Two people have been charged in two separate incidents involving leaving children in hot cars and causing their deaths.

Ricardo Mata faced a judge on Monday. He reportedly admitted to drinking and leaving his 3-month-old son in an SUV in Mission on Saturday. His bond was set at $2 million.

A woman is out of jail on a $10,000 bond.

Brownsville police arrested Karen Silva in connection to a 4-year-old who died inside a daycare's van.

Authorities say heat was a factor in both cases. 

"It could take a matter of minutes," Mission Fire Chief Mike Silva said.

That's how long it takes for a child left alone in a hot vehicle to die.

So far this year, the National Safety Council has tracked 12 child heatstroke deaths in vehicles nationwide.

Texas and California currently have the highest number of deaths, with two reported in each state. The two in Texas happened last week in the Rio Grande Valley, nearly 24 hours apart.

RELATED COVERAGE: Second suspect arrested in connection with Brownsville daycare death

"They are going through a lot of stress, and ultimately they are suffocating. There is no air in the vehicle," Silva said.

Silva demonstrated how quickly a vehicle heats up, even in 80 degree weather. Using a thermal imaging camera, he took the temperature outside around 4 p.m. on Monday.

"Right now, it's marking 87 degrees outside. We are kind of cloudy and there is a little bit of rain," Silva said.

Inside an SUV with all the doors and windows closed, and the engine shut off, in a matter of seconds, the temperatures started to rise inside.

"Right now, we are at 89 it does go up, now it's 92, 93," Silva said.

Silva said even milder temperatures outside can still cause a child to experience heat exhaustion, and when temperatures are in the 90s, or higher, like we see during most of the Valley's summer, the inside of vehicles can become unbearable.

"Even in 90 degree weather, in 30 minutes, we are talking about 120 degrees," Silva said.

Experts say a child's body will heat up three to five times faster than an adult. 

"In a child, their body is a lot smaller, their brain is smaller as well, they are not able to compensate for the amount of heat that goes through their body," Silva said.

Child Passenger Safety Technician and mom of four, Beatrice Sanchez, shared some tips parents can use.

"Have something in the back seat, I have a dinosaur, remove the dinosaur and put it in the front, then put your baby in," Sanchez said. "The dinosaur is going to remind me that my baby is in the back seat."

She also recommends putting your purse or work bag in the back. Sanchez said he hopes through education, other tragedies can be avoided.

"We want to prevent any other heartbreaking situations like the ones that happened last week," Sanchez said.

If you ever see a child or pet stuck in a car, call 911 and try to break a window.

Watch the video above for the full story.