Plattsburgh
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Plattsburgh clear sky chart from 2005-11-06 to 2024-08-30.

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	14% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	95770
	Night	15% 11% 4 9% 5% 5% 4 4 5% 6% 33%	93293
Transparency	Day	51% 4 12% 22% 10% 1	95489
	Night	52% 4 13% 21% 10% 1	93128
Seeing	Day	22% 18% 32% 19% 7% 2	14415
	Night	21% 15% 32% 23% 8% 1	23356

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	13% 13% 6% 13% 6% 5% 5% 4 6% 5% 25%	2517
	11th to 20th	Day	12% 17% 6% 14% 8% 5% 5% 4 5% 4 19%	2520
	21st to end	Day	14% 15% 6% 12% 7% 6% 6% 4 5% 6% 20%	2772
February	1st to 10th	Day	13% 15% 4 12% 8% 7% 5% 3 5% 5% 22%	1681
	11th to 20th	Day	10% 13% 5% 13% 6% 6% 5% 4 6% 5% 28%	1792
	21st to end	Day	14% 15% 5% 9% 6% 6% 5% 5% 4 5% 27%	1570
March	1st to 10th	Day	19% 13% 4 10% 6% 4 5% 3 5% 5% 26%	3116
	11th to 20th	Day	11% 16% 5% 11% 6% 6% 5% 3 5% 6% 27%	3273
	21st to end	Day	14% 9% 4 8% 5% 4 4 3 4 5% 40%	4166
April	1st to 10th	Day	18% 12% 3 8% 5% 4 5% 4 5% 6% 30%	2280
	11th to 20th	Day	17% 9% 3 7% 6% 5% 4 3 5% 5% 37%	2254
	21st to end	Day	21% 8% 3 7% 5% 4 5% 3 5% 6% 33%	2427
May	1st to 10th	Day	19% 9% 3 8% 4 5% 5% 4 5% 6% 30%	4287
	11th to 20th	Day	15% 8% 3 8% 5% 5% 5% 4 6% 7% 34%	4398
	21st to end	Day	12% 6% 2 6% 5% 5% 6% 4 8% 9% 37%	4837
June	1st to 10th	Day	20% 7% 2 7% 5% 5% 5% 5% 6% 8% 30%	2660
	11th to 20th	Day	13% 6% 3 6% 5% 5% 5% 5% 6% 9% 37%	2660
	21st to end	Day	18% 7% 2 7% 5% 5% 6% 4 7% 8% 30%	2660
July	1st to 10th	Day	9% 5% 2 6% 5% 6% 7% 5% 8% 9% 37%	4440
	11th to 20th	Day	10% 4 2 7% 5% 6% 6% 5% 8% 9% 37%	4440
	21st to end	Day	11% 6% 2 6% 5% 5% 5% 4 6% 8% 40%	4814
August	1st to 10th	Day	10% 6% 3 8% 6% 5% 6% 5% 8% 9% 36%	2646
	11th to 20th	Day	9% 6% 2 7% 5% 6% 6% 5% 8% 9% 38%	2365
	21st to end	Day	11% 5% 2 7% 4 5% 5% 5% 6% 7% 41%	2486
September	1st to 10th	Day	11% 6% 2 6% 4 5% 4 4 5% 8% 45%	2160
	11th to 20th	Day	12% 6% 2 5% 4 4 4 4 5% 6% 49%	2070
	21st to end	Day	11% 6% 3 6% 5% 6% 5% 4 6% 8% 41%	1980
October	1st to 10th	Day	18% 8% 3 7% 6% 4 4 4 6% 6% 34%	1882
	11th to 20th	Day	15% 8% 3 8% 4 6% 6% 4 6% 6% 32%	1761
	21st to end	Day	20% 11% 3 9% 6% 4 4 4 4 6% 29%	1782
November	1st to 10th	Day	12% 11% 4 8% 7% 6% 4 4 4 6% 33%	1671
	11th to 20th	Day	16% 10% 3 8% 6% 5% 6% 4 5% 5% 32%	1685
	21st to end	Day	16% 12% 4 8% 7% 5% 6% 4 5% 5% 28%	1520
December	1st to 10th	Day	17% 20% 5% 11% 8% 5% 5% 3 4 5% 18%	1520
	11th to 20th	Day	18% 14% 5% 9% 5% 4 4 4 6% 6% 24%	1906
	21st to end	Day	23% 14% 5% 9% 6% 4 4 3 4 5% 23%	2772
January	1st to 10th	Night	15% 15% 6% 12% 6% 5% 4 3 4 5% 25%	4429
	11th to 20th	Night	11% 15% 7% 13% 6% 5% 5% 4 5% 5% 24%	4440
	21st to end	Night	18% 16% 4 11% 5% 5% 4 3 4 5% 24%	4884
February	1st to 10th	Night	11% 14% 4 13% 8% 7% 5% 5% 6% 5% 23%	2497
	11th to 20th	Night	11% 11% 5% 12% 5% 5% 5% 4 5% 6% 31%	2274
	21st to end	Night	12% 13% 5% 11% 6% 5% 5% 4 5% 5% 30%	1884
March	1st to 10th	Night	19% 12% 4 7% 6% 4 5% 4 4 5% 31%	3724
	11th to 20th	Night	15% 17% 4 9% 5% 5% 4 3 4 4 29%	3681
	21st to end	Night	12% 12% 3 9% 6% 5% 4 3 4 4 38%	3466
April	1st to 10th	Night	17% 11% 4 8% 5% 5% 5% 4 5% 6% 31%	1900
	11th to 20th	Night	19% 10% 3 7% 5% 6% 4 3 4 5% 33%	1875
	21st to end	Night	18% 10% 3 7% 5% 4 4 3 5% 6% 36%	1752
May	1st to 10th	Night	20% 10% 3 7% 5% 5% 5% 4 5% 7% 28%	2683
	11th to 20th	Night	18% 9% 3 8% 6% 4 3 3 4 6% 35%	2495
	21st to end	Night	12% 5% 3 7% 5% 4 5% 4 6% 9% 40%	2738
June	1st to 10th	Night	20% 7% 2 6% 5% 4 4 3 6% 8% 35%	1520
	11th to 20th	Night	14% 6% 2 6% 4 5% 4 4 6% 8% 40%	1520
	21st to end	Night	15% 8% 3 7% 5% 4 4 4 5% 7% 39%	1520
July	1st to 10th	Night	11% 6% 2 7% 6% 6% 6% 5% 7% 8% 37%	2520
	11th to 20th	Night	11% 4 2 5% 4 5% 5% 3 6% 8% 47%	2520
	21st to end	Night	10% 6% 2 7% 6% 5% 5% 4 6% 6% 42%	2739
August	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 6% 9% 47%	1512
	11th to 20th	Night	10% 5% 2 6% 4 5% 6% 4 5% 8% 44%	1733
	21st to end	Night	11% 5% 2 6% 4 5% 5% 4 6% 7% 46%	2080
September	1st to 10th	Night	11% 5% 2 6% 4 4 5% 3 5% 7% 49%	1800
	11th to 20th	Night	12% 5% 2 5% 4 4 3 3 4 6% 52%	1889
	21st to end	Night	15% 5% 1 4 4 4 4 4 5% 7% 46%	1980
October	1st to 10th	Night	18% 8% 3 6% 5% 4 4 3 5% 7% 36%	2075
	11th to 20th	Night	17% 8% 2 7% 5% 6% 5% 3 5% 5% 37%	2197
	21st to end	Night	21% 9% 3 8% 5% 5% 5% 4 5% 6% 29%	2574
November	1st to 10th	Night	16% 10% 3 7% 4 5% 5% 4 6% 6% 35%	2407
	11th to 20th	Night	15% 10% 3 9% 6% 4 5% 3 5% 6% 34%	2493
	21st to end	Night	16% 14% 4 7% 5% 5% 5% 4 6% 6% 28%	2660
December	1st to 10th	Night	18% 19% 6% 9% 6% 5% 4 4 5% 5% 19%	2660
	11th to 20th	Night	20% 13% 5% 10% 5% 5% 4 4 4 4 25%	3288
	21st to end	Night	23% 14% 6% 12% 5% 5% 3 3 4 4 21%	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	59% 3 14% 20% 4 1	2518
	11th to 20th	Day	67% 3 13% 10% 6% 1	2520
	21st to end	Day	67% 3 13% 11% 5% 1	2772
February	1st to 10th	Day	64% 4 8% 17% 5% 2	1681
	11th to 20th	Day	58% 4 10% 19% 8% 1	1801
	21st to end	Day	61% 3 10% 15% 9% 2	1570
March	1st to 10th	Day	61% 3 9% 18% 7% 1	3119
	11th to 20th	Day	59% 2 13% 14% 10% 2	3273
	21st to end	Day	48% 2 7% 22% 19% 2	4166
April	1st to 10th	Day	55% 4 7% 20% 12% 3	2280
	11th to 20th	Day	51% 3 8% 21% 15% 2	2254
	21st to end	Day	54% 3 10% 19% 12% 3	2427
May	1st to 10th	Day	56% 3 9% 20% 11% 1	4301
	11th to 20th	Day	50% 4 15% 21% 9% 1	4402
	21st to end	Day	43% 5% 12% 28% 11% 2	4837
June	1st to 10th	Day	54% 4 10% 20% 11% 1	2660
	11th to 20th	Day	44% 5% 11% 25% 13% 2	2660
	21st to end	Day	51% 5% 12% 21% 9% 1	2660
July	1st to 10th	Day	40% 8% 14% 25% 12% 1	4370
	11th to 20th	Day	39% 9% 14% 30% 8%	4365
	21st to end	Day	40% 7% 13% 31% 9%	4661
August	1st to 10th	Day	42% 6% 16% 25% 9%	2632
	11th to 20th	Day	40% 6% 17% 26% 11%	2365
	21st to end	Day	41% 6% 12% 27% 13% 1	2486
September	1st to 10th	Day	38% 5% 12% 30% 14% 1	2160
	11th to 20th	Day	37% 4 10% 33% 15% 1	2070
	21st to end	Day	41% 5% 16% 28% 9% 1	1980
October	1st to 10th	Day	50% 6% 10% 22% 11%	1882
	11th to 20th	Day	52% 5% 14% 21% 8%	1761
	21st to end	Day	59% 3 13% 18% 7% 1	1782
November	1st to 10th	Day	52% 4 13% 21% 8% 1	1671
	11th to 20th	Day	53% 3 13% 18% 10% 2	1685
	21st to end	Day	58% 4 14% 19% 4 1	1520
December	1st to 10th	Day	70% 3 11% 13% 3	1520
	11th to 20th	Day	59% 4 13% 18% 5%	1906
	21st to end	Day	65% 3 10% 18% 4	2772
January	1st to 10th	Night	61% 2 18% 14% 5%	4429
	11th to 20th	Night	62% 3 14% 15% 5%	4440
	21st to end	Night	63% 2 12% 15% 7% 1	4884
February	1st to 10th	Night	61% 4 11% 16% 7% 1	2497
	11th to 20th	Night	52% 4 13% 21% 10%	2276
	21st to end	Night	55% 3 11% 18% 12% 1	1884
March	1st to 10th	Night	55% 2 11% 20% 10% 2	3734
	11th to 20th	Night	57% 2 10% 19% 10% 2	3682
	21st to end	Night	51% 2 6% 24% 14% 3	3466
April	1st to 10th	Night	55% 3 7% 20% 13% 1	1900
	11th to 20th	Night	53% 3 9% 21% 12% 1	1875
	21st to end	Night	49% 3 10% 20% 14% 3	1752
May	1st to 10th	Night	58% 2 9% 19% 10% 2	2689
	11th to 20th	Night	50% 3 12% 23% 11% 1	2496
	21st to end	Night	40% 4 13% 23% 17% 1	2739
June	1st to 10th	Night	48% 4 12% 22% 12% 2	1520
	11th to 20th	Night	41% 6% 13% 24% 14% 2	1520
	21st to end	Night	43% 5% 16% 23% 12% 1	1520
July	1st to 10th	Night	41% 7% 15% 23% 13% 1	2480
	11th to 20th	Night	34% 8% 15% 33% 10%	2472
	21st to end	Night	40% 7% 15% 24% 13%	2651
August	1st to 10th	Night	34% 5% 20% 30% 11%	1502
	11th to 20th	Night	37% 4 19% 26% 13% 1	1733
	21st to end	Night	36% 5% 16% 30% 13% 1	2080
September	1st to 10th	Night	34% 5% 16% 31% 13% 1	1800
	11th to 20th	Night	35% 3 15% 33% 13% 1	1889
	21st to end	Night	37% 5% 14% 30% 13% 1	1980
October	1st to 10th	Night	48% 4 12% 23% 12% 1	2075
	11th to 20th	Night	49% 4 14% 24% 9%	2197
	21st to end	Night	54% 4 14% 17% 9% 1	2574
November	1st to 10th	Night	50% 4 13% 22% 10% 2	2407
	11th to 20th	Night	51% 3 12% 22% 9% 2	2493
	21st to end	Night	55% 4 16% 19% 6%	2660
December	1st to 10th	Night	66% 3 11% 16% 3	2660
	11th to 20th	Night	62% 4 11% 16% 6% 1	3288
	21st to end	Night	67% 2 12% 16% 3	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	23% 20% 35% 14% 8%	180
	11th to 20th	Day	25% 27% 36% 8% 3 1	180
	21st to end	Day	19% 23% 38% 15% 4 1	198
February	1st to 10th	Day	33% 26% 35% 5% 1	256
	11th to 20th	Day	26% 29% 37% 7% 1	400
	21st to end	Day	32% 22% 32% 12% 2	382
March	1st to 10th	Day	29% 21% 33% 14% 3	460
	11th to 20th	Day	26% 25% 33% 13% 2 1	460
	21st to end	Day	30% 26% 26% 12% 5% 1	506
April	1st to 10th	Day	30% 21% 28% 16% 3 1	460
	11th to 20th	Day	28% 24% 28% 13% 6% 2	452
	21st to end	Day	30% 20% 30% 14% 4 1	460
May	1st to 10th	Day	26% 22% 31% 14% 6% 2	463
	11th to 20th	Day	18% 19% 34% 20% 8% 1	487
	21st to end	Day	16% 18% 36% 23% 7% 1	529
June	1st to 10th	Day	24% 13% 36% 21% 6% 1	490
	11th to 20th	Day	16% 19% 32% 22% 10% 2	490
	21st to end	Day	22% 16% 33% 20% 7% 1	490
July	1st to 10th	Day	15% 8% 34% 31% 9% 2	485
	11th to 20th	Day	14% 9% 35% 30% 11% 2	484
	21st to end	Day	14% 8% 38% 31% 8% 2	532
August	1st to 10th	Day	13% 10% 33% 28% 13% 3	486
	11th to 20th	Day	15% 6% 33% 29% 11% 5%	479
	21st to end	Day	15% 12% 25% 30% 13% 5%	532
September	1st to 10th	Day	14% 10% 34% 23% 15% 4	450
	11th to 20th	Day	14% 13% 26% 26% 14% 7%	450
	21st to end	Day	14% 13% 33% 25% 12% 3	450
October	1st to 10th	Day	23% 16% 29% 16% 14% 3	450
	11th to 20th	Day	21% 20% 35% 15% 7% 1	430
	21st to end	Day	29% 18% 30% 19% 4	396
November	1st to 10th	Day	23% 20% 30% 20% 6% 1	365
	11th to 20th	Day	26% 27% 27% 15% 4 1	345
	21st to end	Day	31% 20% 29% 17% 2	180
December	1st to 10th	Day	22% 25% 31% 17% 4	180
	11th to 20th	Day	29% 23% 35% 11% 1	180
	21st to end	Day	29% 23% 32% 12% 4 1	198
January	1st to 10th	Night	23% 21% 37% 17% 3	760
	11th to 20th	Night	28% 18% 33% 17% 4	760
	21st to end	Night	15% 19% 41% 19% 4 1	836
February	1st to 10th	Night	20% 17% 38% 21% 4	760
	11th to 20th	Night	19% 22% 38% 19% 2	743
	21st to end	Night	21% 22% 35% 20% 3	628
March	1st to 10th	Night	27% 17% 34% 18% 3	760
	11th to 20th	Night	23% 21% 33% 20% 3 1	760
	21st to end	Night	24% 19% 30% 21% 5% 1	836
April	1st to 10th	Night	24% 19% 34% 21% 3	760
	11th to 20th	Night	26% 22% 27% 19% 6% 1	751
	21st to end	Night	24% 20% 31% 18% 6%	612
May	1st to 10th	Night	24% 14% 34% 21% 6% 1	484
	11th to 20th	Night	18% 14% 34% 25% 9%	374
	21st to end	Night	14% 11% 37% 27% 11% 1	411
June	1st to 10th	Night	23% 8% 32% 27% 10% 1	380
	11th to 20th	Night	16% 9% 30% 32% 12%	380
	21st to end	Night	18% 7% 34% 28% 12% 1	380
July	1st to 10th	Night	9% 6% 32% 39% 14%	370
	11th to 20th	Night	10% 3 28% 44% 13% 2	368
	21st to end	Night	11% 5% 31% 38% 14% 1	416
August	1st to 10th	Night	14% 3 25% 40% 17% 1	378
	11th to 20th	Night	11% 6% 27% 35% 17% 4	609
	21st to end	Night	13% 7% 27% 35% 17% 2	832
September	1st to 10th	Night	14% 7% 31% 32% 16% 1	720
	11th to 20th	Night	14% 7% 27% 29% 18% 4	720
	21st to end	Night	17% 9% 32% 23% 16% 3	720
October	1st to 10th	Night	22% 13% 28% 24% 12% 1	720
	11th to 20th	Night	22% 13% 30% 24% 9% 1	720
	21st to end	Night	26% 16% 31% 22% 5%	792
November	1st to 10th	Night	23% 18% 31% 21% 6% 1	740
	11th to 20th	Night	22% 20% 31% 18% 8% 1	760
	21st to end	Night	23% 24% 28% 18% 6% 1	760
December	1st to 10th	Night	28% 21% 29% 17% 5%	760
	11th to 20th	Night	27% 22% 30% 16% 4 1	760
	21st to end	Night	30% 19% 31% 18% 3	836

Page generated at 2024-08-27 09:49:40. Version ac07

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