(Portland, OR)  --  An excessive heat warning is in effect for Portland and most of Oregon.  Temperatures are expected to exceed 100 degrees in Portland today and tomorrow, and it'll remain hot through the weekend.  The heat warning remains in effect through 10 p.m. Saturday.  Meanwhile, the hot weather is causing delays on maintenance work scheduled for Saturday night on the Interstate Bridge.  The work would have closed I-5 northbound overnight.  The new date for the work hasn't been determined.