Body Temperature Was 99.6 After Being Outside And Doing A

Body temperature was 99.6 after being outside and doing a lot of housework. It's 90F outside. Got very nauseous and clammy feeling. I took my pants off and layed down in A/C and my temperature is gradually going down, usually mine tends to be under 98.6 on a normal day. Is this a sign of heat exhaustion? It seems to happen often to me.