Last night the overnight minimum temperature for Plymouth was predicted at +6c, yet I have a work colleague that lives in central Plymouth who reliably informs me she had to scrape ice off her car this morning & the temperature on her car thermometer at 7am was only +2C.

Even allowing for the fact that car thermometers are not 100% accurate, a difference of 4C compared to forecast is substantial.

She also informed me that a motorcyclist was killed in Plymouth this morning, was there ice on the road that contributed to the accident?
http://www.thisisplymouth.co.uk/Bike...ail/story.html

It's not the first time that I've noticed actual temperatures a lot lower than predicted, what's going wrong with the forecasts?