Harrisburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Harrisburg clear sky chart from 2005-11-06 to 2024-01-22.

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	12% 7% 3 5% 5% 3 5% 5% 5% 7% 42%	74877
	Night	13% 7% 3 5% 5% 3 4 4 5% 7% 44%	75073
Transparency	Day	41% 6% 11% 24% 15% 3	74580
	Night	40% 5% 10% 24% 17% 4	74891
Seeing	Day	16% 12% 25% 25% 16% 6%	14373
	Night	17% 10% 27% 28% 15% 2	24313

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	16% 9% 5% 9% 6% 2 4 5% 5% 4 36%	1517
	11th to 20th	Day	19% 9% 4 7% 5% 3 5% 5% 4 6% 32%	1548
	21st to end	Day	12% 11% 4 9% 5% 3 4 4 5% 6% 37%	1791
February	1st to 10th	Day	15% 11% 5% 7% 5% 3 5% 4 4 5% 37%	1764
	11th to 20th	Day	16% 9% 4 7% 6% 3 4 5% 5% 6% 35%	1748
	21st to end	Day	15% 11% 3 8% 5% 3 5% 5% 5% 6% 35%	1480
March	1st to 10th	Day	15% 8% 3 6% 6% 3 4 5% 5% 5% 41%	1800
	11th to 20th	Day	19% 11% 3 6% 7% 3 3 4 4 6% 33%	1870
	21st to end	Day	18% 9% 3 7% 6% 3 5% 5% 5% 7% 32%	2376
April	1st to 10th	Day	10% 5% 2 5% 6% 3 4 4 6% 8% 46%	2160
	11th to 20th	Day	13% 8% 4 6% 5% 3 5% 4 5% 6% 41%	2134
	21st to end	Day	17% 7% 3 5% 5% 3 4 4 5% 6% 40%	2160
May	1st to 10th	Day	17% 5% 3 6% 6% 4 5% 6% 6% 8% 36%	2307
	11th to 20th	Day	16% 7% 2 5% 5% 3 4 5% 6% 7% 40%	2301
	21st to end	Day	8% 6% 3 6% 7% 5% 6% 8% 8% 8% 36%	2672
June	1st to 10th	Day	8% 4 3 5% 5% 3 5% 5% 6% 10% 45%	2520
	11th to 20th	Day	6% 3 2 4 5% 3 6% 6% 7% 10% 49%	2520
	21st to end	Day	6% 3 2 4 6% 4 5% 5% 7% 11% 47%	2520
July	1st to 10th	Day	10% 4 2 4 6% 3 6% 6% 7% 12% 39%	2520
	11th to 20th	Day	5% 3 2 4 5% 4 6% 6% 7% 10% 48%	2520
	21st to end	Day	7% 4 2 5% 5% 4 6% 7% 7% 9% 44%	2730
August	1st to 10th	Day	6% 5% 2 4 6% 3 6% 6% 6% 11% 45%	2162
	11th to 20th	Day	9% 4 2 5% 6% 3 6% 6% 6% 9% 44%	2125
	21st to end	Day	7% 4 2 4 4 3 5% 7% 7% 8% 48%	2376
September	1st to 10th	Day	11% 6% 2 6% 5% 3 5% 5% 5% 7% 46%	2160
	11th to 20th	Day	9% 5% 3 4 5% 3 5% 4 5% 7% 50%	2048
	21st to end	Day	10% 4 3 4 4 2 3 4 4 8% 54%	1980
October	1st to 10th	Day	10% 4 2 4 4 3 3 3 5% 6% 56%	1954
	11th to 20th	Day	12% 5% 3 4 5% 3 4 4 4 7% 50%	1800
	21st to end	Day	18% 7% 3 4 4 2 4 3 4 6% 45%	1868
November	1st to 10th	Day	8% 4 3 5% 3 3 4 5% 4 7% 54%	1672
	11th to 20th	Day	14% 6% 2 5% 5% 3 4 3 5% 5% 47%	1710
	21st to end	Day	18% 9% 3 6% 4 2 3 3 5% 6% 43%	1710
December	1st to 10th	Day	15% 10% 3 5% 6% 3 4 4 5% 7% 38%	1653
	11th to 20th	Day	13% 10% 4 7% 6% 4 5% 5% 5% 6% 35%	1918
	21st to end	Day	19% 15% 4 7% 6% 3 5% 3 4 5% 28%	2783
January	1st to 10th	Night	15% 9% 4 7% 6% 3 4 4 4 6% 38%	2648
	11th to 20th	Night	17% 11% 5% 7% 5% 3 5% 4 4 6% 33%	2629
	21st to end	Night	15% 8% 4 7% 6% 3 4 5% 5% 6% 37%	2600
February	1st to 10th	Night	20% 11% 6% 7% 6% 2 4 3 4 4 33%	2194
	11th to 20th	Night	16% 7% 4 7% 6% 3 4 4 5% 6% 40%	2098
	21st to end	Night	17% 11% 4 6% 5% 3 4 4 5% 4 36%	1776
March	1st to 10th	Night	15% 8% 3 5% 5% 3 5% 4 4 5% 43%	2160
	11th to 20th	Night	18% 8% 3 7% 4 2 4 4 4 7% 39%	2102
	21st to end	Night	19% 9% 4 7% 5% 3 5% 4 5% 6% 34%	1980
April	1st to 10th	Night	11% 5% 2 5% 6% 3 4 4 4 7% 48%	1800
	11th to 20th	Night	16% 5% 2 4 4 2 4 5% 5% 6% 45%	1775
	21st to end	Night	18% 6% 3 6% 5% 3 4 5% 5% 7% 38%	1800
May	1st to 10th	Night	15% 5% 3 5% 5% 2 5% 4 5% 7% 44%	1652
	11th to 20th	Night	12% 6% 3 7% 5% 4 4 5% 6% 7% 42%	1592
	21st to end	Night	6% 4 3 6% 6% 4 6% 5% 6% 10% 44%	1600
June	1st to 10th	Night	10% 5% 1 5% 4 3 4 5% 6% 10% 48%	1440
	11th to 20th	Night	5% 3 2 4 4 3 4 5% 5% 9% 56%	1440
	21st to end	Night	4 3 1 3 4 3 5% 6% 8% 12% 52%	1440
July	1st to 10th	Night	7% 3 2 4 5% 4 5% 6% 6% 10% 49%	1440
	11th to 20th	Night	6% 4 1 4 4 3 5% 4 6% 9% 55%	1440
	21st to end	Night	7% 3 2 5% 5% 3 6% 5% 6% 8% 50%	1584
August	1st to 10th	Night	6% 4 2 4 5% 2 4 4 6% 11% 53%	1774
	11th to 20th	Night	7% 4 2 4 5% 3 4 5% 6% 9% 52%	1776
	21st to end	Night	6% 5% 2 4 5% 3 4 4 6% 8% 53%	1980
September	1st to 10th	Night	11% 5% 2 4 5% 2 4 3 4 6% 54%	1800
	11th to 20th	Night	7% 4 2 5% 4 2 4 4 5% 7% 53%	1894
	21st to end	Night	10% 4 2 3 4 3 4 4 5% 7% 56%	1980
October	1st to 10th	Night	8% 4 2 4 5% 3 4 3 5% 5% 58%	2002
	11th to 20th	Night	15% 4 2 4 4 2 3 3 4 6% 54%	2160
	21st to end	Night	19% 7% 3 5% 4 2 3 3 5% 4 46%	2486
November	1st to 10th	Night	11% 5% 2 4 3 2 3 4 4 6% 57%	2406
	11th to 20th	Night	13% 5% 2 5% 5% 2 3 4 4 7% 50%	2470
	21st to end	Night	18% 6% 3 4 4 2 3 3 4 6% 47%	2470
December	1st to 10th	Night	17% 10% 3 6% 5% 3 4 3 5% 6% 39%	2522
	11th to 20th	Night	16% 9% 4 5% 4 3 5% 4 5% 5% 41%	3279
	21st to end	Night	17% 14% 4 7% 7% 4 4 5% 4 5% 28%	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	52% 3 9% 23% 10% 2	1518
	11th to 20th	Day	53% 4 9% 23% 10%	1548
	21st to end	Day	50% 4 10% 25% 9% 2	1791
February	1st to 10th	Day	51% 4 11% 22% 11% 1	1764
	11th to 20th	Day	50% 4 10% 20% 13% 3	1758
	21st to end	Day	50% 5% 10% 19% 12% 4	1480
March	1st to 10th	Day	46% 6% 6% 24% 16% 2	1800
	11th to 20th	Day	52% 6% 11% 19% 10% 2	1870
	21st to end	Day	53% 5% 12% 20% 9% 1	2376
April	1st to 10th	Day	36% 4 13% 28% 17% 1	2160
	11th to 20th	Day	44% 5% 10% 22% 16% 3	2134
	21st to end	Day	45% 4 10% 26% 12% 2	2160
May	1st to 10th	Day	46% 7% 12% 25% 9% 1	2307
	11th to 20th	Day	43% 7% 13% 22% 14% 1	2305
	21st to end	Day	41% 10% 14% 21% 11% 2	2672
June	1st to 10th	Day	34% 6% 13% 26% 19% 2	2520
	11th to 20th	Day	28% 8% 12% 28% 21% 3	2520
	21st to end	Day	31% 7% 15% 24% 17% 5%	2520
July	1st to 10th	Day	36% 9% 14% 23% 14% 4	2451
	11th to 20th	Day	28% 8% 16% 26% 18% 3	2445
	21st to end	Day	33% 9% 14% 29% 13% 2	2578
August	1st to 10th	Day	32% 9% 14% 29% 15% 1	2149
	11th to 20th	Day	36% 6% 13% 28% 15% 2	2125
	21st to end	Day	31% 7% 14% 25% 17% 5%	2376
September	1st to 10th	Day	37% 5% 9% 28% 17% 4	2160
	11th to 20th	Day	33% 6% 9% 27% 25% 2	2048
	21st to end	Day	30% 5% 7% 28% 26% 4	1980
October	1st to 10th	Day	29% 4 9% 27% 25% 5%	1954
	11th to 20th	Day	35% 4 9% 24% 21% 7%	1800
	21st to end	Day	42% 4 6% 26% 19% 3	1868
November	1st to 10th	Day	31% 6% 10% 29% 19% 6%	1672
	11th to 20th	Day	39% 4 8% 24% 20% 5%	1710
	21st to end	Day	44% 3 8% 25% 16% 2	1710
December	1st to 10th	Day	46% 4 12% 24% 12% 1	1653
	11th to 20th	Day	50% 5% 8% 25% 11% 2	1915
	21st to end	Day	59% 4 11% 16% 10% 1	2783
January	1st to 10th	Night	48% 4 9% 23% 15% 2	2648
	11th to 20th	Night	54% 4 9% 21% 11% 1	2629
	21st to end	Night	49% 4 11% 22% 12% 2	2600
February	1st to 10th	Night	57% 3 8% 20% 11% 1	2194
	11th to 20th	Night	46% 4 8% 24% 15% 2	2099
	21st to end	Night	51% 4 10% 19% 13% 4	1776
March	1st to 10th	Night	44% 5% 7% 19% 20% 4	2160
	11th to 20th	Night	47% 5% 12% 18% 15% 3	2102
	21st to end	Night	51% 5% 12% 20% 11% 2	1980
April	1st to 10th	Night	37% 4 11% 27% 18% 3	1800
	11th to 20th	Night	39% 5% 10% 22% 19% 5%	1775
	21st to end	Night	46% 5% 9% 23% 16% 3	1800
May	1st to 10th	Night	41% 5% 10% 28% 14% 2	1652
	11th to 20th	Night	42% 8% 11% 22% 15% 2	1593
	21st to end	Night	35% 8% 15% 23% 15% 4	1601
June	1st to 10th	Night	31% 6% 14% 24% 23% 3	1440
	11th to 20th	Night	24% 6% 14% 26% 25% 5%	1440
	21st to end	Night	23% 8% 16% 27% 18% 7%	1440
July	1st to 10th	Night	30% 7% 15% 27% 16% 6%	1400
	11th to 20th	Night	27% 6% 15% 29% 18% 6%	1392
	21st to end	Night	28% 6% 15% 32% 18% 2	1496
August	1st to 10th	Night	25% 8% 19% 27% 20% 1	1763
	11th to 20th	Night	28% 7% 13% 28% 22% 3	1776
	21st to end	Night	28% 6% 14% 26% 20% 6%	1980
September	1st to 10th	Night	34% 5% 7% 29% 19% 6%	1800
	11th to 20th	Night	30% 5% 7% 30% 23% 5%	1894
	21st to end	Night	30% 4 9% 25% 26% 6%	1980
October	1st to 10th	Night	29% 4 8% 24% 30% 5%	2002
	11th to 20th	Night	34% 3 7% 25% 25% 7%	2160
	21st to end	Night	42% 4 6% 25% 18% 6%	2486
November	1st to 10th	Night	30% 4 10% 26% 25% 6%	2406
	11th to 20th	Night	36% 3 7% 24% 23% 7%	2470
	21st to end	Night	42% 3 8% 25% 20% 2	2470
December	1st to 10th	Night	48% 3 11% 23% 13% 1	2522
	11th to 20th	Night	45% 4 8% 24% 17% 2	3281
	21st to end	Night	60% 4 9% 17% 9% 2	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	24% 21% 32% 19% 3	270
	11th to 20th	Day	28% 26% 31% 12% 3	270
	21st to end	Day	22% 28% 35% 13% 2	267
February	1st to 10th	Day	25% 26% 36% 10% 2	240
	11th to 20th	Day	28% 31% 31% 8% 1	240
	21st to end	Day	30% 24% 29% 14% 3	198
March	1st to 10th	Day	23% 28% 35% 10% 3	240
	11th to 20th	Day	28% 23% 33% 12% 3	243
	21st to end	Day	26% 23% 28% 17% 5% 1	462
April	1st to 10th	Day	13% 24% 32% 25% 6%	420
	11th to 20th	Day	22% 20% 24% 24% 10%	412
	21st to end	Day	22% 18% 32% 19% 7% 2	420
May	1st to 10th	Day	21% 17% 30% 23% 7% 2	423
	11th to 20th	Day	20% 10% 28% 25% 13% 4	447
	21st to end	Day	11% 7% 27% 30% 18% 7%	626
June	1st to 10th	Day	11% 5% 20% 27% 27% 10%	630
	11th to 20th	Day	6% 5% 22% 38% 22% 7%	630
	21st to end	Day	8% 5% 29% 33% 18% 7%	630
July	1st to 10th	Day	12% 3 14% 26% 25% 21%	621
	11th to 20th	Day	6% 4 16% 33% 28% 12%	618
	21st to end	Day	8% 3 16% 32% 31% 11%	684
August	1st to 10th	Day	9% 3 13% 33% 28% 15%	460
	11th to 20th	Day	15% 2 16% 28% 29% 10%	439
	21st to end	Day	9% 3 15% 27% 31% 15%	495
September	1st to 10th	Day	11% 3 16% 28% 32% 10%	450
	11th to 20th	Day	9% 4 12% 31% 31% 14%	450
	21st to end	Day	14% 7% 22% 24% 24% 10%	450
October	1st to 10th	Day	11% 5% 26% 34% 18% 7%	424
	11th to 20th	Day	17% 16% 35% 23% 7% 1	270
	21st to end	Day	27% 16% 29% 23% 5%	297
November	1st to 10th	Day	11% 16% 34% 24% 13% 2	270
	11th to 20th	Day	17% 23% 30% 24% 7%	270
	21st to end	Day	28% 18% 26% 20% 7% 1	270
December	1st to 10th	Day	19% 24% 33% 14% 7% 3	270
	11th to 20th	Day	23% 19% 36% 18% 5%	270
	21st to end	Day	27% 24% 34% 12% 2	297
January	1st to 10th	Night	22% 19% 33% 23% 3	950
	11th to 20th	Night	24% 22% 34% 17% 3	950
	21st to end	Night	20% 17% 40% 21% 2	1000
February	1st to 10th	Night	26% 17% 34% 21% 2	754
	11th to 20th	Night	22% 20% 36% 21% 2	703
	21st to end	Night	26% 17% 36% 20% 1	592
March	1st to 10th	Night	22% 17% 35% 24% 3	720
	11th to 20th	Night	23% 13% 36% 21% 7%	666
	21st to end	Night	24% 13% 30% 26% 6% 1	594
April	1st to 10th	Night	14% 15% 36% 28% 6%	540
	11th to 20th	Night	18% 13% 28% 27% 13% 1	533
	21st to end	Night	20% 11% 31% 28% 9% 1	540
May	1st to 10th	Night	17% 8% 29% 34% 11% 1	540
	11th to 20th	Night	16% 6% 26% 33% 17% 2	531
	21st to end	Night	8% 4 21% 40% 23% 4	584
June	1st to 10th	Night	11% 2 19% 37% 28% 2	540
	11th to 20th	Night	6% 2 18% 45% 28% 2	540
	21st to end	Night	4 3 21% 42% 27% 3	540
July	1st to 10th	Night	9% 2 9% 33% 38% 9%	525
	11th to 20th	Night	6% 2 11% 37% 38% 6%	522
	21st to end	Night	7% 2 14% 37% 35% 5%	591
August	1st to 10th	Night	8% 1 9% 39% 36% 6%	537
	11th to 20th	Night	9% 1 11% 37% 37% 4	534
	21st to end	Night	7% 2 10% 35% 39% 7%	594
September	1st to 10th	Night	12% 2 13% 31% 37% 5%	540
	11th to 20th	Night	9% 3 14% 31% 37% 6%	634
	21st to end	Night	11% 6% 22% 31% 25% 6%	720
October	1st to 10th	Night	10% 7% 20% 34% 24% 5%	720
	11th to 20th	Night	17% 9% 30% 28% 13% 2	720
	21st to end	Night	22% 12% 32% 25% 8% 1	792
November	1st to 10th	Night	13% 9% 32% 32% 12% 1	740
	11th to 20th	Night	15% 13% 33% 29% 10% 1	760
	21st to end	Night	22% 13% 30% 26% 10% 1	760
December	1st to 10th	Night	23% 13% 33% 26% 5%	812
	11th to 20th	Night	22% 13% 32% 27% 6% 1	950
	21st to end	Night	24% 18% 36% 18% 3	1045

Page generated at 2024-01-19 08:28:31. Version ac07

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