Oakmont Country Club
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oakmont Country Club clear sky chart from 2005-11-06 to 2026-02-01.

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	16% 10% 4 9% 5% 5% 5% 4 5% 7% 30%	127268
	Night	17% 11% 4 9% 5% 4 4 3 5% 6% 31%	124730
Transparency	Day	51% 6% 11% 21% 10% 1	130871
	Night	52% 5% 10% 20% 11% 2	129196
Seeing	Day	22% 14% 26% 21% 12% 5%	16237
	Night	21% 11% 26% 29% 12% 1	26009

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	17% 18% 8% 22% 5% 3 3 2 3 4 13%	4081
	11th to 20th	Day	12% 22% 9% 18% 10% 7% 2 2 2 3 13%	4150
	21st to end	Day	20% 19% 5% 12% 7% 6% 4 3 3 5% 16%	4565
February	1st to 10th	Day	20% 17% 6% 11% 7% 5% 4 3 3 4 21%	1800
	11th to 20th	Day	17% 14% 6% 13% 5% 4 5% 4 4 5% 21%	1753
	21st to end	Day	20% 14% 4 12% 6% 4 3 4 4 6% 24%	1651
March	1st to 10th	Day	17% 12% 5% 9% 5% 4 4 3 5% 5% 31%	4935
	11th to 20th	Day	13% 9% 5% 9% 6% 5% 4 3 5% 6% 35%	4980
	21st to end	Day	17% 11% 4 9% 5% 5% 4 4 5% 6% 30%	5465
April	1st to 10th	Day	17% 12% 3 9% 5% 5% 5% 4 5% 7% 29%	2316
	11th to 20th	Day	16% 10% 3 8% 5% 5% 5% 4 5% 6% 33%	2392
	21st to end	Day	20% 10% 3 7% 5% 4 4 3 5% 7% 33%	2600
May	1st to 10th	Day	21% 9% 3 8% 5% 5% 5% 4 6% 6% 27%	5862
	11th to 20th	Day	18% 8% 3 7% 5% 5% 5% 4 6% 9% 29%	5861
	21st to end	Day	19% 7% 2 7% 4 4 5% 4 7% 9% 32%	6862
June	1st to 10th	Day	13% 7% 3 7% 5% 5% 5% 5% 7% 9% 34%	2800
	11th to 20th	Day	14% 7% 3 8% 5% 5% 6% 4 7% 10% 33%	2800
	21st to end	Day	12% 6% 2 6% 6% 5% 5% 4 6% 10% 38%	2800
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 4 6% 8% 41%	6228
	11th to 20th	Day	11% 7% 3 8% 5% 5% 6% 5% 7% 10% 32%	5900
	21st to end	Day	12% 7% 2 8% 5% 4 5% 4 6% 8% 38%	6424
August	1st to 10th	Day	14% 8% 3 8% 5% 6% 6% 5% 7% 8% 30%	4234
	11th to 20th	Day	12% 6% 3 7% 5% 5% 5% 5% 7% 9% 35%	4174
	21st to end	Day	8% 5% 2 6% 5% 5% 6% 5% 8% 10% 40%	4426
September	1st to 10th	Day	15% 6% 2 5% 3 4 4 4 5% 7% 44%	2400
	11th to 20th	Day	12% 5% 2 6% 4 4 4 4 5% 7% 46%	2225
	21st to end	Day	20% 7% 3 7% 5% 5% 4 4 5% 7% 34%	2188
October	1st to 10th	Day	17% 6% 2 5% 5% 4 4 3 6% 8% 41%	2000
	11th to 20th	Day	18% 8% 3 7% 5% 5% 5% 3 6% 6% 34%	2000
	21st to end	Day	22% 10% 2 8% 4 4 4 3 5% 6% 33%	2200
November	1st to 10th	Day	12% 9% 3 7% 5% 4 4 3 5% 6% 41%	1989
	11th to 20th	Day	17% 14% 4 8% 5% 4 5% 3 5% 6% 30%	1729
	21st to end	Day	19% 15% 6% 9% 5% 5% 4 3 5% 5% 25%	1680
December	1st to 10th	Day	18% 14% 7% 18% 7% 5% 3 2 3 4 18%	2680
	11th to 20th	Day	23% 19% 6% 10% 4 3 3 2 4 5% 21%	3070
	21st to end	Day	23% 20% 6% 11% 5% 5% 4 3 5% 5% 14%	4048
January	1st to 10th	Night	15% 17% 7% 22% 6% 5% 4 3 4 4 15%	6066
	11th to 20th	Night	14% 17% 8% 16% 9% 6% 4 3 3 4 15%	6030
	21st to end	Night	22% 16% 5% 12% 7% 5% 5% 2 3 4 20%	6633
February	1st to 10th	Night	21% 13% 5% 11% 5% 5% 4 4 5% 4 24%	2601
	11th to 20th	Night	19% 13% 5% 12% 6% 4 5% 3 4 5% 24%	2533
	21st to end	Night	20% 13% 4 11% 6% 4 4 4 4 4 25%	1975
March	1st to 10th	Night	22% 11% 4 9% 5% 4 3 2 3 5% 32%	4918
	11th to 20th	Night	14% 11% 4 7% 3 3 4 3 5% 7% 40%	4980
	21st to end	Night	17% 10% 3 8% 5% 5% 4 3 4 5% 35%	5467
April	1st to 10th	Night	19% 13% 3 7% 5% 4 4 3 4 6% 33%	2082
	11th to 20th	Night	17% 8% 3 7% 5% 5% 4 4 6% 6% 37%	1974
	21st to end	Night	16% 9% 3 8% 5% 4 4 3 5% 7% 36%	1800
May	1st to 10th	Night	26% 11% 4 8% 4 4 4 4 5% 6% 25%	4033
	11th to 20th	Night	17% 10% 3 7% 5% 4 4 3 5% 8% 35%	4032
	21st to end	Night	19% 7% 3 6% 4 4 4 4 5% 9% 34%	3977
June	1st to 10th	Night	10% 6% 3 7% 5% 4 4 4 6% 9% 43%	1600
	11th to 20th	Night	12% 6% 2 8% 4 4 5% 5% 7% 8% 40%	1600
	21st to end	Night	11% 5% 2 5% 6% 4 4 6% 7% 10% 42%	1600
July	1st to 10th	Night	10% 8% 3 8% 5% 4 4 3 5% 8% 41%	3725
	11th to 20th	Night	12% 6% 3 8% 4 5% 5% 5% 7% 9% 35%	4057
	21st to end	Night	9% 7% 2 8% 5% 5% 5% 4 5% 8% 42%	4427
August	1st to 10th	Night	12% 9% 3 8% 5% 4 5% 4 7% 7% 35%	2915
	11th to 20th	Night	14% 7% 3 6% 4 4 4 3 5% 8% 42%	2875
	21st to end	Night	9% 5% 2 6% 4 5% 6% 4 7% 9% 44%	3438
September	1st to 10th	Night	12% 5% 1 5% 3 4 4 4 5% 7% 49%	2000
	11th to 20th	Night	9% 5% 2 5% 4 4 3 3 6% 8% 52%	2171
	21st to end	Night	16% 9% 3 7% 5% 4 4 3 5% 6% 39%	2211
October	1st to 10th	Night	14% 6% 2 6% 3 3 4 3 6% 7% 45%	2400
	11th to 20th	Night	18% 6% 2 6% 5% 5% 4 4 5% 6% 40%	2400
	21st to end	Night	22% 9% 2 6% 3 3 4 3 4 6% 38%	2640
November	1st to 10th	Night	13% 8% 3 7% 4 4 4 3 5% 6% 43%	2527
	11th to 20th	Night	19% 12% 3 8% 5% 4 4 4 5% 6% 31%	2888
	21st to end	Night	20% 15% 4 7% 4 3 4 3 5% 6% 28%	2940
December	1st to 10th	Night	19% 14% 10% 14% 5% 4 3 3 4 5% 18%	4720
	11th to 20th	Night	22% 16% 6% 10% 5% 4 3 3 3 5% 23%	5345
	21st to end	Night	23% 18% 5% 11% 6% 4 4 3 5% 5% 17%	7150

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	74% 5% 8% 9% 4	4082
	11th to 20th	Day	78% 2 6% 9% 3 1	4150
	21st to end	Day	72% 4 8% 12% 5%	4565
February	1st to 10th	Day	68% 3 8% 15% 6% 1	1800
	11th to 20th	Day	64% 5% 11% 15% 6%	1762
	21st to end	Day	61% 4 12% 15% 6% 1	1651
March	1st to 10th	Day	54% 5% 11% 22% 8% 1	4935
	11th to 20th	Day	48% 5% 12% 25% 8% 2	4980
	21st to end	Day	53% 5% 9% 20% 12% 1	5465
April	1st to 10th	Day	53% 6% 11% 18% 10% 2	2316
	11th to 20th	Day	49% 6% 12% 18% 13% 2	2392
	21st to end	Day	50% 6% 10% 23% 10% 2	2600
May	1st to 10th	Day	54% 6% 12% 19% 7% 2	5897
	11th to 20th	Day	49% 7% 13% 22% 9% 1	5865
	21st to end	Day	45% 8% 14% 22% 9% 2	6877
June	1st to 10th	Day	43% 8% 15% 22% 11% 1	2800
	11th to 20th	Day	45% 7% 15% 21% 12% 1	2800
	21st to end	Day	41% 7% 13% 25% 12% 1	2800
July	1st to 10th	Day	40% 6% 9% 27% 16% 2	6160
	11th to 20th	Day	44% 8% 13% 24% 11%	5831
	21st to end	Day	42% 7% 9% 22% 19% 1	6240
August	1st to 10th	Day	49% 8% 14% 21% 9%	4221
	11th to 20th	Day	42% 7% 12% 27% 12% 1	4213
	21st to end	Day	36% 8% 12% 28% 14% 2	4426
September	1st to 10th	Day	38% 6% 11% 22% 20% 3	2400
	11th to 20th	Day	35% 6% 13% 29% 16% 1	2225
	21st to end	Day	49% 5% 11% 21% 13%	2188
October	1st to 10th	Day	33% 4 10% 32% 20% 1	3260
	11th to 20th	Day	43% 6% 10% 22% 14% 5%	3240
	21st to end	Day	37% 4 12% 28% 18% 1	3538
November	1st to 10th	Day	43% 5% 12% 22% 16% 2	1989
	11th to 20th	Day	54% 4 11% 19% 10% 2	1729
	21st to end	Day	60% 5% 12% 17% 5% 1	1680
December	1st to 10th	Day	71% 4 12% 11% 3	2680
	11th to 20th	Day	67% 3 12% 14% 4	3066
	21st to end	Day	73% 4 9% 11% 4	4048
January	1st to 10th	Night	73% 4 8% 11% 4	6066
	11th to 20th	Night	73% 4 8% 11% 3 1	6030
	21st to end	Night	70% 4 8% 12% 5% 1	6633
February	1st to 10th	Night	63% 4 10% 17% 6%	2601
	11th to 20th	Night	61% 4 11% 17% 7%	2535
	21st to end	Night	61% 4 9% 15% 9% 1	1975
March	1st to 10th	Night	56% 3 9% 23% 8% 1	4918
	11th to 20th	Night	43% 4 13% 28% 9% 3	4980
	21st to end	Night	50% 5% 9% 19% 15% 1	5467
April	1st to 10th	Night	52% 4 10% 19% 13% 2	2082
	11th to 20th	Night	46% 6% 11% 19% 15% 3	1974
	21st to end	Night	46% 5% 10% 25% 12% 3	1800
May	1st to 10th	Night	59% 6% 9% 14% 9% 3	4060
	11th to 20th	Night	47% 6% 10% 25% 11% 1	4033
	21st to end	Night	45% 7% 13% 22% 10% 3	3984
June	1st to 10th	Night	36% 9% 12% 25% 16% 2	1600
	11th to 20th	Night	40% 8% 14% 23% 14% 2	1600
	21st to end	Night	35% 9% 14% 24% 17% 2	1600
July	1st to 10th	Night	42% 6% 8% 24% 18% 2	3685
	11th to 20th	Night	42% 8% 17% 21% 11% 1	4006
	21st to end	Night	38% 7% 10% 19% 23% 2	4297
August	1st to 10th	Night	45% 8% 13% 22% 10% 1	2904
	11th to 20th	Night	40% 6% 10% 28% 15% 1	2902
	21st to end	Night	35% 7% 12% 31% 13% 2	3438
September	1st to 10th	Night	33% 7% 11% 24% 21% 4	2000
	11th to 20th	Night	31% 6% 13% 28% 22% 1	2171
	21st to end	Night	46% 4 11% 21% 16% 1	2211
October	1st to 10th	Night	35% 5% 8% 27% 23% 2	3920
	11th to 20th	Night	38% 4 10% 25% 15% 7%	3899
	21st to end	Night	35% 3 9% 29% 22% 2	4252
November	1st to 10th	Night	41% 5% 11% 22% 18% 3	2527
	11th to 20th	Night	53% 4 10% 20% 10% 2	2888
	21st to end	Night	57% 5% 10% 21% 6% 1	2940
December	1st to 10th	Night	68% 4 10% 14% 3	4720
	11th to 20th	Night	65% 3 14% 15% 3	5348
	21st to end	Night	69% 5% 10% 13% 2	7150

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	28% 25% 27% 14% 5% 2	316
	11th to 20th	Day	32% 30% 27% 9% 2 1	330
	21st to end	Day	27% 25% 31% 12% 4 1	363
February	1st to 10th	Day	32% 23% 32% 11% 2	300
	11th to 20th	Day	32% 28% 30% 10% 1	300
	21st to end	Day	31% 23% 34% 10% 2	293
March	1st to 10th	Day	26% 22% 30% 18% 4	500
	11th to 20th	Day	30% 19% 32% 12% 5% 1	500
	21st to end	Day	30% 19% 28% 17% 5% 1	550
April	1st to 10th	Day	29% 19% 24% 19% 7% 2	500
	11th to 20th	Day	22% 21% 28% 17% 8% 4	492
	21st to end	Day	27% 16% 28% 19% 8% 2	500
May	1st to 10th	Day	29% 14% 26% 19% 10% 3	503
	11th to 20th	Day	21% 13% 29% 20% 12% 6%	527
	21st to end	Day	17% 9% 24% 25% 19% 6%	573
June	1st to 10th	Day	15% 10% 28% 26% 16% 5%	530
	11th to 20th	Day	17% 10% 25% 26% 18% 4	530
	21st to end	Day	12% 9% 28% 29% 17% 5%	530
July	1st to 10th	Day	13% 6% 20% 30% 20% 12%	525
	11th to 20th	Day	12% 6% 25% 29% 20% 8%	524
	21st to end	Day	14% 6% 20% 33% 21% 7%	576
August	1st to 10th	Day	13% 5% 21% 29% 22% 9%	526
	11th to 20th	Day	14% 7% 19% 27% 22% 10%	519
	21st to end	Day	10% 5% 23% 27% 23% 11%	583
September	1st to 10th	Day	17% 7% 20% 27% 20% 10%	530
	11th to 20th	Day	12% 2 17% 30% 25% 13%	530
	21st to end	Day	26% 9% 21% 23% 15% 6%	530
October	1st to 10th	Day	17% 7% 25% 25% 20% 5%	530
	11th to 20th	Day	21% 16% 28% 23% 9% 2	530
	21st to end	Day	28% 15% 30% 18% 8% 1	583
November	1st to 10th	Day	19% 18% 30% 21% 10% 2	467
	11th to 20th	Day	33% 17% 29% 14% 5% 1	245
	21st to end	Day	27% 21% 39% 10% 2	220
December	1st to 10th	Day	31% 24% 30% 10% 4 1	220
	11th to 20th	Day	34% 16% 35% 11% 4	220
	21st to end	Day	32% 21% 30% 14% 4	242
January	1st to 10th	Night	26% 21% 31% 18% 4	840
	11th to 20th	Night	30% 16% 32% 19% 3	840
	21st to end	Night	27% 18% 30% 22% 3	924
February	1st to 10th	Night	27% 16% 27% 27% 2	801
	11th to 20th	Night	27% 18% 36% 18% 1	783
	21st to end	Night	28% 14% 35% 21% 2	660
March	1st to 10th	Night	24% 16% 32% 25% 4	800
	11th to 20th	Night	26% 17% 28% 22% 6% 1	800
	21st to end	Night	23% 14% 34% 23% 5% 1	880
April	1st to 10th	Night	26% 15% 31% 23% 6%	800
	11th to 20th	Night	23% 11% 31% 25% 9%	790
	21st to end	Night	18% 10% 33% 33% 6%	600
May	1st to 10th	Night	22% 10% 23% 34% 10% 1	600
	11th to 20th	Night	21% 8% 26% 33% 12%	591
	21st to end	Night	12% 3 22% 36% 23% 3	465
June	1st to 10th	Night	11% 6% 21% 45% 17% 1	400
	11th to 20th	Night	13% 6% 22% 40% 19% 1	400
	21st to end	Night	11% 3 28% 36% 20% 2	400
July	1st to 10th	Night	8% 3 19% 43% 21% 5%	437
	11th to 20th	Night	12% 2 20% 33% 29% 5%	582
	21st to end	Night	10% 3 15% 42% 28% 2	657
August	1st to 10th	Night	8% 4 15% 42% 28% 2	597
	11th to 20th	Night	12% 3 13% 39% 29% 4	594
	21st to end	Night	12% 3 18% 35% 27% 5%	784
September	1st to 10th	Night	13% 4 19% 35% 26% 3	800
	11th to 20th	Night	11% 4 14% 36% 30% 4	800
	21st to end	Night	19% 7% 22% 28% 21% 3	800
October	1st to 10th	Night	16% 7% 21% 30% 24% 2	800
	11th to 20th	Night	21% 8% 30% 31% 10% 1	800
	21st to end	Night	26% 11% 25% 29% 8% 1	880
November	1st to 10th	Night	17% 11% 26% 33% 12%	820
	11th to 20th	Night	25% 14% 29% 24% 7% 1	840
	21st to end	Night	28% 13% 29% 24% 6%	840
December	1st to 10th	Night	30% 16% 28% 20% 5%	840
	11th to 20th	Night	27% 17% 30% 22% 4	840
	21st to end	Night	29% 14% 30% 25% 2	924

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

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