37 degrees

My husband's BMW also alerts him as to when the temperature is 37 degrees, so its not just a Prius feature.

 

Best I can find is that 37F/3C was chosen because bridges, etc., may be colder. than the ambient air. The Prius' brief temperature banner is less intrusive than some other car's continuous display or beeps, but is also easier to miss.

 

I have the 2007 Base and I see the snowflake quite often when it's 37 and below. Maybe you folks with the fancy schmancy "high res" MFD display (woo! woo!) didn't get the snowflake?

 

The first time the snowflake warning appeared on my MFD, I about had a seizure.
It looked like some sort of mutant alien spider, and the bright yellow made it look like something was going to explode. Of course, the warning was only there for 2 nanoseconds, so I wasn't able to see what it was.

The next time it appeared, I saw it fully. Oh, it's that thing... the low temp warning. What a stupid place to put that. There isn't any sort of indicator up on the dash, where I'm SUPPOSED to be looking when I'm driving.

It appears randomly... always at 37 degrees, of course, but it just comes on and then vanishes again... repeating when it feels like it.

 

Mine has the snowflake up near the light indicator and cruise indicator and it stays on below 4 degrees C.

 

Research seems to show that 7C or 44.6F is were tyres start to work in a different fashion.

"When ambient temperatures fall below 7C the molecules in tread rubber progressively harden and freeze.

This means the tyre is less able to adapt to the contour of the road surface, which in turn reduces grip levels.

With winter tyre rubber compounds there is a higher proportion of natural rubber and coupled with extended use of silica technology they minimise the hardening effect at low temperatures allowing the tyre to key into the road surface, resulting in higher grip levels."

http://www.tyres-online.co.uk/techinfo/winter.asp

For more details view this site that this quote is from.

In UK the tyres fitted as standard are 195/55 16R BRIDGESTONE TURANZA

I have not yet had chance to drive them but from what I read the first stop when I pick my new car up from the dealer will be the tyre shop to get winter rubber fitted.

Jon the Chief