Lockport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lockport clear sky chart from 2005-11-06 to 2026-07-16.

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	13% 9% 3 8% 5% 5% 5% 4 6% 7% 36%	137921
	Night	14% 10% 4 8% 5% 4 4 3 5% 6% 38%	135067
Transparency	Day	45% 6% 12% 22% 13% 2	141443
	Night	46% 5% 11% 22% 14% 2	139622
Seeing	Day	17% 12% 31% 24% 12% 4	18116
	Night	18% 10% 31% 29% 11% 1	27938

By Month

Percentage Cloud Cover SE (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	12% 14% 7% 12% 6% 6% 5% 4 6% 6% 23%	4691
	11th to 20th	Day	8% 13% 6% 13% 6% 6% 6% 5% 5% 4 27%	4710
	21st to end	Day	13% 16% 4 11% 5% 4 4 3 5% 6% 28%	5335
February	1st to 10th	Day	15% 14% 5% 10% 5% 6% 5% 4 6% 6% 24%	1947
	11th to 20th	Day	14% 11% 4 9% 7% 5% 4 4 5% 5% 33%	2048
	21st to end	Day	15% 13% 5% 10% 5% 4 3 3 5% 6% 30%	1730
March	1st to 10th	Day	18% 12% 3 6% 4 3 3 2 4 5% 40%	4580
	11th to 20th	Day	9% 8% 3 7% 5% 5% 5% 4 6% 8% 41%	4787
	21st to end	Day	19% 14% 6% 12% 6% 5% 5% 4 4 5% 21%	6099
April	1st to 10th	Day	17% 14% 4 8% 5% 4 4 4 5% 6% 30%	2520
	11th to 20th	Day	15% 10% 3 7% 5% 4 4 4 6% 7% 34%	2494
	21st to end	Day	19% 9% 3 8% 5% 4 4 3 5% 6% 34%	2630
May	1st to 10th	Day	17% 7% 3 7% 5% 4 5% 4 6% 8% 34%	7616
	11th to 20th	Day	13% 7% 3 7% 5% 5% 5% 4 6% 8% 39%	7980
	21st to end	Day	14% 7% 3 7% 5% 4 5% 4 6% 9% 38%	9047
June	1st to 10th	Day	10% 5% 2 6% 4 4 5% 5% 6% 8% 44%	2940
	11th to 20th	Day	9% 5% 2 5% 5% 4 5% 4 6% 8% 45%	2940
	21st to end	Day	11% 6% 2 6% 6% 5% 6% 5% 7% 9% 38%	2940
July	1st to 10th	Day	9% 6% 3 8% 5% 6% 6% 5% 7% 9% 36%	6500
	11th to 20th	Day	9% 6% 2 7% 4 5% 5% 5% 7% 10% 41%	6431
	21st to end	Day	11% 7% 2 7% 5% 5% 4 5% 7% 9% 38%	6924
August	1st to 10th	Day	8% 5% 2 6% 5% 5% 4 4 7% 9% 45%	4445
	11th to 20th	Day	11% 4 2 6% 4 4 5% 5% 7% 9% 44%	3854
	21st to end	Day	7% 4 2 6% 4 5% 4 4 6% 10% 48%	4312
September	1st to 10th	Day	11% 5% 2 5% 3 4 4 3 5% 8% 49%	2400
	11th to 20th	Day	11% 4 2 4 3 3 4 4 5% 8% 52%	2270
	21st to end	Day	11% 6% 3 6% 4 4 4 5% 5% 8% 44%	2200
October	1st to 10th	Day	12% 7% 2 6% 4 4 4 3 5% 6% 48%	2154
	11th to 20th	Day	18% 8% 2 8% 4 3 4 4 5% 6% 38%	1990
	21st to end	Day	19% 8% 3 7% 4 4 4 3 5% 6% 36%	1980
November	1st to 10th	Day	12% 9% 2 6% 4 3 4 3 5% 7% 45%	1852
	11th to 20th	Day	16% 10% 4 9% 4 3 4 3 5% 7% 33%	1890
	21st to end	Day	18% 12% 4 10% 5% 4 3 3 4 4 34%	1837
December	1st to 10th	Day	9% 10% 3 9% 5% 4 4 3 3 6% 42%	2690
	11th to 20th	Day	13% 16% 6% 12% 6% 4 5% 4 6% 6% 24%	3088
	21st to end	Day	24% 23% 6% 13% 6% 4 4 2 3 4 11%	4070
January	1st to 10th	Night	13% 14% 7% 11% 5% 5% 4 3 4 5% 29%	8232
	11th to 20th	Night	10% 15% 6% 14% 8% 6% 5% 4 6% 4 22%	8280
	21st to end	Night	15% 13% 6% 8% 5% 4 5% 3 4 5% 32%	8878
February	1st to 10th	Night	15% 14% 4 9% 6% 4 4 3 4 6% 31%	2672
	11th to 20th	Night	15% 11% 3 8% 5% 4 4 3 4 6% 36%	2458
	21st to end	Night	17% 12% 3 9% 5% 4 3 3 4 5% 35%	2076
March	1st to 10th	Night	17% 11% 4 6% 4 4 4 2 4 5% 40%	5493
	11th to 20th	Night	11% 7% 3 7% 4 4 4 3 5% 6% 46%	5436
	21st to end	Night	18% 11% 4 10% 6% 5% 5% 3 5% 5% 28%	5072
April	1st to 10th	Night	17% 10% 3 6% 4 3 4 3 5% 7% 37%	2100
	11th to 20th	Night	18% 8% 3 6% 4 3 4 3 5% 5% 39%	2075
	21st to end	Night	17% 7% 3 7% 5% 5% 5% 4 6% 7% 35%	1990
May	1st to 10th	Night	16% 7% 3 6% 5% 5% 4 4 6% 7% 37%	5237
	11th to 20th	Night	10% 6% 2 5% 4 4 5% 4 7% 9% 44%	4896
	21st to end	Night	14% 8% 3 7% 4 4 4 4 6% 8% 40%	5139
June	1st to 10th	Night	10% 5% 2 6% 5% 4 4 4 5% 6% 49%	1680
	11th to 20th	Night	9% 5% 2 6% 4 4 4 4 7% 10% 45%	1680
	21st to end	Night	10% 7% 2 6% 5% 4 5% 5% 6% 9% 41%	1680
July	1st to 10th	Night	10% 6% 3 7% 5% 5% 5% 4 6% 9% 40%	3698
	11th to 20th	Night	7% 5% 2 6% 4 4 4 4 5% 9% 50%	3657
	21st to end	Night	9% 5% 3 6% 5% 5% 4 4 7% 8% 44%	3947
August	1st to 10th	Night	6% 5% 2 6% 4 4 5% 4 6% 9% 49%	2709
	11th to 20th	Night	9% 4 1 5% 3 3 4 4 6% 8% 52%	3191
	21st to end	Night	8% 4 2 5% 3 4 4 4 5% 9% 53%	3586
September	1st to 10th	Night	10% 5% 3 6% 3 3 3 3 5% 7% 54%	2000
	11th to 20th	Night	8% 4 2 4 4 4 3 3 5% 8% 56%	2110
	21st to end	Night	10% 5% 2 7% 4 4 5% 4 6% 6% 46%	2200
October	1st to 10th	Night	11% 5% 2 6% 3 3 4 3 4 6% 53%	2243
	11th to 20th	Night	17% 8% 2 5% 3 3 3 3 4 6% 46%	2410
	21st to end	Night	20% 8% 3 7% 4 3 4 3 5% 6% 38%	2860
November	1st to 10th	Night	13% 8% 2 6% 3 4 3 3 5% 6% 47%	2666
	11th to 20th	Night	15% 10% 4 7% 5% 4 4 3 5% 6% 37%	2730
	21st to end	Night	17% 10% 4 9% 5% 3 3 3 4 5% 36%	2777
December	1st to 10th	Night	12% 9% 3 7% 5% 4 4 3 5% 6% 42%	4720
	11th to 20th	Night	17% 16% 5% 9% 4 4 3 3 4 5% 30%	5339
	21st to end	Night	25% 19% 5% 10% 5% 4 4 3 4 5% 17%	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	61% 4 15% 14% 6% 1	4692
	11th to 20th	Day	58% 3 8% 15% 12% 3	4710
	21st to end	Day	57% 3 12% 19% 8% 1	5335
February	1st to 10th	Day	59% 6% 12% 14% 8% 2	1947
	11th to 20th	Day	52% 5% 10% 22% 9% 2	2058
	21st to end	Day	54% 6% 11% 20% 7% 2	1730
March	1st to 10th	Day	48% 4 7% 25% 12% 3	4580
	11th to 20th	Day	39% 5% 12% 33% 10% 1	4787
	21st to end	Day	64% 7% 10% 12% 6% 1	6101
April	1st to 10th	Day	54% 6% 10% 19% 11%	2520
	11th to 20th	Day	47% 7% 11% 21% 12% 3	2494
	21st to end	Day	50% 5% 13% 19% 11% 2	2630
May	1st to 10th	Day	46% 6% 11% 22% 13% 1	7651
	11th to 20th	Day	43% 6% 11% 23% 16% 1	7984
	21st to end	Day	42% 6% 11% 21% 15% 5%	9061
June	1st to 10th	Day	36% 9% 11% 25% 18% 2	2940
	11th to 20th	Day	35% 6% 11% 25% 20% 3	2940
	21st to end	Day	40% 9% 13% 21% 14% 3	2940
July	1st to 10th	Day	41% 7% 13% 24% 14% 2	6431
	11th to 20th	Day	36% 7% 15% 27% 14% 1	6356
	21st to end	Day	40% 7% 16% 21% 14% 2	6728
August	1st to 10th	Day	33% 7% 16% 29% 13% 1	4430
	11th to 20th	Day	34% 7% 12% 31% 15% 1	3890
	21st to end	Day	31% 6% 14% 28% 19% 3	4311
September	1st to 10th	Day	33% 7% 12% 25% 18% 4	2400
	11th to 20th	Day	30% 5% 12% 28% 22% 3	2270
	21st to end	Day	37% 6% 10% 25% 20% 2	2200
October	1st to 10th	Day	26% 4 7% 29% 31% 2	3505
	11th to 20th	Day	33% 5% 11% 26% 24% 1	3218
	21st to end	Day	42% 4 9% 26% 15% 3	3180
November	1st to 10th	Day	39% 5% 13% 25% 16% 2	1852
	11th to 20th	Day	50% 5% 12% 21% 11% 1	1890
	21st to end	Day	54% 4 10% 23% 9%	1837
December	1st to 10th	Day	44% 4 16% 27% 9% 1	2690
	11th to 20th	Day	60% 5% 12% 17% 5% 1	3085
	21st to end	Day	79% 3 6% 7% 4	4070
January	1st to 10th	Night	58% 4 11% 18% 8%	8233
	11th to 20th	Night	64% 3 10% 11% 11% 1	8280
	21st to end	Night	55% 3 11% 21% 9%	8878
February	1st to 10th	Night	56% 4 12% 17% 10% 2	2672
	11th to 20th	Night	50% 4 10% 22% 13% 1	2459
	21st to end	Night	51% 5% 12% 19% 11% 2	2076
March	1st to 10th	Night	48% 4 10% 24% 11% 3	5493
	11th to 20th	Night	38% 4 12% 28% 14% 3	5436
	21st to end	Night	57% 6% 9% 19% 8% 1	5072
April	1st to 10th	Night	47% 5% 12% 23% 12% 2	2100
	11th to 20th	Night	46% 5% 10% 20% 16% 4	2075
	21st to end	Night	46% 7% 11% 21% 13% 2	1990
May	1st to 10th	Night	45% 5% 11% 21% 15% 3	5264
	11th to 20th	Night	35% 6% 16% 24% 16% 3	4897
	21st to end	Night	42% 6% 10% 18% 19% 5%	5149
June	1st to 10th	Night	35% 6% 11% 25% 20% 3	1680
	11th to 20th	Night	33% 6% 13% 23% 23% 2	1680
	21st to end	Night	38% 8% 14% 21% 16% 3	1680
July	1st to 10th	Night	40% 6% 13% 24% 14% 3	3660
	11th to 20th	Night	31% 6% 15% 26% 21% 1	3612
	21st to end	Night	36% 6% 16% 22% 17% 3	3832
August	1st to 10th	Night	30% 8% 17% 27% 17% 1	2700
	11th to 20th	Night	29% 6% 14% 30% 20% 1	3221
	21st to end	Night	29% 6% 12% 32% 18% 3	3586
September	1st to 10th	Night	31% 5% 11% 27% 23% 3	2000
	11th to 20th	Night	27% 5% 8% 30% 27% 3	2110
	21st to end	Night	36% 6% 11% 27% 18% 3	2200
October	1st to 10th	Night	21% 4 7% 36% 29% 2	3672
	11th to 20th	Night	35% 4 7% 23% 29% 2	3921
	21st to end	Night	40% 3 9% 25% 20% 3	4610
November	1st to 10th	Night	38% 4 9% 26% 19% 3	2666
	11th to 20th	Night	48% 4 12% 22% 12% 2	2730
	21st to end	Night	51% 4 11% 22% 11%	2777
December	1st to 10th	Night	43% 4 14% 26% 11% 2	4720
	11th to 20th	Night	57% 4 12% 16% 10% 1	5341
	21st to end	Night	71% 5% 8% 10% 6%	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	23% 13% 38% 21% 5%	330
	11th to 20th	Day	22% 23% 37% 14% 3 1	330
	21st to end	Day	23% 19% 37% 17% 3	363
February	1st to 10th	Day	22% 21% 39% 15% 3	330
	11th to 20th	Day	25% 22% 33% 17% 2	330
	21st to end	Day	26% 21% 41% 10% 2	273
March	1st to 10th	Day	25% 22% 39% 13% 2	330
	11th to 20th	Day	28% 16% 36% 15% 4 1	359
	21st to end	Day	29% 18% 30% 16% 5% 1	594
April	1st to 10th	Day	26% 17% 30% 20% 6% 1	540
	11th to 20th	Day	24% 21% 26% 19% 10% 1	532
	21st to end	Day	23% 16% 35% 18% 8% 1	540
May	1st to 10th	Day	24% 14% 30% 22% 8% 2	543
	11th to 20th	Day	19% 12% 33% 22% 11% 3	687
	21st to end	Day	15% 10% 34% 23% 14% 5%	844
June	1st to 10th	Day	11% 10% 32% 28% 15% 4	780
	11th to 20th	Day	13% 8% 33% 27% 14% 3	780
	21st to end	Day	11% 10% 35% 28% 12% 4	780
July	1st to 10th	Day	8% 4 25% 32% 19% 13%	771
	11th to 20th	Day	11% 6% 26% 29% 18% 10%	744
	21st to end	Day	9% 4 27% 35% 19% 6%	794
August	1st to 10th	Day	7% 2 22% 34% 24% 10%	660
	11th to 20th	Day	10% 4 19% 31% 24% 12%	519
	21st to end	Day	6% 4 19% 37% 24% 10%	583
September	1st to 10th	Day	11% 6% 24% 31% 22% 6%	530
	11th to 20th	Day	10% 3 17% 32% 26% 12%	530
	21st to end	Day	14% 8% 25% 27% 20% 6%	530
October	1st to 10th	Day	15% 8% 27% 30% 16% 4	484
	11th to 20th	Day	17% 23% 31% 21% 7% 1	330
	21st to end	Day	30% 12% 36% 17% 6%	363
November	1st to 10th	Day	18% 16% 37% 19% 7% 3	330
	11th to 20th	Day	25% 18% 35% 15% 6% 1	330
	21st to end	Day	25% 11% 43% 16% 4	330
December	1st to 10th	Day	18% 22% 38% 15% 6% 1	330
	11th to 20th	Day	23% 17% 39% 18% 3	330
	21st to end	Day	30% 20% 35% 14% 2	363
January	1st to 10th	Night	20% 15% 38% 23% 4	1050
	11th to 20th	Night	21% 19% 35% 20% 4 1	1050
	21st to end	Night	21% 14% 35% 26% 3	1155
February	1st to 10th	Night	24% 14% 36% 23% 3	992
	11th to 20th	Night	21% 13% 36% 26% 4	823
	21st to end	Night	22% 15% 39% 21% 3	692
March	1st to 10th	Night	21% 16% 37% 21% 5%	840
	11th to 20th	Night	18% 13% 38% 25% 5% 1	824
	21st to end	Night	26% 12% 34% 22% 6%	693
April	1st to 10th	Night	20% 14% 36% 23% 6%	630
	11th to 20th	Night	22% 14% 33% 23% 8% 1	623
	21st to end	Night	21% 10% 33% 28% 7% 1	630
May	1st to 10th	Night	18% 7% 36% 30% 8%	630
	11th to 20th	Night	16% 6% 33% 33% 12%	621
	21st to end	Night	13% 6% 28% 36% 17%	683
June	1st to 10th	Night	11% 4 28% 42% 14%	630
	11th to 20th	Night	11% 5% 30% 42% 12% 1	630
	21st to end	Night	12% 5% 27% 37% 18% 1	630
July	1st to 10th	Night	8% 3 19% 41% 26% 4	615
	11th to 20th	Night	7% 4 20% 39% 27% 3	597
	21st to end	Night	6% 2 17% 48% 25% 2	657
August	1st to 10th	Night	5% 1 14% 49% 28% 4	597
	11th to 20th	Night	8% 2 13% 41% 32% 4	594
	21st to end	Night	8% 1 18% 42% 29% 2	660
September	1st to 10th	Night	10% 4 18% 36% 28% 4	600
	11th to 20th	Night	9% 4 18% 38% 28% 4	710
	21st to end	Night	12% 7% 23% 35% 21% 3	800
October	1st to 10th	Night	12% 6% 25% 37% 18% 2	800
	11th to 20th	Night	20% 13% 30% 28% 9%	800
	21st to end	Night	25% 12% 30% 25% 8%	880
November	1st to 10th	Night	17% 12% 39% 23% 9% 1	820
	11th to 20th	Night	20% 16% 35% 24% 5%	840
	21st to end	Night	23% 13% 37% 21% 6%	887
December	1st to 10th	Night	22% 13% 37% 24% 4	1050
	11th to 20th	Night	24% 13% 35% 23% 4	1050
	21st to end	Night	32% 14% 32% 21% 2	1155

Page generated at 2026-07-13 02:14:53. Version ac07

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