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 2024-11-03.

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% 2 6% 5% 4 4 4 6% 7% 37%	101370
	Night	17% 8% 2 6% 4 4 4 3 5% 7% 39%	97630
Transparency	Day	46% 4 11% 24% 14% 2	101125
	Night	45% 3 12% 24% 14% 2	97495
Seeing	Day	25% 15% 28% 20% 9% 3	14896
	Night	23% 14% 27% 25% 10% 1	24045

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% 9% 3 6% 4 4 4 4 5% 5% 43%	2517
	11th to 20th	Day	14% 10% 4 10% 6% 6% 4 4 6% 5% 32%	2520
	21st to end	Day	21% 12% 3 6% 4 4 4 4 6% 5% 30%	3037
February	1st to 10th	Day	16% 8% 2 9% 6% 6% 5% 5% 6% 6% 33%	1710
	11th to 20th	Day	13% 8% 3 7% 5% 5% 5% 3 5% 6% 39%	1805
	21st to end	Day	18% 9% 3 7% 6% 4 4 3 5% 5% 35%	1570
March	1st to 10th	Day	26% 9% 3 7% 4 4 3 3 4 5% 34%	3116
	11th to 20th	Day	10% 8% 3 7% 6% 6% 5% 4 6% 8% 38%	3406
	21st to end	Day	20% 9% 2 5% 4 3 3 3 4 6% 40%	4092
April	1st to 10th	Day	17% 9% 2 7% 5% 4 5% 3 5% 6% 36%	2280
	11th to 20th	Day	18% 8% 3 6% 4 4 4 3 4 7% 39%	2254
	21st to end	Day	18% 6% 3 7% 5% 5% 4 4 5% 6% 37%	2280
May	1st to 10th	Day	27% 8% 3 6% 4 4 4 3 4 7% 31%	4196
	11th to 20th	Day	22% 8% 3 7% 5% 5% 5% 5% 6% 6% 30%	4398
	21st to end	Day	14% 4 2 5% 4 4 5% 4 7% 9% 42%	4837
June	1st to 10th	Day	15% 5% 2 7% 7% 5% 4 5% 6% 9% 35%	2660
	11th to 20th	Day	16% 7% 2 6% 5% 5% 5% 4 6% 9% 35%	2660
	21st to end	Day	13% 7% 3 7% 5% 4 5% 4 6% 9% 37%	2660
July	1st to 10th	Day	11% 5% 3 8% 5% 6% 6% 5% 7% 9% 35%	4440
	11th to 20th	Day	11% 6% 3 6% 5% 5% 5% 5% 8% 10% 38%	4440
	21st to end	Day	15% 8% 2 8% 5% 5% 5% 5% 7% 8% 34%	4814
August	1st to 10th	Day	22% 5% 3 6% 5% 5% 5% 5% 7% 7% 31%	4205
	11th to 20th	Day	15% 5% 2 5% 4 5% 5% 5% 6% 8% 39%	3739
	21st to end	Day	14% 6% 2 5% 3 4 3 3 6% 9% 45%	4180
September	1st to 10th	Day	16% 6% 2 6% 4 3 4 3 5% 7% 43%	2280
	11th to 20th	Day	14% 5% 1 5% 3 4 5% 3 5% 6% 50%	2228
	21st to end	Day	19% 6% 2 6% 4 4 4 3 6% 6% 40%	2090
October	1st to 10th	Day	20% 7% 2 6% 4 4 4 4 4 6% 39%	1933
	11th to 20th	Day	15% 6% 2 6% 4 4 4 4 5% 8% 42%	1900
	21st to end	Day	22% 6% 2 5% 5% 4 4 5% 6% 6% 36%	1962
November	1st to 10th	Day	14% 6% 2 4 4 3 4 3 4 5% 50%	1689
	11th to 20th	Day	18% 7% 3 5% 4 3 3 4 6% 6% 42%	1710
	21st to end	Day	17% 7% 3 7% 5% 3 5% 4 5% 7% 38%	1564
December	1st to 10th	Day	18% 9% 4 6% 5% 4 4 4 7% 7% 31%	1520
	11th to 20th	Day	21% 6% 3 6% 5% 3 4 3 5% 7% 36%	1906
	21st to end	Day	19% 11% 5% 10% 6% 6% 5% 4 5% 6% 24%	2772
January	1st to 10th	Night	15% 8% 2 5% 4 4 4 3 5% 7% 41%	4429
	11th to 20th	Night	14% 9% 3 9% 5% 4 4 3 5% 6% 36%	4440
	21st to end	Night	22% 11% 2 6% 5% 3 4 4 5% 6% 31%	4615
February	1st to 10th	Night	15% 9% 3 5% 5% 5% 4 3 5% 7% 39%	2470
	11th to 20th	Night	15% 7% 3 6% 5% 4 5% 5% 6% 6% 38%	2261
	21st to end	Night	17% 9% 2 6% 4 4 4 4 5% 5% 39%	1884
March	1st to 10th	Night	24% 10% 3 6% 4 4 3 2 5% 5% 35%	3724
	11th to 20th	Night	11% 8% 2 6% 5% 5% 5% 3 6% 7% 41%	3549
	21st to end	Night	16% 9% 3 7% 4 4 3 3 5% 6% 40%	3540
April	1st to 10th	Night	16% 9% 2 8% 6% 4 4 4 5% 6% 36%	1900
	11th to 20th	Night	18% 8% 2 6% 4 4 5% 4 5% 7% 37%	1875
	21st to end	Night	19% 8% 2 6% 4 4 3 3 5% 6% 41%	1898
May	1st to 10th	Night	29% 8% 3 5% 4 3 4 3 5% 7% 31%	2772
	11th to 20th	Night	24% 10% 3 6% 4 3 4 3 5% 5% 33%	2495
	21st to end	Night	14% 6% 2 6% 5% 4 4 4 6% 9% 40%	2738
June	1st to 10th	Night	16% 6% 2 5% 5% 4 5% 3 5% 7% 42%	1520
	11th to 20th	Night	13% 6% 2 4 4 5% 4 4 5% 9% 43%	1520
	21st to end	Night	12% 4 2 5% 4 4 4 4 7% 9% 45%	1520
July	1st to 10th	Night	12% 5% 2 6% 5% 4 5% 4 7% 10% 39%	2520
	11th to 20th	Night	12% 6% 2 5% 4 5% 5% 4 6% 9% 41%	2520
	21st to end	Night	18% 7% 2 5% 4 5% 5% 4 6% 8% 37%	2739
August	1st to 10th	Night	22% 6% 2 6% 5% 4 4 3 6% 8% 34%	2719
	11th to 20th	Night	15% 7% 3 6% 4 4 4 3 5% 5% 43%	3058
	21st to end	Night	12% 5% 2 5% 3 3 4 3 5% 8% 50%	3476
September	1st to 10th	Night	15% 6% 2 5% 3 3 3 4 5% 8% 46%	1900
	11th to 20th	Night	14% 5% 1 4 3 4 4 2 4 7% 52%	1952
	21st to end	Night	18% 6% 3 5% 3 3 4 3 5% 6% 43%	2090
October	1st to 10th	Night	21% 6% 2 5% 4 4 3 3 3 6% 42%	2243
	11th to 20th	Night	18% 5% 2 5% 4 3 3 3 4 6% 48%	2280
	21st to end	Night	22% 7% 2 5% 3 3 3 3 5% 7% 40%	2635
November	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 6% 48%	2434
	11th to 20th	Night	19% 7% 2 4 3 3 3 3 5% 6% 44%	2470
	21st to end	Night	15% 6% 2 6% 5% 4 4 3 6% 7% 42%	2612
December	1st to 10th	Night	18% 7% 3 7% 4 4 4 3 7% 7% 35%	2660
	11th to 20th	Night	18% 8% 2 6% 4 4 5% 4 6% 7% 36%	3288
	21st to end	Night	21% 10% 3 7% 4 5% 4 3 5% 6% 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	55% 2 9% 21% 11% 2	3119
	11th to 20th	Day	43% 3 11% 30% 11% 2	3406
	21st to end	Day	48% 2 6% 16% 23% 5%	4092
April	1st to 10th	Day	48% 4 7% 22% 14% 4	2280
	11th to 20th	Day	46% 3 11% 22% 16% 3	2254
	21st to end	Day	48% 3 8% 22% 15% 4	2280
May	1st to 10th	Day	55% 2 10% 18% 12% 2	4210
	11th to 20th	Day	55% 2 11% 21% 9% 1	4402
	21st to end	Day	38% 3 12% 29% 16% 2	4837
June	1st to 10th	Day	45% 5% 11% 23% 14% 1	2660
	11th to 20th	Day	45% 4 12% 26% 11% 2	2660
	21st to end	Day	43% 5% 12% 26% 13%	2660
July	1st to 10th	Day	44% 7% 12% 22% 14% 1	4370
	11th to 20th	Day	39% 6% 16% 25% 14% 1	4365
	21st to end	Day	48% 5% 12% 19% 15% 1	4661
August	1st to 10th	Day	51% 4 13% 22% 10%	4191
	11th to 20th	Day	40% 6% 14% 29% 10%	3775
	21st to end	Day	36% 3 12% 33% 15% 1	4180
September	1st to 10th	Day	41% 4 11% 24% 18% 2	2280
	11th to 20th	Day	36% 3 9% 25% 25% 2	2228
	21st to end	Day	45% 3 9% 22% 19% 2	2090
October	1st to 10th	Day	46% 4 8% 23% 16% 3	1933
	11th to 20th	Day	40% 4 13% 25% 17% 1	1900
	21st to end	Day	48% 3 11% 21% 14% 2	1962
November	1st to 10th	Day	37% 3 12% 26% 19% 3	1689
	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	53% 2 9% 22% 12% 2	3734
	11th to 20th	Night	42% 2 14% 28% 13% 2	3550
	21st to end	Night	47% 2 6% 19% 21% 5%	3540
April	1st to 10th	Night	48% 3 10% 21% 15% 3	1900
	11th to 20th	Night	47% 4 9% 21% 19% 1	1875
	21st to end	Night	45% 2 9% 23% 17% 4	1898
May	1st to 10th	Night	54% 3 9% 21% 11% 2	2778
	11th to 20th	Night	54% 3 12% 19% 10% 1	2496
	21st to end	Night	42% 4 14% 27% 12% 2	2739
June	1st to 10th	Night	42% 4 10% 25% 18% 1	1520
	11th to 20th	Night	39% 4 16% 30% 10% 1	1520
	21st to end	Night	34% 5% 16% 29% 15% 1	1520
July	1st to 10th	Night	39% 7% 16% 20% 14% 3	2480
	11th to 20th	Night	38% 6% 15% 27% 13% 1	2472
	21st to end	Night	44% 5% 14% 19% 17% 2	2651
August	1st to 10th	Night	48% 6% 16% 21% 9% 1	2709
	11th to 20th	Night	42% 4 14% 30% 10%	3088
	21st to end	Night	33% 4 11% 34% 16% 1	3476
September	1st to 10th	Night	37% 4 12% 28% 18% 1	1900
	11th to 20th	Night	34% 3 10% 26% 25% 2	1952
	21st to end	Night	42% 3 8% 24% 22% 1	2090
October	1st to 10th	Night	45% 4 10% 24% 16% 2	2243
	11th to 20th	Night	39% 3 13% 29% 16% 2	2280
	21st to end	Night	44% 3 12% 25% 14% 1	2635
November	1st to 10th	Night	38% 4 11% 24% 21% 2	2434
	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% 27% 14% 3 1	460
	21st to end	Day	36% 18% 31% 10% 4 2	506
April	1st to 10th	Day	35% 20% 25% 13% 6% 1	460
	11th to 20th	Day	30% 21% 27% 13% 6% 2	452
	21st to end	Day	30% 18% 32% 13% 5% 2	460
May	1st to 10th	Day	38% 14% 22% 15% 7% 3	463
	11th to 20th	Day	23% 20% 29% 19% 8% 1	487
	21st to end	Day	20% 11% 28% 26% 12% 3	529
June	1st to 10th	Day	21% 12% 31% 23% 10% 2	490
	11th to 20th	Day	23% 12% 25% 26% 13% 1	490
	21st to end	Day	18% 11% 32% 27% 11% 1	490
July	1st to 10th	Day	15% 7% 28% 28% 15% 6%	485
	11th to 20th	Day	15% 5% 27% 30% 20% 2	484
	21st to end	Day	16% 9% 34% 25% 14% 2	532
August	1st to 10th	Day	14% 7% 26% 32% 14% 6%	486
	11th to 20th	Day	18% 6% 24% 29% 17% 5%	479
	21st to end	Day	15% 9% 28% 26% 13% 8%	539
September	1st to 10th	Day	22% 10% 22% 24% 15% 7%	490
	11th to 20th	Day	17% 8% 24% 23% 17% 11%	490
	21st to end	Day	25% 9% 27% 23% 11% 5%	490
October	1st to 10th	Day	27% 12% 22% 21% 14% 4	490
	11th to 20th	Day	20% 16% 30% 20% 11% 2	490
	21st to end	Day	28% 15% 30% 19% 8% 1	472
November	1st to 10th	Day	22% 15% 28% 23% 10% 2	371
	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	760
	21st to end	Night	23% 21% 32% 19% 5% 1	836
April	1st to 10th	Night	27% 18% 32% 18% 5%	760
	11th to 20th	Night	26% 16% 30% 22% 5%	751
	21st to end	Night	25% 16% 28% 23% 7%	758
May	1st to 10th	Night	31% 12% 25% 24% 8%	534
	11th to 20th	Night	24% 12% 28% 29% 7% 1	374
	21st to end	Night	18% 7% 22% 37% 15% 1	411
June	1st to 10th	Night	18% 5% 23% 39% 13% 1	380
	11th to 20th	Night	16% 5% 28% 34% 16%	380
	21st to end	Night	12% 3 25% 46% 13% 1	380
July	1st to 10th	Night	15% 4 16% 43% 19% 2	370
	11th to 20th	Night	14% 4 23% 42% 17% 1	368
	21st to end	Night	14% 4 21% 42% 18% 1	416
August	1st to 10th	Night	14% 2 21% 40% 22% 1	500
	11th to 20th	Night	16% 3 16% 38% 24% 2	723
	21st to end	Night	17% 4 19% 35% 23% 2	836
September	1st to 10th	Night	19% 5% 24% 31% 18% 3	760
	11th to 20th	Night	19% 6% 20% 28% 21% 5%	760
	21st to end	Night	21% 6% 22% 32% 18% 2	760
October	1st to 10th	Night	26% 9% 21% 25% 17% 2	760
	11th to 20th	Night	22% 12% 25% 31% 10%	760
	21st to end	Night	27% 14% 29% 23% 8%	836
November	1st to 10th	Night	18% 16% 29% 26% 9% 1	749
	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 2024-10-31 03:39:26. Version ac07

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