Mt. Whitney Portal Store & Hostel Forums General Mt. Whitney Portal Store Message Board thunderstorms - July vs. August

Getting my application ready to send in next week. Historically, is there any difference btwn July and August in terms of a threat of thunderstorms? At first I thought they were more likely in August than July, but I'm not sure what made me think of that. August is preferable because there should be less snow, of course, but I was wondering if that advantage was potentially off-set by a great likelihood of thunderstorms.

I did it mid-July last year, was thinking of going a little later this year in part because I bet there'll be a lot of snow there this year.

thanks!

Most of the snow should be gone by mid July although sometimes in mid July there remains a few patches high up on the switchbacks. By August there usually isn't much left. That would be the only different between July and August as far as snow goes.

Thundershowers can happen any ol' time. This is just a guess based on a hunch but if you were to look at historical data I think you might find more days in July with thunderstorms than in August. But, I think in general this is a difficult one to predict. Nobody can check their proverbial crystal ball and look into the future for weather predictions

Thunderstorms during this period are typically caused by monsoon conditions, which can affect the entire southwest. Arizona has paid more attention to them because they are particularly impacted, and they refer to the Arizona Monsoon. Further explanation is given by NOAA, and they write about the season beginning around the first of July and extending into September.

Bell-shaped curves being what they are, early July and September would see less-frequent conditions than the middle of the season. My personal rule of thumb is to consider thunderstorms a factor in my planning only between mid-July and the last week in August. Again thinking of the bell curve, you might consider the first week of August being "prime time."

By the way, in all my July and August climbs of Mt. Whitney, I made the summit in all but three attempts. Only one, in August, was due to storm. Part of it is knowing enough about the conditions to discern between "looking scary" and "being scary." Also timing it to be heading down in the very early afternoon. From my logbooks, I have gone to Mt. Whitney:

27 times in June. 24 were in good weather, and 3 in poor.
26 times in July. 21 were in good weather, and 5 in poor.
24 times in August. 22 were in good weather, and 2 in poor.
25 times in September. 22 were in good weather, and 3 in poor.

I made several other ascents in the area during these months, for example of Russell, Thor, and Candlelight, with generally the same results.

Of course, thunderstorms can be caused by conditions other than monsoon, and can come anytime.

As always, the Sierra is going to do what the Sierra wants to do - with zero input from its human visitors. Two data points: I have been going on two-week solo loops out of Horseshoe or Shepherd for years during the period late July through mid-August. Last year I was rained on (including thunderstorms) 9 of the first 11 days. Two and three years ago during the same period, I never unpacked the rain gear. In fact, I commented that my new Black Diamond Hylight had never been wet - until last year.

Always be ready for whatever the so-called "Gentle Wilderness" has to offer in bad weather. Rain can also bring with it high water at stream crossings. Last mid-July, an unanticipated thunderstorm, which lasted 6 hours, had me cowering in a gore-tex bivvy sack; sure glad I had it along. Next year I'll take the one-person tent, in spite of the extra 3 pounds.

For planning purposes this far out, it makes absolutely no difference. Anything after about mid-July is going to be roughly the same odds. Also, it's hard to tell, but you're right that this might be shaping up to be an high snow year with El Nino. That might influence conditions more than the threat of thunderstorms. So that might tip a trip to late July or August.

George