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 2025-02-21.

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%	108751
	Night	15% 10% 4 8% 5% 5% 4 4 5% 7% 33%	109721
Transparency	Day	50% 4 12% 22% 11% 1	112392
	Night	49% 4 11% 22% 12% 1	114243
Seeing	Day	19% 9% 28% 25% 13% 5%	14751
	Night	20% 8% 28% 30% 12% 2	24425

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	12% 17% 7% 11% 6% 5% 5% 3 4 6% 24%	3750
	11th to 20th	Day	10% 20% 9% 19% 9% 5% 5% 3 4 4 11%	4026
	21st to end	Day	19% 16% 6% 16% 7% 5% 5% 3 4 4 17%	4466
February	1st to 10th	Day	15% 18% 5% 12% 7% 6% 5% 3 4 4 19%	1800
	11th to 20th	Day	14% 13% 8% 14% 7% 6% 4 4 4 5% 21%	1753
	21st to end	Day	19% 13% 5% 12% 6% 5% 5% 4 4 5% 23%	1515
March	1st to 10th	Day	20% 12% 4 9% 6% 5% 4 3 4 6% 27%	3422
	11th to 20th	Day	11% 15% 5% 10% 6% 5% 4 3 5% 7% 29%	3480
	21st to end	Day	18% 10% 3 9% 6% 4 4 3 5% 5% 33%	3815
April	1st to 10th	Day	16% 12% 5% 9% 6% 5% 4 3 5% 7% 29%	2199
	11th to 20th	Day	17% 9% 3 9% 5% 4 4 2 5% 7% 35%	2359
	21st to end	Day	19% 10% 3 8% 4 5% 4 4 5% 6% 33%	2470
May	1st to 10th	Day	19% 8% 2 8% 6% 5% 5% 4 6% 7% 32%	4108
	11th to 20th	Day	15% 10% 3 8% 6% 5% 4 4 6% 8% 31%	4198
	21st to end	Day	11% 5% 2 6% 4 4 5% 4 6% 8% 45%	4837
June	1st to 10th	Day	12% 6% 3 7% 5% 5% 4 4 7% 8% 41%	2660
	11th to 20th	Day	11% 6% 2 7% 5% 4 5% 5% 7% 8% 39%	2660
	21st to end	Day	11% 6% 2 6% 4 4 5% 4 7% 9% 41%	2660
July	1st to 10th	Day	9% 5% 2 6% 5% 4 5% 5% 7% 11% 42%	4440
	11th to 20th	Day	10% 6% 2 6% 4 4 5% 5% 8% 10% 41%	4258
	21st to end	Day	6% 5% 2 6% 5% 5% 6% 5% 7% 10% 42%	4466
August	1st to 10th	Day	15% 6% 2 5% 4 4 5% 5% 6% 9% 38%	4104
	11th to 20th	Day	10% 6% 3 7% 5% 5% 7% 5% 7% 10% 35%	4044
	21st to end	Day	9% 6% 2 7% 5% 5% 5% 5% 6% 10% 41%	4390
September	1st to 10th	Day	12% 6% 2 6% 4 5% 5% 4 6% 8% 42%	2280
	11th to 20th	Day	9% 5% 2 5% 5% 4 4 4 7% 9% 47%	2102
	21st to end	Day	15% 7% 3 7% 6% 5% 5% 4 7% 7% 36%	2090
October	1st to 10th	Day	15% 7% 3 7% 5% 4 5% 4 6% 7% 37%	1900
	11th to 20th	Day	17% 10% 4 9% 4 4 5% 3 6% 6% 32%	1900
	21st to end	Day	21% 11% 4 10% 5% 4 4 4 6% 7% 25%	2090
November	1st to 10th	Day	14% 7% 3 8% 6% 4 4 4 6% 7% 37%	1763
	11th to 20th	Day	15% 11% 4 8% 6% 5% 4 4 6% 7% 30%	1600
	21st to end	Day	21% 14% 4 7% 5% 4 6% 5% 7% 7% 21%	1600
December	1st to 10th	Day	18% 17% 4 10% 7% 6% 6% 4 6% 6% 16%	2600
	11th to 20th	Day	21% 18% 5% 7% 5% 4 4 4 5% 6% 21%	2986
	21st to end	Day	26% 19% 5% 10% 5% 5% 5% 3 4 5% 13%	3960
January	1st to 10th	Night	14% 12% 4 12% 6% 6% 5% 4 5% 6% 26%	6193
	11th to 20th	Night	12% 16% 7% 13% 7% 6% 5% 4 6% 7% 18%	5859
	21st to end	Night	20% 14% 7% 13% 7% 4 4 3 4 5% 19%	6490
February	1st to 10th	Night	15% 16% 5% 10% 6% 6% 5% 4 6% 5% 23%	2600
	11th to 20th	Night	15% 13% 4 10% 6% 5% 6% 3 6% 7% 25%	2533
	21st to end	Night	17% 13% 4 11% 5% 5% 5% 4 5% 7% 23%	1938
March	1st to 10th	Night	18% 9% 3 8% 5% 5% 4 3 4 5% 34%	3418
	11th to 20th	Night	14% 10% 3 7% 4 4 4 3 5% 7% 38%	3479
	21st to end	Night	16% 9% 3 6% 4 4 4 4 5% 5% 40%	3817
April	1st to 10th	Night	19% 9% 4 6% 6% 4 4 4 5% 7% 32%	1981
	11th to 20th	Night	18% 8% 2 6% 5% 4 4 3 6% 7% 36%	1786
	21st to end	Night	15% 7% 3 8% 5% 5% 5% 4 6% 7% 36%	1710
May	1st to 10th	Night	19% 8% 3 7% 5% 4 4 3 5% 7% 37%	2833
	11th to 20th	Night	11% 9% 3 9% 5% 6% 5% 4 6% 8% 36%	2691
	21st to end	Night	10% 5% 2 6% 4 3 4 4 6% 10% 48%	2738
June	1st to 10th	Night	11% 6% 2 7% 4 4 5% 4 7% 8% 42%	1520
	11th to 20th	Night	8% 6% 2 6% 5% 5% 5% 5% 7% 9% 41%	1520
	21st to end	Night	10% 5% 2 6% 5% 3 4 4 6% 8% 46%	1432
July	1st to 10th	Night	6% 6% 2 5% 5% 4 4 3 6% 9% 50%	2520
	11th to 20th	Night	8% 5% 2 5% 4 4 5% 3 6% 8% 49%	2698
	21st to end	Night	6% 4 2 6% 5% 4 5% 5% 7% 8% 49%	3087
August	1st to 10th	Night	10% 6% 2 6% 5% 5% 4 4 6% 8% 44%	2825
	11th to 20th	Night	10% 5% 2 6% 4 4 4 4 5% 9% 46%	2785
	21st to end	Night	7% 4 2 5% 4 5% 5% 4 6% 9% 49%	3220
September	1st to 10th	Night	11% 7% 3 7% 4 4 4 3 4 7% 47%	1900
	11th to 20th	Night	9% 4 2 5% 3 4 3 3 5% 7% 56%	2076
	21st to end	Night	16% 6% 2 8% 5% 4 5% 4 6% 6% 40%	2090
October	1st to 10th	Night	14% 6% 2 7% 4 4 4 3 5% 7% 43%	2280
	11th to 20th	Night	16% 11% 3 7% 5% 4 4 3 5% 6% 36%	2280
	21st to end	Night	20% 9% 3 7% 4 4 4 4 5% 6% 33%	2508
November	1st to 10th	Night	14% 8% 2 6% 5% 4 4 4 5% 8% 41%	2530
	11th to 20th	Night	15% 10% 4 8% 5% 6% 5% 4 6% 8% 30%	2800
	21st to end	Night	19% 13% 4 8% 5% 5% 5% 3 6% 6% 27%	2800
December	1st to 10th	Night	15% 16% 4 10% 6% 6% 6% 5% 6% 7% 20%	4580
	11th to 20th	Night	17% 18% 4 10% 6% 4 4 3 4 5% 24%	5208
	21st to end	Night	23% 18% 5% 10% 5% 4 4 3 5% 5% 18%	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	59% 4 13% 14% 11%	3751
	11th to 20th	Day	76% 3 8% 9% 4	4060
	21st to end	Day	72% 3 10% 9% 6%	4466
February	1st to 10th	Day	69% 2 9% 15% 5% 1	1800
	11th to 20th	Day	65% 4 7% 16% 8%	1762
	21st to end	Day	63% 2 11% 16% 7% 1	1515
March	1st to 10th	Day	60% 2 8% 24% 5% 1	3425
	11th to 20th	Day	55% 3 14% 20% 7% 1	3480
	21st to end	Day	54% 2 8% 23% 12% 1	3815
April	1st to 10th	Day	55% 3 11% 18% 13% 1	2199
	11th to 20th	Day	51% 2 11% 22% 12% 1	2359
	21st to end	Day	52% 3 10% 19% 13% 2	2470
May	1st to 10th	Day	52% 2 11% 22% 11% 2	4120
	11th to 20th	Day	53% 3 13% 23% 7% 1	4202
	21st to end	Day	38% 3 13% 24% 19% 3	4837
June	1st to 10th	Day	41% 4 11% 27% 15% 2	2660
	11th to 20th	Day	40% 4 15% 25% 14% 2	2660
	21st to end	Day	38% 5% 13% 27% 16% 1	2660
July	1st to 10th	Day	34% 5% 13% 28% 16% 3	4370
	11th to 20th	Day	35% 5% 14% 31% 14% 1	4184
	21st to end	Day	34% 8% 14% 22% 20% 1	4324
August	1st to 10th	Day	41% 6% 14% 25% 13% 1	4091
	11th to 20th	Day	40% 7% 17% 26% 9% 1	4083
	21st to end	Day	35% 7% 13% 31% 13% 1	4390
September	1st to 10th	Day	39% 5% 14% 27% 13% 1	2280
	11th to 20th	Day	34% 4 13% 32% 17%	2102
	21st to end	Day	46% 4 14% 25% 11% 1	2090
October	1st to 10th	Day	36% 5% 14% 26% 17% 1	3160
	11th to 20th	Day	39% 4 14% 27% 15%	3140
	21st to end	Day	47% 5% 16% 24% 8%	3428
November	1st to 10th	Day	47% 4 12% 26% 9% 2	1763
	11th to 20th	Day	51% 4 15% 19% 11% 1	1600
	21st to end	Day	61% 4 14% 16% 5% 1	1600
December	1st to 10th	Day	67% 5% 14% 11% 3	2600
	11th to 20th	Day	63% 3 14% 11% 9% 1	2986
	21st to end	Day	74% 3 8% 9% 5%	3960
January	1st to 10th	Night	56% 4 12% 21% 8% 1	6193
	11th to 20th	Night	65% 4 10% 16% 5% 1	5900
	21st to end	Night	68% 3 7% 12% 10% 1	6490
February	1st to 10th	Night	63% 3 10% 17% 6% 1	2600
	11th to 20th	Night	59% 3 11% 19% 8% 1	2535
	21st to end	Night	60% 2 10% 19% 8% 1	1938
March	1st to 10th	Night	54% 2 11% 25% 7% 1	3428
	11th to 20th	Night	47% 3 14% 22% 13% 1	3480
	21st to end	Night	46% 2 9% 23% 18% 2	3817
April	1st to 10th	Night	53% 3 9% 19% 15% 1	1981
	11th to 20th	Night	49% 2 8% 21% 17% 2	1786
	21st to end	Night	47% 2 10% 22% 15% 4	1710
May	1st to 10th	Night	49% 2 9% 22% 13% 5%	2840
	11th to 20th	Night	48% 3 14% 25% 8% 2	2692
	21st to end	Night	34% 2 12% 26% 23% 2	2739
June	1st to 10th	Night	40% 3 9% 28% 17% 3	1520
	11th to 20th	Night	38% 4 12% 26% 17% 2	1520
	21st to end	Night	37% 3 13% 25% 19% 2	1432
July	1st to 10th	Night	32% 4 11% 27% 21% 6%	2480
	11th to 20th	Night	32% 5% 13% 32% 16% 1	2649
	21st to end	Night	30% 6% 16% 24% 21% 2	2988
August	1st to 10th	Night	37% 5% 12% 28% 16% 2	2814
	11th to 20th	Night	36% 5% 16% 32% 11% 1	2812
	21st to end	Night	29% 5% 14% 33% 17% 1	3220
September	1st to 10th	Night	38% 3 11% 28% 17% 3	1900
	11th to 20th	Night	30% 3 11% 35% 20% 1	2076
	21st to end	Night	45% 3 12% 26% 14% 1	2090
October	1st to 10th	Night	32% 4 8% 30% 25% 1	3800
	11th to 20th	Night	43% 3 12% 26% 16%	3779
	21st to end	Night	39% 4 15% 26% 15% 1	4120
November	1st to 10th	Night	42% 3 11% 27% 15% 1	2530
	11th to 20th	Night	52% 3 12% 21% 11% 1	2800
	21st to end	Night	57% 3 17% 17% 6%	2800
December	1st to 10th	Night	61% 6% 15% 14% 4	4580
	11th to 20th	Night	62% 3 10% 14% 9% 1	5208
	21st to end	Night	68% 4 11% 11% 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	25% 18% 35% 15% 6% 1	232
	11th to 20th	Day	26% 18% 39% 11% 4 1	300
	21st to end	Day	26% 17% 35% 17% 5% 1	330
February	1st to 10th	Day	25% 18% 38% 14% 4	300
	11th to 20th	Day	23% 24% 37% 15% 1	300
	21st to end	Day	28% 28% 31% 12% 1	225
March	1st to 10th	Day	24% 10% 34% 24% 8%	450
	11th to 20th	Day	23% 10% 37% 21% 6% 2	460
	21st to end	Day	29% 11% 31% 22% 6% 1	506
April	1st to 10th	Day	20% 15% 33% 24% 7% 1	460
	11th to 20th	Day	25% 12% 32% 19% 9% 4	452
	21st to end	Day	25% 7% 34% 23% 9% 3	460
May	1st to 10th	Day	25% 7% 28% 25% 10% 5%	463
	11th to 20th	Day	19% 7% 24% 28% 18% 4	487
	21st to end	Day	13% 6% 25% 29% 19% 7%	529
June	1st to 10th	Day	14% 7% 32% 31% 14% 2	490
	11th to 20th	Day	14% 8% 23% 32% 17% 5%	490
	21st to end	Day	16% 3 29% 33% 14% 4	490
July	1st to 10th	Day	11% 3 20% 31% 23% 11%	485
	11th to 20th	Day	14% 5% 22% 27% 21% 11%	484
	21st to end	Day	9% 2 23% 36% 22% 7%	532
August	1st to 10th	Day	12% 2 21% 30% 19% 15%	486
	11th to 20th	Day	10% 3 20% 32% 20% 15%	479
	21st to end	Day	13% 3 20% 31% 20% 13%	539
September	1st to 10th	Day	14% 4 22% 26% 21% 13%	490
	11th to 20th	Day	9% 3 17% 27% 30% 14%	490
	21st to end	Day	18% 9% 24% 28% 14% 8%	490
October	1st to 10th	Day	20% 7% 25% 23% 19% 6%	490
	11th to 20th	Day	19% 12% 34% 23% 9% 3	490
	21st to end	Day	26% 11% 32% 22% 9% 1	539
November	1st to 10th	Day	19% 19% 34% 19% 8% 2	313
	11th to 20th	Day	23% 20% 32% 18% 6% 3	200
	21st to end	Day	29% 15% 36% 18% 3	200
December	1st to 10th	Day	30% 17% 31% 17% 5% 1	200
	11th to 20th	Day	29% 22% 31% 15% 4	200
	21st to end	Day	29% 15% 37% 15% 5%	220
January	1st to 10th	Night	24% 15% 35% 20% 5%	800
	11th to 20th	Night	28% 16% 32% 20% 5%	800
	21st to end	Night	22% 12% 34% 26% 5%	880
February	1st to 10th	Night	27% 14% 34% 24% 2	800
	11th to 20th	Night	23% 14% 35% 24% 4	783
	21st to end	Night	24% 14% 38% 21% 3	629
March	1st to 10th	Night	19% 10% 36% 28% 7%	760
	11th to 20th	Night	23% 10% 35% 24% 8% 1	760
	21st to end	Night	23% 9% 30% 28% 10% 1	836
April	1st to 10th	Night	22% 10% 31% 30% 6%	760
	11th to 20th	Night	22% 10% 32% 27% 9% 1	662
	21st to end	Night	19% 4 33% 35% 9% 1	570
May	1st to 10th	Night	19% 4 27% 32% 16% 1	570
	11th to 20th	Night	15% 3 25% 40% 15% 2	492
	21st to end	Night	13% 3 23% 39% 19% 3	411
June	1st to 10th	Night	14% 2 30% 39% 15% 1	380
	11th to 20th	Night	11% 3 25% 42% 18%	380
	21st to end	Night	12% 3 23% 46% 15% 1	380
July	1st to 10th	Night	8% 1 21% 44% 23% 2	370
	11th to 20th	Night	11% 1 21% 40% 23% 3	467
	21st to end	Night	8% 1 18% 48% 22% 2	624
August	1st to 10th	Night	8% 3 14% 43% 28% 4	567
	11th to 20th	Night	11% 1 14% 38% 31% 4	564
	21st to end	Night	11% 1 18% 37% 29% 4	684
September	1st to 10th	Night	14% 4 18% 35% 24% 5%	760
	11th to 20th	Night	12% 3 14% 35% 31% 6%	760
	21st to end	Night	19% 4 19% 31% 22% 5%	760
October	1st to 10th	Night	18% 5% 24% 31% 20% 3	760
	11th to 20th	Night	23% 8% 27% 28% 11% 2	760
	21st to end	Night	26% 9% 30% 28% 6%	836
November	1st to 10th	Night	20% 10% 29% 29% 11% 2	780
	11th to 20th	Night	23% 15% 31% 23% 7% 2	800
	21st to end	Night	28% 11% 32% 22% 7%	800
December	1st to 10th	Night	29% 14% 31% 20% 5% 1	800
	11th to 20th	Night	27% 17% 32% 21% 4	800
	21st to end	Night	31% 10% 31% 25% 3	880

Page generated at 2025-02-18 03:26:27. Version ac07

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