Tripoli, Iowa climate: Normal weather by month, frost dates and records
Tripoli's normal year runs from 7°F January nights to 83°F July afternoons, with 38.6 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 8.0°C, January lows of −14°C, July highs of 28°C, 981 mm of precipitation a year.
- NOAA stationTripoli
- Station IDUSC00138339
- Location42.81°N 92.26°W
- Elevation1,055 ft (322 m)
- From the centerunder 1 mile
- Population1,208
On October 23, the normal high in Tripoli is 57°F and the normal low 35°F, and the chance of measurable rain or snow is 26%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Tripoli.
- Jan 25° 7°
- Feb 29° 12°
- Mar 43° 24°
- Apr 58° 36°
- May 70° 48°
- Jun 80° 59°
- Jul 83° 62°
- Aug 81° 59°
- Sep 75° 50°
- Oct 61° 38°
- Nov 44° 26°
- Dec 31° 15°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Tripoli each month?
July is the warmest month, with normal highs of 83°F; January the coldest, with normal lows of 7°F. The most precipitation falls in June (6.03 in), the least in February (1.09 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 25°F | 7°F | 16.1°F | 1.23 | 7 | <1 | 31 | 9 h 20 min |
| February | 29°F | 12°F | 20.3°F | 1.09 | 7 | <1 | 27 | 10 h 30 min |
| March | 43°F | 24°F | 33.4°F | 2.00 | 8 | <1 | 25 | 11 h 50 min |
| April | 58°F | 36°F | 46.6°F | 3.93 | 11 | <1 | 11 | 13 h 20 min |
| May | 70°F | 48°F | 58.9°F | 5.11 | 12 | 1 | 1 | 14 h 40 min |
| June | 80°F | 59°F | 69.1°F | 6.03 | 12 | 3 | <1 | 15 h 20 min |
| July | 83°F | 62°F | 72.2°F | 4.80 | 9 | 4 | <1 | 15 h |
| August | 81°F | 59°F | 69.9°F | 4.29 | 9 | 2 | <1 | 14 h |
| September | 75°F | 50°F | 62.4°F | 3.75 | 9 | 1 | 1 | 12 h 30 min |
| October | 61°F | 38°F | 49.6°F | 2.96 | 9 | <1 | 10 | 11 h 10 min |
| November | 44°F | 26°F | 35.0°F | 1.98 | 7 | <1 | 23 | 9 h 50 min |
| December | 31°F | 15°F | 22.7°F | 1.47 | 7 | <1 | 30 | 9 h |
| Year (annual) | 57°F | 36°F | 46.4°F | 38.64 | 106 | 11 | 158 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −4°C | −14°C | −8.8°C | 31 mm |
| February | −2°C | −11°C | −6.5°C | 28 mm |
| March | 6°C | −4°C | 0.8°C | 51 mm |
| April | 14°C | 2°C | 8.1°C | 100 mm |
| May | 21°C | 9°C | 14.9°C | 130 mm |
| June | 26°C | 15°C | 20.6°C | 153 mm |
| July | 28°C | 16°C | 22.3°C | 122 mm |
| August | 27°C | 15°C | 21.1°C | 109 mm |
| September | 24°C | 10°C | 16.9°C | 95 mm |
| October | 16°C | 3°C | 9.8°C | 75 mm |
| November | 7°C | −4°C | 1.7°C | 50 mm |
| December | −1°C | −10°C | −5.2°C | 37 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, New Hampton (16 miles away), gets 39 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00138339; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Tripoli?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, September has the fewest days with rain (9).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00138339.
When is the last frost in Tripoli?
In Tripoli, the last spring frost (32°F) comes after April 29 in half of years and after May 9 in one year in ten; the first autumn frost comes before October 9 in half of years and before September 25 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 291 year in 10 after May 9; 9 in 10 after April 14
- First autumn frost, half of years before
- October 91 year in 10 before September 25; 9 in 10 before October 22
NOAA puts the median frost-free season at 162 days, and the season without a hard freeze (28°F) at 184 days.
A hard freeze (28°F) comes after April 18 in half of springs and before October 20 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Tripoli in zone 5a in ZIP code 50676, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Tripoli's NOAA station is in zone 5a: the coldest night of a typical year reaches −18°F (25 complete years).
Frost dates for every NOAA station in Iowa · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00138339; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Tripoli?
In a normal year in Tripoli, 11 days a year reach 90°F, 158 nights fall to 32°F or colder and 106 days bring measurable precipitation.
- Days at 90°F or more
- 11a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 158a normal year
- Days that stay below freezing
- 68high of 32°F or less
- Days with 0.01 inch of precipitation
- 106a normal year
The highest temperature in this station's record (since 1946) is 104°F, on August 18, 1988; the lowest is −32°F, on January 21, 1970.
The wettest calendar year on that record is 2018, with 64.31 in; the snowiest season is 1950–51, with 65.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00138339; records: ACIS (NOAA Regional Climate Centers), station USC00138339. Records use complete months only; a month missing more than three days is left out.
How sunny is Tripoli?
Over a year 74% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Tripoli, 4.0 kWh per square metre a day. July is the sunniest month (81%) and December the cloudiest (66%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 70% | 1.9 |
| February | 76% | 3.0 |
| March | 72% | 3.9 |
| April | 69% | 4.8 |
| May | 71% | 5.6 |
| June | 76% | 6.2 |
| July | 81% | 6.3 |
| August | 80% | 5.5 |
| September | 79% | 4.4 |
| October | 71% | 3.0 |
| November | 70% | 2.0 |
| December | 66% | 1.6 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Tripoli need?
A normal year in Tripoli brings 7,436 heating degree days, 38% more than the median U.S. place (5,373), and 682 cooling degree days, 25% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 2,778 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,517 | 0 |
| February | 1,250 | 0 |
| March | 980 | 1 |
| April | 554 | 2 |
| May | 229 | 41 |
| June | 35 | 158 |
| July | 8 | 232 |
| August | 19 | 172 |
| September | 146 | 68 |
| October | 485 | 8 |
| November | 902 | 0 |
| December | 1,310 | 0 |
| Year (annual) | 7,436 | 682 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00138339. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Tripoli been warmer than normal lately?
Over 51 complete years from 1949 to 2020, the station's annual mean temperature rose at a fitted 2.9°F per century (+0.16°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Tripoli's climate compare?
Tripoli is warmer than 27 of the other 131 places with their own NOAA record in Iowa, and wetter than 105. Across the 7,247 U.S. stations with normals, its annual mean of 46.4°F is warmer than 25%.
In the Köppen classification computed from these normals, Tripoli is Dfa: continental, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Tripoli share this climate record?
4 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Sumner, IA2,032 people · 9 mi E
- Readlyn, IA857 people · 8 mi S
- Plainfield, IA392 people · 14 mi W
- Frederika, IA206 people · 5 mi NW
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Tripoli's climate
What is the coldest month in Tripoli?
January, with a normal high of 25°F and a normal low of 7°F. The warmest is July (83°F by day, 62°F at night).
Does it snow in Tripoli?
Yes. NOAA publishes no 1991-2020 snowfall normal for Tripoli's NOAA station; the nearest record that keeps one, New Hampton (16 miles away), records 39 inches of snow in a normal year.
What is the rainiest month in Tripoli?
June, with 6.03 in of precipitation in a normal year; the driest is February with 1.09 in.
What plant hardiness zone is Tripoli in?
The USDA's 2023 map puts Tripoli in zone 5a in ZIP code 50676, the nearest ZIP area. By the same method at Tripoli's NOAA station, the coldest night of a typical year reaches −18°F (25 years, 1991-2020): zone 5a.
How late can frost come in Tripoli?
In half of years the last 32°F night comes after April 29; in one year in ten it comes after May 9. Waiting until May 9 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Iowa climateThe statewide normals and every place in the state
- New Hampton, IA16 miles from this station, 44.7°F a year
- Waterloo, IA19 miles from this station, 49.0°F a year
- Oelwein, IA21 miles from this station, 46.3°F a year
- Fayette, IA22 miles from this station, 45.0°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made