Oshawa
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oshawa clear sky chart from 2005-11-06 to 2025-08-05.

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% 9% 3 8% 5% 5% 5% 4 6% 7% 35%	126056
	Night	16% 9% 3 8% 5% 5% 5% 4 5% 7% 34%	121995
Transparency	Day	46% 7% 14% 21% 11% 1	129645
	Night	47% 7% 14% 20% 11% 1	126492
Seeing	Day	18% 11% 28% 26% 13% 4	15362
	Night	20% 9% 28% 30% 13% 2	24685

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% 10% 4 10% 7% 5% 5% 3 5% 5% 32%	3597
	11th to 20th	Day	10% 17% 7% 17% 9% 6% 5% 4 4 5% 16%	3813
	21st to end	Day	16% 17% 6% 12% 6% 5% 4 3 4 5% 20%	4466
February	1st to 10th	Day	15% 14% 4 12% 7% 6% 6% 4 5% 5% 23%	1800
	11th to 20th	Day	13% 14% 6% 13% 6% 5% 4 3 5% 6% 26%	1753
	21st to end	Day	18% 13% 4 10% 6% 5% 4 3 5% 5% 28%	1530
March	1st to 10th	Day	20% 9% 4 8% 5% 4 4 3 5% 6% 33%	4932
	11th to 20th	Day	11% 12% 4 8% 5% 6% 6% 4 6% 8% 31%	4980
	21st to end	Day	18% 9% 3 8% 5% 4 4 3 4 5% 36%	5465
April	1st to 10th	Day	17% 11% 3 8% 6% 4 4 4 6% 7% 31%	2390
	11th to 20th	Day	19% 9% 3 6% 4 4 4 4 5% 6% 36%	2414
	21st to end	Day	19% 8% 2 7% 5% 5% 4 4 5% 6% 35%	2600
May	1st to 10th	Day	19% 8% 2 8% 4 5% 5% 4 5% 7% 32%	5969
	11th to 20th	Day	16% 9% 3 8% 5% 4 4 4 6% 7% 33%	6318
	21st to end	Day	17% 6% 2 6% 5% 4 4 3 6% 8% 39%	6949
June	1st to 10th	Day	15% 6% 2 7% 5% 4 5% 4 7% 9% 37%	2800
	11th to 20th	Day	11% 5% 2 6% 5% 5% 5% 4 7% 9% 42%	2800
	21st to end	Day	13% 6% 2 6% 4 4 5% 4 7% 9% 41%	2800
July	1st to 10th	Day	9% 5% 2 6% 5% 5% 5% 4 7% 9% 43%	6360
	11th to 20th	Day	9% 4 2 5% 4 4 5% 4 6% 9% 48%	6360
	21st to end	Day	6% 4 1 5% 5% 4 6% 5% 7% 9% 48%	6612
August	1st to 10th	Day	15% 7% 3 6% 4 4 5% 4 6% 7% 41%	4156
	11th to 20th	Day	11% 6% 3 7% 5% 5% 4 4 7% 10% 40%	4044
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 6% 10% 45%	4316
September	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 7% 7% 45%	2280
	11th to 20th	Day	11% 4 2 5% 3 5% 4 4 6% 7% 49%	2209
	21st to end	Day	13% 6% 2 7% 5% 5% 5% 4 5% 8% 40%	2025
October	1st to 10th	Day	16% 7% 3 6% 5% 5% 5% 4 5% 6% 37%	1900
	11th to 20th	Day	19% 8% 2 8% 5% 4 4 4 6% 7% 32%	1900
	21st to end	Day	22% 10% 3 8% 6% 5% 4 3 5% 6% 27%	2090
November	1st to 10th	Day	15% 8% 3 9% 6% 5% 5% 4 5% 7% 33%	1682
	11th to 20th	Day	15% 10% 4 8% 8% 6% 5% 4 7% 7% 27%	1600
	21st to end	Day	20% 11% 4 9% 7% 5% 4 4 4 8% 25%	1600
December	1st to 10th	Day	18% 15% 5% 10% 8% 7% 7% 5% 6% 6% 14%	2600
	11th to 20th	Day	20% 14% 5% 9% 5% 4 4 3 5% 6% 25%	2986
	21st to end	Day	27% 15% 6% 11% 6% 5% 5% 3 4 5% 15%	3960
January	1st to 10th	Night	16% 12% 4 9% 5% 6% 5% 4 6% 7% 27%	6349
	11th to 20th	Night	13% 14% 5% 14% 8% 6% 5% 4 5% 8% 18%	6070
	21st to end	Night	16% 14% 6% 10% 5% 5% 4 4 5% 6% 24%	6490
February	1st to 10th	Night	15% 14% 4 10% 7% 5% 5% 4 6% 5% 25%	2600
	11th to 20th	Night	15% 13% 5% 9% 6% 5% 4 4 6% 5% 28%	2533
	21st to end	Night	15% 10% 4 9% 6% 5% 5% 4 6% 6% 30%	2094
March	1st to 10th	Night	18% 10% 4 7% 5% 5% 5% 4 5% 6% 32%	4908
	11th to 20th	Night	11% 9% 3 8% 5% 5% 5% 4 6% 8% 36%	4979
	21st to end	Night	21% 7% 2 6% 4 4 4 3 4 5% 39%	5467
April	1st to 10th	Night	19% 10% 3 7% 5% 4 4 4 5% 6% 33%	2010
	11th to 20th	Night	16% 7% 3 7% 5% 5% 5% 3 5% 6% 38%	1951
	21st to end	Night	17% 8% 3 7% 4 4 5% 3 6% 7% 36%	1800
May	1st to 10th	Night	24% 8% 3 6% 4 4 4 3 5% 5% 34%	3971
	11th to 20th	Night	15% 7% 3 8% 5% 4 7% 5% 6% 7% 35%	3575
	21st to end	Night	17% 5% 2 6% 5% 4 4 4 5% 7% 41%	3926
June	1st to 10th	Night	12% 5% 2 6% 5% 4 5% 4 7% 8% 42%	1600
	11th to 20th	Night	8% 4 3 7% 6% 4 5% 4 6% 9% 44%	1600
	21st to end	Night	12% 5% 2 6% 4 4 4 6% 7% 9% 42%	1600
July	1st to 10th	Night	8% 5% 2 6% 4 5% 5% 4 6% 9% 46%	3600
	11th to 20th	Night	10% 4 2 5% 4 3 4 4 6% 8% 49%	3600
	21st to end	Night	9% 4 2 5% 3 3 4 4 6% 8% 53%	4236
August	1st to 10th	Night	10% 5% 2 6% 4 4 4 3 6% 8% 48%	2861
	11th to 20th	Night	12% 5% 2 5% 3 4 4 3 5% 8% 50%	2785
	21st to end	Night	10% 5% 2 6% 4 4 5% 4 6% 8% 47%	3307
September	1st to 10th	Night	10% 5% 2 5% 4 4 6% 3 6% 7% 47%	1900
	11th to 20th	Night	11% 4 2 4 3 4 3 3 5% 8% 54%	1966
	21st to end	Night	16% 6% 2 7% 5% 4 4 3 4 6% 43%	2153
October	1st to 10th	Night	16% 6% 3 7% 4 4 3 4 5% 7% 40%	2280
	11th to 20th	Night	20% 9% 3 7% 5% 4 5% 4 5% 6% 33%	2280
	21st to end	Night	22% 8% 3 7% 5% 5% 5% 4 5% 6% 31%	2508
November	1st to 10th	Night	17% 7% 2 6% 5% 5% 4 4 6% 6% 38%	2612
	11th to 20th	Night	17% 10% 3 7% 6% 5% 5% 5% 5% 7% 31%	2800
	21st to end	Night	21% 10% 3 7% 5% 5% 5% 4 7% 7% 25%	2800
December	1st to 10th	Night	18% 14% 4 10% 6% 6% 6% 5% 5% 7% 20%	4580
	11th to 20th	Night	18% 15% 4 9% 5% 5% 5% 4 6% 6% 24%	5208
	21st to end	Night	26% 14% 6% 10% 5% 5% 5% 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	51% 7% 17% 15% 10% 1	3598
	11th to 20th	Day	69% 6% 12% 8% 3	3846
	21st to end	Day	65% 6% 11% 10% 7%	4466
February	1st to 10th	Day	63% 6% 12% 15% 4 1	1800
	11th to 20th	Day	58% 7% 10% 17% 7% 1	1762
	21st to end	Day	57% 6% 12% 18% 7%	1530
March	1st to 10th	Day	50% 6% 15% 14% 14%	4935
	11th to 20th	Day	48% 8% 18% 16% 8% 2	4980
	21st to end	Day	47% 6% 9% 21% 15% 1	5465
April	1st to 10th	Day	51% 7% 11% 19% 11% 2	2390
	11th to 20th	Day	47% 6% 9% 22% 14% 1	2414
	21st to end	Day	48% 6% 11% 19% 12% 3	2600
May	1st to 10th	Day	48% 8% 12% 17% 11% 4	5978
	11th to 20th	Day	48% 9% 12% 14% 15% 1	6322
	21st to end	Day	42% 7% 14% 23% 11% 3	6949
June	1st to 10th	Day	41% 8% 13% 22% 14% 1	2800
	11th to 20th	Day	36% 8% 14% 26% 15% 2	2800
	21st to end	Day	37% 8% 15% 24% 14% 1	2800
July	1st to 10th	Day	33% 8% 15% 26% 15% 1	6290
	11th to 20th	Day	30% 8% 14% 33% 15% 1	6285
	21st to end	Day	29% 9% 15% 31% 15%	6423
August	1st to 10th	Day	40% 8% 15% 24% 13% 1	4143
	11th to 20th	Day	37% 7% 17% 29% 10%	4083
	21st to end	Day	31% 9% 15% 34% 10% 1	4316
September	1st to 10th	Day	36% 8% 15% 29% 11% 1	2280
	11th to 20th	Day	32% 7% 15% 31% 15% 1	2209
	21st to end	Day	40% 8% 15% 26% 10%	2025
October	1st to 10th	Day	36% 6% 16% 28% 14% 1	3160
	11th to 20th	Day	36% 7% 19% 24% 14%	3140
	21st to end	Day	48% 8% 16% 21% 6%	3428
November	1st to 10th	Day	48% 7% 14% 21% 9% 1	1682
	11th to 20th	Day	54% 7% 15% 16% 8% 1	1600
	21st to end	Day	58% 7% 14% 17% 4	1600
December	1st to 10th	Day	67% 9% 13% 9% 2	2600
	11th to 20th	Day	59% 8% 13% 12% 8%	2986
	21st to end	Day	70% 7% 8% 9% 5%	3960
January	1st to 10th	Night	53% 8% 14% 18% 6%	6349
	11th to 20th	Night	62% 10% 14% 9% 4	6112
	21st to end	Night	59% 6% 16% 13% 6% 1	6490
February	1st to 10th	Night	59% 6% 13% 17% 4 1	2600
	11th to 20th	Night	56% 6% 11% 18% 8%	2535
	21st to end	Night	52% 6% 14% 20% 7% 1	2094
March	1st to 10th	Night	52% 5% 11% 18% 12% 3	4918
	11th to 20th	Night	43% 6% 19% 22% 10% 2	4980
	21st to end	Night	45% 6% 9% 21% 17% 2	5467
April	1st to 10th	Night	51% 6% 9% 20% 13% 1	2010
	11th to 20th	Night	46% 6% 10% 19% 17% 2	1951
	21st to end	Night	47% 5% 10% 21% 15% 2	1800
May	1st to 10th	Night	51% 5% 11% 14% 13% 5%	3978
	11th to 20th	Night	43% 8% 14% 19% 13% 2	3576
	21st to end	Night	41% 7% 14% 22% 15% 2	3927
June	1st to 10th	Night	39% 8% 11% 24% 16% 3	1600
	11th to 20th	Night	36% 7% 12% 23% 21% 2	1600
	21st to end	Night	36% 8% 13% 26% 16% 1	1600
July	1st to 10th	Night	32% 7% 16% 24% 19% 2	3560
	11th to 20th	Night	30% 7% 14% 32% 16% 1	3552
	21st to end	Night	28% 7% 13% 29% 22% 1	4110
August	1st to 10th	Night	34% 4 15% 29% 15% 2	2850
	11th to 20th	Night	33% 6% 16% 32% 12% 1	2812
	21st to end	Night	32% 6% 14% 32% 14% 1	3307
September	1st to 10th	Night	34% 6% 16% 28% 14% 1	1900
	11th to 20th	Night	30% 5% 14% 32% 19%	1966
	21st to end	Night	42% 5% 13% 27% 12% 1	2153
October	1st to 10th	Night	33% 5% 11% 28% 22% 1	3800
	11th to 20th	Night	41% 6% 15% 29% 9%	3779
	21st to end	Night	39% 7% 15% 28% 10% 1	4120
November	1st to 10th	Night	45% 5% 13% 23% 12% 1	2612
	11th to 20th	Night	51% 6% 15% 18% 10% 1	2800
	21st to end	Night	55% 8% 18% 15% 4	2800
December	1st to 10th	Night	60% 7% 16% 13% 3	4580
	11th to 20th	Night	60% 8% 11% 13% 8%	5208
	21st to end	Night	68% 7% 12% 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	24% 16% 34% 19% 8% 1	200
	11th to 20th	Day	25% 23% 32% 15% 6% 1	253
	21st to end	Day	25% 22% 33% 17% 3 1	330
February	1st to 10th	Day	24% 24% 35% 12% 4	300
	11th to 20th	Day	23% 24% 39% 13% 2	300
	21st to end	Day	31% 18% 36% 13% 1	294
March	1st to 10th	Day	24% 18% 32% 21% 6%	500
	11th to 20th	Day	22% 17% 33% 21% 6%	500
	21st to end	Day	31% 12% 29% 20% 8% 1	550
April	1st to 10th	Day	22% 14% 36% 23% 5%	500
	11th to 20th	Day	26% 13% 29% 21% 8% 3	492
	21st to end	Day	23% 13% 34% 19% 9% 2	500
May	1st to 10th	Day	21% 11% 29% 25% 10% 5%	503
	11th to 20th	Day	15% 8% 26% 32% 15% 4	527
	21st to end	Day	14% 6% 24% 31% 19% 6%	573
June	1st to 10th	Day	15% 8% 29% 31% 15% 2	530
	11th to 20th	Day	12% 6% 26% 34% 20% 2	530
	21st to end	Day	15% 7% 26% 32% 15% 5%	530
July	1st to 10th	Day	8% 4 20% 36% 24% 8%	525
	11th to 20th	Day	13% 4 19% 34% 22% 8%	524
	21st to end	Day	8% 3 26% 39% 19% 6%	576
August	1st to 10th	Day	10% 4 20% 34% 21% 10%	502
	11th to 20th	Day	10% 5% 19% 30% 28% 8%	479
	21st to end	Day	12% 4 21% 31% 23% 9%	539
September	1st to 10th	Day	12% 7% 22% 30% 19% 10%	490
	11th to 20th	Day	10% 4 19% 28% 24% 16%	490
	21st to end	Day	15% 8% 28% 26% 16% 7%	490
October	1st to 10th	Day	19% 9% 26% 26% 15% 5%	490
	11th to 20th	Day	18% 16% 32% 24% 8% 1	490
	21st to end	Day	27% 12% 32% 21% 8% 1	539
November	1st to 10th	Day	21% 18% 27% 25% 9% 1	296
	11th to 20th	Day	18% 19% 37% 21% 6% 1	200
	21st to end	Day	28% 16% 36% 17% 5% 1	200
December	1st to 10th	Day	22% 18% 33% 19% 7% 3	200
	11th to 20th	Day	31% 20% 27% 17% 6%	200
	21st to end	Day	26% 21% 36% 15% 2	220
January	1st to 10th	Night	25% 15% 38% 17% 6%	800
	11th to 20th	Night	28% 13% 33% 22% 4 1	800
	21st to end	Night	21% 11% 35% 26% 7%	880
February	1st to 10th	Night	22% 15% 38% 23% 3	800
	11th to 20th	Night	22% 14% 36% 22% 5%	783
	21st to end	Night	22% 12% 39% 22% 4	660
March	1st to 10th	Night	21% 13% 34% 27% 5% 1	800
	11th to 20th	Night	21% 12% 35% 27% 5% 1	800
	21st to end	Night	21% 10% 30% 27% 11%	880
April	1st to 10th	Night	24% 10% 32% 28% 6%	800
	11th to 20th	Night	18% 10% 32% 29% 9% 2	767
	21st to end	Night	20% 8% 27% 33% 12%	600
May	1st to 10th	Night	22% 4 26% 29% 17% 2	570
	11th to 20th	Night	14% 4 27% 38% 15%	394
	21st to end	Night	12% 3 19% 42% 21% 2	433
June	1st to 10th	Night	15% 3 22% 42% 18% 1	400
	11th to 20th	Night	9% 5% 22% 42% 21% 1	400
	21st to end	Night	11% 5% 21% 41% 21% 1	400
July	1st to 10th	Night	5% 3 16% 45% 27% 3	390
	11th to 20th	Night	11% 4 15% 37% 30% 2	388
	21st to end	Night	11% 2 14% 47% 25% 2	569
August	1st to 10th	Night	9% 2 12% 41% 31% 4	579
	11th to 20th	Night	8% 2 13% 41% 30% 5%	564
	21st to end	Night	13% 3 18% 37% 27% 3	732
September	1st to 10th	Night	12% 5% 18% 36% 24% 5%	760
	11th to 20th	Night	14% 4 17% 30% 28% 8%	760
	21st to end	Night	21% 5% 18% 31% 21% 5%	760
October	1st to 10th	Night	18% 5% 27% 28% 20% 2	760
	11th to 20th	Night	22% 11% 27% 27% 11% 1	760
	21st to end	Night	26% 7% 29% 30% 6% 1	836
November	1st to 10th	Night	21% 11% 25% 31% 11% 1	780
	11th to 20th	Night	23% 12% 30% 27% 7% 2	800
	21st to end	Night	25% 10% 32% 26% 7%	800
December	1st to 10th	Night	29% 13% 31% 22% 5%	800
	11th to 20th	Night	23% 13% 36% 23% 4 1	800
	21st to end	Night	31% 10% 35% 21% 2	880

Page generated at 2025-08-02 01:32:29. Version ac07

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