Last frost date in Rio Rico, AZ

Average last frost
April 16

In Rio Rico, the last spring frost comes around April 16 in an average year. Wait until May 4 if you want 90% odds of no more frost. The first fall frost usually arrives about November 2, which leaves 199 frost-free days. An early freeze before October 19 happens one year in ten.

Safe after (10% risk)
May 4
Average first frost
Nov 2
Frost-free season
199 days
Hard freeze (28°F) ends
Mar 22
Next 6 nights in Rio Rico

No frost in the next 6 nights

National Weather Service forecast, updated Oct 22, 12:57 UTC

  1. ThuOct 2254°
  2. FriOct 2348°
  3. SatOct 2448°
  4. SunOct 2550°
  5. MonOct 2651°
  6. TueOct 2753°
JanFebMarAprMayJunJulAugSepOctNovDecLast frost Apr 16First frost Nov 2199 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND199 frost-free days
Frost risk through the year at Nogales 6 N, 3.2 miles from Rio Rico.

Planting calendar for Rio Rico

Windows count forward or back from the average frost dates above. Click a crop for dates across Arizona.

Start indoorsPlant outSow outdoorsFall plantingAverage last and first frost
Warm-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
TomatoesApr 23–May 7
PumpkinsApr 30–May 14
SunflowersApr 16–May 7
CucumbersApr 30–May 7
CornApr 23–May 7
Sweet potatoesMay 7–May 21
WatermelonApr 30–May 14
Green beansApr 23–May 14
ZucchiniApr 23–May 7
OkraMay 7–May 21
PeppersApr 30–May 14
BasilApr 23–May 7
Butternut squashApr 23–May 7
CantaloupeApr 30–May 14
EggplantApr 30–May 14
Cool-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
PotatoesMar 19–Apr 2
OnionsMar 5–Mar 26
CarrotsMar 26–Apr 30
LettuceApr 2–Apr 23
BroccoliMar 19–Apr 2
BeetsMar 19–Apr 30
PeasMar 5–Mar 19
CabbageMar 19–Apr 2
RadishesMar 12–Apr 23
Brussels sproutsApr 2–Apr 16
SpinachMar 5–Mar 26
CilantroApr 2–Apr 23
KaleMar 19–Apr 2
Collard greensMar 19–Apr 2
TurnipsMar 19–Apr 2
DillApr 16–Apr 30
CeleryApr 23–Apr 30
CauliflowerApr 2–Apr 16
LeeksApr 2–Apr 16
Swiss chardApr 2–Apr 30
ParsleyApr 2–Apr 23
Fall bulbs and garlic
JanFebMarAprMayJunJulAugSepOctNovDec
Tulip bulbsOct 19–Nov 23
GarlicOct 12–Nov 16
Daffodil bulbsOct 5–Nov 16
Perennials
JanFebMarAprMayJunJulAugSepOctNovDec
StrawberriesMar 19–Apr 2
AsparagusMar 19–Apr 2

Frost probabilities

ThresholdSpring, 90% chance laterSpring, 50%Spring, 10%Fall, 10% chance earlierFall, 50%Fall, 90%
Light frost, 32°FMar 28Apr 16May 4Oct 19Nov 2Nov 16
Hard freeze, 28°FFeb 26Mar 22Apr 15Oct 29Nov 14Nov 29

Read the spring 10% column as the date after which only one year in ten still gets frost. That is the safer date for tomatoes, peppers and basil.

Where these numbers come from

NOAA station Nogales 6 N (USC00025924) sits 3.2 miles from the center of Rio Rico at 3,461 feet. Its averages cover 1991 to 2020. Low spots, valleys and open fields can keep getting frost a week or two after the station stops; city centers and lakeshores usually get less of it.

Questions

When is the last frost in Rio Rico, AZ?

The average last frost date in Rio Rico is April 16, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 4.

When is the first frost in Rio Rico?

The first frost in fall usually comes around November 2. One year in ten it arrives before October 19.

How long is the growing season in Rio Rico?

About 199 days between the average last and first frost.

When should I plant tomatoes in Rio Rico?

Plant tomato seedlings outside from April 23 to May 7. Start seeds indoors six to eight weeks earlier.

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