Experimental short time population and production of aflatoxin B$_1$ by Aspergillus flavus in wheat flour at 20, 25, 30, 35 and 40ºC, as related to different moisture contents 5%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22% and 25%, was studied. Spore suspension of a toxigenic A. flavus containing ~ 3×10$^3$ spore/ml was inoculated in each flask containing 50 g wheat flour and incubated for 15 days. Spore count was observed slightly in flour with a moisture content 5% at all incubation temperature, then increased gradually by rising the moisture content reaching the maximum at 30ºC with moisture content 25%. High performance liquid chromatography analysis of AFB$_1$ showed the lowest quantification (482 ng/kg) at 20ºC with 8% moisture content in comparison to uninoculated control. The higher quantity of AFB$_1$ (637835.4 ng/kg) was produced at 25ºC with 25% moisture content. Accumulation of high amounts of AFB$_1$ was noticed at 20, 30 and 35ºC with moisture content 25%. However, at 40ºC with moisture contents 22% and 25%, high spore count was recorded, but traces of AFB$_1$ were produced. The significance of this investigation is that, in the event of wheat flour contamination with afltoxigenic species, rise in moisture contents are hazardous in the storage of wheat flour around 25ºC.