montana frost dates, county by county.

Beaverhead County

Last spring: 05-30 · First fall: 09-14

Big Horn County

Last spring: 05-10 · First fall: 09-28

Blaine County

Last spring: 05-06 · First fall: 09-30

Broadwater County

Last spring: 05-07 · First fall: 10-01

Carbon County

Last spring: 05-01 · First fall: 10-04

Carter County

Last spring: 05-06 · First fall: 10-01

Cascade County

Last spring: 04-30 · First fall: 10-08

Chouteau County

Last spring: 05-09 · First fall: 09-29

Custer County

Last spring: 05-11 · First fall: 09-25

Daniels County

Last spring: 05-19 · First fall: 09-16

Dawson County

Last spring: 04-24 · First fall: 10-13

Deer Lodge County

Last spring: 05-13 · First fall: 09-28

Fallon County

Last spring: 05-02 · First fall: 10-04

Fergus County

Last spring: 05-02 · First fall: 10-06

Flathead County

Last spring: 04-27 · First fall: 10-14

Gallatin County

Last spring: 05-02 · First fall: 10-03

Garfield County

Last spring: 05-08 · First fall: 09-29

Glacier County

Last spring: 05-19 · First fall: 09-20

Golden Valley County

Last spring: 05-05 · First fall: 10-03

Granite County

Last spring: 05-29 · First fall: 09-12

Hill County

Last spring: 05-12 · First fall: 09-26

Jefferson County

Last spring: 05-21 · First fall: 09-21

Judith Basin County

Last spring: 05-10 · First fall: 10-01

Lake County

Last spring: 04-28 · First fall: 10-16

Lewis and Clark County

Last spring: 05-07 · First fall: 09-28

Liberty County

Last spring: 05-11 · First fall: 09-26

Lincoln County

Last spring: 05-07 · First fall: 10-05

Madison County

Last spring: 05-14 · First fall: 10-01

McCone County

Last spring: 05-06 · First fall: 10-01

Meagher County

Last spring: 05-18 · First fall: 09-25

Mineral County

Last spring: 05-01 · First fall: 10-06

Missoula County

Last spring: 04-28 · First fall: 10-12

Musselshell County

Last spring: 05-07 · First fall: 10-01

Park County

Last spring: 05-04 · First fall: 10-05

Petroleum County

Last spring: 05-07 · First fall: 09-29

Phillips County

Last spring: 04-30 · First fall: 10-06

Pondera County

Last spring: 05-04 · First fall: 10-04

Powder River County

Last spring: 05-03 · First fall: 10-07

Powell County

Last spring: 05-26 · First fall: 09-11

Prairie County

Last spring: 05-01 · First fall: 10-05

Ravalli County

Last spring: 05-05 · First fall: 10-04

Richland County

Last spring: 05-02 · First fall: 10-06

Roosevelt County

Last spring: 05-14 · First fall: 09-22

Rosebud County

Last spring: 04-29 · First fall: 10-08

Sanders County

Last spring: — · First fall: —

Sheridan County

Last spring: 05-15 · First fall: 09-22

Silver Bow County

Last spring: 05-21 · First fall: 09-17

Stillwater County

Last spring: 05-13 · First fall: 09-26

Sweet Grass County

Last spring: 05-02 · First fall: 10-05

Teton County

Last spring: 05-14 · First fall: 09-25

Toole County

Last spring: 05-10 · First fall: 09-26

Treasure County

Last spring: 04-30 · First fall: 10-07

Valley County

Last spring: 05-03 · First fall: 10-05

Wheatland County

Last spring: 05-12 · First fall: 09-27

Wibaux County

Last spring: 05-17 · First fall: 09-26

Yellowstone County

Last spring: 04-30 · First fall: 10-04