Photo: Stephen R. Gold · Public domainPenngrove’s winters are milder and less snowy than most of the U.S.
A typical July afternoon reaches 81°, a January night drops to 39°, and snow is almost unheard of.
A year in Penngrove at a glance
Each month’s typical high and low, and what it brings.
What stands out about Penngrove’s climate
Compared with towns across the U.S., with Penngrove’s place in California beside it.
What a year in Penngrove feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 271 frost-free days a year
In half of years the last 32° night comes by February 28 and the first by November 25. Frost and day counts come from NOAA’s station at Petaluma Airport, 5 miles from the town’s center, 100 ft lower.
The 2023 USDA map puts Penngrove’s center in zone 9a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 24°. 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 31 inches of rain a year
December is the wettest month and July the driest. Rain falls on about 70 days a year. Snow is rare: about 0.0" in a normal year at Petaluma Airport, so most winters see none.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Penngrove
90% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from November through March.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Petaluma Airport.
Living with Penngrove’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
271 frost-free days in zone 9a. The last frost comes by Feb 28 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Nov 25.
Months with highs of 62–84° and lows of 40° or more: March, April, May, June, July, August, September, October and November. 0.0 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Penngrove from natural hazards, river flooding is the largest share (55%). Normals are averages; the hazards page covers the extremes.
Natural hazards →Penngrove and similar climates
TownRatings has no climate map of the towns around Penngrove yet.
Climates most like Penngrove’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Penngrove, CA | 39° | 81° | 31" | 0.0" |
| Tualatin, OR | 36° | 81° | 40" | 1.0" |
| Felida, WA | 35° | 81° | 42" | 0.8" |
| Makawao, HI | 53° | 75° | 23" | 0.0" |
| Swannanoa, NC | 27° | 83° | 48" | 2.1" |
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Penngrove averaged 1.4° warmer than the 1900s. The biggest change is in January (+2.3°).
A bigger shift than in 52% 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 Penngrove compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Penngrove’s place among California’s.
Penngrove weather by month
Highs, lows and precipitation from NOAA’s grid at Penngrove’s center; snow, wet days and snow on the ground from Petaluma Airport. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 58° | 39° | 6.0" | 0.0" | 12 | 0 | 45° – 52° |
| February | 61° | 40° | 6.0" | 0.0" | 11 | 0 | 46° – 55° |
| March | 65° | 42° | 4.2" | 0.0" | 10 | 0 | 48° – 58° |
| April | 68° | 43° | 2.0" | 0.0" | 6 | 0 | 51° – 59° |
| May | 73° | 47° | 1.1" | 0.0" | 4 | 0 | 55° – 64° |
| June | 79° | 50° | 0.3" | 0.0" | 1 | 0 | 61° – 67° |
| July | 81° | 51° | 0.0" | 0.0" | 0 | 0 | 63° – 69° |
| August | 82° | 52° | 0.0" | 0.0" | 0 | 0 | 64° – 71° |
| September | 82° | 50° | 0.1" | 0.0" | 1 | 0 | 63° – 69° |
| October | 76° | 47° | 1.5" | 0.0" | 4 | 0 | 59° – 67° |
| November | 65° | 42° | 3.4" | 0.0" | 8 | 0 | 47° – 57° |
| December | 57° | 38° | 6.4" | 0.0" | 12 | 0 | 45° – 52° |
| Year | 70° | 45° | 31.1" | 0.0" | 70 | 0 |
How much a month can swing
A normal is an average. March swings the most: from 1991 to 2020 its average ranged from 48° to 58°. July is the most reliable, staying within 6°.
Where Penngrove’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 Penngrove’s center.
- Snow: Petaluma Airport.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Petaluma Airport, 5 miles from the town’s center, 100 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 Penngrove’s climate
What is the weather like in Penngrove?
A typical July afternoon reaches 81°, a January night drops to 39°, and snow is almost unheard of. Milder January nights than 86% of U.S. towns; cooler July afternoons than 88% of U.S. towns.
How cold does it get in Penngrove in winter?
December nights average 38°. About 21 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 45°.
How much snow does Penngrove get?
About 0.0 inches in a normal winter at Petaluma Airport, so most winters see none.
How hot does it get in Penngrove?
July, with a typical high of 81° and a low of 51°. About 21 days a year reach 90° and 2 reach 100° (Petaluma Airport).
When is the first and last frost in Penngrove?
In half of years the last spring frost (32°) comes by February 28 and the first fall frost by November 25, about 271 frost-free days, at Petaluma Airport.
What growing zone is Penngrove in?
Zone 9a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 24°.
What is the best time of year to visit Penngrove?
By one simple rule (highs of 62–84° and lows of 40° or more), March, April, May, June, July, August, September, October and November. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Penngrove getting warmer?
Yes: 1991–2020 averaged 1.4° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 52% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Penngrove.
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.