A two-word phrase for a sudden period of frigid temperatures. Keep in mind: The first word may be at the bottom.
Reveal top + bottom answer and reasoning
Answer: COLD WAVE
Top half: COLD - COLD is the first half of "cold wave", the top + bottom answer for the shared final clue: "A two-word phrase for a sudden period of frigid temperatures. Keep in mind: The first word may be at the bottom".
Bottom half: WAVE - WAVE completes "cold wave", so the top and bottom rows answer the shared final clue together.