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 2025-01-07.

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% 3 8% 5% 5% 5% 4 6% 7% 32%	105044
	Night	16% 12% 4 9% 5% 4 4 4 5% 6% 31%	103979
Transparency	Day	49% 9% 14% 19% 9% 1	108649
	Night	52% 8% 13% 17% 9% 1	108463
Seeing	Day	20% 11% 27% 23% 14% 5%	14640
	Night	22% 11% 27% 27% 12% 2	24152

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% 20% 6% 13% 6% 5% 4 3 4 5% 18%	2565
	11th to 20th	Day	12% 23% 7% 18% 10% 5% 4 3 4 4 10%	2776
	21st to end	Day	23% 19% 8% 12% 8% 6% 4 3 3 4 11%	3124
February	1st to 10th	Day	18% 18% 4 13% 7% 6% 4 4 5% 5% 15%	1710
	11th to 20th	Day	13% 19% 6% 16% 8% 5% 5% 4 4 4 18%	1663
	21st to end	Day	19% 15% 4 12% 8% 4 4 3 5% 5% 19%	1480
March	1st to 10th	Day	19% 12% 5% 10% 5% 4 4 3 5% 4 29%	3432
	11th to 20th	Day	10% 20% 4 8% 5% 5% 4 3 5% 6% 29%	3480
	21st to end	Day	17% 10% 3 8% 5% 4 4 4 5% 6% 33%	3815
April	1st to 10th	Day	18% 14% 3 8% 5% 4 4 2 4 5% 32%	2255
	11th to 20th	Day	20% 9% 3 6% 4 4 4 3 5% 6% 35%	2286
	21st to end	Day	19% 9% 3 8% 5% 4 4 4 4 6% 33%	2470
May	1st to 10th	Day	18% 9% 3 8% 4 5% 5% 3 5% 7% 33%	4108
	11th to 20th	Day	14% 10% 3 9% 5% 5% 4 4 6% 8% 30%	4363
	21st to end	Day	11% 6% 2 6% 4 3 4 3 6% 8% 46%	4837
June	1st to 10th	Day	14% 7% 2 6% 4 4 5% 3 6% 8% 39%	2660
	11th to 20th	Day	11% 6% 2 6% 5% 5% 5% 4 7% 9% 40%	2660
	21st to end	Day	14% 6% 2 5% 3 4 5% 4 7% 9% 42%	2660
July	1st to 10th	Day	8% 5% 2 5% 5% 4 5% 5% 7% 10% 44%	4440
	11th to 20th	Day	11% 6% 2 5% 5% 5% 5% 4 7% 10% 41%	4440
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 4 7% 9% 43%	4482
August	1st to 10th	Day	17% 7% 2 6% 4 4 4 4 7% 9% 37%	4104
	11th to 20th	Day	13% 6% 2 6% 5% 5% 5% 4 7% 11% 35%	4044
	21st to end	Day	10% 5% 2 6% 4 4 4 4 6% 9% 46%	4312
September	1st to 10th	Day	13% 7% 2 5% 4 5% 4 3 7% 8% 42%	2280
	11th to 20th	Day	10% 6% 2 6% 4 4 4 4 6% 7% 46%	2190
	21st to end	Day	14% 8% 3 8% 5% 5% 5% 5% 7% 8% 32%	2038
October	1st to 10th	Day	19% 8% 2 7% 5% 4 5% 3 5% 8% 35%	1900
	11th to 20th	Day	20% 10% 3 9% 4 4 5% 4 5% 6% 30%	1900
	21st to end	Day	24% 13% 4 9% 6% 4 5% 3 4 6% 23%	2090
November	1st to 10th	Day	14% 10% 4 8% 6% 5% 5% 3 6% 6% 32%	1734
	11th to 20th	Day	15% 12% 4 7% 6% 5% 5% 4 5% 7% 30%	1600
	21st to end	Day	20% 16% 4 9% 6% 5% 5% 3 5% 6% 22%	1600
December	1st to 10th	Day	20% 17% 4 11% 7% 6% 5% 4 6% 5% 14%	2600
	11th to 20th	Day	21% 17% 6% 9% 5% 4 5% 4 5% 5% 21%	2986
	21st to end	Day	23% 20% 6% 12% 8% 5% 4 2 3 4 12%	3960
January	1st to 10th	Night	18% 19% 6% 11% 6% 5% 4 3 4 5% 20%	4514
	11th to 20th	Night	14% 19% 7% 16% 7% 5% 4 3 5% 4 16%	4182
	21st to end	Night	24% 19% 6% 12% 6% 5% 4 3 4 4 12%	4532
February	1st to 10th	Night	18% 17% 6% 12% 6% 5% 5% 3 5% 5% 20%	2470
	11th to 20th	Night	15% 15% 4 12% 6% 5% 6% 4 5% 5% 22%	2403
	21st to end	Night	18% 14% 4 13% 7% 6% 5% 4 5% 6% 21%	1968
March	1st to 10th	Night	21% 12% 4 8% 5% 5% 4 3 4 5% 31%	3408
	11th to 20th	Night	16% 15% 3 8% 4 4 4 3 5% 7% 30%	3479
	21st to end	Night	16% 8% 3 8% 4 3 4 3 5% 6% 41%	3817
April	1st to 10th	Night	20% 11% 4 9% 5% 4 4 3 4 6% 31%	1924
	11th to 20th	Night	18% 8% 3 7% 5% 4 4 4 6% 5% 36%	1859
	21st to end	Night	16% 9% 3 7% 5% 4 5% 5% 5% 6% 35%	1710
May	1st to 10th	Night	20% 10% 4 7% 4 4 3 3 4 6% 33%	2833
	11th to 20th	Night	12% 8% 3 7% 5% 5% 6% 5% 7% 8% 34%	2527
	21st to end	Night	11% 6% 2 5% 4 4 5% 4 6% 8% 46%	2738
June	1st to 10th	Night	11% 6% 2 9% 5% 6% 5% 5% 7% 7% 36%	1520
	11th to 20th	Night	9% 5% 2 6% 6% 5% 4 5% 7% 7% 43%	1520
	21st to end	Night	13% 6% 1 5% 5% 4 6% 4 6% 8% 41%	1520
July	1st to 10th	Night	7% 6% 2 7% 6% 4 4 4 6% 8% 45%	2520
	11th to 20th	Night	11% 5% 2 6% 4 3 4 4 6% 9% 47%	2520
	21st to end	Night	9% 4 2 6% 4 4 5% 4 7% 7% 48%	3054
August	1st to 10th	Night	10% 6% 2 6% 4 5% 5% 4 5% 9% 44%	2825
	11th to 20th	Night	14% 7% 3 6% 4 4 5% 3 6% 8% 40%	2785
	21st to end	Night	7% 5% 2 6% 4 4 5% 5% 6% 9% 46%	3311
September	1st to 10th	Night	13% 7% 2 5% 4 4 4 2 5% 7% 45%	1900
	11th to 20th	Night	12% 4 2 5% 4 3 4 3 5% 7% 52%	1986
	21st to end	Night	16% 7% 2 7% 5% 5% 5% 4 6% 6% 36%	2142
October	1st to 10th	Night	17% 7% 3 7% 4 4 4 3 5% 7% 38%	2280
	11th to 20th	Night	21% 10% 3 8% 5% 5% 4 3 5% 5% 32%	2280
	21st to end	Night	24% 9% 3 7% 5% 4 6% 4 5% 6% 28%	2508
November	1st to 10th	Night	16% 10% 3 6% 4 4 4 3 4 6% 39%	2560
	11th to 20th	Night	15% 11% 4 8% 6% 5% 5% 4 5% 7% 30%	2800
	21st to end	Night	18% 14% 4 9% 5% 5% 5% 4 6% 6% 24%	2800
December	1st to 10th	Night	17% 19% 6% 12% 6% 5% 5% 3 6% 6% 15%	4580
	11th to 20th	Night	17% 20% 5% 9% 5% 4 4 3 5% 4 23%	5208
	21st to end	Night	25% 17% 6% 10% 6% 5% 4 3 5% 4 15%	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	66% 11% 11% 9% 3	2566
	11th to 20th	Day	77% 10% 7% 5% 1	2776
	21st to end	Day	77% 8% 11% 3 1	3124
February	1st to 10th	Day	71% 8% 10% 10% 2	1710
	11th to 20th	Day	69% 9% 8% 11% 3	1672
	21st to end	Day	66% 8% 12% 10% 5%	1480
March	1st to 10th	Day	55% 8% 12% 19% 5%	3435
	11th to 20th	Day	51% 11% 16% 15% 7% 1	3480
	21st to end	Day	46% 9% 13% 23% 7% 1	3815
April	1st to 10th	Day	54% 6% 12% 18% 9% 1	2255
	11th to 20th	Day	48% 7% 11% 19% 13% 2	2286
	21st to end	Day	50% 7% 11% 17% 12% 2	2470
May	1st to 10th	Day	47% 8% 13% 18% 11% 2	4120
	11th to 20th	Day	47% 13% 14% 19% 7% 1	4367
	21st to end	Day	34% 9% 14% 25% 16% 3	4837
June	1st to 10th	Day	40% 9% 14% 20% 15% 2	2660
	11th to 20th	Day	39% 8% 15% 24% 14% 1	2660
	21st to end	Day	37% 9% 15% 24% 14% 1	2660
July	1st to 10th	Day	32% 9% 14% 27% 17% 2	4370
	11th to 20th	Day	33% 9% 15% 30% 12% 1	4365
	21st to end	Day	34% 10% 16% 23% 16% 1	4339
August	1st to 10th	Day	42% 8% 16% 21% 12% 1	4091
	11th to 20th	Day	41% 9% 17% 24% 8% 1	4083
	21st to end	Day	33% 7% 14% 33% 12% 1	4312
September	1st to 10th	Day	38% 8% 15% 26% 12% 1	2280
	11th to 20th	Day	34% 8% 15% 28% 14% 1	2190
	21st to end	Day	45% 8% 16% 21% 9% 1	2038
October	1st to 10th	Day	35% 8% 18% 25% 13% 1	3160
	11th to 20th	Day	45% 8% 16% 19% 12% 1	3140
	21st to end	Day	51% 7% 16% 20% 6%	3428
November	1st to 10th	Day	52% 9% 12% 18% 8% 1	1734
	11th to 20th	Day	54% 8% 17% 14% 7% 1	1600
	21st to end	Day	64% 8% 14% 11% 3	1600
December	1st to 10th	Day	70% 10% 14% 5% 1	2600
	11th to 20th	Day	64% 11% 9% 8% 7% 1	2986
	21st to end	Day	75% 8% 10% 6% 1	3960
January	1st to 10th	Night	65% 11% 14% 8% 2	4514
	11th to 20th	Night	70% 12% 11% 6% 1	4182
	21st to end	Night	74% 9% 10% 5% 2	4532
February	1st to 10th	Night	68% 8% 11% 11% 2	2470
	11th to 20th	Night	64% 9% 13% 11% 4	2405
	21st to end	Night	64% 7% 12% 12% 5%	1968
March	1st to 10th	Night	55% 7% 11% 21% 6%	3418
	11th to 20th	Night	52% 10% 15% 15% 7% 1	3480
	21st to end	Night	42% 7% 11% 26% 13% 1	3817
April	1st to 10th	Night	55% 6% 9% 19% 10% 1	1924
	11th to 20th	Night	48% 7% 10% 20% 13% 2	1859
	21st to end	Night	47% 7% 11% 18% 13% 3	1710
May	1st to 10th	Night	50% 8% 10% 18% 12% 2	2840
	11th to 20th	Night	43% 11% 18% 19% 8% 1	2528
	21st to end	Night	32% 11% 13% 23% 20% 2	2739
June	1st to 10th	Night	43% 8% 11% 20% 16% 1	1520
	11th to 20th	Night	36% 9% 13% 21% 18% 2	1520
	21st to end	Night	40% 7% 15% 20% 16% 1	1520
July	1st to 10th	Night	36% 7% 12% 22% 20% 2	2480
	11th to 20th	Night	33% 7% 15% 30% 13% 1	2472
	21st to end	Night	32% 8% 17% 23% 17% 2	2957
August	1st to 10th	Night	35% 8% 15% 27% 13% 2	2814
	11th to 20th	Night	41% 8% 15% 26% 10%	2812
	21st to end	Night	31% 8% 16% 32% 13% 1	3311
September	1st to 10th	Night	37% 7% 16% 23% 15% 2	1900
	11th to 20th	Night	32% 7% 13% 29% 18% 1	1986
	21st to end	Night	45% 8% 13% 22% 12%	2142
October	1st to 10th	Night	37% 9% 12% 24% 18% 1	3800
	11th to 20th	Night	48% 7% 13% 21% 11%	3779
	21st to end	Night	43% 7% 17% 24% 8% 1	4120
November	1st to 10th	Night	47% 8% 12% 21% 11% 2	2560
	11th to 20th	Night	54% 8% 14% 16% 8% 1	2800
	21st to end	Night	60% 10% 15% 13% 2	2800
December	1st to 10th	Night	69% 11% 13% 6% 1	4580
	11th to 20th	Night	65% 8% 10% 9% 7% 1	5208
	21st to end	Night	71% 9% 11% 7% 2	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% 19% 33% 15% 6% 2	192
	11th to 20th	Day	26% 26% 31% 13% 3 2	252
	21st to end	Day	23% 20% 34% 17% 5% 1	297
February	1st to 10th	Day	30% 19% 36% 13% 3	270
	11th to 20th	Day	25% 23% 38% 12% 1	270
	21st to end	Day	36% 16% 33% 13% 2	268
March	1st to 10th	Day	24% 15% 34% 19% 7%	460
	11th to 20th	Day	23% 15% 32% 23% 5% 1	460
	21st to end	Day	27% 14% 29% 21% 7% 2	506
April	1st to 10th	Day	21% 14% 33% 23% 7% 1	460
	11th to 20th	Day	28% 13% 27% 19% 10% 4	452
	21st to end	Day	27% 9% 31% 22% 8% 3	460
May	1st to 10th	Day	23% 9% 25% 25% 13% 5%	463
	11th to 20th	Day	17% 6% 25% 28% 19% 6%	487
	21st to end	Day	12% 6% 25% 30% 19% 8%	529
June	1st to 10th	Day	15% 9% 25% 33% 14% 3	490
	11th to 20th	Day	13% 8% 25% 28% 23% 4	490
	21st to end	Day	15% 7% 28% 30% 16% 4	490
July	1st to 10th	Day	9% 4 19% 33% 26% 9%	485
	11th to 20th	Day	14% 6% 19% 29% 21% 10%	484
	21st to end	Day	12% 4 23% 33% 22% 7%	532
August	1st to 10th	Day	14% 2 20% 30% 22% 12%	486
	11th to 20th	Day	11% 7% 17% 30% 24% 11%	479
	21st to end	Day	12% 6% 20% 30% 21% 11%	539
September	1st to 10th	Day	14% 8% 22% 24% 21% 11%	490
	11th to 20th	Day	11% 6% 18% 23% 24% 18%	490
	21st to end	Day	16% 10% 27% 22% 18% 7%	490
October	1st to 10th	Day	22% 12% 23% 19% 15% 9%	490
	11th to 20th	Day	24% 15% 31% 20% 8% 2	490
	21st to end	Day	34% 14% 27% 18% 8%	539
November	1st to 10th	Day	22% 20% 28% 20% 8% 2	330
	11th to 20th	Day	22% 25% 29% 18% 5% 2	200
	21st to end	Day	31% 17% 34% 13% 5%	200
December	1st to 10th	Day	30% 19% 35% 12% 5% 1	200
	11th to 20th	Day	29% 25% 32% 12% 3	200
	21st to end	Day	26% 27% 31% 12% 3 1	220
January	1st to 10th	Night	29% 21% 31% 13% 6%	785
	11th to 20th	Night	31% 16% 30% 19% 4	760
	21st to end	Night	23% 15% 33% 23% 5%	836
February	1st to 10th	Night	25% 20% 31% 21% 3	760
	11th to 20th	Night	23% 19% 34% 20% 4	743
	21st to end	Night	27% 15% 32% 22% 3	628
March	1st to 10th	Night	22% 12% 35% 24% 6%	760
	11th to 20th	Night	24% 17% 28% 24% 6% 1	760
	21st to end	Night	21% 11% 30% 27% 10% 1	836
April	1st to 10th	Night	25% 13% 30% 27% 5%	760
	11th to 20th	Night	21% 10% 32% 26% 9% 1	735
	21st to end	Night	22% 7% 28% 31% 11% 1	570
May	1st to 10th	Night	20% 7% 23% 33% 15% 3	570
	11th to 20th	Night	16% 5% 25% 41% 12% 1	393
	21st to end	Night	12% 6% 23% 36% 20% 3	411
June	1st to 10th	Night	15% 3 32% 34% 15% 1	380
	11th to 20th	Night	12% 5% 26% 38% 18% 1	380
	21st to end	Night	13% 6% 23% 42% 14% 1	380
July	1st to 10th	Night	9% 4 19% 42% 24% 2	370
	11th to 20th	Night	11% 2 23% 40% 21% 3	368
	21st to end	Night	11% 3 18% 43% 23% 2	604
August	1st to 10th	Night	11% 4 14% 38% 29% 4	567
	11th to 20th	Night	10% 4 17% 33% 30% 5%	564
	21st to end	Night	12% 3 18% 37% 26% 4	736
September	1st to 10th	Night	15% 5% 18% 34% 24% 4	760
	11th to 20th	Night	14% 4 16% 30% 28% 7%	760
	21st to end	Night	19% 6% 21% 30% 19% 5%	760
October	1st to 10th	Night	19% 8% 24% 28% 19% 3	760
	11th to 20th	Night	27% 13% 25% 25% 9% 1	760
	21st to end	Night	32% 13% 25% 25% 6%	836
November	1st to 10th	Night	24% 12% 28% 24% 11% 1	780
	11th to 20th	Night	25% 16% 31% 18% 9% 1	800
	21st to end	Night	28% 15% 31% 19% 6%	800
December	1st to 10th	Night	33% 19% 27% 17% 4 1	800
	11th to 20th	Night	27% 20% 31% 18% 4 1	800
	21st to end	Night	31% 16% 31% 19% 3	880

Page generated at 2025-01-04 03:23:59. Version ac07

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