Record Cold Saturday May 9th, 2020

Powerful Storm in the Western U.S.; Heavy Rain and Flooding Threat Across the Central Gulf Coast

A powerful storm system will continue to bring heavy mountain snow, rain, and high winds to the Pacific Northwest and northern California through midweek. Heavy rain and flash flooding potential exists across the central Gulf Coast over the next few days, including the Florida Panhandle. A Slight Risk (level 2 of 4) of excessive rainfall is in effect Tuesday. Read More >

May 9th, 2020 was one of the coldest May days in recorded history as numerous sites set records for coldest low and high temperatures. Please click through the photos as we attempt to contextualize one of the coldest days in May ever observed in Pennsylvania!

May 9th Records

All-Time May Records

Saturday Temperature Anomalies

Eastern US Record Cold

Air Mass Origin

Surface Map Comparisons

Summary Narrative

Minimum and maximum temperatures on Saturday were highly anomalous with low temperatures greater than 15 degrees below normal and high temperatures greater than 25 degrees below normal in Pennsylvania.

Source: https://www.wpc.ncep.noaa.gov/exper/ndfdmxmn/map.html

Records were set across most of the Eastern US Saturday morning. Here's a depiction of the record cold temperatures. Notice the dark blue circles in PA indicating temperatures that break the monthly record low.

Source: http://coolwx.com/record/usamovie.day.php

If we track where Saturday's air mass originated, it becomes clear why it was so cold. Air from northern Canada sunk into the Mid-Atlantic on Saturday, resulting in temperatures in the 30s in northern PA and 40s in southern PA.

Source: https://ready.noaa.gov/HYSPLIT_traj.php

An expansive area of surface high pressure surged into the eastern US, as shown in this NWS Weather Prediction Center map valid at 8AM Saturday. See surface maps from the record-setting May 9ths of 1947 and 1966 below for comparison.

Source: https://www.wpc.ncep.noaa.gov/index.shtml#page=frt

Surface map on May 9th, 1947 when Harrisburg's daily record minimum temperatures were set:

Source: https://library.noaa.gov/Collections/Digital-Collections/US-Daily-Weather-Maps

Surface map on May 9th, 1966 when most of the daily record minimum temperatures were set:

Source: https://library.noaa.gov/Collections/Digital-Collections/US-Daily-Weather-Maps

SNOWFALL: Harrisburg (MDT) also received a trace of snowfall, tying the previous daily record set in 1977.

Powerful Storm in the Western U.S.; Heavy Rain and Flooding Threat Across the Central Gulf Coast

Record Cold Saturday May 9th, 2020

RECORD COLD TEMPERATURES SATURDAY MAY 9TH

May 9th, 2020 was one of the coldest May days in recorded history as numerous sites set records for coldest low and high temperatures. Please click through the photos as we attempt to contextualize one of the coldest days in May ever observed in Pennsylvania!

Here are the observed temperatures and previous cold temperature records for Saturday.

Source: https://w2.weather.gov/climate/xmacis.php?wfo=ctp

Lows and Highs on Saturday were some of the lowest ever observed in the entire month of May.

Source: https://w2.weather.gov/climate/xmacis.php?wfo=ctp

Minimum and maximum temperatures on Saturday were highly anomalous with low temperatures greater than 15 degrees below normal and high temperatures greater than 25 degrees below normal in Pennsylvania.

Source: https://www.wpc.ncep.noaa.gov/exper/ndfdmxmn/map.html

Records were set across most of the Eastern US Saturday morning. Here's a depiction of the record cold temperatures. Notice the dark blue circles in PA indicating temperatures that break the monthly record low.

Source: http://coolwx.com/record/usamovie.day.php

If we track where Saturday's air mass originated, it becomes clear why it was so cold. Air from northern Canada sunk into the Mid-Atlantic on Saturday, resulting in temperatures in the 30s in northern PA and 40s in southern PA.

Source: https://ready.noaa.gov/HYSPLIT_traj.php

An expansive area of surface high pressure surged into the eastern US, as shown in this NWS Weather Prediction Center map valid at 8AM Saturday. See surface maps from the record-setting May 9ths of 1947 and 1966 below for comparison.

Source: https://www.wpc.ncep.noaa.gov/index.shtml#page=frt

Surface map on May 9th, 1947 when Harrisburg's daily record minimum temperatures were set:

Source: https://library.noaa.gov/Collections/Digital-Collections/US-Daily-Weather-Maps

Surface map on May 9th, 1966 when most of the daily record minimum temperatures were set:

Source: https://library.noaa.gov/Collections/Digital-Collections/US-Daily-Weather-Maps

SNOWFALL: Harrisburg (MDT) also received a trace of snowfall, tying the previous daily record set in 1977.