Fresno
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fresno clear sky chart from 2005-11-06 to 2024-04-10.

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 2 3 3 2 3 3 4 6% 64%	83316
	Night	8% 4 2 4 3 2 3 3 4 6% 62%	85541
Transparency	Day	22% 5% 9% 19% 23% 22%	83031
	Night	23% 6% 10% 20% 22% 19%	85349
Seeing	Day	6% 5% 16% 29% 30% 14%	14497
	Night	7% 4 19% 38% 27% 5%	24143

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	11% 10% 4 9% 8% 5% 5% 5% 6% 7% 31%	2539
	11th to 20th	Day	11% 9% 4 8% 8% 4 6% 6% 5% 6% 34%	2778
	21st to end	Day	17% 10% 4 6% 6% 4 6% 5% 5% 7% 30%	3146
February	1st to 10th	Day	14% 5% 3 5% 4 2 4 5% 5% 6% 48%	1800
	11th to 20th	Day	10% 5% 3 4 4 2 4 4 5% 7% 53%	1850
	21st to end	Day	14% 4 2 5% 6% 2 4 4 3 6% 49%	1570
March	1st to 10th	Day	10% 6% 2 6% 6% 3 5% 5% 6% 10% 41%	3138
	11th to 20th	Day	6% 3 1 4 4 2 3 4 4 6% 63%	3449
	21st to end	Day	12% 5% 2 4 4 3 4 5% 6% 7% 47%	4070
April	1st to 10th	Day	9% 3 2 3 4 2 3 3 4 6% 61%	2270
	11th to 20th	Day	7% 3 2 3 3 2 3 3 4 6% 64%	2129
	21st to end	Day	5% 2 1 2 3 2 3 4 4 6% 68%	2160
May	1st to 10th	Day	2 2 1 3 3 2 2 3 4 6% 74%	2188
	11th to 20th	Day	2 1 1 2 2 1 2 3 4 6% 75%	2304
	21st to end	Day	4 2 1 2 2 2 2 3 3 5% 75%	2723
June	1st to 10th	Day	2 1 1 2 2 1 2 2 4 5% 76%	2520
	11th to 20th	Day	1 1 1 1 1 2 2 3 89%	2520
	21st to end	Day	1 2 1 1 2 2 2 87%	2520
July	1st to 10th	Day	1 1 1 1 1 1 2 4 87%	2520
	11th to 20th	Day	1 1 1 1 1 1 2 2 3 3 84%	2520
	21st to end	Day	1 2 1 1 2 1 2 3 4 4 79%	2563
August	1st to 10th	Day	2 1 1 1 1 1 2 2 2 3 85%	2214
	11th to 20th	Day	1 1 1 1 1 2 3 88%	2122
	21st to end	Day	1 1 1 1 1 1 1 2 3 88%	2376
September	1st to 10th	Day	1 1 1 1 1 1 2 2 3 88%	2160
	11th to 20th	Day	1 1 1 2 1 1 2 1 2 3 86%	2119
	21st to end	Day	1 1 1 1 1 1 2 2 3 5% 82%	1980
October	1st to 10th	Day	2 2 1 2 2 1 2 3 4 5% 76%	1864
	11th to 20th	Day	3 1 1 2 2 1 2 3 3 5% 78%	1800
	21st to end	Day	3 2 1 2 3 1 2 3 3 6% 73%	1980
November	1st to 10th	Day	6% 2 1 3 4 2 4 4 5% 7% 63%	1679
	11th to 20th	Day	8% 4 2 3 4 3 4 4 4 6% 58%	1710
	21st to end	Day	8% 5% 3 4 4 2 4 4 5% 7% 55%	1710
December	1st to 10th	Day	11% 6% 3 6% 6% 3 4 4 5% 7% 44%	1603
	11th to 20th	Day	17% 8% 4 7% 6% 4 5% 5% 5% 6% 34%	1928
	21st to end	Day	13% 10% 4 9% 8% 3 5% 5% 6% 8% 28%	2794
January	1st to 10th	Night	14% 8% 4 7% 5% 3 4 3 4 6% 41%	4406
	11th to 20th	Night	14% 7% 3 7% 6% 4 5% 5% 5% 7% 37%	4173
	21st to end	Night	18% 7% 3 7% 5% 3 4 4 5% 8% 37%	4521
February	1st to 10th	Night	13% 5% 2 3 3 2 3 3 4 6% 54%	2378
	11th to 20th	Night	10% 4 1 3 3 2 3 4 4 7% 59%	2218
	21st to end	Night	13% 4 2 4 4 2 3 3 4 6% 56%	1884
March	1st to 10th	Night	12% 5% 2 5% 5% 3 4 5% 6% 7% 46%	3736
	11th to 20th	Night	6% 4 2 4 3 2 3 3 4 6% 64%	3528
	21st to end	Night	17% 5% 2 4 4 2 3 4 4 6% 47%	3581
April	1st to 10th	Night	8% 3 2 3 3 1 3 3 4 6% 62%	1900
	11th to 20th	Night	5% 2 1 3 3 2 3 3 3 6% 69%	1779
	21st to end	Night	4 2 1 2 2 2 3 3 4 6% 71%	1800
May	1st to 10th	Night	4 2 1 2 2 1 2 2 4 6% 74%	1769
	11th to 20th	Night	3 1 1 3 2 1 1 3 3 5% 77%	1587
	21st to end	Night	3 2 1 2 2 1 2 3 2 4 77%	1552
June	1st to 10th	Night	3 2 1 2 2 1 2 3 3 4 78%	1440
	11th to 20th	Night	1 1 1 1 2 2 2 3 88%	1440
	21st to end	Night	1 1 1 1 2 3 90%	1440
July	1st to 10th	Night	1 2 1 1 2 4 88%	1440
	11th to 20th	Night	1 2 1 1 2 1 1 2 3 3 83%	1440
	21st to end	Night	1 1 1 1 2 1 3 3 3 5% 78%	1750
August	1st to 10th	Night	2 1 1 1 1 1 1 2 2 87%	1722
	11th to 20th	Night	1 1 1 1 1 1 2 3 3 86%	1780
	21st to end	Night	1 1 1 1 1 1 1 2 3 90%	1980
September	1st to 10th	Night	1 1 1 2 1 1 1 2 2 90%	1800
	11th to 20th	Night	1 1 1 1 1 1 2 1 2 3 87%	1840
	21st to end	Night	1 1 1 1 1 1 2 2 3 3 84%	1980
October	1st to 10th	Night	2 2 1 2 2 1 3 3 3 5% 75%	2092
	11th to 20th	Night	2 2 1 2 1 1 3 3 5% 5% 75%	2160
	21st to end	Night	3 1 2 1 1 2 2 2 4 81%	2376
November	1st to 10th	Night	6% 4 1 3 3 2 3 2 4 6% 67%	2397
	11th to 20th	Night	5% 3 1 3 3 3 3 3 4 7% 65%	2470
	21st to end	Night	8% 3 1 4 3 2 2 4 5% 7% 60%	2470
December	1st to 10th	Night	11% 6% 3 5% 4 2 3 3 5% 6% 52%	2574
	11th to 20th	Night	18% 6% 3 5% 5% 3 5% 5% 6% 8% 37%	3276
	21st to end	Night	13% 7% 3 8% 8% 4 5% 5% 5% 7% 35%	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% 14% 18% 16% 6% 1	2539
	11th to 20th	Day	47% 11% 14% 15% 9% 4	2778
	21st to end	Day	48% 12% 14% 16% 9% 1	3146
February	1st to 10th	Day	34% 8% 13% 24% 16% 5%	1800
	11th to 20th	Day	31% 6% 12% 24% 20% 6%	1860
	21st to end	Day	36% 7% 13% 26% 16% 2	1570
March	1st to 10th	Day	34% 13% 18% 20% 14% 2	3138
	11th to 20th	Day	21% 6% 14% 32% 17% 10%	3449
	21st to end	Day	32% 10% 15% 24% 15% 4	4070
April	1st to 10th	Day	26% 4 12% 28% 22% 9%	2270
	11th to 20th	Day	23% 5% 11% 25% 25% 11%	2132
	21st to end	Day	17% 5% 11% 30% 29% 8%	2160
May	1st to 10th	Day	14% 3 10% 24% 36% 14%	2188
	11th to 20th	Day	13% 3 7% 25% 34% 17%	2307
	21st to end	Day	13% 4 7% 31% 32% 13%	2724
June	1st to 10th	Day	12% 3 9% 20% 31% 25%	2520
	11th to 20th	Day	4 2 4 14% 37% 39%	2520
	21st to end	Day	6% 1 2 9% 28% 54%	2520
July	1st to 10th	Day	5% 1 2 6% 21% 65%	2451
	11th to 20th	Day	7% 1 3 8% 23% 57%	2445
	21st to end	Day	9% 2 4 10% 23% 52%	2421
August	1st to 10th	Day	8% 2 3 7% 26% 55%	2198
	11th to 20th	Day	5% 1 2 8% 30% 54%	2122
	21st to end	Day	6% 1 2 6% 35% 51%	2376
September	1st to 10th	Day	6% 1 4 7% 27% 55%	2160
	11th to 20th	Day	7% 2 4 16% 38% 33%	2119
	21st to end	Day	8% 2 4 17% 40% 30%	1980
October	1st to 10th	Day	12% 3 7% 20% 28% 30%	1864
	11th to 20th	Day	11% 3 6% 24% 30% 26%	1800
	21st to end	Day	13% 4 7% 22% 31% 23%	1980
November	1st to 10th	Day	22% 6% 11% 25% 27% 9%	1679
	11th to 20th	Day	25% 7% 15% 25% 24% 4	1710
	21st to end	Day	29% 6% 11% 25% 22% 8%	1710
December	1st to 10th	Day	38% 7% 11% 18% 19% 7%	1603
	11th to 20th	Day	48% 9% 12% 17% 11% 3	1928
	21st to end	Day	49% 13% 16% 14% 8% 1	2794
January	1st to 10th	Night	40% 12% 16% 22% 9% 1	4406
	11th to 20th	Night	41% 12% 17% 15% 9% 6%	4173
	21st to end	Night	42% 9% 13% 21% 11% 3	4521
February	1st to 10th	Night	31% 5% 12% 26% 19% 7%	2378
	11th to 20th	Night	25% 5% 11% 27% 24% 6%	2219
	21st to end	Night	29% 6% 14% 28% 19% 4	1884
March	1st to 10th	Night	32% 10% 15% 21% 19% 3	3736
	11th to 20th	Night	21% 5% 15% 29% 21% 8%	3528
	21st to end	Night	36% 8% 13% 25% 14% 3	3581
April	1st to 10th	Night	24% 5% 12% 28% 22% 9%	1900
	11th to 20th	Night	19% 4 11% 28% 28% 11%	1779
	21st to end	Night	16% 4 12% 28% 34% 6%	1800
May	1st to 10th	Night	13% 3 10% 24% 33% 17%	1769
	11th to 20th	Night	12% 3 6% 25% 36% 17%	1588
	21st to end	Night	14% 3 8% 26% 35% 14%	1552
June	1st to 10th	Night	12% 3 7% 22% 32% 24%	1440
	11th to 20th	Night	5% 2 4 14% 35% 40%	1440
	21st to end	Night	4 1 2 7% 28% 58%	1440
July	1st to 10th	Night	5% 1 2 4 23% 67%	1400
	11th to 20th	Night	8% 1 2 7% 22% 59%	1392
	21st to end	Night	10% 2 4 9% 23% 53%	1653
August	1st to 10th	Night	8% 1 1 7% 25% 58%	1713
	11th to 20th	Night	5% 2 3 6% 27% 57%	1780
	21st to end	Night	5% 1 1 7% 30% 56%	1980
September	1st to 10th	Night	5% 2 2 6% 25% 61%	1800
	11th to 20th	Night	6% 2 3 13% 39% 37%	1840
	21st to end	Night	7% 1 2 15% 37% 37%	1980
October	1st to 10th	Night	13% 3 6% 17% 27% 35%	2092
	11th to 20th	Night	12% 3 7% 20% 28% 30%	2160
	21st to end	Night	11% 2 5% 23% 36% 23%	2376
November	1st to 10th	Night	19% 4 10% 24% 28% 15%	2397
	11th to 20th	Night	18% 6% 12% 26% 28% 10%	2470
	21st to end	Night	24% 4 11% 24% 28% 9%	2470
December	1st to 10th	Night	32% 7% 11% 22% 16% 12%	2574
	11th to 20th	Night	43% 9% 13% 18% 14% 3	3276
	21st to end	Night	41% 13% 17% 17% 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	27% 5% 14% 27% 19% 7%	180
	11th to 20th	Day	15% 5% 14% 26% 24% 17%	327
	21st to end	Day	15% 3 14% 23% 32% 13%	407
February	1st to 10th	Day	13% 6% 15% 25% 26% 17%	412
	11th to 20th	Day	12% 7% 16% 31% 20% 13%	455
	21st to end	Day	12% 6% 22% 31% 22% 7%	382
March	1st to 10th	Day	13% 6% 20% 30% 23% 7%	460
	11th to 20th	Day	12% 9% 23% 25% 21% 11%	460
	21st to end	Day	13% 11% 24% 27% 17% 7%	506
April	1st to 10th	Day	11% 10% 25% 26% 17% 11%	457
	11th to 20th	Day	8% 12% 25% 30% 17% 7%	412
	21st to end	Day	3 12% 25% 28% 20% 12%	420
May	1st to 10th	Day	4 8% 25% 35% 19% 8%	423
	11th to 20th	Day	4 8% 25% 33% 25% 6%	448
	21st to end	Day	6% 7% 18% 30% 29% 10%	485
June	1st to 10th	Day	1 4 22% 32% 28% 13%	450
	11th to 20th	Day	2 3 19% 33% 31% 12%	450
	21st to end	Day	2 13% 35% 34% 15%	450
July	1st to 10th	Day	1 1 8% 32% 40% 18%	446
	11th to 20th	Day	1 3 27% 43% 26%	444
	21st to end	Day	1 4 28% 48% 19%	487
August	1st to 10th	Day	3 1 11% 35% 37% 13%	447
	11th to 20th	Day	1 8% 33% 39% 18%	437
	21st to end	Day	2 1 6% 29% 43% 18%	495
September	1st to 10th	Day	2 1 9% 31% 38% 19%	450
	11th to 20th	Day	2 3 16% 36% 31% 13%	450
	21st to end	Day	1 3 13% 27% 38% 18%	450
October	1st to 10th	Day	2 4 16% 30% 30% 19%	450
	11th to 20th	Day	3 5% 14% 27% 30% 21%	450
	21st to end	Day	4 4 14% 24% 35% 20%	495
November	1st to 10th	Day	6% 4 11% 22% 34% 23%	275
	11th to 20th	Day	6% 5% 9% 22% 36% 21%	270
	21st to end	Day	9% 2 10% 30% 31% 18%	270
December	1st to 10th	Day	13% 2 12% 33% 27% 12%	219
	11th to 20th	Day	11% 6% 11% 32% 23% 17%	180
	21st to end	Day	20% 6% 14% 26% 26% 9%	198
January	1st to 10th	Night	18% 2 11% 34% 27% 8%	760
	11th to 20th	Night	11% 2 9% 38% 33% 7%	760
	21st to end	Night	16% 2 11% 36% 30% 5%	836
February	1st to 10th	Night	14% 3 12% 36% 28% 7%	760
	11th to 20th	Night	10% 5% 14% 35% 31% 5%	744
	21st to end	Night	13% 3 16% 40% 24% 3	628
March	1st to 10th	Night	12% 4 19% 39% 23% 3	760
	11th to 20th	Night	10% 5% 21% 36% 24% 5%	760
	21st to end	Night	13% 6% 25% 36% 19% 1	836
April	1st to 10th	Night	9% 8% 30% 29% 21% 3	760
	11th to 20th	Night	5% 11% 33% 30% 19% 2	711
	21st to end	Night	4 10% 33% 29% 20% 4	720
May	1st to 10th	Night	4 8% 36% 32% 19% 2	689
	11th to 20th	Night	4 8% 38% 39% 11%	524
	21st to end	Night	4 9% 36% 42% 8%	389
June	1st to 10th	Night	3 8% 43% 38% 7% 1	360
	11th to 20th	Night	1 6% 40% 43% 10%	360
	21st to end	Night	2 3 41% 44% 11%	360
July	1st to 10th	Night	1 35% 52% 12%	350
	11th to 20th	Night	3 23% 59% 14% 1	348
	21st to end	Night	1 18% 49% 28% 3	568
August	1st to 10th	Night	3 1 25% 48% 21% 2	648
	11th to 20th	Night	1 1 19% 48% 28% 3	712
	21st to end	Night	1 1 14% 45% 37% 3	792
September	1st to 10th	Night	1 1 14% 44% 37% 4	720
	11th to 20th	Night	2 2 26% 38% 28% 5%	720
	21st to end	Night	2 3 17% 33% 38% 7%	720
October	1st to 10th	Night	3 3 17% 37% 33% 8%	720
	11th to 20th	Night	4 2 13% 34% 38% 9%	720
	21st to end	Night	4 2 12% 30% 38% 14%	792
November	1st to 10th	Night	7% 2 10% 33% 38% 10%	740
	11th to 20th	Night	6% 2 8% 40% 36% 8%	760
	21st to end	Night	8% 3 11% 38% 34% 7%	760
December	1st to 10th	Night	12% 3 9% 40% 30% 6%	760
	11th to 20th	Night	16% 2 8% 42% 27% 5%	760
	21st to end	Night	17% 3 11% 42% 23% 4	836

Page generated at 2024-04-07 06:28:09. Version ac07

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