Fort Erie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Erie clear sky chart from 2005-11-06 to 2024-08-15.

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% 12% 3 8% 5% 5% 4 4 5% 7% 31%	95551
	Night	18% 13% 4 9% 5% 4 4 3 5% 6% 28%	93163
Transparency	Day	53% 7% 12% 18% 9% 1	95279
	Night	57% 7% 11% 16% 8% 1	92988
Seeing	Day	20% 15% 28% 22% 11% 3	14207
	Night	23% 14% 27% 24% 11% 1	23607

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	19% 25% 8% 12% 7% 5% 4 3 4 4 11%	2517
	11th to 20th	Day	14% 23% 7% 21% 11% 6% 4 2 3 3 8%	2776
	21st to end	Day	22% 21% 7% 13% 7% 6% 5% 3 3 3 10%	3124
February	1st to 10th	Day	17% 19% 5% 15% 8% 5% 7% 4 4 4 13%	1710
	11th to 20th	Day	14% 18% 7% 14% 8% 6% 5% 4 3 5% 17%	1663
	21st to end	Day	21% 13% 5% 12% 8% 5% 4 4 5% 5% 18%	1486
March	1st to 10th	Day	19% 14% 4 8% 5% 4 4 3 4 6% 29%	3432
	11th to 20th	Day	10% 19% 5% 8% 5% 5% 4 4 5% 6% 29%	3480
	21st to end	Day	18% 11% 3 10% 6% 4 4 3 5% 6% 29%	3815
April	1st to 10th	Day	19% 14% 3 8% 4 5% 3 3 4 6% 31%	2258
	11th to 20th	Day	20% 10% 2 7% 4 4 4 3 5% 6% 34%	2274
	21st to end	Day	21% 10% 3 7% 5% 4 4 3 5% 5% 34%	2470
May	1st to 10th	Day	21% 10% 3 6% 5% 5% 4 4 6% 6% 31%	4108
	11th to 20th	Day	14% 10% 3 9% 5% 5% 5% 4 7% 8% 30%	4362
	21st to end	Day	12% 7% 2 6% 3 4 4 4 6% 7% 45%	4837
June	1st to 10th	Day	15% 8% 2 7% 5% 4 4 4 7% 7% 38%	2660
	11th to 20th	Day	13% 5% 2 6% 4 5% 4 4 7% 9% 40%	2660
	21st to end	Day	15% 6% 2 5% 4 3 5% 3 6% 8% 43%	2660
July	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 6% 9% 45%	4440
	11th to 20th	Day	13% 5% 2 6% 4 5% 4 4 7% 8% 42%	4440
	21st to end	Day	7% 5% 3 7% 4 4 6% 5% 8% 9% 43%	4480
August	1st to 10th	Day	11% 5% 2 5% 5% 4 5% 4 7% 9% 43%	2457
	11th to 20th	Day	10% 6% 3 6% 4 5% 6% 4 7% 10% 38%	2357
	21st to end	Day	12% 6% 2 5% 4 4 4 3 6% 9% 44%	2444
September	1st to 10th	Day	15% 7% 2 5% 4 4 4 4 5% 7% 41%	2160
	11th to 20th	Day	12% 4 2 6% 4 4 4 4 6% 8% 45%	2081
	21st to end	Day	15% 8% 3 6% 5% 6% 5% 5% 6% 8% 33%	1926
October	1st to 10th	Day	20% 9% 3 7% 6% 4 4 3 5% 6% 33%	1800
	11th to 20th	Day	22% 10% 4 8% 5% 5% 5% 4 5% 6% 27%	1800
	21st to end	Day	27% 15% 3 10% 4 5% 4 3 3 5% 21%	1980
November	1st to 10th	Day	15% 12% 3 8% 5% 5% 5% 4 5% 5% 32%	1656
	11th to 20th	Day	16% 15% 4 11% 5% 4 4 4 5% 6% 28%	1520
	21st to end	Day	22% 19% 4 8% 5% 4 5% 3 4 7% 18%	1520
December	1st to 10th	Day	21% 20% 6% 11% 6% 6% 4 4 4 4 13%	1520
	11th to 20th	Day	21% 22% 5% 12% 5% 4 4 4 4 5% 14%	1906
	21st to end	Day	26% 26% 6% 10% 5% 4 3 2 3 3 11%	2772
January	1st to 10th	Night	20% 25% 7% 11% 6% 5% 4 3 3 3 13%	4429
	11th to 20th	Night	15% 22% 8% 20% 10% 6% 3 3 3 3 7%	4180
	21st to end	Night	25% 22% 6% 14% 6% 4 3 2 3 4 10%	4532
February	1st to 10th	Night	19% 20% 7% 13% 6% 4 4 3 5% 4 16%	2470
	11th to 20th	Night	16% 16% 6% 12% 7% 6% 5% 4 4 6% 18%	2403
	21st to end	Night	20% 15% 5% 13% 7% 4 4 3 4 5% 19%	1965
March	1st to 10th	Night	20% 14% 3 8% 5% 4 3 3 3 4 31%	3408
	11th to 20th	Night	20% 18% 4 7% 4 4 3 3 4 6% 26%	3479
	21st to end	Night	17% 9% 3 8% 4 4 4 3 5% 6% 39%	3817
April	1st to 10th	Night	21% 14% 3 7% 5% 3 4 3 5% 4 30%	1920
	11th to 20th	Night	19% 9% 3 8% 5% 4 4 4 5% 6% 34%	1870
	21st to end	Night	18% 10% 3 6% 4 4 5% 4 5% 7% 35%	1710
May	1st to 10th	Night	24% 10% 3 8% 4 3 4 3 5% 6% 31%	2833
	11th to 20th	Night	14% 7% 3 8% 6% 5% 5% 4 7% 9% 33%	2527
	21st to end	Night	13% 6% 3 5% 3 4 4 4 6% 8% 44%	2738
June	1st to 10th	Night	12% 9% 3 6% 6% 5% 6% 5% 7% 7% 36%	1520
	11th to 20th	Night	12% 5% 2 6% 5% 5% 5% 4 6% 8% 41%	1520
	21st to end	Night	15% 7% 2 5% 5% 4 4 5% 6% 8% 39%	1520
July	1st to 10th	Night	10% 6% 2 7% 5% 5% 5% 4 6% 9% 43%	2520
	11th to 20th	Night	13% 6% 2 6% 4 4 4 3 6% 8% 44%	2520
	21st to end	Night	10% 5% 2 6% 5% 4 5% 4 7% 7% 45%	3069
August	1st to 10th	Night	10% 6% 2 6% 5% 4 4 4 7% 8% 44%	1701
	11th to 20th	Night	11% 6% 2 6% 4 5% 5% 4 6% 8% 44%	1643
	21st to end	Night	10% 5% 2 6% 5% 4 6% 4 5% 8% 45%	1894
September	1st to 10th	Night	15% 7% 3 5% 4 4 4 3 5% 8% 43%	1800
	11th to 20th	Night	13% 5% 1 5% 3 3 3 3 5% 7% 51%	1876
	21st to end	Night	17% 7% 2 6% 5% 4 4 5% 6% 7% 37%	2034
October	1st to 10th	Night	19% 6% 3 7% 5% 5% 4 3 5% 7% 38%	2160
	11th to 20th	Night	22% 10% 4 8% 4 5% 5% 4 5% 6% 28%	2160
	21st to end	Night	28% 9% 3 7% 4 5% 5% 4 5% 5% 24%	2376
November	1st to 10th	Night	18% 10% 3 7% 5% 4 3 3 5% 6% 36%	2417
	11th to 20th	Night	16% 13% 3 9% 6% 5% 5% 3 5% 6% 28%	2660
	21st to end	Night	20% 15% 4 10% 6% 5% 4 4 5% 6% 20%	2660
December	1st to 10th	Night	22% 20% 5% 11% 7% 4 4 3 5% 5% 14%	2660
	11th to 20th	Night	19% 22% 6% 11% 7% 5% 4 3 4 4 16%	3288
	21st to end	Night	30% 19% 5% 10% 5% 4 4 3 4 4 11%	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	78% 8% 6% 5% 3	2518
	11th to 20th	Day	81% 8% 6% 4 1	2776
	21st to end	Day	80% 7% 9% 3 1	3124
February	1st to 10th	Day	76% 6% 10% 7% 1	1710
	11th to 20th	Day	71% 6% 9% 11% 3	1672
	21st to end	Day	67% 6% 11% 11% 4	1486
March	1st to 10th	Day	56% 6% 11% 20% 6%	3435
	11th to 20th	Day	54% 8% 18% 14% 6% 1	3480
	21st to end	Day	54% 9% 9% 20% 7% 1	3815
April	1st to 10th	Day	56% 5% 11% 18% 10% 1	2258
	11th to 20th	Day	50% 6% 11% 20% 12% 2	2274
	21st to end	Day	53% 5% 10% 17% 13% 2	2470
May	1st to 10th	Day	51% 6% 13% 18% 10% 2	4120
	11th to 20th	Day	49% 11% 13% 20% 7% 1	4366
	21st to end	Day	36% 7% 14% 25% 14% 3	4837
June	1st to 10th	Day	43% 8% 13% 20% 15% 1	2660
	11th to 20th	Day	40% 8% 15% 23% 12% 1	2660
	21st to end	Day	39% 8% 14% 25% 13% 1	2660
July	1st to 10th	Day	36% 5% 13% 29% 16% 2	4370
	11th to 20th	Day	38% 5% 14% 25% 16%	4365
	21st to end	Day	37% 7% 18% 22% 16% 1	4337
August	1st to 10th	Day	36% 10% 16% 25% 11% 1	2444
	11th to 20th	Day	39% 10% 18% 24% 9% 1	2357
	21st to end	Day	38% 7% 16% 27% 11% 2	2444
September	1st to 10th	Day	42% 8% 14% 24% 11% 1	2160
	11th to 20th	Day	36% 8% 14% 28% 13% 1	2081
	21st to end	Day	48% 7% 14% 21% 10% 1	1926
October	1st to 10th	Day	51% 8% 13% 16% 11% 1	1800
	11th to 20th	Day	58% 7% 14% 15% 6% 1	1800
	21st to end	Day	68% 4 11% 10% 6% 1	1980
November	1st to 10th	Day	55% 7% 11% 17% 8% 2	1656
	11th to 20th	Day	58% 8% 15% 13% 5% 2	1520
	21st to end	Day	68% 6% 12% 10% 3	1520
December	1st to 10th	Day	74% 9% 8% 8% 1	1520
	11th to 20th	Day	76% 8% 9% 6% 1	1906
	21st to end	Day	80% 6% 8% 6%	2772
January	1st to 10th	Night	76% 10% 7% 6% 1	4429
	11th to 20th	Night	80% 9% 6% 3 1	4180
	21st to end	Night	81% 7% 6% 4 1	4532
February	1st to 10th	Night	73% 6% 10% 9% 2	2470
	11th to 20th	Night	69% 6% 10% 12% 3	2405
	21st to end	Night	68% 6% 10% 11% 5%	1965
March	1st to 10th	Night	58% 5% 10% 20% 6%	3418
	11th to 20th	Night	59% 7% 13% 14% 6% 1	3480
	21st to end	Night	47% 5% 11% 22% 13% 1	3817
April	1st to 10th	Night	57% 5% 9% 19% 10% 1	1920
	11th to 20th	Night	51% 6% 10% 18% 14% 2	1870
	21st to end	Night	49% 6% 11% 18% 14% 2	1710
May	1st to 10th	Night	53% 7% 9% 17% 10% 3	2840
	11th to 20th	Night	45% 10% 17% 20% 8% 1	2528
	21st to end	Night	36% 7% 12% 24% 19% 2	2739
June	1st to 10th	Night	44% 9% 10% 22% 14% 1	1520
	11th to 20th	Night	40% 7% 13% 21% 18% 1	1520
	21st to end	Night	42% 7% 14% 22% 13% 2	1520
July	1st to 10th	Night	41% 4 11% 24% 17% 3	2480
	11th to 20th	Night	40% 4 14% 27% 14% 1	2472
	21st to end	Night	37% 6% 17% 22% 15% 2	2971
August	1st to 10th	Night	36% 8% 16% 27% 12% 1	1690
	11th to 20th	Night	36% 9% 16% 28% 11%	1643
	21st to end	Night	38% 7% 14% 27% 12% 2	1894
September	1st to 10th	Night	39% 8% 14% 24% 13% 2	1800
	11th to 20th	Night	34% 6% 14% 28% 17% 1	1876
	21st to end	Night	44% 9% 13% 21% 12% 1	2034
October	1st to 10th	Night	48% 6% 12% 19% 14% 1	2160
	11th to 20th	Night	57% 7% 13% 14% 8%	2160
	21st to end	Night	63% 7% 10% 13% 6% 1	2376
November	1st to 10th	Night	52% 6% 11% 19% 10% 2	2417
	11th to 20th	Night	59% 8% 12% 13% 6% 2	2660
	21st to end	Night	65% 8% 13% 11% 3	2660
December	1st to 10th	Night	74% 8% 11% 6% 1	2660
	11th to 20th	Night	73% 8% 10% 7% 2	3288
	21st to end	Night	78% 7% 8% 6%	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	27% 27% 28% 11% 6% 2	180
	11th to 20th	Day	27% 29% 29% 12% 3 1	252
	21st to end	Day	24% 26% 29% 16% 4	297
February	1st to 10th	Day	29% 26% 31% 11% 2	270
	11th to 20th	Day	26% 29% 35% 10%	270
	21st to end	Day	29% 25% 35% 10% 1	277
March	1st to 10th	Day	23% 20% 35% 17% 3 2	460
	11th to 20th	Day	24% 20% 34% 17% 5% 1	460
	21st to end	Day	28% 14% 32% 19% 6% 1	506
April	1st to 10th	Day	23% 22% 31% 18% 6% 1	460
	11th to 20th	Day	26% 21% 25% 17% 9% 3	452
	21st to end	Day	25% 15% 31% 21% 7% 2	460
May	1st to 10th	Day	26% 13% 27% 21% 10% 3	463
	11th to 20th	Day	16% 11% 28% 27% 14% 3	487
	21st to end	Day	14% 8% 30% 28% 15% 5%	529
June	1st to 10th	Day	17% 16% 27% 29% 11% 1	490
	11th to 20th	Day	12% 13% 23% 31% 17% 3	490
	21st to end	Day	16% 10% 31% 29% 11% 3	490
July	1st to 10th	Day	9% 8% 21% 34% 23% 5%	485
	11th to 20th	Day	13% 9% 25% 29% 19% 5%	484
	21st to end	Day	9% 8% 28% 32% 17% 6%	532
August	1st to 10th	Day	12% 6% 22% 31% 21% 8%	486
	11th to 20th	Day	13% 6% 23% 29% 21% 9%	456
	21st to end	Day	12% 7% 26% 30% 17% 7%	495
September	1st to 10th	Day	14% 9% 24% 28% 18% 7%	450
	11th to 20th	Day	11% 6% 21% 28% 24% 10%	450
	21st to end	Day	16% 14% 26% 21% 16% 6%	450
October	1st to 10th	Day	21% 13% 25% 17% 17% 6%	450
	11th to 20th	Day	25% 19% 30% 19% 5% 2	450
	21st to end	Day	34% 21% 22% 17% 5%	495
November	1st to 10th	Day	24% 18% 30% 19% 7% 2	313
	11th to 20th	Day	32% 27% 23% 14% 3 2	180
	21st to end	Day	33% 26% 29% 11% 1	180
December	1st to 10th	Day	32% 26% 28% 9% 5%	180
	11th to 20th	Day	32% 25% 26% 16% 2	180
	21st to end	Day	31% 32% 25% 11% 2	198
January	1st to 10th	Night	31% 24% 27% 13% 5%	760
	11th to 20th	Night	32% 23% 27% 14% 3	760
	21st to end	Night	24% 17% 36% 18% 5%	836
February	1st to 10th	Night	28% 24% 29% 16% 3	760
	11th to 20th	Night	26% 21% 32% 18% 3	743
	21st to end	Night	28% 20% 32% 18% 2	628
March	1st to 10th	Night	23% 17% 33% 22% 5%	760
	11th to 20th	Night	26% 17% 30% 20% 6% 1	760
	21st to end	Night	24% 12% 34% 20% 9% 1	836
April	1st to 10th	Night	26% 15% 30% 24% 4	760
	11th to 20th	Night	24% 14% 29% 22% 9% 1	746
	21st to end	Night	23% 9% 27% 30% 9% 1	570
May	1st to 10th	Night	21% 9% 23% 32% 13% 2	570
	11th to 20th	Night	13% 9% 26% 42% 10% 1	393
	21st to end	Night	13% 6% 27% 31% 21% 2	411
June	1st to 10th	Night	14% 6% 30% 35% 15% 1	380
	11th to 20th	Night	14% 7% 24% 37% 17% 1	380
	21st to end	Night	14% 8% 25% 38% 14%	380
July	1st to 10th	Night	8% 4 22% 42% 21% 2	370
	11th to 20th	Night	12% 4 26% 36% 20% 2	368
	21st to end	Night	11% 3 24% 36% 23% 2	606
August	1st to 10th	Night	11% 4 17% 39% 25% 3	567
	11th to 20th	Night	9% 6% 18% 33% 30% 3	549
	21st to end	Night	12% 5% 22% 34% 23% 3	706
September	1st to 10th	Night	16% 7% 19% 33% 21% 4	720
	11th to 20th	Night	15% 6% 20% 28% 27% 5%	720
	21st to end	Night	19% 10% 22% 29% 18% 4	720
October	1st to 10th	Night	21% 8% 28% 23% 18% 2	720
	11th to 20th	Night	26% 19% 25% 23% 7% 1	720
	21st to end	Night	32% 16% 28% 19% 4	792
November	1st to 10th	Night	24% 15% 30% 23% 8% 1	740
	11th to 20th	Night	24% 22% 30% 16% 8% 1	760
	21st to end	Night	27% 22% 30% 16% 5%	760
December	1st to 10th	Night	36% 24% 24% 13% 4	760
	11th to 20th	Night	31% 25% 27% 15% 3	760
	21st to end	Night	35% 19% 28% 16% 2	836

Page generated at 2024-08-12 09:52:48. Version ac07

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