Give me the maximum low temperature and average precipitation at the Amersham station.
SELECT max(t1.low_temperature) ,  avg(t1.precipitation) FROM weekly_weather AS t1 JOIN station AS t2 ON t1.station_id  =  t2.id WHERE t2.network_name  =  "Amersham"
maximum low temperature refers to MAX(low_temperature); average precipitation refers to AVG(precipitation); at the Amersham station refers to WHERE network_name = 'Amersham';