Try the free Speccy - do a google search.  There are several other free temperature monitoring programs and they all return different readings.  Speccy seems to be more in line with the Intel supplied monitor for my Intel motherboard.

Best suggestion, whether in a warm climate or not is to locate the PC where it can get adeqate air flow.  A PC desk compartment is usually not a good location.  Same way directly on the floor and in the cleanest environment it can still collect a lot of dust.  

(I live in warmer Florida).

You can also try the free SpeedFan. It will report hard drive, video, and ambient temps in most Dell PCs as a small icon in the system tray near the clock, but it can't control fan speeds on Dell PCs.

Ron

EDIT: I fixed the link

Steve,

I use Core Temp to monitor the temperatures.

Rick