Sierra Weather

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:

(From supertopo.com)

Data!

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 / tom@mmto.org