UPDATE Sunday 24th December: trails are clear of snow below 7500 ft elevation, but are becoming increasingly icy higher up as very thin snow is compacted by hiker traffic and following freeze-thaw cycles. Spikes are strongly recommended everywhere above about 8000 ft at this time. Snow depths are insufficient for snowshoes or crampons even at the highest elevations.
UPDATE Friday 22nd December @ 2010: Precipitation totals for the storm system were rather disappointing. Overnight Idyllwild (at 5550 ft) received 0.28 inch of rain, followed by another 0.12 inch during the day. Long Valley (8600 ft) had about two inches of snow on 22nd, and San Jacinto Peak has an average depth of about 3.5 inches, drifted deeper in places. I recorded a short video report from San Jacinto Peak at 0830 (available here). Snow level dropped down to 7500 ft on Devil’s Slide Trail, with an average depth of one inch at Saddle Junction (8100 ft). Spikes are now useful and recommended everywhere above about 8000 ft elevation.
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A slow-moving storm system over Southern California is producing an unpredictable weather pattern for the remainder of this week. Some precipitation is possible daily on 18th-23rd December. Probabilities increase substantially late on Thursday 21st and throughout Friday 22nd.
On our early morning hike to San Jacinto Peak on Monday 18th, we enjoyed a brief little snow storm up top while there was a very light rain throughout the mid and upper elevations. It snowed between 0910-0930, with 0.25 inch settling above 10,400 ft elevation, plus a dusting down to 9900 ft. Rainfall in Idyllwild (5550 ft) and at Saddle Junction (8100 ft) was barely 0.01 inch.
Brief rains overnight on 18th and occasionally on 19th produced a further 0.21 inch of rain in Idyllwild (5550 ft) by the morning of Wednesday 20th, 0.49 inch at Saddle Junction (8100 ft), and 0.32 inch at Wellman’s Cienega (9300 ft). Above that, it was mild enough that precipitation fell as freezing rain rather than snow, all the way to San Jacinto Peak where rocks were covered in a thin layer of ice.
Another very light rain overnight on 20th produced just 0.02 inch of rain in Idyllwild, and a very light snowfall of 0.25 inch above 10,000 ft in the high country, dusting down to about 9000 ft.
At most elevations, relatively warm rains have finally melted what little patchy snow remained from late November (see for example the photo below from the north side of Tahquitz Peak).
The first significant storm of winter 2023/24 is forecast to bring moderate precipitation to all elevations on 21st-22nd December. However, earlier forecasts suggesting 1-2 inches of rain at mid elevations and 1-2 feet of snow around the highest peaks of the San Jacinto mountains have now largely been replaced by more conservative estimates of an inch or less of rain, and 4-8 inches of snow, respectively.
It appears that the bulk of the energy from this storm system will now be west (and perhaps a little north) of the San Jacinto mountain range, as discussed in the latest National Weather Service video report released on 20th December (linked here).
This will be a mild storm system and the freeze level may remain relatively high, with nearly one inch of rainfall forecast for mid elevations (e.g., Idyllwild), and a mix of rain turning to light snow between about 7000-9000 ft mainly on Friday 22nd. The freeze level may eventually drop as low as 7500 ft, but no significant snowfall is currently forecast below about 7000 ft. Snow forecasts for the high country have varied dramatically from 2-20 inches above 10,000 ft, although the most recent models favor the lower end of that spectrum. Light snowfall at high elevations may be scattered across several days from 18th-23rd December, becoming moderate at times on Friday 22nd and accumulating to 6-8 inches.
Remaining snow from the minor storms at the end of November has now largely melted. For specific details of trail conditions please see the previous Report linked here. At this time, no traction devices are required anywhere on the trail system, but this will change during the course of the week, notably on 22nd-23rd, when spikes (at least) will become recommended.
Daily survey hikes in the San Jacinto mountains include various routes to San Jacinto Peak multiple times per week (most recently on 18th, 20th, 21st, and 22nd December), Tahquitz Peak and area at least once per week (most recently on 19th December), plus a wide variety of other trails on intervening days.
Air temperatures above 10,000 ft elevation are now generally in the 20s-low 30s Fahrenheit (-5 to 1°C), with windchill temperatures well below freezing. On 21st-23rd December at least, air and/or windchill temperatures may at times be far below freezing, requiring appropriate equipment for very cold conditions. A slight warming to near seasonal temperatures on 25th-29th December is expected to be followed by further cooling around the turn of the year.
At San Jacinto Peak (3295m/10,810ft) on Wednesday 20th December 2023 at 0905 the air temperature was 27.2°F (-3°C), with a windchill temperature of 13.5°F (-10°C), 39% relative humidity, and a cool SSW wind sustained at 8 mph gusting to 14.9 mph.
At the Peak on Monday 18th December 2023 at 0850 the air temperature was 34.9°F (2°C), with a windchill temperature of 20.5°F (-7°C), 68% relative humidity, and a sharp WSW wind sustained at 13 mph gusting to 21.6 mph.
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San Jacinto Trail Report 
Hello, wondering if there is yet a sense (or prediction) of whether this will be a low/average/high snow year for the San Jacinto mountain area?
Thanks for all your amazing work for the hiking community!
donna
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Thank you Donna. It is hard to be definitive at this time, as January and February statistically are the most important months for snow in the San Jacinto mountains. That said, 11 of the past 12 winters have seen below average snowfall (last winter of course being the sole exception), and we are likely to have the lowest snow depth on January 1st for many years, possibly ever. Putting those two facts together suggests that a below average winter is more likely than not, but that could all change in the next month or two. Importantly, I would argue that low snow years are more dangerous for hikers as they tend to be less well prepared than in more obviously challenging winters. Safe hiking, Jon.
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