Low temperatures on Thursday, Dec. 13, 2018.

At a Glance

On Thursday morning, the temperature on Mount Washington was warmer than the rest of New Hampshire.This was due to a temperature inversion that developed in the region.

It might sound strange, but it happened Thursday morning: the temperature on was warmer than the rest of New Hampshire and much of northern New England.

In northern New Hampshire, including towns like Berlin and Whitefield, temperatures dropped below zero Thursday morning. Readings in much of southern New Hampshire dipped into the single digits, although near the coast, Portsmouth recorded a low of 10 degrees.

Meanwhile, a low of 11 degrees was observed around midnight on Mount Washington and temperatures rose as high pressure moved into northern New England early Thursday. Temperatures were in the teens by 3 a.m. and stayed in the mid-teens into Thursday afternoon.

In nearby Berlin, New Hampshire, which is at an elevation of 1,020 feet, temperatures continued to fall until about 6 a.m., and a low of minus 17 was observed.

These statewide temperature differences at about 6 a.m. were highlighted by meteorologist .

The reason for this unusual temperature difference between Mount Washington and much of northern New England was a subsidence inversion that developed because of high pressure over the area.

This high pressure brought cold temperatures across New England, but the slowly sinking air warmed due to the increase in atmospheric pressure.

This area of high pressure also resulted in generally clear skies across much of the area, which allowed temperatures at the surface to drop. The cooler air in the valleys became trapped by the warmer air aloft.

This led to temperatures that were slightly warmer at higher altitudes than at nearby lower altitudes – known as a temperature inversion.

The summit of Mount Washington has an altitude of 6,288 feet and, consequently, observed temperatures were warmer than those at lower elevations in the region.

, winter weather expert at The Weather Channel, pointed out the change in temperature with altitude observed Thursday morning.

These types of temperature inversions are not that unusual, especially in the winter and in areas near hills or mountains.