Fremont Peak
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fremont Peak clear sky chart from 2005-11-06 to 2024-12-02.

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% 5% 2 5% 3 3 3 3 5% 7% 58%	105191
	Night	7% 7% 3 6% 4 3 4 3 5% 6% 51%	103206
Transparency	Day	24% 5% 8% 17% 24% 22%	104948
	Night	30% 6% 10% 16% 20% 19%	103039
Seeing	Day	8% 9% 26% 32% 19% 6%	15553
	Night	9% 4 13% 33% 32% 9%	24995

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	12% 10% 4 7% 4 4 3 3 4 6% 42%	2703
	11th to 20th	Day	13% 8% 3 9% 5% 5% 5% 4 5% 7% 35%	2860
	21st to end	Day	18% 11% 3 8% 4 4 4 4 5% 6% 32%	3146
February	1st to 10th	Day	14% 8% 2 5% 4 3 3 3 5% 6% 46%	1710
	11th to 20th	Day	12% 8% 2 6% 4 2 4 4 6% 6% 46%	1811
	21st to end	Day	11% 9% 2 7% 5% 3 4 3 5% 5% 45%	1570
March	1st to 10th	Day	11% 11% 4 9% 7% 5% 7% 5% 7% 7% 27%	3323
	11th to 20th	Day	9% 5% 2 5% 3 3 4 3 5% 7% 54%	3490
	21st to end	Day	10% 10% 4 8% 6% 5% 6% 4 6% 7% 35%	3934
April	1st to 10th	Day	9% 8% 3 6% 5% 3 3 4 5% 7% 47%	2280
	11th to 20th	Day	8% 7% 2 5% 4 4 4 3 5% 7% 51%	2249
	21st to end	Day	6% 7% 2 5% 4 4 3 4 5% 7% 55%	2280
May	1st to 10th	Day	6% 3 2 3 2 2 3 2 4 6% 68%	3800
	11th to 20th	Day	2 4 2 4 2 2 2 3 5% 8% 65%	4145
	21st to end	Day	3 10% 2 5% 3 3 3 2 4 8% 57%	4813
June	1st to 10th	Day	3 6% 2 5% 3 3 3 4 5% 8% 58%	2660
	11th to 20th	Day	2 4 1 3 2 2 2 3 3 7% 71%	2660
	21st to end	Day	2 3 1 3 3 3 3 2 3 6% 72%	2660
July	1st to 10th	Day	2 1 2 1 2 2 1 3 4 82%	4420
	11th to 20th	Day	1 2 1 3 3 3 3 3 5% 8% 70%	4142
	21st to end	Day	1 1 2 3 3 3 3 4 10% 69%	4455
August	1st to 10th	Day	1 3 1 3 2 2 3 2 5% 11% 66%	4091
	11th to 20th	Day	2 1 2 2 1 2 2 4 8% 76%	3728
	21st to end	Day	2 1 3 2 2 2 3 4 8% 72%	4180
September	1st to 10th	Day	1 3 1 2 2 1 2 1 3 6% 78%	2280
	11th to 20th	Day	2 4 2 4 3 3 3 2 4 8% 65%	2280
	21st to end	Day	3 2 1 2 2 2 2 2 4 6% 74%	2043
October	1st to 10th	Day	2 2 1 3 2 3 2 2 3 5% 74%	3180
	11th to 20th	Day	2 4 2 5% 3 3 3 2 3 6% 66%	3161
	21st to end	Day	3 3 1 4 3 3 4 3 5% 7% 62%	3448
November	1st to 10th	Day	6% 5% 2 5% 3 4 4 3 4 7% 56%	1904
	11th to 20th	Day	7% 6% 2 6% 4 3 4 4 5% 6% 54%	1800
	21st to end	Day	10% 4 2 4 3 4 3 3 5% 7% 55%	1735
December	1st to 10th	Day	10% 8% 2 6% 4 3 5% 3 6% 7% 46%	1528
	11th to 20th	Day	18% 11% 3 8% 5% 3 5% 4 6% 6% 32%	1928
	21st to end	Day	12% 10% 4 7% 6% 4 5% 4 6% 7% 37%	2794
January	1st to 10th	Night	11% 10% 3 7% 4 3 4 3 5% 6% 45%	4243
	11th to 20th	Night	14% 8% 3 8% 5% 5% 5% 4 7% 7% 34%	4110
	21st to end	Night	19% 11% 4 8% 4 4 4 3 5% 6% 32%	4521
February	1st to 10th	Night	13% 8% 2 5% 4 4 3 3 4 5% 49%	2470
	11th to 20th	Night	10% 7% 4 6% 4 3 4 4 6% 7% 45%	2256
	21st to end	Night	11% 8% 2 6% 4 4 3 2 4 6% 50%	1884
March	1st to 10th	Night	15% 16% 3 8% 5% 4 4 3 4 5% 32%	3537
	11th to 20th	Night	8% 7% 2 6% 3 4 4 3 4 7% 51%	3490
	21st to end	Night	13% 14% 4 7% 5% 4 4 4 6% 6% 34%	3719
April	1st to 10th	Night	10% 8% 2 5% 5% 4 4 4 5% 6% 47%	1900
	11th to 20th	Night	8% 7% 2 6% 4 3 3 3 5% 7% 52%	1879
	21st to end	Night	5% 8% 2 4 3 3 4 3 6% 8% 54%	1900
May	1st to 10th	Night	2 7% 3 6% 3 3 3 3 4 5% 60%	3180
	11th to 20th	Night	2 10% 6% 10% 5% 3 3 3 5% 7% 44%	2749
	21st to end	Night	3 11% 4 7% 3 3 3 3 4 4 55%	2762
June	1st to 10th	Night	4 8% 3 7% 4 3 4 3 5% 7% 52%	1520
	11th to 20th	Night	2 6% 3 5% 3 3 3 4 5% 7% 59%	1520
	21st to end	Night	1 6% 2 7% 3 4 3 2 4 5% 63%	1520
July	1st to 10th	Night	3 2 4 3 3 2 1 3 5% 73%	2540
	11th to 20th	Night	3 2 6% 3 4 4 3 5% 8% 62%	2822
	21st to end	Night	3 2 7% 5% 5% 7% 8% 9% 10% 44%	3109
August	1st to 10th	Night	1 5% 2 6% 4 3 4 3 5% 9% 58%	2848
	11th to 20th	Night	4 2 3 3 3 3 3 5% 7% 67%	3121
	21st to end	Night	1 5% 3 7% 3 3 4 3 5% 6% 62%	3498
September	1st to 10th	Night	1 4 2 4 3 2 2 2 4 7% 69%	1900
	11th to 20th	Night	3 6% 3 7% 3 3 3 3 5% 6% 58%	1900
	21st to end	Night	2 5% 1 3 3 2 2 2 3 6% 70%	2132
October	1st to 10th	Night	3 3 1 2 2 2 2 2 3 5% 74%	3800
	11th to 20th	Night	3 6% 3 6% 4 4 5% 3 6% 7% 55%	3777
	21st to end	Night	3 5% 2 6% 3 3 3 2 5% 6% 62%	4121
November	1st to 10th	Night	7% 6% 2 5% 3 3 3 3 4 6% 59%	2394
	11th to 20th	Night	8% 7% 3 4 3 3 3 3 5% 9% 53%	2600
	21st to end	Night	8% 5% 2 5% 4 3 4 3 5% 6% 55%	2660
December	1st to 10th	Night	11% 6% 2 5% 4 3 4 3 5% 6% 50%	2686
	11th to 20th	Night	16% 10% 3 8% 5% 4 5% 4 5% 7% 33%	3276
	21st to end	Night	14% 10% 3 7% 6% 5% 6% 4 6% 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	41% 7% 11% 29% 10% 3	2703
	11th to 20th	Day	47% 7% 12% 15% 11% 8%	2860
	21st to end	Day	51% 6% 9% 16% 14% 5%	3146
February	1st to 10th	Day	38% 4 8% 19% 19% 11%	1710
	11th to 20th	Day	37% 6% 10% 18% 22% 8%	1821
	21st to end	Day	41% 5% 8% 22% 19% 5%	1570
March	1st to 10th	Day	47% 13% 12% 11% 14% 2	3323
	11th to 20th	Day	28% 7% 11% 28% 16% 11%	3490
	21st to end	Day	43% 10% 15% 20% 10% 2	3934
April	1st to 10th	Day	36% 7% 10% 25% 17% 5%	2280
	11th to 20th	Day	31% 6% 12% 25% 20% 6%	2252
	21st to end	Day	27% 7% 12% 28% 21% 5%	2280
May	1st to 10th	Day	18% 4 10% 30% 30% 9%	3800
	11th to 20th	Day	14% 4 10% 25% 34% 12%	4148
	21st to end	Day	21% 6% 11% 23% 34% 5%	4814
June	1st to 10th	Day	21% 7% 12% 23% 27% 10%	2660
	11th to 20th	Day	14% 3 9% 20% 36% 20%	2660
	21st to end	Day	12% 3 6% 12% 29% 39%	2660
July	1st to 10th	Day	7% 2 3 6% 12% 70%	4351
	11th to 20th	Day	10% 3 5% 7% 13% 62%	4071
	21st to end	Day	5% 4 7% 10% 28% 46%	4315
August	1st to 10th	Day	12% 2 4 10% 27% 45%	4076
	11th to 20th	Day	6% 2 4 8% 37% 43%	3764
	21st to end	Day	9% 3 5% 11% 30% 42%	4179
September	1st to 10th	Day	9% 3 3 9% 28% 48%	2280
	11th to 20th	Day	16% 4 6% 19% 35% 20%	2280
	21st to end	Day	12% 3 5% 20% 39% 23%	2043
October	1st to 10th	Day	13% 3 5% 10% 27% 42%	3180
	11th to 20th	Day	17% 6% 6% 20% 32% 18%	3161
	21st to end	Day	20% 5% 6% 20% 31% 18%	3448
November	1st to 10th	Day	27% 5% 9% 20% 24% 15%	1904
	11th to 20th	Day	29% 5% 11% 21% 24% 10%	1800
	21st to end	Day	30% 4 9% 16% 27% 14%	1735
December	1st to 10th	Day	35% 6% 11% 16% 18% 13%	1528
	11th to 20th	Day	52% 6% 9% 13% 14% 6%	1928
	21st to end	Day	45% 6% 13% 21% 11% 4	2794
January	1st to 10th	Night	38% 8% 14% 23% 14% 3	4243
	11th to 20th	Night	47% 9% 14% 13% 10% 8%	4110
	21st to end	Night	51% 6% 10% 15% 12% 6%	4521
February	1st to 10th	Night	38% 5% 8% 17% 20% 13%	2470
	11th to 20th	Night	36% 6% 10% 17% 23% 7%	2257
	21st to end	Night	36% 5% 9% 27% 18% 6%	1884
March	1st to 10th	Night	52% 9% 11% 12% 13% 3	3537
	11th to 20th	Night	30% 7% 12% 21% 19% 11%	3490
	21st to end	Night	46% 10% 13% 18% 10% 4	3719
April	1st to 10th	Night	36% 7% 13% 22% 17% 5%	1900
	11th to 20th	Night	32% 6% 13% 25% 18% 6%	1879
	21st to end	Night	27% 6% 12% 27% 22% 5%	1900
May	1st to 10th	Night	24% 6% 8% 24% 25% 13%	3180
	11th to 20th	Night	26% 11% 15% 13% 21% 14%	2750
	21st to end	Night	25% 9% 11% 18% 31% 6%	2762
June	1st to 10th	Night	26% 9% 11% 18% 25% 11%	1520
	11th to 20th	Night	21% 5% 10% 13% 31% 20%	1520
	21st to end	Night	16% 5% 7% 12% 24% 36%	1520
July	1st to 10th	Night	11% 5% 3 6% 11% 65%	2500
	11th to 20th	Night	14% 5% 6% 9% 12% 54%	2770
	21st to end	Night	15% 5% 23% 10% 19% 27%	3011
August	1st to 10th	Night	18% 4 4 10% 18% 47%	2839
	11th to 20th	Night	12% 3 7% 8% 26% 43%	3151
	21st to end	Night	17% 6% 5% 9% 25% 37%	3498
September	1st to 10th	Night	13% 5% 4 7% 24% 47%	1900
	11th to 20th	Night	21% 7% 5% 17% 28% 22%	1900
	21st to end	Night	14% 4 5% 16% 36% 25%	2132
October	1st to 10th	Night	13% 3 6% 10% 22% 46%	3800
	11th to 20th	Night	22% 10% 8% 15% 25% 20%	3777
	21st to end	Night	22% 4 5% 20% 26% 22%	4121
November	1st to 10th	Night	27% 4 9% 20% 24% 16%	2394
	11th to 20th	Night	29% 6% 10% 20% 26% 10%	2600
	21st to end	Night	29% 4 10% 17% 25% 15%	2660
December	1st to 10th	Night	33% 7% 10% 18% 20% 13%	2686
	11th to 20th	Night	51% 6% 9% 14% 15% 5%	3276
	21st to end	Night	46% 10% 12% 16% 11% 5%	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	24% 11% 24% 25% 14% 1	279
	11th to 20th	Day	13% 11% 22% 34% 19% 1	370
	21st to end	Day	18% 7% 27% 27% 19% 2	407
February	1st to 10th	Day	18% 12% 25% 21% 19% 4	370
	11th to 20th	Day	16% 14% 28% 28% 13% 2	437
	21st to end	Day	13% 15% 30% 28% 11% 3	382
March	1st to 10th	Day	20% 17% 30% 24% 9% 1	460
	11th to 20th	Day	17% 15% 28% 24% 12% 4	460
	21st to end	Day	15% 19% 33% 23% 9% 1	506
April	1st to 10th	Day	14% 15% 33% 22% 13% 3	460
	11th to 20th	Day	12% 19% 29% 24% 12% 3	452
	21st to end	Day	7% 18% 29% 28% 13% 5%	460
May	1st to 10th	Day	8% 16% 33% 28% 11% 4	463
	11th to 20th	Day	8% 14% 32% 28% 12% 6%	488
	21st to end	Day	9% 13% 30% 30% 13% 5%	529
June	1st to 10th	Day	5% 6% 35% 30% 16% 8%	490
	11th to 20th	Day	3 10% 31% 33% 16% 6%	490
	21st to end	Day	3 5% 27% 36% 22% 7%	490
July	1st to 10th	Day	1 3 24% 42% 22% 8%	486
	11th to 20th	Day	1 2 14% 48% 25% 10%	484
	21st to end	Day	1 1 19% 44% 23% 13%	531
August	1st to 10th	Day	3 5% 24% 40% 19% 9%	487
	11th to 20th	Day	2 25% 39% 22% 11%	477
	21st to end	Day	1 2 19% 43% 25% 10%	539
September	1st to 10th	Day	2 4 18% 40% 25% 12%	490
	11th to 20th	Day	4 7% 29% 33% 20% 7%	490
	21st to end	Day	4 5% 19% 38% 25% 9%	490
October	1st to 10th	Day	4 8% 23% 33% 23% 8%	490
	11th to 20th	Day	5% 7% 23% 28% 26% 10%	490
	21st to end	Day	8% 7% 21% 34% 23% 7%	539
November	1st to 10th	Day	7% 9% 21% 30% 25% 7%	440
	11th to 20th	Day	7% 5% 20% 34% 26% 7%	300
	21st to end	Day	10% 5% 25% 33% 22% 4	267
December	1st to 10th	Day	14% 9% 20% 32% 20% 5%	182
	11th to 20th	Day	16% 8% 21% 24% 24% 6%	180
	21st to end	Day	18% 9% 25% 28% 17% 3	198
January	1st to 10th	Night	15% 7% 14% 36% 21% 8%	760
	11th to 20th	Night	12% 5% 13% 36% 26% 8%	760
	21st to end	Night	17% 5% 12% 36% 24% 5%	836
February	1st to 10th	Night	17% 5% 14% 34% 24% 6%	760
	11th to 20th	Night	15% 5% 17% 34% 23% 6%	744
	21st to end	Night	13% 7% 15% 41% 19% 4	628
March	1st to 10th	Night	16% 8% 18% 33% 21% 4	760
	11th to 20th	Night	14% 4 18% 36% 22% 6%	760
	21st to end	Night	13% 7% 19% 36% 21% 3	836
April	1st to 10th	Night	12% 5% 16% 39% 25% 3	760
	11th to 20th	Night	9% 9% 21% 32% 24% 6%	751
	21st to end	Night	7% 8% 19% 31% 27% 8%	760
May	1st to 10th	Night	6% 5% 19% 36% 26% 7%	760
	11th to 20th	Night	8% 5% 13% 34% 31% 9%	516
	21st to end	Night	7% 7% 17% 32% 30% 7%	411
June	1st to 10th	Night	6% 5% 13% 35% 33% 7%	380
	11th to 20th	Night	4 2 13% 40% 35% 6%	380
	21st to end	Night	2 4 4 32% 50% 8%	380
July	1st to 10th	Night	1 3 7% 23% 56% 10%	370
	11th to 20th	Night	2 6% 17% 53% 21%	529
	21st to end	Night	1 9% 15% 55% 20%	624
August	1st to 10th	Night	4 2 8% 22% 50% 14%	567
	11th to 20th	Night	2 2 7% 32% 45% 12%	747
	21st to end	Night	2 2 7% 23% 51% 16%	836
September	1st to 10th	Night	2 2 6% 25% 51% 14%	760
	11th to 20th	Night	5% 3 8% 30% 42% 12%	760
	21st to end	Night	4 2 7% 30% 43% 15%	760
October	1st to 10th	Night	6% 2 8% 36% 36% 12%	760
	11th to 20th	Night	7% 3 10% 33% 35% 13%	760
	21st to end	Night	6% 4 11% 33% 30% 17%	836
November	1st to 10th	Night	7% 4 13% 35% 29% 11%	780
	11th to 20th	Night	11% 3 12% 36% 30% 9%	800
	21st to end	Night	9% 3 15% 40% 27% 6%	800
December	1st to 10th	Night	13% 5% 13% 37% 25% 6%	768
	11th to 20th	Night	18% 7% 14% 35% 23% 4	760
	21st to end	Night	18% 6% 19% 35% 18% 4	836

Page generated at 2024-11-29 07:43:05. Version ac07

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