When to plant tomatoes in Arizona

Arizona is not one climate. It holds 10 USDA zones, and tomatoes go in the ground as early as 14–28 January in zone 10a and as late as 29 June – 13 July in zone 5b. Find your zone below.

Arizona holds the widest spread of any state in this database. Zone 5b in the White Mountains has eighty-three frost-free days and three of them reach 90°F; zone 10a near Yuma has three hundred and fifty-five frost-free days and a hundred and seventy-six above 90°F. They are the same state and not remotely the same garden. Note that only the low desert gets a fall tomato at all: the University of Arizona publishes one for zones 9a, 9b and 10a and for nowhere else, because above that elevation the first frost arrives before a July planting could ripen.

Tomatoes in Arizona, by zone. Plant-out windows, worked out from each zone’s own frost dates.
Zone	Last frost	Plant out (spring)	Plant out (fall)	Days ≥90°F
10a	7 January	14–28 January	15 July – 15 August	176
9b	1 February	8–22 February	15 July – 15 August	168
9a	26 February	5–19 March	18 July – 1 August	158
8b	1 April	8–22 April	—	114
7b	6 April	13–27 April	—	81
8a	16 April	23 April – 7 May	—	60
7a	6 May	13–27 May	—	39
6b	21 May	28 May – 11 June	—	28
6a	8 June	15–29 June	—	5
5b	22 June	29 June – 13 July	—	3

Not sure which zone you are in? The app works it out from your postcode.

Where these dates come from

The frost dates for Arizona are NOAA’s 1991–2020 US Climate Normals — the 50% probability of a 32°F freeze, taken per zone from the weather stations standing in each one. Everything else on this page is arithmetic on those two dates: the same inputs give the same answer every time.

Made only for gardeners in the United States

Your zone is one number about one winter night.

Every date above is worked out from Arizona’s own frost records and its summer heat, read together — which is why two gardens in the same zone can be a month apart. ZoneSprout does that for 2,700 plants, in every zone of every state, and tells you what to do this week.

Get ZoneSprout How the dates are worked out