Lake Buffum
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Buffum clear sky chart from 2005-11-06 to 2025-03-27.

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	7% 6% 2 7% 6% 6% 6% 5% 7% 9% 39%	109297
	Night	8% 6% 2 7% 5% 5% 5% 4 7% 9% 42%	110021
Transparency	Day	38% 9% 16% 19% 13% 4	113062
	Night	36% 9% 16% 20% 13% 5%	114395
Seeing	Day	8% 4 17% 25% 25% 22%	16094
	Night	9% 4 19% 34% 26% 8%	26244

By Month

Percentage Cloud Cover SE (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	7% 5% 2 6% 4 3 4 4 5% 8% 52%	4056
	11th to 20th	Day	17% 10% 4 8% 5% 4 5% 4 5% 7% 31%	4060
	21st to end	Day	14% 6% 2 5% 4 3 3 4 6% 8% 45%	4693
February	1st to 10th	Day	11% 6% 2 6% 4 5% 4 4 5% 8% 46%	2000
	11th to 20th	Day	6% 5% 2 5% 4 3 4 4 5% 8% 53%	1948
	21st to end	Day	8% 6% 2 5% 3 4 4 4 6% 8% 49%	1770
March	1st to 10th	Day	6% 6% 3 8% 6% 7% 7% 4 7% 8% 38%	3545
	11th to 20th	Day	5% 3 1 5% 5% 4 5% 4 6% 11% 52%	3590
	21st to end	Day	9% 4 2 5% 3 4 5% 4 5% 8% 51%	3881
April	1st to 10th	Day	6% 3 1 5% 5% 4 6% 5% 7% 8% 49%	2090
	11th to 20th	Day	7% 5% 2 7% 5% 5% 7% 5% 6% 10% 41%	2085
	21st to end	Day	5% 4 1 5% 5% 5% 5% 5% 6% 8% 51%	2280
May	1st to 10th	Day	3 2 1 4 4 4 5% 4 7% 9% 59%	3955
	11th to 20th	Day	7% 5% 2 6% 6% 6% 5% 5% 7% 10% 40%	4081
	21st to end	Day	4 4 1 5% 5% 5% 6% 4 6% 9% 51%	4476
June	1st to 10th	Day	14% 9% 3 9% 6% 7% 6% 6% 8% 9% 22%	2470
	11th to 20th	Day	7% 7% 3 10% 8% 8% 7% 6% 9% 9% 26%	2470
	21st to end	Day	8% 8% 4 9% 8% 8% 8% 6% 8% 9% 26%	2470
July	1st to 10th	Day	6% 7% 3 10% 8% 8% 8% 6% 9% 12% 23%	4120
	11th to 20th	Day	4 5% 3 10% 8% 8% 8% 6% 9% 14% 26%	4120
	21st to end	Day	5% 6% 3 10% 8% 8% 8% 7% 9% 11% 24%	4466
August	1st to 10th	Day	5% 7% 3 11% 8% 7% 7% 6% 9% 12% 26%	4104
	11th to 20th	Day	4 4 2 9% 7% 7% 8% 6% 9% 12% 31%	3749
	21st to end	Day	7% 6% 3 10% 8% 7% 8% 6% 9% 13% 23%	3828
September	1st to 10th	Day	8% 7% 3 10% 8% 7% 8% 7% 8% 11% 23%	2090
	11th to 20th	Day	8% 7% 3 9% 8% 9% 8% 7% 8% 9% 24%	2090
	21st to end	Day	8% 7% 3 10% 7% 8% 6% 5% 9% 9% 28%	2090
October	1st to 10th	Day	11% 7% 3 7% 6% 5% 7% 5% 7% 8% 33%	2079
	11th to 20th	Day	6% 5% 2 7% 6% 5% 5% 4 6% 8% 45%	1900
	21st to end	Day	7% 5% 2 6% 4 5% 5% 4 6% 8% 48%	2090
November	1st to 10th	Day	6% 5% 2 6% 5% 4 4 4 6% 9% 48%	1957
	11th to 20th	Day	8% 6% 3 7% 5% 4 5% 3 6% 8% 46%	2000
	21st to end	Day	8% 6% 2 6% 6% 5% 5% 3 7% 9% 45%	1925
December	1st to 10th	Day	5% 3 2 4 4 3 3 4 5% 7% 59%	2930
	11th to 20th	Day	8% 7% 3 7% 5% 4 5% 4 6% 9% 43%	3373
	21st to end	Day	10% 7% 3 8% 6% 5% 5% 5% 6% 8% 37%	4466
January	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 5% 9% 50%	5889
	11th to 20th	Night	18% 11% 4 8% 4 4 4 3 6% 7% 31%	5900
	21st to end	Night	15% 6% 2 6% 4 3 4 4 6% 7% 43%	6246
February	1st to 10th	Night	10% 7% 2 6% 3 4 4 4 6% 8% 46%	2400
	11th to 20th	Night	9% 5% 2 5% 3 4 5% 3 6% 8% 50%	2338
	21st to end	Night	7% 6% 1 5% 4 3 5% 4 6% 7% 52%	1858
March	1st to 10th	Night	12% 9% 3 8% 5% 5% 5% 4 5% 6% 37%	3528
	11th to 20th	Night	4 4 1 5% 3 4 4 5% 8% 12% 50%	3590
	21st to end	Night	9% 6% 2 5% 3 3 3 3 5% 7% 52%	3890
April	1st to 10th	Night	5% 4 2 4 3 4 3 4 7% 10% 54%	2090
	11th to 20th	Night	5% 5% 2 5% 4 4 5% 4 6% 9% 51%	2043
	21st to end	Night	5% 4 1 5% 3 3 4 4 6% 7% 57%	1900
May	1st to 10th	Night	4 5% 2 6% 4 4 5% 4 5% 8% 53%	2952
	11th to 20th	Night	7% 5% 2 5% 4 4 5% 4 7% 11% 47%	2812
	21st to end	Night	4 3 2 4 3 4 4 4 6% 9% 57%	3079
June	1st to 10th	Night	9% 7% 3 7% 6% 5% 5% 6% 9% 10% 34%	1710
	11th to 20th	Night	6% 7% 3 7% 8% 6% 6% 5% 8% 12% 31%	1710
	21st to end	Night	6% 7% 2 7% 8% 7% 7% 6% 7% 11% 31%	1710
July	1st to 10th	Night	7% 8% 3 11% 7% 6% 7% 6% 8% 11% 26%	2840
	11th to 20th	Night	4 6% 3 10% 8% 8% 7% 7% 9% 12% 26%	2840
	21st to end	Night	6% 9% 4 13% 9% 8% 7% 6% 9% 10% 20%	3087
August	1st to 10th	Night	5% 6% 3 9% 6% 5% 6% 5% 9% 12% 35%	2825
	11th to 20th	Night	4 6% 3 9% 6% 5% 7% 5% 9% 12% 35%	3026
	21st to end	Night	7% 6% 2 9% 6% 6% 8% 6% 10% 12% 28%	3828
September	1st to 10th	Night	8% 7% 3 7% 6% 6% 7% 6% 9% 13% 29%	2090
	11th to 20th	Night	10% 8% 3 10% 7% 6% 6% 5% 8% 10% 27%	2090
	21st to end	Night	11% 7% 3 8% 6% 6% 5% 5% 7% 9% 33%	2090
October	1st to 10th	Night	12% 6% 3 7% 4 4 5% 4 7% 8% 39%	2099
	11th to 20th	Night	6% 6% 2 6% 4 5% 5% 4 6% 8% 49%	2280
	21st to end	Night	8% 5% 2 6% 4 4 4 3 6% 8% 50%	2508
November	1st to 10th	Night	9% 5% 2 6% 4 4 4 4 5% 9% 50%	2341
	11th to 20th	Night	9% 6% 2 6% 5% 3 5% 4 6% 7% 47%	2400
	21st to end	Night	9% 5% 2 6% 5% 4 5% 4 6% 7% 47%	2470
December	1st to 10th	Night	5% 3 1 4 3 3 3 3 6% 9% 60%	4250
	11th to 20th	Night	9% 7% 2 6% 4 4 4 3 6% 8% 48%	4822
	21st to end	Night	11% 8% 4 7% 5% 5% 5% 4 6% 8% 37%	6490

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	29% 6% 8% 20% 27% 11%	4057
	11th to 20th	Day	52% 4 6% 17% 15% 5%	4060
	21st to end	Day	36% 5% 6% 28% 19% 6%	4693
February	1st to 10th	Day	35% 6% 10% 18% 20% 10%	2000
	11th to 20th	Day	28% 5% 11% 21% 23% 11%	1958
	21st to end	Day	33% 6% 11% 17% 24% 10%	1770
March	1st to 10th	Day	39% 11% 12% 17% 14% 6%	3545
	11th to 20th	Day	24% 8% 12% 29% 19% 7%	3590
	21st to end	Day	28% 7% 11% 28% 16% 9%	3881
April	1st to 10th	Day	29% 8% 16% 24% 17% 7%	2090
	11th to 20th	Day	35% 9% 12% 17% 20% 7%	2085
	21st to end	Day	27% 8% 12% 22% 22% 9%	2280
May	1st to 10th	Day	17% 10% 17% 31% 19% 6%	3990
	11th to 20th	Day	34% 12% 20% 21% 13% 1	4085
	21st to end	Day	25% 10% 15% 31% 18% 2	4489
June	1st to 10th	Day	53% 13% 16% 14% 4	2470
	11th to 20th	Day	49% 13% 20% 15% 3	2470
	21st to end	Day	51% 15% 21% 11% 2 1	2470
July	1st to 10th	Day	49% 11% 28% 11% 1	4055
	11th to 20th	Day	45% 13% 34% 8%	4051
	21st to end	Day	49% 14% 26% 10% 1	4324
August	1st to 10th	Day	48% 12% 30% 9% 2	4091
	11th to 20th	Day	41% 12% 25% 16% 6%	3788
	21st to end	Day	49% 13% 27% 11% 1	3828
September	1st to 10th	Day	49% 19% 19% 11% 2	2090
	11th to 20th	Day	52% 16% 19% 11% 3	2090
	21st to end	Day	49% 11% 17% 13% 9% 2	2090
October	1st to 10th	Day	55% 9% 15% 10% 7% 4	3456
	11th to 20th	Day	28% 6% 10% 24% 28% 4	3140
	21st to end	Day	30% 5% 7% 24% 28% 6%	3428
November	1st to 10th	Day	30% 7% 14% 20% 19% 10%	1957
	11th to 20th	Day	36% 6% 10% 20% 19% 8%	2000
	21st to end	Day	35% 7% 11% 19% 19% 9%	1925
December	1st to 10th	Day	24% 5% 15% 29% 18% 9%	2930
	11th to 20th	Day	36% 6% 12% 18% 19% 9%	3370
	21st to end	Day	42% 7% 12% 20% 14% 4	4466
January	1st to 10th	Night	31% 6% 8% 21% 25% 11%	5889
	11th to 20th	Night	52% 5% 10% 17% 12% 4	5900
	21st to end	Night	38% 7% 9% 23% 16% 7%	6246
February	1st to 10th	Night	35% 7% 12% 17% 20% 9%	2400
	11th to 20th	Night	31% 6% 12% 20% 22% 9%	2339
	21st to end	Night	29% 7% 14% 19% 24% 8%	1858
March	1st to 10th	Night	43% 10% 12% 16% 15% 5%	3528
	11th to 20th	Night	22% 9% 21% 26% 15% 6%	3590
	21st to end	Night	30% 7% 11% 25% 22% 6%	3890
April	1st to 10th	Night	24% 8% 18% 27% 16% 7%	2090
	11th to 20th	Night	27% 9% 15% 23% 21% 5%	2043
	21st to end	Night	22% 8% 16% 24% 24% 7%	1900
May	1st to 10th	Night	20% 15% 21% 25% 14% 5%	2982
	11th to 20th	Night	25% 14% 21% 27% 11% 1	2813
	21st to end	Night	19% 11% 20% 34% 16% 1	3087
June	1st to 10th	Night	41% 13% 23% 18% 4	1710
	11th to 20th	Night	43% 13% 22% 18% 3	1710
	21st to end	Night	43% 16% 23% 13% 4	1710
July	1st to 10th	Night	49% 11% 29% 10% 1	2795
	11th to 20th	Night	47% 17% 30% 6%	2786
	21st to end	Night	54% 15% 23% 9%	2988
August	1st to 10th	Night	39% 14% 32% 12% 2	2814
	11th to 20th	Night	39% 13% 26% 15% 6%	3053
	21st to end	Night	45% 14% 32% 9% 1	3828
September	1st to 10th	Night	44% 21% 23% 11% 2	2090
	11th to 20th	Night	49% 15% 20% 14% 1	2090
	21st to end	Night	46% 11% 18% 16% 8% 2	2090
October	1st to 10th	Night	57% 10% 11% 11% 7% 3	3502
	11th to 20th	Night	30% 7% 8% 29% 22% 4	3779
	21st to end	Night	30% 5% 8% 25% 26% 6%	4120
November	1st to 10th	Night	31% 7% 13% 20% 20% 9%	2341
	11th to 20th	Night	33% 8% 10% 23% 18% 8%	2400
	21st to end	Night	34% 7% 10% 21% 20% 8%	2470
December	1st to 10th	Night	21% 4 19% 29% 14% 12%	4250
	11th to 20th	Night	35% 5% 13% 21% 16% 10%	4824
	21st to end	Night	43% 7% 14% 18% 12% 5%	6490

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	10% 8% 36% 33% 12% 1	300
	11th to 20th	Day	8% 12% 36% 28% 14% 3	300
	21st to end	Day	14% 12% 40% 25% 8%	330
February	1st to 10th	Day	10% 11% 22% 31% 20% 6%	300
	11th to 20th	Day	6% 6% 35% 33% 14% 6%	300
	21st to end	Day	8% 7% 26% 33% 22% 4	369
March	1st to 10th	Day	5% 6% 34% 36% 17% 2	500
	11th to 20th	Day	8% 8% 27% 31% 23% 3	500
	21st to end	Day	5% 6% 23% 36% 25% 5%	530
April	1st to 10th	Day	6% 7% 29% 35% 19% 4	460
	11th to 20th	Day	7% 6% 25% 32% 23% 7%	452
	21st to end	Day	7% 3 17% 32% 29% 12%	460
May	1st to 10th	Day	4 2 16% 28% 35% 15%	463
	11th to 20th	Day	9% 3 15% 27% 28% 19%	487
	21st to end	Day	6% 2 8% 20% 33% 31%	529
June	1st to 10th	Day	15% 2 8% 22% 27% 27%	490
	11th to 20th	Day	9% 1 7% 18% 30% 36%	490
	21st to end	Day	5% 2 4 12% 27% 50%	490
July	1st to 10th	Day	6% 2 4 9% 23% 56%	485
	11th to 20th	Day	3 2 3 9% 28% 55%	484
	21st to end	Day	9% 1 3 14% 22% 51%	532
August	1st to 10th	Day	5% 1 7% 13% 23% 52%	486
	11th to 20th	Day	4 1 3 11% 24% 57%	479
	21st to end	Day	8% 2 7% 17% 25% 40%	539
September	1st to 10th	Day	8% 3 7% 11% 27% 45%	490
	11th to 20th	Day	9% 3 5% 19% 29% 36%	490
	21st to end	Day	9% 1 7% 19% 34% 29%	490
October	1st to 10th	Day	15% 2 12% 28% 31% 12%	490
	11th to 20th	Day	6% 4 17% 33% 29% 12%	490
	21st to end	Day	8% 3 15% 37% 30% 7%	539
November	1st to 10th	Day	8% 5% 19% 30% 30% 8%	495
	11th to 20th	Day	12% 5% 22% 36% 21% 5%	500
	21st to end	Day	10% 4 24% 34% 24% 5%	425
December	1st to 10th	Day	6% 9% 30% 30% 19% 7%	300
	11th to 20th	Day	11% 7% 28% 32% 20% 2	300
	21st to end	Day	8% 7% 27% 35% 19% 4	330
January	1st to 10th	Night	11% 7% 29% 39% 13%	800
	11th to 20th	Night	12% 6% 29% 39% 13% 1	800
	21st to end	Night	14% 8% 34% 34% 10%	880
February	1st to 10th	Night	13% 6% 29% 37% 15%	800
	11th to 20th	Night	9% 6% 29% 41% 13% 1	783
	21st to end	Night	9% 5% 32% 43% 12%	660
March	1st to 10th	Night	5% 6% 34% 45% 10% 1	800
	11th to 20th	Night	6% 7% 30% 42% 15% 1	800
	21st to end	Night	7% 5% 28% 44% 16%	863
April	1st to 10th	Night	6% 3 29% 46% 16%	760
	11th to 20th	Night	6% 4 29% 47% 14% 1	751
	21st to end	Night	6% 3 27% 44% 20%	760
May	1st to 10th	Night	5% 2 17% 50% 24% 2	660
	11th to 20th	Night	7% 2 14% 40% 33% 4	561
	21st to end	Night	6% 1 11% 35% 42% 6%	617
June	1st to 10th	Night	10% 2 7% 30% 44% 8%	570
	11th to 20th	Night	6% 2 5% 21% 44% 23%	570
	21st to end	Night	6% 1 4 15% 43% 30%	570
July	1st to 10th	Night	7% 1 4 10% 47% 31%	555
	11th to 20th	Night	6% 1 1 9% 45% 38%	552
	21st to end	Night	5% 1 3 10% 46% 36%	624
August	1st to 10th	Night	6% 1 3 10% 51% 31%	567
	11th to 20th	Night	4 1 4 11% 42% 38%	609
	21st to end	Night	11% 2 6% 22% 37% 23%	836
September	1st to 10th	Night	11% 2 6% 19% 40% 23%	760
	11th to 20th	Night	12% 2 6% 26% 38% 17%	760
	21st to end	Night	13% 2 8% 27% 38% 11%	760
October	1st to 10th	Night	14% 2 15% 39% 26% 5%	760
	11th to 20th	Night	7% 3 16% 35% 36% 4	760
	21st to end	Night	10% 2 18% 40% 27% 2	836
November	1st to 10th	Night	12% 3 22% 38% 22% 3	780
	11th to 20th	Night	9% 4 21% 42% 23% 1	800
	21st to end	Night	9% 4 26% 44% 17% 1	800
December	1st to 10th	Night	7% 5% 26% 39% 23% 1	800
	11th to 20th	Night	10% 7% 24% 37% 22% 1	800
	21st to end	Night	10% 5% 25% 40% 19% 1	880

Page generated at 2025-03-24 09:04:25. Version ac07

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