Health alerts are in place as very high humidity adds to danger of heat stress for the most vulnerable The Met Office has expanded its extreme heat warning for the UK, predicting record-breaking highs of 38C (100.4F) this week. The Met Office forecasts that extremely high temperatures could last from Monday until Thursday, leading to health concerns for elderly and vulnerable people. The forecaster said there was “growing confidence” that this week may break the record for the hottest June temperature of 35.6C, which was set in 1976 in Southampton and Camden Square, London, in June 1957.