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 2025-03-12.

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% 4 4 4 6% 7% 36%	108712
	Night	14% 10% 4 8% 5% 4 4 3 5% 6% 38%	110498
Transparency	Day	45% 6% 12% 22% 14% 2	112279
	Night	46% 5% 11% 21% 15% 2	115072
Seeing	Day	17% 11% 30% 24% 13% 4	16175
	Night	18% 10% 30% 29% 11% 1	26203

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% 12% 7% 12% 7% 6% 5% 4 6% 6% 24%	3617
	11th to 20th	Day	11% 13% 6% 13% 6% 6% 4 5% 6% 4 26%	3620
	21st to end	Day	15% 19% 5% 10% 4 3 3 3 5% 5% 28%	4119
February	1st to 10th	Day	16% 14% 5% 9% 6% 6% 5% 4 5% 6% 24%	1854
	11th to 20th	Day	15% 11% 4 9% 7% 5% 3 3 5% 5% 33%	1948
	21st to end	Day	16% 13% 5% 10% 5% 4 3 3 5% 6% 30%	1650
March	1st to 10th	Day	17% 15% 4 6% 5% 4 4 2 4 5% 34%	3220
	11th to 20th	Day	10% 7% 3 7% 5% 5% 4 4 6% 8% 39%	3278
	21st to end	Day	19% 12% 6% 12% 6% 5% 5% 4 4 5% 20%	4165
April	1st to 10th	Day	16% 14% 4 8% 5% 4 4 4 5% 6% 31%	2280
	11th to 20th	Day	16% 9% 2 7% 5% 4 4 4 6% 7% 35%	2254
	21st to end	Day	20% 9% 3 8% 5% 4 4 3 5% 6% 33%	2380
May	1st to 10th	Day	18% 6% 2 6% 5% 4 5% 4 7% 8% 34%	4082
	11th to 20th	Day	15% 8% 2 5% 4 5% 4 4 6% 7% 41%	4267
	21st to end	Day	11% 6% 2 6% 4 4 5% 4 6% 9% 43%	4824
June	1st to 10th	Day	10% 5% 2 6% 4 4 4 5% 6% 8% 45%	2660
	11th to 20th	Day	9% 5% 2 5% 5% 4 5% 4 6% 8% 45%	2660
	21st to end	Day	11% 6% 2 6% 6% 5% 6% 5% 7% 9% 37%	2660
July	1st to 10th	Day	10% 7% 3 8% 6% 6% 6% 5% 7% 9% 34%	4440
	11th to 20th	Day	8% 4 2 6% 4 4 4 4 7% 10% 47%	4440
	21st to end	Day	9% 6% 2 8% 5% 5% 4 5% 7% 9% 40%	4813
August	1st to 10th	Day	8% 5% 2 6% 5% 5% 4 4 7% 9% 45%	4309
	11th to 20th	Day	11% 4 2 6% 4 4 5% 5% 7% 9% 44%	3734
	21st to end	Day	7% 5% 2 6% 4 4 4 4 6% 10% 48%	4180
September	1st to 10th	Day	11% 5% 2 6% 3 4 4 3 5% 8% 48%	2280
	11th to 20th	Day	11% 4 2 4 4 4 4 4 5% 8% 51%	2157
	21st to end	Day	11% 6% 3 6% 4 4 4 5% 5% 8% 44%	2090
October	1st to 10th	Day	12% 7% 2 6% 3 4 4 3 5% 6% 47%	2047
	11th to 20th	Day	18% 8% 2 8% 4 3 4 4 5% 6% 38%	1891
	21st to end	Day	20% 8% 3 7% 4 4 4 3 5% 6% 35%	1881
November	1st to 10th	Day	12% 10% 2 6% 4 3 4 3 5% 7% 45%	1762
	11th to 20th	Day	16% 10% 4 9% 5% 4 5% 3 5% 6% 33%	1800
	21st to end	Day	18% 11% 4 9% 5% 4 3 3 4 4 34%	1750
December	1st to 10th	Day	9% 10% 3 9% 5% 4 4 3 3 6% 43%	2610
	11th to 20th	Day	12% 16% 6% 12% 6% 4 5% 4 6% 6% 24%	3008
	21st to end	Day	24% 23% 6% 13% 6% 5% 4 2 3 4 10%	3982
January	1st to 10th	Night	14% 14% 7% 11% 5% 5% 4 3 4 4 29%	6348
	11th to 20th	Night	13% 16% 6% 12% 7% 6% 4 4 6% 4 21%	6360
	21st to end	Night	18% 13% 6% 9% 5% 4 4 3 4 4 31%	6858
February	1st to 10th	Night	16% 15% 4 8% 6% 4 4 3 4 6% 31%	2545
	11th to 20th	Night	15% 11% 3 8% 5% 4 4 3 4 6% 35%	2338
	21st to end	Night	17% 12% 3 8% 5% 4 3 3 4 5% 35%	1980
March	1st to 10th	Night	18% 11% 3 6% 4 4 4 3 4 5% 39%	3853
	11th to 20th	Night	10% 7% 3 7% 4 4 4 3 4 6% 48%	3739
	21st to end	Night	19% 11% 5% 10% 5% 5% 5% 3 5% 5% 27%	3466
April	1st to 10th	Night	15% 11% 3 6% 4 3 4 3 5% 8% 38%	1900
	11th to 20th	Night	19% 9% 3 6% 4 3 3 3 5% 5% 40%	1875
	21st to end	Night	18% 7% 3 8% 4 5% 5% 4 6% 7% 35%	1800
May	1st to 10th	Night	17% 7% 3 7% 5% 5% 4 3 7% 8% 35%	2813
	11th to 20th	Night	13% 7% 2 6% 4 4 5% 4 7% 8% 40%	2630
	21st to end	Night	11% 7% 2 6% 4 4 5% 4 6% 7% 44%	2743
June	1st to 10th	Night	10% 5% 2 5% 5% 4 4 4 6% 6% 50%	1520
	11th to 20th	Night	9% 4 2 6% 4 4 4 4 6% 10% 47%	1520
	21st to end	Night	10% 7% 2 6% 5% 4 5% 5% 6% 9% 41%	1520
July	1st to 10th	Night	12% 6% 3 7% 5% 5% 5% 4 6% 9% 39%	2530
	11th to 20th	Night	6% 4 2 6% 4 4 4 4 5% 8% 55%	2530
	21st to end	Night	5% 4 2 6% 5% 6% 5% 5% 8% 8% 46%	2750
August	1st to 10th	Night	6% 5% 2 6% 5% 4 5% 4 6% 9% 48%	2626
	11th to 20th	Night	9% 4 1 5% 3 3 4 3 6% 8% 52%	3091
	21st to end	Night	8% 4 2 5% 3 4 4 4 5% 8% 52%	3476
September	1st to 10th	Night	10% 5% 3 6% 3 3 3 3 5% 6% 53%	1900
	11th to 20th	Night	9% 4 2 3 3 4 3 3 5% 8% 55%	2004
	21st to end	Night	10% 5% 2 6% 4 4 5% 5% 7% 6% 45%	2090
October	1st to 10th	Night	11% 5% 2 6% 3 3 4 3 5% 6% 53%	2131
	11th to 20th	Night	17% 8% 2 5% 3 3 3 3 4 6% 46%	2289
	21st to end	Night	20% 8% 3 7% 4 3 4 3 5% 6% 37%	2717
November	1st to 10th	Night	13% 8% 2 6% 3 4 3 3 5% 5% 48%	2536
	11th to 20th	Night	15% 10% 4 8% 5% 4 4 3 5% 6% 36%	2600
	21st to end	Night	17% 10% 3 9% 5% 3 4 3 4 5% 37%	2645
December	1st to 10th	Night	12% 9% 3 7% 4 4 4 3 5% 6% 43%	4580
	11th to 20th	Night	17% 16% 5% 9% 4 4 3 3 4 5% 31%	5199
	21st to end	Night	25% 19% 5% 10% 5% 4 4 3 4 5% 16%	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	60% 4 13% 16% 7% 1	3618
	11th to 20th	Day	59% 4 10% 10% 14% 4	3620
	21st to end	Day	58% 3 12% 18% 8% 1	4119
February	1st to 10th	Day	59% 6% 11% 14% 8% 2	1854
	11th to 20th	Day	52% 5% 10% 22% 9% 2	1958
	21st to end	Day	54% 6% 11% 20% 8% 2	1650
March	1st to 10th	Day	52% 6% 9% 21% 11% 2	3220
	11th to 20th	Day	40% 7% 13% 29% 11% 1	3278
	21st to end	Day	63% 9% 12% 13% 3	4165
April	1st to 10th	Day	53% 6% 10% 19% 11%	2280
	11th to 20th	Day	47% 7% 10% 21% 12% 3	2254
	21st to end	Day	50% 6% 13% 17% 12% 2	2380
May	1st to 10th	Day	45% 9% 12% 23% 11%	4120
	11th to 20th	Day	41% 7% 12% 27% 13%	4271
	21st to end	Day	35% 7% 13% 22% 19% 4	4837
June	1st to 10th	Day	35% 9% 11% 25% 18% 2	2660
	11th to 20th	Day	35% 7% 11% 24% 20% 3	2660
	21st to end	Day	41% 10% 13% 20% 13% 3	2660
July	1st to 10th	Day	45% 6% 13% 22% 12% 2	4371
	11th to 20th	Day	30% 7% 17% 29% 16% 1	4365
	21st to end	Day	38% 8% 17% 16% 18% 3	4662
August	1st to 10th	Day	34% 7% 16% 29% 13% 1	4294
	11th to 20th	Day	34% 7% 12% 31% 16% 1	3770
	21st to end	Day	31% 6% 14% 27% 19% 3	4179
September	1st to 10th	Day	34% 7% 13% 24% 18% 4	2280
	11th to 20th	Day	30% 5% 12% 28% 22% 3	2157
	21st to end	Day	37% 6% 10% 25% 20% 2	2090
October	1st to 10th	Day	26% 4 8% 30% 31% 2	3398
	11th to 20th	Day	32% 5% 12% 26% 24% 1	3119
	21st to end	Day	42% 4 9% 26% 15% 3	3081
November	1st to 10th	Day	40% 5% 13% 24% 16% 2	1762
	11th to 20th	Day	51% 5% 12% 20% 11% 1	1800
	21st to end	Day	54% 4 10% 23% 9%	1750
December	1st to 10th	Day	43% 4 16% 28% 9%	2610
	11th to 20th	Day	60% 5% 12% 17% 5% 1	3005
	21st to end	Day	79% 3 6% 7% 4	3982
January	1st to 10th	Night	58% 5% 10% 18% 10%	6348
	11th to 20th	Night	65% 4 10% 9% 12% 1	6360
	21st to end	Night	58% 3 11% 16% 10% 1	6858
February	1st to 10th	Night	56% 4 11% 17% 10% 2	2545
	11th to 20th	Night	50% 5% 9% 21% 13% 1	2339
	21st to end	Night	51% 5% 12% 19% 11% 3	1980
March	1st to 10th	Night	48% 5% 12% 23% 10% 3	3853
	11th to 20th	Night	37% 5% 11% 26% 18% 2	3739
	21st to end	Night	58% 7% 10% 18% 6% 1	3466
April	1st to 10th	Night	45% 5% 12% 23% 13% 2	1900
	11th to 20th	Night	45% 5% 10% 20% 16% 4	1875
	21st to end	Night	48% 7% 11% 19% 13% 3	1800
May	1st to 10th	Night	45% 6% 13% 21% 12% 2	2840
	11th to 20th	Night	39% 8% 17% 25% 10% 1	2631
	21st to end	Night	36% 9% 12% 18% 21% 5%	2751
June	1st to 10th	Night	33% 6% 12% 26% 19% 4	1520
	11th to 20th	Night	32% 6% 13% 24% 22% 2	1520
	21st to end	Night	38% 8% 14% 20% 16% 3	1520
July	1st to 10th	Night	42% 6% 15% 20% 12% 5%	2490
	11th to 20th	Night	27% 6% 15% 28% 22% 2	2482
	21st to end	Night	32% 7% 17% 18% 22% 4	2662
August	1st to 10th	Night	31% 8% 17% 27% 17% 1	2617
	11th to 20th	Night	29% 6% 14% 30% 20% 1	3121
	21st to end	Night	29% 6% 12% 32% 17% 3	3476
September	1st to 10th	Night	31% 5% 12% 25% 24% 3	1900
	11th to 20th	Night	27% 5% 8% 29% 27% 3	2004
	21st to end	Night	36% 6% 12% 27% 17% 3	2090
October	1st to 10th	Night	21% 4 7% 37% 29% 2	3560
	11th to 20th	Night	35% 4 7% 24% 29% 2	3800
	21st to end	Night	40% 3 9% 25% 19% 4	4467
November	1st to 10th	Night	38% 4 9% 26% 19% 3	2536
	11th to 20th	Night	48% 4 12% 21% 12% 2	2600
	21st to end	Night	50% 4 11% 23% 11%	2645
December	1st to 10th	Night	42% 4 14% 27% 11% 2	4580
	11th to 20th	Night	57% 4 12% 16% 10% 1	5201
	21st to end	Night	71% 5% 8% 10% 6%	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	22% 13% 38% 21% 6%	300
	11th to 20th	Day	23% 21% 37% 14% 4 1	300
	21st to end	Day	24% 18% 37% 17% 4	330
February	1st to 10th	Day	23% 22% 39% 14% 3	300
	11th to 20th	Day	25% 23% 32% 18% 2	300
	21st to end	Day	25% 22% 40% 11% 2	249
March	1st to 10th	Day	26% 21% 39% 13% 1	300
	11th to 20th	Day	26% 15% 36% 17% 5% 1	299
	21st to end	Day	30% 16% 29% 17% 6% 1	506
April	1st to 10th	Day	23% 18% 30% 21% 7% 1	460
	11th to 20th	Day	23% 20% 26% 19% 10% 1	452
	21st to end	Day	23% 16% 35% 18% 7% 1	460
May	1st to 10th	Day	24% 13% 32% 21% 8% 3	463
	11th to 20th	Day	19% 9% 34% 23% 11% 3	595
	21st to end	Day	14% 10% 33% 23% 14% 5%	734
June	1st to 10th	Day	11% 9% 31% 30% 15% 5%	680
	11th to 20th	Day	13% 7% 33% 28% 16% 4	680
	21st to end	Day	12% 10% 33% 28% 13% 4	680
July	1st to 10th	Day	8% 4 24% 30% 20% 14%	671
	11th to 20th	Day	12% 6% 26% 29% 17% 10%	668
	21st to end	Day	8% 4 26% 35% 20% 7%	739
August	1st to 10th	Day	8% 2 22% 33% 24% 10%	614
	11th to 20th	Day	10% 4 19% 31% 23% 12%	479
	21st to end	Day	7% 3 18% 38% 24% 10%	539
September	1st to 10th	Day	12% 6% 23% 32% 22% 5%	490
	11th to 20th	Day	10% 3 18% 32% 25% 11%	490
	21st to end	Day	15% 9% 24% 26% 20% 6%	490
October	1st to 10th	Day	16% 8% 28% 28% 16% 4	447
	11th to 20th	Day	17% 24% 32% 19% 7% 1	300
	21st to end	Day	31% 13% 35% 16% 6%	330
November	1st to 10th	Day	18% 14% 38% 20% 7% 3	300
	11th to 20th	Day	25% 16% 37% 15% 6% 1	300
	21st to end	Day	25% 10% 43% 17% 5%	300
December	1st to 10th	Day	18% 21% 38% 16% 6% 1	300
	11th to 20th	Day	22% 16% 40% 18% 4	300
	21st to end	Day	29% 20% 35% 15% 2	330
January	1st to 10th	Night	20% 15% 37% 23% 5%	1000
	11th to 20th	Night	22% 18% 34% 21% 4 1	1000
	21st to end	Night	21% 14% 35% 27% 3	1100
February	1st to 10th	Night	24% 14% 36% 23% 3	945
	11th to 20th	Night	21% 13% 36% 26% 4	783
	21st to end	Night	22% 15% 38% 21% 4	660
March	1st to 10th	Night	21% 16% 37% 21% 5%	800
	11th to 20th	Night	17% 12% 39% 26% 6% 1	753
	21st to end	Night	26% 12% 32% 23% 6%	627
April	1st to 10th	Night	19% 13% 36% 24% 7%	570
	11th to 20th	Night	21% 13% 33% 23% 8% 1	563
	21st to end	Night	22% 10% 33% 27% 7% 1	570
May	1st to 10th	Night	19% 7% 35% 30% 9%	570
	11th to 20th	Night	17% 5% 31% 34% 13%	561
	21st to end	Night	12% 6% 28% 36% 18%	617
June	1st to 10th	Night	11% 4 28% 43% 14% 1	570
	11th to 20th	Night	10% 4 29% 43% 12% 1	570
	21st to end	Night	12% 5% 27% 38% 18% 1	570
July	1st to 10th	Night	8% 3 18% 40% 26% 4	555
	11th to 20th	Night	7% 4 21% 39% 27% 3	552
	21st to end	Night	5% 1 18% 49% 25% 2	624
August	1st to 10th	Night	5% 1 13% 49% 28% 4	567
	11th to 20th	Night	8% 2 13% 40% 32% 4	564
	21st to end	Night	8% 1 18% 41% 30% 2	627
September	1st to 10th	Night	11% 4 18% 37% 28% 3	570
	11th to 20th	Night	9% 4 19% 37% 27% 4	674
	21st to end	Night	12% 7% 24% 34% 20% 3	760
October	1st to 10th	Night	13% 6% 26% 36% 18% 2	760
	11th to 20th	Night	20% 13% 30% 27% 9%	760
	21st to end	Night	25% 12% 30% 25% 8%	836
November	1st to 10th	Night	17% 12% 38% 23% 9% 1	780
	11th to 20th	Night	20% 16% 34% 24% 6%	800
	21st to end	Night	22% 13% 38% 21% 6%	845
December	1st to 10th	Night	22% 13% 37% 24% 4	1000
	11th to 20th	Night	24% 13% 35% 23% 5%	1000
	21st to end	Night	31% 14% 32% 21% 2	1100

Page generated at 2025-03-09 07:08:44. Version ac07

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