Simcoe
Clear Sky Chart
History

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

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 9% 5% 5% 5% 4 6% 7% 32%	137751
	Night	14% 10% 4 9% 5% 5% 5% 4 5% 7% 33%	134148
Transparency	Day	49% 5% 12% 22% 11% 1	141348
	Night	49% 4 11% 21% 13% 1	138638
Seeing	Day	19% 10% 29% 24% 13% 5%	16484
	Night	20% 9% 28% 30% 12% 1	26059

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% 16% 6% 12% 6% 5% 5% 3 4 6% 22%	4856
	11th to 20th	Day	9% 21% 9% 21% 9% 6% 4 3 4 4 10%	5246
	21st to end	Day	15% 14% 6% 17% 7% 6% 5% 3 4 5% 17%	5780
February	1st to 10th	Day	15% 18% 4 12% 7% 6% 6% 3 4 4 20%	1890
	11th to 20th	Day	14% 13% 8% 14% 7% 5% 4 4 4 5% 21%	1843
	21st to end	Day	18% 13% 5% 12% 6% 5% 5% 4 4 6% 22%	1670
March	1st to 10th	Day	18% 11% 5% 12% 6% 5% 4 3 4 5% 28%	5031
	11th to 20th	Day	11% 13% 5% 9% 6% 5% 4 3 5% 8% 31%	5090
	21st to end	Day	19% 11% 4 10% 6% 5% 4 3 4 5% 31%	5586
April	1st to 10th	Day	17% 12% 5% 9% 5% 5% 4 3 5% 6% 29%	2431
	11th to 20th	Day	16% 10% 3 9% 5% 4 4 3 5% 7% 34%	2611
	21st to end	Day	18% 10% 3 8% 4 5% 4 4 5% 6% 34%	2730
May	1st to 10th	Day	18% 9% 3 9% 5% 5% 5% 4 5% 6% 30%	7642
	11th to 20th	Day	14% 9% 3 8% 5% 5% 4 4 6% 7% 34%	7841
	21st to end	Day	15% 5% 2 6% 5% 4 5% 3 5% 7% 42%	9060
June	1st to 10th	Day	11% 6% 3 7% 4 5% 4 4 6% 8% 42%	2940
	11th to 20th	Day	11% 6% 3 7% 5% 5% 5% 5% 7% 8% 38%	2870
	21st to end	Day	11% 6% 2 6% 4 4 5% 4 7% 9% 41%	2800
July	1st to 10th	Day	7% 5% 2 7% 5% 5% 5% 5% 7% 11% 41%	6360
	11th to 20th	Day	8% 6% 2 6% 5% 4 5% 4 7% 10% 42%	6094
	21st to end	Day	7% 5% 2 6% 5% 4 5% 4 6% 9% 47%	6424
August	1st to 10th	Day	15% 6% 2 5% 4 4 5% 5% 7% 9% 39%	4234
	11th to 20th	Day	10% 6% 3 7% 5% 5% 6% 5% 7% 10% 35%	4174
	21st to end	Day	9% 6% 2 7% 5% 5% 5% 5% 6% 10% 41%	4529
September	1st to 10th	Day	12% 6% 2 6% 4 5% 5% 4 6% 8% 42%	2400
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 7% 9% 48%	2212
	21st to end	Day	15% 7% 3 7% 6% 5% 5% 4 7% 7% 36%	2200
October	1st to 10th	Day	15% 7% 3 6% 5% 4 5% 4 6% 7% 39%	2000
	11th to 20th	Day	17% 9% 4 9% 5% 4 5% 3 6% 6% 33%	2000
	21st to end	Day	21% 10% 4 10% 5% 4 4 4 6% 7% 26%	2200
November	1st to 10th	Day	14% 8% 3 8% 6% 4 4 4 6% 8% 36%	1853
	11th to 20th	Day	15% 12% 4 8% 6% 5% 4 4 6% 7% 30%	1680
	21st to end	Day	20% 14% 4 8% 5% 5% 6% 5% 7% 7% 21%	1680
December	1st to 10th	Day	17% 17% 4 10% 7% 5% 6% 4 6% 6% 15%	2680
	11th to 20th	Day	21% 18% 5% 7% 5% 5% 4 4 5% 6% 21%	3066
	21st to end	Day	26% 19% 6% 10% 5% 5% 5% 3 4 5% 13%	4048
January	1st to 10th	Night	14% 15% 4 12% 6% 5% 5% 4 5% 6% 23%	8036
	11th to 20th	Night	10% 17% 7% 14% 7% 6% 5% 4 5% 6% 18%	7639
	21st to end	Night	16% 14% 6% 14% 8% 5% 5% 3 4 5% 20%	8401
February	1st to 10th	Night	15% 16% 5% 10% 6% 6% 5% 4 5% 5% 24%	2730
	11th to 20th	Night	15% 13% 4 10% 6% 5% 6% 3 6% 7% 25%	2663
	21st to end	Night	16% 13% 5% 11% 5% 5% 5% 4 5% 7% 23%	2134
March	1st to 10th	Night	15% 9% 4 8% 6% 6% 5% 4 5% 6% 33%	5029
	11th to 20th	Night	11% 8% 3 8% 4 4 4 3 6% 8% 39%	5089
	21st to end	Night	16% 10% 4 7% 5% 4 4 3 5% 5% 37%	5588
April	1st to 10th	Night	19% 9% 4 7% 6% 4 4 4 5% 7% 30%	2189
	11th to 20th	Night	17% 9% 3 7% 5% 4 5% 4 6% 7% 35%	1976
	21st to end	Night	15% 6% 3 8% 5% 5% 5% 4 6% 7% 36%	1890
May	1st to 10th	Night	19% 8% 3 8% 5% 4 4 4 5% 7% 33%	5257
	11th to 20th	Night	13% 9% 3 9% 5% 5% 5% 3 5% 7% 36%	5001
	21st to end	Night	19% 6% 2 5% 4 3 4 3 6% 8% 41%	5114
June	1st to 10th	Night	10% 6% 2 7% 4 4 5% 4 7% 8% 43%	1680
	11th to 20th	Night	8% 6% 2 6% 5% 5% 5% 5% 7% 9% 41%	1640
	21st to end	Night	10% 5% 2 6% 5% 3 4 4 6% 8% 47%	1507
July	1st to 10th	Night	6% 6% 2 5% 5% 4 5% 4 6% 10% 48%	3600
	11th to 20th	Night	8% 5% 2 6% 5% 4 5% 4 6% 8% 47%	3862
	21st to end	Night	7% 5% 2 6% 4 4 5% 4 6% 7% 50%	4428
August	1st to 10th	Night	10% 6% 2 6% 5% 5% 4 4 7% 8% 44%	2915
	11th to 20th	Night	11% 5% 2 6% 4 4 4 4 5% 9% 46%	2875
	21st to end	Night	7% 4 2 5% 4 5% 5% 4 6% 9% 49%	3322
September	1st to 10th	Night	11% 6% 3 7% 4 4 4 3 5% 7% 48%	2000
	11th to 20th	Night	9% 4 2 4 3 4 3 3 5% 7% 57%	2185
	21st to end	Night	16% 6% 2 7% 5% 4 5% 4 6% 6% 40%	2200
October	1st to 10th	Night	14% 5% 2 7% 4 3 4 3 5% 7% 45%	2400
	11th to 20th	Night	16% 11% 3 7% 5% 4 4 3 5% 6% 37%	2400
	21st to end	Night	20% 8% 3 7% 5% 4 4 4 5% 6% 34%	2640
November	1st to 10th	Night	13% 9% 2 6% 5% 4 4 4 5% 7% 41%	2660
	11th to 20th	Night	15% 10% 4 8% 5% 6% 5% 4 6% 8% 29%	2940
	21st to end	Night	19% 13% 4 8% 5% 5% 5% 3 6% 6% 27%	2940
December	1st to 10th	Night	15% 16% 4 10% 6% 6% 6% 4 6% 7% 21%	4720
	11th to 20th	Night	17% 18% 4 10% 6% 4 4 3 4 5% 24%	5348
	21st to end	Night	23% 17% 5% 10% 5% 4 4 3 5% 5% 18%	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	61% 4 13% 13% 9%	4857
	11th to 20th	Day	77% 4 6% 8% 4	5280
	21st to end	Day	70% 4 10% 10% 6%	5780
February	1st to 10th	Day	68% 2 9% 15% 6% 1	1890
	11th to 20th	Day	65% 4 7% 17% 7%	1852
	21st to end	Day	63% 3 11% 16% 6% 1	1670
March	1st to 10th	Day	59% 3 12% 19% 7%	5034
	11th to 20th	Day	51% 3 16% 20% 7% 2	5090
	21st to end	Day	56% 3 7% 22% 11% 1	5586
April	1st to 10th	Day	56% 4 10% 17% 12% 1	2431
	11th to 20th	Day	52% 3 10% 22% 12% 1	2611
	21st to end	Day	51% 3 10% 21% 13% 2	2730
May	1st to 10th	Day	52% 5% 11% 20% 9% 4	7651
	11th to 20th	Day	49% 5% 12% 23% 11% 1	7845
	21st to end	Day	41% 4 10% 26% 17% 2	9061
June	1st to 10th	Day	39% 4 11% 27% 17% 2	2940
	11th to 20th	Day	41% 5% 15% 25% 13% 2	2870
	21st to end	Day	38% 5% 13% 27% 16% 1	2800
July	1st to 10th	Day	35% 6% 13% 27% 17% 2	6290
	11th to 20th	Day	35% 6% 14% 29% 16% 1	6020
	21st to end	Day	32% 7% 13% 26% 21% 1	6240
August	1st to 10th	Day	41% 6% 14% 25% 14% 1	4221
	11th to 20th	Day	40% 7% 16% 26% 10% 1	4213
	21st to end	Day	35% 7% 13% 31% 12% 1	4529
September	1st to 10th	Day	38% 5% 14% 28% 13% 1	2400
	11th to 20th	Day	33% 4 13% 34% 17%	2212
	21st to end	Day	46% 4 14% 24% 11% 1	2200
October	1st to 10th	Day	35% 5% 14% 27% 17% 1	3260
	11th to 20th	Day	39% 4 14% 27% 15%	3240
	21st to end	Day	47% 5% 15% 24% 8%	3538
November	1st to 10th	Day	47% 4 12% 26% 9% 2	1853
	11th to 20th	Day	52% 4 14% 19% 10% 1	1680
	21st to end	Day	60% 4 14% 16% 5% 1	1680
December	1st to 10th	Day	67% 5% 14% 12% 3	2680
	11th to 20th	Day	63% 4 13% 11% 9%	3066
	21st to end	Day	74% 3 8% 9% 5%	4048
January	1st to 10th	Night	59% 4 12% 18% 6% 1	8036
	11th to 20th	Night	64% 4 9% 15% 7% 1	7680
	21st to end	Night	66% 3 7% 13% 11%	8401
February	1st to 10th	Night	62% 3 10% 18% 6% 1	2730
	11th to 20th	Night	59% 4 11% 19% 8% 1	2665
	21st to end	Night	60% 2 10% 19% 8% 1	2134
March	1st to 10th	Night	51% 4 12% 21% 10% 2	5039
	11th to 20th	Night	43% 4 16% 23% 13% 1	5090
	21st to end	Night	49% 3 10% 20% 17% 2	5588
April	1st to 10th	Night	54% 3 9% 18% 14% 1	2189
	11th to 20th	Night	49% 3 8% 21% 16% 2	1976
	21st to end	Night	46% 3 10% 23% 15% 3	1890
May	1st to 10th	Night	52% 4 9% 16% 14% 6%	5264
	11th to 20th	Night	48% 4 12% 24% 11% 2	5002
	21st to end	Night	42% 3 9% 25% 18% 2	5115
June	1st to 10th	Night	39% 4 9% 27% 18% 4	1680
	11th to 20th	Night	38% 4 13% 26% 17% 2	1640
	21st to end	Night	37% 4 13% 24% 20% 2	1507
July	1st to 10th	Night	32% 6% 12% 25% 20% 4	3560
	11th to 20th	Night	34% 5% 12% 30% 17% 2	3813
	21st to end	Night	31% 6% 13% 23% 26% 2	4297
August	1st to 10th	Night	36% 5% 12% 27% 17% 2	2904
	11th to 20th	Night	35% 5% 16% 32% 11% 1	2902
	21st to end	Night	29% 5% 14% 34% 17% 1	3322
September	1st to 10th	Night	37% 3 11% 30% 16% 2	2000
	11th to 20th	Night	29% 3 12% 36% 20% 1	2185
	21st to end	Night	44% 3 12% 26% 14% 1	2200
October	1st to 10th	Night	31% 4 7% 31% 25% 1	3920
	11th to 20th	Night	43% 3 12% 26% 16%	3899
	21st to end	Night	39% 4 15% 26% 15% 1	4252
November	1st to 10th	Night	43% 4 11% 27% 15% 1	2660
	11th to 20th	Night	52% 3 12% 21% 10% 1	2940
	21st to end	Night	57% 3 16% 17% 6%	2940
December	1st to 10th	Night	61% 6% 15% 14% 4	4720
	11th to 20th	Night	62% 4 10% 14% 10% 1	5348
	21st to end	Night	68% 4 11% 11% 6%	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% 18% 36% 14% 6% 1	255
	11th to 20th	Day	27% 21% 37% 10% 4 1	330
	21st to end	Day	26% 18% 34% 17% 5% 1	363
February	1st to 10th	Day	24% 18% 37% 16% 5% 1	330
	11th to 20th	Day	23% 22% 37% 17% 2	330
	21st to end	Day	27% 28% 32% 12% 1	273
March	1st to 10th	Day	23% 12% 35% 22% 8%	529
	11th to 20th	Day	25% 13% 35% 19% 6% 1	540
	21st to end	Day	29% 13% 32% 20% 6% 1	594
April	1st to 10th	Day	22% 17% 32% 22% 6% 1	540
	11th to 20th	Day	25% 14% 32% 18% 8% 3	532
	21st to end	Day	24% 8% 35% 23% 8% 2	540
May	1st to 10th	Day	25% 9% 30% 23% 9% 4	543
	11th to 20th	Day	17% 9% 27% 26% 16% 4	567
	21st to end	Day	15% 6% 28% 28% 17% 6%	617
June	1st to 10th	Day	13% 9% 32% 31% 13% 2	570
	11th to 20th	Day	14% 10% 25% 30% 16% 5%	550
	21st to end	Day	15% 4 30% 33% 15% 4	530
July	1st to 10th	Day	11% 4 20% 32% 22% 11%	525
	11th to 20th	Day	14% 5% 23% 28% 20% 11%	524
	21st to end	Day	9% 2 22% 37% 22% 7%	576
August	1st to 10th	Day	11% 2 20% 31% 20% 15%	526
	11th to 20th	Day	9% 4 20% 32% 20% 15%	519
	21st to end	Day	13% 3 20% 31% 21% 12%	583
September	1st to 10th	Day	14% 5% 22% 25% 22% 12%	530
	11th to 20th	Day	8% 3 16% 27% 31% 15%	530
	21st to end	Day	18% 8% 23% 28% 15% 8%	530
October	1st to 10th	Day	20% 7% 24% 24% 19% 6%	530
	11th to 20th	Day	18% 12% 35% 23% 8% 3	530
	21st to end	Day	26% 12% 32% 22% 8% 1	583
November	1st to 10th	Day	20% 18% 34% 19% 7% 2	343
	11th to 20th	Day	23% 20% 30% 18% 6% 3	220
	21st to end	Day	29% 16% 35% 17% 3	220
December	1st to 10th	Day	30% 17% 30% 17% 4 1	220
	11th to 20th	Day	28% 22% 31% 14% 4	220
	21st to end	Day	30% 16% 36% 14% 4	242
January	1st to 10th	Night	24% 16% 35% 20% 5%	840
	11th to 20th	Night	28% 17% 32% 19% 5%	840
	21st to end	Night	22% 13% 35% 25% 5%	924
February	1st to 10th	Night	25% 14% 33% 25% 2	840
	11th to 20th	Night	22% 14% 36% 24% 4	823
	21st to end	Night	24% 14% 37% 21% 3	692
March	1st to 10th	Night	19% 12% 35% 27% 7%	840
	11th to 20th	Night	23% 10% 36% 23% 8%	840
	21st to end	Night	23% 10% 31% 27% 9% 1	924
April	1st to 10th	Night	22% 12% 32% 29% 5%	840
	11th to 20th	Night	22% 10% 32% 28% 8% 1	732
	21st to end	Night	18% 5% 33% 34% 9%	630
May	1st to 10th	Night	20% 5% 28% 31% 15% 1	630
	11th to 20th	Night	16% 3 27% 38% 14% 2	544
	21st to end	Night	14% 4 24% 38% 18% 2	455
June	1st to 10th	Night	13% 2 29% 40% 15%	420
	11th to 20th	Night	11% 4 26% 42% 17%	410
	21st to end	Night	12% 3 23% 45% 16% 1	400
July	1st to 10th	Night	7% 2 21% 45% 23% 2	390
	11th to 20th	Night	11% 2 21% 40% 23% 3	493
	21st to end	Night	9% 1 18% 48% 22% 2	657
August	1st to 10th	Night	8% 3 13% 44% 28% 4	597
	11th to 20th	Night	11% 1 14% 39% 31% 4	594
	21st to end	Night	11% 2 19% 37% 28% 3	720
September	1st to 10th	Night	14% 4 18% 35% 25% 5%	800
	11th to 20th	Night	11% 3 13% 35% 32% 6%	800
	21st to end	Night	19% 5% 19% 32% 22% 5%	800
October	1st to 10th	Night	17% 4 23% 31% 20% 4	800
	11th to 20th	Night	23% 8% 28% 28% 11% 2	800
	21st to end	Night	25% 9% 31% 29% 6%	880
November	1st to 10th	Night	20% 11% 29% 28% 11% 2	820
	11th to 20th	Night	22% 16% 31% 23% 6% 2	840
	21st to end	Night	28% 12% 32% 21% 7%	840
December	1st to 10th	Night	29% 14% 30% 20% 6% 1	840
	11th to 20th	Night	27% 17% 32% 20% 4	840
	21st to end	Night	31% 11% 31% 24% 3	924

Page generated at 2026-06-13 02:31:39. Version ac07

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