Isotropic velocity and scalar fluctuations are closely approximated by slightly stretching a heated grid flow through a short (1.36:1) contraction. The heating is such that temperature serves as a passive scalar, and the velocity/scalar time scale ratio is about one. At small values of Taylor microscale Reynolds number (10 < Rλ < 102), the spectrum of the temperature fluctuations has a more discernible scaling range than the spectrum of the velocity fluctuations. The scaling-range exponent for the thermal spectrum, mθ, exhibits a power-law function of Rλ and tends to the Kolmogorov value of 5/3 more rapidly than that for the velocity spectrum, mu. Both mθ and mu are closer to the Kolmogorov value with the contraction than with no contraction. The trends for the present measurements supplemented with previously published data for larger Rλ (>102) indicate that, to obtain a 5/3 scaling range, Rλ must exceed 103. The ratio (5/3 + mu)/mθ is approximately 2, in close conformity with the proposal of Danaila and Antonia [“Spectrum of a passive scalar in moderate Reynolds number homogeneous isotropic turbulence,” Phys. Fluids 21, 111702 (2009)10.1063/1.3264881].