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 2024-02-15.

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% 10% 5% 9% 7% 4 6% 5% 6% 7% 36%	78233
	Night	4 10% 5% 10% 8% 4 5% 6% 6% 7% 35%	80857
Transparency	Day	48% 6% 13% 18% 12% 4	77935
	Night	48% 7% 14% 19% 10% 3	80676
Seeing	Day	15% 22% 31% 21% 9% 2	14447
	Night	12% 16% 30% 29% 12% 1	24206

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 12% 9% 18% 12% 5% 6% 6% 5% 7% 17%	2219
	11th to 20th	Day	2 13% 6% 12% 11% 5% 5% 5% 4 7% 28%	2587
	21st to end	Day	2 25% 11% 10% 6% 3 5% 4 4 5% 24%	3146
February	1st to 10th	Day	2 13% 10% 16% 10% 5% 6% 5% 6% 5% 23%	1710
	11th to 20th	Day	2 13% 8% 16% 11% 5% 5% 6% 5% 6% 22%	1611
	21st to end	Day	3 13% 9% 16% 12% 5% 6% 7% 4 5% 20%	1396
March	1st to 10th	Day	2 12% 6% 15% 12% 5% 6% 5% 6% 6% 25%	1934
	11th to 20th	Day	3 13% 5% 12% 9% 4 7% 5% 4 7% 31%	1980
	21st to end	Day	5% 16% 8% 12% 9% 5% 6% 5% 5% 6% 21%	2178
April	1st to 10th	Day	6% 15% 6% 12% 9% 4 6% 5% 6% 6% 24%	2088
	11th to 20th	Day	6% 12% 7% 11% 8% 5% 6% 6% 6% 7% 26%	2278
	21st to end	Day	8% 16% 6% 10% 8% 5% 5% 5% 5% 7% 26%	2340
May	1st to 10th	Day	9% 13% 5% 8% 7% 5% 6% 6% 5% 7% 29%	2340
	11th to 20th	Day	9% 9% 4 8% 8% 4 6% 6% 7% 8% 29%	2437
	21st to end	Day	14% 14% 5% 8% 7% 4 6% 6% 6% 7% 22%	2724
June	1st to 10th	Day	12% 8% 3 8% 6% 5% 7% 7% 6% 9% 30%	2634
	11th to 20th	Day	12% 9% 3 6% 7% 4 6% 5% 5% 8% 34%	2700
	21st to end	Day	4 3 2 4 5% 4 5% 6% 7% 8% 53%	2700
July	1st to 10th	Day	3 3 2 4 5% 3 5% 6% 7% 10% 52%	2700
	11th to 20th	Day	3 2 2 4 5% 4 5% 5% 6% 7% 57%	2674
	21st to end	Day	3 3 2 3 5% 3 5% 6% 7% 8% 56%	2549
August	1st to 10th	Day	6% 5% 2 5% 6% 4 5% 6% 6% 9% 47%	2328
	11th to 20th	Day	4 3 1 5% 5% 3 5% 5% 6% 8% 55%	2299
	21st to end	Day	5% 4 2 4 5% 4 5% 5% 6% 7% 55%	2562
September	1st to 10th	Day	6% 5% 2 5% 4 3 4 3 5% 7% 57%	2160
	11th to 20th	Day	8% 5% 2 4 5% 3 4 4 6% 8% 51%	1986
	21st to end	Day	6% 6% 2 4 6% 2 6% 5% 5% 7% 51%	1980
October	1st to 10th	Day	10% 10% 3 7% 8% 4 4 5% 6% 6% 38%	1823
	11th to 20th	Day	8% 10% 5% 7% 5% 3 5% 4 4 6% 44%	1800
	21st to end	Day	6% 11% 4 8% 7% 4 5% 4 5% 9% 38%	1926
November	1st to 10th	Day	7% 13% 6% 8% 7% 4 5% 5% 5% 6% 35%	1594
	11th to 20th	Day	4 12% 6% 11% 9% 3 6% 5% 5% 6% 33%	1520
	21st to end	Day	2 10% 6% 10% 9% 4 7% 5% 5% 6% 36%	1520
December	1st to 10th	Day	2 10% 8% 14% 11% 4 8% 6% 6% 6% 26%	1520
	11th to 20th	Day	4 17% 6% 13% 10% 4 7% 6% 6% 8% 20%	1848
	21st to end	Day	3 17% 5% 11% 10% 5% 6% 6% 5% 7% 24%	2442
January	1st to 10th	Night	2 11% 7% 15% 12% 6% 7% 8% 7% 6% 19%	4726
	11th to 20th	Night	3 13% 5% 12% 12% 6% 6% 5% 6% 6% 25%	4387
	21st to end	Night	3 23% 10% 13% 8% 4 6% 6% 5% 5% 18%	4521
February	1st to 10th	Night	2 13% 8% 14% 10% 5% 6% 6% 6% 7% 22%	2470
	11th to 20th	Night	2 11% 6% 13% 10% 5% 8% 7% 7% 6% 25%	2330
	21st to end	Night	1 9% 7% 16% 11% 6% 8% 5% 5% 7% 24%	1857
March	1st to 10th	Night	1 11% 7% 13% 9% 5% 5% 5% 7% 7% 29%	2026
	11th to 20th	Night	3 10% 4 7% 7% 4 6% 7% 6% 8% 37%	1980
	21st to end	Night	4 13% 5% 11% 8% 4 6% 6% 6% 9% 27%	2178
April	1st to 10th	Night	5% 13% 5% 9% 8% 5% 6% 5% 7% 6% 33%	1872
	11th to 20th	Night	5% 10% 5% 7% 7% 4 5% 6% 7% 9% 35%	1629
	21st to end	Night	7% 12% 3 6% 5% 3 6% 5% 5% 8% 39%	1620
May	1st to 10th	Night	6% 9% 4 7% 8% 4 6% 6% 5% 6% 39%	1620
	11th to 20th	Night	7% 7% 2 7% 7% 3 6% 6% 6% 8% 40%	1455
	21st to end	Night	12% 9% 3 8% 8% 4 5% 6% 7% 9% 29%	1552
June	1st to 10th	Night	11% 7% 2 6% 5% 2 5% 6% 6% 10% 41%	1322
	11th to 20th	Night	10% 7% 2 5% 5% 4 4 5% 7% 8% 42%	1260
	21st to end	Night	3 1 1 3 4 2 5% 6% 6% 10% 59%	1260
July	1st to 10th	Night	3 3 1 2 3 3 5% 5% 7% 11% 58%	1260
	11th to 20th	Night	2 3 1 3 5% 3 4 4 6% 8% 61%	1282
	21st to end	Night	2 2 1 3 4 3 4 4 6% 8% 61%	1765
August	1st to 10th	Night	4 4 2 6% 5% 3 6% 7% 8% 8% 48%	1611
	11th to 20th	Night	2 2 1 4 3 2 4 4 6% 10% 60%	1602
	21st to end	Night	5% 3 2 4 5% 3 3 4 5% 8% 59%	1793
September	1st to 10th	Night	5% 4 2 3 4 2 4 5% 5% 7% 58%	1800
	11th to 20th	Night	6% 3 2 4 4 3 5% 4 6% 7% 56%	1970
	21st to end	Night	7% 5% 2 4 5% 2 3 3 4 6% 57%	1980
October	1st to 10th	Night	9% 8% 3 5% 4 2 5% 5% 6% 8% 45%	2137
	11th to 20th	Night	8% 8% 3 6% 4 3 4 4 5% 6% 50%	2160
	21st to end	Night	5% 9% 4 9% 6% 4 4 5% 5% 7% 42%	2430
November	1st to 10th	Night	7% 11% 5% 9% 6% 5% 4 5% 5% 7% 35%	2466
	11th to 20th	Night	4 12% 6% 10% 8% 4 5% 7% 6% 6% 31%	2660
	21st to end	Night	3 9% 7% 9% 7% 5% 5% 5% 6% 8% 36%	2660
December	1st to 10th	Night	3 11% 6% 15% 9% 6% 8% 6% 6% 5% 25%	2660
	11th to 20th	Night	3 14% 6% 15% 10% 4 6% 6% 8% 8% 21%	3342
	21st to end	Night	3 17% 7% 14% 8% 5% 6% 7% 6% 7% 20%	5214

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	63% 8% 10% 15% 3	2219
	11th to 20th	Day	56% 6% 14% 10% 7% 6%	2587
	21st to end	Day	64% 4 9% 15% 7% 1	3146
February	1st to 10th	Day	65% 6% 13% 12% 4	1710
	11th to 20th	Day	64% 7% 14% 13% 2 1	1620
	21st to end	Day	69% 6% 7% 9% 6% 3	1396
March	1st to 10th	Day	62% 7% 13% 13% 4 1	1934
	11th to 20th	Day	54% 7% 16% 15% 8% 1	1980
	21st to end	Day	65% 7% 14% 11% 2	2178
April	1st to 10th	Day	62% 7% 12% 14% 5%	2088
	11th to 20th	Day	58% 7% 14% 17% 4	2281
	21st to end	Day	58% 5% 15% 17% 4 1	2340
May	1st to 10th	Day	52% 7% 14% 19% 7%	2340
	11th to 20th	Day	50% 8% 19% 17% 5%	2441
	21st to end	Day	60% 8% 16% 12% 4	2724
June	1st to 10th	Day	49% 9% 18% 20% 4	2634
	11th to 20th	Day	48% 7% 11% 18% 13% 3	2700
	21st to end	Day	27% 7% 11% 28% 21% 6%	2700
July	1st to 10th	Day	24% 7% 11% 25% 25% 8%	2626
	11th to 20th	Day	25% 5% 8% 20% 25% 17%	2593
	21st to end	Day	23% 5% 7% 20% 29% 15%	2407
August	1st to 10th	Day	32% 6% 9% 22% 24% 8%	2313
	11th to 20th	Day	25% 5% 10% 27% 25% 8%	2299
	21st to end	Day	27% 5% 8% 25% 26% 9%	2562
September	1st to 10th	Day	28% 4 7% 21% 32% 8%	2160
	11th to 20th	Day	32% 5% 12% 23% 23% 5%	1986
	21st to end	Day	32% 6% 13% 30% 15% 4	1980
October	1st to 10th	Day	46% 5% 13% 22% 12% 2	1823
	11th to 20th	Day	43% 5% 17% 25% 9% 1	1800
	21st to end	Day	46% 7% 17% 22% 8% 1	1926
November	1st to 10th	Day	52% 8% 13% 18% 8% 1	1594
	11th to 20th	Day	53% 8% 17% 15% 5% 2	1520
	21st to end	Day	51% 6% 16% 16% 9% 2	1520
December	1st to 10th	Day	58% 8% 12% 12% 7% 2	1520
	11th to 20th	Day	62% 6% 16% 12% 3	1846
	21st to end	Day	57% 4 9% 13% 5% 11%	2442
January	1st to 10th	Night	62% 6% 10% 15% 6% 1	4726
	11th to 20th	Night	59% 6% 12% 13% 7% 4	4387
	21st to end	Night	66% 5% 11% 12% 5% 1	4521
February	1st to 10th	Night	64% 6% 11% 14% 5%	2470
	11th to 20th	Night	61% 7% 13% 12% 5%	2331
	21st to end	Night	63% 7% 8% 12% 7% 3	1857
March	1st to 10th	Night	55% 7% 14% 16% 6% 2	2026
	11th to 20th	Night	45% 8% 18% 20% 7% 1	1980
	21st to end	Night	56% 8% 18% 14% 4	2178
April	1st to 10th	Night	53% 9% 14% 17% 7% 1	1872
	11th to 20th	Night	46% 8% 19% 21% 5% 1	1629
	21st to end	Night	44% 8% 20% 23% 5%	1620
May	1st to 10th	Night	43% 8% 16% 26% 6%	1620
	11th to 20th	Night	41% 9% 19% 25% 7%	1456
	21st to end	Night	51% 9% 19% 16% 4	1552
June	1st to 10th	Night	39% 11% 20% 24% 5%	1322
	11th to 20th	Night	39% 7% 17% 21% 14% 2	1260
	21st to end	Night	19% 7% 15% 30% 22% 6%	1260
July	1st to 10th	Night	18% 8% 15% 28% 23% 7%	1225
	11th to 20th	Night	20% 5% 11% 20% 27% 16%	1240
	21st to end	Night	19% 6% 11% 22% 29% 13%	1667
August	1st to 10th	Night	28% 7% 14% 22% 21% 8%	1602
	11th to 20th	Night	20% 6% 12% 29% 26% 8%	1602
	21st to end	Night	24% 5% 10% 25% 28% 8%	1793
September	1st to 10th	Night	25% 5% 9% 24% 28% 9%	1800
	11th to 20th	Night	27% 6% 15% 25% 22% 5%	1970
	21st to end	Night	29% 5% 13% 31% 19% 3	1980
October	1st to 10th	Night	37% 5% 18% 24% 15% 1	2137
	11th to 20th	Night	36% 5% 17% 28% 12% 2	2160
	21st to end	Night	42% 7% 18% 23% 10% 1	2430
November	1st to 10th	Night	51% 7% 15% 20% 7% 1	2466
	11th to 20th	Night	54% 7% 17% 15% 6% 1	2660
	21st to end	Night	48% 7% 19% 14% 10% 2	2660
December	1st to 10th	Night	61% 8% 12% 11% 6% 1	2660
	11th to 20th	Night	60% 7% 14% 15% 3 1	3343
	21st to end	Night	58% 5% 8% 14% 7% 8%	5214

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	19% 26% 32% 17% 6% 1	180
	11th to 20th	Day	18% 30% 29% 13% 8% 2	213
	21st to end	Day	11% 28% 37% 20% 4	297
February	1st to 10th	Day	19% 39% 29% 11% 1	270
	11th to 20th	Day	23% 27% 31% 14% 2 2	252
	21st to end	Day	23% 30% 29% 15% 3	262
March	1st to 10th	Day	20% 36% 30% 11% 1	420
	11th to 20th	Day	17% 30% 30% 18% 3 1	420
	21st to end	Day	22% 28% 32% 12% 5% 1	462
April	1st to 10th	Day	27% 30% 31% 10% 2	420
	11th to 20th	Day	23% 31% 31% 12% 3	412
	21st to end	Day	23% 25% 27% 17% 6% 2	420
May	1st to 10th	Day	16% 21% 32% 22% 8% 1	423
	11th to 20th	Day	15% 18% 29% 22% 13% 2	584
	21st to end	Day	20% 16% 25% 22% 15% 2	679
June	1st to 10th	Day	16% 18% 24% 24% 16% 3	630
	11th to 20th	Day	21% 25% 27% 19% 7% 1	630
	21st to end	Day	7% 15% 32% 30% 14% 1	630
July	1st to 10th	Day	5% 15% 30% 30% 18% 2	621
	11th to 20th	Day	4 14% 37% 30% 13% 1	618
	21st to end	Day	4 14% 37% 30% 11% 3	491
August	1st to 10th	Day	9% 12% 40% 26% 11% 2	447
	11th to 20th	Day	7% 14% 30% 30% 16% 3	437
	21st to end	Day	9% 18% 35% 22% 13% 3	495
September	1st to 10th	Day	9% 21% 34% 24% 11% 1	450
	11th to 20th	Day	14% 21% 30% 24% 9% 2	450
	21st to end	Day	15% 20% 35% 19% 9% 2	450
October	1st to 10th	Day	15% 18% 30% 21% 12% 4	293
	11th to 20th	Day	21% 17% 30% 18% 8% 5%	270
	21st to end	Day	19% 28% 33% 16% 4 1	297
November	1st to 10th	Day	24% 28% 24% 16% 7% 1	270
	11th to 20th	Day	16% 32% 32% 15% 5%	270
	21st to end	Day	11% 24% 39% 22% 4	270
December	1st to 10th	Day	20% 28% 27% 18% 6%	270
	11th to 20th	Day	17% 35% 28% 17% 2	246
	21st to end	Day	21% 28% 26% 16% 8% 2	198
January	1st to 10th	Night	16% 20% 33% 26% 6%	950
	11th to 20th	Night	14% 20% 37% 19% 8% 2	808
	21st to end	Night	8% 23% 40% 22% 6% 1	836
February	1st to 10th	Night	12% 27% 36% 21% 3	760
	11th to 20th	Night	13% 22% 37% 22% 5%	722
	21st to end	Night	14% 21% 36% 21% 8%	592
March	1st to 10th	Night	10% 24% 35% 24% 6% 1	720
	11th to 20th	Night	11% 19% 30% 29% 10% 1	720
	21st to end	Night	14% 16% 31% 31% 8% 1	792
April	1st to 10th	Night	14% 19% 36% 23% 8%	612
	11th to 20th	Night	11% 19% 37% 25% 8%	533
	21st to end	Night	15% 12% 25% 31% 16% 1	540
May	1st to 10th	Night	11% 14% 28% 30% 17% 1	540
	11th to 20th	Night	10% 9% 27% 33% 19% 1	531
	21st to end	Night	16% 11% 28% 30% 14% 1	584
June	1st to 10th	Night	14% 10% 23% 33% 20%	422
	11th to 20th	Night	13% 12% 32% 29% 14%	360
	21st to end	Night	4 5% 23% 46% 22% 1	360
July	1st to 10th	Night	5% 4 16% 42% 33% 1	350
	11th to 20th	Night	2 5% 21% 53% 18%	370
	21st to end	Night	3 5% 24% 46% 22% 1	591
August	1st to 10th	Night	6% 3 20% 44% 25% 1	537
	11th to 20th	Night	4 4 19% 46% 27% 1	534
	21st to end	Night	6% 7% 23% 38% 25% 1	594
September	1st to 10th	Night	8% 5% 26% 39% 20% 2	540
	11th to 20th	Night	8% 6% 22% 40% 21% 3	710
	21st to end	Night	11% 9% 26% 32% 20% 2	720
October	1st to 10th	Night	14% 7% 27% 35% 16% 1	720
	11th to 20th	Night	14% 13% 27% 32% 13% 2	720
	21st to end	Night	13% 18% 34% 24% 8% 3	792
November	1st to 10th	Night	16% 20% 32% 25% 6%	801
	11th to 20th	Night	15% 27% 31% 23% 3	950
	21st to end	Night	13% 19% 34% 26% 6%	950
December	1st to 10th	Night	16% 25% 30% 22% 6% 1	950
	11th to 20th	Night	15% 26% 32% 21% 5% 1	950
	21st to end	Night	18% 23% 33% 19% 6%	1045

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