Buffalo Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Buffalo Point clear sky chart from 2005-11-06 to 2026-05-02.

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	10% 8% 3 8% 5% 5% 5% 4 5% 7% 40%	135576
	Night	10% 10% 4 10% 6% 5% 5% 4 5% 6% 35%	135726
Transparency	Day	30% 38% 10% 15% 7%	135274
	Night	34% 37% 9% 14% 6%	135609
Seeing	Day	15% 11% 32% 27% 12% 3	18214
	Night	16% 8% 32% 31% 12% 1	28259

By Month

Percentage Cloud Cover NW (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	6% 13% 7% 15% 6% 5% 6% 4 6% 6% 25%	4125
	11th to 20th	Day	4 10% 5% 15% 9% 9% 9% 7% 7% 7% 18%	4119
	21st to end	Day	4 10% 8% 14% 7% 7% 8% 6% 8% 8% 23%	5176
February	1st to 10th	Day	7% 11% 5% 11% 6% 6% 8% 4 6% 7% 30%	1890
	11th to 20th	Day	6% 9% 3 9% 5% 5% 5% 4 8% 8% 38%	1844
	21st to end	Day	3 8% 4 10% 7% 5% 6% 4 7% 8% 37%	1557
March	1st to 10th	Day	8% 9% 3 6% 7% 6% 5% 4 6% 7% 41%	4902
	11th to 20th	Day	10% 7% 3 11% 6% 5% 5% 4 6% 8% 35%	5088
	21st to end	Day	11% 12% 3 8% 5% 4 4 3 5% 6% 39%	5585
April	1st to 10th	Day	10% 9% 2 7% 5% 4 5% 4 6% 7% 42%	2510
	11th to 20th	Day	12% 9% 3 8% 5% 4 5% 4 6% 7% 38%	2702
	21st to end	Day	15% 8% 3 7% 4 4 4 2 5% 7% 41%	2730
May	1st to 10th	Day	12% 6% 2 5% 4 3 4 3 4 6% 51%	6269
	11th to 20th	Day	13% 7% 3 7% 4 4 5% 4 5% 8% 41%	6319
	21st to end	Day	12% 7% 2 6% 3 3 4 3 4 6% 51%	7381
June	1st to 10th	Day	11% 5% 2 6% 4 4 4 4 5% 8% 45%	3000
	11th to 20th	Day	11% 5% 2 6% 4 3 4 4 5% 7% 48%	3000
	21st to end	Day	12% 5% 2 6% 4 4 4 4 7% 9% 43%	3000
July	1st to 10th	Day	7% 4 2 5% 4 4 5% 4 6% 10% 50%	6800
	11th to 20th	Day	11% 5% 2 5% 3 3 4 4 6% 9% 48%	6800
	21st to end	Day	11% 5% 2 6% 5% 5% 5% 3 5% 7% 45%	7323
August	1st to 10th	Day	8% 5% 2 6% 4 4 5% 4 5% 8% 48%	4302
	11th to 20th	Day	11% 4 2 5% 3 3 5% 4 6% 8% 48%	4171
	21st to end	Day	12% 6% 2 6% 3 3 4 3 5% 8% 47%	4675
September	1st to 10th	Day	11% 6% 2 6% 3 4 4 3 5% 8% 47%	2424
	11th to 20th	Day	13% 7% 2 7% 4 4 4 4 6% 7% 42%	2275
	21st to end	Day	15% 6% 2 6% 4 4 5% 3 5% 7% 44%	2170
October	1st to 10th	Day	13% 8% 2 6% 4 4 4 3 5% 6% 45%	3260
	11th to 20th	Day	13% 8% 4 7% 4 4 4 3 5% 7% 42%	3240
	21st to end	Day	14% 11% 4 9% 4 4 5% 3 4 7% 33%	3236
November	1st to 10th	Day	13% 13% 6% 10% 6% 5% 4 3 5% 5% 32%	1647
	11th to 20th	Day	11% 14% 6% 14% 6% 5% 5% 3 3 4 30%	1680
	21st to end	Day	11% 13% 4 17% 9% 5% 4 3 3 5% 26%	1680
December	1st to 10th	Day	11% 16% 4 17% 12% 6% 5% 4 4 5% 16%	2412
	11th to 20th	Day	10% 16% 5% 12% 6% 5% 6% 4 4 5% 28%	2709
	21st to end	Day	11% 15% 8% 18% 8% 7% 5% 3 4 4 18%	3575
January	1st to 10th	Night	4 12% 6% 16% 9% 7% 6% 4 5% 7% 24%	8799
	11th to 20th	Night	4 12% 6% 15% 9% 7% 8% 8% 8% 6% 18%	8809
	21st to end	Night	6% 13% 7% 11% 6% 6% 9% 5% 7% 7% 24%	9022
February	1st to 10th	Night	6% 12% 4 11% 7% 5% 6% 4 6% 6% 33%	2730
	11th to 20th	Night	7% 9% 3 9% 4 5% 7% 4 6% 7% 40%	2663
	21st to end	Night	5% 8% 3 12% 6% 5% 6% 4 6% 8% 37%	2249
March	1st to 10th	Night	8% 9% 4 10% 6% 6% 4 4 6% 7% 35%	5221
	11th to 20th	Night	6% 10% 4 11% 7% 5% 5% 4 6% 7% 35%	5090
	21st to end	Night	13% 15% 5% 10% 4 4 3 3 4 4 35%	5588
April	1st to 10th	Night	13% 8% 4 7% 5% 3 4 3 5% 6% 43%	2107
	11th to 20th	Night	14% 9% 4 6% 3 4 4 4 4 5% 43%	1869
	21st to end	Night	12% 10% 3 8% 5% 4 4 3 5% 6% 40%	1890
May	1st to 10th	Night	14% 6% 2 6% 3 3 3 2 4 6% 51%	3732
	11th to 20th	Night	16% 7% 2 5% 3 4 4 3 5% 7% 43%	3597
	21st to end	Night	13% 5% 2 6% 4 4 5% 3 5% 7% 47%	3513
June	1st to 10th	Night	12% 4 2 6% 3 4 4 3 6% 8% 49%	1400
	11th to 20th	Night	12% 4 2 6% 3 4 3 4 5% 7% 52%	1400
	21st to end	Night	9% 6% 2 5% 3 5% 4 3 5% 7% 51%	1400
July	1st to 10th	Night	8% 4 1 5% 3 4 4 3 7% 9% 51%	3180
	11th to 20th	Night	8% 4 1 4 3 3 4 4 6% 10% 53%	3180
	21st to end	Night	8% 4 2 5% 4 4 4 4 6% 9% 49%	3542
August	1st to 10th	Night	7% 4 1 5% 5% 5% 5% 4 7% 9% 47%	2855
	11th to 20th	Night	11% 4 2 4 3 4 4 3 6% 9% 51%	2888
	21st to end	Night	11% 5% 2 7% 4 3 4 3 5% 8% 48%	3234
September	1st to 10th	Night	11% 5% 2 4 3 3 4 3 5% 7% 53%	1975
	11th to 20th	Night	13% 6% 2 5% 2 3 4 3 6% 7% 48%	2123
	21st to end	Night	15% 6% 2 6% 4 3 3 3 5% 7% 47%	2210
October	1st to 10th	Night	14% 7% 2 5% 4 3 4 3 4 7% 47%	3920
	11th to 20th	Night	14% 10% 3 7% 4 4 4 3 5% 7% 40%	3899
	21st to end	Night	15% 12% 4 9% 5% 5% 4 3 4 5% 34%	4543
November	1st to 10th	Night	13% 12% 4 10% 5% 4 5% 3 4 5% 34%	2871
	11th to 20th	Night	11% 15% 5% 13% 6% 4 5% 3 4 5% 30%	2940
	21st to end	Night	10% 13% 5% 15% 7% 6% 5% 4 4 5% 27%	2940
December	1st to 10th	Night	9% 17% 7% 19% 10% 6% 5% 3 4 4 17%	4984
	11th to 20th	Night	7% 14% 5% 13% 8% 7% 6% 5% 5% 6% 24%	5718
	21st to end	Night	10% 14% 8% 19% 8% 6% 4 3 4 4 19%	7645

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	50% 23% 6% 14% 8%	4125
	11th to 20th	Day	53% 22% 7% 13% 5%	4140
	21st to end	Day	47% 24% 9% 15% 5%	5176
February	1st to 10th	Day	26% 60% 6% 6% 2	1890
	11th to 20th	Day	22% 59% 6% 10% 3	1853
	21st to end	Day	20% 60% 5% 7% 6%	1557
March	1st to 10th	Day	30% 30% 13% 13% 10% 4	4902
	11th to 20th	Day	35% 31% 11% 14% 9%	5090
	21st to end	Day	37% 30% 6% 17% 10%	5585
April	1st to 10th	Day	20% 60% 5% 9% 6%	2510
	11th to 20th	Day	20% 60% 6% 10% 4 1	2702
	21st to end	Day	20% 59% 4 12% 4 1	2730
May	1st to 10th	Day	24% 31% 10% 20% 14%	6268
	11th to 20th	Day	32% 31% 9% 16% 12%	6323
	21st to end	Day	25% 30% 7% 21% 15% 2	7381
June	1st to 10th	Day	15% 63% 6% 11% 5%	3000
	11th to 20th	Day	18% 62% 6% 10% 4	3000
	21st to end	Day	18% 62% 7% 10% 3	3000
July	1st to 10th	Day	26% 29% 18% 23% 4	6726
	11th to 20th	Day	28% 28% 16% 24% 4	6719
	21st to end	Day	33% 28% 14% 21% 5%	7117
August	1st to 10th	Day	22% 38% 12% 18% 9% 1	4287
	11th to 20th	Day	24% 38% 17% 18% 3	4210
	21st to end	Day	27% 37% 16% 18% 2	4674
September	1st to 10th	Day	16% 58% 8% 13% 4	2424
	11th to 20th	Day	20% 58% 9% 10% 1	2275
	21st to end	Day	21% 58% 6% 11% 3	2170
October	1st to 10th	Day	24% 36% 10% 20% 9%	3260
	11th to 20th	Day	23% 36% 10% 15% 15%	3240
	21st to end	Day	32% 36% 11% 16% 5%	3236
November	1st to 10th	Day	30% 54% 6% 7% 2	1647
	11th to 20th	Day	27% 55% 9% 6% 2	1680
	21st to end	Day	31% 54% 5% 7% 2	1680
December	1st to 10th	Day	49% 37% 8% 5% 2	2412
	11th to 20th	Day	40% 32% 7% 13% 7%	2710
	21st to end	Day	55% 28% 5% 9% 2	3575
January	1st to 10th	Night	51% 23% 9% 9% 8%	8800
	11th to 20th	Night	53% 22% 6% 14% 5%	8850
	21st to end	Night	48% 23% 8% 15% 6%	9022
February	1st to 10th	Night	24% 59% 6% 6% 4	2730
	11th to 20th	Night	21% 59% 7% 10% 3	2664
	21st to end	Night	21% 59% 4 10% 5%	2249
March	1st to 10th	Night	34% 32% 12% 12% 8% 2	5221
	11th to 20th	Night	35% 32% 12% 13% 9%	5090
	21st to end	Night	42% 29% 4 15% 9%	5588
April	1st to 10th	Night	19% 60% 5% 9% 7% 1	2107
	11th to 20th	Night	20% 59% 3 10% 7% 1	1869
	21st to end	Night	20% 59% 4 13% 3 1	1890
May	1st to 10th	Night	25% 30% 7% 22% 16%	3732
	11th to 20th	Night	33% 30% 7% 16% 14%	3597
	21st to end	Night	27% 31% 6% 21% 13% 3	3513
June	1st to 10th	Night	14% 62% 8% 9% 6%	1400
	11th to 20th	Night	16% 63% 4 10% 7% 1	1400
	21st to end	Night	15% 62% 8% 12% 3	1400
July	1st to 10th	Night	25% 29% 19% 21% 4 1	3145
	11th to 20th	Night	21% 28% 18% 28% 5%	3138
	21st to end	Night	26% 28% 19% 24% 4	3443
August	1st to 10th	Night	22% 37% 13% 23% 4	2846
	11th to 20th	Night	21% 38% 18% 21% 2	2915
	21st to end	Night	26% 36% 16% 18% 4	3234
September	1st to 10th	Night	14% 58% 9% 14% 4	1975
	11th to 20th	Night	17% 59% 11% 10% 2	2123
	21st to end	Night	20% 57% 7% 10% 5%	2210
October	1st to 10th	Night	23% 36% 6% 26% 8%	3920
	11th to 20th	Night	26% 36% 10% 24% 4	3899
	21st to end	Night	35% 35% 6% 19% 5%	4543
November	1st to 10th	Night	27% 54% 8% 8% 2 1	2871
	11th to 20th	Night	26% 56% 9% 7% 3	2940
	21st to end	Night	31% 56% 6% 5% 3	2940
December	1st to 10th	Night	51% 35% 6% 7% 1	4984
	11th to 20th	Night	41% 32% 7% 9% 10%	5716
	21st to end	Night	53% 29% 6% 9% 3	7645

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	13% 12% 38% 26% 10% 2	330
	11th to 20th	Day	12% 9% 37% 34% 8%	330
	21st to end	Day	13% 10% 38% 27% 10% 1	363
February	1st to 10th	Day	15% 13% 40% 24% 8% 1	330
	11th to 20th	Day	8% 17% 38% 24% 9% 3	330
	21st to end	Day	11% 17% 43% 19% 8% 1	273
March	1st to 10th	Day	14% 13% 41% 24% 8% 1	330
	11th to 20th	Day	15% 16% 35% 21% 10% 3	330
	21st to end	Day	11% 17% 37% 26% 9% 1	363
April	1st to 10th	Day	15% 14% 35% 25% 11% 1	530
	11th to 20th	Day	18% 15% 30% 26% 9% 1	740
	21st to end	Day	20% 8% 33% 27% 11% 1	750
May	1st to 10th	Day	18% 11% 35% 26% 8% 2	709
	11th to 20th	Day	17% 13% 31% 26% 10% 3	725
	21st to end	Day	19% 8% 27% 31% 13% 2	789
June	1st to 10th	Day	14% 11% 29% 27% 15% 3	730
	11th to 20th	Day	14% 11% 36% 27% 12% 1	730
	21st to end	Day	16% 9% 29% 27% 14% 5%	730
July	1st to 10th	Day	10% 6% 28% 32% 19% 6%	721
	11th to 20th	Day	12% 9% 25% 31% 19% 4	718
	21st to end	Day	8% 6% 28% 34% 18% 6%	794
August	1st to 10th	Day	9% 7% 26% 33% 20% 6%	726
	11th to 20th	Day	11% 7% 24% 32% 19% 7%	715
	21st to end	Day	13% 8% 30% 26% 19% 3	803
September	1st to 10th	Day	12% 9% 34% 26% 17% 2	554
	11th to 20th	Day	19% 13% 34% 25% 9% 1	405
	21st to end	Day	20% 14% 34% 23% 7% 2	330
October	1st to 10th	Day	19% 16% 31% 24% 10% 1	330
	11th to 20th	Day	19% 17% 34% 27% 3	330
	21st to end	Day	24% 20% 31% 20% 4	363
November	1st to 10th	Day	22% 17% 33% 21% 7%	330
	11th to 20th	Day	19% 20% 35% 19% 6%	330
	21st to end	Day	19% 19% 35% 24% 2 1	330
December	1st to 10th	Day	18% 13% 36% 23% 8% 1	330
	11th to 20th	Day	18% 17% 43% 20% 2	330
	21st to end	Day	17% 10% 37% 23% 10% 3	363
January	1st to 10th	Night	12% 8% 35% 30% 12% 2	1050
	11th to 20th	Night	15% 7% 35% 33% 9% 1	1050
	21st to end	Night	15% 9% 37% 30% 8% 1	1155
February	1st to 10th	Night	13% 7% 35% 33% 10% 1	1050
	11th to 20th	Night	12% 8% 34% 31% 12% 3	1029
	21st to end	Night	11% 9% 37% 29% 12% 2	865
March	1st to 10th	Night	14% 10% 35% 28% 12% 1	725
	11th to 20th	Night	11% 10% 40% 31% 8% 1	630
	21st to end	Night	21% 8% 30% 26% 12% 3	693
April	1st to 10th	Night	17% 8% 31% 31% 11% 1	630
	11th to 20th	Night	20% 7% 30% 30% 13%	623
	21st to end	Night	19% 7% 28% 35% 11%	630
May	1st to 10th	Night	17% 7% 31% 33% 10% 1	603
	11th to 20th	Night	20% 7% 28% 32% 12% 1	591
	21st to end	Night	19% 4 28% 36% 13%	650
June	1st to 10th	Night	16% 7% 27% 34% 16% 1	600
	11th to 20th	Night	15% 6% 30% 36% 13% 1	600
	21st to end	Night	10% 5% 27% 36% 21% 1	600
July	1st to 10th	Night	7% 3 23% 41% 24% 3	585
	11th to 20th	Night	6% 5% 28% 38% 20% 2	582
	21st to end	Night	7% 4 22% 43% 21% 2	657
August	1st to 10th	Night	8% 4 20% 42% 24% 1	597
	11th to 20th	Night	13% 5% 22% 34% 24% 3	594
	21st to end	Night	12% 6% 25% 36% 21%	660
September	1st to 10th	Night	12% 6% 30% 35% 16% 2	600
	11th to 20th	Night	16% 7% 31% 30% 15% 1	600
	21st to end	Night	16% 7% 33% 29% 12% 2	610
October	1st to 10th	Night	18% 11% 35% 29% 6% 1	800
	11th to 20th	Night	22% 10% 34% 27% 7% 1	800
	21st to end	Night	23% 13% 30% 26% 7% 1	1020
November	1st to 10th	Night	19% 10% 37% 25% 8% 1	1025
	11th to 20th	Night	19% 11% 35% 27% 7% 1	1050
	21st to end	Night	18% 13% 41% 22% 6% 1	1050
December	1st to 10th	Night	14% 7% 37% 30% 10% 1	1050
	11th to 20th	Night	20% 11% 37% 25% 6% 1	1050
	21st to end	Night	19% 9% 32% 29% 10% 1	1155

Page generated at 2026-04-29 01:21:45. Version ac07

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