If a girl who is 13 and the boy is 16, is that statutory rape?

Not likely.

Ultimately, the final decsion on the charges for the 16 year old would be up to a judge, but this appears to fall under a felony offense due to the age of the victim involved. A judge may also be faced with recommending the case for adult court.

See (d) last paragraph below.

800.04 Lewd or lascivious offenses committed upon or in the presence of persons less than 16 years of age.

(4) LEWD OR LASCIVIOUS BATTERY.--A person who:

(a) Engages in sexual activity with a person 12 years of age or older but less than 16 years of age; or

(b) Encourages, forces, or entices any person less than 16 years of age to engage in sadomasochistic abuse, sexual bestiality, prostitution, or any other act involving sexual activity

commits lewd or lascivious battery, a felony of the second degree, punishable as provided in s. 775.082, s. 775.083, or s. 775.084.

(5) LEWD OR LASCIVIOUS MOLESTATION.--

(a) A person who intentionally touches in a lewd or lascivious manner the breasts, genitals, genital area, or buttocks, or the clothing covering them, of a person less than 16 years of age, or forces or entices a person under 16 years of age to so touch the perpetrator, commits lewd or lascivious molestation.

(b) An offender 18 years of age or older who commits lewd or lascivious molestation against a victim less than 12 years of age commits a life felony, punishable as provided in s. 775.082(3)(a)4.

(c)1. An offender less than 18 years of age who commits lewd or lascivious molestation against a victim less than 12 years of age; or

2. An offender 18 years of age or older who commits lewd or lascivious molestation against a victim 12 years of age or older but less than 16 years of age

commits a felony of the second degree, punishable as provided in s. 775.082, s. 775.083, or s. 775.084.

(d) An offender less than 18 years of age who commits lewd or lascivious molestation against a victim 12 years of age or older but less than 16 years of age commits a felony of the third degree, punishable as provided in s. 775.082, s. 775.083, or s. 775.084.