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 2024-11-05.

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	5% 3 1 3 2 2 2 2 3 5% 70%	104956
	Night	7% 3 1 4 2 2 3 2 4 5% 67%	102830
Transparency	Day	18% 4 8% 17% 24% 28%	104708
	Night	20% 5% 9% 18% 23% 24%	102669
Seeing	Day	6% 5% 16% 29% 30% 15%	15328
	Night	7% 4 20% 38% 26% 5%	24829

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% 4 11% 7% 6% 4 4 6% 7% 31%	2539
	11th to 20th	Day	11% 10% 3 9% 6% 6% 6% 4 5% 6% 34%	2778
	21st to end	Day	17% 10% 4 7% 5% 5% 5% 4 6% 8% 30%	3146
February	1st to 10th	Day	14% 5% 2 5% 4 3 4 4 5% 6% 48%	1800
	11th to 20th	Day	10% 6% 2 4 4 3 3 4 5% 7% 52%	1850
	21st to end	Day	14% 5% 2 5% 5% 3 4 4 4 6% 49%	1570
March	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 4 7% 10% 40%	3138
	11th to 20th	Day	6% 3 1 4 3 3 3 3 4 6% 63%	3449
	21st to end	Day	12% 5% 2 5% 4 4 4 4 6% 7% 47%	4070
April	1st to 10th	Day	8% 4 2 4 3 2 3 3 4 6% 61%	2280
	11th to 20th	Day	6% 4 1 3 3 3 3 3 4 6% 63%	2249
	21st to end	Day	4 2 1 2 3 2 3 3 4 5% 69%	2280
May	1st to 10th	Day	3 2 1 2 1 1 1 1 2 4 81%	3854
	11th to 20th	Day	1 1 1 1 1 1 2 3 4 83%	4087
	21st to end	Day	2 1 1 1 1 1 1 2 3 84%	4813
June	1st to 10th	Day	2 1 1 3 2 2 2 2 4 5% 76%	2660
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 89%	2660
	21st to end	Day	1 1 1 1 1 2 2 2 87%	2660
July	1st to 10th	Day	1 1 1 1 1 1 2 92%	4420
	11th to 20th	Day	1 1 1 1 1 1 2 2 3 3 85%	4420
	21st to end	Day	1 1 1 1 1 1 1 2 3 87%	4485
August	1st to 10th	Day	2 1 1 1 1 1 1 1 2 3 86%	3886
	11th to 20th	Day	1 1 1 1 1 1 2 93%	3724
	21st to end	Day	1 1 1 1 1 1 1 1 2 91%	4180
September	1st to 10th	Day	1 1 1 1 1 1 1 2 2 89%	2280
	11th to 20th	Day	1 1 1 2 1 1 2 1 2 3 85%	2236
	21st to end	Day	1 1 1 1 1 1 2 3 4 83%	2090
October	1st to 10th	Day	1 1 2 1 2 2 2 3 5% 81%	3283
	11th to 20th	Day	2 1 1 2 2 2 2 2 3 4 80%	3161
	21st to end	Day	2 2 1 3 3 3 3 3 4 6% 70%	3448
November	1st to 10th	Day	6% 3 1 4 4 3 4 3 5% 6% 63%	1715
	11th to 20th	Day	8% 4 2 3 4 3 4 3 5% 6% 58%	1710
	21st to end	Day	7% 6% 2 4 4 3 4 3 5% 7% 55%	1710
December	1st to 10th	Day	11% 7% 3 7% 5% 5% 3 3 5% 7% 44%	1603
	11th to 20th	Day	16% 9% 3 8% 6% 5% 4 4 5% 6% 34%	1928
	21st to end	Day	13% 10% 4 11% 6% 5% 5% 4 6% 7% 28%	2794
January	1st to 10th	Night	14% 8% 3 8% 4 4 4 3 4 6% 41%	4406
	11th to 20th	Night	14% 7% 3 8% 4 5% 5% 4 5% 7% 37%	4173
	21st to end	Night	18% 7% 2 8% 4 4 4 3 5% 8% 37%	4521
February	1st to 10th	Night	12% 5% 2 4 3 3 3 3 4 7% 54%	2378
	11th to 20th	Night	10% 4 1 4 3 2 3 3 5% 7% 59%	2218
	21st to end	Night	13% 4 1 4 3 3 3 2 4 6% 56%	1884
March	1st to 10th	Night	12% 5% 2 5% 4 4 4 4 6% 7% 46%	3736
	11th to 20th	Night	6% 4 2 4 3 3 3 2 4 5% 64%	3528
	21st to end	Night	16% 6% 2 6% 4 3 3 3 4 6% 47%	3581
April	1st to 10th	Night	8% 4 2 4 3 3 3 2 4 6% 62%	1900
	11th to 20th	Night	5% 3 1 3 3 2 2 3 3 6% 69%	1879
	21st to end	Night	4 3 1 2 2 3 3 3 4 6% 71%	1900
May	1st to 10th	Night	4 1 1 2 1 1 1 1 3 4 82%	3121
	11th to 20th	Night	2 1 2 1 1 1 2 2 4 85%	2813
	21st to end	Night	2 1 2 1 1 1 1 1 3 87%	2762
June	1st to 10th	Night	3 2 1 2 1 2 2 2 3 4 78%	1520
	11th to 20th	Night	1 1 1 1 1 1 2 3 88%	1520
	21st to end	Night	1 1 1 1 1 2 3 90%	1520
July	1st to 10th	Night	1 1 1 1 1 2 93%	2540
	11th to 20th	Night	1 2 1 1 1 1 1 3 3 84%	2540
	21st to end	Night	1 1 1 1 1 2 1 2 3 87%	3072
August	1st to 10th	Night	1 1 1 1 1 1 1 3 3 85%	3057
	11th to 20th	Night	1 1 1 1 1 2 2 92%	3126
	21st to end	Night	1 1 1 1 1 1 1 2 91%	3498
September	1st to 10th	Night	1 1 1 1 1 1 2 90%	1900
	11th to 20th	Night	1 1 1 2 1 1 2 1 2 3 86%	1943
	21st to end	Night	1 1 1 1 1 1 2 2 3 3 85%	2090
October	1st to 10th	Night	1 1 1 1 1 1 2 2 2 4 83%	3693
	11th to 20th	Night	1 1 1 2 1 2 2 2 3 4 81%	3777
	21st to end	Night	3 2 1 3 1 2 2 1 3 4 79%	4121
November	1st to 10th	Night	6% 4 1 4 2 2 2 2 4 6% 67%	2461
	11th to 20th	Night	5% 4 1 3 2 3 3 2 4 7% 65%	2470
	21st to end	Night	8% 4 1 4 3 2 3 3 5% 7% 60%	2470
December	1st to 10th	Night	10% 6% 3 6% 3 3 3 3 5% 6% 52%	2574
	11th to 20th	Night	18% 6% 3 6% 5% 5% 4 4 6% 8% 37%	3276
	21st to end	Night	13% 7% 3 9% 6% 5% 5% 4 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	25% 4 12% 28% 22% 8%	2280
	11th to 20th	Day	22% 5% 12% 26% 25% 11%	2252
	21st to end	Day	16% 5% 10% 30% 30% 8%	2280
May	1st to 10th	Day	11% 2 7% 23% 36% 20%	3854
	11th to 20th	Day	7% 2 6% 23% 43% 19%	4090
	21st to end	Day	8% 2 5% 26% 38% 21%	4814
June	1st to 10th	Day	11% 3 9% 21% 32% 24%	2660
	11th to 20th	Day	4 1 4 13% 38% 39%	2660
	21st to end	Day	6% 1 2 8% 26% 56%	2660
July	1st to 10th	Day	3 1 1 3 12% 80%	4351
	11th to 20th	Day	7% 1 3 5% 14% 70%	4345
	21st to end	Day	5% 1 2 6% 27% 59%	4344
August	1st to 10th	Day	7% 1 2 5% 27% 58%	3871
	11th to 20th	Day	3 1 1 5% 24% 67%	3760
	21st to end	Day	5% 1 1 7% 29% 58%	4179
September	1st to 10th	Day	6% 1 3 6% 27% 56%	2280
	11th to 20th	Day	7% 2 4 17% 38% 32%	2236
	21st to end	Day	7% 1 4 16% 39% 32%	2090
October	1st to 10th	Day	9% 2 4 12% 24% 48%	3283
	11th to 20th	Day	11% 2 6% 23% 40% 19%	3161
	21st to end	Day	15% 3 6% 19% 37% 19%	3448
November	1st to 10th	Day	22% 6% 11% 26% 26% 9%	1715
	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% 29% 22% 9%	1900
	11th to 20th	Night	19% 4 11% 29% 27% 10%	1879
	21st to end	Night	15% 4 12% 28% 34% 6%	1900
May	1st to 10th	Night	9% 3 8% 27% 35% 18%	3121
	11th to 20th	Night	7% 2 5% 22% 45% 19%	2814
	21st to end	Night	8% 2 5% 25% 45% 16%	2762
June	1st to 10th	Night	12% 3 7% 22% 32% 24%	1520
	11th to 20th	Night	5% 2 4 13% 37% 40%	1520
	21st to end	Night	4 1 2 7% 26% 60%	1520
July	1st to 10th	Night	3 1 2 13% 81%	2500
	11th to 20th	Night	8% 1 2 4 14% 71%	2492
	21st to end	Night	5% 1 2 6% 24% 61%	2976
August	1st to 10th	Night	8% 2 5% 23% 62%	3048
	11th to 20th	Night	3 1 2 3 19% 72%	3156
	21st to end	Night	5% 1 7% 23% 64%	3498
September	1st to 10th	Night	5% 1 1 6% 25% 62%	1900
	11th to 20th	Night	7% 2 3 13% 39% 36%	1943
	21st to end	Night	7% 1 2 14% 37% 38%	2090
October	1st to 10th	Night	8% 2 3 10% 23% 55%	3693
	11th to 20th	Night	9% 2 5% 22% 40% 23%	3777
	21st to end	Night	12% 1 4 19% 42% 22%	4121
November	1st to 10th	Night	19% 4 10% 25% 27% 14%	2461
	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% 25% 17% 12%	460
	11th to 20th	Day	9% 11% 24% 30% 18% 8%	452
	21st to end	Day	3 12% 25% 28% 20% 12%	460
May	1st to 10th	Day	5% 8% 27% 33% 19% 8%	463
	11th to 20th	Day	3 7% 23% 34% 26% 7%	488
	21st to end	Day	5% 7% 18% 31% 30% 10%	529
June	1st to 10th	Day	1 4 21% 33% 28% 13%	490
	11th to 20th	Day	2 4 19% 33% 31% 12%	490
	21st to end	Day	2 12% 35% 35% 15%	490
July	1st to 10th	Day	1 1 8% 31% 41% 18%	486
	11th to 20th	Day	1 3 27% 44% 25%	484
	21st to end	Day	1 5% 28% 47% 19%	531
August	1st to 10th	Day	3 1 10% 35% 37% 15%	487
	11th to 20th	Day	1 9% 35% 37% 18%	477
	21st to end	Day	1 1 8% 29% 41% 19%	539
September	1st to 10th	Day	1 1 9% 31% 37% 20%	490
	11th to 20th	Day	2 3 18% 35% 30% 13%	490
	21st to end	Day	1 2 14% 27% 37% 18%	490
October	1st to 10th	Day	1 3 15% 30% 30% 20%	490
	11th to 20th	Day	3 5% 14% 28% 30% 21%	490
	21st to end	Day	4 4 13% 24% 34% 20%	539
November	1st to 10th	Day	6% 4 11% 22% 34% 22%	287
	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% 32% 30% 20% 2	751
	21st to end	Night	4 10% 33% 29% 20% 4	760
May	1st to 10th	Night	4 7% 37% 32% 18% 2	727
	11th to 20th	Night	4 7% 38% 40% 10%	553
	21st to end	Night	4 9% 37% 43% 8%	411
June	1st to 10th	Night	3 8% 44% 37% 7% 1	380
	11th to 20th	Night	1 6% 41% 42% 10%	380
	21st to end	Night	2 3 40% 44% 11%	380
July	1st to 10th	Night	1 34% 52% 13%	370
	11th to 20th	Night	3 23% 60% 14% 1	368
	21st to end	Night	1 19% 50% 27% 3	600
August	1st to 10th	Night	3 1 24% 48% 21% 2	685
	11th to 20th	Night	1 1 21% 48% 27% 3	752
	21st to end	Night	1 1 15% 44% 36% 3	836
September	1st to 10th	Night	1 1 14% 44% 36% 4	760
	11th to 20th	Night	2 2 27% 38% 26% 5%	760
	21st to end	Night	2 2 16% 35% 38% 7%	760
October	1st to 10th	Night	3 3 16% 36% 34% 8%	760
	11th to 20th	Night	4 3 13% 34% 38% 9%	760
	21st to end	Night	4 2 12% 31% 37% 13%	836
November	1st to 10th	Night	7% 2 10% 33% 38% 10%	760
	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 2024-11-02 23:11:08. Version ac07

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