Are Miami's winters milder?

[Wizardmiami]

I am located southwest of Miami International Airport and low temperatures here track a few degrees lower than the airport.

I use two indicators, the lowest winter temperature and the number of nights the temperature falls below 50 (my arbitrary indicator)

I use 50 as a benchmark based on the point I will see leaf burn or stress on various palms or ornamental shrubs.

The two graphs reflect minimums back to 1957 as does the "cold night" chart.

Some notable points-

1. Lows below 50 are less frequent (average now 9.58 nights a year- 1962-2022)

2. The last time the airport went below 32 was Christmas 1989

3. Average annual low 40.14 (1965-2022)

4. Consider that the airport is much larger, more paved area and the urban area now extends around and way past the airport, so heat island impact seems likely.

5. If you are starting out, here's some suggestions-  locate the nearest official weather reporting location, airport, local weather service office, and determine the typical difference in low temperatures compared to your location. Check on the forum for the experience of others in your area, ask local nurseryman, citrus growers, farmers, they are often a valuable source of frost/freeze information. Keep in mind the place you live may not have existed until recently, so long time locals may be the best sources. While the heat island created by the expanding developed areas can moderate the impact of winter cold, best to treat this factor conservatively. The last period of extreme cold was from 1977-1989, so there may not be any clear indication of what impact might be felt in your location.

Miami winter seasonal minimum history.pdf winter nights below 50 Miami.pdf

[chinandega81]

I notice a sharp warming as of the early 90s. So while I am sure that the urban heat island plays a role, what is less clear to me is why the warming started so abruptly as of 1990? Miami was very urbanized in the 1980s as well. Perhaps because of growth in Doral? I'm really not sure. Regardless, yes, MIA has warmed, as have most official stations in urban SE FL, presumably for the same reasons...but I don't understand why there wasn't more sudden warming with development prior to the 90s? 

I think that cold air masses that historically would have brought temps to the SE FL coast to near 30 are now equivalent to our 40 degree type lows. The equivalent of the 20s is closer to freezing nowadays. Is it because we live in a warmer world, or a more urbanized are or both? Not sure.

I have looked at numbers from Key West, other Florida sites and I don't see the same warming trends as abrupt or pronounced as in the Miami area, so that makes me think it could be more localized due to urbanization, warmer lakes, canals, bays, ocean temps, etc. But I also think that Miami may just be the canary in the cold mine for warming temps in the rest of Florida, so other areas may vary well start seeing warmer winter temps too. 

I know people are growing coconuts in Orlando now, there seem to be some great microclimates there, most likely aided by UHIs as well. It will be interesting to see if coconuts can be grown without conssitent damage outside of the UHIs in Central Florida over the future winters.

I can also refer you to weather underground, if you check it on winter AMs, you will see exactly where the consistently warmer and cooler locations in SE FL area, they will probably surprise you. Hint, they are the areas with older homes on big lots, EAST of US 1 near Pincrecrest, North Miami Dade near the Golden Glades, and of course the Redlands. Basically wherever there are few manmade lakes and large, wooded lots.

[kinzyjr]

@chinandega81 You bring up a lot of good points in your post.

There are palms and other plants that would have been unthinkable in both cities 20+ years ago.  You mentioned Miami was already urbanized in the 1980s so the impact couldn't be from just urbanization alone.  Likewise, when cities smaller than 30,000 people show a sharp warming trend, there must be more than urbanization in play.  Here are some 30-year intervals for Bartow which had a population of just under 20,000 people in 2020.  A 6F increase in 30 year averages over 100 years is a pretty significant increase.  That takes you from a low zone 9b to a mid-zone 10a and exponentially increases your options for exotic plants.

 

[chinandega81]

21 hours ago, kinzyjr said:

@chinandega81 You bring up a lot of good points in your post.

There are palms and other plants that would have been unthinkable in both cities 20+ years ago.  You mentioned Miami was already urbanized in the 1980s so the impact couldn't be from just urbanization alone.  Likewise, when cities smaller than 30,000 people show a sharp warming trend, there must be more than urbanization in play.  Here are some 30-year intervals for Bartow which had a population of just under 20,000 people in 2020.  A 6F increase in 30 year averages over 100 years is a pretty significant increase.  That takes you from a low zone 9b to a mid-zone 10a and exponentially increases your options for exotic plants.

 

 

Now imagine if we look at, say, Tampa, where there was dramatic growth around the airport. I am sure their temperatures must reflect something similar or moreso. It's too bad we dont have records furthur back. I have seen old pics of Royal Palms in Central FL from whenever the area was settled initially. I don't know if they were shipped in some how? Or if the climate was much warmer 100 years ago? I know they used to grow citrus much farthur north in Florida, so presumably, it was warmer back then. And then it got colder and citrus moved south and the presence of Royal Palms in Central FL seems to have disappeared until somewhat recently. Not sure what to make of this, random fluctuations perhaps? I think FL still has the potential to get cold under the right circumstances, but the current weather patterns don't support quite as intense cold as from previous decades. Who knows if this trend will intensify, continue or revert? Regardless, if a gardener from Florida of 100 years ago was here today, and could see what we grow and where we can grow, I think they would be shocked, at least from the numbers I have seen in historical temps. 

[kinzyjr]

1 hour ago, chinandega81 said:

Now imagine if we look at, say, Tampa, where there was dramatic growth around the airport. I am sure their temperatures must reflect something similar or moreso. It's too bad we dont have records furthur back. I have seen old pics of Royal Palms in Central FL from whenever the area was settled initially. I don't know if they were shipped in some how? Or if the climate was much warmer 100 years ago? I know they used to grow citrus much farthur north in Florida, so presumably, it was warmer back then. And then it got colder and citrus moved south and the presence of Royal Palms in Central FL seems to have disappeared until somewhat recently. Not sure what to make of this, random fluctuations perhaps? I think FL still has the potential to get cold under the right circumstances, but the current weather patterns don't support quite as intense cold as from previous decades. Who knows if this trend will intensify, continue or revert? Regardless, if a gardener from Florida of 100 years ago was here today, and could see what we grow and where we can grow, I think they would be shocked, at least from the numbers I have seen in historical temps. 

I'm not too familiar with the cold events back further than the 1835 freeze, but my understanding is that the 1700s were overall a mild century. 

Bartram described Royal Palms up the St. Johns river: https://www.palmtalk.org/forum/index.php?/topic/34769-roystonea-regia-in-flagler-beach-north-florida/&do=findComment&comment=551056

Before the 1957-1958 freeze and the more severe1962 freeze, there were a lot more tropicals in areas like Daytona and Orlando.  There were some old photos shared on the site of coconuts in Orlando before they got zeroed out in 1962.  The 1980s really hammered citrus and palms in Central FL.  The CFPACS president tells everyone to enjoy the current milder regime while it lasts because it was difficult to even keep a queen palm alive in some areas during the 80s.

We still have the potential to get decked by a cold front since there is a lot of land between us and the north pole.  If we had an east-west mountain range at the top of Canada, that would help.  Or of there was more water between us and the north pole.  Until then, keep our fingers crossed.