Smiths Falls
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Smiths Falls clear sky chart from 2005-11-06 to 2026-09-29.

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% 3 8% 5% 5% 5% 4 5% 7% 32%	149950
	Night	16% 11% 4 9% 5% 4 4 3 5% 6% 31%	141452
Transparency	Day	51% 5% 12% 21% 10% 1	153443
	Night	53% 5% 11% 20% 10% 1	146048
Seeing	Day	24% 16% 30% 19% 8% 2	16903
	Night	23% 14% 30% 24% 8% 1	25945

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% 18% 6% 13% 6% 5% 5% 3 5% 5% 20%	4661
	11th to 20th	Day	12% 18% 7% 15% 7% 6% 4 3 4 4 19%	4650
	21st to end	Day	11% 15% 6% 14% 8% 9% 6% 4 4 5% 19%	5454
February	1st to 10th	Day	16% 14% 5% 12% 7% 5% 5% 4 4 5% 24%	1890
	11th to 20th	Day	13% 16% 5% 10% 7% 5% 4 3 4 6% 26%	1847
	21st to end	Day	19% 15% 5% 10% 7% 5% 4 4 4 5% 22%	1730
March	1st to 10th	Day	19% 14% 4 11% 5% 4 4 4 4 5% 26%	4618
	11th to 20th	Day	12% 12% 4 8% 5% 6% 6% 4 6% 7% 30%	5090
	21st to end	Day	19% 11% 4 7% 5% 3 3 2 4 5% 37%	5867
April	1st to 10th	Day	21% 12% 4 7% 5% 4 4 3 5% 6% 30%	2520
	11th to 20th	Day	22% 10% 3 7% 4 4 4 3 4 5% 35%	2494
	21st to end	Day	23% 9% 3 8% 5% 4 4 2 4 5% 32%	2640
May	1st to 10th	Day	23% 9% 3 8% 5% 5% 4 4 5% 7% 27%	8237
	11th to 20th	Day	17% 9% 3 8% 5% 5% 4 4 5% 7% 33%	8221
	21st to end	Day	20% 9% 3 7% 4 4 4 4 5% 7% 35%	9060
June	1st to 10th	Day	21% 8% 3 7% 5% 4 5% 4 6% 7% 31%	2940
	11th to 20th	Day	15% 6% 3 6% 5% 4 5% 5% 6% 9% 37%	2940
	21st to end	Day	18% 8% 3 6% 6% 5% 5% 4 6% 7% 33%	2940
July	1st to 10th	Day	11% 6% 2 7% 5% 5% 5% 4 7% 10% 37%	8280
	11th to 20th	Day	10% 4 2 6% 4 4 4 4 6% 9% 47%	8280
	21st to end	Day	12% 5% 2 6% 4 5% 5% 4 7% 10% 40%	8993
August	1st to 10th	Day	18% 8% 3 8% 5% 5% 5% 3 5% 6% 35%	6301
	11th to 20th	Day	16% 6% 2 6% 4 4 5% 4 6% 9% 38%	5882
	21st to end	Day	15% 6% 3 7% 5% 5% 5% 4 7% 11% 34%	6080
September	1st to 10th	Day	14% 5% 2 6% 4 5% 5% 4 6% 8% 41%	2520
	11th to 20th	Day	11% 6% 2 6% 4 3 4 4 5% 8% 47%	2520
	21st to end	Day	18% 6% 2 6% 4 4 4 4 5% 6% 41%	2217
October	1st to 10th	Day	20% 8% 3 7% 5% 4 3 3 4 6% 39%	2000
	11th to 20th	Day	20% 9% 3 8% 5% 4 5% 4 5% 7% 30%	2000
	21st to end	Day	25% 11% 3 7% 4 5% 4 3 5% 5% 28%	2060
November	1st to 10th	Day	16% 9% 4 7% 5% 6% 5% 4 5% 6% 32%	1851
	11th to 20th	Day	17% 14% 3 9% 6% 4 4 4 4 6% 29%	1693
	21st to end	Day	22% 14% 5% 10% 6% 4 5% 3 5% 5% 21%	1680
December	1st to 10th	Day	22% 18% 6% 11% 6% 5% 4 3 5% 5% 16%	2680
	11th to 20th	Day	18% 17% 5% 11% 6% 4 4 3 4 4 24%	3066
	21st to end	Day	21% 17% 4 13% 5% 3 3 3 3 4 22%	4048
January	1st to 10th	Night	14% 17% 7% 14% 6% 4 4 3 4 5% 21%	8234
	11th to 20th	Night	12% 18% 7% 16% 7% 5% 5% 3 4 4 18%	8235
	21st to end	Night	13% 15% 5% 12% 7% 6% 5% 4 5% 5% 22%	8722
February	1st to 10th	Night	14% 16% 5% 12% 6% 6% 4 4 5% 5% 23%	2730
	11th to 20th	Night	13% 15% 5% 11% 6% 5% 4 3 5% 5% 28%	2658
	21st to end	Night	16% 15% 4 9% 6% 5% 4 3 4 4 29%	2076
March	1st to 10th	Night	22% 13% 3 9% 5% 5% 4 2 3 4 29%	5441
	11th to 20th	Night	14% 12% 4 8% 5% 4 5% 4 6% 8% 31%	5089
	21st to end	Night	19% 10% 4 9% 5% 4 4 3 5% 5% 33%	5307
April	1st to 10th	Night	21% 10% 4 7% 5% 4 3 3 4 6% 32%	2100
	11th to 20th	Night	22% 9% 3 7% 5% 3 3 3 4 5% 37%	2075
	21st to end	Night	21% 10% 3 7% 5% 3 5% 3 4 6% 34%	1998
May	1st to 10th	Night	22% 10% 3 8% 5% 5% 5% 4 6% 7% 25%	4660
	11th to 20th	Night	16% 8% 3 6% 5% 4 4 3 5% 7% 39%	4639
	21st to end	Night	19% 8% 2 6% 4 4 4 4 6% 8% 35%	5114
June	1st to 10th	Night	17% 7% 2 6% 6% 5% 5% 4 6% 7% 35%	1680
	11th to 20th	Night	15% 6% 2 5% 4 4 5% 3 6% 8% 41%	1680
	21st to end	Night	17% 7% 2 7% 5% 5% 5% 4 6% 7% 35%	1680
July	1st to 10th	Night	11% 6% 2 7% 5% 5% 5% 4 7% 11% 37%	4680
	11th to 20th	Night	11% 4 2 5% 4 4 4 3 5% 8% 48%	4680
	21st to end	Night	12% 6% 2 6% 4 5% 5% 4 6% 7% 42%	5084
August	1st to 10th	Night	14% 8% 3 7% 4 5% 5% 4 6% 7% 38%	3844
	11th to 20th	Night	12% 7% 2 7% 4 4 5% 4 6% 8% 42%	4117
	21st to end	Night	10% 6% 2 7% 5% 5% 5% 5% 6% 8% 41%	5045
September	1st to 10th	Night	11% 6% 3 7% 5% 5% 4 4 4 6% 47%	2100
	11th to 20th	Night	13% 4 2 4 4 3 3 4 6% 6% 51%	2100
	21st to end	Night	17% 6% 2 6% 4 4 3 4 4 7% 43%	2355
October	1st to 10th	Night	16% 8% 3 6% 5% 3 5% 3 5% 6% 40%	2400
	11th to 20th	Night	21% 8% 2 7% 4 4 4 4 6% 7% 33%	2400
	21st to end	Night	23% 11% 3 7% 5% 4 4 4 5% 6% 30%	2780
November	1st to 10th	Night	19% 11% 4 7% 4 3 4 3 4 6% 35%	2667
	11th to 20th	Night	17% 11% 4 8% 5% 4 5% 3 5% 6% 32%	2924
	21st to end	Night	21% 14% 5% 9% 5% 4 5% 3 4 6% 24%	2940
December	1st to 10th	Night	19% 17% 6% 12% 6% 5% 4 3 5% 5% 17%	4720
	11th to 20th	Night	22% 15% 4 9% 5% 4 4 3 4 4 26%	5348
	21st to end	Night	26% 16% 4 12% 5% 3 3 3 4 4 19%	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	65% 5% 12% 13% 4 1	4662
	11th to 20th	Day	69% 3 9% 10% 8% 1	4680
	21st to end	Day	68% 5% 9% 9% 9% 1	5454
February	1st to 10th	Day	63% 5% 8% 18% 5% 1	1890
	11th to 20th	Day	58% 5% 11% 17% 8% 1	1856
	21st to end	Day	65% 5% 9% 12% 9% 1	1730
March	1st to 10th	Day	59% 5% 9% 14% 11% 2	4621
	11th to 20th	Day	52% 5% 17% 15% 10% 1	5090
	21st to end	Day	51% 4 6% 19% 18% 3	5867
April	1st to 10th	Day	55% 4 7% 19% 13% 3	2520
	11th to 20th	Day	52% 5% 7% 19% 16% 2	2494
	21st to end	Day	54% 4 8% 16% 14% 3	2640
May	1st to 10th	Day	56% 5% 8% 19% 10% 1	8249
	11th to 20th	Day	49% 6% 12% 22% 10% 1	8225
	21st to end	Day	49% 5% 11% 23% 11% 1	9061
June	1st to 10th	Day	51% 6% 9% 19% 13% 1	2940
	11th to 20th	Day	43% 6% 11% 25% 12% 2	2940
	21st to end	Day	49% 7% 12% 20% 11% 1	2940
July	1st to 10th	Day	41% 5% 16% 27% 11%	8210
	11th to 20th	Day	33% 5% 14% 34% 14% 1	8205
	21st to end	Day	38% 6% 14% 33% 9%	8795
August	1st to 10th	Day	50% 5% 13% 19% 11% 2	6287
	11th to 20th	Day	41% 6% 17% 29% 7% 1	5921
	21st to end	Day	44% 5% 19% 23% 8%	6080
September	1st to 10th	Day	39% 7% 13% 29% 12%	2520
	11th to 20th	Day	35% 5% 13% 32% 15%	2520
	21st to end	Day	43% 6% 13% 25% 12%	2217
October	1st to 10th	Day	45% 4 11% 31% 8%	3260
	11th to 20th	Day	46% 5% 15% 25% 8% 1	3240
	21st to end	Day	48% 5% 16% 23% 7%	3311
November	1st to 10th	Day	51% 6% 13% 21% 8% 1	1851
	11th to 20th	Day	57% 5% 11% 17% 10% 1	1693
	21st to end	Day	65% 6% 12% 11% 6%	1680
December	1st to 10th	Day	70% 5% 13% 10% 2	2680
	11th to 20th	Day	66% 4 10% 14% 6%	3066
	21st to end	Day	67% 4 8% 15% 5%	4048
January	1st to 10th	Night	67% 4 12% 12% 5%	8234
	11th to 20th	Night	70% 4 9% 10% 7%	8280
	21st to end	Night	64% 4 7% 13% 11% 1	8722
February	1st to 10th	Night	63% 4 10% 16% 6% 1	2730
	11th to 20th	Night	58% 5% 11% 20% 6%	2660
	21st to end	Night	59% 4 9% 17% 10% 1	2076
March	1st to 10th	Night	60% 4 6% 17% 10% 3	5451
	11th to 20th	Night	50% 5% 19% 16% 8% 3	5090
	21st to end	Night	52% 4 7% 22% 13% 2	5307
April	1st to 10th	Night	53% 4 9% 20% 13% 2	2100
	11th to 20th	Night	52% 4 7% 19% 16% 2	2075
	21st to end	Night	51% 5% 8% 17% 16% 3	1998
May	1st to 10th	Night	57% 6% 10% 17% 8% 2	4666
	11th to 20th	Night	45% 5% 13% 22% 14% 1	4640
	21st to end	Night	46% 6% 12% 20% 15% 1	5115
June	1st to 10th	Night	47% 7% 12% 21% 12% 1	1680
	11th to 20th	Night	41% 6% 12% 23% 16% 2	1680
	21st to end	Night	47% 8% 11% 21% 13%	1680
July	1st to 10th	Night	40% 5% 17% 22% 14% 1	4640
	11th to 20th	Night	34% 5% 13% 33% 14% 1	4632
	21st to end	Night	40% 6% 12% 28% 13% 1	4967
August	1st to 10th	Night	45% 5% 15% 20% 12% 3	3834
	11th to 20th	Night	40% 5% 15% 32% 7%	4144
	21st to end	Night	39% 6% 17% 27% 9% 1	5045
September	1st to 10th	Night	38% 6% 12% 30% 13% 1	2100
	11th to 20th	Night	32% 5% 14% 35% 13% 1	2100
	21st to end	Night	41% 5% 12% 28% 12% 2	2355
October	1st to 10th	Night	40% 5% 12% 30% 12% 1	3920
	11th to 20th	Night	43% 4 16% 27% 9%	3899
	21st to end	Night	47% 5% 16% 23% 8%	4479
November	1st to 10th	Night	49% 5% 14% 22% 9% 1	2667
	11th to 20th	Night	53% 6% 12% 18% 10% 1	2924
	21st to end	Night	62% 5% 12% 16% 4	2940
December	1st to 10th	Night	69% 4 12% 11% 3	4720
	11th to 20th	Night	63% 5% 8% 15% 9% 1	5348
	21st to end	Night	69% 4 6% 12% 9%	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	26% 21% 36% 13% 4	220
	11th to 20th	Day	33% 19% 30% 15% 2	220
	21st to end	Day	27% 21% 34% 15% 4	301
February	1st to 10th	Day	30% 24% 30% 14% 2	330
	11th to 20th	Day	27% 28% 34% 8% 1	334
	21st to end	Day	32% 19% 36% 11% 1	446
March	1st to 10th	Day	28% 22% 31% 16% 3	540
	11th to 20th	Day	31% 20% 31% 14% 3	540
	21st to end	Day	32% 22% 27% 13% 5% 1	594
April	1st to 10th	Day	31% 25% 26% 12% 4 1	540
	11th to 20th	Day	35% 20% 22% 14% 7% 2	532
	21st to end	Day	32% 18% 30% 13% 6% 1	540
May	1st to 10th	Day	25% 18% 31% 17% 6% 1	543
	11th to 20th	Day	22% 16% 34% 19% 7% 2	567
	21st to end	Day	23% 16% 30% 19% 9% 2	617
June	1st to 10th	Day	24% 13% 31% 21% 9% 1	570
	11th to 20th	Day	16% 17% 34% 22% 9% 2	570
	21st to end	Day	21% 13% 33% 20% 11% 3	570
July	1st to 10th	Day	12% 9% 32% 31% 13% 2	565
	11th to 20th	Day	13% 12% 32% 26% 13% 3	564
	21st to end	Day	14% 10% 32% 31% 11% 3	620
August	1st to 10th	Day	16% 9% 28% 31% 13% 3	566
	11th to 20th	Day	15% 7% 29% 28% 15% 6%	559
	21st to end	Day	17% 10% 29% 25% 11% 7%	627
September	1st to 10th	Day	16% 12% 29% 24% 11% 6%	570
	11th to 20th	Day	12% 9% 26% 26% 17% 11%	570
	21st to end	Day	20% 12% 28% 23% 13% 4	562
October	1st to 10th	Day	23% 14% 27% 20% 12% 4	530
	11th to 20th	Day	27% 19% 31% 17% 6% 1	530
	21st to end	Day	31% 16% 30% 20% 4	506
November	1st to 10th	Day	29% 20% 28% 16% 6%	425
	11th to 20th	Day	26% 21% 32% 12% 7% 2	233
	21st to end	Day	31% 23% 32% 12% 2	220
December	1st to 10th	Day	35% 17% 33% 13% 3	220
	11th to 20th	Day	34% 25% 30% 7% 2	220
	21st to end	Day	37% 17% 29% 13% 3 1	242
January	1st to 10th	Night	28% 19% 32% 18% 3	840
	11th to 20th	Night	31% 18% 28% 20% 3	840
	21st to end	Night	22% 16% 34% 23% 5%	924
February	1st to 10th	Night	24% 21% 32% 20% 3	840
	11th to 20th	Night	23% 19% 38% 17% 2	823
	21st to end	Night	26% 21% 31% 18% 4	692
March	1st to 10th	Night	27% 15% 34% 20% 4	840
	11th to 20th	Night	27% 20% 29% 20% 4	840
	21st to end	Night	26% 15% 31% 22% 5% 1	924
April	1st to 10th	Night	28% 16% 30% 23% 3	840
	11th to 20th	Night	28% 18% 28% 19% 7%	831
	21st to end	Night	25% 14% 30% 23% 7% 1	738
May	1st to 10th	Night	26% 9% 27% 27% 9% 1	420
	11th to 20th	Night	17% 13% 36% 27% 8%	414
	21st to end	Night	15% 9% 38% 26% 11%	455
June	1st to 10th	Night	17% 9% 30% 35% 8%	420
	11th to 20th	Night	19% 10% 30% 29% 12%	420
	21st to end	Night	19% 7% 32% 30% 12%	420
July	1st to 10th	Night	9% 7% 32% 39% 13%	410
	11th to 20th	Night	13% 6% 26% 40% 13% 1	408
	21st to end	Night	11% 5% 29% 41% 13% 1	460
August	1st to 10th	Night	12% 4 26% 37% 20%	492
	11th to 20th	Night	13% 3 23% 37% 22% 2	633
	21st to end	Night	13% 7% 29% 33% 16% 2	924
September	1st to 10th	Night	15% 7% 31% 32% 15% 1	840
	11th to 20th	Night	16% 7% 22% 28% 23% 4	840
	21st to end	Night	18% 10% 27% 25% 19% 1	833
October	1st to 10th	Night	20% 12% 29% 23% 16% 2	800
	11th to 20th	Night	25% 12% 31% 24% 8% 1	800
	21st to end	Night	29% 13% 27% 25% 5%	880
November	1st to 10th	Night	28% 16% 28% 21% 8%	820
	11th to 20th	Night	26% 17% 31% 18% 9%	840
	21st to end	Night	31% 17% 27% 18% 6%	840
December	1st to 10th	Night	31% 17% 30% 19% 4	840
	11th to 20th	Night	29% 19% 31% 17% 3	840
	21st to end	Night	34% 17% 27% 20% 2	924

Page generated at 2026-09-26 04:18:39. Version ac07

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