Grand Tetons Weather

wettest months: May, June, Dec. and March

warmest (average highs): Aug, July, June, Sept, May

coldest (average highs): Jan, Dec, Feb, (in single digits) March, Nov. (in the teens)

and yet another source said that in the town of Jackson, January is the snowiest month, May the wettest; hottest recorded temp 98 (more likely a 89 to 90 degree max), coldest 63 below zero (more likely a -9 to -10 degree minimum).

National Park Service stats from Moose, Wyoming for fifty recent years had an

Average snow depth of 28 inches in January, 34 inches Feb., 32 March, 13 April, 4 November and 16 inches in December.

Average snow fall was January 44.4 inches, February 30, March 20.6, April 9.3, May 2.8, June .1, September .5, Oct. 4.4, November 25.2 and December 39.2 inches.

Average maximum temperature was January 25.7, February 31.1, March 39, April 49, May 60.9, June 70.6, July 79.8, August 78.8, September 68.9, Oct. 55.9, November 38 and December 26 degrees.

Average minimum temperature was January 1.2, February 3.6, March 11.9, April 22.1, May 30.9, June 37.2, July 41.2, August 39.6, September 32.2, Oct. 23.2, November 13.7 and December 1.5 degrees.

Hiking trails: The park service says: Grand Teton/Jackson Hole "Valley trails are often snow covered until late May." "Snow melts gradually, leaving valley trails by mid-June, canyon trails by mid-July." "Many mountain passes remain snow covered throughout most of the summer and an ice axe, and the ability to use it, may be recommended to ensure safe travel... Consider bringing an ice axe through mid-july and know how to use it to self-arrest and self-belay on snow. Snowfield crossings can be extremely hazardous and are the source of serious accidents in the Tetons.""

Afternoon thundershowers are common in the summer and into fall. During a thunderstorm, don't take a shower or use a sink, including washing dishes. Don't talk on a land line phone. Don't use your I pod. Don't get zapped! Please read Thunderstorm and lightning safety

My 1965 copy of A Climber's Guide to the Teton Range warns "The Tetons are big mountains, big enough to make their own weather, to hide some of the early signs of changing weather... very severe storms can come up quickly. Be equipped for them - this includes reserve food and warm clothing... The one regularity of Teton weather is that the storms almost always come from the southwest. This characteristic means that there is usually very little warning of an approaching storm for climbers on the north and northeast sides of the peaks. It should be kept in mind that these storms can sometimes be quite severe; the driving sleet or snow can convert an ordinary climb into a fight for life."

When it rains in the flats it may snow up near the peaks; at least one period of interesting weather with snowfall at the higher elevations occurs in late August every year. Cold early mornings and overnights could bring a few snow flakes to lower elevations even in August, the warmest month. The park warns: "Low temperatures at the high elevations may be at or below freezing at any time of the year."

Watch a Grand Teton National Park summer weather video:

http://www.nps.gov/grte/photosmultimedia/tp.htm

Most of our club trips are in the Fall . Nights and early mornings are cold. September temperatures average 68 max, 34 minimum in the lower elevations of the park, at least 5 degrees colder on the upper elevation trails. Extreme high at 93, extreme low at 7. September has an average of 14 nights below 32 degrees.

There is usually a big temp difference at different altitudes. One forecast had highs of 75 degrees in the valley at 6,000 feet elevation, 68 degrees at 8,000 feet and 60 degrees at 10,000 feet. Another forecast had 68 degrees in the valley at 6,000 feet, 61 degrees at 8,000 feet and 53 degrees at 10,000 feet.

Overnight lows can be 48 degrees in the valley at 6,000 feet elevation, 45 degrees at 8,000 feet and 39 degrees at 10,000 feet. Another forecast had 47 degrees in the valley at 6,000 feet, 41 degrees at 8,000 feet and 32 degrees at 10,000 feet.

We've had a light dusting of snow and hail in the lower elevation where we camp as well, (didn't need chains for the cars so far but we have always brought them, even for the four wheel drive vehicles with snow tires). The hiking trails/passes are usually okay through our fall trips since the first real thick snow fall usually isn't until late October.

We've also had lots of fall days sunny enough for swimming in a lake if you are intrepid (or if you wear a couple of pairs of jammers or borrow a club springsuit size wetsuit).

Below, Eric Marxmiller, Michael Gregg, Alan Ahlstrand, Mouzhan Yousefi, Duong Nguyen and Raquel Garza:

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The local weather report almost always predicts at least a slight chance, or more likely a 20% chance of a thunderstorm, even if none show themselves to us. A report of possible "isolated showers and thunderstorms" also almost always says that "some storms could produce gusty winds" or "some storms could produce small hail and gusty winds."

In 2000 we had some thunderstorms (the park averages 2 each month in September) and occasionally long bouts of rain. (We kayak/canoe in the rain and wind, but not during thunderstorms.)

Thunderstorms can have 0.40 inches of rain in less than an hour, or that much in 24 hours.

In 2002 we just missed a previous 2.4 inches of rain in three days and it didn't rain on us at all until the last morning. The last two nights of the 2004 trip we were woken by heavy rain around midnight and had drizzle/rain and occasional downpours during the last two days. 2007 we had two evenings of magnificent local lightning displays, one of which sent the campers into one of our rental cabins for safety.

People on the 2005 trip said, after the kayaking overnight, that they didn't think I stressed the probability of cold nights enough.

In September 2005 and 2007 it snowed on hikers at lake Solitude and rained on those lower down in Cascade Canyon.

In 2007 one long evening-into-night storm had lightning as often as three hits in ten seconds with heavy rain that flooded streets.

In 2010 we had many rainy or drizzly days and it did not snow on us but we did wake up to snow covered mountains near the end of the trip:

September 10, 2010 was the first big snow storm with a foot or so of snow at 9,000 feet elevation.

For paddling, bring your full rain suit, warm clothes for under it and a dry bag (the club intends to provide some dry bags) for your camera as we do not turn back when rain starts unless there is a thunderstorm.

June has one and a half times as much precipitation as September. June temps average 70 max, 38 minimum in the lower elevations of the park, at least 5 degrees colder on the upper elevation trails. June has an average of one day over 90 degrees, and two nights (days?) below 32 degrees. Extreme high at 98, low at 18. Average number of thunderstorms in June is 11.

In June 2011 it was still snowing occasionally in the mountains.

Jackson Hole weather, usually also including a 10,000 foot forecast:

http://www.mountainweather.net/

http://www.crh.noaa.gov/ifps/MapClick.php?MapType=3&site=RIW&CiTemplate=1&map.x=34&map.y=115

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Winter lasts about six or seven months in the Grand Teton, Jackson Hole area. One source had the snowiest months: Jan, Dec, Feb, Nov, March. Another source said: The most snow, in this order: February, March, January, December, April, November. Grand Teton park says that "the first heavy snows fall by November 1 and continue through March; snow and frost are possible during any month."

One blogger described 'nine months of winter and three months of bad skiing.'

Watch a Winter Safety in Grand Teton video:

http://www.nps.gov/grte/photosmultimedia/tp.htm

Snow generally covers roads from early November through mid-April. Blowing snow is frequent in the winter, even to the extent that you can't see very far in front of your vehicle. Cloud cover can prevent you from seeing the mountains for days at a time, even within a few miles of the range.

The inner park road is closed from just beyond the Taggart lake parking lot all the way to Signal Mountain (and not plowed) from November 1 over the winter until sometime around May 1. Once snow accumulates the road is used for cross-country skiing, skate skiing and snow-shoeing.

Grand Teton park recommends vehicles with four-wheel drive or all weather tires and warns that all roads can be closed during blizzards. "Winter driving can be challenging; park roads are often covered with ice or hard packed snow; winter storms can create white-out driving conditions."

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What are the chances of....?

for our anticipated mid-September trips from around Sept 10 to 18, Wunderground said:

"Weather statistics based on searched dates from 1975 to present. Probabilities (chance of) statistics indicate the chance of an event or condition per day (ie. a 30 percent chance of a cloudy day indicates that each day has a 30 percent chance of being cloudy).

Average High Temperature is 68 F (historical range 39 F to 88 F)

Average Low Temperature is 33 F (historical range 18 F to 51 F)

There is a 0% chance of a Hot Day (temperature over 90°F) (0 days out of 251 in historical record).

There is a 82% chance of a Warm Day (temperature over 60°F) (207 days out of 251 in historical record). Most consecutive days found in historic record: 8

There is a 37% chance of a Freezing Day (temperature below 32°F) (93 days out of 251 in historical record). Most consecutive days found in historic record: 8

Average Daily Precipitation is 0.20 (historical range 0.00 to 8.71)

There is a 26% chance of a Precipitation Day (65 days out of 249 in historical record). Most consecutive days found in historic record: 6

Average Cloud Cover is mostly sunny There is a 16% chance of a Cloudy Day (13 days out of 81 in historical record). Most consecutive days found in historic record: 3"

photo above © E J Peiker http://www.ejphoto.com/grand_teton_page.htm used with permission