Gualala
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gualala clear sky chart from 2005-11-06 to 2026-09-29.

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	9% 4 1 4 3 3 3 3 4 7% 59%	157733
	Night	12% 5% 2 4 3 3 3 3 4 6% 55%	151264
Transparency	Day	26% 4 7% 20% 25% 19%	152599
	Night	31% 4 7% 18% 22% 19%	147394
Seeing	Day	13% 10% 25% 28% 18% 6%	17896
	Night	15% 6% 17% 29% 25% 7%	27062

By Month

Percentage Cloud Cover SW (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	22% 7% 2 5% 4 3 4 4 6% 7% 37%	5215
	11th to 20th	Day	16% 5% 2 4 3 3 3 3 4 6% 51%	5340
	21st to end	Day	18% 7% 3 5% 3 4 4 3 5% 7% 42%	5843
February	1st to 10th	Day	22% 6% 3 5% 3 3 4 3 3 5% 42%	1890
	11th to 20th	Day	18% 6% 3 6% 3 4 4 4 7% 8% 37%	1845
	21st to end	Day	20% 5% 2 5% 4 3 4 4 5% 6% 42%	1757
March	1st to 10th	Day	21% 10% 2 5% 4 3 4 4 5% 8% 35%	5062
	11th to 20th	Day	18% 5% 1 4 3 3 3 3 5% 8% 46%	5110
	21st to end	Day	21% 10% 2 4 3 4 5% 4 7% 9% 30%	5607
April	1st to 10th	Day	16% 7% 1 4 4 3 4 4 6% 8% 42%	2488
	11th to 20th	Day	11% 5% 2 5% 4 4 4 3 6% 9% 47%	2489
	21st to end	Day	8% 4 1 3 3 4 4 4 7% 10% 53%	2561
May	1st to 10th	Day	4 3 1 3 2 3 3 3 5% 6% 66%	7627
	11th to 20th	Day	3 1 1 2 1 2 3 3 4 7% 75%	7594
	21st to end	Day	2 2 1 3 2 2 2 2 4 7% 72%	8936
June	1st to 10th	Day	6% 5% 1 3 3 3 3 3 6% 10% 58%	2940
	11th to 20th	Day	2 2 1 3 2 2 2 2 3 7% 73%	2940
	21st to end	Day	3 1 1 2 2 1 2 2 4 5% 77%	2940
July	1st to 10th	Day	1 1 1 3 2 2 2 1 3 5% 81%	8048
	11th to 20th	Day	2 4 2 6% 4 3 3 2 3 7% 66%	7650
	21st to end	Day	1 3 1 3 2 2 2 1 3 6% 76%	8304
August	1st to 10th	Day	1 1 1 1 1 2 2 2 3 6% 81%	7547
	11th to 20th	Day	1 3 1 4 3 2 3 2 4 8% 69%	7511
	21st to end	Day	2 2 1 5% 3 3 3 2 5% 9% 66%	7750
September	1st to 10th	Day	1 2 1 2 2 2 3 3 3 8% 74%	2520
	11th to 20th	Day	4 3 1 4 3 3 2 2 4 9% 66%	2435
	21st to end	Day	5% 2 3 2 2 2 2 4 6% 72%	2235
October	1st to 10th	Day	5% 3 1 3 2 2 2 2 3 6% 73%	3280
	11th to 20th	Day	11% 2 1 2 2 2 3 2 4 8% 62%	3261
	21st to end	Day	9% 5% 2 5% 3 3 4 3 6% 9% 52%	3558
November	1st to 10th	Day	12% 5% 2 4 3 3 4 3 5% 9% 49%	2059
	11th to 20th	Day	16% 6% 2 5% 3 3 4 3 5% 7% 45%	1811
	21st to end	Day	13% 4 1 4 4 4 4 4 5% 9% 51%	1680
December	1st to 10th	Day	12% 4 2 3 3 3 4 4 7% 9% 50%	2700
	11th to 20th	Day	30% 8% 2 6% 4 4 4 3 7% 7% 25%	3108
	21st to end	Day	28% 8% 3 5% 3 4 5% 4 6% 8% 26%	4092
January	1st to 10th	Night	24% 7% 2 4 3 3 4 4 6% 7% 36%	7701
	11th to 20th	Night	14% 5% 2 4 3 3 3 2 4 6% 53%	7650
	21st to end	Night	20% 7% 3 6% 3 3 3 3 4 7% 41%	8371
February	1st to 10th	Night	19% 6% 2 4 3 3 3 4 5% 6% 44%	2730
	11th to 20th	Night	18% 8% 2 5% 3 4 3 4 7% 7% 38%	2662
	21st to end	Night	18% 7% 1 3 3 3 4 3 6% 6% 46%	2042
March	1st to 10th	Night	18% 12% 3 6% 4 4 4 4 6% 6% 34%	5052
	11th to 20th	Night	21% 5% 1 4 3 3 3 2 4 6% 49%	5110
	21st to end	Night	19% 11% 3 6% 4 3 4 3 6% 8% 34%	5610
April	1st to 10th	Night	14% 7% 2 6% 4 3 4 3 5% 7% 45%	2131
	11th to 20th	Night	11% 5% 3 5% 4 4 4 3 5% 6% 51%	2079
	21st to end	Night	7% 4 1 4 3 3 4 3 5% 8% 59%	2055
May	1st to 10th	Night	4 4 2 4 2 2 2 2 4 6% 68%	5321
	11th to 20th	Night	3 2 1 3 2 2 2 2 3 7% 73%	5295
	21st to end	Night	3 4 2 4 1 2 2 2 3 5% 72%	5222
June	1st to 10th	Night	5% 7% 2 4 3 3 3 2 5% 8% 56%	1680
	11th to 20th	Night	3 3 2 2 2 2 2 2 3 7% 73%	1680
	21st to end	Night	2 3 1 2 2 2 2 2 3 4 77%	1680
July	1st to 10th	Night	1 1 1 5% 3 2 2 1 2 3 78%	4914
	11th to 20th	Night	3 6% 3 6% 4 3 2 2 2 4 64%	5340
	21st to end	Night	1 5% 1 3 2 2 2 2 3 5% 75%	5806
August	1st to 10th	Night	1 2 1 2 2 3 2 2 2 4 80%	5275
	11th to 20th	Night	1 3 2 3 2 3 3 2 4 7% 71%	5344
	21st to end	Night	2 3 2 6% 4 4 3 2 4 6% 65%	6499
September	1st to 10th	Night	2 1 1 3 2 1 2 3 4 6% 76%	2100
	11th to 20th	Night	4 4 2 4 2 2 2 2 4 7% 67%	2181
	21st to end	Night	4 4 1 3 2 2 2 3 2 5% 70%	2341
October	1st to 10th	Night	3 3 1 3 2 2 2 2 3 4 75%	3920
	11th to 20th	Night	8% 5% 2 4 2 2 2 2 3 6% 64%	3897
	21st to end	Night	12% 3 1 3 3 3 3 3 5% 7% 57%	4253
November	1st to 10th	Night	13% 5% 2 4 3 3 4 4 6% 8% 48%	2460
	11th to 20th	Night	18% 5% 2 4 4 4 4 4 6% 8% 43%	2801
	21st to end	Night	14% 5% 2 4 3 3 3 3 5% 7% 52%	2940
December	1st to 10th	Night	13% 5% 1 4 3 3 3 3 5% 8% 52%	4700
	11th to 20th	Night	31% 6% 2 5% 4 4 4 3 7% 7% 27%	5316
	21st to end	Night	36% 8% 2 5% 3 2 3 2 4 5% 30%	7106

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	46% 5% 13% 20% 10% 5%	5216
	11th to 20th	Day	35% 2 6% 12% 22% 23%	5340
	21st to end	Day	43% 3 7% 18% 14% 15%	5843
February	1st to 10th	Day	45% 3 7% 18% 18% 9%	1890
	11th to 20th	Day	44% 4 9% 20% 18% 5%	1854
	21st to end	Day	42% 4 11% 23% 15% 5%	1757
March	1st to 10th	Day	50% 3 7% 21% 18% 2	5062
	11th to 20th	Day	38% 4 14% 21% 13% 9%	5110
	21st to end	Day	51% 4 14% 21% 9% 1	5607
April	1st to 10th	Day	41% 3 13% 26% 14% 3	2488
	11th to 20th	Day	34% 4 15% 23% 18% 6%	2492
	21st to end	Day	26% 4 14% 31% 21% 5%	2561
May	1st to 10th	Day	20% 3 10% 25% 30% 13%	7627
	11th to 20th	Day	12% 3 7% 31% 35% 13%	7597
	21st to end	Day	12% 3 7% 39% 36% 2	8938
June	1st to 10th	Day	23% 4 10% 28% 28% 7%	2940
	11th to 20th	Day	12% 3 8% 21% 38% 17%	2940
	21st to end	Day	10% 4 3 16% 38% 29%	2940
July	1st to 10th	Day	6% 3 1 10% 34% 46%	7983
	11th to 20th	Day	15% 4 1 6% 20% 54%	7581
	21st to end	Day	10% 4 4 12% 30% 40%	8119
August	1st to 10th	Day	9% 3 2 9% 27% 50%	5976
	11th to 20th	Day	14% 6% 2 24% 34% 20%	5922
	21st to end	Day	14% 4 3 21% 37% 21%	6077
September	1st to 10th	Day	11% 3 2 15% 33% 36%	2520
	11th to 20th	Day	19% 4 5% 28% 35% 10%	2435
	21st to end	Day	15% 3 4 24% 32% 23%	2235
October	1st to 10th	Day	16% 2 3 16% 24% 39%	3280
	11th to 20th	Day	22% 4 8% 25% 29% 12%	3261
	21st to end	Day	30% 3 10% 23% 24% 10%	3558
November	1st to 10th	Day	31% 4 9% 29% 18% 9%	2059
	11th to 20th	Day	40% 3 12% 22% 15% 7%	1811
	21st to end	Day	32% 4 13% 20% 21% 12%	1680
December	1st to 10th	Day	30% 4 7% 24% 27% 8%	2700
	11th to 20th	Day	59% 4 9% 16% 10% 3	3108
	21st to end	Day	58% 3 10% 19% 8% 2	4092
January	1st to 10th	Night	47% 4 16% 16% 12% 5%	7701
	11th to 20th	Night	36% 2 6% 16% 19% 22%	7650
	21st to end	Night	45% 3 6% 14% 16% 16%	8371
February	1st to 10th	Night	40% 3 8% 20% 18% 10%	2730
	11th to 20th	Night	43% 5% 8% 21% 18% 6%	2664
	21st to end	Night	38% 3 12% 24% 17% 5%	2042
March	1st to 10th	Night	52% 3 7% 19% 14% 4	5052
	11th to 20th	Night	38% 3 10% 22% 18% 9%	5110
	21st to end	Night	49% 4 13% 21% 10% 2	5610
April	1st to 10th	Night	39% 4 12% 24% 17% 4	2131
	11th to 20th	Night	35% 5% 11% 24% 19% 6%	2079
	21st to end	Night	25% 4 10% 34% 22% 6%	2055
May	1st to 10th	Night	20% 3 6% 20% 33% 18%	5319
	11th to 20th	Night	14% 3 4 27% 34% 18%	5296
	21st to end	Night	17% 2 7% 32% 38% 4	5223
June	1st to 10th	Night	25% 5% 8% 22% 29% 11%	1680
	11th to 20th	Night	14% 4 7% 20% 37% 19%	1680
	21st to end	Night	13% 4 4 11% 33% 35%	1680
July	1st to 10th	Night	9% 5% 1 9% 26% 51%	4872
	11th to 20th	Night	22% 7% 2 4 13% 52%	5286
	21st to end	Night	13% 6% 1 9% 25% 46%	5679
August	1st to 10th	Night	10% 4 1 6% 24% 55%	4169
	11th to 20th	Night	14% 7% 2 18% 35% 25%	4208
	21st to end	Night	18% 5% 1 12% 37% 27%	5092
September	1st to 10th	Night	10% 4 1 14% 28% 42%	2100
	11th to 20th	Night	18% 4 5% 20% 37% 16%	2181
	21st to end	Night	17% 3 3 19% 28% 29%	2341
October	1st to 10th	Night	17% 2 3 12% 22% 44%	3920
	11th to 20th	Night	23% 3 5% 22% 30% 16%	3897
	21st to end	Night	27% 2 5% 24% 27% 14%	4253
November	1st to 10th	Night	33% 5% 11% 23% 18% 11%	2460
	11th to 20th	Night	38% 4 13% 21% 18% 6%	2801
	21st to end	Night	33% 4 10% 21% 21% 12%	2940
December	1st to 10th	Night	31% 3 6% 27% 23% 11%	4700
	11th to 20th	Night	56% 3 8% 15% 13% 4	5316
	21st to end	Night	59% 2 9% 18% 8% 3	7106

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	32% 15% 22% 16% 13% 2	389
	11th to 20th	Day	26% 9% 21% 21% 19% 4	430
	21st to end	Day	22% 9% 22% 29% 15% 3	473
February	1st to 10th	Day	26% 11% 23% 20% 16% 4	430
	11th to 20th	Day	29% 15% 24% 18% 12% 2	425
	21st to end	Day	22% 13% 28% 22% 10% 3	436
March	1st to 10th	Day	29% 14% 28% 19% 9% 1	540
	11th to 20th	Day	27% 11% 28% 20% 11% 3	540
	21st to end	Day	23% 16% 31% 21% 7% 3	594
April	1st to 10th	Day	22% 16% 28% 23% 8% 3	540
	11th to 20th	Day	16% 16% 33% 21% 10% 4	532
	21st to end	Day	14% 17% 32% 22% 11% 4	540
May	1st to 10th	Day	10% 13% 33% 27% 13% 4	543
	11th to 20th	Day	16% 13% 29% 25% 14% 3	568
	21st to end	Day	10% 12% 29% 30% 14% 5%	617
June	1st to 10th	Day	8% 11% 35% 28% 14% 4	570
	11th to 20th	Day	5% 15% 35% 29% 15% 2	570
	21st to end	Day	2 6% 28% 36% 22% 5%	570
July	1st to 10th	Day	3 6% 25% 41% 19% 6%	566
	11th to 20th	Day	1 2 26% 41% 24% 6%	564
	21st to end	Day	1 3 19% 42% 26% 8%	619
August	1st to 10th	Day	1 3 25% 39% 24% 8%	567
	11th to 20th	Day	3 4 24% 34% 28% 8%	557
	21st to end	Day	2 4 19% 38% 28% 9%	627
September	1st to 10th	Day	4 6% 22% 33% 27% 8%	570
	11th to 20th	Day	5% 8% 22% 32% 24% 8%	570
	21st to end	Day	6% 7% 24% 27% 28% 8%	563
October	1st to 10th	Day	9% 7% 23% 24% 28% 10%	530
	11th to 20th	Day	13% 7% 18% 24% 26% 12%	530
	21st to end	Day	13% 6% 22% 27% 25% 7%	583
November	1st to 10th	Day	16% 9% 21% 25% 22% 8%	535
	11th to 20th	Day	22% 9% 17% 22% 22% 9%	306
	21st to end	Day	17% 4 22% 24% 22% 11%	220
December	1st to 10th	Day	20% 9% 22% 20% 16% 12%	220
	11th to 20th	Day	31% 8% 17% 19% 14% 10%	220
	21st to end	Day	33% 10% 20% 17% 13% 7%	242
January	1st to 10th	Night	26% 8% 17% 26% 18% 5%	840
	11th to 20th	Night	22% 6% 15% 30% 20% 6%	840
	21st to end	Night	21% 7% 15% 29% 23% 6%	924
February	1st to 10th	Night	24% 7% 17% 27% 21% 4	840
	11th to 20th	Night	24% 9% 20% 23% 17% 6%	824
	21st to end	Night	22% 10% 20% 30% 15% 3	692
March	1st to 10th	Night	26% 11% 18% 24% 16% 4	840
	11th to 20th	Night	24% 8% 17% 31% 18% 3	840
	21st to end	Night	22% 10% 24% 27% 14% 3	924
April	1st to 10th	Night	18% 10% 24% 27% 17% 4	840
	11th to 20th	Night	16% 11% 25% 27% 16% 5%	831
	21st to end	Night	11% 11% 30% 25% 18% 5%	795
May	1st to 10th	Night	7% 10% 27% 30% 20% 6%	630
	11th to 20th	Night	7% 6% 24% 34% 23% 5%	621
	21st to end	Night	8% 10% 25% 29% 23% 5%	470
June	1st to 10th	Night	8% 8% 29% 29% 23% 3	420
	11th to 20th	Night	3 10% 26% 38% 21% 2	420
	21st to end	Night	4 4 19% 41% 28% 4	420
July	1st to 10th	Night	2 3 18% 34% 34% 9%	465
	11th to 20th	Night	2 1 12% 34% 38% 13%	612
	21st to end	Night	2 1 11% 31% 40% 16%	690
August	1st to 10th	Night	2 2 12% 33% 37% 13%	627
	11th to 20th	Night	1 1 12% 32% 38% 15%	637
	21st to end	Night	3 2 10% 28% 45% 12%	924
September	1st to 10th	Night	2 3 14% 29% 38% 14%	840
	11th to 20th	Night	6% 4 13% 33% 35% 9%	840
	21st to end	Night	6% 5% 12% 30% 35% 12%	832
October	1st to 10th	Night	7% 6% 14% 30% 31% 11%	800
	11th to 20th	Night	10% 5% 12% 26% 36% 12%	800
	21st to end	Night	14% 4 13% 27% 31% 11%	880
November	1st to 10th	Night	15% 6% 15% 25% 30% 9%	820
	11th to 20th	Night	21% 5% 15% 27% 26% 6%	840
	21st to end	Night	16% 6% 16% 31% 24% 7%	840
December	1st to 10th	Night	25% 4 13% 29% 22% 8%	840
	11th to 20th	Night	29% 6% 15% 27% 18% 4	840
	21st to end	Night	29% 8% 19% 25% 16% 3	924

Page generated at 2026-09-26 01:18:44. Version ac07

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