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 2025-02-06.

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% 10% 3 8% 6% 5% 5% 4 6% 7% 32%	108399
	Night	15% 11% 4 9% 5% 5% 5% 4 5% 6% 31%	109858
Transparency	Day	50% 5% 12% 22% 10% 1	111903
	Night	51% 5% 13% 21% 10% 1	114518
Seeing	Day	22% 18% 32% 19% 7% 2	14868
	Night	21% 16% 32% 23% 8% 1	23993

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	12% 16% 6% 16% 7% 5% 4 3 5% 5% 21%	3597
	11th to 20th	Day	10% 16% 6% 16% 7% 5% 5% 4 5% 5% 20%	3570
	21st to end	Day	11% 12% 5% 11% 7% 7% 6% 4 6% 6% 24%	3960
February	1st to 10th	Day	13% 15% 4 12% 8% 7% 5% 3 5% 5% 22%	1725
	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	13% 7% 3 8% 5% 5% 6% 5% 7% 8% 33%	4423
	11th to 20th	Day	10% 6% 3 8% 6% 6% 6% 5% 8% 9% 36%	3910
	21st to end	Day	12% 5% 2 7% 4 5% 5% 5% 6% 8% 40%	4180
September	1st to 10th	Day	11% 5% 2 6% 4 5% 4 4 5% 8% 46%	2280
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 5% 6% 49%	2185
	21st to end	Day	11% 6% 3 6% 5% 6% 5% 4 7% 8% 40%	2090
October	1st to 10th	Day	17% 8% 3 7% 6% 4 4 4 6% 6% 35%	1986
	11th to 20th	Day	15% 8% 3 7% 4 5% 6% 4 6% 6% 34%	1858
	21st to end	Day	19% 11% 3 8% 6% 4 4 4 4 6% 31%	1881
November	1st to 10th	Day	12% 11% 4 8% 7% 6% 4 4 4 6% 33%	1761
	11th to 20th	Day	15% 10% 3 8% 6% 5% 6% 4 5% 5% 33%	1773
	21st to end	Day	17% 13% 4 8% 6% 5% 5% 4 5% 5% 28%	1600
December	1st to 10th	Day	13% 20% 7% 15% 8% 5% 4 3 4 4 16%	2600
	11th to 20th	Day	16% 12% 5% 8% 5% 4 4 4 6% 6% 29%	2986
	21st to end	Day	19% 14% 5% 9% 5% 4 4 3 4 5% 26%	3960
January	1st to 10th	Night	13% 20% 7% 15% 6% 4 4 3 4 4 21%	6349
	11th to 20th	Night	9% 17% 8% 14% 7% 5% 5% 4 5% 5% 21%	6315
	21st to end	Night	14% 14% 5% 12% 7% 7% 5% 3 5% 6% 22%	6996
February	1st to 10th	Night	12% 14% 4 13% 8% 7% 5% 5% 6% 5% 24%	2564
	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	13% 7% 3 7% 5% 4 4 4 6% 7% 40%	2506
	11th to 20th	Night	11% 6% 3 7% 5% 5% 6% 5% 5% 7% 40%	2883
	21st to end	Night	11% 5% 2 5% 4 5% 5% 3 6% 8% 46%	3476
September	1st to 10th	Night	10% 5% 2 6% 4 4 5% 3 5% 7% 50%	1900
	11th to 20th	Night	12% 5% 2 5% 4 4 4 3 4 6% 52%	1994
	21st to end	Night	15% 5% 1 4 4 4 5% 4 5% 7% 46%	2090
October	1st to 10th	Night	18% 8% 3 6% 5% 4 4 3 5% 7% 36%	2191
	11th to 20th	Night	17% 8% 2 7% 5% 6% 5% 3 4 5% 38%	2320
	21st to end	Night	20% 9% 3 8% 4 5% 4 4 5% 6% 31%	2717
November	1st to 10th	Night	15% 9% 3 8% 4 5% 5% 4 6% 6% 35%	2537
	11th to 20th	Night	15% 10% 3 9% 6% 4 5% 3 5% 6% 34%	2625
	21st to end	Night	16% 14% 4 8% 5% 5% 5% 5% 6% 6% 28%	2800
December	1st to 10th	Night	15% 21% 7% 12% 7% 5% 4 4 5% 4 16%	4580
	11th to 20th	Night	20% 14% 5% 11% 5% 5% 4 3 4 5% 25%	5208
	21st to end	Night	19% 14% 6% 11% 5% 5% 4 3 5% 7% 22%	6996

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	62% 4 12% 19% 3 1	3598
	11th to 20th	Day	65% 6% 11% 11% 5% 3	3600
	21st to end	Day	59% 5% 13% 14% 8% 1	3960
February	1st to 10th	Day	64% 4 8% 17% 6% 2	1725
	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	45% 8% 16% 23% 9% 1	4409
	11th to 20th	Day	41% 8% 17% 28% 7%	3950
	21st to end	Day	39% 9% 15% 23% 14%	4180
September	1st to 10th	Day	37% 5% 12% 31% 14% 1	2280
	11th to 20th	Day	37% 4 11% 33% 14% 1	2185
	21st to end	Day	41% 5% 16% 28% 10% 1	2090
October	1st to 10th	Day	38% 8% 14% 30% 10%	3298
	11th to 20th	Day	41% 6% 17% 26% 10%	3061
	21st to end	Day	41% 5% 18% 28% 8% 1	3081
November	1st to 10th	Day	52% 4 13% 21% 9% 1	1761
	11th to 20th	Day	51% 4 13% 18% 11% 2	1773
	21st to end	Day	59% 4 14% 19% 4 1	1600
December	1st to 10th	Day	70% 5% 10% 13% 2	2600
	11th to 20th	Day	52% 6% 14% 19% 9% 1	2986
	21st to end	Day	60% 4 9% 18% 9%	3960
January	1st to 10th	Night	63% 5% 15% 13% 4	6349
	11th to 20th	Night	63% 5% 12% 15% 5% 1	6360
	21st to end	Night	59% 5% 11% 13% 11% 1	6996
February	1st to 10th	Night	61% 4 11% 16% 7% 1	2564
	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	42% 7% 16% 27% 9%	2496
	11th to 20th	Night	41% 6% 21% 23% 9%	2909
	21st to end	Night	34% 7% 16% 28% 15% 1	3476
September	1st to 10th	Night	33% 5% 16% 32% 13% 1	1900
	11th to 20th	Night	34% 3 15% 33% 13% 1	1994
	21st to end	Night	37% 5% 14% 29% 14% 1	2090
October	1st to 10th	Night	42% 6% 14% 28% 10%	3659
	11th to 20th	Night	39% 5% 13% 28% 15%	3856
	21st to end	Night	43% 5% 15% 26% 11% 1	4467
November	1st to 10th	Night	49% 4 13% 22% 10% 2	2537
	11th to 20th	Night	51% 3 12% 22% 11% 2	2625
	21st to end	Night	54% 5% 16% 19% 6%	2800
December	1st to 10th	Night	66% 7% 11% 13% 3	4580
	11th to 20th	Night	60% 4 11% 14% 10% 1	5208
	21st to end	Night	61% 4 11% 16% 8%	6996

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	22% 22% 36% 13% 8%	200
	11th to 20th	Day	24% 27% 37% 9% 3 1	200
	21st to end	Day	19% 26% 37% 13% 3 1	220
February	1st to 10th	Day	33% 26% 35% 5% 1	270
	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	16% 12% 25% 29% 13% 4	539
September	1st to 10th	Day	14% 12% 33% 23% 14% 4	490
	11th to 20th	Day	13% 12% 25% 27% 16% 8%	490
	21st to end	Day	14% 13% 33% 25% 12% 3	490
October	1st to 10th	Day	22% 16% 30% 16% 13% 3	490
	11th to 20th	Day	22% 20% 34% 15% 7% 1	467
	21st to end	Day	28% 18% 30% 20% 4	429
November	1st to 10th	Day	24% 22% 29% 19% 5% 1	395
	11th to 20th	Day	25% 26% 26% 17% 4 1	373
	21st to end	Day	33% 21% 30% 16% 2	200
December	1st to 10th	Day	23% 25% 32% 17% 5%	200
	11th to 20th	Day	30% 23% 36% 11% 1	200
	21st to end	Day	27% 23% 32% 13% 4 1	220
January	1st to 10th	Night	22% 22% 37% 16% 3	800
	11th to 20th	Night	27% 18% 33% 18% 4	800
	21st to end	Night	15% 19% 42% 19% 4 1	880
February	1st to 10th	Night	21% 17% 38% 20% 4	781
	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	836
September	1st to 10th	Night	13% 7% 32% 31% 16% 1	760
	11th to 20th	Night	13% 7% 26% 29% 20% 4	760
	21st to end	Night	17% 9% 32% 23% 16% 3	760
October	1st to 10th	Night	21% 13% 27% 24% 13% 1	760
	11th to 20th	Night	22% 13% 30% 24% 9% 1	760
	21st to end	Night	26% 15% 31% 22% 5%	836
November	1st to 10th	Night	23% 18% 31% 21% 6% 1	780
	11th to 20th	Night	22% 20% 31% 19% 8% 1	800
	21st to end	Night	23% 24% 28% 18% 6% 1	800
December	1st to 10th	Night	27% 21% 29% 18% 5%	800
	11th to 20th	Night	28% 21% 30% 16% 4 1	800
	21st to end	Night	29% 19% 30% 18% 3	880

Page generated at 2025-02-03 03:05:50. Version ac07

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