Niagara Falls
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Niagara Falls clear sky chart from 2005-11-06 to 2026-05-02.

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% 11% 4 9% 5% 5% 5% 4 5% 7% 31%	131978
	Night	15% 12% 4 9% 5% 5% 5% 4 5% 6% 30%	130478
Transparency	Day	50% 8% 13% 18% 10% 1	135572
	Night	53% 8% 12% 17% 9% 1	134971
Seeing	Day	21% 12% 27% 23% 13% 5%	16321
	Night	22% 12% 27% 26% 12% 1	25860

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% 19% 5% 15% 7% 5% 4 3 5% 5% 16%	4661
	11th to 20th	Day	11% 23% 8% 20% 9% 5% 4 3 4 3 9%	5126
	21st to end	Day	15% 16% 7% 14% 11% 8% 6% 3 4 4 12%	5780
February	1st to 10th	Day	17% 18% 4 13% 8% 6% 5% 4 5% 6% 15%	1890
	11th to 20th	Day	14% 18% 6% 15% 8% 5% 5% 3 4 4 17%	1843
	21st to end	Day	19% 15% 4 12% 8% 4 4 3 5% 6% 18%	1632
March	1st to 10th	Day	17% 11% 6% 12% 5% 4 4 3 5% 5% 29%	5042
	11th to 20th	Day	10% 17% 4 8% 5% 5% 4 3 5% 6% 31%	5090
	21st to end	Day	19% 12% 4 9% 5% 4 4 3 5% 5% 31%	5586
April	1st to 10th	Day	18% 14% 3 8% 5% 4 4 3 4 5% 31%	2493
	11th to 20th	Day	19% 10% 3 7% 4 5% 4 3 5% 6% 33%	2530
	21st to end	Day	19% 9% 3 8% 5% 4 5% 4 4 6% 33%	2730
May	1st to 10th	Day	20% 9% 3 8% 5% 5% 5% 3 4 7% 31%	5901
	11th to 20th	Day	15% 10% 3 9% 5% 5% 4 4 5% 7% 32%	6269
	21st to end	Day	17% 7% 3 7% 4 3 4 4 6% 6% 38%	6949
June	1st to 10th	Day	14% 7% 2 6% 4 4 5% 3 6% 8% 39%	2800
	11th to 20th	Day	11% 6% 2 7% 6% 5% 5% 4 7% 9% 38%	2800
	21st to end	Day	13% 6% 2 5% 3 4 5% 4 7% 9% 42%	2800
July	1st to 10th	Day	8% 6% 2 6% 4 5% 5% 5% 7% 10% 43%	6360
	11th to 20th	Day	10% 6% 2 6% 5% 5% 5% 4 6% 10% 41%	6360
	21st to end	Day	9% 5% 2 6% 4 4 5% 4 6% 8% 47%	6454
August	1st to 10th	Day	16% 7% 2 6% 4 4 4 4 7% 9% 38%	4234
	11th to 20th	Day	13% 6% 2 6% 5% 5% 5% 4 7% 11% 35%	4174
	21st to end	Day	10% 5% 2 6% 4 4 4 4 6% 9% 45%	4448
September	1st to 10th	Day	13% 7% 2 5% 4 5% 4 4 7% 8% 42%	2400
	11th to 20th	Day	10% 6% 2 5% 4 5% 5% 4 6% 7% 47%	2305
	21st to end	Day	14% 8% 3 8% 5% 5% 5% 5% 7% 8% 32%	2145
October	1st to 10th	Day	19% 7% 2 6% 4 4 5% 3 5% 7% 38%	2000
	11th to 20th	Day	20% 10% 3 9% 5% 4 5% 4 5% 7% 30%	2000
	21st to end	Day	23% 13% 4 9% 6% 4 5% 3 4 6% 23%	2200
November	1st to 10th	Day	15% 10% 4 8% 6% 5% 5% 3 6% 6% 32%	1822
	11th to 20th	Day	15% 11% 4 7% 6% 5% 5% 4 5% 7% 30%	1680
	21st to end	Day	20% 16% 4 9% 6% 5% 5% 4 5% 6% 22%	1680
December	1st to 10th	Day	20% 17% 4 11% 7% 6% 5% 4 6% 5% 14%	2680
	11th to 20th	Day	20% 17% 6% 9% 5% 4 5% 4 5% 5% 21%	3066
	21st to end	Day	23% 20% 6% 12% 8% 5% 4 2 3 4 12%	4048
January	1st to 10th	Night	15% 17% 6% 12% 6% 5% 5% 3 7% 5% 19%	8234
	11th to 20th	Night	12% 19% 8% 16% 7% 5% 4 3 5% 5% 15%	7743
	21st to end	Night	16% 15% 6% 14% 8% 7% 5% 3 5% 6% 15%	8401
February	1st to 10th	Night	17% 16% 6% 12% 6% 5% 5% 3 5% 5% 21%	2730
	11th to 20th	Night	15% 15% 5% 12% 6% 5% 5% 4 5% 5% 22%	2663
	21st to end	Night	17% 15% 5% 13% 7% 5% 5% 4 4 6% 20%	2168
March	1st to 10th	Night	18% 11% 5% 9% 7% 5% 5% 3 4 5% 29%	5018
	11th to 20th	Night	14% 12% 3 7% 4 4 5% 3 6% 8% 35%	5089
	21st to end	Night	19% 9% 3 8% 4 4 4 3 5% 6% 35%	5588
April	1st to 10th	Night	19% 11% 4 9% 6% 5% 4 3 4 6% 30%	2126
	11th to 20th	Night	19% 8% 3 7% 5% 4 5% 4 5% 5% 36%	2057
	21st to end	Night	16% 9% 3 7% 5% 4 5% 5% 5% 6% 35%	1890
May	1st to 10th	Night	23% 12% 4 8% 4 4 3 3 4 5% 30%	4062
	11th to 20th	Night	11% 7% 3 8% 5% 6% 5% 5% 6% 7% 36%	3621
	21st to end	Night	16% 7% 3 6% 4 4 4 4 5% 7% 39%	3926
June	1st to 10th	Night	11% 6% 2 8% 5% 6% 6% 5% 7% 7% 37%	1600
	11th to 20th	Night	9% 6% 2 6% 6% 5% 4 5% 7% 7% 42%	1600
	21st to end	Night	12% 6% 1 6% 6% 4 6% 4 5% 8% 42%	1600
July	1st to 10th	Night	8% 6% 2 7% 5% 4 4 4 6% 9% 44%	3600
	11th to 20th	Night	9% 5% 2 6% 5% 4 4 4 6% 9% 46%	3600
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 6% 7% 50%	4381
August	1st to 10th	Night	10% 6% 2 6% 4 5% 5% 4 6% 9% 44%	2915
	11th to 20th	Night	14% 7% 3 6% 4 4 5% 3 6% 8% 40%	2875
	21st to end	Night	7% 5% 2 6% 4 4 5% 5% 6% 9% 46%	3416
September	1st to 10th	Night	13% 7% 2 5% 4 4 4 3 5% 7% 46%	2000
	11th to 20th	Night	11% 4 1 5% 3 3 4 3 5% 7% 53%	2091
	21st to end	Night	16% 7% 2 7% 5% 5% 5% 4 6% 6% 37%	2255
October	1st to 10th	Night	16% 6% 3 6% 4 4 4 3 5% 7% 40%	2400
	11th to 20th	Night	21% 9% 3 8% 5% 5% 4 3 5% 5% 32%	2400
	21st to end	Night	23% 9% 3 7% 5% 4 6% 4 4 5% 30%	2640
November	1st to 10th	Night	15% 10% 3 6% 4 4 4 3 4 6% 38%	2691
	11th to 20th	Night	15% 11% 4 8% 6% 5% 5% 4 5% 7% 30%	2940
	21st to end	Night	18% 15% 4 9% 5% 5% 5% 4 6% 6% 23%	2940
December	1st to 10th	Night	17% 19% 6% 12% 6% 5% 5% 3 6% 6% 15%	4720
	11th to 20th	Night	17% 20% 5% 9% 5% 4 4 3 5% 4 23%	5348
	21st to end	Night	25% 17% 6% 11% 6% 5% 4 3 5% 4 15%	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	70% 9% 11% 7% 3	4662
	11th to 20th	Day	77% 8% 7% 5% 3 1	5160
	21st to end	Day	75% 8% 11% 4 3	5780
February	1st to 10th	Day	71% 8% 10% 10% 2	1890
	11th to 20th	Day	70% 9% 9% 10% 2	1852
	21st to end	Day	67% 7% 12% 10% 4	1632
March	1st to 10th	Day	56% 7% 14% 15% 8%	5045
	11th to 20th	Day	50% 9% 17% 15% 7% 1	5090
	21st to end	Day	52% 8% 10% 21% 9% 1	5586
April	1st to 10th	Day	55% 6% 12% 18% 9% 1	2493
	11th to 20th	Day	49% 7% 10% 19% 13% 1	2530
	21st to end	Day	50% 7% 12% 18% 12% 2	2730
May	1st to 10th	Day	51% 8% 12% 16% 10% 5%	5910
	11th to 20th	Day	48% 11% 11% 18% 12% 1	6273
	21st to end	Day	43% 8% 12% 22% 12% 2	6949
June	1st to 10th	Day	40% 9% 14% 20% 15% 2	2800
	11th to 20th	Day	40% 8% 14% 24% 13% 1	2800
	21st to end	Day	37% 9% 15% 24% 14% 1	2800
July	1st to 10th	Day	33% 9% 14% 26% 17% 1	6290
	11th to 20th	Day	34% 9% 15% 28% 14% 1	6285
	21st to end	Day	32% 9% 15% 28% 17% 1	6269
August	1st to 10th	Day	41% 8% 16% 21% 13% 1	4221
	11th to 20th	Day	41% 9% 17% 24% 9% 1	4213
	21st to end	Day	33% 8% 14% 33% 11% 1	4448
September	1st to 10th	Day	38% 8% 16% 27% 11% 1	2400
	11th to 20th	Day	33% 8% 14% 30% 14% 1	2305
	21st to end	Day	45% 9% 16% 20% 9% 1	2145
October	1st to 10th	Day	35% 8% 18% 25% 14% 1	3260
	11th to 20th	Day	45% 7% 16% 19% 12% 1	3240
	21st to end	Day	51% 7% 16% 20% 7%	3538
November	1st to 10th	Day	52% 9% 12% 18% 8% 1	1822
	11th to 20th	Day	54% 8% 16% 14% 7% 1	1680
	21st to end	Day	64% 8% 14% 11% 3	1680
December	1st to 10th	Day	70% 10% 13% 6% 1	2680
	11th to 20th	Day	64% 11% 9% 8% 6% 1	3066
	21st to end	Day	75% 8% 10% 6% 1	4048
January	1st to 10th	Night	69% 9% 13% 8% 2	8234
	11th to 20th	Night	69% 10% 10% 6% 4	7784
	21st to end	Night	70% 8% 10% 6% 5%	8401
February	1st to 10th	Night	67% 8% 11% 12% 3	2730
	11th to 20th	Night	63% 9% 13% 11% 3	2665
	21st to end	Night	64% 7% 12% 11% 5%	2168
March	1st to 10th	Night	57% 6% 12% 17% 7% 1	5028
	11th to 20th	Night	46% 8% 17% 19% 8% 2	5090
	21st to end	Night	49% 7% 10% 21% 12% 1	5588
April	1st to 10th	Night	56% 6% 9% 18% 10% 1	2126
	11th to 20th	Night	48% 7% 11% 19% 13% 2	2057
	21st to end	Night	47% 7% 11% 18% 13% 2	1890
May	1st to 10th	Night	56% 7% 8% 14% 11% 5%	4069
	11th to 20th	Night	43% 10% 16% 19% 12% 1	3622
	21st to end	Night	42% 9% 12% 20% 15% 1	3927
June	1st to 10th	Night	43% 8% 11% 20% 16% 2	1600
	11th to 20th	Night	37% 9% 14% 22% 17% 2	1600
	21st to end	Night	39% 7% 15% 20% 17% 2	1600
July	1st to 10th	Night	36% 8% 13% 23% 20% 2	3560
	11th to 20th	Night	34% 7% 14% 28% 15% 2	3552
	21st to end	Night	32% 7% 14% 24% 22% 1	4252
August	1st to 10th	Night	35% 8% 16% 26% 13% 2	2904
	11th to 20th	Night	40% 8% 15% 26% 11%	2902
	21st to end	Night	31% 8% 16% 32% 13% 1	3416
September	1st to 10th	Night	36% 7% 16% 24% 15% 2	2000
	11th to 20th	Night	31% 7% 13% 31% 17% 1	2091
	21st to end	Night	44% 8% 12% 21% 12% 1	2255
October	1st to 10th	Night	36% 8% 11% 25% 19% 1	3920
	11th to 20th	Night	48% 7% 13% 21% 11%	3899
	21st to end	Night	43% 7% 17% 24% 8% 1	4252
November	1st to 10th	Night	47% 8% 12% 22% 10% 1	2691
	11th to 20th	Night	54% 8% 14% 16% 8% 1	2940
	21st to end	Night	60% 10% 15% 13% 2	2940
December	1st to 10th	Night	69% 11% 13% 6% 2	4720
	11th to 20th	Night	65% 8% 10% 9% 7% 1	5348
	21st to end	Night	71% 9% 11% 7% 2	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% 19% 36% 14% 5% 2	220
	11th to 20th	Day	30% 27% 28% 11% 3 1	308
	21st to end	Day	26% 22% 32% 15% 4 1	363
February	1st to 10th	Day	30% 20% 34% 14% 3	330
	11th to 20th	Day	28% 23% 36% 12% 1	330
	21st to end	Day	36% 17% 33% 12% 2	321
March	1st to 10th	Day	26% 16% 33% 18% 6%	540
	11th to 20th	Day	27% 16% 31% 21% 5% 1	540
	21st to end	Day	28% 16% 29% 20% 6% 2	594
April	1st to 10th	Day	24% 16% 32% 21% 6% 1	540
	11th to 20th	Day	30% 14% 27% 18% 8% 3	532
	21st to end	Day	26% 10% 33% 21% 8% 2	540
May	1st to 10th	Day	24% 9% 27% 23% 12% 4	507
	11th to 20th	Day	18% 7% 25% 27% 18% 6%	527
	21st to end	Day	14% 7% 25% 29% 17% 8%	573
June	1st to 10th	Day	15% 10% 27% 32% 14% 3	530
	11th to 20th	Day	13% 8% 27% 27% 21% 4	530
	21st to end	Day	15% 7% 29% 29% 16% 4	530
July	1st to 10th	Day	9% 4 20% 33% 25% 9%	525
	11th to 20th	Day	14% 6% 20% 29% 21% 10%	524
	21st to end	Day	12% 4 25% 32% 21% 6%	576
August	1st to 10th	Day	13% 2 20% 32% 22% 11%	526
	11th to 20th	Day	11% 7% 17% 30% 24% 11%	519
	21st to end	Day	12% 7% 21% 30% 20% 10%	583
September	1st to 10th	Day	14% 8% 22% 24% 21% 11%	530
	11th to 20th	Day	10% 5% 18% 25% 24% 18%	530
	21st to end	Day	15% 10% 26% 23% 18% 7%	530
October	1st to 10th	Day	21% 11% 24% 19% 16% 9%	530
	11th to 20th	Day	24% 15% 32% 20% 7% 2	530
	21st to end	Day	33% 14% 27% 19% 7%	583
November	1st to 10th	Day	23% 21% 28% 18% 8% 2	358
	11th to 20th	Day	24% 25% 28% 16% 5% 3	220
	21st to end	Day	32% 17% 34% 12% 5%	220
December	1st to 10th	Day	31% 18% 34% 12% 5%	220
	11th to 20th	Day	30% 25% 32% 11% 2	220
	21st to end	Day	29% 26% 30% 11% 3 1	242
January	1st to 10th	Night	28% 21% 32% 13% 5%	840
	11th to 20th	Night	31% 18% 30% 17% 3	840
	21st to end	Night	23% 17% 34% 21% 5%	924
February	1st to 10th	Night	25% 20% 31% 21% 3	840
	11th to 20th	Night	24% 20% 33% 20% 4	823
	21st to end	Night	27% 16% 33% 21% 3	692
March	1st to 10th	Night	23% 14% 35% 23% 6%	840
	11th to 20th	Night	24% 17% 29% 22% 6% 1	840
	21st to end	Night	22% 12% 30% 27% 9% 1	924
April	1st to 10th	Night	25% 13% 31% 26% 5%	840
	11th to 20th	Night	23% 10% 31% 26% 9% 1	813
	21st to end	Night	21% 7% 28% 32% 10% 1	630
May	1st to 10th	Night	21% 7% 23% 33% 14% 3	603
	11th to 20th	Night	15% 5% 27% 41% 12% 1	414
	21st to end	Night	13% 6% 24% 36% 19% 3	433
June	1st to 10th	Night	15% 4 31% 35% 15% 1	400
	11th to 20th	Night	12% 6% 27% 38% 17% 1	400
	21st to end	Night	13% 6% 23% 42% 14% 1	400
July	1st to 10th	Night	9% 4 19% 43% 24% 2	390
	11th to 20th	Night	11% 3 22% 41% 21% 3	388
	21st to end	Night	11% 3 18% 42% 24% 2	636
August	1st to 10th	Night	11% 4 14% 39% 29% 4	597
	11th to 20th	Night	10% 4 17% 33% 31% 5%	594
	21st to end	Night	12% 4 18% 37% 25% 4	775
September	1st to 10th	Night	15% 5% 19% 33% 25% 4	800
	11th to 20th	Night	14% 4 16% 31% 29% 7%	800
	21st to end	Night	19% 6% 21% 31% 20% 5%	800
October	1st to 10th	Night	19% 7% 24% 28% 20% 3	800
	11th to 20th	Night	27% 12% 27% 25% 9% 1	800
	21st to end	Night	31% 13% 25% 25% 5%	880
November	1st to 10th	Night	24% 13% 27% 24% 10% 1	820
	11th to 20th	Night	25% 16% 31% 18% 9% 1	840
	21st to end	Night	29% 15% 32% 19% 6%	840
December	1st to 10th	Night	33% 19% 27% 17% 4	840
	11th to 20th	Night	27% 21% 31% 17% 4	840
	21st to end	Night	32% 17% 30% 18% 3	924

Page generated at 2026-04-29 02:21:43. Version ac07

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