September
September · May · October
United States · 1991–2020
September leads for comfortable weather in Island: typically 27.7°C by day, 15.5°C at night, with 76 mm of rain. Based on measured 1991–2020 NOAA station history.
September · May · October
August · July · June
October · April · May
The weakest month is January, scoring 5 against September’s 79 — days reach only 6.3°C, 18° below the 24°C the score treats as ideal.
Month by month
The bars show the comfort score. Day and night temperatures come from daily observed highs and lows; rain is the historical monthly estimate.
| Month | Day | Night | Rain | Wet days | Daylight | Comfort | Coverage |
|---|---|---|---|---|---|---|---|
| January | 6.3°C | -3°C | 91 mm | 7.9 | 9 h 50 | 5 | Good coverage |
| February | 7.6°C | -2.1°C | 85 mm | 6.7 | 10 h 45 | 5 | Good coverage |
| March | 14.4°C | 3.2°C | 104 mm | 9.1 | 11 h 51 | 32 | Good coverage |
| April | 20.5°C | 8.6°C | 105 mm | 8.5 | 13 h 06 | 62 | Good coverage |
| May | 24.9°C | 13.9°C | 116 mm | 9.2 | 14 h 10 | 78 | Good coverage |
| June | 29.4°C | 18.4°C | 99 mm | 8.1 | 14 h 44 | 63 | Good coverage |
| July | 30.6°C | 20°C | 98 mm | 7.1 | 14 h 30 | 57 | Good coverage |
| August | 30.6°C | 19.5°C | 66 mm | 5.5 | 13 h 36 | 64 | Good coverage |
| September | 27.7°C | 15.5°C | 76 mm | 5.5 | 12 h 23 | 79 | Good coverage |
| October | 21.2°C | 8.9°C | 86 mm | 6.1 | 11 h 10 | 70 | Good coverage |
| November | 14.2°C | 2.8°C | 82 mm | 7.3 | 10 h 06 | 35 | Good coverage |
| December | 8.2°C | -0.9°C | 105 mm | 8 | 9 h 35 | 5 | Good coverage |
| Month | Record high | Record low | Wettest day | Wettest / driest month | Years |
|---|---|---|---|---|---|
| January | 21.7°C3 Jan 2006 | -18.9°C5 Jan 2014 | 76 mm20 Jan 2016 | 161 mm2016 · driest 29 mm in 2012 | 18 |
| February | 26.1°C20 Feb 2018 | -20.6°C19 Feb 2015 | 54 mm15 Feb 2003 | 198 mm2019 · driest 12 mm in 2009 | 19 |
| March | 28.9°C28 Mar 2012 | -17.2°C6 Mar 2015 | 51 mm18 Mar 2013 | 158 mm2013 · driest 38 mm in 2019 | 19 |
| April | 31.1°C30 Apr 2007 | -4.4°C8 Apr 2007 | 56 mm4 Apr 2008 | 273 mm2011 · driest 14 mm in 2012 | 19 |
| May | 32.8°C14 May 2018 | 2.2°C1 May 2005 | 81 mm2 May 2008 | 199 mm2008 · driest 54 mm in 2018 | 19 |
| June | 40.0°C29 Jun 2012 | 7.2°C3 Jun 2009 | 76 mm28 Jun 2020 | 224 mm2019 · driest 17 mm in 2010 | 20 |
| July | 39.4°C7 Jul 2012 | 7.8°C7 Jul 2008 | 89 mm12 Jul 2016 | 270 mm2016 · driest 1 mm in 2010 | 19 |
| August | 38.9°C20 Aug 2007 | 7.2°C8 Aug 2008 | 48 mm27 Aug 2005 | 161 mm2005 · driest 1 mm in 2008 | 18 |
| September | 37.2°C2 Sep 2011 | 3.3°C23 Sep 2012 | 103 mm2 Sep 2003 | 218 mm2006 · driest 0 mm in 2019 | 19 |
| October | 36.1°C2 Oct 2019 | -2.8°C19 Oct 2018 | 98 mm6 Oct 2013 | 164 mm2017 · driest 6 mm in 2005 | 19 |
| November | 28.9°C1 Nov 2016 | -12.8°C18 Nov 2014 | 45 mm2 Nov 2004 | 201 mm2011 · driest 23 mm in 2009 | 17 |
| December | 22.8°C3 Dec 2012 | -22.2°C25 Dec 2004 | 117 mm15 Dec 2007 | 253 mm2007 · driest 40 mm in 2019 | 20 |
| Month | Days 25°C+ | Days 30°C+ | Frost nights | Heavy rain (10 mm+) | Snow days |
|---|---|---|---|---|---|
| January | 0 | 0 | 20 | 3 | <1 |
| February | <1 | 0 | 17 | 3 | <1 |
| March | 2 | 0 | 8 | 3 | <1 |
| April | 7 | <1 | 1 | 4 | 0 |
| May | 15 | 4 | 0 | 4 | 0 |
| June | 25 | 14 | 0 | 4 | 0 |
| July | 28 | 19 | 0 | 4 | 0 |
| August | 28 | 19 | 0 | 3 | 0 |
| September | 22 | 9 | 0 | 3 | 0 |
| October | 9 | 2 | <1 | 3 | 0 |
| November | <1 | 0 | 9 | 3 | 0 |
| December | 0 | 0 | 16 | 3 | <1 |
| Month | Warm & dry days | Wet days | Washouts | Week with 3+ wet days | Daytime mean has ranged |
|---|---|---|---|---|---|
| January | <1% | 25% | 9% | 29% | 2.9–9.2°C |
| February | 3% | 26% | 10% | 30% | 3.7–10.5°C |
| March | 18% | 30% | 11% | 36% | 11.9–17.4°C |
| April | 44% | 30% | 13% | 36% | 18.5–22.9°C |
| May | 62% | 30% | 13% | 36% | 22.7–27.4°C |
| June | 75% | 27% | 11% | 29% | 28.0–30.4°C |
| July | 77% | 25% | 12% | 25% | 28.6–32.9°C |
| August | 82% | 20% | 8% | 18% | 28.6–33.1°C |
| September | 82% | 20% | 8% | 17% | 25.9–29.6°C |
| October | 49% | 20% | 8% | 20% | 19.0–23.6°C |
| November | 14% | 26% | 11% | 28% | 11.4–16.7°C |
| December | 2% | 28% | 11% | 33% | 5.0–11.0°C |
A warm and dry day reaches 20°C with under 1 mm of rain; a wet day gets 1 mm or more; a washout gets 10 mm or more. The week column is the share of seven-day stretches in that month, across the station’s whole daily record, that contained three or more wet days — the odds a week-long trip is rained on repeatedly, counted rather than modelled. The last column is the 10th to 90th percentile of that month’s daytime average across individual years: a narrow band means the average is what you will get, a wide one means the average is a midpoint between years that felt quite different.
The evidence behind this page