BOSTON (CBS) — The WBZ-TV weather team is declaring Wednesday a Storm Watch Weather Alert day. This is due to the likelihood of widespread downpours and high potential for some severe thunderstorms.

RELATED: Tornado Warnings Issued In Mass., NH

The National Weather Service has issued a severe thunderstorm watch for all of Massachusetts and southern New Hampshire until 9 p.m.

TIMING:

The main action and highest period of impact will be between 2 p.m. and 10 p.m. If clouds and showers linger longer than anticipated Wednesday morning from any early showers, the severe weather threat will lower for the afternoon, but if clearing develops fast enough, expect the severe weather risk to increase.

LOCATION:

Through mid-afternoon, most of the action will be well to the north and west of Boston. By late afternoon and early evening, the main areas of focus will move from the northwest suburbs of Boston to the immediate Boston metro area.

Later in the day, after 8 p.m., the area of heaviest rain and strongest storms will move from the Boston area south.

IMPACTS:

The atmosphere will be primed for severe storms on Wednesday with very high humidity levels and lots of lift available to grow storms rapidly. There is a high likelihood for heavy downpours and some localized flooding. There is also a high threat of damaging winds within these storms as well as some hail.

As with any thunderstorm, lightning will pose a risk to anyone with outdoor activities, at the beach or in the water.

Finally, we cannot rule out an isolated tornado somewhere in the area on Wednesday.

Wednesday will be, by far, the most active weather day of the week and the most active day we will have for a while as a much quieter pattern sets in later this week. We urge you to stay tuned to updates on WBZ-TV and CBSBoston.com all day long.

Follow Terry on Twitter @TerryWBZ.