Portal State Bank · Photo: Andrew Filer · CC BY-SA 2.0Few U.S. towns have colder winter nights than Portal
The warmest part of a July day comes in at 80° on average. Its July afternoons stay fresher than in 93% of U.S. towns. Warming shows here too: 1.3° more than in 1901–2000, led by January. The frost-free window for a garden runs roughly May 20 to September 19.
A year in Portal at a glance
Each month’s typical high and low, and what it brings.
What stands out about Portal’s climate
Compared with towns across the U.S., with Portal’s place in North Dakota beside it.
What a year in Portal feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 121 frost-free days a year
In half of years the last 32° night comes by May 20 and the first by September 19. Frost and day counts come from NOAA’s station at Northgate 5 Ese, ND, 17 miles from the town’s center, 110 ft lower.
The 2023 USDA map puts Portal’s center in zone 3b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −31°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 18 inches of rain a year
June is the wettest month and February the driest.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Portal
98% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through May.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Northgate 5 Ese, ND.
Living with Portal’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
121 frost-free days in zone 3b. The last frost comes by May 20 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Sep 19.
Months with highs of 62–84° and lows of 40° or more: June, July, August and September. 1.1 miles of trails are waiting.
Parks & trails →Cold waves are 51% of the yearly building losses FEMA expects in Portal from natural hazards, the largest share. Normals are averages; the hazards page covers the extremes.
Natural hazards →Portal and its neighbors
Every town next door is within a degree of Portal in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Portal averaged 1.3° warmer than the 1900s. The biggest change is in January (+4.3°).
A smaller shift than in 53% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Portal compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Portal’s place among North Dakota’s.
Portal weather by month
Highs, lows and precipitation from NOAA’s grid at Portal’s center. 1991–2020 normals.
| Month | High | Low | Rain + melt | 30-yr range |
|---|---|---|---|---|
| January | 17° | −2° | 0.6" | −5° – 25° |
| February | 22° | 2° | 0.5" | −7° – 25° |
| March | 34° | 15° | 0.7" | 11° – 37° |
| April | 52° | 28° | 1.1" | 28° – 47° |
| May | 65° | 39° | 2.5" | 47° – 59° |
| June | 73° | 50° | 3.5" | 57° – 67° |
| July | 80° | 54° | 2.8" | 60° – 72° |
| August | 80° | 52° | 1.9" | 59° – 71° |
| September | 69° | 42° | 1.7" | 49° – 63° |
| October | 52° | 30° | 1.2" | 32° – 47° |
| November | 34° | 15° | 0.7" | 13° – 37° |
| December | 21° | 3° | 0.5" | 0° – 24° |
| Year | 50° | 27° | 17.7" |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from -7° to 25°. June is the most reliable, staying within 10°.
Where Portal’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Portal’s center.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Northgate 5 Ese, ND, 17 miles from the town’s center, 110 ft lower; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Portal’s climate
What is the weather like in Portal?
A typical July afternoon reaches 80°, a January night drops to −2°. Colder January nights than all but 29 U.S. towns; cooler July afternoons than 93% of U.S. towns.
How cold does it get in Portal in winter?
January nights average −2°. About 202 nights a year reach 32° or below and 55 reach 0° or below. In the coldest January of the last 30 years the month averaged −5°.
How hot does it get in Portal?
July, with a typical high of 80° and a low of 54°. About 5 days a year reach 90° (Northgate 5 Ese, ND).
When is the first and last frost in Portal?
In half of years the last spring frost (32°) comes by May 20 and the first fall frost by September 19, about 121 frost-free days, at Northgate 5 Ese, ND.
What growing zone is Portal in?
Zone 3b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −31°.
What is the best time of year to visit Portal?
By one simple rule (highs of 62–84° and lows of 40° or more), June, July, August and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Portal getting warmer?
Yes: 1991–2020 averaged 1.3° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 53% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Portal.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.