Seneca City Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Seneca City Park clear sky chart from 2005-11-06 to 2025-05-26.

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	10% 7% 3 7% 4 4 4 3 5% 7% 47%	114112
	Night	10% 7% 3 6% 4 3 4 3 5% 6% 50%	115349
Transparency	Day	36% 6% 12% 25% 18% 3	117790
	Night	34% 5% 11% 26% 20% 4	119800
Seeing	Day	13% 10% 31% 29% 14% 3	16417
	Night	13% 10% 35% 32% 10% 1	26388

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% 10% 4 11% 6% 5% 5% 3 5% 6% 33%	4077
	11th to 20th	Day	6% 9% 4 10% 6% 7% 6% 3 4 5% 40%	4080
	21st to end	Day	8% 11% 5% 12% 5% 3 4 3 3 5% 42%	4488
February	1st to 10th	Day	10% 12% 4 9% 5% 5% 4 4 4 7% 37%	1800
	11th to 20th	Day	10% 9% 3 8% 5% 4 4 3 7% 7% 40%	1814
	21st to end	Day	8% 9% 2 6% 5% 4 4 2 5% 7% 48%	1650
March	1st to 10th	Day	12% 8% 2 5% 3 3 3 2 3 5% 53%	4922
	11th to 20th	Day	9% 8% 2 5% 3 3 4 3 4 7% 52%	4980
	21st to end	Day	11% 10% 5% 9% 4 5% 4 3 5% 7% 37%	5462
April	1st to 10th	Day	13% 7% 3 6% 4 4 4 3 4 6% 47%	2247
	11th to 20th	Day	12% 8% 3 7% 5% 4 4 4 5% 7% 41%	2450
	21st to end	Day	19% 8% 2 6% 4 3 4 4 6% 7% 37%	2600
May	1st to 10th	Day	12% 9% 3 7% 5% 3 4 3 5% 7% 42%	4212
	11th to 20th	Day	15% 6% 3 6% 4 4 4 3 5% 7% 43%	4212
	21st to end	Day	14% 6% 2 5% 5% 4 4 3 6% 8% 43%	4543
June	1st to 10th	Day	6% 5% 1 5% 4 4 5% 4 6% 9% 52%	2565
	11th to 20th	Day	7% 5% 2 5% 4 4 4 4 6% 9% 49%	2660
	21st to end	Day	7% 5% 2 5% 3 5% 4 4 7% 9% 49%	2501
July	1st to 10th	Day	11% 5% 2 6% 4 4 4 4 6% 9% 44%	4120
	11th to 20th	Day	7% 4 1 5% 4 5% 5% 4 6% 9% 51%	4120
	21st to end	Day	5% 4 1 5% 3 4 4 4 6% 9% 54%	4465
August	1st to 10th	Day	7% 4 2 6% 4 4 5% 4 6% 8% 51%	4104
	11th to 20th	Day	12% 5% 2 6% 4 4 4 3 5% 7% 47%	4041
	21st to end	Day	5% 4 2 5% 4 4 4 4 6% 9% 54%	4414
September	1st to 10th	Day	10% 3 1 4 3 4 4 4 5% 6% 55%	2194
	11th to 20th	Day	8% 5% 2 6% 4 4 4 3 4 8% 51%	2090
	21st to end	Day	9% 5% 2 5% 3 3 3 3 4 5% 58%	2090
October	1st to 10th	Day	12% 5% 2 4 3 3 3 3 5% 5% 54%	1948
	11th to 20th	Day	10% 5% 2 5% 3 2 3 3 4 5% 59%	1900
	21st to end	Day	12% 7% 2 5% 3 3 3 3 3 6% 52%	2090
November	1st to 10th	Day	9% 6% 2 5% 3 3 3 3 5% 7% 55%	1830
	11th to 20th	Day	10% 10% 2 5% 3 2 3 2 4 5% 55%	1800
	21st to end	Day	12% 8% 3 5% 3 3 4 3 4 6% 49%	1630
December	1st to 10th	Day	5% 5% 2 5% 5% 4 3 3 6% 7% 56%	2610
	11th to 20th	Day	7% 8% 3 9% 4 4 3 2 4 6% 50%	3008
	21st to end	Day	16% 12% 6% 14% 4 4 4 3 4 5% 28%	4395
January	1st to 10th	Night	10% 8% 4 16% 6% 5% 4 3 5% 6% 33%	5888
	11th to 20th	Night	6% 7% 3 8% 4 4 6% 4 5% 6% 48%	5900
	21st to end	Night	12% 11% 5% 8% 4 3 3 2 3 4 44%	6490
February	1st to 10th	Night	10% 12% 3 8% 5% 4 5% 3 5% 6% 39%	2600
	11th to 20th	Night	10% 9% 3 6% 6% 4 4 4 5% 6% 43%	2491
	21st to end	Night	9% 7% 3 6% 3 4 3 4 5% 6% 49%	1980
March	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 4 5% 54%	4931
	11th to 20th	Night	8% 6% 2 4 3 3 3 3 5% 7% 57%	4980
	21st to end	Night	11% 10% 3 7% 4 4 4 4 5% 7% 40%	5467
April	1st to 10th	Night	11% 6% 2 6% 4 3 4 3 5% 7% 50%	2151
	11th to 20th	Night	11% 8% 3 6% 4 4 3 4 5% 6% 47%	1896
	21st to end	Night	17% 7% 2 6% 4 4 4 3 4 7% 43%	1800
May	1st to 10th	Night	15% 7% 2 5% 4 4 4 3 5% 6% 44%	2913
	11th to 20th	Night	16% 6% 2 5% 3 2 2 2 4 8% 49%	2913
	21st to end	Night	13% 5% 2 4 3 3 4 4 5% 7% 50%	3140
June	1st to 10th	Night	6% 4 1 4 4 4 4 3 6% 11% 54%	1606
	11th to 20th	Night	6% 4 1 4 3 3 4 5% 6% 10% 54%	1520
	21st to end	Night	5% 3 1 4 3 3 3 3 6% 9% 60%	1667
July	1st to 10th	Night	10% 6% 2 5% 4 4 4 4 6% 7% 49%	2850
	11th to 20th	Night	3 3 1 4 3 3 4 4 6% 8% 61%	2850
	21st to end	Night	5% 3 1 3 3 3 4 3 5% 9% 59%	3098
August	1st to 10th	Night	3 2 2 4 4 4 4 4 6% 9% 59%	2836
	11th to 20th	Night	11% 5% 2 5% 4 3 4 3 5% 7% 49%	2798
	21st to end	Night	5% 4 2 4 3 3 3 3 5% 8% 59%	3249
September	1st to 10th	Night	9% 4 1 4 3 2 4 3 4 7% 59%	1983
	11th to 20th	Night	8% 4 1 4 3 3 3 3 4 7% 58%	2090
	21st to end	Night	7% 4 2 4 4 3 3 3 4 5% 62%	2090
October	1st to 10th	Night	12% 5% 2 4 3 3 3 3 5% 6% 54%	2212
	11th to 20th	Night	12% 6% 1 3 2 2 3 2 3 6% 59%	2280
	21st to end	Night	11% 8% 2 4 3 3 2 2 4 5% 55%	2508
November	1st to 10th	Night	8% 5% 1 3 3 2 4 3 5% 6% 59%	2464
	11th to 20th	Night	9% 5% 2 4 3 3 3 4 5% 7% 54%	2600
	21st to end	Night	11% 8% 2 4 3 3 3 3 5% 5% 53%	2765
December	1st to 10th	Night	5% 6% 2 4 3 3 3 2 5% 5% 61%	4580
	11th to 20th	Night	8% 8% 3 8% 3 3 4 3 5% 7% 48%	5199
	21st to end	Night	17% 13% 6% 10% 4 3 3 2 3 4 34%	6564

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	50% 7% 9% 21% 12% 1	4078
	11th to 20th	Day	47% 4 10% 21% 16% 3	4080
	21st to end	Day	46% 4 11% 20% 18% 1	4488
February	1st to 10th	Day	47% 5% 15% 20% 10% 3	1800
	11th to 20th	Day	43% 6% 12% 22% 14% 3	1823
	21st to end	Day	35% 5% 11% 26% 18% 4	1650
March	1st to 10th	Day	34% 4 8% 21% 23% 9%	4922
	11th to 20th	Day	33% 4 9% 20% 27% 7%	4980
	21st to end	Day	46% 6% 17% 23% 6% 2	5464
April	1st to 10th	Day	39% 4 13% 23% 17% 3	2247
	11th to 20th	Day	41% 6% 12% 24% 16% 2	2450
	21st to end	Day	45% 7% 10% 26% 11% 1	2600
May	1st to 10th	Day	41% 8% 11% 25% 13% 3	4250
	11th to 20th	Day	40% 7% 11% 24% 18%	4216
	21st to end	Day	37% 8% 11% 28% 13% 2	4555
June	1st to 10th	Day	27% 9% 14% 32% 16% 2	2565
	11th to 20th	Day	30% 8% 14% 28% 18% 2	2660
	21st to end	Day	28% 8% 16% 28% 16% 4	2501
July	1st to 10th	Day	35% 7% 14% 25% 17% 3	4056
	11th to 20th	Day	29% 7% 12% 33% 18% 2	4051
	21st to end	Day	24% 7% 16% 30% 20% 4	4325
August	1st to 10th	Day	29% 7% 14% 26% 21% 2	4090
	11th to 20th	Day	38% 5% 16% 24% 17% 1	4080
	21st to end	Day	26% 6% 16% 28% 17% 7%	4413
September	1st to 10th	Day	29% 6% 13% 25% 21% 5%	2194
	11th to 20th	Day	32% 6% 12% 25% 23% 2	2090
	21st to end	Day	30% 4 8% 31% 26% 2	2090
October	1st to 10th	Day	19% 4 7% 18% 46% 5%	3234
	11th to 20th	Day	18% 3 8% 29% 33% 10%	3140
	21st to end	Day	30% 4 10% 26% 27% 4	3428
November	1st to 10th	Day	29% 5% 12% 29% 21% 4	1830
	11th to 20th	Day	33% 3 9% 28% 23% 3	1800
	21st to end	Day	37% 4 10% 27% 19% 2	1630
December	1st to 10th	Day	28% 4 14% 35% 18% 1	2610
	11th to 20th	Day	37% 4 14% 33% 11% 1	3005
	21st to end	Day	59% 4 9% 19% 7% 1	4395
January	1st to 10th	Night	53% 5% 10% 20% 12% 1	5888
	11th to 20th	Night	37% 4 11% 25% 20% 4	5900
	21st to end	Night	44% 4 11% 18% 17% 5%	6490
February	1st to 10th	Night	45% 5% 12% 20% 15% 4	2600
	11th to 20th	Night	40% 6% 12% 24% 15% 4	2492
	21st to end	Night	34% 5% 10% 23% 21% 8%	1980
March	1st to 10th	Night	33% 4 8% 25% 27% 4	4931
	11th to 20th	Night	28% 4 7% 23% 31% 9%	4980
	21st to end	Night	42% 7% 16% 27% 7% 2	5467
April	1st to 10th	Night	34% 5% 11% 25% 21% 4	2151
	11th to 20th	Night	37% 6% 9% 28% 17% 3	1896
	21st to end	Night	41% 7% 11% 23% 17% 1	1800
May	1st to 10th	Night	38% 7% 11% 23% 18% 2	2940
	11th to 20th	Night	35% 6% 11% 25% 22% 1	2914
	21st to end	Night	32% 8% 15% 26% 19% 1	3149
June	1st to 10th	Night	24% 8% 16% 34% 15% 3	1606
	11th to 20th	Night	24% 7% 15% 32% 17% 5%	1520
	21st to end	Night	20% 5% 15% 33% 22% 4	1667
July	1st to 10th	Night	34% 6% 13% 22% 21% 5%	2805
	11th to 20th	Night	20% 5% 14% 31% 27% 3	2796
	21st to end	Night	21% 6% 17% 33% 23% 1	2999
August	1st to 10th	Night	21% 7% 17% 26% 25% 5%	2826
	11th to 20th	Night	34% 6% 14% 26% 19% 2	2825
	21st to end	Night	24% 5% 15% 32% 17% 6%	3249
September	1st to 10th	Night	25% 6% 11% 27% 23% 8%	1983
	11th to 20th	Night	26% 6% 10% 31% 24% 4	2090
	21st to end	Night	25% 4 9% 26% 32% 4	2090
October	1st to 10th	Night	21% 4 7% 18% 45% 6%	3693
	11th to 20th	Night	19% 3 6% 32% 28% 12%	3779
	21st to end	Night	30% 3 8% 30% 27% 3	4120
November	1st to 10th	Night	26% 4 13% 27% 25% 6%	2464
	11th to 20th	Night	29% 5% 10% 28% 23% 4	2600
	21st to end	Night	33% 4 12% 27% 21% 3	2765
December	1st to 10th	Night	26% 4 13% 37% 18% 1	4580
	11th to 20th	Night	37% 3 14% 29% 16% 2	5201
	21st to end	Night	55% 3 10% 22% 8% 1	6564

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	16% 15% 38% 22% 7% 1	300
	11th to 20th	Day	18% 19% 39% 20% 3	300
	21st to end	Day	14% 11% 45% 27% 3	330
February	1st to 10th	Day	16% 23% 42% 17% 2	300
	11th to 20th	Day	16% 18% 43% 18% 5% 1	300
	21st to end	Day	11% 19% 48% 19% 3	249
March	1st to 10th	Day	15% 15% 47% 22% 2	300
	11th to 20th	Day	25% 17% 33% 19% 6% 1	300
	21st to end	Day	26% 24% 35% 13% 2 1	330
April	1st to 10th	Day	22% 15% 37% 20% 5%	347
	11th to 20th	Day	18% 17% 40% 21% 5%	568
	21st to end	Day	23% 17% 31% 19% 9% 1	700
May	1st to 10th	Day	17% 13% 37% 23% 9% 1	703
	11th to 20th	Day	18% 13% 28% 27% 11% 3	725
	21st to end	Day	19% 11% 30% 26% 12% 2	760
June	1st to 10th	Day	4 4 26% 33% 26% 6%	680
	11th to 20th	Day	8% 4 34% 34% 17% 3	680
	21st to end	Day	7% 7% 36% 35% 12% 2	680
July	1st to 10th	Day	9% 4 17% 35% 26% 9%	671
	11th to 20th	Day	5% 4 21% 42% 22% 6%	668
	21st to end	Day	7% 2 18% 40% 28% 6%	739
August	1st to 10th	Day	8% 3 18% 41% 27% 4	676
	11th to 20th	Day	9% 3 21% 42% 22% 4	665
	21st to end	Day	10% 3 18% 32% 31% 5%	682
September	1st to 10th	Day	11% 3 20% 41% 22% 3	404
	11th to 20th	Day	6% 5% 23% 40% 21% 5%	300
	21st to end	Day	14% 7% 31% 31% 15% 1	300
October	1st to 10th	Day	18% 8% 26% 27% 16% 5%	300
	11th to 20th	Day	8% 16% 42% 24% 7% 2	300
	21st to end	Day	17% 17% 38% 20% 7% 2	330
November	1st to 10th	Day	15% 14% 38% 23% 10% 1	300
	11th to 20th	Day	18% 17% 38% 21% 6%	300
	21st to end	Day	19% 12% 36% 23% 8% 1	300
December	1st to 10th	Day	8% 13% 43% 28% 6% 1	300
	11th to 20th	Day	17% 17% 34% 26% 5%	300
	21st to end	Day	22% 17% 40% 18% 3	330
January	1st to 10th	Night	11% 14% 40% 29% 7%	1000
	11th to 20th	Night	12% 14% 41% 28% 5% 1	1000
	21st to end	Night	14% 10% 44% 27% 4	1100
February	1st to 10th	Night	15% 11% 45% 25% 3	1000
	11th to 20th	Night	15% 14% 39% 27% 4	937
	21st to end	Night	15% 13% 44% 23% 4	660
March	1st to 10th	Night	13% 15% 43% 24% 5%	612
	11th to 20th	Night	17% 13% 38% 27% 5%	600
	21st to end	Night	23% 14% 40% 18% 4	660
April	1st to 10th	Night	15% 12% 46% 22% 5%	600
	11th to 20th	Night	16% 15% 39% 27% 3	593
	21st to end	Night	19% 12% 39% 25% 6% 1	600
May	1st to 10th	Night	16% 10% 33% 32% 8%	600
	11th to 20th	Night	15% 9% 30% 35% 10% 1	591
	21st to end	Night	14% 6% 30% 36% 13%	634
June	1st to 10th	Night	6% 6% 24% 43% 20% 1	570
	11th to 20th	Night	8% 3 31% 44% 15%	570
	21st to end	Night	5% 4 35% 45% 11%	570
July	1st to 10th	Night	6% 3 19% 46% 26% 1	555
	11th to 20th	Night	3 2 20% 51% 22% 2	552
	21st to end	Night	6% 2 15% 50% 26% 1	624
August	1st to 10th	Night	4 1 20% 49% 25% 2	567
	11th to 20th	Night	7% 2 16% 49% 23% 2	564
	21st to end	Night	7% 2 18% 44% 26% 3	627
September	1st to 10th	Night	11% 3 24% 42% 19% 2	570
	11th to 20th	Night	9% 2 28% 41% 18% 2	570
	21st to end	Night	8% 6% 32% 38% 15% 1	570
October	1st to 10th	Night	14% 7% 30% 34% 13% 2	692
	11th to 20th	Night	15% 9% 40% 28% 8%	760
	21st to end	Night	18% 12% 34% 29% 7%	836
November	1st to 10th	Night	10% 12% 33% 35% 10%	904
	11th to 20th	Night	12% 13% 41% 28% 6%	1000
	21st to end	Night	14% 13% 36% 29% 7%	1000
December	1st to 10th	Night	12% 14% 39% 30% 6% 1	1000
	11th to 20th	Night	16% 12% 40% 28% 5%	1000
	21st to end	Night	16% 15% 38% 26% 4	1100

Page generated at 2025-05-23 08:20:58. Version ac07

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