Frost/Freeze — Western and Central Hillsborough, New Hampshire

2023-05-18 · Western and Central Hillsborough, New Hampshire

Event narrative

A hard freeze impacted the region shortly after midnight on May 18th with widespread sub-freezing temperatures. Temperatures ranged from freezing to the mid-20s. Peterborough reported a low of 29 degrees. The temperatures were some of the coldest this late in spring in over the past 30 years based on official records. The hard freeze impacted blooming fruit trees and berries the most. The hardest hit orchards were those at lower elevations in valleys with less impacts at orchards located at slightly higher elevations on hills. There were reports of flower mortality rate as high as 90% in some areas. In addition, leaf kill was prevalent with some oak species due to these tree species being more vulnerable to freezing.

Wider weather episode

Early on May 17th a strong cold front pushed through the region, allowing for an unseasonably cold and dry Canadian airmass to settle in across the region. Gusty winds during the afternoon quickly diminished during the evening as surface high pressure crested over the region. The cold airmass, clear skies and no winds allowed for perfect radiational cooling temperatures. Temperatures quickly dropped through the night with widespread sub-freezing conditions all the way to the coast. Many areas dropped down into the upper 20s, with the coldest conditions across low-lying valley locations. Leave-out had already occurred away from the mountains with agriculture impacts reported to berry and fruit tree crops.

Source: NOAA Storm Events Database, event_id 1105029. Narrative written by the NWS forecast office that issued the report.