The warning is in place is for Sunday (June 5) from midnight until 6pm.
The national weather service says the thunderstorm could “cause travel disruption and, in a few places, flooding”.
Local forecaster Jamie Dunlop, from @NNweather, said: “Showers or longer spells of rain with a risk of thunderstorms, hail and torrential rain could affect parts of the county tomorrow.”
For Northampton, Met Office is predicting a 90 percent chance of rain between 6am and 7am and a 80 percent chance of rain at 9am.
For Kettering, the service is predicting a 90 percent chance of rain between 6am and 9am.