Auburn
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Auburn clear sky chart from 2005-11-06 to 2024-04-03.

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	21% 9% 4 7% 6% 3 5% 5% 5% 6% 29%	79118
	Night	23% 9% 4 7% 6% 3 4 4 5% 6% 28%	80820
Transparency	Day	55% 8% 13% 15% 7% 1	78838
	Night	57% 8% 12% 14% 7% 1	80680
Seeing	Day	24% 10% 20% 25% 17% 4	14157
	Night	28% 8% 17% 26% 18% 2	22700

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	36% 15% 4 9% 6% 3 4 4 4 4 10%	2450
	11th to 20th	Day	24% 11% 5% 8% 6% 3 4 4 4 7% 23%	2516
	21st to end	Day	40% 12% 5% 8% 6% 3 4 3 4 4 11%	2890
February	1st to 10th	Day	31% 12% 4 8% 7% 3 4 3 5% 8% 17%	1710
	11th to 20th	Day	32% 12% 4 7% 6% 3 4 4 4 6% 19%	1665
	21st to end	Day	27% 13% 5% 9% 7% 4 5% 3 4 4 19%	1484
March	1st to 10th	Day	23% 13% 4 8% 7% 4 5% 5% 5% 6% 19%	1943
	11th to 20th	Day	30% 11% 4 6% 6% 3 5% 6% 4 6% 20%	2090
	21st to end	Day	25% 13% 5% 8% 7% 4 7% 6% 5% 6% 14%	2376
April	1st to 10th	Day	25% 10% 4 8% 7% 4 6% 6% 5% 7% 17%	2185
	11th to 20th	Day	23% 9% 4 8% 7% 4 5% 5% 5% 6% 23%	2141
	21st to end	Day	19% 11% 4 9% 8% 4 6% 5% 5% 6% 22%	2376
May	1st to 10th	Day	16% 10% 3 7% 6% 4 6% 6% 5% 7% 31%	2520
	11th to 20th	Day	18% 8% 4 7% 6% 4 6% 6% 6% 8% 28%	2477
	21st to end	Day	23% 10% 4 8% 5% 4 6% 5% 5% 6% 24%	2723
June	1st to 10th	Day	20% 10% 3 7% 6% 4 5% 5% 5% 8% 26%	2520
	11th to 20th	Day	21% 10% 4 8% 7% 4 7% 5% 6% 7% 21%	2696
	21st to end	Day	12% 6% 3 6% 6% 3 6% 5% 6% 7% 39%	2700
July	1st to 10th	Day	10% 6% 3 5% 4 3 4 5% 4 5% 50%	2700
	11th to 20th	Day	10% 5% 3 5% 4 2 5% 4 5% 7% 51%	2545
	21st to end	Day	8% 4 2 3 3 2 3 3 5% 5% 62%	2741
August	1st to 10th	Day	9% 5% 2 4 4 2 3 4 5% 7% 54%	2459
	11th to 20th	Day	8% 4 2 4 4 2 4 4 5% 8% 56%	2298
	21st to end	Day	11% 6% 3 6% 6% 3 3 5% 5% 8% 45%	2460
September	1st to 10th	Day	10% 6% 2 5% 5% 3 3 4 5% 7% 50%	2160
	11th to 20th	Day	14% 7% 3 6% 7% 3 5% 4 6% 7% 38%	2160
	21st to end	Day	17% 8% 3 6% 5% 3 4 4 5% 7% 38%	1905
October	1st to 10th	Day	20% 8% 4 7% 5% 4 5% 5% 6% 7% 30%	1800
	11th to 20th	Day	25% 10% 3 6% 5% 4 5% 4 5% 7% 28%	1800
	21st to end	Day	30% 9% 3 8% 6% 3 5% 4 4 6% 24%	1874
November	1st to 10th	Day	32% 10% 4 7% 6% 2 5% 5% 4 6% 18%	1541
	11th to 20th	Day	30% 12% 3 7% 6% 3 4 4 3 6% 22%	1520
	21st to end	Day	30% 9% 4 8% 6% 3 5% 4 5% 6% 21%	1520
December	1st to 10th	Day	29% 9% 4 6% 6% 3 5% 4 4 6% 23%	1520
	11th to 20th	Day	32% 12% 3 6% 7% 4 5% 6% 6% 6% 13%	1925
	21st to end	Day	26% 14% 5% 10% 8% 4 5% 5% 4 5% 14%	2728
January	1st to 10th	Night	35% 15% 5% 8% 7% 4 5% 4 4 4 11%	4412
	11th to 20th	Night	27% 11% 4 6% 5% 3 3 4 4 7% 25%	4382
	21st to end	Night	37% 11% 4 7% 6% 4 5% 4 4 5% 14%	4768
February	1st to 10th	Night	31% 12% 4 7% 7% 4 4 4 4 6% 18%	2470
	11th to 20th	Night	27% 12% 3 7% 7% 3 5% 4 4 5% 23%	2402
	21st to end	Night	28% 11% 4 7% 6% 3 5% 5% 5% 6% 21%	1970
March	1st to 10th	Night	24% 11% 4 6% 6% 3 5% 6% 6% 6% 23%	2234
	11th to 20th	Night	26% 9% 4 7% 6% 3 4 4 5% 6% 25%	2089
	21st to end	Night	26% 13% 5% 8% 7% 4 6% 5% 5% 5% 16%	2221
April	1st to 10th	Night	22% 10% 4 8% 6% 3 6% 7% 5% 7% 21%	1820
	11th to 20th	Night	19% 9% 4 8% 6% 4 6% 5% 6% 6% 28%	1766
	21st to end	Night	19% 10% 4 7% 7% 4 5% 5% 6% 8% 25%	1584
May	1st to 10th	Night	16% 8% 4 8% 6% 4 4 5% 6% 6% 32%	1440
	11th to 20th	Night	15% 6% 4 6% 7% 3 6% 6% 7% 8% 31%	1416
	21st to end	Night	16% 7% 4 8% 8% 4 4 6% 6% 6% 31%	1552
June	1st to 10th	Night	15% 7% 5% 7% 8% 4 5% 5% 5% 6% 32%	1440
	11th to 20th	Night	17% 8% 4 7% 7% 3 5% 7% 6% 8% 28%	1260
	21st to end	Night	10% 6% 4 6% 4 2 4 4 5% 6% 47%	1260
July	1st to 10th	Night	7% 6% 3 5% 5% 2 5% 4 6% 6% 53%	1260
	11th to 20th	Night	6% 6% 2 4 4 1 4 4 4 5% 59%	1412
	21st to end	Night	5% 2 1 3 2 2 3 3 5% 6% 68%	1576
August	1st to 10th	Night	5% 4 1 4 4 3 3 4 5% 7% 59%	1476
	11th to 20th	Night	6% 3 2 3 4 2 3 4 4 6% 64%	1602
	21st to end	Night	9% 5% 3 4 5% 3 3 4 5% 6% 54%	1895
September	1st to 10th	Night	9% 5% 2 4 4 2 3 5% 5% 6% 55%	1800
	11th to 20th	Night	14% 7% 2 5% 5% 3 5% 4 5% 5% 44%	1800
	21st to end	Night	15% 6% 3 6% 5% 3 4 4 5% 6% 42%	2052
October	1st to 10th	Night	19% 6% 3 7% 6% 4 4 4 5% 6% 36%	2160
	11th to 20th	Night	23% 8% 3 6% 5% 3 5% 4 5% 5% 32%	2160
	21st to end	Night	27% 8% 2 6% 5% 2 4 4 5% 7% 30%	2481
November	1st to 10th	Night	32% 8% 3 7% 6% 3 4 4 6% 5% 21%	2536
	11th to 20th	Night	30% 10% 3 6% 6% 3 5% 4 4 5% 23%	2660
	21st to end	Night	29% 10% 4 7% 6% 3 5% 4 5% 7% 22%	2660
December	1st to 10th	Night	28% 11% 4 6% 6% 3 4 5% 4 5% 24%	2660
	11th to 20th	Night	29% 13% 4 8% 7% 3 5% 5% 5% 6% 16%	3280
	21st to end	Night	28% 13% 5% 10% 8% 4 5% 4 5% 5% 14%	4864

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	77% 7% 7% 6% 2 1	2450
	11th to 20th	Day	61% 8% 13% 12% 5% 1	2540
	21st to end	Day	76% 7% 7% 7% 2	2890
February	1st to 10th	Day	68% 9% 10% 9% 4 1	1710
	11th to 20th	Day	68% 8% 8% 10% 5% 1	1674
	21st to end	Day	68% 6% 12% 10% 4	1484
March	1st to 10th	Day	65% 8% 12% 12% 2	1943
	11th to 20th	Day	66% 8% 9% 14% 3 1	2090
	21st to end	Day	72% 8% 11% 9%	2376
April	1st to 10th	Day	66% 8% 17% 8% 1	2185
	11th to 20th	Day	63% 7% 12% 13% 5% 1	2141
	21st to end	Day	64% 9% 12% 10% 4 1	2376
May	1st to 10th	Day	53% 9% 17% 15% 5%	2520
	11th to 20th	Day	54% 11% 18% 13% 4	2480
	21st to end	Day	61% 10% 14% 13% 2	2724
June	1st to 10th	Day	57% 9% 18% 11% 5%	2520
	11th to 20th	Day	63% 9% 15% 10% 3	2696
	21st to end	Day	43% 10% 18% 19% 8% 2	2700
July	1st to 10th	Day	37% 9% 14% 24% 13% 3	2626
	11th to 20th	Day	34% 6% 14% 28% 16% 1	2468
	21st to end	Day	24% 7% 12% 36% 18% 4	2589
August	1st to 10th	Day	32% 7% 16% 28% 14% 2	2442
	11th to 20th	Day	27% 8% 19% 29% 14% 3	2298
	21st to end	Day	39% 7% 14% 30% 9% 1	2460
September	1st to 10th	Day	33% 8% 16% 26% 13% 5%	2160
	11th to 20th	Day	43% 10% 13% 17% 14% 3	2160
	21st to end	Day	45% 8% 18% 16% 11% 2	1905
October	1st to 10th	Day	52% 10% 12% 20% 7% 1	1800
	11th to 20th	Day	54% 10% 15% 16% 5% 1	1800
	21st to end	Day	62% 7% 11% 12% 8%	1874
November	1st to 10th	Day	66% 7% 12% 10% 4	1541
	11th to 20th	Day	67% 8% 9% 9% 7% 1	1520
	21st to end	Day	65% 8% 8% 10% 8% 1	1520
December	1st to 10th	Day	62% 7% 9% 13% 8% 1	1520
	11th to 20th	Day	68% 11% 9% 9% 2 1	1928
	21st to end	Day	69% 10% 12% 7% 2	2728
January	1st to 10th	Night	76% 8% 7% 5% 2 1	4412
	11th to 20th	Night	58% 6% 12% 17% 5% 1	4420
	21st to end	Night	73% 8% 8% 7% 4 1	4768
February	1st to 10th	Night	68% 6% 12% 8% 5%	2470
	11th to 20th	Night	62% 10% 11% 9% 7% 1	2404
	21st to end	Night	64% 8% 12% 10% 5%	1970
March	1st to 10th	Night	60% 8% 13% 15% 4	2234
	11th to 20th	Night	60% 6% 12% 16% 4 1	2090
	21st to end	Night	68% 11% 12% 9% 1	2221
April	1st to 10th	Night	62% 11% 16% 10% 2	1820
	11th to 20th	Night	57% 8% 14% 14% 5% 1	1766
	21st to end	Night	61% 8% 14% 11% 5% 1	1584
May	1st to 10th	Night	51% 10% 16% 15% 8% 1	1440
	11th to 20th	Night	50% 12% 17% 14% 6% 1	1416
	21st to end	Night	55% 12% 16% 15% 3	1552
June	1st to 10th	Night	53% 9% 17% 15% 5%	1440
	11th to 20th	Night	56% 10% 20% 11% 3	1260
	21st to end	Night	39% 8% 23% 20% 9% 2	1260
July	1st to 10th	Night	33% 11% 15% 25% 13% 5%	1225
	11th to 20th	Night	30% 6% 13% 32% 17% 2	1366
	21st to end	Night	19% 7% 13% 35% 21% 5%	1488
August	1st to 10th	Night	26% 6% 15% 31% 19% 3	1468
	11th to 20th	Night	23% 8% 17% 32% 16% 4	1602
	21st to end	Night	33% 7% 16% 31% 13% 1	1895
September	1st to 10th	Night	30% 8% 16% 26% 15% 5%	1800
	11th to 20th	Night	44% 8% 11% 19% 14% 5%	1800
	21st to end	Night	43% 9% 13% 21% 11% 3	2052
October	1st to 10th	Night	48% 7% 15% 21% 7% 1	2160
	11th to 20th	Night	54% 7% 11% 19% 7% 1	2160
	21st to end	Night	55% 8% 12% 15% 10%	2481
November	1st to 10th	Night	64% 8% 12% 11% 4	2536
	11th to 20th	Night	65% 7% 11% 9% 6% 3	2660
	21st to end	Night	63% 9% 9% 10% 8% 1	2660
December	1st to 10th	Night	63% 6% 11% 12% 7% 1	2660
	11th to 20th	Night	67% 11% 11% 8% 3	3276
	21st to end	Night	69% 11% 11% 7% 2	4864

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	36% 14% 18% 14% 13% 4	180
	11th to 20th	Day	33% 13% 22% 19% 9% 4	180
	21st to end	Day	38% 15% 17% 16% 11% 3	255
February	1st to 10th	Day	39% 12% 20% 16% 11% 3	370
	11th to 20th	Day	43% 13% 21% 12% 10% 1	365
	21st to end	Day	34% 17% 21% 20% 7% 1	341
March	1st to 10th	Day	30% 17% 24% 19% 9% 1	460
	11th to 20th	Day	29% 16% 19% 22% 12% 3	460
	21st to end	Day	33% 14% 24% 19% 8% 2	506
April	1st to 10th	Day	32% 16% 19% 19% 11% 3	429
	11th to 20th	Day	26% 17% 26% 17% 8% 5%	412
	21st to end	Day	23% 16% 25% 24% 10% 1	420
May	1st to 10th	Day	21% 11% 23% 29% 14% 3	423
	11th to 20th	Day	27% 8% 19% 28% 14% 4	448
	21st to end	Day	25% 9% 21% 26% 15% 3	485
June	1st to 10th	Day	26% 8% 23% 21% 18% 5%	450
	11th to 20th	Day	22% 12% 24% 26% 13% 2	626
	21st to end	Day	13% 7% 21% 31% 25% 4	630
July	1st to 10th	Day	14% 5% 17% 32% 28% 4	621
	11th to 20th	Day	10% 4 21% 35% 24% 6%	467
	21st to end	Day	7% 3 15% 36% 33% 6%	487
August	1st to 10th	Day	12% 4 14% 30% 29% 11%	447
	11th to 20th	Day	7% 4 10% 35% 35% 10%	437
	21st to end	Day	15% 7% 21% 31% 20% 6%	495
September	1st to 10th	Day	14% 5% 24% 34% 18% 4	450
	11th to 20th	Day	19% 6% 18% 30% 20% 7%	450
	21st to end	Day	18% 11% 22% 26% 20% 3	450
October	1st to 10th	Day	25% 10% 18% 22% 19% 6%	450
	11th to 20th	Day	30% 10% 14% 25% 14% 6%	450
	21st to end	Day	34% 14% 19% 18% 10% 5%	389
November	1st to 10th	Day	37% 15% 16% 20% 11% 1	206
	11th to 20th	Day	39% 13% 16% 10% 15% 6%	180
	21st to end	Day	35% 12% 20% 15% 9% 9%	180
December	1st to 10th	Day	45% 12% 12% 14% 12% 6%	180
	11th to 20th	Day	42% 8% 18% 22% 8% 2	180
	21st to end	Day	39% 11% 16% 20% 14% 2	198
January	1st to 10th	Night	42% 14% 17% 17% 9% 1	760
	11th to 20th	Night	38% 9% 16% 24% 12% 1	760
	21st to end	Night	37% 7% 17% 28% 11%	836
February	1st to 10th	Night	37% 9% 18% 25% 9% 2	760
	11th to 20th	Night	34% 13% 16% 26% 12% 1	744
	21st to end	Night	37% 11% 20% 22% 9% 1	628
March	1st to 10th	Night	31% 11% 20% 23% 13% 1	760
	11th to 20th	Night	31% 11% 19% 25% 13% 1	760
	21st to end	Night	35% 12% 18% 24% 10% 1	836
April	1st to 10th	Night	30% 8% 21% 25% 13% 2	728
	11th to 20th	Night	25% 11% 21% 27% 15% 2	698
	21st to end	Night	27% 8% 21% 29% 13% 2	504
May	1st to 10th	Night	20% 11% 17% 32% 19% 1	360
	11th to 20th	Night	18% 6% 18% 32% 24% 3	354
	21st to end	Night	20% 5% 17% 28% 26% 3	389
June	1st to 10th	Night	19% 6% 22% 28% 24% 2	360
	11th to 20th	Night	23% 6% 23% 28% 20% 1	360
	21st to end	Night	14% 3 17% 34% 29% 2	360
July	1st to 10th	Night	11% 2 16% 33% 35% 4	350
	11th to 20th	Night	10% 1 12% 40% 33% 3	348
	21st to end	Night	6% 3 11% 31% 44% 5%	394
August	1st to 10th	Night	10% 2 11% 28% 40% 9%	402
	11th to 20th	Night	8% 1 9% 28% 45% 9%	534
	21st to end	Night	13% 3 13% 31% 36% 4	707
September	1st to 10th	Night	13% 3 13% 34% 33% 3	720
	11th to 20th	Night	18% 4 13% 23% 35% 7%	720
	21st to end	Night	20% 5% 17% 30% 26% 2	720
October	1st to 10th	Night	23% 4 13% 29% 27% 3	720
	11th to 20th	Night	28% 7% 15% 26% 20% 5%	720
	21st to end	Night	31% 8% 18% 26% 14% 3	792
November	1st to 10th	Night	37% 9% 21% 26% 7%	740
	11th to 20th	Night	35% 12% 18% 23% 10% 1	760
	21st to end	Night	35% 9% 18% 25% 12% 1	760
December	1st to 10th	Night	32% 9% 21% 25% 12% 1	760
	11th to 20th	Night	40% 10% 18% 23% 8% 1	760
	21st to end	Night	45% 11% 17% 19% 7%	836

Page generated at 2024-03-31 03:08:55. Version ac07

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