ICYMI: A look back at America's worst tornado, weather and the spread of COVID-19, and BIG snow out west

ICYMI: A look back at America's worst tornado, weather and the spread of COVID-19, and BIG snow out westWhat's the link, if any, between weather and the spread of COVID-19 cases in the Northern Hemisphere? Some new research shows that high temperatures and other factors may reduce the disease's spread.As spread of the new coronavirus illness exploded in the U.S., anxiety also grew this week. Officials issued extreme measures in attempts to slow cases, including in California, where Gov. Gavin Newsom has ordered all Californians to stay home. A bit of good news came during this surreal time as a mostly dry season in California was transformed with the arrival of a considerable amount of snow. Meanwhile, Hawaiian residents experienced something out of the ordinary this week. Here's a look back at the week in weather news.Promising research shows possible weather keys to decreased COVID-19 spreadAs spring settles across the Northern Hemisphere over the next few months, transmission of the new coronavirus may be reduced because of higher temperatures and higher humidity. Researchers have recently looked at the effect warmer weather might have on the spread of the virus, and it now appears that the triple threat of increased ultraviolet (UV) exposure, high temperature and high relative humidity could all factor into the decreased spread of COVID-19, the disease that has infected more than 14,000 people in the U.S. by week's end, and claimed more than 10,000 lives globally.Findings from the study of 100 Chinese cities that were each plagued by over 40 COVID-19 cases between Jan. 21 and 23, showed that an increase of both one degree Celsius and 1% relative humidity can substantially lower the spread.The study period ended the day before China began taking action to prevent further infections, and doing so helped researchers explore the disease's activity before public health measures were implemented. The researchers concluded warmer weather "significantly reduce" the disease's transmission.Meanwhile, AccuWeather found a link between increased UV exposure and a slowdown in the spread of COVID-19. We compiled data of the daily UV Index from seven major global cities between Jan. 1, 2019, to mid-March 2020 and compared it to those cities' 10-year-average of the daily UV index.Read more on AccuWeather's research by clicking here.Coronavirus lockdown leaves Italian streets barren despite nice weatherUnder normal circumstances, residents of Lombardy, Italy, surely would've spent the past week basking in the pleasant weather conditions outdoors with temperatures from the low to mid-60s F. However, right now, 16 million people of Northern Italy are under quarantine, imposed by their government, amid a devastating COVID-19 outbreak that has killed at least 3,400 people in Italy alone. The country just passed China in the number of COVID-19 deaths. Roadways in Northern Italy were deserted as far at the eye could see amid a national shutdown over COVID-19 fears. (Reuters) If you've ever wondered what a nation under lockdown looks like, check out this jaw-dropping video. Drone footage over Baranzate, near Milan, shows what appears to be a ghost town as roads and streets are left almost completely deserted while people isolated themselves in their homes to prevent further spread of the deadly virus.On March 16, the European Union (EU) proposed a suspension of all non-essential inbound travel for the next 30 days, according to The Guardian.Winter storm delivers feet of snow and major turnaround in Northern California California's Sierra Nevada mountain range region finally saw a hefty amount of snow during what has been a wet season that has been largely dry for the state. "The amount of snow and rain created by this over the Sierra and over northern and central parts of California could not have come at a better time," said AccuWeather Senior Meteorologist Dan Kottlowski.Some parts of the region received between 3 and 5 feet of snow since it began Sunday. The winter storm dumped 52 inches of snow over Kingvale, California, by 9 a.m. PDT Monday, and over 5 feet of snow- 62 inches-fell over Blue Canyon. AccuWeather meteorologists expect another round of stormy weather to head into the region through the weekend into next week.CLICK HERE FOR THE FREE ACCUWEATHER APPAccuWeather predicts above-average US temperatures over the next 3 monthsOver the next few months, AccuWeather meteorologists predict, much of the U.S. will experience higher-than-normal temperatures. "There is almost no part of the country that we are predicting to be below normal in any of the three months, which is unusual," Myers said. "This may be a first, but if the coronavirus is slowed by heat, then this is a good thing." Cities expected to feel the warmth this spring include Orlando, where temperatures are expected to be 3.5 degrees Fahrenheit above the long-term norm, as well as Atlanta, Memphis and Detroit, where temperatures will be 2.5 F above average for each, according to the long-range AccuWeather forecast.Meteorologists do say, though, that higher temperatures do not necessarily mean these and other locations will experience constant warmth during this period. Check out AccWeather's temperature predictions for additional U.S. cities this season by clicking here.Hawaii gets 2 rare tornado warnings during severe weather Now, here's something people living in Hawaii don't see everyday. For the first time in more than 10 years, the National Weather Service (NWS) issued two tornado warnings -- a rarity -- for the western portions of the state on Tuesday morning, Forbes reported. The island of Niihau received the first warning just before 1:30 a.m. Tuesday, local time, and Kauai, which took the most serious hit from the storms, received the second tornado warning at around 6 a.m.A Kona low is behind Hawaii's unsettled weather this past week. While residents were warned of wind gusts reaching a possible 60 mph, there were no reports of storm-related damage.95 years ago, nearly 700 people died in the most-devastating US tornado People in Hawaii were able to escape the impacts of tornadoes this week, but 95 years ago, residents across southern Indiana, eastern Missouri and southern Illinois were not as lucky. Wednesday, March 18, marked the anniversary of the single-most devastating tornado in U.S. history, killing 695 people and harming 13,000 as it roared across 219 miles through the three states in 1925. AccuWeather National Reporter Blake Naftel this week took a look back at the catastrophe. Southern Illinois took the biggest hit - more than 500 of the total killed were based there, according to History.com. The Tri-State Tornado reportedly spent more than three hours on the ground as it traveled at speeds over 70 mph, destroying just about everything over the 164 square miles that it traveled.Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.