Showery and stormy weather this week will increase humidity levels and overnight discomfort in Sydney and suburbs. This week a broad trough stretching from the NT into southeastern Australia is bringing a large area of instability and increased moisture. The instability is forecast to trigger showers and storms across much of NSW in the next few days. Storms combined with hot northwesterlies across much of NSW and sea breezes along the state's coasts will lead to increased humidity, particularly in the state's capital. Over the next couple of days, Sydney's day time temperatures will reach towards the high twenties with western suburbs aiming for mid-thirties. Showers and storms look likely to develop each day, especially in the afternoons and evenings, particularly in western suburbs. At night, temperatures are likely to struggle to fall below twenty with Thursday morning's minimum forecast at 22 degrees. While these temperatures aren't particularly special for the start of summer, the combination of showers and moist onshore winds at the coast will lead to increased moisture. As the temperature cools each night or in evening downpours, the humidity will increase to as much as 90% as the air-mass struggles to hold as much moisture. Sydney-siders without air-conditioning will need to grab a fan to avoid an uncomfortable night, especially overnight into Thursday.