When to go?
It depends on what kind of snow year this is, and what kind of weather you prefer.
Here is a crude summary of the seasons in the Sierra, adapted from Secor's introduction:
Winter begins with the first major storm (the first storm with snow that fails to melt).
This is typically in mid November, but can be mid-October through mid-January.
Typical winter weather is relatively mild, with nights dropping to 15 degrees F.
Spring lasts from late April to June. Note that winter storms are still a possibility.
Some people feel this to be a superb time to visit the Sierra, as long as you are
experienced with snow and well equiped.
Summer lasts from the end of June through mid-September.
Early summer yields lots of mosquitos (and wild flowers!)
Autumn lasts from mid-September till the first major winter storm (typically mid-November).
In many ways this is the best time, with crisp, cold nights, no mosquitos, and few people.
- May -
Only in low snow years will climbs be easily accessible.
In general, most of the approaches will be snow-covered and
many of the access roads may not be plowed.
May is mostly dry but expect a few storms.
There are no crowds in May.
- June -
Aside from a rare storm, June is usually dry with warm temps and nice long days.
Most of the access roads are plowed but there will still be snow on most approaches.
Thunderstorms begin to develop so keep a close eye on the weather.
The crowds start showing at the end of June and it becomes more competitive
to get overnight camping permits.
Charlotte Dome and Temple Crag are usually the first climbs to easily access.
- July and August -
Prime Sierra climbing weather.
Temperatures are hot at the trailheads but perfect on the climbs.
This is also prime thunderstorm season so watch the weather closely.
There are lots of crowds and it is competitive for overnight camping permits
(get reservations at least a month in advance).
- September -
Still great climbing conditions but the nights are cool.
Some north-facing routes may be uncomfortably cold in the shade.
The crowds start to thin out.
- October -
Shorter days and cold nights mean less people.
Climbing in the shade is no fun.
Weather is mostly dry but the first winter storm can
arrive late in the month.
Easy to get overnight camping permits.
- November -
Frigid nights and short days keep most people out of the High Sierra.
Winter storms begin to arrive more frequently.
A rare time to get some solitude before the heavy snow sets in.
- December - April
Frequent winter storms and icy temperatures make the High Sierra
only accessible to those that enjoy suffering.
In exceptionally dry years, during a warm spell,
you may be able to run up one of the peaks in-a-day in December.
The California Department of Water Resources has a number of
monitoring stations in the Sierra with data posted online.
There is a single key number to get from their website, namely
what percent this years snowpack is of normal (As of June 1,
the 2009-2010 winter snowpack was estimated at 143 percent of normal).
Look at the yearly summaries to find this figure,
"Normal" is a 50 year average. Secor discusses these numbers and says
that in a 43 percent year he could easily cross passes in mid-June without
an ice-axe, whereas in a 205 percent year a large cornice made crossing the
same pass very difficult. In a 100 percent year most passes crossing the
Sierra crest will be more or less snow free by July 1.
Manual stations just provide snow depth (usually monthly),
Satellite stations give temperature, snow depth, usually daily
or even hourly.
There is LOTS of information available here. The Historical Data link gives something I want,
namely access to entire years of hourly temperature data for stations for which it is available.
Here are a couple of temperature plots from the Charlotte Lake Station:
The first (below) shows the average air temperature for the year of 2009.
The second (below) also shows a 1 year period, but beginning and ending
in the last week of May (which happens to be when I got intrigued by this data).
Here are 6 years of snow depth data
(from November 2004 to May 2010 - that is a far back as the online
data for this station allows).
The snowfall the last 3 years looks quite similar.
The 2006-2007 winter was a mild one, but the two
before that were more severe.
Here are the snowfall records for the year of 2009.
By late May, the snow was gone at this station.
The first storm, in October, dropped a foot of snow.
Have any comments? Questions?
Drop me a line!
Uncle Tom's hiking pages / firstname.lastname@example.org