Data of grass minimum temperature (RELVA) and difference between screen and grass minimum temperature (DIF) were analyzed in ten localities of São Paulo State, Brazil, utilizing historical data of nights with frost. These informations were correlated with the following meteorological elements: air minimum temperature obtained in meteorological screen (TMÍN); mean wind speed (VENTO); air temperature at 9:00pm obtained in meteorological screen (T21h); dew point temperature at 9:00pm (To21h); and cloud cover (NEB). The average value of DIF was 4.1°C, ranging from 3.3 to 5.7°C. To21h and TMIN were the elements that presented best correlation with RELVA while VENTO and To21h showed good fit with DIF. Regression equations to estimate RELVA and DIF were obtained for each locality so as a general equation. RELVA estimative was that presented the best fit in relation to DIF.
grass minimum temperature; air minimum temperature; estimate; frost