 6% 4 4 5% 3 4 6% 31%	2400
	11th to 20th	Day	22% 10% 3 6% 4 3 4 3 5% 4 35%	2374
	21st to end	Day	21% 10% 3 7% 5% 4 4 3 4 5% 32%	2591
May	1st to 10th	Day	20% 9% 3 7% 4 5% 4 3 5% 7% 32%	6340
	11th to 20th	Day	15% 9% 3 7% 4 4 4 4 5% 7% 37%	6318
	21st to end	Day	19% 9% 3 7% 5% 4 4 3 4 6% 35%	6949
June	1st to 10th	Day	19% 8% 3 8% 5% 5% 5% 4 6% 6% 32%	2800
	11th to 20th	Day	14% 6% 2 6% 4 5% 5% 4 6% 7% 40%	2800
	21st to end	Day	16% 7% 3 6% 6% 5% 5% 4 6% 8% 33%	2800
July	1st to 10th	Day	13% 6% 3 7% 5% 5% 6% 5% 7% 8% 34%	6360
	11th to 20th	Day	10% 4 2 6% 5% 4 5% 4 6% 8% 44%	6360
	21st to end	Day	8% 4 2 6% 4 4 4 4 7% 10% 47%	6926
August	1st to 10th	Day	12% 5% 3 8% 6% 6% 7% 5% 6% 8% 35%	4371
	11th to 20th	Day	16% 7% 2 6% 5% 4 5% 4 6% 8% 38%	4174
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 5% 6% 10% 42%	4388
September	1st to 10th	Day	13% 6% 3 6% 4 4 5% 4 7% 7% 41%	2400
	11th to 20th	Day	12% 5% 2 7% 5% 5% 4 4 5% 6% 46%	2400
	21st to end	Day	18% 7% 2 7% 6% 4 4 3 5% 7% 36%	2100
October	1st to 10th	Day	19% 8% 2 7% 5% 5% 4 4 5% 6% 36%	2000
	11th to 20th	Day	22% 11% 4 8% 7% 5% 4 3 5% 6% 26%	2000
	21st to end	Day	26% 12% 3 9% 6% 5% 5% 3 5% 5% 23%	2099
November	1st to 10th	Day	16% 11% 4 7% 5% 5% 6% 4 6% 6% 31%	1753
	11th to 20th	Day	18% 15% 4 12% 6% 5% 5% 3 5% 5% 24%	1656
	21st to end	Day	26% 16% 5% 9% 6% 5% 5% 3 4 5% 17%	1600
December	1st to 10th	Day	18% 21% 5% 11% 6% 7% 6% 4 4 4 14%	2600
	11th to 20th	Day	16% 17% 7% 13% 6% 5% 3 3 3 4 22%	2986
	21st to end	Day	22% 18% 5% 15% 4 4 4 3 3 3 18%	3960
January	1st to 10th	Night	13% 21% 8% 17% 6% 4 4 3 4 4 16%	6349
	11th to 20th	Night	11% 14% 6% 16% 8% 6% 6% 4 4 5% 20%	6315
	21st to end	Night	10% 19% 8% 13% 7% 7% 5% 3 4 5% 19%	6675
February	1st to 10th	Night	13% 15% 6% 12% 7% 5% 6% 4 4 6% 22%	2600
	11th to 20th	Night	13% 15% 5% 12% 6% 5% 5% 3 5% 5% 26%	2533
	21st to end	Night	14% 14% 5% 10% 7% 5% 4 4 5% 5% 26%	2051
March	1st to 10th	Night	18% 16% 4 10% 5% 4 4 3 4 4 28%	5180
	11th to 20th	Night	12% 13% 4 9% 6% 5% 6% 5% 7% 8% 26%	4979
	21st to end	Night	16% 11% 4 10% 5% 4 4 3 5% 6% 31%	5292
April	1st to 10th	Night	19% 12% 4 9% 5% 4 4 4 4 5% 31%	2000
	11th to 20th	Night	20% 10% 3 7% 4 3 4 2 4 5% 36%	1975
	21st to end	Night	22% 10% 3 7% 5% 5% 4 3 4 6% 32%	1825
May	1st to 10th	Night	23% 8% 3 7% 5% 4 5% 3 5% 7% 30%	3599
	11th to 20th	Night	15% 7% 2 6% 5% 4 4 4 5% 6% 42%	3575
	21st to end	Night	18% 7% 3 7% 6% 5% 5% 4 5% 6% 35%	3926
June	1st to 10th	Night	16% 7% 3 8% 5% 4 5% 4 6% 7% 35%	1600
	11th to 20th	Night	15% 6% 2 5% 4 5% 4 5% 6% 7% 42%	1600
	21st to end	Night	17% 8% 2 5% 5% 4 5% 4 5% 8% 37%	1600
July	1st to 10th	Night	13% 6% 3 8% 5% 5% 5% 4 7% 7% 36%	3600
	11th to 20th	Night	12% 5% 2 6% 5% 4 4 4 6% 8% 44%	3600
	21st to end	Night	8% 6% 2 6% 4 4 4 4 6% 8% 49%	3926
August	1st to 10th	Night	12% 5% 2 6% 3 4 5% 4 6% 8% 44%	2775
	11th to 20th	Night	16% 6% 2 6% 3 4 4 3 7% 7% 43%	2875
	21st to end	Night	13% 6% 2 6% 4 4 5% 4 6% 8% 42%	3477
September	1st to 10th	Night	11% 6% 3 7% 5% 4 4 3 4 8% 45%	2000
	11th to 20th	Night	14% 6% 2 6% 3 3 4 3 5% 6% 49%	2000
	21st to end	Night	18% 7% 2 6% 5% 4 4 3 5% 6% 41%	2296
October	1st to 10th	Night	20% 7% 2 6% 4 4 3 3 4 7% 40%	2400
	11th to 20th	Night	21% 11% 3 7% 6% 5% 5% 3 5% 5% 30%	2400
	21st to end	Night	23% 13% 4 7% 6% 5% 4 3 4 6% 26%	2740
November	1st to 10th	Night	19% 12% 3 8% 5% 5% 5% 3 4 6% 31%	2762
	11th to 20th	Night	17% 14% 5% 9% 6% 4 4 4 5% 5% 26%	2899
	21st to end	Night	23% 16% 5% 11% 5% 4 5% 3 4 5% 19%	2800
December	1st to 10th	Night	19% 20% 6% 12% 6% 5% 5% 4 5% 5% 13%	4580
	11th to 20th	Night	19% 16% 6% 12% 5% 4 4 3 4 4 22%	5208
	21st to end	Night	25% 18% 4 13% 5% 4 4 3 3 4 17%	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	69% 6% 8% 11% 6%	3598
	11th to 20th	Day	68% 5% 9% 11% 7%	3600
	21st to end	Day	66% 4 9% 13% 8% 1	4264
February	1st to 10th	Day	65% 5% 8% 16% 6% 1	1800
	11th to 20th	Day	59% 6% 13% 13% 8% 1	1762
	21st to end	Day	61% 5% 8% 15% 10% 1	1578
March	1st to 10th	Day	59% 5% 8% 13% 13% 2	4661
	11th to 20th	Day	53% 7% 15% 15% 9% 1	4980
	21st to end	Day	50% 4 7% 20% 16% 3	5638
April	1st to 10th	Day	55% 4 8% 19% 12% 3	2400
	11th to 20th	Day	52% 3 7% 21% 15% 2	2374
	21st to end	Day	53% 5% 7% 16% 16% 3	2591
May	1st to 10th	Day	50% 6% 9% 20% 10% 5%	6351
	11th to 20th	Day	45% 7% 10% 23% 14% 1	6322
	21st to end	Day	50% 6% 10% 19% 13% 2	6949
June	1st to 10th	Day	51% 7% 10% 20% 12% 1	2800
	11th to 20th	Day	41% 7% 12% 24% 14% 2	2800
	21st to end	Day	47% 8% 11% 20% 12% 1	2800
July	1st to 10th	Day	42% 8% 13% 27% 9%	6290
	11th to 20th	Day	35% 8% 14% 32% 12%	6285
	21st to end	Day	32% 6% 16% 36% 11%	6728
August	1st to 10th	Day	44% 7% 15% 23% 10%	4357
	11th to 20th	Day	42% 7% 17% 26% 7%	4213
	21st to end	Day	36% 7% 15% 31% 10% 1	4388
September	1st to 10th	Day	39% 6% 16% 27% 11%	2400
	11th to 20th	Day	38% 7% 11% 32% 11% 1	2400
	21st to end	Day	47% 7% 13% 23% 10%	2100
October	1st to 10th	Day	50% 7% 9% 26% 7% 1	3260
	11th to 20th	Day	52% 6% 12% 23% 6%	3240
	21st to end	Day	57% 7% 17% 15% 4 1	3363
November	1st to 10th	Day	51% 6% 14% 22% 7%	1753
	11th to 20th	Day	61% 6% 13% 13% 6% 1	1656
	21st to end	Day	70% 7% 10% 8% 5%	1600
December	1st to 10th	Day	74% 7% 9% 9% 2	2600
	11th to 20th	Day	65% 7% 5% 14% 8%	2986
	21st to end	Day	71% 5% 7% 14% 4	3960
January	1st to 10th	Night	72% 6% 9% 10% 3	6349
	11th to 20th	Night	64% 8% 10% 12% 5%	6360
	21st to end	Night	67% 5% 8% 9% 10%	6675
February	1st to 10th	Night	63% 6% 10% 15% 6% 1	2600
	11th to 20th	Night	61% 4 11% 17% 6% 1	2535
	21st to end	Night	58% 6% 8% 19% 8% 1	2051
March	1st to 10th	Night	59% 5% 9% 14% 10% 3	5190
	11th to 20th	Night	52% 7% 17% 15% 8% 1	4980
	21st to end	Night	52% 5% 9% 19% 13% 2	5292
April	1st to 10th	Night	55% 5% 8% 17% 12% 2	2000
	11th to 20th	Night	50% 4 8% 22% 14% 2	1975
	21st to end	Night	53% 5% 7% 17% 16% 3	1825
May	1st to 10th	Night	50% 8% 9% 20% 10% 4	3605
	11th to 20th	Night	40% 8% 13% 20% 15% 3	3576
	21st to end	Night	48% 8% 11% 18% 13% 2	3927
June	1st to 10th	Night	46% 8% 11% 23% 11% 1	1600
	11th to 20th	Night	37% 8% 11% 26% 16% 2	1600
	21st to end	Night	45% 7% 13% 20% 13% 1	1600
July	1st to 10th	Night	42% 9% 15% 23% 11% 1	3560
	11th to 20th	Night	36% 7% 13% 31% 12%	3552
	21st to end	Night	32% 6% 12% 37% 13%	3809
August	1st to 10th	Night	36% 8% 15% 28% 13%	2765
	11th to 20th	Night	38% 8% 16% 29% 9%	2902
	21st to end	Night	37% 8% 15% 27% 11% 2	3477
September	1st to 10th	Night	37% 7% 13% 30% 13%	2000
	11th to 20th	Night	35% 6% 16% 33% 11%	2000
	21st to end	Night	43% 7% 13% 26% 11%	2296
October	1st to 10th	Night	39% 6% 13% 30% 12%	3920
	11th to 20th	Night	49% 5% 15% 21% 8%	3899
	21st to end	Night	52% 7% 17% 18% 6%	4413
November	1st to 10th	Night	54% 6% 13% 19% 8%	2762
	11th to 20th	Night	59% 6% 12% 15% 7% 1	2899
	21st to end	Night	66% 7% 11% 13% 3	2800
December	1st to 10th	Night	71% 6% 11% 9% 2	4580
	11th to 20th	Night	64% 5% 8% 12% 10%	5208
	21st to end	Night	71% 4 6% 11% 7%	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	21% 15% 35% 24% 5% 1	200
	11th to 20th	Day	27% 14% 33% 21% 4 3	200
	21st to end	Day	22% 14% 34% 21% 8% 1	287
February	1st to 10th	Day	27% 20% 35% 14% 4 1	300
	11th to 20th	Day	23% 24% 38% 15% 1	300
	21st to end	Day	29% 17% 31% 22% 2	342
March	1st to 10th	Day	25% 16% 33% 21% 4 1	500
	11th to 20th	Day	23% 17% 32% 22% 5% 1	500
	21st to end	Day	29% 16% 29% 18% 7% 1	550
April	1st to 10th	Day	28% 18% 30% 14% 9% 2	500
	11th to 20th	Day	31% 16% 23% 16% 10% 3	492
	21st to end	Day	28% 13% 33% 16% 7% 2	500
May	1st to 10th	Day	25% 12% 29% 24% 7% 3	503
	11th to 20th	Day	20% 15% 29% 23% 11% 3	527
	21st to end	Day	18% 12% 32% 23% 12% 3	573
June	1st to 10th	Day	24% 10% 33% 20% 11% 1	530
	11th to 20th	Day	16% 11% 28% 26% 13% 5%	530
	21st to end	Day	18% 12% 32% 23% 12% 3	530
July	1st to 10th	Day	11% 6% 26% 38% 14% 4	525
	11th to 20th	Day	14% 7% 27% 32% 16% 4	524
	21st to end	Day	10% 9% 30% 29% 17% 5%	576
August	1st to 10th	Day	12% 7% 25% 32% 18% 7%	526
	11th to 20th	Day	15% 5% 22% 29% 22% 8%	519
	21st to end	Day	15% 9% 26% 24% 19% 7%	583
September	1st to 10th	Day	15% 7% 28% 23% 19% 8%	530
	11th to 20th	Day	13% 7% 23% 23% 21% 14%	530
	21st to end	Day	16% 11% 28% 22% 16% 6%	530
October	1st to 10th	Day	23% 13% 23% 20% 17% 4	530
	11th to 20th	Day	25% 18% 30% 17% 8% 2	530
	21st to end	Day	29% 15% 24% 23% 7% 1	527
November	1st to 10th	Day	26% 17% 29% 20% 9%	327
	11th to 20th	Day	25% 16% 38% 14% 6% 1	214
	21st to end	Day	33% 20% 29% 13% 3 3	200
December	1st to 10th	Day	28% 13% 35% 17% 7% 1	200
	11th to 20th	Day	28% 18% 33% 15% 5% 2	200
	21st to end	Day	30% 15% 30% 16% 6% 2	220
January	1st to 10th	Night	27% 12% 32% 24% 5%	800
	11th to 20th	Night	28% 11% 26% 26% 8% 1	800
	21st to end	Night	19% 10% 31% 30% 9% 1	880
February	1st to 10th	Night	21% 12% 35% 26% 6% 1	800
	11th to 20th	Night	23% 13% 33% 26% 5%	783
	21st to end	Night	21% 16% 30% 27% 6%	660
March	1st to 10th	Night	23% 15% 30% 27% 5%	800
	11th to 20th	Night	21% 16% 31% 25% 7% 1	800
	21st to end	Night	21% 13% 31% 26% 9%	880
April	1st to 10th	Night	27% 12% 27% 27% 6%	800
	11th to 20th	Night	26% 12% 28% 25% 9%	791
	21st to end	Night	25% 10% 26% 26% 11% 1	625
May	1st to 10th	Night	22% 6% 27% 33% 11% 1	405
	11th to 20th	Night	20% 9% 28% 32% 10% 1	394
	21st to end	Night	16% 5% 33% 33% 12%	433
June	1st to 10th	Night	17% 5% 30% 40% 8% 1	400
	11th to 20th	Night	16% 7% 25% 35% 17% 1	400
	21st to end	Night	21% 6% 22% 37% 15% 1	400
July	1st to 10th	Night	9% 5% 26% 41% 17% 1	390
	11th to 20th	Night	11% 4 22% 43% 19% 1	388
	21st to end	Night	9% 4 22% 44% 20% 1	438
August	1st to 10th	Night	10% 3 19% 38% 29% 1	509
	11th to 20th	Night	12% 3 15% 37% 29% 3	594
	21st to end	Night	14% 5% 24% 34% 20% 3	810
September	1st to 10th	Night	13% 5% 27% 31% 22% 2	800
	11th to 20th	Night	17% 5% 19% 30% 26% 4	800
	21st to end	Night	22% 7% 21% 29% 20% 2	800
October	1st to 10th	Night	22% 7% 28% 27% 15% 2	800
	11th to 20th	Night	29% 8% 28% 24% 10% 1	800
	21st to end	Night	29% 11% 26% 28% 6%	880
November	1st to 10th	Night	25% 13% 24% 28% 9% 1	820
	11th to 20th	Night	25% 14% 32% 20% 9% 1	829
	21st to end	Night	32% 15% 24% 23% 6%	800
December	1st to 10th	Night	32% 14% 29% 18% 7%	800
	11th to 20th	Night	27% 12% 30% 24% 6%	800
	21st to end	Night	34% 13% 25% 23% 6%	880

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