Capital Weather Gang's NatCast for tonight has 'Could see a shower or storm in the area early, but rain chances decrease by mid-evening' with low 80's at first pitch, upper 70's by ninth inning, 35% chance of rain.
weather.com's hour-by-hour forecast has 50% chance of rain ('scattered thunderstorms') throughout the core game hours 19.00-22.00, and 40% in the hours immediately flanking this.