Marathon FL Average Temperatures by Month

The numbers here tell you how hot and cold the weather usually is at Marathon, in the Florida Keys during each month of the year.

The average high and low temperatures are listed below monthly and annually for Boot Key and its neighbors, in both degrees Fahrenheit and Celsius.

Maximums and minimums are only part of the temperature picture. To fill in the rest, there's information on how many days a month get above or below a given temperature.

To find out how often it rises over 70, 80 or 90 °F each month in Marathon, scroll down farther. There are also monthly and yearly counts of days with cool weather.

The first set of high and low temperatures are averages for 2010 to 2019. Everything else here is based on 1981 to 2010 weather.

10-year temperature averages for Marathon, 2010 to 2019
High °F	Low °F		High °C	Low °C
76	65	January	24	18
79	68	February	26	20
81	69	March	27	21
85	74	April	30	24
88	77	May	31	25
91	80	June	33	26
91	80	July	33	27
92	80	August	33	27
90	79	September	32	26
86	77	October	30	25
82	72	November	28	22
79	69	December	26	21
85	74	Year	29	23

30-year temperature averages for Marathon, 1981 to 2010
High °F	Low °F		High °C	Low °C
75	64	January	24	18
77	66	February	25	19
79	69	March	26	20
83	72	April	28	22
87	76	May	30	25
90	79	June	32	26
91	79	July	33	26
91	79	August	33	26
89	79	September	32	26
86	76	October	30	24
81	71	November	27	22
77	67	December	25	19
84	73	Year	29	23

Days of Hot Weather in Marathon

Winters are warm and summers hot at Marathon. From May to October, the islands average 81 days with highs in the 90s Fahrenheit. Even so, usually only once every two years does it get as hot as 100 °F (38 °C) in this stretch of Florida Keys.

Days per month in Marathon of at least 70, 80 or 90 °F
	70 °F 21 °C	80 °F 27 °C	90 °F 32 °C
January	24	8	0
February	24	9	0
March	24	16	0
April	30	25	0
May	31	31	3
June	30	30	18
July	31	31	22
August	31	31	24
September	30	30	13
October	31	29	1
November	29	18	0
December	27	11	0
Year	348	268	81

How Often Marathon Has Cool Temperatures

Cool temperatures are rare at Marathon. Just two nights a year on average have lows of 50 °F or less. Temperatures colder than 40 °F (4 °C) are not expected here.

Days per month on average in Key Largo when the minimum temperature drops to 60 or 50 °F or lower
	50 °F 10 °C	60 °F 16 °C
January	1	9
February	0	5
March	0	2
April	0	1
May	0	0
June	0	0
July	0	0
August	0	0
September	0	0
October	0	0
November	0	1
December	1	6
Year	2	24

Marathon Temperatures: Averages by Month

Days of Hot Weather in Marathon

How Often Marathon Has Cool Temperatures

References

More on Weather in Florida