I don't think that temerature alone is going to cause famine. Crops are quite heat tollerant but don't like drought. Crops are more likely to be wiped out by high winds, heavy rain or cloudy cold weather as harvest time approaches. As long as plenty of rainwater is collected and preserved carefully then I can't see a problem in the near future at least.

I guess genetically modified crops are the long term sollution in the hottest of climates but would you seriously want to go down that road without far more research into possible long term side effects, not just for human health but also the environment?