Buffalo
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Buffalo clear sky chart from 2005-11-06 to 2025-10-04.

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	8% 7% 3 6% 4 4 4 4 5% 7% 48%	135572
	Night	7% 7% 3 7% 4 4 4 4 5% 7% 47%	131227
Transparency	Day	34% 5% 13% 28% 17% 3	130274
	Night	35% 5% 14% 27% 16% 3	127532
Seeing	Day	12% 9% 29% 30% 16% 4	17300
	Night	11% 8% 32% 37% 11% 1	27185

By Month

Percentage Cloud Cover SW (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	5% 10% 5% 13% 6% 5% 6% 4 5% 6% 34%	3638
	11th to 20th	Day	1 8% 5% 12% 7% 5% 5% 3 6% 8% 40%	3640
	21st to end	Day	2 6% 4 11% 6% 4 4 2 3 6% 52%	4004
February	1st to 10th	Day	9% 10% 5% 10% 6% 5% 5% 5% 5% 6% 34%	1745
	11th to 20th	Day	5% 9% 5% 9% 6% 6% 5% 4 5% 7% 39%	1867
	21st to end	Day	3 9% 4 9% 6% 5% 5% 5% 6% 8% 42%	1650
March	1st to 10th	Day	3 9% 3 8% 4 3 4 3 6% 8% 50%	4500
	11th to 20th	Day	5% 7% 3 6% 3 3 4 4 6% 10% 47%	4677
	21st to end	Day	14% 15% 5% 10% 4 4 4 3 5% 5% 31%	5969
April	1st to 10th	Day	13% 8% 3 7% 4 4 5% 4 6% 8% 38%	2400
	11th to 20th	Day	13% 10% 4 9% 5% 4 4 4 6% 7% 34%	2371
	21st to end	Day	15% 9% 3 6% 4 4 5% 4 6% 6% 39%	2572
May	1st to 10th	Day	13% 6% 2 5% 4 4 4 4 5% 7% 46%	6199
	11th to 20th	Day	17% 7% 2 5% 4 4 4 4 6% 7% 41%	6298
	21st to end	Day	14% 7% 3 6% 4 4 4 4 5% 7% 42%	6925
June	1st to 10th	Day	11% 5% 2 5% 4 3 5% 5% 6% 8% 46%	2800
	11th to 20th	Day	8% 5% 2 5% 4 5% 4 5% 8% 8% 46%	2800
	21st to end	Day	5% 3 1 4 3 4 4 4 6% 7% 58%	2800
July	1st to 10th	Day	4 3 2 5% 4 4 5% 5% 7% 9% 53%	6339
	11th to 20th	Day	9% 4 1 3 3 2 3 3 5% 6% 61%	6340
	21st to end	Day	7% 4 1 6% 4 4 4 4 6% 8% 52%	6903
August	1st to 10th	Day	8% 4 2 4 3 3 4 3 5% 7% 56%	6232
	11th to 20th	Day	7% 4 2 5% 4 4 4 4 5% 7% 56%	5794
	21st to end	Day	9% 4 1 4 2 3 3 3 5% 7% 59%	5984
September	1st to 10th	Day	6% 4 1 4 3 3 3 3 4 6% 63%	2400
	11th to 20th	Day	8% 4 1 4 3 3 4 3 6% 8% 57%	2326
	21st to end	Day	12% 4 1 4 3 2 2 3 4 6% 59%	2200
October	1st to 10th	Day	10% 4 1 3 2 2 2 2 4 6% 62%	3309
	11th to 20th	Day	9% 5% 2 4 2 3 3 2 5% 6% 59%	3061
	21st to end	Day	9% 6% 2 6% 4 3 4 4 5% 7% 48%	3091
November	1st to 10th	Day	7% 8% 2 5% 4 3 5% 4 6% 7% 48%	1763
	11th to 20th	Day	5% 7% 2 6% 4 4 5% 4 6% 8% 49%	1725
	21st to end	Day	5% 8% 4 6% 5% 4 5% 5% 6% 8% 44%	1600
December	1st to 10th	Day	4 9% 6% 11% 6% 5% 4 3 5% 6% 42%	2620
	11th to 20th	Day	2 9% 4 12% 6% 5% 5% 3 5% 6% 41%	3026
	21st to end	Day	6% 9% 3 9% 5% 4 5% 3 4 6% 46%	4004
January	1st to 10th	Night	6% 14% 5% 12% 7% 4 5% 4 5% 5% 35%	6327
	11th to 20th	Night	3 9% 4 10% 5% 5% 7% 5% 7% 7% 39%	6340
	21st to end	Night	2 5% 3 11% 5% 5% 4 3 5% 7% 51%	6974
February	1st to 10th	Night	7% 11% 4 10% 5% 5% 5% 4 6% 7% 35%	2670
	11th to 20th	Night	3 10% 3 9% 7% 5% 4 4 5% 7% 41%	2420
	21st to end	Night	5% 9% 3 7% 5% 5% 5% 4 6% 7% 45%	1980
March	1st to 10th	Night	4 7% 3 7% 4 3 3 3 6% 9% 50%	5374
	11th to 20th	Night	6% 7% 2 5% 4 4 4 4 8% 11% 44%	5302
	21st to end	Night	12% 14% 4 9% 6% 5% 5% 4 5% 7% 28%	4984
April	1st to 10th	Night	13% 10% 3 6% 4 3 4 5% 5% 6% 42%	2000
	11th to 20th	Night	11% 9% 4 7% 5% 5% 4 4 6% 7% 40%	1977
	21st to end	Night	13% 6% 2 6% 4 4 4 4 6% 8% 42%	1826
May	1st to 10th	Night	12% 6% 2 5% 3 3 4 3 5% 7% 50%	3777
	11th to 20th	Night	16% 7% 1 5% 4 4 4 4 6% 8% 38%	3617
	21st to end	Night	13% 7% 3 6% 5% 4 4 4 6% 7% 41%	3972
June	1st to 10th	Night	9% 4 1 5% 4 4 4 4 6% 9% 49%	1600
	11th to 20th	Night	12% 5% 1 5% 4 4 5% 5% 7% 7% 44%	1600
	21st to end	Night	6% 4 1 4 3 3 4 4 5% 9% 58%	1600
July	1st to 10th	Night	6% 4 1 5% 4 4 4 4 6% 9% 54%	3640
	11th to 20th	Night	6% 2 1 3 3 3 4 4 5% 9% 60%	3640
	21st to end	Night	7% 5% 2 5% 4 4 4 4 6% 8% 51%	3970
August	1st to 10th	Night	6% 4 2 4 3 4 3 3 4 7% 59%	3580
	11th to 20th	Night	6% 4 1 4 3 4 5% 4 7% 9% 54%	4038
	21st to end	Night	8% 4 2 4 3 3 4 3 6% 7% 55%	4993
September	1st to 10th	Night	6% 4 1 3 2 3 3 2 5% 7% 63%	2000
	11th to 20th	Night	9% 4 2 4 4 3 4 4 5% 7% 55%	2072
	21st to end	Night	10% 4 1 4 3 3 3 3 4 6% 59%	2200
October	1st to 10th	Night	8% 4 1 3 2 2 3 2 4 5% 65%	3722
	11th to 20th	Night	8% 5% 2 5% 3 3 3 3 5% 7% 55%	3835
	21st to end	Night	8% 8% 2 7% 4 4 3 3 4 7% 51%	4467
November	1st to 10th	Night	7% 7% 3 6% 4 4 4 4 5% 7% 48%	2535
	11th to 20th	Night	5% 9% 3 8% 4 4 4 4 5% 6% 47%	2670
	21st to end	Night	5% 7% 3 6% 4 4 5% 5% 6% 8% 47%	2800
December	1st to 10th	Night	4 8% 5% 10% 6% 4 5% 3 5% 6% 43%	4570
	11th to 20th	Night	4 8% 4 11% 6% 5% 4 4 6% 7% 41%	5181
	21st to end	Night	7% 10% 3 10% 5% 4 4 3 5% 6% 43%	6974

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	48% 7% 16% 22% 7%	3639
	11th to 20th	Day	41% 7% 17% 16% 17% 2	3640
	21st to end	Day	34% 6% 17% 31% 12% 1	4004
February	1st to 10th	Day	49% 6% 12% 19% 13% 1	1745
	11th to 20th	Day	43% 6% 16% 21% 12% 2	1876
	21st to end	Day	39% 6% 16% 26% 11% 2	1650
March	1st to 10th	Day	31% 4 12% 30% 21% 1	4500
	11th to 20th	Day	30% 6% 16% 32% 16% 1	4677
	21st to end	Day	54% 6% 14% 17% 9%	5969
April	1st to 10th	Day	43% 6% 15% 23% 11% 2	2400
	11th to 20th	Day	48% 6% 13% 23% 10% 1	2374
	21st to end	Day	45% 5% 15% 25% 10% 1	2572
May	1st to 10th	Day	35% 6% 11% 28% 18% 1	6199
	11th to 20th	Day	41% 6% 11% 27% 13% 2	6302
	21st to end	Day	39% 7% 13% 28% 13%	6926
June	1st to 10th	Day	33% 8% 19% 27% 12% 1	2800
	11th to 20th	Day	32% 8% 17% 28% 14% 2	2800
	21st to end	Day	24% 6% 15% 31% 20% 4	2800
July	1st to 10th	Day	25% 6% 15% 34% 18% 2	6271
	11th to 20th	Day	24% 4 8% 33% 24% 7%	6265
	21st to end	Day	28% 5% 12% 26% 23% 5%	6705
August	1st to 10th	Day	27% 5% 10% 30% 18% 11%	4536
	11th to 20th	Day	30% 6% 13% 30% 17% 4	4190
	21st to end	Day	20% 4 10% 28% 33% 6%	4311
September	1st to 10th	Day	22% 4 9% 32% 26% 8%	2400
	11th to 20th	Day	25% 5% 13% 30% 22% 5%	2326
	21st to end	Day	27% 4 9% 34% 23% 3	2200
October	1st to 10th	Day	25% 3 8% 25% 28% 11%	3309
	11th to 20th	Day	27% 3 11% 33% 23% 2	3061
	21st to end	Day	35% 4 12% 30% 16% 3	3091
November	1st to 10th	Day	34% 5% 13% 26% 18% 3	1763
	11th to 20th	Day	32% 5% 15% 28% 17% 2	1725
	21st to end	Day	35% 7% 17% 29% 11% 2	1600
December	1st to 10th	Day	42% 5% 14% 25% 12% 2	2620
	11th to 20th	Day	44% 4 15% 30% 7%	3024
	21st to end	Day	40% 3 9% 33% 14% 1	4004
January	1st to 10th	Night	50% 6% 11% 23% 9%	6327
	11th to 20th	Night	39% 7% 17% 20% 15% 2	6340
	21st to end	Night	32% 6% 18% 28% 15% 1	6974
February	1st to 10th	Night	47% 5% 15% 19% 13% 1	2670
	11th to 20th	Night	41% 5% 15% 24% 12% 2	2421
	21st to end	Night	37% 6% 14% 25% 15% 2	1980
March	1st to 10th	Night	31% 5% 11% 34% 17% 2	5374
	11th to 20th	Night	31% 5% 17% 30% 16% 1	5302
	21st to end	Night	53% 7% 14% 20% 5%	4984
April	1st to 10th	Night	43% 5% 13% 25% 12% 2	2000
	11th to 20th	Night	41% 6% 13% 26% 13% 1	1977
	21st to end	Night	39% 6% 14% 29% 11% 1	1826
May	1st to 10th	Night	33% 6% 12% 32% 17% 1	3777
	11th to 20th	Night	41% 9% 15% 24% 10% 1	3618
	21st to end	Night	39% 8% 13% 26% 14% 1	3972
June	1st to 10th	Night	31% 8% 18% 29% 13% 1	1600
	11th to 20th	Night	35% 8% 18% 22% 15% 2	1600
	21st to end	Night	23% 6% 18% 30% 19% 3	1600
July	1st to 10th	Night	26% 5% 17% 32% 18% 1	3600
	11th to 20th	Night	21% 4 14% 29% 26% 5%	3592
	21st to end	Night	31% 6% 14% 26% 18% 5%	3856
August	1st to 10th	Night	26% 5% 10% 30% 19% 10%	2600
	11th to 20th	Night	28% 6% 20% 24% 18% 4	2918
	21st to end	Night	22% 6% 9% 30% 27% 6%	3597
September	1st to 10th	Night	22% 3 10% 30% 25% 9%	2000
	11th to 20th	Night	29% 4 13% 28% 21% 5%	2072
	21st to end	Night	27% 3 10% 30% 26% 4	2200
October	1st to 10th	Night	23% 3 8% 25% 26% 14%	3722
	11th to 20th	Night	30% 3 8% 34% 22% 2	3835
	21st to end	Night	35% 3 11% 26% 18% 6%	4467
November	1st to 10th	Night	35% 6% 14% 26% 16% 4	2535
	11th to 20th	Night	35% 6% 12% 27% 16% 3	2670
	21st to end	Night	33% 6% 18% 27% 15% 2	2800
December	1st to 10th	Night	40% 5% 16% 25% 12% 1	4570
	11th to 20th	Night	41% 6% 18% 25% 9%	5182
	21st to end	Night	42% 4 8% 30% 15% 1	6974

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	8% 11% 33% 29% 12% 6%	300
	11th to 20th	Day	11% 13% 37% 24% 13% 2	300
	21st to end	Day	10% 18% 38% 25% 8% 1	330
February	1st to 10th	Day	13% 12% 39% 31% 5%	300
	11th to 20th	Day	13% 9% 43% 28% 6% 1	300
	21st to end	Day	12% 13% 36% 31% 6% 2	249
March	1st to 10th	Day	11% 12% 40% 22% 11% 4	300
	11th to 20th	Day	12% 9% 35% 30% 11% 4	342
	21st to end	Day	19% 13% 30% 23% 11% 4	550
April	1st to 10th	Day	20% 15% 30% 28% 7%	500
	11th to 20th	Day	20% 16% 36% 20% 6% 1	492
	21st to end	Day	21% 10% 25% 28% 14% 3	672
May	1st to 10th	Day	18% 8% 26% 27% 16% 5%	703
	11th to 20th	Day	21% 6% 21% 30% 16% 5%	725
	21st to end	Day	17% 7% 27% 29% 15% 5%	789
June	1st to 10th	Day	11% 9% 22% 29% 24% 6%	730
	11th to 20th	Day	11% 8% 35% 30% 14% 2	730
	21st to end	Day	9% 6% 26% 34% 21% 4	730
July	1st to 10th	Day	6% 3 20% 39% 27% 5%	721
	11th to 20th	Day	4 5% 26% 38% 23% 3	718
	21st to end	Day	7% 3 22% 40% 22% 6%	794
August	1st to 10th	Day	8% 4 21% 37% 23% 6%	726
	11th to 20th	Day	7% 4 21% 36% 26% 6%	631
	21st to end	Day	6% 7% 24% 33% 21% 9%	583
September	1st to 10th	Day	6% 6% 27% 34% 20% 7%	530
	11th to 20th	Day	9% 4 25% 32% 24% 7%	456
	21st to end	Day	15% 8% 21% 26% 22% 7%	330
October	1st to 10th	Day	18% 7% 21% 25% 21% 7%	309
	11th to 20th	Day	14% 12% 33% 21% 16% 4	300
	21st to end	Day	16% 14% 34% 18% 13% 4	330
November	1st to 10th	Day	13% 12% 34% 25% 10% 5%	300
	11th to 20th	Day	10% 13% 41% 24% 8% 3	300
	21st to end	Day	13% 9% 38% 26% 13% 1	300
December	1st to 10th	Day	12% 15% 36% 24% 11% 2	300
	11th to 20th	Day	10% 14% 39% 28% 7% 1	300
	21st to end	Day	10% 10% 40% 27% 10% 2	330
January	1st to 10th	Night	8% 12% 39% 29% 11% 1	1000
	11th to 20th	Night	10% 14% 39% 27% 8% 1	1000
	21st to end	Night	9% 15% 37% 32% 8%	1100
February	1st to 10th	Night	10% 10% 39% 32% 9%	870
	11th to 20th	Night	9% 11% 39% 34% 7% 1	784
	21st to end	Night	8% 7% 37% 36% 11% 1	660
March	1st to 10th	Night	10% 9% 36% 35% 9% 1	800
	11th to 20th	Night	10% 7% 36% 37% 10% 2	793
	21st to end	Night	15% 8% 28% 39% 9% 1	660
April	1st to 10th	Night	18% 9% 30% 36% 8%	600
	11th to 20th	Night	14% 10% 37% 32% 6%	593
	21st to end	Night	17% 8% 25% 37% 14%	600
May	1st to 10th	Night	13% 6% 25% 40% 15% 2	600
	11th to 20th	Night	18% 6% 23% 38% 15% 1	591
	21st to end	Night	18% 5% 29% 35% 12%	650
June	1st to 10th	Night	11% 8% 26% 38% 17% 1	600
	11th to 20th	Night	14% 8% 36% 35% 8%	600
	21st to end	Night	8% 3 33% 44% 12% 1	600
July	1st to 10th	Night	6% 2 25% 48% 18% 1	585
	11th to 20th	Night	6% 3 28% 51% 11%	582
	21st to end	Night	5% 3 23% 53% 16%	657
August	1st to 10th	Night	6% 4 26% 47% 16% 1	597
	11th to 20th	Night	7% 3 22% 48% 20% 1	594
	21st to end	Night	7% 3 24% 48% 16% 1	660
September	1st to 10th	Night	7% 4 23% 47% 19% 1	600
	11th to 20th	Night	10% 6% 24% 46% 14% 1	600
	21st to end	Night	10% 6% 28% 40% 15% 1	600
October	1st to 10th	Night	14% 7% 27% 36% 15%	697
	11th to 20th	Night	13% 7% 30% 34% 15% 1	792
	21st to end	Night	14% 10% 34% 31% 9% 2	1045
November	1st to 10th	Night	10% 10% 34% 34% 11% 1	975
	11th to 20th	Night	9% 11% 37% 33% 9% 1	1000
	21st to end	Night	9% 12% 37% 33% 9%	1000
December	1st to 10th	Night	9% 11% 40% 30% 10%	1000
	11th to 20th	Night	9% 11% 37% 35% 8% 1	1000
	21st to end	Night	13% 11% 36% 30% 8% 1	1100

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