Visalia
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Visalia 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	4 3 1 3 2 2 3 2 3 5% 71%	157054
	Night	6% 3 1 3 2 2 3 2 4 5% 68%	151935
Transparency	Day	17% 4 7% 18% 28% 26%	152127
	Night	20% 4 9% 20% 26% 21%	147851
Seeing	Day	6% 3 12% 27% 34% 19%	17863
	Night	7% 2 11% 38% 36% 6%	27391

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	10% 10% 3 7% 6% 5% 5% 4 5% 7% 38%	4722
	11th to 20th	Day	5% 4 2 6% 4 5% 4 3 5% 6% 56%	5142
	21st to end	Day	10% 7% 3 7% 5% 4 4 3 5% 7% 46%	5843
February	1st to 10th	Day	12% 7% 2 5% 4 3 4 3 5% 5% 49%	2052
	11th to 20th	Day	11% 5% 2 4 4 4 4 3 5% 8% 51%	2050
	21st to end	Day	12% 6% 2 5% 4 3 4 3 5% 7% 49%	1730
March	1st to 10th	Day	13% 6% 2 6% 4 4 4 4 7% 8% 43%	4618
	11th to 20th	Day	9% 4 2 5% 3 3 4 3 5% 7% 55%	4964
	21st to end	Day	11% 4 2 5% 4 4 5% 4 5% 7% 51%	6027
April	1st to 10th	Day	7% 3 1 3 3 3 3 3 5% 7% 62%	2520
	11th to 20th	Day	6% 3 1 4 4 2 3 3 5% 6% 62%	2489
	21st to end	Day	5% 3 1 3 2 3 2 3 5% 6% 68%	2520
May	1st to 10th	Day	4 2 1 2 2 1 2 1 2 3 79%	7222
	11th to 20th	Day	1 1 1 1 1 1 1 2 4 85%	7596
	21st to end	Day	2 1 2 1 1 2 2 2 3 83%	8797
June	1st to 10th	Day	2 1 1 2 2 2 2 2 4 6% 76%	2940
	11th to 20th	Day	1 1 1 1 1 1 2 2 91%	2940
	21st to end	Day	1 1 1 1 1 1 2 2 89%	2940
July	1st to 10th	Day	1 1 1 1 1 2 94%	8219
	11th to 20th	Day	1 1 1 1 1 2 1 3 3 87%	8220
	21st to end	Day	1 1 1 1 1 2 3 90%	8420
August	1st to 10th	Day	1 1 1 1 1 1 1 2 3 90%	7013
	11th to 20th	Day	1 1 1 1 1 2 3 89%	7001
	21st to end	Day	2 1 1 1 1 1 1 1 3 4 83%	7750
September	1st to 10th	Day	1 1 1 1 1 1 1 1 2 89%	2520
	11th to 20th	Day	1 1 1 1 1 1 1 1 2 3 86%	2442
	21st to end	Day	1 1 2 1 1 2 2 3 4 84%	2289
October	1st to 10th	Day	2 1 1 1 1 2 3 3 5% 80%	3473
	11th to 20th	Day	1 2 1 2 2 2 3 2 3 4 78%	3261
	21st to end	Day	2 2 1 3 2 2 3 3 4 6% 71%	3528
November	1st to 10th	Day	6% 3 1 3 3 3 3 3 4 7% 64%	1854
	11th to 20th	Day	9% 5% 2 5% 3 3 3 2 5% 6% 57%	1890
	21st to end	Day	8% 6% 2 5% 3 3 4 3 6% 6% 53%	1890
December	1st to 10th	Day	6% 5% 2 7% 5% 6% 6% 5% 5% 6% 46%	2972
	11th to 20th	Day	13% 7% 3 9% 6% 4 5% 4 6% 8% 36%	3108
	21st to end	Day	16% 13% 4 9% 5% 4 5% 5% 5% 6% 27%	4092
January	1st to 10th	Night	14% 7% 3 6% 4 4 4 3 4 6% 44%	8172
	11th to 20th	Night	6% 4 2 4 3 4 4 3 4 7% 59%	7821
	21st to end	Night	11% 6% 2 6% 4 4 4 3 6% 7% 46%	8371
February	1st to 10th	Night	14% 5% 2 4 3 3 3 3 4 6% 53%	2565
	11th to 20th	Night	11% 5% 1 5% 3 3 2 3 4 6% 57%	2458
	21st to end	Night	12% 4 1 4 3 4 3 3 4 6% 56%	2076
March	1st to 10th	Night	12% 5% 2 6% 3 3 4 4 6% 7% 47%	5496
	11th to 20th	Night	9% 4 2 4 3 4 4 3 5% 7% 56%	5252
	21st to end	Night	14% 5% 2 6% 4 3 4 3 4 5% 51%	5189
April	1st to 10th	Night	8% 4 1 3 3 3 3 3 4 6% 62%	2100
	11th to 20th	Night	6% 3 1 4 3 2 3 3 5% 6% 65%	2079
	21st to end	Night	6% 2 1 3 2 2 3 3 4 6% 69%	2100
May	1st to 10th	Night	4 2 1 2 2 2 2 1 3 5% 76%	5744
	11th to 20th	Night	2 1 1 1 1 2 1 3 4 84%	5296
	21st to end	Night	2 1 1 2 1 1 1 1 1 2 86%	5368
June	1st to 10th	Night	3 1 1 2 1 2 2 3 6% 79%	1680
	11th to 20th	Night	1 1 1 1 2 2 3 89%	1680
	21st to end	Night	1 1 1 1 2 2 91%	1680
July	1st to 10th	Night	1 1 1 2 94%	4740
	11th to 20th	Night	1 1 1 2 1 1 1 1 2 2 86%	4740
	21st to end	Night	1 1 1 1 1 2 3 90%	5678
August	1st to 10th	Night	1 1 1 1 1 1 1 2 2 91%	5824
	11th to 20th	Night	1 1 1 1 1 2 3 89%	5886
	21st to end	Night	1 1 1 1 1 2 2 2 3 5% 82%	6499
September	1st to 10th	Night	1 1 1 1 1 1 1 2 3 89%	2100
	11th to 20th	Night	1 1 2 1 1 2 1 3 3 84%	2176
	21st to end	Night	1 1 1 1 1 1 1 3 5% 83%	2288
October	1st to 10th	Night	2 1 1 1 1 1 1 2 4 84%	3723
	11th to 20th	Night	2 1 1 1 1 1 2 2 3 4 81%	3897
	21st to end	Night	3 2 1 2 1 2 2 1 3 4 80%	4279
November	1st to 10th	Night	5% 3 1 3 3 3 2 2 3 6% 69%	2665
	11th to 20th	Night	6% 3 1 3 3 3 3 3 5% 7% 64%	2730
	21st to end	Night	8% 6% 2 4 4 3 3 3 5% 6% 56%	2730
December	1st to 10th	Night	6% 4 2 5% 4 5% 5% 4 6% 6% 54%	4431
	11th to 20th	Night	13% 5% 2 7% 5% 5% 5% 4 6% 9% 39%	5316
	21st to end	Night	11% 8% 3 8% 5% 6% 6% 4 7% 8% 32%	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	41% 10% 19% 16% 13% 1	4723
	11th to 20th	Day	25% 8% 10% 16% 26% 15%	5142
	21st to end	Day	34% 7% 11% 20% 23% 4	5843
February	1st to 10th	Day	34% 5% 14% 26% 16% 5%	2052
	11th to 20th	Day	32% 7% 12% 25% 18% 6%	2060
	21st to end	Day	34% 8% 13% 28% 15% 3	1730
March	1st to 10th	Day	36% 8% 13% 20% 20% 3	4618
	11th to 20th	Day	28% 7% 14% 33% 12% 5%	4964
	21st to end	Day	31% 7% 14% 30% 16% 3	6027
April	1st to 10th	Day	24% 4 12% 31% 22% 7%	2520
	11th to 20th	Day	23% 5% 13% 27% 24% 8%	2492
	21st to end	Day	18% 6% 11% 31% 28% 7%	2520
May	1st to 10th	Day	13% 3 8% 22% 38% 15%	7222
	11th to 20th	Day	7% 2 4 24% 44% 19%	7599
	21st to end	Day	9% 3 5% 22% 48% 14%	8798
June	1st to 10th	Day	11% 3 8% 20% 35% 22%	2940
	11th to 20th	Day	4 2 4 11% 38% 40%	2940
	21st to end	Day	5% 1 2 8% 28% 55%	2940
July	1st to 10th	Day	3 1 1 4 19% 73%	8151
	11th to 20th	Day	6% 1 2 7% 20% 64%	8145
	21st to end	Day	4 1 1 12% 32% 50%	8232
August	1st to 10th	Day	5% 1 2 5% 35% 52%	5556
	11th to 20th	Day	6% 1 2 14% 31% 46%	5517
	21st to end	Day	8% 1 2 12% 36% 41%	6077
September	1st to 10th	Day	5% 1 4 8% 32% 50%	2520
	11th to 20th	Day	7% 2 3 16% 42% 30%	2442
	21st to end	Day	7% 2 5% 16% 41% 29%	2289
October	1st to 10th	Day	9% 2 4 14% 24% 47%	3473
	11th to 20th	Day	12% 3 5% 24% 35% 20%	3261
	21st to end	Day	16% 3 7% 18% 36% 20%	3528
November	1st to 10th	Day	19% 6% 11% 25% 28% 11%	1854
	11th to 20th	Day	27% 4 16% 22% 24% 5%	1890
	21st to end	Day	31% 7% 8% 23% 22% 9%	1890
December	1st to 10th	Day	30% 9% 15% 23% 17% 5%	2972
	11th to 20th	Day	42% 9% 13% 20% 14% 3	3108
	21st to end	Day	52% 9% 15% 16% 6% 1	4092
January	1st to 10th	Night	38% 9% 19% 21% 12% 1	8172
	11th to 20th	Night	22% 7% 14% 19% 29% 9%	7821
	21st to end	Night	35% 6% 10% 26% 20% 3	8371
February	1st to 10th	Night	34% 4 10% 28% 18% 6%	2565
	11th to 20th	Night	29% 4 13% 27% 20% 7%	2459
	21st to end	Night	31% 5% 13% 30% 17% 4	2076
March	1st to 10th	Night	33% 8% 12% 24% 20% 3	5496
	11th to 20th	Night	27% 7% 17% 33% 12% 5%	5252
	21st to end	Night	36% 6% 16% 24% 16% 2	5189
April	1st to 10th	Night	24% 5% 11% 30% 22% 8%	2100
	11th to 20th	Night	20% 6% 10% 29% 26% 9%	2079
	21st to end	Night	18% 4 10% 30% 33% 4	2100
May	1st to 10th	Night	14% 3 7% 25% 37% 13%	5742
	11th to 20th	Night	8% 2 3 22% 41% 24%	5297
	21st to end	Night	8% 2 3 20% 50% 17%	5369
June	1st to 10th	Night	10% 3 7% 21% 36% 23%	1680
	11th to 20th	Night	4 2 4 12% 34% 43%	1680
	21st to end	Night	3 1 2 6% 29% 58%	1680
July	1st to 10th	Night	2 1 1 2 19% 76%	4700
	11th to 20th	Night	8% 1 2 6% 15% 68%	4692
	21st to end	Night	4 1 1 11% 32% 51%	5554
August	1st to 10th	Night	5% 1 1 5% 31% 57%	4608
	11th to 20th	Night	4 1 2 15% 31% 47%	4636
	21st to end	Night	7% 1 2 12% 32% 46%	5092
September	1st to 10th	Night	5% 1 2 9% 30% 54%	2100
	11th to 20th	Night	8% 1 4 14% 41% 32%	2176
	21st to end	Night	7% 1 3 17% 39% 33%	2288
October	1st to 10th	Night	8% 2 2 11% 27% 49%	3723
	11th to 20th	Night	9% 2 4 21% 42% 21%	3897
	21st to end	Night	12% 2 5% 21% 39% 21%	4279
November	1st to 10th	Night	18% 5% 10% 25% 29% 13%	2665
	11th to 20th	Night	20% 5% 15% 24% 27% 9%	2730
	21st to end	Night	28% 4 11% 21% 27% 8%	2730
December	1st to 10th	Night	25% 7% 16% 27% 18% 6%	4431
	11th to 20th	Night	37% 9% 16% 19% 16% 2	5316
	21st to end	Night	44% 10% 18% 20% 6% 1	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	19% 6% 11% 31% 22% 10%	220
	11th to 20th	Day	11% 4 9% 33% 25% 18%	362
	21st to end	Day	14% 3 10% 29% 31% 14%	473
February	1st to 10th	Day	14% 3 11% 30% 25% 16%	515
	11th to 20th	Day	13% 4 16% 35% 23% 9%	535
	21st to end	Day	10% 5% 17% 34% 27% 7%	446
March	1st to 10th	Day	12% 6% 16% 35% 24% 8%	540
	11th to 20th	Day	9% 5% 19% 31% 25% 11%	540
	21st to end	Day	11% 6% 22% 31% 21% 8%	594
April	1st to 10th	Day	10% 5% 18% 28% 25% 14%	540
	11th to 20th	Day	6% 7% 21% 28% 29% 9%	532
	21st to end	Day	4 6% 20% 31% 24% 16%	540
May	1st to 10th	Day	4 6% 22% 29% 28% 12%	543
	11th to 20th	Day	2 2 21% 32% 26% 17%	568
	21st to end	Day	3 4 16% 24% 36% 16%	617
June	1st to 10th	Day	1 3 12% 27% 36% 22%	570
	11th to 20th	Day	2 2 13% 24% 43% 16%	570
	21st to end	Day	1 1 8% 29% 39% 22%	570
July	1st to 10th	Day	1 3 24% 48% 23%	566
	11th to 20th	Day	1 1 2 16% 44% 37%	564
	21st to end	Day	2 1 16% 49% 32%	619
August	1st to 10th	Day	2 7% 22% 44% 25%	567
	11th to 20th	Day	1 3 21% 46% 28%	557
	21st to end	Day	1 1 3 22% 44% 29%	627
September	1st to 10th	Day	1 1 5% 27% 42% 25%	570
	11th to 20th	Day	2 2 10% 28% 42% 16%	570
	21st to end	Day	1 2 11% 25% 38% 23%	563
October	1st to 10th	Day	2 2 11% 28% 33% 23%	530
	11th to 20th	Day	4 3 11% 25% 38% 20%	530
	21st to end	Day	2 4 10% 27% 34% 23%	565
November	1st to 10th	Day	5% 2 8% 26% 36% 22%	330
	11th to 20th	Day	10% 4 7% 30% 31% 18%	330
	21st to end	Day	10% 3 11% 28% 31% 17%	330
December	1st to 10th	Day	11% 3 11% 30% 30% 15%	308
	11th to 20th	Day	10% 4 9% 32% 22% 23%	220
	21st to end	Day	23% 6% 10% 29% 25% 7%	242
January	1st to 10th	Night	19% 2 9% 36% 27% 8%	840
	11th to 20th	Night	9% 2 8% 41% 33% 8%	840
	21st to end	Night	15% 2 9% 36% 32% 6%	924
February	1st to 10th	Night	14% 2 10% 38% 28% 8%	840
	11th to 20th	Night	13% 3 14% 38% 26% 6%	824
	21st to end	Night	12% 3 11% 46% 25% 3	692
March	1st to 10th	Night	10% 4 13% 45% 25% 3	840
	11th to 20th	Night	10% 4 12% 40% 29% 6%	840
	21st to end	Night	12% 3 17% 39% 27% 3	924
April	1st to 10th	Night	8% 3 21% 37% 27% 2	840
	11th to 20th	Night	6% 5% 20% 39% 28% 2	831
	21st to end	Night	6% 5% 20% 37% 27% 5%	840
May	1st to 10th	Night	5% 4 20% 41% 27% 2	780
	11th to 20th	Night	5% 4 20% 41% 30%	621
	21st to end	Night	3 5% 25% 38% 28% 1	526
June	1st to 10th	Night	3 3 21% 47% 24% 2	420
	11th to 20th	Night	1 3 17% 49% 29% 1	420
	21st to end	Night	1 17% 50% 30% 1	420
July	1st to 10th	Night	7% 50% 40% 2	410
	11th to 20th	Night	1 5% 40% 53% 2	408
	21st to end	Night	1 3 30% 57% 9%	639
August	1st to 10th	Night	3 5% 35% 51% 6%	820
	11th to 20th	Night	4 35% 54% 7%	832
	21st to end	Night	1 2 28% 61% 8%	924
September	1st to 10th	Night	1 5% 30% 57% 7%	840
	11th to 20th	Night	2 1 10% 37% 44% 7%	840
	21st to end	Night	2 2 8% 34% 46% 9%	832
October	1st to 10th	Night	4 1 8% 39% 40% 8%	800
	11th to 20th	Night	3 2 8% 35% 42% 10%	800
	21st to end	Night	4 1 7% 34% 40% 14%	880
November	1st to 10th	Night	6% 2 8% 30% 42% 12%	820
	11th to 20th	Night	7% 1 6% 41% 36% 9%	840
	21st to end	Night	10% 2 9% 37% 35% 8%	840
December	1st to 10th	Night	11% 1 8% 41% 32% 8%	840
	11th to 20th	Night	14% 2 8% 41% 29% 7%	840
	21st to end	Night	14% 3 10% 42% 26% 3	924

Page generated at 2026-09-26 01:18:42. Version ac07

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