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 2024-01-31.

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% 10% 4 7% 6% 3 5% 5% 6% 7% 32%	74819
	Night	16% 10% 4 8% 6% 4 5% 5% 5% 6% 31%	75303
Transparency	Day	50% 8% 13% 18% 9% 1	74535
	Night	53% 8% 12% 16% 9% 1	75122
Seeing	Day	20% 14% 27% 23% 12% 4	13426
	Night	21% 13% 28% 26% 11% 1	22986

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	16% 16% 7% 12% 10% 4 6% 5% 5% 5% 15%	1517
	11th to 20th	Day	16% 17% 7% 13% 10% 4 5% 5% 4 5% 14%	1669
	21st to end	Day	16% 16% 7% 12% 13% 6% 6% 5% 4 5% 11%	1872
February	1st to 10th	Day	19% 15% 5% 13% 8% 5% 5% 4 5% 5% 15%	1620
	11th to 20th	Day	13% 17% 7% 13% 10% 4 6% 4 4 5% 17%	1573
	21st to end	Day	20% 13% 5% 11% 10% 3 5% 3 5% 5% 19%	1396
March	1st to 10th	Day	16% 10% 6% 12% 9% 4 5% 4 5% 5% 25%	1977
	11th to 20th	Day	14% 15% 4 7% 6% 3 4 4 5% 7% 32%	1980
	21st to end	Day	19% 10% 4 8% 6% 3 4 4 4 6% 31%	2178
April	1st to 10th	Day	17% 12% 5% 7% 6% 3 4 4 5% 5% 32%	2137
	11th to 20th	Day	20% 8% 3 6% 5% 3 4 4 5% 6% 36%	2162
	21st to end	Day	19% 8% 3 6% 6% 3 5% 4 4 6% 34%	2340
May	1st to 10th	Day	16% 9% 3 6% 6% 3 5% 5% 5% 8% 34%	2340
	11th to 20th	Day	14% 7% 4 6% 5% 3 5% 5% 6% 7% 38%	2460
	21st to end	Day	10% 6% 2 5% 5% 3 5% 4 6% 9% 45%	2725
June	1st to 10th	Day	14% 6% 3 5% 5% 2 4 5% 6% 8% 41%	2520
	11th to 20th	Day	11% 6% 2 5% 6% 3 5% 5% 6% 9% 41%	2520
	21st to end	Day	13% 5% 2 5% 4 3 4 5% 7% 9% 42%	2520
July	1st to 10th	Day	6% 4 3 4 4 3 5% 6% 6% 9% 49%	2520
	11th to 20th	Day	11% 6% 3 5% 5% 4 6% 6% 8% 9% 38%	2520
	21st to end	Day	10% 6% 2 5% 6% 4 7% 6% 7% 9% 39%	2565
August	1st to 10th	Day	8% 5% 2 5% 5% 3 5% 6% 8% 10% 42%	2327
	11th to 20th	Day	9% 5% 2 5% 6% 4 6% 7% 7% 11% 38%	2303
	21st to end	Day	11% 6% 3 5% 5% 3 4 5% 5% 9% 44%	2450
September	1st to 10th	Day	14% 7% 3 4 6% 3 4 4 7% 8% 41%	2160
	11th to 20th	Day	11% 5% 3 5% 5% 3 5% 5% 6% 8% 45%	2077
	21st to end	Day	13% 8% 3 6% 6% 4 5% 6% 7% 8% 35%	1929
October	1st to 10th	Day	20% 8% 3 6% 6% 3 5% 4 4 8% 34%	1800
	11th to 20th	Day	21% 10% 3 7% 6% 3 5% 5% 6% 6% 28%	1800
	21st to end	Day	25% 14% 4 9% 6% 3 4 5% 4 5% 22%	1980
November	1st to 10th	Day	13% 11% 3 8% 7% 3 6% 3 6% 7% 32%	1644
	11th to 20th	Day	16% 10% 5% 8% 7% 3 5% 5% 6% 7% 29%	1520
	21st to end	Day	20% 14% 5% 8% 7% 3 4 5% 5% 6% 22%	1520
December	1st to 10th	Day	18% 18% 7% 10% 9% 3 5% 4 5% 5% 17%	1520
	11th to 20th	Day	20% 16% 7% 10% 8% 3 5% 5% 5% 6% 16%	1906
	21st to end	Day	27% 21% 6% 11% 6% 4 4 3 3 4 12%	2772
January	1st to 10th	Night	17% 17% 7% 11% 7% 4 5% 5% 4 4 18%	2649
	11th to 20th	Night	19% 18% 7% 12% 9% 4 4 4 4 5% 14%	2508
	21st to end	Night	16% 15% 7% 12% 10% 6% 6% 4 4 5% 16%	2711
February	1st to 10th	Night	18% 16% 6% 12% 7% 4 4 4 5% 5% 19%	2340
	11th to 20th	Night	16% 14% 5% 11% 8% 4 5% 5% 5% 6% 21%	2273
	21st to end	Night	19% 13% 6% 12% 8% 3 5% 4 4 6% 20%	1856
March	1st to 10th	Night	15% 11% 5% 9% 8% 4 6% 5% 4 6% 28%	1970
	11th to 20th	Night	18% 11% 4 8% 5% 3 4 4 5% 6% 31%	1979
	21st to end	Night	17% 10% 4 8% 6% 3 4 4 4 5% 35%	2178
April	1st to 10th	Night	19% 10% 4 8% 6% 3 4 4 5% 5% 32%	1823
	11th to 20th	Night	18% 7% 2 6% 6% 4 4 5% 5% 5% 37%	1763
	21st to end	Night	17% 9% 4 6% 5% 3 5% 6% 4 7% 35%	1620
May	1st to 10th	Night	16% 8% 3 6% 6% 3 4 5% 6% 8% 35%	1620
	11th to 20th	Night	13% 6% 3 5% 5% 3 6% 5% 6% 7% 40%	1433
	21st to end	Night	11% 6% 2 4 5% 4 5% 5% 6% 8% 45%	1550
June	1st to 10th	Night	11% 5% 3 8% 6% 4 5% 7% 7% 7% 36%	1440
	11th to 20th	Night	10% 5% 3 6% 5% 5% 5% 6% 6% 7% 43%	1440
	21st to end	Night	12% 5% 2 5% 6% 3 5% 5% 6% 8% 43%	1440
July	1st to 10th	Night	6% 4 2 4 6% 3 4 4 5% 7% 54%	1440
	11th to 20th	Night	10% 4 2 6% 5% 3 5% 5% 7% 9% 45%	1440
	21st to end	Night	10% 4 2 5% 6% 3 5% 5% 6% 8% 46%	1749
August	1st to 10th	Night	8% 5% 2 5% 5% 4 5% 5% 7% 9% 46%	1611
	11th to 20th	Night	8% 6% 2 5% 5% 3 5% 6% 7% 7% 45%	1598
	21st to end	Night	9% 5% 2 6% 6% 3 4 6% 5% 9% 46%	1886
September	1st to 10th	Night	14% 6% 3 5% 5% 3 4 4 5% 8% 44%	1800
	11th to 20th	Night	13% 4 2 4 5% 2 3 4 5% 7% 51%	1880
	21st to end	Night	16% 6% 3 6% 5% 4 4 5% 6% 8% 38%	2030
October	1st to 10th	Night	17% 7% 4 6% 5% 3 4 5% 5% 7% 37%	2160
	11th to 20th	Night	22% 9% 3 7% 5% 4 4 4 5% 6% 30%	2160
	21st to end	Night	26% 10% 3 6% 6% 3 5% 5% 4 5% 26%	2376
November	1st to 10th	Night	15% 9% 3 6% 5% 3 4 4 4 7% 38%	2428
	11th to 20th	Night	15% 11% 4 8% 7% 4 5% 4 5% 7% 30%	2660
	21st to end	Night	19% 13% 6% 8% 6% 4 5% 5% 6% 7% 23%	2660
December	1st to 10th	Night	21% 17% 6% 9% 7% 3 5% 4 4 5% 18%	2660
	11th to 20th	Night	16% 18% 6% 10% 7% 4 5% 4 5% 5% 19%	3288
	21st to end	Night	30% 16% 6% 9% 7% 4 5% 4 5% 4 12%	4884

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% 9% 9% 2	1518
	11th to 20th	Day	73% 9% 9% 7% 1	1669
	21st to end	Day	77% 7% 10% 5% 2	1872
February	1st to 10th	Day	72% 8% 9% 9% 1	1620
	11th to 20th	Day	71% 8% 8% 10% 3	1582
	21st to end	Day	68% 7% 11% 9% 5%	1396
March	1st to 10th	Day	61% 8% 12% 14% 5% 1	1980
	11th to 20th	Day	52% 7% 14% 16% 10% 1	1980
	21st to end	Day	54% 7% 8% 20% 9% 2	2178
April	1st to 10th	Day	54% 6% 12% 18% 9% 1	2137
	11th to 20th	Day	48% 7% 11% 19% 13% 2	2162
	21st to end	Day	50% 6% 12% 18% 12% 2	2340
May	1st to 10th	Day	47% 7% 11% 22% 11% 2	2340
	11th to 20th	Day	43% 10% 11% 22% 12% 2	2464
	21st to end	Day	36% 8% 17% 23% 14% 2	2725
June	1st to 10th	Day	40% 9% 14% 21% 15% 2	2520
	11th to 20th	Day	39% 7% 15% 25% 14% 1	2520
	21st to end	Day	36% 9% 15% 24% 15% 1	2520
July	1st to 10th	Day	28% 10% 15% 25% 19% 3	2450
	11th to 20th	Day	37% 10% 17% 25% 11%	2445
	21st to end	Day	38% 10% 17% 21% 12% 1	2422
August	1st to 10th	Day	34% 9% 19% 25% 12% 1	2314
	11th to 20th	Day	38% 10% 17% 24% 10% 1	2303
	21st to end	Day	36% 7% 15% 28% 12% 2	2450
September	1st to 10th	Day	39% 8% 16% 25% 11% 1	2160
	11th to 20th	Day	35% 8% 15% 27% 14% 1	2077
	21st to end	Day	44% 9% 17% 21% 9% 1	1929
October	1st to 10th	Day	49% 7% 14% 17% 11% 1	1800
	11th to 20th	Day	55% 9% 15% 16% 6% 1	1800
	21st to end	Day	65% 6% 11% 12% 5% 1	1980
November	1st to 10th	Day	52% 9% 12% 18% 8% 1	1644
	11th to 20th	Day	54% 8% 17% 14% 6% 1	1520
	21st to end	Day	63% 8% 14% 11% 3	1520
December	1st to 10th	Day	70% 10% 13% 7% 1	1520
	11th to 20th	Day	68% 12% 12% 7% 2	1906
	21st to end	Day	77% 8% 9% 5% 1	2772
January	1st to 10th	Night	69% 9% 10% 9% 3	2649
	11th to 20th	Night	74% 9% 10% 6% 1	2508
	21st to end	Night	71% 8% 10% 7% 3	2711
February	1st to 10th	Night	69% 8% 10% 10% 2	2340
	11th to 20th	Night	65% 8% 12% 11% 4	2275
	21st to end	Night	65% 7% 11% 11% 5%	1856
March	1st to 10th	Night	56% 8% 13% 16% 6% 1	1980
	11th to 20th	Night	54% 7% 10% 18% 10% 1	1980
	21st to end	Night	53% 6% 8% 20% 12% 2	2178
April	1st to 10th	Night	54% 6% 9% 19% 10% 1	1823
	11th to 20th	Night	47% 7% 10% 20% 14% 2	1763
	21st to end	Night	48% 7% 11% 18% 13% 2	1620
May	1st to 10th	Night	46% 8% 9% 19% 15% 3	1620
	11th to 20th	Night	41% 7% 12% 23% 14% 2	1434
	21st to end	Night	35% 9% 13% 22% 17% 3	1551
June	1st to 10th	Night	43% 8% 11% 20% 17% 1	1440
	11th to 20th	Night	36% 9% 13% 21% 18% 2	1440
	21st to end	Night	38% 8% 16% 21% 17% 2	1440
July	1st to 10th	Night	29% 7% 13% 26% 21% 4	1400
	11th to 20th	Night	34% 7% 15% 26% 16% 2	1392
	21st to end	Night	34% 8% 16% 22% 16% 3	1652
August	1st to 10th	Night	31% 11% 18% 27% 13% 1	1600
	11th to 20th	Night	34% 10% 16% 28% 12%	1598
	21st to end	Night	34% 9% 14% 29% 13% 2	1886
September	1st to 10th	Night	38% 7% 17% 22% 14% 2	1800
	11th to 20th	Night	33% 7% 13% 29% 17% 1	1880
	21st to end	Night	43% 9% 13% 22% 13%	2030
October	1st to 10th	Night	45% 9% 12% 19% 14% 1	2160
	11th to 20th	Night	54% 8% 14% 17% 8% 1	2160
	21st to end	Night	60% 7% 12% 12% 8% 1	2376
November	1st to 10th	Night	47% 8% 12% 21% 11% 2	2428
	11th to 20th	Night	53% 8% 15% 16% 7% 1	2660
	21st to end	Night	60% 10% 15% 13% 2	2660
December	1st to 10th	Night	69% 10% 12% 7% 2	2660
	11th to 20th	Night	67% 9% 12% 9% 2	3288
	21st to end	Night	74% 10% 11% 5% 1	4884

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% 22% 29% 16% 5% 2	180
	11th to 20th	Day	24% 31% 29% 12% 3 1	251
	21st to end	Day	23% 25% 30% 17% 4	294
February	1st to 10th	Day	32% 25% 33% 10%	240
	11th to 20th	Day	26% 28% 36% 10%	240
	21st to end	Day	36% 18% 32% 13% 2	240
March	1st to 10th	Day	23% 20% 35% 17% 5%	420
	11th to 20th	Day	24% 16% 35% 21% 3 1	420
	21st to end	Day	29% 15% 29% 20% 6% 2	462
April	1st to 10th	Day	22% 19% 32% 20% 7% 1	420
	11th to 20th	Day	27% 17% 24% 20% 9% 3	412
	21st to end	Day	25% 12% 36% 17% 8% 2	420
May	1st to 10th	Day	24% 13% 29% 19% 11% 4	423
	11th to 20th	Day	18% 9% 28% 26% 16% 3	447
	21st to end	Day	14% 9% 27% 29% 16% 6%	485
June	1st to 10th	Day	15% 12% 30% 30% 11% 2	450
	11th to 20th	Day	14% 11% 24% 32% 17% 2	450
	21st to end	Day	16% 9% 28% 32% 12% 3	450
July	1st to 10th	Day	9% 5% 20% 33% 26% 7%	445
	11th to 20th	Day	13% 8% 23% 30% 19% 8%	444
	21st to end	Day	11% 6% 29% 31% 18% 5%	488
August	1st to 10th	Day	10% 4 24% 32% 20% 10%	446
	11th to 20th	Day	10% 6% 22% 30% 21% 10%	439
	21st to end	Day	12% 8% 23% 30% 20% 8%	495
September	1st to 10th	Day	14% 8% 22% 28% 18% 10%	450
	11th to 20th	Day	12% 7% 20% 24% 25% 12%	450
	21st to end	Day	15% 13% 28% 20% 17% 7%	450
October	1st to 10th	Day	22% 15% 22% 17% 17% 6%	450
	11th to 20th	Day	24% 21% 28% 20% 6% 2	450
	21st to end	Day	36% 17% 24% 17% 6%	495
November	1st to 10th	Day	22% 21% 31% 16% 8% 2	302
	11th to 20th	Day	25% 28% 23% 19% 3 2	180
	21st to end	Day	29% 25% 30% 14% 2	180
December	1st to 10th	Day	28% 25% 32% 9% 6% 1	180
	11th to 20th	Day	29% 29% 27% 13% 2	180
	21st to end	Day	29% 32% 29% 8% 2	198
January	1st to 10th	Night	28% 23% 31% 14% 5%	760
	11th to 20th	Night	30% 21% 29% 16% 3	760
	21st to end	Night	23% 18% 34% 21% 5%	835
February	1st to 10th	Night	27% 23% 31% 17% 2	720
	11th to 20th	Night	23% 20% 35% 17% 4	703
	21st to end	Night	28% 18% 32% 21% 2	592
March	1st to 10th	Night	22% 15% 35% 23% 5%	720
	11th to 20th	Night	23% 17% 31% 22% 6% 1	720
	21st to end	Night	20% 12% 33% 25% 9% 1	792
April	1st to 10th	Night	23% 16% 32% 25% 4	720
	11th to 20th	Night	20% 13% 32% 25% 9% 1	699
	21st to end	Night	21% 8% 30% 31% 10%	540
May	1st to 10th	Night	19% 8% 26% 31% 14% 3	540
	11th to 20th	Night	15% 5% 29% 41% 9% 1	372
	21st to end	Night	12% 7% 25% 36% 18% 2	389
June	1st to 10th	Night	13% 5% 33% 35% 14%	360
	11th to 20th	Night	11% 7% 30% 35% 16% 1	360
	21st to end	Night	12% 6% 28% 42% 12%	360
July	1st to 10th	Night	8% 3 23% 43% 22% 1	350
	11th to 20th	Night	10% 5% 26% 39% 20% 1	348
	21st to end	Night	11% 3 22% 42% 20% 2	569
August	1st to 10th	Night	9% 4 15% 41% 26% 3	537
	11th to 20th	Night	9% 4 19% 35% 30% 3	534
	21st to end	Night	12% 4 21% 36% 24% 3	698
September	1st to 10th	Night	15% 5% 20% 36% 21% 4	720
	11th to 20th	Night	15% 5% 19% 31% 25% 6%	720
	21st to end	Night	18% 8% 23% 30% 18% 4	720
October	1st to 10th	Night	19% 8% 27% 26% 17% 2	720
	11th to 20th	Night	26% 16% 27% 24% 7% 1	720
	21st to end	Night	32% 14% 26% 24% 4	792
November	1st to 10th	Night	23% 13% 29% 24% 10% 1	740
	11th to 20th	Night	22% 19% 32% 18% 8% 1	760
	21st to end	Night	26% 18% 31% 18% 6%	760
December	1st to 10th	Night	32% 22% 26% 17% 4	760
	11th to 20th	Night	24% 23% 32% 16% 4	760
	21st to end	Night	32% 19% 33% 15% 2	836

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