Oakdale
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oakdale clear sky chart from 2005-11-06 to 2025-11-18.

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	15% 10% 4 8% 5% 5% 5% 4 6% 7% 33%	126730
	Night	15% 11% 4 8% 5% 4 4 3 5% 6% 34%	123685
Transparency	Day	48% 5% 12% 21% 12% 1	130328
	Night	49% 5% 11% 21% 12% 1	128156
Seeing	Day	18% 10% 28% 24% 14% 5%	16537
	Night	19% 9% 28% 30% 12% 1	25901

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	13% 16% 8% 16% 6% 4 4 3 5% 5% 21%	3617
	11th to 20th	Day	14% 19% 7% 18% 8% 8% 6% 3 3 4 10%	3909
	21st to end	Day	22% 17% 7% 12% 6% 4 4 3 4 5% 16%	4466
February	1st to 10th	Day	16% 15% 5% 13% 7% 6% 5% 3 4 6% 20%	1800
	11th to 20th	Day	14% 14% 6% 12% 7% 5% 4 4 6% 5% 23%	1808
	21st to end	Day	16% 15% 4 11% 7% 5% 4 3 4 5% 24%	1650
March	1st to 10th	Day	17% 13% 6% 10% 6% 4 4 3 4 5% 28%	4743
	11th to 20th	Day	13% 12% 4 9% 5% 4 4 3 5% 6% 34%	4980
	21st to end	Day	19% 14% 5% 9% 5% 4 4 3 5% 5% 27%	5465
April	1st to 10th	Day	16% 12% 3 7% 5% 5% 4 4 5% 7% 30%	2264
	11th to 20th	Day	18% 11% 3 6% 4 4 5% 4 6% 7% 33%	2572
	21st to end	Day	19% 10% 3 7% 4 4 4 4 5% 7% 33%	2600
May	1st to 10th	Day	19% 9% 3 7% 4 4 4 3 5% 7% 35%	5862
	11th to 20th	Day	17% 8% 2 7% 4 5% 5% 4 6% 8% 34%	5861
	21st to end	Day	16% 6% 2 7% 4 4 4 4 5% 7% 39%	6698
June	1st to 10th	Day	11% 6% 3 7% 5% 5% 4 5% 6% 8% 40%	2852
	11th to 20th	Day	10% 6% 2 6% 5% 5% 5% 5% 6% 8% 41%	3000
	21st to end	Day	11% 6% 2 6% 4 4 5% 5% 8% 9% 40%	3000
July	1st to 10th	Day	9% 5% 2 7% 4 5% 5% 4 7% 10% 41%	6553
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 4 6% 10% 44%	6181
	21st to end	Day	8% 5% 2 6% 4 5% 4 4 7% 10% 44%	6424
August	1st to 10th	Day	12% 5% 2 5% 5% 5% 6% 4 7% 9% 39%	4234
	11th to 20th	Day	9% 6% 2 7% 4 6% 6% 6% 8% 10% 36%	4174
	21st to end	Day	9% 6% 2 7% 5% 5% 5% 5% 6% 9% 42%	4675
September	1st to 10th	Day	11% 6% 2 6% 4 5% 6% 5% 6% 9% 42%	2280
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 4 6% 9% 47%	2200
	21st to end	Day	16% 8% 2 7% 4 4 5% 4 6% 8% 36%	2200
October	1st to 10th	Day	13% 7% 3 6% 4 4 5% 4 6% 7% 41%	2080
	11th to 20th	Day	18% 8% 3 7% 5% 6% 4 3 5% 7% 34%	2000
	21st to end	Day	21% 10% 3 8% 5% 5% 4 3 5% 7% 29%	2120
November	1st to 10th	Day	14% 10% 4 8% 6% 4 5% 3 5% 7% 34%	1852
	11th to 20th	Day	15% 13% 5% 8% 4 4 5% 5% 5% 7% 29%	1788
	21st to end	Day	20% 13% 5% 10% 7% 4 5% 4 5% 6% 22%	1600
December	1st to 10th	Day	17% 13% 5% 11% 5% 5% 4 3 5% 8% 23%	2600
	11th to 20th	Day	22% 18% 5% 9% 5% 4 3 3 5% 6% 19%	2990
	21st to end	Day	27% 20% 6% 12% 5% 4 4 2 4 4 12%	3632
January	1st to 10th	Night	14% 14% 5% 12% 5% 5% 4 3 5% 6% 27%	6348
	11th to 20th	Night	12% 19% 7% 16% 8% 7% 8% 3 4 4 13%	6039
	21st to end	Night	19% 17% 7% 9% 5% 4 4 3 4 4 23%	6490
February	1st to 10th	Night	16% 16% 5% 11% 7% 5% 5% 3 5% 5% 22%	2600
	11th to 20th	Night	16% 15% 5% 9% 6% 4 5% 3 5% 6% 27%	2477
	21st to end	Night	19% 11% 5% 10% 6% 4 5% 4 4 5% 26%	1980
March	1st to 10th	Night	16% 13% 4 8% 5% 4 4 3 4 6% 33%	5109
	11th to 20th	Night	10% 8% 3 7% 6% 5% 5% 4 6% 8% 39%	4980
	21st to end	Night	16% 11% 4 8% 4 4 4 3 4 4 37%	5467
April	1st to 10th	Night	17% 11% 3 7% 5% 4 4 4 5% 5% 34%	2151
	11th to 20th	Night	17% 8% 3 6% 5% 4 4 3 5% 8% 37%	1777
	21st to end	Night	16% 10% 3 6% 4 5% 4 3 5% 7% 37%	1800
May	1st to 10th	Night	20% 9% 3 7% 5% 4 4 3 5% 6% 34%	4033
	11th to 20th	Night	13% 9% 3 8% 5% 5% 4 4 6% 7% 37%	4032
	21st to end	Night	16% 9% 2 4 4 4 5% 3 5% 6% 43%	4152
June	1st to 10th	Night	11% 5% 3 5% 4 4 5% 3 6% 8% 46%	1542
	11th to 20th	Night	9% 5% 2 6% 4 4 5% 4 7% 9% 45%	1400
	21st to end	Night	9% 5% 2 6% 4 3 5% 3 5% 8% 49%	1400
July	1st to 10th	Night	7% 4 2 7% 4 5% 5% 4 6% 11% 46%	3420
	11th to 20th	Night	9% 4 2 6% 4 4 4 4 7% 9% 46%	3785
	21st to end	Night	8% 4 2 5% 4 4 4 4 7% 8% 51%	4427
August	1st to 10th	Night	11% 6% 3 5% 4 4 4 3 5% 8% 46%	2915
	11th to 20th	Night	9% 7% 2 6% 4 4 4 3 6% 6% 49%	2875
	21st to end	Night	8% 5% 2 6% 4 4 5% 4 6% 7% 49%	3223
September	1st to 10th	Night	9% 7% 2 6% 4 4 4 3 5% 7% 49%	2097
	11th to 20th	Night	8% 5% 2 5% 3 3 3 3 5% 7% 56%	2200
	21st to end	Night	15% 7% 2 8% 5% 4 4 3 5% 6% 41%	2200
October	1st to 10th	Night	12% 7% 3 6% 4 4 3 3 5% 6% 47%	2320
	11th to 20th	Night	20% 9% 3 7% 4 4 3 3 5% 5% 38%	2400
	21st to end	Night	21% 8% 3 7% 5% 4 4 3 5% 6% 32%	2716
November	1st to 10th	Night	13% 9% 3 6% 5% 4 4 3 6% 7% 40%	2666
	11th to 20th	Night	16% 11% 3 8% 5% 5% 4 3 6% 7% 31%	2763
	21st to end	Night	21% 14% 3 8% 4 4 4 3 6% 6% 28%	2800
December	1st to 10th	Night	15% 15% 5% 11% 5% 5% 5% 4 6% 7% 22%	4580
	11th to 20th	Night	17% 19% 5% 10% 5% 4 4 3 4 5% 23%	5205
	21st to end	Night	24% 20% 6% 11% 5% 5% 4 3 4 5% 13%	7316

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	63% 6% 10% 13% 8% 1	3618
	11th to 20th	Day	76% 7% 6% 7% 4	3909
	21st to end	Day	70% 5% 10% 9% 6%	4466
February	1st to 10th	Day	65% 6% 10% 14% 6%	1800
	11th to 20th	Day	62% 5% 10% 15% 8% 1	1817
	21st to end	Day	62% 4 11% 15% 6% 1	1650
March	1st to 10th	Day	58% 4 13% 17% 7%	4743
	11th to 20th	Day	50% 4 16% 21% 7% 1	4980
	21st to end	Day	58% 5% 11% 16% 8% 1	5465
April	1st to 10th	Day	51% 5% 12% 20% 11% 1	2264
	11th to 20th	Day	49% 5% 11% 20% 13% 2	2572
	21st to end	Day	50% 5% 13% 18% 13% 2	2600
May	1st to 10th	Day	49% 5% 11% 20% 12% 4	5897
	11th to 20th	Day	46% 8% 13% 21% 11% 1	5865
	21st to end	Day	44% 5% 10% 19% 16% 6%	6713
June	1st to 10th	Day	40% 5% 13% 27% 13% 2	2852
	11th to 20th	Day	37% 6% 15% 23% 16% 2	3000
	21st to end	Day	36% 7% 14% 25% 17% 1	3000
July	1st to 10th	Day	37% 5% 11% 28% 16% 2	6484
	11th to 20th	Day	34% 5% 13% 29% 17% 1	6106
	21st to end	Day	34% 5% 15% 24% 20% 1	6240
August	1st to 10th	Day	39% 6% 15% 24% 15% 1	4221
	11th to 20th	Day	38% 8% 13% 32% 8% 1	4213
	21st to end	Day	37% 6% 13% 31% 12% 1	4674
September	1st to 10th	Day	38% 7% 14% 26% 13% 1	2280
	11th to 20th	Day	33% 6% 12% 33% 16% 1	2200
	21st to end	Day	45% 5% 13% 24% 12% 1	2200
October	1st to 10th	Day	33% 5% 12% 29% 19% 1	3392
	11th to 20th	Day	43% 3 10% 25% 17%	3240
	21st to end	Day	45% 5% 14% 24% 11%	3409
November	1st to 10th	Day	49% 6% 11% 23% 9% 2	1852
	11th to 20th	Day	52% 5% 15% 18% 9% 1	1788
	21st to end	Day	63% 5% 12% 16% 5%	1600
December	1st to 10th	Day	59% 4 18% 14% 4	2600
	11th to 20th	Day	67% 3 12% 10% 7%	2986
	21st to end	Day	77% 4 7% 8% 3	3632
January	1st to 10th	Night	57% 4 10% 20% 7% 2	6348
	11th to 20th	Night	70% 9% 8% 9% 4	6039
	21st to end	Night	64% 4 8% 15% 8%	6490
February	1st to 10th	Night	63% 6% 10% 15% 6% 1	2600
	11th to 20th	Night	58% 4 11% 17% 10% 1	2479
	21st to end	Night	58% 4 10% 19% 8% 1	1980
March	1st to 10th	Night	52% 4 13% 20% 10% 1	5109
	11th to 20th	Night	42% 5% 15% 25% 12% 1	4980
	21st to end	Night	50% 4 10% 20% 15% 1	5467
April	1st to 10th	Night	51% 5% 10% 19% 13% 2	2151
	11th to 20th	Night	46% 5% 10% 21% 17% 1	1777
	21st to end	Night	47% 5% 9% 20% 15% 4	1800
May	1st to 10th	Night	51% 4 10% 15% 13% 7%	4060
	11th to 20th	Night	45% 6% 12% 23% 11% 2	4033
	21st to end	Night	41% 5% 11% 22% 16% 4	4159
June	1st to 10th	Night	35% 6% 11% 27% 19% 2	1542
	11th to 20th	Night	35% 6% 14% 24% 19% 2	1400
	21st to end	Night	34% 6% 12% 27% 20% 1	1400
July	1st to 10th	Night	34% 5% 14% 27% 16% 4	3382
	11th to 20th	Night	33% 4 14% 29% 18% 1	3740
	21st to end	Night	30% 6% 13% 22% 26% 2	4297
August	1st to 10th	Night	36% 4 15% 26% 17% 2	2904
	11th to 20th	Night	34% 5% 13% 31% 15% 1	2902
	21st to end	Night	34% 5% 11% 32% 17% 1	3223
September	1st to 10th	Night	35% 6% 12% 28% 16% 2	2097
	11th to 20th	Night	27% 6% 13% 33% 20% 2	2200
	21st to end	Night	43% 5% 11% 26% 14% 1	2200
October	1st to 10th	Night	29% 4 8% 30% 27% 1	3788
	11th to 20th	Night	47% 3 10% 21% 18%	3899
	21st to end	Night	42% 4 13% 27% 13% 1	4377
November	1st to 10th	Night	43% 6% 10% 26% 14% 1	2666
	11th to 20th	Night	52% 5% 12% 20% 10% 1	2763
	21st to end	Night	57% 4 15% 18% 6% 1	2800
December	1st to 10th	Night	61% 4 18% 14% 3	4580
	11th to 20th	Night	63% 5% 11% 14% 7% 1	5208
	21st to end	Night	74% 4 10% 9% 3	7316

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	21% 20% 36% 14% 8% 1	300
	11th to 20th	Day	24% 16% 42% 13% 4 1	300
	21st to end	Day	29% 14% 33% 18% 4 1	330
February	1st to 10th	Day	25% 20% 38% 13% 3 1	300
	11th to 20th	Day	25% 20% 34% 19% 1	300
	21st to end	Day	27% 22% 35% 14% 2	249
March	1st to 10th	Day	25% 16% 35% 19% 4 1	407
	11th to 20th	Day	21% 15% 33% 24% 6% 1	500
	21st to end	Day	28% 13% 30% 22% 5% 1	550
April	1st to 10th	Day	20% 15% 34% 22% 8%	500
	11th to 20th	Day	27% 14% 27% 18% 9% 5%	492
	21st to end	Day	24% 12% 30% 23% 9% 2	500
May	1st to 10th	Day	22% 11% 29% 25% 10% 3	503
	11th to 20th	Day	19% 8% 28% 26% 13% 6%	527
	21st to end	Day	17% 7% 23% 27% 19% 8%	573
June	1st to 10th	Day	12% 9% 30% 29% 17% 4	582
	11th to 20th	Day	12% 7% 31% 33% 14% 4	730
	21st to end	Day	12% 7% 28% 33% 15% 4	730
July	1st to 10th	Day	9% 4 24% 30% 23% 10%	721
	11th to 20th	Day	11% 5% 26% 29% 20% 9%	643
	21st to end	Day	9% 3 21% 28% 26% 11%	576
August	1st to 10th	Day	9% 4 19% 27% 26% 14%	526
	11th to 20th	Day	12% 5% 15% 32% 22% 14%	519
	21st to end	Day	12% 5% 19% 28% 27% 10%	583
September	1st to 10th	Day	12% 5% 22% 26% 22% 13%	530
	11th to 20th	Day	8% 2 16% 25% 32% 16%	530
	21st to end	Day	17% 11% 20% 25% 18% 9%	530
October	1st to 10th	Day	17% 7% 23% 25% 20% 8%	530
	11th to 20th	Day	19% 12% 30% 27% 9% 3	530
	21st to end	Day	25% 11% 38% 18% 6% 1	503
November	1st to 10th	Day	17% 17% 37% 19% 7% 2	330
	11th to 20th	Day	28% 14% 31% 18% 8% 1	283
	21st to end	Day	23% 18% 40% 15% 5% 1	200
December	1st to 10th	Day	25% 15% 34% 17% 9% 1	200
	11th to 20th	Day	30% 19% 33% 17% 2	200
	21st to end	Day	34% 15% 29% 18% 3	230
January	1st to 10th	Night	24% 14% 38% 18% 6% 1	1000
	11th to 20th	Night	30% 12% 33% 22% 3	861
	21st to end	Night	24% 10% 32% 27% 6%	880
February	1st to 10th	Night	24% 14% 35% 24% 4	800
	11th to 20th	Night	24% 14% 31% 25% 6%	783
	21st to end	Night	25% 13% 38% 21% 3	660
March	1st to 10th	Night	21% 12% 35% 27% 6%	800
	11th to 20th	Night	18% 13% 39% 24% 7% 1	800
	21st to end	Night	22% 12% 31% 27% 8%	880
April	1st to 10th	Night	22% 15% 32% 27% 4 1	784
	11th to 20th	Night	22% 9% 32% 25% 10% 1	593
	21st to end	Night	21% 7% 34% 30% 7% 1	600
May	1st to 10th	Night	19% 7% 30% 33% 11% 1	600
	11th to 20th	Night	16% 6% 28% 36% 14% 1	591
	21st to end	Night	13% 3 24% 42% 17% 1	536
June	1st to 10th	Night	13% 2 29% 42% 14%	400
	11th to 20th	Night	11% 4 23% 48% 14% 1	400
	21st to end	Night	11% 5% 25% 42% 17% 1	400
July	1st to 10th	Night	7% 2 16% 45% 27% 3	491
	11th to 20th	Night	9% 2 19% 41% 25% 4	582
	21st to end	Night	9% 2 15% 46% 26% 2	657
August	1st to 10th	Night	7% 2 13% 42% 32% 4	597
	11th to 20th	Night	8% 1 14% 40% 32% 5%	594
	21st to end	Night	11% 2 15% 39% 30% 3	660
September	1st to 10th	Night	11% 4 19% 35% 26% 5%	780
	11th to 20th	Night	9% 4 16% 35% 31% 6%	800
	21st to end	Night	16% 7% 18% 37% 18% 5%	800
October	1st to 10th	Night	14% 7% 25% 33% 19% 3	800
	11th to 20th	Night	23% 8% 28% 29% 11% 2	800
	21st to end	Night	24% 11% 30% 30% 5%	880
November	1st to 10th	Night	19% 11% 29% 28% 13% 1	820
	11th to 20th	Night	22% 14% 34% 22% 6% 1	829
	21st to end	Night	28% 12% 31% 22% 7%	800
December	1st to 10th	Night	27% 12% 34% 20% 7%	800
	11th to 20th	Night	23% 15% 36% 22% 4	800
	21st to end	Night	32% 11% 30% 23% 3	1043

Page generated at 2025-11-15 00:55:57. Version ac07

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