Grand Tetons WeatherThis is info for the De Anza College Outdoor Club fall and summer trips to Grand Tetons National Park. The main trip information page is at Grand Tetons.
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.
In 2000 we had some thunderstorms (the park averages 2 each month in September) and occasionally long bouts of rain. (We kayak in the rain and wind, but not during thunderstorms.) We've had a light dusting of snow and hail as well, (didn't need chains for the cars so far). The hiking trails are usually okay through our fall trips since the first real snow fall usually isn't until late October, but there was a significant snowfall Sept. 7, 2001.
We've also had fall days sunny enough for swimming in a lake if you are intrepid (or if you wear your springsuit size wetsuit).
In 2002 we just missed a previous 2.4 inches of rain in three days and it didn't rain on us 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.
September has an average of 14 nights (days?) below 32 degrees. Extreme high at 93, extreme low at 7.
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.
Afternoon thrundershowers are common in the summer. 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.
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
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.
Jackson Hole weather
http://www.mountainweather.com/JACKSON.htm
http://www.crh.noaa.gov/ifps/MapClick.php?MapType=3&site=RIW&CiTemplate=1&map.x=34&map.y=115
The Teton Saddle weather station (about halfway between the Grand Teton and Middle Teton summits at 11,610 feet elevation) stats are at:
http://www.met.utah.edu/cgi-bin/droman/meso_base.cgi?stn=TETWY
The stats from the weather station just east of Timbered Island, at 6690 feet elevation, are at:
http://www.met.utah.edu/cgi-bin/droman/meso_base.cgi?stn=GTGW4
The stats from the weather station just north east of the old Moose Visitor Center, at 6478 feet elevation, are at:
http://www.met.utah.edu/cgi-bin/droman/meso_base.cgi?stn=GTPW4
The stats from the weather station just north of the Jackson Lake dam, at 6779 feet elevation, are at:
http://www.met.utah.edu/cgi-bin/droman/meso_base.cgi?stn=JLKW4
The stats from the weather station at Moran, at 6749 feet elevation, are at:
http://www.met.utah.edu/cgi-bin/droman/meso_base.cgi?stn=DO414
The stats from the weather station a few miles north east of Two Ocean Lake, at 7030 feet elevation, are at:
http://www.met.utah.edu/cgi-bin/droman/meso_base.cgi?stn=BSCW4
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online searches found this info:
a chart of monthly seasonal weather averages for Jackson Hole, Wyoming, with high and low temperature; average and record rainfall and snowfall.
http://www.wunderground.com/NORMS/DisplayNORMS.asp?AirportCode=KJAC&SafeCityName=KJAC&StateCode=WY&Units=none
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"
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snowiest months: Jan, Dec, Feb, Nov, March
(another source said:
The most snow, in this order: February, March, January, December, April, November)
Another source said that in the town of Jackson, January is the snowiest month, May the wettest, hottest recorded temp 98, coldest 63 below zero.
Snow generally covers roads from early
November through mid-April.
wettest months: May, June, Dec. and March
driest: Feb, July
warmest (average highs): Aug, July, June, Sept, May
coldest (average highs): Jan, Dec, Feb, (in single digits) March, Nov. (in the teens)
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