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 2024-03-01.

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	6% 4 1 3 3 2 3 3 4 5% 66%	78625
	Night	8% 4 2 3 3 2 3 3 4 6% 63%	80796
Transparency	Day	21% 5% 9% 19% 25% 21%	78338
	Night	24% 5% 10% 20% 23% 18%	80605
Seeing	Day	6% 3 12% 27% 34% 17%	14357
	Night	7% 2 11% 37% 36% 6%	24062

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% 14% 4 7% 7% 4 5% 5% 5% 6% 33%	2539
	11th to 20th	Day	9% 8% 3 8% 8% 5% 5% 5% 6% 7% 36%	2746
	21st to end	Day	16% 10% 3 6% 6% 4 5% 5% 6% 7% 33%	3146
February	1st to 10th	Day	12% 7% 3 4 4 2 4 4 4 6% 51%	1856
	11th to 20th	Day	11% 5% 2 4 4 3 3 4 5% 7% 53%	1850
	21st to end	Day	13% 6% 2 5% 5% 3 5% 4 5% 6% 48%	1570
March	1st to 10th	Day	12% 5% 2 5% 5% 3 4 5% 6% 7% 46%	1801
	11th to 20th	Day	9% 5% 2 4 4 2 4 5% 6% 8% 50%	1916
	21st to end	Day	9% 3 2 4 4 2 4 3 4 6% 58%	2343
April	1st to 10th	Day	8% 3 1 3 4 3 3 3 5% 7% 61%	2160
	11th to 20th	Day	7% 3 1 3 4 2 3 4 4 6% 63%	2129
	21st to end	Day	5% 2 1 3 2 2 2 3 5% 6% 69%	2160
May	1st to 10th	Day	2 2 1 2 2 1 3 3 3 4 76%	2209
	11th to 20th	Day	2 2 1 3 2 1 3 2 4 6% 74%	2301
	21st to end	Day	4 2 1 2 2 2 3 3 4 6% 74%	2658
June	1st to 10th	Day	2 1 1 2 2 2 2 3 3 7% 76%	2520
	11th to 20th	Day	1 1 1 1 1 1 2 3 90%	2520
	21st to end	Day	1 1 1 1 2 2 2 3 88%	2520
July	1st to 10th	Day	1 1 1 1 1 1 1 2 3 88%	2520
	11th to 20th	Day	1 1 1 1 1 1 2 2 3 4 83%	2520
	21st to end	Day	1 1 1 1 2 1 2 2 4 5% 80%	2585
August	1st to 10th	Day	2 1 1 1 1 1 2 2 3 85%	2163
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 88%	2122
	21st to end	Day	1 1 1 1 1 1 1 2 4 88%	2376
September	1st to 10th	Day	1 1 1 1 1 1 2 1 2 88%	2160
	11th to 20th	Day	1 1 1 1 1 1 2 2 3 87%	2094
	21st to end	Day	1 1 1 2 1 2 2 4 4 83%	1980
October	1st to 10th	Day	3 2 1 1 2 1 3 3 3 5% 74%	1909
	11th to 20th	Day	2 2 1 1 2 1 3 3 4 4 77%	1800
	21st to end	Day	3 2 1 2 3 1 2 2 3 5% 76%	1964
November	1st to 10th	Day	6% 3 1 2 3 2 3 4 4 7% 64%	1674
	11th to 20th	Day	8% 5% 2 4 3 2 3 3 5% 5% 59%	1710
	21st to end	Day	8% 5% 2 4 4 2 4 4 6% 6% 56%	1710
December	1st to 10th	Day	10% 7% 2 5% 4 3 5% 5% 5% 6% 48%	1672
	11th to 20th	Day	17% 6% 4 8% 6% 3 5% 4 6% 7% 35%	1928
	21st to end	Day	14% 12% 4 8% 6% 3 6% 6% 5% 6% 30%	2794
January	1st to 10th	Night	15% 9% 3 6% 5% 2 4 3 4 6% 42%	4406
	11th to 20th	Night	12% 8% 3 7% 5% 3 4 4 5% 8% 41%	4203
	21st to end	Night	18% 7% 3 5% 5% 3 4 4 5% 8% 38%	4521
February	1st to 10th	Night	14% 5% 2 4 3 2 3 4 4 6% 54%	2321
	11th to 20th	Night	11% 4 1 4 3 2 3 3 3 7% 60%	2218
	21st to end	Night	14% 4 2 4 3 2 4 4 4 6% 54%	1884
March	1st to 10th	Night	11% 4 2 4 3 3 4 4 6% 8% 51%	2165
	11th to 20th	Night	10% 4 1 4 4 3 5% 4 5% 8% 52%	2041
	21st to end	Night	12% 3 2 3 4 2 3 2 4 6% 58%	2012
April	1st to 10th	Night	9% 3 2 3 3 2 3 3 4 5% 63%	1800
	11th to 20th	Night	6% 2 1 3 3 1 3 4 5% 6% 66%	1779
	21st to end	Night	5% 2 1 2 2 2 3 3 4 6% 70%	1800
May	1st to 10th	Night	4 2 1 2 3 2 2 2 4 7% 72%	1749
	11th to 20th	Night	4 1 1 2 1 1 3 3 3 5% 75%	1594
	21st to end	Night	3 2 1 2 3 1 2 3 2 4 76%	1613
June	1st to 10th	Night	3 1 1 1 2 1 2 3 3 6% 77%	1440
	11th to 20th	Night	1 1 1 1 2 2 3 88%	1440
	21st to end	Night	1 1 1 1 2 3 90%	1440
July	1st to 10th	Night	1 1 1 1 2 2 4 88%	1440
	11th to 20th	Night	1 1 1 2 2 1 2 2 2 4 83%	1440
	21st to end	Night	1 1 1 2 2 2 3 3 3 5% 78%	1728
August	1st to 10th	Night	2 2 1 1 1 1 1 1 2 3 85%	1776
	11th to 20th	Night	1 1 1 1 1 1 2 3 89%	1780
	21st to end	Night	1 1 1 1 1 1 1 2 2 3 87%	1980
September	1st to 10th	Night	1 1 1 1 1 1 1 2 3 89%	1800
	11th to 20th	Night	1 1 2 1 2 2 3 3 86%	1864
	21st to end	Night	1 1 1 1 1 1 1 2 3 5% 84%	1980
October	1st to 10th	Night	4 1 1 2 2 1 2 3 2 6% 75%	2047
	11th to 20th	Night	2 2 1 2 2 1 2 2 4 6% 76%	2160
	21st to end	Night	4 1 1 1 2 1 1 2 3 3 81%	2389
November	1st to 10th	Night	5% 2 1 3 3 2 3 3 3 6% 68%	2405
	11th to 20th	Night	6% 2 1 3 3 2 3 3 4 7% 67%	2470
	21st to end	Night	8% 4 2 3 3 3 4 3 5% 7% 59%	2470
December	1st to 10th	Night	10% 5% 2 5% 5% 2 3 4 4 6% 54%	2503
	11th to 20th	Night	17% 6% 3 5% 5% 3 4 5% 6% 7% 40%	3276
	21st to end	Night	12% 7% 4 6% 6% 4 6% 5% 6% 7% 37%	4862

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% 12% 17% 17% 7% 1	2539
	11th to 20th	Day	42% 14% 16% 15% 9% 4	2746
	21st to end	Day	46% 10% 16% 17% 10% 2	3146
February	1st to 10th	Day	33% 5% 14% 25% 17% 5%	1856
	11th to 20th	Day	31% 7% 12% 25% 19% 6%	1860
	21st to end	Day	37% 8% 11% 27% 16% 2	1570
March	1st to 10th	Day	37% 6% 12% 23% 18% 4	1801
	11th to 20th	Day	31% 8% 13% 23% 20% 3	1916
	21st to end	Day	29% 7% 15% 28% 17% 5%	2343
April	1st to 10th	Day	25% 5% 12% 30% 21% 8%	2160
	11th to 20th	Day	23% 5% 12% 26% 24% 10%	2132
	21st to end	Day	17% 6% 11% 30% 28% 7%	2160
May	1st to 10th	Day	14% 3 10% 24% 37% 12%	2209
	11th to 20th	Day	14% 3 8% 26% 34% 14%	2304
	21st to end	Day	14% 4 8% 31% 32% 11%	2658
June	1st to 10th	Day	12% 3 9% 20% 34% 22%	2520
	11th to 20th	Day	4 2 5% 13% 38% 38%	2520
	21st to end	Day	5% 2 2 9% 29% 53%	2520
July	1st to 10th	Day	6% 1 2 6% 25% 59%	2451
	11th to 20th	Day	7% 2 4 8% 28% 50%	2445
	21st to end	Day	9% 1 4 12% 28% 46%	2441
August	1st to 10th	Day	7% 1 4 7% 30% 51%	2148
	11th to 20th	Day	5% 1 4 9% 31% 50%	2122
	21st to end	Day	5% 1 3 7% 35% 49%	2376
September	1st to 10th	Day	6% 1 4 7% 29% 53%	2160
	11th to 20th	Day	6% 2 3 16% 42% 30%	2094
	21st to end	Day	7% 2 4 16% 43% 28%	1980
October	1st to 10th	Day	14% 3 6% 21% 28% 28%	1909
	11th to 20th	Day	13% 4 6% 23% 29% 26%	1800
	21st to end	Day	14% 3 8% 21% 32% 23%	1964
November	1st to 10th	Day	20% 7% 10% 23% 28% 12%	1674
	11th to 20th	Day	25% 5% 17% 22% 26% 6%	1710
	21st to end	Day	28% 7% 8% 24% 23% 10%	1710
December	1st to 10th	Day	33% 7% 15% 19% 18% 8%	1672
	11th to 20th	Day	47% 8% 12% 16% 13% 4	1928
	21st to end	Day	49% 10% 14% 17% 8% 2	2794
January	1st to 10th	Night	42% 9% 16% 23% 9% 1	4406
	11th to 20th	Night	39% 10% 21% 15% 9% 5%	4203
	21st to end	Night	43% 8% 14% 20% 11% 3	4521
February	1st to 10th	Night	34% 4 10% 27% 18% 6%	2321
	11th to 20th	Night	27% 4 12% 28% 22% 7%	2219
	21st to end	Night	33% 5% 12% 29% 17% 3	1884
March	1st to 10th	Night	31% 7% 13% 24% 20% 5%	2165
	11th to 20th	Night	31% 6% 14% 24% 22% 3	2041
	21st to end	Night	30% 5% 13% 30% 17% 4	2012
April	1st to 10th	Night	24% 5% 11% 29% 21% 9%	1800
	11th to 20th	Night	20% 6% 10% 27% 27% 10%	1779
	21st to end	Night	17% 4 10% 31% 33% 5%	1800
May	1st to 10th	Night	16% 3 8% 25% 36% 13%	1749
	11th to 20th	Night	15% 3 6% 23% 38% 16%	1595
	21st to end	Night	14% 5% 8% 24% 35% 15%	1613
June	1st to 10th	Night	11% 3 8% 20% 34% 24%	1440
	11th to 20th	Night	5% 3 5% 14% 34% 40%	1440
	21st to end	Night	3 1 3 7% 31% 55%	1440
July	1st to 10th	Night	4 1 3 5% 24% 64%	1400
	11th to 20th	Night	8% 2 4 9% 20% 58%	1392
	21st to end	Night	11% 2 3 9% 26% 48%	1632
August	1st to 10th	Night	8% 1 2 8% 28% 53%	1767
	11th to 20th	Night	4 1 3 9% 32% 51%	1780
	21st to end	Night	6% 1 2 7% 36% 49%	1980
September	1st to 10th	Night	5% 1 2 8% 28% 56%	1800
	11th to 20th	Night	7% 1 4 14% 41% 33%	1864
	21st to end	Night	8% 1 2 17% 40% 33%	1980
October	1st to 10th	Night	14% 3 4 18% 31% 30%	2047
	11th to 20th	Night	12% 3 7% 21% 30% 27%	2160
	21st to end	Night	12% 2 5% 25% 33% 22%	2389
November	1st to 10th	Night	19% 6% 10% 23% 28% 14%	2405
	11th to 20th	Night	19% 4 15% 24% 28% 10%	2470
	21st to end	Night	26% 4 11% 21% 29% 9%	2470
December	1st to 10th	Night	31% 6% 13% 21% 18% 11%	2503
	11th to 20th	Night	42% 8% 13% 19% 15% 4	3276
	21st to end	Night	41% 10% 17% 21% 9% 2	4862

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	22% 7% 10% 31% 24% 7%	180
	11th to 20th	Day	13% 4 10% 33% 23% 16%	308
	21st to end	Day	15% 3 11% 28% 30% 12%	407
February	1st to 10th	Day	14% 3 11% 30% 25% 16%	439
	11th to 20th	Day	13% 4 17% 34% 23% 10%	455
	21st to end	Day	11% 5% 18% 34% 25% 6%	382
March	1st to 10th	Day	13% 5% 17% 34% 24% 8%	421
	11th to 20th	Day	10% 5% 20% 30% 25% 10%	420
	21st to end	Day	12% 6% 24% 30% 21% 6%	462
April	1st to 10th	Day	11% 5% 20% 28% 25% 11%	420
	11th to 20th	Day	7% 8% 24% 29% 26% 6%	412
	21st to end	Day	4 6% 22% 31% 23% 15%	420
May	1st to 10th	Day	3 6% 24% 29% 28% 11%	423
	11th to 20th	Day	3 2 21% 34% 26% 14%	448
	21st to end	Day	4 5% 19% 22% 35% 15%	485
June	1st to 10th	Day	1 3 13% 29% 33% 21%	450
	11th to 20th	Day	2 2 14% 23% 43% 16%	450
	21st to end	Day	1 1 7% 30% 40% 22%	450
July	1st to 10th	Day	1 3 22% 50% 23%	446
	11th to 20th	Day	1 2 16% 44% 36%	444
	21st to end	Day	2 1 16% 51% 30%	487
August	1st to 10th	Day	2 8% 24% 46% 20%	447
	11th to 20th	Day	2 4 21% 47% 27%	437
	21st to end	Day	1 1 2 23% 47% 26%	495
September	1st to 10th	Day	1 1 5% 26% 44% 22%	450
	11th to 20th	Day	1 2 11% 27% 44% 15%	450
	21st to end	Day	1 2 11% 23% 40% 22%	450
October	1st to 10th	Day	2 2 12% 31% 32% 21%	450
	11th to 20th	Day	3 3 11% 26% 37% 20%	450
	21st to end	Day	1 4 10% 28% 35% 23%	479
November	1st to 10th	Day	6% 2 9% 28% 36% 19%	270
	11th to 20th	Day	7% 3 5% 30% 34% 21%	270
	21st to end	Day	9% 2 12% 27% 33% 17%	270
December	1st to 10th	Day	12% 3 12% 35% 27% 10%	252
	11th to 20th	Day	11% 5% 9% 33% 21% 21%	180
	21st to end	Day	22% 5% 10% 29% 25% 9%	198
January	1st to 10th	Night	19% 2 9% 34% 28% 9%	760
	11th to 20th	Night	9% 2 9% 40% 32% 7%	760
	21st to end	Night	16% 2 9% 36% 31% 6%	836
February	1st to 10th	Night	15% 2 11% 36% 28% 8%	760
	11th to 20th	Night	12% 2 13% 38% 28% 7%	744
	21st to end	Night	14% 4 12% 43% 24% 3	628
March	1st to 10th	Night	11% 3 12% 44% 26% 4	722
	11th to 20th	Night	11% 3 12% 38% 30% 6%	720
	21st to end	Night	13% 2 17% 39% 26% 3	792
April	1st to 10th	Night	9% 3 22% 36% 28% 2	720
	11th to 20th	Night	6% 5% 21% 38% 27% 3	711
	21st to end	Night	6% 6% 20% 35% 28% 5%	720
May	1st to 10th	Night	5% 4 21% 40% 28% 3	669
	11th to 20th	Night	5% 3 21% 40% 31%	531
	21st to end	Night	4 5% 25% 36% 28% 1	451
June	1st to 10th	Night	4 3 21% 46% 24% 2	360
	11th to 20th	Night	1 3 16% 48% 30% 2	360
	21st to end	Night	1 16% 50% 31% 2	360
July	1st to 10th	Night	6% 49% 43% 2	350
	11th to 20th	Night	1 5% 38% 55% 2	348
	21st to end	Night	1 1 2 27% 59% 10%	546
August	1st to 10th	Night	3 5% 36% 50% 6%	702
	11th to 20th	Night	3 33% 56% 7%	712
	21st to end	Night	1 2 25% 64% 8%	792
September	1st to 10th	Night	1 1 4 26% 60% 8%	720
	11th to 20th	Night	1 9% 36% 46% 8%	720
	21st to end	Night	2 2 7% 33% 47% 10%	720
October	1st to 10th	Night	4 1 8% 40% 39% 8%	720
	11th to 20th	Night	3 2 8% 35% 43% 10%	720
	21st to end	Night	4 1 7% 32% 40% 15%	792
November	1st to 10th	Night	6% 2 7% 31% 41% 12%	740
	11th to 20th	Night	6% 1 6% 40% 38% 9%	760
	21st to end	Night	10% 2 8% 38% 35% 8%	760
December	1st to 10th	Night	12% 1 9% 42% 31% 6%	760
	11th to 20th	Night	15% 1 8% 42% 29% 5%	760
	21st to end	Night	14% 3 10% 42% 27% 4	836

Page generated at 2024-02-27 03:30:13. Version ac07

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