I'm a professional programmer, but I'm new to AVR. I'm also a geocacher and I've got an idea for a cache that will use a microcontroller. (It would be something like a Mastermind game.) However, as a geocache, it will have to be able to take outdoor temperatures of -20 F (-29C) to 100 F (38C). The Butterfly only goes down to 0C (32F). I could put the microcontroller in the ground (appropriately waterproofed) to moderate the temperature (because ground temperature doesn't vary as much), but it will still go outside the temperature range of the Butterfly.

I can use LEDs for output and BCD rotary switches for input, so those should take the temperature range, but the LCD won't take the lows. (I've had other LCDs ruined by 32F.) I'll power it with the power system from outdoor solar lights.

I also use Linux, but I know that there are development tools for this.

However, I need to know the best (cheapest) places to get AVR microcontrollers and a basic programmer, USB preferably. So if the Butterfly will work to program the AVR then I can remove the chip, that would probably be the best for programming.

Any suggestions would be appreciated.