Port Jervis
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Jervis clear sky chart from 2005-11-06 to 2024-03-18.

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% 7% 3 6% 5% 3 5% 5% 6% 7% 37%	78567
	Night	17% 7% 3 5% 5% 3 4 4 5% 7% 40%	81210
Transparency	Day	46% 4 11% 23% 14% 2	78272
	Night	44% 3 12% 24% 15% 2	81039
Seeing	Day	26% 15% 28% 19% 9% 3	13986
	Night	23% 14% 27% 25% 9% 1	23319

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	14% 8% 3 5% 5% 3 4 5% 5% 5% 43%	2517
	11th to 20th	Day	14% 9% 4 9% 7% 4 5% 5% 6% 5% 32%	2520
	21st to end	Day	22% 12% 4 5% 5% 3 4 4 5% 5% 30%	3037
February	1st to 10th	Day	16% 7% 2 7% 7% 4 6% 5% 6% 6% 33%	1710
	11th to 20th	Day	13% 8% 3 6% 6% 3 5% 4 5% 6% 39%	1805
	21st to end	Day	19% 8% 3 6% 6% 3 4 4 5% 6% 35%	1570
March	1st to 10th	Day	15% 7% 3 7% 6% 3 4 4 5% 6% 39%	1897
	11th to 20th	Day	14% 7% 3 7% 6% 4 4 4 5% 8% 36%	2010
	21st to end	Day	19% 8% 3 5% 6% 3 4 4 4 6% 37%	2330
April	1st to 10th	Day	17% 8% 3 6% 5% 4 5% 5% 5% 6% 38%	2160
	11th to 20th	Day	17% 6% 3 5% 5% 3 4 4 4 7% 40%	2134
	21st to end	Day	19% 5% 3 6% 5% 3 5% 4 5% 7% 36%	2160
May	1st to 10th	Day	24% 7% 3 5% 5% 3 4 4 4 6% 34%	2388
	11th to 20th	Day	19% 6% 3 5% 5% 3 5% 6% 6% 7% 36%	2478
	21st to end	Day	15% 5% 2 5% 5% 3 5% 5% 6% 8% 40%	2725
June	1st to 10th	Day	16% 4 2 6% 7% 4 5% 5% 6% 9% 36%	2520
	11th to 20th	Day	17% 6% 2 5% 6% 4 6% 5% 6% 8% 34%	2520
	21st to end	Day	14% 6% 3 6% 6% 3 5% 5% 6% 9% 38%	2520
July	1st to 10th	Day	13% 5% 3 6% 5% 4 7% 6% 6% 9% 37%	2520
	11th to 20th	Day	12% 4 3 5% 6% 3 5% 5% 8% 9% 40%	2520
	21st to end	Day	13% 6% 2 5% 6% 3 5% 6% 7% 9% 38%	2744
August	1st to 10th	Day	12% 5% 3 5% 6% 4 6% 7% 8% 9% 36%	2386
	11th to 20th	Day	14% 5% 2 5% 5% 5% 7% 7% 6% 8% 36%	2135
	21st to end	Day	15% 7% 2 5% 4 3 4 5% 6% 8% 41%	2376
September	1st to 10th	Day	17% 5% 3 6% 4 3 4 4 5% 7% 42%	2160
	11th to 20th	Day	15% 5% 2 5% 4 3 5% 4 5% 6% 49%	2111
	21st to end	Day	17% 6% 2 5% 5% 3 5% 5% 6% 6% 41%	1980
October	1st to 10th	Day	21% 6% 2 5% 5% 3 4 5% 4 7% 38%	1832
	11th to 20th	Day	16% 6% 3 5% 5% 3 4 4 5% 8% 41%	1800
	21st to end	Day	23% 6% 2 4 6% 3 4 6% 5% 6% 34%	1859
November	1st to 10th	Day	14% 6% 2 4 4 3 4 3 4 5% 50%	1671
	11th to 20th	Day	18% 6% 3 4 5% 3 3 4 5% 6% 42%	1710
	21st to end	Day	17% 7% 3 6% 6% 2 4 5% 5% 7% 38%	1564
December	1st to 10th	Day	19% 8% 4 5% 5% 3 5% 5% 7% 7% 32%	1520
	11th to 20th	Day	21% 6% 3 5% 6% 2 4 5% 5% 8% 36%	1906
	21st to end	Day	19% 10% 5% 9% 7% 4 6% 5% 5% 6% 24%	2772
January	1st to 10th	Night	15% 7% 3 5% 4 3 4 4 5% 7% 42%	4429
	11th to 20th	Night	14% 9% 3 8% 6% 3 4 4 5% 6% 36%	4440
	21st to end	Night	22% 11% 3 5% 6% 3 4 4 5% 6% 32%	4615
February	1st to 10th	Night	15% 8% 3 5% 5% 3 6% 4 5% 7% 39%	2470
	11th to 20th	Night	15% 7% 3 6% 5% 3 5% 5% 6% 7% 38%	2261
	21st to end	Night	18% 9% 3 6% 4 3 4 5% 5% 6% 39%	1884
March	1st to 10th	Night	16% 8% 2 5% 5% 3 4 3 5% 7% 42%	2270
	11th to 20th	Night	16% 7% 2 5% 5% 3 5% 4 5% 7% 41%	2111
	21st to end	Night	16% 6% 3 5% 5% 3 4 5% 6% 7% 39%	2026
April	1st to 10th	Night	16% 9% 3 7% 6% 3 5% 4 5% 6% 36%	1800
	11th to 20th	Night	18% 7% 2 5% 5% 3 5% 4 5% 7% 38%	1775
	21st to end	Night	20% 7% 3 5% 4 3 3 4 5% 6% 40%	1799
May	1st to 10th	Night	23% 9% 3 5% 4 3 4 4 4 6% 35%	1586
	11th to 20th	Night	19% 6% 3 5% 5% 3 4 5% 5% 6% 39%	1415
	21st to end	Night	14% 5% 3 5% 5% 3 4 4 6% 8% 42%	1550
June	1st to 10th	Night	16% 5% 3 5% 5% 3 5% 4 5% 8% 42%	1440
	11th to 20th	Night	14% 6% 2 4 4 4 5% 5% 5% 9% 42%	1440
	21st to end	Night	12% 3 2 4 4 3 4 4 7% 9% 47%	1440
July	1st to 10th	Night	13% 4 3 5% 4 3 4 4 6% 9% 44%	1440
	11th to 20th	Night	13% 5% 2 4 5% 4 5% 4 6% 9% 43%	1440
	21st to end	Night	12% 5% 1 3 4 3 6% 6% 7% 10% 43%	1574
August	1st to 10th	Night	11% 5% 2 5% 5% 2 5% 5% 7% 10% 43%	1547
	11th to 20th	Night	13% 6% 3 5% 6% 4 5% 5% 6% 7% 39%	1748
	21st to end	Night	15% 4 3 4 5% 3 5% 4 6% 8% 44%	1980
September	1st to 10th	Night	16% 6% 2 5% 4 2 4 4 5% 8% 45%	1800
	11th to 20th	Night	15% 5% 2 3 3 2 4 3 4 6% 52%	1849
	21st to end	Night	17% 6% 2 4 3 3 4 5% 5% 7% 45%	1980
October	1st to 10th	Night	22% 6% 2 4 4 3 3 4 3 6% 43%	2124
	11th to 20th	Night	19% 5% 2 4 4 2 3 4 4 6% 46%	2160
	21st to end	Night	23% 7% 2 4 3 2 3 4 5% 7% 39%	2496
November	1st to 10th	Night	13% 6% 2 5% 4 3 4 3 4 7% 48%	2407
	11th to 20th	Night	19% 6% 3 4 4 2 4 4 5% 6% 44%	2470
	21st to end	Night	15% 6% 2 5% 6% 3 4 4 6% 7% 42%	2612
December	1st to 10th	Night	19% 6% 3 6% 6% 3 4 4 6% 7% 35%	2660
	11th to 20th	Night	19% 8% 3 5% 5% 3 5% 5% 6% 7% 36%	3288
	21st to end	Night	21% 10% 4 6% 5% 3 5% 4 4 7% 32%	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	43% 2 9% 34% 9% 3	2518
	11th to 20th	Day	53% 2 11% 22% 9% 3	2520
	21st to end	Day	56% 2 10% 22% 10% 1	3037
February	1st to 10th	Day	51% 4 11% 20% 13% 1	1710
	11th to 20th	Day	46% 4 8% 23% 17% 2	1814
	21st to end	Day	52% 2 9% 23% 12% 2	1570
March	1st to 10th	Day	46% 3 12% 23% 13% 3	1900
	11th to 20th	Day	46% 4 10% 24% 14% 2	2010
	21st to end	Day	50% 3 7% 18% 18% 4	2330
April	1st to 10th	Day	47% 4 7% 23% 15% 4	2160
	11th to 20th	Day	45% 3 11% 22% 16% 3	2134
	21st to end	Day	48% 3 8% 22% 14% 5%	2160
May	1st to 10th	Day	52% 3 7% 21% 14% 3	2388
	11th to 20th	Day	47% 4 9% 23% 15% 3	2482
	21st to end	Day	42% 4 15% 23% 13% 2	2725
June	1st to 10th	Day	46% 5% 12% 22% 14% 1	2520
	11th to 20th	Day	47% 4 11% 25% 11% 2	2520
	21st to end	Day	43% 5% 11% 27% 13%	2520
July	1st to 10th	Day	43% 5% 13% 22% 15% 2	2450
	11th to 20th	Day	38% 5% 15% 27% 15% 1	2445
	21st to end	Day	42% 5% 13% 21% 17% 2	2591
August	1st to 10th	Day	43% 4 13% 26% 13% 1	2372
	11th to 20th	Day	43% 7% 13% 26% 11% 1	2135
	21st to end	Day	40% 3 11% 25% 18% 2	2376
September	1st to 10th	Day	42% 4 12% 23% 17% 2	2160
	11th to 20th	Day	37% 3 9% 24% 25% 2	2111
	21st to end	Day	43% 3 9% 22% 20% 2	1980
October	1st to 10th	Day	47% 4 9% 23% 15% 3	1832
	11th to 20th	Day	41% 4 13% 25% 16% 1	1800
	21st to end	Day	50% 3 11% 21% 13% 2	1859
November	1st to 10th	Day	38% 3 12% 25% 19% 3	1671
	11th to 20th	Day	43% 2 10% 24% 18% 3	1710
	21st to end	Day	45% 4 13% 26% 10% 2	1564
December	1st to 10th	Day	50% 4 14% 19% 12% 1	1520
	11th to 20th	Day	47% 3 15% 23% 10% 1	1906
	21st to end	Day	61% 3 9% 19% 8%	2772
January	1st to 10th	Night	43% 1 11% 30% 11% 3	4429
	11th to 20th	Night	50% 3 11% 24% 11% 2	4440
	21st to end	Night	55% 2 10% 22% 10% 1	4615
February	1st to 10th	Night	46% 3 14% 23% 13% 1	2470
	11th to 20th	Night	45% 4 10% 20% 17% 3	2263
	21st to end	Night	47% 2 7% 24% 16% 3	1884
March	1st to 10th	Night	43% 3 12% 25% 15% 3	2280
	11th to 20th	Night	43% 3 11% 26% 15% 2	2112
	21st to end	Night	44% 2 10% 20% 19% 4	2026
April	1st to 10th	Night	47% 3 10% 22% 15% 3	1800
	11th to 20th	Night	46% 4 9% 22% 19% 1	1775
	21st to end	Night	46% 3 9% 23% 16% 4	1799
May	1st to 10th	Night	51% 3 9% 19% 16% 2	1586
	11th to 20th	Night	45% 3 10% 22% 18% 2	1416
	21st to end	Night	40% 5% 16% 25% 11% 3	1551
June	1st to 10th	Night	42% 4 11% 25% 17% 1	1440
	11th to 20th	Night	40% 4 15% 30% 10% 1	1440
	21st to end	Night	33% 5% 16% 29% 15% 1	1440
July	1st to 10th	Night	37% 5% 15% 25% 14% 3	1400
	11th to 20th	Night	38% 5% 14% 30% 12% 1	1392
	21st to end	Night	35% 6% 17% 22% 18% 2	1486
August	1st to 10th	Night	37% 5% 15% 28% 15% 1	1537
	11th to 20th	Night	43% 4 15% 25% 12% 1	1748
	21st to end	Night	39% 4 12% 23% 20% 2	1980
September	1st to 10th	Night	38% 4 13% 28% 16% 1	1800
	11th to 20th	Night	35% 3 10% 25% 25% 2	1849
	21st to end	Night	40% 3 8% 25% 23% 1	1980
October	1st to 10th	Night	45% 3 10% 24% 16% 2	2124
	11th to 20th	Night	40% 3 13% 29% 14% 1	2160
	21st to end	Night	45% 3 12% 25% 14% 1	2496
November	1st to 10th	Night	38% 4 11% 24% 21% 2	2407
	11th to 20th	Night	42% 3 10% 23% 18% 3	2470
	21st to end	Night	41% 3 15% 30% 11% 1	2612
December	1st to 10th	Night	47% 3 13% 24% 12% 1	2660
	11th to 20th	Night	48% 2 13% 21% 14% 2	3288
	21st to end	Night	55% 2 12% 23% 9%	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	36% 22% 29% 12% 2 1	180
	11th to 20th	Day	40% 24% 27% 8% 1 1	180
	21st to end	Day	31% 23% 34% 7% 5%	274
February	1st to 10th	Day	35% 23% 30% 10% 3	270
	11th to 20th	Day	33% 28% 28% 10% 1	413
	21st to end	Day	33% 22% 30% 13% 3	382
March	1st to 10th	Day	30% 22% 30% 14% 5%	460
	11th to 20th	Day	31% 23% 28% 15% 3 1	449
	21st to end	Day	35% 18% 31% 10% 5% 2	462
April	1st to 10th	Day	35% 21% 24% 13% 6% 1	420
	11th to 20th	Day	28% 20% 29% 14% 7% 2	412
	21st to end	Day	32% 18% 31% 13% 4 2	420
May	1st to 10th	Day	39% 15% 22% 14% 7% 3	423
	11th to 20th	Day	23% 21% 30% 17% 7% 1	447
	21st to end	Day	21% 10% 26% 26% 13% 4	485
June	1st to 10th	Day	21% 12% 31% 22% 11% 2	450
	11th to 20th	Day	25% 12% 26% 24% 12% 2	450
	21st to end	Day	18% 10% 32% 28% 12% 1	450
July	1st to 10th	Day	15% 7% 28% 28% 16% 6%	445
	11th to 20th	Day	16% 4 27% 29% 21% 3	444
	21st to end	Day	15% 9% 35% 25% 14% 2	488
August	1st to 10th	Day	13% 6% 26% 34% 15% 6%	446
	11th to 20th	Day	18% 5% 25% 29% 17% 6%	439
	21st to end	Day	15% 9% 28% 26% 13% 8%	495
September	1st to 10th	Day	22% 10% 22% 24% 15% 7%	450
	11th to 20th	Day	18% 9% 26% 22% 15% 10%	450
	21st to end	Day	22% 9% 28% 23% 12% 6%	450
October	1st to 10th	Day	29% 10% 22% 20% 14% 4	450
	11th to 20th	Day	21% 15% 30% 20% 11% 1	450
	21st to end	Day	31% 15% 29% 18% 7% 1	435
November	1st to 10th	Day	22% 15% 28% 23% 10% 2	365
	11th to 20th	Day	29% 21% 22% 21% 6% 1	370
	21st to end	Day	31% 20% 30% 14% 4	224
December	1st to 10th	Day	34% 23% 27% 11% 4 1	180
	11th to 20th	Day	41% 21% 25% 11% 2	180
	21st to end	Day	32% 24% 28% 13% 3	198
January	1st to 10th	Night	24% 23% 34% 16% 3	760
	11th to 20th	Night	28% 19% 28% 20% 4	760
	21st to end	Night	23% 21% 33% 20% 2	836
February	1st to 10th	Night	25% 19% 34% 20% 2	760
	11th to 20th	Night	25% 26% 33% 14% 2	743
	21st to end	Night	31% 21% 29% 15% 4	628
March	1st to 10th	Night	28% 20% 32% 16% 4	760
	11th to 20th	Night	25% 24% 28% 20% 4 1	752
	21st to end	Night	23% 21% 32% 19% 5% 1	792
April	1st to 10th	Night	27% 19% 31% 18% 5%	720
	11th to 20th	Night	25% 16% 31% 23% 5%	711
	21st to end	Night	26% 16% 27% 24% 7%	719
May	1st to 10th	Night	30% 12% 25% 24% 8%	506
	11th to 20th	Night	23% 12% 29% 28% 7% 1	354
	21st to end	Night	19% 7% 22% 37% 15% 1	389
June	1st to 10th	Night	19% 4 23% 39% 14% 1	360
	11th to 20th	Night	17% 5% 28% 34% 16%	360
	21st to end	Night	12% 3 24% 48% 13% 1	360
July	1st to 10th	Night	16% 4 16% 42% 20% 2	350
	11th to 20th	Night	15% 3 22% 41% 17% 1	348
	21st to end	Night	13% 4 22% 41% 18% 2	394
August	1st to 10th	Night	13% 1 21% 41% 22% 1	473
	11th to 20th	Night	16% 3 16% 37% 25% 2	684
	21st to end	Night	18% 4 19% 35% 23% 2	792
September	1st to 10th	Night	20% 5% 23% 31% 18% 3	720
	11th to 20th	Night	19% 7% 22% 28% 19% 5%	720
	21st to end	Night	20% 6% 22% 32% 18% 2	720
October	1st to 10th	Night	27% 8% 20% 26% 16% 2	720
	11th to 20th	Night	23% 12% 25% 31% 9%	720
	21st to end	Night	28% 14% 29% 22% 7%	792
November	1st to 10th	Night	19% 16% 29% 27% 9% 1	740
	11th to 20th	Night	25% 18% 26% 22% 8% 1	760
	21st to end	Night	21% 18% 30% 23% 7% 1	760
December	1st to 10th	Night	27% 19% 29% 19% 5%	760
	11th to 20th	Night	25% 23% 26% 22% 4	760
	21st to end	Night	29% 19% 31% 18% 2	836

Page generated at 2024-03-15 14:01:42. Version ac07

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