The first two days of January were warm. Since then, temperatures have been below normal.

What You Need To Know

  • December 2020 was two degrees below normal

  • With the next 7 to 10 days cool, January may follow
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  • March 2018 was the last time a month was below normal

  • Tampa's official sensor has read warm for several years

December 2020 was the first month cooler than normal in Tampa since March 2018. January 2021 has been a bit below average so far, despite the very warm start. The forecast for the next 7 to 10 days will feature below-normal temperatures. Should that forecast hold, it would be difficult for the month to end above average.

Tampa hasn't had two consecutive months with below average temperatures since January and February 2016. 

A Few Factors

There are a few reasons for Tampa's generally warm reading over the last few years. 

The average temperature is calculated for each month by taking each day's high and low temperature, dividing by two, and then dividing by the number of days in the month. So, with an above-normal pattern, the high and low should account for about the same difference from average.

But, over the last several years, the low temperature in Tampa has accounted for most of the difference above average. In fact, even on cooler than normal days and weather patterns, the low in Tampa has been rather warm. 

An "urban heat island" effect has been in place in Tampa for the last decade due to the construction around the airport and the specific location of the temperature sensor. We have addressed this as a poor location for an "official Tampa Bay temperature" in the past. 

This mostly affects the morning low temperature on potentially cooler mornings with radiational cooling. On those mornings, the official Tampa observation has been as much as 5 to 7 degrees warmer than most surrounding observation sites.

Next, the summer normals changed in the early 2000s to a cooler high temperature. Back at the beginning of the 2000s, the hottest time of the year had a normal high of 92 for Tampa and a normal low of 76. When the updated climate normals came out in the early 2000s, that changed to a "normal" or "average" high of 90.

Since 2010, only two summer months have had temperatures below normal – June 2012 and July 2013. Both months had excessive rainfall and a few days each with highs well below normal.

Typically, our summer months don't see much variability. Our records are only a few degrees off from our normals. So, in the last 10 years, our three summer months of June, July, and August have almost essentially been all above normal, but only by 0.5 to 1.5 degrees.

It is very likely that several of those months would have been below average with the old 92-degree "normal" high temperature.

Every ten years, new 30-year "normals" are calculated and implemented. That has typically occurred sometime in the first quarter of the first year of the new decade. So, we shall see if there are any changes to what is normal for 1991-2020.