Merced
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Merced 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 2 3 3 2 3 3 4 5% 64%	78621
	Night	9% 4 2 4 3 2 3 3 4 6% 61%	80816
Transparency	Day	23% 4 8% 19% 24% 22%	78337
	Night	25% 5% 9% 20% 22% 19%	80621
Seeing	Day	6% 4 16% 29% 31% 14%	14321
	Night	8% 2 17% 42% 27% 4	23893

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	13% 10% 4 9% 8% 4 4 5% 5% 7% 31%	2539
	11th to 20th	Day	14% 9% 4 9% 8% 4 5% 4 5% 6% 32%	2831
	21st to end	Day	18% 10% 4 7% 7% 4 5% 4 5% 7% 29%	3146
February	1st to 10th	Day	14% 6% 3 5% 4 2 3 5% 4 8% 46%	1728
	11th to 20th	Day	11% 5% 2 4 4 2 3 4 5% 8% 51%	1850
	21st to end	Day	13% 5% 1 5% 5% 3 4 3 4 6% 51%	1570
March	1st to 10th	Day	12% 6% 3 5% 4 3 6% 4 7% 8% 43%	1823
	11th to 20th	Day	13% 4 2 4 4 3 4 6% 6% 7% 47%	1980
	21st to end	Day	10% 4 2 4 4 2 4 4 5% 7% 54%	2286
April	1st to 10th	Day	10% 4 2 4 3 2 3 4 5% 5% 57%	2160
	11th to 20th	Day	7% 3 2 3 3 2 2 4 4 6% 64%	2129
	21st to end	Day	5% 3 1 3 3 2 2 3 3 6% 69%	2160
May	1st to 10th	Day	2 2 1 3 3 2 2 2 4 6% 72%	2160
	11th to 20th	Day	2 2 1 2 2 2 2 4 3 6% 74%	2386
	21st to end	Day	4 2 1 2 2 1 3 3 4 6% 72%	2723
June	1st to 10th	Day	2 3 1 2 2 1 2 2 3 6% 76%	2520
	11th to 20th	Day	1 1 1 1 1 2 2 3 87%	2520
	21st to end	Day	2 1 1 2 1 1 2 1 2 2 87%	2520
July	1st to 10th	Day	1 1 1 2 1 2 3 90%	2520
	11th to 20th	Day	1 1 1 1 1 2 2 2 3 85%	2502
	21st to end	Day	1 1 1 1 1 2 3 3 5% 81%	2546
August	1st to 10th	Day	1 2 1 2 1 1 1 1 2 3 85%	2283
	11th to 20th	Day	1 1 1 1 2 3 3 88%	2122
	21st to end	Day	1 1 1 1 1 1 1 2 3 89%	2376
September	1st to 10th	Day	1 1 1 1 1 1 1 2 2 89%	2160
	11th to 20th	Day	1 1 1 1 1 2 2 2 3 85%	2153
	21st to end	Day	2 1 1 1 1 1 1 1 2 4 84%	1980
October	1st to 10th	Day	2 2 1 2 2 1 2 2 3 6% 78%	1800
	11th to 20th	Day	3 1 1 2 2 2 2 3 4 6% 75%	1800
	21st to end	Day	4 2 1 3 2 2 2 3 4 6% 70%	1980
November	1st to 10th	Day	5% 3 2 4 4 3 5% 4 4 7% 60%	1712
	11th to 20th	Day	7% 6% 2 4 4 2 4 3 4 7% 58%	1710
	21st to end	Day	9% 5% 3 4 4 2 4 4 5% 7% 52%	1704
December	1st to 10th	Day	13% 6% 3 6% 5% 3 4 4 3 8% 44%	1520
	11th to 20th	Day	20% 9% 4 9% 6% 3 4 4 4 6% 31%	1928
	21st to end	Day	13% 8% 4 8% 8% 4 5% 6% 7% 9% 29%	2794
January	1st to 10th	Night	14% 7% 3 7% 5% 3 4 4 5% 7% 42%	4406
	11th to 20th	Night	17% 7% 3 7% 6% 3 4 4 5% 7% 34%	4136
	21st to end	Night	19% 7% 3 7% 6% 3 4 4 4 7% 35%	4521
February	1st to 10th	Night	13% 5% 2 5% 4 2 3 3 4 7% 52%	2451
	11th to 20th	Night	12% 4 2 3 3 2 3 4 4 7% 56%	2218
	21st to end	Night	14% 5% 2 3 3 3 3 4 4 5% 54%	1884
March	1st to 10th	Night	13% 6% 2 5% 4 2 5% 4 4 7% 48%	2139
	11th to 20th	Night	12% 5% 2 4 5% 3 4 3 5% 7% 50%	1980
	21st to end	Night	12% 3 2 4 3 1 4 3 4 6% 58%	2068
April	1st to 10th	Night	10% 4 1 3 2 2 3 4 5% 7% 58%	1800
	11th to 20th	Night	6% 2 1 3 3 2 4 4 4 6% 65%	1779
	21st to end	Night	4 2 1 3 3 1 3 3 4 7% 69%	1800
May	1st to 10th	Night	2 3 1 2 2 2 2 2 5% 6% 72%	1800
	11th to 20th	Night	4 2 1 1 2 2 2 2 3 6% 75%	1499
	21st to end	Night	3 1 1 2 2 1 3 3 3 5% 75%	1552
June	1st to 10th	Night	2 2 1 2 2 1 3 3 3 6% 76%	1440
	11th to 20th	Night	1 1 1 1 1 2 2 4 88%	1440
	21st to end	Night	1 1 1 1 2 1 2 3 88%	1440
July	1st to 10th	Night	1 1 2 1 2 2 91%	1440
	11th to 20th	Night	1 1 1 2 1 2 1 2 4 85%	1453
	21st to end	Night	2 1 1 1 2 2 3 2 3 4 79%	1773
August	1st to 10th	Night	2 1 1 1 1 1 1 2 2 87%	1654
	11th to 20th	Night	1 1 2 1 2 2 3 4 83%	1780
	21st to end	Night	1 1 1 1 1 1 1 1 3 90%	1980
September	1st to 10th	Night	1 1 2 1 1 1 1 3 90%	1800
	11th to 20th	Night	2 1 1 1 1 1 1 2 2 3 86%	1805
	21st to end	Night	2 1 1 1 1 1 2 2 2 4 84%	1980
October	1st to 10th	Night	3 2 1 2 2 1 2 3 3 4 78%	2156
	11th to 20th	Night	2 2 1 2 2 1 3 3 4 5% 76%	2160
	21st to end	Night	4 1 2 2 1 1 2 3 5% 78%	2376
November	1st to 10th	Night	7% 4 2 2 2 2 3 3 4 6% 65%	2364
	11th to 20th	Night	6% 3 2 4 3 2 3 3 5% 8% 62%	2470
	21st to end	Night	8% 4 2 3 3 2 3 4 5% 6% 60%	2474
December	1st to 10th	Night	13% 5% 3 5% 4 2 3 3 4 7% 51%	2660
	11th to 20th	Night	16% 7% 3 6% 5% 3 5% 5% 6% 9% 36%	3276
	21st to end	Night	15% 7% 3 7% 8% 4 5% 6% 5% 7% 33%	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	50% 9% 16% 19% 5% 1	2539
	11th to 20th	Day	52% 8% 11% 16% 10% 3	2831
	21st to end	Day	51% 9% 11% 19% 8% 1	3146
February	1st to 10th	Day	36% 5% 12% 25% 15% 6%	1728
	11th to 20th	Day	33% 5% 12% 25% 20% 6%	1860
	21st to end	Day	35% 5% 11% 26% 20% 2	1570
March	1st to 10th	Day	37% 7% 13% 24% 17% 3	1823
	11th to 20th	Day	36% 4 11% 25% 20% 4	1980
	21st to end	Day	29% 5% 16% 26% 20% 4	2286
April	1st to 10th	Day	28% 4 13% 26% 19% 10%	2160
	11th to 20th	Day	23% 4 10% 27% 25% 10%	2132
	21st to end	Day	20% 3 9% 30% 31% 7%	2160
May	1st to 10th	Day	14% 3 10% 25% 34% 13%	2160
	11th to 20th	Day	14% 3 6% 26% 34% 16%	2389
	21st to end	Day	14% 4 9% 32% 28% 13%	2724
June	1st to 10th	Day	12% 2 8% 24% 30% 23%	2520
	11th to 20th	Day	6% 2 5% 18% 35% 35%	2520
	21st to end	Day	7% 1 2 9% 30% 51%	2520
July	1st to 10th	Day	4 1 2 6% 21% 66%	2451
	11th to 20th	Day	7% 2 3 9% 21% 59%	2427
	21st to end	Day	8% 3 2 6% 23% 57%	2405
August	1st to 10th	Day	8% 1 2 8% 26% 55%	2267
	11th to 20th	Day	4 1 2 7% 31% 55%	2122
	21st to end	Day	5% 1 1 7% 34% 52%	2376
September	1st to 10th	Day	5% 1 2 7% 26% 59%	2160
	11th to 20th	Day	7% 1 2 19% 40% 30%	2153
	21st to end	Day	8% 2 3 17% 39% 32%	1980
October	1st to 10th	Day	13% 2 5% 20% 29% 31%	1800
	11th to 20th	Day	13% 3 5% 25% 28% 26%	1800
	21st to end	Day	16% 3 7% 22% 31% 21%	1980
November	1st to 10th	Day	24% 5% 10% 26% 27% 9%	1712
	11th to 20th	Day	29% 4 14% 26% 24% 4	1710
	21st to end	Day	32% 4 12% 25% 22% 7%	1704
December	1st to 10th	Day	38% 6% 13% 18% 18% 6%	1520
	11th to 20th	Day	55% 5% 10% 16% 11% 3	1928
	21st to end	Day	46% 12% 16% 17% 8% 2	2794
January	1st to 10th	Night	38% 11% 16% 23% 9% 1	4406
	11th to 20th	Night	46% 9% 13% 17% 9% 7%	4136
	21st to end	Night	46% 7% 12% 19% 12% 3	4521
February	1st to 10th	Night	33% 4 12% 25% 20% 7%	2451
	11th to 20th	Night	29% 3 10% 26% 26% 6%	2219
	21st to end	Night	32% 4 9% 30% 20% 5%	1884
March	1st to 10th	Night	37% 6% 12% 21% 19% 6%	2139
	11th to 20th	Night	34% 5% 9% 23% 22% 7%	1980
	21st to end	Night	29% 4 16% 26% 18% 7%	2068
April	1st to 10th	Night	25% 4 16% 26% 20% 9%	1800
	11th to 20th	Night	20% 4 13% 28% 26% 10%	1779
	21st to end	Night	16% 5% 12% 29% 30% 8%	1800
May	1st to 10th	Night	14% 3 9% 25% 35% 14%	1800
	11th to 20th	Night	13% 2 7% 29% 34% 15%	1499
	21st to end	Night	13% 3 10% 31% 32% 12%	1552
June	1st to 10th	Night	13% 3 9% 22% 33% 20%	1440
	11th to 20th	Night	5% 2 5% 18% 35% 36%	1440
	21st to end	Night	6% 1 2 9% 29% 53%	1440
July	1st to 10th	Night	4 1 1 5% 22% 67%	1400
	11th to 20th	Night	8% 2 2 6% 22% 61%	1405
	21st to end	Night	12% 2 2 6% 21% 57%	1674
August	1st to 10th	Night	7% 1 2 10% 27% 54%	1645
	11th to 20th	Night	7% 1 2 9% 27% 54%	1780
	21st to end	Night	5% 1 1 8% 29% 56%	1980
September	1st to 10th	Night	5% 1 3 6% 25% 61%	1800
	11th to 20th	Night	7% 1 2 17% 40% 32%	1805
	21st to end	Night	8% 2 3 15% 38% 35%	1980
October	1st to 10th	Night	13% 3 5% 19% 25% 35%	2156
	11th to 20th	Night	12% 3 7% 20% 26% 32%	2160
	21st to end	Night	11% 2 6% 21% 33% 26%	2376
November	1st to 10th	Night	22% 3 8% 25% 26% 16%	2364
	11th to 20th	Night	22% 4 11% 27% 29% 8%	2470
	21st to end	Night	26% 4 10% 24% 29% 8%	2474
December	1st to 10th	Night	34% 5% 12% 22% 18% 10%	2660
	11th to 20th	Night	44% 8% 13% 17% 15% 3	3276
	21st to end	Night	44% 10% 15% 20% 8% 3	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	26% 7% 17% 24% 18% 7%	180
	11th to 20th	Day	15% 5% 16% 25% 25% 14%	354
	21st to end	Day	14% 4 18% 21% 27% 16%	407
February	1st to 10th	Day	16% 7% 18% 20% 22% 18%	379
	11th to 20th	Day	11% 8% 22% 26% 22% 11%	455
	21st to end	Day	12% 7% 21% 30% 24% 7%	382
March	1st to 10th	Day	14% 8% 20% 31% 19% 9%	421
	11th to 20th	Day	16% 7% 18% 29% 17% 13%	420
	21st to end	Day	14% 9% 21% 27% 21% 8%	462
April	1st to 10th	Day	13% 8% 24% 29% 17% 10%	420
	11th to 20th	Day	9% 9% 25% 31% 17% 10%	412
	21st to end	Day	5% 8% 24% 32% 19% 13%	420
May	1st to 10th	Day	3 8% 25% 35% 22% 8%	423
	11th to 20th	Day	4 6% 21% 35% 26% 9%	448
	21st to end	Day	4 7% 17% 30% 29% 13%	485
June	1st to 10th	Day	3 4 20% 31% 30% 12%	450
	11th to 20th	Day	2 3 19% 35% 33% 8%	450
	21st to end	Day	1 1 13% 34% 37% 13%	450
July	1st to 10th	Day	7% 32% 47% 13%	446
	11th to 20th	Day	3 29% 50% 18%	444
	21st to end	Day	1 3 32% 47% 18%	487
August	1st to 10th	Day	2 1 9% 38% 38% 11%	447
	11th to 20th	Day	8% 35% 40% 16%	437
	21st to end	Day	7% 29% 48% 15%	495
September	1st to 10th	Day	1 1 8% 29% 45% 16%	450
	11th to 20th	Day	2 2 16% 31% 33% 16%	450
	21st to end	Day	1 2 12% 29% 37% 20%	450
October	1st to 10th	Day	2 2 20% 23% 31% 22%	450
	11th to 20th	Day	4 4 13% 23% 34% 22%	450
	21st to end	Day	4 4 15% 21% 35% 20%	495
November	1st to 10th	Day	6% 4 13% 23% 29% 25%	308
	11th to 20th	Day	3 6% 12% 24% 36% 19%	270
	21st to end	Day	9% 1 12% 30% 33% 15%	266
December	1st to 10th	Day	16% 2 19% 27% 19% 16%	180
	11th to 20th	Day	9% 7% 20% 24% 23% 17%	180
	21st to end	Day	18% 6% 15% 25% 26% 10%	198
January	1st to 10th	Night	18% 3 14% 34% 25% 6%	760
	11th to 20th	Night	13% 3 11% 37% 30% 6%	760
	21st to end	Night	17% 3 12% 36% 29% 4	836
February	1st to 10th	Night	15% 4 14% 36% 26% 6%	760
	11th to 20th	Night	12% 4 18% 33% 29% 5%	744
	21st to end	Night	15% 4 18% 43% 18% 3	628
March	1st to 10th	Night	15% 4 18% 39% 22% 2	722
	11th to 20th	Night	12% 6% 19% 33% 25% 4	720
	21st to end	Night	14% 4 23% 37% 21% 1	792
April	1st to 10th	Night	10% 3 27% 37% 22% 1	720
	11th to 20th	Night	7% 5% 30% 37% 18% 3	711
	21st to end	Night	4 4 28% 41% 21% 2	720
May	1st to 10th	Night	2 4 28% 43% 20% 2	720
	11th to 20th	Night	5% 3 30% 46% 17%	437
	21st to end	Night	3 4 30% 46% 17%	389
June	1st to 10th	Night	3 4 31% 48% 12% 1	360
	11th to 20th	Night	1 3 28% 53% 16%	360
	21st to end	Night	1 1 24% 55% 19%	360
July	1st to 10th	Night	17% 65% 17%	350
	11th to 20th	Night	1 11% 66% 22%	361
	21st to end	Night	1 10% 51% 35% 2	591
August	1st to 10th	Night	2 13% 55% 27% 3	580
	11th to 20th	Night	16% 54% 28% 2	712
	21st to end	Night	1 1 8% 54% 35% 2	792
September	1st to 10th	Night	1 10% 52% 35% 2	720
	11th to 20th	Night	2 1 18% 45% 32% 3	720
	21st to end	Night	2 1 15% 40% 38% 5%	720
October	1st to 10th	Night	4 2 16% 39% 34% 6%	720
	11th to 20th	Night	3 2 14% 39% 36% 7%	720
	21st to end	Night	4 2 10% 36% 34% 13%	792
November	1st to 10th	Night	8% 1 14% 34% 35% 8%	740
	11th to 20th	Night	8% 1 10% 43% 32% 6%	760
	21st to end	Night	9% 2 12% 37% 35% 6%	760
December	1st to 10th	Night	14% 3 12% 41% 26% 5%	760
	11th to 20th	Night	16% 2 13% 38% 27% 3	760
	21st to end	Night	18% 4 14% 40% 21% 3	836

Page generated at 2024-02-27 03:30:15. Version ac07

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