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 2025-05-26.

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	17% 10% 3 8% 5% 5% 4 4 5% 7% 32%	114125
	Night	17% 12% 4 9% 5% 4 4 3 5% 6% 31%	115141
Transparency	Day	51% 5% 12% 21% 10% 1	117664
	Night	54% 5% 11% 19% 10% 1	119766
Seeing	Day	24% 16% 30% 19% 8% 2	15134
	Night	23% 14% 30% 24% 9% 1	24355

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% 5% 13% 6% 5% 5% 3 4 5% 22%	3597
	11th to 20th	Day	12% 16% 7% 14% 7% 5% 4 4 5% 5% 21%	3570
	21st to end	Day	14% 17% 6% 14% 6% 6% 5% 3 4 5% 20%	4208
February	1st to 10th	Day	17% 15% 5% 12% 7% 5% 5% 4 4 5% 23%	1800
	11th to 20th	Day	13% 16% 5% 10% 7% 5% 4 3 4 6% 26%	1757
	21st to end	Day	19% 15% 5% 9% 7% 5% 4 4 4 5% 22%	1650
March	1st to 10th	Day	19% 14% 4 11% 5% 4 4 3 4 5% 26%	4517
	11th to 20th	Day	11% 12% 4 8% 5% 6% 6% 4 6% 7% 31%	4980
	21st to end	Day	19% 11% 4 7% 5% 3 3 2 4 5% 38%	5740
April	1st to 10th	Day	21% 12% 4 7% 5% 4 4 3 5% 6% 31%	2400
	11th to 20th	Day	21% 10% 3 7% 4 4 4 3 4 5% 35%	2374
	21st to end	Day	23% 9% 3 8% 4 4 4 3 5% 5% 32%	2515
May	1st to 10th	Day	20% 9% 3 8% 5% 5% 4 4 5% 6% 31%	4566
	11th to 20th	Day	17% 10% 3 8% 5% 4 4 4 5% 7% 33%	4538
	21st to end	Day	15% 6% 2 6% 4 4 5% 4 5% 8% 39%	4907
June	1st to 10th	Day	21% 8% 3 7% 5% 4 5% 4 5% 7% 30%	2660
	11th to 20th	Day	15% 6% 2 6% 5% 4 5% 5% 6% 8% 37%	2660
	21st to end	Day	19% 8% 3 7% 6% 5% 5% 4 6% 7% 32%	2660
July	1st to 10th	Day	12% 6% 2 7% 5% 5% 5% 5% 7% 10% 36%	4440
	11th to 20th	Day	13% 6% 2 6% 4 5% 5% 4 7% 9% 40%	4440
	21st to end	Day	11% 5% 2 6% 4 5% 6% 4 6% 9% 42%	4814
August	1st to 10th	Day	17% 8% 3 7% 4 5% 5% 3 5% 7% 36%	4301
	11th to 20th	Day	17% 6% 2 6% 4 4 5% 4 6% 8% 38%	3990
	21st to end	Day	15% 5% 2 6% 4 4 5% 4 6% 9% 39%	4180
September	1st to 10th	Day	14% 5% 2 5% 5% 5% 6% 4 6% 8% 41%	2280
	11th to 20th	Day	12% 6% 2 6% 4 3 4 4 6% 8% 46%	2280
	21st to end	Day	18% 6% 2 6% 4 4 4 4 5% 6% 40%	2024
October	1st to 10th	Day	21% 8% 3 7% 5% 4 3 3 4 6% 37%	1900
	11th to 20th	Day	21% 10% 3 8% 5% 4 5% 4 5% 6% 30%	1900
	21st to end	Day	25% 11% 3 7% 4 5% 4 3 4 5% 27%	1957
November	1st to 10th	Day	16% 8% 4 7% 5% 6% 6% 4 5% 6% 33%	1761
	11th to 20th	Day	17% 13% 3 9% 6% 4 4 4 5% 6% 30%	1613
	21st to end	Day	21% 14% 5% 9% 7% 5% 5% 3 5% 5% 21%	1600
December	1st to 10th	Day	22% 18% 6% 11% 6% 5% 4 3 5% 5% 16%	2600
	11th to 20th	Day	18% 17% 5% 11% 6% 4 4 3 4 4 24%	2986
	21st to end	Day	22% 17% 5% 13% 5% 3 3 3 3 4 22%	3960
January	1st to 10th	Night	14% 18% 7% 14% 6% 4 4 3 4 4 22%	6349
	11th to 20th	Night	12% 16% 7% 15% 8% 6% 5% 3 4 5% 19%	6315
	21st to end	Night	16% 17% 6% 12% 6% 6% 5% 3 4 5% 20%	6743
February	1st to 10th	Night	15% 17% 5% 12% 6% 6% 3 4 5% 5% 23%	2600
	11th to 20th	Night	14% 15% 5% 11% 6% 5% 4 4 5% 4 28%	2528
	21st to end	Night	16% 15% 4 9% 6% 5% 4 3 4 4 29%	1980
March	1st to 10th	Night	22% 13% 3 9% 5% 5% 4 2 3 4 29%	5322
	11th to 20th	Night	14% 12% 3 8% 5% 4 5% 4 6% 8% 31%	4979
	21st to end	Night	18% 10% 4 8% 5% 4 4 3 5% 5% 34%	5192
April	1st to 10th	Night	21% 10% 4 7% 5% 4 4 3 4 6% 32%	2000
	11th to 20th	Night	22% 8% 2 7% 5% 3 3 3 4 5% 37%	1975
	21st to end	Night	21% 10% 3 7% 5% 3 5% 3 4 6% 33%	1902
May	1st to 10th	Night	23% 9% 3 7% 5% 4 5% 4 6% 6% 29%	2594
	11th to 20th	Night	20% 9% 3 6% 4 4 4 3 5% 6% 37%	2575
	21st to end	Night	15% 7% 3 5% 4 4 4 3 6% 8% 41%	2784
June	1st to 10th	Night	17% 7% 2 6% 6% 5% 5% 4 6% 7% 34%	1520
	11th to 20th	Night	15% 7% 2 5% 5% 4 5% 3 7% 8% 41%	1520
	21st to end	Night	17% 8% 2 7% 5% 5% 5% 4 6% 8% 34%	1520
July	1st to 10th	Night	11% 7% 3 8% 7% 5% 5% 4 6% 9% 36%	2520
	11th to 20th	Night	14% 5% 2 6% 4 4 5% 4 6% 8% 43%	2520
	21st to end	Night	11% 5% 2 6% 4 5% 5% 4 6% 7% 43%	2739
August	1st to 10th	Night	11% 7% 3 7% 4 4 5% 4 6% 7% 42%	2624
	11th to 20th	Night	12% 7% 2 7% 4 4 4 4 6% 8% 41%	2806
	21st to end	Night	11% 5% 3 6% 5% 5% 5% 5% 6% 8% 43%	3476
September	1st to 10th	Night	12% 6% 3 7% 5% 4 3 3 4 6% 47%	1900
	11th to 20th	Night	14% 4 2 4 3 3 3 4 6% 7% 51%	1900
	21st to end	Night	17% 6% 2 6% 4 4 3 4 4 8% 42%	2151
October	1st to 10th	Night	17% 8% 3 6% 5% 4 5% 3 5% 6% 38%	2280
	11th to 20th	Night	21% 9% 2 7% 4 4 4 4 5% 6% 33%	2280
	21st to end	Night	23% 11% 3 7% 5% 4 4 4 5% 6% 29%	2641
November	1st to 10th	Night	19% 10% 4 6% 4 3 4 3 4 6% 36%	2537
	11th to 20th	Night	17% 11% 4 8% 5% 4 5% 3 5% 6% 32%	2785
	21st to end	Night	21% 14% 5% 8% 5% 4 5% 3 4 6% 24%	2800
December	1st to 10th	Night	19% 17% 6% 12% 6% 5% 4 3 5% 5% 17%	4580
	11th to 20th	Night	23% 15% 4 9% 5% 4 4 3 4 4 26%	5208
	21st to end	Night	26% 16% 4 12% 5% 4 3 3 4 4 19%	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	64% 5% 11% 14% 5% 1	3598
	11th to 20th	Day	66% 4 11% 12% 8% 1	3600
	21st to end	Day	66% 5% 9% 10% 8% 1	4208
February	1st to 10th	Day	63% 5% 8% 17% 5% 1	1800
	11th to 20th	Day	58% 5% 11% 17% 8% 1	1766
	21st to end	Day	64% 5% 9% 12% 9% 1	1650
March	1st to 10th	Day	60% 5% 9% 14% 11% 3	4520
	11th to 20th	Day	51% 5% 17% 15% 11% 1	4980
	21st to end	Day	50% 4 6% 19% 18% 3	5740
April	1st to 10th	Day	54% 4 6% 19% 14% 3	2400
	11th to 20th	Day	51% 5% 7% 19% 17% 2	2374
	21st to end	Day	54% 5% 8% 16% 14% 3	2515
May	1st to 10th	Day	52% 6% 10% 20% 10% 2	4580
	11th to 20th	Day	49% 7% 13% 20% 9% 1	4542
	21st to end	Day	41% 7% 12% 23% 14% 1	4907
June	1st to 10th	Day	52% 6% 10% 19% 12% 1	2660
	11th to 20th	Day	43% 6% 11% 25% 12% 2	2660
	21st to end	Day	50% 7% 12% 19% 11% 1	2660
July	1st to 10th	Day	41% 6% 13% 28% 12% 1	4370
	11th to 20th	Day	38% 6% 15% 31% 9%	4365
	21st to end	Day	38% 7% 13% 31% 11%	4661
August	1st to 10th	Day	48% 5% 14% 23% 10%	4287
	11th to 20th	Day	42% 6% 15% 28% 9%	4029
	21st to end	Day	41% 5% 16% 27% 11%	4180
September	1st to 10th	Day	40% 7% 14% 27% 12%	2280
	11th to 20th	Day	37% 5% 13% 31% 14%	2280
	21st to end	Day	44% 6% 14% 26% 10%	2024
October	1st to 10th	Day	46% 4 11% 31% 7%	3160
	11th to 20th	Day	46% 5% 15% 26% 8%	3140
	21st to end	Day	48% 5% 17% 23% 7%	3208
November	1st to 10th	Day	50% 6% 14% 22% 7% 1	1761
	11th to 20th	Day	56% 5% 10% 17% 10% 1	1613
	21st to end	Day	64% 6% 12% 11% 6%	1600
December	1st to 10th	Day	70% 5% 13% 10% 2	2600
	11th to 20th	Day	66% 4 10% 14% 6%	2986
	21st to end	Day	67% 4 8% 15% 5%	3960
January	1st to 10th	Night	66% 4 12% 13% 4	6349
	11th to 20th	Night	68% 5% 11% 10% 5%	6360
	21st to end	Night	68% 4 7% 10% 10% 1	6743
February	1st to 10th	Night	63% 4 10% 16% 6% 1	2600
	11th to 20th	Night	58% 5% 11% 19% 7%	2530
	21st to end	Night	59% 4 9% 17% 9% 1	1980
March	1st to 10th	Night	60% 4 6% 16% 10% 3	5332
	11th to 20th	Night	49% 5% 19% 16% 8% 3	4980
	21st to end	Night	52% 4 7% 23% 13% 2	5192
April	1st to 10th	Night	53% 4 9% 20% 13% 2	2000
	11th to 20th	Night	51% 4 7% 19% 16% 2	1975
	21st to end	Night	51% 5% 8% 16% 15% 3	1902
May	1st to 10th	Night	54% 6% 11% 17% 9% 3	2600
	11th to 20th	Night	47% 6% 13% 21% 11% 1	2576
	21st to end	Night	40% 6% 14% 21% 17% 2	2785
June	1st to 10th	Night	47% 8% 13% 20% 11% 1	1520
	11th to 20th	Night	41% 6% 12% 22% 17% 2	1520
	21st to end	Night	47% 8% 12% 20% 13%	1520
July	1st to 10th	Night	44% 6% 13% 22% 14% 1	2480
	11th to 20th	Night	39% 5% 13% 34% 8%	2472
	21st to end	Night	38% 7% 15% 24% 14% 1	2651
August	1st to 10th	Night	40% 7% 14% 26% 12% 1	2614
	11th to 20th	Night	41% 5% 16% 30% 7%	2833
	21st to end	Night	37% 7% 15% 28% 11% 1	3476
September	1st to 10th	Night	38% 6% 12% 29% 14% 1	1900
	11th to 20th	Night	33% 5% 15% 34% 12% 1	1900
	21st to end	Night	41% 6% 12% 30% 11% 1	2151
October	1st to 10th	Night	41% 5% 12% 30% 12%	3800
	11th to 20th	Night	43% 4 16% 27% 9%	3779
	21st to end	Night	48% 5% 16% 22% 8%	4340
November	1st to 10th	Night	48% 5% 14% 22% 9% 1	2537
	11th to 20th	Night	53% 6% 12% 17% 10% 1	2785
	21st to end	Night	61% 5% 13% 16% 4	2800
December	1st to 10th	Night	70% 5% 12% 11% 2	4580
	11th to 20th	Night	62% 5% 8% 15% 9% 1	5208
	21st to end	Night	69% 4 6% 12% 9%	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	26% 21% 36% 13% 4	200
	11th to 20th	Day	31% 18% 32% 17% 3 1	200
	21st to end	Day	27% 21% 35% 14% 3	273
February	1st to 10th	Day	33% 26% 29% 11% 1	300
	11th to 20th	Day	29% 28% 34% 8% 1	304
	21st to end	Day	33% 18% 35% 12% 1	414
March	1st to 10th	Day	29% 20% 31% 17% 3	500
	11th to 20th	Day	29% 21% 32% 15% 4	500
	21st to end	Day	33% 20% 27% 13% 6% 1	550
April	1st to 10th	Day	32% 24% 26% 13% 5% 1	500
	11th to 20th	Day	33% 20% 23% 13% 8% 3	492
	21st to end	Day	33% 18% 30% 13% 6% 1	500
May	1st to 10th	Day	25% 17% 32% 18% 7% 2	503
	11th to 20th	Day	22% 15% 34% 20% 7% 2	527
	21st to end	Day	22% 14% 31% 21% 10% 2	549
June	1st to 10th	Day	26% 12% 30% 22% 9% 1	490
	11th to 20th	Day	15% 16% 33% 23% 10% 2	490
	21st to end	Day	22% 12% 32% 20% 11% 3	490
July	1st to 10th	Day	13% 8% 29% 33% 14% 3	485
	11th to 20th	Day	13% 11% 32% 27% 14% 3	484
	21st to end	Day	14% 8% 32% 32% 11% 3	532
August	1st to 10th	Day	16% 10% 27% 30% 13% 3	486
	11th to 20th	Day	16% 6% 27% 29% 16% 6%	479
	21st to end	Day	16% 11% 30% 24% 11% 7%	539
September	1st to 10th	Day	16% 13% 29% 24% 12% 7%	490
	11th to 20th	Day	13% 8% 25% 24% 18% 12%	490
	21st to end	Day	20% 11% 27% 24% 13% 4	490
October	1st to 10th	Day	24% 15% 26% 19% 12% 4	490
	11th to 20th	Day	28% 19% 29% 17% 6% 1	490
	21st to end	Day	32% 16% 29% 19% 4	469
November	1st to 10th	Day	27% 19% 29% 17% 7% 1	395
	11th to 20th	Day	26% 22% 33% 10% 8% 2	213
	21st to end	Day	30% 25% 30% 13% 3	200
December	1st to 10th	Day	35% 17% 32% 14% 3	200
	11th to 20th	Day	35% 27% 28% 8% 3 1	200
	21st to end	Day	35% 18% 29% 14% 4 1	220
January	1st to 10th	Night	29% 19% 32% 17% 3	800
	11th to 20th	Night	31% 17% 28% 20% 4 1	800
	21st to end	Night	22% 16% 35% 23% 5%	880
February	1st to 10th	Night	26% 22% 32% 19% 2	800
	11th to 20th	Night	24% 19% 38% 17% 2	783
	21st to end	Night	26% 21% 31% 18% 4	660
March	1st to 10th	Night	27% 15% 34% 21% 4	800
	11th to 20th	Night	26% 21% 29% 20% 4 1	800
	21st to end	Night	25% 15% 30% 23% 5% 1	880
April	1st to 10th	Night	28% 16% 30% 23% 4	800
	11th to 20th	Night	28% 19% 27% 19% 7% 1	791
	21st to end	Night	26% 14% 30% 23% 7% 1	702
May	1st to 10th	Night	27% 8% 26% 28% 9% 2	400
	11th to 20th	Night	17% 12% 34% 28% 8%	394
	21st to end	Night	15% 9% 38% 27% 11%	423
June	1st to 10th	Night	17% 9% 29% 34% 9%	380
	11th to 20th	Night	18% 9% 29% 31% 13% 1	380
	21st to end	Night	20% 7% 31% 29% 13%	380
July	1st to 10th	Night	9% 7% 31% 39% 14% 1	370
	11th to 20th	Night	13% 5% 26% 40% 15% 1	368
	21st to end	Night	11% 4 29% 42% 13% 1	416
August	1st to 10th	Night	12% 5% 26% 37% 20%	444
	11th to 20th	Night	13% 3 22% 37% 23% 2	572
	21st to end	Night	13% 6% 30% 33% 16% 2	836
September	1st to 10th	Night	15% 6% 32% 31% 15% 1	760
	11th to 20th	Night	17% 7% 21% 28% 23% 4	760
	21st to end	Night	18% 10% 26% 24% 19% 1	760
October	1st to 10th	Night	20% 12% 28% 23% 15% 2	760
	11th to 20th	Night	26% 12% 30% 24% 8% 1	760
	21st to end	Night	29% 14% 27% 25% 5%	836
November	1st to 10th	Night	27% 16% 28% 21% 8%	780
	11th to 20th	Night	26% 16% 31% 18% 9% 1	800
	21st to end	Night	31% 17% 27% 18% 7%	800
December	1st to 10th	Night	32% 16% 29% 19% 4	800
	11th to 20th	Night	29% 19% 31% 17% 4 1	800
	21st to end	Night	34% 16% 28% 20% 3	880

Page generated at 2025-05-23 09:21:00. Version ac07

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