Mammoth Hot Springs
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mammoth Hot Springs clear sky chart from 2005-11-06 to 2026-07-31.

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	4 9% 3 8% 5% 5% 5% 4 6% 8% 42%	147312
	Night	3 9% 4 9% 5% 5% 5% 4 6% 8% 42%	143133
Transparency	Day	40% 6% 14% 22% 15% 4	142024
	Night	40% 6% 17% 22% 12% 3	139428
Seeing	Day	15% 22% 31% 21% 9% 2	17880
	Night	12% 16% 31% 30% 11% 1	27353

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	2 11% 6% 18% 9% 8% 8% 6% 7% 8% 17%	4124
	11th to 20th	Day	1 8% 3 10% 6% 5% 5% 5% 6% 10% 43%	4857
	21st to end	Day	1 14% 6% 9% 5% 4 4 4 6% 7% 41%	5844
February	1st to 10th	Day	2 13% 9% 16% 8% 7% 6% 4 7% 5% 24%	1890
	11th to 20th	Day	2 13% 7% 18% 8% 6% 6% 4 6% 7% 23%	1845
	21st to end	Day	2 16% 7% 16% 9% 6% 7% 4 5% 5% 23%	1633
March	1st to 10th	Day	1 11% 5% 14% 7% 5% 5% 4 5% 6% 37%	4966
	11th to 20th	Day	2 12% 5% 10% 6% 6% 7% 5% 6% 8% 33%	5110
	21st to end	Day	2 15% 6% 13% 8% 8% 8% 5% 8% 8% 20%	5607
April	1st to 10th	Day	4 17% 5% 12% 7% 6% 6% 4 6% 6% 27%	2436
	11th to 20th	Day	4 14% 5% 11% 7% 6% 5% 5% 6% 7% 29%	2664
	21st to end	Day	7% 16% 5% 11% 7% 6% 5% 4 6% 7% 25%	2730
May	1st to 10th	Day	7% 11% 3 7% 4 4 5% 4 6% 8% 41%	7626
	11th to 20th	Day	5% 9% 3 8% 6% 7% 6% 5% 8% 9% 33%	8068
	21st to end	Day	9% 10% 3 7% 5% 5% 6% 4 7% 8% 37%	9026
June	1st to 10th	Day	10% 8% 3 8% 5% 6% 6% 5% 7% 8% 33%	3074
	11th to 20th	Day	10% 9% 3 7% 6% 5% 5% 4 5% 7% 39%	3150
	21st to end	Day	4 4 2 5% 4 5% 5% 4 7% 8% 52%	3150
July	1st to 10th	Day	2 2 1 4 4 5% 5% 5% 8% 9% 56%	6929
	11th to 20th	Day	2 2 1 4 3 4 5% 4 6% 8% 59%	6851
	21st to end	Day	1 2 1 2 3 4 5% 4 7% 9% 61%	6536
August	1st to 10th	Day	3 3 1 5% 5% 5% 6% 5% 7% 10% 51%	5779
	11th to 20th	Day	2 2 1 3 3 4 5% 4 6% 7% 63%	5798
	21st to end	Day	7% 4 1 4 3 4 4 3 5% 7% 58%	6430
September	1st to 10th	Day	5% 5% 2 5% 4 3 4 2 5% 7% 58%	2400
	11th to 20th	Day	7% 5% 2 5% 4 4 4 4 7% 8% 49%	2206
	21st to end	Day	6% 5% 2 5% 4 4 5% 3 5% 7% 54%	2200
October	1st to 10th	Day	6% 6% 2 5% 4 4 3 2 3 4 60%	3308
	11th to 20th	Day	5% 8% 3 6% 3 3 3 3 4 6% 56%	3250
	21st to end	Day	4 9% 4 8% 5% 5% 6% 4 6% 7% 42%	3442
November	1st to 10th	Day	6% 13% 5% 9% 5% 5% 4 4 5% 6% 36%	1765
	11th to 20th	Day	4 13% 5% 12% 7% 6% 5% 5% 6% 6% 32%	1680
	21st to end	Day	2 11% 5% 11% 7% 6% 7% 4 5% 6% 36%	1680
December	1st to 10th	Day	1 7% 4 11% 6% 5% 6% 5% 8% 7% 41%	2700
	11th to 20th	Day	2 14% 7% 16% 7% 7% 6% 5% 7% 8% 21%	2983
	21st to end	Day	2 15% 5% 15% 8% 7% 6% 6% 6% 8% 22%	3575
January	1st to 10th	Night	1 9% 6% 16% 9% 8% 7% 6% 8% 8% 22%	8768
	11th to 20th	Night	1 8% 3 11% 7% 6% 5% 4 6% 8% 41%	8139
	21st to end	Night	2 13% 5% 10% 5% 5% 6% 5% 6% 7% 36%	8370
February	1st to 10th	Night	2 14% 7% 15% 9% 7% 5% 5% 6% 7% 23%	2730
	11th to 20th	Night	2 12% 5% 15% 9% 6% 7% 5% 7% 7% 26%	2662
	21st to end	Night	1 11% 6% 16% 9% 8% 7% 5% 6% 6% 26%	2170
March	1st to 10th	Night	9% 5% 16% 7% 6% 5% 4 5% 6% 37%	5148
	11th to 20th	Night	1 10% 4 7% 5% 5% 6% 5% 7% 10% 39%	5110
	21st to end	Night	2 12% 5% 11% 6% 6% 7% 5% 7% 9% 29%	5610
April	1st to 10th	Night	3 14% 4 9% 7% 6% 5% 4 7% 6% 34%	2184
	11th to 20th	Night	4 11% 3 8% 6% 5% 4 5% 7% 9% 37%	1903
	21st to end	Night	7% 13% 3 7% 5% 5% 5% 4 5% 8% 39%	1890
May	1st to 10th	Night	5% 9% 3 7% 5% 5% 4 4 5% 6% 48%	5321
	11th to 20th	Night	6% 9% 4 7% 5% 5% 5% 5% 6% 9% 39%	4821
	21st to end	Night	8% 8% 2 6% 4 4 4 4 6% 10% 43%	5181
June	1st to 10th	Night	9% 6% 2 7% 4 4 6% 5% 6% 10% 41%	1541
	11th to 20th	Night	8% 7% 2 5% 5% 5% 4 5% 7% 8% 45%	1470
	21st to end	Night	4 2 1 4 4 4 5% 5% 6% 9% 58%	1470
July	1st to 10th	Night	3 2 1 3 4 4 4 4 6% 9% 59%	3250
	11th to 20th	Night	2 3 1 4 4 3 4 4 6% 8% 61%	3315
	21st to end	Night	2 2 1 3 2 3 4 4 7% 11% 63%	4554
August	1st to 10th	Night	2 2 1 4 3 4 5% 5% 8% 11% 54%	4033
	11th to 20th	Night	2 1 1 3 2 4 4 4 7% 8% 64%	4051
	21st to end	Night	5% 4 2 5% 4 3 3 2 4 6% 62%	4546
September	1st to 10th	Night	5% 4 2 4 3 2 4 4 5% 7% 60%	2000
	11th to 20th	Night	6% 4 2 4 4 4 4 4 7% 7% 55%	2190
	21st to end	Night	7% 5% 2 5% 4 3 3 2 4 6% 60%	2200
October	1st to 10th	Night	5% 5% 1 3 2 2 3 3 5% 6% 64%	3883
	11th to 20th	Night	6% 8% 2 5% 4 3 4 3 5% 6% 55%	3898
	21st to end	Night	4 9% 3 8% 4 4 4 3 5% 8% 47%	4345
November	1st to 10th	Night	6% 11% 4 10% 5% 6% 5% 3 5% 8% 37%	2733
	11th to 20th	Night	3 13% 5% 11% 7% 5% 6% 6% 6% 7% 31%	2940
	21st to end	Night	2 10% 5% 10% 6% 6% 5% 4 7% 8% 36%	2940
December	1st to 10th	Night	2 8% 4 11% 6% 6% 6% 3 6% 6% 43%	4710
	11th to 20th	Night	2 11% 6% 16% 7% 6% 6% 5% 8% 9% 24%	5434
	21st to end	Night	2 14% 6% 15% 6% 7% 7% 6% 7% 8% 22%	7623

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	59% 8% 17% 12% 3	4125
	11th to 20th	Day	37% 5% 24% 17% 12% 5%	4857
	21st to end	Day	44% 4 15% 21% 14% 1	5844
February	1st to 10th	Day	62% 6% 13% 13% 4	1890
	11th to 20th	Day	62% 6% 14% 13% 3 1	1854
	21st to end	Day	65% 6% 8% 13% 6% 3	1633
March	1st to 10th	Day	47% 7% 16% 17% 10% 3	4966
	11th to 20th	Day	46% 5% 19% 23% 6%	5110
	21st to end	Day	60% 7% 17% 12% 3	5607
April	1st to 10th	Day	58% 7% 13% 15% 6%	2436
	11th to 20th	Day	54% 7% 15% 19% 5%	2667
	21st to end	Day	57% 6% 15% 18% 4 1	2730
May	1st to 10th	Day	39% 5% 13% 31% 11% 1	7626
	11th to 20th	Day	42% 7% 14% 25% 10% 2	8072
	21st to end	Day	41% 7% 17% 26% 8%	9027
June	1st to 10th	Day	45% 8% 17% 22% 7% 1	3074
	11th to 20th	Day	43% 7% 11% 20% 16% 3	3150
	21st to end	Day	27% 7% 11% 28% 21% 6%	3150
July	1st to 10th	Day	20% 6% 7% 25% 31% 11%	6856
	11th to 20th	Day	21% 5% 7% 24% 29% 15%	6770
	21st to end	Day	16% 5% 6% 23% 35% 14%	6351
August	1st to 10th	Day	29% 7% 9% 23% 23% 10%	4208
	11th to 20th	Day	21% 4 8% 29% 29% 8%	4197
	21st to end	Day	24% 4 7% 25% 29% 12%	4637
September	1st to 10th	Day	26% 4 8% 24% 31% 7%	2400
	11th to 20th	Day	33% 5% 13% 24% 21% 5%	2206
	21st to end	Day	30% 5% 13% 30% 18% 5%	2200
October	1st to 10th	Day	30% 3 8% 24% 32% 3	3308
	11th to 20th	Day	31% 3 17% 32% 15% 2	3250
	21st to end	Day	42% 5% 18% 26% 8% 1	3442
November	1st to 10th	Day	50% 7% 15% 19% 8% 1	1765
	11th to 20th	Day	51% 8% 19% 15% 5% 2	1680
	21st to end	Day	49% 6% 18% 16% 9% 1	1680
December	1st to 10th	Day	40% 7% 27% 20% 5% 1	2700
	11th to 20th	Day	60% 6% 20% 11% 2	2981
	21st to end	Day	57% 4 14% 13% 4 7%	3575
January	1st to 10th	Night	56% 4 17% 17% 5%	8769
	11th to 20th	Night	39% 6% 26% 16% 9% 4	8139
	21st to end	Night	45% 5% 15% 23% 11% 1	8370
February	1st to 10th	Night	61% 6% 12% 14% 6%	2730
	11th to 20th	Night	59% 7% 13% 13% 7% 1	2663
	21st to end	Night	60% 8% 9% 14% 6% 3	2170
March	1st to 10th	Night	49% 5% 14% 20% 9% 4	5148
	11th to 20th	Night	36% 5% 24% 27% 6% 1	5110
	21st to end	Night	50% 7% 23% 16% 4	5610
April	1st to 10th	Night	50% 8% 16% 18% 6% 1	2184
	11th to 20th	Night	43% 7% 19% 23% 7% 1	1903
	21st to end	Night	43% 8% 19% 24% 6%	1890
May	1st to 10th	Night	36% 5% 17% 34% 9%	5319
	11th to 20th	Night	39% 6% 15% 28% 9% 4	4822
	21st to end	Night	37% 8% 18% 31% 6% 1	5182
June	1st to 10th	Night	38% 10% 19% 25% 7%	1541
	11th to 20th	Night	36% 6% 17% 20% 18% 3	1470
	21st to end	Night	22% 7% 15% 28% 22% 6%	1470
July	1st to 10th	Night	19% 5% 9% 30% 30% 7%	3215
	11th to 20th	Night	20% 4 10% 26% 31% 10%	3273
	21st to end	Night	14% 4 12% 29% 33% 8%	4427
August	1st to 10th	Night	24% 6% 13% 26% 22% 9%	2928
	11th to 20th	Night	20% 4 12% 31% 26% 7%	2928
	21st to end	Night	20% 3 9% 27% 32% 10%	3270
September	1st to 10th	Night	23% 5% 10% 25% 28% 8%	2000
	11th to 20th	Night	28% 6% 15% 26% 20% 5%	2190
	21st to end	Night	27% 5% 12% 31% 22% 3	2200
October	1st to 10th	Night	23% 3 11% 30% 31% 2	3883
	11th to 20th	Night	31% 4 19% 29% 16% 1	3898
	21st to end	Night	36% 5% 19% 27% 12% 1	4345
November	1st to 10th	Night	48% 6% 17% 21% 7% 1	2733
	11th to 20th	Night	52% 7% 18% 16% 6% 1	2940
	21st to end	Night	46% 7% 21% 15% 10% 2	2940
December	1st to 10th	Night	42% 6% 27% 20% 4 1	4710
	11th to 20th	Night	55% 6% 24% 12% 2	5435
	21st to end	Night	56% 5% 15% 13% 5% 6%	7623

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	20% 27% 31% 16% 5% 1	220
	11th to 20th	Day	15% 26% 34% 16% 7% 2	261
	21st to end	Day	10% 24% 38% 23% 4 1	363
February	1st to 10th	Day	22% 35% 29% 12% 3	330
	11th to 20th	Day	21% 28% 30% 15% 4 2	330
	21st to end	Day	25% 32% 26% 15% 3	349
March	1st to 10th	Day	20% 34% 30% 12% 3 1	540
	11th to 20th	Day	21% 30% 27% 18% 4 1	540
	21st to end	Day	21% 30% 31% 12% 4 1	594
April	1st to 10th	Day	25% 27% 31% 12% 4	540
	11th to 20th	Day	21% 28% 33% 14% 3	532
	21st to end	Day	21% 25% 29% 17% 7% 3	540
May	1st to 10th	Day	17% 19% 31% 23% 8% 2	543
	11th to 20th	Day	16% 18% 29% 23% 11% 2	728
	21st to end	Day	19% 16% 26% 23% 14% 2	844
June	1st to 10th	Day	14% 18% 27% 24% 14% 3	780
	11th to 20th	Day	21% 24% 27% 20% 8% 1	780
	21st to end	Day	8% 18% 31% 29% 12% 1	780
July	1st to 10th	Day	5% 15% 30% 32% 18% 2	771
	11th to 20th	Day	4 13% 36% 31% 15% 2	768
	21st to end	Day	4 15% 38% 29% 12% 3	620
August	1st to 10th	Day	8% 11% 41% 26% 12% 2	527
	11th to 20th	Day	6% 13% 32% 30% 16% 3	517
	21st to end	Day	10% 18% 33% 22% 13% 4	583
September	1st to 10th	Day	8% 19% 32% 26% 13% 3	530
	11th to 20th	Day	14% 19% 31% 24% 10% 2	530
	21st to end	Day	13% 18% 33% 22% 11% 2	530
October	1st to 10th	Day	13% 18% 31% 21% 14% 3	355
	11th to 20th	Day	20% 18% 29% 18% 8% 6%	330
	21st to end	Day	18% 26% 33% 17% 5% 1	363
November	1st to 10th	Day	23% 25% 26% 16% 7% 2	330
	11th to 20th	Day	16% 31% 31% 16% 5% 1	330
	21st to end	Day	12% 24% 37% 22% 4	330
December	1st to 10th	Day	19% 26% 28% 20% 6%	330
	11th to 20th	Day	19% 33% 28% 17% 2	300
	21st to end	Day	22% 27% 26% 17% 7% 1	242
January	1st to 10th	Night	15% 20% 34% 25% 5%	1050
	11th to 20th	Night	13% 19% 40% 19% 7% 2	892
	21st to end	Night	7% 21% 42% 23% 6% 1	924
February	1st to 10th	Night	12% 26% 36% 21% 3	840
	11th to 20th	Night	12% 22% 38% 23% 5%	824
	21st to end	Night	13% 25% 35% 20% 7%	692
March	1st to 10th	Night	10% 23% 35% 25% 6% 1	840
	11th to 20th	Night	12% 19% 31% 28% 10% 1	840
	21st to end	Night	13% 16% 33% 31% 7% 1	924
April	1st to 10th	Night	12% 19% 36% 25% 7%	714
	11th to 20th	Night	12% 17% 37% 27% 7%	623
	21st to end	Night	16% 11% 27% 32% 14% 1	630
May	1st to 10th	Night	10% 13% 27% 33% 16%	630
	11th to 20th	Night	10% 11% 28% 32% 17% 1	621
	21st to end	Night	16% 10% 28% 33% 13% 1	683
June	1st to 10th	Night	12% 11% 25% 34% 19%	491
	11th to 20th	Night	11% 10% 34% 32% 13%	420
	21st to end	Night	6% 5% 23% 46% 20%	420
July	1st to 10th	Night	4 3 15% 45% 31% 1	410
	11th to 20th	Night	2 5% 20% 54% 19%	434
	21st to end	Night	2 5% 24% 47% 21% 1	687
August	1st to 10th	Night	6% 3 21% 45% 24% 1	597
	11th to 20th	Night	4 4 20% 46% 26% 1	594
	21st to end	Night	6% 7% 24% 39% 23% 1	660
September	1st to 10th	Night	7% 4 25% 40% 22% 2	600
	11th to 20th	Night	8% 5% 23% 41% 20% 2	790
	21st to end	Night	11% 9% 25% 34% 20% 2	800
October	1st to 10th	Night	13% 7% 27% 36% 16% 1	800
	11th to 20th	Night	14% 13% 27% 32% 13% 2	800
	21st to end	Night	12% 18% 35% 24% 8% 3	880
November	1st to 10th	Night	15% 20% 33% 25% 7%	888
	11th to 20th	Night	14% 27% 32% 23% 3	1050
	21st to end	Night	13% 19% 36% 26% 6%	1050
December	1st to 10th	Night	16% 24% 31% 23% 5% 1	1050
	11th to 20th	Night	15% 27% 32% 20% 5% 1	1050
	21st to end	Night	17% 24% 34% 19% 6%	1155

Page generated at 2026-07-28 01:25:23. Version ac07

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