Weed emergence models require the estimation of base temperature for germination (T_b) that was estimated for Abutilon theophrasti, Echinochloa crus-galli, Amaranthus retroflexus, Sorghum halepense, Amaranthus albus and Amaranthus hybridus in Iran, to calibrate an existing model called AlertInf. Two statistical procedures were adopted: Model 1--linear regression of germination rate and Model 2--probit analysis. Model 1 provided lower T_b values. Abutilon theophrasti and A. hybridus presented lower T_b values (about 4 and 8 C), while the remaining species had values above 10 C. Since the estimated values of Tb were in agreement with those adopted for the Alertinf model in Italy, the first step was achieved to adapt AlertInf to Iranian conditions.