Today is Friday, Sept. 7. Here are five things you need to know:

1. There is a chance of showers and thunderstorms this afternoon, mainly between 2 and 3 p.m., according to the National Weather Service. Overall, today should go from mostly cloudy to sunny with a high near 85. There’s a slight chance of showers and thunderstorms Saturday morning, and then it should be partly sunny with a high near 83. Showers are likely Sunday morning, before 10 a.m.

2. The 3rd Annual Running with Friends 5K is at 10 a.m. this Sunday, Sept. 9, in front of Arlington Town Hall. The race benefits Arlington’s Council on Aging and the town’s more than 9,000 senior citizens. Walk-up registration, from 9-10 a.m., is $25. The first 200 entrants get a free T-shirt; there will also be food, awards and prizes, a raffle and music. Complete details.

3. The Friends of Spy Pond Park are having a “Work Day” at 1 p.m. this Saturday, Sept. 8. Sunday’s the rain date. Complete details.

4. Despite losing every precinct in Belmont, Dave Rogers won the Democratic primary for state representative in the 24th Middlesex District Thursday. Here’s how he did it.

5. Obituary: Marc Aaron Butler, Former Arlington Children's Theatre President.