Dear Elizabeth,

Thanks for contacting Ask Extension. The average date of the last frosts in Salem is April 23; however, historical records show that we can still get a frost through the first week of May.

If your soil is warm (i.e. you are planting in a raised bed or container), you can plant your tomatoes now. But you must still be prepared to cover them anytime the temperatures are predicted to reach 36 degrees F. because plants can sustain frost damage at that point. 

That being said, it is generally recommended to wait a bit longer, making sure the soil is thoroughly warm for both tomatoes and annual plants. Cold soils will hold them back, so you do not lose anything by keeping them indoors for an extra week or two. 

I hope this information is helpful. Feel free to write again if you have more questions.

Best regards,