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 2024-01-27.

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	17% 11% 4 7% 6% 3 4 4 5% 7% 31%	74749
	Night	18% 14% 5% 8% 6% 3 4 4 4 6% 28%	75284
Transparency	Day	54% 6% 11% 18% 9% 1	74469
	Night	59% 5% 10% 16% 9% 1	75099
Seeing	Day	23% 15% 28% 22% 9% 2	13460
	Night	26% 15% 27% 22% 10% 1	23159

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	18% 21% 8% 15% 9% 3 3 4 4 4 10%	1602
	11th to 20th	Day	17% 22% 11% 15% 8% 2 4 3 3 5% 11%	1710
	21st to end	Day	16% 19% 10% 16% 10% 3 4 4 4 4 9%	1836
February	1st to 10th	Day	19% 17% 7% 15% 11% 4 4 3 3 4 12%	1620
	11th to 20th	Day	16% 17% 11% 12% 10% 4 4 4 3 3 16%	1573
	21st to end	Day	20% 15% 6% 12% 5% 3 4 5% 5% 5% 21%	1436
March	1st to 10th	Day	18% 14% 7% 9% 5% 3 3 3 5% 6% 26%	1977
	11th to 20th	Day	16% 14% 6% 7% 5% 4 4 4 4 6% 28%	1980
	21st to end	Day	22% 14% 4 7% 5% 3 4 4 3 5% 27%	2178
April	1st to 10th	Day	18% 12% 5% 6% 5% 3 4 4 5% 7% 32%	2088
	11th to 20th	Day	19% 11% 3 5% 4 3 4 4 4 6% 35%	2204
	21st to end	Day	21% 9% 3 6% 5% 3 4 4 5% 6% 34%	2340
May	1st to 10th	Day	19% 8% 4 6% 5% 3 4 5% 5% 6% 34%	2340
	11th to 20th	Day	19% 7% 2 5% 5% 3 5% 4 6% 7% 36%	2342
	21st to end	Day	12% 5% 3 5% 5% 3 5% 6% 6% 9% 42%	2725
June	1st to 10th	Day	16% 5% 2 5% 5% 3 4 4 6% 9% 41%	2520
	11th to 20th	Day	13% 5% 3 6% 5% 2 5% 5% 6% 9% 41%	2520
	21st to end	Day	14% 5% 2 4 4 2 5% 5% 6% 9% 44%	2520
July	1st to 10th	Day	10% 4 2 4 5% 2 4 5% 7% 9% 48%	2520
	11th to 20th	Day	14% 5% 3 5% 4 2 4 5% 7% 11% 41%	2391
	21st to end	Day	11% 5% 2 5% 6% 3 5% 6% 7% 9% 42%	2547
August	1st to 10th	Day	11% 4 2 5% 6% 4 4 5% 7% 9% 44%	2327
	11th to 20th	Day	12% 5% 2 5% 6% 4 5% 6% 7% 9% 39%	2303
	21st to end	Day	14% 6% 3 4 5% 4 4 5% 6% 9% 41%	2480
September	1st to 10th	Day	16% 7% 2 5% 4 3 4 4 6% 8% 39%	2160
	11th to 20th	Day	13% 4 2 5% 6% 3 5% 4 6% 8% 44%	1998
	21st to end	Day	19% 6% 3 6% 6% 4 5% 4 4 7% 36%	1974
October	1st to 10th	Day	20% 7% 2 6% 5% 4 5% 5% 4 8% 34%	1800
	11th to 20th	Day	24% 10% 3 7% 7% 3 4 4 5% 6% 27%	1800
	21st to end	Day	31% 13% 4 7% 7% 2 4 4 4 5% 20%	1980
November	1st to 10th	Day	17% 16% 4 7% 5% 3 3 4 5% 7% 29%	1720
	11th to 20th	Day	18% 22% 3 8% 6% 3 4 4 5% 6% 21%	1520
	21st to end	Day	21% 24% 5% 9% 6% 3 4 4 4 5% 14%	1520
December	1st to 10th	Day	20% 28% 12% 8% 5% 2 2 3 4 3 12%	1520
	11th to 20th	Day	19% 23% 13% 10% 5% 2 4 4 3 4 13%	1906
	21st to end	Day	25% 22% 8% 12% 7% 3 4 3 2 3 11%	2772
January	1st to 10th	Night	20% 24% 9% 15% 7% 3 3 3 2 3 11%	2559
	11th to 20th	Night	21% 21% 9% 13% 8% 3 3 2 3 3 13%	2470
	21st to end	Night	17% 21% 10% 14% 10% 3 4 3 3 3 13%	2664
February	1st to 10th	Night	20% 19% 7% 13% 9% 3 4 3 3 4 15%	2340
	11th to 20th	Night	18% 17% 7% 13% 9% 3 5% 3 4 4 17%	2273
	21st to end	Night	20% 14% 8% 12% 6% 3 3 4 4 4 22%	1818
March	1st to 10th	Night	16% 15% 7% 9% 7% 3 4 4 5% 6% 24%	1970
	11th to 20th	Night	18% 14% 5% 8% 5% 2 5% 3 5% 6% 30%	1979
	21st to end	Night	18% 15% 5% 8% 5% 3 4 4 4 4 29%	2178
April	1st to 10th	Night	18% 14% 5% 6% 4 3 4 4 4 5% 31%	1872
	11th to 20th	Night	19% 10% 3 6% 5% 3 4 4 5% 7% 34%	1720
	21st to end	Night	16% 10% 3 6% 5% 3 5% 5% 5% 7% 33%	1620
May	1st to 10th	Night	21% 8% 3 6% 6% 3 4 5% 5% 7% 34%	1620
	11th to 20th	Night	16% 8% 3 6% 7% 3 4 4 5% 7% 36%	1549
	21st to end	Night	13% 4 3 4 3 2 4 5% 6% 10% 45%	1550
June	1st to 10th	Night	11% 7% 2 5% 6% 3 5% 5% 6% 9% 40%	1440
	11th to 20th	Night	12% 6% 3 6% 5% 3 4 5% 4 7% 43%	1440
	21st to end	Night	13% 5% 2 5% 6% 3 5% 5% 6% 8% 40%	1440
July	1st to 10th	Night	9% 5% 2 5% 5% 3 5% 4 5% 8% 49%	1440
	11th to 20th	Night	12% 4 2 5% 4 4 5% 4 6% 10% 44%	1565
	21st to end	Night	10% 5% 2 5% 5% 3 6% 6% 6% 8% 44%	1771
August	1st to 10th	Night	10% 5% 2 5% 5% 3 5% 4 7% 9% 45%	1611
	11th to 20th	Night	11% 6% 2 5% 6% 3 6% 5% 7% 8% 42%	1598
	21st to end	Night	14% 5% 2 5% 6% 3 4 6% 6% 8% 42%	1856
September	1st to 10th	Night	15% 7% 3 4 4 3 4 5% 5% 7% 44%	1800
	11th to 20th	Night	15% 5% 2 5% 4 2 4 4 5% 7% 47%	1957
	21st to end	Night	17% 7% 3 6% 5% 3 5% 5% 5% 7% 36%	1984
October	1st to 10th	Night	21% 9% 3 5% 5% 3 3 4 5% 6% 37%	2160
	11th to 20th	Night	26% 9% 3 6% 6% 3 5% 4 5% 6% 27%	2160
	21st to end	Night	32% 11% 3 6% 5% 3 4 3 3 5% 24%	2376
November	1st to 10th	Night	20% 14% 4 6% 5% 3 4 3 5% 6% 31%	2352
	11th to 20th	Night	20% 21% 4 7% 6% 3 4 4 5% 5% 21%	2660
	21st to end	Night	22% 24% 7% 6% 4 3 3 4 4 4 19%	2660
December	1st to 10th	Night	23% 29% 11% 7% 5% 2 2 3 3 3 12%	2660
	11th to 20th	Night	18% 26% 11% 10% 5% 2 4 3 3 4 13%	3288
	21st to end	Night	25% 24% 7% 10% 7% 3 4 4 4 4 8%	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	79% 4 8% 8% 2	1603
	11th to 20th	Day	80% 4 8% 6% 1	1710
	21st to end	Day	81% 4 6% 6% 3	1836
February	1st to 10th	Day	79% 4 8% 7% 3	1620
	11th to 20th	Day	75% 5% 5% 10% 5%	1582
	21st to end	Day	66% 6% 9% 13% 4 2	1436
March	1st to 10th	Day	59% 6% 12% 17% 5%	1980
	11th to 20th	Day	58% 6% 9% 17% 9% 2	1980
	21st to end	Day	62% 5% 5% 18% 9% 2	2178
April	1st to 10th	Day	54% 5% 12% 18% 11%	2088
	11th to 20th	Day	51% 5% 10% 20% 12% 2	2204
	21st to end	Day	52% 5% 10% 18% 12% 2	2340
May	1st to 10th	Day	51% 5% 9% 22% 10% 2	2340
	11th to 20th	Day	48% 6% 11% 20% 13% 2	2346
	21st to end	Day	39% 7% 15% 24% 14% 1	2725
June	1st to 10th	Day	42% 6% 13% 24% 14% 1	2520
	11th to 20th	Day	40% 7% 15% 24% 13% 1	2520
	21st to end	Day	37% 8% 13% 26% 15% 1	2520
July	1st to 10th	Day	33% 7% 13% 28% 17% 2	2450
	11th to 20th	Day	37% 8% 13% 26% 14% 1	2319
	21st to end	Day	38% 9% 14% 24% 14% 1	2405
August	1st to 10th	Day	36% 8% 16% 29% 11% 1	2314
	11th to 20th	Day	39% 9% 15% 27% 8% 1	2303
	21st to end	Day	39% 7% 13% 25% 14% 1	2480
September	1st to 10th	Day	43% 7% 15% 22% 12% 1	2160
	11th to 20th	Day	39% 7% 13% 26% 14%	1998
	21st to end	Day	48% 7% 11% 23% 10% 1	1974
October	1st to 10th	Day	50% 7% 14% 17% 11% 1	1800
	11th to 20th	Day	58% 6% 14% 15% 6% 1	1800
	21st to end	Day	68% 5% 10% 12% 5% 1	1980
November	1st to 10th	Day	55% 7% 10% 17% 10% 2	1720
	11th to 20th	Day	65% 5% 10% 13% 6% 2	1520
	21st to end	Day	73% 4 8% 9% 5%	1520
December	1st to 10th	Day	79% 3 8% 8% 1	1520
	11th to 20th	Day	77% 4 9% 9% 1	1906
	21st to end	Day	82% 3 8% 6%	2772
January	1st to 10th	Night	81% 4 6% 6% 3	2559
	11th to 20th	Night	79% 3 8% 7% 2	2470
	21st to end	Night	79% 4 6% 7% 3	2664
February	1st to 10th	Night	76% 4 9% 9% 3	2340
	11th to 20th	Night	73% 4 7% 11% 4	2275
	21st to end	Night	67% 5% 9% 11% 7% 1	1818
March	1st to 10th	Night	62% 6% 8% 17% 7% 1	1980
	11th to 20th	Night	58% 5% 9% 18% 9% 2	1980
	21st to end	Night	59% 5% 5% 16% 13% 3	2178
April	1st to 10th	Night	55% 6% 10% 18% 11% 1	1872
	11th to 20th	Night	51% 5% 11% 18% 13% 3	1720
	21st to end	Night	50% 6% 9% 20% 10% 4	1620
May	1st to 10th	Night	51% 5% 9% 21% 11% 3	1620
	11th to 20th	Night	47% 6% 11% 19% 13% 3	1550
	21st to end	Night	35% 7% 14% 28% 14% 2	1551
June	1st to 10th	Night	41% 8% 10% 24% 15% 2	1440
	11th to 20th	Night	41% 6% 11% 24% 16% 2	1440
	21st to end	Night	41% 8% 12% 24% 15% 1	1440
July	1st to 10th	Night	35% 7% 12% 24% 19% 4	1400
	11th to 20th	Night	35% 6% 14% 26% 17% 3	1515
	21st to end	Night	36% 9% 15% 24% 16% 2	1672
August	1st to 10th	Night	35% 6% 14% 31% 13% 2	1600
	11th to 20th	Night	38% 9% 16% 27% 10% 1	1598
	21st to end	Night	40% 6% 15% 23% 14% 3	1856
September	1st to 10th	Night	40% 6% 13% 25% 14% 2	1800
	11th to 20th	Night	37% 6% 14% 25% 17% 1	1957
	21st to end	Night	48% 6% 11% 20% 14% 1	1984
October	1st to 10th	Night	47% 6% 11% 21% 14% 1	2160
	11th to 20th	Night	57% 6% 12% 15% 10% 1	2160
	21st to end	Night	65% 4 9% 14% 7% 2	2376
November	1st to 10th	Night	55% 5% 11% 18% 9% 2	2352
	11th to 20th	Night	65% 5% 9% 13% 5% 2	2660
	21st to end	Night	70% 4 10% 12% 4 1	2660
December	1st to 10th	Night	80% 3 9% 6% 2	2660
	11th to 20th	Night	77% 4 10% 7% 1	3288
	21st to end	Night	81% 5% 8% 6% 1	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	29% 28% 30% 9% 4	220
	11th to 20th	Day	33% 31% 26% 7% 2	270
	21st to end	Day	28% 33% 28% 10% 1 1	282
February	1st to 10th	Day	33% 24% 38% 5%	240
	11th to 20th	Day	34% 27% 33% 6%	240
	21st to end	Day	33% 27% 31% 9%	206
March	1st to 10th	Day	27% 25% 33% 10% 4	420
	11th to 20th	Day	26% 22% 36% 13% 2 1	420
	21st to end	Day	34% 16% 29% 17% 3 1	462
April	1st to 10th	Day	22% 24% 33% 16% 4 1	420
	11th to 20th	Day	29% 16% 29% 16% 8% 2	412
	21st to end	Day	26% 15% 34% 18% 5% 1	420
May	1st to 10th	Day	29% 14% 30% 20% 5% 1	423
	11th to 20th	Day	24% 12% 26% 29% 8% 2	447
	21st to end	Day	15% 8% 29% 30% 14% 4	485
June	1st to 10th	Day	18% 12% 30% 31% 8% 2	450
	11th to 20th	Day	16% 11% 26% 30% 15% 2	450
	21st to end	Day	16% 9% 31% 31% 10% 2	450
July	1st to 10th	Day	11% 6% 23% 35% 21% 4	445
	11th to 20th	Day	16% 7% 25% 29% 17% 5%	444
	21st to end	Day	11% 7% 31% 32% 16% 4	488
August	1st to 10th	Day	10% 7% 25% 32% 19% 7%	446
	11th to 20th	Day	15% 6% 19% 35% 19% 6%	439
	21st to end	Day	15% 6% 26% 30% 18% 5%	495
September	1st to 10th	Day	17% 11% 22% 27% 18% 5%	450
	11th to 20th	Day	13% 6% 24% 29% 22% 7%	450
	21st to end	Day	20% 12% 28% 22% 12% 5%	450
October	1st to 10th	Day	22% 14% 22% 22% 15% 4	450
	11th to 20th	Day	30% 18% 30% 17% 5% 1	450
	21st to end	Day	39% 17% 28% 15% 2	495
November	1st to 10th	Day	29% 21% 27% 17% 4 2	323
	11th to 20th	Day	36% 22% 28% 9% 4	180
	21st to end	Day	34% 22% 34% 10%	180
December	1st to 10th	Day	39% 27% 22% 8% 2 1	180
	11th to 20th	Day	32% 30% 27% 11%	180
	21st to end	Day	37% 23% 28% 10% 1	198
January	1st to 10th	Night	33% 27% 28% 10% 4	760
	11th to 20th	Night	32% 22% 31% 14% 1	760
	21st to end	Night	25% 24% 32% 15% 3	820
February	1st to 10th	Night	32% 24% 29% 14% 2	720
	11th to 20th	Night	26% 25% 32% 14% 3	703
	21st to end	Night	30% 23% 31% 15% 1	592
March	1st to 10th	Night	26% 18% 32% 19% 5%	720
	11th to 20th	Night	27% 18% 31% 18% 5%	720
	21st to end	Night	27% 14% 28% 23% 7% 1	792
April	1st to 10th	Night	24% 15% 33% 23% 6%	720
	11th to 20th	Night	26% 11% 32% 22% 7% 1	656
	21st to end	Night	23% 10% 32% 27% 7% 1	540
May	1st to 10th	Night	26% 9% 22% 32% 11% 1	540
	11th to 20th	Night	19% 7% 29% 35% 9% 1	488
	21st to end	Night	15% 6% 25% 33% 18% 4	389
June	1st to 10th	Night	15% 4 31% 34% 16% 1	360
	11th to 20th	Night	14% 6% 28% 35% 17% 1	360
	21st to end	Night	16% 5% 25% 37% 16% 1	360
July	1st to 10th	Night	10% 5% 19% 38% 23% 5%	350
	11th to 20th	Night	13% 5% 22% 31% 26% 3	471
	21st to end	Night	13% 5% 19% 40% 23% 1	591
August	1st to 10th	Night	13% 3 20% 37% 23% 4	537
	11th to 20th	Night	14% 3 16% 35% 27% 4	534
	21st to end	Night	16% 5% 19% 30% 24% 5%	668
September	1st to 10th	Night	19% 7% 17% 32% 20% 5%	720
	11th to 20th	Night	16% 7% 18% 31% 23% 5%	720
	21st to end	Night	21% 10% 22% 27% 15% 4	720
October	1st to 10th	Night	23% 9% 24% 24% 17% 2	720
	11th to 20th	Night	33% 15% 26% 20% 7% 1	720
	21st to end	Night	39% 16% 27% 16% 2	792
November	1st to 10th	Night	31% 14% 27% 21% 6%	740
	11th to 20th	Night	34% 20% 29% 12% 4 1	760
	21st to end	Night	37% 20% 29% 10% 4	760
December	1st to 10th	Night	41% 22% 26% 7% 4	760
	11th to 20th	Night	35% 27% 25% 12% 2	760
	21st to end	Night	34% 24% 30% 10% 1	836

Page generated at 2024-01-24 09:37:31. Version ac07

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