By the following day, it had strengthened into a hurricane.

The depression moved west and strengthened into a storm the same day.

We were dressed, and the dawn light had strengthened into day.

It strengthened into a tropical storm soon after and head to the north.

The storm strengthened into a hurricane, though, late on September 11.

Later that day, the system strengthened into a tropical storm.

Three and a half days later, it strengthened into a tropical storm.

The next day, it rapidly strengthened into a hurricane and turned north.

It strengthened into a storm June 19 and a hurricane the next day.

By the morning of June 21, the system had strengthened into a tropical storm.