Big Meadows
Clear Sky Chart
History

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

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	14% 7% 3 7% 5% 5% 5% 4 6% 7% 38%	101056
	Night	14% 7% 2 6% 4 4 4 4 5% 7% 43%	97887
Transparency	Day	40% 8% 12% 22% 15% 3	104704
	Night	38% 7% 13% 23% 16% 4	102378
Seeing	Day	19% 13% 27% 23% 13% 5%	14982
	Night	17% 10% 27% 31% 14% 2	24651

By Month

Percentage Cloud Cover SE (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	15% 6% 2 6% 4 4 4 3 5% 5% 45%	2811
	11th to 20th	Day	11% 12% 4 8% 5% 4 5% 3 4 4 38%	2840
	21st to end	Day	15% 10% 3 7% 6% 4 5% 4 4 5% 37%	3124
February	1st to 10th	Day	11% 9% 4 8% 6% 4 5% 4 5% 5% 39%	1710
	11th to 20th	Day	15% 9% 3 6% 4 5% 4 4 5% 7% 39%	1663
	21st to end	Day	17% 10% 4 7% 3 4 5% 3 5% 6% 38%	1616
March	1st to 10th	Day	18% 11% 4 8% 4 4 4 3 5% 5% 35%	3435
	11th to 20th	Day	9% 6% 2 6% 4 4 4 4 6% 7% 49%	3480
	21st to end	Day	18% 8% 3 7% 5% 4 5% 4 5% 4 37%	3815
April	1st to 10th	Day	10% 7% 2 7% 6% 5% 5% 4 5% 7% 43%	2251
	11th to 20th	Day	14% 7% 2 6% 4 4 4 3 5% 6% 44%	2254
	21st to end	Day	17% 8% 2 8% 5% 4 4 4 5% 6% 38%	2318
May	1st to 10th	Day	18% 8% 3 9% 6% 6% 6% 4 6% 7% 28%	4082
	11th to 20th	Day	23% 8% 3 6% 4 5% 5% 4 6% 7% 30%	4081
	21st to end	Day	11% 5% 2 6% 5% 5% 5% 5% 7% 10% 39%	4783
June	1st to 10th	Day	12% 6% 2 6% 5% 6% 5% 4 6% 8% 40%	2660
	11th to 20th	Day	11% 6% 3 7% 5% 7% 5% 5% 7% 10% 35%	2660
	21st to end	Day	9% 5% 2 6% 5% 5% 6% 6% 7% 10% 39%	2660
July	1st to 10th	Day	7% 5% 3 6% 5% 6% 6% 6% 8% 11% 39%	4323
	11th to 20th	Day	10% 6% 2 7% 5% 6% 7% 6% 8% 12% 32%	4120
	21st to end	Day	13% 8% 3 8% 7% 6% 7% 5% 6% 9% 28%	4466
August	1st to 10th	Day	15% 6% 2 7% 6% 7% 7% 5% 7% 10% 29%	4104
	11th to 20th	Day	10% 5% 3 7% 5% 6% 7% 6% 9% 9% 33%	3965
	21st to end	Day	10% 5% 2 6% 4 5% 5% 5% 6% 8% 43%	4180
September	1st to 10th	Day	13% 7% 2 6% 4 5% 4 5% 5% 6% 43%	2280
	11th to 20th	Day	14% 7% 3 5% 4 4 4 4 5% 8% 43%	2212
	21st to end	Day	23% 7% 2 6% 5% 4 4 5% 5% 5% 34%	2019
October	1st to 10th	Day	16% 6% 2 6% 3 4 4 2 5% 6% 44%	1900
	11th to 20th	Day	15% 5% 3 5% 3 3 4 3 4 6% 49%	1900
	21st to end	Day	14% 5% 2 5% 4 3 4 3 4 5% 50%	2090
November	1st to 10th	Day	12% 6% 2 5% 3 3 3 2 4 5% 54%	1887
	11th to 20th	Day	14% 5% 2 4 3 5% 4 3 6% 6% 49%	1645
	21st to end	Day	14% 5% 2 5% 4 4 4 4 4 6% 48%	1520
December	1st to 10th	Day	15% 8% 3 7% 5% 5% 4 3 6% 7% 38%	1520
	11th to 20th	Day	14% 6% 2 6% 3 3 3 3 4 7% 49%	1910
	21st to end	Day	18% 8% 3 6% 4 4 4 5% 7% 7% 35%	2772
January	1st to 10th	Night	11% 8% 2 5% 4 4 4 4 5% 7% 47%	4130
	11th to 20th	Night	15% 9% 2 5% 3 3 4 3 4 6% 45%	4120
	21st to end	Night	19% 9% 3 6% 3 4 3 3 5% 4 42%	4532
February	1st to 10th	Night	13% 8% 2 6% 4 5% 4 4 7% 5% 41%	2470
	11th to 20th	Night	18% 9% 2 6% 4 3 4 4 4 5% 40%	2403
	21st to end	Night	14% 9% 3 6% 4 3 4 4 6% 6% 41%	1832
March	1st to 10th	Night	20% 8% 3 7% 4 3 5% 4 5% 5% 36%	3418
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 5% 7% 50%	3480
	21st to end	Night	13% 7% 2 6% 4 4 3 3 5% 6% 48%	3817
April	1st to 10th	Night	13% 8% 2 5% 3 5% 5% 5% 5% 7% 42%	1929
	11th to 20th	Night	11% 7% 2 5% 4 3 4 3 6% 8% 45%	1875
	21st to end	Night	15% 7% 3 5% 4 4 4 4 5% 7% 42%	1876
May	1st to 10th	Night	20% 8% 3 7% 5% 4 5% 4 5% 8% 31%	2813
	11th to 20th	Night	24% 7% 2 7% 4 4 4 3 6% 6% 34%	2812
	21st to end	Night	11% 5% 2 6% 4 4 4 4 7% 9% 44%	2767
June	1st to 10th	Night	11% 5% 3 5% 5% 3 5% 4 7% 9% 43%	1520
	11th to 20th	Night	11% 6% 2 5% 5% 5% 5% 4 6% 10% 40%	1520
	21st to end	Night	9% 5% 2 6% 5% 5% 6% 5% 6% 10% 42%	1520
July	1st to 10th	Night	7% 5% 2 6% 4 5% 6% 5% 8% 10% 42%	2632
	11th to 20th	Night	9% 6% 2 7% 5% 6% 5% 5% 8% 10% 38%	2840
	21st to end	Night	10% 8% 2 8% 6% 5% 4 5% 8% 9% 35%	3087
August	1st to 10th	Night	16% 6% 3 6% 5% 5% 4 4 7% 10% 34%	2825
	11th to 20th	Night	12% 7% 3 9% 5% 5% 5% 4 6% 8% 36%	2817
	21st to end	Night	12% 5% 2 6% 4 3 4 4 5% 8% 47%	3476
September	1st to 10th	Night	14% 6% 2 5% 4 4 3 4 5% 8% 45%	1900
	11th to 20th	Night	14% 6% 2 5% 4 3 4 4 5% 6% 47%	1965
	21st to end	Night	24% 7% 2 5% 4 3 3 3 4 5% 40%	2160
October	1st to 10th	Night	18% 6% 3 5% 4 4 4 2 4 6% 45%	2280
	11th to 20th	Night	13% 6% 2 5% 3 4 4 3 4 7% 50%	2280
	21st to end	Night	14% 5% 1 5% 3 4 4 3 4 6% 52%	2508
November	1st to 10th	Night	12% 8% 2 6% 3 3 3 2 4 6% 50%	2264
	11th to 20th	Night	13% 6% 2 4 4 4 4 3 5% 6% 49%	2530
	21st to end	Night	14% 6% 2 4 4 4 4 3 5% 7% 47%	2660
December	1st to 10th	Night	15% 8% 3 7% 3 4 4 4 4 6% 41%	2660
	11th to 20th	Night	15% 7% 2 5% 4 4 3 3 5% 6% 45%	3285
	21st to end	Night	15% 6% 2 6% 4 5% 5% 4 6% 7% 38%	4884

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% 4 9% 26% 16% 4	2812
	11th to 20th	Day	46% 6% 8% 18% 15% 6%	2840
	21st to end	Day	47% 6% 9% 21% 15% 2	3124
February	1st to 10th	Day	45% 5% 11% 22% 14% 3	1710
	11th to 20th	Day	44% 6% 9% 21% 18% 3	1672
	21st to end	Day	46% 6% 11% 16% 16% 5%	1616
March	1st to 10th	Day	48% 6% 10% 18% 14% 5%	3435
	11th to 20th	Day	32% 6% 9% 27% 22% 4	3480
	21st to end	Day	48% 6% 10% 18% 15% 3	3815
April	1st to 10th	Day	38% 7% 12% 19% 17% 7%	2251
	11th to 20th	Day	38% 6% 11% 19% 21% 5%	2254
	21st to end	Day	45% 6% 11% 21% 14% 4	2318
May	1st to 10th	Day	51% 9% 11% 18% 10% 1	4120
	11th to 20th	Day	50% 8% 11% 22% 8% 1	4085
	21st to end	Day	35% 11% 16% 20% 16% 2	4797
June	1st to 10th	Day	39% 8% 13% 23% 15% 1	2660
	11th to 20th	Day	41% 10% 14% 21% 13% 2	2660
	21st to end	Day	35% 10% 16% 24% 14% 2	2660
July	1st to 10th	Day	35% 13% 18% 19% 9% 5%	4256
	11th to 20th	Day	39% 11% 18% 24% 8% 1	4051
	21st to end	Day	47% 10% 10% 21% 11% 1	4324
August	1st to 10th	Day	45% 12% 17% 21% 6%	4091
	11th to 20th	Day	38% 13% 12% 25% 11% 1	4004
	21st to end	Day	35% 9% 15% 29% 11% 1	4180
September	1st to 10th	Day	39% 8% 13% 16% 19% 4	2280
	11th to 20th	Day	39% 5% 8% 26% 18% 3	2212
	21st to end	Day	49% 6% 9% 17% 16% 2	2019
October	1st to 10th	Day	36% 5% 6% 19% 28% 6%	3160
	11th to 20th	Day	25% 5% 8% 26% 22% 13%	3140
	21st to end	Day	22% 4 10% 30% 24% 11%	3428
November	1st to 10th	Day	33% 4 9% 25% 24% 5%	1887
	11th to 20th	Day	35% 5% 11% 21% 22% 6%	1645
	21st to end	Day	37% 4 10% 25% 22% 3	1520
December	1st to 10th	Day	44% 7% 11% 23% 13% 4	1520
	11th to 20th	Day	36% 4 11% 30% 14% 5%	1906
	21st to end	Day	44% 8% 14% 23% 11% 1	2772
January	1st to 10th	Night	35% 5% 12% 23% 20% 4	4130
	11th to 20th	Night	39% 5% 12% 22% 18% 5%	4120
	21st to end	Night	45% 5% 9% 23% 18% 1	4532
February	1st to 10th	Night	41% 6% 12% 23% 16% 2	2470
	11th to 20th	Night	44% 6% 9% 20% 16% 6%	2405
	21st to end	Night	42% 6% 12% 20% 15% 5%	1832
March	1st to 10th	Night	46% 7% 9% 23% 13% 2	3418
	11th to 20th	Night	32% 5% 12% 24% 24% 4	3480
	21st to end	Night	38% 6% 10% 22% 20% 4	3817
April	1st to 10th	Night	39% 7% 12% 19% 19% 4	1929
	11th to 20th	Night	35% 6% 14% 20% 20% 5%	1875
	21st to end	Night	39% 6% 12% 26% 14% 4	1876
May	1st to 10th	Night	50% 9% 11% 19% 9% 2	2840
	11th to 20th	Night	49% 8% 12% 22% 8% 1	2813
	21st to end	Night	34% 10% 18% 25% 10% 3	2774
June	1st to 10th	Night	34% 9% 15% 28% 13% 1	1520
	11th to 20th	Night	37% 10% 16% 24% 12% 1	1520
	21st to end	Night	35% 9% 18% 19% 18% 3	1520
July	1st to 10th	Night	32% 13% 23% 15% 14% 3	2589
	11th to 20th	Night	37% 10% 21% 23% 8% 1	2786
	21st to end	Night	41% 11% 17% 20% 11%	2988
August	1st to 10th	Night	44% 8% 19% 23% 6% 1	2814
	11th to 20th	Night	41% 11% 13% 23% 12% 1	2844
	21st to end	Night	34% 7% 17% 31% 10% 1	3476
September	1st to 10th	Night	36% 8% 14% 20% 17% 5%	1900
	11th to 20th	Night	36% 7% 10% 26% 19% 2	1965
	21st to end	Night	47% 5% 10% 19% 17% 2	2160
October	1st to 10th	Night	40% 6% 8% 19% 22% 5%	3800
	11th to 20th	Night	24% 7% 10% 20% 26% 13%	3779
	21st to end	Night	22% 5% 10% 30% 22% 11%	4120
November	1st to 10th	Night	34% 4 10% 22% 23% 6%	2264
	11th to 20th	Night	36% 5% 8% 22% 23% 6%	2530
	21st to end	Night	35% 5% 11% 24% 21% 4	2660
December	1st to 10th	Night	43% 6% 10% 23% 14% 3	2660
	11th to 20th	Night	39% 5% 10% 23% 19% 4	3288
	21st to end	Night	41% 7% 16% 21% 14% 1	4884

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	28% 25% 32% 12% 4	265
	11th to 20th	Day	29% 30% 27% 11% 4	270
	21st to end	Day	25% 28% 35% 10% 2 1	297
February	1st to 10th	Day	23% 34% 29% 12% 2	270
	11th to 20th	Day	38% 27% 29% 5% 1	270
	21st to end	Day	31% 21% 29% 16% 2	371
March	1st to 10th	Day	25% 22% 28% 20% 5%	460
	11th to 20th	Day	24% 23% 29% 17% 6% 1	460
	21st to end	Day	26% 19% 33% 15% 6% 1	506
April	1st to 10th	Day	22% 25% 27% 18% 7% 1	460
	11th to 20th	Day	21% 19% 27% 21% 11% 3	452
	21st to end	Day	24% 17% 31% 17% 10% 2	460
May	1st to 10th	Day	21% 20% 28% 16% 12% 2	463
	11th to 20th	Day	22% 14% 29% 21% 11% 3	487
	21st to end	Day	20% 5% 26% 27% 16% 6%	529
June	1st to 10th	Day	16% 8% 28% 27% 17% 5%	490
	11th to 20th	Day	15% 8% 29% 28% 14% 6%	490
	21st to end	Day	10% 7% 31% 29% 19% 4	490
July	1st to 10th	Day	14% 4 21% 28% 24% 8%	485
	11th to 20th	Day	5% 4 22% 34% 25% 11%	484
	21st to end	Day	13% 3 22% 31% 22% 9%	532
August	1st to 10th	Day	12% 5% 22% 26% 24% 11%	486
	11th to 20th	Day	13% 6% 20% 28% 22% 11%	479
	21st to end	Day	10% 4 18% 33% 20% 15%	539
September	1st to 10th	Day	16% 5% 20% 26% 19% 14%	490
	11th to 20th	Day	17% 4 19% 27% 23% 10%	490
	21st to end	Day	30% 9% 20% 23% 13% 4	490
October	1st to 10th	Day	20% 7% 22% 30% 16% 6%	490
	11th to 20th	Day	16% 16% 26% 25% 15% 2	490
	21st to end	Day	17% 15% 33% 23% 10% 2	539
November	1st to 10th	Day	16% 13% 30% 28% 10% 3	467
	11th to 20th	Day	19% 14% 31% 24% 11% 1	293
	21st to end	Day	21% 17% 37% 20% 5%	180
December	1st to 10th	Day	19% 25% 36% 14% 6% 1	180
	11th to 20th	Day	23% 16% 37% 17% 7% 1	180
	21st to end	Day	22% 21% 33% 17% 7%	198
January	1st to 10th	Night	18% 18% 36% 23% 4	760
	11th to 20th	Night	21% 15% 32% 28% 4	760
	21st to end	Night	18% 14% 39% 26% 2	836
February	1st to 10th	Night	17% 15% 37% 29% 2	760
	11th to 20th	Night	25% 20% 36% 18% 1	743
	21st to end	Night	20% 18% 39% 19% 3	628
March	1st to 10th	Night	17% 18% 36% 24% 4	760
	11th to 20th	Night	22% 18% 32% 21% 5% 1	760
	21st to end	Night	17% 18% 36% 23% 6% 1	836
April	1st to 10th	Night	17% 19% 34% 25% 5%	760
	11th to 20th	Night	16% 13% 32% 28% 9% 1	751
	21st to end	Night	18% 10% 32% 32% 7%	736
May	1st to 10th	Night	18% 10% 26% 28% 17% 1	570
	11th to 20th	Night	19% 4 25% 35% 16% 1	561
	21st to end	Night	14% 3 20% 38% 23% 2	434
June	1st to 10th	Night	11% 2 21% 43% 21% 2	380
	11th to 20th	Night	12% 5% 14% 43% 24% 1	380
	21st to end	Night	9% 3 19% 47% 21% 2	380
July	1st to 10th	Night	13% 2 17% 33% 30% 4	427
	11th to 20th	Night	7% 2 14% 33% 40% 5%	552
	21st to end	Night	7% 3 14% 40% 31% 5%	624
August	1st to 10th	Night	10% 2 12% 42% 31% 3	567
	11th to 20th	Night	12% 3 14% 37% 30% 3	583
	21st to end	Night	13% 2 15% 35% 32% 4	836
September	1st to 10th	Night	16% 3 14% 33% 28% 6%	760
	11th to 20th	Night	15% 3 14% 35% 29% 4	760
	21st to end	Night	27% 3 19% 30% 19% 2	760
October	1st to 10th	Night	19% 8% 19% 29% 20% 4	760
	11th to 20th	Night	16% 9% 28% 31% 16% 1	760
	21st to end	Night	17% 10% 29% 31% 11% 2	836
November	1st to 10th	Night	15% 9% 28% 33% 12% 2	755
	11th to 20th	Night	17% 12% 30% 32% 8% 1	760
	21st to end	Night	16% 12% 31% 30% 10% 1	760
December	1st to 10th	Night	20% 12% 33% 27% 7%	760
	11th to 20th	Night	16% 10% 34% 35% 5%	760
	21st to end	Night	18% 12% 30% 36% 3	836

Page generated at 2024-11-01 22:47:29. Version ac07

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