When are the dangerous seasons of time when it’s not safe to be in the Sierra?

Predicting the weather, much less the typical time frames when it may do “this” or “that” is like watching a bubble floating on a creek, it moves all over the place, constantly varying its location, but still in the creek.

Historically, and after a “normal” Sierra winter, the dangerous period of loose powder snow laying on steep slopes all around you causing avalanches that can kill you ends around Easter, so by May 1st the powder snowpack has settled and consolidated down into one, big, frozen mass that is easy to walk on and not likely to move by itself anywhere.

The month of May, otherwise called the “Secret Season,” offers ideal snow-hiking surfaces and ambient weather conditions as the environment slowly warms up to the start to the Sierra Thaw, right around the end of May, the first of June.

Thus, the NoBo PCT thru-hiker has this window of opportunity to enjoy the Sierra under a blanket of white and, still, have fairly safe surface conditions and an easy walk to get through the Sierra before encountering the deadly, whitewater, raging creeks of the Thaw period.

The other bookend to the Secret Season when the Sierra can be specifically dangerous is after the Thaw starts and until most of the snowpack has melted away and that duration can vary from 6 to 12 or more weeks long.

Though this period of early summer has enticingly long and warm days, all that solar radiation is melting countless square miles of snowpack into the creeks of the high country, transforming them into raging, whitewater torrents that have killed people attempting to cross them.

The other agony of this wet timeframe comes from trying to wallow through the soupy, mushy snowpack that is busy melting! “Suncups” as big and deep as garbage cans form that hikers have to walk through (without falling in) and “Postholing” conditions prevail from mid-morning throughout the day causing sudden spinal jarring and serious exhaustion.

Therefore, after a “heavy” winter, like the one we’re experiencing right now, the Thaw’s danger-period can include June, July, August, and even into September. Indeed, after a really “huge” winter, all the snow in the Sierra may never melt off by the time winter’s fresh powder starts falling, again!