Erie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Erie clear sky chart from 2005-11-06 to 2025-02-06.

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% 4 9% 5% 4 4 3 5% 6% 30%	108583
	Night	17% 16% 5% 10% 5% 4 4 3 4 5% 26%	109638
Transparency	Day	54% 6% 12% 19% 9% 1	112226
	Night	59% 6% 10% 16% 8% 1	114159
Seeing	Day	23% 16% 28% 21% 9% 2	14780
	Night	26% 15% 26% 22% 10% 1	24471

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	15% 25% 10% 27% 5% 3 2 2 2 2 7%	3804
	11th to 20th	Day	12% 24% 10% 21% 7% 5% 4 2 3 4 9%	4026
	21st to end	Day	19% 18% 9% 17% 7% 5% 4 3 4 3 10%	4466
February	1st to 10th	Day	18% 19% 5% 16% 10% 4 4 2 3 4 14%	1755
	11th to 20th	Day	15% 18% 10% 15% 7% 5% 4 3 3 3 16%	1663
	21st to end	Day	20% 16% 5% 12% 5% 4 4 4 4 5% 22%	1524
March	1st to 10th	Day	19% 15% 5% 8% 4 4 3 3 4 6% 28%	3432
	11th to 20th	Day	12% 20% 5% 9% 4 4 4 3 4 6% 29%	3480
	21st to end	Day	20% 14% 5% 10% 4 4 4 3 4 5% 27%	3815
April	1st to 10th	Day	18% 13% 3 7% 4 4 4 3 5% 7% 32%	2204
	11th to 20th	Day	19% 12% 3 6% 4 4 4 4 4 6% 34%	2328
	21st to end	Day	21% 9% 3 7% 5% 4 4 3 5% 5% 34%	2470
May	1st to 10th	Day	19% 9% 3 7% 5% 4 4 4 5% 7% 32%	4108
	11th to 20th	Day	19% 9% 3 7% 4 4 4 3 5% 7% 35%	4164
	21st to end	Day	12% 5% 2 6% 4 4 5% 4 6% 7% 44%	4837
June	1st to 10th	Day	16% 6% 2 6% 4 4 4 3 6% 9% 40%	2660
	11th to 20th	Day	12% 5% 3 6% 4 4 5% 4 7% 9% 41%	2660
	21st to end	Day	15% 5% 2 5% 4 4 4 4 7% 9% 42%	2660
July	1st to 10th	Day	9% 4 2 6% 4 4 4 4 7% 10% 45%	4440
	11th to 20th	Day	13% 6% 2 5% 4 3 4 3 6% 9% 45%	4199
	21st to end	Day	10% 5% 2 6% 4 4 5% 4 6% 8% 45%	4466
August	1st to 10th	Day	15% 5% 2 7% 5% 5% 5% 4 6% 8% 38%	4104
	11th to 20th	Day	14% 6% 2 7% 5% 5% 5% 5% 7% 10% 34%	4044
	21st to end	Day	12% 5% 2 5% 4 5% 4 4 6% 9% 42%	4354
September	1st to 10th	Day	16% 8% 2 6% 3 4 4 3 6% 8% 41%	2280
	11th to 20th	Day	12% 5% 2 6% 5% 4 4 3 6% 8% 45%	2109
	21st to end	Day	19% 7% 3 8% 5% 4 5% 3 4 7% 34%	2083
October	1st to 10th	Day	19% 8% 2 7% 4 5% 5% 4 5% 8% 34%	1900
	11th to 20th	Day	23% 10% 3 7% 5% 4 4 3 5% 6% 29%	1900
	21st to end	Day	28% 13% 4 8% 5% 4 3 3 4 6% 21%	2090
November	1st to 10th	Day	17% 16% 4 8% 4 4 3 3 5% 7% 29%	1812
	11th to 20th	Day	17% 23% 3 8% 5% 4 5% 3 5% 6% 21%	1600
	21st to end	Day	22% 26% 5% 10% 5% 4 4 3 4 5% 13%	1600
December	1st to 10th	Day	19% 32% 11% 12% 5% 4 3 2 3 2 8%	2600
	11th to 20th	Day	22% 25% 9% 13% 4 3 4 3 3 3 11%	2986
	21st to end	Day	23% 24% 7% 15% 5% 4 4 3 2 3 10%	3960
January	1st to 10th	Night	15% 25% 12% 26% 4 3 2 2 2 3 7%	6137
	11th to 20th	Night	11% 23% 12% 20% 8% 6% 4 3 4 3 7%	5859
	21st to end	Night	21% 20% 8% 16% 5% 3 3 2 3 4 13%	6490
February	1st to 10th	Night	19% 21% 6% 14% 7% 4 3 2 3 4 17%	2536
	11th to 20th	Night	16% 19% 6% 16% 7% 4 4 2 4 4 18%	2403
	21st to end	Night	20% 16% 6% 14% 5% 4 3 3 4 4 22%	1928
March	1st to 10th	Night	22% 16% 4 8% 4 3 3 2 4 5% 30%	3408
	11th to 20th	Night	17% 20% 6% 8% 3 3 3 2 4 5% 29%	3479
	21st to end	Night	16% 14% 5% 10% 4 4 3 3 4 4 34%	3817
April	1st to 10th	Night	18% 16% 5% 7% 4 3 4 3 4 5% 30%	1976
	11th to 20th	Night	20% 11% 3 7% 4 4 3 3 6% 6% 33%	1816
	21st to end	Night	16% 11% 3 6% 5% 5% 5% 4 5% 7% 33%	1710
May	1st to 10th	Night	25% 9% 3 6% 4 4 3 3 5% 7% 32%	2833
	11th to 20th	Night	16% 8% 2 7% 5% 5% 4 3 6% 8% 35%	2727
	21st to end	Night	13% 5% 2 5% 3 3 4 4 6% 10% 45%	2738
June	1st to 10th	Night	12% 7% 3 6% 5% 5% 5% 4 7% 8% 39%	1520
	11th to 20th	Night	11% 7% 3 7% 5% 4 4 4 5% 7% 42%	1520
	21st to end	Night	14% 6% 2 6% 5% 4 5% 4 7% 8% 39%	1520
July	1st to 10th	Night	11% 7% 2 6% 5% 4 4 3 6% 9% 43%	2520
	11th to 20th	Night	11% 5% 2 6% 4 5% 5% 4 6% 9% 43%	2743
	21st to end	Night	8% 5% 2 7% 5% 5% 5% 5% 6% 8% 45%	3087
August	1st to 10th	Night	11% 7% 3 8% 5% 5% 5% 4 7% 8% 39%	2825
	11th to 20th	Night	17% 8% 3 7% 5% 4 5% 3 5% 6% 36%	2785
	21st to end	Night	10% 6% 2 6% 5% 4 5% 4 6% 9% 42%	3268
September	1st to 10th	Night	15% 7% 3 5% 3 3 4 4 5% 7% 45%	1900
	11th to 20th	Night	14% 5% 2 6% 4 3 4 3 5% 7% 48%	2066
	21st to end	Night	18% 8% 3 8% 5% 5% 5% 4 6% 6% 34%	2095
October	1st to 10th	Night	20% 9% 2 6% 4 3 4 3 5% 6% 38%	2280
	11th to 20th	Night	25% 9% 3 7% 5% 4 4 3 5% 5% 28%	2280
	21st to end	Night	30% 11% 3 7% 3 3 4 3 4 5% 26%	2508
November	1st to 10th	Night	20% 15% 4 7% 4 4 3 3 5% 6% 31%	2480
	11th to 20th	Night	20% 22% 3 8% 5% 4 4 3 5% 5% 21%	2800
	21st to end	Night	22% 26% 6% 7% 4 3 3 3 4 4 18%	2800
December	1st to 10th	Night	17% 32% 10% 10% 5% 3 4 3 3 3 10%	4580
	11th to 20th	Night	19% 29% 9% 12% 4 3 3 2 4 4 12%	5208
	21st to end	Night	22% 23% 6% 12% 6% 4 4 3 4 5% 12%	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	86% 4 6% 4 1	3805
	11th to 20th	Day	81% 4 9% 5% 1	4060
	21st to end	Day	78% 5% 7% 8% 3	4466
February	1st to 10th	Day	76% 4 8% 8% 3	1755
	11th to 20th	Day	74% 5% 5% 11% 5%	1672
	21st to end	Day	65% 6% 10% 14% 4 2	1524
March	1st to 10th	Day	55% 7% 11% 22% 5%	3435
	11th to 20th	Day	56% 7% 16% 15% 5% 1	3480
	21st to end	Day	58% 7% 7% 19% 9% 1	3815
April	1st to 10th	Day	54% 6% 12% 18% 11%	2204
	11th to 20th	Day	51% 6% 10% 20% 11% 2	2328
	21st to end	Day	52% 5% 10% 18% 12% 2	2470
May	1st to 10th	Day	51% 5% 10% 23% 9% 2	4120
	11th to 20th	Day	50% 5% 16% 20% 8% 1	4168
	21st to end	Day	38% 7% 14% 22% 16% 4	4837
June	1st to 10th	Day	42% 6% 13% 24% 13% 1	2660
	11th to 20th	Day	40% 7% 14% 24% 13% 1	2660
	21st to end	Day	38% 8% 13% 26% 15% 1	2660
July	1st to 10th	Day	34% 8% 14% 26% 17% 2	4370
	11th to 20th	Day	35% 8% 13% 27% 17% 1	4127
	21st to end	Day	36% 9% 14% 25% 16% 1	4324
August	1st to 10th	Day	42% 9% 15% 23% 11%	4091
	11th to 20th	Day	42% 9% 17% 25% 7% 1	4083
	21st to end	Day	36% 8% 13% 30% 13% 1	4354
September	1st to 10th	Day	42% 7% 14% 23% 13% 1	2280
	11th to 20th	Day	38% 7% 13% 26% 15%	2109
	21st to end	Day	50% 7% 11% 22% 9% 1	2083
October	1st to 10th	Day	40% 7% 15% 22% 14% 1	3160
	11th to 20th	Day	49% 5% 13% 19% 11% 2	3140
	21st to end	Day	49% 6% 15% 23% 7%	3428
November	1st to 10th	Day	54% 7% 10% 17% 10% 2	1812
	11th to 20th	Day	64% 5% 9% 13% 7% 2	1600
	21st to end	Day	74% 4 8% 8% 4	1600
December	1st to 10th	Day	84% 4 6% 5% 1	2600
	11th to 20th	Day	78% 5% 7% 9% 1	2986
	21st to end	Day	80% 5% 8% 6% 1	3960
January	1st to 10th	Night	86% 3 5% 5% 1	6137
	11th to 20th	Night	82% 3 8% 4 1	5900
	21st to end	Night	76% 3 8% 8% 4	6490
February	1st to 10th	Night	74% 4 9% 10% 3	2536
	11th to 20th	Night	72% 5% 7% 12% 4	2405
	21st to end	Night	67% 5% 9% 12% 7% 1	1928
March	1st to 10th	Night	58% 5% 11% 20% 6%	3418
	11th to 20th	Night	58% 7% 11% 16% 7% 1	3480
	21st to end	Night	51% 7% 9% 18% 12% 2	3817
April	1st to 10th	Night	56% 6% 9% 17% 11% 1	1976
	11th to 20th	Night	52% 5% 11% 18% 12% 2	1816
	21st to end	Night	50% 6% 10% 20% 11% 3	1710
May	1st to 10th	Night	52% 6% 9% 19% 10% 4	2840
	11th to 20th	Night	47% 5% 15% 22% 9% 2	2728
	21st to end	Night	33% 8% 13% 27% 16% 3	2739
June	1st to 10th	Night	41% 8% 10% 24% 15% 3	1520
	11th to 20th	Night	41% 6% 12% 23% 17% 2	1520
	21st to end	Night	41% 8% 12% 23% 15% 1	1520
July	1st to 10th	Night	39% 6% 12% 21% 17% 4	2480
	11th to 20th	Night	35% 7% 14% 25% 16% 3	2693
	21st to end	Night	36% 9% 14% 21% 19% 1	2988
August	1st to 10th	Night	41% 7% 12% 28% 11% 1	2814
	11th to 20th	Night	47% 8% 13% 23% 9% 1	2812
	21st to end	Night	35% 8% 16% 28% 12% 1	3268
September	1st to 10th	Night	39% 6% 12% 25% 15% 2	1900
	11th to 20th	Night	36% 6% 13% 25% 19% 1	2066
	21st to end	Night	50% 6% 11% 19% 13% 1	2095
October	1st to 10th	Night	40% 8% 10% 22% 19% 1	3800
	11th to 20th	Night	51% 5% 11% 16% 14% 2	3779
	21st to end	Night	46% 4 14% 22% 13% 1	4120
November	1st to 10th	Night	54% 5% 11% 19% 9% 2	2480
	11th to 20th	Night	66% 5% 9% 12% 6% 3	2800
	21st to end	Night	71% 4 10% 12% 3 1	2800
December	1st to 10th	Night	81% 5% 9% 4 1	4580
	11th to 20th	Night	77% 5% 9% 8% 1	5208
	21st to end	Night	75% 6% 9% 9% 1	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	31% 29% 29% 8% 3	245
	11th to 20th	Day	34% 33% 25% 7% 2	300
	21st to end	Day	28% 32% 30% 10% 1 1	330
February	1st to 10th	Day	32% 25% 35% 8%	285
	11th to 20th	Day	33% 25% 34% 7%	270
	21st to end	Day	35% 25% 32% 8%	234
March	1st to 10th	Day	27% 24% 34% 10% 4	460
	11th to 20th	Day	27% 23% 36% 12% 2 1	460
	21st to end	Day	34% 19% 27% 16% 3 1	506
April	1st to 10th	Day	23% 23% 34% 16% 3 1	460
	11th to 20th	Day	31% 17% 29% 15% 7% 2	452
	21st to end	Day	26% 16% 35% 18% 5% 1	460
May	1st to 10th	Day	29% 14% 31% 20% 5% 2	463
	11th to 20th	Day	24% 11% 26% 28% 8% 2	487
	21st to end	Day	16% 8% 30% 30% 13% 3	529
June	1st to 10th	Day	18% 14% 29% 30% 8% 2	490
	11th to 20th	Day	15% 11% 26% 32% 14% 2	490
	21st to end	Day	17% 9% 32% 30% 10% 2	490
July	1st to 10th	Day	11% 7% 25% 34% 19% 4	485
	11th to 20th	Day	16% 8% 27% 28% 16% 5%	484
	21st to end	Day	11% 6% 30% 33% 16% 4	532
August	1st to 10th	Day	11% 9% 25% 31% 18% 6%	486
	11th to 20th	Day	15% 8% 20% 34% 18% 6%	479
	21st to end	Day	15% 6% 26% 31% 18% 4	539
September	1st to 10th	Day	17% 11% 22% 26% 19% 4	490
	11th to 20th	Day	12% 5% 24% 29% 22% 7%	490
	21st to end	Day	21% 12% 29% 21% 12% 4	490
October	1st to 10th	Day	22% 14% 24% 22% 14% 3	490
	11th to 20th	Day	29% 18% 29% 17% 7% 1	490
	21st to end	Day	37% 18% 28% 15% 2	539
November	1st to 10th	Day	30% 20% 28% 16% 4 1	355
	11th to 20th	Day	36% 22% 30% 9% 4	200
	21st to end	Day	36% 23% 33% 9%	200
December	1st to 10th	Day	39% 27% 24% 8% 2 1	200
	11th to 20th	Day	35% 28% 28% 10%	200
	21st to end	Day	36% 25% 27% 11% 1	220
January	1st to 10th	Night	32% 28% 27% 9% 3	800
	11th to 20th	Night	32% 23% 31% 13% 1	800
	21st to end	Night	26% 24% 31% 15% 3	880
February	1st to 10th	Night	31% 23% 28% 15% 2	781
	11th to 20th	Night	26% 26% 31% 14% 3	743
	21st to end	Night	29% 24% 31% 15% 1	628
March	1st to 10th	Night	26% 18% 32% 19% 5%	760
	11th to 20th	Night	27% 19% 31% 18% 5%	760
	21st to end	Night	27% 15% 28% 23% 6% 1	836
April	1st to 10th	Night	24% 16% 32% 22% 5%	760
	11th to 20th	Night	26% 11% 32% 22% 7% 1	692
	21st to end	Night	23% 11% 32% 27% 7% 1	570
May	1st to 10th	Night	25% 9% 22% 32% 11% 1	570
	11th to 20th	Night	19% 6% 29% 35% 10% 1	515
	21st to end	Night	15% 6% 25% 34% 18% 3	411
June	1st to 10th	Night	16% 5% 31% 33% 16% 1	380
	11th to 20th	Night	14% 6% 27% 35% 17% 1	380
	21st to end	Night	16% 6% 25% 37% 15% 1	380
July	1st to 10th	Night	11% 5% 19% 38% 22% 5%	370
	11th to 20th	Night	13% 5% 22% 32% 25% 3	498
	21st to end	Night	12% 5% 18% 41% 22% 1	624
August	1st to 10th	Night	13% 4 21% 37% 23% 3	567
	11th to 20th	Night	14% 4 17% 35% 26% 4	564
	21st to end	Night	16% 5% 19% 31% 24% 4	706
September	1st to 10th	Night	19% 7% 18% 31% 20% 5%	760
	11th to 20th	Night	15% 6% 17% 32% 25% 5%	760
	21st to end	Night	22% 10% 22% 27% 14% 4	760
October	1st to 10th	Night	23% 9% 24% 25% 17% 2	760
	11th to 20th	Night	32% 15% 25% 20% 7% 1	760
	21st to end	Night	37% 16% 27% 17% 2	836
November	1st to 10th	Night	31% 15% 27% 21% 6%	780
	11th to 20th	Night	35% 20% 29% 11% 4 1	800
	21st to end	Night	38% 21% 28% 10% 4	800
December	1st to 10th	Night	41% 23% 26% 7% 3	800
	11th to 20th	Night	36% 26% 25% 12% 2	800
	21st to end	Night	34% 23% 30% 11% 1	880

Page generated at 2025-02-03 03:05:51. Version ac07

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