Project Diary: Maximum-minimum thermometer

My Dad's very predictable. Every day, before he goes to work, he goes out to check the thermometer hung in the back garden. It registers the maximum and minimum temperatures since its last reset – which is every morning just after he's read it. Then he comes back in and tells us what the values imply for today's weather, his plants, the stock market, global warming… So I thought I'd have a go at building him an electronic equivalent, a box that displays the highest and lowest temperatures it's been exposed to. He could have it for Christmas.