A cold snap is pushing across the UK this week as forecasters warn of outbreaks of hail and thunder amid heavy showers . Temperatures are several degrees below the mid-May average across the midlands and northern areas on Wednesday as the country wakes up to a unsettled and blustery morning. It comes as northerly winds drag in cold air from northern Scandinavia and the Arctic circle. Average temperatures for the time of year range from around 12 to 17C across the country. But forecasters say the mercury will hover at around 14C in the south west and 9C in parts of Scotland at the warmest on Wednesday. It has been an unsettled start to the day with blustery showers in the north and south east. The Met Office has warned wet conditions could turn thundery with a risk of heavy rain and hail in the east later in the afternoon. Below average temperatures for May are expected on Wednesday (Met Office) However, sunshine is forecast in some areas, particularly in the west of England.…