“There is some evidence to suggest that [coronavirus] may transmit less efficiently in environments with higher ambient temperature and humidity; however, given the lack of host immunity globally, this reduction in transmission efficiency may not lead to a significant reduction in disease spread without the concomitant adoption of major public health interventions,” according to the letter.
Previous studies from China suggested that even with maximum testing temperature and humidity the disease spreads exponentially. This means April and May won't see a reduction in infections just because of improved weather.
But there's a piece of good news anyway: with states and federal authorities introducing further measures by the day, a slowdown is expected regardless of temperature and humidity. Total expected death toll (estimated by the Trump Administration to be within 100,000 and 240,000) could be too high. Institute for Health Metrics and Evaluation at the University of Washington (Seattle) released an updated estimate on Tuesday, expecting 82,000 deaths. Then on Wednesday the number was further revised down by the Institute to just over 60,000.
