Isadora, yes you will need to feed more but you might find the pattern of feeds are more shorter ones during the day (the foremilk which comes first is more watery and thirst quenching) and then longer feeds at night (for the calories in the richer hindmilk). Make sure you drink plenty of fluids and more yourself. There is a good fact sheet on keeping baby cool on the ABA website: http://www.breastfeeding.asn.au/bfinfo/cool.html