Sydneysiders may want to leave work a bit early today to avoid being caught in the rain during this evening's commute. A rain band tracking across NSW today from west to east will reach the city during peak hour tonight. Rain bands that move into Sydney from the west often drop their heaviest falls on and west of the ranges, leaving the most of Sydney's suburbs with lighter falls. This is caused by air becoming drier as it moves down the eastern slopes of the Blue Mountains into the Sydney Basin. However, while this evening's rain won't be too heavy for Sydney, it will be enough to slow traffic and catch those without an umbrella by surprise. Light, intermittent showers could develop from the mid-afternoon before steadier rain spreads over the Sydney Basin at around 5-7pm. The rain should only last 2-3 hours before clearing offshore by around 10pm. Rain will reach the western suburbs first and spread east during the evening commute, so leaving work a bit early today may mean missing the wet weather. Those commuting towards the end of peak hour are more likely to be affected by the rain. Most suburbs will pick up 2-5mm this evening, with some suburbs possibly seeing 10mm in the space of a few hours. Heavier falls of 10-20mm are likely on the ranges west of Sydney today, which will be a welcome change for the parched region. Katoomba only registered 2.8mm of rain last month, making it their driest July since 1972. Drier weather will return to Sydney on Friday and last through the weekend.