Here are a few things I got from the manufacturers spec sheet on their web-site http://www.2t.com/index.htmStorage temperature
-20° to +70°C
Operating temperature
-20° to +50°C
Charging temperature
-20° to +40°C
Humidity
5 to 95% non condensing
They also have an article on their website:"JETT PASSES RAIN SHOWER TEST
When put to an impromptu rain shower test, our IP65 rated JETT®•ce passes with high marks. Its competitor, however, does not.
For two hours, our unit and an unidentified hand held, were subjected to a steady rain shower, simulated by an outdoor hose. The JETT IP65 showed its true colors under this intensive soaking: the keys, the display and most importantly, the guts of the JETT, came away in perfect working order. What happened to the other unit? It was simply bogged down.
Thanks to our testers in rainy British Columbia for proving once again that the JETT IP65 has what it takes to survive even the harshest of environments."
I hope this helps.
Cheers,
Glen W. Cameron, C.E.T.
City of North Bay, Ontario