Only starts when it is hot outside

I have a 2002 civic DX that only starts when it is hot outside. It starts right up and runs great if I try to start it during the hot part of the day. If I try to start it in the morning when it is cooler or normal temp it will not start. I checked and there is no spark when it will not start. Any ideas why it would act this way? We changed out the ignition switch and the brown relay behind the glove box, but it still acts the same. Thanks.