Thundery showers are forecast to affect the Western Isles overnight.
A Met Office a yellow warning of heavy rain, thunder and hail is in place until Wednesday evening.
A band of warm, moist air bringing heavy rain and lightning is expected to move northwards from Barra late tonight.
Earlier, morning fog patches cleared to a warm, sunny day with afternoon temperatures predicted to reach around 20°C in Stornoway.
The Met Officer chief forecaster said: "Rainfall will be very variable, and the extent of thunderstorms is uncertain.
Rain showers are forecast to develop over the Hebrides on Wednesday afternoon.